JP4356502B2 - Method of manufacturing nitride semiconductor device - Google Patents

Description

The present invention is used for nitride semiconductors (In _X Al _Y Ga _1-XY N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1) such as LED (light emitting diode) and LD (laser diode). The present invention relates to a method for manufacturing a GaN substrate.

  The present applicant has various light-emitting diodes (LEDs), such as blue, which are stacked on a nitride semiconductor substrate, and blue laser diodes that enable continuous oscillation over a long period of time at room temperature (LEDs). (LD) has been realized. Further, the use of nitride semiconductors is not limited to this, and use for other nitride semiconductor devices has been proposed, and extensive research has been conducted by various research institutions.

  Such a nitride semiconductor is generally manufactured by stacking various layers on a nitride semiconductor layer laminated on a heterogeneous substrate such as sapphire. ing. As a specific example of a light emitting device, after epitaxially growing a nitride semiconductor layer on a sapphire substrate, an n layer and a p layer are stacked, and electrodes corresponding to the respective layers are provided.

  As described above, the demand for the realization of a nitride semiconductor substrate that is lattice-matched with a nitride semiconductor is increasing, but GaN bulk crystal is taken as an example in spite of attempts by various research institutions. Only a few millimeters have been reported.

  JP-A-7-202265 discloses a method of manufacturing a nitride semiconductor substrate, in which a zinc oxide intermediate layer is formed on a sapphire substrate, a nitride semiconductor is laminated, and the intermediate layer is peeled off by wet etching. It is disclosed in the publication. However, a nitride semiconductor substrate with good crystallinity cannot be obtained with the nitride semiconductor layer obtained by this method.

  However, when the GaN single crystal sapphire substrate is thinned, stress is generated due to lattice mismatch between the sapphire substrate and GaN, and the substrate is warped, and a nitride semiconductor is formed on the substrate to form a good nitride semiconductor. There was a limit even when trying to obtain an element.

  Japanese Laid-Open Patent Publication No. 11-1399 discloses a method of forming GaN on an oxide substrate and then polishing from the sapphire substrate side to make only GaN. In this method, GaN is grown on an oxide substrate, primary GaN having a certain thickness is formed by HVPE, and the nitride semiconductor substrate on which the primary GaN layer is grown is polished to obtain an oxide substrate. On the primary and secondary GaN layers from which the nitride semiconductor substrate has been completely removed, by growing a secondary GaN layer on the primary GaN layer and polishing and removing it again. A GaN layer having a predetermined thickness is again grown to grow a GaN single crystal, and finally the GaN single crystal is polished to obtain a GaN substrate.

  However, the GaN substrate obtained by this method has many defects, and even if a nitride semiconductor is produced using this substrate, an element having good characteristics cannot be obtained, and a nitride semiconductor laser element having a complicated layer structure has been obtained. Did not even oscillate.

  The present invention has been made in view of the above circumstances, and in a GaN substrate that is a nitride semiconductor element formed by laminating a nitride semiconductor on a GaN substrate, GaN having very few crystal defects with reduced warpage occurring during fabrication. An object of the present invention is to provide a method for manufacturing a substrate, and to obtain a nitride semiconductor device having good device characteristics with a high yield.

  As a result of studying the GaN substrate to achieve the above-mentioned object, the present inventor has warped if the sapphire substrate is formed from a thick film and then polished from the sapphire substrate side to make only GaN. Further, by stacking GaN with a thick film on this GaN substrate, the strain stress caused by lattice mismatch between sapphire and GaN was alleviated, and a good GaN substrate with reduced warpage was successfully obtained.

  Furthermore, since the GaN substrate obtained by the manufacturing method of the present invention is fabricated using laterally grown GaN, a GaN substrate with very few crystal defects can be obtained as a relatively thick film, and resonance can be achieved by cleaving GaN. Since the surface can be produced, it is particularly useful for producing a nitride semiconductor laser device having a complicated layer structure.

