JPH0794480A - Plasma processing and plasma processing device - Google Patents

Abstract

PURPOSE:To reduce charge-up damage on a processed substrate by performing plasma processing of a substrate to be processed while protecting the underside and the peripheral part of the processed substrate where an insulating film is formed on the conductive base plate from plasma. CONSTITUTION:Plasma processing of a substrate S to be processed is performed while protecting the underside and the peripheral part of a processed substrate S having a insulating film on a conductive base plate from a plasma by a peripheral ring 15. The peripheral ring 15 is made of alumina and can be divided in two. At the time of placing the processed substrate S on an electrostatic chuck 25, the peripheral ring 15 is opened and the substrate S to be treated is placed on the electrostatic chuck 25 followed by closing the peripheral ring 15. Here, due to a structure where the peripheral ring 15 comes in contact with the peripheral part of the substrate S to be processed, the peripheral part of the processed substrate S and the surface peripheral part can be prevented from being exposed to plasma during plasma processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method and a plasma processing apparatus, and more particularly to a plasma processing method in a semiconductor element manufacturing process and a plasma processing apparatus used for the plasma processing and the like.

[0002]

2. Description of the Related Art A microwave is introduced into a vacuum vessel under a reduced pressure or a low gas pressure to cause a gas discharge to generate plasma, and the plasma is guided to the surface of a substrate for treatment such as etching or resist removal. Alternatively, a plasma processing apparatus for forming a thin film by CVD or the like is indispensable for manufacturing highly integrated semiconductor elements and the like.

In addition, plasma is generated more efficiently,
Alternatively, a magnetic field microwave plasma processing apparatus or an electron cyclotron resonance (ECR) that applies a magnetic field to confine the plasma in a certain region.
e) An apparatus for generating plasma by excitation has an advantage that plasma with high activity can be generated in a low gas pressure region, and is expected to be promising in the future.

In the various plasma processing apparatuses described above, various processes (hereinafter referred to as plasma processing) are performed on the semiconductor substrate or the like by utilizing the action of ions, radicals, electrons, etc. in the generated plasma. When a plasma treatment is applied to a semiconductor substrate or the like in which an insulating film is formed on a conductive base substrate, a potential difference (voltage) is generated between the substrate surface and the base substrate. There was a problem of degrading performance.

Deterioration of the semiconductor substrate due to local voltage generation (charge-up distribution) in the semiconductor substrate causes uneven distribution of ions or electrons in plasma in the vicinity of the substrate, and these uneven distributions. It has been considered that the ions or electrons in the state are attached to the surface of the substrate.

Various proposals have been made to prevent the above-described deterioration of the semiconductor due to charge-up distribution. For example, in Japanese Patent Laid-Open No. 5-29269, a semiconductor substrate to be processed placed on a substrate support is proposed. A magnetron plasma processing apparatus in which a conductive ring is placed so as to surround the outer circumference is disclosed. In the present invention, since the device is equipped with the conductive ring, electrons near the outer peripheral portion of the plasma generation region are taken in and the electron density is prevented from increasing in a part of the outer peripheral portion of the substrate to be processed. It is described that the effect that the charge-up distribution can be reduced can be obtained.

Further, JP-A-3-22422 describes a plasma etching apparatus in which a portion of a wafer holder for holding a semiconductor wafer which is exposed to plasma is an insulating film, and the inside which is not exposed to plasma is made of a conductive material. There is. According to the present invention, it is described that the apparatus is equipped with the wafer retainer having the above-mentioned configuration, so that it is possible to obtain the effect that the charge existing on the surface of the semiconductor wafer can be discharged through the wafer retainer.

[0008]

On the other hand, the inventors of the present invention, in the apparatus for performing the plasma treatment as described above, have a mechanism of causing a charge-up when actually performing a treatment such as etching on a semiconductor substrate. We investigated whether or not to do so and obtained the following findings.

FIG. 6 is a conceptual diagram schematically showing how a charge-up distribution is generated on the substrate to be processed when the substrate to be processed is subjected to etching treatment by irradiating plasma.

