JP2013179145A - Method for manufacturing sapphire substrate and sapphire substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a sapphire substrate capable of shortening a manufacturing step and reducing a manufacturing cost by easily and quickly reducing unevenness of thickness of the sapphire substrate and a processing amount, and to provide the sapphire substrate.SOLUTION: A method for manufacturing a sapphire substrate by applying processing covering a plurality of steps to a substrate obtained by slicing a sapphire ingot includes the steps of: grinding one or both sides of a substrate 10; processing the one or both sides of the ground substrate 10 by wet blasting after the grinding step; lapping the one or both sides of the substrate 10 processed by wet blasting after the wet blasting step; and polishing the one or both sides of the lapped substrate 10 by CMP after the lapping step.

Description

  The present invention relates to a method for manufacturing a sapphire substrate and a sapphire substrate.

  Nitride III-V compound semiconductors have been put into practical use as light-emitting devices such as LEDs (Light Emitting Diodes) and electronic devices that make use of features excellent in heat resistance and environmental resistance. This group III-V nitride semiconductor is often grown on a single crystal sapphire substrate, and the sapphire substrate is generally mirror-polished.

  For the manufacture of sapphire substrates, a cutting process for cutting a substrate from a sapphire ingot, a surface attaching process for attaching the surface of the substrate to a ceramic block using wax, and a back surface for lapping the back surface of the substrate supported by the ceramic block A single-sided lapping step, a heat treatment step for reducing processing distortion caused by lapping after removing the ceramic block and the substrate, a backside attaching step for attaching the backside of the substrate to the ceramic block using wax, And a main surface mechanochemical polishing step in which the surface is subjected to CMP (Chemical Mechanical Polishing) (see Patent Document 1).

  In addition, instead of the front surface bonding process and the back surface single-sided lapping process, a double-sided lapping process for lapping both surfaces of the sapphire substrate or a lapping process before the main surface mechanochemical polishing process is performed and rough polishing is performed in advance. This process is also known as the prior art (see FIG. 7).

  The double-sided lapping machine used in double-sided lapping has, for example, a lapping surface plate to which loose abrasive grains having a particle size of several tens to a hundred μm are supplied, and presses the substrate against this lapping surface plate. While rotating the lap platen, both sides of the substrate are scraped by the supplied free abrasive grains. Since the particle size of the loose abrasive is larger than the loose abrasive for CMP polishing described later, it is used for rough polishing of the substrate.

  A CMP apparatus used in CMP polishing includes a rotatable polishing table, a polishing pad placed thereon, a polishing head that presses the polishing surface of the substrate against the polishing surface of the polishing pad, and the polishing pad and the substrate. A cleaning liquid supply nozzle that injects a cleaning liquid for cleaning, a free abrasive grain supply nozzle that supplies free abrasive grains, and a motor for rotating the polishing table.

  In the main surface mechanochemical polishing step, for example, alkaline colloidal silica having a particle size of several nm is used as the free abrasive grains. This is smaller than the particle size of the loose abrasive used in lapping.

  With such a CMP apparatus, free abrasive grains are dropped on the polishing pad from the free abrasive supply nozzle, the surface to be polished of the substrate is pressed against the polishing surface of the polishing pad by the polishing head, and the polishing table and the polishing head are rotated. Thus, the free abrasive grains of the colloidal silica which are alkaline and the substrate are chemically reacted and polished chemically and mechanically. Thus, polishing is performed more precisely than lapping.

JP 2006-347776 A

  In recent years, demands for reducing the cost of semiconductor elements such as LED elements have increased, and therefore it has become necessary to shorten and reduce the process and to reduce the substrate cost by increasing the diameter of the sapphire substrate.

  In the conventional method for manufacturing a sapphire substrate disclosed in Patent Document 1, a substrate cut from a sapphire ingot (thickness 850 μm, thickness unevenness ± 20 μm) is subjected to double-sided lapping so that the thickness unevenness is several μm or less. .

  However, the surface plate of the double-sided lapping apparatus is generally slightly warped, and the more the substrate having a large diameter is processed, the more difficult it is to process with high precision due to the warpage. That is, even if a large-diameter substrate of 4 inches or more is placed on a surface plate and lapping is performed, accurate processing is difficult. If a substrate of 4 inches or more is lapped using a double-sided lapping machine, the processing rate is set to be relatively slow (several μm / min) in order to reduce the substrate thickness unevenness to several μm or less. The amount needed to be 50 μm or more on one side (100 μm or more on both sides). Thereby, thickness unevenness of several μm or less can be obtained, but lapping took several hours. Therefore, it was necessary to shorten the process.

