JP2748354B2 - Method of manufacturing gallium nitride based compound semiconductor chip - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a blue, green or red light emitting diode, the method for manufacturing a laser gallium nitride compound used in the light-emitting device such as a diode semiconductor chip, in particular the general formula In _X on a sapphire substrate A
The present invention relates to a method of cutting a gallium nitride-based compound semiconductor wafer on which a gallium nitride-based compound semiconductor represented by l _Y Ga _{1 -XYN} (0 ≦ X <1, 0 ≦ Y <1) is laminated into chips.

[0002]

2. Description of the Related Art In general, a light emitting device such as a light emitting diode or a laser diode has a semiconductor chip as a light emitting source on a stem. As a material constituting the semiconductor chip, for example, GaAs, GaAlAs, GaP, and the like are known for red, orange, yellow, and green diodes,
For blue diodes, ZnSe, InAlGa
N, SiC and the like are known.

Conventionally, a dicer or a scriber is generally used as an apparatus for cutting out chips for light emitting devices from a wafer on which semiconductor materials are stacked. A dicer is generally called a dicing saw, and the wafer is directly full-cut by a rotating motion of a blade having a diamond edge, or a groove having a width wider than the edge width is cut (half-cut), and then the wafer is cut by an external force. Is a device that divides On the other hand, a scriber is a device that draws an extremely thin scribe line (scribed line) on a wafer, for example, in a grid pattern by reciprocating linear movement of a needle having a diamond tip, and then breaks the wafer by an external force.

[0004] When the above semiconductor material is cut into chips using these devices, for example, crystals having a spiral zinc structure such as GaP or GaAs have a cleavage property in the "110" direction. By inserting a scribe line in this direction with a scriber, it can be easily separated into chips.

However, since a gallium nitride-based compound semiconductor is generally laminated on a sapphire substrate, the wafer does not have a cleavage property due to the hexagonal sapphire crystal property and is difficult to cut with a scriber. Met. On the other hand, even when the wafer is cut with a dicer, the gallium nitride-based compound semiconductor wafer has a so-called heteroepitaxial structure in which the gallium nitride-based compound semiconductor is stacked on sapphire as described above, and therefore has a large lattice constant irregularity and a high thermal conductivity. There is a problem that the gallium nitride-based compound semiconductor is easily peeled off from the sapphire substrate due to different expansion coefficients. Furthermore, since both sapphire and gallium nitride-based compound semiconductors are very hard substances having a Mohs hardness of approximately 9, cracks and chippings are apt to be generated on the cut surface, so that accurate cutting cannot be performed.

[0006]

If the wafer can be accurately separated into chips without damaging the crystallinity of the gallium nitride-based compound semiconductor, the output and efficiency of the light emitting device can be improved. Since many chips can be obtained from one wafer, productivity can be improved. Accordingly, the present invention has been made in view of such circumstances, and an object of the present invention is to separate a gallium nitride-based compound semiconductor wafer using sapphire as a substrate into chips, thereby cracking the cut surface and causing chipping. It is an object of the present invention to provide a method of manufacturing a chip which prevents occurrence of a chip and has a desired shape and size with a good yield.

[0007]

According to the present invention, there is provided a method of manufacturing a gallium nitride-based compound semiconductor chip, comprising forming a protective film having a property that a gallium nitride-based compound semiconductor does not grow on a surface in a desired chip shape on a sapphire substrate. Forming a gallium nitride-based compound semiconductor wafer by selectively growing a gallium nitride-based compound semiconductor on the sapphire substrate on which the protective film is formed; Cutting the system compound semiconductor wafer into chips.

In the method of the present invention, the material of the protective film formed on the sapphire substrate may be any material that has the property of withstanding the growth temperature of the gallium nitride-based compound semiconductor and that does not allow the gallium nitride-based compound semiconductor to grow. Any material may be used. Specifically, it is preferable to use either silicon dioxide or silicon nitride. These materials can be easily formed into a chip-shaped pattern by providing a mask on the surface of the sapphire substrate using a technique such as vapor deposition or sputtering.

Next, a gallium nitride-based compound semiconductor is laminated on the sapphire substrate on which the protective film has been formed by using a vapor phase growth method such as MOCVD or MBE.
A gallium nitride-based compound semiconductor wafer having a junction can be produced. Gallium nitride based compound semiconductors
Since it grows on sapphire but does not grow on the protective film, a wafer is obtained in which gallium nitride-based compound semiconductors selectively grown in advance to have a desired chip shape are stacked.

