JP2002018711A - Cylindrical grinding device and cylindrical grinding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce grinding damage left on a monocrystal by eliminating overload to a grinding tool in cylindrical grinding of the semiconductor monocrystal. SOLUTION: In the case of applying cylindrical grinding to a monocrystal ingot, the ingot is chucked by a loader and rotated to measure an eccentric quantity. A grinding quantity is determined by correcting the eccentric quantity, and a grinding-cutting quantity per one time is computed. A grinding tool is driven on the basis of the cutting quantity to carry out cylindrical grinding. As a result, the grinding damage of the semiconductor monocrystal ingot after grinding can be minimized, and the service life of the grinding tool is lengthened. The appropriate cutting quantity corresponding to the monocrystal is obtained from the diameter of material and a discrepancy between a material crystal axis and a rotary shaft of a grinding machine. The eccentric quantity is added to the diameter to compute the cutting quantity when grinding. The cutting quantities of plural times are computed to reduce load each time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cylindrical grinding apparatus and a cylindrical grinding method, and more particularly, to an apparatus and a method for cylindrically grinding a semiconductor single crystal ingot.

[0002]

2. Description of the Related Art A single crystal silicon ingot pulled up by a CZ method is subjected to a band saw,
By using an ingot slicer or the like, the cones at both ends of the ingot are cut off and cut into a plurality of ingot blocks. Thereafter, each ingot block is subjected to cylindrical grinding by a grinding wheel, and further, an outer peripheral portion thereof is subjected to orientation flat (OF) processing or notch processing. Thereafter, the ingot block is cut into many silicon wafers by a wire saw or the like. here,
In the cylindrical grinding, the wafer is generally finished to be about 1 mm thicker than the finished wafer diameter. That is, first, the centering operation of the cut surface of the ingot is performed. In this centering operation, the irregular shape of the ingot is read, the least squares method is performed, and the point where the kerf loss is reduced is determined as the center. In cylindrical grinding, for example, a wheel, which is a grinding wheel, is rotated at a high speed and ground on the surface of an ingot for grinding. In this wheel, diamond abrasive grains are fixed to a base metal with a binder. The cylindrical grinding of the ingot is usually repeated several times. There is a method in which rough grinding is performed first and finish grinding is performed second time. The ingot is processed into a perfect circle by this cylindrical grinding.

[0003] In a fully automatic grinder conventionally used as this cylindrical grinding apparatus, cylindrical grinding is performed in the following procedure. That is, the finishing diameter and the orientation flat dimensions are input to the control device in advance. Next, the single crystal (work) is centered by the loader chuck. Then, the work is chucked between the main and sub shafts. In this supporting state, the work is ground by using a wheel while rotating the work so that the work has a finished diameter. In this case, a single grinding amount (cutting amount) is constant, and a plurality of traverse grindings are performed. Next, after the outer diameter grinding is completed, the finished diameter is measured. If the measured value is different from the set value,
Automatically correct. Further, the crystal orientation is searched and the crystal peak position angle is stored. Then, perform automatic indexing,
Grind the orientation flat surface. Notch processing is performed for notch products.

[0004]

In such a conventional fully automatic grinder, when the outer periphery of a silicon single crystal rod is ground, a single cut amount of a wheel of the grinder is always fixed. As a result, depending on the diameter of the material and the deviation (distance, angle, etc.) between the crystal axis of the material and the rotation axis (spindle axis) when the material is chucked,
The loads on the wheels were different. In some cases, overload may occur. When an overload acts on the wheel, surface roughness and grinding damage remain in the crystal.

[0005] Therefore, as a result of earnest research, the inventor has measured the misalignment of a semiconductor single crystal ingot during cylindrical grinding, and determined the amount of cut per operation with this misalignment corrected. The inventors have found that no overload occurs in the grinding tool, and have completed the present invention.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce grinding damage remaining on a single crystal by eliminating overload on a grinding tool. It is another object of the present invention to provide a cylindrical grinding method capable of producing a semiconductor single crystal ingot block with reduced grinding damage. Another object of the present invention is to provide a cylindrical grinding device used for the method.

[0007]

According to the first aspect of the present invention, there is provided a supporting means for holding a semiconductor single crystal ingot between a main shaft and a sub shaft so as to rotatably support the semiconductor single crystal ingot around its axis. A cylindrical grinding device provided with a grinding tool for grinding an outer peripheral surface of a semiconductor single crystal ingot supported by the support means; a diameter measuring means for measuring a diameter of the semiconductor single crystal ingot; and finishing of the semiconductor single crystal ingot. Finishing diameter setting means for setting the diameter, misalignment measuring means for measuring misalignment between the axis of the semiconductor single crystal ingot supported by the supporting means and the axis of the supporting means, the finishing diameter, the diameter, and A cut amount calculating means for calculating a cut amount per one time of the grinding tool based on the misalignment amount; and controlling the driving of the grinding tool based on the cut amount. A cylindrical grinding apparatus with a that control means.

The raw material of the semiconductor single crystal ingot is not limited. For example, silicon, gallium arsenide, etc. As the semiconductor single crystal ingot, for example, an ingot pulled up by the Czochralski method (CZ method) can be used. Further, the cylindrical grinding can be performed before cutting the block of the semiconductor single crystal ingot. Naturally, cylindrical grinding can also be performed after block cutting. Examples of a grinding tool for cylindrically grinding a semiconductor single crystal ingot include a grinding wheel in which diamond abrasive grains are bonded to a core material by metal, porcelain, synthetic resin, or the like. It is also possible to use grinding tools instead of grinding wheels.

According to a second aspect of the present invention, the misalignment amount measuring means rotates the semiconductor single crystal ingot in a state where the semiconductor single crystal ingot is chucked by a loader and a measuring terminal is attached to the semiconductor single crystal ingot. The cylindrical grinding device according to claim 1, wherein the misalignment amount is measured.

As a method of measuring the crystal orientation of a cut surface of a semiconductor single crystal ingot, there are an X-ray diffraction method, an optical image method, and the like. This crystal orientation is a desired orientation determined in advance by a seed crystal when growing a semiconductor single crystal ingot. A crystal plane orthogonal to the desired crystal orientation is a crystal reference plane (cut plane). For example, the crystal reference plane may be a (100) plane or a (110) plane. Further, the (111) plane may be used.

According to a third aspect of the present invention, there is provided a semiconductor single crystal ingot sandwiched between a main axis and a sub-axis, a step of measuring a diameter of the semiconductor single crystal ingot, and a step of measuring a finished diameter of the semiconductor single crystal ingot. Setting the step, measuring the amount of misalignment between the axis of the semiconductor single crystal ingot and the axis of the supporting means, and calculating the amount of cut per one time of the grinding tool based on the finishing diameter, diameter, and the amount of misalignment. This is a cylindrical grinding method including a calculating step and a step of driving a grinding tool based on the cut amount.

[0012]

