JPH0761647B2 - Slicing method of semiconductor crystal ingot - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor crystal ingot slicing method in which a semiconductor crystal ingot is sliced with a rotating blade to obtain a wafer, and particularly, the cutting direction of the rotating blade is the crystal plane. The present invention relates to a device which eliminates the damage of the wafer due to the warp of the wafer which occurs at the time of slicing, in association with the direction of.

[Prior Art] Conventionally, in order to obtain a wafer from an ingot of a semiconductor crystal, for example, a compound semiconductor single crystal, when the ingot is sliced in a radial direction by a rotating inner peripheral blade slicer or the like, the orientation of the peripheral side surface of the ingot is arbitrary, Slices were made ignoring the radial crystal direction with respect to the cutting direction of.

[Problems to be Solved by the Invention] However, when slicing while ignoring the crystal direction of the ingot radial direction with respect to the cutting direction of the blade, there is a problem that the wafer being sliced is attracted to the blade and scratches occur. It was

Since the scratches due to the suction penetrate deeply into the wafer, they become defective such as cracks in the subsequent process, and the processing yield is remarkably reduced.

The cause of this damage is that the coolant that rotates with the blade acts as a suction force when flowing between the wafer and the blade to attract the wafer to the blade, but it does not always occur and there is a difference depending on the ingot. As such, the mechanism of its occurrence is unknown, and effective measures cannot be taken.

In addition, a plurality of cutting positions where slicing proceeds easily by a preliminary test and the rotation direction of the blade at each cutting position are set, and the semiconductor crystal ingot is sliced while switching the cutting position and the rotation direction of the blade. A method has been proposed (JP-A-56-129114). With this method, the wafer is unlikely to be bent or warped, and the risk of the wafer being attracted to the blade may be small, but when the cutting position and the rotating direction of the blade are changed, scratches occur on the sliced surface. However, the risk of breaking the wafer is very high.
On the other hand, the workability is poor because a lot of time is required for the preliminary test for setting the cutting position of the ingot, and the apparatus becomes expensive, so that there are many problems for industrial commercialization.

[Object of the Invention] An object of the present invention is to solve the above-mentioned problems by associating the cutting direction of the rotary blade with the direction of the warp of the sliced wafer, and to obtain a high processing yield in which the wafer is not scratched. A method of slicing a semiconductor crystal ingot made of a GaAs single crystal or a silicon single crystal.

[Summary of the Invention] When a semiconductor single crystal made of GaAs or silicon is sliced, warpage occurs due to strain of the crystal itself, and the direction of this warpage is constant regardless of the direction of the slice and the direction of the crystal plane. The present inventor has found that the attraction of the wafer to the blade and the blade are greatly affected by the warp of the wafer itself.

That is, in the cross section 6 perpendicular to the cutting direction of the blade 3 shown in FIG. 3 corresponding to the embodiment, as shown in FIG. 2, the warp of the wafer 4 is formed on both sides of the cut end or both sides along the cross section 6 of the ingot 1. When the wafer approaches the side and separates at the center, scratches due to the suction of the wafer occur, and when the warp of the wafer 4 has the opposite shape, that is, when the shape is as shown in FIG. We found that it does not occur.

Based on this knowledge, according to the present invention, both sides of the wafer 4 to be sliced by the rotary blade 3 are ingot slice surfaces 5.
The direction of the crystal plane of the ingot 1 which is separated from the ingot 1 is previously investigated, and the ingot 1 is sliced by matching this direction with the cutting direction v of the rotary blade 3.

[Embodiment] The embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

As shown in FIG. 3, a columnar semiconductor crystal (here, a compound semiconductor single crystal, GaAs) ingot 1 grown in the [001] direction has an ingot fixing jig 2 with its axis oriented horizontally. The wafer 4 is sliced in the radial direction by the rotating blade 3 which is set in the vertical direction v, which is the cutting direction, and which rotates in the direction r of the arrow while descending.

In the illustrated example, the rotary blade 3 is an inner peripheral blade, but may be an outer peripheral blade. Further, the slice target can be a silicon single crystal as well as a GaAs single crystal.

When GaAs is sliced, warpage occurs in the wafer 4 due to crystal distortion, and this warpage has a shape as shown in FIG. The surface that appears in the figure is the slice surface,
In the [011] direction, the ingot slice surface 5 is concave as shown in FIG. 5 (a), and in the [01] direction orthogonal to this, it is convex as shown in FIG. 5 (b).

Therefore, at the time of slicing, in the cross section 6 perpendicular to the cutting direction v of the blade 3, the direction [011] of the (011) plane among the crystal planes forming the ingot peripheral side surface 7 is made to coincide with the cutting direction of the blade 3, When the ingot 1 is set on the ingot fixing jig 2 so that the direction [01] of the (01) plane is parallel to the cross section 6, the warp of the wafer 4 during slicing is not shown in FIG. As shown in FIG. 3, both sides of the wafer 4 are separated from the ingot slice surface 5. In this case, the upper and lower sides of the wafer 4 come close to the ingot slice surface. However, unlike the left and right warpage that occurs after the middle of the slice, the upper and lower warpage becomes maximum after the completion of slicing, so that the wafer 3 is attracted to the blade 3. Not a factor. As a result, the wafer 4 is sliced without adhering to the blade 3 and the wafer 4 is not scratched, and the processing yield of particularly expensive GaAs single crystal can be significantly improved.

In the case of the present embodiment, the crystal plane direction described above is KO
It can be easily identified by the shape of the etch pits that appear when etching with H. Further, in the pull-up crystal, it can also be identified by the shape of the growth stripe. Therefore, it is possible to easily set the orientation of the ingot fixing jig 2 by determining the orientation of the crystal surface of the ingot and marking the orientation in advance.

[Effects of the Invention] In short, according to the present invention, an ingot in which the cross section of the wafer in a plane passing through the center of the sliced wafer and perpendicular to the cutting direction of the rotating blade is convex toward the ingot slice surface By slicing by deciding the crystal axis direction of, the wafer can be sliced without causing any scratches, and therefore expensive Ga
The processing yield of a semiconductor crystal ingot made of As single crystal or silicon single crystal can be significantly improved.

[Brief description of drawings]

1 is a plan sectional view showing an ingot in a slice according to the method of the present invention, FIG. 2 is a plan sectional view showing an ingot in a slice when a wafer is scratched, and FIG. 3 is an ingot being cut. FIG. 4 is a perspective view showing a warp of a wafer obtained by slicing from a GaAs single crystal ingot, FIG. 5 is a sectional view of FIG. 4, and (a) is [01]
1] direction, (b) is a cross section in the [01] direction. In the figure, 1 is an ingot, 3 is a rotating blade, 4 is a wafer, 5 is an ingot slice surface, 6 is a plane perpendicular to the cutting direction of the rotating blade, and v is a cutting direction of the rotating blade.

Claims (1)

[Claims] 1. A semiconductor crystal ingot made of a GaAs single crystal or a silicon single crystal in which the axial direction of the ingot coincides with the [100] direction is sliced in a predetermined cutting direction by a rotating blade and is perpendicular to the [100] direction. In order to obtain a wafer having a uniform surface, the predetermined cutting direction of the rotating blade is made to coincide with the [011] direction perpendicular to the [100] direction, and the cutting direction of the rotating blade passes through the center of the sliced wafer. And slicing the ingot while separating the slicing start end of the wafer from the ingot slice surface so that the cross section of the wafer in a plane parallel to the [100] direction is curved convexly toward the ingot slice surface. A method for slicing a semiconductor crystal ingot, which comprises: