JP2005175503A - Plasma processing device and plasma processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing device, which controls the generation of active species and the uniformity of a plasma process, prevents a change in the characteristics of a semiconductor element, and optimizes process conditions in a separate manner. <P>SOLUTION: The plasma processing device controls the state of electric energy generated by electromagnetic waves emitted into a plasma and magnetic fields, and the state of capacitive coupling discharge, of inductive coupling discharge, and of electronic cyclotron resonance discharge, thereby controls the generation of active species. The device also controls the power distribution of radiation electromagnetic waves by a displacement current control method to control a plasma distribution, thereby controls the uniformity of the plasma processing. The device further controls the density distribution of high-frequency currents flowing through a process substrate to prevent a change in the characteristics of the semiconductor element. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a plasma processing apparatus and a plasma processing method provided with a plasma generation means, and more particularly, to form a fine pattern of a semiconductor device or a liquid crystal display element, and to perform plasma etching suitable for uniform processing on a large-diameter substrate. The present invention relates to a plasma processing apparatus and a plasma processing method such as plasma CVD and plasma polymerization suitable for formation.

  In a plasma processing apparatus for processing semiconductor elements and liquid crystal display elements using plasma, the active species that affect the processing performance, the energy of ions incident on the processing substrate, the direction of ions, the uniformity of plasma processing, and the semiconductor by processing It is necessary that the electrical characteristics of the device do not change.

  Regarding generation control of active species, Patent Document 1 describes that plasma processing with excellent active species generation controllability is realized by generating plasma in which capacitive coupling and inductive coupling are mixed.

  Regarding ion energy control and ion directionality, a method of applying a high frequency bias to an electron cyclotron resonance discharge and a substrate support electrode disclosed in Patent Document 2, an inductive RF coupling discharge and a substrate support electrode disclosed in Patent Document 3 By applying a high frequency bias to the substrate, improvement in ion directionality by generation of high density plasma at a low pressure and ion energy control by applying a high frequency bias are realized.

  Regarding uniformity control, Patent Document 1 describes that plasma processing with excellent plasma density distribution controllability is realized by generating plasma in which capacitive coupling property and inductive coupling property are mixed.

  In addition, regarding the uniformity control of plasma processing, Patent Document 4 discloses a method of dividing the electrode to which high-frequency power is applied into a plurality of parts and independently controlling the power applied to each electrode to improve the uniformity. .

  Further, Patent Document 5 describes that the plasma density distribution is controlled by controlling the radiation distribution of electromagnetic waves.

  A problem in processing a semiconductor element substrate using plasma is that the electrical characteristics of the semiconductor element change due to an electrical influence during the plasma processing. Patent Document 6 describes a method for reducing the influence of plasma treatment on electrical characteristics.

  Non-Patent Document 1 discloses electron cyclotron resonance at a frequency of several tens of MHz to 300 MHz in Non-Patent Document 1 and Patent Document 7.

JP-A-8-195379 JP-A-60-158629 JP-A-5-206072 JP-A-61-283127 JP-A-11-260596 JP 2000-3903 A JP-A-6-318565 Oda, Noda, and Matsumura (Tokyo Tech): Generation of Electron Cyclotron Resonance Plasma in the VHF Band: JJAP Vol. 28, No 10, Octobeer, 1989, pp. 1860-1862,

  Ion energy control alone is insufficient to satisfy the processing characteristics necessary for production of semiconductor elements and liquid crystal display elements. The active species greatly affects the processing characteristics, and a general control method thereof is a method of changing processing conditions such as high-frequency power generating plasma and pressure in the processing chamber.

  However, there is a limit to the control of active species depending on the processing conditions, and when the discharge method is different, such as the electron cyclotron resonance method, the inductive RF coupling method, the most common parallel plate electrode method, etc. given in the previous conventional example, The difference in processing performance cannot be covered only by changing processing conditions.

  Therefore, there is a problem that the processing performance that can be realized by the parallel plate electrode method cannot be realized by the electron cyclotron resonance method, the inductive RF coupling method, or the like.

  In the electron cyclotron resonance method, electrons are efficiently accelerated by resonance, so that the energy level of the electrons is high, and it is difficult to perform processing under conditions in which decomposition of the processing gas is suppressed. Even in the inductive RF coupling method, a high-density plasma is locally formed by the electromagnetic wave radiated from the antenna, and this is diffused on the substrate. Therefore, the energy level of electrons in the plasma generation unit is high, and the decomposition of the processing gas is suppressed. Processing under conditions is difficult.

  On the other hand, in the parallel plate method, electrons are accelerated at the interface between the sheath formed on the electrode surface and the plasma, and the energy level thereof is low.

  Thus, the difference in the acceleration mechanism of electrons in plasma depending on the discharge method is a factor that cannot cover the performance difference of each method depending on the processing conditions.

  Another problem is the problem of uniform processing over the entire substrate. In order to improve productivity, the diameter of the processed substrate is increased from φ150 mm to φ200 mm, and the diameter is further increased to φ300 mm in the future. In the prior art, uniformity has been realized by changing processing conditions.

  However, as described above, changing the processing conditions is an important means for controlling the active species, though insufficient. Therefore, there is a need for a uniformity control means that can achieve both the processing conditions for realizing the optimum etching characteristics and film forming characteristics and the processing uniformity.

  The prior arts disclosed in Patent Document 1 and Patent Document 4 are not sufficient in terms of mutual independence between plasma processing uniformity and active species generation control, compatibility between uniformity control and low pressure processing, and the like. Further, the method for controlling the plasma density distribution described in Patent Document 5 has a problem that the plasma distribution control range is not sufficient.

  When processing a semiconductor element substrate using plasma, the problem that the electrical characteristics of the semiconductor element change due to the electrical influence during plasma processing is due to the self-bias potential generated in the sheath between the substrate being processed and the plasma. Due to non-uniformity.

  In order to control the energy of ions, high-frequency power is applied to the substrate support electrode. The main cause of non-uniform self-bias potential is that the high-frequency current distribution due to the application of high-frequency power becomes non-uniform on the substrate.

The method for controlling the self-bias potential disclosed in Patent Document 6 cannot control the distribution of the self-bias potential, and is not sufficient for reducing the change in electrical characteristics.

