JP2003318138A - Method for manufacturing semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor wafer which can reduce the lapped amount in a subsequent lapping process by enhancing the efficiency and the accuracy in slicing an ingot. <P>SOLUTION: When the ingot I is sliced, the going and returning frequency of a wire 11a per minute is set to 8 times or more. Herewith, since the abrasive action per unit of time of free abrasive grains against the ingot I is increased, the efficiency and the accuracy in slicing the ingot I is enhanced. Hence, the thickness irregularity and the warpage in a silicon wafer can be suppressed, and the lapped amount in the subsequent lapping process can be reduced. <P>COPYRIGHT: (C)2004,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor wafer, and more particularly to a method of manufacturing a semiconductor wafer by reciprocating a wire at a high speed at the time of cutting an ingot, thereby improving the cutting accuracy of the ingot. The present invention relates to a method for manufacturing a semiconductor wafer for reducing the amount. [0002] In the production of general silicon wafers,
After slicing the ingot to produce a large number of silicon wafers, each step of chamfering, lapping, etching, and mirror polishing is sequentially performed on the silicon wafer. Among these, in the slicing process, ingot cutting methods using a wire saw capable of producing a large number of silicon wafers at one time are becoming mainstream in recent years. The wire saw is configured such that an ingot cutting wire derived from a wire feeding bobbin is wound around a plurality of groove rollers in a coil shape, and is wound around a wire winding bobbin. In the groove roller, an outer peripheral surface of a cylindrical base metal is covered with a lining material (urethane rubber) having a predetermined thickness, and a plurality of wire grooves are engraved on the outer peripheral surface of the lining material. The groove roller is rotatably supported by a pair of bearings disposed at both ends in the axial direction. At the time of cutting the ingot, a single crystal silicon ingot is pressed relatively against a wire row reciprocating at a high speed while supplying a slurry-like abrasive liquid containing free abrasive grains (hereinafter, abrasive grains) in wrapping oil. .
The ingot is cut into many wafers by the grinding action of the abrasive grains. [0003] By the way, in the conventional wire saw, the number of reciprocating movements of this wire row is only about several times per minute. As a result, the cutting efficiency of the ingot and the cutting accuracy have been reduced, and the thickness unevenness of the wafer and the warpage of the wafer have occurred.
As a result, the amount of lapping on both the front and back surfaces of the wafer in the lapping process has increased. [0004] Therefore, as a result of earnest research, the inventor of the present invention has found that if the reciprocating traveling speed of the wire is reduced and the sharpness of the wire at the time of cutting the ingot is generally improved, the cutting efficiency and cutting accuracy of the ingot are increased. The present inventors have found that the present invention suppresses the occurrence of wafer thickness unevenness and wafer warpage, thereby reducing the amount of lapping on both the front and back surfaces of the wafer in a subsequent lapping step, and completed the present invention. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a semiconductor wafer capable of increasing the cutting efficiency and cutting accuracy of an ingot and thereby reducing the amount of lapping in a subsequent lapping process. For that purpose. According to the first aspect of the present invention, a wire wound between a plurality of groove rollers is reciprocated to supply an abrasive liquid containing free abrasive grains. An ingot is relatively pressed against a wire, and the grinding action of the loose abrasive grains includes an ingot cutting step of cutting the ingot, and a lapping step of wrapping the front and back surfaces of the semiconductor wafer obtained by the ingot cutting step. In the method for manufacturing a semiconductor wafer, the wire is reciprocated at least eight times / minute during cutting the ingot. [0007] As the wire saw to be used, for example, one having a configuration in which an ingot is moved to press and contact the wire to cut the wire can be adopted. On the contrary,
The wire may be moved to press and contact the ingot to cut it. Further, the lower surface of the ingot may be in contact with the upper portion of the wire. Further, a type in which the upper surface of the ingot is pressed against the lower part of the wire may be used. The number of groove rollers assembled and arranged on the wire saw may be two or three or more. Examples of the ingot cut by the wire saw include silicon single crystal, silicon polycrystal, and compound semiconductor single crystal.
