JP2006315908A - Apparatus for liquid phase growth - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for liquid phase growth equipped with a mechanism stirring a raw material solution in a cooling process, by which the temperature of the raw material solution is homogenized and the difference of the film thickness of the epitaxial layer grown on a substrate, even on a substrate with a large area, between its periphery and center is minimized. <P>SOLUTION: In an apparatus for liquid phase growth for growing a semiconductor epitaxial layer on a substrate 5 by bringing the substrate 5 into contact with a raw material solution 6 or 7 while cooling from a specified temperature, where a slider 2 having a substrate holder 1 and a holder 11 for raw material solution holders 3 which form the raw material solution pool are faced to be slidable each other, a stirring mechanism 10 having blades 9 in the raw material solution pool for stirring the raw material solutions 6, 7 in the cooling process after bringing the raw material solutions into contact with the substrate 5 is installed in the raw material solution holders 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid phase growth apparatus by a slide boat method excellent in in-plane uniformity of the film thickness of an epitaxial layer.

  In recent years, the brightness of red light emitting diodes using AlGaAs has been improved, and it has come to be used as a display panel or a high-mount stop lamp for automobiles.

  In order to be used for these applications, it is required that the luminance is high enough to be recognized even in daylight. In order to meet this demand, light emitting diodes (LEDs) such as a single hetero structure (SH structure), a double hetero structure (DH structure), and a back-reflection type DH structure have been developed in terms of structure.

  The LED emits light in the vicinity of the pn interface, and as described above, the pn interface of the high-power LED is formed of a heterojunction. However, in the SH structure and DH structure, most of the light emitted to the GaAs substrate side is absorbed by the GaAs substrate. On the other hand, in the backside reflection type DH structure, high output is realized by sufficiently transmitting and reflecting the emission wavelength so as to transmit the emitted light. These epitaxial wafers for LEDs are manufactured by a liquid phase epitaxial method because (1) an epitaxial layer with excellent crystallinity can be obtained, and (2) a thick epitaxial layer of several tens of μm can be easily obtained. There are many.

  Further, from the viewpoint of growth conditions, studies are being made to increase the output of growth temperature, growth rate, and the like.

  Furthermore, an important characteristic with increasing output is in-plane uniformity of the film thickness of each epitaxial layer. If the thickness of each epitaxial layer varies, in-plane crystallinity, electrical characteristics, etc. can vary, resulting in in-plane characteristics non-uniformity and a reduction in device yield in the device manufacturing process. is there.

  FIG. 2 shows a schematic view of a liquid phase growth apparatus comprising a conventional slide boat for growing a GaAs thin film by liquid phase epitaxial growth. A slide boat made of graphite has a raw material solution holder holding body 11 having two or more raw material solution holders 3 forming a raw material solution reservoir for containing the raw material solution 6 in the sliding direction (only one is shown in FIG. 2 representatively). And a slider 2 having a substrate holder 1 on which a GaAs substrate 5 is placed by digging a part of the surface.

  The raw material solution holder 3 and the substrate holder 1 can be moved in the horizontal direction. The slide boat is put into a furnace and heated to saturate the Ga melt contained in the raw material solution holder 3 with GaAs to prepare a raw material solution, and then cooled to bring the raw material solution into a supercooled state. Thereafter, the slider 2 is moved so that the raw material solution holder 3 containing the raw material solution 6 comes onto the GaAs substrate 5 while gradually cooling, and the raw material solution is brought into contact with the GaAs substrate 5. As a result, a GaAs epitaxial layer grows on the GaAs substrate 5. After the thin film having a predetermined thickness is grown, the raw material solution holder 3 containing the raw material solution 6 is moved from above the GaAs substrate 5 by moving the slider 2 to stop the growth.

  Although the film thickness of the epitaxial layer of the epitaxial wafer grown by the conventional method depends on the structure of the furnace and the slide boat, 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 a temperature difference occurs between the outer peripheral portion and the central portion on the GaAs substrate 5 in the cooling process.

  Therefore, it has been proposed to improve the in-plane temperature non-uniformity on the GaAs substrate 5 by making the thermal conductivity of the material of the substrate holder 1 higher than the thermal conductivity of the material of the slider 2 (for example, , See Patent Document 1).

