JP2000357659A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a film on an insulating film formed on a semiconductor substrate, without mixing contaminants into the insulating film by heat treating, within a furnace the semiconductor substrate to such a temperature level that chlorides are produced through reaction in a gas atmosphere containing chlorine. SOLUTION: A semiconductor substrate, having an oxide silicon. film formed on the surface thereof, is introduced into a silicon film forming low pressure vapor deposition furnace. Nitrogen gas is introduced into the furnace, until the temperature of the semiconductor substrate stabilizes. Flow rate of nitrogen gas, and the temperature and pressure within the furnace are varied. Upon stopping the supply of nitrogen gas, HCl gas is introduced into the furnace, and the temperature and pressure within the furnace are maintained. Upon stopping the supply of HCl gas, nitrogen gas is introduced into the furnace, and the temperature and pressure within the furnace are varied. Silane gas is introduced into the furnace. The silane gas is replaced with nitrogen gas, the pressure within the furnace is increased, and the temperature within the furnace is decreased. The semiconductor substrate is taken out of the vapor deposition furnace.

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 in which a film is formed on an insulating film without causing foreign matter to adhere to the surface of the insulating film, and more particularly to a semiconductor field effect transistor (hereinafter referred to as FET). The present invention relates to a method for manufacturing a semiconductor device in which heat treatment after formation of a gate oxide film and formation of a gate electrode can be continuously performed in the same device.

[0002]

2. Description of the Related Art A silicon oxide film, which is a gate insulating film of an FET, is a material that determines the reliability of a transistor.
Any contaminants must be eliminated. For this reason, conventionally, the FET has been manufactured by a manufacturing method including a step of forming a silicon oxide film on the surface of a silicon substrate and a step of forming a silicon film on the silicon oxide film thereafter. FIG. 2 is a graph showing manufacturing conditions in a conventional process of forming a silicon film on a silicon oxide film. FIG. 2 (a) shows the furnace temperature on the vertical axis and the time on the horizontal axis showing the manufacturing conditions of the silicon film. , (B) shows the furnace pressure on the vertical axis, the time on the horizontal axis, and the silicon film manufacturing conditions, and (c) shows the gas flow rate on the vertical axis, and the silicon film manufacturing conditions on the horizontal axis, time.

A conventional silicon film forming process will be described in detail with reference to the accompanying drawings. First, a semiconductor substrate is introduced into a low-pressure vapor deposition furnace for forming a silicon film. Next, as shown in FIG. 2A, the furnace temperature was set to 300 ° C., and FIG.
As shown in FIG. 2, the furnace pressure, the furnace pressure, and the gas flow rate from the initial state t ₀ to t _{1 in} which the furnace pressure is 760 Torr and the nitrogen gas flow rate is 10 liters / minute as shown in FIG. Hold.

Next, as shown in FIG. 2 (a), the temperature in the furnace is increased from 300 ° C. to 500 ° C. between times t ₁ and t ₂ , and as shown in FIG. Pressure 760 Torr
The gas flow rate is set to 1 liter / minute as shown in FIG. 2 (c).

Next, from time t ₂ to time t ₃ , silane gas (SiH ₄ ) is introduced into the furnace at a flow rate of 0.1 liter / min while maintaining the furnace temperature at 500 ° C. and the furnace pressure at 1 Torr. To deposit a silicon film.

Next, from time t ₃ to time t ₄ , FIG.
(A) As shown in FIG.
Then, as shown in FIG. 2B, the furnace pressure is changed from 1 Torr to 760 Torr. Thus, a silicon film is formed on the silicon oxide film without causing contaminants to adhere.

However, in the above-mentioned conventional method, various contaminants may actually adhere to the surface of the silicon oxide film between the formation of the silicon oxide film and the formation of the silicon film. For example, when a floating substance adheres to the air in a manufacturing factory, when dust is generated from a robot or the like that automatically transports a semiconductor substrate, or when it is transferred from a member or the like that physically contacts the semiconductor substrate during transport. There is. At this time, a metal contaminant such as iron degrades the reliability of the FET most, and a metal contaminant having an area density of about 10 ¹¹ atoms / cm ² may adhere to the semiconductor substrate. That is, in the conventional method, there is a problem that the contaminant attached to the surface of the silicon oxide film cannot be removed, and the contaminant is sandwiched between the silicon oxide film and the silicon film.

In order to solve part of this problem, various techniques have been proposed for preventing impurities from being mixed into the interface between the films to be laminated (Japanese Patent Publication No. 6-60401,
JP-A-5-335337, etc.).

In a temperature range of 400 to 600 ° C.,
The pretreatment is performed in an atmosphere containing a mixed gas of hydrogen gas and chlorine gas or a hydrogen chloride gas, and further an inert gas, and the monosilane is continuously exposed at a temperature in the range of 500 to 600 ° C. without exposing the substrate to the outside air, or Next silane 400 to 6
There is a silicon thin film manufacturing method in which a silicon thin film is deposited by introducing the silicon thin film in a temperature range of 00 ° C. (JP-B-6-60401).

In forming a thin film transistor, immediately before forming a gate insulating film on a semiconductor thin film, a halogen gas is used as an atmosphere gas, and light energy is used to convert impurities on the semiconductor thin film into volatile chloride. There is a method of manufacturing a thin film transistor which is removed from the surface of a semiconductor thin film as an object (Japanese Patent Application Laid-Open No. 5-335337).

[0011]

However, in the above-mentioned Japanese Patent Publication No. 6-60401, the pre-processing of the substrate is performed by 50 times.
The temperature is in the range of 0 to 600 ° C. If the temperature is exceeded, impurities may be mixed in and the substrate surface may be roughened.

In the above-mentioned Japanese Patent Application Laid-Open No. 5-335337, since a plurality of devices are used to remove impurities on a semiconductor thin film, the processes cannot be performed in the same device.
There is a possibility that impurities may be mixed in with the movement of the semiconductor thin film. In addition, there is a problem that a means for supplying light energy is required, and the manufacturing apparatus is increased in size.

The present invention has been made in view of the above problems, and has as its object to provide a method of manufacturing a semiconductor device capable of forming a film on an insulating film without contamination. .

[0014]

According to a method of manufacturing a semiconductor device according to the present invention, a semiconductor substrate having an insulating film formed thereon is heated in a furnace in a gas atmosphere containing chlorine to a temperature at which chloride reacts. And a step of forming a film on the insulating film in the furnace.

In this case, for example, the film is a polycrystalline silicon film or an amorphous silicon film.

In the present invention, the gas preferably contains hydrogen chloride gas or chlorine gas.

In the present invention, the step of heat-treating the semiconductor substrate preferably includes heating the insulating film to a temperature of 600 ° C. or higher.

Further, in the present invention, for example, the insulating film is a gate insulating film of a field effect transistor, and the film is a gate electrode film of the field effect transistor.

In the present invention, the semiconductor substrate on which the insulating film is formed is heat-treated in a furnace in a gas atmosphere containing chlorine to a temperature at which chloride reacts and is formed on the insulating film in the same furnace. By forming, the metal contaminants attached to the surface of the insulating film can be removed, and the film is continuously formed on the insulating film in the same furnace, so that re-adhesion of the metal contaminants can be prevented. .

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a semiconductor device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a graph showing manufacturing conditions of a method of manufacturing a semiconductor device according to an embodiment of the present invention. FIG. 1A shows a furnace temperature on a vertical axis, a time on a horizontal axis showing manufacturing conditions of a silicon film, (B) indicates the furnace pressure on the vertical axis, the time on the horizontal axis indicates the manufacturing conditions of the silicon film, and (c) indicates the gas flow rate on the vertical axis and the time on the horizontal axis indicates the manufacturing conditions of the silicon film.