According to the present invention, when a semiconductor single crystal ingot is cylindrically ground, the semiconductor single crystal ingot is chucked by a loader, a measuring terminal is attached to the semiconductor single crystal ingot, and then the semiconductor single crystal ingot is rotated. Measure the displacement. Then, the grinding amount is determined by correcting the misalignment amount. Further, the cut amount per grinding is calculated. The grinding tool is driven based on the cut amount to perform cylindrical grinding. As a result, grinding damage in the semiconductor single crystal ingot after grinding is reduced as much as possible. In addition, the effect of extending the life of the grinding tool is produced.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 to 3, a cylindrical grinding device 11 includes a main shaft 13 and a sub shaft 14 that rotatably support a silicon single crystal rod 12, a grinding wheel 15 that grinds the outer peripheral surface of the silicon single crystal rod 12, have. Both the main shaft 13 and the sub shaft 14 are configured to be driven and rotated synchronously by driving means 16 and 17. Each driving means 1
Each of the motors 6 and 17 includes a motor, a speed reducer, and the like, and its driving is controlled by the control unit 18. The grinding wheel 15 is provided so as to be able to reciprocate in the axial direction of the main shaft 13 and the sub shaft 14 and to be able to approach and separate from the silicon single crystal rod 12. The control unit 18 controls the traveling and rotational driving of the grinding wheel 15. Reference numeral 19 denotes a rotation speed sensor for detecting the rotation speeds of the main shaft 13 and the sub shaft 14;
Is a sensor for measuring the crystal orientation of the cut surface of the silicon single crystal rod 12. This sensor 20 is a silicon single crystal rod 12
Are provided so as to be capable of moving toward and away from. The outputs of these sensors 19 and 20 are configured to be sent to the control unit 18.

As shown in FIG. 3, the control unit 18 includes a CPU 181 as an arithmetic unit, a ROM 182 storing a program to be executed in cylindrical grinding, and an RA for temporarily storing the program.
M183, an input unit 184 such as a touch panel,
Monitor 1 that displays necessary items when executing a program
85 and an I / O 186 for controlling input / output with an external device, which are interconnected by a bus. FIG. 2 shows, using a block diagram, a main part of the cylindrical grinding device according to the present invention, which is configured in the control unit 18. That is, this device is provided with the input unit 1
A finishing diameter setting means 21 comprising a sensor 84;
And a misalignment amount measuring means 23 for measuring the misalignment amount between the axis of the silicon single crystal rod 12 and the axes 13 and 14 of the supporting means based on a signal from the sensor 20. Contains. In addition, the cylindrical grinding device 11
The grinding amount of the silicon single crystal rod 12 is calculated based on these finishing diameters, the diameter of the silicon single crystal rod 12, and the amount of misalignment, and one of the grinding wheels 15 is determined based on the grinding amount.
Cut amount calculating means 2 for calculating the cut amount per turn
4 is included. Furthermore, in this cylindrical grinding device 11,
Control means 25 for controlling the driving of the grinding wheel 15 based on the cut amount is provided.

Next, an outline of a procedure for manufacturing a silicon wafer from a silicon single crystal rod will be described. For example, a single crystal silicon ingot pulled up by the CZ method using a seed crystal rod having a reference crystal plane (100) at the tip surface is cylindrically ground, subjected to orientation flat processing, and cut into a plurality of ingot blocks by a band saw. After that, it is fixed to the carbon bed. The ingot block is attached to the wire saw while being fixed to the carbon bed. In the wire saw, the wire is reciprocated and the ingot block is sliced along a direction perpendicular to the axis. As a result, all the silicon wafers become silicon wafers of a predetermined thickness with the front and back surfaces being the same reference crystal plane (100) as the tip surface of the seed crystal rod. Next, the outer peripheral portion of the sliced wafer is chamfered with a grinding wheel. The front and back surfaces of the silicon wafer after the chamfering are wrapped. Subsequently, the wrapped wafer is etched. A mixed acid solution containing a mixture of hydrofluoric acid and nitric acid (room temperature to 50
C)). Thereafter, the silicon wafer is cleaned with an RCA-based cleaning solution, and the surface of the silicon wafer is mirror-polished. After the final cleaning, various types of wafer inspection are performed, and only non-defective products are packed and shipped to, for example, a device maker.

