JP2005243667A - Heat treatment equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide heat treatment equipment which heats the outer part of a testpiece by high-frequency induction heating while heating an inner part thereof by an infrared lamp, and can rapidly heat up an SiC substrate having a diameter of some inches or above to a high temperature as high as 1,200°C or above, while keeping the temperature evenly distributed in a plane by covering a testpiece and a testpiece stand with a shielding plate. <P>SOLUTION: The testpiece 12 is placed on the conductive testpiece stand 10 installed in a vacuum chamber 4 which can apply heat treatment in a vacuum or in various gas atmospheres. A high-frequency coil 7 is installed around the testpiece stand 10, and an infrared generator composed of an infrared lamp 1 and a rotary elliptical reflection mirror 2 is installed at one end side of an infrared introduction quartz pillar 3. On the upper side and/or lower side of the test piece 12, one or a plurality of such infrared introduction quartz pillars 3 are arranged. Inside the high-frequency coil 7, double quartz tubes 6 are installed, and cooling water can be caused to flow between the double quartz tubes 6. By allowing the cooling water to flow outside the infrared lamp 1 or by cooling the infrared lamp 1 by air cooling, heating by the infrared lamp 1 can be prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat treatment apparatus used in a manufacturing process that requires heat treatment at a high temperature for a short time, such as an activation heat treatment process after ion implantation of impurities into silicon carbide SiC.

In order to generate carriers in which impurities are activated after ion implantation of impurities such as phosphorus and nitrogen into a silicon carbide substrate, it is necessary to perform heat treatment at a high temperature of 1500 ° C. or higher. So far, a heat treatment method using a resistance heating furnace has been reported. However, the temperature rise time when raising the temperature to 1500 ° C. or higher is too long. Further, since the heat treatment takes about 30 minutes, Si evaporates from the SiC surface and the surface becomes uneven. Further, the impurities are evaporated together with Si, and the resistance value of the region into which the impurities are ion-implanted becomes high, and there is a problem that a normal SiC element cannot be manufactured. There is also a heat treatment using high-frequency heating, but this method has a problem in that temperature distribution is likely to occur because it is heated from the outer periphery. Furthermore, a rapid heat treatment apparatus using an infrared lamp and a heating method thereof are disclosed (for example, Non-Patent Document 1). In this method, the temperature can be raised to 1700 ° C. in 1 minute, and the evaporation of Si from the SiC surface can be suppressed. However, in this method, since heating is performed by converging infrared rays, the temperature can be increased to a high temperature in a short time, but only an SiC substrate having an area of about 1 cm ² can be heated. Therefore, it was not a device that could be used for mass production of SiC elements. Accordingly, there is a need for a heat treatment apparatus that can raise the temperature to a high temperature in a short time and reduce the temperature distribution even with a large area SiC substrate having a diameter of 2 inches or more.
Basics and applications of SiC devices, Kazuo Arai and Sadayoshi Yoshida, edited by Ohm P110

As described above, a heat treatment apparatus using a conventional infrared lamp cannot be used for mass production of SiC elements using a SiC substrate having a diameter of several inches or more. A heat treatment method using a high-frequency heating furnace has also been proposed, but in the case of high-frequency heating, since the outer periphery of the SiC substrate is heated, the temperature of the outer periphery is high and the center is low. Therefore, the temperature distribution becomes large, and there are portions where the impurities are activated and portions which are not activated in the SiC substrate. Finally, the in-plane non-uniformity of the electrical characteristics of the SiC element becomes large, which can be used for mass production. This is not possible, thus hindering the industrialization of SiC elements.
The present invention has been proposed in view of the above. In an SiC substrate having a diameter of several inches or more, the outside is heated by high frequency induction and the inside is heated by an infrared lamp, and at the same time, the sample and the sample stage are covered with a shielding plate. An object of the present invention is to provide a heat treatment apparatus excellent in high-speed temperature rise to a high temperature of 1200 ° C. or higher and in-plane uniformity of temperature. In addition, in the infrared lamp heating using the quartz column, when heated at a high temperature, there is a problem that impurities generated from the sample stage adhere to the quartz column and the infrared ray does not transmit.
In the present invention, in order to solve this problem, a quartz plate is placed between the sample or the sample stage and the quartz column to prevent impurities generated from the sample stage from adhering to the quartz column. It aims at providing the heat processing apparatus which infrared rays permeate | transmit. In addition, in the infrared lamp heating, as shown in FIG. 1A, the temperature at the center is high and the outer periphery is low. On the other hand, as shown in FIG. 1B, in the high frequency heating, there is a problem that the temperature of the outer peripheral portion is high and the center is low in order to mainly warm the outer peripheral portion of the sample. By using them simultaneously, the temperature distribution can be made uniform as shown in FIG.

