JP2003078164A - Gallium nitride-based compound semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gallium nitride-based compound semiconductor light emitting element that can be manufactured without compromising the crystallinity of a p-type layer or an n-type layer. SOLUTION: This gallium nitride-based compound semiconductor light emitting element is manufactured by dividing a wafer provided with a gallium nitride-based compound semiconductor constituted by successively laminating the n-type layer and p-type layer on a sapphire substrate, and etching the p-type layer so that the electrode forming surface of the n-type layer may be exposed by forming dividing grooves on the surface of the wafer. The light emitting element has dividing groove forming surfaces which are positioned lower than the electrode forming surface and provided for forming the dividing grooves and the thickness of the sapphire substrate is set at <=200 μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride-based compound semiconductor chip used in a light emitting device such as a blue, green or red light emitting diode and a laser diode, and more particularly to a general formula In _X Al _Y on a sapphire substrate. Ga
_{The present invention} relates to a gallium nitride-based compound semiconductor light emitting device in which a gallium nitride-based compound semiconductor represented by _1-XY N (0 ≦ X <1, 0 ≦ Y <1) (hereinafter referred to as a nitride semiconductor) is stacked.

[0002]

2. Description of the Related Art Generally, a dicer or a scriber is generally used in an apparatus for cutting a wafer in which a semiconductor material is laminated on a substrate into chips for a light emitting device. The dicer is generally called a dicing saw, and the wafer is either fully cut directly by the rotational movement of the blade with the cutting edge as a diamond, or after cutting a groove with a width wider than the width of the cutting edge (half cut), then the wafer is cut by an external force. It is a device for breaking. On the other hand, a scriber is a device for drawing an extremely thin scribe line (scoring line) on the wafer by reciprocating linear motion of a needle having a diamond tip, for example, in a grid pattern, and then breaking the wafer by an external force.

Conventionally, when a semiconductor wafer is cut into chips using these devices, for example, GaP and GaAs are used.
Since the crystal having a zinc-zinc structure such as Cleavage has a cleavage property in the "110" direction, it can be easily separated into chips by using this property, for example, by inserting a scribe line in this direction with a scriber. However, since the nitride semiconductor is laminated on the sapphire substrate, the wafer does not have a cleavage property due to the property of the sapphire crystal of the hexagonal system, and it is difficult to cut it with a scriber.
On the other hand, even when cutting with a dicer, the gallium nitride-based compound semiconductor wafer has a so-called heteroepitaxial structure in which a gallium nitride-based compound semiconductor is laminated on sapphire as described above, so that the lattice constant irregularity is large and Since the expansion coefficients are also different, there is a problem that the gallium nitride-based compound semiconductor is likely to be peeled off from the sapphire substrate when an external force is applied. Furthermore, since both sapphire and gallium nitride-based compound semiconductors are very hard materials having a Mohs hardness of about 9, cracks and chippings tend to occur on the cut surface, making it impossible to cut accurately.

Since the nitride semiconductor is laminated on the sapphire insulating substrate as described above, p
In order to take out the electrode from the type layer and the n-type layer, etching is usually performed on the same surface side of the nitride semiconductor layer to leave both layers exposed. When separating the nitride semiconductor wafer in this state into chips, using the scribe, dicer, etc., if directly cutting from the nitride semiconductor side of the etching surface, cracks occur in the cut surface, yield is not good There was a problem.

[0005]

It is very important to obtain as many light emitting chips as possible from a single wafer to improve productivity, and to obtain many chips without damaging the crystallinity of the nitride semiconductor. Is an essential requirement. Chips made of nitride semiconductors have not yet been put to practical use, but in the near future, in order to put blue, green light-emitting diodes, laser diodes, etc. into practical use by utilizing nitride semiconductors, more and more advanced chipping technology will be required. It has been demanded. Therefore, the present invention has been made in view of such circumstances,
The purpose is to prevent the occurrence of cracks and chippings on the cut surface when separating a nitride semiconductor wafer using sapphire as a substrate into chips, and to obtain a nitride semiconductor having a desired shape and size with good yield. To provide a method of manufacturing a chip and to provide electrodes by this method, a p-type layer,
Another object of the present invention is to provide a gallium nitride-based compound semiconductor light emitting device that can be manufactured without impairing the crystallinity of the nitride semiconductor with the n-type layer etched.

