JPH05166923A - Method for cutting gallium nitride compound semiconductor wafer - Google Patents

Abstract

PURPOSE:To prevent generation of cracks and chippings in the surface of cutting, and to cut a gallium nitride compound semiconductor wafer into chips of desired shape and size at a high yield rate by grinding a sapphire substrate to optimize the thickness of the substrate. CONSTITUTION:A gallium nitride compound semiconductor wafer, having a structure made by forming an N-type GaxAl1-xN (0<=X<=1) layer 2 on a sapphire substrate 1 and then forming a P-type or i-type GaxAl1-xN (0<=X<=1) layer 3 thereon, is cut into chips. At this time, the sapphire substrate 1 is ground by a grinder to 100 to 250mum in thickness. Further, the substrate side of the wafer or the side of the gallium nitride compound semiconductor, or both sides of them, are scribed and cut. The scribing depth should by 10% or more of the thickness of the substrate 1, and the wafer is scribed in such a manner that the length of the shortest sides of the sapphire substrate of the cut chips is made longer than the thickness of the substrate 1. As a result, the cutting operation can be conducted at a high yield rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a gallium nitride compound semiconductor chip used in a light emitting device such as a blue light emitting diode or a blue laser diode, and more particularly to a gallium nitride compound compound laminated on a sapphire substrate. The present invention relates to a cutting method for cutting a semiconductor wafer into chips.

[0002]

2. Description of the Related Art Generally, a light emitting device such as a light emitting diode or a laser diode is provided with a semiconductor chip as a light emitting source on a stem. Ga is used in the case of red, orange, yellow, and green diodes as the material for the semiconductor chip.
As, GaAlAs, GaP, etc. are known, and ZnSe, GaN, SiC are known for blue diodes.

Conventionally, a dicer or a scriber is generally used as a method for cutting a wafer in which those materials are laminated into chips. The dicer is generally called a dicing saw, and the wafer is directly cut by the rotational movement of the disk with the cutting edge as a diamond.
Alternatively, it is a device that cuts a groove having a width wider than the width of the cutting edge and then cuts by an external force. On the other hand, the scriber is a device for drawing an extremely thin scribe line (scoring line) on the wafer by a reciprocating linear motion of a needle having a diamond tip, for example, in a grid pattern, and then cutting it by an external force.

Since the cleavage of the crystal having a zinc-zinc structure such as GaP and GaAs is in the "110" direction, a scriber is used to take advantage of this property to easily separate chips into chips. it can. However, since the gallium nitride-based compound semiconductor is laminated on sapphire, and the sapphire does not have the cleavage property due to the crystal property of hexagonal system, it is impossible to cut it with a scriber. In addition, a diode using a gallium nitride-based compound semiconductor as a blue light emitting element has not yet been put into practical use, and in reality, a means for industrially separating a wafer into chips has not been developed.

[0005]

A gallium nitride-based compound semiconductor wafer uses a very hard material called sapphire for its substrate, and the gallium nitride-based compound semiconductor crystal laminated on it is the same as sapphire. Since it is a very hard substance, when cut with a dicer, cracks and chipping are likely to occur on the cut surface,
I couldn't cut it cleanly.

Therefore, according to the present invention, when a gallium nitride compound semiconductor wafer using sapphire as a substrate is cut into chips, cracks and chippings on the cut surface are prevented from occurring, and the desired shape and size are obtained with good yield. The purpose is to provide a method.

[0007]

Means for Solving the Problems The present inventors have found that even if a gallium nitride compound semiconductor wafer, which has a hexagonal crystal form and no cleavage, can be cut into chips only by a dicer, It was found that the cutting can be easily performed with a scriber by optimizing the above, and the present invention has been accomplished.

The cutting method of the present invention has the general formula Ga _x Al _{1 -x.}
In a method of cutting a gallium nitride compound semiconductor wafer in which a gallium nitride compound semiconductor represented by N (0 ≦ X ≦ 1) is laminated on a sapphire substrate into chips, the thickness of the sapphire substrate is 100 to 250 μm. Further, the substrate side of the wafer, the gallium nitride compound semiconductor layer side, or both sides thereof are scribed and cut. In addition, scribing (Scribe) is to engrave a line with a scoring needle.
That is, it means to put a ruled line.