  In order to solve the above problems, the heat treatment apparatus according to the first aspect of the present invention has a sample placed on a conductive sample stage provided in a vacuum chamber that can be heat-treated in vacuum or in various gas atmospheres. , A high-frequency coil around the sample stage, an infrared generator having an infrared lamp and a spheroid reflector at one end of the infrared-introduced quartz column, and the infrared-introduced quartz column on at least one of the upper side and the lower side of the sample One or a plurality of quartz tubes are arranged, and a double quartz tube is placed inside the high-frequency coil, and the cooling water can flow between the double quartz tubes. Heating by an infrared lamp can be prevented by adopting a structure in which cooling water can flow outside the lamp or a structure capable of air cooling.

The apparatus according to claim 2 is characterized in that, in the apparatus according to claim 1, a quartz plate is placed between the sample and the infrared-introduced quartz column.
The apparatus according to claim 3 is the apparatus according to claim 1 or 2, wherein the periphery of the sample and the sample stage is covered with a shielding plate.
The apparatus according to claim 4 is the apparatus according to any one of claims 1 to 3, wherein the periphery of the sample stage is covered with a conductive shielding plate having a gap of 1 mm to 30 mm. .
The apparatus according to claim 5 is the apparatus according to any one of claims 1 to 4, wherein either one or both of the sample stage and the shielding plate are tungsten, molybdenum, or tantalum. It is characterized by.

The apparatus according to claim 6 is the apparatus according to any one of claims 1 to 4, wherein one or both of the sample stage and the shielding plate is made of carbon, or the surface is covered with silicon carbide. It is characterized by being carbon.
The device according to claim 7 is the device according to any one of claims 1 to 6, wherein the frequency of the high frequency is 50 kHz or less.
The apparatus according to claim 8 is the apparatus according to any one of claims 1 to 7, wherein the distance between the end face of the quartz column and the sample can be changed between 0.5 mm and 20 mm. It is characterized by having.
The apparatus according to claim 9 is the apparatus according to any one of claims 1 to 8, wherein an infrared lamp or a high-frequency coil is used while measuring the temperature of the sample stage or sample with a pyrometer or thermocouple. And a device for controlling the temperature of the sample by controlling the voltage or current applied to the substrate.

The device according to claim 10 is the device according to any one of claims 1 to 9, characterized in that the quartz pillars are inclined.
An apparatus according to claim 11 is the apparatus according to any one of claims 1 to 10, wherein the temperature of the SiC substrate is raised from room temperature to 1200 ° C. or more in 10 seconds to 5 minutes and from 10 seconds. It is programmed to heat up to 1200 ° C. or lower in 10 seconds to 30 minutes after heating for 10 minutes.
The apparatus according to claim 12 is the apparatus according to claim 11, wherein the SiC substrate is heated in advance at 1200 ° C. or lower in advance, and then heated from room temperature to 1200 ° C. or higher in 10 seconds to 5 minutes, It is programmed to be heated to 10O <0> C or lower in 10 seconds to 30 minutes after heating for 10 seconds to 10 minutes.

