JP2000323443A - Manufacture of semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor wafer, where a processing load can be lessened in a chamfering process, and all the surfaces of all wafers are conformed to a prescribed crystal plane when ingot materials are collectively sliced into wafers. SOLUTION: In a cylinder grinding process, a silicon ingot block 10 is ground into a cylinder with a grinding wheel 11 around an axis (a) which extends in the same direction with a required crystal orientation, when a single crystal silicon ingot is grown in crystal. As a result, if the ground ingot cylinder is sliced at a right angle with the axis (a), all silicon wafers become all true circles each possessed of a front and a rear surface in parallel with a required crystal plane (100). Therefore, a silicon wafer is not required to be previously rounded in a chamfering process, so that a processing load can be lessened in a chamfering process. When ingot materials are collectively sliced, the surfaces of all wafers are conformed to a prescribed crystal plane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor wafer, and more particularly, to a method for manufacturing a semiconductor wafer in which a step of grinding a grown ingot is improved.

[0002]

2. Description of the Related Art According to a general method for manufacturing a silicon wafer (semiconductor wafer), a single crystal silicon ingot (semiconductor single crystal ingot) pulled up by a CZ method is used in a subsequent block cutting step to form a band saw and an ingot. The end cones at both ends of the ingot are cut off and sliced into a plurality of ingot blocks by a slicer or the like. Thereafter, each ingot block is subjected to cylindrical grinding by a grinding wheel, and a part of the outer peripheral portion is subjected to an orientation flat (OF) process or a notch process. In the subsequent slicing step, each ingot block is cut into a large number of silicon wafers by a wire saw or the like, and thereafter, each silicon wafer is subjected to chamfering, lapping, etching, gettering, and oxygen donor erasing. Then, the wafer surface is polished.

[0003]

Incidentally, in a single crystal silicon ingot pulled up by the CZ method, a slight shift may occur between the pulling axis and its crystal orientation. Therefore, in order to obtain a silicon wafer in which the front and rear surfaces of the wafer are aligned with the reference crystal plane, it is necessary to slice the ingot block obliquely with respect to the pulling axis during slicing. Strictly speaking, the sliced silicon wafer is an elliptical wafer. Thereby, at the time of chamfering for processing the outer peripheral portion of the wafer, the outer peripheral surface of the silicon wafer is pressed against the flat processing surface of the chamfering grindstone (the portion of the outer periphery of the grindstone parallel to the grindstone axis) in advance, and the wafer is perfectly circularly processed. I had to.
Therefore, the number of steps is increased by that much, and the processing time is lengthened. As a result, the burden of the processing operation in the chamfering step is increased.

Therefore, as a conventional means for solving this,
For example, when slicing an ingot block by the wire saw, specifically, when fixing the ingot block to the carbon bed, before and after that, for example, by an X-ray diffraction device described later, the crystal orientation of the cut surface of this block,
Single crystal silicon ingot lifting shaft (rotation center shaft)
Was measured, and the slice angle of the wire saw was adjusted based on the measurement data to correct the inclination of the crystal orientation of the ingot block. Here, the pulling axis direction is a direction equal to the crystal orientation of the tip end face of the seed crystal rod. Slicing is performed after correcting the inclination of the crystal orientation.

However, the method of correcting the inclination of the crystal orientation in the slicing process has the following problems. That is, when the single crystal silicon ingot is cut into blocks, ingot scraps as cut pieces are generated.
Therefore, when a plurality of ingot scraps respectively discharged from different single crystal silicon ingots are collectively fixed to one carbon bed via an adhesive and then sliced, the surface of the obtained silicon wafer is Is a predetermined reference crystal plane (for example, crystal plane (10
A defective wafer different from 0)) occurred. This is because the inclination of the crystal orientation of each ingot scrap differs from each other as described above. The term “reference crystal plane” used herein means that when growing a semiconductor single crystal ingot,
A crystal plane orthogonal to a desired crystal orientation determined in advance by a seed crystal rod.

Accordingly, as a result of earnest research, the inventor measured a desired crystal orientation of a semiconductor single crystal ingot during cylindrical grinding (outer diameter grinding), and performed cylindrical grinding around an axis extending in the same direction as the crystal orientation. Is performed, all the ingots subjected to the cylindrical grinding have the same crystal orientation regardless of the lot or the like. Therefore, even when ingot scraps from different lots are sliced collectively by a wire saw, many wafers after slicing all have a surface following a reference crystal plane (a crystal plane orthogonal to a desired crystal orientation). Knowing that it will be a wafer,
The present invention has been completed.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a semiconductor wafer, which can reduce a load of a processing operation in a chamfering process. Another object of the present invention is to provide a method for manufacturing a semiconductor wafer in which the slice efficiency is increased by using the entire wire saw. Further, the present invention provides a method of manufacturing a semiconductor wafer that can align the main surfaces of all wafers with a preset reference crystal plane when a plurality of ingot scraps are sliced at once. That is the purpose. Another object of the present invention is to provide a method of manufacturing a semiconductor wafer capable of reducing the outer diameter, shortening the slicing time, and increasing the durability of the wire groove of the groove roller of the wire saw. .

