JP2000357663A - Method of manufacturing iii nitride base compound semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a large-area III nitride base compound semiconductor substrate with a satisfactory yield and satisfactory reproducibility. SOLUTION: First, a first semiconductor film 13 that is formed of a first III nitride based compound semiconductor having a stepped portion 13c is formed on a substrate 11 (Fig. b). Thereafter, a second semiconductor film 14a composed of a second III nitride based compound semiconductor having a thermal expansion coefficient that is different from that of the first III nitride based compound semiconductor is formed (Fig. c). Thereafter, the substrate 11 is cooled, and the second semiconductor film 14a is isolated from the first semiconductor film 13 to obtain the III nitride based compound semiconductor substrate 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a group III nitride compound semiconductor substrate.

[0002]

2. Description of the Related Art The general formula is Al _X Ga _{1 -XY} In _Y N (where 0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, 0 ≦ X + Y ≦ 1).
The group III nitride compound semiconductor represented by the formula (1) can change the band gap energy in a wide range of 1.9 eV to 6.2 eV. For this reason, group III nitride-based compound semiconductors are promising as semiconductor materials for light-emitting and light-receiving devices that cover the visible region to the ultraviolet region.

As a substrate for fabricating a group III nitride compound semiconductor device, a large-area, high-quality group III nitride compound semiconductor substrate is required. On the other hand, a method of manufacturing a group III nitride-based compound semiconductor substrate has been reported (for example, Japanese Journal of Applied Physics, Vol. 37 (19)).
1998) L309 page-L312 page, Japan
ese Journal of Applied Ph
ysics Vol. 37 (1998) pp. L309-
L312). Hereinafter, this conventional manufacturing method will be described with reference to FIG.

[0004] In the above-mentioned conventional manufacturing method, first, a diameter of 5.
An 08 cm (2 inch) sapphire substrate 1 is placed in a metal organic vapor phase epitaxy apparatus (hereinafter sometimes referred to as a MOVPE apparatus). Then, on the sapphire substrate 1, M
The GaN buffer layer 2 and the GaN layer 3 are formed by the OVPE method.
Are sequentially formed (FIG. 8A). Hereinafter, the sapphire substrate 1 on which any layer is formed may be referred to as a wafer.

Next, the wafer is taken out of the MOVPE apparatus. Then, an SiO ₂ film 4 is formed on the surface of the GaN layer 3, and stripe-shaped windows 4 a are formed on the SiO ₂ film 4 at a pitch of several μm (FIG. 8B).

Thereafter, the wafer is placed in a hydride vapor phase epitaxy (hereinafter sometimes referred to as HVPE) apparatus, and a GaN thick film 5 a (about 100 nm thick) is formed on the SiO ₂ film 4.
μm) (FIG. 8C).

After that, the wafer is taken out of the HVPE apparatus. Finally, the wafer is polished from the sapphire substrate 1 side to the GaN thick film 5a, so that the
A GaN substrate 5 of about μm is obtained (FIG. 8D).

[0008]

However, the above-mentioned conventional method has the following problems.

In the above method, the sapphire substrate 1 and the GaN
Since the lattice constant and the thermal expansion coefficient of the GaN thick film 5a differ from those of the thick film 5a, the sapphire substrate 1 and the GaN thick film 5
a is applied to the substrate. Therefore, in the above method, the wafer is warped, cracks are generated in a direction perpendicular to the main surface of the GaN thick film 5a, or the GaN thick film 5a is partially peeled. As a result, the size of the GaN substrate 5 obtained by the conventional method is at most about 1 cm square, and it is difficult to obtain a GaN substrate 5 having a large area equivalent to that of the sapphire substrate 1 with good yield and good reproducibility. Was. In particular, in the above-mentioned conventional method, stress is concentrated between the sapphire substrate 1-GaN buffer layer 2-GaN layer 3, and these are in close contact with each other over the entire main surface, so that cracks are formed randomly. There was a problem.

In order to solve the above problems, the present invention provides a large area group III nitride compound semiconductor substrate with a high yield,
It is another object of the present invention to provide a method of manufacturing a group III nitride compound semiconductor substrate that can be manufactured with good reproducibility.

[0011]

In order to achieve the above object, a method of manufacturing a group III nitride compound semiconductor substrate according to the present invention comprises the steps of (a) forming a first group III nitride compound semiconductor on a substrate; Forming a first semiconductor film having a step, and (b) forming a second II having a different thermal expansion coefficient on the first semiconductor film from that of the first group III nitride compound semiconductor.
A step of forming a second semiconductor film made of a group I nitride-based compound semiconductor; and (c) a step of cooling the substrate and separating the second semiconductor film from the first semiconductor film. I do. In the manufacturing method of the present invention, when the substrate is cooled in the step (c), the direction from the step portion of the first semiconductor film to the direction parallel to the main surface of the second semiconductor film in the second semiconductor film. Cracks occur in For this reason, according to the manufacturing method of the present invention, a large-area group III nitride-based compound semiconductor substrate can be manufactured with high yield and good reproducibility. a-1)
Forming a film made of a first group III nitride compound semiconductor on a substrate; and (a-2) forming a first semiconductor film having a plurality of grooves by removing a part of the film. And a step. According to the above configuration, the first semiconductor film having a step can be easily formed.

Further, in the manufacturing method of the present invention, (a)
The step (a-1) includes forming a film made of a first group III nitride compound semiconductor and an insulating film on a substrate in this order, and removing (a-2) a part of the film. And forming a first semiconductor film having a plurality of grooves. According to the above configuration, the first III
Cracks are more likely to occur between the film made of the group III nitride compound semiconductor and the insulating film or between the insulating film and the second semiconductor film. For this reason, according to the above-described configuration, a group III nitride-based compound semiconductor substrate having a particularly large area can be easily manufactured.

In the manufacturing method of the present invention, the insulating film is made of S
It is preferable that it be made of at least one selected from iO ₂ and Si ₃ N ₄ . According to the above configuration, SiO ₂ or S
Since iN _X Group III nitride compound is deposited on the surface of the semiconductor and are different from each other in materials and crystal structures,
A stable chemical bond is not formed at the interface between the two, and the second semiconductor film is easily separated.

Preferably, the method of the present invention further includes a step of selectively removing the insulating film after the step (b) and before the step (c). According to the above configuration, when the group III nitride compound semiconductor substrate is separated from the first semiconductor film, no insulating film remains on the group III nitride compound semiconductor substrate. Substrates can be manufactured with high yield and productivity.

In the manufacturing method of the present invention, in the step (a-2), a plurality of grooves are preferably formed in a stripe shape. According to the above configuration, a large-sized group III nitride-based compound semiconductor substrate can be easily manufactured.

In the manufacturing method of the present invention, the substrate is (00
It is preferable that the (01) plane sapphire substrate has grooves formed in the [11-20] direction. According to the above configuration, the second semiconductor film having good crystallinity can be easily formed.

In the manufacturing method of the present invention, the lattice constant of the first group III nitride compound semiconductor is preferably smaller than the lattice constant of the second group III nitride compound semiconductor. According to the above configuration, since tensile strain is applied to the first semiconductor film, a particularly large-sized group III nitride-based compound semiconductor substrate can be manufactured.

[0018] In the manufacturing method of the present invention, the first Group III nitride compound semiconductor is Al _X Ga _{1- X} N (where 0 <
X ≦ 1), and the second group III nitride compound semiconductor is preferably GaN. According to the above configuration, the first
Can be made smaller than the lattice constant of the second semiconductor film.

In the manufacturing method of the present invention, it is preferable that the step (c) includes a step of cooling the substrate and then heating and cooling the substrate. According to the above configuration, cracks are surely formed, and a group III nitride compound semiconductor substrate can be manufactured with high yield.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a process diagram showing a method of manufacturing a group III nitride compound semiconductor substrate according to the present invention. FIG.
3 shows only a part of the substrate.

In the manufacturing method of the present invention, first, a buffer layer 12 made of a group III nitride compound semiconductor is formed on a substrate 11.
And a film 13 made of the first group III nitride compound semiconductor
a are formed in this order (FIG. 1A). As the substrate 11, for example, a sapphire substrate, a silicon carbide substrate, a spinel substrate, silicon, gallium arsenide, indium phosphide, or the like can be used. Specifically, a (0001) plane sapphire substrate can be used. By using a (0001) plane sapphire substrate, III
The crystal growth of the group nitride-based compound semiconductor can be facilitated. Note that the buffer layer 1 may be used depending on the type of the substrate 11.
2 can be omitted. The buffer layer 12
Another group III nitride-based compound semiconductor may be laminated between the film and the film 13a.

Next, by removing a part of the film 13a, a first semiconductor film 13 made of a first group III nitride compound semiconductor and having a step is formed. Part of the film 13a can be removed by dry etching or wet etching. For example, as shown in FIG. 1B, a first semiconductor film 13 having a step 13c may be formed by forming a stripe-shaped groove 13b. 1st semiconductor film 13 in the step of FIG.
2 is shown in FIG. As shown in FIG.
3b is formed substantially parallel. Striped groove 1
3b is preferably formed in the [11-20] direction when the substrate 11 is made of a (0001) plane sapphire substrate. In the expression “[11-20] direction”, a minus sign before 2 means a bar, and [11-2].
0]

[0024]

(Equation 1)

Represents Also, the [11-20] direction is
The <11-20> direction and directions equivalent thereto, that is, the <1-210> direction and the <-2110> direction.

FIG. 3 shows an enlarged view of the groove 13b. Groove 13b
The width Wop of the opening is preferably 1 μm to 10 μm. Preferably, the depth D of the groove 13b is 0.5 μm or more. By setting the depth D to 0.5 μm or more, the stress applied to the second semiconductor film increases, and it becomes easy to peel the group III nitride-based compound semiconductor substrate. The groove 13b adjacent to the center of the groove 13b
The distance (period) P from the center and the width Wop are P ≧ 0.
It is preferable to satisfy the relationship of 5 Wop. As a result, the volume of the portion to which the stress is applied increases, and the separation can be easily performed. In the groove 13b, the width Wop of the opening is preferably larger than the width Wbt of the bottom. Although FIG. 3 shows a groove having a forward mesa-shaped cross section, a step having another shape may be formed. For example, a step having an inverted mesa cross section or a step having a vertical side surface may be formed.
Further, the groove 13b may be formed in a lattice shape instead of a stripe shape.

Next, so as to cover the first semiconductor film 13,
A second semiconductor film 14a made of a second group III nitride-based compound semiconductor is formed on the first semiconductor film 13 (FIG. 1).
(C)). Here, the second group III nitride-based compound semiconductor has a different composition and a different coefficient of thermal expansion from the first group III nitride-based compound semiconductor. Note that the formation of the second semiconductor film 14a is performed while heating the substrate 11.

Finally, the substrate 11 on which the second semiconductor film 14a is formed is cooled, and the second semiconductor film 14a is separated from the first semiconductor film 13 to obtain a group III nitride compound semiconductor substrate 14. (See FIG. 1 (d)). As shown in FIG. 1D, the portion 15 of the second semiconductor film 14a formed in the groove 13b may remain in the groove 13b.
Thus, a group III nitride compound semiconductor substrate can be manufactured. Note that, in order to facilitate separation of the second semiconductor film 14a, heating and cooling may be further repeated after the substrate 11 is cooled. If necessary, the back surface of the group III nitride-based compound semiconductor substrate 14 (the side in contact with the first semiconductor film 13) may be polished. Even when a part of the second semiconductor film 13 adheres to the back surface of the group III nitride-based compound semiconductor substrate 14, since the film is thin, it can be easily removed by polishing.

In the above steps, the first group III nitride compound semiconductor (first semiconductor film 13) and the second group III nitride compound semiconductor
The group nitride-based compound semiconductor (second semiconductor film 14a) has a composition of Al _X Ga _{1 -XY} In _Y N (where 0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, 0 ≦ X + Y ≦ 1). ) Can be used. Then, as described above, the first group III nitride compound semiconductor and the second
It has a different composition and a different thermal expansion coefficient from the group III nitride-based compound semiconductor. Note that an impurity may be added to the second semiconductor film 14a to form a p-type or n-type semiconductor film. Thus, a p-type or n-type group III nitride compound semiconductor substrate is obtained.

It is preferable that the first semiconductor film 13 and the second semiconductor film 14a have significantly different coefficients of thermal expansion. For example, when manufacturing a substrate made of GaN, the second semiconductor film 14a is made of GaN, and the first semiconductor film 13 is made of Al _x Ga ₁ -xN (where 0.1 ≦ X ≦
0.3). Also, Al _X Ga _1-X
In the case where a substrate made of N (0.1 ≦ X ≦ 0.2) is manufactured, the second semiconductor film 14a is formed of Al _x Ga ₁ -xN
(However, 0.1 ≦ X ≦ 0.2), and the first semiconductor film 13 is preferably made of GaN.

The second semiconductor film 14a has a thickness of 2
It is preferably at least 00 μm. 200 μm thickness
With the above, stress can be concentrated on the interface between the first semiconductor film 13 and the second semiconductor film 14a, so that the second semiconductor film 14a can be easily separated.

In the above process, the film 13a made of the first group III nitride-based compound semiconductor and the second semiconductor film 14a can be formed by, for example, HVPE, MOVPE, or the like.

In the manufacturing method of the present invention, as described in the following embodiments, a step of forming an insulating film at a part of the interface between the first semiconductor film 13 and the second semiconductor film 14a is performed. It may further include. Thereby, the second semiconductor film 1
4a can be more easily peeled off. For the insulating film, for example, SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , or the like can be used. In this case, the method may further include a step of selectively removing the insulating film after forming the second semiconductor film 14a. By selectively removing the insulating film,
Separation of the second semiconductor film 14a is further facilitated.

In the manufacturing method of the present invention, the thermal expansion coefficient of the first semiconductor film 13 is different from the thermal expansion coefficient of the second semiconductor film 14a, and the first semiconductor film 13 has a step 13c. I have. Therefore, cracks occur from the step 13c in parallel with the surface of the second semiconductor film 14a.
Therefore, according to the manufacturing method of the present invention, a large-area group III nitride compound semiconductor substrate can be easily manufactured.

[0035]

The present invention will be described in more detail with reference to the following examples.

Example 1 In Example 1, an example of manufacturing a group III nitride compound semiconductor substrate by the manufacturing method of the present invention will be described with reference to FIG.

First, a sapphire substrate 41 (diameter: 5.08 cm (2 inches), thickness: 300 μm) as a substrate is immersed in a mixed solution of phosphoric acid and hydrochloric acid (heated to 90 ° C.) for 15 minutes. The surface of the substrate 41 was etched. Next, the sapphire substrate 41 was washed with water and dried. Next, the sapphire substrate 41 was introduced into the MOVPE apparatus. Then, under a nitrogen atmosphere of 1.013 × 10 ⁻⁵ Pa (1 atm.), The sapphire
The sapphire substrate 41 was thermally cleaned by heating to 0 ° C.

Next, the crystal growth temperature (sapphire substrate 41)
Temperature) is 500 ° C., and the GaN buffer layer 42
(Thickness: 50 nm) was epitaxially grown on the sapphire substrate 41. Next, under the condition that the crystal growth temperature is 1000 ° C., the GaN layer 43 and the Al _0.1 Ga _0.9 N layer 44 a
Each of them was epitaxially grown to a thickness of 1 μm (FIG. 4A). For the crystal growth, trimethylgallium, trimethylaluminum and ammonia were used as source gases. The Al _0.1 Ga _0.9 N layer 44a corresponds to the film 13a in FIG. Hereinafter, the sapphire substrate 41 on which any layer is formed is referred to as a wafer.

Next, the wafer was taken out of the MOVPE apparatus. Then, [11-2] of the Al _0.1 Ga _0.9 N layer 44a
0] direction, the plurality of grooves 44b (the width Wop of the opening is about 5
μm and a depth D of about 0.8 μm) by dry etching to form an Al _0.1 Ga _0.9 N layer 44 (FIG. 4).
(B)). The Al _0.1 Ga _0.9 N layer 44 is the first semiconductor film 1
Equivalent to 3. At this time, the step 44c is formed by the groove 44b.
Was formed. The groove 44b was formed in a stripe shape, and the distance P between the adjacent grooves 44b (see FIG. 3) was 10 μm.

Thereafter, the wafer is introduced into a hydride vapor phase epitaxy apparatus (hereinafter sometimes referred to as an HVPE apparatus),
The GaN film 45a (thickness 20) is formed on the Al _0.1 Ga _0.9 N layer 44.
0 μm) was epitaxially grown (FIG. 4C).
Note that the GaN and Al _0.1 Ga _{0 .9} N, as shown in Table 1, are different linear thermal expansion coefficients.

[0041]

[Table 1]

The method for forming the GaN film 45a will be described below. FIG. 5 is a sectional view of an example of the HVPE apparatus.
Is shown schematically in FIG. In FIG. 5, hatching is partially omitted for easy understanding. Referring to FIG. 5, the HVPE apparatus includes a reactor 51 made of quartz and a reactor 5.
1, a susceptor 52, a nitrogen introduction pipe 53 a attached to the reaction furnace 51, and an ammonia introduction pipe 53.
b, a hydrogen chloride introducing pipe 53c and an exhaust pipe 54, and a raw material chamber 55 disposed at the tip of the hydrogen chloride introducing pipe 53c. In the raw material chamber 55, a tray 57 containing a raw material (metal gallium) 56 is arranged. The HVPE apparatus further includes a substrate heater 58 for heating the wafer 52a disposed on the susceptor 52 and a raw material heater 59 for heating the raw material 56. Note that the substrate heater 58 can slide in parallel with the reaction furnace 51.

The method of growing the crystal of the GaN film 45a will be described below.

