HK1101220B - Method for manufacturing nitride semiconductor substrate - Google Patents

Description

Method for processing nitride semiconductor substrate

Technical Field

The present invention relates to a nitride semiconductor substrate and a method for processing the nitride semiconductor substrate.

Background

Conventionally, various substrates have been known as gallium nitride substrates (GaN substrates) (see documents 1 to 3). Document 2 describes a gallium nitride wafer having an Orientation Flat (OF) as a mark indicating a crystal orientation. Such an orientation flat is formed by grinding after confirming the crystal orientation by X-ray diffraction.

Document 4 describes a method of forming an orientation flat on a wafer made of a compound semiconductor such as GaAs, GaP, and InP, instead of GaN. Further, document 5 describes a method of detecting the position of an orientation flat formed on a wafer.

Document 1: japanese laid-open patent publication No. 2003-183100

Document 2: japanese laid-open patent publication No. 2004-335645

Document 3: japanese laid-open patent publication No. 2000-12900

Document 4: japanese unexamined patent publication Hei 7-307316

Document 5: japanese unexamined patent publication No. 2-291146

However, the positional accuracy of the orientation flat of the gallium nitride substrate is not necessarily sufficient, and further improvement of the positional accuracy is desired.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a nitride semiconductor substrate and a method of processing a nitride semiconductor substrate, which can specify the position of a mark indicating crystal orientation with high accuracy.

In order to solve the above problems, a method for processing a nitride semiconductor substrate according to the present invention includes: preparing a disk-shaped nitride semiconductor substrate having a plurality of stripe (stripe) regions having a defect concentrated region in which a crystal defect density is higher than that of a surrounding low-defect region; and forming a notch at a predetermined position on the edge of the nitride semiconductor substrate with reference to a direction in which at least one of the plurality of stripe regions extends.

In the method for processing a nitride semiconductor substrate according to the present invention, a nitride semiconductor substrate having a plurality of stripe regions is used. When the plurality of stripe regions are formed, the extending direction of the stripe regions can be aligned with a desired crystal orientation with high accuracy. Therefore, by using the direction in which the stripe region extends as a reference, the position of the notch, which is a mark indicating the crystal orientation, can be determined with high accuracy without using an X-ray diffraction method.

In addition, it is preferable that the cutout is an orientation flat. In this case, the position of the orientation plane can be determined with high accuracy.

In addition, it is preferable to form the orientation flat using a dicing saw (dicing saw). Thereby, the orientation flat can be simply formed.

In addition, preferably, the notch is a notch (notch). In this case, the cut-out portion can be reduced in forming the notch.

Preferably, the step of forming the notch includes: observing the nitride semiconductor substrate through a microscope, thereby determining a straight line passing through the center of the nitride semiconductor substrate along a direction in which at least one of the plurality of stripe regions extends; and rotating the nitride semiconductor substrate by a predetermined angle with respect to the straight line and with respect to the center of the nitride semiconductor substrate. In this case, the position of the notch can be determined with higher accuracy.

In the step of determining the straight line, it is preferable that the nitride semiconductor substrate is irradiated with ultraviolet rays. Thus, the low-defect region and the defect-concentrated region are more clearly distinguished from each other, and therefore, the straight line can be easily determined with high accuracy.

The nitride semiconductor substrate of the present invention is a nitride semiconductor substrate having an arc-shaped edge, and includes: a plurality of stripe regions having a defect concentrated region having a higher density of crystal defects than surrounding low-defect regions; an orientation flat provided on an edge of the nitride semiconductor substrate and extending substantially at right angles to a direction in which at least one of the plurality of stripe regions extends.

In the nitride semiconductor substrate of the present invention, the direction in which the stripe region extends can be made to coincide with a desired crystal orientation with high accuracy. The orientation plane extends substantially at right angles to the direction in which the fringe areas extend. Therefore, in the nitride semiconductor substrate, the position of the orientation flat can be determined with high accuracy.

In addition, it is preferable that the orientation flat is provided on the cleavage plane. In this case, the orientation flat can be formed with high accuracy.

The nitride semiconductor substrate of the present invention is a nitride semiconductor substrate having an arc-shaped edge, and includes: a plurality of stripe regions having a defect concentrated region having a higher density of crystal defects than surrounding low-defect regions; a notch provided on an edge of the nitride semiconductor substrate, the notch being located on a straight line passing through a center of the nitride semiconductor substrate along a direction in which at least one of the plurality of stripe regions extends.

