JP2002184712A - Silicon carbide semiconductor manufacturing apparatus and method of manufacturing silicon carbide semiconductor using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon carbide semiconductor manufacturing apparatus that can uniformly heat the whole body of a silicon carbide substrate. SOLUTION: A top lamp 3 is positioned above a wafer stage 6 on which the SiC substrate 1 is mounted and side lamps 4 are arranged at regular intervals so as to surround the state 6. In a housing 5 to which the top and side lamps 3 and 4 are fixed, passages 5a are extended toward the stage 6 from the top lamp 3 or side lamps 4 and the internal walls of the passages 5a are constructed in mirror structures. Consequently, the light rays emitted from the top lamp 3 or side lamps 4 are reflected by the internal walls of the passages 5a and uniformly projected upon the SiC substrate 1 mounted on the wafer stage 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a semiconductor manufacturing device made of silicon carbide (hereinafter referred to as SiC) and a silicon carbide semiconductor manufacturing method using the device.

[0001]

2. Description of the Related Art Impurity layers are formed in SiC by ion implantation and heat treatment for activating the implanted ions. In SiC, since the p-type impurity is hard to be activated by the heat treatment, the activation rate of the p-type impurity is improved by increasing the heat treatment temperature for activation.

[0002]

For example, in order to facilitate formation of an epitaxial film (hereinafter referred to as an epi film), a wafer having an off-angle is used, and after performing an activation heat treatment at 1600 ° C., the epitaxial film is formed. AF on the surface of the formed impurity layer
Observation with M confirmed that step-like surface roughness had occurred. When the magnitude of the surface roughness was examined, the surface roughness Ra was 9.5 nm.

[0003] Such surface roughness is considered to be caused by migration that occurs during activation heat treatment. That is, in the case of a wafer having an off-angle, there are fine steps on the surface, and therefore, activation heat treatment (particularly,
Activation heat treatment for p-type impurities requiring high temperature heat treatment)
In this case, Si escape occurs at the edge portion of the most energetically unstable step, migration occurs due to the Si escape, and the migrated atoms are recrystallized while forming a stable (0001) plane. As a result, surface roughness occurs.

[0004] It was also confirmed that a carbonized layer was formed on the surface of the epi layer. This is considered to be due to the Si-extraction from the surface of the epitaxial film caused by the high temperature of the activation heat treatment, resulting in carbon-rich formation.

[0005] In order to suppress the formation of a carbonized film due to such migration or Si loss, a method of lowering the heat treatment temperature or a method of shortening the heat treatment time so as not to give time for causing migration is considered.

However, since the heat treatment temperature required for activating the p-type impurity is higher than the migration occurrence temperature (the activation heat treatment temperature is 1500 ° C. or higher, the migration occurrence temperature is 1420 ° C.) The method of lowering the heat treatment temperature cannot be selected.

Therefore, from the viewpoint of simultaneously improving the activation rate of the p-type impurity and suppressing the surface roughness, a method of shortening the heat treatment time so as not to give time for causing migration is selected.

Various studies have been made on such a method. First, when a conventional heat treatment program was analyzed, the rate of temperature rise during heat treatment was as slow as 20 ° C./min.
The time during which the temperature is higher than the temperature at which migration occurs (1420 ° C.) is sufficiently long. Therefore, it is considered that this causes a large surface roughness as described above. For this reason, the activation heat treatment was performed by increasing the temperature raising rate to 150 ° C./min. In this case, the same result as described above was obtained.

Therefore, a lamp annealing apparatus (for example, a heating rate of 350 ° C./min.)
), The activation heat treatment was performed. In other words, by using the lamp annealing device, the time during which the heat treatment at a temperature higher than the temperature at which migration occurs is shortened. As a result, the surface roughness Ra could be reduced until Ra = 3.4 nm.

However, even when performing an activation heat treatment using a lamp annealing apparatus, there is a possibility that the entire wafer cannot be heated uniformly with one lamp, and this poses a problem especially when the diameter of the wafer is increased.

In view of the above, it is an object of the present invention to provide a silicon carbide semiconductor manufacturing apparatus capable of uniformly heating an entire silicon carbide substrate and a method for manufacturing a silicon carbide semiconductor using the apparatus.

[0012]

To achieve the above object, according to the first aspect of the present invention, a top lamp (3) disposed above a wafer stage (6) on which a silicon carbide substrate (1) is mounted. ) And a side lamp (4) arranged so as to surround the periphery of the wafer stage. The top lamp and the side lamp are configured to irradiate light to a silicon carbide substrate arranged on the wafer stage. It is characterized by having. With such a configuration, the activation heat treatment time can be reduced, and the entire silicon carbide substrate can be uniformly heated.

According to the second aspect of the present invention, the top lamp and the side lamp are arranged in the housing (5), and the housing has a passage extending from the top lamp or the side lamp toward the wafer stage. 5
a), wherein the inner wall of the passage has a mirror structure for reflecting light emitted by the top lamp or the side lamp. With such a configuration, the silicon carbide substrate can be uniformly irradiated with light,
The silicon carbide substrate can be heated uniformly.

According to a third aspect of the present invention, there is provided a cooling means (7) for cooling the wafer stage, and the cooling means cools the silicon carbide substrate disposed on the wafer stage. It is characterized by having.
The silicon carbide substrate has the front side (the side on which the epi film is formed) directed to the wafer stage side.
Therefore, by cooling the wafer stage by the cooling means, the front side of the silicon carbide substrate can be cooled, and surface roughness can be suppressed.

[0015] As described in claim 4, a spherical lamp can be used as the side lamp, and the side lamp can be formed by arranging the spherical lamps at equal intervals. Also, as a side lamp, at least two lamps (1) having an arc shape are used as side lamps.
1) can also be used. In this case, the temperature distribution in the plane of the silicon carbide substrate can be further reduced.

[0016] The inventions described in claims 6 to 9 correspond to claim 1.
And a method for manufacturing a silicon carbide semiconductor using the silicon carbide semiconductor manufacturing apparatus according to any one of (1) to (5).

According to the present invention, the surface of the silicon carbide substrate on which the epi film is formed faces the wafer stage, and the activation of impurities is performed using a top lamp and a side lamp. It is characterized by heating to a temperature. By irradiating the back surface of the silicon carbide substrate on which the epi film is not formed with the light of the lamp, the surface of the epi film can be prevented from being roughened.

In the invention according to claim 7, in the heating step, a first heating step using only a side lamp and a second heating step using a side lamp and a top lamp are performed, and the first heating step is performed. A second heating step is performed after the step. By doing so, migration can be prevented from occurring on the surface of the epi film, and surface roughness can be suppressed.

According to the present invention, a cap layer is formed on the surface of the silicon carbide substrate on which the epi layer is formed, and then the silicon carbide substrate is mounted on a wafer stage. I have. By covering the surface of the epi film with the cap layer in this manner, it is possible to prevent migration from occurring on the surface of the epi film and to suppress surface roughness.

According to a ninth aspect of the present invention, after forming a light absorbing layer on the back surface of the silicon carbide substrate on which the epi layer is not formed, the silicon carbide substrate is mounted on a wafer stage. Features. By forming the light absorbing layer on the back surface of the silicon carbide substrate, the rate of temperature rise can be improved, and the activation heat treatment time can be further reduced.

Note that the reference numerals in parentheses of the above means indicate the correspondence with specific means described in the embodiments described later.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a schematic diagram of a lamp annealing apparatus as an SiC semiconductor manufacturing apparatus used in one embodiment of the present invention. In addition, FIG.
FIG. Hereinafter, the configuration of the lamp annealing apparatus will be described with reference to these drawings.

