JPH08222739A - Method of manufacturing semiconductor device - Google Patents

Abstract

PURPOSE: To prevent formation of low quality oxide film due to abnormal oxidation when forming oxide film by a heat treatment step on the surface of a silicide layer. CONSTITUTION: When a WSi layer (silicide layer) 15 is formed on a semiconductor substrate 11 to form an oxide film 18 on the surface of the WSi layer 15 by thermal oxidizing process, the oxygen contamination in a heat treatment furnace in the case of feeding semiconductor device in the furnace is checked later to be slowly oxidized at high temperature. Through these procedures, the rapid oxidation of the WSi layer can be checked by checking the oxygen contamination in the furnace, thereby checking the abnormal oxidation of the WSi layer. Furthermore, a high quality oxide film can be formed by forming the oxide film at high temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device in which a silicide layer is formed on a wiring layer made of polycrystalline silicon to speed up the operation.

[0002]

2. Description of the Related Art Conventionally, there has been proposed one using polycrystalline silicon as a wiring layer of a semiconductor device, and one having a silicide layer formed on the wiring layer in order to reduce the wiring resistance and increase the operation speed. ing. For example, FIG. 3 is a diagram showing an example thereof in the order of manufacturing steps. First, FIG. 3 (a)
As shown in FIG. 3, the silicon substrate 21 is oxidized to form an element isolation oxide film 22 and a gate oxide film 23, and CVD is performed thereon.
A polycrystalline silicon film 24 having a thickness of about 100 nm to 200 nm is deposited by a sputtering method,
A WSi film (tungsten silicide film) 25 having a thickness of about 300 nm is formed.

Then, by the photolithography method,
The WSi film 25 and the polycrystalline silicon film 24 are patterned to form a gate electrode 26 as shown in FIG. After that, ion implantation of impurities is performed using the gate electrode 26 as a mask to form a shallow source / drain diffusion layer 29 of low concentration. After this, LD including impurity activation
In order to form the D structure, a SiO ₂ film 27 is formed to a thickness of about 200 nm by a high temperature low pressure CVD method at about 800 ° C. as shown by a chain line.
3C is deposited, and this is etched by reactive ion etching to form a side wall while leaving the SiO ₂ film 27 on the side surface of the gate electrode 26 as shown in FIG. 3C.

By forming the side wall 27, WS
Since the upper surface of the i film 25 is exposed, a high temperature depressurized CV of about 800 ° C. is formed on the entire surface as a mask for the subsequent ion implantation.
The D film 28 is grown to about 20 nm. However, if oxygen in the atmosphere is trapped in the heat treatment step of the WSi film 25, the WSi film 25 is deeply oxidized and an abnormal oxide film 28A is formed on the upper surface of the WSi film 25 as shown in FIG. 3D. . It is considered that the abnormal oxide film 28A is composed of SiO ₂ and WO _3, and the volume expansion reaches about 2.7 times, and the resistance of the gate electrode 26 is greatly increased by the abnormal oxide film 28A, and the film is often peeled off. Such a problem occurs.

Examining the cause of the formation of the abnormal oxide film, the abnormal oxidation of the WSi film 25 is shown in FIG.
Since it did not occur in the subsequent step of forming the oxide film 27,
It is premised that WSi is crystallized. The abnormality in the description disclosed in Japanese Patent Laid-Open No. 4-266031 is to oxidation, WSi _x when this phenomenon WSi _x film is exposed to oxygen contamination atmosphere in an amorphous state
The Si inside is mainly oxidized to form an oxide film (SiO ₂ ), which covers the surface and suppresses the subsequent oxidation. On the other hand, the WSi _x film is crystallized and WSi ₂
When the crystal grains cover the surface, it is considered that when exposed to an oxygen-containing atmosphere, the supply of Si is insufficient with respect to the consumption of Si due to oxidation and W is directly oxidized.

Therefore, in the above publication, after the metal silicide is crystallized by the first heat treatment, the exposed metal silicide film surface is again covered with the silicon film before the heat treatment of oxygen mixture, and then the oxidation heat treatment is performed. Then, the silicon film is converted into an oxide film to prevent abnormal oxidation of the metal silicide film.