In the method of manufacturing a semiconductor device according to this embodiment, first, a silicon oxide film is formed on a surface of a semiconductor substrate made of silicon as an insulating film serving as a gate insulating film. This semiconductor substrate is introduced into a low-pressure vapor deposition furnace for forming a silicon film. At this time, the temperature in the furnace of the reduced pressure vapor phase growth furnace for forming a silicon film is about 300 ° C. Note that the reduced-pressure vapor deposition furnace for forming a silicon film has a furnace temperature of 300
C. to 900.degree. C. and the furnace pressure at atmospheric pressure (76
From 0 Torr) to 0.2 Torr, the flow rate of the gas flowing into the furnace can be controlled in the range of 0 to 10 liters / minute, and these variables (furnace temperature, furnace pressure, gas flow rate) can be controlled by a computer. ) Can be programmed to change in any combination and any number of steps.

Next, after the semiconductor substrate is introduced into the furnace, time t
_{From 0} to t ₁ , as shown in FIG. 1C, while the nitrogen gas is being flowed into the furnace at a flow rate of 10 liter / min, the process waits for the temperature of the semiconductor substrate to stabilize.

Next, from time t ₁ to time t ₂ , FIG.
As shown in FIG. 1 (c), the flow rate of the nitrogen gas is set to 1 liter / minute, and at the same time, as shown in FIG.
The temperature is raised to 00 ° C., and the furnace pressure is changed to 10 Torr as shown in FIG.

Next, from time t ₂ to time t ₃ , as shown in FIG.
1 gas was introduced into the furnace at a flow rate of 1 liter / min.
As shown in (a) and (b), the furnace temperature and the furnace pressure are maintained. While this HCl gas is flowing,
Reacting metallic contaminants having adhered to the surface of the silicon oxide film on the semiconductor substrate between the time t ₂ of t ₃ is the HCl gas, the metal contaminants are removed by it to the chloride, which is vaporized . In particular, when the metal contaminant is Fe, it is removed by a reaction formula as shown in the following chemical formula 1.

[0025]

Embedded image Fe + 2HCl → FeCl ₂ + H ₂

Next, between time t ₃ and time t ₄ , as shown in FIG. 1C, the flow of HCl gas is stopped, and at the same time, nitrogen gas is flowed into the furnace at a flow rate of 0.1 liter / minute. Let it. As shown in FIG. 1A, the furnace temperature is changed from 800 ° C. to 500 ° C., and as shown in FIG. 1B, the pressure is changed from 10 Torr to 1 Torr.

Next, from time t ₄ to t ₅ , as shown in FIG. 1C, while maintaining the furnace temperature and the furnace pressure, silane gas (SiH ₄ ) was supplied at a rate of 0.1 liter / minute. Flow into the furnace at a flow rate. Between t ₅ the silane gas from the time t ₄ when being caused to flow into the furnace, the amorphous silicon film as a gate electrode film grows pressure chemical vapor over the silicon oxide film. The thickness of this amorphous silicon film is, for example, 1000 to 3000.
Å.

Next, at time t ₅ , the gas flowing into the furnace is changed from silane gas to nitrogen gas, and the flow rate is also set to 10 liter / minute. Between the time t ₅ the t _6, as shown in FIG. 1 (b), the reactor pressure was increased from 1Torr to 760 Torr, as shown in FIG. 1 (a), up to 300 ° C. The furnace temperature from 500 ° C. Lower. Next, the semiconductor substrate is taken out of the vapor phase growth furnace. Thus, an amorphous silicon film is formed as a gate electrode film on the gate insulating film.

