JP2000101195A - Manufacture and structure of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor device for easily cutting a substrate and for cleaving a semiconductor layer in a semiconductor device, that is made of gallium nitride semiconductor layer which is formed on a hexagonal system substrate such as a sapphire substrate. SOLUTION: When a semiconductor element made of a nitride semiconductor layer is to be formed on such hexagonal system substrate as a sapphire substrate 1 and to be divided into each semiconductor element, a nitride metal thin film 1 is provided on the reverse side of the sapphire substrate 1, thus easily cutting the sapphire substrate 1 into an arbitrary direction. The cutting direction of the substrate is selected for the cleavage direction of the semiconductor layer which is formed on the sapphire substrate 1.

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 semiconductor device comprising a gallium nitride-based semiconductor layer formed on a hexagonal system substrate such as a sapphire substrate. The present invention relates to a method for manufacturing a semiconductor device capable of cleavage.

[0002]

2. Description of the Related Art Light emitting devices such as laser diodes and light emitting diodes having relatively long wavelengths currently used are made of GaAs or Ga having a zinc blend (Zinc Blende) structure.
GaAs, InGaP, AlG on a substrate of P, InP, etc.
A compound semiconductor material such as aAs is crystal-grown, and is made into a chip. Since the single crystal substrate having such a zinc blend structure has cleavage in the <110> direction, a scribe line is formed in this direction using a needle-shaped scriber, and the substrate is pressed along the scribe line to be cleaved. Thereby, it can be easily separated into chips. In a laser diode, such a cleavage plane can be used as a cavity end face.

[0003]

A gallium nitride-based III-V compound semiconductor represented by GaN used for a blue light emitting device is usually grown on a sapphire substrate.
Since the sapphire substrate is a hexagonal crystal, the cleavage property is weak, and the cleavage direction is different from that of the GaN layer grown thereon. For this reason, when dicing or scribing is performed, the substrate must be forcibly cut to separate each chip, and an unnecessary force is applied to the substrate. For this reason, there has been a problem that the device has an adverse effect such as deterioration of crystallinity due to propagation of dislocation or the like, which causes a reduction in luminous efficiency of the device, a deterioration in life, and the like. In particular, in a laser diode, the cavity end face could not be formed from the cleavage plane, so that a method of using dry etching for manufacturing the cavity end face or a method of scribing after polishing a sapphire substrate has been used. But,
There are problems such as deterioration of the end face shape and cracks during polishing, which causes deterioration of device characteristics and reduction of manufacturing yield. Therefore, the present invention provides a method of manufacturing a semiconductor device comprising a gallium nitride-based semiconductor layer formed on a hexagonal substrate such as a sapphire substrate, wherein the substrate can be easily cut and the semiconductor layer can be cleaved. The purpose is to provide.

[0004]

Therefore, as a result of intensive studies, the present inventors have formed a semiconductor element comprising a nitride semiconductor layer on a hexagonal single crystal substrate such as a sapphire substrate and divided the semiconductor element into individual semiconductor elements. In this case, by providing a metal nitride thin film on the back surface of the substrate, the substrate can be easily cut in any direction, and thereby, the cutting direction of the substrate can be adjusted in accordance with the cleavage direction of the semiconductor layer formed on the substrate. Have been found, and the present invention has been completed.

That is, according to the present invention, a gallium nitride-based semiconductor layer is grown and grown on a hexagonal single-crystal substrate, electrodes are formed on the semiconductor layer to form a plurality of semiconductor elements, and the single-crystal substrate is cut. Forming a metal thin film on the back surface of the single crystal substrate, nitriding the metal thin film into a metal nitride thin film, and forming the metal thin film from the metal nitride thin film side. A method for manufacturing a semiconductor device, comprising forming a scribe line reaching a single crystal substrate, and cutting the single crystal substrate and the semiconductor layer along the scribe line. As described above, by forming the metal nitride thin film on the back surface of the substrate, the force for breaking the substrate is only about 1/10 of that of the conventional method, and no extra force is applied to the substrate. It is possible to suppress the occurrence of chipping. Further, since the substrate can be easily split in any direction of the substrate, the substrate and the semiconductor layer can be split along the cleavage direction of the gallium nitride based semiconductor layer formed on the substrate. . Thus, the cleavage plane can be used as a cavity end face of the laser diode.

In addition, the direction of cleavage of the gallium nitride based semiconductor layer formed on the substrate is the same as the cleavage direction of the semiconductor layer.