As an abrasive used for cutting, for example, an average particle diameter of 5 to 5
What contains loose abrasives, such as 0 micrometer SiC, is employ | adopted. [0008] The structure of the groove roller is not limited. For example, a roller or the like in which the outer peripheral surface of a cylindrical base metal is covered with a lining material (urethane rubber) having a predetermined thickness, and a wire groove is engraved on the outer peripheral surface of the lining material can be employed. As the wire, for example, carbon is 0.7 to 0.8%
A contained piano wire or the like can be employed. The diameter of the wire is 50 to 50 when the ingot is a silicon single crystal.
200 μm, 80 to 120 in the case of a compound semiconductor single crystal
μm, 80 to 140 μm for magnetic materials, 80 to 160 μm for quartz, 50 to 20 for ceramics
It is about 0 μm. The preferred number of reciprocating runs of the wire per minute is 8 or more. If it is less than 8 times / minute, swelling occurs (h1 is 5 μm or more), and the allowance in the lapping process must be increased by the amount of swelling. The distance of the going and returning of the reciprocating wire is, for example, about 300 to 800 m in the case of an ingot for an 8-inch wafer. The reciprocating traveling speed of the wire is, for example, 500 on average.
km / min. [0009] The semiconductor wafer after slicing is usually chamfered on the outer periphery of the wafer by a chamfering grindstone. In the lapping step, the front and back surfaces of the chamfered semiconductor wafer are mechanically wrapped to increase the parallelism of the front and back surfaces of the wafer. That is, a semiconductor wafer is arranged between lapping plates parallel to each other, and a lapping liquid, for example, a mixture of alumina abrasive grains, a dispersant, and water is poured between the lapping plate and the wafer. Then, the front and back surfaces of the semiconductor wafer are wrapped by rotating and grinding under pressure.
The amount of wrap at this time is 4
It is about 0 to 60 μm. According to the present invention, the number of reciprocating runs of the wire per minute is eight or more at the time of cutting the ingot. Thereby, the grinding effect of the free abrasive grains per unit time on the ingot is increased, and the cutting efficiency and the cutting accuracy of the ingot are increased. As a result, unevenness in thickness of the semiconductor wafer and occurrence of warpage of the semiconductor wafer are suppressed, and the amount of lapping in the subsequent lapping step can be reduced. For example, in the conventional method, 5 μm
m and larger swell h1 (FIG. 3 (a)) and 15-1
Processing damage of about 6 μm occurred. However, as is clear from the graph of FIG. 4, if the wire is reciprocated at least 8 times / min when cutting the ingot, a small undulation h2 of 1 μm or less (FIG. 3B). Further, the processing damage is less than 15 μm. This reduces the amount of wrap. Here, FIG. 3A is a partially enlarged cross-sectional view of the surface of a wafer obtained by a conventional semiconductor wafer manufacturing method. FIG. 3B is a partially enlarged cross-sectional view of the surface of a wafer obtained by the method of manufacturing a semiconductor wafer according to the present invention. FIG. 4 is a graph showing the relationship between the number of reciprocating runs per minute of the wire according to the present invention and the amount of undulation. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is an enlarged schematic view showing a main part of a wire saw according to a method for manufacturing a semiconductor wafer according to one embodiment of the present invention. FIG. 1B is a partially enlarged view of a groove roller incorporated in a wire saw according to one embodiment of the present invention. FIG. 2 is a flow sheet showing a method for manufacturing a semiconductor wafer according to one embodiment of the present invention. As shown in FIG. 2, in one embodiment,
A silicon wafer is manufactured through the steps of slicing, chamfering, lapping, etching, mirror polishing, and finishing cleaning.
Hereinafter, each step will be described in detail. The silicon ingot pulled up by the CZ method is subjected to a slicing step (S10
In 1), an 8-inch silicon wafer having a thickness of about 860 μm is sliced by a wire saw. Hereinafter, FIG.