Next, the wafer can be cut into chips by cutting the wafer from the portion where the protective film has been formed. The cutting method is not particularly limited. For example, a method such as scribing with a scriber, half-cutting or full-cutting with a dicer can be applied, and a laser or the like can also be used. The cutting line may be inserted from any of the sapphire substrate side and the protective film side of the wafer. Needless to say, when a cutting line is inserted from the sapphire substrate side, the position of the cutting line is made to coincide with the position where the protective film is formed.
Before the cutting, the protective film of the wafer may be removed by using an etching technique such as wet etching. By removing the protective film in advance, for example, when breaking the wafer by inserting a scribe line from the protective film side, the scribe line can be directly inserted into the sapphire substrate surface from which the protective film has been peeled off, making it very easy to split preferable.

Further, when a cutting line is cut from the gallium nitride-based compound semiconductor layer side and cut, the line width of the protective film is formed in advance to be wider than the cutting width of the gallium nitride-based compound semiconductor wafer. It is very preferable because it does not damage the semiconductor. This is particularly effective when cutting from the protective film side with a dicer. Because the dicer has a blade several times thicker than the scriber
It is several tens of times larger. Therefore, when cutting the wafer from the protective film side with a dicer having a large blade thickness, if the width of the protective film is small, the gallium nitride-based compound semiconductor will be damaged by the tip of the blade to be cut, the side surface of the blade, and the like. is there. On the other hand, even when cutting with a scriber, if the width of the portion where the protective film is peeled off is smaller than the scribe line, the gallium nitride-based compound semiconductor is damaged at the tip of the scriber. Similarly, when cutting with a laser or the like, it is preferable that the width of the portion where the protective film is peeled is wider than the spot diameter of the laser.

After the gallium nitride-based compound semiconductor wafer is formed, it is preferable that the sapphire substrate side is polished and thinned before cutting the wafer, and the thickness of the sapphire substrate after polishing is adjusted to 200 μm or less, more preferably 150 μm or less. It is desirable to do. This means is particularly effective when a scriber is used to insert a scribe line from the sapphire substrate side and when a dicer is used to make a half cut from the sapphire substrate side. This is because, when the thickness of the sapphire substrate is greater than 200 μm, the wafer tends to be less likely to crack when divided into chips. Also, when performing full cutting with a dicer, laser, or the like, if the wafer is polished and thinned, the cutting time can be reduced. The lower limit of the thickness of the substrate is not particularly limited. However, if the thickness is too small, the wafer itself is easily broken during polishing. Therefore, a practical value is preferably 50 μm or more.

[0013]

The operation of the manufacturing method of the present invention will be described with reference to the drawings. FIGS. 1 to 4 are views for explaining the steps of one manufacturing method of the present invention with schematic cross-sectional views. FIG. 1 shows that a protective film 11 is formed on a surface of a sapphire substrate 1 so as to have a predetermined chip shape. FIG. 2 shows a state in which a gallium nitride-based compound semiconductor 2 is selectively grown and stacked on a sapphire substrate 1 on which a protective film 11 is formed. FIG. 3 shows a state in which the protective film 11 has been peeled off, and FIG. 4 shows a state in which the protective film 11 has been peeled off and the sapphire substrate 1 has been polished and thinned. 2 shows a state in which a scribe line is formed from the gallium nitride-based compound semiconductor layer 2 side.

As shown in FIGS. 1 and 2, a protective film 11 on which a gallium nitride-based compound semiconductor does not grow is formed on a sapphire substrate 1, and the gallium nitride-based compound semiconductor 2 is formed on the sapphire by the action of the protective film 11. And a wafer in which a gallium nitride-based compound semiconductor is selectively grown can be realized. The protective film 11 is formed in a desired chip shape in a linear shape. (Since the chip shape is usually square, the protective film 11 is formed in a grid pattern.)

The wafer shown in FIG.
Is indicated by a broken line from the position where the is cut off, and can be cut, for example, by half-cutting or full-cutting with a dicer. Further, the wafer shown in FIG. 4 can be cut from the position shown by the broken line of the scribe line by polishing and thinning the substrate. By removing the protective film in advance as shown in FIG. 4, the scribe line can be directly inserted into the sapphire substrate, so that the wafer is easily broken. In addition, the gallium nitride-based compound semiconductor is not subject to the scriber stress, so there is no fear of peeling. If the protective film 11 is not peeled off, it is necessary to increase the depth of the scribe line.

As shown in FIGS. 1 to 4, when the line width of the protective film 11 is widened so that cutting lines such as scribe and dicing do not reach the gallium nitride-based compound semiconductor layer 2, the gallium nitride-based compound semiconductor Layer 2 is not damaged. Furthermore, when the protective film 11 is peeled off, the cut portion becomes only the sapphire substrate 1, and the gallium nitride-based compound semiconductor layer 2 can be cut into chips accurately without stress.

[0017]

EXAMPLE 1 A mask having a predetermined shape is formed on a sapphire substrate 1 having a thickness of 400 μm and a size of 2 inches φ. After depositing SiO ₂ on the mask by vapor deposition, sapphire is immersed in a solvent to remove the mask. As a result, a line width of 50 μm, 5
A pattern consisting of the SiO ₂ protective film 11 on a grid having a pitch of 00 μm is completed. FIG. 5 is a plan view of the sapphire substrate viewed from the protective film side in this step.