[0006]

In the gallium nitride-based compound semiconductor light emitting device according to the present invention, an n-type layer and a p-type layer are sequentially stacked on a sapphire substrate so that an electrode formation surface of the n-type layer is exposed. In the gallium nitride-based compound semiconductor light-emitting device produced by dividing the wafer provided with the gallium nitride-based compound semiconductor etched in, to form the split groove, the split groove is located below the electrode formation surface. It has a split groove forming surface provided as a surface to be formed,
The sapphire substrate has a thickness of 200 μm or less. Further, in the gallium nitride-based compound semiconductor light emitting device according to the present invention, it is preferable that the split groove forming surface is formed by etching. Further, the gallium nitride-based compound semiconductor light emitting device according to the present invention is preferably manufactured by dividing the wafer with a scriber. Furthermore, in the gallium nitride-based compound semiconductor light emitting device according to the present invention, the sapphire substrate preferably has a thickness of 50 μm or more. Furthermore, the gallium nitride-based compound semiconductor light emitting device according to the present invention can be manufactured by the following manufacturing method. That is, the method for manufacturing a nitride semiconductor chip according to the device of the present invention comprises a sapphire substrate provided with a gallium nitride-based compound semiconductor which is previously etched so that the electrode formation surface of the p-type layer or the n-type layer is exposed. A method for separating a gallium-based compound semiconductor wafer into chips, wherein the gallium nitride-based compound semiconductor surface is newly etched separately from the etching of the electrode formation surface of the gallium-nitride-based compound semiconductor to form a first split groove. A step of linearly forming a desired chip size, and then, from above the first split groove, further forming a second split groove linearly at a depth of reaching the sapphire substrate or more, and The line width (W2) of the second split groove is larger than the line width (W1) of the split groove of
And a step of separating the wafer into chips along the second split groove.

In the method of manufacturing the element of the present invention, either wet etching or dry etching may be used as an etching means for forming the first split groove. In the case of wet etching, for example, sulfuric acid and phosphoric acid may be used. On the other hand, mixed acid can be used. On the other hand, if it is dry etching, reactive ion etching (RIE), ion milling, focused beam etching, ECR etching or the like can be used. Preferably, dry etching is less likely to damage the nitride semiconductor crystal. However, it goes without saying that a mask having a predetermined shape is formed on the surface of the nitride semiconductor so as to have a desired chip size before etching.

Next, in order to form the second split groove, a method such as dicing, scribing or etching can be used. The second split groove is formed on the first split groove, that is, at the mark of the first split groove. This second split groove must be formed to a depth that reaches the sapphire substrate,
Furthermore, it is necessary to make it narrower than the width of the first split groove. The forming method is not particularly limited, but scribe is particularly preferably used. This is because the scribe easily makes the line width of the second split groove narrower than the line width of the first split groove, and the split groove can be formed more quickly than etching. further,
Compared to dicing, the sapphire substrate is cut off in a smaller area when the wafer is cut, which is advantageous in that many chips can be obtained from a single wafer.

Further, it is preferable to polish the sapphire substrate to be thin before forming the first split groove or before forming the second split groove. The thickness of the sapphire substrate after polishing is 200 μm or less, more preferably 150 μm
The following adjustments are desirable. This is because the nitride semiconductor wafer usually has a sapphire substrate thickness of 300 to 8
The thickness of the nitride semiconductor layer is 00 μm, and the thickness of the nitride semiconductor stacked thereon is at most several tens of μm. Moreover, as described above, the nitride semiconductor is laminated on the materials having different lattice constants and different coefficients of thermal expansion, and therefore has a property that it is very difficult to cut. Therefore, by adjusting the thickness of the sapphire substrate within the above range, the sapphire substrate can be split substantially vertically. In particular, when the second split groove is formed by scribing, by polishing the sapphire substrate in the above range, a substantially vertical cut surface can be obtained by one scribing. The lower limit of the thickness of the substrate is not particularly limited, but if it is too thin, the wafer itself is likely to break during polishing, so a practical value of 50 μm or more is preferable.