That is, the present invention
A method of manufacturing a nitride semiconductor device having a nitride semiconductor stacked on a nitride semiconductor substrate,
The nitride semiconductor different foreign substrate, the first nitride semiconductor is lateral growth, a first crystal growth step Ru second nitride semiconductor is grown with a thickness of 400μm or more 10μm thereon,
Removing the dissimilar substrate to make the nitride semiconductor a warped nitride semiconductor substrate; and
A second crystal growth step of growing a third nitride semiconductor on the nitride semiconductor substrate at a thickness of 10 μm to 800 μm ;
In the state having the nitride semiconductor grown in the first crystal growth step and the nitride semiconductor grown in the second crystal growth step, the side of the nitride semiconductor substrate from which the dissimilar substrate is removed is polished. Removing the laterally grown nitride semiconductor crystal, and reducing the thickness of the nitride semiconductor substrate to reduce the thickness of the nitride semiconductor substrate;
It is characterized by comprising.
The manufacturing method of the nitride semiconductor device of the present invention can combine the following. In the substrate thinning step, the polished nitride semiconductor substrate has a warp. The substrate removing step includes a first substrate polishing step of removing the dissimilar substrate and then polishing the dissimilar substrate side of the nitride semiconductor substrate to reduce the thickness of the nitride semiconductor substrate. After the substrate polishing step, a cleaving step of cleaving the nitride semiconductor substrate is provided on the polishing surface side of the nitride semiconductor substrate having a nitride semiconductor element. The nitride semiconductor element is a laser element, and the laser element has a resonance surface formed by cleavage in the cleavage step. After the substrate polishing step, the method includes a step of forming an electrode on the polishing surface side of the nitride semiconductor substrate having the nitride semiconductor element. In the first crystal growth step, irregularities are formed in the first layer made of GaN, and a nitride semiconductor is grown on the first layer.
Moreover, the other aspect of this invention is shown below.
A method of manufacturing a GaN substrate, which is a nitride semiconductor element obtained by laminating a nitride semiconductor on a GaN substrate,
A first step of growing a first nitride semiconductor layer containing GaN by lateral growth on a different substrate different from the nitride semiconductor;
A second step of growing a second nitride semiconductor thereon;
After the second step, a third step of removing at least the dissimilar substrate;
And a fourth step of growing a third nitride semiconductor on the second nitride semiconductor after the third step.

  The first step is a step of growing GaN on a heterogeneous substrate, forming irregularities on the GaN surface, and growing GaN substantially laterally from at least the concave portion to the convex surface. And

  After the fourth step, there is a fifth step of removing a part or all of the second nitride semiconductor or a part of the third nitride semiconductor from the side where the heterogeneous substrate is removed. To do.

  The thickness of the second nitride semiconductor layer is adjusted to 10 μm or more and 400 μm or less, and the thickness of the third nitride semiconductor layer is adjusted to 100 μm or more and 400 μm or less. .

  Further, the first step is characterized in that a nitride semiconductor is grown by MOVPE, and the second and fourth steps are grown by HVPE.

  After the fifth step, the GaN substrate is polished to a thickness of 100 μm to 300 μm, and a device structure is fabricated thereon. This is because, by setting the total film thickness of the GaN substrate having a structure of three or more layers within this range, the characteristics of the nitride semiconductor element obtained by stacking the nitride semiconductor thereon are improved.

  The dissimilar substrate different from the nitride semiconductor is a sapphire substrate that is off-angled with respect to the C plane.

  The second nitride semiconductor layer and / or the third nitride semiconductor layer is doped with Si or Sn.

  As described above, in the conventional method of obtaining the GaN substrate, stress is generated due to lattice mismatch between the dissimilar substrate and GaN, and the substrate is greatly warped. However, according to the method of the present invention, from the dissimilar substrate side. When polishing and making only GaN, warping will occur, but by laminating GaN with a thick film on this GaN substrate, the strain stress generated due to lattice mismatch between the dissimilar substrate and GaN is relaxed, Warpage is reduced and a good GaN substrate can be obtained.

  Furthermore, since the GaN substrate obtained by the manufacturing method of the present invention is produced by using epitaxially grown GaN, a GaN substrate with very few crystal defects can be obtained as a relatively thick film, and in particular, nitriding with a complicated layer structure. This is useful for manufacturing a semiconductor laser device.

