JP2003273036A - Method for manufacturing group 3-5 compound semiconductor and semiconductor device - Google Patents

Abstract

(57) [PROBLEMS] To reduce the generation of small-angle grain boundaries generated when a group III-V compound semiconductor is manufactured by lateral selective growth using a stripe-shaped mask. A stripe-shaped mask layer (4) is formed on a c-plane (3A) of a first group III-V compound semiconductor layer (3) serving as a base crystal so that the stripe direction is 0.095 degrees or more from the <1-100> direction. Formed so as to be shifted within a range of less than 6 degrees,
Using the mask layer 4, the second group III-V compound semiconductor layer 5 is selectively grown laterally on the c-plane 3A. By shifting the stripe direction of the mask layer 4 from the predetermined <1-100> direction within the range described above, the fluctuation of the c-axis of the required compound semiconductor layer that is selectively grown laterally on the c-plane of the base crystal can be reduced. In addition, the small angle grain boundaries generated in the second group III-V compound semiconductor layer 5 are reduced.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to gallium nitride (G
The present invention relates to a method for manufacturing an aN) group 3-5 group compound semiconductor and a semiconductor device using the same.

[0002]

2. Description of the Related Art The general formula In _x Ga _y Al _z N (however,
x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦
In the GaN-based 3-5 group compound semiconductor represented by 1), the band gap energy of the direct type can be adjusted by changing the composition of the 3 group element, and can correspond to the light energy of the wavelength from ultraviolet to red. Therefore, it can be used as a material for a highly efficient light emitting device in the ultraviolet to visible region. In addition, since it has a larger bandgap than the semiconductors such as Si or GaAs that have been generally used so far, it has the characteristics as a semiconductor even at high temperatures that conventional semiconductors cannot operate, and it can be used as an environment-resistant device. In principle, it is possible to manufacture an electronic device having excellent properties.

However, since the above-mentioned GaN-based Group 3-5 compound semiconductor has a very high vapor pressure near the melting point, it is very difficult to grow a large crystal, and it is used as a substrate for semiconductor device fabrication. Crystals of a practical size capable of producing are not obtained. Therefore, in manufacturing the compound semiconductor, a material having a crystal structure similar to that of the compound semiconductor, such as sapphire and SiC, and capable of forming a large crystal is used as a substrate, and a required single crystal thin film layer is epitaxially grown on the substrate. It is generally done. At present, by using such a method, a crystal of the compound semiconductor having a relatively good quality can be obtained. But,
Even in this case, the substrate material and the lattice constant of the compound semiconductor,
Alternatively, it is difficult to reduce crystal defects due to the difference in thermal expansion coefficient, and it is common to have a defect density of about 10 ⁸ cm ^-2 or more. However, in order to manufacture a high-performance GaN-based device, the compound semiconductor crystal having a low dislocation density is strongly required.

Therefore, conventionally, in a heteroepitaxial growth method using a substrate such as sapphire, a method of reducing the dislocation density by once forming a mask pattern on the crystal surface and then re-growing the compound semiconductor is tried. Has been. This method is characterized in that the compound semiconductor is laterally grown on a mask, and epitaxial lateral overgrowth (Epitaxial Lateral Overgrown
owth, hereinafter sometimes referred to as ELO. ) Called the law.

According to this method, at the initial stage of re-growth, so-called selective growth occurs in which crystal growth does not occur on the mask made of, for example, SiO ₂ but only in the opening. If the crystal growth is further continued from this stage, the crystal grown in the opening also spreads on the mask, eventually forming a buried structure in which the mask is buried, and finally a flat crystal surface can be obtained. By forming the buried structure as described above, the dislocation density in the regrown layer can be significantly reduced as compared with the underlying crystal.

[0006]

[Problems to be Solved by the Invention]
In the case of applying the above-mentioned ELO method in the case of a Group 5 compound semiconductor, crystal growth with the c-plane as the surface is generally performed, and the stripe direction of the striped mask is lateral growth on the mask. To efficiently perform
In general, the direction is 1-100>. But E
According to the LO method, it depends on the material used for the mask,
It is known that the c-axis direction of the crystal grown on the mask deviates from the c-axis of the base crystal. Then, a dislocation-concentrated portion called a small-angle grain boundary is generated in the joint portion between the regions where the c-axis is displaced.