Since this invention consists of an above-described structure, there exists an effect which is demonstrated below.
In the heat treatment apparatus according to the first aspect of the present invention, a sample is placed on a conductive sample stage provided in a vacuum chamber that can be heat-treated in vacuum or in various gas atmospheres, and around the sample stage. There is a high-frequency coil, and an infrared ray generator and a spheroidal mirror are provided at one end of the infrared-introduced quartz column, and one or more infrared-introduced quartz columns are arranged on at least one of the upper or lower side of the sample. In addition, a double quartz tube is placed inside the high frequency coil so that the cooling water can flow between the double quartz tubes. Further, the cooling water is placed outside the infrared lamp. By adopting a structure that can be flowed or capable of air cooling, heating by an infrared lamp is prevented, and destruction of the apparatus is prevented, and the temperature can be raised from room temperature to 1800 ° C. in 1 minute, ± 50 There is an effect that was able to achieve the temperature distribution of.

In the invention according to claim 2, in the apparatus according to claim 1, since the quartz plate is placed between the sample and the infrared introducing quartz column, impurities may adhere to the end face of the infrared introducing quartz column. By replacing the quartz plate, there is an effect that infrared irradiation can be performed for a long time without replacing the infrared-introducing quartz column.
According to a third aspect of the present invention, in the apparatus according to the first or second aspect, the sample and the sample stage are covered with a shielding plate so that the temperature can be raised to a high temperature of 1200 ° C. or higher in a short time. There is an effect.
According to a fourth aspect of the present invention, in the apparatus according to any one of the first to third aspects, the periphery of the sample stage is covered with a conductive shielding plate with a gap of 1 mm to 30 mm, so that induction by high frequency is performed. There is an effect that heating is prevented and an increase in the temperature of the double quartz tube due to an increase in the temperature of the conductive shielding plate can be suppressed.
In the invention according to claim 5, in the apparatus according to any one of claims 1 to 4, either one or both of the sample table and the shielding plate are any one of tungsten, molybdenum, and tantalum. Therefore, there is an effect that the shape can be maintained without melting the shielding plate even at a high temperature.

According to a sixth aspect of the present invention, in the apparatus according to any one of the first to fourth aspects, the material of either or both of the sample stage and the shielding plate is covered with carbon, or the surface is covered with silicon carbide. By using carbon, there is an effect that the heat treatment can be stably performed even at a high temperature.
According to a seventh aspect of the present invention, in the apparatus according to any one of the first to sixth aspects, when the high frequency is 50 kHz or less, the high frequency enters the inside of the sample and is close to the center of the sample. The temperature can be raised and the temperature distribution can be reduced.
According to an eighth aspect of the present invention, in the apparatus according to any one of the first to seventh aspects, a structure capable of changing the distance between the end face of the quartz column and the sample between 0.5 mm and 20 mm. By providing, there exists an effect which could raise the heating effect of infrared rays.
According to a ninth aspect of the present invention, in the apparatus according to any one of the first to eighth aspects, an infrared lamp or a high-frequency coil is used while measuring the temperature of a sample stage or sample with a pyrometer or a thermocouple. By providing a device for controlling the temperature of the sample by controlling the voltage or current applied to the substrate, there is an effect that the temperature can be controlled by controlling the output of the infrared lamp and the high frequency.

In the invention according to claim 10, in the apparatus according to any one of claims 1 to 9, it is possible to arrange more quartz pillars by arranging the quartz pillars to be inclined, and infrared rays can be arranged. There is an effect that the irradiation area of can be increased.
According to an eleventh aspect of the present invention, in the apparatus according to any one of the first to tenth aspects, the SiC substrate is heated from room temperature to 1200 ° C. or more in 10 seconds to 5 minutes, and from 10 seconds. SiC substrate in which impurities such as phosphorus, nitrogen, aluminum, and boron are ion-implanted by being programmed to be heated to 1200 ° C. or lower in 10 seconds to 30 minutes after being heated for 10 minutes In addition, the resistance value of the SiC substrate can be sufficiently reduced, and at the same time, Si can be prevented from evaporating from the SiC substrate to become uneven, and an excellent SiC element can be produced.
In the invention according to claim 12, in the apparatus according to claim 11, after the SiC substrate is heated in advance at 1200 ° C. or less, the temperature is raised from room temperature to 1200 ° C. or more in 10 seconds to 5 minutes, After being heated for 10 seconds to 10 minutes, it is programmed to drop to 1200 ° C. or less in 10 seconds to 30 minutes, thereby implanting impurities such as phosphorus, nitrogen, aluminum, boron, etc. In addition, the resistance value of the SiC substrate can be sufficiently lowered, and at the same time, Si can be prevented from evaporating from the SiC substrate to become uneven, thereby producing an excellent SiC element.