  Hereinafter, the present invention will be described in detail. FIGS. 1-6 is a schematic diagram which shows the specific example of the manufacturing method of this invention.

  As a first step, as shown in FIG. 1, a nitride semiconductor underlayer is grown on a heterogeneous substrate 1 different from a nitride semiconductor such as a sapphire substrate by MOVPE, and this is referred to as a first layer. A nitride semiconductor is formed by epitaxial growth. Epitaxial growth refers to growth of a single crystal with few crystal defects. In particular, in a nitride semiconductor, crystal growth does not grow in the thickness direction by selective growth (lateral growth) in a direction transverse to the thickness direction. It is known that a good epitaxial growth layer can be obtained.

  Specifically, as a method of selectively growing in the lateral direction (lateral growth), a first layer made of GaN is formed, and the first layer is partially uneven (2a). A surface capable of lateral growth of the semiconductor is exposed, and a nitride semiconductor is grown thereon (2b).

As another lateral growth method, a mask such as SiO ₂ is partially formed on a nitride semiconductor layer made of GaN (for example, in a stripe shape), and a nitride semiconductor is grown thereon. Both methods allow lateral growth of nitride semiconductors, and both can provide an epitaxially grown layer with very few crystal defects, but the mask material such as SiO ₂ can be used at a temperature at which the nitride semiconductor is obtained as a good single crystal, for example, Since there is a risk of decomposition at a temperature of 1000 ° C. or higher, and also causes abnormal growth of the nitride semiconductor, it is preferable to perform lateral growth by a method of forming irregularities.

In addition, the heterogeneous substrate 1 different from the nitride semiconductor includes an insulating substrate such as spinel (MgAl ₂ O ₄ ), SiC (including 6H, 4H, and 3C) in addition to sapphire including C-plane, R-plane, and A-plane. A substrate material different from a conventionally known nitride semiconductor such as ZnS, ZnO, GaAs, or Si can be used.

  In addition, it is desirable that a different substrate 1 different from the nitride semiconductor used in the present invention is a step-off substrate (inclined). When using a sapphire substrate, the off-angle is perpendicular to the sapphire A plane (parallel to the M-axis direction of sapphire), and the off-angle of the off-angle is in the range of 0.1 ° to 0.3 °. A nitride semiconductor device can be obtained.

  When the off-angle is in the range of 0.1 ° to 0.3 °, the surface forms of the second nitride semiconductor and the third nitride semiconductor stacked by the HVPE method are stripes parallel to the steps of the different substrates. Become. The step on the surface of the nitride semiconductor (the direction along the step) is the same as the waveguide direction when the laser element is manufactured, and it is best that there is no stepped step in the waveguide structure. More preferably, the angle is 0.15 ° to 0.25 °.

  When sapphire having an off-angle smaller than 0.1 ° or not off-angle is used, the surface forms of the second nitride semiconductor layer and the third nitride semiconductor layer are hexagonal pyramids (or similar to hexagonal pyramids). The hexagonal pattern is also reflected on the surface of the nitride semiconductor fabricated thereon, resulting in poor device characteristics. In addition, when sapphire with an off angle larger than 0.3 ° is used, the surface becomes rough, and the deviation of sapphire from the C-plane increases, making epitaxial growth difficult.

The first step of lateral growth of the present invention may be repeated twice or more.
By repeating the process, the number of crystal defects in the nitride semiconductor layer formed thereon can be further reduced. When the lateral growth is repeatedly formed, the concave and convex portions are formed on the convex portion and the convex portion on the concave portion with respect to the concave and convex portions at the time of the lateral growth performed before that.

  Next, as a second step, as shown in FIG. 2, a second nitride semiconductor 3 is grown on the epitaxially grown first nitride semiconductor layer 2 using the HVPE method. The nitride semiconductor formed by the HVPE method is preferably formed as a thick film and is 400 μm or less including the base layer. When grown to a thickness of more than 400 μm, warpage caused by lattice mismatch with a different substrate or a difference in thermal expansion coefficient becomes too large, which causes inconvenience when stacking nitride semiconductors that form an element structure. This is caused by lattice mismatch or thermal expansion coefficient difference between the nitride semiconductor and the dissimilar substrate, and initially due to lattice mismatch or thermal expansion coefficient difference because the dissimilar substrate has a larger film thickness. The stress depends on the dissimilar substrate 1, and the nitride semiconductor is in a state of receiving a strain stress. However, when the nitride semiconductor becomes larger than 400 μm, since the stress gradually depends on the nitride semiconductor, the strain stress applied to the nitride semiconductor starts to be relieved. Will receive a large warp there.

