JPH0645273A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a semiconductor device in which aggregate of metal silicide is alleviated when a metal film is silicified by heat treating. CONSTITUTION:After an insulating film 3 having an opening is formed on a silicon substrate 1, the substrate 1 is dipped in fluorine series solution using pure water controlled to 10ppb or less of dissolved oxygen, washed with controlled pure water, a titanium thin film 4 is then deposited, and heat treated to form a titanium silicide film 5.

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, and more particularly to improvement of a method of forming a silicide which is advantageous for miniaturization of elements.

[0002]

2. Description of the Related Art With the miniaturization of elements, it is necessary to form a diffusion layer shallow. Therefore, there is a problem that the surface resistance of the diffusion layer increases due to the miniaturization of the device. As a technique for reducing this type of surface resistance, a so-called "silicide" is adhered to the diffusion layer in a self-aligned manner.
Salicide technology is known.

A problem with this salicide technique is that when the thickness of the silicide film is increased, the diffusion layer is eroded and the silicide is aggregated by the high temperature treatment to form a mesh-like film structure, which increases the surface resistance. It has been known.
In order to reduce the erosion of the diffusion layer, the silicide film thickness may be made as thin as possible.

However, when the silicide is thinned, thermal treatment tends to cause aggregation, and an increase in surface resistance cannot be avoided. When a shallower diffusion layer is required in the future, further reduction in the thickness of silicide causes a problem that cohesion resistance is lowered and surface resistance is increased.

[0005]

As described above, the conventional salicide technique has a problem that sufficient cohesion resistance cannot be obtained when a shallower diffusion layer is required in the future.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of manufacturing a semiconductor device capable of improving the cohesion resistance of silicide and coping with the miniaturization of elements. is there.

[0007]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention comprises forming an insulating film having an opening on a silicon substrate and then forming a dissolved oxygen amount of 10 p.
A process of immersing the silicon substrate in a fluorine-based solution using pure water controlled to pb or less and a rinsing process using the controlled pure water are performed, and then a metal thin film is deposited on the silicon substrate and heat treatment is performed. It is characterized by forming a metal silicide. In the above-mentioned present invention, preferably, the fluorine-based solution is a hydrofluoric acid solution or an ammonium fluoride solution,
Alternatively, a mixed solution of these solutions may be used.

[0008] It is also desirable that the temperature of the silicon substrate be kept below the freezing point until a metal thin film is deposited on the silicon substrate after the washing process and a predetermined vacuum degree is reached in the vapor deposition apparatus. And good. Further, it is desirable that the silicon substrate be heat-treated at a temperature of 150 ° C. or higher immediately before depositing the metal thin film on the silicon substrate. Furthermore, preferably, after the step of forming the metal silicide, heat treatment is performed at a temperature higher than or longer than the temperature at which the metal silicide is formed. Furthermore, desirably, the metal thin film may be a titanium thin film.

[0009]

The present invention uses pure water whose dissolved oxygen amount is controlled to 10 ppb or less, performs a fluorinated solution treatment followed by a cleaning treatment, and then deposits a thin metal film such as a titanium film to dissolve the dissolved oxygen amount. It is based on the fact that the cohesion resistance of the silicide generated by heating is improved as compared with a similar sample treated with pure water of about 1 ppm. FIG. 2 is a diagram showing the heat treatment temperature dependence of the surface resistance when a titanium thin film is formed using the present invention and titanium silicide is formed by heat treatment.

As can be seen from this figure, at a high temperature of 850 ° C. or higher, the method according to the present invention significantly prevents the increase in surface resistance as compared with the method according to the prior art.

An advantage of the present invention is that the surface of the silicon substrate is hydrogen-terminated by using the above-mentioned controlled pure water.
It is considered that this is because the silicon surface is stabilized, and thus the growth of the natural oxide film is suppressed, which suppresses the aggregation of silicide.

As described above, according to the present invention, it is possible to obtain a salicide technique in which agglomeration of silicide is suppressed in the salicide process, and thus the surface resistance can be reduced even if the thickness of the silicide is further reduced.

[0013]

Embodiments will be described below with reference to the drawings. 1A to 1D are process sectional views showing a method of manufacturing a semiconductor device according to an embodiment of the present invention.

First, as shown in FIG. 1A, a diffusion layer 2 is formed on the surface of a silicon substrate 1. Next, after depositing the insulating film 3 on the entire surface, a contact hole (opening) is formed in the insulating film 3 on the diffusion layer 2 by using photolithography or the like.

Next, the silicon substrate 1 is filled with 10
Using pure water controlled to ppb or less, it is immersed in a hydrofluoric acid aqueous solution having a concentration of 1% for 3 minutes. Here, the hydrofluoric acid aqueous solution may be an ammonium fluoride solution or a mixed solution of a hydrofluoric acid aqueous solution and an ammonium fluoride solution. At this time, the processing atmosphere is a nitrogen atmosphere or an inert gas atmosphere in which the oxygen concentration is controlled to 1 ppm or less.

Then, the atmosphere is controlled in the same manner, and pure water whose dissolved oxygen amount is controlled to 10 ppb or less is used.
Wash with water for at least one minute. Next, the silicon substrate 1 is transferred to a closed container filled with nitrogen or an inert gas and transported to a metal vapor deposition device. By controlling the atmospheric oxygen in this manner, the features of the present invention can be obtained more effectively.

Next, the degree of vacuum in the metal vapor deposition apparatus is set to 10 ⁻⁷ T.
Evacuate to about orr. At this time, the silicon substrate 1 is kept at a temperature below the freezing point. Here, the reason why the temperature of the silicon substrate is kept below the freezing point is as follows.

That is, it was found that a titanium thin film was formed by vapor deposition in a high vacuum in a later step, but at this time, hydrogen was desorbed from the surface of the hydrogen-terminated silicon substrate 1 and the stable surface was destroyed. In order to prevent this, it was found that the temperature of the silicon substrate should be controlled below the freezing point in vacuum. By doing so, the effect of the present invention can be obtained more stably.

Next, as shown in FIG. 1B, the silicon substrate 1 is heated to 200 to 400 ° C. to remove water adsorbed on the silicon substrate 1, and then a titanium thin film 4 is deposited on the silicon substrate 1. To do. Here, vapor deposition may be selectively performed, or may be selectively removed after vapor deposition on the entire surface. Further, either a sputtering method or a CVD method may be used. Finally, Figure 1
As shown in (c), the titanium thin film 4 is reacted with the silicon substrate 1 by heat treatment to form a titanium silicide film 5.

As described above, the present invention is characterized by the wet pretreatment. In the case of this treatment, adsorption of water molecules on the surface of the silicon substrate 1 cannot be avoided. This water molecule easily becomes an oxidation source by heat treatment. To prevent this,
As described above, 150 ° C. before depositing a metal thin film such as titanium.
It is effective to perform the above heat treatment. By incorporating this step in the present invention, the effect of the present invention becomes more remarkable.

The present invention is not limited to the above embodiment. For example, instead of the titanium film 4, Co,
The same effect can be obtained by using a film made of another metal such as Ni, Pd, or Pt. In addition, various modifications can be made without departing from the scope of the present invention.

[0022]

As described in detail above, according to the present invention, agglomeration of silicide, which is a problem in the salicide process, can be suppressed, and salicide having a low surface resistance can be obtained.

[Brief description of drawings]

FIG. 1 is a process sectional view showing a method of manufacturing a semiconductor device according to an embodiment of the invention.

FIG. 2 is a characteristic diagram showing the relationship between the surface resistance of silicide and the temperature of heat treatment for forming silicide.

[Explanation of symbols]

1 ... Silicon substrate, 2 ... Diffusion layer, 3 ... Insulating film, 4 ... Titanium thin film, 5 ... Titanium silicide film.

Claims (1)

[Claims] 1. A process of immersing the silicon substrate in a fluorine-based solution using pure water whose dissolved oxygen amount is controlled to 10 ppb or less after forming an insulating film having an opening on the silicon substrate and the controlled pure water. And a metal thin film is deposited on the silicon substrate, and a metal silicide is formed by heat treatment.