The lamp annealing apparatus shown in FIG. 1 is arranged such that the vertical direction on the paper coincides with the vertical direction. This lamp annealing apparatus is configured to include a case portion 2 that forms a room in which a SiC substrate 1 is housed, and a housing portion 5 in which a plurality of lamps 3 and 4 are installed.

The case section 2 is provided with a wafer stage 6 on which the SiC substrate 1 is mounted. The wafer stage 6 has a cooler 7 composed of, for example, a cryopump.
And a He gas from a gas supply source 8. With these configurations, when lamp annealing the SiC substrate 1, the cooling gas supplied from the cooler 7 can cool the SiC substrate 1 via the wafer stage 6, and the H gas supplied from the gas supply source 8 can be used.
Uniform cooling can be performed with the assistance of e-gas.

On the other hand, the housing 5 is provided with a plurality of lamps 3 and 4. As the plurality of lamps 3 and 4, for example, halogen lamps, xenon lamps, and infrared lamps are used. The plurality of lamps 3 and 4 are fixed to the housing 5 via the reflector 9. Specifically, one lamp 3 is arranged at a position of the housing 5 located above the wafer stage 6, and four lamps 4 are arranged at equal intervals around the wafer stage 6 around the wafer stage 6. They are arranged at equal intervals. Hereinafter, the lamp 3 arranged above the wafer stage 6 is referred to as a top lamp,
Is also referred to as a side lamp.

The housing 5 has a passage 5a extending from the position where the lamps 3 and 4 are arranged to the wafer stage 6 side. The inner wall of the passage 5a has a mirror structure capable of guiding the light of the lamps 3 and 4, and the light emitted by each lamp 3 and 4 is reflected on the inner wall of the passage 5a.
The windows 5b are formed so as to have an area that can irradiate one surface of the SiC substrate 1. It is possible to uniformly heat one surface of the SiC substrate 1 by the collected light.

Next, an activation heat treatment method using the lamp annealing apparatus having the above configuration will be described with reference to FIG.

First, n⁺N for the mold substrate 1a^-Type epi film
1b and n^-Impurities in the epitaxial film 1b
For example, it is formed by ion implantation of a p-type impurity.
An SiC substrate 1 is prepared. Then, this SiC substrate 1 is
It is mounted on the wafer stage 6. At this time, the SiC substrate 1
Among n^-The surface on which the type epi film 1b is formed is c
It should be directed to the eha stage 6 side. That is,
N of the SiC substrate 1 ^-Type epi film 1b is not formed
The other side, that is, n⁺The back side which is the mold substrate 1a side is exposed.
So that

Subsequently, the head lamp 3 and the side lamp 4 are turned on. As a result, light emitted from each of the lamps 3 and 4 is reflected on the inner wall surface of the passage 5a, bundled at the upper part of the wafer stage 6, and directed toward the back surface of the SiC substrate 1 through the window 5b on the side stage 6. Irradiated. For this reason, the temperature on the back surface side of the SiC substrate 1 increases at a high temperature increasing rate.

At this time, in the case of lamp heating, the temperature of the portion irradiated with light is the highest, but the SiC
Because of its good heat conduction, heat is easily transmitted from the back side to the front side. For this reason, even if the surface side of the SiC substrate 1 into which the impurities are implanted is not directly irradiated with light, the surface side also becomes hot.

However, when a xenon lamp or the like is used for the lamps 3 and 4 at this time, a cooling gas or a He gas is supplied from the cooler 7 and the gas supply source 8, and the SiC
The temperature on the front side of the substrate 1 is controlled. This is because temperature control is more difficult when using a xenon lamp or the like than when a halogen lamp or the like is used, and the temperature rises at a very high rate of temperature rise.

In this manner, the impurities implanted in n ⁻ -type epi film 1b are activated, and an impurity layer is formed. At this time, since the activation heat treatment is performed by lamp annealing as in the present embodiment, the rate of temperature rise can be increased, and the activation heat treatment time can be shortened. As described above, since the plurality of lamps 3 and 4 are used, and the lights of the plurality of lamps 3 and 4 are collected and irradiated to the SiC substrate 1, the SiC substrate 1 can be uniformly heated. it can.