(Equation 3) It is preferable to form the scribe line in a direction (hereinafter, referred to as “direction of Equation 3”). Thus, Equation 3
By forming the scribe lines in the direction of, the gallium nitride based semiconductor layer on the substrate can be divided at the cleavage plane.

[0007] Sapphire (0001) is applied to the single crystal substrate.
When a substrate is used, the sapphire substrate

(Equation 4) It is preferable to form the scribe line in a direction (hereinafter, referred to as “direction of Equation 4”). Sapphire (00
01) When a gallium nitride-based semiconductor layer is formed on a substrate, the direction of the number 4 of the sapphire substrate corresponds to the direction of the number 3 of the gallium nitride-based semiconductor layer.

The melting point of the metal thin film is preferably 1200 ° C. or higher. This is so that the metal thin film formed on the back surface of the substrate does not adversely affect the crystal growth process on the substrate.

In particular, the melting point of the metal thin film is 1300 ° C.
It is preferable that it is above.

Preferably, the metal thin film is made of one selected from the group consisting of titanium, molybdenum, tungsten, tantalum, and niobium. This is because such a metal material is a high melting point metal, and using these metal thin films does not adversely affect the growth layer even in a crystal growth step on a substrate.

[0011] The present invention also provides a hexagonal single crystal substrate, a gallium nitride-based semiconductor layer laminated on one surface of the single crystal substrate, and an electrode formed on the semiconductor layer. , Wherein the single crystal substrate is provided with a metal nitride thin film on the other surface.

Further, the present invention provides the gallium nitride-based semiconductor layer including at least a first clad layer, an active layer, and a second clad layer sequentially formed on the single crystal substrate. The semiconductor device is also characterized in that a cleavage plane formed by cutting is used as a cavity end face of the laser diode. By providing the metal thin film on the back surface of the substrate, the semiconductor layer can be cut at the cleavage plane, and the cleavage plane can be used as a cavity end face of the laser diode. Therefore, it is not necessary to form the end face of the resonator by etching or the like as in the related art.

The metal nitride thin film is preferably made of one selected from the group consisting of titanium nitride, molybdenum nitride, tungsten nitride, tantalum nitride, and niobium nitride.

It is preferable that the metal nitride thin film does not thermally decompose at 1200 ° C. or lower.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 shows a method of manufacturing a semiconductor device according to a first embodiment of the present invention.
This will be described with reference to FIG. First, as shown in FIG.
The surface of the growth sapphire (0001) single crystal substrate 1 having a thickness of 100 μm on the side opposite to the side on which the semiconductor layer is grown (hereinafter referred to as “back side”) is formed by sputtering or the like.
The metal thin film 2 made of i, Ta, W, Mo, Nb,
It is formed in a thickness of about 0 to 500 nm.

Next, a gallium nitride-based compound semiconductor layer is grown on the surface of the sapphire substrate 1 by using a metal organic chemical vapor deposition (MOCVD) method. Hereinafter, the process will be specifically described. The sapphire substrate 1 having the metal thin film 2 formed on the back surface is placed on a susceptor in a reaction furnace, evacuated, and then heated to about 1100 ° C. in a hydrogen stream to clean the sapphire substrate surface.

Thereafter, the substrate temperature is raised to about 550 ° C., and ammonia (NH ₃ ) as a group V material is introduced into the reaction tube. After a certain period of time, trimethylgallium (TMG) as a group III material is added. The buffer layer 3 is supplied to grow the buffer layer 3. In this step, the metal thin film 2 formed on the back surface of the sapphire substrate 1 is nitrided immediately after the introduction of NH ₃ , and becomes a stable metal nitride thin film 4.

On the back surface of the sapphire substrate 1, a metal thin film 2 of Ti or the like
After the formation of about m, the sapphire substrate 1 may be heat-treated in an NH ₃ atmosphere, and crystal growth may be performed in advance using the sapphire substrate 1 in which the metal thin film 2 is the metal nitride thin film 4. Instead of heat treatment in an NH ₃ atmosphere, the metal thin film 2 may be irradiated with a nitrogen ion beam to nitride the metal thin film 2 to form a metal nitride thin film 4.

Next, the substrate temperature is raised to about 1100 ° C.
TMG, NH ₃ , SiH _{4 and the} like are supplied as a dopant, and the n-GaN layer 5 is grown to about 2 to 5 μm.

Next, trimethylaluminum (TMA) is added to the above-described gas, and Si-added n-type Al _x G
An a _1-x N (0 <x <1) layer is formed as the n-type cladding layer 6 with a thickness of about 0.1 to 0.5 μm.