  Conventional technologies such as higher integration of semiconductor elements, selection ratio with the base material, higher performance of processing shape, uniform processing of large-diameter substrates, and reduction of effects on device characteristics as production substrates increase in diameter There is a need for a technology with even better controllability.

  Regarding the uniformity of plasma processing, as the processing substrate becomes larger in diameter, the processing gas flows from the center of the substrate to the outer periphery in the etching processing and CVD processing, so that the active species concentration distribution and the distribution of the deposited film become obvious. It is becoming difficult to perform uniform processing over the entire surface of a large-diameter substrate.

  Therefore, in order to solve these problems, it is necessary to cancel out such a factor that the distribution cannot be uniformed by another etching characteristic control factor. As one control factor for that purpose, it is necessary to be able to adjust the plasma distribution to be uneven, independently of the processing conditions such as plasma generation power and pressure.

  The active species is generated by collision of the processing gas and electrons in the plasma, and is one of the factors that greatly affect the processing characteristics such as the selection ratio, processing shape, and film quality in the etching process and the CVD process. The amount and type of active species generated are determined by the energy state of electrons in the plasma.

  Further, in order to control the self-bias potential distribution with respect to the influence of the plasma treatment on the semiconductor element, it is necessary to control the high-frequency current distribution flowing through the substrate.

  One of the objects of the present invention is to realize a plasma processing apparatus and a processing method capable of controlling the generation of active species independently of the processing conditions and uniformity control, with a wide control range of the electron energy state.

  Another object of the present invention is to achieve compatibility of plasma uniformity with active species control, ion energy control, and ion directivity improvement by generation of low-pressure and high-density plasma, and independent of processing conditions such as plasma generation power and pressure. An object of the present invention is to realize a plasma processing apparatus and a processing method having a uniformity control means that can be controlled at high speed.

  Another object of the present invention is to provide a plasma processing apparatus and a processing method having means capable of controlling the distribution of high-frequency current flowing through a substrate while achieving both plasma uniformity, active species control, ion energy controllability, and ion directionality improvement. Is to realize.

  In order to achieve the above object, the present invention is configured as follows.

  (1) In a plasma processing apparatus having a plasma processing gas supply means, a plasma processing chamber exhaust means, a plasma generating means, and a means for performing plasma processing with the generated plasma, the plasma generating means emits electromagnetic waves by a displacement current. Means and magnetic field forming means. The electromagnetic wave radiating means has means for controlling the high frequency displacement current flowing between the conductors by forming electrodes of the capacitively coupled discharge means for applying a high frequency voltage from a plurality of insulated conductors.

  (2) Plasma processing apparatus having plasma processing gas supply means, plasma processing chamber exhaust means, plasma generation means, and means for applying high-frequency power to control the energy of ions incident on the processing substrate placed on the stage The counter electrode in which the high-frequency current generated by the high-frequency power flows through the plasma is composed of a plurality of insulated conductors, and includes means for varying the impedance between these conductors and the ground.

  (3) Plasma processing apparatus having plasma processing gas supply means, plasma processing chamber exhaust means, plasma generating means, and means for applying high-frequency power to control the energy of ions incident on the processing substrate placed on the stage And a means for placing the counter electrode through which the high-frequency current generated by the application of the high-frequency power flows through the plasma in a floating state with respect to the ground.

  (4) Concerning uniformity, the distribution of plasma is controlled by controlling the distribution of radiated electromagnetic power and by controlling the high-frequency power supplied to the plasma by capacitive coupling between multiple conductors that apply high-frequency power. To do.

  The mechanism by which energy is given to the electrons in the plasma from the electric field of the electromagnetic wave is a method of increasing the power of the electromagnetic wave and directly accelerating with the electric field of the electromagnetic wave (inductive RF coupling), the direction of movement in which the electron rotates by the magnetic field, There is a method (electron cyclotron resonance) for accelerating electrons by matching the electric field direction of electromagnetic waves.

  In the absence of a magnetic field, energy is supplied by the former mechanism, and in the condition of applying a magnetic field, electromagnetic waves easily travel through the plasma, and energy is supplied by the latter mechanism.

  Under the condition where a magnetic field is applied, the direction of movement of the electron and the direction of the electric field of the electromagnetic wave coincide with each other when the frequency of rotation of the electron by the magnetic field matches the frequency of the electromagnetic wave (electron cyclotron resonance condition). To a high energy state. When the magnetic field condition deviates from the electron cyclotron resonance condition, the direction of movement of electrons and the direction of the electric field of electromagnetic waves gradually deviate, and the electrons repeat acceleration and deceleration.

  As the magnetic field condition deviates from the electron cyclotron resonance condition, the maximum energy reached by the electrons becomes smaller, and the energy state of the electrons becomes lower than the electron cyclotron resonance condition.

  By controlling the magnetic field conditions in this way, the energy state of electrons can be freely controlled, and the amount and type of active species generated by the decomposition of the processing gas can be controlled.

  Regarding the relationship between the deviation from the resonance condition and the maximum energy reached by the electrons, the rate of decrease in the maximum energy of the electron increases in proportion to the frequency of the electromagnetic wave with respect to the ratio at which the magnetic field condition deviates from the resonance condition. Under the normally used 2.45 GHz condition, the energy drop of electrons due to deviation from the electron cyclotron condition is abrupt, and practical control is difficult. The frequency range that can be practically controlled is 200 MHz to 10 MHz.

  Note that although electron cyclotron resonance at a frequency of several tens of MHz to 300 MHz is disclosed in Non-Patent Document 1 and Patent Document 7, the relationship between the electron energy state and the magnetic field strength is not described.

  As means for emitting electromagnetic waves, a displacement current was passed between insulated conductors, and electromagnetic waves were emitted by this displacement current. A resonant circuit having the same resonant frequency as the high frequency to be applied is formed between the conductors, including the capacitance formed between the conductors, and the displacement current is controlled by controlling the resonance conditions, and the power of the radiated electromagnetic wave is reduced. Can be controlled.

  Under no magnetic field, the electromagnetic wave hardly progresses in the plasma. By setting the condition close to the resonance condition under the non-magnetic field condition and increasing the power of the radiated electromagnetic wave, energy is supplied from the electromagnetic wave to the electrons in the plasma in the vicinity of the radiated electromagnetic wave. Under such conditions, the energy of the electrons partially increases in the vicinity where the electromagnetic waves are radiated, the decomposition of the processing gas proceeds, and it is difficult to control to a low dissociation state.