As shown in FIG. 6, the substrate 40 to be processed is
An insulating layer 42 is formed on a base substrate 41 that constitutes the conductive layer 4 such as electrodes laminated on the insulating layer 42.
3 is subjected to etching treatment to form a predetermined pattern. Since the conductive layer 43 having a predetermined pattern is formed on the conductive layer 43 by etching, the resist layer 45
Are formed.

As described above, the conductive layer 4 is formed on the substrate 40 to be processed.
In order to form No. 3, when the target substrate 40 placed in the plasma processing apparatus is irradiated with plasma 44 and plasma processing such as etching is performed, the plasma of the target substrate 40 is processed during the plasma processing. Charged particles from the plasma 44 flow into the conductive layer 43 which is in contact with 44 and are charged. In FIG. 6, ions flow into the conductive layer 43 to be positively (+) charged, but normally the charged state (+, −) and its size are also changed depending on the state of the plasma 44 and the state of the substrate 40 to be processed. different.

The base substrate 41 corresponds to the charged state of the conductive layer 43 or reflects the state of the plasma 44 and the like.
Also, charged particles flow from the plasma 44 into the conductive layer 43.
A potential difference occurs between the base substrate 41 and the base substrate 41.

From the plasma 44 thus generated around the substrate 40 to be processed, the underlying substrate 4 which becomes the underlying portions of the conductive layer 43 and the insulating layer 42 which are the surface portion of the substrate 40 to be processed.
When the charged particles flow into both of the first and second electrodes, and a potential difference (voltage) is generated between the two, dielectric breakdown occurs in the target substrate 40 during or after plasma irradiation, or the target substrate 40 is processed.
The withstand voltage of will decrease.

It is considered that when the substrate 40 to be processed is irradiated with the plasma 44, a charge-up distribution is actually generated in the substrate 40 to be processed by the mechanism as described above.
In the magnetron plasma processing apparatus disclosed in JP-A-5-29269 and the plasma etching apparatus disclosed in JP-A-3-22422, the amount of charged particles in the plasma 44 flowing into the surface of the substrate 40 to be processed is set. Only control has been attempted,
Almost no consideration was given to the charged particles flowing into the conductive underlying substrate 41 which is the underlying substrate of the substrate 40 to be processed.

Therefore, in the above-described conventional plasma processing apparatus, there is a space around this conductive base substrate 41, and charged particles in the plasma 44 flow into the base substrate 41 from this space, and the substrate 40 to be processed 40 is processed. However, there is a problem in that a charge-up distribution occurs in the substrate, and the substrate 40 to be processed is deteriorated (charge-up damage).

The present invention has been made in view of the above problems, and an object of the present invention is to provide a plasma processing method and a plasma processing apparatus capable of reducing charge-up damage caused on a substrate to be processed by plasma irradiation. There is.

[0017]

In order to achieve the above-mentioned object, a plasma processing method according to the present invention is a method of plasma-treating a back surface and an outer peripheral portion of a substrate to be processed in which an insulating film is formed on a conductive base substrate. It is characterized in that the substrate to be processed is plasma-processed while being protected from (1).

Further, the plasma processing apparatus according to the present invention is a plasma processing apparatus in which a substrate to be processed is processed by plasma, and a sample holder that is in close contact with the back surface of the substrate to be processed and an outer peripheral portion of the substrate to be processed. It is characterized by having a close outer ring (2).

Further, the plasma processing apparatus according to the present invention is
In a plasma processing apparatus in which a substrate to be processed is processed by plasma, a recess having substantially the same shape as the substrate to be processed is formed on a sample holder (3).

In the plasma processing method according to the present invention, the back surface and the outer peripheral portion of the substrate to be processed are protected from the plasma when performing the plasma processing, but the protection method is not particularly limited, and for example, the above (2) or Like the plasma processing apparatus described in (3) above, a plasma processing apparatus that includes the sample holder that closely contacts the back surface of the substrate to be processed and an outer peripheral ring that closely contacts the outer peripheral portion of the substrate to be processed may be used. ,
A plasma processing apparatus may be used in which a recess having substantially the same shape as the substrate to be processed is formed on the sample holder. Further, for example, the outer peripheral portion and the back surface portion of the substrate to be processed may be protected by being covered with an insulating resin or the like, and further, for example, a recessed portion having substantially the same shape as the substrate to be processed is formed. After placing the substrate to be processed in the protective case,
This may be set on a sample holder and plasma treated.