In the conventional ELO having the mask stripe in the <1-100> direction, the GaN crystal grown on the mask is thus deviated from the c-axis direction of the GaN crystal grown on the mask in this way. Many dislocations are generated in the layer, which is a major cause of deterioration in quality of the completed Group 3-5 compound semiconductor.

An object of the present invention is to provide a method for manufacturing a 3-5 group compound semiconductor and a semiconductor device capable of solving the above-mentioned problems in the prior art.

[0009]

The present invention reduces the low-angle grain boundaries that occur when a Group 3-5 compound semiconductor is manufactured by lateral selective growth using a stripe-shaped mask to reduce the dislocation density. A mask pattern for lateral selective growth in order to provide a method for manufacturing a 3-5 group compound semiconductor and a semiconductor device capable of obtaining a low quality 3-5 group compound semiconductor. By slightly shifting the mask stripe direction of (3) from a predetermined direction, fluctuations of the c-axis of the Group 3-5 compound semiconductor grown thereon can be reduced, thereby reducing small-angle grain boundaries.

That is, a stripe-shaped mask formed on the c-plane of a base crystal containing a GaN-based 3-5 group compound semiconductor allows a desired GaN-based 3-5 group compound semiconductor layer to be laterally formed on the c-plane. In the method of manufacturing a Group 3-5 compound semiconductor, which is adapted to selectively grow, a stripe-shaped mask is formed on a base crystal within a range of 0.095 degrees to less than 9.6 degrees from a <1-100> direction. GaN is formed so as to be offset, and GaN is formed using the stripe-shaped mask.
The system 3-5 group compound semiconductor layer is selectively grown in the lateral direction.

As described above, the stripe direction of the stripe-shaped mask used for the lateral selective growth is set to a predetermined <1-100.
By shifting from the> direction within the above range, the fluctuation of the c-axis of the required compound semiconductor layer laterally selectively grown on the c-plane of the underlying crystal is reduced. As a result, the low-angle grain boundaries generated in the required compound semiconductor layer are reduced, and a high-quality Group 3-5 compound semiconductor layer can be formed on the underlying crystal.

The required compound semiconductor layer can be formed by using, for example, the metal organic chemical vapor deposition method or the hydride vapor phase epitaxy method. However, it is necessary to form the compound semiconductor layer by an appropriate vapor phase epitaxy method other than these. You can also

According to the invention of claim 1, a general formula In _a Ga _b Al _c N (where 0 ≦ a ≦ 1,
0 ≦ b ≦ 1,0 ≦ c ≦ 1, a + b + c = after forming a stripe-shaped mask on the underlying crystal layer comprising a Group III-V compound semiconductor represented by 1), further the general formula In _x Ga _y A
l _z N (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦
1, x + y + z = 1) in the method of growing a Group 3-5 compound semiconductor layer on the underlying crystal layer, the stripe-shaped mask having a stripe direction of <1-100
3 is formed so as to be formed on the underlying crystal layer by being displaced within a range of 0.1 degree to 10 degrees from the> direction.
A method for manufacturing a Group-5 compound semiconductor is proposed.

According to the invention of claim 2, in the invention of claim 1, the group 3-5 compound semiconductor is obtained by growing the group 3-5 compound semiconductor layer by metalorganic vapor phase epitaxy or hydride vapor phase epitaxy. A manufacturing method is proposed.