  Further, in order to maintain the flatness of the surface of the surface plate of the double-sided lapping apparatus, a fading operation on the surface of the surface plate is required, and a maintenance operation is always required.

  The present invention has been made in view of such points, and the object of the present invention is to shorten or reduce the manufacturing process of the sapphire substrate, and to reduce the thickness unevenness even on a substrate having a large diameter of 4 inches or more. It is in providing the manufacturing method of a sapphire substrate, and a sapphire substrate.

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

  A method for manufacturing a sapphire substrate according to the present invention is a method for manufacturing a sapphire substrate in which a substrate obtained by slicing from a sapphire ingot is processed over a plurality of steps to manufacture a sapphire substrate. A grinding step for grinding, a wet blasting step for wet blasting one or both sides of the ground substrate after the grinding step, and a one or both sides of the substrate subjected to wet blasting after the wet blasting step A lapping step for lapping, and a polishing step for CMP polishing one or both sides of the lapped substrate after the lapping step.

  Moreover, the sapphire substrate of this invention is a sapphire substrate manufactured by said manufacturing method of a sapphire substrate.

  By such a specific matter, the substrate processing can be performed faster than the double-sided lapping process by replacing the double-sided lapping process of the prior art with a grinding process in the grinding process by wet blasting. The generated grinding marks on the substrate can be removed, and thickness unevenness can be reduced even on a substrate having a large diameter of 4 inches or more.

  In the method for manufacturing the sapphire substrate, the amount of grinding on both sides of the substrate in the grinding step is set to an amount not exceeding 100 μm, and the amount of wet blasting on one side of the substrate in the wet blasting exceeds 25 μm The amount of wet blasting on both sides of the substrate is an amount not exceeding 50 μm.

  Due to such a specific matter, since the processing amount of the substrate by the double-sided lapping process of the prior art is less, the material loss of the substrate can be reduced, and a substrate with a thickness unevenness of several μm can be manufactured. Further, if the wet blasting amount on one side of the substrate is 25 μm, grinding marks generated by the grinding process can be removed.

  The manufacturing process of a sapphire substrate can be shortened or reduced, and a sapphire substrate manufacturing method and a sapphire substrate with reduced thickness unevenness can be provided even for a substrate having a large diameter of 4 inches or more.

It is sectional drawing which shows the grinding process of the manufacturing method of the sapphire substrate which concerns on this invention. It is a schematic diagram which shows the wet blasting process of the manufacturing method of the sapphire substrate which concerns on this invention. It is a manufacturing flow of the manufacturing method of the sapphire substrate concerning the present invention. It is sectional drawing which shows the sticking process of the manufacturing method of the sapphire substrate which concerns on this invention. The lapping process of the manufacturing method of the sapphire substrate which concerns on this invention is shown, (a) is a top view which shows a lapping apparatus, (b) is sectional drawing which shows a lapping apparatus. The CMP process of the manufacturing method of the sapphire substrate which concerns on this invention is shown, (a) is a top view which shows a CMP apparatus, (b) is sectional drawing which shows a CMP apparatus. It is a manufacturing flow of the conventional sapphire substrate.

  FIG. 3 is a manufacturing flow of the method for manufacturing a sapphire substrate according to the present invention.

  The manufacturing method of the sapphire substrate according to the present embodiment includes a grinding step of grinding one or both sides of the substrate 10 sliced from the sapphire ingot, a wet blasting step of processing one or both sides of the substrate 10 with a wet blasting apparatus, and grinding An annealing step for relaxing the processing stress and processing strain generated by the step and the wet blasting step, an attaching step for attaching the substrate 10 to the substrate holding member 300, a lapping step for roughly polishing the surface 10A of the substrate 10, and lapping processing This includes a CMP process for CMP polishing the surface 10A of the substrate 10 and a precision cleaning process for cleaning the substrate 10.

  A method of manufacturing a sapphire substrate will be described along this process. In addition, all of the embodiments described below are examples embodying the present invention, and are not of a nature that limits the technical scope of the present invention.