The gallium nitride compound semiconductor wafer is
Basically, n-type Ga _X Al _1-X N on a sapphire substrate
(0 ≦ X ≦ 1) layer and p-type or i-type Ga _X Al on it
_It has a structure in which _1-X N (0 ≦ X ≦ 1) layers are stacked.
The total thickness of the substrate is usually 300 to 500 μm, and the total thickness of the gallium nitride layers is only several μm to several tens of μm at most, and most of them are occupied by the thickness of the substrate. According to the cutting method of the present invention, the thickness of this substrate is 100 μm.
By adjusting the thickness to ˜250 μm, a scriber can be used for cutting.

The substrate having a thickness of 100 μm to 250 μm can be realized by polishing with a polishing machine. The substrate may be thinned by polishing before or after the growth of the gallium nitride layer. Substrate thickness is 10
If the thickness is less than 0 μm, the whole wafer is easily broken and it becomes difficult to scribe. On the other hand, if the thickness is more than 250 μm, the scribe must be deepened, and it tends to be difficult to form fine chips. Further, by polishing the substrate, the polished surface becomes a mirror surface, so that when scribing from both sides, it is easy to match the scribe line from the gallium nitride compound semiconductor layer side with the scribe line from the substrate side. it can.

The depth of the scribe line is 1 of the thickness of the substrate.
It is preferably 0% or more. To draw a scribe line as described above, an automatic device generally called a scriber is used, but in the case of a material such as GaAs,
Since the material itself has cleavability, for example, 500μ
Even in the case of obtaining a chip having a size of m square or less, the depth of the scribe line (that is, the scribe depth) usually needs to be 1% or less at most, and at most a few% of the total thickness of the wafer. You can cut it well. However, since sapphire does not have cleavability, in chips of 500 μm square or less, it is preferable to make the scribe depth 10% or more deeper than the thickness of the substrate after polishing the substrate to reduce its thickness. it can.

Further, it is preferable that the shortest side of the sapphire substrate of the desired chip to be cut is made longer than the thickness of the substrate. FIG. 1 is a perspective view showing a cross-sectional structure of a gallium nitride-based compound semiconductor chip obtained by an embodiment of the cutting method of the present invention, where 1 is a sapphire substrate and 2 is n.
The type GaN layer 3 is a p-type or i-type GaN layer. As shown in this figure, for example, a desired chip is short side a
In the case of a rectangular parallelepiped having a substrate of 1, long side a2 and thickness d1, the shortest side a1 of the substrate of the chip is adjusted to be longer than the thickness d1 of the substrate. If a1 is shorter than d1, when a scribe line is drawn and then cut by an external force, the cross section and the GaN layer are likely to be cracked or chipped. Preferably, the shortest side has a length of 30% or more, more preferably 50% or more, with respect to d1, so that the cutting can be reliably performed and the yield is improved.

[0013]

In the cutting method of the present invention, as described above, the sapphire substrate is polished to a thickness of 100 to 250 μm, whereby the cutting can be performed by scribing. Further polishing makes the substrate have a mirror-like surface, so that the scribe line inserted from the gallium nitride layer can be observed and can be aligned with the scribe line inserted from the substrate side. Preferably, by setting the depth of the scribe line to be 10% or more of the thickness of the substrate, even a chip size of 500 μm or less can be cut by the scribe.

[0014]

EXAMPLES The cutting method of the present invention will be described in detail below with reference to examples. [Example 1] Ga for a light-emitting diode, in which an n-type GaN layer and p-type GaN were grown to a total thickness of 5 μm on a sapphire substrate having a thickness of 350 μm and a size of 2 inches φ.
The substrate of N wafer is polished by a polisher to 120 μm.
And Further, an adhesive tape is attached to the substrate side, stuck on the table of the scriber, and fixed with a vacuum chuck. The table moves on the x-axis (left and right) and y-axis (front and back), 1
It has a structure that can rotate horizontally by 80 degrees. Next, the GaN layer was scribed with a diamond blade of a scriber to attach Ga to the table.
A scribe line having a pitch of 350 μm is drawn on the GaN layer of the N wafer. The bar provided with a diamond blade has a structure that can move in the z-axis (up and down) and y-axis (back and forth) directions. The weight of the diamond blade is 100g,
In order to increase the depth of the scribe line, the same line is scribed 5 times to obtain a depth of 20 μm. After pulling the scribe line, rotate the table 90 degrees, and similarly, at a pitch of 350 μm, draw a line that is orthogonal to the scribe line that was drawn at a depth of 20 μm. A GaN wafer with a scribe line drawn in a grid pattern is peeled off from the table, pressure is applied from the sapphire substrate side by a roller, and the wafer is crushed by 350 μ
An m-square GaN chip was obtained. 3 obtained in this way
The yield was 95% or more when the defect due to the outer shape was removed from the 50 μm square GaN chip.

