JPH1174199A - Semiconductor manufacture and manufacturing device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a GaN semiconductor crystal having few defects. SOLUTION: An H atom layer 12 for terminating dangling bonds on the major surface of a wafer 11 is formed by dipping the wafer 11, of which the face orientation is (111) surface and which is made of Si into hydrofluoric acid as a pre-processing of the wafer. After that the wafer is loaded into a high vacuum reaction vessel of an MBE device, and a buffer layer 13 made of GaSe which is a Van der Waals crystal body is grown on the H-atom layer 12 of the loaded wafer 12 by applying a Ga molecular beam and an Se molecular beam. Next, a semiconductor layer 14 made of GaN is grown on the buffer layer 13 of the wafer 11, by stopping the Se beam application and supplying activated N2 gas using high-frequency or electron cyclotron resonance in stead.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to gallium (Ga).
The present invention relates to a method for manufacturing a GaN-based semiconductor crystal containing nitrogen and nitrogen (N) and an apparatus for manufacturing the same.

[0002]

_2. Description of the Related Art In recent years, a high-quality GaN-based crystal thin film can be obtained by using a metal organic chemical vapor deposition (MOVPE) method for growing a GaN-based semiconductor crystal on a substrate made of sapphire (Al ₂ O ₃ ). Accordingly, a short wavelength light emitting element is being realized. Under these circumstances, blue light-emitting diode elements (LEDs) can emit light in a wavelength band from blue to green, and practical use has begun as a full-color LED display device and a traffic signal together with a red LED. Further, by realizing a blue laser element using a GaN-based crystal, there is an increasing possibility that high-quality video information can be recorded on a compact disk recording medium in the future.

Further, with the development of GaN-based crystal growth technology, a high-frequency electronic device having both high withstand voltage and environmental resistance has been realized. That is, GaAs or InP
For high-frequency electronic devices using system-based semiconductors, high-frequency power devices used in large power regions where the withstand voltage is insufficient, and applications that conventionally require additional mechanisms such as heat dissipation or cooling Attention has been paid that omitting these additional mechanisms allows the device set to be simplified and compact.

[0004] For example, an example in which a GaN-based semiconductor crystal is grown on a sapphire substrate for the purpose of a short-wavelength light-emitting device is described in the first document "Jpn. J. Appl. Phy.
s. 30, L1705 (1991) ". An example of growing a GaN-based semiconductor crystal on a substrate made of silicon carbide (SiC) intended for a high-withstand-voltage electronic element is disclosed in the second document “Appl. Phys. Let.
t. 62, 702 (1993).

[0005] As shown in these documents, MOVP
In the E method or the molecular beam epitaxy (MBE) method, when different materials are used for the substrate and the crystal layer grown on the substrate, the material is formed on the substrate to reduce the discontinuity at the interface between the substrate and the crystal layer. Often, a buffer layer is grown, and a desired crystal layer is grown on the buffer layer.

[0006]

However, the method of growing a GaN-based crystal on a sapphire substrate in the first document has several problems as described below.

That is, the crystal structures of sapphire and GaN are both hexagonal, and 500 ° C.
Although a GaN-based crystal grown at a relatively low temperature is used, the lattice constants of sapphire and GaN are significantly different, and the lattice constant of sapphire is 2.74 °, whereas the lattice constant of GaN is 3.189 °, with about 14% lattice mismatch. Such a large difference between the lattice constants leads to the introduction of a large strain near the interface between sapphire and the GaN-based crystal and the generation of floating dangling bonds. There's a problem. As a result, the defect density of LEDs currently in practical use is 1 × 10 ¹⁰ c
Since the value is m ⁻³ or more, a large number of non-light emitting regions exist inside the element due to this defect. In addition, since light scattering and the like due to defects also occur, the luminous efficiency of the element is significantly deteriorated. In addition, during operation of the device, defective portions multiply and expand, thereby deteriorating the performance of the device and eventually leading to destruction of the device. That is, it is a cause of shortening the life and reliability of the element.

Further, a substrate made of sapphire has the advantage that it is inexpensive and can be obtained with stable quality, but since it cannot be cleaved, it is difficult to separate elements by dividing the substrate, which is a great inconvenience in manufacturing. In addition, a substrate made of sapphire itself is insulative and cannot have an element structure in which an electrode is provided on a surface of the substrate opposite to an element formation surface, and thus has a problem that an element manufacturing process is complicated.

On the other hand, the method of growing a GaN-based crystal on a substrate made of SiC in the second document has several problems as described below.

Since the SiC crystal is hexagonal and has a small lattice mismatch with GaN of 3%, it is less susceptible to crystal deterioration due to the lattice mismatch than sapphire. In addition, Si
Since C itself has conductivity, if SiC is used as a substrate, an electrode can be formed on the surface opposite to the element formation surface, and thus it is considered to be superior to using sapphire for the substrate.

However, usually available substrates of SiC have etch pits of 1 × 10 ⁵ cm ⁻² or more, and these etch pits introduce a large number of defects into the epitaxial crystal layer grown on the substrate. There is a problem. Therefore, it is difficult to increase the yield of the epitaxial crystal layer, and it is very difficult to perform efficient production.

Further, SiC has a defect called a micropipe other than the etch pit. This micropipe usually has a density of about 1 × 10 ² cm ⁻² , but the cross-sectional area of one micropipe is about 0.1 mm ² , which deteriorates the yield of the epitaxial crystal layer. Furthermore, S
Since iC is difficult to manufacture, it is very expensive, and there is a problem that it is difficult to reduce the cost of an element using this SiC as a substrate.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems at once, and to surely obtain a GaN-based semiconductor crystal having few defects.

[0014]

In order to achieve the above-mentioned object, the present invention provides a method for producing a cubic substrate on which a layer adjacent to each other has a weak intermolecular force (van der Waals force: van d
The structure is such that a Van der Waals crystal layer bonded by er Waals force is grown, and a GaN-based semiconductor layer is grown on the van der Waals crystal layer.

A first method for manufacturing a semiconductor according to the present invention comprises:
A buffer layer forming step of forming a buffer layer made of van der Waals crystals on a substrate having a crystal structure; and a semiconductor layer forming step of forming a semiconductor layer containing gallium and nitrogen on the buffer layer. .

According to the first method of manufacturing a semiconductor, since a van der Waals crystal is used for the buffer layer, when a GaN-based crystal is grown on the buffer layer, the substrate and the G
The difference in lattice constant between the aN-based crystal and the aN-based crystal can be reduced.

Since the van der Waal crystal can absorb or reduce the fluctuation of the lattice constant due to temperature fluctuation, it forms a multilayer structure containing not only GaN but also InGaN or AlGaN, or changes the substrate temperature during manufacturing. In this case, the introduction of distortion due to a change in the lattice constant can be reduced.

In the first method for manufacturing a semiconductor, the crystal structure of the substrate is preferably cubic. In this case, widely used silicon (Si), gallium arsenide (GaAs), and the like are cubic, and available substrates of Si and GaAs are of high quality. Is definitely improved. further,
Since Si or GaAs has conductivity, an electrode can be formed on the surface opposite to the element formation surface.

