JP2009266892A - Method for manufacturing compound semiconductor crystalline substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a compound semiconductor crystalline substrate for making the compound semiconductor crystalline substrate with high accuracy and good yielding by laser machining. <P>SOLUTION: A compound semiconductor crystal such as a single AlN crystal is grown on a principal plane of a base substrate such as a SiC substrate. Laser 1a is irradiated from one of the compound semiconductor crystal and the base substrate to reach the other, thereby cutting the compound semiconductor crystal together with the base substrate. The compound semiconductor crystal may also be cut by irradiating the laser in a direction parallel to an interface between the compound semiconductor crystal and the base substrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a compound semiconductor crystal substrate such as an aluminum nitride crystal substrate using a laser.

  Conventionally, dicing processing, wire saw processing, laser processing, and the like have been used as processing methods for semiconductor single crystals. Moreover, the said processing method is utilized also for processes other than a semiconductor single crystal.

  The dicing process is to cut the semiconductor single crystal with a blade to which diamond abrasive grains are attached, and the wire saw process is a mechanical process to cut the semiconductor single crystal with a wire to which diamond abrasive grains are attached.

As a technique for processing a semiconductor single crystal with a laser, for example, there is a technique described in JP-A-11-224865. In the technique described in this document, an oxide single crystal or the like is cut using a CO ₂ laser. ing. More specifically, grooving is performed by laser on the oxide single crystal that is the workpiece, and the oxide single crystal is cleaved by the thermal stress stored in the lower part of the groove. Similarly, Japanese Patent Application Laid-Open No. 2006-82232 describes a method of cleaving a single crystal substrate with a cleavage plane of a crystal by thermal stress using a laser.

On the other hand, in the method described in Japanese Patent Laid-Open No. 2005-38459, single crystal silicon having a thickness of 0.4 mm to 1 mm is cut using a YAG laser, and Japanese Patent Laid-Open No. 2002-93751 and Japanese Patent Laid-Open No. 2004-39931 are cut. In the publication, after forming a device on a semiconductor single crystal substrate, grooving is performed by a laser, and breaking is used for cleaving.
Japanese Patent Laid-Open No. 11-224865 JP 2006-82232 A JP 2005-38459 A JP 2002-93751 A JP 2004-39931 A

  In the above-described conventional laser processing method, machining such as cleaving due to thermal stress or breaking is performed after grooving a crystal as a workpiece. For this reason, there is a problem in that the planned cleave position varies due to the influence of the cleavage plane (slip plane) of the crystal.

  In the case of machining such as dicing or wire sawing, mechanical stress is generated in the workpiece by physically contacting the workpiece (blade or wire) and the crystal as the workpiece. For this reason, there is still a problem that the expected cleaving position varies and cracks, cracks and chips occur.

  From the above, the conventional method has a problem that it is difficult to cut a crystal as designed, and cracks, cracks, and chips are likely to occur, resulting in poor yield and processing accuracy.

  The present invention has been made in order to solve the above-described problems, and a compound semiconductor crystal base material capable of manufacturing a compound semiconductor crystal base material with high accuracy and good yield by laser processing. An object is to provide a manufacturing method.

  In one aspect, the method for producing a compound semiconductor crystal substrate according to the present invention includes the following steps. A compound semiconductor crystal is grown on the main surface of the base substrate. By irradiating a laser so that one of the compound semiconductor crystal and the base substrate reaches the other, the compound semiconductor crystal is cut along with the base substrate.

  An example of the compound semiconductor crystal is an aluminum nitride crystal. In this case, the base substrate may be made of any of silicon carbide, aluminum nitride, and boron nitride. The thickness of the compound semiconductor crystal may be, for example, about 1 μm to 20 mm. The laser may be incident from the main surface side of the compound semiconductor crystal, or may be incident from the back surface side of the base substrate.

  In another aspect, the method for producing a compound semiconductor crystal substrate according to the present invention includes the following steps. A compound semiconductor crystal is grown on the main surface of the base substrate. The compound semiconductor crystal is cut by irradiating a laser in a direction parallel to the interface between the compound semiconductor crystal and the base substrate.