Next, the outer peripheral ring used in the plasma processing apparatus described in the above (2) is, for example, a gas species used in performing the plasma processing, a plasma density, or a type of the plasma processing, such as CVD, etching, and ashing. The plasma treatment can be stably performed by appropriately selecting a stable material that does not change under each condition. A high-frequency voltage may be applied to the electrode provided on the sample holder in order to increase the energy of ions incident on the surface of the semiconductor substrate to be processed.
By making the outer peripheral ring an insulator, the application of a high frequency voltage to the outer peripheral ring is prevented, and the impurity emission from the outer peripheral ring due to the sputtering of high energy ions is prevented. Further, when the chemical reaction on the surface is important such as etching, by making the material of the outer peripheral ring in consideration of the chemical reaction, the processing such as etching can be stably performed.

In consideration of the above-mentioned various points, it is preferable that the material of the outer peripheral ring has an insulating property or the same material as the substrate to be processed. Specifically, for example, oxide ceramics such as alumina and zirconia. , AlN, Si
Non-oxide ceramics such as ₃ N ₄ , heat resistant resins such as fluororesins, silicone resins and polyimide resins, substrate materials such as Si, etc. may be mentioned. Then, actually, an appropriate material may be selected from the above substances in consideration of the purpose of the plasma processing apparatus and the processing conditions.

As for the sample holder which is in close contact with the back surface of the substrate to be processed, a sample holder having a front surface having the same shape as the back surface of the sample is preferable. Since the back surface of the substrate to be processed is usually flat, the front surface of the sample holder may be flat, but a sample holder provided with an electrostatic chuck or other means is preferable in order to increase the adhesion.

Similarly, in the plasma processing apparatus described in (3), it is preferable that the sample holder of the plasma processing apparatus is configured to be in close contact with the substrate to be processed.

[0025]

According to the plasma processing method of the present invention, the back surface and the outer peripheral portion of the substrate to be processed in which the insulating film is formed on the conductive base substrate are protected from the plasma while the substrate to be processed is plasma-treated. Since the treatment is performed, charged particles cannot flow from the plasma to the base substrate, charge-up distribution between the base substrate and the surface of the target substrate is less likely to occur, and charge-up damage such as dielectric breakdown of the target substrate is prevented. Will be reduced.

Further, according to the plasma processing apparatus of the present invention, in the plasma processing apparatus in which the substrate to be processed is processed by plasma, the sample holder and the outer periphery of the substrate to be processed are in close contact with the back surface of the substrate to be processed. Since the outer peripheral ring that is in close contact with the base is provided, charged particles cannot flow from the plasma to the base substrate, and charge-up distribution between the base substrate and the surface of the target substrate is less likely to occur. Charge-up damage such as dielectric breakdown is reduced.

Further, according to the plasma processing apparatus of the present invention, in the plasma processing apparatus in which the substrate to be processed is processed by the plasma, the sample holder is provided with the recess having substantially the same shape as the substrate to be processed. Therefore, similarly to the plasma processing apparatus described in (2), charged particles cannot flow from the plasma to the base substrate, and charge-up distribution between the base substrate and the surface of the substrate to be processed is less likely to occur.
Charge-up damage such as dielectric breakdown of the substrate to be processed is reduced.

[0028]

EXAMPLES AND COMPARATIVE EXAMPLES Examples of a plasma processing method using a plasma processing apparatus according to the present invention will be described below with reference to the drawings. A plasma processing method using a conventional plasma processing apparatus will be described as a comparative example.