  Further, the following effects can be obtained by performing the second step. When the first nitride semiconductor layer 2 is grown by lateral growth in the first step, the number of crystal defects on the surface of the first nitride semiconductor layer is not uniform. When the layer 3 is grown, crystal defects are diffused in the second nitride semiconductor, become substantially uniform on the surface of the second nitride semiconductor layer, and the nitride semiconductor grown thereon grows as a uniform layer. Can do.

  Further, when the second nitride semiconductor layer 3 is grown, it is desirable to dope an Si or Sn n-type impurity. This is to improve the ohmic property with the n-electrode. When an element structure is formed on the GaN substrate in the order of the n layer, the active layer, and the p-layer, the p-electrode is formed on the p-layer side. When the n electrode is formed on the opposite n layer side, that is, on the GaN substrate, doping with Si or Sn improves the ohmic property.

The n-type impurity of Si or Sn is preferably doped in the range of 5 × 10 ¹⁶ / cm ^{3 to} 5 × 10 ²¹ / cm ³ . When the amount is less than 5 × 10 ¹⁶ / cm ³ , ohmic properties are deteriorated. When the amount is more than 5 × 10 ²¹ / cm ³ , the crystallinity is deteriorated due to a large impurity concentration, and crystal defects tend to increase. is there. A preferable range is 1 × 10 ¹⁷ / cm ³ to 1 × 10 ²⁰ / cm ³ .

Next, as a third step, as shown in FIG. 3, after forming up to the second nitride semiconductor 3, polishing is performed from the exposed surface side of the heterogeneous substrate 1, and at least the heterogeneous substrate is removed. When the epitaxial growth layer is formed using a mask material such as SiO _{2, the} layer removed by polishing is desirably removed up to the mask material. When this heterogeneous substrate 1 is removed by polishing, the stress dependent on the heterogeneous substrate becomes dependent on the nitride semiconductor, as described above, and as a result, all the heterogeneous substrate 1 is removed. A nitride semiconductor in a greatly warped state is obtained in stages.

  Next, as shown in FIG. 4, a third nitride semiconductor 4 is grown by using the HVPE method as a fourth step of the nitride semiconductor having large warpage. A GaN substrate with reduced warpage can be obtained by forming the third nitride semiconductor 4 by HVPE as a thick film. This is because the second nitride semiconductor 3 that has been subjected to strain stress due to lattice mismatch with the heterogeneous substrate 1 is further laminated with the nitride semiconductor stacked in a state where the heterogeneous substrate is removed, so that the strain stress is gradually removed. It seems that warpage has been reduced. The third nitride semiconductor is formed with a thickness of 10 μm to 800 μm, preferably with a thickness of 200 μm to 500 μm.

Next, preferably, as a fifth step, as shown in FIG. 5, a part or all of the second nitride semiconductor 3 or the third nitride is obtained from the side of the obtained GaN substrate from which the heterogeneous substrate 1 is removed. A part of the semiconductor 4 is removed. This is because the first nitride semiconductor 2 includes a mask of SiO ₂ or the like in order to obtain lateral growth, or a nitride semiconductor is formed on an uneven surface, and strain stress is difficult to be removed. Therefore, it is desirable to remove part or all of the first nitride semiconductor layer and the second nitride semiconductor layer by polishing. By this polishing, the final film thickness of the GaN substrate is 50 μm to 500 μm, preferably 100 μm to 300 μm.