  The compound semiconductor crystal may be cut by a crystal plane parallel to any of the (0001) plane, (11-20) plane, (1-100) plane, and (1-102) plane of the compound semiconductor crystal. In addition, the compound semiconductor crystal is tilted by 0.1 ° to 5 ° with respect to a crystal plane parallel to any of the (0001) plane, (11-20) plane, (1-100) plane, and (1-102) plane. The compound semiconductor crystal may be cut and processed on the other surface.

  A solid Nd: YAG laser is used as the laser. The laser has a wavelength of 1064 nm, an output of 13 W to 15 W, a processing frequency of 3 kHz to 5 kHz, a pulse energy of 3.0 mJ to 4.3 mJ, and a maximum peak output. May be irradiated in an electromagnetic field mode of TEM00 mode.

  It is preferable to cut the compound semiconductor crystal while changing the irradiation trajectory of the laser to the compound semiconductor crystal.

  According to the present invention, since the compound semiconductor crystal can be cut using a laser without machining, problems such as generation of strain due to mechanical machining can be avoided, and high accuracy and good A compound semiconductor crystal base material can be manufactured with a yield.

  Hereafter, the manufacturing method of the compound semiconductor crystal base material in one embodiment of this invention is demonstrated.

  In this embodiment mode, a compound semiconductor crystal such as an aluminum nitride (hereinafter referred to as “AlN”) crystal is cut by only laser processing without machining, and cut into various shapes. By cutting the compound semiconductor crystal only by laser processing without performing machining in this way, it is possible to avoid problems such as distortion caused by mechanical processing, and cracks, cracks, chips, etc. of the compound semiconductor crystal Can also be suppressed. As a result, a compound semiconductor crystal substrate can be produced with high accuracy and good yield.

  Examples of compound semiconductor crystals include various compound semiconductor crystals such as AlN single crystals and AlN polycrystals. The compound semiconductor crystal can be grown on the base substrate by, for example, a sublimation method or a vapor phase growth method. In the case of an AlN single crystal, a silicon carbide (hereinafter referred to as “SiC”) substrate or an AlN single crystal substrate can be used as the base substrate, and in the case of AlN polycrystal, boron nitride (hereinafter referred to as “BN”) is used as the base substrate. Substrate) can be used.

  After a compound semiconductor crystal such as an AlN single crystal is grown on the base substrate by the method as described above, the compound semiconductor crystal grown on the base substrate is applied to, for example, a wafer process using a laser. Therefore, it is cut into various shapes such as a circle and a rectangle.

  At this time, the compound semiconductor crystal formed on the base substrate may be cut together with the base substrate, or slice processing may be performed to cut the compound semiconductor crystal along the interface between the base substrate and the compound semiconductor crystal.

  By using the laser in this way, the compound semiconductor crystal can be easily and accurately processed into various shapes such as a circle and a polygon. More specifically, a compound semiconductor crystal can be easily processed into a shape suitable for a susceptor of a synthesis furnace, or can be easily processed into a shape applicable to a wafer process such as photolithography. .

  When performing laser processing, first, a compound semiconductor crystal such as an AlN single crystal is placed together with a base substrate on an XY stage of a laser processing machine. Then, for example, the compound semiconductor crystal is irradiated with a laser from the main surface (surface opposite to the surface in contact with the base substrate) side of the compound semiconductor crystal.

  At this time, the compound semiconductor crystal can be cut into a desired shape by moving the XY stage on which the compound semiconductor crystal is placed. For example, when a compound semiconductor crystal is cut into a circle, the XY stage on which the compound semiconductor crystal is placed may be moved so as to draw a circular orbit several times. Here, the XY stage is driven so that the laser irradiation trajectory to the compound semiconductor crystal changes little by little. Specifically, when the cutting process is performed by irradiating a laser along a circular orbit, the cutting process may be performed by irradiating the compound semiconductor crystal with a laser along a plurality of circular orbits having different diameters. Thereby, even when the thickness of the compound semiconductor crystal is large, the compound semiconductor crystal can be efficiently processed into a desired shape using only a laser.

