JPH07267795A - Growth method of silicon carbide single crystal - Google Patents

Abstract

PURPOSE:To provide a method for growing a good-quality SiC single crystal while suppressing generation of crystal grains varying in crystal bearings from a seed crystal by using the specific crystal face of the SiC single crystal as the seed crystal in a sublimation recrystallization method. CONSTITUTION:The hatched face (a) in Fig. is a face inclined by an off angle thetain the (0001) C face direction from the (1100) face. The seed crystal substrate having such face is obtd. by cutting out a SiC single crystal ingot, which is grown on the {0001} face by, for example, the conventional sublimation method, with an inclination by the off angle theta from the angle perpendicular to the {0001} base face. The substrate cut out by inclining only the desired face is mounted as the seed crystal into a crucible of a single crystal producing apparatus and the inside of a vessel is evacuated to vacuum. An inert gas is admitted into the vessel and is kept at 600Torr and the raw material temp. is heated up to 2100 to 2500 deg.C in 10 to 90 minutes from 2000 deg.C under an atmosphere of l to 50Torr to start growth. The seed crystal is kept lower by 40 to 100 deg.C than the raw material temp. and the temp. gradient is kept at 5 to 25 deg.C/cm. The growth speed of the single crystal is so regulated as to attain 0.4 to 1.6mm/ h.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a SiC single crystal. For more details, please refer to the blue LED,
The present invention relates to a method for growing a high-quality SiC single crystal which is useful as a seed crystal substrate wafer when applied to an electronic device or when growing an ingot.

[0002]

2. Description of the Related Art Since SiC single crystal is a material which is chemically stable and can withstand high temperature and radiation, it is expected to be applied as an environment resistant semiconductor device material. Also,
Due to its large forbidden band width, it is used as a short-wavelength light emitting diode material. Actually, 6H-SiC (H means hexagonal crystal form, 6 means the number of atomic stacks in a unit cell) has a band gap of about 3.0 eV at room temperature, and is a material for blue light emitting diodes.

Japanese Unexamined Patent Publication (Kokai) No. 05-262599 discloses a method of growing a crystal on a crystal plane perpendicular or nearly perpendicular to a (0001) basal plane used as a seed crystal. A single crystal obtained by this method is polytype. It has been shown to be very good quality as well as easy to control. Also, the Journal of
In Crystal Growth 135 (1994) 61-70, the crystal grown by this method is compared with the conventional grown crystal on the {0001} plane, and a hollow defect (enpty tube) penetrating the {0001} wafer is observed. It has been shown to be removed.

However, in such a growth method,
It is often seen that crystal grains having different crystal orientations from the seed crystal are generated on the crystal surface. When such crystal grains are generated, the grown ingot contains grains having different crystal orientations, and the ingot becomes a polycrystal rather than a perfect single crystal. The wafer cut out from this not only significantly reduces the yield when the device is manufactured, but also cannot be used as a seed crystal in the sublimation method.

[0005]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for growing a high quality SiC single crystal while suppressing the generation of crystal grains having different crystal orientations from the seed crystal.

[0006]

SUMMARY OF THE INVENTION The above-mentioned problems are caused by the (0001) basal plane of SiC single crystal in the sublimation recrystallization method.

[Outside 5] Solved by the method of growing. Particularly, the off angle is preferably 5 to 30 degrees.

[0007]

[Outside 6] It is solved by a method of growing on a tilted crystal plane. Particularly, the off angle is preferably 5 to 30 degrees.

[0008]

Since SiC is a polar crystal, the plane polarity appears on all planes except the crystal plane perpendicular to the (0001) basal plane.
This surface polarity property affects the etching rate by molten KOH, the oxide film formation rate by thermal oxidation, and the like.
This property also affects the ease with which crystal grains with different orientations are generated during crystal growth.

When a SiC crystal is grown on the surface of a SiC seed crystal substrate, the crystal plane perpendicular to the (0001) basal plane is (0
001) Compared to the surface turned off in the Si surface direction,

[Outside 7] Due to this plane polarity property, crystals having different crystal orientations from the seed crystal are unlikely to occur. In addition, compared to the non-polar (0001) basal plane,

[Outside 8] The occurrence of such grains is small.