When the GaN substrate 4 ′ manufactured as described above is used, when a nitride semiconductor device is manufactured by forming an n-type nitride semiconductor, an active layer, and a p-type nitride semiconductor on the GaN substrate, warpage is small, In addition, since there are few defects, a nitride semiconductor device with good yield and excellent luminous efficiency can be obtained.
[Example 1]
As a heterogeneous substrate 1, a sapphire substrate 1 having a 2 inch φ, C-plane as the main surface and an orientation flat surface as the A-plane is set in the MOVPE reaction vessel, the temperature is set to 510 ° C., the carrier gas is hydrogen, the source gas is A buffer layer (not shown) made of GaN is grown on the sapphire substrate 1 to a thickness of about 200 Å using ammonia and TMG (trimethylgallium).

  After growing the buffer layer, only TMG is stopped and the temperature is raised to 1050 ° C. When the temperature reaches 1050 ° C., the nitride semiconductor layer 2 made of GaN is further grown to a thickness of 2.5 μm using TMG.

After the nitride semiconductor layer 2 is grown, a striped photomask is formed, and is patterned with a CVD apparatus to a stripe width (a portion that becomes the top of the convex portion) of 2 μm and a stripe interval (a portion that becomes the bottom of the concave portion) of 10 μm. ₂ films are formed, and then the RIE apparatus is used to etch the first nitride semiconductor layer 2 where the SiO ₂ film is not formed halfway to the extent that the first nitride semiconductor 2 remains, thereby forming irregularities. Thus, the first nitride semiconductor 2 is exposed on the side surface of the recess (2a in FIG. 1). After forming the unevenness as shown in FIG. 1, the SiO ₂ on the upper portion of the convex portion is removed. The stripe direction is formed in a direction perpendicular to the orientation flat surface (M-axis direction of GaN) as shown in FIG.

  Next, it is set in a MOVPE reaction vessel, a temperature is set to 1050 ° C., TMG and ammonia are used as source gases, and a nitride semiconductor layer 2b made of undoped GaN is grown to a thickness of 15 μm. The nitride semiconductor layer 2 is used.

After the growth of the first nitride semiconductor layer 2, the wafer was subsequently transferred to an HVPE apparatus, the temperature was 1050 ° C., gallium chloride, ammonia, and silane gas were used as source gases, and Si was doped at 1 × 10 ¹⁸ / cm ³ . A second nitride semiconductor layer 3 made of GaN is grown to a thickness of 250 μm.

At this time, when the number of crystal defects is observed with a cross-sectional TEM (transmission electron microscope), the crystal defect density on the surface of the first nitride semiconductor layer 2 is 10 ¹⁰ pieces / cm on the convex portion and 10 ⁴ on the concave portion. The number of particles / cm ² or less was approximately uniform on the surface of the second nitride semiconductor layer 3 and was 10 ⁶ / cm ² .

  Subsequently, the wafer is taken out of the reaction vessel and polished from the sapphire substrate side until the sapphire substrate 1 is completely removed and the underlying GaN is exposed. When the sapphire substrate is completely removed, the wafer is greatly warped.

Next, the wafer from which the sapphire substrate has been removed is transferred again to the HVPE apparatus, and is similarly made of GaN doped with Si at 1 × 10 ¹⁸ / cm ³ using gallium chloride, ammonia, silane gas as source gases at 1050 ° C. The third nitride semiconductor layer 4 is grown to a thickness of 300 μm. The warp is reduced by growing the third nitride semiconductor layer.

  After the third nitride semiconductor layer 4 is grown, the wafer is taken out from the reaction vessel, and the first nitride semiconductor layer 2 and a part of the second nitride semiconductor layer 3 are removed from the sapphire substrate side removed earlier. Polishing is finally performed to obtain a GaN substrate 4 ′ having a total film thickness of 250 μm.

  Since the obtained GaN substrate 4 ′ had a small warp and few defects, a nitride semiconductor device formed on the GaN had a good yield and an excellent luminous efficiency.

[Example 2]
A GaN substrate 4 ′ is produced in the same manner as in Example 1. On the obtained GaN substrate, as shown in FIG. 7, a crack prevention layer made of InGaN (this can be omitted), an n-side cladding layer 6 made of a superlattice of AlGaN and Si-doped GaN, made of GaN An n-side light guide layer 7, an active layer 8 having a multiple quantum well structure (MQW) made of InGaN, a p-side cap layer 9 made of Mg-doped AlGaN, a p-side light guide layer 10 made of Mg-doped GaN, AlGaN and Mg A p-side cladding layer 11 made of a superlattice with doped GaN and a p-side contact layer 12 made of Mg-doped GaN are sequentially stacked.