First, a wafer was placed on the susceptor 52 so as to face the ammonia introducing pipe 53b and the raw material chamber 55. Then, nitrogen is introduced into the reaction furnace 51 from the nitrogen introduction pipe 53a, and the inside of the reaction furnace 51 is set to 1.013 × 10 ⁻⁵ Pa (1
Atm) nitrogen atmosphere.

Thereafter, the temperature of the wafer was set to 1000 ° C. and the temperature of the source 56 was set to 800 ° C. by using the substrate heater 58 and the raw material heater 59. Then, ammonia was introduced into the reaction furnace 51 from the ammonia introduction pipe 53b. Further, hydrogen chloride was introduced into the raw material chamber 55 through the hydrogen chloride introduction pipe 53c, and the metal gallium of the raw material 56 was reacted with hydrogen chloride in the raw material chamber 55 to generate gallium chloride.

Then, using gallium chloride and ammonia introduced into the reaction chamber 51 as raw material gas, Ga
The N film 45a was crystal-grown (FIG. 4C).

Thereafter, the GaN film 45a and Al _0.1 Ga _0.9
A GaN substrate 45 was obtained by separating from the N layer 44. Specifically, after the crystal growth of the GaN film 45a, the temperature of the wafer is lowered to room temperature by natural cooling in an HVPE apparatus in a nitrogen atmosphere for 20 minutes.
The film 45 a was separated from the Al _0.1 Ga _0.9 N layer 44. Finally, the separated GaN substrate 45 was taken out from the HVPE apparatus. Thus, a GaN substrate 45 was obtained. At this time, a part 46 of the GaN film 45a remains in the groove 44b.

In order to observe the state of cracks formed in the GaN film 45a, the thickness of the GaN film 45a was changed to 2 μm instead of the GaN film 45a.
A wafer in which the m m GaN layer 61 was grown was prepared and cooled in the same manner as in Example 1 above. Then, the wafer was cleaved, and the cleaved surface was observed with an electron microscope to examine the state of defects and cracks generated in the GaN layer 61. FIG. 6 schematically shows the results. In FIG. 6, the GaN layer 6
The hatching of 1 is omitted.

As shown in FIG. 6, in the GaN layer 61,
A threading transition 62 and a crack 63 are formed. The crack 63 is formed from the stepped portion 44c formed on the Al _0.1 Ga _0.9 N layer 44 toward the center of the groove 44b.
It was formed parallel to the main surface of the layer 61. This crack 6
_{3, (1) Al 0.1 Ga 0.9} N layer 44 and the thermal expansion coefficient differs between the GaN layer 61, (2) Al _0.1 lattice constant of Ga _0.9 N is smaller than the lattice constant of GaN, Al _0.1 G
The tensile strain was applied to the a _0.9 N layer 44, and (3) the step 44c was formed in the Al _0.1 Ga _0.9 N layer 44, and GaN crystal was grown on the slope of the step 44c. It is believed that there is. In the case of the GaN film 45a, as in the case of the GaN layer 61, it is considered that cracks occur parallel to the main surface from the step 44c, and the GaN film 45a is easily peeled.

Actually, in Example 1, cracks occurred in the step 44c of the GaN film 45a in about 60% of the area of the wafer, and the GaN film 45a could be separated. As a result, a GaN substrate 45 having a diameter of about 2.54 cm (about 1 inch) was obtained.

As described above, in the manufacturing method of the first embodiment,
Thermal expansion coefficient of Al _0.1 Ga _0.9 N layer 44 and GaN film 45a
And the thermal expansion coefficient of the Al _0.1 Ga _0.9 N layer 44
Formed a step 44c. Therefore, the GaN film 45
In FIG. 5A, a crack was generated from the step 44c in parallel with the surface of the GaN film 45a, and the GaN thick film 45a could be separated. As a result, a GaN substrate 4 having a large area
5 could be obtained.

In particular, the lattice constant of Al _0.1 Ga _0.9 N is Ga
Smaller than the lattice constant of N, because the tensile strain is applied against Al _{0. 1} Ga _0.9 N layer 44, Al _0.1 Ga _0.9 N layer 4
Cracks easily formed between the GaN film 45a and the GaN film 45a, and the GaN film 45a having a large area could be separated. As a result, a large-area GaN substrate 45 was obtained.

Embodiment 2 In Embodiment 2, another example in which a group III nitride compound semiconductor substrate is manufactured by the manufacturing method of the present invention will be described. The manufacturing method according to the second embodiment is different from the manufacturing method according to the first embodiment only in the method for cooling the substrate.