In the first method of manufacturing a semiconductor, it is preferable that the plane orientation of the main surface of the substrate is the (111) plane. By doing so, the van der Waals crystal forming the buffer layer often belongs to a hexagonal system,
(111) of a crystal belonging to the cubic system such as aAs or Si
The consistency of the atomic arrangement with the hexagonal structure appearing on the surface is improved. In addition, since the GaN-based crystal grown on the buffer layer is also hexagonal, the buffer layer can have high atomic arrangement consistency with both the substrate and the semiconductor layer (epitaxial layer). In addition, van der Waals buffer crystals and GaN crystals belonging to the hexagonal system
Since there is only one kind of crystal structure that can exist with respect to the C-axis, there is no possibility of introducing a defect due to occurrence of an anti-phase boundary.

In the first method of manufacturing a semiconductor, the buffer layer is formed of gallium selenide (GaSe), gallium sulfide (GaS), indium selenide (InSe), indium sulfide (InS), molybdenum selenide (MoSe).
₂ ) or molybdenum sulfide (MoS ₂ ).

The first semiconductor manufacturing method may further comprise, between the buffer layer forming step and the semiconductor layer forming step, a step of replacing atoms exposed on the surface of the buffer layer with Group V atoms, for example, nitrogen atoms. Preferably, it is provided. In this case, the last layer of the buffer layer and the semiconductor layer continuously grow by covalent bonding.

In the first semiconductor manufacturing method, it is preferable that the buffer layer forming step uses an atomic layer controlled epitaxy method or a migration enhanced epitaxy method.

In the first semiconductor manufacturing method, a buffer layer growing reaction vessel for forming a buffer layer in the buffer layer forming step and a semiconductor layer growing reaction vessel for forming a semiconductor layer in the semiconductor layer forming step are provided. Are preferably different from each other. In this way, the van der Waals crystal forming the buffer layer is
When a group VI element is contained, in the semiconductor layer forming step performed after the formation of the buffer layer, the control of the desired conductivity type becomes difficult by mixing the group VI element into the semiconductor layer as an n-type dopant. In order to use a separate reaction vessel for growing a buffer layer and a reaction vessel for growing a semiconductor layer,
There is no possibility that the elements constituting the buffer layer are mixed into the semiconductor layer.

In the first semiconductor manufacturing method, the semiconductor layer forming step includes a step of supplying a gallium source and a step of supplying a nitrogen source to a reaction vessel for growing a crystal layer on the substrate, It is preferable to supply ammonia gas to the reaction vessel in an amount necessary for growing the semiconductor layer and not to lower the degree of vacuum in the reaction vessel.
In this case, since the ammonia gas is used as the nitrogen source, the quality of the GaN-based crystal is improved as compared with the normally used nitrogen gas. In addition, in order to supply ammonia gas as a nitrogen source to the reaction vessel in an amount necessary for the growth of the semiconductor layer and without lowering the degree of vacuum, an MBE method that requires a high vacuum in the reaction vessel can be used. Further, corrosion of the reaction vessel due to excess ammonia gas that does not contribute to the reaction in the reaction vessel can be prevented.

In the first semiconductor manufacturing method, the semiconductor layer forming step includes a substrate storing step of storing the substrate on which the buffer layer is formed in a reaction vessel, and a gallium supplying step of supplying gallium as a molecular beam on the buffer layer. And an ammonia gas supply step of supplying ammonia gas onto the buffer layer via an electromagnetic valve provided in the reaction vessel. In this case, the ammonia gas, which is a nitrogen source, is supplied to the reaction vessel via the electromagnetic valve. Therefore, when the electromagnetic valve is used, the opening and closing operation of the valve can be performed in an extremely short time unlike a manual valve.

In the first semiconductor manufacturing method, it is preferable to provide a time interval between the gallium supply step and the ammonia gas supply step. In this way, each raw material is uniformly diffused on the substrate in order to allow time for each raw material to diffuse on the substrate.

In the first method for manufacturing a semiconductor, it is preferable that the semiconductor layer forming step includes a nitrogen gas supplying step of supplying a plasma processing nitrogen gas to the reaction vessel as a nitrogen source. By doing so, the crystal growth rate of the semiconductor layer can be increased, and the production of a so-called ternary mixed crystal or quaternary mixed crystal, in which aluminum (Al), indium (In), boron (B), or the like is simultaneously grown, is easy. And the degree of freedom of the process is improved.

The second method for manufacturing a semiconductor according to the present invention comprises:
A semiconductor for forming a semiconductor layer containing gallium and nitrogen while supplying at least a gallium source and a nitrogen source on a substrate housed in a reaction vessel and reacting the supplied gallium source and nitrogen source on the substrate The method for producing a semiconductor device further comprises a semiconductor layer forming step of supplying an ammonia gas serving as a nitrogen source to the reaction vessel in an amount necessary for growing the semiconductor layer and without lowering the degree of vacuum of the reaction vessel.

According to the second method for producing a semiconductor, since ammonia gas is used as a nitrogen source, the quality of GaN-based crystals is improved as compared with a commonly used nitrogen gas. Also,
In order to supply an ammonia gas of a nitrogen source to the reaction vessel in an amount necessary for the growth of the semiconductor layer and without lowering the degree of vacuum, an MBE method requiring a high vacuum in the reaction vessel can be used. Corrosion of the reaction vessel due to excess ammonia gas can be prevented.

The second semiconductor manufacturing method shown here is different from the first semiconductor manufacturing method in that the buffer layer is not limited.

In the second method of manufacturing a semiconductor, the semiconductor layer forming step includes a substrate storing step of storing the substrate in a reaction vessel, and a gallium supplying step of supplying gallium as a gallium source on the main surface of the substrate as a molecular beam. And a step of supplying ammonia gas onto the main surface of the substrate via an electromagnetic valve provided in the reaction vessel.

In the second semiconductor manufacturing method, it is preferable to provide a time interval between the gallium supply step and the ammonia gas supply step.

In the second method for manufacturing a semiconductor, it is preferable that the semiconductor layer forming step includes a nitrogen gas supply step of supplying a plasma-generated nitrogen gas as a nitrogen source to the reaction vessel.

The semiconductor manufacturing apparatus according to the present invention supplies at least a gallium source and a nitrogen source onto a substrate housed in a reaction vessel, and reacts the supplied gallium source and the nitrogen source on the substrate. A semiconductor manufacturing apparatus for forming a semiconductor layer containing gallium and nitrogen, wherein the reaction vessel includes a gallium source supply unit for supplying a gallium source, and an ammonia gas introduction unit for introducing ammonia gas. Has an electromagnetic valve for intermittently controlling the flow of the introduced ammonia gas.

According to the semiconductor manufacturing apparatus of the present invention, ammonia gas as a nitrogen source is supplied via the solenoid valve of the ammonia gas introducing means, and the solenoid valve opens and closes the valve for 0.1 second. Therefore, the degree of vacuum in the reaction vessel does not decrease during the opening operation, and the leak rate can be reliably suppressed to 1 × 10 ⁻⁵ cc / sec or less even during the closing operation.