  The laser incident on the compound semiconductor crystal cuts the compound semiconductor crystal and finally reaches the base substrate. Here, the laser may be irradiated so as to cut the base substrate, but the laser may be adjusted so as to stop within the base substrate. By irradiating the laser so as to cut the base substrate, both the compound semiconductor crystal and the base substrate can be processed into a desired shape such as a circle.

  The thickness of the compound semiconductor crystal such as AlN crystal is preferably 1 μm or more and 20 mm or less, more preferably 5 mm or more and 10 mm or less. When the thickness of the compound semiconductor crystal is 1 μm or more, since the thickness of the compound semiconductor crystal itself is thin, the compound semiconductor crystal including the base substrate can be easily cut. Further, when the thickness of the compound semiconductor crystal is 20 mm or less, the possibility of cracking can be reduced because the compound semiconductor crystal itself is thick. Furthermore, when the thickness of the compound semiconductor crystal is 5 mm or more, the occurrence of cracks and cracks can be suppressed as compared to the thickness of about 1 μm, and when the thickness of the compound semiconductor crystal is 10 mm or less, In addition to shortening the processing time as compared with the case where the thickness is 20 mm, cracks and cracks can also be prevented.

  Laser processing of the compound semiconductor crystal can also be performed by irradiating a laser from the back side of the base substrate. In this case, for example, the compound semiconductor crystal may be placed on the XY stage of the laser processing machine with the base substrate facing up, and the back side of the base substrate may be irradiated with the laser in this state.

  At this time, both the base substrate and the compound semiconductor crystal can be cut by irradiating the laser from the base substrate side so as to penetrate both the base substrate and the compound semiconductor crystal.

  Further, when the material of the base substrate and the compound semiconductor crystal are different, for example, when an AlN single crystal is grown on the base substrate, and a material different from the AlN single crystal such as SiC is used as the base substrate, the base substrate Stress is generated in the vicinity of the interface between the crystal and the compound semiconductor crystal due to a lattice mismatch or a difference in physical properties. In such a case, the laser can be incident from the back surface of the base substrate as described above to release these stresses, and the compound semiconductor crystal can be cut without causing cracks, cracks, or chips. Is possible.

  Next, the case where the slicing process for cutting the compound semiconductor crystal along the interface between the base substrate and the compound semiconductor crystal is described.

  When the materials of the base substrate and the compound semiconductor crystal are different, the stress as described above is generated, causing cracks and cracks. Therefore, the compound semiconductor crystal is cut and processed along the interface between the base substrate and the compound semiconductor crystal using a laser.

  By slicing the compound semiconductor crystal, the compound semiconductor crystal can be released from the stress caused by the presence of the base substrate, and the compound semiconductor crystal with very few cracks and cracks can be taken out. Further, since there is no machining stress due to machining, damage such as cracks and cracks resulting from machining can be reduced.

  When a large number of compound semiconductor crystals are obtained by laser slicing as described above, a substrate of the same material may be used as a base substrate without using a substrate of a different material.

  A compound semiconductor crystal such as an AlN single crystal has a C plane (plane perpendicular to the plane orientation (0001)), an A plane (plane perpendicular to the plane orientation (11-20)), and an M plane (plane orientation (1-100). ) And a plane parallel to the R plane (plane perpendicular to the plane orientation (1-102)) and the like. Thereby, a crystal substrate having a polar surface, a nonpolar surface, and a semipolar surface can be produced.

  In addition, slicing can be performed on a plane parallel to the off-angle plane having an off-angle of 0.1 ° to 5 ° with respect to the four planes, and slicing can be performed on the entire surface.

  As the laser, for example, a solid Nd: YAG laser can be used. When using the laser, the wavelength is 1064 nm, the output is 13 W or more and 15 W or less, the processing frequency is 3 kHz or more and 5 kHz or less, the pulse energy is 3.0 mJ or more and 4.3 mJ or less, the maximum peak output is 35 kW or more and 60 kW or less, and the electromagnetic field mode is set. The TEM00 mode may be set.

  Next, an embodiment of the present invention will be described with reference to FIGS.