The steps shown in FIGS. 4A to 4C are performed, and A
l _0.1 Ga _0.9 N layer 44 on the GaN film 45a (thickness of 200
μm) was grown. Then, HVP in nitrogen atmosphere
The temperature of the wafer was lowered to room temperature by natural cooling in the E apparatus for 20 minutes. Then, HVP in nitrogen atmosphere
In the E apparatus, the temperature of the wafer was set to 10 over 30 minutes.
The temperature was raised to 00 ° C. By repeating a heat cycle of heating to 1000 ° C. and then cooling to room temperature five times, A
The GaN film 45a is separated from the l _0.1 Ga _0.9 N layer 44,
An aN substrate 45 was obtained (see FIG. 4D). Finally, the separated GaN substrate 45 was taken out from the HVPE apparatus.
Thus, a group III nitride compound semiconductor substrate was obtained.

According to the manufacturing method of the second embodiment, in addition to the effect obtained by the manufacturing method of the first embodiment, the effect of performing a thermal cycle when separating the GaN substrate can be obtained. Therefore, according to the manufacturing method of the second embodiment, the GaN film 45a having a larger area than that of the first embodiment can be separated.
A substrate was obtained.

In fact, in the second embodiment, the GaN film 45 extends in a direction parallel to the surface of the GaN film 45a from the step 44c toward the center of the groove 44b over the entire surface of the wafer.
A crack was generated in a, and the GaN film 45a could be separated. As a result, a GaN substrate 45 having a diameter of about 5.08 cm (about 2 inches) was obtained.

By performing a thermal cycle, the GaN substrate 45 having a larger area can be separated from the Al substrate.
_This is considered to be because the stress was repeatedly applied to the interface between the _0.1 Ga _0.9 N layer 44 and the GaN film 45a, and cracks were more likely to occur.

Example 3 In Example 3, another example in which a group III nitride compound semiconductor substrate was manufactured by the manufacturing method of the present invention will be described. The manufacturing method according to the third embodiment is different from the manufacturing method according to the first embodiment only in the method of cooling the substrate, and thus redundant description is omitted.

By performing the steps of FIGS. 4A to 4C,
l _0.1 Ga _0.9 N layer 44 on the GaN film 45a (thickness of 200
μm) was grown. Immediately after the crystal growth of the GaN film 45a, the substrate heater 58 was slid, and nitrogen gas was blown onto the wafer to rapidly cool the wafer (within 3 minutes), thereby lowering the temperature of the wafer to room temperature. By cooling with this nitrogen gas, the GaN film 45a is separated,
A GaN substrate 45 was obtained. Then, the obtained GaN substrate 4
5 was taken out of the HVPE apparatus.

When cooling the wafer, the substrate heater 58 is used.
The reason for sliding is to prevent the cooling of the wafer from taking a long time due to the heat of the substrate heater 58. By sliding the substrate heater 58, the wafer could be rapidly cooled to room temperature.

In the manufacturing method of the third embodiment, in addition to the same effects as those of the manufacturing method of the first embodiment, an effect of cooling the wafer more rapidly than in the first embodiment can be obtained. Therefore, Example 3
According to the manufacturing method described above, the GaN film 45a having a larger area can be separated, and as a result, a GaN substrate having a larger area can be obtained.

Actually, in the third embodiment, the GaN film 45 extends in a direction parallel to the surface of the GaN film 45a from the step 44c toward the center of the groove 44b over the entire surface of the wafer.
A crack was generated in a, and the GaN film 45a could be separated. As a result, a GaN substrate 45 having a diameter of about 5.08 cm (about 2 inches) was obtained.

A large-area GaN substrate can be obtained by the manufacturing method of the third embodiment because the Al _0.1 Ga _0.9 N layer 44 and the GaN film 4
It is considered that stress was rapidly applied to the interface with 5a, and cracks were more likely to occur.

Example 4 In Example 4, another example of manufacturing a group III nitride compound semiconductor substrate by the manufacturing method of the present invention will be described with reference to FIG.
The manufacturing method according to the fourth embodiment is a method for forming an insulating film between the first semiconductor film and the second semiconductor film. Note that the same parts as those in the first embodiment will not be described repeatedly.

First, the (0001) plane sapphire substrate 41
(A diameter of 5.08 cm (2 inches) and a thickness of 300 μm) were prepared, and washed, etched and etched in the same manner as in Example 1.
And thermal cleaning. Then, a GaN buffer layer 42 (thickness: 50 nm) and a GaN layer 43 (thickness: 1 nm) are formed on the sapphire substrate 41 in the same manner as in the first embodiment.
μm) and an Al _0.1 Ga _0.9 N layer 44a (thickness 1 μm).
m) was sequentially crystal-grown (FIG. 7A).

