JP2005123417A - Liquid phase epitaxial growing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To furthermore uniformize a temperature at a center and a temperature at an outer circumferential part of a growing substrate in a graphite tool during liquid phase epitaxial growing. <P>SOLUTION: An epitaxial layer on a substrate 2 is grown by including a growing solution 6 to a plurality of solution pools 1 of the solution holder 10 of a slide boat, placing the substrate 2 to the substrate mount 7 of a substrate holder 3, cooling the substrate holder 3 and the solution holder 10, and making the growing solution 6 in contact with the substrate 2. A solution thermal buffer 5 made of a solution with a thermal conductivity equivalent to that of the growing solution is provided to both sides of each solution pool 1 of the solution holder 10 in its sliding direction to uniformize the thermal environment around the substrate 1, thereby uniformizing the thickness of the epitaxial layer grown on the substrate 1 within the substrate face. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid phase epitaxial growth method using a slide boat method, and more particularly to a technique for achieving a uniform film thickness for epitaxial growth.

  FIG. 2 is a schematic view of a conventional slide boat for growing a GaAs thin film by liquid phase epitaxial growth. A slide boat made of graphite digs a part of the surface of a solution holder 10 in which a plurality of solution reservoirs 1 for containing a growth solution 6 are formed in a sliding direction and a substrate mounting portion 7 on which a GaAs substrate 2 is mounted. And a substrate holder 3 formed by being embedded. The solution holder 10 and the substrate holder 3 can be moved in the horizontal direction by operating the operation rod 4.

  The slide boat is placed in a furnace and heated to saturate the Ga melt contained in the solution reservoir 1 with GaAs to form a growth solution, and then cooled to bring the growth solution 6 into a supercooled state. Thereafter, the solution reservoir 1 is moved onto the GaAs substrate 2 while gradually cooling, and the growth solution 6 is brought into contact with the GaAs substrate 2. As a result, a GaAs epitaxial layer grows on the GaAs substrate 2. After the thin film having a predetermined thickness is grown, the solution reservoir 1 is moved again from the GaAs substrate 2 to stop the growth.

  The film thickness of the epitaxial layer of the epitaxial wafer grown by the above method generally depends on the shape of the furnace and the slide boat, but generally the periphery is thick and the center tends to be thin. This is because the cooling itself is performed by radiation and heat transfer from the outside of the slide boat, and the temperature in the surface of the substrate mounting portion becomes non-uniform during the cooling process.

Therefore, conventionally, a pyrolytic graphite plate is used for the substrate mounting portion on which the substrate is mounted, and the thermal conductivity here is made higher than the thermal conductivity of the substrate holder, so that the temperature in the substrate surface is made uniform. It is known that the thickness of the epitaxial layer formed on the substrate is cooled so that there is no difference between the periphery and the center (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 9-221388

  However, in the structure of the graphite jig used in the above liquid phase epitaxial growth method, a plurality of solution reservoirs 1 are arranged apart from each other in the sliding direction of the solution holder 10, and each solution reservoir 1 has the same size as this. The substrate mounting portion 7 provided in this way is configured to slide and oppose. Therefore, when the substrate platform 7 faces each raw material solution reservoir 1, the thermal environment around the substrate 2 is not uniform. That is, the temperature at the center of the substrate is the same as that of the solution reservoir 1, but the outer periphery of the substrate approaches the outer periphery of the solution reservoir 1 (solution holder 10) and is affected by the temperature.

  For this reason, the temperature at the growth substrate center and the growth substrate outer periphery becomes non-uniform, and the temperature uniformity at the growth substrate center and the growth substrate outer periphery is poor. As a result, the thickness variation in the plane of the grown LED epitaxial wafer is large. That is, the thickness uniformity is poor and the production yield is poor.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems and to further uniform the temperature at the center portion and the outer peripheral portion of the growth substrate in the graphite jig during liquid phase epitaxial growth.

  In order to achieve the above object, the present invention is configured as follows.

  In the liquid phase epitaxial growth method according to the first aspect of the present invention, a growth solution is stored in a solution reservoir of the solution holder of a slide boat provided with a substrate holder and a solution holder, and the substrate is placed on the substrate mounting portion of the substrate holder. When the epitaxial layer is grown on the substrate by placing it and bringing the growth solution into contact with the substrate, it is formed with a solution having a thermal conductivity equivalent to that of the growth solution on both sides of the solution reservoir in the slide direction of the solution holder. The thickness of the epitaxial layer grown on the substrate in the substrate surface is made uniform by providing the solution heat buffer portion and making the thermal environment around the substrate uniform.

  In the liquid phase epitaxial growth method according to the second aspect of the present invention, a growth solution is accommodated in a plurality of solution reservoirs of the solution holder of a slide boat provided with a substrate holder and a solution holder, and the substrate mounting portion of the substrate holder is provided with the growth solution. When the epitaxial layer is grown on the substrate by placing the substrate and bringing the growth solution into contact with the substrate, the thermal conductivity is equivalent to that of the growth solution on both sides in the sliding direction of each solution reservoir of the solution holder. A thickness of the epitaxial layer grown on the substrate is made uniform in the substrate surface by providing a solution thermal buffer formed of a solution to make the thermal environment around the substrate uniform. .

