JPH0745610A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the stress migration in the wiring by forming a two-layer of silicon nitride films having different internal stress. CONSTITUTION:A silicon oxide film 2 is formed over the silicon substrate 1, and aluminum is deposited on the oxide film by sputtering. Thereafter the aluminum wiring 3 is formed by lithography techniques. Next, the silicon nitride film 4 with a tensile internal stress is formed as a protective film, and a silicon nitride film 5 with a compressive internal stress is formed on the silicon nitride film by plasma CVD.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a protective film or an interlayer insulating film for a semiconductor device.

[0002]

2. Description of the Related Art In recent years, a silicon nitride film formed by a plasma CVD method has been used as a protective film or an interlayer insulating film after forming wirings of a semiconductor device. The silicon nitride film has excellent moisture resistance and mechanical strength, and is a source of pollution (Na
It has the advantage of being a protective film against ions, etc.).

The silicon nitride film formed by the plasma CVD method is supplied with silane gas, ammonia gas, and nitrogen gas in the reaction chamber, and then a high-frequency voltage is applied between the electrodes to generate plasma and become excited. It is formed by the reaction of molecules.

[0004]

The above-mentioned conventional plasma C
In the case of a silicon nitride film formed by the VD method, the film itself has 1 × 10 ⁸
High compressive stress of about 10 ⁹ dynes / cm ² is generated. Therefore, when this silicon nitride film is formed on the wiring as a protective film, there is a problem that the wiring causes stress migration.

[0005]

In order to solve the above problems, a method of manufacturing a semiconductor device according to the present invention comprises a step of forming wiring on the main surface of a semiconductor substrate, and a plasma CV on the wiring.
When forming a silicon nitride film by the D method, the silicon nitride film is composed of a first silicon nitride film whose internal stress is compressive stress and a second silicon nitride film whose internal stress is tensile stress. .

[0006]

According to the method of manufacturing a semiconductor device according to the present invention, the internal stress of the silicon nitride film and the internal stress of the compressive stress can be almost canceled by the tensile stress. When formed on,
It is possible to solve the problem that the wiring causes stress migration.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a semiconductor device showing steps in order to explain an embodiment of the present invention. The present embodiment is an example in which a silicon nitride film having a compressive stress and a silicon nitride film having a tensile stress as an internal stress are used by the plasma CVD method as a protective film for aluminum wiring.

First, as shown in FIG. 1A, a silicon oxide film 2 is formed on a silicon substrate 1. Aluminum is formed on this by sputtering. After that, the aluminum wiring 3 is formed by using the lithography technique. Next, as shown in FIG. 1B, a silicon nitride film 4 having an internal stress of tensile stress is formed as a protective film by a plasma CVD method, and subsequently, a silicon nitride film 5 having an internal stress of compressive stress is continuously formed. To form. At this time, for the silicon nitride film to be formed, silane gas, ammonia gas, and nitrogen gas are supplied to the reaction chamber, and high frequency power is applied. On this occasion,
The internal stress of the silicon nitride film is controlled only by the high frequency power applied.

The conditions for forming the silicon nitride film 4 in which the internal stress is tensile stress are as follows: silane gas flow rate; 150 sccm ammonia gas flow rate; 50 sccm nitrogen gas flow rate; 3500 sccm formation temperature; 360 ° C. formation pressure; 5.5 Torr interelectrode distance; 9.9 mm Applied high frequency power; 1.7 w / cm ² .

Under these forming conditions, a silicon nitride film having an internal stress of about 1 to 2 × 10 ⁹ dynes / cm ² is obtained.

When the film thickness of the silicon nitride film 4 in which the internal stress is tensile stress can be formed to about half of the total target film thickness, the high frequency power is adjusted. Then, a silicon nitride film whose internal stress is compressive stress is formed next time. As a result, the film thickness of the other half is formed.

At this time, the conditions for forming the silicon nitride film 5 in which the internal stress is compressive stress are as follows: silane gas flow rate; 150 sccm ammonia gas flow rate; 50 sccm nitrogen gas flow rate; 3500 sccm formation temperature; 360 ° C. formation pressure; 5.5 Torr interelectrode distance; 9.9 mm high-frequency power applied; 2.0 w / cm ² .

Under these forming conditions, the internal stress is 1 × compressive stress.
A silicon nitride film of about 10 ^{9 to} 2 × 10 ⁹ dynes / cm ² is obtained.

By forming the silicon nitride films 4 and 5 as described above, the stress of the silicon nitride films 4 and 5 exerted on the aluminum wiring 3 can be relaxed, and the stress migration of the aluminum wiring 3 can be suppressed. In addition,
The continuous formation is for increasing the adhesion between the silicon nitride film 5 having internal stress and compressive stress and the silicon nitride film having tensile stress. Furthermore, controlling with only high-frequency power has the highest responsiveness among the above-mentioned formation conditions, and therefore does not reduce throughput. For example, when the internal stress of the silicon nitride film is controlled by changing the gas flow rate, it takes several seconds to ten and several seconds until a stable gas is supplied into the reaction chamber, which lowers the productivity.

[0015]

As described above, according to the method of manufacturing a semiconductor device of the present invention, the internal stress of the protective film applied to the aluminum wiring can be relaxed, and the stress migration of the wiring can be suppressed.

[Brief description of drawings]

1A to 1C are cross-sectional views in order of steps of a semiconductor device for explaining an embodiment of the present invention.

[Explanation of symbols]

 1 Silicon substrate 2 Silicon oxide film 3 Aluminum wiring 4,5 Silicon nitride film

Claims (1)

[Claims] 1. A step of forming a wiring on a main surface of a semiconductor substrate and a step of forming a silicon nitride film on the wiring by a plasma CVD method, wherein the internal stress of the silicon nitride film is a compressive stress. And a second silicon nitride film whose internal stress is tensile stress.