Next, after the substrate temperature is raised to about 750 to 850 ° C., trimethylindium (TMI) is introduced instead of the above-mentioned TMA, and the band gap is reduced to the cladding layer 6.
It becomes smaller than such materials _{In y Ga ly N (0 ≦} y <
The active layer 7 of 1) is formed in a thickness of about 0.05 to 0.1 μm.

Next, the same source gas as that used for growing the n-type cladding layer 6 was used, and SiH was used as a dopant gas.
Instead of ₄ , a p-type dopant cyclopentadienyl magnesium (Cp ₂ Mg) is added to grow a p-Al _{x Gal x} N (0 <x <1) layer as the p-type cladding layer 8.

Next, in order to form the contact layer 9, T
A mixed gas of MG, NH ₃ and Cp ₂ Mg was introduced, and p-Ga
The N layer 9 is grown by about 0.3 to 1 μm.

Next, heat treatment is performed on the entire substrate in a nitrogen atmosphere at about 800 ° C. to activate Mg.

Next, in order to form an n-side electrode, patterning is performed using a photolithography technique.
A part of the grown semiconductor layer is removed by dry etching to expose a part of the n-GaN layer 5. Subsequently, a metal such as Au / Ni or Al / Ti is sequentially laminated at a predetermined position by a sputtering method or the like, and the p-side electrode 10 and the n-side electrode
Prepare No. 1.

Through the above steps, a plurality of light emitting diodes as shown in FIG. 2 are formed on the same substrate. continue,
According to the following steps, such a plurality of light emitting diodes,
Divide into each light emitting diode. That is, a scribe line is formed by cutting the substrate 1 from the back surface using a needle-shaped scriber along a separation pattern (not shown) formed on the substrate in the above process. The separation pattern is formed such that the scribe line is in the cleavage direction (direction of Equation 3) of the gallium nitride based semiconductor layer such as GaN formed on the sapphire substrate 1. Note that the cleavage direction of the gallium nitride-based semiconductor layer (the direction of Expression 3) corresponds to the direction of Expression 4 of the sapphire (0001) substrate 1.

In the present embodiment, since the metal nitride thin film 4 of about 50 to 500 nm is formed on the back surface of the sapphire substrate 1, the scribe lines are
The sapphire substrate 1 is formed such that the back surface thereof is cut out.

In this case, in the conventional scribing method in which the metal nitride thin film 4 is not formed, the sapphire substrate has a low cleavage property, so that the sapphire substrate 1 is formed along the scribe line.
In addition, the gallium nitride based semiconductor layer formed thereon has to be mechanically cut. For this reason, when cutting, an extra force is applied to the sapphire substrate 1 to cause chipping or chipping, and the cut surface has a shape having irregularities. On the other hand, in the present method in which the metal nitride thin film 4 is formed on the back surface, the force for breaking the sapphire substrate 1 is about 1/10 as compared with the conventional method in which the metal nitride thin film 4 is not formed. No force is applied to the sapphire substrate 1, and it is possible to suppress the occurrence of chipping and chipping. Further, the sapphire substrate 1 can be easily split in any direction of the sapphire substrate 1 as described above. Further, since the element structure has the metal nitride thin film 4 formed on the back surface of the sapphire substrate 1, the adhesiveness between the element and the die pad is improved, and die bonding can be easily performed.

It should be noted that a plurality of laser diodes can be formed on the sapphire substrate 1 by using substantially the same steps as the above steps instead of the light emitting diodes. When a laser diode is formed as described above, it is necessary to divide the gallium nitride-based semiconductor layer along a cleavage plane and to use the cleavage plane as a cavity end face in the step of dividing into laser diodes. However, since it is difficult to cut the sapphire substrate 1 by the conventional dividing method, it is difficult to cut the sapphire substrate 1 and simultaneously divide the semiconductor layer along the cleavage plane. On the other hand, in the method according to the present embodiment, the sapphire substrate 1 is moved in an arbitrary direction and with a force of about 1/10 of the conventional one.
Can be cut, a scribe line is formed on the sapphire substrate 1 along the cleavage direction of the gallium nitride based semiconductor layer (3 directions), and the sapphire substrate 1 is cut along the scribe line. Gallium nitride layer can be divided by the cleavage plane. Therefore, it becomes possible to use such a cleavage plane as a cavity end face of the laser diode.

Embodiment 2 FIG. A method for manufacturing a semiconductor device according to a second embodiment of the present invention will be described with reference to FIGS. First, a sapphire (0001) substrate 1 having a thickness of 300 μm is placed on a susceptor in a reaction furnace, evacuated, and then heated to about 1100 ° C. in a hydrogen stream to clean the surface of the sapphire substrate 1. Do.

