JPH1064854A - Method for cutting wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cut a gallium nitride group compound semiconductor wafer having a sapphire substrate to a chip shape with a conventionally used dicing saw in a simple process. SOLUTION: Relating to a method for cutting a gallium nitride group compound semiconductor wafer 2, whose substrate is sapphire and its thickness is 50-450μm, to a chip shape with a dicing saw, a V shape rotary blade of tool angle 30 deg.-75 deg. is used as a blade 2 of the dicing saw, and after a lattice groove 3 is formed, by cutting, only on one surface of the wafer 2 with the dicing saw, the wafer 2 is press-split.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cutting a gallium nitride-based compound semiconductor wafer whose substrate is made of sapphire into chips using a dicing saw.

[0002]

[Technical Background] Light emitting diodes for blue and ultraviolet (LE
D), gallium nitride based compound semiconductors (GaN, AlGaN, etc.) are currently the most promising semiconductor materials used for semiconductor light emitting devices such as laser diodes (LD).
III-V based on gallium nitride such as InGaN
Group semiconductors). For example, a blue light emitting diode having an output of several candela [cd] has been put to practical use and commercialized. In this type of semiconductor device, sapphire is used as a substrate.

Generally, a dicing saw or a scriber is used for cutting a semiconductor wafer in a semiconductor device manufacturing process. As a cutting technique using a dicing saw, a cutting method using a flat blade as a blade is conventionally known. in this way,
First, as shown in FIG. 4A, using a blade (not shown) having a flat blade edge, a groove having a rectangular cross section (hereinafter, “rectangular groove”)
(See FIG. 4A) is cut in a grid on one surface of the wafer 32 (in FIG. 4A, the surface on which the semiconductor layer 36 is formed). Thereafter, the stress (wafer 3)
2 are indicated by P1 and P2) to break the wafer 32 into chips.

However, when this method is applied to a wafer 32 whose substrate 34 is made of sapphire, there are the following disadvantages. In other words, sapphire crystal has weak cleavage,
Moreover, the hardness is high. Therefore, when the rectangular groove 33 is cut on the wafer 32 using a dicing saw, chips are scattered during the cutting of the rectangular groove 33, and the cutting direction F is not specified as shown in FIG. , Cracks (cracks off the cut line), and FIG. 4 (B) (i),
As shown in (ii), the shape of the cut chip 36 becomes uneven, and the yield of the cut is extremely low, which is not suitable for practical use.

For this reason, conventionally, a method has been proposed in which a scriber is used for cutting a gallium nitride-based compound semiconductor wafer into chips as shown in Japanese Patent Application Laid-Open No. 6-283758. In this method, FIG.
As shown in (A), first, a sapphire substrate 44 is polished thinly, and a predetermined pattern is formed on a back surface side (a side on which the semiconductor layer 45 is not formed) of a wafer 42 by a scriber (a needle whose tip is made of diamond) 41. Cuts a V-shaped cutting groove (hereinafter, referred to as a “V-shaped groove”) 43. Then, as shown in FIG. 5B, a warp stress is applied to the wafer 42 to divide the wafer into chips. However, even with this method, there are disadvantages, such as cracks, generated when the wafer 42 is divided into chips.

Further, according to this method, when the wafer 42 is thin, the cutting direction is specified because the cross section of the cut groove is V-shaped, so that cracks can be formed by appropriately adjusting the pressing force of the needle. It does not occur, and the shape of the obtained chip does not become uneven. However, when the sapphire substrate 44 is thick, cracks occur when the wafer 42 is divided into chips.

To solve this inconvenience, Japanese Patent Laid-Open Publication No.
As disclosed in Japanese Patent Publication No. 315646, a cutting method in which a scriber and a dicing saw are combined has been proposed. In this method, as shown in FIG. 6, first, a dicing saw (not shown) is used to reach the sapphire substrate from the surface side (the side on which the semiconductor layer 55 is formed) of the wafer 52 (preferably 5 to 5 sapphire substrates). The groove 53a is cut to a thickness of 10%). Then, a scribe groove 53b is formed on the bottom of the groove 53a by a scriber (not shown).
Is formed, and the wafer 52 is divided into chips. According to this method, the wafer 52 can be divided into chips without impairing the crystallinity of the semiconductor layer 55 formed on the sapphire substrate. However, since a step of cutting the groove 53a by a dicing saw and a step of cutting the scribe groove 53b by a scriber are required, there is a problem that the number of steps is increased.

Further, as disclosed in Japanese Patent Application Laid-Open No. Sho 60-212858, a method is known in which the wafer is fully cut from both sides of the wafer with a dicing saw. In this method, as shown in FIG.
The first groove (rectangular groove or V-shaped groove, at a depth of at least half the thickness of the sapphire substrate 64) is formed on the back side of the wafer 62 (the side on which the semiconductor layer 65 is not formed) by using the following blade. In this figure, a V-shaped groove 63a is cut, and then a second blade (not shown) (not shown) is used to cut the second groove 63a from the front surface side of the wafer to the first groove 63a. (A rectangular groove or a V-shaped groove, V-shaped groove in the figure) 63b is cut. However, this method requires cutting from both sides of the sapphire substrate 64 and fully cuts the wafer 62 (that is, does not cut the wafer), so the cutting time becomes longer. In addition, there is a problem that chips are scattered or cracks occur when the second groove 63b is actually cut.
In particular, by this method, the side of the wafer 62 is several hundred μm.
If an attempt is made to cut into small chips, the scattering and cracking of the chips become remarkable, making them unsuitable for practical use.

