JP2003257966A - Method of forming thermal oxide film using high-speed temperature up-and-down furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a uniform oxide film in a plane of a substrate, in the formation of a thermal oxide film on a semiconductor substrate using a high-speed temperature up-and-down furnace. <P>SOLUTION: In the method of forming the thermal oxide film with a little variation in the temperature of the plane of the semiconductor substrate, the high-speed temperature up of the furnace is stopped at a prescribed temperature in order to reduce the variations in the temperature of the plane of the semiconductor substrate when the furnace is heated up, and a temperature stabilizing step for keeping the temperature of the furnace constant for a prescribed period of time is set up thereafter, and then the furnace is heated up at a prescribed low speed to an oxide film formation temperature. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thermal oxide film on a semiconductor substrate using a fast heating / cooling furnace.

[0002]

2. Description of the Related Art A thermal oxide film forming method using a conventional high-speed heating / cooling furnace will be described below with reference to the drawings.

FIG. 1 is a block diagram of a fast heating / cooling furnace. Reference numeral 1 is an outlet for cooling air in the furnace during high-speed cooling. 2 is a reaction tube. 3 is a thermocouple in the reaction tube. 4 is a boat. Reference numeral 5 is a cooling air outlet for high-speed cooling. 6
Is a heat retention jig. 7 is a cap of the reaction tube. Reference numeral 8 is a thermocouple of the heater section. 9 is a gas outlet. 10 is a heater. Reference numeral 11 is a semiconductor substrate.

The operation of the thermal oxide film forming apparatus configured as described above will be described below.

After inserting the boat of No. 4 having the semiconductor substrate of No. 11 into the reaction tube of No. 2, the temperature inside the furnace is stabilized for a predetermined time. This is step 1 in FIG. Next, by heating with a heater of 10, the temperature is rapidly raised at 30 ° C. to 100 ° C. per minute to 850 ° C. to 1000 ° C. which is the set temperature for oxide film formation. This is step 2 in FIG. Then 850 ℃ ~ 1
A gas is introduced from the gas outlet 9 to form a thermal oxide film on the semiconductor substrate 11 at the oxide film forming temperature set in the range of 000 ° C. This is step 3 in FIG. Next, the introduction of the gas from the gas outlet 9 is stopped, and the cooling air introduced from the cooling air outlet 5 is exhausted to the outside of the device through the cooling air exhaust outlet 1 and at a high speed of 30 ° C. or more per minute. The temperature is lowered. This is step 4 in FIG. Finally, the temperature inside the furnace is stabilized. This is step 5 in FIG.

As described above, the high-speed temperature raising / lowering furnace is a manufacturing apparatus that realizes high throughput by rapidly raising and lowering the temperature in the formation of a thermal oxide film, which is a method of manufacturing a semiconductor device.

[0007]

In the above structure, since the gas is introduced in a state where the temperature variation in the semiconductor substrate surface is large, it is possible to form a uniform thermal oxide film in the semiconductor substrate surface. There is a problem that cannot be done.

Further, when the temperature in the furnace is lowered after the gas introduction is stopped, a thermal oxide film is formed due to the residual gas. However, since the temperature within the substrate surface varies widely, a uniform thermal oxide film can be formed within the substrate surface. Can not.

In view of the above problems, the present invention is directed to a semiconductor substrate using a high-speed heating / cooling furnace for stably ensuring in-plane uniformity in forming a thermal oxide film on the semiconductor substrate using the high-speed heating / cooling furnace. The present invention provides a method for forming a thermal oxide film.

[0010]

In order to solve the above-mentioned problems, the following three methods are used as a method for forming a thermal oxide film on a semiconductor substrate using the fast heating / cooling furnace of the present invention. As a method for forming a thermal oxide film in a state where the temperature variation in the semiconductor substrate surface is small, one method is to perform high-speed heating at a temperature of 850 ° C. or less in order to reduce the temperature variation in the semiconductor substrate surface when the temperature is raised in the furnace. And a temperature stabilization step for keeping the temperature inside the furnace constant for 5 minutes or more, and then slowly increasing the temperature to the oxide film forming temperature at 1 ° C to 8 ° C per minute.

First, in order to reduce the temperature variation in the surface of the semiconductor substrate before further introducing a gas to form an oxide film, a temperature that keeps the furnace temperature constant for 5 minutes or more after reaching the oxide film formation temperature. Introducing gas after providing a stable step,
This is a method of forming an oxide film.

Further, even when the oxide film is formed by the residual gas after the gas introduction is stopped, in order to reduce the temperature variation in the surface of the semiconductor substrate, the temperature is lowered after the oxide film is formed for about 10 minutes at 1 ° C. to 4 ° C. per minute. This is a method in which the temperature is lowered at a low temperature at about 0 ° C., and after the oxide film formation by the residual gas is completed, the temperature is rapidly lowered.

According to the present invention, the temperature variation in the plane of the semiconductor substrate is reduced when gas is introduced. Further, it is possible to reduce the temperature variation in the surface of the semiconductor substrate even when the oxide film is formed by the residual gas after the gas introduction is stopped. As a result, it is possible to form a uniform thermal oxide film on the semiconductor substrate.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to the drawings.

The structure of the fast heating / cooling furnace is the same as that shown in FIG.
FIG. 3 shows the processing steps of the method for forming a thermal oxide film on a semiconductor substrate using the fast heating / cooling furnace according to the embodiment of the present invention. What corresponds to the first embodiment is shown in FIG. Steps 1 to 4. Step 1 is a step of stabilizing the temperature in the furnace. Step 2 is a high speed temperature raising step. Step 3 is a furnace temperature stabilization step. 4 is a low speed temperature raising step.

FIG. 4 shows the temperature characteristics in the furnace and the temperature distribution in the surface of the semiconductor substrate when the temperature is raised in the prior art.
FIG. 4 shows the temperature characteristics in the furnace and the in-plane temperature distribution of the semiconductor substrate at the time of temperature rise in the present embodiment.

As described above, according to this embodiment, as shown in FIG.
In step 2 of FIG. 3, after the temperature is rapidly raised to a temperature of 850 ° C. or lower, in step 3 of FIG. 3, the furnace temperature is kept constant for 5 minutes or more, and in step 4 of FIG. As shown in FIG.
The in-furnace temperature characteristic during temperature increase and the in-plane temperature distribution of the semiconductor substrate in the prior art shown in FIG. 5 become the in-furnace temperature characteristic during temperature increase and the in-plane temperature distribution of the semiconductor substrate in the present embodiment shown in FIG. The temperature variation in the plane of the semiconductor substrate can be reduced. According to the temperature characteristics in the furnace and the temperature distribution in the surface of the semiconductor substrate at the time of temperature rise in the conventional technique shown in FIG. Although there is a difference in film thickness, in the temperature characteristic in the furnace and the temperature distribution in the surface of the semiconductor substrate in the present embodiment shown in FIG. 5, the temperature difference between the substrate outer peripheral portion and the substrate central portion is small. The difference in oxide film thickness between the outer peripheral portion of the substrate and the central portion of the substrate becomes small.

Although FIG. 10 shows the relationship between the rate of temperature rise and the amount of overshoot, the amount of overshoot increases from around the rate of temperature rise of 8 ° C. From this example, the low temperature increase rate is set to 1 ° C to 8 ° C. In FIG. 4, overshoot occurs at the oxide film formation temperature.
In FIG. 5, overshooting occurs after high-speed heating, but at the oxide film forming temperature, the heating rate is 1 to 8
There is no overshoot because the temperature is slowly rising at ℃.

Further, step 2 in FIG. 3 of the present embodiment.
In the above, the reason why the high-speed temperature increase end temperature is set to 850 ° C. or lower is that the warp in the plane of the semiconductor substrate increases from around 850 ° C. when the high-speed temperature increase is performed. FIG. 6 shows the relationship between the high temperature rising temperature and the warp in the plane of the semiconductor substrate.

The second embodiment of the present invention will be described below.
A description will be given with reference to the drawings.

