JPH0296336A - Formation of silicon nitride film - Google Patents

Abstract

PURPOSE:To form an SiN film with high reliability and excellent wet-resistance by performing plasma chemical vapor phase growth by introducing into a reaction container silane gas, disilicon hexafluoride gas, hydrogen gas, and nitrogen gas as main reaction gases and subjecting them to glow discharge. CONSTITUTION:A substrate 11 is introduced into a reaction container, and SiH4 gas or Si2F6 gas, H2 gas, and N2 gas are introduced into the reaction container as main reaction gases and subjected to plasma CVD to form an SiN film 113 on the substrate 11. Accordingly, the SiN film 113 excellent in thermal resistance can be obtained at a high speed of film formation. Hereby, this is applicable as the final protective film for a semiconductor device to improve the reliability.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a silicon nitride film that is used as a final protective film for semiconductor devices by plasma chemical vapor deposition (hereinafter referred to as CVD).
It is related to the method of forming by the method called ).

(Prior Art) Generally, a silicon nitride film (hereinafter referred to as SiN film) is used as the final protective film of a semiconductor device. This Si
The N film is described in the literature IEDM (IEDM)
, December 9-12, 1984, pages 630-633, SiH4 (silane) gas and NH
3 (ammonia) gas or SiH4 gas and N2 (nitrogen)
It is formed by plasma CVD using gas. However, SiN films obtained using these gases contain a large amount of hydrogen in the film. This hydrogen causes traps to be generated in the underlying gate oxide film of the semiconductor device. Therefore, the electrical characteristics of the semiconductor device vary due to electrical stress. Furthermore, this document describes the use of S'IF4 (silicon tetrafluoride) gas, N2 gas, and 82 (hydrogen) gas, or 5t2F6 (6
An SiN film formed by a plasma CVD method using a disilicone fluoride gas, N2 gas, and N2 gas is used. This SiN film contains fluorine, and it is thought that this fluorine fixes hydrogen in the film.

(Problem to be solved by the invention) However, this 5LNII! If the fluorine content is high, the moisture resistance of the film will deteriorate and it will no longer function as a final protective film. Etching rate (buffered hydrofluoric acid) is an indicator of the moisture resistance of a film. , 5tF4 or Si2F6 exhibits an etching rate that is more than 10 times faster than a film using SiH4.

A high etching rate means that the material has poor moisture resistance. Furthermore, when a humidification test is performed on a SiN film formed using Si2F6, N2, and H2, the water reacts with the SiN film and it becomes a Si02 film within a short time. It can be seen that the film formed using H2 is weak in moisture resistance.

As described above, the fluorine-containing SiN film formed by plasma CVD using SiF4 and Si2F6 has a problem of poor moisture resistance and easy penetration of moisture.

The purpose of this invention is to produce highly reliable SiN with excellent moisture resistance.
An object of the present invention is to provide a method for forming a film.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention, when forming a SiN film, introduces a substrate into a reaction vessel, and mixes SiH4 gas or Si2H6 gas, Si2F6 gas, N2 gas, and N2 gas.
A SiN film is formed on the substrate by introducing a gas as a main reaction gas into the reaction vessel and performing plasma CVD by causing glow discharge.

(Function) According to the present invention, as described above, Si2 is used as the main reaction gas.
Since the SiN film is formed on the substrate by the plasma CVD method using F6 gas, N2 gas, N2 gas, and Si-H4 or Si2H6 gas, the SiN film can be formed at a high film formation rate and has excellent moisture resistance. can be obtained.

(Example) FIGS. 1(a) to (c) are cross-sectional views of a semiconductor element for explaining the present invention in detail, and FIGS. 2(a) and (b) are SiN
It is a diagram showing changes in the infrared absorption peak of a film, and will be explained below using the drawings.

First, Fig. 1(a) shows a silicon substrate (P type, 4-6Ω
・On the oxide film 11, an element isolation region 12, an element active region 13, a transistor section 14, a capacitor section 15, a wiring 16, an N diffusion region 17, a silicon oxide film 18, etc. are formed, and then BPSG ( Boron phosphorus silicate glass)
Insulation between the eyebrows using etc.! 19 is a cross-sectional view of the element after surface smoothing. Here, the transistor section 14, the capacitor section 15, and the wiring 16 are made of polycrystalline Si and W-
It shows that it is made of 2Mm such as Si.