Next, the sapphire substrate 41 (hereinafter sometimes referred to as a wafer) on which the Al _0.1 Ga _0.9 N layer 44a was formed was placed in a normal pressure CVD apparatus. And CVD
By the method, SiO _{2 is formed} on the Al _0.1 Ga _0.9 N layer 44a.
A film 71 (about 0.3 μm in thickness) was formed.

Thereafter, the wafer was taken out of the atmospheric pressure CVD apparatus. Then, [11−] of the Al _0.1 Ga _0.9 N layer 44a
20] direction, width Wop is 5 μm and depth D is 0.8 μm
m, distance (period) P is the groove 44b of 10μm was formed by dry etching to form the Al _{0. 1} Ga _0.9 N layer 44 (FIG. 7 (b)).

Further, in the same manner as in the first embodiment,
A GaN film 45a of 00 μm was crystal-grown (FIG. 7).
(C)). The crystal growth temperature was set to 1 as in the first embodiment.
000 ° C.

Thereafter, in an HVPE apparatus in an N ₂ atmosphere,
The wafer was naturally cooled for 20 minutes, the temperature of the wafer was lowered to room temperature, and the GaN film 45a was separated. Finally, the separated GaN substrate 45 was taken out from the HVPE apparatus to obtain a GaN substrate 45 (FIG. 7D).

In the manufacturing method of the fourth embodiment, (1) Al _0.1
It is different from the thermal expansion coefficient of the thermal expansion coefficient of Ga _0.9 N layer 44 and GaN layer 45a, a (2) Al _0.1 Ga _0.9 N layer 44,
A groove-shaped step 44c is formed, and (3) Al _0.1 G
An SiO ₂ film 71 is formed on a _0.9 N44.

In the manufacturing method of the fourth embodiment, the SiO ₂ film 71
Therefore, the crystal grows from the Al _0.1 Ga _0.9 N layer 44 in the groove 44b to the SiO ₂ film 71. Therefore, stress due to crystal distortion is applied to the interface between the SiO ₂ film 71 and the GaN film 45a, and cracks are more likely to occur at this interface. Therefore, according to the manufacturing method of Example 4, a GaN substrate 45 having a larger area could be obtained.

In fact, in the fourth embodiment, the GaN film 45 extends in a direction parallel to the surface of the GaN film 45a from the step 44c toward the center of the groove 44b over the entire surface of the wafer.
A crack was generated in a, and the GaN film 45a could be separated. As a result, a GaN substrate 45 having a diameter of about 5.08 cm (about 2 inches) was obtained.

In Example 4, after the wafer was taken out from the HVPE apparatus, the wafer was immersed in dilute hydrofluoric acid (volume ratio: H ₂ O: HF = 10: 1) for 30 minutes to obtain SiO ₂
Only the film 71 may be selectively etched. And
Further, a thermal cycle may be performed to separate the GaN substrate. With this configuration, when the GaN film 45a is separated, the SiO ₂ film 71 does not remain on the surface of the GaN substrate 45, so that the GaN substrate 45 having a large area can be obtained with higher yield.

In the manufacturing method of the fourth embodiment, similarly to the above-described embodiment, a thermal cycle may be performed or the wafer may be rapidly cooled.

In place of the SiO ₂ film 71, Si ₃ N
_A film made of ₄ may be used.

Although the embodiments of the present invention have been described with reference to the examples, the present invention is not limited to the above embodiments, but can be applied to other embodiments based on the technical idea of the present invention. .

For example, in the above embodiment, Al _0.1 Ga
The depth D of the groove 44b to be formed in _0.9 N layer 44 was set to 0.8μm is the depth that does not reach the GaN layer 43. But,
The depth D may be a depth reaching the GaN layer 43 or a depth at which the sapphire substrate 41 is exposed. Even if the GaN layer 43 or the sapphire substrate 41 is exposed by forming the groove, the GaN film having good crystallinity can be obtained by optimizing the growth conditions such as the gas flow rate and the growth temperature at the initial growth of the GaN film 45a. 45a can be obtained.

[0078]

As described above, the method for manufacturing a group III nitride compound semiconductor substrate of the present invention forms a first semiconductor film made of a first group III nitride compound semiconductor and having a step. Forming a first III film on the first semiconductor film;
Forming a second semiconductor film made of a second group III nitride compound semiconductor having a different coefficient of thermal expansion from the group III nitride compound semiconductor; cooling the substrate; Separating from the semiconductor film. Therefore, according to the manufacturing method of the present invention, a large-area group III nitride compound semiconductor substrate can be manufactured with good yield and good reproducibility.

