JP2008177286A - Method for manufacturing epitaxial wafer, epitaxial wafer and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing epitaxial wafer for obtaining a wafer having a uniform in-plane film thickness. <P>SOLUTION: In the method for manufacturing epitaxial wafer wherein solution holders 5 for storing a raw material solution L are provided opposed with each other at the upper part of a substrate holder 3 for storing a substrate 2, and the substrate holder 3 or the solution holder 5 are slid until the substrate 2 is placed in contact with the raw material solution L to permit a semiconductor crystal to grow on the substrate 2, an upper part of the side surface of the substrate 2 is placed in contact with the raw material solution L. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an epitaxial wafer, an epitaxial wafer, and an apparatus for improving the in-plane film thickness of a semiconductor crystal (epitaxial layer) grown on a substrate using a liquid phase epitaxial growth method.

  With respect to red light emitting diodes (red LEDs), demand for outdoor displays, mobile phones, and the like has expanded due to the progress of higher brightness. Along with this, red LEDs are required to be compact and inexpensive, and an improvement in the acquisition rate of the number of chips that can be acquired from one wafer is required. The uniformity of the in-plane film thickness greatly affects the chip acquisition rate, but when manufacturing wafers using the liquid phase epitaxial growth method, the growth jig (substrate holder) comes into contact with the raw material solution (melt). Currently, it is difficult to make the film thickness around the periphery of the wafer uniform.

  The prior art document information related to the invention of this application includes the following.

JP 2006-80169 A

  In the conventional manufacturing method using the liquid phase epitaxial growth method, a solution reservoir is provided facing the upper portion of the growth jig, and the growth substrate set portion of the slider in the jig is placed directly below the solution reservoir (substrate surface). The semiconductor crystal is grown on the substrate while the slider is sequentially moved so that the raw material solution comes into contact) and the heater around the jig is cooled.

  However, since the substrate setting portion and the solution reservoir portion have the same width, the raw material solution around the portion where the jig and the raw material solution are in contact is unlikely to fall on the substrate due to surface tension and does not sufficiently contact the substrate. .

  In addition, since the jig is cooled faster than the wafer, the semiconductor crystal to be grown on the periphery of the wafer surface grows thicker than the center of the wafer.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an epitaxial wafer manufacturing method, an epitaxial wafer and an apparatus capable of obtaining a wafer having a uniform in-plane film thickness.

  The present invention has been devised to achieve the above object, and the invention of claim 1 is provided with a solution holder for storing the raw material solution facing the upper portion of the substrate holder for storing the substrate. In the method of manufacturing an epitaxial wafer in which the substrate holder or the solution holder is slid to bring the substrate into contact with the raw material solution, and a semiconductor crystal is grown on the substrate, the upper part of the side surface of the substrate is brought into contact with the raw material solution. It is a manufacturing method of an epitaxial wafer.

  A second aspect of the present invention is the epitaxial wafer manufacturing method according to the first aspect, wherein the substrate holder positioned around the substrate surface is brought into contact with the raw material solution.

  A third aspect of the present invention is an epitaxial wafer produced by growing a semiconductor crystal on the substrate using the method for producing an epitaxial wafer according to the first or second aspect.

  In the invention of claim 4, a solution holder for storing a raw material solution is provided on an upper portion of a substrate holder for storing a substrate, and the substrate holder or the solution holder is slid to the raw material solution. In an epitaxial wafer manufacturing apparatus in which a substrate is brought into contact and a semiconductor crystal is grown on the substrate, manufacturing of an epitaxial wafer provided with a recess for exposing an upper portion of the substrate side surface around a substrate storage portion of the substrate holder Device.

  A fifth aspect of the present invention is the epitaxial wafer manufacturing apparatus according to the fourth aspect, wherein the lower part of the solution reservoir of the solution holder is formed in a tapered shape so that the lower part is widened.

  According to the present invention, an excellent effect that a wafer having a uniform in-plane film thickness can be manufactured is exhibited.

  First, an example of an epitaxial wafer manufactured using the manufacturing method according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 2, the LED epitaxial wafer 21 according to the present embodiment has a plurality of epitaxial layers (semiconductor crystals), that is, a p-type GaAlAs layer (p-GaAlAs active layer) 23 on a GaAs substrate 22. , An epitaxial wafer having a single heterostructure formed by sequentially growing n-type GaAlAs layers (n-GaAlAs cladding layers) 24.

  The p-type GaAlAs layer 23 is made to have an Al mixed crystal ratio (for example, about 0.35 to 0.4 when red) necessary for the desired light emission wavelength of the LED. The n-type GaAlAs layer 24 is a layer that prevents backflow of electrons and becomes a window transparent to the light emitted from the p-type GaAlAs layer 23. For this reason, the n-type GaAlAs layer 24 has an Al mixed crystal ratio (for example, about 0.6 to 0.8) larger than that of the p-type GaAlAs layer 23. As the p-type impurity, for example, Zn is used, and as the n-type impurity, for example, Te is used.

