JP3243816B2 - Method of forming insulating film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming an insulating film, and more particularly to a method for forming a silicon nitride film having good adhesion and film quality on a semiconductor substrate.

[0002]

2. Description of the Related Art Conventionally, as a method of forming a silicon nitride film, a CVD method using a silane (SiH ₄ ) -ammonia (NH ₃ ) -based gas and utilizing a thermal decomposition reaction at a temperature of 750 to 800 ° C. has been proposed. A high-frequency electric field is applied to the reaction gas using a SiH ₄ —NH ₃ gas, and the gas is activated using the electric energy.
There is a plasma CVD method for forming a thin film of a silicon nitride film on a substrate surface at low temperatures before and after.

The silicon nitride film is important as a protective film (passivation) of a semiconductor device, and the temperature and the stress of the film when growing the silicon nitride film have an important effect on Al fine wiring. From such a point, the silicon nitride film is mainly formed by the plasma CVD method described above. Also, in order to meet the demands for growing high-strength films at low temperatures and for increasing the diameter of wafers,
Controlling the plasma on the wafer surface using a single-wafer plasma CVD apparatus is considered as one direction.

[0004]

However, when a silicon nitride film is formed by the above-mentioned single-wafer plasma CVD apparatus, there is a problem that the silicon nitride film is peeled off on the surface of the silicon substrate or the surface of the SiO ₂ film. . To solve this problem, NH ₃ + N ₂ just before the silicon nitride film is formed.
It has been found that film discharge is eliminated by plasma discharge using only a gas system. However, when the plasma discharge NH ₃ + N ₂ below (1), problems occur such as (2).

[0005] (1) When there is an Al wiring on the base, an Al disappearance phenomenon occurs.

(2) When the film quality near the base interface of the silicon nitride film is deteriorated and the silicon nitride film is processed by plasma isotropic etching or wet etching, the etching rate of the silicon nitride film near the interface becomes high. There is a problem that the etching of the portion proceeds rapidly and the processed shape deteriorates.

As described above, the problems (1) and (2) newly occur, and the adhesion to the base, the film quality, and the A
The effect on the l wiring could not be solved at the same time.

The present invention has been made in view of such conventional problems, and can prevent the silicon nitride film from peeling off and prevent the silicon nitride film near the base interface from deteriorating. An object of the present invention is to provide a method for forming a possible insulating film.

[0009]

Therefore SUMMARY OF THE INVENTION The present invention is a silane as an initial film on a substrate (SiH _4, flow 10~60s
ccm) and nitrogen (N ₂ ) as source gas, and RF
After forming the first insulating film by film formation immediately after applying the output,
The solution is to form a second insulating film using silane, nitrogen and ammonia (NH ₃ ) as source gases continuously in the same chamber. The time of film formation immediately after RF application is set to 1 to 5 seconds.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the method for forming an insulating film according to the present invention will be described below based on embodiments.

This embodiment is an example in which the present invention is applied to the formation of a silicon nitride film by a single-wafer plasma CVD apparatus.

First, the procedure of this embodiment is as follows. A silicon substrate (wafer) is placed in a CVD chamber of a single-wafer plasma CVD apparatus.
Is loaded, the silicon substrate is heated, silane (SiH ₄ ) and nitrogen (N ₂ ) are introduced into the chamber, and the pressure in the chamber is stabilized. And in this state, RF
The output is applied, and the first silicon nitride film 2 is pre-deposited on the silicon substrate 1 as shown in FIG.

Next, ammonia (NH ₃ ) is introduced in addition to SiH ₄ and N ₂ to deposit the second silicon nitride film 3 as shown in FIG. Turn off RF output after depositing silicon nitride film of desired thickness
To

After that, the inside of the chamber is evacuated,
Unload the silicon substrate from the chamber.

In accordance with the above procedure, a silicon nitride film forming method in which a pre-deposition step as a first insulating film forming step is performed before a deposition step as a second insulating film forming step. Each example in which a film is formed on a 4-inch wafer will be described.