  Under the condition where a magnetic field is applied, the electromagnetic wave is likely to travel into the plasma, and the energy supply from the electromagnetic wave to the electrons in the plasma is performed in the entire plasma generation space, and the distribution of the electron energy state becomes uniform. In addition, the energy level of the electrons is lowered and can be controlled to a low dissociation state.

  When energy is supplied in the vicinity of the electromagnetic wave radiation portion as in the non-magnetic field condition, high-density plasma is formed in this portion, and the plasma reaches the processing substrate by diffusion from here. Accordingly, in such a mechanism, the diffusion changes depending on the pressure, and the plasma density and the plasma distribution on the processing substrate are affected by the pressure.

  On the other hand, when energy is supplied in the entire plasma generation space by applying a magnetic field, it is not affected by the diffusion of the plasma, so that the processing conditions such as the pressure hardly affect the plasma distribution. Such a condition is a necessary condition for independently controlling the processing conditions and the plasma distribution.

  As means for controlling the uniformity, in the present invention, a plurality of portions that radiate electromagnetic waves by displacement current are provided, and at least one of the electromagnetic wave radiation amounts can be controlled. The control method is based on the method for controlling the resonance condition described above. If the portions that radiate electromagnetic waves are provided in a ring shape, the plasma distribution can be controlled to be uneven by controlling the respective radiated electromagnetic waves.

  Furthermore, since plasma is generated in the entire plasma generation space under the condition where a magnetic field is applied, the plasma distribution hardly changes depending on the processing conditions, and the distribution control of the plasma by controlling the resonance conditions can be performed independently of the processing conditions. it can. In addition, the generation amount and type of active species can be controlled independently of these uniformity control and processing conditions by a magnetic field.

  If a conductor portion that emits electromagnetic waves is provided close to the plasma, electric power can be supplied to the plasma by capacitive coupling. Therefore, in the present invention, discharge can be performed with the same capacitive coupling as that of the parallel plate electrode method under the condition that the magnetic field is not applied and the current of the resonant circuit is reduced, and induction by electromagnetic wave radiation is caused by increasing the current of the resonant circuit. A combined discharge is generated, and a discharge under an electron cyclotron resonance condition can be generated by applying a magnetic field.

  The capacitively coupled discharge, the inductively coupled discharge, and the electron cyclotron discharge have different electron energy conditions, and the processing gas decomposition conditions also differ. In the present invention, in addition to the active species control by the magnetic field described above, the active species can be controlled by controlling the discharge method.

  The ion energy of ions incident on the processing substrate placed on the stage is controlled by applying high frequency power. The high-frequency current generated by the high-frequency power flows to the counter electrode through the plasma.

  Concerning the problem that the electrical characteristics of the semiconductor element change due to the electrical influence during plasma processing, this counter electrode is composed of multiple insulated conductors, and the impedance between these conductors and ground is optimized so that it can be used on the stage. The high-frequency current flowing through the processing substrate placed thereon was made uniform. Thereby, the self-bias potential distribution on the processing substrate is made uniform, and the change in the electrical characteristics of the semiconductor element due to the electrical influence during the plasma processing is reduced.

  Further, the stage and the counter electrode through which the high-frequency current flows through the plasma are floated with respect to the ground. Thereby, the ratio of the high-frequency current flowing in the plasma from the stage to the conductor grounded to the ground other than the counter electrode is significantly reduced by applying the high-frequency power.

  As a result, most high-frequency current flows between the stage and the counter electrode. Further, by providing the counter electrode in parallel with the stage, the high-frequency current on the stage can be made uniform, and the change in the electrical characteristics of the semiconductor element due to the electrical influence during the plasma processing can be reduced.

  According to the present invention, in the plasma processing apparatus, the energy state of electrons can be controlled independently, thereby controlling the generation of active species, such as high selective etching and high accuracy, high speed etching or film quality and film forming speed. It is possible to achieve characteristics that are difficult to achieve with technology.

  In addition, the plasma density distribution can be controlled without changing the hardware configuration, and fine pattern high-precision etching and uniform film formation can be performed over the entire large-diameter substrate.

  In addition, the plasma distribution can be controlled during the plasma processing independently of the process conditions, etc. By controlling the plasma distribution according to the progress of the plasma processing state, more accurate etching and uniform film formation can be achieved. it can.

  In the present invention, an electromagnetic wave is radiated by controlling the high-frequency displacement current. However, in this method, as described in the embodiment, the gap through which the electromagnetic wave is radiated can be very narrow, about 0.2 mm. The inductive RF coupling method is the same in that it emits electromagnetic waves, but the radiation part of the electromagnetic waves cannot be made so narrow. As a result, the present invention is not affected by the deposited film adhering to the electromagnetic wave radiation portion, and has an effect of being able to perform a stable treatment as compared with the prior art.

  According to the present invention, it is possible to further reduce the occurrence of a change in electrical characteristics of a semiconductor element due to plasma treatment, and to improve the yield in semiconductor element production.

  As a result, the processing performance of semiconductor elements, liquid crystal display elements, etc. can be improved, and it is possible to produce higher performance devices. That is, according to the present invention, it is possible to realize a plasma processing apparatus and a processing method capable of independently optimizing processing conditions, uniformity control, active species generation control, and electrical characteristic change prevention.

  In addition, the processing conditions such as pressure and power are not restricted in terms of uniformity and prevention of changes in electrical characteristics, and there is an effect that a wide range of processing conditions can be used.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of a plasma processing apparatus according to a first embodiment of the present invention.

  The processing chamber 1 is composed of an inner wall surface 1a and an inner wall surface 1b. Both inner wall surfaces are insulated by an insulating material 4c, and opposed electrodes 2a, 2b and a stage electrode 3 are disposed facing each other. The counter electrode 2b is insulated by an insulating material 4a, and the stage electrode 3 is insulated by an insulating material (not shown). The counter electrodes 2a and 2b are insulated from each other by an insulating material 4b.

