METHOD FOR CUTTING SUBSTRATE WAFER FROM INDIUM PHOSPHIDE CRYSTAL BAR

Abstract

The invention discloses a method for cutting a substrate wafer from an indium phosphide crystal, and belongs to the field of semiconductor substrate preparation, comprises the following steps of: 1) orientating, cutting the head and the tail of a crystal bar, adjusting the orientation and trying to cut the crystal bar until a wafer with a required crystal orientation cut, wherein the cutting end face is an orientation end face; 2) multi-wire cutting, on a multi-wire cutting apparatus, dividing a crystal bar parallel to an orientation end face into wafers; 3) cleaning, cleaning the wafer until no residue and no dirt existing on the surface; 4) circle cutting, performing circle cutting on the wafer to cut the desired crystal orientation area. According to the technical scheme, for the indium phosphide crystal bar which is difficult to control in diameter and easy to twinning/ poly in the growth process, a barreling process which may grind and remove a large amount of InP materials is abandoned, the crystal bar is multi-wire cut into a wafer, and then the substrate wafer which is available in the crystal direction close to the standard size is cut from the wafer to the maximum extent, so that the wafer output can be greatly increased, and the material loss and the waste can be reduced.

Claims

1. A method for cutting a substrate crystal wafer from an indium phosphide crystal characterized by comprising following steps of: 1) orientating: cutting a head and a tail of a crystal bar, adjusting the orientation and trying to cut the crystal bar until a wafer with a required crystal orientation cut, wherein the cutting end face is an orientation end face; 2) multi-wire cutting: on a multi-wire cutting apparatus, dividing the crystal bar parallel to an orientation end face into wafers; 3) cleaning: cleaning the wafer until no residue and no dirt existing on the surface; 4) circle cutting: performing circle cutting on the wafer to cut the desired crystal orientation area.

2. The method for cutting a substrate crystal wafer from an indium phosphide crystal of claim 1, characterized in that: in the step 1), the parallelism error of the orientation end face and the required crystal orientation is +/−0.02°.

3. The method for cutting a substrate crystal wafer from an indium phosphide crystal of claim 2, characterized in that: in the step 2), the cutting steel wire is parallel to the orientation end face of the crystal bar.

4. The method for cutting a substrate crystal wafer from an indium phosphide crystal of claim 1, characterized in that: in the steps 1) and 2), the crystal bar is bonded to a carrier plate, and the carrier plate is provided with a placing groove matched with the shape of the side edge of the crystal bar.

5. The method for cutting a substrate crystal wafer from an indium phosphide crystal of claim 4, characterized in that: the carrier plate is a graphite plate or a resin plate.

6. The method for cutting a substrate crystal wafer from an indium phosphide crystal of claim 1, characterized in that: the wafer thickness divided in the step 2) is less than or equal to 2000 μm.

7. The method for cutting a substrate crystal wafer from an indium phosphide crystal of claim 6, characterized in that: in the step 4), the circle cutting is performed by a laser having a wavelength of 510-550 nm, a power of 50-200 W, and a cutting rate of 10-50 mm/s.

8. The method for cutting a substrate crystal wafer from an indium phosphide crystal of claim 7, characterized in that: in the step 4), each removal amount of the laser cutting is 10-50 μm.

9. The method for cutting a substrate crystal wafer from an indium phosphide crystal of claim 1, characterized in that: in the step 4), pumping and deslagging are performed in the laser cutting process.

10. The method for cutting a substrate crystal wafer from an indium phosphide crystal of claim 1, characterized in that: the type of the cleaning agent in the step 3) is matched with the type of the multi-wire cutting cutting fluid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a schematic view showing the structure of a crystal bar and twinning of a cut wafer;

[0023] FIG. 2 is a schematic diagram of the structure of a crystal bar;

[0024] FIG. 3 is a schematic flow diagram of a conventional barreling process for substrate wafer;

[0025] FIG. 4 is a schematic view showing a crystal orientation structure of a crystal bar in an embodiment;

[0026] FIG. 5 is a schematic view of a usable area for conventional barreling processing of a wafer in an embodiment;

[0027] FIG. 6 is a schematic view of a usable area for processing a wafer of the present invention in an embodiment;

[0028] FIG. 7 is a schematic flow chart for processing a substrate wafer according to the present invention;

[0029] FIG. 8 is a schematic view showing the structure of a carrier plate supporting a crystal bar in an embodiment;

[0030] In the drawings, 1 represents a positive crystal orientation portion, 2 represents a rotational crystal orientation portion, 3 represents an upper portion, 4 represents a middle portion, 5 represents a scrap wafer, 6 represents a degraded wafer, 7 represents a seed crystal, 8 represents a crystal bar, 9 represents an oriented crystal, 10 represents a 3-inch crystal bar, 11 represents a positive crystal orientation wafer, 12 represents a carrier plate, 13 represents a 2-inch wafer, and 14 represents a positive crystal orientation wafer area, 15 represents a 3-inch degraded wafer area and 16 represents a 2-inch wafer area. Dimensions are given in millimeters.

DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] In the present embodiment, as shown in FIG. 4, the indium phosphide crystal bar 8 has an internally chopped twinning line and has a non-uniform diameter. The <100> crystal orientation wafer needs to be processed as an InP substrate product. A desired substrate wafer has a thickness of 1 mm and a diameter of 3 inches, and a non <100> crystal orientation portion within 10 mm from the wafer edge is a degraded wafer. Due to the specificity of crystal growth, the probability of growing the same crystal bar is extremely low, and according to the process in the prior art, cutting head and tail for orientation.fwdarw.barreling.fwdarw.multi-wire cutting.fwdarw.obtaining wafers of corresponding specifications, see FIG. 5, a substrate wafer with a thickness of 1 mm is cut, the shaded portion is an available area of the crystal bar, and according to theoretical and empirical calculations, a positive crystal orientation wafer area 14 can be cut into a 3-inch positive crystal orientation wafer 23; the 3-inch degraded wafer area 15 may be cut into a 3-inch degraded wafers 22.

[0033] The crystal bar is processed into a substrate wafer in accordance with the method of the present invention, see FIG. 6, the shaded portion is the available area of the crystal bar. Theoretically, the positive crystal orientation wafer area 14 can be cut into a 3-inch positive crystal orientation wafer with yield of 45 wafers; 3-inch degraded wafer area 15 can be cut into a 3-inch degraded wafer with yield of 21 wafers, and a 2-inch wafer area 16 can be cut into a 2-inch positive crystal orientation wafer with yield of 20 wafers. A 2-inch InP wafer with twinning or poly crystal is less valuable and is not calculated. 3-inch positive crystal orientation wafer has a value calculated at a market average price of 3000 yuan, and the 3-inch degraded wafer has a value of 70% of the positive crystal orientation wafer value, i.e., 2100 yuan, 2-inch positive crystal orientation wafer has a value of 1200 yuan. See Table 1 for comparison of wafer yield and value for both methods.

TABLE-US-00001 3-inch positive 2-inch positive Wafer total crystal 3-inch crystal value Processing orientation degraded orientation Total improvement method wafer amount wafer amount wafer wafer value ratio Conventional 23 22 0 115200 76.3% barreling method Method of the 45 21 20 203100 present invention

[0034] Processing the crystal bar into a substrate wafer according to the process shown in FIG. 7, the specific steps are as follows:

[0035] 1) orientation: as shown in FIG. 8, the crystal bars are longitudinally bonded on a graphite carrier plate 12, the carrier plate 12 is fixed on a three-dimensional sample table of a cutting machine, and the end surfaces of the crystal bars 8 serve as reference surfaces. A sample is cut from the head of the crystal bar 8, the surface crystal orientation of the cutting surface is tested by an X-ray director, the deviation angle of the cutting surface from the <100> ideal crystal plane is calculated, the orientation of the crystal bar 8 is adjusted according to the deviation angle value, and the cyclic operation is performed until the crystal orientation of the cut end face meets the requirement, and the orientation precision of the end surface is ±0.02°. The tail cutting orientation step of the crystal bar 8 is consistent with the head, and an oriented crystal 9 is obtained. The cutting machine used PLN-27 type internal circle cutting machine produced by Tokyo Seimitsu Co. Ltd., and X-ray orientation instrument used YX-3 type produced by Liaodong Radioactive Instrument Co. Ltd.

[0036] 2) multi-wire cutting: the oriented crystal 9 and the carrier plate 12 are clamped on a workbench of the multi-wire cutting apparatus, the parallelism of a cutting steel wire and an orientation end face is detected, and the orientation of the workbench is adjusted, so that the parallelism error is less than 0.02°. Setting cutting parameters: the wire speed is 250 m/min, the wire tension is 22 N, the wire supply speed is 30 m/min, and the cutting speed is 0.6 mm/min, the crystal bar 8 is cut into wafers with a thickness of 1 mm. The wire saw adopts a U-600 type manufactured by Yasunage Corporation Japan.

[0037] 3) cleaning: cleaning the wafer with water until no residue and no dirt exist on the surface.

[0038] 4) circle cutting: determining the circle cutting position of each piece according to the area of the positive crystal direction in combination with the required 3-inch specification; A laser with a wavelength of 532 nm is used, a laser power of 70 W is selected, a cutting rate of 30 mm/s is selected, a removal amount per time is 30 μm, a set cutting pattern is repeatedly cut, cutting completely for 3 min, and the wafer is taken out. In the cutting process, cutting residues, gas and the like are collected by using a suction system. As shown in FIG. 7, a 3-inch positive crystal orientation wafer 11, a 3-inch degraded wafer 6 are cut, with some a 3-inch wafer cannot be cut from, but a 2-inch wafer 13 can be cut. The scrap wafers 5 and the processed bulk scrap can be used as a material for remelt.

[0039] In this embodiment, a 3-inch positive crystal orientation wafer 44, a 3-inch degraded wafer 19, a 2-inch positive crystal orientation wafer 20, and a 2-inch InP wafer with twinning or poly crystal are less valuable and not calculated. The edge of the wafer is smooth, neat, non-focal, burr-free, and the crystal orientation of the crystal plane is accurate. The 3-inch positive crystal orientation wafer is 1 piece less than the theoretical value, and the 3-inch degraded wafer is 2 pieces less than the theoretical value, compared with the pre-cut wafers calculated by the existing barreling method, the total value of the pre-cut wafers was increased by 70.1%.