Although the structure is different from the above slide boat in that the sliding direction is not a linear direction but a rotating direction in a horizontal plane, a mechanism for quickly homogenizing the concentration of the raw material solution by forcibly stirring the raw material solution Is known, a vertical phase dipping method liquid phase growth apparatus in which a raw material solution is stirred until immediately before epitaxial growth is performed (see Patent Documents 2 and 3).
JP-A-9-221388 Japanese Unexamined Patent Publication No. 3-258894 Japanese Patent Laid-Open No. 7-69784

  However, in recent years, the area of a substrate has been increased in order to reduce the cost of manufacturing a light emitting element. Therefore, as the substrate becomes larger, the temperature difference between the outer peripheral portion and the central portion on the substrate becomes larger during the cooling process. As in Patent Document 1, just increasing the thermal conductivity of the material of the substrate holder 1 than the thermal conductivity of the material of the slider 2 limits the thermal conductivity of the material that can be used. It is difficult to make it uniform.

  Patent Documents 2 and 3 disclose a technique in which a raw material solution is stirred until immediately before epitaxial growth is performed in a liquid phase growth apparatus of a vertical dip method. There is no mention of the problem that the temperature difference between the parts becomes larger.

  Accordingly, an object of the present invention is to solve the above-mentioned problems and to homogenize the temperature of the raw material solution by providing a mechanism for stirring the raw material solution in the cooling process, so that the substrate can be grown on a large area substrate. It is an object of the present invention to provide a liquid phase growth apparatus in which the film thickness of an epitaxial layer is such that no difference occurs between the periphery and the center.

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

  The liquid phase growth apparatus according to the invention of claim 1 is configured such that a slider having a substrate holder and a raw material solution holder holding body having a raw material solution holder for forming a raw material solution reservoir are slidable relative to each other. In the liquid phase growth apparatus for growing a semiconductor epitaxial layer on a substrate by bringing the substrate into contact with the raw material solution while cooling from a predetermined temperature, the cooling process after bringing the raw material solution into contact with the raw material solution holder And a stirring mechanism having a blade for stirring the raw material solution in the raw material solution reservoir.

  Here, relative sliding of the slider having the substrate holder and the raw material solution holder forming the raw material solution reservoir rotates around a common central axis, in addition to the case where the sliding direction is linear. The case of the direction of rotation is also included. Further, in many cases, the number of raw material solution holders formed on the raw material solution holder holding body is two or more in the sliding direction, but a form having one raw material solution holder is also included in the present invention.

  A typical form of this liquid phase growth apparatus is that the slider and the raw material solution holder holder can be slid linearly with each other, and a raw material solution holder for forming a raw material solution reservoir is formed on the raw material solution holder holder. It is the form of the liquid phase growth apparatus by the slide boat method provided 2 or more in the sliding direction.

  According to a second aspect of the present invention, in the liquid phase growth apparatus according to the first aspect, the substrate is a large-area compound semiconductor substrate having a maximum outer diameter of 50 mm to 150 mm. Even in such a large-area compound semiconductor substrate, there is a feature that there is no difference in the film thickness of the epitaxial layer formed on the periphery between the periphery and the center. In this case, the maximum outer diameter indicates the size of one side when the substrate is rectangular, and the size of the diameter when the substrate is circular.

<Key points of the invention>
In a typical embodiment of the present invention, a slider having a substrate holder that accommodates a growth substrate and a raw material solution holder holding body having two or more raw material solution holders forming a raw material solution reservoir in a sliding direction are opposed to each other. In the liquid phase growth apparatus according to the slide boat method in which the substrate is brought into contact with the raw material solution while being cooled from a predetermined temperature and the epitaxial layer of the compound semiconductor is grown on the substrate, the raw material solution is slidable relatively linearly. In this embodiment, the holder is provided with a stirring mechanism having blades in the raw material solution reservoir for stirring the raw material solution in the cooling process after bringing the raw material solution into contact with the substrate.

  In such a liquid phase growth apparatus, when the epitaxial layer is grown on the substrate by cooling the substrate holder and the raw material solution holder and bringing the raw material solution into contact with the substrate, the blades are rotated during the cooling process. Therefore, the temperature of the central part and the outer peripheral part in the raw material solution can be made uniform, and the film thickness of the epitaxial layer formed even on a large-area substrate should not be different between the periphery and the center. Can do.

