JPH0342832A - Forming method for multilayer insulating film - Google Patents

Abstract

PURPOSE:To equalize film thickness by using an HTO(High Temperature CVD Thin Oxide) film, which can be formed at a lower heat-treating temperature, through a CVD method in place of a polysilicon thermal oxide film on a polysilicon electrode. CONSTITUTION:A thin gate insulating film 2 is shaped onto the surface of a semiconductor substrate 1, and a polysilicon electrode 3 as a first layer is deposited onto the gate insulating film 2 through a CVD method. An HTO film 4 is deposited onto the polysilicon electrode 3 through the high-temperature CVD method of SiH2Cl2 and N2O. An interface is thermally oxidized in a high- temperature thermal oxidation atmosphere in a very short time, thus forming a thin silicon thermal oxide film 5. A CVD silicon nitride film 6 is deposited onto the silicon thermal oxide film 5. The CVD silicon nitride film 6 is thermally oxidized, thus shaping a thermal oxidation silicon nitride film 7 onto the surface of the silicon nitride film 6. A polysilicon electrode 8 as a second layer is deposited through the CVD method. Accordingly, multilayer insulating films having the uniformity of film thickness and excellent film quantity is acquired by multilayer insulating films using the HTO film through the CVD method in place of a polysilicon thermal oxide film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is directed to silicon semiconductor devices, such as polysilicon 2
This invention relates to a method for forming an insulating film on polysilicon with high performance and high reliability, which is used in layered semiconductor nonvolatile memories, polysilicon stacked type random access memories, etc.

[Summary of the invention]

In the present invention, SiH1C1z and Nt are formed on a polysilicon electrode.
A silicon oxide film (hereinafter referred to as HTO (formerly GH Temperature C
A VD Th1nOxide film) was deposited. Next, thermal oxidation was performed for a short time in a high-temperature oxidizing atmosphere to form a thin silicon thermal oxide film at the interface between the HTO film and the polysilicon electrode. Furthermore, a CVD silicon nitride film was deposited on this HTO film by the CVD method. Then, by thermally oxidizing this CVD silicon nitride film, a thermally oxidized silicon nitride film is formed on the film surface. The above process makes it possible to form a multilayer insulating film on polysilicon with high performance and high reliability.

[Conventional technology]

A conventional technique will be explained using drawings. Figure 2 fat~I
cI is a cross-sectional view showing the process of forming a multilayer insulating film on a polysilicon electrode created using a conventional technique. First, a thin gate insulating film 2 is formed on the surface of a semiconductor substrate 1, and a first layer of polysilicon electrode 3 is deposited on it by the CVD method (Fig. 2 (al)). Thermal oxidation of silicon electrode 3 results in thin polysilicon thermal oxidation W
:1.9 is formed, and a CVD silicon nitride film 6 is deposited thereon by the CVD method (FIG. 2(b)). Further, this CVD silicon nitride film 6 is thermally oxidized to form a thermally oxidized silicon nitride film 7 on the surface of the film. Finally, a second layer of polysilicon electrode 8 was deposited using CvDi (FIG. 2(C)).

[Problem to be solved by the invention]

However, the conventional forming process has the following two problems. First, when polysilicon oxidation is performed on an IN-th polysilicon electrode doped with a high phosphorus concentration, the oxidation rate is fast, making it difficult to obtain in-plane film thickness uniformity on a large-diameter silicon wafer.

Second, when polysilicon is oxidized in a high-temperature oxidation atmosphere of 1000°C or higher, if a thin gate insulating film of 100 Å or less is formed and then a high-temperature heat treatment process is performed after the first layer of polysilicon is deposited, the thin gate insulating film will become thinner. The result has been obtained that the film quality is significantly deteriorated.

[Means to solve the problem]

In order to solve the above problems, in the present invention, instead of the polysilicon thermal oxide film on the polysilicon electrode, an HTO film (CVD method) which can be formed at a lower heat treatment temperature is used.

[Effect]

When forming a multilayer insulating film on a polysilicon electrode as described above, since the HTO film is a CVD film, the in-plane uniformity of the wafer is good even on a large-diameter silicon wafer, regardless of the Linnean obtuse concentration. Furthermore, since the aS degree of the )HTO film is about 200°C lower than that of polysilicon thermal oxidation,
It is possible to prevent the following modification of the thin gate insulating film from significantly deteriorating. Furthermore, since HTOlc: 1 cvo ta, polysilicon asperities are not generated.

As described above, the multilayer insulating film of the present invention has excellent film thickness uniformity and film quality, and also has the excellent feature of having almost no adverse effect on the thin gate insulating film formed in the previous process. .

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings. FIG. 1 (al~(C1) is a sectional view showing the formation process of a multilayer insulating film on a polysilicon electrode created using the technique of the present invention. First, a thin gate insulating film 2 is formed on the surface of a semiconductor substrate l. is formed, and a first layer of polysilicon electrode 3 is deposited thereon by the CVD method (Fig. 1(a)).Next, SiHIC is deposited on this polysilicon electrode 3.
j! HTO by high temperature CVD method at 850℃ of z and N, 0
Deposit film 4. Furthermore, in order to improve the state of the interface between the ITO film 4 and the eleventh polysilicon electrode 3, the interface is thermally oxidized for a very short time in a high temperature thermal oxidation atmosphere to form a thin silicon thermal oxide film 5. Then, a CVD silicon nitride film 6 is deposited thereon (first enclosure)), and this CVD silicon nitride film 6 is further thermally oxidized to form a thermally oxidized silicon nitride film 7 on the film surface. And finally 2N
Eye polysilicon electrodes 8 were deposited by CVD method (
Figure 1 (C1).

When forming a multilayer insulating film on a polysilicon electrode as described above, since the HTO film is a CVD film, the in-plane film thickness uniformity is good even on a large diameter silicon wafer, regardless of the concentration of Linnean obtuse. Furthermore, since the formation temperature of the HTO film is about 200° C. lower than that of thermal oxidation of polysilicon, it is possible to prevent the film quality of a thin gate insulating film of 100 Å or less from being significantly deteriorated. Furthermore, since the HTO film is a CVD film, polysilicon asperities do not occur.

〔Effect of the invention〕

As explained above, the present invention is a multilayer insulating film that uses a CVD IITO film instead of a polysilicon thermal oxide film, and has excellent film thickness uniformity and film quality. There is almost no adverse effect on the thin gate insulating film.

[Brief explanation of drawings]

FIG. 1 (al~(C1) is a cross-sectional view of the process of forming a multilayer insulating film on a polysilicon electrode created using the technique of the present invention. FIG. These are cross-sectional views in order of the formation process of a multilayer insulating film on a polysilicon electrode created by: - Semiconductor substrate - Thin gate insulating film - First layer polysilicon electrode - HTO film - Thin silicon thermal oxide film - CVO silicon nitride Film, thermal oxidation silicon nitride film, 2Nth polysilicon electrode or higher

Claims (1)

[Claims] A step of depositing a CVD silicon oxide film by a high temperature chemical vapor deposition (CVD) method of SiH_2Cl_2 and N_2O to form a multilayer insulating film, and thermally oxidizing the CVD silicon oxide film,
A step of forming a thin silicon thermal oxide film at the interface between the CVD silicon oxide film and the silicon substrate or polysilicon, and a step of forming a thin silicon thermal oxide film on the CVD silicon oxide film.
) A method for forming a multilayer insulating film comprising the steps of: depositing a CVD silicon nitride film by a method; and thermally oxidizing the CVD silicon nitride film to form a thin thermally oxidized silicon nitride film on the surface of the CVD silicon nitride film.