[0008]

According to a first aspect of the present invention, there is provided a method of growing a semiconductor single crystal ingot by rotating the semiconductor single crystal ingot by rotating a desired crystal orientation around a rotation center axis, and cylindrically grinding the grown semiconductor single crystal ingot. And a step of slicing the cylindrically-ground semiconductor single crystal ingot, wherein the crystal orientation is measured for the grown semiconductor single crystal ingot, and the same direction as the crystal orientation is measured. This is a method for manufacturing a semiconductor wafer in which the above-mentioned cylindrical grinding is performed about an axis extending in the direction of the center.

[0009] The type of semiconductor wafer is not limited. For example, a silicon wafer, a gallium arsenide wafer, or the like can be used. Therefore, the raw material of the semiconductor single crystal ingot is not limited. For example, silicon, gallium arsenide, magnetic materials, quartz, ceramics and the like can be mentioned. The method for growing the semiconductor single crystal ingot is not limited. For example, in addition to the Czochralski method (CZ method) of claim 3, a floating zone method (FZ method) and the like can be mentioned. The timing of cylindrical grinding of the semiconductor single crystal ingot is not limited. The semiconductor single crystal ingot may be before or after block cutting. An apparatus for cylindrically grinding a semiconductor single crystal ingot is not limited. For example, porcelain,
A general-purpose type having a grinding wheel in which various abrasive grains are hardened by a binder such as a synthetic resin can be employed. However, at the time of cylindrical grinding, it is necessary to move not only tools such as a grinding wheel in the axial direction of the semiconductor single crystal ingot but also in the block radial direction. It is to be noted that a cutting tool can be used instead of the grinding wheel.

The method for measuring the crystal orientation of the semiconductor single crystal ingot obtained by pulling is not limited. For example, an X-ray diffraction method, a light image method and the like can be mentioned. The crystal orientation referred to here is a desired orientation determined in advance by a seed crystal rod when growing a semiconductor single crystal ingot. The crystal plane orthogonal to the desired crystal orientation is the crystal reference plane. For example, even if the crystal reference plane is (100) plane, (11)
0) plane. Further, the (111) plane may be used.
Further, a plane having an off angle shifted from the reference plane by a predetermined angle may be used. For example, X = 0 for the plane (100)
Degrees, and a plane having an off angle such as Y = 0.5 degrees may be used.

According to a second aspect of the present invention, there is provided the method of manufacturing a semiconductor wafer according to the first aspect, further comprising the step of cutting the grown semiconductor single crystal ingot into ingot blocks of a predetermined length. The timing of the block cutting is not limited.

A third aspect of the present invention is the method of manufacturing a semiconductor wafer according to the first or second aspect, wherein the growth of the semiconductor single crystal ingot is performed by a Czochralski method.

The invention according to claim 4 is the method for manufacturing a semiconductor wafer according to claim 2 or 3, wherein the ingot block is sliced by a wire saw while being fixed to a slice base. The type of slice base is not limited. Usually a carbon bed. The wire saw may be of any type. For example, a semiconductor single crystal ingot may be moved to press and contact a wire row to cut it, or conversely, a wire row may be moved to press and contact a semiconductor single crystal ingot to cut it. Further, the lower surface of the ingot may be in contact with the upper portion of the wire array, or the upper surface of the ingot may be pressed against the lower portion of the wire array.

[0014]

According to the present invention, when a semiconductor single crystal ingot is cylindrically ground, the crystal orientation (rotation center axis) of the growth of the semiconductor single crystal ingot is measured and the same direction as the measured desired crystal orientation is measured. Cylindrical grinding around the axis extending to Therefore, at the time of slicing, simply slicing along a plane orthogonal to this axis, all the semiconductor wafers will have a perfect circular wafer whose front and back surfaces are along a preset crystal plane (reference crystal plane). Become. Thereby, the burden of the processing operation in the chamfering step can be reduced.

