JP2011098406A - Manufacturing method of wafer and manufacturing device of wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To use a cone part of a single crystal ingot manufactured by an FZ method as an ingot for a new wafer and obtain a wafer of high quality. <P>SOLUTION: The cone part 11 is cut from the single crystal ingot 10, which has the cone part 11 and a straight body part 12 and is manufactured by the FZ method, in a direction orthogonal to a central axis X of the single crystal ingot 10. The cone part 11 is used as the ingot 14 for a small diameter wafer to obtain a small diameter wafer 30 having a diameter W1 smaller than a diameter W of a wafer obtained from the straight body part 12. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for manufacturing a wafer, in particular, from a single crystal ingot having a cone portion and a straight body portion manufactured by an FZ method, in which the cone portion is perpendicular to the central axis of the single crystal ingot. The present invention relates to a manufacturing method and a manufacturing apparatus used as a new wafer ingot for cutting out.

  Currently, single crystal growth methods such as silicon mainly include CZ method (Czochralski method) and FZ method (floating zone method). The FZ method is a method in which a crystal raw material such as silicon is partially heated and melted to form a melting zone, and a single crystal is grown from the melting zone, and a quartz crucible is not used. There are advantages such as low contamination of impurities such as heavy metals, and growth of high resistivity single crystals.

  The single crystal ingot obtained by the above-described FZ method has a cone part, a straight body part, and a tail part. However, the ingot can have a constant diameter and a large-diameter wafer. The straight body part is used as a product. Therefore, the cone part and the tail part are usually cut and removed.

  Thereafter, the straight body portion is ground into a cylindrical shape, and then subjected to processing such as slicing, grinding / polishing, etc., to obtain a wafer. As a method of cylindrical grinding, for example, as disclosed in Patent Document 1, an upper limit setting value indicating a maximum diameter value that can be ground, a lower limit setting value indicating a final diameter value targeted for cylindrical grinding, and an upper limit setting. One or a plurality of intermediate setting values that are set between the value and the lower limit setting value and indicate the diameter value that determines the grinding conditions for partial grinding are set, and a portion for the ingot having the straight body portion is set based on these setting values. There is a method of performing cylindrical grinding by combining grinding and straight body grinding.

JP 2004-58185 A

  However, if the present inventor can effectively use not only the straight body portion of the single crystal ingot but also the cone portion that has been cut and removed in the past, it can utilize resources and obtain a high-quality wafer. I thought it was effective in that

  SUMMARY OF THE INVENTION An object of the present invention is to make it possible to use a cone portion of a single crystal ingot manufactured by the FZ method as a new wafer ingot, and further to provide a wafer manufacturing method and apparatus capable of obtaining a high-quality wafer. Is to provide.

As a result of repeated studies to solve the above-mentioned problems, the present inventor, from a single crystal ingot having a cone portion and a straight body portion, manufactured by the FZ method, the cone portion with respect to the central axis of the single crystal ingot. Cutting out in a direction perpendicular to each other, the cone portion is used as a small-diameter wafer ingot for obtaining a small-diameter wafer having a diameter smaller than the diameter of the wafer obtained from the straight body portion. It was found that it can be used as an ingot.
Furthermore, the wafer obtained from the ingot for a reduced-diameter wafer obtained from the cone part is processed into a normal straight body part in order to grind the outer peripheral part having poor in-plane uniformity in the resistivity distribution within the wafer surface. It was also found that the wafer has a high quality that is inferior to the wafer obtained in this way.

In order to achieve the above object, the gist of the present invention is as follows.
(1) From the single crystal ingot having a cone part and a straight body part manufactured by the FZ method, the cone part is cut in a direction orthogonal to the central axis of the single crystal ingot, and the cone part is separated from the straight body part. A method for producing a wafer, characterized in that it is an ingot for a reduced diameter wafer for obtaining a reduced diameter wafer having a diameter smaller than the diameter of the obtained wafer.