According to the invention of claim 3, claim 1 or 2
A semiconductor device using a 3-5 group compound semiconductor manufactured by the method described in 1. is proposed.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a 3 produced by the method of the present invention.
It is sectional drawing which shows typically an example of the structure of a -5 group compound semiconductor. The group 3-5 compound semiconductor 1 is a sapphire substrate 2
The first 3-5 group compound semiconductor layer 3 to be a base crystal is grown on the above by MOVPE method (metal organic chemical vapor deposition method), and the first 3-5 group compound semiconductor layer 3 is grown.
A SiO ₂ layer deposited by RF sputtering or the like is formed as a mask layer 4 on the above. Here, the first 3
The thickness of the -5 group compound semiconductor layer 3 is 3 to 4 (μm). In order to produce a good base crystal, GaN,
A two-step growth method using a known buffer layer such as AlN, GaAlN, or SiC is effective.

As shown in FIG. 2, the mask layer 4 is a striped mask having a window portion 4A formed on the c-plane 3A of the first Group 3-5 compound semiconductor layer 3, and the mask layer 4 is formed. Is formed on the c-plane 3A so that its stripe direction is slightly displaced from the <1-100> direction with a displacement angle θ as described later. In FIG. 1, the direction perpendicular to the paper surface is the <1-100> direction.

The mask layer 4 has a stripe direction of <1.
As a method of forming it by slightly displacing it from the −100> direction, a photomask having a stripe pattern is used, and a first group 3-5 compound that is selectively grown by displacing from the <1-100> direction A method of transferring onto the semiconductor layer 3 can be used. Alternatively, a method may be used in which adjacent stripe-shaped patterns in a photomask having a stripe-shaped pattern are not parallel but have a desired angle in advance and are transferred. As another method, a method may be used in which adjacent stripe-shaped patterns in a photomask having a stripe-shaped pattern are parallel but meander at a desired angle and are transferred. Of course, these methods may be appropriately combined and used.

Returning to FIG. 1, the semiconductor of the first group 3-5 compound
The body layer 3 has the general formula In_aGa_bAl _cN (where 0 ≦
a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1, a + b + c = 1)
Becomes a GaN-based 3-5 group compound semiconductor crystal layer represented
ing. On the other hand, the mask layer 4 is made of SiO.₂Layers of appropriate thickness
It is formed by depositing on the
A plurality of windows 4A are formed in the shape of slits. This
These window portions 4A have strikes with a width of about 5 (μm), for example.
It can be formed with a patterned pattern.

Then, the first group 3-5 compound semiconductor layer 3
On the mask layer 4 and the mask layer 4, the general formula In _x Ga _y Al _z N
(Where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x +
The second 3-5 group compound semiconductor layer 5 represented by y + z = 1) is formed by regrowth. The second Group 3-5 compound semiconductor layer 5 is formed as follows. Second
In the initial stage of growth of the 3-5 group compound semiconductor layer 5, crystal growth does not occur on the mask layer 4, and crystal growth selectively occurs only in the window portion 4A. As the crystal growth progresses in this way, the crystal that has grown in the window portion 4A eventually spreads over the mask layer 4 and increases in thickness, and the grown crystal region that spreads laterally from both sides of the pattern of the mask layer 4 becomes the pattern. Meet and bond near the center to form a buried structure.

In the above-mentioned growth process of the second 3-5 group compound semiconductor layer 5, generally, the c-axis direction of the second 3-5 group compound semiconductor layer 5 is the first 3-5 group compound semiconductor layer. Three
There is a case where a small tilt grain boundary 6 is generated at the joint portion between the grown crystal regions laterally spreading from both sides of the pattern of the mask layer 4 due to the deviation from the c-axis.

However, here, since the mask layer 4 is formed so that the stripe direction thereof is deviated from the <1-100> direction by the shift angle θ, on the first Group 3-5 compound semiconductor layer 3. 2-5 to grow laterally selectively in
Fluctuations in the c-axis of the group compound semiconductor layer 5 are reduced, which can effectively suppress the occurrence of a low-angle grain boundary at the junction.

