JPS62119917A - Formation of single crystal of silicon carbide - Google Patents

Abstract

PURPOSE:To simplify the operation and process steps by providing a heat shielding mask to form the regions of different growth temperature on a substrate of SiC single crystal and to grow SiC single crystals of different crystal structure in the respective regions at the same time. CONSTITUTION:A heater 17 as a heating means is arranged on the opposite side to the molecular beam incident side from a molecular beam source 16 of an SiC single crystal substrate 15. Between this heater 17 and the substrate 5, a heat-shielding mask 19 for adjusting a substrate temperature provided with a light transmitting part 18 arranged in its center is arranged. The substrate 15 is heated by the heater 17 through the mask 19 to form a high temperature region 15a of the growth temperature of 6H-type SiC in the central part of the substrate 15. Simultaneously, a low temperature region 15b of the growth temperature of 3C-type SiC is formed around the region 15a. Under such condition, the substrate 15 is irradiated with molecular beams from the molecular beam source 16 to grow 6H-type and 3C-type SiC single crystals in the regions 15a and 15b, respectively. Thus, there is no need of exchanging mechanical masks for each growth of SiC single crystals of different crystal structure and both the operation and process steps can be simplified.

Description

Detailed Description of the Invention [Industrial Application Field] This invention is a method of carbonization in which silicon carbide single crystals of a plurality of different crystals are selectively grown by molecular beam epitaxy in different regions on a silicon carbide single crystal substrate. This invention relates to a method for forming silicon single crystals.

[Conventional technology]

In general, a method of selectively growing semiconductor crystals in a predetermined pattern on a semiconductor substrate by molecular beam epitaxial growth (hereinafter referred to as MBE) is described in "Molecular Beam Epitaxy Technology" (Kogyo Kenkyukai Co., Ltd.), pages 82 and 83, by Sei Takashi. As previously mentioned, a method using a mechanical mask is well known.

For example, as shown in Figure 4, this is a molecular beam source (1).
A molecular beam cut mask (4) serving as a mechanical mask in which a through hole (3) of a predetermined shape is formed is disposed between the semiconductor substrate (2) and the molecular beam source (1). The semiconductor crystal is epitaxially grown only in the region corresponding to the hole (3) by passing only through the hole (3) of the mask (4).

Then, by the method described above, a plurality of SiCs with different crystal structures are formed in different regions on a silicon carbide (SiC) single crystal substrate.
When selectively epitaxially growing single crystals, for example, 5iCO with two types of crystal structures, 6H type and 3C type, is used.
) Assuming that a pn junction is formed, Fig. 5(a), (
As shown in Figure b), a first mask (6) having a through hole (5) in the center and a second mask (8) having through holes (7) at both ends were prepared. ), a buffer layer αQ made of 6H type SiC single crystal is formed on a 6H type SiC single crystal substrate (9), and then a first mask (
6) is placed between the molecular beam source and the substrate (9), and the substrate (9) is placed between the molecular beam source and the substrate (9).
) is heated by a heating means to TIC, which is the growth temperature of a 6H type SiC single crystal, and a molecular beam from a molecular beam source is irradiated onto the substrate (9) through the first mask (6), as shown in FIG. As shown in FIG. 2, an n-layer αυ made of 6H type SiC single crystal is epitaxially grown in the center of the buffer layer 00.

Next, a second mask (8) is placed between the molecular beam source and the substrate (9), and the substrate (9) is heated using heating means to heat the 3C type SiC.
The substrate (9) is heated to T2 (<TI) C, which is the growth temperature of a single crystal, and the molecular beam from the molecular beam source is irradiated to the substrate (9) through the second mask (8), as shown in Figure 6 (C). As shown, n-layers (2) made of 3C type SiC single crystal are epitaxially grown on both ends of the buffer layer OQ.

Furthermore, after forming the n-layer (2) of 3C type SiC, the substrate temperature was set to Tl c in the same manner as in the growth of the n-layer αη of 6H type SiC, and the molecular beam was irradiated through the first mask (6). By irradiation, as shown in Figure @6 (d), nine layers α3 made of 6H type SiC single crystal are epitaxially grown on the n layer 01) to form a pn junction of 6H type SiC, and then the above-mentioned 3C type SiC As in the case of growing the n-layer (2), the substrate temperature was set to 72 C, and both n-layers (b) were grown by irradiation with molecular beams through the @2 mask (8), as shown in Figure (e). 4 is epitaxially grown on nine layers each made of 3C type SiC single crystal to form a 3C type SiC pn junction.