[0010]

[Outside 9] Although the generation of the above-described crystal grains having different crystal orientations can be suppressed, it becomes impossible to grow a good quality crystal obtained on the crystal plane perpendicular to or near the (0001) basal plane.
That is, polymorphs are likely to be mixed, and a large number of hollow defects and crystal defects corresponding to hexagonal etch pits are generated, which deteriorates the crystal quality. for that reason,
The off angle from the plane perpendicular to the (0001) basal plane is 5 to 3
0 degree is preferable.

[0011]

[Outside 10] When used as a seed crystal substrate, the tip of the grown crystal is covered with facets, and defects due to thermal etching on the surface of the grown crystal are eliminated, which is desirable.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows an example of a single crystal growth apparatus used in the method for growing a SiC single crystal of the present invention.

As shown in FIG. 1, the graphite crucible used in the single crystal growth apparatus comprises a bottomed crucible 1 and SiC.
It comprises a graphite crucible lid 3 covering the opening of the crucible 1 having a mounting portion 4 for the substrate seed crystal 5, and the side surface and the upper and lower sides of the crucible 1 and the crucible lid 3 are made of graphite felt heat insulating material 6
It is placed in a container which is covered with a vacuum exhaust device and which can be vacuum-exhausted by a vacuum exhaust device and whose pressure can be controlled by an inert gas such as the internal atmosphere Ar. The heating is performed by, for example, a high frequency induction coil wound outside the container. The crucible temperature is measured, for example, by always using a two-color thermometer by providing an optical path 7a having a diameter of 2 to 4 mm in the center of the felt covering the lower part of the crucible and extracting the light from the lower part of the crucible. This temperature is regarded as the raw material temperature. Further, a similar optical path 7b is previously provided in the upper felt, the temperature of the crucible lid is measured, and this is regarded as the seed crystal temperature.

The plane perpendicular to the (0001) basal plane is

[Outside 11] There are an infinite number (it can be expressed as {hki0} in the surface index). The surface used in the present invention is

[Outside 12]

FIG. 2 is a drawing for explaining an example of a crystal plane used in the present invention.

[Outside 13] It means a surface inclined by an off angle θ. In this case, the back surface of the oblique line surface a is a surface inclined by the off angle θ in the (0001) Si direction and is not included in the present invention.

The seed crystal substrate having such a surface is, for example, S grown on the {0001} surface by the conventional sublimation method.
It is obtained by cutting an iC single crystal ingot by inclining it by an off angle θ from a direction perpendicular to the (0001) basal plane. The substrate having this desired surface is mounted as a seed crystal 5 on the mounting portion 4 of the crucible lid 3, and crystal growth is performed as follows, for example.

The container is evacuated and the raw material temperature is about 2000.
Raise to ℃. After that, while keeping the inert gas at about 600 Torr, the raw material temperature is raised to the target temperature. Decompression takes 10 to 90 minutes, and the atmospheric pressure is 1
˜50 Torr, more preferably 5˜20 Torr, raw material temperature 2100˜2500 ° C., more preferably 220
It is desirable to set the temperature to 0 to 2400 ° C. and start the growth. If the temperature is lower than this, the raw material is less likely to be vaporized, and if the temperature is higher than this, it is difficult to grow a good quality single crystal due to thermal etching or the like. Further, the seed crystal temperature is 40 to
100 ° C., more preferably 50 to 70 ° C. lower, temperature gradient 5 to 25 ° C./cm, more preferably 10 to 20 ° C./c
It is desirable to set m. Furthermore, the relationship between temperature and pressure is that the growth rate of a single crystal is 0.4 to 1.6 mm /
h, more preferably 0.7 to 1.3 mm / h. If the speed is higher than this, the crystallinity is deteriorated, which is not suitable, and if the speed is lower than this, the productivity is not good.

