JPH04257224A - Forming method for insulating film - Google Patents

Abstract

PURPOSE:To form an insulating film having uniform thickness and homogeneous quality on a substrate by using an ECR plasma CVD device having a plasma generating chamber including a microwave transmitting window and a plasma drawing window in an opposing state on an axial line surrounded coaxially by a coil, and a reaction chamber communicating with the generating chamber through the window and including the substrate arranged therein. CONSTITUTION:A forming method for an insulating film having steps of so disposing a coil that a geometrical center of the coil is disposed at an opposite side to a plasma generating chamber of a microwave transmitting window, forming an ECR magnetic field region surface of the coil at a position of a microwave electric field intensity peak value in the generating chamber, and applying a high frequency bias to a substrate to form an insulating film, is provided. The position of the peak value to be formed with the ECR magnetic field region surface is disposed at a peak value position nearest the window, thereby further improving a film forming speed.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method of manufacturing a semiconductor device equipped with an insulating film, and in particular, to a method for manufacturing a semiconductor device equipped with an insulating film, and in particular, a method for manufacturing a semiconductor device equipped with an insulating film. The present invention relates to a technology for forming an insulating film. In this invention, an ECR plasma CVD apparatus to which the ECR plasma CVD method is applied,
An axially symmetrical plasma generation chamber with a microwave transmission window on the axis to turn the introduced gas into plasma, and an electron cyclotron resonance magnetic field area surface with the microwave that surrounds the plasma generation chamber on the same axis. The apparatus includes a coil and a reaction chamber that communicates with the plasma generation chamber through a plasma extraction window provided on the side facing the microwave transmission window of the plasma generation chamber and in which a substrate to be deposited is disposed. .

0002

[Prior Art] Interlayer insulating films and passivation films (surface protective films) for semiconductor integrated circuits are usually formed using thermal CVD methods that use thermal energy to excite gas molecules, which are the raw materials for insulating films, or plasma using high-frequency voltage application. Oxide films, nitride films, etc. formed by the high-frequency plasma CVD method, in which gas molecules are excited by electric discharge, are used. but,
In recent years, as semiconductor devices have become more integrated and denser, and structural dimensions such as interconnect spacing and interconnect width have moved to the submicron range, higher quality insulating films have been required. Various methods other than film formation methods have been attempted. One of these is ECR plasma CVD, which can be formed at low temperatures and can form insulating films with excellent acid resistance and density.
laws are being developed.

[0003] This ECR plasma CVD method introduces gas into a magnetic field of a predetermined strength and injects microwaves with a frequency corresponding to the magnetic field strength, thereby causing the microwave energy to be resonantly absorbed by incidental electrons. In this method, gas molecules are ionized by the collision of energy-gathered incidental electrons, and the electrons that proliferate also absorb energy. This generates a high-density plasma, which is then guided onto the substrate along with the reactive gas to form a film. be.

[0004] When forming an insulating film on a level difference on a substrate (for example, an uneven surface due to electrodes, wiring, etc. formed on a substrate), it is necessary to improve the insulation properties or to form a multilayer structure. In order to enable formation, it is necessary to perform a planarization process. As a method for forming an insulating film that can be flattened without requiring special planarization treatment and that provides good step coverage on the substrate, a high-frequency bias is applied to the substrate, and the self-bias effect of the substrate can be applied. A bias sputtering method is known in which etching and deposition are performed simultaneously by generating a negative potential on the substrate surface. Application of this high frequency bias can also be applied in the ECR plasma CVD method, and is expected to improve the step coverage of the insulating film and the film quality.

FIG. 5 shows an example of the structure of an ECR plasma CVD apparatus to which the present invention is applied, as an apparatus to which this ECR plasma CVD method is applied. When the insulating film is, for example, an SiO2 film, the insulating film is formed using the apparatus shown in FIG. After forming an electron cyclotron resonance magnetic field region surface (hereinafter abbreviated as ECR region surface or ECR surface), O2 gas is introduced into the plasma generation chamber 5 from the first gas introduction system 3, and is oscillated by a microwave source (not shown). ECR is achieved by introducing the generated microwaves through the waveguide 1, through the microwave transmission window 2, and into the plasma generation chamber 5.
O2 gas is highly ionized near the region surface to generate O2 gas plasma, and this plasma is guided into the reaction chamber 6 along the divergent magnetic field formed by the coil 4, and the reaction gas is introduced from the second gas introduction system 7. This is carried out by introducing SiH4 gas into the reaction chamber 6, decomposing and activating it by O2 gas plasma, and depositing SiO2 molecules on the substrate.