  As shown in FIGS. 1A and 1B, a SiC substrate 3 having a principal surface of (0001), an off angle of 3 °, a thickness of 400 μm, and a diameter of 30 mm was prepared as a base substrate. An AlN single crystal 2 having a thickness of 20 mm was grown on the main surface portion of the SiC substrate 3 by using a sublimation method.

  The AlN single crystal 2 is fixed to the stage of a laser processing machine, and the laser 1a is irradiated from the main surface side of the AlN single crystal 2 along the circular orbit 1 shown in FIGS. 1 (a) and 1 (b). The AlN single crystal 2 was cut. A solid Nd: YAG laser was used as the laser 1a. The wavelength of the laser 1a is 1064 nm, the output is 13 W to 15 W, the processing frequency is 3 kHz to 5 kHz, the pulse energy is 3.0 mJ to 4.3 mJ, the maximum peak output is 35 kW to 60 kW, and the electromagnetic field mode is the TEM00 mode. .

  In Example 1, as shown in FIG. 1C, the AlN single crystal 2 was cut while gradually changing the irradiation trajectory of the laser 1a. For example, the AlN single crystal 2 is cut by irradiating the laser 1a to the AlN single crystal 2 so as to draw a circular orbit having a different diameter multiple times while gradually moving the laser 1a in the radial direction of the AlN single crystal 2 (the radial direction of the circular orbit 1). What is necessary is just to process. In each of the following examples, the cutting process was performed in the same manner.

  By irradiating the AlN single crystal 2 with the laser 1a as described above, the AlN single crystal 2 having a thickness of 20 mm was cut, and further, the SiC substrate 3 as a base substrate could be cut. The cutting time at this time was about 4 hours.

  After cutting, the state of the AlN single crystal 2 was confirmed using an optical microscope, visual observation, and a scanning electron microscope (SEM), and it was confirmed that no cracks or cracks were generated.

  Moreover, since the inventors of this application compared the presence or absence of the generation | occurrence | production of the crack by a laser processing and grinding processing when changing the thickness of the AlN single crystal 2, the result is shown in following Table 1.

  As shown in Table 1, when the thickness of the AlN single crystal 2 is 1 μm or more and 20 mm or less, it can be seen that the laser processing can suppress the generation of cracks and cracks more than the grinding processing. Similarly, in the case of a compound semiconductor crystal other than an AlN single crystal, the occurrence of cracks and cracks can be suppressed by cutting by laser processing when the thickness is in the above range.

  In Example 2, an AlN single crystal substrate 4 was used as the base substrate. As the AlN single crystal substrate 4, a substrate having a plane orientation (0001), an off angle of 0.5 °, a thickness of 1 mm, and a diameter of 50 mm was prepared. As shown in FIGS. 2A and 2B, an AlN single crystal 22 having a thickness of 10 mm was grown on the main surface portion of the AlN single crystal substrate 4 by using a sublimation method.

  The AlN single crystal 22 is fixed to the stage of the laser processing machine together with the AlN single crystal substrate 4, and the laser 1a is formed along the rectangular track 21 from the back side of the AlN single crystal substrate 4 as shown in FIG. Was irradiated. In order to irradiate the laser 1a from the back surface side of the AlN single crystal substrate 4, for example, the AlN single crystal substrate 4 may be placed on the stage of the laser processing machine with the back surface of the AlN single crystal substrate 4 facing up and irradiated with the laser 1a from above. .

  The laser 1a was irradiated as described above, and as shown in FIGS. 2A and 2B, the AlN single crystal 22 was cut so as to have a square shape with one side of 10 mm. Laser irradiation conditions are the same as in Example 1. As a result, the AlN single crystal substrate 4 and the AlN single crystal 22 could be cut in a processing time of about 6 hours. Although the cut surface turned into a white film due to the generation of a work-affected layer, the white film on the surface could be removed by washing with an organic solvent and alcohol.

  After the cutting process, when the state of the AlN single crystal 22 was observed with an optical microscope, visual observation, and scanning electron microscope (SEM), it was confirmed that no cracks or cracks occurred.