FIG. 1 is a schematic sectional view of a plasma processing apparatus according to an embodiment, and 11 in the drawing indicates a plasma generation chamber. The peripheral wall of the plasma generation chamber 11 is formed in a double structure, and a cooling water flow chamber 11a is formed inside the microwave generation port 11c sealed by a quartz glass plate 11b at the center of the upper wall. Further, a plasma extraction window 11d is formed at a position facing the microwave introduction port 11c in the center of the lower wall. The microwave introduction port 11c is connected to one end of a waveguide 12 whose other end is connected to a microwave oscillator (not shown), and a sample chamber 13 is arranged so as to face the plasma extraction window 11d. Further, an exciting coil 14 is arranged concentrically with the plasma generation chamber 11 and the waveguide 12 connected to the plasma generation chamber 11 so as to surround them.

On the other hand, a sample holder 17 is disposed in the sample chamber 13 at a position facing the plasma extraction window 11d, and a substrate S to be processed such as a wafer is attached to and detached from the sample holder 17 by an electrostatic chuck (not shown). The target substrate S is mounted so that it can be mounted thereon, and is fixed by an outer peripheral ring 15 that is disposed in close contact with the outer periphery of the target substrate S. The structure of the sample holder 17 on which the outer ring 15 and the substrate S to be processed are placed is shown in FIG.
explain in detail. Further, an exhaust port 13a connected to an exhaust device (not shown) is formed on the lower wall of the sample chamber 13.

In the figure, 11g is a plasma generation chamber 11
13g indicates a reaction gas supply system connected to the sample chamber 13, and 13g indicates a reaction gas inlet connected to the sample chamber 13, 11h, 1
Reference numeral 1i indicates a supply system and a discharge system of cooling water.

FIG. 2 is a sectional view schematically showing a sample holder 17 on which the substrate S to be processed is placed and an outer peripheral ring 15 for protecting the substrate S to be processed in the plasma processing apparatus shown in FIG. is there.

As shown in FIG. 2, a sample table 21 is placed on the base table 20, and a flow path for circulating cooling water for controlling the temperature of the substrate to be processed is mounted on the sample table 21. 22
Are formed. An introduction pipe 23 and a discharge pipe 24 are connected to the flow passage 22, and the cooling liquid is configured to be discharged from the introduction pipe 23 through the flow passage 22 and the discharge pipe 24. An electrostatic chuck 25 is placed above the sample table 21, and the substrate S to be processed is placed on the electrostatic chuck 25. Electrostatic chuck 25
Is formed such that an electrode layer 27 is embedded inside an insulator 26 made of, for example, ceramics, and an electrode rod 28 is connected to the electrode layer 27. A DC voltage is applied to the electrode layer 27 of the electrostatic chuck 25 to generate an electrostatic attraction force when the substrate S to be processed is placed, and a high frequency wave is applied when the plasma is irradiated. Is applied.

An outer peripheral ring 15 made of alumina is arranged on the sample holder 17. The outer peripheral ring 15 is divided into two, one end of each of which is fixed in a state in which it can be opened and closed by a pin (not shown) so that it can be opened when the substrate S to be processed is placed or taken out. Has become. Therefore, when placing the substrate S to be processed 25 on the electrostatic chuck, the outer peripheral ring 15 is opened,
After placing the substrate S to be processed on the electrostatic chuck 25, the outer peripheral ring 25 is closed. The other ends of the outer peripheral ring 15 which are not fixed have a structure in which they can be easily connected and fixed to each other by a magnet or the like after closing the outer peripheral ring 15. Then, by closing the outer peripheral ring 15,
Is in contact with the outer peripheral portion of the substrate to be processed 19, the outer peripheral portion of the substrate to be processed S,
Also, it is possible to prevent the plasma from being irradiated to the outer peripheral portion of the surface.

In consideration of the generation of particles and the like,
The outer peripheral ring 15 may be covered over the substrate 19 to be processed.

In the plasma processing apparatus configured as described above, after the inside of the plasma generating chamber 11 and the sample chamber 13 is set to a predetermined vacuum degree, the plasma processing chamber 11 is supplied with the required gas through the reaction gas supply system 11g. Gas is supplied so that a gas pressure is obtained, a magnetic field is formed by the excitation coil 14, and the plasma generation chamber 11 is supplied through the microwave introduction port 11c.
A microwave of 2.45 GHz is introduced into the inside of the plasma generation chamber 11 and the gas is resonantly excited by using the plasma generation chamber 11 as a cavity resonator to generate plasma. The generated plasma has a divergent magnetic field whose magnetic flux density decreases toward the sample chamber 13 side formed by the exciting coil 14 and causes the substrate S to be processed in the sample chamber 13 to be processed.
The surface of the substrate S to be processed in the sample chamber 13 is projected to the periphery and plasma-processed.

In order to evaluate the charge-up damage of the substrate S to be processed by using the plasma processing apparatus according to the above-mentioned embodiment, the substrate S to be processed on which the MOS capacitor is formed is evaluated.
The top surface was irradiated with argon plasma, and the withstand voltage of the MOS capacitor was examined. Plasma generation conditions are as follows: microwave power 1.2 kW, introduced argon gas pressure 0.6 To.
A high frequency voltage of 400 kHz was applied to the sample holder with an electric power of 300 W. In order to attract the substrate S to be processed, 400 V is applied to the electrode 20 in the electrostatic chuck.
DC voltage was applied.

FIG. 3 is a plan view showing the withstand voltage distribution of the substrate S to be processed on which the MOS capacitor is formed when the plasma processing under the above conditions is performed, and the numbers shown in FIG. The withstand voltage of the MOS capacitor formed on the processing substrate S is shown, and each numeral corresponds to the withstand voltage of each element of the MOS capacitor.

As a comparative example, the case where the conventional plasma processing apparatus in which the substrate to be processed is directly placed on the sample holder is used without using the outer peripheral ring 15 shown in FIG. 2 is similar to the case of the embodiment. The experiment was done. The results are shown in FIG. 4 as in the example.

As can be seen from FIG. 4, when the substrate S to be processed was subjected to the plasma processing by the plasma processing apparatus according to the comparative example, dielectric breakdown was observed in the central portion and the peripheral portion of the substrate S to be processed.

On the other hand, when the plasma processing apparatus according to the example was used, no deterioration of withstand voltage was observed in the MOS capacitor element on the substrate S to be processed.

As described above, when the substrate S to be processed is subjected to the plasma processing by using the plasma processing apparatus according to the above-described embodiment, it is possible to prevent the charged particles from flowing from the plasma to the base substrate, and the processed substrate S is processed. Generation of charge-up distribution between the base substrate and the surface of the substrate can be suppressed, and as a result, charge-up damage such as dielectric breakdown of the substrate to be processed can be reduced.

Next, the outer peripheral ring 15 made of polycrystalline Si
Using a plasma processing apparatus according to another embodiment provided with, an Si substrate on which a 1 μm oxide film was formed was subjected to etching processing. When the etching process is performed, the etching gas is C ₄ H ₈ : 25 sccm, O ₂ : 13 sc
cm, the pressure is 1 mTorr, the microwave power is 1.3 kW, and the high frequency applied to the sample holder 17 is 400.
The etching treatment was performed under the conditions of kHz and etching time of 3 minutes.

As a result, the etching process could be stably performed, and the obtained substrate S to be processed did not show deterioration in withstand voltage due to charge-up.

Next, an embodiment of a plasma processing apparatus in which a concave portion having substantially the same shape as the substrate to be processed is formed on the sample holder will be described.

FIG. 5 is a sectional view schematically showing a sample holder having a concave portion formed on the electrostatic chuck. In the plasma processing apparatus according to this embodiment, the recess 3 is formed in the electrostatic chuck 32.
1, except that the sample holder 30 on which 1 is formed is used,
It is configured similarly to the plasma processing apparatus shown in FIG. Further, the structure of the sample holder 30 is the same as that of the sample holder 17 shown in FIG. 2 except that the concave portion 31 is formed in the electrostatic chuck 32. Therefore, here, only the matters relating to the concave portion 31 formed in the electrostatic chuck 32 will be briefly described below.