[0006]

[Problem to be solved by the invention] ECR plasma CVD
Insulating films formed by this method are said to have poor uniformity in film thickness and film quality because there is a bias in the density and energy of the plasma that reaches the substrate during film formation. It has disadvantages, such as a lack of adaptability to fine structures and stability of insulation properties that accompany the increase in the degree of integration of semiconductor devices, and a problem of a lack of coverage of stepped portions such as wiring.

[0007] The object of the present invention is to
without any substantial structural changes to the equipment or increased costs.
An object of the present invention is to provide a method for forming an insulating film that can form an insulating film with uniform thickness and quality.

[0008]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides an axially symmetrical plasma generation chamber that has a microwave transmission window on the axis and converts introduced gas into plasma; Coaxially surrounds the plasma generation chamber to form an electron cyclotron resonance magnetic field area with microwaves in the plasma generation chamber, and a plasma extraction window provided on the side facing the microwave transmission window of the plasma generation chamber. As an insulating film forming method when forming an insulating film on a deposition target substrate using an ECR plasma CVD apparatus equipped with a reaction chamber in which the deposition target substrate is placed in communication with the coil, the geometric center of the coil is The coil is placed so that the surface of the microwave transmission window facing the plasma generation chamber interior space is located on the opposite side of the plasma generation chamber interior space, and the electron cyclotron resonance magnetic field area surface due to the coil is The insulating film forming method is such that the insulating film is formed at the peak value of the electric field strength of the transmitted microwave, and a high frequency bias is applied to the substrate on which the film is formed. Here, it is more preferable to set the position of the peak value of the electric field strength of the microwave where the electron cyclotron resonance magnetic field region surface is formed to the position of the first peak value of the microwave transmitted through the microwave transmission window. In addition, the film forming conditions when forming an insulating film by this method are as follows: The temperature of the film-forming substrate is from room temperature to
°C, gas pressure 1 x 10-4 to 5 x 10-3 tor
r, the microwave power incident on the plasma generation chamber is 2
The purpose of this method can be effectively achieved by forming an insulating film by setting the high frequency bias power applied to the substrate to be 50 to 450 W and 600 to 1000 W.

[0009]

[Operation] The plasma generated in the plasma generation chamber flows along the magnetic lines of force onto the substrate due to the magnetic field strength gradient of the diverging magnetic field formed by the coil coaxially surrounding the axially symmetrical plasma generation chamber. An attempt is made to form a film thickness distribution that becomes thinner on the edge side. On the other hand, a high frequency bias is applied to the substrate, and a negative bias potential is generated on the substrate surface, and the electric field due to this potential is directed toward the peripheral wall of the reaction chamber, so the electric field strength is larger at the periphery than at the center of the substrate. Attempts are made to more strongly attract ions in the plasma toward the substrate on the peripheral edge side. As a result, an insulating film with a more uniform thickness is formed on the substrate surface, and since ions are accelerated by the negative potential on the substrate surface, the deposited film is sputtered by the ion collision, and the deposited film is sputtered at the same time. It is thought that a dense film is formed by forming a film.

[0010] Furthermore, by forming the ECR region surface of the coil at the peak value of the electric field strength of the microwave that has passed through the microwave, the energy of the microwave that is absorbed by the electrons that ionize gas molecules is increased, and this High-density plasma is generated near the region surface, and near the wave height of the microwave, the axial width of the electric field region near the wave height is wide, so even if the ECR region surface is somewhat curved, , the ECR region surface exists within this width, plasma is uniformly formed in the radial direction of the plasma generation chamber, and together with the application of a high frequency bias, the plasma density reaching the substrate is made uniform in the radial direction of the substrate. Can be done. In addition, since the geometric center of the coil is located on the opposite side of the plasma generation chamber interior space from the surface of the microwave transmission window on the plasma generation chamber interior space side, the magnetic field formed by the coil can be applied at any position within the plasma generation chamber. The plasma in the plasma generation chamber is dispersed toward the plasma extraction window, and the plasma in the plasma generation chamber does not go toward the microwave transmission window. This prevents the microwave transmission window from being damaged and enables stable operation of the device.