  In Example 3, a boron nitride (BN) substrate 5 having a thickness of 2 mm and a diameter of 55 mm was prepared as a base substrate. As shown in FIGS. 3A and 3B, an AlN polycrystal 23 having a thickness of 20 mm was grown on the main surface portion of the BN substrate 5 by using a sublimation method.

  The AlN polycrystal 23 is fixed to a stage of a laser processing machine, and the laser 1a is irradiated along the circular orbit 21 from the back surface of the BN substrate 5, and an AlN polycrystal having a diameter of 25 mm as shown in FIG. 23 cutting processes were performed. Laser irradiation conditions are the same as in Example 1. Also in the case of this example, when the BN substrate 5 as the base substrate was cut and processed, the processing time was about 5 hours.

  After the cutting process, when the state of the AlN polycrystal 23 was observed with an optical microscope, visual observation, and scanning electron microscope (SEM), it was confirmed that no cracks or cracks occurred.

  In Example 4, an SiC substrate 3 having a plane orientation (0001), an off angle of 3 °, a thickness of 400 μm, and a diameter of 20 mm was prepared as a base substrate. On the main surface portion of this SiC substrate 3, as shown in FIGS. 4A and 4B, an AlN single crystal 2 having a thickness of 10 mm was grown using a sublimation method.

  The AlN single crystal 2 was fixed to a stage of a laser processing machine, and lasers 1a and 1b were irradiated to the side surface portion of the AlN single crystal 2. In Example 4, as shown in FIG. 4B, the lasers 1a and 1b are alternately irradiated along the linear trajectory 21 from both sides of the AlN single crystal 2 to have a diameter of 20 mm and a thickness of 9 Slicing of 7 mm AlN single crystal 2 was performed. Laser irradiation conditions are the same as in Example 1. The processing time was about 10 hours and the cutting allowance was 300 μm. In Example 4, the slicing process was also used to remove the SiC substrate 3 as the base substrate.

  After the cutting process, when the state of the AlN polycrystal 23 was observed with an optical microscope, visual observation, and scanning electron microscope (SEM), it was confirmed that no cracks or cracks occurred.

  In Example 5, a SiC substrate having a plane orientation (0001), an off angle of 3 °, a thickness of 400 μm, and a diameter of 15 mm was prepared as a base substrate. An AlN single crystal 2 (see FIG. 5A) having a thickness of 20 mm was grown on the main surface portion of the SiC substrate using a sublimation method.

  As shown in FIG. 5B, the laser 1a and 1b were irradiated to the AlN single crystal 2 in a direction parallel to the plane 6 (C plane) perpendicular to the plane orientation (0001) 5. Also in Example 5, the AlN single crystal 2 was processed by alternately irradiating the lasers 1a and 1b from both sides of the AlN single crystal 2, and the free-standing substrate 7 was cut out by slicing. Specifically, five substrates having a thickness of 1 mm and a diameter of about 16 mm were cut out.

  When the cut-out self-supporting substrate 7 was observed with an optical microscope, visual observation, and a scanning electron microscope (SEM), it was confirmed that the self-supporting substrate 7 was not cracked or cracked.

  In Example 6, a SiC substrate having a plane orientation (0001), an off angle of 3 °, a thickness of 400 μm, and a diameter of 15 mm was prepared as a base substrate. An AlN single crystal 2 (see FIG. 6A) having a thickness of 20 mm was grown on the main surface portion of the SiC substrate using a sublimation method.

  As shown in FIG. 6B, the laser 1a and 1b were irradiated to the AlN single crystal 2 in a direction parallel to the plane 61 (M plane) parallel to the plane orientation (0001) 5. Also in Example 6, the AlN single crystal 2 was processed by alternately irradiating the lasers 1a and 1b from both sides of the AlN single crystal 2, and the free-standing substrate 7 was cut out by slicing. Specifically, five square substrates having a thickness of 400 μm and a side of about 15 mm were cut out.

  When the cut-out self-supporting substrate 7 was observed with an optical microscope, visual observation, and a scanning electron microscope (SEM), it was confirmed that the self-supporting substrate 7 was not cracked or cracked.