(2) The method for manufacturing a wafer according to (1), further comprising a step of grinding the ingot for a reduced diameter wafer into a cylindrical shape so as to have a predetermined diameter.

(3) The method for manufacturing a wafer according to (2), wherein the cylindrical grinding of the ingot for a reduced-diameter wafer is performed in a state where both ends are fixed and held so that a central axis of the ingot is horizontal.

(4) Prior to the grinding step, the wafer according to (2) or (3), further including a transfer step of transferring the small-diameter wafer ingot in a state where the central axis of the ingot is held horizontal. Manufacturing method.

(5) The method for manufacturing a wafer according to (4), wherein the holding of the ingot in the transfer step is performed by a horizontal holding tool corresponding to a shape of the cone portion.

(6) The method for manufacturing a wafer according to any one of (5), wherein at least a portion of the horizontal holder that contacts the cone portion is made of rubber, resin, or cloth.

(7) Cutting means for separating the cone portion as a small diameter wafer ingot from a single crystal ingot having a cone portion and a straight body portion manufactured by the FZ method, and conveyance for conveying the separated small diameter wafer ingot. And a peripheral grinder that grinds cylindrically so as to have a predetermined diameter after the transported ingot for a reduced diameter wafer is fixed and held, and the transport means is configured to level the central axis of the cone portion. An apparatus for manufacturing a wafer, comprising: a horizontal holder corresponding to the shape of the ingot for a reduced-diameter wafer to be held on the wafer.

(8) The wafer manufacturing apparatus according to (7), wherein the horizontal holder has at least a portion in contact with the cone portion made of rubber, resin, or cloth.

  According to the present invention, it is possible to use the cone portion of a single crystal ingot manufactured by the FZ method as a new wafer ingot, and further, a wafer manufacturing method and apparatus capable of obtaining a high-quality wafer. Is now available.

It is a flowchart for demonstrating the manufacturing method of the wafer according to this invention. It is the figure which showed typically the silicon single crystal ingot manufactured by FZ method. It is the perspective view which showed typically about the outer periphery grinding machine of the manufacturing apparatus by this invention. It is the perspective view which showed typically about the conveyance means of the manufacturing apparatus by this invention.

A method for producing a wafer according to the present invention will be described with reference to the drawings.
As shown in FIG. 1, the wafer manufacturing method of the present invention is based on a single crystal ingot 10 having a cone part 11 and a straight body part 12 manufactured by the FZ method (FIG. 1 (a)). Is cut out in a direction perpendicular to the central axis X of the single crystal ingot 12, and the cone portion 11 has a small diameter for obtaining a reduced diameter wafer 30 having a diameter W 1 smaller than the diameter W of the wafer obtained from the straight body portion 12. This is a wafer manufacturing method characterized in that the wafer ingot 14 is made into a generalized wafer ingot 14 (FIG. 1B).

By adopting the above configuration, the cone portion 11 can be used as a new wafer ingot 14.
Further, since the wafer 30 obtained from the small-diameter wafer ingot 14 obtained from the cone portion 11 can grind the outer peripheral portion thereof, the in-plane impurity concentration of the wafer can be made uniform. Even when compared with a wafer obtained by processing the portion 12, a wafer having no high quality and uniform distribution of resistivity within the wafer surface can be obtained. Furthermore, a more uniform resistivity distribution within the wafer surface can be obtained by performing neutron irradiation as necessary.

  Here, the single crystal ingot 10 is a single crystal ingot 10 manufactured by the FZ method and having a cone portion 11, a straight body portion 12, and a tail portion 13, as shown in FIG. The FZ method is a method in which a silicon crystal raw material is heated and melted to form a molten zone, and a silicon single crystal is grown from the molten zone. The type of the single crystal is not particularly limited, and a single crystal ingot 10 other than silicon can be manufactured. In addition, the single crystal ingot 10 shown in FIG. 1A and FIG. 2 is an ingot obtained by cutting the both ends of the single crystal manufactured by the FZ method and then grinding the outer periphery of the straight body portion 12. Say.