  The inner wall surface of the processing chamber 1, the electrode and the insulating material joint have a vacuum seal structure. Refrigerant channels 5a and 5b and process gas supply channels 6a and 6b are provided in the counter electrode. The refrigerant channels 5a and 5b are connected to a circulator (not shown) so that the temperature of the counter electrode can be maintained at a set temperature.

  The process gas supply paths 6a and 6b are connected to a process gas supply source 27 so as to supply process process gas at a set flow rate. Covers 8a, 8b, 8c, and 8d are attached to the surface of the counter electrode, and each cover is installed with a gap of 0.2 mm.

  The process gas is supplied from the process gas supply paths 6a and 6b to the back surfaces of the covers 8a, 8b and 8c through the gas supply holes 7a and 7b, and is supplied to the processing chamber 1 through a 0.2 mm gap between the covers. .

  A high frequency power source 18 and a matching box 19 are connected to the inner wall surface 1a. A high-pass filter 20 that matches the frequency of the high-frequency power source 9 is also connected so that the high-frequency current from the high-frequency power source 9 flows to the ground.

  A high frequency power source 9 is connected to the counter electrode 2a via a matching box 10 and a variable capacitor 11, and a high frequency power source 9 is connected to the counter electrode 2b via a matching box 10 and inductances 12a and 12b.

  The counter electrodes 2a and 2b are connected to low-pass filters 13a and 13b that match the frequency of the bias power source 17, and a high-frequency current from the bias power source 17 applied to the stage electrode 3 passes through the counter electrodes 2a and 2b, 29 flows.

  A coil 14 is provided on the outer periphery of the processing chamber 1 to form a magnetic field orthogonal to the counter electrodes 2a and 2b in the processing chamber.

  The stage electrode 3 has a structure in which the processing substrate 15 can be placed. The stage substrate 3 is fixed to the surface of the stage electrode 3 by an electrostatic adsorption mechanism (not shown), and a coolant is supplied from a circulator 16 to a temperature control mechanism (not shown). The temperature of the processing substrate 15 during processing can be controlled.

  A bias power source (2 MHz) 17 is connected to the stage electrode 3 via a transformer 29 in order to control the energy of ions incident on the processing substrate during the plasma processing. The transformer 29 is in a floating state with respect to the ground, and the capacitance component between the transformer 29 and the ground is also reduced. The outer peripheral portion of the stage electrode 3 is composed of a member grounded to the ground.

  The inside of the processing chamber 1 is evacuated to a vacuum by an exhaust control mechanism 24, so that the exhaust capacity can be adjusted and adjusted to a set pressure. In addition, a monitor device 25 for monitoring the progress of plasma processing is connected in the processing chamber 1.

  The capacitance value of the variable capacitor 11 is controlled by the drive motor 26 controlled by the distribution control unit 28.

  Next, an operation example in the etching process according to the first embodiment of the present invention will be described. The processing substrate 10 is carried in and placed on the stage electrode 3. An etching gas (fluorocarbon gas) having a set flow rate is supplied from the etching gas supply source 27, and the exhaust is controlled so that the pressure in the processing chamber becomes 1 Pa.

  The etching gas is supplied from the process gas supply passages 6a and 6b to the back surfaces of the covers 8a, 8b and 8c through the gas supply holes 7a and 7b, and is supplied to the processing chamber 1 through a 0.2 mm gap between the covers. Therefore, the pressure on the back surface of the cover is increased, and each cover is cooled by the counter electrodes 2a and 2b.

  A silicon oxide film and a silicon film which are insulating films of semiconductor devices are formed on the processing substrate. The treated substrate is electrostatically attracted to the stage electrode 3 and He gas is supplied between the substrate and the stage electrode 3 from a helium gas supply source (not shown) to reduce the thermal resistance from the substrate to the stage electrode 3. The temperature rise of the processing substrate during the etching process is prevented.

  High frequency power of 100 MHz and 2000 W is input from the high frequency power source 9 to the counter electrodes 2a and 2b, and plasma is formed by capacitively coupled discharge.

  First, the principle of radiation of electromagnetic waves from the peripheral insulating material 4a will be described.

  When high-frequency power is supplied to the counter electrode, a high-frequency potential is generated at the counter electrode 2b, and the inner wall surface 1a is grounded to the ground by a high-pass filter, so that a high-frequency displacement current is generated between the counter electrode 2b and the inner wall surface 1a. Flowing. Since this displacement current flows through the insulating material 4a, an electromagnetic wave is radiated by this high-frequency displacement current, and the electromagnetic wave is radiated into the processing chamber 1 through the gap between the covers 8c and 8d.

  Next, radiation of electromagnetic waves from the insulating material 4b portion on the inner peripheral portion will be described.

  The insulating material 4b between the counter electrodes 2a and 2b is modeled by a capacitor. A resonance circuit shown in FIG. 2 is formed by the capacitor 4c, the variable capacitor 11, and the inductances 12a and 12b.

  When the capacity of the variable capacitor 11 approaches the resonance condition, the high-frequency current flowing through this circuit increases, and when the capacity of the variable capacitor 11 deviates from the resonance condition, the high-frequency current flowing through this circuit decreases.

  Thus, the displacement current flowing through the insulating material 4b can be controlled by the variable capacitor 11, and is proportional to the high-frequency displacement current flowing through the insulating material 4b, and electromagnetic waves are radiated, and further through the gap between the covers 8b and 8c, Electromagnetic waves are radiated. By controlling the high-frequency displacement current flowing in the resonance circuit by the capacitance of the variable capacitor 11, the radiated power of this electromagnetic wave can be controlled.

  The density distribution of the plasma generated by the electromagnetic wave radiated from the insulating material 4a on the outer periphery is a concave distribution with a high outer peripheral portion like a plasma distribution 51 shown in FIG. The density distribution of the plasma generated by the electromagnetic wave radiated from the insulating material 4b on the inner periphery is a convex distribution with a high central portion like a plasma distribution 52 shown in FIG.

  The entire plasma distribution is a distribution obtained by superimposing the plasma distribution due to the electromagnetic waves radiated from the outer peripheral portion and the plasma distribution due to the electromagnetic waves radiated from the inner peripheral portion. By adjusting the power of the electromagnetic wave radiated from the inner peripheral portion, the plasma density distribution in the vicinity of the processing substrate 15 in the range of φ300 mm can form a uniform plasma within ± 5% like the plasma density distribution 53.