In the nitride semiconductor substrate of the present invention, the direction in which the stripe region extends can be made to coincide with a desired crystal orientation with high accuracy. Therefore, in the nitride semiconductor substrate, the position of the notch can be determined with high accuracy.

Drawings

Fig. 1 is a plan view schematically showing a nitride semiconductor substrate according to the present embodiment;

fig. 2 is a plan view schematically showing a nitride semiconductor substrate according to another embodiment;

fig. 3 is a plan view schematically showing a nitride semiconductor substrate;

fig. 4 is a plan view schematically showing a nitride semiconductor substrate;

fig. 5 is a plan view schematically showing a step in the method for processing a nitride semiconductor substrate according to the present embodiment;

fig. 6 is a perspective view schematically showing a processing apparatus for a nitride semiconductor substrate.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or equivalent elements will be denoted by the same reference numerals, and redundant description thereof will be omitted.

Fig. 1 is a plan view schematically showing a nitride semiconductor substrate according to this embodiment. The nitride semiconductor substrate 10 shown in fig. 1 has an arc-shaped edge E. The nitride semiconductor substrate 10 is, for example, a gallium nitride wafer. The nitride semiconductor substrate 10 is preferably used for semiconductor optical devices such as semiconductor lasers and LEDs.

The nitride semiconductor substrate 10 includes: a plurality of stripe regions 2; a plurality of monocrystalline domains 4 separated by stripe domains 2. The plurality of stripe regions 2 are constituted by defect concentrated regions having a higher crystal defect density (dislocation density) than the surrounding single crystal regions 4 (low defect regions). Therefore, the crystal defect density of the streak region 2 is larger than that of the single crystal region 4. In addition, the crystal orientation of the stripe region 2 is different from that of the single crystal region 4.

On the edge OF the nitride semiconductor substrate 10, an orientation flat OF (notch) extending substantially at right angles to the direction ST in which at least one OF the plurality OF stripe regions 2 extends is provided. Therefore, a straight line SL passing through the center O OF the nitride semiconductor substrate 10 along the direction ST is substantially perpendicular to the orientation flat OF. The nitride semiconductor substrate 10 having the orientation flat OF has an advantage that the orientation flat is easily mechanically positioned, as compared with a nitride semiconductor substrate having an orientation flat extending parallel to the stripe region. In addition, when nitride semiconductor substrate 10 is a transparent substrate such as a GaN substrate, it is easy to automate the manufacturing process.

The orientation flat OF is an example OF a notch as a mark indicating crystal orientation. The orientation flat OF serves as a mark in the process OF manufacturing a semiconductor laser from the nitride semiconductor substrate 10, for example. This facilitates automatic conveyance, automatic positioning (alignment), and the like of the nitride semiconductor substrate 10.

The direction ST in which the stripe region 2 extends is along the <1-100> direction or the <11-20> direction of the single-crystal region 4. The <1-100> direction represents a crystal orientation equivalent to the [1-100] direction of the single crystal region 4 or the like. The <11-20> direction indicates a crystal orientation equivalent to the [11-20] direction of the single crystal region 4 and the like.

In the case where direction ST is along the <1-100> direction OF single-crystal region 4, orientation plane OF extends along the <11-20> direction OF single-crystal region 4. In the case where direction ST is along the <11-20> direction OF single-crystal region 4, orientation plane OF extends along the <1-100> direction OF single-crystal region 4.

The nitride semiconductor substrate can be obtained, for example, by forming a mask having a window on a GaAs substrate, epitaxially (epitaxial) growing a nitride semiconductor on the mask, and then removing the GaAs substrate. In the nitride semiconductor substrate 10, for example, by forming the nitride semiconductor substrate 10 using a stripe mask extending in the [ -110] direction of the GaAs substrate, the direction ST in which the stripe region 2 extends and the [11-20] direction of the single crystal region 4 can be made to coincide with high accuracy.

Thus, in the nitride semiconductor substrate 10, the direction ST in which the stripe region 2 extends can be made to coincide with a desired crystal orientation with high accuracy. Therefore, the position OF the orientation plane OF can be determined with high accuracy by using the direction ST as a reference. For example, in the case where the directions ST and [1-100] coincide with high accuracy, the orientation flat OF and the [11-20] direction OF the single crystal region 4 can coincide with high accuracy.