  Now, an epitaxial wafer manufacturing apparatus used in the manufacturing method according to the present embodiment will be described with reference to FIG.

  FIG. 1 is a longitudinal sectional view of an epitaxial wafer manufacturing apparatus used in an epitaxial wafer manufacturing method showing a preferred embodiment of the present invention, and an enlarged view of a main part thereof.

  As shown in FIG. 1, an epitaxial wafer manufacturing apparatus (liquid phase epitaxial growth apparatus, hereinafter also referred to as an apparatus) 1 according to this embodiment includes a slidable substrate holder (growth jig) 3 for storing a substrate 2. The pedestal (solution receiver) 4 on which the substrate holder 3 is placed and the slidable solution holder 5 that is provided facing the upper portion of the substrate holder 3 and that stores the raw material solution L are mainly configured. .

  This apparatus 1 is an apparatus for producing an epitaxial wafer by growing a semiconductor crystal on a substrate 2 by a liquid phase epitaxial growth (LPE) method. The LPE method is a method in which an epitaxial layer is grown and formed on a substrate by sequentially contacting and separating the substrate with a supersaturated solution (raw material solution) of a raw material installed at a predetermined location in the apparatus. Since the LPE method is a growth method close to thermal equilibrium, there is an advantage that defects that hinder light emission are not easily formed in the epitaxial layer, and that the cost of equipment and raw materials is less than that of the vapor phase method.

  In the present embodiment, the GaAs substrate 22 used for manufacturing the LED epitaxial wafer 21 described with reference to FIG.

  The substrate holder 3 is a carbon graphite jig, and includes a flat slider 3a and an operation rod 3b provided at the other end of the slider 3a. A substrate storage portion (substrate holder portion) 6 for storing the substrate 2 is formed on the upper end of the slider 3a.

  The substrate storage portion 6 is formed so that the height of the surface of the substrate 2 and the surface of the slider 3a coincide when the substrate 2 is stored. In order to horizontally store the substrate 2 in the substrate storage unit 6, the bottom surface of the substrate storage unit 6 is subjected to countersink processing. The substrate holder 3 is provided on the base 4 so as to be movable relative to the solution holder 5 (in the left-right direction in FIG. 1).

  Around the substrate storage portion 6 of the slider 3a, a recess 7 is provided for exposing the upper portion of the side surface of the substrate 2. Although not shown in detail, the recess 7 is formed in a substantially annular shape or a substantially frame shape in plan view. The depth of the recess 7 is set to about 1/3 of the thickness of the substrate 2. The width of the recess 7 is set to about 1/3 of the diameter or length of the substrate 2.

  The solution holder 5 includes a plurality of solution reservoirs 8 that store raw material solutions that are raw materials for semiconductor crystals. The solution reservoirs 8 are provided at predetermined intervals along the moving direction of the substrate holder 3. A cap holder 9 that keeps the inside of the solution reservoir 8 airtight is provided on the upper portion of the solution reservoir 8.

  As raw materials for semiconductor crystals, Ga, GaAs, Al, Zn, and Te are used. In the raw material solution L, the above-described raw materials (or their compounds) are usually set in the solution reservoir 8 in a solid state, the substrate holder 3 is installed at a predetermined location in the apparatus 1, and then provided in the apparatus 1. It is obtained by dissolving raw materials (or their compounds) with a heater to make a liquid.

  The lower part of the solution reservoir 8 is a tapered part 8t formed in a tapered shape so that the lower part becomes wider. The width of the lowermost end of the taper portion 8t is made wider than the width of the substrate 2.

  Next, an epitaxial wafer manufacturing method according to the present embodiment will be described together with the operation of the apparatus 1.

  First, the raw material described above is set in the solution reservoir 8 of the solution holder 5, and the raw material solution L is prepared by melting the raw material with a heater. The substrate 2 is accommodated in the substrate accommodating portion 6 of the slider 3 a of the substrate holder 3.

  The substrate holder 3 (or the solution holder 5 may be left) is slid (to the left in FIG. 1), and the substrate holder 3 is moved to a position where the first stage (leftmost in FIG. 1) solution reservoir 8 and the center of the surface of the substrate 2 are located. Move 3. The surface of the substrate 2 is in contact with the raw material solution L.

  At the same time, since the recess 7 is provided around the substrate storage portion 6 of the slider 3a, the upper portion of the side surface of the substrate 2 is exposed from the slider 3a, and the upper portion of the side surface of the substrate 2 contacts the raw material solution L. Furthermore, since the lower portion of the solution reservoir 8 is a tapered portion 8t, the entire surface of the substrate 2 and the surface portion of the slider 3a of the substrate holder 3 located around the surface of the substrate 2 are in contact with the raw material solution L. .