After the lamination, the p-side contact layer 12 and the p-side cladding layer 11 are etched to form a ridge-shaped surface, an insulating film 31 such as ZrO ₂ and the p ohmic electrode 20 are formed on the ridge, and finally the p pad electrode 21 The n-ohmic electrode 22 and the n-pad electrode 23 are formed on the GaN substrate side opposite to the p-electrode, and finally, a resonance surface is formed by cleaving GaN to form a chip.

A nitride semiconductor laser device was obtained as described above, and this was placed on the heat sink face-up (in a state where the substrate and the heat sink faced each other). Each electrode was wire-bonded, and continuous oscillation was attempted at room temperature. However, continuous oscillation was confirmed at a threshold current density of ² kA / cm ² and an output of 20 mW, indicating a lifetime of 2000 hours or more.

[Example 3]
In the same manner as in Example 2, on the GaN substrate obtained in Example 1, as shown in FIG. 8, an n-side contact layer 5 made of AlGaN as an element structure, a crack prevention layer (can be omitted), and an n-side cladding layer 6 The n-side light guide layer 7, the active layer 8, the p-side cap layer 9, the p-side light guide layer 10, the p-side cladding layer 11, and the p-side contact layer 12 are laminated.

Next, a part of the p-side contact layer 12 is etched to expose the n-side contact layer 5. Further, the p-side layer is dry-etched to the p-side cladding layer 11 by RIE to form a ridge, an insulating film 31 such as ZrO ₂ as a protective film on the ridge, and a p-ohmic electrode 20 and a p-pad electrode on each contact layer 21. An n-ohmic electrode 22 and an n-pad electrode 23 are formed. Finally, a resonant surface is formed by cleaving GaN to form a chip.

A nitride semiconductor laser device was obtained as described above, and this was placed on the heat sink face-up (in a state where the substrate and the heat sink faced each other). Each electrode was wire-bonded, and continuous oscillation was attempted at room temperature. However, continuous oscillation was confirmed at a threshold current density of ² kA / cm ² and an output of 20 mW, indicating a lifetime of 1000 hours or more.

[Example 4]
As a heterogeneous substrate 1, a sapphire substrate 1 having a 2 inch φ, C-plane as the main surface and an orientation flat surface as the A-plane is set in the MOVPE reaction vessel, the temperature is set to 510 ° C., the carrier gas is hydrogen, the source gas is A buffer layer (not shown) made of GaN is grown on the sapphire substrate 1 to a thickness of about 200 Å using ammonia and TMG (trimethylgallium).

  After growing the buffer layer, only TMG is stopped and the temperature is raised to 1050 ° C. When the temperature reaches 1050 ° C., a nitride semiconductor layer 2a made of GaN is grown to a thickness of 2.5 μm using TMG.

After growing the nitride semiconductor layer 2a, a striped photomask is formed, and a protective film 30 made of SiO _{2 having a} stripe width of 10 μm and a window portion of 2 μm is formed to a thickness of 0.5 μm by a CVD apparatus. The stripe direction is formed in a direction perpendicular to the orientation flat surface.

  After the protective film 30 is formed, the wafer is transferred to a MOVPE reaction vessel, and at 1050 ° C., TMG and ammonia are used as source gases, and a nitride semiconductor layer 2b made of undoped GaN is grown to a thickness of 15 μm. 1 nitride semiconductor layer 2.

After the growth of the first nitride semiconductor layer 2, the wafer was subsequently transferred to an HVPE apparatus, the temperature was 1050 ° C., gallium chloride, ammonia, and silane gas were used as source gases, and Si was doped at 1 × 10 ¹⁸ / cm ³ . A second nitride semiconductor layer 3 made of GaN is grown to a thickness of 250 μm (FIG. 6).