As a result, even when a semiconductor laser with strict requirements for positioning accuracy, for example, within 0.02 degrees, is manufactured, a semiconductor laser can be preferably manufactured by using the nitride semiconductor substrate 10. In this case, it is preferable that an error (for example, an angle formed by the direction ST and the [1-100] direction) when forming the stripe region 2 is controlled to be within 0.01 degrees, and an error (an angle formed by the direction ST rotated by 90 degrees and the orientation plane OF) when processing the orientation plane OF is controlled to be within 0.01 degrees. Thus, the angle formed by the orientation flat OF and the [11-20] direction OF the single crystal region 4 can be controlled within 0.02 degrees. Further, by controlling the error in forming the fringe region 2 to be within 0.03 degrees and the error in processing the orientation flat OF to be within 0.01 degrees, the angle formed by the orientation flat OF and the [11-20] direction OF the single crystal region 4 can be controlled to be within 0.04 degrees.

In addition, the orientation flat OF is preferably provided on the cleavage plane. In this case, since the nitride semiconductor substrate is easily cut when the oriented flat OF is formed, the oriented flat OF can be formed with high accuracy. In addition, a semiconductor device such as a semiconductor laser can be preferably manufactured. When the nitride semiconductor substrate 10 is made of, for example, gallium nitride, the [1-100] direction of the single crystal region 4 is the normal direction of the cleavage plane.

In addition, when the nitride semiconductor substrate 10 is a 2-inch wafer, the length OF the orientation flat OF is preferably 16 ± 1 mm.

Furthermore, the orientation flat OF is chamfered as required. For example, the orientation flat OF is preferably chamfered with an R radius OF 0.1 to 0.25 mm. In this case, chipping is less likely to occur when the nitride semiconductor substrate 10 is conveyed. For example, the orientation flat OF may be chamfered with an R radius OF 2 μm. In this case, the chamfering amount is reduced, and therefore the optical positioning accuracy of the nitride semiconductor substrate 10 is improved.

The edge E OF the nitride semiconductor substrate 10 (edge where the orientation flat OF is not formed) hardly affects the optical positioning accuracy OF the nitride semiconductor substrate 10. Therefore, the edge E of the nitride semiconductor substrate 10 is preferably chamfered with an R radius of 0.1 to 0.25mm, for example.

The entire stripe region 2 may not be a defect concentrated region. For example, the defect concentrated region and the single crystal region (low defect region) may be repeatedly arranged alternately in the direction ST in the stripe region 2.

The nitride semiconductor substrate 10 may be made of a group III nitride semiconductor other than gallium nitride (e.g., aluminum nitride, indium nitride, etc.). Further, an Index Flat (IF) having a length shorter than the orientation flat OF may be provided on the edge E OF the nitride semiconductor substrate 10. When the nitride semiconductor substrate 10 is a 2-inch wafer, the length of the IF is preferably 7 ± 1 mm.

Further, the direction ST in which the stripe region 2 extends and the [11-20] direction of the single crystal region 4 can be aligned with high accuracy. In this case, the orientation flat OF and the [1-100] direction OF the single crystal region 4 can be aligned with high accuracy.

Fig. 2 is a plan view schematically showing a nitride semiconductor substrate according to another embodiment. The nitride semiconductor substrate 10a shown in fig. 2 has an arc-shaped edge E. The nitride semiconductor substrate 10a includes stripe regions 2 and single crystal regions 4. The nitride semiconductor substrate 10a is provided with notches NT (cutouts) on its edge.

The notch NT is located on a straight line SL passing through the center O of the nitride semiconductor substrate 10a along the direction ST in which the stripe region 2 extends. The notch NT can reduce the cut-off portion compared to the oriented flat OF. As a result, a large number of semiconductor optical devices can be obtained from the nitride semiconductor substrate 10 a. In addition, the material yield is also improved.

Like nitride semiconductor substrate 10, nitride semiconductor substrate 10a can also make direction ST coincide with a desired crystal orientation with high accuracy. Therefore, in the nitride semiconductor substrate 10a, the position of the notch NT can be determined with high accuracy.