Embodiments of the present invention will be described below with reference to examples shown in the drawings.
FIG. 1 is an explanatory diagram of temperature distribution by infrared and high-frequency heating, A is a temperature distribution of only infrared overheating, B is a temperature distribution of only high-frequency heating, and C is a temperature when both infrared heating and high-frequency heating are used. Show the distribution. FIG. 2 is a schematic sectional view of the heat treatment apparatus of the present invention. FIG. 3 is a diagram showing an example of the structure of the shielding plate. The material used is tantalum, but it may be tungsten, molybdenum, carbon, or carbon covered with SiC. FIG. 4 shows various arrangements of infrared lamps, and at least one infrared lamp is provided on at least one of the top and bottom of the sample stage. FIG. 5 is a graph showing a temperature rise result using only high-frequency heating in a 2-inch diameter substrate, where the solid line indicates the temperature at the center and the dotted line indicates the temperature at the outer periphery. FIG. 6 is a graph showing the temperature rise results using both infrared heating and high frequency heating on a 2 inch diameter substrate. Up to about 50 seconds, only infrared heating results are obtained, and thereafter both heating times are obtained. The law is used. The solid line indicates the temperature at the center and the dotted line indicates the temperature at the outer periphery.

  Infrared rays generated by the infrared lamp 1 are collected by the spheroid reflecting mirror 2, transmitted through the infrared-introduced quartz column 3, and irradiated from the end surface of the quartz column 3 to the sample 12 and the sample stage 10. The outer surface of the spheroid reflecting mirror 2 is constituted by a hollow body, and has an inlet 18 and an outlet 19 for cooling water, and can be cooled with water. This water cooling may be a structure capable of air cooling. The sample stage 10 needs to be formed of a conductive material. In the present invention, a refractory metal such as tungsten, molybdenum, or tantalum is used so as to withstand use at high temperatures. Or remove nitrogen, boron, aluminum, and phosphorus as much as possible from metal substrates such as titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and N-type and P-type impurities. High purity carbon or carbon coated with SiC is used.

  The sample 12 such as the SiC substrate is heated by heat conduction from the sample table 10 heated by infrared rays. Further, the sample stage 10 is warmed by induction heating by high frequency applied to the high frequency coil 7 from the high frequency oscillator, and the sample 12 is heated by heat conduction. When the sample 12 is conductive, the sample 12 itself is also warmed by induction heating with high frequency. Further, a shielding plate 11 is provided to suppress heat dissipation. When the shielding plate 11 is made of a conductive material, it generates heat by itself, like the sample table 10, and heats the periphery of the sample table 10 such as the quartz tube 6 for cooling water, and finally Leads to dissolution, cracking and other destruction. Therefore, in the same manner as the sample stage 10, when a high melting point metal such as tungsten, molybdenum, tantalum or the like, high-purity carbon, or carbon coated with SiC is used, a gap is formed as shown in FIG. It is necessary to prevent induced current from flowing by providing 20. In the present invention, a gap of 4 mm is provided. Naturally, if the gap is increased, the induced current is less likely to flow, but the shielding effect is weakened. Therefore, the gap should be set to 1 mm or more so that the shielding effect is not lost. The shielding plate 11 may be provided with a lid 22 in which a hole 21 for the infrared introducing quartz column 3 is opened.