In the example of FIG. 1, since the second 3-5 group compound semiconductor layer 5 is formed by the lateral selective growth as described above, the first 3-5 group compound semiconductor layer which is a base crystal. Among the large number of dislocations generated in No. 3 of FIG. 3, only threading dislocations D which do not terminate by the mask layer 4 and penetrate the window portion 4A are inherited in the second Group 3-5 compound semiconductor layer 5.
By forming the second group 3-5 compound semiconductor layer 5 as described above, in the second group 3-5 compound semiconductor layer 5 on the mask layer 4, the mask layer 4 is the first group 3-5. Since the dislocations in the compound semiconductor layer 3 are terminated and no dislocations are generated in the second 3-5 group compound semiconductor layer 5 thereabove, the second 3-5
The dislocation density in the group compound semiconductor layer 5 can be reduced. A facet is formed when the second 3-5 group compound semiconductor layer 5 is grown, and the propagation form of the threading dislocation D in the second 3-5 group compound semiconductor layer 5 is controlled by the formation form of this facet. Therefore, the threading dislocation D may not reach the surface of the second 3-5 group compound semiconductor layer 5.

As a method used for forming a film for manufacturing the Group 3-5 compound semiconductor 1, molecular beam epitaxy (hereinafter, referred to as
Sometimes referred to as MBE. ) Method, MOVPE method, HVP
Method E is mentioned. The MBE method is important because it is a method suitable for producing a laminated structure having a steep interface. The MOVPE method is important because it is suitable for producing a laminated structure having a steep interface and, at the same time, suitable for uniform film formation over a large area. The HVPE method is important because crystals containing few impurities can be produced at a high film formation rate. When the HVPE method is used to grow the second Group 3-5 compound semiconductor layer 5, a high growth rate can be obtained, so that a good crystal can be obtained in a short time.

As described above, the stripe direction of the mask layer 4 is slightly deviated from the <1-100> direction. This shift angle θ is perpendicular to the direction of the mask pattern <1
It is preferable that one step (a-axis length) in the 1-20> direction is included in the mask pattern direction once every 600 times to 6 times the a-axis length. That is, by setting the shift angle θ of the mask layer 4 to be 0.095 degrees or more and less than 9.6 degrees from the <1-100> direction, it is possible to effectively suppress the occurrence of the small tilt grain boundaries. More preferable shift angle θ of the mask layer 4 is 1 degree or more and 5 degrees or less, and most preferably 1 degree or more and 3 degrees.
It is below the degree.

When the stripe direction of the mask layer 4 is slightly shifted as described above, c of the first 3-5 group compound semiconductor layer 3 is changed.
The fluctuation of the c-axis of the second 3-5 group compound semiconductor layer 5 laterally selectively grown on the surface 3A is reduced, whereby the junction of the second 3-5 group compound semiconductor layer 5 immediately above the mask layer 4 is reduced. It is possible to suppress the occurrence of the low-angle grain boundary 6 in the part,
The 3-5 group compound semiconductor layer 5 can be made of high quality.

As a result of various experiments, the shift angle θ of the stripe direction of the mask layer 4 from the <1-100> direction was
When it was less than 0.095 degrees, it was not possible to confirm the decrease in the low-angle grain boundaries. Further, the shift angle θ is 9.
In the case of 6 degrees or more, a good embedded structure could not be obtained. That is, it was confirmed by experiments that the shift angle θ of the mask layer 4 in the stripe direction from the <1-100> direction needs to be in the range of 0.095 degrees or more and less than 9.6 degrees.

<1-10 in the stripe direction of the mask layer 4
The following experiment was conducted in order to confirm to what extent the generation of the small-angle grain boundaries was improved by the degree of deviation from the 0> direction.

A GaN layer having a thickness of 3 μm was formed on a 2-inch sapphire wafer by MOVPE, and 5 μm /
A striped mask layer having a pattern of 5 μm was formed.
A GaN layer of 6μ is further formed on this substrate by the MOVPE method.
A film was formed at 1020 ° C. and 1/2 atm to obtain a buried structure. Then, the stripe direction of this mask layer is set to <1-10.
The rocking curve according to (0004) when slightly deviated from the 0> direction was evaluated.

The shift angle θ of the mask layer is set to 1 degree, 3
The measurement result was evaluated between the comparative example in which the shift angle θ is 0 degree and the shift angle θ is 0 degree. 3, 4, and 5 show the measurement results when the offset angle θ is 1 degree, 3 degrees, and 5 degrees, respectively. FIG. 6 shows the measurement results of the comparative example when the offset angle θ is 0 degree.