Fig. 3 is a plan view schematically showing a nitride semiconductor substrate. The nitride semiconductor substrate 10b shown in fig. 3 has an arc-shaped edge E. The nitride semiconductor substrate 10b includes stripe regions 2 and single crystal regions 4. An orientation flat OF1 (notch) is provided on the edge OF the nitride semiconductor substrate 10 b. The orientation flat OF1 extends substantially at right angles to a straight line a obtained by rotating the straight line SL by a predetermined angle α around the center O OF the nitride semiconductor substrate 10 b. The predetermined angle α is preferably from +10 degrees to +80 degrees and from-10 degrees to-80 degrees. In this case, the front and back of the nitride semiconductor substrate 10b can be recognized without forming IF. The prescribed angle α is, for example, 45 degrees.

Fig. 4 is a plan view schematically showing a nitride semiconductor substrate. The nitride semiconductor substrate 10c shown in fig. 4 has an arc-shaped edge E. The nitride semiconductor substrate 10c includes the stripe region 2, the single crystal region 4, and a notch NT1 (notch) provided on the edge of the nitride semiconductor substrate 10 c. Since the notch NT1 is located on the straight line a, the front and back of the nitride semiconductor substrate 10b can be recognized.

Next, a method for processing a nitride semiconductor substrate according to the present embodiment will be described with reference to fig. 1, 5, and 6. Fig. 5 is a plan view schematically showing a step in the method for processing a nitride semiconductor substrate according to the present embodiment. Fig. 6 is a perspective view schematically showing a processing apparatus for a nitride semiconductor substrate.

(substrate preparation Process)

First, as shown in fig. 5, a disc-shaped nitride semiconductor substrate 20 is prepared, which includes a plurality of stripe regions 12, and the plurality of stripe regions 12 are constituted by defect concentrated regions having a higher crystal defect density than the surrounding single crystal regions 14 (low defect regions). The monocrystalline domains 14 are separated by the striped domains 12. In the stripe region 12, the defect concentrated region and the single crystal region (low defect region) may be alternately arranged repeatedly in the direction ST.

(notch formation step)

Then, as shown in fig. 1 and 5, an orientation flat OF as a notch is formed at a predetermined position on the edge OF the nitride semiconductor substrate 20 with reference to the direction ST in which at least one OF the plurality OF stripe regions 12 extends. Thereby, stripe region 2 is formed by stripe region 12, and single crystal region 4 is formed by single crystal region 14. As a result, the nitride semiconductor substrate 10 can be obtained from the nitride semiconductor substrate 20.

The orientation flat OF is formed by, for example, grinding, laser machining, electric discharge machining, ultrasonic machining, or the like. Although the material cost increases, the oriented plane OF may be formed by cleavage. Alternatively, etching or polishing may be performed after the formation OF the orientation flat OF.

The orientation flat OF is preferably formed by using a processing device 30 such as shown in fig. 6. The machining device 30 includes: a drive mechanism 70 movable along an X axis and a Y axis (horizontal direction); and a stage (stage)60 on which the nitride semiconductor substrate 20 provided on the drive mechanism 70 is placed. For example, the nitride semiconductor substrate 20 can be moved in the X-axis direction or the Y-axis direction by moving the driving mechanism 70 in the X-axis direction or the Y-axis direction. In addition, for example, the nitride semiconductor substrate 20 can be rotated by rotating the stage 60.

Further, the processing device 30 preferably includes: a microscope 50 for observing the surface of the nitride semiconductor substrate 20; and a dicing saw 40 for forming the oriented flat OF. If the microscope 50 is used, the oriented plane OF can be formed at low cost and easily. In addition, if the dicing saw 40 is used, the orientation flat OF can be simply formed. Further, the use of a commercially available dicing saw can reduce the cost. When the oriented plane OF is formed, the nitride semiconductor substrate 20 may be moved, and the dicing saw 40 may be moved.

Instead OF the dicing saw 40, the orientation flat OF may be formed by using, for example, a grinding wheel for grinding, a laser power source for laser processing, an electrode for electric discharge processing, a tool for ultrasonic processing, or the like. When a grinding wheel is used, for example, a cylindrical grinding wheel, a grinding wheel having a shape corresponding to a chamfered shape, an outer peripheral edge grinding wheel, or the like can be preferably used.

