JPH0938958A - Wafer dividing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the extension of a crack from the adjacent initial cracks of a wafer narrow in dividing interval. SOLUTION: A plurality of initial cracks 12, 13-1 are formed to one side 11a of an almost square wafer 11 composed of a fragile material and the wafer 11 is irradiated with laser beam to be heated in the vicinity of the initial cracks 12, 13-1 and the initial cracks 12, 13-1 are advanced by heat stress to divide the wafer 11. In this method, a plurality of the initial cracks 12, 13-l are made different in length between the adjacent initial cracks. The vicinity of the long initial crack 13 among the adjacent initial cracks 12, 13-1 is prefentially heated by the irradiation with laser beam to advance a crack from the initial cracks 12, 13-1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaving a substantially rectangular wafer made of a brittle material, and more particularly to a method for cleaving a wafer substantially in parallel.

[0002]

2. Description of the Related Art A laser scribing method used for scribing a wafer is a method in which a CO2 laser or a YAG laser in a pulse mode is focused on a minute spot and scanned, and a minute hole is continuously formed in a perforated shape. Contamination is likely to occur due to reattachment of the scattered molten particles.

[0003] Therefore, a cutting method utilizing heating by laser irradiation which does not have these problems has been developed. An example of a conventional splitting method for splitting semiconductor wafers in close proximity to each other using this splitting method will be described with reference to FIG.
In the figure, 1 is a rectangular semiconductor wafer made of a brittle material, and 2-1 to 2-15 are a plurality of semiconductor wafers 1 of a plurality of fixed lengths which are provided at a narrow fixed interval at a diamond point from an upper end 1a to a lower side 1b. In the first crack, 2-7 for the 7th first crack from the left end 1c, 2-8 for the 8th first crack,
The ninth first crack is denoted by 2-9. Reference numeral 3 denotes a laser irradiation point on the extension of the first crack and which is heated by laser irradiation at a certain distance, 3-8 denotes a laser irradiation point at the tip of the eighth first crack 2-8, and 4 denotes an eighth laser irradiation point. 3 shows a planned cutting line starting from the first crack 2-8.

[0004] This cutting method will be described below. An upper side 1a and a lower side 1b of a substantially rectangular semiconductor wafer 1 made of a brittle material
A plurality of initial cracks 2-1 to 2-15 whose intervals are narrow in the direction and which are constant are formed at diamond points.
Subsequently, for example, in order to cleave along the planned cleavage line 4 of the eighth first crack 2-8 from the left end 1c, on the extension of the eighth first crack 2-8 and at a constant distance from the tip of the first crack 2-8. When the laser irradiation point 3 is heated by irradiating the laser at a distance, the first laser irradiation point 3 starts from the eighth first crack 2-8.
The first crack 2-8 progresses on the scheduled cutting line 4 until this point. Repeat this operation to cut.

[0005]

However, if the distance between the first cracks is small, for example, the distance between the eighth first crack 2-8 and the first laser irradiation point 3 is the next seventh crack 2 -7
Alternatively, the difference from the distance from the ninth first crack 2-9 to the laser irradiation point 3 is small, and sometimes the first crack 2
In some cases, the laser irradiation point 3 was reached from the first crack 2-7 or the ninth crack 2-9.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been proposed to solve the above-mentioned problems, and comprises forming a plurality of initial cracks on one side of a substantially rectangular wafer made of a brittle material, and starting from the initial crack as a starting point. A method in which the vicinity of the first crack is heated by laser irradiation, the first crack is advanced by thermal stress, and the wafer is cleaved.The plurality of first cracks form adjacent first cracks having different lengths, and the adjacent first cracks are formed by laser irradiation. Provided is a wafer cutting method in which a crack is preferentially advanced from a longer first crack among matching first cracks.

Another object of the present invention is to provide a wafer cutting method in which the wafer cutting method is repeated to cut the wafer into strips or to irradiate a laser with a position within 5 mm from the first crack.

Further, the present invention provides a wafer cutting method in which the wafer is a compound semiconductor wafer.