[0010]

The operation of the manufacturing method according to the element of the present invention will be described with reference to the drawings. 1 to 8 are schematic cross-sectional views for explaining one step of the manufacturing method of the present invention, and particularly FIGS. 7 and 8 show an enlarged view of the state of the wafer when forming the second split groove. .

FIG. 1 is a schematic sectional view of a wafer in which an n-type nitride semiconductor layer 2 (n-type layer) and a p-type nitride semiconductor layer 3 (p-type layer) are stacked on a sapphire substrate 1. The p-type layer 3 is pre-etched to expose the n-type layer 2 for providing the negative electrode.

Next, as shown in FIG. 2, the first split groove 11 is formed into W1 from the exposed n-type layer 2 by etching.
Is formed into a linear shape with a width of. Before etching, p-type layer 3
It goes without saying that a mask for forming the first split groove is formed on the exposed surface of the n-type layer 2. Compared to other techniques such as scribing and dicing, the means for forming the first split groove 11 by etching is less likely to damage the crystal of the nitride semiconductor, and the physical stress is a pn junction of the nitride semiconductor. It has an effect of making it independent of the interface and the interface between the sapphire and the nitride semiconductor. Further, as shown in this figure, when the first split groove 11 is formed until it reaches the sapphire substrate 1, the exposed surface at the position where the second split groove 22 is formed next is only sapphire. Groove 22
It is most preferable that the cutting edge of a dicer, a scriber or the like, which is a means for forming a ridge, never touches the nitride semiconductor.

Next, as shown in FIG. 3, the first split groove 11 is formed.
From the above, the second split groove 22 is newly formed in a linear shape with a width W2 narrower than the line width W1 of the first split groove 11. Moreover, the depth thereof is not less than the depth reaching the sapphire substrate 1. (In FIG. 3, the first split groove 11 is formed until it reaches the sapphire substrate, so in this case, the depth of the second split groove 22 naturally becomes equal to or greater than the depth at which it reaches the sapphire substrate.) Line width W of the second split groove 22
By making 2 smaller than the line width W1 of the first split groove 11, the cutting edge of the dicer, scriber or the like, which is the means for forming the second split groove 22, should form the side surface of the nitride semiconductor, that is, the electrode. Since the mold layer 2 is not touched, the crystallinity is not impaired. Furthermore, since the depth of the second split groove 22 is set to reach the sapphire substrate or more, the sapphire substrate is the only substantial cut point, and the shape of the target nitride semiconductor can be accurately controlled, and the chip is separated into chips. be able to. Further, in this figure, since the sapphire substrate 1 is not polished and the second split groove 22 is formed by scribing,
As shown by the broken line, there is a possibility that sapphire will be broken at an angle, but if the dicing groove 22 is half-cut to reduce the thickness of the sapphire substrate to 200 μm or less, or if it is full-cut. Sapphire can be cut vertically.

In FIG. 4, the sapphire substrate 1 side of the wafer shown in FIG. 1 or 2 is polished to a thickness of 200 μm.
The following shows the state. By polishing and thinning the substrate in this manner, the second split groove 22 is scribed.
However, the sapphire substrate 1 can be split almost vertically even if the above is formed. However, it is preferable to perform the step of polishing the sapphire substrate before forming the first split groove or before forming the second split groove. Because of the second split groove 22
This is because if the substrate is polished after forming, the substrate tends to be cracked at an unintended position during polishing.