Further, the light of the lamps 3 and 4 is transmitted to the SiC substrate 1.
The following effects can be obtained since the light is irradiated to the back side of the substrate.

When performing an activation heat treatment using a lamp annealing apparatus, it is generally assumed that the heat treatment is directly applied to the surface of the SiC substrate 1 on which the ion implantation has been performed. However, after performing such activation heat treatment, the cross-sectional TEM observation showed that the depth of the p-type impurity layer before heat treatment was 0.5 μm, whereas the depth after heat treatment was 0.3 μm. It turned out to be shallow. In addition, SIMS analysis was also performed, and the analysis yielded similar results.

Such a result was obtained because direct irradiation of the impurity layer with the lamp light caused the temperature of the irradiated portion to exceed the epitaxial film growth temperature of about 1550 ° C., and sublimation of SiC from the surface. This is considered to be the cause of the surface roughness.

On the other hand, in the present embodiment, the light from the lamps 3 and 4 is applied to the back side of the SiC substrate 1, that is, the n ⁺ type substrate 1a. The growth temperature of this n ⁺ type substrate 1a is about 2300 ° C., which is sufficiently higher than the activation heat treatment temperature. For this reason, even if light is directly irradiated on the n ⁺ type substrate 1a side, it is possible to prevent SiC from subliming much. Thereby, it becomes possible to suppress the surface roughness of the SiC substrate 1.

As a reference, FIG.
The results of examining the surface roughness of each of the n ⁺ -type substrate 1a and the n ⁻ -type epitaxial film 1b when the in heat treatment is performed are shown. As shown in this figure, before and after the heat treatment, the n ⁺ type substrate 1
In the case of a, the surface roughness has not changed much, but n ⁻
In the case of the type epi film 1b, the surface roughness is significantly increased. Also from this result, irradiating light to the n ⁺ -type substrate 1a side whose growth temperature is higher than the heat treatment temperature is more effective than irradiating light to the n ⁻ -type epi layer 1b side whose growth temperature is lower than the heat treatment temperature. It can be said that surface roughness can be prevented.

As described above, by using the lamp annealing apparatus having the plurality of lamps 3 and 4 shown in this embodiment, the activation heat treatment time can be shortened, and
It is possible to heat the SiC substrate 1 uniformly. Further, by irradiating the light of the lamps 3 and 4 to the back surface side of the SiC substrate 1, the surface roughness of the SiC substrate 1 can be suppressed.

Although the diameter of the SiC substrate 1 is not particularly described here, when the SiC substrate 1 has a large diameter, the window 5 on the wafer stage 6 is adjusted accordingly.
What is necessary is just to adjust the diameter of b.

(Second Embodiment) In the first embodiment, in order to improve the light absorption on the back side of the SiC substrate 1 before the activation heat treatment, n ^{+ which is} on the back side of the SiC substrate 1 is used.
The light absorbing layer may be formed by applying a carbon resist to the mold substrate 1a, or making a part of the n + type substrate amorphous by ion implantation of P (phosphorus) or N (nitrogen).

(Third Embodiment) In the first and second embodiments, a cap layer may be formed on the surface of the SiC substrate 1 before the activation heat treatment. By forming such a cap layer, migration on the surface of the SiC substrate 1 and occurrence of sublimation of Si and C can be suppressed. As such a cap layer,
For example, an AlN film or a carbon film can be used.

(Fourth Embodiment) In the first to third embodiments, a spherical lamp is used as a lamp used in a lamp annealing apparatus. However, as shown in FIG. 4, a filament 10 is provided in an arc shape. The lamp 11 may be used. When such a lamp 11 is used, when the light of the lamp 11 is collected and irradiated on the SiC substrate 1, the temperature distribution in the plane of the SiC substrate 1 can be reduced as compared with the case where a spherical lamp is used. it can.