As another countermeasure, Japanese Patent Laid-Open No. 2-740
In Japanese Patent Laid-Open No. 31-31, after the silicide is crystallized, the exposed silicide surface is treated at 500 ° C. or lower to form an oxide film. Therefore, since the crystallized WSi ₂ surface is not oxidized due to the low temperature treatment, the oxidation of WSi is prevented.

[0008]

However, in the measures described in these publications, the surface is covered with a silicon film before the heat treatment after the silicide is crystallized by the first heat treatment, which is disclosed in JP-A-4-266031. The countermeasure of the publication has a problem that the number of steps of the oxidation treatment after forming the silicon film is extra and the number of steps is increased.

In addition, in the countermeasure of Japanese Patent Laid-Open No. 2-74031, in which SiO _{2 is} deposited at 500 ° C. or lower, instability of characteristics is caused by deterioration of film quality such as increase of impurities in the film and deterioration of uniformity of thin film. In addition, there is a problem that the heat treatment step for diffusion of ion implantation and the step of depositing a film for preventing abnormal oxidation take two steps, and the number of steps increases.

[0010]

The object of the present invention is to increase the number of manufacturing steps without increasing
Moreover, it is an object of the present invention to provide a method for manufacturing a semiconductor device, which can prevent abnormal oxidation of a silicide layer while stabilizing the characteristics.

[0011]

According to the manufacturing method of the present invention, when a silicide layer is formed on a semiconductor substrate and an oxide film is formed on the surface of the silicide layer by thermal oxidation, the semiconductor substrate is placed in a heat treatment furnace. At that time, it is characterized in that oxygen is prevented from being mixed in the furnace, and then a gentle oxidation treatment is performed at a high temperature.

For example, when the semiconductor substrate is put into the heat treatment furnace, the furnace is filled with nitrogen to prevent oxygen from being mixed into the furnace. When the silicide layer is a tungsten silicide layer and a silicon oxide film is formed on its surface by heat treatment, the temperature when the semiconductor substrate is put in the heat treatment furnace is set to 500 ° C. or lower, and then high temperature treatment of 500 ° C. or higher is performed. Therefore, it is preferable to perform mild oxidation.

[0013]

When the oxide film is grown on the silicide layer, oxygen is prevented from being mixed into the furnace, whereby the silicide layer can be prevented from being rapidly oxidized and abnormal oxidation in the silicide layer can be prevented. Further, by forming the oxide film at a high temperature thereafter, it becomes possible to form a high quality oxide film.

[0014]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an embodiment in which the present invention is applied to a MOS semiconductor device in the order of manufacturing steps. First, Fig. 1
As shown in (a), the surface of the silicon substrate 11 is oxidized to form an element isolation oxide film 12 and a gate oxide film 13 made of a SiO ₂ film (silicon oxide film). Then, 100 nm to 200 nm is formed thereon by the CVD method.
A polycrystalline silicon film 14 having a thickness of about 100 nm to 300 nm is deposited by a sputtering method.
A film (tungsten silicide film) 15 is formed.

Next, as shown in FIG. 1B, these W's are formed by a photolithography method using a photoresist.
Patterning the Si film 15 and the polycrystalline silicon film 14,
The gate electrode 16 and the wiring not shown are formed. After that, ion implantation of impurities is performed using the gate electrode as a mask to form a low concentration shallow source / drain diffusion layer 19.

After that, as shown by the chain line in FIG.
Approximately 8 to form LDD structure including impurity activation
A SiO ₂ film (silicon oxide film) 17 having a thickness of about 200 nm is deposited by a high-temperature low-pressure CVD method at 00 ° C., and then this is etched by reactive ion etching to leave the SiO ₂ film 17 on the side surface of the gate electrode and form a sidewall. To do.
The upper surface of the WSi film 15 is exposed by this etching.

Thereafter, as shown in FIG. 1D, a SiO ₂ film 18 is formed on the entire surface by high temperature decompression CVD at about 800 ° C.
It grows to about 0 nm. This SiO ₂ film 18 is for masking the gate electrode at the time of ion implantation for forming an LDD structure in a later step. At this time, N ₂ is filled in the furnace and at the bottom of the furnace at the time of entering the furnace to prevent oxygen from being mixed into the atmosphere to prevent rapid oxidation. As a result, the high-quality thin oxide film formed by the high-temperature heat treatment causes the W
The surface of the Si film is covered, and in this case WSi
The SiO ₂ film 18 can grow without abnormal oxidation of the film 15.