The sapphire substrate is set in a MOCVD apparatus, and an n-type GaN layer and a p-type GaN
The gallium nitride-based compound semiconductor wafer is grown by combining the layers with a thickness of 5 μm. When the wafer was taken out of the apparatus and the growth surface was observed, G was found on the sapphire.
Although aN grew to show transparency, nothing grew on the SiO ₂ protective film.

After the wafer on which GaN is selectively grown as described above is immersed in hydrofluoric acid to remove the SiO ₂ protective film, the sapphire substrate side of the wafer is polished to a thickness of 100 μm. .

Next, an adhesive tape is stuck on the sapphire substrate side, set on a scriber, and fixed with a vacuum chuck.
A scribe line is inserted at a depth of 5 μm. FIG. 6 shows a partially enlarged cross-sectional view of the wafer including the scribe line. In this way, by making the line width of the SiO ₂ protective film wider than the width of the scribe line in advance, that is, by making the line width of the protective film wider than the cutting width of the wafer, gallium nitride can be formed during scribe or split. The surface and side surfaces of the compound semiconductor are not damaged.

After scribing, the vacuum chuck was released, the wafer was peeled off from the table, and lightly pressed from the sapphire substrate side with a roller to obtain a large number of chips of 500 μm square from the wafer of 2 inch φ. Cracks, chipping, etc., did not occur on the cut surface of the chip, and the GaN layer was not peeled off and had no external defects. The yield was 95% or more.

Example 2 A 500 μm square chip was obtained in the same manner as in Example 1, except that an adhesive tape was applied to the GaN layer side and a scribe line was inserted from the sapphire substrate side. Yields were also over 95%. The scribe line on the sapphire substrate side was also placed at the center line of the line from which the protective film on the GaN layer side was peeled off.

[Embodiment 3] In the step of forming the protective film of the embodiment 1, the shape of the mask is changed and a protective film made of SiO ₂ is formed in a grid pattern with a line width of 200 μm and a pitch of 500 μm.

Next, a GaN layer is laminated on the protective film to form a wafer, and then the sapphire substrate is polished to adjust the thickness of the substrate to 200 μm.

An adhesive tape is stuck to the sapphire substrate side of the polished wafer and fixed to a dicer, and the center line of the protective film is diced with a 150 μm-width blade to cut the wafer completely. FIG. 7 shows a partially enlarged cross-sectional view of the wafer during the dicing process. This is the same as S
making the line width of the iO ₂ protective film wider than the blade width in advance;
That is, by making the line width of the protective film wider than the cutting width of the wafer, the surface and side surfaces of the gallium nitride-based compound semiconductor are not damaged during cutting.

A number of 500 μm square chips were obtained from the diced wafer. Similarly, a chip having no cracks, chippings, or the like on the cut surface of the chip and having no external defects was obtained, and the yield was 95% or more.

Example 4 In the dicing step of Example 3, an adhesive tape was applied to the GaN layer side, and the full cut was performed from the sapphire substrate side.
When the corner chips were obtained, the yield was also 95% or more.

[0028]

As described above, according to the method of the present invention, even a gallium nitride based compound semiconductor wafer having no cleavage can be accurately cut with a high yield using various cutting devices. , And productivity is improved.

[Brief description of the drawings]

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

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sapphire substrate 2 ... Gallium nitride compound semiconductor 11 ... Protective film

Claims (5)

(57) [Claims] 1. A step of forming a protective film having a property that a gallium nitride-based compound semiconductor does not grow on the surface in a linear shape in a desired chip shape on a sapphire substrate, and forming a protective film on the sapphire substrate on which the protective film is formed. Selectively growing a gallium nitride-based compound semiconductor to form a gallium nitride-based compound semiconductor wafer; and cutting the wafer from a portion where the protective film is formed and separating the wafer into chips. For manufacturing a gallium nitride-based compound semiconductor chip. 2. The method of manufacturing a gallium nitride-based compound semiconductor chip according to claim 1, further comprising a step of removing the protective film after forming the gallium nitride-based compound semiconductor wafer. 3. After preparing the gallium nitride based compound semiconductor wafer, the sapphire substrate side of the wafer is
3. The method for manufacturing a gallium nitride-based compound semiconductor chip according to claim 1, further comprising a step of polishing to a thickness of not more than 00 μm. 4. The method according to claim 1, wherein said protective film is made of one of silicon dioxide and silicon nitride.
4. The method for manufacturing a gallium nitride-based compound semiconductor chip according to claim 1. 5. The gallium nitride-based semiconductor device according to claim 1, wherein a line width of the protective film is wider than a cutting width of the gallium nitride-based compound semiconductor wafer. A method for manufacturing a compound semiconductor chip.