In particular, according to the fourth aspect of the present invention, after a plurality of ingot scraps are fixed to a slice base for a wire saw, and the ingot scraps are sliced collectively by the wire saw, the surface of all wafers is reduced. Can be aligned with a preset reference crystal plane.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view showing a cylindrical grinding step in a method for manufacturing a semiconductor wafer according to one embodiment of the present invention. FIG. 2 is a flowchart showing a method for manufacturing a semiconductor wafer according to one embodiment of the present invention. FIG. 3 is an explanatory diagram showing the inclination of the crystal orientation between the cut plane of the ingot block and the reference crystal plane. FIG. 4 is an explanatory view showing a slicing step in the method for manufacturing a semiconductor wafer according to one embodiment of the present invention.

As shown in FIG. 2, in this embodiment, generally, ingot pulling, block cutting, measurement of crystal orientation, cylindrical grinding, slicing, chamfering, lapping,
A silicon wafer is manufactured through the steps of etching and polishing. Hereinafter, each step will be described in detail. A single crystal silicon ingot (S20) pulled up by the CZ method using a seed crystal rod having a reference crystal face (100)
1) is cut into a plurality of ingot blocks 10 (see FIG. 1) by a band saw in a block cutting step (S202). At this time, ingot scraps are generated. Next, the crystal orientation of the cut surface of the cut ingot block 10 is measured by an X-ray diffraction method (S20).
3).

The X-ray diffraction method is a method of recording a diffraction X-ray pattern or intensity diffracted on a crystal lattice plane. The measurement of the crystal orientation of the cut surface by this diffraction method is performed by an X-ray diffraction device using a counter tube called a diffractometer. The diffractometer is mainly composed of an X-ray generator for generating X-rays, a goniometer for measuring the reflection angle of X-rays, a coefficient device for measuring X-ray intensity, and a control operation for controlling these to calculate a count value. It is composed of four devices called devices.

When the incident beam, reflected beam, and normal of the reflecting surface of the X-ray emitted from the X-ray generator are all on the same plane, and the reflection intensity of the X-ray is maximized, it is called a Bragg condition. 2d sin θ = nλ holds. Here, λ is the wavelength of the irradiated monochromatic X-ray, and d is the reflecting surface (h, k,
l) lattice spacing, θ is the Bragg angle, n is the reflection order, h, k, l
Is the Miller index. Using these conditions, the inclination of the crystal orientation between the cut plane and the reference crystal plane (100) is measured. First,
The data base is set so that the angle between the cut surface and the incident beam becomes the Bragg angle, and X-rays are irradiated. Next, the counter tube is rotated around the data base, and the rotation angle Ψ1 of the counter tube at which the X-ray intensity becomes the highest is obtained. Similarly, the rotation angle of the counter tube at each angle when the material is rotated at 90, 180, and 270 degrees around the normal line of the cut surface as {2,}
Find 3 and $ 4. Here, as shown in FIG. 3, the crystal orientation of the cut plane in the XY axis and the crystal orientation of the reference crystal plane (100), in other words, the pulling axis of the ingot block 10 (the center axis of rotation or the tip face of the seed crystal rod). Assuming α and β as the inclinations with respect to the crystal orientation, respectively, Equation (1),
It is expressed by equation (2).

Α = (Ψ1-Ψ3) / 2 (1) β = (Ψ2-Ψ4) / 2 (2) The maximum inclination Φ of the crystal orientation between the cut plane and the reference crystal plane (100) is expressed by the following equation. 3) It is obtained by the equation. tan ² Φ = tan ² α + tan ² β (3) It should be noted that this equation (3) should be simplified to the following equation (4) when the measured values α and β are 5 degrees or less. Can be. Φ ² = α ² + β ² (4)

When the measurement of the crystal orientation of the cut plane is completed, a crystal orientation orthogonal to the reference crystal plane (100) calculated by calculation based on the measured value is measured, and the crystal orientation is measured in the same direction as the crystal orientation. Cylindrical grinding with the grinding wheel 11 for cylindrical grinding around the extending axis a (S204)
(See FIG. 1). At this time, the axis a is α, with respect to the center axis b of the actual ingot block 10 in the XY directions.
It is inclined by β. The diameter of the ingot block 10 after the cylindrical grinding is about 8 inches. Thereafter, the cylindrically ground ingot block 10 is subjected to orientation flat processing, and is fixed to a carbon bed (slice base) 12 (see FIG. 4). In the subsequent slicing step (S205),
The ingot block 10 is attached to the wire saw while being fixed to the carbon bed 12. What is a wire saw?
This is a device in which a long wire 13 is wound in a coil shape between a plurality of groove rollers, and as shown in FIG. It is sliced along a direction perpendicular to the axis a. As a result, all the obtained silicon wafers had the same reference crystal plane (100) as the cut surface of the seed crystal rod (not shown) on the front and back surfaces, and had a thickness of about 860 μm.
The result is a round wafer of about 8 inches.