The shape of the recess 31 formed in the electrostatic chuck 32 is almost the same as the shape of the substrate S to be processed, and the substrate S to be processed can be placed in the recess 31. When taking out the substrate S to be processed, a disengagement knock pin (not shown) is used.

As described above, when the substrate S to be processed is placed on the electrostatic chuck 32 in which the concave portion 31 having the shape shown in FIG. 5 is formed and plasma processing is performed, charged particles flow from the plasma into the base substrate. Can be prevented, and the occurrence of charge-up distribution between the base substrate and the surface of the substrate S to be processed can be suppressed. As a result, charge-up damage such as dielectric breakdown of the substrate S to be processed can be reduced. be able to.

[0049]

As described in detail above, in the plasma processing method according to the present invention, the back surface and the outer peripheral portion of the substrate to be processed having the insulating coating formed on the conductive base substrate are protected from the plasma. At the same time, since the substrate to be processed is plasma-processed, it is possible to prevent charged particles from flowing into the base substrate from the plasma, and suppress the occurrence of charge-up distribution between the base substrate and the surface of the target substrate. You can
As a result, charge-up damage such as dielectric breakdown of the substrate to be processed can be reduced.

Further, according to the plasma processing apparatus of the above (2), in the plasma processing apparatus in which the substrate to be processed is processed by the plasma, the sample holder and the substrate to be processed which are in close contact with the back surface of the substrate to be processed. Since it has an outer peripheral ring that is in close contact with the outer peripheral portion of the substrate, it is possible to prevent charged particles from flowing into the underlying substrate from the plasma, and to generate a charge-up distribution between the underlying substrate and the surface of the substrate to be processed. Can be suppressed, and as a result, charge-up damage such as dielectric breakdown of the substrate to be processed can be reduced.

Further, according to the plasma processing apparatus of the above (3), in the plasma processing apparatus in which the substrate to be processed is processed by the plasma, the sample holder is provided with the recess having substantially the same shape as the substrate to be processed. (2)
Similar to the described plasma processing apparatus, it is possible to prevent charged particles from flowing into the base substrate from the plasma, and it is possible to suppress the occurrence of charge-up distribution between the base substrate and the surface of the target substrate. As a result, charge-up damage such as dielectric breakdown of the substrate to be processed can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically showing a sample holder on which a substrate to be processed is placed in the plasma processing apparatus according to the embodiment shown in FIG.

FIG. 3 is a diagram illustrating a MOS using a plasma processing apparatus according to an embodiment.
FIG. 6 is a plan view showing a withstand voltage distribution of a substrate to be processed when a plasma treatment is applied to the substrate to be processed on which a capacitor is formed.

FIG. 4 is a schematic view of a MOS using a plasma processing apparatus according to a comparative example.
FIG. 6 is a plan view showing a withstand voltage distribution of a substrate to be processed when a plasma treatment is applied to the substrate to be processed on which a capacitor is formed.

FIG. 5 shows a plasma processing apparatus according to another embodiment,
It is sectional drawing which showed typically the sample holding stand in which a to-be-processed substrate is mounted.

FIG. 6 is a conceptual diagram schematically showing how a charge-up distribution is generated on a substrate to be processed when the conductive layer is etched by irradiating the substrate to be processed with plasma in a conventional plasma processing apparatus. It is a figure.

[Explanation of symbols]

 S substrate to be processed 15 outer peripheral ring 17, 30 sample holder 31 recess

Claims (3)

[Claims] 1. A method of treating a substrate to be processed with plasma while protecting a back surface and an outer peripheral portion of the substrate to be processed in which an insulating film is formed on a conductive base substrate from plasma. Plasma treatment method. 2. A plasma processing apparatus for processing a substrate to be processed with plasma, comprising: a sample holder that is in close contact with a back surface of the substrate to be processed; and an outer peripheral ring that is in close contact with an outer peripheral portion of the substrate to be processed. A plasma processing apparatus characterized in that 3. A plasma processing apparatus in which a substrate to be processed is processed by plasma, wherein a recess having substantially the same shape as that of the substrate to be processed is formed on a sample holder.