[0036] In the semiconductor manufacturing apparatus of the present invention, it is preferable that the reaction vessel is further provided with a nitrogen gas introducing means for introducing a plasma-converted nitrogen gas.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an outline of a semiconductor manufacturing method according to the present invention will be described.

According to the present invention, when manufacturing a semiconductor in which it is extremely difficult to obtain a high-quality gallium nitride (GaN) -based crystal, a van der Waal is formed between a substrate and a GaN-based crystal layer grown on the substrate. A Waals crystal is formed as a buffer layer, and a high-quality GaN-based crystal with few defects is realized by the buffer layer.

The van der Waals crystal used for the buffer layer is a crystal having a multilayer structure, for example, gallium selenide (GaSe). One layer is a covalent bond. The other layer is a general term for crystals bonded by van der Waals force, which is a kind of weak intermolecular force, not a covalent bond.

The van der Waals crystal has a function of alleviating lattice mismatch between a substrate and a desired epitaxial growth layer grown on the substrate, and as a result, defects are less likely to be introduced into the epitaxial growth layer.

As a crystal growth method using a van der Waals crystal layer, as an example of crystal growth using Si, which is inexpensive and easily obtains high-quality crystals, as a substrate,
The third document "J. Crystal Growth, 15
0 (1995) 685 ".

According to the third document, a buffer layer when a GaAs crystal layer is grown on a substrate made of Si using the MBE method is provided with a van der Waals crystal GaS.
e is used.

Specifically, first, the plane orientation of the main surface is (11)
The substrate made of Si on the surface 1) was treated with ammonium persulfide ((N
By dipping in an alcohol solution of H ₄ ) ₂ S _x ), the dangling bonds on the main surface of the substrate are terminated with sulfur (S). Subsequently, the substrate is carried into an MBE apparatus, and a Se molecular beam and a Ga molecular beam are supplied to the substrate, respectively, thereby forming a buffer layer of about 20 to 30 atomic layers of GaSe. And then S
By stopping the supply of e and supplying As, a semiconductor layer made of GaAs is continuously formed.

However, in this method, the desired Ga
An As crystal layer cannot be grown. The inventors of the present application have studied the cause of the inability to obtain a stable GaAs crystal layer, and found that the cause is due to the growth of the GaAs crystal itself on the buffer layer made of van der Waals crystals. I found it.

According to the GaAs crystal growth method disclosed in the third document, although the GaAs crystal can be grown on a substrate made of Si with a van der Waals crystal interposed, Is (111)
Anti-phase boundary (ant) generated when growing GaAs having a (111) plane orientation on Si plane
This is because it is not possible to avoid i phase boundary (APB). For this reason, many defects occur in the GaAs crystal, and the original effect of the buffer layer of improving the crystal quality cannot be obtained.

Here, the anti-phase boundary refers to a crystal structure having a uniform and continuous structure when GaAs composed of atoms different from Ga and As is grown on the (111) plane of Si composed of a single atom. Is a boundary surface that occurs at random when the two types of crystal structures are grown in a mixed state because of the existence of two types, the so-called A-plane and the B-plane. Therefore, this boundary surface is a discontinuous surface of the crystal and becomes a defect.

On the other hand, the inventors of the present application have grown a GaN-based crystal on a van der Waals crystal,
Since the system crystal is hexagonal, there is no knowledge that a plurality of structures different from each other exist in the crystal structure of the semiconductor crystal grown on the van der Waals crystal body, and thus it has been found that the anti-phase boundary does not occur. Therefore, in order to obtain a high-quality GaN-based crystal with few defects, a van der Waals crystal is used as a buffer layer, and Ga is deposited on the buffer layer.
What is necessary is just to grow an N-type crystal.

Hereinafter, a method of manufacturing a GaN-based semiconductor, an apparatus for manufacturing the same, and a semiconductor laser device using the method of manufacturing a semiconductor according to an embodiment of the present invention will be specifically described.

(First Embodiment) A first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a crystal structure of a GaSe crystal which is a Van der Waals crystal used for a buffer layer in the method for manufacturing a semiconductor according to the first embodiment of the present invention,
(A) schematically shows a unit layer, (b) shows a C plane, and (c) to (e) show different crystal systems. Here, white circles represent Se and black circles represent Ga, respectively.

As shown in FIG. 1A, GaSe has a layered structure, and the crystal lattice 1 shown by a broken line in FIG. 1B rotates three times in the normal direction of the unit layer. It has a crystal structure belonging to the hexagonal system with a symmetry point group symbol D ₃ representing the axis. As shown in FIG. 1A, trivalent Ga and hexavalent Se are in a one-to-one relationship with each other in the whole crystal.
A unit layer is formed by bonding in the order of Ga-Ga-Se, and there is no dangling bond by covalent bond in Se located on the interface side between the layers of the unit layer. The original crystal is composed of a plurality of unit layers, and one unit layer and another unit layer are not covalently bonded, but are formed by van der Waals (VDW).
It is loosely bound by the intermolecular force of force. For this reason, the overlapping manner of the units is not limited to one, but has a degree of freedom. Therefore, as shown in FIGS. 1C to 1E, a plurality of different crystal systems (polytype, morphology) exist. . That is, in the bonding between the unit layers made of Se-Ga-Ga-Se, the S
e do not necessarily have to be bonded to each other. In actual crystals, three crystal systems called γ-GaSe shown in FIG. 1C, β-GaSe shown in FIG. 1D and ε-GaSe shown in FIG. R3 each
m, P6 ₃ / mmc and are classified to the space group of P¯6m2 "A.Koebel et al,:. J.Cr
ystal Growth, 154 (1995) 269
-274 ".

Therefore, even if the lattice constants of the unit layers may be different, the unit layers can be present with different lattice constants, so that the stress applied to the coupling distance and the coupling angle in the unit lattice is reduced. . For this reason, the strain generated inside the crystal is also reduced, and a large change in the crystal structure does not occur in the crystal. As a result, by interposing the Van der Waals crystal as a buffer layer between different crystals, a change in crystal structure due to a difference in lattice constant between crystals facing each other with the buffer layer interposed therebetween is extremely reduced. And the factor for introducing defects such as dislocations can be significantly reduced.

FIG. 2 schematically shows a crystal structure of a semiconductor obtained by using the semiconductor manufacturing method according to the first embodiment of the present invention. In FIG. 2, reference numeral 11 denotes a plane orientation (1
11) a surface of a substrate made of, for example, Si;
, A hydrogen (H) atomic layer terminating the (111) plane, a buffer layer 13 of van der Waals crystal, for example, GaSe, and a semiconductor layer 14 of GaN.

As shown in FIG. 2, Si of diamond type crystal or Ga of zinc blende type crystal used for the substrate 11 is used.
Cubic crystal of such as As has a symmetry of D ₃ in the point group symbol (111) plane crystallographic plane orientation as described above, hexagonal appear on C-plane. The GaN of the semiconductor layer 14 originally has a wurtzite-type hexagonal crystal structure. Therefore, the atoms belonging to the (111) plane of the substrate 11 correspond to the atoms of the semiconductor layer 14, and there is a high possibility that the crystal layer and the semiconductor layer 14 of the substrate 11 can be regularly bonded at the atomic level. .