The structure of the fast heating / cooling furnace is the same as that shown in FIG.
FIG. 3 shows the processing steps of the method for forming a thermal oxide film on a semiconductor substrate using the fast heating / cooling furnace according to the embodiment of the present invention. What corresponds to the second embodiment is as follows. Steps 5 to 6. Step 5 is a step of stabilizing the temperature in the furnace at the oxide film forming temperature. Step 6 is an oxide film formation step.

FIG. 7 shows the temperature changes in the furnace and in the plane of the semiconductor substrate at the oxide film forming temperature in the second embodiment.

As described above, according to this embodiment, as shown in FIG.
In step 5, the temperature in the furnace is kept constant for 5 minutes or more at the oxide film forming temperature, so that the temperature variation in the surface of the semiconductor substrate can be increased before the gas is introduced and the oxide film is formed in step 6 in FIG. Is made smaller. In FIG. 7, when the gas is introduced according to the related art, the temperature of the outer peripheral portion of the substrate is high and the temperature of the central portion of the substrate is low, so that a difference in oxide film thickness between the outer peripheral portion of the substrate and the central portion of the substrate occurs. When the gas is introduced, the temperature difference between the outer peripheral portion of the substrate and the central portion of the substrate is small, so that the difference in oxide film thickness between the outer peripheral portion of the substrate and the central portion of the substrate is small.

The third embodiment of the present invention will be described below.
A description will be given with reference to the drawings.

The structure of the fast heating / cooling furnace is the same as that shown in FIG.
FIG. 3 shows the processing steps of the method for forming a thermal oxide film on a semiconductor substrate using the fast heating / cooling furnace according to the embodiment of the present invention. What corresponds to the third embodiment is as follows. Steps 7 to 8. Step 7 is a low temperature cooling step. Step 8 is a high temperature cooling step.

FIG. 8 shows the temperature characteristics in the furnace and the temperature distribution in the surface of the semiconductor substrate when the temperature is lowered in the prior art, and FIG. 9 is the temperature characteristics in the furnace and the semiconductor substrate surface when the temperature is lowered in the present embodiment. It shows the internal temperature distribution.

As described above, according to this embodiment, as shown in FIG.
Step 7 of 10 minutes, 1 ℃ ~ 4 ℃ per minute
By lowering the temperature at a low rate at a low speed and then rapidly lowering the temperature in step 8 of FIG. 3, the temperature characteristics in the furnace and the in-plane temperature distribution of the semiconductor substrate in the conventional technique shown in FIG. The in-furnace temperature characteristics and the in-plane temperature distribution of the semiconductor substrate are obtained, and a uniform in-plane temperature of the semiconductor substrate can be secured even when the oxide film is formed by the residual gas. In the temperature characteristics in the furnace and the in-plane temperature distribution of the semiconductor substrate in the conventional technique shown in FIG. 8, the temperature of the outer peripheral portion of the substrate is low and the temperature of the central portion of the substrate is high. There will be a difference in thickness,
In the temperature characteristics in the furnace and the temperature distribution in the surface of the semiconductor substrate at the time of temperature rise in the present embodiment shown in FIG. 9, since the temperature difference between the substrate outer peripheral portion and the substrate central portion is small, oxidation of the substrate outer peripheral portion and the substrate central portion is performed. The film thickness difference becomes small.

The reason why the slow cooling time is about 10 minutes is that the residual gas is exhausted in about 10 minutes and replaced with N ₂ as shown in FIGS. Further, the reason for setting the low temperature-decreasing rate to 1 to 4 ° C. is that, as shown in FIG. 11, when the temperature-decreasing rate is 4 ° C. or more, the temperature variation between the positions in the reaction tube is large, as shown in the temperature-decreasing rate and temperature distribution by position in the reaction tube. This is because the temperature variation of the semiconductor substrate increases depending on the reaction tube position, and the oxide film thickness variation of the semiconductor substrate increases depending on the reaction tube position.

Table 1 shows the oxide film thickness uniformity, which is the effect of the above-described three embodiments.

[0030]

[Table 1]

From Table 1, it is possible to form a uniform thermal oxide film in the surface of the semiconductor substrate by reducing the temperature variation in the surface of the semiconductor substrate, which is the effect of the present invention.