  According to the present invention, the raw material solution holder of the raw material solution holder holding body that is slidable relative to each other with the slider having the substrate holder is provided with a stirring mechanism, and the blade located in the raw material solution reservoir includes: Since the raw material solution is stirred in the cooling process after the raw material solution is brought into contact with the substrate, the epitaxial semiconductor grown on the large-area substrate having a maximum outer diameter of 50 to 150 mm is obtained. Regarding the layer, the difference between the film thickness around the substrate and the film thickness at the center can be reduced.

  Hereinafter, the present invention will be described based on the illustrated embodiments.

  FIG. 1 shows a liquid phase growth apparatus according to this embodiment, which is composed of a slide boat made of graphite having basically the same structure as a conventional one. That is, this slide boat includes a raw material solution holder holder 11 having two or more raw material solution holders 3 (two in FIG. 1, 3A and 3B) in the sliding direction, which form a raw material solution reservoir into which the raw material solution 6 or 7 is placed. And a slider 2 formed with a substrate holder 1 on which a GaAs substrate 5 as a growth substrate is placed by digging a part of the surface.

  The raw material solution holder holder 11 of the raw material solution holders 3A and 3B and the slider 2 of the substrate holder 1 can be moved in the horizontal direction.

  Each raw material solution holder 3A, 3B is provided with a stirring mechanism 10 for forcibly stirring the raw material solution to homogenize the temperature of the raw material solution. Specifically, the stirring mechanism 10 includes a blade 9 that stirs the raw material solution disposed in each of the raw material solution holders 3A and 3B, and one end fixed to the center of the blade 9 and the other end of the raw material solution holder holder. 11 includes a drive rod 8 led out to the outside of the motor 11 and a motor (not shown) that rotates the drive rod 8.

  This slide boat is put into a furnace and heated up, for example, a Ga melt contained in the raw material solution holder 3A is saturated with GaAs to prepare a raw material solution, and then cooled to bring the raw material solution into a supercooled state. Thereafter, the slider 2 is moved so that the raw material solution holder 3 </ b> A containing the raw material solution 6 comes on the GaAs substrate 5 while gradually cooling, and the raw material solution is brought into contact with the GaAs substrate 5. As a result, a GaAs epitaxial layer grows on the GaAs substrate 5. The same operation is performed for the raw material solution holder 3B. After a thin film having a predetermined thickness is grown for each, the raw material solution holder 3A or 3B containing the raw material solution 6 or 7 is moved from above the GaAs substrate 5 by moving the slider 2, and the growth is stopped.

  However, in the case of this embodiment, when the epitaxial layer is grown on the substrate by bringing the raw material solution into contact with the substrate, that is, in the above cooling process, the blade 9 of the stirring mechanism 10 is rotated by the motor via the drive rod 8. Let As a result, the temperature of the raw material solution is homogenized so that the thickness of the epitaxial layer grown on the GaAs substrate 5 immediately below the raw material solution reservoir does not differ between the periphery and the center of the GaAs substrate 5. It has become.

  In order to confirm the effects of the liquid phase growth apparatus of the present invention, trial production was performed using growth apparatuses such as the following Examples 1 and 2 and Comparative Examples 1 and 2.

<Example 1>
As Example 1, a graphite slide boat as shown in FIG. 4 was produced, and a single heterostructure AlGaAs was epitaxially grown using this. Here, the concave portion of the substrate holder 1 was a square having a side of 50 mm. The raw material solution holders 3A and 3B each have a prismatic shape with a bottom of 50 mm square. The stirring mechanism 10 is made of a graphite plate having a diameter of 40 mm and a thickness of 20 mm, and the tip of the graphite driving rod 8 is fixed to the center of the stirring mechanism 10. The rod 8 was extended upward to pass through a lid (not shown) of the raw material solution holder holder 11 and led out to the outside.

  In addition, as Comparative Example 1, a graphite slide boat having a substrate holder 1 having a square recess having a side of 50 mm as shown in FIG. 3 and prismatic raw material solution holders 3A and 3B having a bottom of 50 mm square. This was used to epitaxially grow a single heterostructure AlGaAs.