However, when Si is used for the substrate 11, the lattice constant of Si on the (111) plane (3.
84 °) and the lattice constant of GaN of the semiconductor layer 14 (3.18)
9 °), a large difference in lattice constant may introduce a large number of defects into the semiconductor layer 14.

On the other hand, G which is a van der Waals crystal
The buffer layer 13 made of aSe is hexagonal, and its atomic arrangement corresponds well to both the (111) plane of Si forming the substrate 11 and the C plane of GaN forming the semiconductor layer 14. As described above, the buffer layer 13 composed of a plurality of layers absorbs a difference in lattice constant between the substrate 11 and the semiconductor layer 14 grown in the normal direction of the unit layer of the buffer layer 13.

As described above, by providing the buffer layer 14 made of van der Waals crystal on the (111) plane of the substrate 11 made of cubic Si, the semiconductor layer 14 made of GaN crystal having few defects is formed. can do.

Hereinafter, the method for manufacturing a semiconductor according to the present embodiment will be specifically described with reference to the drawings.

FIGS. 3A to 3C schematically show each crystal layer in the order of steps of the method for manufacturing a semiconductor according to the present embodiment. First, as shown in FIG. 3A, as a pretreatment of the substrate, a dangling bond on the main surface of the substrate 11 is formed by immersing the substrate 11 made of Si having a (111) plane orientation in hydrofluoric acid. A hydrogen atom layer 12 to be terminated is formed.

Next, as shown in FIG. 3B, the pre-processed substrate 11 is carried into, for example, a high-vacuum reaction vessel in an MBE apparatus, and the hydrogen atom layer 12 of the carried substrate 11 is transferred. By supplying a Ga molecular beam using a metal Ga as a gallium source and a Se molecular beam using a metal Se as a selenium source, the buffer layer 13 made of GaSe is grown thereon.

Next, as shown in FIG. 3C, the supply of Se is stopped, and instead, a high frequency (RF) or electron cyclotron resonance (EC)
By supplying an activated N ₂ gas as a nitrogen source using R) or the like, the semiconductor layer 14 made of GaN is grown.

As described above, according to the present embodiment, the semiconductor layer 14 made of GaN is grown on the buffer layer 13 made of the Van der Waals crystal. Layer 1
4, and the semiconductor layer 14 to be grown is made of hexagonal GaN, thereby preventing the occurrence of anti-phase boundaries.
As a result, a GaN semiconductor crystal with extremely few defects can be obtained.

Although the MBE method was used for crystal growth of the semiconductor layer 14, metal organic chemical vapor deposition (MOVPE or MOC
VD) method may be used.

(Second Embodiment) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 4 schematically shows a crystal structure of a semiconductor obtained by using the method for manufacturing a semiconductor according to the second embodiment of the present invention. In FIG. 4, reference numeral 11 denotes a plane orientation of (1).
11) A substrate made of Si, and 12 is a substrate (11
1) A hydrogen atom layer terminating the surface, 13 is a buffer layer made of van der Waals crystal GaSe, 23 is a nitrogen-substituted buffer layer in which Se atoms on the surface (termination layer) of the buffer layer 13 are replaced with N atoms. , 14 represent semiconductor layers made of GaN, respectively.

As described above, in the semiconductor manufacturing method according to the present embodiment, the group VI element (Se) of the crystal layer on the semiconductor layer forming side of the buffer layer 13 made of the Van der Waals crystal is changed to the group V element (N). Since the crystal constituting the nitrogen-substituted buffer layer 23, which is the uppermost layer of the buffer layer 13, and the crystal constituting the semiconductor layer 14 are covalently bonded to each other, the buffer layer 13 and the semiconductor layer 14 Are continuous in crystal structure.

That is, as described in the first embodiment, the buffer layer 13 composed of a plurality of layers and the nitrogen-substituted buffer layer 23 connected by van der Waals force make the lattice constant between the semiconductor layer 14 and the substrate 11 smaller. By absorbing and relaxing the difference, the crystal layer on the semiconductor layer 14 side of the buffer layer 13 becomes substantially equal to the lattice constant of the GaN crystal.

Further, by forming the nitrogen-substituted buffer layer 23 in which the terminal atom of the final layer of the buffer layer 13 is replaced with N, the bonds between atoms between the buffer layer 13 and the semiconductor layer 14 are continued. . Therefore, Ga atoms on the buffer layer 13 side of the semiconductor layer 14 shown in FIG. 2 are bonded to Se atoms of the buffer layer 13 by intermolecular force.
G on the buffer layer 13 side in the semiconductor layer 14 shown in FIG.
The a atoms can be covalently bonded to the substituted N atoms in the nitrogen-substituted buffer layer 23, so that the introduction of defects such as dislocations into the semiconductor layer 14 according to the present embodiment can be further suppressed.

Hereinafter, a method for manufacturing a semiconductor according to the present embodiment will be specifically described with reference to the drawings.

FIGS. 5A to 5C schematically show the crystal structures in the order of steps of the method for manufacturing a semiconductor according to the present embodiment. First, as shown in FIG. 5A, as a pretreatment of the substrate, a substrate 11 made of Si having a (111) plane orientation is immersed in hydrofluoric acid to terminate dangling bonds on the main surface of the substrate 11. A hydrogen atom layer 12 is formed.

Next, as shown in FIG. 5B, the pre-processed substrate 11 is carried into, for example, a high-vacuum reaction vessel in an MBE apparatus, and the hydrogen atom layer 12 of the carried substrate 11 is carried out. A Ga molecular beam and a Se molecular beam, respectively, to supply a buffer layer 1 made of GaSe.
Grow 3. Here, a Ga molecular beam and a Se molecular beam may be supplied simultaneously, or a supply pattern of supplying one of them and stopping the supply of the other may be alternately performed. Among them, the method of supplying each raw material so as to grow one atomic layer at a time uses an atomic layer controlled epitaxy (At
omic Layer Epitaxy (ALE) method or Migration Enhanced Epitaxy (Mi)
grant Enhanced Epitaxy:
MEE) method. Using this method, the buffer layer 13
Are supplied one atomic layer at a time in the order of Se-Ga-Ga-Se so as to form one unit layer, and this supply pattern is repeated a plurality of times so as to form a multilayer structure. After that, Se-
Finally, N atoms are supplied instead of Se so that the nitrogen-substituted buffer layer 23 is formed in the order of Ga-Ga-N-. Therefore, N atoms in the uppermost layer have a dangling bond.

Next, as shown in FIG.
By supplying a Ga molecular beam and an activated N ₂ gas onto the nitrogen-substituted buffer layer 23, dangling bonds of N atoms in the nitrogen-substituted buffer layer 23 are shared with Ga atoms in the semiconductor layer 14. Coupled and terminated, then Ga
A semiconductor layer 14 of N is grown.