Next, as shown in FIG. 1(b), the silicon oxide film 18 and the interlayer insulating film 19 are selectively removed by photolithography and etching steps, and the electrical connection between the wiring 16 and the N+ diffusion region 17 and the upper layer wiring is established. contact hole 110 for obtaining
Next, an upper layer wiring material such as aluminum containing silicon is applied to the entire surface by sputtering to a thickness of 600 mm.
The aluminum layer is formed by 0 to 8,000 people, and then the aluminum is selectively etched away by a photolithography and etching process to form the upper layer wiring 111.

Next, as shown in Fig. 1(c), the entire surface is coated with P by CVD method.
An SG (phosphosilicate glass) film 112 is formed. At this time, the phosphorus concentration in the PSG film 112 is H3-12wt%
(P2O5) and the film thickness is 1000 to 5000. Next, an SiN film 113 is formed as a final protective film over the entire surface by plasma CVD to a thickness of 2,000 to 10,000 layers. At this time, the temperature for forming the SiN film is 200″C to 45°C.
0'C1 is preferably 300''C. In this case, 400 KHz was used as the high frequency for plasma generation, but there is no problem with other frequencies such as 13.56M2.0 As the reaction gas, Si2F6 gas and SiH4 gas and H
2 and N2 were introduced into the reaction vessel so that the internal pressure was 0.2 to 5 Torr, preferably 3 Torr.

At this time, the ratio of Si2F6 flow rate to SiH4 flow rate is Si2
The F6/SiH4 ratio is set to 10 to 90%. In addition, the flow rate of H2 is about 10 to 30 times that of Si2F6, and the flow rate of N2 is 3 times the sum of the flow rates of Si2F6
0 to 50 times.

According to the SiNM formation method described above, a final protective film with strong moisture resistance can be obtained at a high film formation rate without adversely affecting the electrical characteristics of the device. The film properties will be described below. FIGS. 2(a) and (b) show S formed using Si2F6, N2, and N2 according to the prior art, respectively.
Humidification test (12
It shows the change in infrared absorption peak at 0°C, 100% R, H,).

The horizontal axis shows the wave number, and the vertical axis shows the absorbance (non-quantitative). The 0-dot line is the characteristic before humidification, and the solid line is the characteristic after humidification. As shown in Figure 2 (a), in the case where only Si2F6 was used as the silicon source gas, the Si-0 peak increased rapidly during the 16-hour humidification test, and the film changed from SiN to SiO due to moisture intrusion. . On the other hand, as the silicon source gas, Si2F6 and SiH4 are used as the present invention.
As shown in FIG. 2, the infrared absorption peak of the film using the above film hardly changed even after 256 hours of humidification test, indicating that the film had sufficiently strong moisture resistance.

Furthermore, since the present invention uses Si2F6 gas, SiF
It has the advantage of having a higher degree of dissociation and a faster film formation rate than the four gases. Furthermore, it has been confirmed that there is almost no change in electrical characteristics due to stress in the device using the SiN film according to the present invention.

(Effects of the Invention) As explained in detail above, according to the present invention, in addition to Si2F6 gas, N2 gas, and N2 gas, S
Since the SiN film is formed on the substrate by plasma CVD using iH4 or Si2H6 gas, a SiN film with excellent moisture resistance can be obtained at a high film formation rate. Therefore, it can be applied as a final protective film for semiconductor devices, and can be expected to improve the reliability of semiconductor devices.

[Brief explanation of drawings]

FIGS. 1(a) to (c) are cross-sectional views of a semiconductor element for explaining the present invention in detail, and FIGS. 2(a) and (b) are diagrams showing changes in infrared absorption peaks. . 11... Substrate, 12... Element isolation region, 13...
Element active area, 14...1-transistor section, 15...
・Capacitive part, 16... Wiring, 17... N+ diffusion region,
18...Silicon oxide film, 1...Interlayer insulating film, 1
10... Contact hole, 111... Upper layer wiring,
112...PSG film, 113...SiNJF! ! 7° interlayer r>P! ,t&JIL 1to:Contact/L-L fN::tnovat4 tt2:ps
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Claims (1)

[Claims] The substrate was introduced into the reaction vessel, and silane gas (SiH_4
or Si_2H_6) and disilicon hexafluoride gas (Si_
2F_6), hydrogen gas (H_2) and nitrogen gas (N_2)
A method for forming a silicon nitride film, characterized in that a silicon nitride film is formed on the substrate by introducing into the reaction vessel as a main reaction gas and performing glow discharge to perform plasma chemical vapor deposition.