  The invention according to claim 3 is the liquid phase epitaxial growth method according to claim 1 or 2, wherein a graphite jig is used for the substrate holder and the solution holder, and a Ga solution is formed by Ga solution on both sides of the solution reservoir of the solution holder. A thermal buffer unit is provided.

  According to the present invention, the following excellent effects can be obtained.

  According to the first aspect of the present invention, the solution heat buffer section formed of a solution (semiconductor solution or the like) having the same thermal conductivity as the growth solution is provided on both sides of the solution holder in the solution reservoir in the sliding direction. The thermal environment around the substrate during epitaxial growth becomes uniform, and the film thickness of the epitaxial layer formed on the substrate does not differ between the periphery and the center.

  According to the second aspect of the present invention, the solution holder is formed of a solution (semiconductor solution or the like) having a thermal conductivity equivalent to that of the growth solution, on both sides in the sliding direction of each solution reservoir or between the solution reservoir and the solution reservoir. Since the solution heat buffer section is provided, the thermal environment around the substrate during epitaxial growth becomes uniform, and the film thickness of the epitaxial layer formed on the substrate does not differ between the periphery and the center.

  According to the invention of claim 3, a graphite jig is used for the substrate holder and the solution holder, and the Ga solution thermal buffer portion formed of Ga solution is provided on both sides of the solution reservoir of the solution holder. When handled, a Ga solution thermal buffer formed of a Ga solution having a thermal conductivity equivalent to that of the growth solution is present on both sides of the solution reservoir, so that the ambient thermal environment of the substrate is easily made uniform. Therefore, a GaAlAs epitaxial layer having a uniform in-plane film thickness can be grown on the GaAs substrate.

<Key points of the invention>
In the present invention, in the liquid phase epitaxial growth, as shown in FIGS. 1A and 1B, the left and right sides of the solution reservoir of the graphite jig are formed of a solution such as a semiconductor solution having a thermal conductivity equivalent to that of the growth solution. A solution heat buffer portion, for example, a Ga heat buffer portion formed of a Ga solution, is provided to achieve uniformity in the heat capacity of the solution reservoir and its surroundings. As a result, the uniformity of the temperature at the center of the growth substrate and the outer periphery of the growth substrate is achieved, and the LED epitaxial layer having a uniform thickness in the plane of the LED epitaxial wafer, for example, the active layer and the cladding layer for the LED are formed. Grow sequentially.

  In accordance with the present invention, by performing liquid phase epitaxial growth using a slide boat provided with a Ga thermal buffer formed of a Ga solution, the difference in film thickness (Max-Min) in the epitaxial wafer for LEDs can be reduced with a conventional graphite jig. As compared with the case of using, it can be about 1/15.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. A horizontal slide boat made of graphite includes a solution holder 10 in which a plurality of solution reservoirs 1 for storing a growth solution 6 are formed in a sliding direction, and a substrate holder (in which a GaAs substrate 2 is placed) and a substrate holder 7 on which a GaAs substrate 2 is placed ( It is substantially the same as the conventional slide boat of FIG. 2 that the solution holder 10 and the substrate holder 3 can be moved in the horizontal direction. .

  However, unlike the case of FIG. 2, in the present embodiment, in the solution holder 10 in which a plurality of solution reservoirs 1 are formed in the sliding direction, the same solution as the growth solution is provided on both sides of each solution reservoir 1 in the sliding direction. A Ga solution thermal buffer section 5 formed of a semiconductor solution having thermal conductivity is provided, thereby making the thermal environment around the substrate uniform, and the thickness of the epitaxial layer grown on the substrate in the substrate plane. The structure is made uniform. In the case of this embodiment, the Ga solution heat buffer unit 5 is provided in such a size as to fill the gap between the solution reservoir 1 and the solution reservoir 1.

  In the liquid phase epitaxial growth method, the growth solution 6 is accommodated in the plurality of solution reservoirs 1 of the solution holder 10 of the slide boat, the GaAs substrate 2 is mounted on the substrate mounting portion 7 of the substrate holder 3, and the substrate holder 3. The solution holder 10 is cooled, and the growth solution 6 is brought into contact with the substrate 2 to grow a GaAlAs epitaxial layer on the GaAs substrate. At this time, the Ga solution heat buffer section 5 is provided on both sides of the solution reservoir 1 with the substrate 2 in contact with the growth solution 6 as the center, and the ambient thermal environment of the substrate is made uniform. An epitaxial layer having a uniform film thickness is grown.

  As a growth jig, a graphite jig (slide boat) provided with a Ga solution heat buffer portion formed of a Ga solution on the left and right sides of the solution reservoir 1 shown in FIG. 1 was used.

