JP2006339431A - Method of processing nitride semiconductor substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of processing a nitride semiconductor substrate capable of drastically shortening a contour processing time of an independent type nitride semiconductor substrate. <P>SOLUTION: First, a substrate 1 of a circular independent type GaN grown by an HVPE method, etc. is prepared. A mark-off line 2 is provided to the substrate 1 in parallel to a crystal azimuth for performing an OF process by use of an X-ray diffraction instrument. Next, after the substrate 1 is set so as to make the mark-off line 2 of the substrate 1 parallel with a straight part of an OF 3a of a tool 3 for performing ultrasonic process, the ultrasonic process is performed. Thus, the substrate 1 is precisely hollowed out in a circle having a flat OF and IF complying with a shape of the tool 3. Thus, the OF process, the IF process and an outer diameter process can be simultaneously performed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a nitride semiconductor substrate processing method for processing the external shape of a free-standing nitride semiconductor substrate grown by HVPE (Hydride Vapor Phase Epitaxy) method or the like.

  In recent years, low dislocation free-standing GaN substrates grown by the HVPE method or the like have been manufactured as GaN substrates used for high-lifetime blue lasers, high-intensity blue LEDs, and high-performance electronic devices. This GaN substrate is usually circular immediately after growth and has variations in thickness and outer diameter, and crystal defects are likely to occur on the outer periphery of the substrate.

  In addition, the normal substrate is a flat surface for improving accuracy in the epitaxial device process, has a uniform outer diameter for setting on the susceptor, is mainly chamfered to prevent cracking, and is further crystallized. Cleavage and OF (orientation flat) processing are performed as orientation positioning, and IF (index flat) processing for distinguishing the front and back surfaces and a satin-like back surface processing are performed.

  Therefore, conventionally, in order to adjust the substrate shape, an outside diameter processing, OF / IF processing, and chamfering processing are performed using an NC processing machine or a copying type processing machine, and grinding / lapping is performed to obtain a flat surface.・ Polishing is performed.

Conventionally, as a microfabrication for a silicon substrate or a substrate bonded with a silicon substrate, a groove or a depression is formed on the surface of the substrate by ultrasonic processing, a hole is formed in the substrate, or an epitaxial layer on the substrate is formed. On the other hand, a method of performing cleavage by ultrasonic vibration is known (for example, see Patent Document 1).
JP-A-6-37404

  However, substrate processing by machining using the above-described conventional NC processing machine or copying type processing machine has the following problems.

  Since the shape of the self-standing GaN substrate grown by the HVPE method is circular and the GaN substrate is transparent, if the front and back surfaces of the substrate are polished in a circular shape, the distinction between the front and back surfaces cannot be visually determined. For this reason, for example, when polishing one surface, the crystal orientation position where OF processing is performed on the surface opposite to the surface to be polished is marked, and then when the opposite surface is polished, the surface polished now It is necessary to take a procedure such as making the front and back different by marking the same position.

  In addition, since it is difficult to perform an OF processing with high accuracy on a crystal orientation determined by a single processing by a NC outer shape processing machine or a copying type outer shape processing machine, a temporary OF processing is performed once. Since the GaN substrate is a hard and brittle material, the processing speed cannot be increased and the processing time becomes very long.

  Furthermore, the outer peripheral portion of the free-standing GaN substrate grown by the HVPE method or the like is prone to crystal defects, and the GaN substrate is a hard and brittle material. turn into.

  An object of the present invention is to provide a method for processing a nitride semiconductor substrate that solves the above-described problems and can significantly reduce the outer shape processing time of the nitride semiconductor substrate.

  In the first invention, a self-standing nitride semiconductor substrate is hollowed out into a circle, a circle including one or more flat sides, or a circle including one or more notches by ultrasonic processing. A method for processing a nitride semiconductor substrate characterized by the following.

The substrate can be processed to the required outer diameter by removing the crystal defects on the outer periphery of the substrate by hollowing out the substrate in a circular shape by ultrasonic processing, and compared with general machining such as NC contour processing machines. Therefore, it can be processed quickly and without causing cracks, work-affected layers, or work distortion, and is optimal for processing a semiconductor substrate of a hard and brittle material such as a GaN substrate.
In addition, if one or more flat sides or a circular shape including a notch is cut out, not only the outer diameter processing but also the orientation flat processing and notch processing can be performed simultaneously, and the processing time can be greatly reduced.

