JPH03280539A - Fabrication method for semiconductor device with insulation layer - Google Patents

Abstract

PURPOSE:To form an insulator film with excellent step coverage without damaging a substrate surface and step areas by executing multiple process steps which vary the high-frequency bias output applied to the substrate, the presence of Ar gas and other gases, and other conditions of a process which uses an ECR plasma CVD method. CONSTITUTION:An interconnection 22 is formed on the surface of a silicon substrate 21 and over this a lower layer protection oxide layer 23 is formed. In order to prevent damage, hillocks, or stress migration on the surface of interconnection 22, this sealing protection oxide layer 23 is formed by either applying no RF bias or low-output RF bias to the silicon substrate 21. Furthermore, this layer is made as thin as possible to shorten the later planarization step. Next, high-output RF bias is applied to the silicon substrate 21 and a high-coverage oxide film 24 with enhanced step coverage is formed to increase film thickness. Finally, Ar and He gases are introduced into a reaction chamber 6, sputter etching is performed, and a planar oxide layer 25 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device equipped with an insulating film, and in particular, the present invention relates to a method for manufacturing a semiconductor device equipped with an insulating film.
For example, it relates to a technique for forming an amorphous film on electrodes, wiring, etc.

[Prior Art] As a glabellar insulating film or a passivation film of a semiconductor integrated circuit, an oxide film, a nitride film, or the like formed by a thermal CVD method or a high-frequency plasma CVD method is usually used. However, 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 the film forming method have been attempted. As one of these methods, an ECR (echo cyclotron resonance) plasma CVD method has been developed, which can be formed at a low temperature and can form an insulating film with excellent acid resistance and density.

In this ECR plasma CVD method, a gas is introduced into a magnetic field of a predetermined strength, and by injecting microwaves with a frequency corresponding to the magnetic field strength, the energy of the microwaves is resonantly absorbed, thereby producing high-density gas. The resulting plasma is introduced onto a substrate together with a reactive gas to form a film.

Here, when an insulating film is formed on a step on a substrate (for example, unevenness due to electrodes, wiring, etc. formed on a substrate), it is necessary to improve insulation properties or to form a multilayer structure. It is necessary to perform a flattening process. In order to eliminate the need for this planarization process, a bias sputtering method is used to achieve planarization during the formation of an insulating film, in which a high frequency bias is applied to the substrate and etching and day positioning are performed simultaneously using the self-bias effect of the substrate. Are known. 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.

[Problem to be solved by the invention]

However, when an insulating film is formed on a substrate using the ECR plasma CVD method under the application of a high-frequency bias, hillocks, stress migration, and other damage may occur in the wiring on the substrate due to ion bombardment caused by the high-frequency bias. There was a problem that occurred.

Furthermore, because the film quality of the part of the insulating film that covers the stepped portion is particularly poor, cavities may occur within the film, and the film thickness distribution becomes uneven as the output of the applied high-frequency bias increases. However, there was a problem in that the overall M quality deteriorated.

SUMMARY OF THE INVENTION The present invention aims to solve the above-mentioned problems, and its object is to form an insulating film through multiple steps with different film formation conditions by utilizing the characteristics of the ECR plasma CVD method. It is an object of the present invention to provide a method for manufacturing an insulating film that can form an insulating film with excellent coverage and flatness and does not cause damage to the underlying layer.

[Means to solve the problem]

In order to solve the above problems, the measures taken by the present invention are to protect the base on the circumferential surface of the step portion on the substrate by not applying a high frequency bias to the substrate or by applying a low output high frequency bias to the substrate. The method includes a step of forming an insulating film, and then a step of forming a highly covering insulating film on the base protective insulating film under a high-power high-frequency bias.

In addition, after the step of forming a highly covering insulating film, a step of mixing Ar or Ar and He into the film forming gas and forming a film under high frequency bias may be provided to form a flattened insulating film. .