FIGS. 5 and 6 are schematic sectional views showing the structure of a wafer obtained in one step according to another embodiment of the present invention. FIG. 5 shows the first split groove 11 until reaching the sapphire substrate 1. FIG. 6 shows a state in which the n-layer 2 is not formed and is stopped halfway, and FIG. 6 shows a depth at which the second split groove 22 newly reaches the sapphire substrate 1 from above the first split groove 11 shown in FIG. The state formed as described above is shown. If the second split groove 22 can be formed to a depth that reaches the sapphire substrate 1 as shown in FIG. 6, it is necessary to etch until the first split groove 11 reaches the sapphire substrate, as shown in FIG. There is no. However, if the nitride semiconductor (n-type layer 2 in this case) at the position where the second split groove should be formed after forming the first split groove 11 is thick, the second split groove will be formed later. Since the stress due to the scriber and the dicer acts when forming the sapphire layer, the interface between the sapphire substrate 1 and the n layer 2 is easily peeled off.
It is preferable to adjust the thickness of the layer 2 to 5 μm or less.

FIG. 7 and FIG. 8 are schematic cross-sectional views showing an enlarged structure of the wafer when the second split groove 22 is formed, and FIG. 7 shows the second split groove 22 formed by using a scriber. FIG. 8 shows that it is formed by a dicer. In either case, it can be seen that after the scratch is formed on the surface of the sapphire substrate 1 by the second split groove 22, the wafer can be separated along the scratch, but as shown in FIG. It can be seen that a larger number of chips can be obtained because the width W1 of the first dividing groove 11 can be narrowed by forming the first dividing groove 11. Further, since the width W2 of the second split groove 22 is made narrower than W1, the side surface of the nitride semiconductor is not damaged by the blade edge of the scriber, the blade of the dicer, or the like. In addition, in FIG.
The circled portion shows the state in which the first split groove 11 leaves the n-type layer 2, that is, the same state as in FIG. 5, but this portion cut off by the second split groove 22 is Since it is not the n-type layer 2 for which the negative electrode is to be provided by etching, even if the side surface is slightly scratched, it is a portion that is not particularly important for the chip, and therefore does not affect the light emission characteristics of the chip.

[0017]

Example 1 An n-type layer 2 (n-type GaN in this case) of 6 μm and a p-type layer 3 (p-type in this case) were sequentially formed on a sapphire substrate 1 having a thickness of 400 μm and a size of 2 inches φ. Ga
A wafer having N) and 1 μm stacked is prepared. However, the p-type GaN layer of this wafer was previously etched in a predetermined shape to a depth of 2 μm to partially expose the n-type layer 2 on which an electrode should be provided, as shown in FIG. (Thus, the thickness of the n-type layer 2 exposed by etching is 5 μm.)
FIG. 9 is a plan view of the etched wafer as seen from the nitride semiconductor layer side.

Next, on the p-type layer 3 and the etched n-type GaN layer 2 of this wafer, SiO is formed by a photolithography technique so as to have a predetermined chip size.
After applying the mask made of 2, the n-type GaN layer 2 is further etched by RIE until the sapphire substrate is exposed to form the first split groove 11. The first split grooves have a line width (W1) of 40 μm and a pitch of 350 μm. The line width and pitch of this first split groove are shown in FIG.

After the first split groove 11 is formed as described above, the sapphire substrate 1 side of the wafer is polished by a polisher, and the substrate is lapped and polished to a thickness of 100 μm.

Next, an adhesive tape is attached to the sapphire substrate 1 side of the wafer after polishing, the wafer is attached on the table of the scriber, and fixed by a vacuum chuck. The table can move in the X-axis (left and right) and Y-axis (front and back) directions, and has a rotatable structure.
After fixing, a scriber diamond needle is used to scribe the center line of the first split groove in the X-axis direction once at a pitch of 350 μm, a depth of 5 μm, and a line width (W2) of 5 μm. Rotate the table 90 degrees and scribe in the same way in the Y-axis direction this time. In this way, a scribe line is formed so as to form a 350 μm square chip, and a second split groove is formed.