  When the power of the electromagnetic wave radiated from the inner peripheral portion is lowered, the plasma density distribution due to the electromagnetic wave radiated from the inner peripheral portion decreases as shown in the plasma density distribution 54 shown in FIG. As shown in the plasma density distribution 55, it has a concave distribution.

  When the power of the electromagnetic wave radiated from the inner peripheral part is increased, the plasma density distribution due to the electromagnetic wave radiated from the inner peripheral part increases like the plasma density distribution 56 shown in FIG. As shown in the plasma density distribution 57, it has a convex distribution.

  FIG. 6 shows the relationship between the capacitance of the variable capacitor 11 and the plasma density uniformity. It can be seen that when the capacitor capacity is increased, the plasma density distribution changes from a convex distribution to a flat distribution and further changes to a concave distribution, and the plasma density distribution can be controlled by the capacity of the variable capacitor 11.

  The capacity of the variable capacitor 11 is controlled by the control from the distribution control unit 28 and the drive motor 26. These controls are also possible during the etching process.

  Under conditions where no magnetic field is formed, electromagnetic waves are reflected by the generated plasma, and the influence on the plasma is small. In this case, since the discharge is almost capacitively coupled discharge, the electron energy distribution of the plasma is close to the Maxwell-Boltzmann distribution.

The condition for forming the magnetic field is to pass a current through the coil 14 to form the magnetic field. This magnetic field is formed approximately in accordance with the radiation direction of the electromagnetic wave, and in the vicinity of the condition (35G (35 × 10 ⁻⁴ T)) in which the magnetic field strength causes electron cyclotron resonance with respect to the frequency of the emitted electromagnetic wave, Energy is efficiently supplied to the electrons in the plasma from the electromagnetic field, and the energy of the electrons can be increased.

  As in the first embodiment of the present invention, in electron cyclotron resonance at 100 MHz, the rotational angular velocity of electrons decreases in proportion to the frequency of electromagnetic waves, compared to conventional electron cyclotron resonance using microwaves of 2.45 GHz. The electric field of the electromagnetic wave for accelerating electrons does not change as long as the power density is the same regardless of the frequency, and can give the same energy to the electrons.

When the frequency is low, the angular velocity is decreased, so that the tolerance for energy transfer due to the shift of the cyclotron frequency by the magnetic field and the frequency of the electromagnetic wave is increased. For example, in the case of 100 MHz, the magnetic field strength is at a level necessary for ionization and generation of active species in a wide magnetic field range from 10 G (10 × 10 ⁻⁴ T) to around 70 G (70 × 10 ⁻⁴ T). Electrons can be accelerated.

  At this time, the maximum energy of the accelerated electrons decreases as the electron cyclotron condition deviates, and the energy state of the electrons can be controlled by the magnetic field strength. That is, by changing the magnetic field strength, the energy of electrons can be controlled from a level suitable for generating active species to a level higher than the ionization level.

In the first embodiment of the present invention, the magnetic field strength is set to 50 G (50 × 10 ⁻⁴ T) higher than the electron cyclotron condition, and the maximum electron energy is set to a lower condition.

Such an effect is measured in the region where the frequency of the electromagnetic wave is in the range of 200 MHz to 10 MHz, and in particular, 100 MHz to 50 MHz is easy to use and the effect is large. When the frequency of the electromagnetic wave is 200 MHz, the range in which the effect of controlling the energy state of the electrons by the magnetic field strength is narrowed in inverse proportion to the frequency, and is up to about 100 G (100 × 10 ⁻⁴ T). Under the condition of 10 MHz, the effect of the magnetic field is measured from the magnetic field strength of about 2 G (2 × 10 ⁻⁴ T).

  When 1000 W is applied to the stage electrode 3 by applying 2 MHz high frequency power from the bias power source 17, a voltage of 700 Vpp is generated, and ions from the plasma are accelerated by this voltage and incident on the processing substrate 15, and ions assist on the surface of the processing substrate 15. As a result, the etching gas (carbon fluoride gas) decomposed by the plasma reacts with the silicon oxide film and the silicon film, and the etching proceeds.

  When the energy level of electrons is high, decomposition of the fluorocarbon gas proceeds, the amount of fluorine-based active species increases, and the etching rate of the silicon film improves. Moreover, the etching cross-sectional shape becomes nearly vertical under such a gas decomposition condition, and a forward taper shape is likely to occur under the condition where the decomposition does not proceed.

  In the manufacture of semiconductor devices, it is necessary to make the etching rate of the silicon film as small as possible relative to the etching rate of the silicon oxide film that is an insulating film, and to make the etching cross-sectional shape as close as possible to the vertical. For that purpose, it is necessary to appropriately control the decomposition state of the fluorocarbon-based gas and find a condition for making both compatible.

  Under the condition that electromagnetic waves are not radiated (magnetic field: 0T), the etching gas does not decompose and a forward tapered etching shape is obtained. By increasing the magnetic field strength, gas decomposition progresses, the shape approaches vertical, and the etching rate increases, so the etching rate ratio increases conversely.

  As described above, in the present invention, by changing the magnetic field intensity, it is possible to control the decomposition state of the carbon fluoride gas, and to optimize the etching characteristics such as the etching rate ratio between the silicon oxide film and the silicon film and the etching shape. Can do.

  In addition, since the optimization of the etching characteristics can be controlled by a magnetic field independently of the process conditions such as pressure, etching gas flow rate, and high-frequency power, the process conditions can be determined from fine workability, processing speed, etc. Can be widely used.

  A high frequency power is applied from the bias power source 17 to the stage electrode 3 via the transformer 29, and a high frequency current flows through the processing substrate 15 and plasma and flows to the counter electrodes 2a and 2b. Since the transformer 29 is in a floating state with respect to the ground, most of the high-frequency current flowing from the stage electrode 3 flows to the counter electrodes 2a and 2b and does not flow to other portions.

  A normal path for the high-frequency bias current path for controlling the energy of ions incident on the processing substrate 15 is shown in FIG. 7 as a model, the path of this embodiment is shown in FIG. 8, and the difference will be described.