At this time, when the number of crystal defects is observed with a cross-sectional TEM (transmission electron microscope), the crystal defect density on the surface of the first nitride semiconductor layer is 10 ⁴ / cm ² on the convex portion and 10 ¹⁰ on the concave portion. The number of pieces / cm ² or less was almost uniform on the second nitride semiconductor layer, which was 10 ⁶ pieces / cm ² .

Subsequently, the wafer is taken out from the reaction container, and the part of the first nitride semiconductor layer 2 is polished from the sapphire substrate side to completely remove the sapphire substrate and SiO ₂ of the protective film. When all of the sapphire and SiO ₂ are removed, the wafer is greatly warped.

Next, the wafer from which the sapphire substrate 1 has been removed is transferred again to the HVPE apparatus. Similarly, the temperature is 1050 ° C., gallium chloride TMG, ammonia, silane gas is used as the source gas, and GaN doped with Si at 1 × 10 ¹⁸ / cm ³ is used. A third nitride semiconductor layer is grown to a thickness of 300 μm. The warpage is reduced by growing the third nitride semiconductor layer 4.

  After the third nitride semiconductor layer 4 is grown, the wafer is taken out of the reaction vessel, and the remaining first nitride semiconductor layer 2 and a part of the second nitride semiconductor layer 3 are removed from the sapphire substrate side removed earlier. The final GaN substrate 4 ′ having a total film thickness of 250 μm is obtained.

  Since the obtained GaN substrate 4 ′ has a small warp and few defects, a nitride semiconductor device formed on the GaN has a good yield and an excellent luminous efficiency.

[Example 5]
A GaN substrate 4 ′ was obtained in the same manner as in Example 1, except that the third nitride semiconductor 4 was undoped GaN.

  On the GaN substrate 4 ′, as shown in FIG. 7, a crack prevention layer made of InGaN (this can be omitted), an n-side cladding layer 6 made of a superlattice of AlGaN and Si-doped GaN, and from GaN An n-side optical guide layer 7, an active layer 8 having a multiple quantum well structure (MQW) made of InGaN, a p-side cap layer 9 made of Mg-doped AlGaN, a p-side light guide layer 10 made of Mg-doped GaN, AlGaN A p-side cladding layer 11 made of a superlattice with Mg-doped GaN and a p-side contact layer 12 made of Mg-doped GaN are sequentially stacked.

After the lamination, the p-side contact layer and the p-side cladding layer are etched to form a ridge shape, and an insulating film 31 such as ZrO ₂ and a p ohmic electrode 20 are formed on the ridge, and finally the p pad electrode 21 is formed. Further, an n ohmic electrode 22 and an n pad electrode 23 are formed on the side of the GaN substrate opposite to the p electrode, and finally a resonance surface is formed by cleaving GaN to form a chip.

A nitride semiconductor laser device was obtained as described above, and this was placed on the heat sink face-up (in a state where the substrate and the heat sink faced each other). Each electrode was wire-bonded, and continuous oscillation was attempted at room temperature. However, continuous oscillation was confirmed at a threshold current density of ² kA / cm ² and an output of 20 mW, indicating a lifetime of 1000 hours or more.

[Example 6]
In the sapphire substrate 1 having a 2 inch φ, C-plane as the main surface and the orientation flat surface as the A-plane as the heterogeneous substrate 1, it is further over-stepped, its off-angle is 0.13 °, and the direction along the step (step) A nitride semiconductor laser device was obtained in the same manner as in Example 2 except that a substrate whose direction was perpendicular to the A plane was used, and when continuous oscillation was attempted at room temperature, the threshold current density was ² kA / cm ² and 20 mW. In the output, continuous oscillation was confirmed, indicating a lifetime of 3000 hours or more.

[Example 7]
A GaN substrate 4 ′ is produced in the same manner as in Example 1. An n-side contact layer 5 made of AlGaN, a crack prevention layer made of InGaN (this can be omitted), an n-side cladding layer 6 made of a superlattice of AlGaN and Si-doped GaN on the obtained GaN substrate, Multiple quantum well structure (MQW) active layer 8 made of InGaN, p-side cap layer 9 made of Mg-doped AlGaN, p-side cladding layer 11 made of a superlattice of AlGaN and Mg-doped GaN, and Mg-doped GaN The p-side contact layer 12 is sequentially laminated.