As the self-standing nitride semiconductor substrate, a substrate grown by the HVPE (Hydride Vapor Phase Epitaxy) method or the like is used. In addition to the HVPE method, it is of course possible to use a self-supporting nitride semiconductor substrate formed by using a MOVPE (Metal Organic Chloride) method, a MOVPE (Metal Organic Chemical Vapor Deposition) method, or the like.
Ultrasonic machining, for example, presses the tool against the substrate with an appropriate pressure while supplying a machining fluid in which abrasive grains are mixed into a liquid such as water between the tool that vibrates ultrasonically and the workpiece substrate. Thus, the substrate is crushed and removed by the impact energy of the abrasive grains between the tool and the substrate. If ultrasonic processing is used, the substrate can be precisely cut into a desired shape (a shape including a flat side or a notch) corresponding to the cross-sectional shape of the tool in one processing.

  A second invention is a method for processing a nitride semiconductor substrate according to the first invention, wherein the nitride semiconductor is any one of GaN, AlN, and InN.

  According to a third invention, in the first or second invention, the flat side has an orientation flat (OF) indicating the crystal orientation of the substrate and / or an index flat (IF) for distinguishing the front and back surfaces of the substrate. And the notch is a notch indicating the crystal orientation of the substrate and / or a sub-notch for distinguishing the front and back surfaces of the substrate.

  If the substrate is cut into a circular shape including OF and IF, OF and sub-notch, notch and IF, or notch and sub-notch, both sides of the substrate can be visually discriminated after both surfaces are polished.

  A fourth aspect of the invention is the flat part of a cylindrical ultrasonic vibration tool having one or more flat parts or a cylindrical ultrasonic vibration tool having one or more notch parts for performing the ultrasonic processing in the first to third aspects. The method for processing a nitride semiconductor substrate is characterized in that ultrasonic processing is performed by positioning the notch portion based on the crystal orientation of the substrate measured by X-ray diffraction.

  Since ultrasonic processing is performed by aligning the flat portion or notch portion of the ultrasonic vibration tool based on the crystal orientation of the substrate obtained by X-ray diffraction, OF processing and notching processing can be performed with high accuracy.

  According to a fifth invention, in the first to third inventions, a flat part of a cylindrical ultrasonic vibration tool having one or more flat parts or a cylindrical ultrasonic tool having one or more notch parts for performing the ultrasonic processing or A method for processing a nitride semiconductor substrate, wherein the notch portion is positioned based on a marking line measured by X-ray diffraction and indicating the crystal orientation of the substrate attached to the substrate to perform ultrasonic processing. It is.

  Since alignment is performed using a marking line indicating the crystal orientation obtained from X-ray diffraction, alignment can be performed by visual observation, and OF processing and notch processing can be performed easily and accurately.

  According to the present invention, the outer diameter processing time of the substrate can be significantly shortened because the outer diameter processing or orientation flat processing of the substrate can be performed by hollowing out the substrate into a desired shape by ultrasonic processing.

  An embodiment of a method for processing a nitride semiconductor substrate according to the present invention will be described below with reference to the drawings. FIGS. 1A to 1D are diagrams showing processing steps in one embodiment of the present invention.

  First, a circular self-standing GaN substrate 1 grown by HVPE or the like is prepared (FIG. 1A). In many cases, crystal defects are generated in the outer peripheral portion 1a of the circular substrate 1 grown by the HVPE method or the like, and it is usually necessary to perform outer diameter processing for removing the crystal defects in the outer peripheral portion 1a.

  A marking line 2 parallel to the crystal orientation is attached to the substrate 1 with a diamond pen as a mark of crystal orientation to be subjected to OF processing using an X-ray diffractometer (FIG. 1 (b)).

  The substrate 1 with the marking line 2 is attached to a glass plate using solid wax, and a tool 3 is attached to the tip of the horn of an ultrasonic processing machine. As shown in the cross section of FIG. 1C, the tool 3 has a cylindrical and flat OF (orientation flat) portion 3a and an IF (index flat) portion 3b smaller in diameter than the substrate 1. The IF unit 3b of the tool 3 is at a position that forms 90 degrees from the OF unit 3a.

Next, the glass plate to which the substrate 1 is attached is placed on the work table of the ultrasonic vibrator, and visually, the marking line 2 of the substrate 1 and the straight portion of the OF portion 3a of the tool 3 are in parallel. The substrate 1 is set (FIG. 1 (c)). Thereafter, the tool 3 and the substrate 1 are brought into contact with each other with a predetermined pressing force, and after a slurry-like processing liquid in which a liquid and abrasive grains are mixed is poured onto the substrate 1, the ultrasonic processing machine is operated. The ultrasonic vibration generated by the vibrator of the ultrasonic processing machine is enlarged and transmitted to the tool 3 through the horn, and the substrate 1 is crushed by the impact of the abrasive grains repelled by the ultrasonic vibration.
Specific processing conditions will be described.
Processing fluid: Pure water mixed with abrasive grains. The abrasive grains were boron carbide (B ₄ C), the particle size was # 280, and the working fluid was supplied at 16 liters / min.
Tool: The material used was S45C (H _S = 40 ° tempered), 1 mm thick, and the pressing force of the tool was 2 kg / cm ² .
Vibration: Resonance frequency 16KHz, output (500) ~ 1000W, amplitude 30μm or more Solid wax: Alco wax (product name) made by Nikka Seiko