  In order to maximize the effect of infrared irradiation, the quartz column 3 is moved up and down by the infrared-introduced quartz column up-and-down mechanism 9 so that the temperature rise rate is as fast as possible and the temperature distribution becomes small. In addition, if the end face of the infrared-introduced quartz column 3 is soiled, infrared rays are not transmitted and the temperature does not increase. This prevents it from adhering to the end face of the product and getting dirty. Since the heat treatment is performed in a vacuum or in various atmospheres such as argon, nitrogen, helium, and hydrogen, the heat treatment portion of the apparatus is provided in the vacuum chamber 4. A vacuum exhaust port 8 and a gas introduction port 16 for connection to a vacuum pump are provided.

  In order to prevent the temperature in the vicinity of the sample stage 10 from becoming too high and destroying the apparatus, a double quartz tube 6 and a cooling water tube 5 are provided outside the shielding plate 11 for flowing cooling water. Yes. The temperature of the sample is measured with a thermocouple and an infrared temperature sensor, and the temperature can be controlled. A temperature sensor outlet 14 for passing a lead wire of the thermocouple and a temperature sensor port 15 for an infrared temperature sensor are provided. In this embodiment, one infrared ray generator is provided at the top and bottom, but as shown in FIGS. 4 (1) and (2), two to three only from the bottom, and only from the top (3) Also, various structures such as two pieces each on the top and bottom (4), two pieces on the bottom, one piece on the top (5), and three pieces on the top and bottom (6) are possible. As a result, when the SiC substrate becomes larger, it is possible to increase the infrared irradiation area by increasing the number of infrared-introducing quartz pillars 3. Further, for example, the sample 12 may be arranged only on the top or only on the bottom in accordance with an actual use method such as making it easy to take out the sample 12.

  5 and 6 show the results of heating experiments on a 2 inch diameter SiC substrate. The output of the infrared lamp was 100 V, 30 A (3 KW), the high frequency output was 14688 W, and the frequency was 25.5 KHz. As for the atmosphere of the heat treatment, first, a turbo molecular pump was used to draw the inside of the vacuum chamber to about 0.1 Pascal, and then argon gas was flowed at about 1 L / min. The temperature is measured by an infrared temperature sensor 15 attached to the sample stage 12. First, when heated only by high frequency (FIG. 5), the temperature of the outer peripheral portion is high, the central portion is low, and the maximum temperature is about 1750 ° C. The activation heat treatment temperature of impurities that become P-type such as aluminum or boron with respect to SiC needs to be about 1800 ° C., and 1750 ° C. is insufficient. Further, the temperature difference between the outer peripheral portion and the central portion is about 300 ° C., the temperature distribution is very large, and the electrical characteristics of the SiC element vary greatly, so that it cannot be used for actual mass production.

On the other hand, the case of only infrared lamp heating is shown in 30 seconds or less in FIG. The maximum temperature is about 1000 ° C., which is insufficient for the activation heat treatment of the impurities ion-implanted into the SiC substrate. Moreover, unlike the case of high frequency heating, the center part is high and the outer peripheral part is low. The temperature difference between the central part and the outer peripheral part is about 600 ° C., and the electrical characteristics of the SiC element change greatly, so that it cannot be used during mass production. When high-frequency heating is started after holding at 1000 ° C. or lower for 30 seconds, the temperature rises rapidly and reaches 1800 ° C. or higher in 40 seconds. The activation heat treatment temperature of impurities on the SiC substrate could reach a sufficiently high temperature. After the heat treatment is completed, the temperature is 1200 ° C. or less in about 10 seconds, and there is almost no evaporation of Si from the SiC surface, and the SiC surface is suppressed from becoming uneven. The unevenness of the surface of the SiC substrate measured with an atomic force microscope was almost the same as that before the heat treatment, and it was confirmed that the surface was sufficiently flat. If the unevenness is large, it becomes a defect and deteriorates the electrical characteristics such as the breakdown voltage of the SiC element, but such deterioration was not observed in the product of the present invention. Further, the temperature difference between the outer peripheral portion and the central portion at the time of heat treatment at 1800 ° C. is 44 ° C., which is very small and does not affect the in-plane uniformity of the electrical characteristics of the SiC element heat-treated at the outer peripheral portion and the central portion. Sufficient use is possible even during mass production.
In addition, although the SiC substrate was demonstrated as an example of a sample, it is not limited to a SiC substrate.