As described above, the in-plane uniformity of the thickness and quality of the insulating film formed on the substrate is improved. By controlling the high frequency bias, it is also possible to improve the step coverage and flatness of electrodes, wiring, etc. Note that the effect of forming the ECR region surface at the position of the first wave peak value of the electric field strength of the microwave transmitted through the microwave transmission window, and the film formation conditions such as substrate temperature and gas pressure are set as described above. The effect in this case will be explained in the Example section together with the structure of an example of an ECR plasma CVD apparatus to which the above insulating film forming method is applied.

0012

[Embodiment] First, FIG. 1 shows an embodiment of the structure of an ECR plasma CVD apparatus to which the insulating film forming method according to the present invention is applied. In the figure, the same members as in FIG. 5 are given the same reference numerals. The difference between this device and the device in FIG. 5 is shown in FIG.
As shown in detail in , the geometric center of the coil 4 is located at a position sufficiently far away from the plasma generation chamber interior space side of the surface of the microwave transmission window 2 on the plasma generation chamber interior space side. and the lower end surface of the coil is the microwave transmitting window 2
The coil is arranged so as to be located near the first peak value of the electric field strength of the microwave transmitted through the microwave, and the high frequency power source 11 is connected to the substrate table 10 on which the substrate 9 is placed.

When the device is formed in this way and the current flowing through the coil 4 is adjusted to form the ECR region surface near the lower end surface of the coil, which is the position of the first peak value of the electric field strength of the microwave, the ECR region surface can be formed into a relatively flat surface, and therefore, the ECR region surface can be made to exist within the axial width of the region near the peak value of the microwave electric field strength. Furthermore, once plasma is formed in the plasma generation chamber, the peak value of the electric field strength of the microwave is attenuated in the direction of propagation of the microwave. Forming the ECR region surface at a position where the electric field strength first reaches its peak value is also effective for increasing the film formation rate.

Therefore, ECR plasma CVD shown in FIG.
Various characteristics of the SiO2 film will be described below when the film forming conditions for forming the SiO2 film using the apparatus are set as shown in Table 1. Note that, compared to conventional normal film forming conditions, this film forming condition requires less high frequency bias power applied to the substrate than microwave power input into the plasma generation chamber (
It is characterized by a large RF power. In other words, under these film-forming conditions, the difference between microwave power and high-frequency bias power is caused by the ratio of the pulse width and pulse period of the power applied in a pulsed manner, that is, the difference in duty. By increasing the duty of electric power, a dense film can be formed. Further, when the insulating film is a SiN film, the insulating film is formed by changing the flow rate ratio of N2 gas to SiH4 gas to the gas flow rate ratio shown in this table.

[0015]

[Table 1]

As seen in FIG. 3, which shows the film thickness distribution, the film thickness of the SiO2 film formed by the conventional divergent magnetic field is
It becomes thinner toward the outside in the radial direction of the substrate. This is thought to reflect the bias in plasma density generated within the plasma generation chamber 3, but the SiO2 film formed in this example has a uniform film thickness up to the outer periphery of the substrate. are doing. This seems to be due to the fact that by applying a high frequency bias to the substrate 8, the plasma density becomes uniform, and the sputtering effect flattens the substrate 8, making the unevenness more relaxed than before.

FIG. 4 shows the etching rate distribution when a SiO2 film is etched with BHF (buffered hydrofluoric acid, a solution of 50% hydrofluoric acid diluted with water). SiO2 formed under the film forming conditions of this example
The in-plane uniformity of the etching rate of the film is extremely superior to that of the conventional film formed using a divergent magnetic field. In addition, the etching rate is slower across the board than in the past, and the film quality is improved overall. This is thought to be due to the fact that ions in the plasma collide with the substrate due to the high frequency bias application under the film forming conditions of this example, resulting in the formation of a denser film than in the past.