This wire saw will be described in detail based on FIG. FIG.
1A, reference numeral 10 denotes a wire saw according to one embodiment of the present invention. The wire saw 10 is a device for cutting the silicon ingot I into a large number of wafers. The wire saw 10 has three groove rollers 12 arranged in an inverted triangular shape when viewed from the front in FIG.
A, 12B and 12C. A single wire 11 is provided between the groove rollers 12A, 12B, and 12C.
a are wound parallel to each other and at a constant pitch.
Thereby, the wire array 11 appears between the groove rollers 12A, 12B, and 12C. The wire array 11 is reciprocated by the drive motor between the three groove rollers 12A, 12B, and 12C. The middle of the two groove rollers 12A and 12B arranged on the upper side is the ingot cutting position a of the wire row 11 for cutting the ingot I. The ingot I is fixed via a carbon bed 19a to the lower surface of a lifting table 19 for raising and lowering the ingot I. Above both sides of the ingot cutting position a, for example, a pair of abrasive fluid supply units (not shown) for continuously supplying the abrasive fluid onto the wire row 11 are provided. These groove rollers 12A, 12B, and 12C have a cylindrical shape, and their outer peripheral surfaces are covered with lining materials 12a, 12b, and 12c of a predetermined thickness made of urethane rubber. Wire grooves 12d are engraved on the outer peripheral surfaces of the lining members 12a, 12b, and 12c, respectively (FIG. 1).
(B)). The wire 11a is a piano wire having a diameter of 150 μm. This wire 11a is led out from the bobbin 20 of the feeding device 13, and is supplied with a guide roller (not shown) on the supply side.
Through these groove rollers 12A, 12B, 1
After being wound around 2C, it is wound around the bobbin 21 of the winding device 15 via a guide roller (not shown) on the outlet side. Each rotation axis of the bobbins 20 and 21 is
6, 17 corresponding output shafts respectively.
When the drive motors 16 and 17 are driven synchronously, the bobbins 20 and 21 supported by the pair of bearings 18 rotate clockwise or counterclockwise in FIG. 1A around their axes. Then, the wire 11a reciprocates. At this time, the number of reciprocating runs of the wire 11a is eight times or more per minute. Next, a method of cutting the ingot I by the wire saw 10 will be described. As shown in FIG. 2, in the wire saw 10, the bobbin 20 of the feeding device 13 is rotated by the drive motor 16 while the abrasive liquid is supplied to the wire row 11 from the abrasive liquid supply unit, and the wire 11 a is supplied to the guide roller on the supply side. To the groove rollers 12A, 12B, and 12C. At the same time, the bobbin 21 of the winding device 15 is rotated by the drive motor 17, and the groove rollers 12A,
The wire 11a is wound up via guide rollers 12B, 12C and the outlet side. At that time, the rotation direction of each bobbin 20, 21 is changed at a short cycle of 8 times or more per minute,
The wire 11a is reciprocated at high speed. This gives 2
The book groove rollers 12A and 12B rotate, and both guide rollers also rotate. At this time, the groove roller 12C is rotated by a rotation motor (not shown) to assist the wire row 11 in reciprocating travel. On the other hand, during the reciprocation of the wire row 11, the ingot I is pressed against the wire row 11 from above. Thereby, the ingot I is cut into many wafers. That is, at the time of reciprocation of the wire array 11, loose abrasive grains in the abrasive fluid are rubbed against the bottom of the cutting groove by the wire 11a of the wire array 11, and the bottom is gradually scraped off by the grinding action. Is cut into wafers. At this time, since the reciprocating movement of the wire array 11 is at a high speed of eight times or more per minute, the grinding effect of the free abrasive grains on the ingot I per unit time is increased. Thereby, the cutting efficiency and the cutting accuracy of the ingot I are improved. As a result, compared to the surface of the silicon wafer W cut by the conventional method shown in FIG. 3A, the surface of the silicon wafer W cut by the method of the present invention shown in FIG.