  In this state, a first-layer semiconductor crystal is grown on the substrate 2 using the raw material stored in the first-stage solution reservoir 8. After the growth of the first layer semiconductor crystal, the substrate holder 3 is slid in the same manner, and the substrate holder 3 is moved to the position where the second and third stage solution reservoirs 8 and the center of the surface of the substrate 2 are located. The second semiconductor layer and the third semiconductor crystal are sequentially grown on the first semiconductor crystal.

  As described above, for example, the epitaxial wafer 21 as shown in FIG. 2 is obtained.

  When the semiconductor crystal of the second and subsequent layers is grown, the semiconductor crystal also grows on the side surface of the substrate 2. However, since this semiconductor crystal is a thin film that is sufficiently thinner than the substrate thickness, there is no effect.

  Further, when the device 1 is used for a long time, the concave portion 7 may become shallow, but when the concave portion 7 becomes shallow, the slider 3a may be replaced.

  The operation of this embodiment will be described.

  In the manufacturing method according to this embodiment, the slider of the substrate holder 3 is brought into contact with the raw material solution L by contacting the upper portion of the side surface of the substrate 2 and further the surface portion of the slider 3a of the substrate holder 3 positioned around the surface of the substrate 2. The contact area between 3a and the side surface of the substrate 2 is reduced, and further, the contact area between the entire surface of the substrate 2 and the raw material solution L is increased.

  That is, since the area of the portion where the slider 3a and the raw material solution L are in contact with each other increases, the surface tension hardly acts on the raw material solution L around the surface of the substrate 2, and the raw material solution L around the surface of the substrate 2 is formed on the substrate 2. It is easy to fall and fully contacts the entire surface of the substrate 2.

  In general, the cooling rate of the substrate holder is faster than that of the wafer (substrate). However, in the manufacturing method according to the present embodiment, the entire surface of the substrate 2 and the upper part of the side surface are in contact with the raw material solution L during the growth of the semiconductor crystal. Therefore, it is difficult to cool the periphery of the substrate storage portion 6 of the substrate holder 3. Thereby, the semiconductor crystal to be grown on the wafer periphery can be grown with the same thickness as the wafer center.

  Therefore, according to the manufacturing method according to the present embodiment, the epitaxial wafer 21 having a uniform in-plane film thickness can be manufactured.

  According to the apparatus 1 according to the present embodiment, the concave portion 7 for exposing the upper portion of the side surface of the substrate 2 is provided around the substrate storage portion 6 of the substrate holder 3. Can be contacted. Further, in the apparatus 1, the lower part of the solution reservoir 8 is a tapered part 8 t formed in a tapered shape so that the lower part is widened, so that the substrate holder 3 positioned around the surface of the substrate 2 is placed in the raw material solution L. The surface portion of the slider 3a can be brought into contact.

  Thereby, according to the apparatus 1, the manufacturing method mentioned above can be implemented and the epitaxial wafer 21 with a uniform in-plane film thickness can be manufactured.

  In the above-described embodiment, the method for manufacturing an epitaxial wafer having a single hetero structure has been described. However, the present invention can also be applied to a method for manufacturing an epitaxial wafer having a double hetero structure, and in this case, the same effect as described above can be obtained.

  As an epitaxial wafer having a double hetero structure for LED, a p-type GaAlAs cladding layer, a p-type GaAlAs active layer, and a second conductivity-type cladding layer as a first conductivity type cladding layer on a conductive p-type GaAs substrate. The n-type GaAlAs cladding layer is formed by sequentially growing.

  The present invention can also be applied to a method for manufacturing an epitaxial wafer for a back-reflection type LED. This epitaxial wafer is produced, for example, by removing a p-type GaAs substrate from an epitaxial wafer having a double hetero structure.

  The present invention is very useful when used in the manufacture of epitaxial wafers for LEDs, particularly red LEDs, but may also be used in the manufacture of epitaxial wafers for semiconductor lasers (LDs), and in this case as described above. Similar effects can be obtained.

  The compound semiconductor constituting the epitaxial layer is not limited to the above-described compound semiconductor, and a ternary mixed crystal system such as InGaP or a quaternary mixed crystal compound semiconductor such as GaInPAs, AlGaInAs, AlGaInP, and InPAsSb may be used.

(Example)
The epitaxial wafer 31 for LED as shown in FIG. 3 was produced by the manufacturing method mentioned above using the epitaxial wafer manufacturing apparatus 1 of FIG. This epitaxial wafer 31 is obtained by appropriately designing the Al mixed crystal ratio of the epitaxial layer in accordance with the emission wavelength of the LED desired to be obtained in the epitaxial wafer 21 of FIG.