Crystal grains having different crystal orientations can be easily determined by visually observing the surface of the grown crystal. Furthermore, in order to examine the inside of the crystal, a {0001} wafer cut out from the growth ingot and mirror-polished is observed with a polarization microscope.

Example 1

[Outside 14] On a seed crystal substrate with an off angle of 15 degrees, the raw material temperature was 2340 ° C, the substrate temperature was 2280 ° C, and the atmospheric pressure was 10
Growth was performed as Torr. The growth rate was about 1 mm / h in the direction perpendicular to the substrate surface.

The front end of the grown crystal was covered with a large number of facets substantially parallel to the substrate. No crystal grain having a different orientation from that of the seed crystal was observed on the surface. In addition, even if a {0001} wafer was cut out from this ingot and mirror-polished, the crystal grain could not be observed with a polarizing microscope.

Growth was carried out several times under the same conditions, but generation of crystal grains having a different orientation from that of the seed crystal was not recognized.

Example 2

[Outside 15] On a seed crystal substrate with an off angle of 20 degrees, the raw material temperature was 2340 ° C., the substrate temperature was 2280 ° C., and the atmospheric pressure was 10.
Growth was performed as Torr. The growth rate was about 1 mm / h in the direction perpendicular to the substrate surface.

A plane almost parallel to the substrate appeared at the tip of the grown crystal. No crystal grain having a different orientation from that of the seed crystal was observed on the surface. In addition, even if a {0001} wafer was cut out from this ingot and mirror-polished, the crystal grain could not be observed with a polarizing microscope.

[Outside 16] The same result was obtained when used for seed crystals.

Comparative Example 1

[Outside 17] On a seed crystal substrate with an off angle of 15 degrees, the raw material temperature was 2340 ° C, the substrate temperature was 2280 ° C, and the atmospheric pressure was 10
Growth was performed as Torr. The growth rate was about 1 mm / h in the direction perpendicular to the substrate surface.

The surface of the grown crystal was covered with a large number of facets substantially parallel to the substrate. Several crystal grains having different orientations from the seed crystal could be observed on the surface. Also,
When a {0001} wafer was cut out from this ingot and mirror-polished, it was observed with a polarization microscope, and a portion in which such crystal grains expanded in the growth direction could be observed.

Comparative Example 2

[Outside 18] Growth was performed at a source temperature of 2340 ° C., a substrate temperature of 2280 ° C., and an atmospheric pressure of 10 Torr. The growth rate was about 1 mm / h in the direction perpendicular to the substrate surface. Almost parallel to the substrate on the surface of the grown crystal,

[Outside 19] Several crystal grains having different orientations from the seed crystal could be observed on the surface. Also, from this ingot {0001}
When the wafer was cut out and mirror-finished, it was observed with a polarization microscope, and a portion in which such crystal grains were enlarged in the growth direction was observed.

[0028]

By using the present invention, it is possible to grow a good-quality SiC single crystal ingot that does not contain crystal grains whose crystal orientation is different from that of the seed crystal. It is possible to supply high quality single crystal wafers useful for various applications such as electronic devices.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing an example of the structure of a single crystal growth apparatus used for growing a SiC single crystal of the present invention.

FIG. 2 is a drawing for explaining an example of a crystal plane of a seed crystal used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Crucible, 2 ... SiC raw material powder, 3 ... Crucible lid, 4 ... Seed crystal attachment part, 5 ... Seed crystal, 6 ... Adiabatic felt, 7a, 7b ... Optical path, 8 ... SiC single crystal.

Claims (4)

[Claims] 1. In the sublimation recrystallization method, as a seed crystal, a surface perpendicular to a (0001) basal plane of a SiC single crystal is used. Method for growing SiC single crystal. 2. In the sublimation recrystallization method, as a seed crystal, a plane perpendicular to a (0001) basal plane of a SiC single crystal is used. A method for growing a SiC single crystal, which is used. 3. A sublimation recrystallization method comprising: A method for growing a SiC single crystal, which comprises using an inclined crystal plane. 4. A sublimation recrystallization method comprising: A method for growing a SiC single crystal, which comprises using a crystal plane having an off angle of 5 to 30 degrees.