In the first and second embodiments,
Although GaN was grown as the semiconductor layer 14, the semiconductor layer 1
4 may be a ternary mixed crystal or a quaternary mixed crystal containing a group III element In, Al, B in a gallium source.

Further, GaS was added to the van der Waals crystal.
e, but GaS, InSe, InS, MoSe ₂
And MoS ₂ may be used. However, since the lattice mismatch between GaS and GaN is smaller than that of GaSe, it is preferable to use S instead of Se as the van der Waals crystal, and when the semiconductor layer 14 of GaN is grown, , Ga is preferably used. Even if GaS is excellent in physical properties, S molecular beams cannot be generated as easily as Se molecular beams at present.

As the substrate 11, it is preferable to use a high-quality, inexpensive and stably supplied substrate or a conductive substrate. For example, Si, GaAs, InP
Alternatively, GaP may be used, and Z of the II-VI group compound may be used.
nS.

The substrate 11 may not have conductivity like ZnO or Al ₂ O ₃ .

Here, Si, GaAs, In
When a cubic material such as P and GaP is used, as described above, the (111) plane is used as the main surface of the substrate, and
In the case of a hexagonal system such as nO, ZnS, and Al ₂ O ₃ , the C plane may be used as the main surface.

Although hydrogen is used for terminating dangling bonds on the main surface of the substrate 11, sulfur (S) may be used. In this case, for example, the substrate 11 may be immersed in an alcohol solution of ammonium persulfide ((NH ₄ ) ₂ S _x ).

(Third Embodiment) Hereinafter, a third embodiment of the present invention will be described.

The inventors of the present invention have proposed that a III-V
When growing a group III-V semiconductor layer, a group VI element such as Se contained in the van der Waals crystal used for the buffer layer acts as an n-type dopant of the group III-V semiconductor. A first problem of inhibiting the desired conductivity type control.

In general, an MBE method using an N ₂ gas converted into an RF plasma as a nitrogen source is obtained by the MBE method.
Mobility of group III nitride (III-N) semiconductors is MOVP
They have also found a second problem that the electron mobility is lower than that of a III-N semiconductor obtained by using the E method. This is considered to be because the crystallinity of the semiconductor manufactured using the MBE method is low.

As a result of various studies on the cause of low crystallinity, the present inventors have found that the MBE method has a higher III-
It has been found that the crystal growth of the N semiconductor is more three-dimensional, and the growth mechanism will be described with reference to the drawings.

FIG. 6 shows N ₂ converted into RF plasma in a nitrogen source.
4 schematically illustrates a GaN crystal growth mechanism in an MBE method using a gas. As shown in FIG. 6, among the Ga source and the nitrogen source supplied on the substrate 31, the N ₂ gas converted into RF plasma contains N ₂ molecules 32A, N atoms 32B and N ions 32C. On the other hand, while the Ga atoms 33 that have reached the main surface of the substrate 31 are diffusing on the main surface, radical N atoms 32B and N ions 32C which are reactive species
And crystallized into GaN34. Where G
Since the diffusion length of the a atom 33 is large and the reactivity of the N ion 32C is relatively low, a new crystal nucleus is not easily generated. As a result, it is more dominant that the generated GaN 34 grows while reaching and attaching to the already generated crystal nucleus, rather than generating a new crystal nucleus. Therefore, since the number of crystal nuclei generated on the main surface of the substrate 31 is small, three-dimensional growth is performed so as to form the islands 35, and columnar domains are formed. Can be

However, if the substrate 31 is made of GaN having high planarity, even if the generated GaN 34 adheres to the existing crystal nucleus and the growth proceeds, the substrate itself is already made of the same material as the crystal nucleus. Therefore, tertiary growth due to the formation of a new island is unlikely to occur.

However, when the substrate and the desired semiconductor are made of different materials as in the present application, the three-dimensional growth that occurs on the main surface of the substrate also affects the subsequent crystal growth, and deteriorates the crystallinity. It is thought to invite. This is the same regardless of whether Si is used for the substrate with the (111) plane orientation or when a van der Waals crystal is used.

On the other hand, a III-N semiconductor can be grown by MBE using ammonia (NH ₃ ) gas as a nitrogen source. In this case, the RF plasma N
The crystallinity of the III-N semiconductor is improved as compared with the case where _two gases are used. This is presumably because the MBE method using NH ₃ gas as a nitrogen source promotes two-dimensional crystal growth similar to the crystal growth using the MOVPE method. That is,
The supplied NH ₃ gas is decomposed by the catalytic action of Ga atoms, and the decomposed N ions immediately react with the Ga atoms. Therefore, new crystal nuclei are used instead of attaching to and growing on already generated crystal nuclei. Is more dominant. Therefore, uniform two-dimensional growth proceeds over the entire main surface of the substrate, and as a result, high crystallinity is expected.

However, when NH ₃ gas is used as the nitrogen source, there are a plurality of obstacles as a third problem as described below. First, since the decomposition of the NH ₃ gas requires the catalytic action of Ga, it is difficult to produce a ternary mixed crystal of AlN or InGaN or a quaternary mixed crystal of AlInGaN or the like. Second,
H ions generated by the decomposition of the NH ₃ gas stay in the reaction vessel, and the H ions are taken in as impurities in the crystal, lowering the activation rate of the p-type carrier. Third,
If a large amount of NH ₃ gas is used, the reaction vessel may be corroded, and the life of the reaction vessel may be shortened.

Hereinafter, a semiconductor manufacturing apparatus according to a third embodiment, which has been made in view of the above-described first to third problems, will be described with reference to the drawings.

FIG. 7 is a front view showing a sectional configuration of a semiconductor manufacturing apparatus according to the third embodiment of the present invention. As shown in FIG. 7, the present manufacturing apparatus is configured by connecting a first reaction vessel 41 and a second reaction vessel 42 to each other by an airtight connection pipe 43.

In the first reaction vessel 41, a first substrate holder 44A whose holding surface faces the center of the container, and each irradiation port faces the holding surface of the first substrate holder 44A, for example, The first Knudsen cel
1) A 45A and a second Knudsen cell 45B are provided.

In the second reaction container 42, a second substrate holder 44B whose holding surface is directed toward the center of the container, and each irradiation port faces the holding surface of the second substrate holder 44B, for example, A third Knudsen cell 45C, a fourth Knudsen cell 45D, and a fifth Knudsen cell 45E as Group III element source supply means or dopant source supply means;
An RF plasma cell 46 as a nitrogen gas introducing means provided with an RF coil on the outer peripheral surface of the cell, and a solenoid valve 47 as an ammonia gas introducing means are provided respectively. In the RF plasma cell 46, one nitrogen source, N ₂
The gas is supplied through a first manual valve 48A, which is connected to an external nitrogen cylinder or nitrogen gas supply line through a highly airtight supply pipe. Also, NH ₃ gas as another nitrogen source is supplied to the second reaction vessel 42.
And a second manual valve 48B are connected to each other by a supply pipe, and the second manual valve 48B is connected to an external ammonia gas cylinder or an ammonia gas supply line through a highly airtight supply pipe. I have.