In each of the above steps, a cusp magnetic field (a magnetic field formed by two divergent magnetic fields in opposite directions) is formed around the substrate, and the cusp surface (magnetic field strength in the normal direction) in this cusp magnetic field is In some cases, the substrate is placed near a plane or curved surface (which is a plane or curved surface on which the angle is zero), and the substrate surface is placed parallel to the cusp surface.

[Effect]

According to this method, a base protective insulating film is first formed on the step portion on the substrate by applying no high-frequency bias or applying a low-power high-frequency bias.

This insulating film is formed in a state where the self-bias effect of the substrate is absent or weak due to the application of a high-frequency bias.
There is less risk of damaging the stepped portion or the substrate surface, and it is possible to prevent hillocks and stress migration in the electrodes and wiring portions.

Next, a high-coverage insulating film is formed by applying a high-power high-frequency bias to the upper layer of the base protective insulating film, so the coverage of the stepped portion is improved due to the self-bias effect of the substrate, and the insulating film is The flatness of the top surface is improved. During this step, due to the presence of the base protective insulating film, damage to the stepped portions and the like due to high frequency bias application does not occur.

Furthermore, if a step of forming a film by mixing Ar into the film forming gas is provided after this, the sputtering effect due to the self-bias effect is strengthened, and even on stepped portions such as wiring with a high aspect ratio, A flatter insulating film can be formed. When He is mixed with Ar, the sputter etching rate of Ar is reduced, which has the effect of preventing the incorporation of Ar into the insulating film and improving the in-plane uniformity of the sputtering rate. Therefore, by adjusting the flow rate and mixing ratio of Ar and He, it is possible to planarize the insulating film according to the shape of the stepped portion, and furthermore, it is possible to improve the film quality and make the film thickness uniform. .

In this way, the insulating film is formed step by step through multiple processes with different film formation conditions, so there is no damage to the substrate surface or step areas, and the step coverage is good and the insulating film is sufficiently flattened. A high quality insulating film can be formed.

In each of the above steps, when a caps magnetic field is formed around the substrate and the substrate is placed in parallel near the caps surface, the plasma flow reaching the substrate is made uniform due to the sudden divergence of the magnetic flux on the caps surface. The uniformity of the thickness and quality of the insulating film is further improved. This effect is not lost even when a high-power, high-frequency bias is applied, so it is particularly effective for the above method.

〔Example〕

Next, an embodiment of a method for manufacturing a semiconductor device according to the present invention will be described with reference to the accompanying drawings.

First, with reference to FIG. 1, the structure of the ECR plasma CVDI device used in this example will be explained. The waveguide 1 is connected via a microwave introduction window 2 to a plasma generation chamber 5 in which a magnetic field is formed by a main magnetic coil 4, and the microwave frequency and When the magnetic field strength satisfies the ECR condition, the 0□ gas flowing from the first gas introduction system 3 absorbs energy resonantly,
It becomes a high-density plasma. This 0! The plasma is drawn out from the plasma generation chamber 5 to the reaction chamber 6 by a divergent magnetic field formed near the opening 8 . At this time, when SiH, (silane) gas is introduced from the second gas introduction system 7, 0! 5iHa gas is decomposed by plasma energy,
A Si0g film is formed on the surface of the substrate 9 placed on the sample stage 10. Here, the sample stage IO has a high frequency power supply 12.
is connected so that an RF bias can be applied to the substrate 9, and an auxiliary magnetic coil 11 is provided below the sample stage 10, and the diverging magnetic field formed by the main magnetic coil 4 and the auxiliary magnetic coil 2 A cusp magnetic field is formed in the reaction chamber 6 from the magnetic field formed by the magnetic field.

Next, using the above ECR plasma CVD apparatus, SiO
□The method for forming the film will be explained with reference to FIG. As shown in FIG. 2(a), a wiring 22 is formed on the surface of the silicon base Fi.