[Grinding process]
First, the grinding process will be described. FIG. 1 is a cross-sectional view showing a grinding process of a method for manufacturing a sapphire substrate according to the present invention.

  In the grinding step, both sides of the substrate 10 are ground by grinding the 4-inch substrate 10 (thickness 850 μm, thickness unevenness ± 20 μm) sliced from the sapphire ingot one by one.

  Grinding apparatus 600 used in the grinding process confronts ceramic plate 620 on which substrate 10 is placed by suction, ceramic plate 620, grindstone 610 for grinding substrate 10, and vacuum suction of substrate 10 and ceramic plate 620. A vacuum pump (not shown). A plurality of holes (not shown) are formed on the surface of the ceramic plate 620, and these holes are connected to a vacuum pump.

  The surface 10 </ b> A of the substrate 10 is attached to the ceramic plate 620 via a suction plate 630 that holds the substrate 10. The suction plate 630 is also formed with a plurality of holes (not shown), and when the vacuum pump is operated, the ceramic plate 620 and the substrate 10 are sucked.

  With the front surface 10 </ b> A of the substrate 10 being adsorbed by the ceramic plate 620, the back surface 10 </ b> B of the substrate 10 is ground by 25 μm with the grindstone 610. After grinding the back surface 10B of the substrate 10, the vacuum suction pump is stopped, the substrate 10 is turned over, and the surface 10A of the substrate 10 is ground by 25 μm in the same manner as described above. The grindstone 610 for grinding the substrate 10 is preferably a diamond grindstone.

  When the grinding apparatus 600 is used, the processing rate can be about several tens of μm / min, and the process time can be shortened compared to the processing rate (several μm / min) when the conventional double-sided lapping apparatus is used. Can do.

  Further, the thickness of the substrate 10 is ground by 50 μm on both sides by the grinding process, the thickness of the substrate 10 at the end of the grinding process is 800 μm, and the thickness unevenness is ± 2 μm. Preferably, the thickness of the substrate 10 can be further reduced by grinding 100 μm on both sides.

  Thereby, the thickness nonuniformity of the board | substrate 10 can be controlled by several micrometers or less by a grinding process. However, when the substrate 10 is ground by the grinding process, a grinding mark by the grindstone 610 remains on the surface of the ground substrate 10. Grinding marks are removed by the next wet blasting process.

[Wet blasting process]
Next, the wet blast process will be described. FIG. 2 is a schematic diagram showing a wet blasting process of the method for manufacturing a sapphire substrate according to the present invention.

  In the wet blasting process, both surfaces of the substrate are wet blasted. Note that only the surface of the sapphire substrate (the ground surface described above) may be wet blasted.

  A wet blasting apparatus 500 used for wet blasting is disposed so as to face a stage 510 on which a substrate 10 is placed, a stage moving mechanism (not shown) that moves the stage 510 in one direction, and the stage 510. A wet blast nozzle 520 for spraying loose abrasive grains 530 in which loose abrasive grains and compressed air are mixed is provided on 510.

  The wet blast nozzle 520 includes a free abrasive grain introduction part 521 into which free abrasive grains are introduced, an air introduction part 522 into which compressed air is introduced, and a mixing chamber in which the introduced free abrasive grains and compressed air are mixed. 523 and a slit-like injection unit 524 that injects the free abrasive grains 530 sent together with the compressed air from the mixing chamber 523 onto a straight line orthogonal to the moving direction of the stage 510 in the same plane as the stage 510. ing.

  In the present embodiment, the wet blast nozzle 520 is disposed at an angle of 90 ° with the substrate 10, but the angle between the wet blast nozzle 520 and the substrate 10 is not limited to this angle.

  The substrate 10 is placed on the stage 510 so that the surface 10A of the substrate 10 is wet-blasted, and the stage 510 is moved at a speed of 1 mm / sec by the stage moving mechanism, and the wet blast nozzle 520 is set to 0. The loose abrasive grains 530 are sprayed vertically toward the substrate 10 at a pressure of 4 MPa. As a result of the movement of the stage 510 on which the substrate 10 is placed, the free abrasive grains 530 are sprayed onto the entire surface 10A of the substrate 10, so that the entire surface 10A of the substrate 10 is wet blasted.