The solenoid valve 47 has an extremely precise valve, and the opening time of the valve can be set to 0.1 second or less.
The leak rate when the valve is closed is 1 × 10 ^-5
cc / sec or less. Further, the pressure resistance of the valve is 85 atm or more. As a result, an extremely low back pressure can be achieved, and a high-density gas can be supplied in a pulsed manner to the space of the second reaction vessel 42 in an extremely short time. .

At the junction between the first reaction vessel 41 and the connection pipe 43, a first gate 49A for separating the first reaction vessel 41 and the connection pipe 43 is provided. The second reaction vessel 4 is connected to the joint between the vessel 42 and the connection pipe 43.
A second gate 49B for partitioning the connection pipe 2 from the connection pipe 43 is provided.

Normally, the growth temperature of van der Waals crystals is around 500 ° C., so that once the surface of the buffer layer is exposed to the air and contaminants such as oxygen or carbon are adsorbed on the surface. In addition, the heat treatment of heating the substrate on which the buffer layer is formed to a high temperature to clean the surface of the buffer layer cannot be performed.

However, a buffer layer made of van der Waals crystals is formed in the first reaction vessel 41, and then a desired III-N semiconductor is formed on the substrate on which the buffer layer is formed in the second reaction vessel 42. If crystals are formed, the III
The -N semiconductor crystal is not contaminated by the Group VI element constituting the buffer layer, and the transferred substrate is not exposed to the atmosphere when the substrate is transferred from the first reaction container to the second reaction container. The quality of a III-N semiconductor crystal in which a high-quality crystal is difficult to obtain can be reliably improved.

Hereinafter, a method for manufacturing a III-N semiconductor crystal using the semiconductor manufacturing apparatus configured as described above will be described with reference to the drawings.

The manufacturing method according to the present embodiment includes a buffer layer growing step of growing a buffer layer made of van der Waals crystals in the first reaction vessel 41 shown in FIG. A semiconductor layer growing step of growing a desired semiconductor layer on the buffer layer.

First, a group III element source made of, for example, Ga or In is stored in the first Knudsen cell 45A. Further, a high melting point metal such as Mo may be heated and evaporated by an electron beam heating device. The second Knudsen cell 45B includes Se, S, GaS, GaSe or M
The source of the group VI element of oS ₂ is stored. Here, when Se and S are used, a cell having a cracking mechanism may be used in addition to the Knudsen cell. Further, Knudsen cells may be newly added and a plurality of Group III element sources or Group VI element sources may be combined. Here, a Ga source is stored in the first Knudsen sensor 45A, and Se is stored in the second Knudsen sensor 45B.

On the other hand, the first to fourth reaction vessels 42
A desired group III element source or dopant source is stored in the third Knudsen cells 45C, 45D, and 45E, respectively. For example, Ga, Al or In is used as the group III element source, and in the case of a high melting point metal such as B, it is heated and evaporated by an electron beam heating device before use. As the dopant source, Si as an n-type dopant and Mg as a p-type dopant are used. Further, these group III elements and dopants may be combined.

Next, a substrate for semiconductor growth which has been subjected to a predetermined pretreatment is loaded into the first reaction vessel 41, and the loaded substrate is held in a first substrate holder 44A. As described above, when a cubic crystal such as Si or GaAs is used for the substrate, the main surface has a (111) plane orientation, and a hexagonal crystal such as ZnO or Al ₂ O ₃ is used. When a crystal is used, its main surface is a C-plane. Here, Si is used.

Next, the inside of the first reaction vessel 41 is ^filled with 10 ^-8 To
As shown in FIG. 3B, a buffer layer is grown under an ultra-high vacuum of rr or less.

Next, the substrate on which the buffer layer is formed is
From the first reaction vessel 41 to the second reaction vessel 42. During this manufacturing, only at this time, if the first gate 49A and the second gate 49B are opened, the contamination of the group VI element in the first reaction vessel 41 in the second reaction vessel 42 is ensured. Can be prevented.

FIG. 8 schematically shows a crystal growth mechanism of a GaN crystal layer when NH ₃ is used as a nitrogen source in the semiconductor manufacturing apparatus according to the present embodiment. As shown in FIG. 8, the NH ₃ molecules 52 supplied in a pulse form from the tip of the solenoid valve 47 of the second reaction vessel 42 onto the substrate 51 reach the main surface of the substrate, and are already diffused and crystallized. Interaction with Ga atoms 54 forming 53 decomposes into radical N atoms 55 and H atoms 56. The H atoms 56 diffuse into the second reaction vessel 42, and the N atoms 55 are directly bonded to the Ga atoms 54 at the decomposed position and crystallized.

Thus, the decomposition of the NH ₃ molecule 52 and the Ga
Since the crystallization of N proceeds in a catalytic reaction by Ga and a series of subsequent reaction processes, the substrate 51 and the desired crystal layer 53
Even if the materials are different from each other, a flat crystal layer 53 can be obtained without forming the island 35 as shown in FIG.

FIG. 9 shows the opening / closing sequence of each Knudsen cell and valve in the semiconductor manufacturing apparatus according to the present embodiment. FIG. 9A shows the opening / closing state of the cell or valve of the nitrogen source, and FIG. Indicates the open / closed state of the group III element cell. Here, it is assumed that the III-N semiconductor crystal is grown on a buffer layer made of a Van der Waals crystal. However, as described above, since the NH ₃ is used as a nitrogen source, the growing crystal layer is As shown in FIG.
May be directly grown on the substrate 51 as shown in FIG.

First, as shown in FIG. 9B, in a first step t1, Ga from the third Knudsen cell 45C is supplied onto the substrate. Next, as shown in FIG. 9A, in a second step t2 after a lapse of a predetermined time t0, N
By opening the electromagnetic valve 47 for supplying H ₃ gas for about 0.1 second, a high-density NH ₃ gas is supplied onto the substrate.
Here, the opening time of the solenoid valve 47 may be adjusted according to the substrate temperature or the pumping speed of the pump, and may be 0.5 seconds or 0.01 seconds or less. Also,
The number of times of supplying Ga and NH ₃ gas in the second step t2 may be appropriately selected depending on the flatness of the crystal and the growth rate. For example, when the crystallinity is not so important, it may be repeated several times, and when high quality crystallinity is required, it may be repeated several thousand times or more. The predetermined time t0 is 1
It is desirable to be about 0 ^-1 second to about 10 seconds, and here, about 1 second.

Next, in a third step t 3, a nitrogen source is supplied from the RF plasma cell 46 of the second reaction vessel 42 to N _2.
Switch to gas. This increases the growth rate and facilitates the growth of a ternary or quaternary mixed crystal containing Al, In or B. That is, Ga as a group III element
Not only that, for example, Al from the fourth Knudsen sensor 45D or In from the fifth Knudsen sensor 45E
And the like are supplied singly or simultaneously on the substrate. here,
If a pulse-like NH ₃ gas is supplied at an appropriate interval between the supply of the RF plasma-formed nitrogen, the improvement of the crystallinity and the growth of the mixed crystal become easy. Further, the RF plasma-converted nitrogen and the NH ₃ gas may be simultaneously supplied.