[0032]

As described above, according to the present invention, in order to reduce the temperature variation in the surface of the semiconductor substrate when the temperature inside the furnace is raised, the high-speed temperature rising is stopped at a temperature of 850 ° C. or lower, and the temperature inside the furnace is kept higher than 5 minutes. After providing the temperature stabilizing step for keeping the temperature constant, by slowly increasing the temperature to the oxide film forming temperature at about 1 ° C to 8 ° C per minute,
It is possible to reduce the temperature variation in the semiconductor substrate surface and form a uniform thermal oxide film in the semiconductor substrate surface.

Further, before the gas is introduced to form the oxide film, a temperature stabilization step for keeping the temperature in the furnace constant for 5 minutes or more after the temperature for forming the oxide film is provided, so that the in-plane temperature of the semiconductor substrate can be prevented from varying. The size can be reduced, and a uniform thermal oxide film can be formed within the surface of the semiconductor substrate.

Further, by lowering the temperature after the oxide film is formed at a low speed for about 10 minutes at a rate of 1 ° C. to 4 ° C. per minute and then at a high speed, even when the oxide film is formed by the residual gas after the gas introduction is stopped. Further, it is possible to reduce the variation in the temperature within the semiconductor substrate surface and form a uniform thermal oxide film within the semiconductor substrate surface.

[Brief description of drawings]

[Fig. 1] Block diagram of fast heating / cooling furnace

[Figure 2] Step diagram under conventional conditions

[Figure 3] Step diagram for improvement conditions

FIG. 4 is a diagram showing variations in temperature within a substrate surface during temperature increase under conventional conditions.

FIG. 5 is a diagram showing variations in temperature within the substrate surface when the temperature is raised under the improved conditions.

FIG. 6 is a diagram showing the temperature and the warp of the semiconductor substrate during high-speed temperature increase / decrease.

FIG. 7 is a diagram showing a temperature variation in a surface of a semiconductor substrate at a temperature of forming an oxide film.

FIG. 8 is a diagram showing variations in in-plane temperature of the semiconductor substrate when the temperature is lowered under the conventional conditions.

FIG. 9 is a diagram showing variations in the in-plane temperature of the semiconductor substrate when the temperature is lowered under the improved conditions.

FIG. 10 is a diagram showing a heating rate and an overshoot amount.

FIG. 11 is a diagram showing a temperature drop rate and a temperature difference for each position in the reaction tube.

[Explanation of symbols]

1 Cooling air exhaust port during high-speed cooling 2 reaction tubes 3 Thermocouple in the reaction tube 4 boats 5 Cooling air outlet for high-speed cooling 6 Heat insulation jig 7 Reaction tube cap 8 Thermocouple of heater part 9 gas outlet 10 heater 11 Semiconductor substrate

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tsutomu Nobuhara             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 5F058 BA06 BC02 BF52 BF62 BJ01

Claims (5)

[Claims] 1. The temperature rise in the furnace up to the oxide film formation temperature is carried out at a high speed up to a predetermined temperature, and after the furnace temperature is kept constant for a predetermined time, the temperature is slowly raised up to the oxide film formation temperature. A method for forming a thermal oxide film using a high-speed heating / cooling furnace. 2. A method for forming a thermal oxide film using the fast heating / cooling furnace according to claim 1, wherein the predetermined temperature is 850 ° C. or lower. Forming method. 3. The method for forming a thermal oxide film using the fast heating / cooling furnace according to claim 1, wherein the predetermined time for stabilizing the temperature inside the furnace is 5 minutes or more. Method for forming thermal oxide film using. 4. The method for forming a thermal oxide film using the high-speed heating / cooling furnace according to claim 1, wherein the low temperature-rising rate is 1 ° C. to 8 minutes per minute.
A method for forming a thermal oxide film using a high-speed heating / cooling furnace, which is characterized in that the temperature is about ℃. 5. A method for forming a thermal oxide film using the fast heating / cooling furnace according to claim 1, wherein the temperature inside the furnace is kept constant for a predetermined time after reaching the temperature for forming the thermal oxide film. A method for forming a thermal oxide film using a fast heating / cooling furnace, characterized in that a gas is then introduced to form the thermal oxide film.