  Although the embodiments and examples of the present invention have been described above, the configurations of the above embodiments and examples can be combined as appropriate. The embodiments and examples disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and includes meanings equivalent to the terms of the claims and all modifications within the scope.

(A) is a top view which shows the AlN single crystal before the cutting process in Example 1 of this invention, (b) is a side view of the AlN single crystal shown to (a), (c) is laser processing It is a cross-sectional schematic diagram for demonstrating a method. (A) is a top view which shows the AlN single crystal before the cutting process in Example 2 of this invention, (b) is a side view of the AlN single crystal shown to (a). (A) is a top view which shows the AlN polycrystal before the cutting process in Example 3 of this invention, (b) is a side view of the AlN polycrystal shown to (a). (A) is a top view which shows the AlN single crystal before the cutting process in Example 4 of this invention, (b) is a side view of the AlN single crystal shown to (a). (A) is a top view which shows the AlN single crystal before the cutting process in Example 5 of this invention, (b) is a side view of the AlN single crystal shown to (a). (A) is a top view which shows the AlN single crystal before the cutting process in Example 6 of this invention, (b) is a side view of the AlN single crystal shown to (a).

Explanation of symbols

  1,21 orbit, 1a, 1b laser, 2,22 AlN single crystal, 3 SiC substrate, 4 BN substrate, 5 plane orientation (0001), 6 (0001) plane, 7 freestanding substrate, 23 AlN polycrystal.

Claims (10)

A step of growing a compound semiconductor crystal on the main surface of the base substrate;
Cutting the compound semiconductor crystal together with the base substrate by irradiating a laser so as to reach the other from one of the compound semiconductor crystal and the base substrate;
A method for producing a compound semiconductor crystal substrate comprising: The compound semiconductor crystal is an aluminum nitride crystal,
The method for producing a compound semiconductor crystal base material according to claim 1, wherein the base substrate is composed of any one of silicon carbide, aluminum nitride, and boron nitride.   The manufacturing method of the compound semiconductor crystal base material of Claim 1 or Claim 2 whose thickness of the said compound semiconductor crystal is 1 micrometer or more and 20 mm or less.   The manufacturing method of the compound semiconductor crystal base material in any one of Claims 1-3 which makes a laser inject from the main surface side of the said compound semiconductor crystal, and cuts the said compound semiconductor crystal and the said base substrate.   The manufacturing method of the compound semiconductor crystal base material in any one of Claims 1-3 which makes a laser inject from the back surface side of the said base substrate, and cuts the said base substrate and the said compound semiconductor crystal. A step of growing a compound semiconductor crystal on the main surface of the base substrate;
Cutting the compound semiconductor crystal by irradiating a laser in a direction parallel to the interface between the compound semiconductor crystal and the base substrate;
A method for producing a compound semiconductor crystal substrate comprising:   The compound semiconductor crystal is cut by a crystal plane parallel to any of a (0001) plane, a (11-20) plane, a (1-100) plane, and a (1-102) plane of the compound semiconductor crystal. 6. A method for producing a compound semiconductor crystal substrate according to 6.   The compound semiconductor crystal is tilted by 0.1 ° to 5 ° with respect to a crystal plane parallel to any of the (0001) plane, (11-20) plane, (1-100) plane, and (1-102) plane. The method for producing a compound semiconductor crystal substrate according to claim 6, wherein the compound semiconductor crystal is cut and processed on a surface.   A solid Nd: YAG laser is used as the laser, and the laser has a wavelength of 1064 nm, an output of 13 W to 15 W, a processing frequency of 3 kHz to 5 kHz, a pulse energy of 3.0 mJ to 4.3 mJ, and a maximum peak output. The manufacturing method of the compound semiconductor crystal base material in any one of Claims 1-8 which irradiates in 35 to 60 kW, and electromagnetic field mode is TEM00 mode.   The method for producing a compound semiconductor crystal substrate according to any one of claims 1 to 9, wherein the compound semiconductor crystal is cut while changing an irradiation trajectory of the laser to the compound semiconductor crystal.

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