Hereinafter, a method of cylindrically grinding the silicon single crystal rod 12 using the cylindrical grinding device 11 will be described with reference to the flowchart of FIG. First, the CPU of the control unit 18
Initialize a memory or the like (S401). next,
A set value, for example, a reference value for calculating the notch amount and a set value for confirming the setting state of the silicon single crystal rod 12 are read from the storage device into the RAM 183 (S40).
2). Next, the length and diameter of the crystal are measured, and the measured values are input (S403). Further, the finishing diameter of the silicon single crystal rod 12 is input (S404). Next, the silicon single crystal rod 12 is set between the main shaft 13 and the sub shaft 14 (S405). Then, the misalignment amount is detected (S406). The amount of deviation between the rotation axis and the axis of the silicon single crystal rod 12 (the axis perpendicular to the cutting plane and passing through the center of the cutting plane) is detected by a signal from the sensor 20. here,
It is determined whether the misalignment amount is smaller than a set value (S40).
7). If not, reset the crystal (S40)
8). If it is smaller, the grinding amount is calculated (S409). This grinding amount is obtained by subtracting the finishing diameter from the value obtained by adding the misalignment amount to the diameter. Next, the amount of one cut in the grinding wheel 15 is calculated based on the amount of grinding (S41).
0). By performing the grinding in a plurality of times, the load on the grinding wheel 15 is reduced. Then, the grinding wheel 15 is driven based on the cut amount (S4).
11). As a result, the silicon single crystal rod 12 is cylindrically ground to a finished diameter. The appropriate cutting depth according to the single crystal is determined from the diameter of the material and the deviation between the crystal axis of the material and the rotation axis of the grinding machine. The notch amount at the time of grinding is calculated by adding the misalignment amount to the diameter. A plurality of cut amounts are calculated for the total of the cut amounts, and the load for each time is reduced.

[0017]

According to the present invention, in the cylindrical grinding of a semiconductor single crystal ingot, an overload is not applied to the grinding tool of the cylindrical grinding device, so that the grinding damage generated in the semiconductor single crystal can be reduced. In addition, the life of the grinding tool can be extended.

[Brief description of the drawings]

FIG. 1 is a front view showing a schematic configuration of a cylindrical grinding device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a main part of the cylindrical grinding device according to one embodiment of the present invention.

FIG. 3 is a block diagram showing a control unit of the cylindrical grinding device according to one embodiment of the present invention.

FIG. 4 is a flowchart showing a cylindrical grinding method according to one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 11 cylindrical grinding device, 12 silicon single crystal rod, 13 main shaft, 14 counter shaft, 15 grinding wheel, 21 finishing diameter setting means, 22 diameter measuring means, 23 misalignment measuring means, 24 cutting amount calculating means, 25 control means.

Claims (3)

[Claims] 1. A supporting means for sandwiching a semiconductor single crystal ingot between a main shaft and a sub-shaft to rotatably support the semiconductor single crystal ingot about its axis, and a semiconductor single crystal ingot supported by the supporting means. A cylindrical grinding device provided with a grinding tool for grinding an outer peripheral surface; a diameter measuring means for measuring a diameter of the semiconductor single crystal ingot; a finishing diameter setting means for setting a finishing diameter of the semiconductor single crystal ingot; and the supporting means. Misalignment measuring means for measuring the amount of misalignment between the axis of the semiconductor single crystal ingot supported by the shaft and the axis of the supporting means; and A cylindrical grinding device comprising: a notch amount calculating means for calculating a notch amount; and a control means for controlling driving of the grinding tool based on the notch amount. 2. The semiconductor laser device according to claim 1, wherein the misalignment amount measuring unit measures the misalignment amount by chucking the semiconductor single crystal ingot with a loader, rotating the semiconductor single crystal ingot with the measurement terminal attached to the semiconductor single crystal ingot. Item 2. A cylindrical grinding device according to Item 1. 3. A step of clamping a semiconductor single crystal ingot between a main axis and a sub-axis, a step of measuring a diameter of the semiconductor single crystal ingot, a step of setting a finishing diameter of the semiconductor single crystal ingot, A step of measuring the amount of misalignment between the axis of the crystal ingot and the axis of the support means; a step of calculating a cut amount per grinding tool based on the finishing diameter, the diameter, and the amount of misalignment; Driving the grinding tool based on the amount.