As explained above, it was possible to improve the in-plane uniformity of both the film thickness and film quality, and the film quality itself was also able to be improved more than ever.

[0019]

Effects of the Invention In the present invention, ECR plasma CV
Since the method for forming an insulating film by method D is as described above, the following effects can be achieved.

In the method of claim 1, the position of the ECR region surface and the peak value position of the microwave electric field strength coincide with each other in the plasma generation chamber, and the axial width of the region near the peak value of the microwave electric field strength is wide. Even if the ECR area surface has some curvature, the ECR area surface will exist within this width, so
High-density plasma is formed uniformly in the radial direction, and this plasma reaches the substrate at a uniform density due to the divergent magnetic field and the negative bias potential on the substrate surface due to the high-frequency bias applied to the substrate. In addition to improving the uniformity of the film, the film quality itself also improves due to the ion bombardment effect caused by the negative bias potential on the substrate surface.

In the method of claim 2, since the ECR region surface is formed at the position of the maximum wave peak value of the microwave electric field strength that is closest to the microwave transmission window, the density of the generated plasma is maximized. Therefore, the film formation rate is further improved.

In the method of claim 3, since the microwave power input to the plasma generation chamber is small and the high frequency bias power applied to the substrate is large, the film thickness can be adjusted by adjusting both powers within this setting range. It becomes possible to improve the film quality while controlling the radial inclination between the film and the film quality in a direction that eliminates the inclination.

[Brief explanation of the drawing]

[Fig. 1] ECR applying the insulating film forming method according to the present invention
A vertical cross-sectional view showing an example of a plasma CVD device structure

FIG. 2 is an explanatory diagram showing the insulating film forming method according to the present invention.

[Figure 3]
A diagram showing the film thickness distribution when a SiO2 film is formed according to an example of the film forming conditions under the insulating film forming method according to the present invention, in comparison with when the SiO2 film is formed using the conventional technique.

FIG. 4 is a diagram showing the etching rate when an SiO2 film is formed using the insulating film forming method according to the present invention under the same film forming conditions as in FIG. 3, in comparison with when the SiO2 film is formed using the conventional technique.

[Fig. 5] A vertical cross-sectional view showing a structural example of an ECR plasma CVD apparatus to which a conventional insulating film forming method is applied.

[Explanation of symbols]

2 Microwave transmission window 4 Coil 5 Plasma generation chamber 6 Reaction chamber 8 Plasma drawer window 9 Substrate (substrate to be film-formed) 11 High frequency power supply

Claims (3)

[Claims] Claim 1: An axially symmetrical plasma generation chamber that has a microwave transmission window on the axis and converts introduced gas into plasma, and an electron cyclotron resonance magnetic field with the microwave that coaxially surrounds the plasma generation chamber. A reaction chamber is connected to the plasma generation chamber through a plasma extraction window provided on the side facing the microwave transmission window of the plasma generation chamber, and a reaction chamber in which a substrate to be deposited is arranged. An insulating film forming method for forming an insulating film on a substrate to be film-formed using an ECR plasma CVD apparatus equipped with The coil is placed so that the plane is located on the opposite side of the plasma generation chamber interior space, and the electron cyclotron resonance magnetic field area plane by the coil is formed at the peak value of the electric field strength of the microwave transmitted through the microwave transmission window. , and a method for forming an insulating film, characterized in that the insulating film is formed by applying a high frequency bias to a substrate on which the film is to be formed. 2. In the method for forming an insulating film according to claim 1, the position of the peak value of the electric field strength of the microwave at which the electron cyclotron resonance magnetic field region surface is formed is determined by adjusting the position of the peak value of the electric field strength of the microwave at the first point of the microwave transmitted through the microwave transmission window. A method of forming an insulating film characterized by forming the film at a peak value position. 3. In the method for forming an insulating film according to claim 1 or 2, the temperature of the substrate on which the film is formed is set at room temperature to 150°C.
, gas pressure 1 x 10-4 to 5 x 10-3 torr,
The microwave power input to the plasma generation chamber is 250
A method for forming an insulating film, characterized in that the insulating film is formed by applying a high frequency bias power of 600 to 1000 W to a substrate on which the film is to be formed.