When it is necessary to increase the growth rate and increase the mixed crystal composition after securing the crystallinity of the semiconductor layer to be grown, as shown in the fourth step t4, a nitrogen source and a group III element are used. The shutter of the cell requiring the element source may be continuously opened.

According to the semiconductor manufacturing method according to the present embodiment, as shown in the second step t2, the NH ₃ gas is supplied onto the substrate in a very short time in a pulsed manner. The amount of NH ₃ required for the reaction can be reliably supplied onto the substrate without lowering the degree of vacuum. In addition, since a predetermined interval t0 is provided after supplying Ga, Ga atoms are sufficiently diffused and uniformly dispersed on the main surface of the substrate. As a result, the uniformly dispersed Ga atoms react simultaneously with the NH ₃ molecules and crystallize, so that the flatness and in-plane uniformity of the GaN crystal are significantly improved.

[0110] Further, since the ratio of NH ₃ which does not contribute to the reaction of contributing NH ₃ in the reaction is increased, it is not necessary to supply an extra amount of NH ₃ gas. For this reason,
The so-called memory effect, which is caused by excess ammonia and decomposition product hydrogen staying in the second reaction vessel 42, is less likely to occur, so that the excess ammonia or hydrogen causes inhibition of doping or NH ₃ In the case where the RF plasma nitrogen gas is continuously supplied as a nitrogen source after the gas is supplied, there is no adverse effect on crystal growth.

(Fourth Embodiment) Hereinafter, a fourth embodiment of the present invention will be described with reference to the drawings.

FIG. 10 shows a sectional configuration of a short wavelength semiconductor laser device according to the fourth embodiment of the present invention. FIG.
As shown in the figure, n-type Si of which main surface has a (111) plane orientation
On a substrate 61 made of a van der Waals crystal having a unit layer of about several tens of layers in order from the substrate 61 side.
buffer layer 62 made of aSe, first n-type cladding layer 63 made of n-type GaN, second layer made of n-type AlGaN
, An optical confinement layer 65 made of n-type GaN, a multiple quantum well active layer 66 made of InGaN,
P-type clad layer 67 made of p-type AlGaN and p-type G
An epitaxial layer having a contact layer 68 of aN is formed.

At both ends of the contact layer 68, for example, a high-resistance buried current confinement layer 69 formed by oxidation or proton implantation is formed. A p-type electrode 70 is formed on the upper surface of the contact layer 69, and an n-type electrode 71 is formed on a surface opposite to the main surface of the substrate 61.

The epitaxial layer according to the present embodiment is realized by using the method and the apparatus for manufacturing a GaN-based semiconductor according to the present invention. Therefore, as described above, by using the inexpensive and high-quality substrate 61 made of Si,
Since the buffer layer 62 made of a Van der Waals crystal having a large degree of freedom of coupling is provided on the substrate 1, the crystal quality of each layer of the GaN-based epitaxial layer is excellent, and the short wavelength (blue ) A semiconductor laser device can be realized reliably at low cost. Further, deterioration due to defects and distortion of the element is suppressed, and the life of the element can be significantly extended. In addition, due to the reduction in defects, the luminous efficiency of the device increases, and the operating voltage value and operating current value decrease.
Therefore, an element with high efficiency and low power consumption can be obtained.

Further, since the substrate 61 has conductivity, the n-type electrode 71 can be provided on the surface of the substrate 61 opposite to the element forming surface, so that the manufacturing process can be simplified as compared with the case where an insulating substrate is used. .

Although n-type Si is used for the substrate 61, the present invention is not limited to this, and n-type GaAs, n-type InP substrate or n-type G
aP may be used. Alternatively, hexagonal n-type ZnO or n-type ZnS may be used for the substrate 61, and in this case, the main surface of the substrate 61 is a C-plane.

Although GaSe is used for the buffer layer 62, a layered van der Waals crystal such as GaS, InSe, or MoS ₂ may be used. The buffer layer 6
2 has a multilayer structure composed of several to several tens of unit layers, and therefore has a sufficiently small thickness as a crystalline body.
Therefore, even when a current flows in the buffer layer 62 in the vertical direction, the resistance value of the buffer layer 62 does not significantly affect the electrical characteristics of the device, so that the buffer layer 62 becomes n-type or p-type. It may be doped or undoped.

(Fifth Embodiment) Hereinafter, a fifth embodiment of the present invention will be described with reference to the drawings.

FIG. 11 shows a cross-sectional structure of a MESFET of a high withstand voltage electronic device according to a fifth embodiment of the present invention.
As shown in FIG. 11, the plane orientation of the main surface is S
On the substrate 81 made of i, in order from the substrate 81 side, a buffer layer 82 made of GaSe of van der Waals crystal, a semiconductor layer 83 made of GaN, a first barrier layer 84 made of AlN, and an n-type GaN Channel layer 8
5. An epitaxial layer having a second barrier layer 86 made of AlGaN is formed. Here, the first barrier layer 84 and the second barrier layer 86 have a function of confining electrons serving as carriers in the channel layer.

On the upper surface of the second barrier layer 86, a gate electrode 87 made of metal which is in Schottky contact with the second barrier layer 86 is selectively formed. In the region in the gate length direction, a source electrode 88 and a drain electrode 89 spaced apart from both sides of the gate electrode 87 in the gate length direction are formed so as to make ohmic contact with the upper surface of the channel layer 85, respectively. Here, a four-terminal transistor may be formed by using an n-type or p-type doped substrate for the substrate 81. The substrate 81 is not limited to Si,
nP or GaP may be used, and ZnS, ZnO or Si
C or the like may be used.

The epitaxial layer according to the present embodiment is realized by using the method and the apparatus for manufacturing a GaN-based semiconductor according to the present invention. That is, inexpensive and high quality S
Since the buffer layer 82 made of a van der Waals crystal having a high degree of freedom of coupling is provided on the substrate 81 using the substrate 81 made of i, the quality of the crystal of the GaN-based epitaxial layer is excellent. M having the operating characteristics of
An ESFET can be realized reliably at low cost.

Further, a predetermined withstand voltage and electron mobility suppressed by the defect are realized, the device has high withstand voltage and high frequency characteristics, does not require an additional mechanism for heat dissipation, and can withstand an unusual use environment. Transistor that can be realized.

(Sixth Embodiment) Hereinafter, a sixth embodiment of the present invention will be described with reference to the drawings.

FIGS. 12A to 12D schematically show plan configurations in the order of steps of a method for manufacturing an optoelectronic integrated circuit (OEIC) device according to the sixth embodiment of the present invention.

First, as shown in FIG. 12A, a first epitaxial layer 92A made of a GaN-based semiconductor and a second epitaxial layer 92A made of a GaN-based semiconductor are placed on a substrate 91A made of Si whose main surface has a (111) plane orientation. Are grown respectively. The first epitaxial layer 92A and the second epitaxial layer 93A are formed so as to be predetermined epitaxial layers, respectively, since elements to be manufactured are different from each other. For example, the first epitaxial layer 92A
Has a cross section as shown in FIG. 10, and the second epitaxial layer 93A has a cross section as shown in FIG.