  The method for cutting out the cone portion 11 from the single crystal ingot 10 is not particularly limited, and a conventionally used method may be used. For example, the cone part 11 can be cut out using a band saw.

  In the wafer manufacturing method according to the present invention, in order to obtain the diameter-reduced wafer 30, the diameter-reduced wafer ingot 14 is ground into a cylindrical shape so as to have a predetermined diameter W1 (FIG. 1 (c)). It is preferable to further comprise. This is because the desired diameter-reduced wafer 30 can be obtained by slicing the ingot 20 obtained by cylindrical grinding of the diameter-reduced wafer ingot 14 and performing processing such as grinding and polishing (FIG. 1). (d)).

  Further, it is more preferable that the cylindrical grinding (FIG. 1C) of the ingot 14 for a reduced diameter wafer is performed in a state where both ends are fixed and held so that the central axis X of the ingot 14 is horizontal. This is for reliably grinding the small-diameter wafer ingot 14 into a cylindrical shape. If the central axis X is not horizontal, the small-diameter wafer ingot 14 cannot be reliably ground into a cylindrical shape, or the cylindrical shape This is because the diameter W1 obtained by processing the ingot 20 may be smaller than the desired diameter. Further, even if grinding is possible, there is a risk that the product will be out of specification with respect to the surface orientation standard.

Here, the cylindrical grinding can be performed by using an outer peripheral grinding machine 50 having a grinding means 51 and a pair of fixed holding means 52 as shown in FIG. If such an outer peripheral grinding machine 50 is used, as shown in FIG. 3A, the both ends 14a, so that the center axis X of the reduced-diameter wafer ingot 14 becomes horizontal by the fixed holding means 52. 14b can be fixed and held, and the ingot 14 can be ground into a cylindrical shape by the grinding means 51.
Further, even if the both ends 14a and 14b cannot be fixed so that the central axis X of the small-diameter wafer ingot 14 is horizontal (when it deviates from a predetermined horizontal standard), grinding is performed. It is also possible to adjust the level to be horizontal by measuring the amount of blurring with a dial gauge or the like and fine-tuning it.

In addition, various sizes can be selected for the diameter W1 of the reduced diameter wafer 30 obtained through the cylindrical grinding step and the subsequent processing. The diameter W1 can be adjusted, for example, by changing the amount of grinding in the cylindrical grinding step (FIG. 1 (c)).
In addition, it is possible to obtain a plurality of wafers 30 having different diameters W1 as the diameter-reduced wafer 30. For example, a small wafer 30 having a relatively large diameter W1 can be produced at a position close to the straight body, and a small wafer 30 having a relatively small diameter W1 can be produced at a position close to the tip.

Further, in the wafer manufacturing method according to the present invention, prior to the grinding step (FIG. 1 (c)), the diameter-decreasing wafer ingot 14 is held in a state where the central axis X of the ingot 14 is horizontal. It is preferable to have a carrying step (not shown) for carrying.
Cylindrical grinding by the grinder 50 (FIG. 4 (a)), as shown in FIG. 3 (a), is preferably carried out in a state where the center axis X holds the diameter of wafer ingots 14 so that the horizontal However, the small-diameter wafer ingot 14 (cone portion 11) has a very large mass, and is adjusted so that the central axis X becomes horizontal after the ingot 14 is transported to the grinding machine 50 by a conventional transport method. It was very difficult to do so and cylindrical grinding could not be performed reliably. Therefore, in the present invention, since the center axis X of the ingot 14 is held so as to be horizontal, it can be transported as it is and fixed and held by the fixing and holding means 52 of the outer peripheral grinding machine 50. Grinding can be performed.