[Problem that the invention seeks to solve]

However, in the case of the method for forming the SiC single crystal described above,
There are the following three problems. First, each SiC single crystal layer αυ
~α4 epitaxial growth is performed separately, so four growth steps are required, which requires a large number of steps and a long time.Secondly, two masks (6) and (8) are required, and each layer Mask (6) for each growth of αυ~g stations.

(8) must be set alternately, which is very time-consuming.Moreover, since the alignment of masks (6) and (8) is done in a vacuum chamber, which makes autopsy difficult, it is necessary to carefully align the masks. It cannot be contaminated, resulting in a decrease in the flatness and quality of the growing crystal surface, and requires a fairly large manipulator to hold and drive the two masks (6) and (8) at @3. Therefore, such a large manipulator must be housed in the vacuum chamber, which may cause contamination within the vacuum chamber and a decrease in the degree of vacuum, which may adversely affect the quality of the grown crystal.

Therefore, this invention eliminates operations such as mask replacement, simplifies the process and shortens the required time, prevents contamination in the vacuum chamber and decreases in the degree of vacuum, and provides a SiC monolayer with excellent flatness and quality. The technical challenge is to be able to form crystals.

[Means for solving problems]

The present invention has been made with the above-mentioned points in mind, and provides a silicon carbide single crystal that selectively forms a plurality of silicon carbide single crystals with different crystal structures in different regions on a silicon carbide single crystal substrate by molecular beam epitaxial growth. In the method for forming a single crystal, a thermal mask for temperature adjustment of the substrate is disposed on the opposite side of the molecular beam incident side of the substrate, and the substrate is heated by a heating means through the thermal mask to cause different growths on the substrate. This method of forming a silicon carbide single crystal is characterized in that temperature regions are formed and silicon carbide single crystals having different crystal structures are grown in each region.

[For 1] Therefore, in this invention, a heat shield mask for substrate temperature adjustment is provided on the side opposite to the molecular beam incident side of the silicon carbide single crystal substrate, and the substrate is heated by the heating means through the heat shield mask, and the substrate is heated by the heating means through the heat shield mask. Different growth temperature regions are formed, and a silicon carbide single crystal having a crystal structure corresponding to the temperature of each region of the substrate is epitaxially grown.

At this time, unlike when using conventional mechanical masks, there is no need to change the mask each time silicon carbide single crystals with different crystal structures are grown, which greatly simplifies the operation and process. This eliminates the need for a manipulator that has a replacement function, and prevents contamination within the vacuum chamber and a decrease in the degree of vacuum.

〔Example〕

Next, the present invention will be explained in detail with reference to FIGS. 1 to 3 showing one embodiment thereof.

Now, as shown in FIG. 1, a heater Q7) as a heating means is disposed on the side opposite to the molecular beam incidence side by the molecular beam source 0I of a 6H type SiC single crystal substrate αQ, for example.
Between η and the substrate Qi19, a heat shield mask made of a high-melting point metal and having a rectangular through hole in the center is placed for controlling the substrate temperature, and the substrate is heated by the heater αη through the mask damage. Heat the center part of the substrate α0 on day 0.

That is, the shaded area in FIG. 1 shows a high temperature region (15a
, ), and a high temperature region (15a
) is the growth temperature of 30 type SiC, 950~12
A low temperature region (15b) of 50 C is formed, and the substrate αQ is irradiated with a molecular beam from a molecular beam source αQ to form both regions (15a),
6H type and 3C type SiC single crystals are grown on (15b), respectively.

At this time, the distance between the substrate 0υ and the mask injury is kept constant, and the substrate/IFJ is placed in the temperature range (15a) described above.
, (15b), the substrate Qυ and the mask 09 are supported by a holder holder as shown in FIG. 2. Next, the structure of this holder (1) will be explained.

In FIG. 2, Qυ is a first cylindrical body that has a stepped part (21b) for mounting the board aυ formed inside an opening (21a) at one end, and a female thread (2IC) formed on the inner periphery of the other end. , (support) is a holding ring that presses down the mounted board αQ with its peripheral edge in contact with the stepped portion (21b), and (e) is a ring device @
The fixing bolt (c) is fixed to the cylindrical body Q]), and the flange part (24b) having a stepped part (24a) for attaching a mask injury is formed integrally in the center part of the inside, and has a female thread (24b) on the outer periphery of one end. 2
1c) The retaining ring that holds down the mask Q, and the fin are fixing bolts, and are designed to fix the ring (to) to the flange of the cylinder (c) @22.