  In wet blasting, the processing rate is set to a speed of 3.0 μm / min. The processing rate of wet blast processing depends on the moving speed of the stage 510. That is, the slower the moving speed of the stage 510, the longer the time during which the substrate 10 is exposed to the loose abrasive grains 530, and the greater the processing amount. Conversely, the faster the moving speed of the stage 510, the shorter the time during which the substrate 10 is exposed to the loose abrasive grains 530, and the smaller the processing amount.

  In the wet blasting process, the surface 10A of the substrate 10 is processed by at least 5 μm. Grinding marks generated on the substrate 10 in the above-described grinding process can be removed by processing of 5 μm or more, but the surface of the substrate 10 subjected to wet blasting is a matte surface (mat surface). This can make the substrate 10 into a specular specification by lapping and CMP polishing, which will be described later.

  In addition, since the material loss increases when the processing amount is 25 μm or more, the processing amount is preferably an amount not exceeding 25 μm. Further, when the wet blasting process is performed on both surfaces of the substrate 10, it is preferable that the processing amount on both surfaces does not exceed 50 μm.

  If the processing rate is 5 μm at a processing rate of 3.0 μm / min, the wet blasting time for the surface 10A of the substrate 10 is 1 minute 40 seconds. Therefore, even if the processing time of the grinding process described above is added, the process can be performed in a shorter time than the double-sided lapping time (several hours) when using a conventional double-sided lapping machine, so the process can be shortened. Can be achieved.

  In addition, although the wafer size of the substrate 10 of the present embodiment is assumed to be 4 inches, the 6-inch substrate 10 can be wet-blasted using a 6-inch stage. By manufacturing a 6-inch sapphire substrate, more semiconductor elements can be formed on the surface of the sapphire substrate than on a 4-inch sapphire substrate, so that the amount of collected semiconductor elements increases. Therefore, the manufacturing cost can be reduced.

  Moreover, since wet blasting does not require management of the surface plate, maintenance can be easily performed.

  The free abrasive grains used for the free abrasive grains 530 are desirably free abrasive grains having a uniform particle diameter in order to improve the flatness of the substrate 10, and alumina having an average particle diameter of 100 μm is used.

[Annealing process]
Next, the annealing process performed after the wet blast process in the manufacturing method of the sapphire substrate of this invention is demonstrated.

  In the annealing process, the processing stress and the processing distortion generated in the substrate 10 by the above-described grinding process and wet blasting process are alleviated. Specifically, the substrate 10 is placed in a high temperature furnace (not shown) and held at a heating temperature of 1600 ° C. for 3 hours.

  Thereby, the processing stress and processing distortion of the substrate 10 can be relaxed.

  Here, the annealing temperature and annealing time are merely examples, and are not limited to the above temperature and time.

  Further, this annealing process may be performed after the above-described grinding process and before the wet blasting process.

[Pasting process]
Next, the attaching process will be described. FIG. 4 is a cross-sectional view showing the attaching process of the method for manufacturing a sapphire substrate according to the present invention.

  In the attaching step, the substrate holding member 300 is attached to the surface opposite to the surface of the substrate 10 to be lapped in the lapping step described later (in this embodiment, the back surface 10B of the substrate 10).

  The substrate holding member 300 includes a plate 310, a holding member 320 that is fixed on the plate 310 and has an opening, and a suction pad 330 that is accommodated in the opening of the holding member 320 and attached to the plate 310.

  The suction pad 330 is attached to the back surface 10B of the substrate 10, and the holding member 320 and the back surface 10B of the substrate 10 are attached to the back surface 10B of the substrate 10 using wax as an adhesive. At the time of pasting, pressure is applied from the surface 10A of the substrate 10 for pasting.

  Therefore, the substrate 10 and the plate 310 are attached, and the substrate 10 and the substrate holding member 300 are attached. Note that an acrylic resin or a glass epoxy resin may be used as the adhesive. The plate 310 is a ceramic plate.

  Thereby, when the substrate 10 is lapped in a lapping process described later, the substrate holding member 300 is attached to the back surface 10B of the substrate 10, so that the substrate 10 is protected even if the substrate 10 is loaded. Can do.

[Lapping process]
Next, the lapping process will be described. FIG. 5 shows a lapping process of the method for manufacturing a sapphire substrate according to the present invention, (a) is a plan view showing a lapping apparatus, and (b) is a cross-sectional view showing the lapping process.