After the scribing, the vacuum chuck was released, the wafer was peeled from the table, and slightly pressed from the sapphire substrate side with a roller to obtain a large number of 350 μm square chips from the 2-inch φ wafer. The chip can be cut almost vertically from the second kerf, no cracks are generated on the cut surface, and a nitride semiconductor is taken out from the sapphire substrate,
The yield was 99% or more.

[Embodiment 2] In the step of forming the first dividing groove of Embodiment 1, chips are separated in the same manner except that the etching depth is 4 μm (that is, the second dividing groove 22 is formed next). (The thickness of the n-type layer 2 in the portion where the is formed is 1 μm) Other than the above, when the chips are separated into 350 μm square chips, the yield is also 99% or more.

[Embodiment 3] Similar to Embodiment 1, the first groove is formed until the first groove reaches the sapphire substrate. However, the line width (W1) is 100μm, 500μm
The pitch.

Next, the sapphire substrate 1 side of the wafer was polished by a polisher, and the substrate was lapped to a thickness of 200 μm and polished. By polishing the substrate, the dicing time can be shortened in the next step of forming the second split groove.

The wafer after polishing was fixed on the table of the dicer, and the center line of the first split groove was similarly moved in the X-axis direction by using a blade having a blade width of 80 μm.
00 μm pitch, depth 50 μm, line width (W2) 80 μm
The second split groove is formed by dicing and half cutting. In this way, by making the second split groove deep with a dicer and thinning the thickness of the sapphire substrate at the cut portion, the cut surface can be made substantially vertical.

After the half-cutting, the wafer was peeled off from the table and lightly pressed from the sapphire substrate side by a roller to obtain a large number of chips of 500 μm square from a 2-inch φ wafer. The yield of this chip is also 99%
That was all.

[0027]

As described above, according to the method of the present invention, even a nitride semiconductor wafer having no cleavability can be accurately cut with good yield by a method such as scribing and dicing. Productivity is improved. Moreover, since the nitride semiconductor on which the electrode is formed is not damaged at all, when the chip separated by the method of the present invention is used as a light emitting device, the device yield is dramatically improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view illustrating one step of the manufacturing method of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating one step of the manufacturing method of the present invention.

FIG. 3 is a schematic cross-sectional view illustrating one step of the manufacturing method of the present invention.

FIG. 4 is a schematic cross-sectional view illustrating one step of the manufacturing method of the present invention.

FIG. 5 is a schematic cross-sectional view illustrating one step of the manufacturing method of the present invention.

FIG. 6 is a schematic cross-sectional view illustrating one step of the manufacturing method of the present invention.

FIG. 7 is an enlarged schematic cross-sectional view illustrating one step of the manufacturing method of the present invention.

FIG. 8 is an enlarged schematic cross-sectional view explaining one step of the manufacturing method of the present invention.

FIG. 9 is a plan view illustrating one step of the manufacturing method of the present invention.

[Explanation of symbols]

1 ... Sapphire substrate 2 ... N-type layer 3 ... P-type layer 11 ... First split groove 22 ... Second split groove

Claims (4)

[Claims] 1. A wafer provided with a gallium nitride-based compound semiconductor, in which an n-type layer and a p-type layer are sequentially stacked on a sapphire substrate and etched so that an electrode formation surface of the n-type layer is exposed, a split groove. In a gallium nitride-based compound semiconductor light-emitting device produced by forming and dividing, having a split groove forming surface provided as a surface for forming the split groove and located below the electrode forming surface, and A gallium nitride-based compound semiconductor light-emitting device, wherein the sapphire substrate has a thickness of 200 μm or less. 2. The gallium nitride-based compound semiconductor light emitting device according to claim 1, wherein the split groove forming surface is formed by etching. 3. The gallium nitride-based compound semiconductor light emitting device according to claim 1, which is manufactured by dividing the wafer using a scriber. 4. The gallium nitride-based compound semiconductor light emitting device according to claim 1, wherein the sapphire substrate has a thickness of 50 μm or more.