That is, the epitaxial wafer 31 is an epitaxial wafer having a single hetero structure formed by sequentially growing a p-type GaAl _0.35 As layer 33 on a conductive p-type GaAs substrate 32 by 20 μm and an n-type GaAl _0.60 As layer 34 by 40 μm. It is. As the p-type GaAs substrate 32, a 10 mm × 10 mm square substrate was used.

  The substrate holder 3 used was a carbon graphite jig shown. The concave portion 7 was processed so that the upper portion of the substrate 2 protruded 1/3 from the substrate storage portion 6 and the periphery of the substrate storage portion 6 was recessed with a width of 3 mm. A tapered portion 8t having a length of 5 mm and an angle of 30 ° was provided on the solution side below the solution reservoir 8.

  The substrate holder 3 holding and holding the substrate 32 in the substrate storage unit 6 is installed at a predetermined location in the apparatus 1, the apparatus 1 is heated to 900 ° C. in a hydrogen stream, held for 3 hours, and then up to 700 ° C. The temperature was lowered at a rate of 1 ° C./min.

  The substrate 32 is brought into contact with the raw material solution L during the growth of the semiconductor crystal by moving the slider 3a so as to be directly below the solution reservoir 8 at each stage. After the raw material solution L came into contact with the substrate 32, the epitaxial layer was grown on the substrate 32 by lowering the ambient temperature, and the epitaxial wafer 31 was produced.

  Using the obtained epitaxial wafer 31, the in-plane film thickness (including the substrate 32) was measured with a microscope (x1000), and the uniformity was evaluated.

(Comparative example)
For comparison, an epitaxial layer is grown on the substrate 32 in the same manner as in the embodiment using a conventional liquid phase epitaxial growth apparatus in which the substrate holder and the solution reservoir are not processed. The film thickness (including the substrate) was measured with a microscope (× 1000 times), and the uniformity was evaluated.

  Table 1 shows the evaluation results of the epitaxial wafer 31 of the example manufactured and the epitaxial wafer of the comparative example.

  As shown in Table 1, the wafer 31 of the example and the wafer of the comparative example were measured. As a result, in the wafer 31 of the example, the in-plane film thickness is uniform from a position 4 mm inside from one side of the wafer edge (the same result for the remaining three sides), and 2 mm outward from the comparative example, The uniformity of the in-plane film thickness was improved.

  That is, since a 10 mm × 10 mm square substrate was used as the substrate 32, the area of the portion having a uniform in-plane film thickness increased 2.25 times in the wafer 31 of the example compared to the wafer of the comparative example. I understand.

  In the embodiment, the example of the epitaxial wafer 31 having the p / n structure in which the p-type active layer and the n-type cladding layer are sequentially formed on the p-type substrate 32 has been described. However, the present invention relates to the n-type substrate. Further, it can be applied to an epitaxial wafer having an n / p structure in which an n-type active layer and a p-type cladding layer are sequentially formed.

It is the longitudinal cross-sectional view of the manufacturing apparatus of the epitaxial wafer used for the manufacturing method of the epitaxial wafer which shows suitable embodiment of this invention, and its principal part enlarged view. It is sectional drawing which shows an example of the epitaxial wafer produced using the manufacturing method which concerns on this embodiment. It is sectional drawing which shows an example of the epitaxial wafer produced using the manufacturing method which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Epitaxial wafer manufacturing apparatus 2 Substrate 3 Substrate holder 5 Solution holder 6 Substrate storage part 7 Recess 8 Solution reservoir part 8t Taper part

Claims (5)

  A solution holder for storing a raw material solution is provided on an upper part of a substrate holder for storing a substrate, and the substrate holder or the solution holder is slid to bring the substrate into contact with the raw material solution. An epitaxial wafer manufacturing method for growing a semiconductor crystal thereon, the method comprising bringing the upper part of the side surface of the substrate into contact with the raw material solution.   The method for producing an epitaxial wafer according to claim 1, wherein the substrate holder located around the substrate surface is brought into contact with the raw material solution.   An epitaxial wafer produced by growing a semiconductor crystal on the substrate using the method for producing an epitaxial wafer according to claim 1.   A solution holder for storing a raw material solution is provided on an upper part of a substrate holder for storing a substrate, and the substrate holder or the solution holder is slid to bring the substrate into contact with the raw material solution. An epitaxial wafer manufacturing apparatus for growing a semiconductor crystal thereon, wherein a recess for exposing an upper portion of a side surface of the substrate is provided around a substrate storage portion of the substrate holder.   The epitaxial wafer manufacturing apparatus according to claim 4, wherein a lower portion of the solution reservoir portion of the solution holder is formed in a tapered shape so that a lower portion is widened.

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