  In the lapping step, lapping is performed on the substrate 10 side (surface 10A of the substrate 10) to which the substrate holding member 300 described above is attached.

  The lapping apparatus 400 used in the lapping process discharges a surface plate 410 for lapping the substrate 10, a fixture 420 to which the substrate 10 is attached so as to face the surface plate 410, and free abrasive grains used during lapping. And a motor (not shown) that rotates independently with the center of the fixture 420 as the rotation axis and the center of the surface plate 410 as the rotation axis. As the surface plate 410 of this embodiment, a relatively soft metal-based surface plate containing copper or tin is used.

  After attaching the substrate 10 to which the substrate holding member 300 described above is attached to the fixture 420, the fixture 420 is loaded in the direction of the surface plate 410, whereby the surface 10A of the substrate 10 is pressed against the surface plate 410. .

  In this state, the surface plate 410 and the fixture 420 are rotated so as to be opposite to each other, and free abrasive grains are discharged from the nozzle 430. The platen 410 is preferably rotated at a rotational speed from 30 rpm to 80 rpm.

  The loose abrasive has a particle size of several μm, and for example, diamond slurry is used.

  Thereafter, the surface 10A of the substrate 10 is polished with a soft foamed urethane or a suede type polishing cloth using silica particles having a particle diameter of several tens of nm.

  Note that the lapping process may be performed also on the back surface of the substrate 10.

[CMP process and precision cleaning process]
Next, the CMP process will be described. 6A and 6B show a lapping process of the method for manufacturing a sapphire substrate according to the present invention, wherein FIG. 6A is a plan view showing a CMP apparatus, and FIG. 6B is a cross-sectional view showing the CMP process.

  In the CMP process, after performing the lapping described above, the surface 10A of the substrate 10 on which lapping has been performed is subjected to CMP polishing.

  The CMP apparatus 450 used in the CMP process and the lapping apparatus 400 described above include a cleaning liquid nozzle 460 that discharges a cleaning liquid for precisely cleaning chemicals such as free abrasive grains, Since only the point of using colloidal silica having a particle diameter of several tens of nanometers is different, only the difference will be described below, and the same components are denoted by the same reference numerals and the description thereof is omitted. .

  In the CMP polishing, the surface plate 410 and the mounting tool 420 are rotated by the rotation shaft of the surface plate 410 and the rotation shaft of the mounting tool 420, and free abrasive grains are discharged from the nozzle 430 to perform the CMP polishing. After that, the cleaning nozzle is used to remove foreign substances such as polishing scraps (scraps such as workpieces and polishing pads) and aggregates of loose abrasive grains, and cleaning colloidal silica, which is an alkaline chemical. While discharging from 460, the surface 10A of the substrate 10 is precisely cleaned.

  The CMP process and the precision cleaning process may be performed on the back surface of the substrate 10 as well.

  As a result, the sapphire substrate is shortened compared to the prior art, the thickness unevenness is reduced, and the sapphire substrate having a matte surface (matte surface) after the wet blasting process is used as a specular surface after the precision cleaning process. Can be manufactured.

10 Substrate 10A Surface 400 Lapping device 450 CMP device 500 Wet blasting device 600 Grinding device

Claims (3)

In the method for manufacturing a sapphire substrate, a substrate obtained by slicing from a sapphire ingot is manufactured by performing processing over a plurality of steps.
A grinding step of grinding one or both sides of the substrate;
A wet blasting process for performing wet blasting on one or both sides of the ground substrate after the grinding process;
After the wet blasting process, a lapping process for lapping one side or both sides of the wet-blasted substrate;
After the lapping step, a polishing step for CMP polishing one or both sides of the lapped substrate;
A method for manufacturing a sapphire substrate, comprising: A method for producing a sapphire substrate according to claim 1,
The amount of grinding on both sides of the substrate in the grinding step is an amount not exceeding 100 μm,
A method for producing a sapphire substrate, characterized in that the wet blasting amount on one side of the substrate in the wet blasting is an amount not exceeding 25 μm, and the wet blasting amount on both sides of the substrate is an amount not exceeding 50 μm. .   A sapphire substrate manufactured by the method for manufacturing a sapphire substrate according to claim 1.

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