Then, a base protective oxide film 23 is formed on the substrate as shown in FIG. 2(b). This base protective oxide film 2
3 is formed by applying no RF bias to the silicon substrate 21 or by applying a low-output RF bias to the silicon substrate 21 in order to prevent damage, hillocks, and stress migration from occurring on the surface of the wiring 22. In addition, in order to shorten the planarization process later, a high-power RF bias is applied to the silicon substrate 21 to form it as thin as possible.
is applied to form a high coverage oxide film 24 with improved step coverage and increase the film thickness to some extent. lastly,
As shown in FIG. 2(d), Ar and He are present in the reaction chamber 6.
A gas is introduced to produce a sputter etching effect to form a planarized oxide film 25.

In this way, it is possible to form a completely flattened oxide film through a plurality of steps in which the film formation conditions are changed stepwise.Moreover, the underlying protective oxide film 23 protects the surface of the silicon substrate 21 and the surface of the silicon substrate 21. Damage to the metal 22 is reduced, and hillocks, stress migration, etc. do not occur. Here, in each of the steps shown in FIGS. It is also possible to form a plurality of oxide films, and a step of forming a film under conditions that are intermediate to the film forming conditions of the previous and subsequent steps can also be provided between each step. As an example of the formation method described in 2, Table 1 shows the basic film formation conditions of the ECR plasma CVD method, and Table 2 shows the respective process η in the first example.
The film formation conditions for each are shown below.

Table 1 Here, in the pretreatment process, only the 02 gas from the first gas introduction system 3 is introduced, and the Si gas is introduced from the second gas introduction system 7.
No H gas is introduced. This is because the surface of the silicon substrate 21 is irradiated with 02 plasma to activate the surface and produce a cleaning effect. Furthermore, between the first step of forming the first layer oxide film and the third step of forming the film by applying a high-power RF bias,
A second step is provided in which a low-power RF bias is applied to form a film. Furthermore, in the fourth step, the A gas and the He gas may be used to form a film by adjusting the flow rate and mixing ratio of each while observing the progress of planarization of the oxide film. For example, the sputter etching rate may be reduced. If you want to
This can be dealt with by decreasing the flow rate of Ar gas or increasing the flow rate of He gas. In addition, the mixing of He gas is caused by A
It reduces the sputter etching speed by r gas to some extent, prevents the phenomenon that Ar is mixed into the oxide film and At degass after film formation and destroys the oxide film, and furthermore makes the film thickness distribution uniform. effective. On the other hand, He gas has low reactivity with other substances, so it does not affect the film quality. Figure 4 shows the case where Ar gas is not mixed and the case where both Ar gas and He gas are mixed. For comparison, BHF (HF, H
! The etching rate (which is a measure of acid resistance) using a mixed solution of 0, NH, and F, and the rate of oxide film formation are shown.

In this way, while the mixing of Ar gas and He gas does not have a large effect on the film quality, it is possible to change the film formation rate etc. by changing the RF low output mixing ratio, so it is considered as a means to control the film formation conditions. In addition, it becomes possible to change the film forming conditions within the same process by changing the mixing ratio of A gas and He gas, and it is possible to omit and shorten the process.

The above effects are similarly achieved in the second embodiment, the conditions of each step of which are shown in Table 3. In this second embodiment, in the first step of forming the underlying protective insulating film, a small output R
By applying F bias to the substrate, a certain level of step coverage can be maintained. Here, the second step was introduced to improve the uniformity of the film thickness.

Table 3 Furthermore, by adding the two steps shown in Table 4 after the four steps shown in the first and second examples above, it is possible to more completely planarize the film. It is also possible to form a flat oxide film on a substrate on which a wiring portion with a high aspect ratio is formed.

Table 4 In the above embodiments, a magnetic field is generated by the auxiliary magnetic coil 11 in addition to the magnetic field by the main magnetic coil 4, and a cusp magnetic field is formed in the reaction chamber 6 by both magnetic fields, and the silicon substrate 21 is They are arranged parallel to each other along the cusp surface. As a result, it is thought that the density and energy of the plasma reaching the silicon substrate 9 become uniform,
In fact, the in-plane distribution of film thickness and film quality is made uniform. As shown in Figure 4, unlike conventional film formation under a divergent magnetic field, this effect is not lost even when the RF specific output is high, so RF application can be performed without reducing uniformity. .

〔Effect of the invention〕

As explained above, the present invention is applicable to ECR plasma CVD
A method for manufacturing semiconductor devices using the method, characterized by forming an insulating film on the stepped portion of the substrate through multiple steps in which conditions such as the output of the high-frequency bias applied to the substrate and the presence or absence of mixing of Ar gas, etc. Since it has the following effects.

■ A base protective insulating film and a high-coverage insulating film are formed by applying or not applying a high-frequency bias and increasing or decreasing the output of the high-frequency bias, so an insulating film with good step coverage can be formed without damaging the substrate surface or step portion. Can be formed.

■ If a step is provided to form a flattened insulating film by mixing Ar gas, the sputtering effect by applying a high frequency bias will be strengthened, and the insulating film will have sufficient flatness even on stepped portions with high aspect ratios. can be formed. Here, when He gas is mixed, the sputter etching conditions can be adjusted and changed, the in-plane uniformity can be improved, and furthermore, the incorporation of Ar into the insulating film can be prevented.

(2) When a cusp magnetic field is formed around the substrate and the substrate is placed near the cusp surface, the uniformity of film thickness and film quality is improved. Further, even when applying a high-power high-frequency bias, the uniformity does not deteriorate, so that flattening control using the high-frequency bias can be performed more effectively.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing the structure of an ECR plasma CVD apparatus used in an embodiment of the method of manufacturing a semiconductor device according to the present invention. FIG. 2 is a process sectional view showing the manufacturing method of the same embodiment. FIG. 3 shows the dependence of the etching rate and deposition rate of the insulating film on the RF specific output power in the same example, when the insulating film was formed without mixing Ar gas into the deposition gas, and when it was formed using Ar gas and He gas.
It is a graph diagram shown in comparison with a case where a gas is mixed into a film forming gas. FIG. 4 is a graph showing the in-plane uniformity of the thickness of the insulating film formed in the same example in comparison with the prior art. [Explanation of symbols] l... Waveguide 2... Microwave introduction window 3... First gas introduction system 4... Main magnetic coil 5... Plasma generation chamber 6... Reaction chamber 7 . . . Second gas introduction system 8 . . . Opening 9 . . . Substrate 10 . ...Underlying protective oxide film 24...High coverage oxide film 25...Flattening oxide film. Exhaust system] Diagram 00 00 300 400 500 RF-Power (W) 00 Section Distance from the center of the sample Diagram

Claims (3)

[Claims] (1) In a method for manufacturing a semiconductor device that includes a step of forming an insulating film on a stepped portion formed on a substrate by an ECR plasma CVD method that can apply a high frequency bias to the substrate, the high frequency bias is not applied or the high frequency bias is low. A step of forming a base protective insulating film on the circumferential surface of the stepped portion by applying an output high frequency bias, and then forming a high coverage layer on the base protective insulating film under a higher output high frequency bias. 1. A method for manufacturing a semiconductor device including an insulating film, the method comprising: forming an insulating film. (2) After the step of forming the high coverage insulating film, Ar
2. A method for manufacturing a semiconductor device having an insulating film according to claim 1, further comprising the step of forming a planarized insulating film under a high frequency bias using a film forming gas mixed with Ar and He. (3) In each of the above steps, a cusp magnetic field is formed around the substrate, the substrate is placed near the cusp surface in the cusp magnetic field, and the surface of the substrate is arranged parallel to the cusp surface. Claim 1 characterized in that
A method for manufacturing a semiconductor device comprising the insulating film according to item 1 or 2.