Here, in the present invention, as shown in FIG. 2, high-temperature low-pressure CVD for the above-mentioned ion implantation mask is used.
Approximately 80 after the furnace was evacuated at a temperature of 500 ° C. or less, the furnace was evacuated, and the furnace was filled with N ₂ when the oxide film was blasted.
When the temperature is raised to 0 ° C. and the CVD film is grown, the WSi film 1
The abnormal oxidation of No. 5 can be prevented. The reason for this is that if you enter the furnace below 500 ° C, you can prevent the rapid oxidation at the time of entering the furnace and
_A thin oxide film can be formed on the WSi film 15 by heat treatment at 800 ° C. in ₂
The thin oxide film on 5 can prevent abnormal oxidation of the WSi film 15.

Incidentally, when comparing the oxide film formed by the manufacturing method of the present invention with the oxide film grown at 500 ° C. or lower as in the above-mentioned Japanese Patent Application Laid-Open No. 2-74031, it is 20 nm or less in the technique disclosed in the publication. Thickness uniformity (R / 2
X) was 5 to 10%, whereas in the method of the present invention, the high temperature decompression CVD oxide film was used, so that the film thickness uniformity could be improved to about 1 to 6%, and the transistor characteristics were further improved. It was possible to obtain stability.

In the above embodiments, the case where WSi is used as the silicide layer of the present invention has been described as an example.
The present invention can be similarly applied to a silicide layer using a metal such as o (molybdenum) or Ti (titanium). However, in this case, it may be necessary to make the temperature slightly different depending on the type of metal used.

[0021]

As described above, according to the present invention, when the oxide film is formed on the surface of the silicide layer by the thermal oxidation treatment, oxygen is prevented from being mixed in the furnace when the semiconductor substrate is put into the heat treatment furnace, and then the high temperature Since a gentle oxidation process is performed with
Abrupt oxidation in the silicide layer can be prevented to prevent abnormal oxidation, and on the other hand, high-temperature oxidation can form a high-quality oxide film.

For example, when the semiconductor substrate is put into the heat treatment furnace, by filling the furnace with nitrogen, oxygen can be prevented from entering the furnace. When the silicide layer is a tungsten silicide layer, the temperature when the semiconductor substrate is put in the heat treatment furnace is set to 500 ° C. or lower, and then 5
By performing gentle oxidation in a high temperature of 00 ° C. or higher, for example, 800 ° C., abnormal oxidation of the silicide layer is prevented and a high quality oxide film is formed.

Further, according to the method of the present invention, Japanese Patent Laid-Open No. 4-26 is used.
Compared with the technique of the 6031 publication, the silicon film formation and the subsequent oxidation process can be reduced, and the manufacturing process can be simplified. Further, as compared with the technique disclosed in Japanese Patent Application Laid-Open No. 2-74031, the oxide film can be grown at a high temperature, the film thickness uniformity can be improved, and the quality can be improved. Further, there is an effect that the high temperature heat treatment for activating the impurities and the oxide film growth can be performed in one step.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention in the order of manufacturing steps.

FIG. 2 is a diagram for explaining a temperature control state of a part of the process in the present invention.

FIG. 3 is a cross-sectional view showing an example of a conventional manufacturing method in the order of steps.

[Explanation of symbols]

11 silicon substrate 14 polycrystalline silicon film 15 WSi film 16 gate electrode 17 SiO ₂ film 18 SiO ₂ film

Claims (4)

[Claims] 1. A silicide layer is formed on a semiconductor substrate,
In a method for manufacturing a semiconductor device including a step of forming an oxide film on the surface of the silicide layer by thermal oxidation, when the semiconductor substrate is put in a heat treatment furnace, oxygen in the furnace is prevented from being mixed, and thereafter the temperature is moderated at a high temperature. A method for manufacturing a semiconductor device, which comprises performing an oxidation treatment. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the furnace is filled with nitrogen when the semiconductor substrate is put into the heat treatment furnace. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the silicide layer is a tungsten silicide layer, and a silicon oxide film is formed on the surface thereof by heat treatment. 4. The method of manufacturing a semiconductor device according to claim 3, wherein the temperature at which the semiconductor substrate is put in the heat treatment furnace is set to 500 ° C. or lower, and then the mild oxidation is performed during a high temperature treatment of 500 ° C. or higher.