[0009]

SUMMARY OF THE INVENTION The present invention provides a method for cutting a gallium nitride-based compound semiconductor wafer having a sapphire substrate into chips by using a conventionally used dicing saw and by a simple process. That is.

[0010]

SUMMARY OF THE INVENTION The present inventor has stated that the technique of forming a groove on one surface of a wafer with a dicing saw and cutting the wafer into chips by pressing is not applicable to a wafer whose substrate is made of sapphire. As a result of abandoning the conventional wisdom and repeating experiments, if the blade angle is within a specific range and the thickness of the sapphire substrate is appropriate, cracks will not occur and chips will also scatter. Instead, the present inventors have found that the wafer can be cut into extremely small chips, and have completed the present invention.

That is, the cutting method of the present invention is a dicing method for cutting a gallium nitride-based compound semiconductor wafer having a substrate of sapphire and a substrate thickness of 50 to 450 μm into chips using a dicing saw. As the blade of the dicing saw, a V-shaped rotating blade having a blade edge angle (angle of the blade edge inclined surface with respect to a plane perpendicular to the blade as a reference (0 °)) of 30 ° to 75 ° is used. Thus, after forming a V-shaped groove in a lattice pattern only on one surface of the wafer, the wafer is cracked. The grooves formed in the lattice shape are formed from two sets of orthogonal straight lines, and one of the straight lines is set to be parallel to the a-axis of the sapphire substrate to cut along a desired cut line. Can be performed more reliably. The V-shape of the cutting edge is various, and may be a shape in which the inclined surface of the cutting edge is formed on both sides of the blade, or a shape formed on one side.

In the wafer cutting method of the present invention, as described above, the blade having a specific range of the included angle is used.
A V-shaped groove having an appropriate depth is formed in a lattice shape on one surface of the wafer. Therefore, for example, when stress is applied to the wafer so that the surface of the wafer becomes a curved surface (usually, the surface on which the V-shaped groove is formed is outside the curved surface), stress concentrates on the bottom of the V-shaped groove, and V The wafer is cut into chips along the groove. In the present invention, the red or yellow L
The use of a highly controllable dicing saw used in the manufacture of ED, etc., can keep equipment costs low, and in terms of work efficiency and yield, it is different from the conventional method using a scriber. Equal or better effects can be obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 (A) and 1 (B) are explanatory views in the case of using a blade having an inclined surface of a cutting edge formed on both sides (FIG. 1 (A) is a front view as viewed from the moving direction of the blade).
(B) shows a plan view). 1A and 1B, the blade 1 is made of a metal having excellent wear resistance. According to the experiment, when the blade tip angle θ of the blade 1 is smaller than 30 °, the width WG of the V-shaped groove 3 becomes too large, and when the wafer 2 is cracked, the shape of the chip 4 becomes uneven. Further, if the angle of the cutting edge is larger than 75 °, the width WG of the V-shaped groove 3 is reduced, but it is not easy to manufacture such a cutting edge. In addition, such a cutting edge is expected to have low physical strength and shorten the blade life. Also, depending on the rotation speed and moving speed of the blade 1, it is expected that cracks are likely to occur in the wafer 2. Therefore, in the present invention, the blade angle θ of the blade 1 is
Is 30 ° to 75 °. 45 ° to 6
When the angle is set to 0 °, the wafer 2 has an extremely high yield.
Can be cut (crushed) into chips.

The cutting depth (that is, the sapphire substrate 21
If the depth (DG) of the V-shaped groove 3) is too shallow, it cannot be cut along a desired cut line. In addition, as the width of the V-shaped groove 3 is increased, the ridges (edges) of the V-shaped groove 3 are more likely to be jagged, which may adversely affect the semiconductor layer formed on the sapphire substrate 21. . For this reason, although the cutting depth DG depends on the thickness T of the sapphire substrate 21, it is preferably 10 to 50% of the thickness.

In FIG. 1, the V-shaped groove is cut from the front surface of the wafer 2 (the surface on which the semiconductor layer 22 is formed), but may be cut from the back surface. When cutting the wafer 2, the sapphire substrate 21
If the thickness T is too thick, cutting is not performed according to the desired cut line at the time of pressing, and even if the thickness T is too thin, unexpected cracks may occur during cutting of the V-shaped groove 3. And the chips 4 may be scattered. Blade 1 having a general thickness WB (about 200 μm)
When the thickness T of the sapphire substrate 2 is 100 to 450 μm as described above, a crack can be formed along a desired cut line L, and unexpected cracks occur during the cutting of the V-shaped groove 3. And no chips 4 are scattered.

The pressing force of the blade 1 against the wafer 2 depends on the shape of the blade 1 (thickness WB, diameter, cutting edge degree θ).
Etc.) and cutting conditions (rotational speed, moving speed, etc. of the blade)
Is determined as appropriate.