The deposition conditions were the same as those described below in each embodiment.

○ Introduced gas and its flow rate SiH ₄ ... 140 _SCCM NH ₃ ... 60 _SCCM N ₂ ... 1500 _SCCM ○ RF power ・ ・ ・ 400 W ○ Pressure ・ ・ ・ 4.0 torr ○ Temperature ・ ・ ・ 370 ° C ○ Electrode distance ・ ・ ・ 430mils And predeposition Table 1 below shows the correspondence between the film peeling on the silicon substrate surface when the flow rates of SiH ₄ and NH ₃ were changed and the presence / absence of film quality deterioration near the base under the above deposition conditions. is there. In addition, Examples 1 to
In the _{sample No. 6} , N ₂ was introduced at a flow rate of 1500 _SCCM in the pre-deposition step in addition to the gases shown in the table below.

[0018]

[Table 1]

[0019] As is apparent from Table 1, the peeling and film quality of the silicon nitride film, there is a flow rate dependency of SiH _4, NH _3, the film quality lowers the underlying vicinity generated by flowing NH _3, and It can be seen that the greater the flow rate of SiH _{4, the} worse the adhesion between the silicon substrate surface and the silicon nitride film. The reason for this is that the activation energy is SiH ₄ <NH ₃ <
Since the order is N ₂ , until the output is stabilized for a few seconds immediately after the RF output is turned on, the ion and radical density ratios are different from those in the stable plasma state thereafter. By controlling the radical species and each density, the adhesion to the underlying silicon is good, and the upper layer S
It is considered that an intermediate layer film that does not degrade the i-nitride film quality is formed.

In particular, SiH ₄ flow rate of 100-200 _SCCM ,
NH ₃ flow rate 30 to 90 _SCCM, N ₂ flow rate 1000-2000
_SCCM , pressure 3-6 torr, temperature 350-400 ° C, R
F power 380W or more, electrode interval 390-700mil
In a single-wafer plasma CVD apparatus for growing a silicon nitride film on a substrate under the conditions of s, the SiH ₄ flow rate is set to 10 to 60 _SCCM , the NH ₃ flow rate is set to _OSCCM , and the other parameters are set immediately before the film formation. As a result, the predeposition for 1 to 5 seconds was performed without change, thereby preventing the silicon nitride film from peeling off and improving the film quality.

Although the embodiments have been described above, the present invention
The present invention is not limited to these, and various changes accompanying the gist of the configuration are possible.

[0022]

As is clear from the above description, according to the present invention, the peeling of the silicon nitride film observed on the surface of the base is eliminated, and the deterioration of the film quality of the silicon nitride film in the vicinity of the base interface is prevented. There is an effect that can be done. As a result, the silicon nitride film formed by the single-wafer plasma CVD apparatus has a film quality comparable to that of the conventional batch-type plasma CVD apparatus, and the large-diameter wafer having the advantage of the single-wafer method. It has the effect of responding to the transition and making the most of the cluster tools. In particular, when forming the first insulating film, SiH ₄
The film was peeled off by controlling the flow rate of
Can be prevented.

Further, since the film quality is improved in this manner, when the silicon nitride film is processed by plasma isotropic etching or wet etching, there is an effect that the cross-sectional processed shape becomes good.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a process of an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the steps of the embodiment of the present invention.

[Explanation of symbols]

Reference numeral 1 denotes a silicon substrate, 2 denotes a first silicon nitride film, and 3 denotes a second silicon nitride film.

Claims (2)

(57) [Claims] 1. An silane (Si) film as an initial film on a substrate.
Using H ₄ and a flow rate of 10 to 60 sccm) and nitrogen (N ₂ ) as a source gas, a first insulating film is formed by film formation immediately after RF output is applied, and then silane is continuously formed in the same chamber. A method for forming an insulating film, comprising forming a second insulating film using nitrogen and ammonia (NH ₃ ) as a source gas. 2. The time of film formation immediately after the application of the RF output is one.
2. The method for forming an insulating film according to claim 1, wherein the time is from 5 to 5 seconds .