[Second Embodiment] Same as the first embodiment. As in Example 1, scribe lines with a pitch of 150 μm are inserted from the GaN layer. However, the number of times of scribing is 2 and the depth is 8 μm. The table is rotated in the same manner as in Example 1, and a direct scribing line is drawn with two times of scribing. After the scribe line has been drawn on the GaN layer as described above, the adhesive tape attached to the sapphire substrate is removed by a solvent, and then the Ga having the scribe line is again formed.
Adhesive tape is attached to the N layer, and similarly placed on the table 11 of the scriber. At this time, the blade edges are aligned so that the trajectory of the blades of the scriber coincides with the scribe line of the GaN layer that was previously drawn. After that, in the same manner as the steps from to, a grid-shaped scribe line is drawn on the substrate side. A GaN wafer of 150 μm was formed in the same manner as in Example 1.
When cut into square chips, the yield was also 95% or higher.

Example 3 A sapphire substrate having a thickness of 350 μm was polished in advance to a thickness of 200 μm, and then Ga was formed.
G for light-emitting diode with N layer grown to a thickness of 5 μm
It is fixed on the table 11 in the same manner as in Example 1 except that an aN wafer is used. When a 350 μm square chip was prepared in the same manner as in Example 1, the yield was 95% or more.

[Embodiment 4] The sapphire substrate of Embodiment 1 is set on a table of a scriber in the same manner except that the sapphire substrate is polished to 250 μm. ~ Same as Example 1 except that the GaN layer is scribed twice at 350 μm pitch and 8 μm deep scribe lines are formed in a grid pattern. When chips having a size of 350 μm square were prepared in the same manner as in Example 1, the yield was 90%.

Comparative Example 1 The same 350 as in Example 1
A GaN wafer having a diameter of μm is polished to have a thickness of 300 μm, and the GaN wafer is set on a table of a scriber in the same manner as in the embodiment. -Similarly to Example 1, the GaN layer is scribed 5 times at a pitch of 350 μm to form a grid-like scribe line. Similarly, when making a chip of 350 μm square,
The crack was irregularly cracked from a place different from the scribe line, and some cracked and non-cracked from the scribe line, and the yield was only 40%.

[Comparative Example 2] The same as Example 1, 350 μm
Blade rotation speed of 3 GaN wafer using dicer
When a chip of 350 μm square was cut under the conditions of 0000 rpm and a cutting speed of 0.3 mm / sec, countless cracks were generated on the cutting line and the yield was 20% or less.

[0020]

As described above, according to the cutting method of the present invention, a gallium nitride-based compound semiconductor wafer, which has hitherto been cut only by a dicer because it does not have cleavability, can be cut with a good yield. Also, compared to cutting with a dicer, the dicer scrapes and cuts the wafer by rotating the blade, whereas the scriber scratches the front surface, the back surface, etc. of the wafer and only cracks from that place. The work process time is short, and because the blade of the scriber is very thin compared to the blade of the dicer,
By cutting off a small volume when cutting,
When obtaining small-sized chips, the yield per unit area is also improved.

As described above, the thickness of the substrate is 100 to 250 μm.
By adjusting to m, the chip can be cut into chips with a yield of 90% or more by scribe, and the yield rate can be further improved by inserting a scribe line of 10% or more.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic cross section of a chip obtained according to an embodiment of the present invention.

[Explanation of symbols]

 1-Sapphire substrate 2-n-type GaN layer 3-p-type GaN layer

Claims (3)

[Claims] 1. A general formula Ga _X Al _1-X on a sapphire substrate.
Ga _X Al _1-X N represented by N (0 ≦ X ≦ 1) (0 ≦ X ≦
1) In a method of cutting a wafer in which a compound semiconductor is laminated into chips, the sapphire substrate has a thickness of 100 to 250 μm,
Further, the gallium nitride-based compound semiconductor wafer is cut by scribing the substrate side, the gallium nitride-based compound semiconductor layer side, or both sides of the wafer. 2. The method for cutting a gallium nitride-based compound semiconductor wafer according to claim 1, wherein the scribe depth is 10% or more of the thickness of the sapphire substrate. 3. The method for cutting a gallium nitride-based compound semiconductor wafer according to claim 1, wherein the sapphire substrate of the cut chips is scribed so that the length of the shortest side of the sapphire substrate is longer than the thickness of the substrate.