Tsukini, high temperature, low temperature area (15a), (15b) D6
To explain in detail the procedure for forming a pn junction light emitting diode by growing H-type and 3C-type SiC single crystals, first, as shown in FIG.
Forming a buffer layer (goods) made of H-type SiC single crystal,
Thereafter, as described above, the substrate αQ is exposed to high temperature and low temperature regions (15
A) and (15b) are formed by irradiating with a molecular beam that hunts NH3 gas, and as shown in the same figure (b), 6H type is formed on both regions (15a) and (15b) through the buffer layer (b), respectively. N layer (to) and 3 made of SiC single crystal
At the same time, an n-layer film made of C-type SiC single crystal is epitaxially grown.

Here, since there is a temperature gradient at the boundary between the high temperature area (15a) and the low temperature area (15b), the black area in Figure 3) corresponding to the peripheral area of the high temperature area 05a) has a 6H type. Both the 3C type and 5iCON type single crystals coexist, and this is hereinafter referred to as an n-type mixed layer.

Furthermore, after the growth of the n layer (to) and the layer, by irradiation with a molecular beam containing At as a dopant, as shown in FIG.
Layer (to), p layer (to) consisting of 6H type SiC single crystal and 9 layers 01 consisting of 3C type SiC single crystal on the top layer, respectively.
) was epitaxially grown at the same time, and 6H type 5iC (7
) pn junction (to) and 3C type SiC pn junction (to)
form.

At this time, a p-type mixed layer is formed on the n-type mixed layer for the same reason.

Then, as shown in FIG. 3(d), 02. After selectively removing the n-type and p-type mixed layer by vapor phase etching with Ct2 mixed gas,
A lower electrode and an upper electrode (g) are respectively formed on the lower surface of the substrate/I6 and on the p-layer (7), 0]), and as shown in FIG. and cut it into multiple 6H type SiC pn junction light emitting diodes (
) and 3C type 5iCQ) pn junction light emitting diode (
b)).

Here, the heat shield O9 used was made of tungsten and had a thickness of 50 μm, and the substrate 09 was attached to the holder (1).
The distance between the mask and the mask Q was 8 mm.

By the way, when the light emitting diodes (G) and (B) produced in this way were given a DC power of 4V and 20 mA to emit light, the 6H type SiC light emitting diode (G)
emitted blue or bluish-white light, and the 3C type SiC light emitting diode (b) emitted red or orange light.

In the above embodiment, the case where two different growth temperature regions are formed on the substrate 0Q is explained, but it is also possible to have three or more kinds of growth temperature regions. Of course, it may be allowed to grow.

Also, by appropriately changing the diameter of the cylindrical body Qυ, 6!4 of the holder (A), SiC single crystals can be grown on SiC single crystal substrates of various sizes! It's no good.

〔Effect of the invention〕

As described above, according to the method for forming a silicon carbide single crystal of the present invention, the SiC single crystal substrate a9 is
In order to simultaneously grow silicon carbide single crystals with different crystal structures in each region by forming different growth temperature regions, the mechanical mask is replaced each time silicon carbide single crystals with different crystal structures are grown, as in the conventional method. This eliminates the need for large-scale manipulators, which greatly simplifies the operation and process, shortens the required time, and eliminates the need for large-scale manipulators, which prevents contamination within the vacuum chamber and a decrease in the degree of vacuum. This makes it possible to grow silicon carbide single crystals with excellent flatness and quality, and the effect is extremely large.

[Brief explanation of drawings]

@Figures 1 to 3 show one embodiment of the method for forming a silicon carbide single crystal of the present invention, and Figure 1 is a perspective view during formation, @
Figures 2 (a) and (b) are cross-sectional views of the substrate and the thermal mask support holder when separated and assembled, respectively, and Figure 3 (
a) to (e) are cross-sectional views of the formation process, respectively, @4 The following drawings show the conventional method of forming silicon carbide single crystals, and Fig. 4 is a perspective view during formation, Fig. 5 (a), 6(b) is a plan view of a molecular beam cut mask used in the formation, and FIGS. 6(a) to 6(e) are sectional views of the forming steps, respectively. α9...Substrate, (15a), (15b)...High temperature,
Low temperature region, αQ... molecular beam source, 'Jη... heater,
α1...Heat mask, (to), @...n layer, (7)
, 0◇...p layer.

Claims (1)

[Claims] (1) In a method for forming a silicon carbide single crystal in which a plurality of silicon carbide single crystals with different crystal structures are selectively formed in different regions on a silicon carbide single crystal substrate by a molecular beam epitaxial growth method, the molecular beam incident side of the substrate A heat shield mask for temperature adjustment of the substrate is disposed on the opposite side of the substrate, and the substrate is heated by a heating means through the heat shield mask to form different growth temperature regions on the substrate, and each region has a different crystal structure. A method for forming a silicon carbide single crystal, comprising growing a silicon carbide single crystal.