  In the normal configuration, as shown in FIG. 7, one of the outputs of the bias power supply 17 connected to the stage electrode 3 is grounded to the ground, and the high-frequency voltage output terminal is connected to the stage electrode 3. The high-frequency current flows through the processing substrate 15, flows through the plasma to the counter electrodes 2 a and 2 b and the processing chamber wall 1 a, and returns to the bias power source 17 through the ground.

  In the outer peripheral portion of the stage electrode 3, since a high frequency current can flow through both the counter electrode 2b and the processing chamber inner wall 1a, the impedance of the current path becomes low, and the high frequency current easily flows. For this reason, the high-frequency current density flowing through the processing substrate 15 has a distribution in which the outer peripheral portion is high and the central portion is low. This is one major factor that changes the electrical characteristics when the semiconductor element substrate is processed.

  In the present embodiment, as shown in FIG. 8, the output of the bias power supply 17 is connected to the stage electrode 3 through a transformer 29 so as to float from the ground. A current circuit is provided from the counter electrodes 2a, 2b back to the transformer via low-pass filters 13a, 13b.

  By configuring the capacitance component between the current circuit returning to the transformer and the ground to be small, the impedance of the path flowing from the stage electrode 3 to the processing chamber wall 1a and returning to the transformer is increased, and the high-frequency current flowing through this path is greatly increased. To drop. Accordingly, most of the high-frequency current flowing from the stage electrode 3 flows to the counter electrodes 2a and 2b.

  Therefore, by providing the stage electrode 3 and the counter electrodes 2a and 2b in parallel, the high-frequency current distribution becomes almost uniform, and the problem that the electrical characteristics of the semiconductor element change due to the electrical influence during plasma processing is greatly reduced. it can.

  By shifting the characteristics of the low-pass filters 13a and 13b with respect to the frequency of the bias power source 17, the impedance with respect to the frequency of the bias power source 17 can be made variable.

  When the low-pass filter 13a is set so that the impedance is minimized and the impedance of the low-pass filter 13b is set higher than that, the high-frequency current flowing through the processing substrate 15 has a high current density in the central portion and a current density in the outer peripheral portion. Low distribution. If the impedance setting of the low-pass filter is reversed, the current density in the outer peripheral portion is high and the current distribution in the central portion is low.

  Thus, by optimizing the impedances of the low-pass filters 13a and 13b, the self-bias potential distribution generated on the processing substrate 15 can be more uniformly controlled, and the occurrence of changes in the electrical characteristics of the semiconductor element due to the plasma processing can be further increased. Can be reduced.

  In addition, if the low-pass filters 13a and 13b are controlled by a drive motor and distribution control in the same manner as the variable capacitor 11, the electrical characteristics of the semiconductor element do not change with respect to changes in the processing conditions and state changes during processing. Can be controlled.

  When the etching process is continued, a deposited film is formed on the inner wall surface of the processing chamber 1 and peels off, and becomes a source of dust. In the counter electrodes 2a and 2b, ions from the plasma are accelerated and made incident by the high frequency power applied, so that no deposited film is deposited on the electrode surface and no dust is generated.

  By supplying high frequency power of 400 KHz from the high frequency power source 18 to the inner wall surface 1a, the high frequency current flows through the plasma to the inner wall surface 1b grounded to the ground and the outer peripheral portion of the stage electrode 3, and ions incident on these inner walls Can be prevented from adhering to the inner wall surface.

  The covers 8a to 8d are made of silicon, and the effect differs depending on the resistance value of silicon. In the embodiment described above, the case where silicon having high resistance is used has been described.

  When silicon with low resistance is used, since the distance between the covers 8a to 8d is as narrow as 0.2 mm, the displacement current flowing between the counter electrodes 2a and 2b does not flow through the insulating material 4b, but mainly between the cover 8b and the cover 8c. The high frequency displacement current flowing between the counter electrode 2b and the processing chamber 1a mainly flows between the cover 8c and the cover 8d.

  As shown in the figure, when the distance between the cover and the cover is set to be inclined with respect to the magnetic field, the displacement current flows at right angles to the inclined surface, and the electromagnetic wave is radiated in the inclination direction of the interval.

  In the state in which plasma is generated, a sheath is formed between the cover and the plasma, and the electromagnetic wave radiated with an inclination to the magnetic field is divided into a component that travels along the magnetic field in the plasma and a component that travels through the sheath.

  Since the electromagnetic wave traveling through the sheath portion gradually proceeds in the magnetic field direction, the distribution of the electromagnetic wave becomes flatter than when the electromagnetic wave is radiated in the direction parallel to the magnetic field. If such a method is used, a uniform plasma can be formed even if the electromagnetic wave radiation portion has a single ring-shaped electrode structure, but the plasma distribution cannot be controlled by electrical control.

  However, even when the electromagnetic radiation portion has a double ring electrode configuration, both the plasma distribution due to electromagnetic waves from the inner electromagnetic radiation portion and the plasma distribution due to electromagnetic waves from the outer electromagnetic radiation portion are both flattened. This has the effect of improving the distribution controllability.

  In the present embodiment, the covers 8a to 8d are divided parts, but the present invention is not limited to this. FIG. 9 shows a cover structure according to another embodiment. In the cover 30, quartz rings 32a and 32b are embedded between the silicon rings 31a to 31c.

  The cover 30 can be handled as a single disk, and workability such as replacement can be improved.

Next, the case of plasma CVD will be described.
As a process gas, an organic silane gas containing fluorine and an oxygen gas are mixed and supplied. The process gas is decomposed by plasma in the processing chamber to form a silicon oxide film on the processing substrate.

  The silicon oxide film adheres not only on the processing substrate 15 but also on the covers 8a to 8d on the surface of the counter electrode, the inner wall surface 1a, and the like. However, as described above, ions are accelerated and incident on the surfaces 8a to 8d and the inner wall surface 1a of the counter electrode surface by application of high-frequency power, and this ion assist effect and the organic silane gas are included. The silicon oxide film is removed and no film is formed by fluorine radicals generated from the generated fluorine.

  As described above, according to the first embodiment of the present invention, a plasma processing apparatus capable of controlling the generation of active species independently of the processing conditions and uniformity control, and the control range of the electron energy state is wide. A processing method can be realized.