  After the lamination, a p-ohmic electrode (transparent electrode) 20 and a p-pad electrode 21 are formed on the p-side contact layer 12, and an n-ohmic electrode 22 and an n-pad electrode 23 are formed on the GaN substrate side opposite to the p-electrode. Finally, a chip is formed by cleaving GaN.

  The LED element obtained as described above emitted blue light with a forward voltage of 3.4 V and 465 nm at a forward current of 20 mA, and the light emission output was 9 mW.

  The schematic cross section which shows the structure of the GaN substrate explaining the 1st process of this invention.   The schematic cross section which shows the structure of the GaN substrate explaining the 2nd process of this invention.   The schematic cross section which shows the structure of the GaN substrate explaining the 3rd process of this invention.   The schematic cross section which shows the structure of the GaN substrate explaining the 4th process of this invention.   The schematic cross section which shows the structure of the GaN substrate explaining the 5th process of this invention.   FIG. 6 is a schematic cross-sectional view showing the structure of a laser device using a GaN substrate for explaining another embodiment of the present invention.   The schematic cross section which shows the structure of the laser element using the GaN substrate obtained by the Example of this invention.   The schematic cross section which shows the structure of the laser element using the GaN substrate obtained by the other Example of this invention.   The schematic cross section which shows the structure of the laser element using the GaN substrate obtained by the other Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Dissimilar substrate 2 ... 1st nitride semiconductor layer 3 ... 2nd nitride semiconductor layer 4 ... 3rd nitride semiconductor layer 4 '... GaN substrate 5 ... n-side contact layer 6 ... n-side cladding layer 7 ... n-side light guide layer 8 ... active layer 9 ... p-side cap layer 10 ... p-side light guide layer 11 ... p-side Cladding layer 12 ... p-side contact layer 20 ... p ohmic electrode 21 ... p pad electrode 22 ... n ohmic electrode 23 ... n pad electrode 30 ... SiO ₂
31 ... Insulating film

Claims (7)

A method of manufacturing a nitride semiconductor device having a nitride semiconductor stacked on a nitride semiconductor substrate,
The nitride semiconductor different foreign substrate, the first nitride semiconductor is lateral growth, a first crystal growth step Ru second nitride semiconductor is grown with a thickness of 400μm or more 10μm thereon,
Removing the dissimilar substrate to make the nitride semiconductor a warped nitride semiconductor substrate; and
A second crystal growth step of growing a third nitride semiconductor on the nitride semiconductor substrate at a thickness of 10 μm to 800 μm ;
In the state having the nitride semiconductor grown in the first crystal growth step and the nitride semiconductor grown in the second crystal growth step, the side of the nitride semiconductor substrate from which the dissimilar substrate is removed is polished. Removing the laterally grown nitride semiconductor crystal, and reducing the thickness of the nitride semiconductor substrate to reduce the thickness of the nitride semiconductor substrate;
A method for producing a nitride semiconductor device comprising:   The method for manufacturing a nitride semiconductor device according to claim 1, wherein in the substrate thinning step, the polished nitride semiconductor substrate has a warp. 3. The nitride semiconductor device according to claim 1, further comprising a first substrate polishing step of removing at least a part of the second nitride semiconductor from a side where the different substrate is removed in the substrate removing step. Production method.   The nitride according to any one of claims 1 to 3, further comprising a cleavage step of cleaving the nitride semiconductor substrate on a polishing surface side of the nitride semiconductor substrate having a nitride semiconductor element after the substrate polishing step. A method for manufacturing a semiconductor device.   The method for manufacturing a nitride semiconductor device according to claim 4, wherein the nitride semiconductor device is a laser device, and the laser device has a resonance surface formed by cleavage in the cleavage step.   6. The method for manufacturing a nitride semiconductor device according to claim 1, further comprising a step of forming an electrode on a polishing surface side of a nitride semiconductor substrate having a nitride semiconductor device after the substrate polishing step. .   The nitriding according to any one of claims 1 to 6, wherein in the first crystal growth step, irregularities are formed in the first layer made of GaN, and a nitride semiconductor is grown on the first layer. Method for manufacturing a semiconductor device.

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