Next, as shown in FIG. 1, the outer peripheral portion of the sliced wafer is chamfered with a resinoid grinding wheel # 600 to # 2000 (S206). At this time,
Since the sliced silicon wafers are all rounded as described above, as in the conventional method, during the chamfering process, the wafer peripheral surface is pressed against the flat processing surface of the chamfering grindstone in advance, and the wafer is rounded. Work load is small. Therefore, it is possible to reduce the burden of the processing operation in the chamfering step. For example, an ingot block conventionally cylindrically ground to 201.5 mm is 2 in the present invention.
It can be finished to 00.5 mm, and will be ground to 200 mm in the chamfering step. Therefore, the chamfering operation can be performed in a short time, and the wear of the chamfering grindstone can be reduced. Next, the front and back surfaces of the chamfered silicon wafer are wrapped (S20).
7). In the lapping step, a silicon wafer is placed between lapping plates parallel to each other, and then a lapping liquid, which is a mixture of alumina abrasive grains, a dispersant, and water, is poured between the lapping plates. Then, both sides of the wafer are mechanically wrapped by rotating and grinding under pressure.

Subsequently, the wrapped wafer is etched (S208). Specifically, the silicon wafer is immersed in a mixed acid solution (normal temperature to 50 ° C.) in which hydrofluoric acid and nitric acid are mixed. Thereafter, the silicon wafer is cleaned with an RCA-based cleaning solution, and then the surface of the silicon wafer is polished (S209). Then, after the final cleaning, various wafer inspections are performed, and only the non-defective products are packed,
For example, it is shipped to a device maker or the like.

FIG. 5 shows the technical idea of cylindrical grinding of the ingot block 10 about the axis a extending in the same direction as the crystal orientation at the time of crystal growth of the single crystal silicon ingot. As described above, in a single-crystal silicon ingot of a different lot, a plurality of ingot scraps 10A,
This is convenient when the 10Bs are joined together on the same carbon bed 12 and sliced at a time. That is, all of the obtained silicon wafers have the same reference crystal plane (100) on the front and back surfaces. FIG. 5 is an explanatory view showing a slicing step in a method of manufacturing a semiconductor wafer according to another embodiment of the present invention.

[0025]

According to the present invention, the semiconductor single crystal ingot is cylindrically ground around the axis extending in the same direction as the crystal orientation during the cylindrical grinding.
During the subsequent chamfering, the burden of round processing of the semiconductor wafer can be reduced. As a result, it is possible to reduce the burden of the processing operation in the chamfering step.

In particular, according to the invention of claim 4, since the ingot block is fixed to the slice base and then sliced by a wire saw, all wafer surfaces are aligned with a preset reference crystal surface. be able to.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a cylindrical grinding step in a method for manufacturing a semiconductor wafer according to one embodiment of the present invention.

FIG. 2 is a flowchart showing a method for manufacturing a semiconductor wafer according to one embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a tilt of a crystal orientation between a cut plane of an ingot block and a reference crystal plane.

FIG. 4 is an explanatory view showing a slicing step in the method for manufacturing a semiconductor wafer according to one embodiment of the present invention.

FIG. 5 is an explanatory view showing a slicing step in a method for manufacturing a semiconductor wafer according to another embodiment of the present invention.

[Explanation of symbols]

 10 ingot block, 10A, 10B ingot scraps, a-axis.

Claims (4)

[Claims] 1. A step of growing a semiconductor single crystal ingot by rotating a desired crystal orientation around a rotation center axis, a step of subjecting the grown semiconductor single crystal ingot to cylindrical grinding, and a step of cylindrically grinding the semiconductor single crystal ingot. Subjecting the grown semiconductor single crystal ingot to a crystal orientation, and performing the cylindrical grinding around an axis extending in the same direction as the crystal orientation. Manufacturing method. 2. The method of manufacturing a semiconductor wafer according to claim 1, further comprising the step of cutting the grown semiconductor single crystal ingot into ingot blocks of a predetermined length. 3. The method for manufacturing a semiconductor wafer according to claim 1, wherein the growing of the semiconductor single crystal ingot is performed by a Czochralski method. 4. The method for manufacturing a semiconductor wafer according to claim 2, wherein the ingot block is sliced by a wire saw while being fixed to a slice base.