  The growth conditions experimentally produced in Example 1 are as follows. A 50 mm × 50 mm GaAs substrate 5 is set on the substrate holder 1. The raw material solution holder 3A was charged with Ga, GaAs, Al, and Te, and the raw material solution holder 3B was charged with Ga, GaAs, Al, and Zn. This slide boat (FIG. 4) is placed in a furnace, and in a hydrogen gas atmosphere, the blade 9 in the raw material solution holder 3 is rotated at 5 rpm, and the raw material solution is stirred and gradually cooled from 900 ° C. to 650 ° C. By epitaxial growth, followed by rapid cooling and removal from the furnace.

  On the other hand, the growth conditions made as a trial according to Comparative Example 1 are as follows. A 50 mm × 50 mm GaAs substrate 5 is set on the substrate holder 1. The raw material solution holder 3A was charged with Ga, GaAs, Al, and Te, and the raw material solution holder 3B was charged with Ga, GaAs, Al, and Zn. This slide boat (FIG. 3) was placed in a furnace and epitaxially grown by gradually cooling from 900 ° C. to 650 ° C. in a hydrogen gas atmosphere, and then rapidly cooled and taken out from the furnace.

  The obtained epitaxial wafer was scribed, and the film thickness of the 16-point epitaxial layer was measured at 10 mm intervals as shown in FIG. The film thickness measurement results of the epitaxial layer are shown in FIGS.

  As shown in FIG. 6, the measurement result when using the slide boat of FIG. 3 (liquid phase growth apparatus of Conventional Example 1) shows that the variation in the thickness of the epitaxial film grown by the raw material solution holder 3A is 11%. The variation of the film thickness of the epitaxial grown by the holder 3B was 12%. On the other hand, as shown in FIG. 7, the measurement result when using the slide boat of FIG. 4 (liquid phase growth apparatus of Example 1) shows that the variation in the thickness of the epitaxial film grown by the raw material solution holder 3A is 4. The variation in the thickness of the epitaxial film grown by the raw material solution holder 3B was 4.5%.

  Therefore, by rotating the graphite blade 9 as shown in FIG. 4 (liquid phase growth apparatus of Example 1) and stirring the raw material solution, the variation in the film thickness of the substrate was reduced.

<Example 2>
As Example 2, epitaxial growth of AlGaAs having a single heterostructure was performed using a graphite slide boat as shown in FIG. 9 (liquid phase growth apparatus of Example 2). Here, the concave portion of the substrate holder 1 was a square having a side of 150 mm. The raw material solution holders 3A and 3B each have a prismatic shape with a bottom surface of 150 mm square. The stirring mechanism 10 is made of a graphite plate having a diameter of 120 mm and a thickness of 20 mm, and the tip of a graphite driving rod 8 is fixed to the center of the stirring mechanism 10. The rod 8 was extended upward to pass through a lid (not shown) of the raw material solution holder holder 11 and led out to the outside.

  Further, as Comparative Example 2, a graphite slide boat having a substrate holder 1 having a square concave portion with a side of 150 mm as shown in FIG. 8 and prismatic raw material solution holders 3A and 3B having a bottom surface of 150 mm square is manufactured. This was used for epitaxial growth of single heterostructure AlGaAs.

  The growth conditions made as a prototype according to Example 2 are as follows. A GaAs substrate 5 of 150 mm × 150 mm is set on the substrate holder 1. The raw material solution holder 3A was charged with Ga, GaAs, Al, and Te, and the raw material solution holder 3B was charged with Ga, GaAs, Al, and Zn. This slide boat (FIG. 9) is placed in a furnace, and in a hydrogen gas atmosphere, the blade 9 in the raw material solution holder 3 is rotated at 5 rpm, and the raw material solution is stirred and gradually cooled from 900 ° C. to 650 ° C. By epitaxial growth, followed by rapid cooling and removal from the furnace.

  On the other hand, the growth conditions made as a trial by the comparative example 2 are as follows. A GaAs substrate 5 of 150 mm × 150 mm is set on the substrate holder 1. The raw material solution holder 3A was charged with Ga, GaAs, Al, and Te, and the raw material solution holder 3B was charged with Ga, GaAs, Al, and Zn. This slide boat (FIG. 8) was placed in a furnace and epitaxially grown by gradually cooling from 900 ° C. to 650 ° C. in a hydrogen gas atmosphere, and then rapidly cooled and taken out from the furnace.

  The obtained epitaxial wafer was scribed, and the film thickness of the 16-point epitaxial layer was measured at intervals of 30 mm as shown in FIG. The film thickness measurement results of the epitaxial layer are shown in FIGS.