[0009]

[Advantage] The lengths of the adjacent first cracks of the adjacent substantially parallel splitting lines are made different, and the adjacent first cracks are preferentially on the extension of the tip of the first crack that is longer and at a certain distance from the splitting line. The laser irradiation point is heated by irradiating the laser irradiation point with a laser, and the cutting is advanced to the laser irradiation point by thermal stress, so that the cleavage can be prevented from progressing from the next initial crack to the laser irradiation point.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. In the figure, 11 is a square semiconductor wafer made of a brittle material, and 12 is the upper side 11a of the semiconductor wafer 11.
A plurality of short initial cracks of approximately parallel and narrow in width, and of a constant length at a constant interval, 13-1 to 13-7 are provided between all of the short initial cracks 12 provided at the diamond points toward the lower side 11b. A short initial crack 1 formed at the approximate midpoint by a diamond point from the upper side 11a toward the lower side 11b
A first long crack longer than 2, 14 is a first laser irradiation point to be heated by irradiating a laser at a certain distance on the extension of the fourth long first crack 13-4 from the left side 11c of the semiconductor wafer 11, and 15 is 4 This is the planned cutting line of the first long first crack 13-4.

This cutting method will be described below. A plurality of short initial cracks 12 that are narrow at regular intervals are formed at the upper side 11a of the substantially rectangular semiconductor wafer 11 made of a brittle material at diamond points toward the lower side 11b. Continuing,
From the upper side 11a to the lower side 11b at approximately the midpoint between the short initial cracks 12.
Along the direction, long initial cracks 13-1 to 13-7 longer than the short initial cracks 12 are formed at the diamond points. Subsequently, for example, when the first laser irradiation point 14 that is on the extension of the fourth long initial crack 13-4 from the left end 11c and is separated by a certain distance is irradiated with a laser and heated, the fourth long initial crack 13-4 is heated. Proceeds to the laser irradiation point 14. This operation is repeated to cut at the scheduled cutting line 15.

In this case, the distance from the first laser irradiation point 14, which is an extension of the long primary crack 13-4 and separated by a certain distance, to the long primary crack 13-4 is equal to the distance to the adjacent short primary crack 12. The difference becomes large. Therefore, the short initial crack 12
From the laser irradiation point 14 does not occur.

In the case of the semiconductor wafer 11, a certain distance from an extension of the first cracks 12, 13-1 to 13-7 is generally 5 mm or less, and an interval between the first cracks 12, 13-1 to 13-7 is also 5 mm. It is as follows.

In this description, the lengths of the initial cracks are two types, but are not limited to two types, and the initial cracks 12 and 13 having three or more types of lengths may be sequentially formed. If the lengths of the adjacent first cracks 12 and 13-1 to 13-7 are different, it is not necessary to limit the type of length.

The first cracks 12, 13-1 to 13-7 may be formed at positions other than the diamond points. Also, the start of the cleaving is not limited to the center.

Also, the semiconductor wafer has been described as an example,
As long as the wafer is made of a brittle material such as ceramic or glass, it can be applied in either amorphous or single crystal form. When a single crystal is cleaved along a crystal plane, a planned cleavage line along the crystal plane appears. Especially when it is applied to a compound semiconductor wafer, the effect is great.

Further, in the present method, since the wafer is cleaved using brittle fracture due to thermal stress, the wafer is not heated to a high temperature unlike the laser scribing method. do not do.

[0018]

According to the present invention, the positions of the tips of adjacent cracks adjacent to each other are made different from each other, and the longer adjacent cracks are preferentially advanced. At this time, the distance between the adjacent shorter initial crack and the laser irradiation point becomes longer, the adjacent initial crack advances, and the cutting does not proceed to the laser irradiation point.

[Brief description of drawings]

FIG. 1 is a cutaway plan view of a rectangular semiconductor wafer in which an initial crack and an intended cut line are inserted according to the method of the present invention

FIG. 2 is a cutaway plan view of a conventional rectangular semiconductor wafer.

[Explanation of symbols]

 Reference Signs List 11 wafer (semiconductor wafer) 11a one side (upper side) 12 short initial crack 13-1 to 13-7 long first crack (long initial crack) 14 laser irradiation point 15 scheduled cutting line

Claims (4)

[Claims] 1. A method of forming a plurality of initial cracks on one side of a substantially rectangular wafer made of a brittle material, irradiating a laser with the initial cracks as a starting point, and advancing the initial cracks by thermal stress to cut the wafer, The method according to claim 1, wherein the plurality of first cracks form adjacent first cracks having different lengths, and the laser irradiation preferentially progresses a crack from a longer one among the adjacent first cracks. 2. The wafer cutting method according to claim 1, wherein the wafer cutting method is repeated to cut the wafer into strips. 3. The wafer cutting method according to claim 1, wherein the position for irradiating the laser is a position on a division line within 5 mm from the first crack. 4. The wafer cutting method according to claim 1, wherein said wafer is a compound semiconductor wafer.