  In addition, plasma uniformity is compatible with active species control, ion energy control, and improved ion directionality by low-pressure and high-density plasma generation, and can be controlled independently of processing conditions such as plasma generation power and pressure. A plasma processing apparatus and processing method having uniformity control means can be realized.

  In addition, it is possible to reduce the phenomenon in which the electrical characteristics of the semiconductor element change due to the electrical influence during plasma processing, to reduce the uniformity of plasma, active species control, ion energy control, and low pressure high density plasma generation. Plasma processing having means for reducing changes in electrical characteristics of semiconductor elements due to electrical influence during plasma processing, which can be controlled independently of processing conditions such as plasma generation power and pressure An apparatus and a processing method can be realized.

  FIG. 10 is a schematic configuration diagram of a plasma processing apparatus according to the second embodiment of the present invention. In the second embodiment, common parts with the first embodiment described above are omitted, and differences will be mainly described.

  The difference between the second embodiment and the first embodiment is that a ring block 21 is provided on the outer periphery of the counter electrodes 2a, 2b. The ring block 21 is insulated from the counter electrode 2b, the processing chamber 1c, and the cover 8d by an insulating material 4d.

  The inductances 12a and 12b and the ring block 21 are connected via variable capacitors 22a and 22b, and the ring block 21 and the processing chamber 1c are connected via capacitors 23a and 23b.

Next, process processing in the second embodiment will be described.
The electromagnetic wave radiation from the insulating material 4b and its control are the same as described in the first embodiment. The radiation of electromagnetic waves from between the ring block 21 and the counter electrode 2b is a resonance circuit formed by the inductance 12a and the variable capacitor 22a, and the resonance state of the resonance circuit formed by the inductance 12b and the variable capacitor 22b is changed to the variable capacitor 22a, By controlling at 22b, the high-frequency displacement current between the counter electrode 2b and the ring block 21 and its circumferential distribution are controlled, and electromagnetic waves are radiated in proportion to this high-frequency displacement current.

  In the second embodiment, radiation of electromagnetic waves on the inner and outer circumferences of the processing chamber 1c can be controlled independently, and distribution control in the circumferential direction is also possible, so that a more optimal plasma distribution can be obtained.

  In FIGS. 3 to 5 described above, the plasma distribution is controlled by the plasma density distributions 52, 54, and 56 due to the electromagnetic waves radiated from the central portion. In this embodiment, it is possible to control the plasma density distribution 51 due to the electromagnetic waves radiated from the outer periphery, and it is possible to control not only the axial symmetry condition but also the distribution in the circumferential direction. .

Next, an example of the etching process of the wiring film in the second embodiment will be described below.
A processing substrate 15 in which an aluminum film is formed on a silicon oxide film is placed on the stage electrode 3. Subsequently, after supplying a chlorine-based etching gas into the processing chamber 1c and setting the pressure to 1 Pa, 1000 W of high-frequency power is supplied to the counter electrodes 2a and 2b to generate plasma. 100 high-frequency power is applied to the stage electrode 3 and ions incident on the processing substrate 15 from the plasma are accelerated by this high-frequency bias.

  A patterned resist mask or the like is decomposed by plasma on the surface of the processing substrate 15, and a deposited film is formed by the decomposition gas or the like. The deposited film is removed by ion incidence, and the exposed aluminum film reacts with the chlorine-based active species generated in the plasma, so that etching proceeds.

  The deposited film formed on the surface of the processing substrate 15 is not uniformly formed, and the deposition amount in the central portion increases. Therefore, in order to perform uniform etching, it is necessary to increase the ion amount in the central portion.

  On the other hand, when the etching of aluminum is completed and the underlying silicon oxide film is exposed, etching proceeds in proportion to the amount of ions in the silicon oxide film. Is etched a lot.

  Therefore, during the etching of the aluminum film and the etching of the silicon oxide film that is the base film, it is necessary to appropriately control the plasma distribution in accordance with each state and in-process.

  In the second embodiment, the variable capacitors 11, 22a and 22b can be varied by the drive motor 26, the distribution control unit 28, and the same drive mechanism and control mechanism. Thereby, the plasma distribution can be controlled by the control mechanism of the plasma processing apparatus in the same manner as the process conditions such as pressure and power.

  In the etching processing apparatus, several processing conditions are set in the control unit. In one setting condition, the processing pressure, the high frequency power to be input, the type of etching gas flowing into the processing chamber, the flow amount, and the like are stored. The etching process is performed by combining several setting conditions. This combination is also stored in the control unit, and the etching apparatus executes processing by instructing the setting conditions and the combination (referred to as a normal recipe).

  In the present embodiment, the setting condition is a control program in which the plasma uniformity is put in the same way as the pressure and power, and the variable capacitor capacity is controlled by this instruction.

  A processing procedure in the case of performing etching processing by incorporating plasma uniformity into this condition setting will be described in the aluminum film etching example described above. FIG. 11 shows the relationship between the plasma uniformity control and the passage of time in this etching process procedure.

  The plasma distribution is controlled based on the result of monitoring the end point of etching by the monitor 25 to detect and control the time point when the aluminum film etching is changed to the silicon oxide film etching.

  During the etching of the aluminum film, the plasma density distribution is set to a convex distribution, and when the end point of the etching process is detected by the monitor 25, the capacity of the variable capacitor 11 is increased by the drive motor so as to obtain a uniform plasma distribution. Then, this state is maintained until etching is completed.

  The aluminum film is not uniformly formed but has a distribution in film thickness. In order to form a fine pattern with high accuracy, it is necessary to accurately control an over-etching time after the etching is completed, and the etching of the aluminum film needs to be completed simultaneously on the entire surface of the processing substrate 15.

  In the embodiment of the present invention, the film thickness of the film to be etched is measured by a film thickness measuring means (not shown), and the plasma distribution is calculated so that the etching is completed simultaneously on the entire surface of the substrate by calculating back from the film thickness distribution measurement result. It was made to control every time.

  This control calculates the etching processing speed distribution that completes etching of the etching target film simultaneously on the entire surface of the processing substrate from the data of the etching target film input to the etching treatment control unit, and the plasma density distribution required for the etching processing speed. Create Based on the relationship between the capacitor capacity and the plasma distribution shown in FIG. 6, the capacity of the variable capacitors 11, 22 a and 22 b is calculated, and the plasma distribution is controlled by the distribution control unit 28 and the drive motor 26 to perform the etching process.