The occurrence of thickness unevenness and warpage is suppressed. In particular, the undulation of the wafer surface is 5 μm of the undulation h1 generated by the conventional method.
In the present invention, it is as small as 1 μm or less as compared with m or more. The processing damage at the time of wire cutting is also 15 to 1 of the conventional method.
Less than 15 μm, less than about 6 μm. Therefore,
The lap amount in the lapping step (S103) can be reduced as compared with the lap amount according to the conventional method. Next, the silicon wafer thus obtained is chamfered (S102). That is, the outer peripheral surface of the wafer is chamfered into a predetermined shape by the metal chamfering grindstones # 600 to # 1500. Thereby, the outer peripheral portion of the wafer is formed into a predetermined rounded shape (for example, a MOS type chamfered shape). Thereafter, the silicon wafer after the chamfering is subjected to a lapping process (S1).
03). In this lapping step, the silicon wafer is placed between lapping plates kept parallel to each other, and a lapping liquid, which is a mixture of alumina abrasive grains, a dispersant and water, is placed between the lapping plate and the silicon wafer. Pour into Then, by rotating and grinding under pressure, the front and back surfaces of the wafer are mechanically wrapped. The amount of wrap at that time is 40
〜60 μm. Subsequently, the silicon wafer after the lapping process is etched (S104). Alkaline etching solution used for etching has a concentration of 4
A 5 wt% NaOH solution is used. The etching conditions are an etching temperature of 90 ° C. and an etching time of 5 to 15 minutes. Acid etching using mixed acid may be used instead of alkali etching. The etching amount is about 10 to 40 μm on both the front and back surfaces of the wafer. Thereafter, the surface of the etched wafer is subjected to mirror polishing using a batch-type mirror polishing device (S105). The polishing amount is about 10 to 15 μm. Next, finish cleaning is performed on the mirror-polished silicon wafer (S10).
6). Specifically, RCA cleaning is used. According to the present invention, when cutting the ingot, the number of reciprocating movements of the wire per minute is set to eight or more times, so that the grinding effect of the free abrasive grains per unit time on the ingot is increased. . Thereby, the cutting efficiency and the cutting accuracy of the ingot are enhanced, the thickness unevenness of the semiconductor wafer and the warpage of the semiconductor wafer are suppressed, and the lapping amount in the lapping step can be reduced.
For example, the thickness is conventionally 80 to 100 μm, but is 40 to 60 μm in the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (a) is an enlarged schematic view showing a main part of a wire saw according to a method for manufacturing a semiconductor wafer according to one embodiment of the present invention. (B) is a partial enlarged view of the groove roller incorporated in the wire saw according to one embodiment of the present invention. FIG. 2 is a flow sheet showing a method for manufacturing a semiconductor wafer according to one embodiment of the present invention. FIG. 3A is a partially enlarged cross-sectional view of a surface of a wafer obtained by a conventional method of manufacturing a semiconductor wafer. (B) is a partially enlarged cross-sectional view of the surface of the wafer obtained by the method for manufacturing a semiconductor wafer of the present invention. FIG. 4 is a graph showing the relationship between the number of reciprocating runs per minute of a wire according to the present invention and the amount of undulation. [Description of Signs] 10 wire saw, 11a wire, 12A, 12B, 12C groove roller, I ingot.

Claims (1)

Claims: 1. An ingot is pressed relatively to a wire while reciprocating a wire bridged between a plurality of groove rollers and supplying an abrasive liquid containing free abrasive grains. A method of manufacturing a semiconductor wafer, comprising: an ingot cutting step of cutting the ingot by a grinding action of the loose abrasive grains; and a lapping step of wrapping both front and back surfaces of the semiconductor wafer obtained by the ingot cutting step. A method of manufacturing a semiconductor wafer in which the wire is reciprocated at least eight times / minute during cutting.