  Here, the conveyance of the small-diameter wafer ingot 14 can be performed using a conveyance means 40 as shown in FIG. By using such a transfer means 40, as shown in FIG. 4A, transfer can be performed while holding the ingot 14 for a reduced diameter wafer so that the central axis X is horizontal. 4 (a) and 4 (b), the conveying means 40 has a V-shaped groove so that the shape thereof can easily hold the ingot 14, but the shape is particularly limited. However, it may have a U-shaped groove, or any other method may be used as long as the ingot 14 can be held by a method other than the groove (for example, a method using a fixing pin or the like).

  Furthermore, it is more preferable that the holding of the ingot 14 in the transporting process is performed by a horizontal holding tool 41 corresponding to the shape of the cone portion 11 as shown in FIG. This is because the diameter-reduced wafer ingot 14 can be held with a relatively simple configuration so that the central axis X is horizontal.

  Furthermore, in the horizontal holder 41, it is preferable that at least a portion 41a in contact with the cone portion is made of rubber, resin, or cloth. This is because, when the contact portion 41a is made of a material other than these, when the ingot 14 and the horizontal holder 41 are in contact with each other, there is a possibility that a chipped portion, a crack, or the like may occur at the contact portion of the ingot 14.

Next, a wafer manufacturing apparatus according to the present invention will be described.
The wafer manufacturing apparatus according to the present invention includes a cutting means (not shown) for cutting the cone portion 11 as a small-diameter wafer ingot 14 from a single crystal ingot 10 having a cone portion 11 and a straight body portion 12 manufactured by the FZ method. And the transfer means 40 (FIG. 4 (b)) for transferring the separated small-diameter wafer ingot 14 and the conveyed small-diameter wafer ingot 14 are fixedly held, and then the predetermined diameter W1 is obtained. In this way, the outer peripheral grinding machine 50 for grinding into a cylindrical shape is provided, and the transfer means 40 is horizontally held in accordance with the shape of the cone portion 11 for holding the central axis X of the small-diameter wafer ingot 14 horizontally. It has a tool 41.

By adopting the above configuration, the cone portion 11 can be used as a new wafer ingot 14.
Further, since the wafer 30 obtained from the small-diameter wafer ingot 14 obtained from the cone portion 11 can grind the outer peripheral portion thereof, the in-plane impurity concentration of the wafer can be made uniform. Even when compared with a wafer obtained by processing the portion 12, a wafer having no high quality and uniform distribution of resistivity within the wafer surface can be obtained. Furthermore, a more uniform distribution of resistivity within the wafer surface can be obtained by performing neutron irradiation as necessary.

  The above description is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.

(Example)
As Example 1, as shown in FIG. 1, from a silicon single crystal ingot 10 having a cone part 11, a straight body part 12 and a tail part 13 manufactured by the FZ method (FIG. 1 (a)), the cone part 11 is cut out in a direction perpendicular to the central axis X of the single crystal ingot 12, and the cone portion 11 is obtained to obtain a reduced diameter wafer 30 having a diameter W1 smaller than the diameter W of the wafer obtained from the straight body portion 12. As the small-diameter wafer ingot 14 (FIG. 1 (b)), as shown in FIG. 4 (a), a conveying means 40 having a horizontal holder 41 (the surface 41a in contact with the ingot 14 is made of resin) is used. Then, it is conveyed to the outer peripheral grinding machine 50 in a state where the central axis X is positioned horizontally, and the central axis X of the ingot 14 is made horizontal by the fixed holding means 52 as shown in FIG. Both ends 14a of the ingot 14, the cylindrical grinding was carried out while fixedly holding the b (FIG. 1 (c)).
Thereafter, the cylindrically ground ingot 20 was sliced and subjected to various grinding and polishing, thereby obtaining a small-diameter silicon wafer 30 having a diameter of 76 mm as a sample (FIG. 1 (d)).

(Comparative example)
As a comparative example, the straight body 12 of the silicon single crystal ingot (for 125 mm) 10 is cylindrically ground by a conventional method, and then the cylindrically ground straight body is sliced and subjected to various grinding and polishing. A silicon wafer having a diameter of 76 mm was obtained as a sample.