Thereafter, the temperature of the substrate is lowered to about 550 ° C., and ammonia (NH ₃ ), which is a group V material, is introduced into the reaction tube. After a certain period of time, trimethylgallium (TMG), which is a group III material, is supplied. Then, the buffer layer 3 is grown.

Next, the substrate temperature is raised to about 1100 ° C.
TMG, NH ₃ , SiH _{4 and the} like are supplied as a dopant, and the n-GaN layer 5 is grown to about 2 to 5 μm.

Next, trimethylaluminum (TMA) is added to the above-mentioned gas, and n-Al _x Ga to which Si is added is added.
_{The lxN} (0 <x <1) layer is used as an n-type
Grow by about 1 to 0.5 μm.

Next, after lowering the substrate temperature to about 750 to 850 ° C., trimethylindium (TMI) is introduced instead of the above-described TMA, and the band gap is reduced to the cladding layer 6.
It becomes smaller than such materials _{In y Ga ly N (0 ≦} y <
The active layer 7 of 1) is grown to a thickness of about 0.05 to 0.1 μm.

Furthermore, the same raw material gas as the gas used for the growth of n-type cladding layer 6, as a dopant gas, SiH ₄
Instead of cyclopentadienyl magnesium (Cp ₂ M
g) and p-Al _{x Gal x} as the p-type cladding layer 8.
A N (0 <x <1) layer is grown.

Next, TMG, N
H ₃ and Cp ₂ Mg are introduced, and the p-GaN contact layer 9 is grown by about 0.3 to 1 μm. By the above steps, FIG.
Is formed.

Subsequently, after the sapphire substrate 1 is polished to a thickness of about 150 μm and thinned, a step of forming a metal nitride thin film 4 on the back surface of the sapphire substrate 1 is performed as shown in FIG. In this step, first, a metal thin film of Ti, Ta, W, Mo, Nb, or the like is formed on the back surface of the sapphire substrate 1 by a sputtering method or the like.
The entire substrate is treated in an NH ₃ atmosphere at a temperature of ° C., and the metal thin film is nitrided to form a metal nitride thin film 4. Thereafter, the reaction tube is evacuated once, and then heat treatment is performed in a nitrogen atmosphere at about 800 ° C. to activate Mg.

Next, after patterning using photolithography technology to form an n-side electrode, a part of the grown semiconductor layer is removed by dry etching to expose a part of the n-GaN layer 5. Let it. Then, Au /
A metal such as Ni or Al / Ti is formed by a sputtering method or the like, and a p-side electrode 9 and an n-side electrode 10 are formed, respectively. Through the above steps, a plurality of laser diodes are formed on the sapphire substrate 1 as shown in FIG.

Subsequently, the substrate 1 is cut out from the back surface using a needle-like scriber along a separation pattern (not shown) formed on the substrate in the same process as in the first embodiment. Form a scribe line. The separation pattern is formed such that the scribe line is in the cleavage direction (direction of Equation 3) of the gallium nitride based semiconductor layer such as GaN formed on the sapphire substrate 1. Note that the cleavage direction of the gallium nitride-based semiconductor layer (the direction of Expression 3) corresponds to the direction of Expression 4 of the sapphire (0001) substrate 1.

Also in this embodiment, about 50 to 500
Since the metal nitride thin film 4 of nm is formed on the back surface of the sapphire substrate 1, the scribe line is formed such that the back surface of the sapphire substrate 1 is cut off through the metal nitride thin film 4.

In the method according to the present embodiment, similarly to the first embodiment, the force for breaking down the sapphire substrate 1 is about 1/10 compared to the conventional method in which the metal nitride thin film 4 is not formed. And the extra force is applied to the sapphire substrate 1
Regardless, the occurrence of chipping and chipping can be suppressed. Further, the sapphire substrate 1 can be easily split in any direction of the sapphire substrate 1. Further, since the element structure has the metal nitride thin film 4 formed on the back surface of the sapphire substrate 1, the adhesiveness between the element and the die pad is improved, and the die bonding can be easily performed.

In the method according to the present embodiment, a plurality of laser diodes can be formed on the sapphire substrate 1 instead of the light emitting diodes by using substantially the same steps as those described above. . In this case, in the method according to the present embodiment, since the sapphire substrate 1 can be cut in an arbitrary direction and with a force of about 1/10 of the conventional one, the cleavage direction of the gallium nitride-based semiconductor layer (number 3 directions)
A scribe line is formed on the sapphire substrate 1 along the scribe line, and the sapphire substrate 1 is formed along the scribe line.
By cutting, the gallium nitride layer on the sapphire substrate 1 can be divided by the cleavage plane. Therefore, it becomes possible to use such a cleavage plane as a cavity end face of the laser diode.