(Other Embodiments) In the first to third embodiments, one top lamp 3 and four side lamps 4 are used. However, the number of these lamps 3 and 4 may be arbitrarily adjusted. Is possible. For example, eight side lamps may be provided by further increasing the number of lamps between the side lamps 4 shown in FIG.

In the first embodiment, an example in which both the top lamp 3 and the side lamp 4 are used from the beginning of the activation heat treatment has been described. First, migration occurs only in the side lamp 4 as the first heating step. Temperature (1
(About 420 ° C.), and then the temperature may be further increased using the top lamp 3 as a second heating step. By doing so, it is possible to prevent occurrence on the surface of the n ⁻ -type epi film 1b and to suppress surface roughness.

[Brief description of the drawings]

FIG. 1 is a schematic view of a lamp annealing apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the lamp annealing apparatus taken along line AA of FIG. 1;

FIG. 3 is a table showing the results of examining the surface roughness of each of an n + -type substrate 1a and an n − -type epi layer 1b when an activation heat treatment is performed.

FIG. 4 is a schematic diagram of a lamp used in a lamp annealing apparatus according to a fourth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... SiC substrate, 1a ... n ⁺ type | mold substrate, 1b ... n ^- type epilayer, 2 ... case part, 3 ... top lamp, 4 ... side lamp, 5 ... housing, 5a ... passage, 5b ... window part, 6 ... Wafer stage, 7: cooler, 8: gas supply source.

Claims (9)

[Claims] 1. A top lamp (3) arranged above a wafer stage (6) on which a silicon carbide substrate (1) is mounted.
And a side lamp (4) arranged so as to surround the periphery of the wafer stage, and the top lamp and the side lamp irradiate the silicon carbide substrate arranged on the wafer stage with light. A silicon carbide semiconductor manufacturing apparatus characterized by being configured as described above. 2. The top lamp and the side lamp are arranged in a housing (5), and a passage (5a) extending from the top lamp or the side lamp toward the wafer stage is provided in the housing.
2. The silicon carbide semiconductor manufacturing apparatus according to claim 1, wherein an inner wall of the passage has a mirror structure for reflecting light emitted from the top lamp or the side lamp. 3. 3. A cooling means (7) for cooling the wafer stage, wherein the cooling means cools the silicon carbide substrate disposed on the wafer stage. The silicon carbide semiconductor manufacturing apparatus according to claim 1 or 2, wherein: 4. The side lamp is a spherical lamp,
4. The silicon carbide semiconductor manufacturing apparatus according to claim 1, wherein said spherical lamps are arranged at equal intervals. 5. The silicon carbide semiconductor device according to claim 1, wherein said side lamp comprises at least two lamps having an arc shape. 6. A method for manufacturing a silicon carbide semiconductor using the silicon carbide semiconductor manufacturing apparatus according to claim 1, wherein an epi layer is formed on a substrate, and an impurity of impurity is contained in the epi layer. Prepare a silicon carbide substrate with ion implantation,
A step of mounting the silicon carbide substrate on the wafer stage such that a surface side of the silicon carbide substrate on which the epi layer is formed faces the wafer stage side; and using the top lamp and the side lamp Heating to the activation temperature of the impurity. 7. In the heating step, a first heating step performed using only the side lamp and a second heating step performed using the side lamp and the top lamp are performed.
The method of manufacturing a silicon carbide semiconductor according to claim 6, wherein the second heating step is performed after the first heating step. 8. After forming a cap layer on a surface of the silicon carbide substrate on which the epi layer is formed,
The method of manufacturing a silicon carbide semiconductor according to claim 6, wherein the silicon carbide substrate is mounted on the wafer stage. 9. The method according to claim 1, wherein a light absorbing layer is formed on the back surface of the silicon carbide substrate on which the epi layer is not formed, and the silicon carbide substrate is mounted on the wafer stage. Item 10. The method for manufacturing a silicon carbide semiconductor according to any one of Items 6 to 8.