In the present invention, the cutting direction F is limited to the V-shaped tip direction as shown in FIG. 2 (a front view as viewed from the moving direction of the blade) without performing full cutting of the wafer 2. Therefore, the cut line L
(The stress applied to the wafer 2 is indicated by P1 and P2 in FIG. 2).
Therefore, the chips 4 are not scattered during the formation of the V-shaped groove 3, so that the side of the chip
Chips 4 of a very small size (in the case of a square shape) can be obtained with a high yield. Note that the size of the chip 4 (for example, the length W of one side in the case of a square) is preferably larger than the thickness T of the sapphire substrate 2.

Instead of the blade shown in FIGS. 1A and 1B, an inclined surface of the cutting edge is formed on one side as shown in FIG. 3 (a front view as viewed from the moving direction of the blade). A blade 1 'can also be used. When this blade 1 'is used, the cutting direction F' is limited to the side of the blade 1 'where the inclined surface is not formed, as shown in FIG.

[0020]

【Example】

<Example 1> [Sapphire substrate] Plane direction; c-axis direction, thickness (T): 300 μm [Semiconductor layer formed on sapphire substrate] IGaN [Dicing saw] Model: DISCO DDAC0630, DAD32
0, blade diameter (R); 52 mm, blade thickness (W
B): 200 μm, shape of blade edge; inclined surface of blade edge formed on both sides, blade angle (θ): 60 ° [Dicing saw operating conditions] Blade rotation speed: 30,000 rpm, blade moving speed: 3.0 mm / sec [V Groove) pattern; consisting of two sets of orthogonal straight lines, one of which is parallel to the a-axis of the sapphire substrate.
50 μm square lattice, groove depth (DG); 110 μm

Under the above conditions, a V-shaped groove was formed in the wafer. In cutting the V-shaped groove, the wafer was fixed to a predetermined film with wax. After that, when the wafer is cut together with the above film by bending the V-shaped groove to the outside, LED chips of equal quality (ie, substantially uniform in shape) can be obtained with a yield of about 70%. Was completed.

Comparative Example 1 The surface direction and thickness of the sapphire substrate, and the semiconductor layer formed on the sapphire substrate were the same as those in the first embodiment. The dicing saw used had a flat blade edge. The model, blade diameter, and the like are the same as in the first embodiment. However, when cutting the wafer, the cutting process was repeated many times while changing the pitch at a depth of 10 μm. The pattern of the grooves (rectangular grooves) was the same as in Example 1.

Under these conditions, when a rectangular groove was formed in the wafer and the wafer was cut, cracks frequently occurred in the wafer, and the obtained LED chips were uneven in shape, the cut surface was not vertical, and the yield was high. It was 10% or less.

[0024]

As described above in detail, according to the present invention, a gallium nitride-based compound semiconductor wafer having a sapphire substrate can be formed in a very small size by using a conventionally used dicing saw and by a simple process. Chips can be cut at a high yield.

[Brief description of the drawings]

FIG. 1 is a diagram showing a preferred embodiment of the present invention;
It is explanatory drawing at the time of using the blade in which the inclined surface of the blade edge was formed on both sides as a blade, (A) is a front explanatory drawing seen from the moving direction of the blade, (B) is a plane explanatory drawing.

FIG. 2 is an explanatory diagram when performing a split in FIG. 1;

FIG. 3 is an explanatory view when performing a split using a blade having an inclined surface of a cutting edge formed on one side as a blade.

FIG. 4A is a view for explaining a conventional method of forming a rectangular groove in a wafer by using a dicing saw and cutting the wafer, and FIG. 4B is a view showing a shape of a cut chip; .

FIG. 5A is a view for explaining a conventional method of forming a rectangular groove in a wafer by using a scriber to cut the wafer, and FIG. 5B is a view showing a state of cutting the wafer.

FIG. 6 is an explanatory view of a conventional method for forming a rectangular groove and a V-shaped groove on a wafer by using a dicing saw and a scriber to cut the wafer.

FIG. 7 is an explanatory diagram of a conventional method for performing a full cut of a wafer using a dicing saw.

[Explanation of symbols]

 Reference Signs List 1 blade 2 wafer 21 sapphire substrate 22 semiconductor layer 3 V-shaped groove 4 chip F cutting direction DG cutting depth (depth of V-shaped groove) WG V-shaped groove width L cut line T sapphire substrate thickness WB blade thickness The angle of the blade W The length of one side of the tip

Claims (2)

[Claims] 1. A method for cutting a gallium nitride-based compound semiconductor wafer having a substrate thickness of 50 to 450 μm into chips using a dicing saw, wherein the substrate is made of sapphire. 30 ° angle
A method of cutting a wafer, comprising: using a rotary blade having a V-shape of about 75 °, forming grooves in a lattice shape only on one surface of the wafer with the dicing saw, and then breaking the wafer. 2. The groove formed in a lattice shape comprises two sets of orthogonal straight lines, one of which is parallel to the a-axis of the sapphire substrate. 2. The method for cutting a wafer according to 1.