In this embodiment, the semiconductor substrate is not exposed to the air within the time from the step of forming the gate insulating film (silicon oxide film) to the step of forming the gate electrode film (amorphous silicon film). The heat treatment and the reduced pressure vapor phase growth are continuously performed without contacting any other substance. This allows
Metal contaminants attached to the surface of the gate insulating film can be removed, and the gate electrode film can be continuously formed on the gate insulating film in a vapor phase growth furnace. Reattachment of the substance can be prevented. In addition, the heat treatment of the insulating film in an atmosphere containing chlorine can remove metal contaminants attached on the gate insulating film and prevent the gate insulating film from malfunctioning,
And the effect of improving the yield of the semiconductor device can be obtained.

In this embodiment, HCl gas is used as the chlorine-containing gas. However, the present invention is not particularly limited to this, and a halogen-based gas such as Cl ₂ may be used. Further, the heating in the atmosphere of the gas containing chlorine was performed at 800 ° C., but any temperature may be used as long as it can react with chloride. Generally, the temperature at which this chloride can react is generated. It is about 600 ° C. or higher.

Although an amorphous silicon film is formed, the present invention is not limited to this, and a gate electrode material for a FET such as a polycrystalline silicon film or a silicon-germanium compound may be deposited. In the present embodiment, it goes without saying that the deposition temperature of the silicon film or the introduction and withdrawal temperature of the semiconductor substrate is not limited to special conditions.

[0032]

As described in detail above, in the present invention,
The semiconductor substrate on which the insulating film is formed is heated in a furnace in a gas atmosphere containing chlorine to a temperature at which chloride reacts,
By forming a film on the insulating film in the same furnace, metal contaminants attached to the insulating film surface can be removed,
Since the film is continuously formed on the insulating film in the same furnace, reattachment of metal contaminants can be prevented.

[Brief description of the drawings]

FIG. 1 is a graph showing the manufacturing conditions of a method for manufacturing a semiconductor device according to an embodiment of the present invention. FIG. 1 (a) shows the furnace temperature on the vertical axis and the time on the horizontal axis showing the silicon film manufacturing conditions. ,
(B) indicates the furnace pressure on the vertical axis, the time on the horizontal axis indicates the manufacturing conditions of the silicon film, and (c) indicates the gas flow rate on the vertical axis and the time on the horizontal axis indicates the manufacturing conditions of the silicon film.

FIG. 2 is a graph showing manufacturing conditions in a conventional process of forming a silicon film on a silicon oxide film. FIG. 2 (a) shows the furnace temperature on the vertical axis, and the time on the horizontal axis. (B) shows the furnace pressure on the vertical axis, the time on the horizontal axis shows the manufacturing conditions of the silicon film, and (c) shows the gas flow rate on the vertical axis and the time on the horizontal axis shows the manufacturing conditions of the silicon film. .

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 AA07 BA29 BA30 BB03 DA03 FA10 JA10 LA15 5F040 DA00 DC01 EC04 EC07 FC00 5F045 AA06 AB03 AB04 AC01 AC13 AC15 AD07 AD08 AD09 AD10 AD11 AD12 AE21 AE23 AE25 AF01 BB14 HA06 HA23

Claims (6)

[Claims] 1. A step of heating a semiconductor substrate on which an insulating film is formed to a temperature at which chloride reacts and generates in a furnace in a gas atmosphere containing chlorine, and forming a film on the insulating film in the furnace. And a method of manufacturing a semiconductor device. 2. The method according to claim 1, wherein the film is a polycrystalline silicon film. 3. The method according to claim 1, wherein the film is an amorphous silicon film. 4. The gas according to claim 1, wherein the gas contains hydrogen chloride gas or chlorine gas.
13. The method for manufacturing a semiconductor device according to the above item. 5. The step of heating the semiconductor substrate,
5. The method according to claim 1, wherein the insulating film is heated at a temperature of 600 ° C. or higher. 6. 6. The semiconductor according to claim 1, wherein the insulating film is a gate insulating film of a field-effect transistor, and the film is a gate electrode film of the field-effect transistor. Device manufacturing method.