It is explanatory drawing of temperature distribution. It is a cross-sectional schematic diagram of this invention heat processing apparatus. It is a figure which shows an example of the structure of a shielding board. The layout of an infrared lamp is shown. It is a graph which shows the temperature rising measurement result using only high frequency heating in a 2 inch diameter substrate. It is a graph which shows the temperature rising measurement result using both infrared heating and high frequency heating in a 2 inch diameter board | substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Infrared lamp 2 Rotating ellipsoidal reflector 3 Infrared introduction quartz pillar 4 Vacuum chamber 5 Cooling water pipe 6 Quartz tube 7 High frequency coil 8 Vacuum exhaust port 9 Infrared introduction quartz pillar up-and-down mechanism 10 Sample stand 11 Shielding plate 12 Sample 13 Quartz plate 14 Temperature sensor Extraction port 15 Infrared temperature sensor port 16 Gas introduction port 17 Gas exhaust port 18 Inlet port 19 Outlet port 20 Clearance

Claims (12)

  A sample is placed on a conductive sample stage provided in a vacuum chamber that can be heat-treated in vacuum or in various gas atmospheres, and there is a high-frequency coil around the sample stage. An infrared generator having an infrared lamp and a spheroid reflector, and one or more infrared introduction quartz columns are arranged on at least one of the upper side and the lower side of the sample, and a double quartz tube is provided inside the high frequency coil. It has a structure that allows cooling water to flow between the double quartz tubes, and has a structure that allows cooling water to flow outside the infrared lamp, or a structure that allows air cooling. A heat treatment apparatus characterized in that heating by an infrared lamp can be prevented.   2. The heat treatment apparatus according to claim 1, wherein a quartz plate is placed between the sample and the infrared-introduced quartz column.   3. The heat treatment apparatus according to claim 1, wherein the periphery of the sample and the sample stage is covered with a shielding plate.   4. The heat treatment apparatus according to claim 1, wherein the periphery of the sample stage is covered with a conductive shielding plate having a gap of 1 mm to 30 mm.   5. The heat treatment apparatus according to claim 1, wherein one or both of the sample stage and the shielding plate are tungsten, molybdenum, or tantalum.   5. The apparatus according to claim 1, wherein the material of either or both of the sample stage and the shielding plate is carbon, or carbon whose surface is covered with silicon carbide. Heat treatment equipment.   The heat treatment apparatus according to any one of claims 1 to 6, wherein the high frequency is 50 kHz or less.   8. The apparatus according to claim 1, further comprising a structure capable of changing a distance between the end face of the quartz column and the sample between 0.5 mm and 20 mm. Heat treatment equipment.   9. The apparatus according to claim 1, wherein a voltage or a current value applied to the infrared lamp or the high-frequency coil is measured while measuring the temperature of the sample stage or the sample with a pyrometer or a thermocouple. A heat treatment apparatus comprising a device for controlling the temperature of a sample by controlling.   The heat treatment apparatus according to any one of claims 1 to 9, wherein the quartz column is disposed so as to be inclined.   The apparatus according to any one of claims 1 to 10, wherein the SiC substrate is heated from room temperature to 1200 ° C or higher in 10 seconds to 5 minutes, heated from 10 seconds to 10 minutes, and then from 10 seconds. A heat treatment apparatus programmed to drop to 1200 ° C. or lower in 30 minutes. In the apparatus of Claim 11, after heating a SiC substrate previously at 1200 degrees C or less, after heating up from room temperature to 1200 degrees C or more in 10 seconds to 5 minutes, and heating from 10 seconds to 10 minutes, A heat treatment apparatus programmed to drop to 1200 ° C. or lower in 10 seconds to 30 minutes.

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