When X-rays were incident in the stripe direction of the mask layer, each showed a pattern consisting of a single peak, and the half value width was about 250 seconds. On the other hand, when the X-ray is incident from the direction perpendicular to the stripe direction of the mask layer, the shift angle θ is 0 in the measurement object manufactured this time.
In the case of degrees, a main peak and two side peaks on both sides of the main peak were seen. The full width at half maximum of the main peak was about 250 seconds, which was about the same as that of the base substrate. Stripe direction <1-100>
The peaks on the high angle side become weaker when they are gradually shifted from the angle compared to when they are not shifted. In particular, it was remarkable when the shift angle θ was 1 degree and 3 degrees. By shifting the stripe direction,
Since the intensity of the side peak is reduced, it is considered that the generation of the small tilt grain boundaries is suppressed. A good semiconductor device can be obtained using this substrate.

[0033]

According to the present invention, as described above, the stripe-shaped mask formed on the c-plane of the underlying crystal in order to carry out the lateral selective growth is 0.09 in the predetermined direction <1-100>.
Generation of small-angle grain boundaries can be extremely effectively reduced only by shifting within a range of 5 degrees or more and less than 9.6 degrees. As a result, a GaN-based compound semiconductor having good crystallinity can be manufactured without a significant increase in cost. Further, by using this manufacturing method, it is possible to manufacture a semiconductor element having excellent electric characteristics at a low cost as compared with the related art.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing an example of the structure of a Group 3-5 compound semiconductor manufactured by the method of the present invention.

FIG. 2 is an explanatory view for explaining a shift of a mask layer in the 3-5 group compound semiconductor shown in FIG. 1 from a predetermined direction.

FIG. 3 is a graph showing a measurement result of a rocking curve when the shift angle of the mask layer stripe is 1 degree.

FIG. 4 is a graph showing a measurement result of a rocking curve when the shift angle of the stripe of the mask layer is 3 degrees.

FIG. 5 is a graph showing a measurement result of a rocking curve when the shift angle of the stripe of the mask layer is 5 degrees.

FIG. 6 is a graph showing a measurement result of a rocking curve when the shift angle of the mask layer stripe is 0 degree.

[Explanation of symbols]

1 Group 3-5 compound semiconductors 2 sapphire substrate 3 First Group 3-5 Compound Semiconductor Layer 4 Mask layer 5 Second Group 3-5 Compound Semiconductor Layer 6 Low-angle grain boundary D threading dislocation θ offset angle

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshinobu Ono             6 Kitahara, Tsukuba-shi, Ibaraki Sumitomo Chemical Co., Ltd.             Inside the company F-term (reference) 5F041 AA40 CA23 CA40 CA46 CA65                       CA66 CA67                 5F045 AA03 AA04 AB14 AB17 AB18                       AF13 BB12 DA53 DB02 DB04

Claims (3)

[Claims] 1. A general formula In _a Ga _b A having _a c-plane as a surface.
l _c N (where 0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦
1, a + b + c = 1), a stripe-shaped mask is formed on a base crystal layer containing a Group 3-5 compound semiconductor, and then a general formula In _x Ga _y Al _z N (where 0 ≦
x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x + y + z = 1) in the method of growing a Group 3-5 compound semiconductor layer on the underlying crystal layer, wherein the stripe-shaped mask is arranged in the stripe direction. <1-10
The method for producing a Group 3-5 compound semiconductor, wherein the group 3-5 compound semiconductor is formed on the underlying crystal layer by being shifted from the 0> direction within a range of 0.095 degrees or more and less than 9.6 degrees. 2. The method for producing a Group 3-5 compound semiconductor according to claim 1, wherein the Group 3-5 compound semiconductor layer is grown by a metal organic chemical vapor deposition method or a hydride vapor phase epitaxy method. 3. A semiconductor device using a Group 3-5 compound semiconductor manufactured by the method according to claim 1.