(Evaluation methods)
(1) As the evaluation item 1, the silicon wafer quality obtained by measuring the resistivity at any location within the wafer surface and calculating the variation of the silicon wafer obtained in each of the examples and comparative examples. Was evaluated. Regarding the variation in resistivity,
Δρ (%) = ((ρmax−ρmin) × 100) / ρmin
ρmax: Maximum resistivity in the wafer surface ρmin: Calculated by the minimum resistivity in the wafer surface. Here, Δρ serving as an index indicates that the smaller the value, the smaller the variation in resistivity and the higher the quality.
(2) As evaluation item 2, for each of the examples and comparative examples, the amount of silicon wafer obtained from one silicon single crystal ingot (the example is the amount of silicon wafer obtained from the cone portion and the straight body portion, In the comparative example, the amount of silicon wafer obtained from the straight body portion was calculated, and the yield was evaluated.

As a result of calculating the variation in resistivity within the wafer surface after neutron irradiation for the obtained sample, the sample of the example is Δρ: 2.5%, the sample of the comparative example is Δρ: 3.0%, and each is equivalent. It turns out that it has quality.
Further, in the embodiment, it can be seen that the diameter-reduced wafer 30 can be manufactured from the cone portion 11, the cone portion can be effectively used, and the yield is improved by about 2.6% compared to the comparative example. I understood.

  According to this invention, the cone part of the single crystal ingot manufactured by the FZ method can be used as a new wafer ingot, and a high-quality wafer can be obtained.

DESCRIPTION OF SYMBOLS 10 Single-crystal ingot 11 Cone part 12 Straight body part 13 Tail part 14 Ingot 20 for diameter-reduced wafers Ingot 30 cylindrically ground 30 Diameter-reduced wafer 40 Conveying means 41 Horizontal holding tool 50 Peripheral grinding machine 51 Grinding means 52 Fixed holding means

Claims (8)

  A wafer obtained by cutting the cone part in a direction perpendicular to the central axis of the single crystal ingot from a single crystal ingot having a cone part and a straight body part manufactured by the FZ method, and obtaining the cone part from the straight body part A method for producing a wafer, characterized in that an ingot for a reduced-diameter wafer for obtaining a reduced-diameter wafer having a diameter smaller than the diameter of the wafer is obtained.   The method for manufacturing a wafer according to claim 1, further comprising a step of grinding the cylindrical ingot for a reduced diameter wafer so as to have a predetermined diameter.   The method for manufacturing a wafer according to claim 2, wherein the cylindrical grinding of the ingot for a reduced diameter wafer is performed in a state where both ends are fixed and held so that a central axis of the ingot is horizontal.   4. The wafer manufacturing method according to claim 2, further comprising a transporting step of transporting the small-diameter wafer ingot in a state where the center axis of the ingot is held horizontal before the grinding step. 5.   The wafer manufacturing method according to claim 4, wherein the holding of the ingot in the transfer step is performed by a horizontal holding tool corresponding to the shape of the cone portion.   The method for manufacturing a wafer according to claim 5, wherein at least a portion of the horizontal holder that contacts the cone portion is made of rubber, resin, or cloth. Cutting means for separating the cone part from the single crystal ingot having a cone part and a straight body part manufactured by the FZ method as an ingot for a reduced diameter wafer, a conveying means for conveying the separated ingot for a reduced diameter wafer, After fixing and holding the transported ingot for small diameter wafer, comprising an outer peripheral grinding machine that grinds into a cylindrical shape so as to have a predetermined diameter,
The apparatus for manufacturing a wafer according to claim 1, wherein the transport means includes a horizontal holder according to the shape of the ingot for a reduced diameter wafer for horizontally holding the central axis of the cone portion.   The wafer manufacturing apparatus according to claim 7, wherein at least a portion of the horizontal holder that contacts the cone portion is made of rubber, resin, or cloth.

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