  In this second embodiment, from the viewpoint of electron energy control, the explanation will focus on plasma processing by discharge that controls the energy state of electrons from capacitively coupled discharge conditions in which no magnetic field is applied to electron cyclotron resonance conditions in which a magnetic field is applied. However, plasma distribution control and gas decomposition control by discharge under conditions that do not use a magnetic field are also possible.

  In the second embodiment shown in FIG. 10, when the displacement current flowing in the resonance circuit formed by the variable capacitor 11 and the inductances 12a and 12b is increased, the electromagnetic wave power radiated to the central portion of the processing chamber 1c is increased, and induction is induced. Similarly to the coupling, electromagnetic wave power is supplied to the plasma. However, there are many reflections from plasma, and it is necessary to flow a large amount of high-frequency displacement current as compared with conditions using a magnetic field.

  By increasing the displacement current flowing in the resonance circuit formed by the variable capacitors 22a and 22b and the inductances 12a and 12b, the electromagnetic wave power radiated from the outer peripheral portion can be controlled in the same manner as the central portion described above.

  Thereby, double ring-shaped plasma of the center part and the outer peripheral part by inductive coupling can be formed in the processing chamber 1c, and uniform plasma can be formed on the large-diameter processing substrate 15. Further, by controlling the displacement current at the central portion and the high-frequency displacement current at the outer peripheral portion, the plasma distribution can be controlled from a concave distribution to a convex distribution.

  Under this condition where no magnetic field is used, energy is intensively supplied to the plasma in the vicinity where the electromagnetic wave is radiated, so that the energy state of electrons is at a high level, and the decomposition of the processing gas is likely to proceed.

  Therefore, 1) a condition in which the high-frequency displacement current is reduced and the discharge is performed under almost capacitive coupling conditions, 2) a condition in which the high-frequency displacement current is increased, a strong plasma is locally formed to promote decomposition of the processing gas, and 3) a magnetic field is generated. The variable capacitor 11 shown in this embodiment can be used up to the condition that the electromagnetic wave easily travels into the plasma by being formed, and the process gas is gradually decomposed by supplying energy from the electromagnetic wave to the plasma throughout the processing chamber. .22a, 22b and the magnetic field formed by the coil 14 can be controlled.

  That is, according to the second embodiment of the present invention, as in the first embodiment, the control range of the electronic energy state is wide, and the generation of active species is controlled independently of the processing conditions and uniformity control. It is possible to realize a plasma processing apparatus and a processing method capable of

  In the above-described embodiment of the present invention, the description has been made mainly on the etching process and the plasma CVD process. However, the present invention is not limited to this, and is a process using plasma such as plasma polymerization and sputtering. It is clear that if applicable, it can be applied as well.

  Further, regarding the frequency of the high frequency power source for generating plasma, in the above-described embodiment of the present invention, the case where the frequency is 100 MHz has been described, but this is from 200 MHz as described in the first embodiment. Similar effects can be obtained in the range of 10 MHz.

  It is also possible to store the processing procedure for controlling the distribution of the plasma processing described above in the storage means, and to perform the plasma processing by controlling the plasma distribution by the control means in accordance with the stored processing procedure.

It is a schematic block diagram of the plasma processing apparatus in 1st Embodiment by this invention. It is a figure which shows the resonance circuit model in 1st Embodiment by this invention. It is a figure which shows the plasma density distribution control in 1st Embodiment by this invention. It is a figure which shows the plasma density distribution control in 1st Embodiment by this invention. It is a figure which shows the plasma density distribution control in 1st Embodiment by this invention. It is a figure which shows the relationship between the variable capacitor capacity | capacitance and plasma density distribution uniformity in 1st Embodiment by this invention. It is a figure which shows the high frequency current path model by the conventional high frequency bias application. It is a figure which shows the high frequency current path | route model by the high frequency bias application in 1st Embodiment by this invention. It is a figure which shows the cover member structure in 1st Embodiment by this invention. It is a schematic block diagram of the plasma processing apparatus in 2nd Embodiment by this invention. It is a figure which shows the etching process progress in 2nd Embodiment by this invention.

Explanation of symbols

1, 1c ... treatment chambers 1a, 1b ... inner wall surfaces 2a, 2b ... counter electrodes,
3 ... Stage electrodes 4a, 4b, 4c ... Insulating materials 5a, 5b ... Refrigerant flow paths 6a, 6b ... Process gas supply paths 7a, 7b ... Gas supply ports 8a-8d ... Covers 9, 18 ... High frequency power supplies 10, 19 ... Matching Box 11, 22a, 22b ... Variable capacitors 12a, 12b ... Inductance 13a, 13b ... Low pass filter 14 ... Coil 15 ... Processing board 16 ... Circulator 17 ... Bias power supply 20 ... High pass filter 21 ... Ring blocks 23a, 23b ... Capacitor 24 ... Gas Exhaust device 25 ... monitor device 26 ... drive motor 27 ... gas supply source 28 ... distribution control unit.

Claims (2)

In a plasma processing apparatus comprising a plasma processing gas supply means, a plasma processing chamber exhaust means, and a plasma generation means, and plasma-treats a substrate with plasma,
The plasma generating means comprises capacitively coupled discharge means comprising a plurality of conductors insulated from each other, electromagnetic wave radiating means for emitting a high frequency displacement current between the conductors to emit electromagnetic waves, and magnetic field forming means, and the electromagnetic wave radiating means Comprises a radiated electromagnetic wave power control means for controlling the radiated electromagnetic power by means of a high frequency displacement current control means in which a resonance circuit is formed. In a plasma processing apparatus having a plasma processing gas supply means, a plasma processing chamber exhaust means, a plasma generation means, and a means for performing plasma processing using the generated plasma,
The plasma generating means has capacitively coupled discharge means composed of a plurality of conductors insulated from each other, and electromagnetic wave emission means for emitting an electromagnetic wave by flowing a high-frequency displacement current between the conductors,
The said electromagnetic wave radiation | emission means has a radiated electromagnetic wave power control means which controls radiated electromagnetic wave power by the high frequency displacement current control means which formed the resonance circuit, The plasma processing apparatus characterized by the above-mentioned.

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