[Brief description of the drawings]

FIG. 1 is a process chart showing one example of a method for producing a group III nitride compound semiconductor substrate of the present invention.

FIG. 2 is a plan view showing an example of the shape of a groove 13b in the step of FIG. 1 (b).

FIG. 3 is a cross-sectional view illustrating an example of the shape of a groove 13b.

FIG. 4 is a process chart showing another example of the method for producing a group III nitride compound semiconductor substrate of the present invention.

FIG. 5 is a cross-sectional view schematically showing one example of an HVPE apparatus used in the method for manufacturing a group III nitride compound semiconductor substrate of the present invention.

FIG. 6 is a diagram schematically showing a state of a crack generated at a boundary between the Al _0.1 Ga _0.9 N layer 44 and the GaN layer 71.

FIG. 7 is a process drawing showing another example of the method for producing a group III nitride compound semiconductor substrate of the present invention.

FIG. 8 is a process chart showing an example of a conventional method for manufacturing a group III nitride-based compound semiconductor substrate.

[Explanation of symbols]

Reference Signs List 11 substrate 12 buffer layer 13 first semiconductor film 13a film 13b, 44b groove 13c, 44c step 14a second semiconductor film 14 group III nitride compound semiconductor substrate 41 sapphire substrate 42 GaN buffer layer 43 GaN layer 44, 44a Al _0.1 Ga _0.9 N layer 45 GaN substrate 45 a GaN film 61 GaN layer 62 penetration transition 63 crack 71 insulating film

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Nakamura 1-1, Yukicho, Takatsuki-shi, Osaka Matsushita Electronics Co., Ltd. (72) Inventor Masahiro Ishida 1-1, Yukicho, Takatsuki-shi, Osaka Matsushita Electronics (72) Inventor Kenji Orita 1-1, Sachimachi, Takatsuki-shi, Osaka Matsushita Electronics Co., Ltd.

Claims (10)

[Claims] 1. A method of manufacturing a group III nitride compound semiconductor substrate, comprising: (a) forming a first semiconductor film made of a first group III nitride compound semiconductor and having a step on a substrate; And (b) a second step having a different thermal expansion coefficient on the first semiconductor film from that of the first group III nitride compound semiconductor.
Forming a second semiconductor film made of a group III nitride compound semiconductor; and (c) cooling the substrate and separating the second semiconductor film from the first semiconductor film. A method for producing a group III nitride-based compound semiconductor substrate, comprising: 2. The step (a) includes: (a-1) forming a film made of the first group III nitride compound semiconductor on the substrate; and (a-2) the film. Forming a first semiconductor film having a plurality of trenches by removing a part of the first semiconductor film. 3. The method of manufacturing a group III nitride-based compound semiconductor substrate according to claim 1, further comprising: 3. The step (a) includes: (a-1) forming a film made of the first group III nitride compound semiconductor and an insulating film on the substrate in this order; (A-2) forming a first semiconductor film provided with a plurality of grooves by removing a part of the film to form a first semiconductor film having a plurality of grooves. . 4. The insulating film is made of SiO ₂ and Si ₃ N ₄
The method according to claim 3, comprising at least one selected from the group consisting of:
A method for manufacturing a group III nitride compound semiconductor substrate. 5. The group III nitride-based material according to claim 3, further comprising a step of selectively removing the insulating film after the step (b) and before the step (c). A method for manufacturing a compound semiconductor substrate. 6. The method of manufacturing a group III nitride compound semiconductor substrate according to claim 2, wherein in the step (a-2), the plurality of grooves are formed in a stripe shape. 7. The method according to claim 6, wherein the substrate is a (0001) plane sapphire substrate, and the groove is formed in a [11-20] direction. 8. The semiconductor device according to claim 1, wherein a lattice constant of said first group III nitride compound semiconductor is smaller than a lattice constant of said second group III nitride compound semiconductor.
A method for manufacturing a group III nitride compound semiconductor substrate. 9. The first group III nitride compound semiconductor is Al _x Ga ₁ -xN (where 0 <X ≦ 1), and the second group III nitride compound semiconductor is GaN. A method for manufacturing a group III nitride compound semiconductor substrate according to any one of claims 1 to 7. 10. The group III nitride-based compound semiconductor substrate according to claim 1, wherein said step (c) includes a step of cooling said substrate, and further heating and cooling said substrate. Manufacturing method.