  As shown in FIGS. 11 (a) and 11 (b), the measurement result when using the slide boat shown in FIG. 8 (liquid phase growth apparatus of Conventional Example 2) is the film thickness of the epitaxial layer grown by the raw material solution holder 3A. Of the epitaxial layer grown by the raw material solution holder 3B was 17%. In contrast, as shown in FIGS. 12 (a) and 12 (b), the measurement results when using the slide boat shown in FIG. 9 (liquid phase growth apparatus of Example 2) are as follows. The film thickness variation was 5.3%, and the film thickness variation of the epitaxial film grown by the raw material solution holder 3B was 6.4%.

  Therefore, as shown in FIG. 9 (liquid phase growth apparatus of Example 2), the dispersion of film thickness was reduced by rotating the graphite blade 9 and stirring the raw material solution.

  In the embodiment described above, the rotation method and conditions, that is, the blade structure, the blade driving method, the speed, the rotation speed, the direction, and the like are not described, but this is the optimum condition depending on the conditions of each liquid phase epitaxial growth method. These optimum conditions may be optimized so as to satisfy the object of the present invention. That is, according to the present invention, when the raw material solution is brought into contact with the substrate and then grown at a lower temperature, the raw material solution is stirred by rotating the blades during epitaxial growth so that the temperature is lowered uniformly in the substrate surface. The structure itself is meaningful, and the structure of the blades and the driving method for rotating the blades are arbitrary.

In the above-described embodiment, the growth example of the single heterostructure in which the Ga _1-x Al _x As epitaxial layer is grown on the GaAs substrate is described. However, the present invention is not limited to this, and the double heterostructure and the back surface reflection are described. It can also be used when growing a type double heterostructure, and the type and composition of the material are not limited thereto.

It is the schematic for demonstrating the liquid phase growth apparatus (slide boat) of this invention. It is the schematic for demonstrating the liquid phase growth apparatus (slide boat) of a prior art. 1 is a schematic view of a conventional liquid phase growth apparatus (slide boat) according to Comparative Example 1. FIG. It is the schematic of the liquid phase growth apparatus (slide boat) which concerns on Example 1 of this invention. It is the figure which showed the position (16 points | pieces at 10 mm intervals) which measured the film thickness of the epitaxial layer in Example 1 and Comparative Example 1. FIG. It is a figure which shows the measurement result of the film thickness of the epitaxial layer grown with the liquid phase growth apparatus (slide boat) of the comparative example 1. It is a figure which shows the measurement result of the film thickness of the epitaxial layer grown with the liquid phase growth apparatus (slide boat) of Example 1. FIG. 6 is a schematic view of a conventional liquid phase growth apparatus (slide boat) according to Comparative Example 2. FIG. It is the schematic of the liquid phase growth apparatus (slide boat) which concerns on Example 2 of this invention. It is the figure which showed the position (16 points | pieces at 30 mm intervals) which measured the film thickness of the epitaxial layer in Example 2 and Comparative Example 2. FIG. It is a figure which shows the measurement result of the film thickness of the epitaxial layer grown with the liquid phase growth apparatus (slide boat) of the comparative example 2. It is a figure which shows the measurement result of the film thickness of the epitaxial layer grown with the liquid phase growth apparatus (slide boat) which concerns on Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate holder 2 Slider 3 Raw material solution holder 3A Raw material solution holder 3B Raw material solution holder 4 Operation rod 5 GaAs substrate 6, 7 Raw material solution 8 Drive rod 9 Blade 10 Stirring mechanism 11 Raw material solution holder holder

Claims (2)

A slider having a substrate holder and a raw material solution holder holder having a raw material solution holder that forms a raw material solution reservoir are slidable relative to each other, and the substrate is placed on the raw material solution while cooling from a predetermined temperature. In a liquid phase growth apparatus that grows an epitaxial layer of a semiconductor on a substrate by contact,
A liquid phase growth apparatus, wherein the raw material solution holder is provided with a stirring mechanism in a raw material solution reservoir for stirring the raw material solution in a cooling process after the raw material solution is brought into contact with the substrate. The liquid phase growth apparatus according to claim 1,
A liquid phase growth apparatus, wherein the substrate is a large-area compound semiconductor substrate having a maximum outer diameter of 50 mm to 150 mm.

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