The microscope 50 preferably includes: an objective lens 51 disposed opposite to the surface of the nitride semiconductor substrate 20; an optical system 53 that receives light from the objective lens 51; and a display unit 55 for displaying the surface state of the nitride semiconductor substrate 20 upon receiving light from the optical system 53. Preferably, the axis adjustment is performed in advance so that the X axis and the Y axis of the microscope 50 and the X axis and the Y axis of the driving mechanism 70 coincide with each other. The dicing saw 40 preferably includes: a diamond blade 41 for cutting the nitride semiconductor substrate 20; and a driving part 43 for driving the diamond blade 41.

The processing apparatus 30 may also include a processing apparatus (not shown) for processing the end face of the nitride semiconductor substrate 20. By using this machining device, the orientation flat OF can be chamfered.

The notch forming step will be described in more detail below. The notch forming step preferably includes the following observation step and rotation step. First, in the observation step, the nitride semiconductor substrate 20 is observed with the microscope 50. Thereby, a straight line SL along a direction ST, which is a direction in which the stripe region 12 extends, is determined. As the light source of the microscope 50, for example, a white light source, a green light source, an ultraviolet light source, or the like can be used. If a green light source is used, it is easy to clearly distinguish the single crystal region 14 from the stripe region 12.

In addition, the nitride semiconductor substrate 20 is preferably irradiated with ultraviolet rays. In this case, since the constituent material of the nitride semiconductor substrate 20 emits fluorescence, the single crystal region 14 and the stripe region 12 are more clearly distinguished, and the straight line SL can be easily and highly accurately determined.

Next, in the rotation step, the nitride semiconductor substrate 20 is rotated by a predetermined angle about the center O of the nitride semiconductor substrate 20 with reference to the straight line SL. Thereby, the nitride semiconductor substrate 20 can be adjusted to a desired position. As a result, the position OF the orientation plane OF can be determined with higher accuracy. For example, the nitride semiconductor substrate 20 is rotated so that the stripe region 12 is included in a band-like region within ± 8 μm in the direction from the X axis to the Y axis of the microscope 50. Thus, the angle between the direction ST in which the stripe region 12 extends and the X axis of the drive mechanism 70 can be controlled to be within 0.01 degrees. Thereafter, the oriented plane OF may be formed by moving the dicing saw 40 in the Y-axis direction.

As described above, in the method for processing a nitride semiconductor substrate according to the present embodiment, the nitride semiconductor substrate 20 including the stripe region 12 is used. When the stripe region 12 is formed, the direction ST in which the stripe region 12 extends can be aligned with a desired crystal orientation with high accuracy. Therefore, by using the direction ST as a reference, the position OF the orientation plane OF can be determined with high accuracy without using the X-ray diffraction method.

In the notch forming step, the nitride semiconductor substrate 20 may be rotated by the predetermined angle α to form the orientation flat OF1 instead OF the orientation flat OF (see fig. 3). In the notch forming step, the notch NT (see fig. 2) or the notch NT1 (see fig. 4) may be formed instead OF the orientation flat OF. In either case, the position of the notch can be determined with high accuracy by using the direction ST as a reference without using the X-ray diffraction method.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments.

According to the present invention, it is possible to provide a nitride semiconductor substrate and a method of processing a nitride semiconductor substrate, in which the position of a mark indicating crystal orientation can be determined with high accuracy.

Claims (2)

1. A method for processing a nitride semiconductor substrate, wherein,

the method comprises the following steps: preparing a disk-shaped nitride semiconductor substrate having a plurality of stripe regions having a defect concentrated region in which a crystal defect density is higher than that of a surrounding low-defect region;

forming a notch at a predetermined position of an edge of the nitride semiconductor substrate with reference to a direction in which at least one of the plurality of stripe regions extends,

the step of forming the notch includes:

observing the nitride semiconductor substrate through a microscope, thereby determining a straight line passing through the center of the nitride semiconductor substrate along a direction in which at least one of the plurality of stripe regions extends;

and rotating the nitride semiconductor substrate by a predetermined angle with respect to the straight line and with respect to the center of the nitride semiconductor substrate.

2. The method for processing a nitride semiconductor substrate according to claim 1,

in the step of determining the straight line, ultraviolet rays are irradiated to the nitride semiconductor substrate.