  In this way, the substrate 1 is precisely cut into a circular shape having a flat OF and IF corresponding to the shape of the tool 3 (FIG. 1 (d)). This makes it possible to simultaneously perform temporary OF attachment processing, IF processing, and outer diameter processing that removes crystal defects on the outer periphery of the substrate, which have been conventionally performed with an external shape processing machine, greatly reducing the occupation time of the external shape processing machine. it can. Further, since the substrate 1 has the OF and IF, the front and back of the substrate after the front and back polishing can be visually observed.

  The substrate 1 hollowed out by ultrasonic vibration is removed from the glass plate and cleaned for wax removal. Thereafter, the back surface of the substrate 1 is lapped and polished and flattened according to circumstances. Furthermore, outer diameter machining, high-precision OF machining, and chamfering are performed according to the specification shape. Here, in the high-precision OF processing, the OF orientation of the ultrasonically processed substrate 1 is measured with an X-ray diffractometer, and the final orientation processing is performed by correcting the deviation of the OF orientation with an outline processing machine. It is. Next, the surface of the substrate 1 is lapped and polished.

  In this way, by combining ultrasonic processing and X-ray diffraction, it is possible to perform OF processing with high accuracy, and in the device manufacturing process using the obtained substrate, the device yield can be greatly improved. In the above-described embodiment, an OF orientation marking line 2 is attached to the substrate 1 using an X-ray diffractometer, and the marking line 2 and the straight portion of the OF section 3a of the tool 3 are visually aligned to perform ultrasonic processing. However, if an ultrasonic processing apparatus having an X-ray diffraction mechanism is manufactured, ultrasonic OF processing can be performed with the crystal orientation measured and the substrate positioned with high accuracy. Therefore, an extremely accurate OF processing equivalent to cleavage can be performed.

  In the above-described embodiment, the back surface of the substrate 1 cut out by ultrasonic processing is flattened, and then the surface is flattened. Thereafter, according to the specification shape, outer diameter processing, high-precision OF orientation processing, A chamfering process may be performed. In this case, since the front and back surfaces of the substrate 1 are mirror surfaces, the front and back surfaces cannot be distinguished in the apparent surface state, but since OF and IF processing are performed by an ultrasonic processing machine before flat processing of the front and back surfaces, The front and back can be discriminated by the positional relationship between OF and IF.

It is a figure which shows the manufacturing process in one Embodiment of the processing method of the nitride semiconductor substrate which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 1a Outer peripheral part 2 Marking wire 3 Tool 3a OF part 3b IF part

Claims (5)

  Nitride characterized by hollowing a self-standing nitride semiconductor substrate into a circle, a circle containing one or more flat sides, or a circle containing one or more notches by ultrasonic processing A method for processing a semiconductor substrate.   2. The method for processing a nitride semiconductor substrate according to claim 1, wherein the nitride semiconductor is any one of GaN, AlN, and InN.   The method for processing a nitride semiconductor substrate according to claim 1 or 2, wherein the flat side is an orientation flat indicating a crystal orientation of the substrate and / or an index flat for distinguishing the front and back surfaces of the substrate, A method for processing a nitride semiconductor substrate, wherein the notch is a notch indicating a crystal orientation of the substrate and / or a sub-notch for distinguishing the front and back surfaces of the substrate.   4. The method of processing a nitride semiconductor substrate according to claim 1, wherein the ultrasonic processing is performed in a cylindrical shape having one or more flat portions or a cylindrical shape having one or more notches. A method for processing a nitride semiconductor substrate, characterized in that ultrasonic processing is performed by positioning a flat portion or notch portion of a tool based on the crystal orientation of the substrate measured by X-ray diffraction.   4. The method of processing a nitride semiconductor substrate according to claim 1, wherein the ultrasonic processing is performed in a cylindrical shape having one or more flat portions or a cylindrical shape having one or more notches. Nitride characterized in that ultrasonic processing is performed by positioning a flat portion or notch portion of a tool based on a marking line measured by X-ray diffraction and indicating a crystal orientation of the substrate. A method for processing a semiconductor substrate.

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