In the first and second embodiments, Ga is used.
MOCVD for growing gallium nitride based semiconductor layers such as N layer 5
Although the method was used, other commonly used crystal growth methods can be used, and the materials are not limited to those described in the embodiment.

In the first and second embodiments, the device separation of the light emitting diode and the laser diode has been described.
These methods can be used for other light emitting and receiving devices,
The present invention can be applied to element isolation of electronic devices such as T, HBT, FET, and HFET.

[0045]

As is clear from the above description, by using the method according to the present invention, the force for breaking the hexagonal substrate such as sapphire in the dividing step of the semiconductor element is smaller than that of the conventional method. Only about 1/10 is required, and the occurrence of chipping and chipping can be suppressed. Thereby, the production yield of the semiconductor device can be improved.

Further, the sapphire substrate can be easily split in any direction of the sapphire substrate.

In particular, by dividing the sapphire substrate in the direction of cleavage of the gallium nitride based semiconductor layer formed on the sapphire substrate, the gallium nitride based semiconductor layer can be divided by the cleavage plane, and the cleavage plane is formed by the laser diode resonance. It can be used as a container end face.

Further, since the completed semiconductor device has a structure in which a metal nitride thin film is formed on the back surface of the sapphire substrate, the adhesiveness between the semiconductor device and the die pad is improved, and die bonding can be easily performed. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a substrate used in Embodiment 1 of the present invention.

FIG. 2 is a sectional view of a semiconductor device formed by the method according to the first embodiment of the present invention;

FIG. 3 is a process cross-sectional view of the method according to the second embodiment of the present invention;

FIG. 4 is a process cross-sectional view of the method according to the second embodiment of the present invention.

FIG. 5 is a sectional view of a semiconductor device formed by a method according to a second embodiment of the present invention;

[Explanation of symbols]

1 sapphire substrate, 2 metal thin film, 3 buffer layer,
4 Metal nitride thin film, 5n-GaN layer, 6n-AlGa
N clad layer, 7 InGaN active layer, 8p-AlGa
N clad layer, 9 p-GaN layer, 10 p-side electrode, 1
1 n-side electrode.

Claims (10)

[Claims] A gallium nitride-based semiconductor layer is grown on a hexagonal single-crystal substrate, and electrodes are formed on the semiconductor layer to form a plurality of semiconductor elements. A method of manufacturing a semiconductor device which is divided into elements, comprising: forming a metal thin film on a back surface of the single crystal substrate; nitriding the metal thin film to form a metal nitride thin film; A method for manufacturing a semiconductor device, comprising: forming a scribe line that reaches; and cutting the single crystal substrate and the semiconductor layer along the scribe line. 2. A semiconductor device according to claim 1, wherein said gallium nitride-based semiconductor layer formed on said substrate is in a cleavage direction of said semiconductor layer. 2. The method according to claim 1, wherein the scribe line is formed in a direction. 3. The method according to claim 1, wherein the sapphire (000)
1) Using a substrate, the following formula 2. The method according to claim 1, wherein the scribe line is formed in a direction. 4. The method according to claim 1, wherein the melting point of the metal thin film is 1200 ° C. or higher. 5. The method according to claim 1, wherein the melting point of the metal thin film is 1300 ° C. or higher. 6. The method according to claim 1, wherein the metal thin film is titanium, molybdenum,
2. The method for manufacturing a semiconductor device according to claim 1, comprising one selected from the group consisting of tungsten and tantalum. 7. A semiconductor device including at least a hexagonal single crystal substrate, a gallium nitride semiconductor layer laminated on one surface of the single crystal substrate, and an electrode formed on the semiconductor layer. A semiconductor device, comprising: a metal nitride thin film on the other surface of the single crystal substrate. 8. The gallium nitride-based semiconductor layer includes at least a first cladding layer, an active layer, and a second cladding layer sequentially formed on the single crystal substrate, and cutting the semiconductor layer. 8. The semiconductor device according to claim 7, wherein the formed cleavage plane is a cavity end face of the laser diode. 9. The semiconductor device according to claim 7, wherein said metal nitride thin film is made of one selected from the group consisting of titanium nitride, molybdenum nitride, tungsten nitride, and tantalum nitride. 10. The semiconductor device according to claim 9, wherein the metal nitride thin film does not thermally decompose at 1200 ° C. or less.