  Ga, GaAs, Al, Zn, and Te, which are raw materials for the P-type GaAs substrate 2 and the epitaxial layer, were set on a growth jig and placed at predetermined positions in the liquid phase epitaxial growth apparatus. The growth apparatus was heated to 900 ° C. in a hydrogen atmosphere, held for 3 hours, and then cooled to 700 ° C. at a rate of 1 ° C./min. The substrate 2 was sequentially brought into contact with the growth solution 6 while the temperature was lowered, and the P-type GaAlAs cladding layer, the P-type GaAlAs active layer, and the N-type GaAlAs cladding layer for LED were sequentially grown by liquid phase epitaxial growth. The in-plane film thickness of the LED epitaxial wafer grown on the P-type GaAs substrate 2 was measured.

  In addition, using a graphite jig (slide boat) that is not provided with a Ga solution thermal buffer formed of Ga solution on the left and right of a commonly used solution reservoir shown in FIG. The epitaxial wafer for LED was produced using conditions, and the film thickness in the surface of the epitaxial wafer for LED was measured.

表１のＬＥＤ用エピタキシャルウェハ面内膜厚のＭａｘ−Ｍｉｎの差から明らかな通り、成長させたＬＥＤ用エピタキシャルウェハの面内膜厚分布の差（Ｍａｘ−Ｍｉｎ）は、比較例では３．０であるのに対し、本実施例の場合は０．２と小さくなった。すなわち、本実施例のグラファイト治具の溶液溜の左右にＧａ溶液で形成されたＧａ溶液熱バッファ部５を設けたグラファイト治具（図１）を用いて成長を行った場合の方が、従来グラファイト治具（図２）を用いて成長を行った場合（比較例）と比較して、ウェハの面内膜厚分布の差（Ｍａｘ−Ｍｉｎ）を１／１５と少なくすることができた。 Table 1 shows the measurement results. The film thickness was measured at five locations (four corners and the center) shown in FIG. 3 in the plane of the LED epitaxial wafer. That is, on a substrate having a side of 40 mm, the film thickness was measured at each of the four corners I, II, IV, V 5 mm inside from each side and the central part III 20 mm inside from each side.

As is clear from the difference in Max-Min of the in-plane film thickness of the LED epitaxial wafer in Table 1, the difference in the in-plane film thickness distribution (Max-Min) of the grown epitaxial wafer for LED is 3.0 in the comparative example. On the other hand, in the case of the present Example, it became small with 0.2. That is, the case where the growth was performed using a graphite jig (FIG. 1) provided with a Ga solution thermal buffer section 5 formed of a Ga solution on the left and right of the solution reservoir of the graphite jig of the present embodiment is conventional. The difference (Max-Min) in the in-plane film thickness distribution of the wafer could be reduced to 1/15 compared to the case where growth was performed using a graphite jig (FIG. 2) (Comparative Example).

The structure of the slide boat used for the liquid phase epitaxial growth of this invention is shown, (a) is sectional drawing, (b) is B-B 'sectional drawing. The structure of the slide boat used for the conventional liquid phase epitaxial growth is shown, (a) is sectional drawing, (b) is A-A 'sectional drawing. It is the figure which looked at the epitaxial wafer for LED manufactured with the growth method of this invention from the surface, and is the figure which showed the position which measured the film thickness of the epitaxial wafer for LED.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solution reservoir 2 Substrate 3 Substrate holder 4 Operation rod 5 Ga solution thermal buffer part 6 Growth solution 7 Substrate mounting part 10 Solution holder

Claims (3)

A growth solution is accommodated in a solution reservoir of the solution holder of a slide boat having a substrate holder and a solution holder, the substrate is placed on the substrate placement portion of the substrate holder, and the growth solution is brought into contact with the substrate. When growing an epitaxial layer on the substrate by
By providing a solution heat buffer part formed of a solution having a thermal conductivity equivalent to that of the growth solution on both sides of the solution holder in the slide direction of the solution holder, and making the thermal environment around the substrate uniform, A liquid phase epitaxial growth method characterized in that the thickness of the epitaxial layer grown on the substrate is made uniform in the substrate plane. A growth solution is stored in a plurality of solution reservoirs of the solution holder of a slide boat including a substrate holder and a solution holder, the substrate is placed on the substrate placement portion of the substrate holder, and the growth solution is brought into contact with the substrate. When growing an epitaxial layer on the substrate by
By providing a solution heat buffer section formed of a solution having a thermal conductivity equivalent to that of the growth solution on both sides in the slide direction of each solution reservoir of the solution holder to make the thermal environment around the substrate uniform, A liquid phase epitaxial growth method characterized in that the thickness of an epitaxial layer grown on the substrate is made uniform in the substrate plane. In the liquid phase epitaxial growth method according to claim 1 or 2,
A liquid phase epitaxial growth method, wherein a graphite jig is used for the substrate holder and the solution holder, and a Ga solution thermal buffer portion formed of a Ga solution is provided on both sides of a solution reservoir of the solution holder.

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