Next, as shown in FIG. 12B, a semiconductor laser device 92B is formed on the first epitaxial layer 92A, and a transistor circuit portion 93B is formed on the second epitaxial layer 93A. Here, a region excluding the semiconductor laser element 92B in the first epitaxial layer 92A and a region excluding the transistor circuit portion 93B region in the second epitaxial layer 93A are removed to expose the main surface of the substrate 91A.

Next, as shown in FIG. 12C, a photodiode 91B is selectively formed on the main surface of the substrate 91A made of Si, and thereafter, as shown in FIG.
Photodiode 91B on the main surface of substrate 91A
The first MOS transistor circuit portion 91C is formed in a region including the semiconductor laser element 92B, and the second MOS transistor circuit portion 91D is formed in a region including the semiconductor laser element 92B.

The first and second epitaxial layers 92A and 93A according to the present embodiment are realized by using the method and apparatus for manufacturing a GaN-based semiconductor according to the present invention. In other words, even if the substrate 81 made of inexpensive and high-quality Si is used, since the crystal quality of the GaN-based epitaxial layer is excellent, a short-wavelength semiconductor laser and a high-breakdown-voltage MESFET each having desired operating characteristics can be used as one substrate. A monolithic optoelectronic integrated circuit device integrated on the 91A can be realized.

As described above, an electronic element or a light emitting element is formed on a substrate made of Si, GaAs or InP, and a high breakdown voltage electronic element or a short wavelength light emitting element is also formed on a GaN-based epitaxial layer grown on the substrate. Can be integrated.

In the present invention, the case where a III-N based semiconductor crystal is grown has been described. However, the present invention is not limited to a III-N based semiconductor crystal, and a hexagonal system crystal in which a high-quality semiconductor crystal having no defects is difficult to grow. This is effective even when the crystal is grown.

Further, the van der Waals crystal is easily separated from the layers inside the crystal or from a different kind of crystal grown continuously with the crystal. After the GaN crystal layer is grown to a sufficient thickness, the van der Waals crystal body and the GaN crystal layer are separated at or near the interface, whereby GaN
It is also possible to manufacture a substrate made of.

[0132]

According to the first method of manufacturing a semiconductor of the present invention, the buffer layer made of van der Waals crystal has a lattice constant of crystal between a substrate having a crystal structure and a semiconductor layer containing Ga and N. In order to reduce the difference, introduction of defects due to lattice distortion or lattice mismatch is prevented, and the crystallinity of the semiconductor layer is improved.

In the first semiconductor manufacturing method, when the crystal structure of the substrate is cubic, the crystallinity of the semiconductor layer grown on the substrate can be surely improved by using Si, GaAs, or the like for the substrate. Further, since the substrate made of Si or GaAs is relatively inexpensive, the cost of the device can be easily reduced. further,
Since Si or GaAs has conductivity, an electrode can be formed on the surface opposite to the element formation surface. For example, in the case of a light-emitting element, a p-type electrode can be formed on the element formation surface side, and an n-type electrode can be formed on a surface opposite to the element formation surface, which simplifies the manufacturing process as compared with an insulating substrate. Can be

In the first method for manufacturing a semiconductor, if the plane orientation of the main surface of the substrate is the (111) plane, GaAs or Si
If the (111) plane of a crystal belonging to the cubic system is used as the main surface of the substrate, the consistency of the atomic arrangement with the hexagonal structure appearing on the (111) plane is further improved.

In the first method of manufacturing a semiconductor, the buffer layer is made of GaSe, GaS, InSe, InS, MoS.
If they are made of e ₂ or MoS ₂ , they constitute a Van der Waals crystal, so that the buffer layer can be reliably formed.

The first method for manufacturing a semiconductor further comprises a step of, between the buffer layer forming step and the semiconductor layer forming step, replacing the atoms exposed on the surface of the buffer layer with Group V atoms, for example, nitrogen atoms. When the buffer layer is provided, the final layer of the buffer layer and the semiconductor layer are continuously grown by covalent bonding, so that crystal defects such as dislocations are less likely to be introduced at the interface between the buffer layer and the semiconductor layer.

In the first method for manufacturing a semiconductor, in the buffer layer forming step, if an atomic layer control epitaxy method or a migration enhanced epitaxy method is used, atoms serving as a raw material can be supplied to the substrate for each atomic layer. In addition, the buffer layer and the GaN-based semiconductor layer made of the Van der Waals crystal can be reliably formed, and the atoms exposed on the surface of the buffer layer can be surely replaced with the group V atoms.

In the first method of manufacturing a semiconductor, a reaction vessel for growing a buffer layer for forming a buffer layer in a buffer layer forming step and a reaction vessel for forming a semiconductor layer in a semiconductor layer forming step are provided. However, if the containers are different from each other, there is no possibility that the semiconductor layer is contaminated by the elements constituting the van der Waals crystal, so that the conduction type of the GaN-based semiconductor layer can be reliably controlled.

In the first method for manufacturing a semiconductor, the step of forming a semiconductor layer includes a step of supplying a gallium source and a step of supplying a nitrogen source to a reaction vessel for growing a crystal layer on a substrate; Is supplied to the reaction vessel in an amount necessary for the growth of the semiconductor layer and so as not to lower the degree of vacuum of the reaction vessel. The quality of the GaN-based crystal is improved as compared with nitrogen gas. In addition, in order to supply ammonia gas as a nitrogen source to the reaction vessel so as not to lower the degree of vacuum, a high vacuum is required for the reaction vessel.
The method can be used reliably, and further, since no excess ammonia gas is generated, corrosion of the reaction vessel can be prevented.

In the first semiconductor manufacturing method, the semiconductor layer forming step includes a substrate storing step of storing the substrate on which the buffer layer is formed in a reaction vessel, and a gallium supplying step of supplying gallium as a molecular beam on the buffer layer. And an ammonia gas supply step of supplying ammonia gas onto the buffer layer via an electromagnetic valve provided in the reaction vessel,
Unlike the manual valve, the solenoid valve can open and close the valve in a very short time, so the degree of vacuum in the reaction vessel does not decrease during the opening operation, and the cell for supplying the molecular beam also during the closing operation. Unlike the normal shutter used in the above, the leak rate can be kept sufficiently low. Thereby, the quality of the crystal of the semiconductor layer containing gallium and nitrogen can be surely improved.

In the first method of manufacturing a semiconductor, if a time interval is provided between the gallium supply step and the ammonia gas supply step, each material is uniformly diffused on the substrate, so that the growth of the growing semiconductor layer The crystallinity is further improved.

In the first semiconductor manufacturing method, when the semiconductor layer forming step includes a nitrogen gas supply step of supplying a plasma-generated nitrogen gas to the reaction vessel as a nitrogen source, the crystal growth rate of the semiconductor layer is further increased. And Al,
Since a ternary mixed crystal or a quaternary mixed crystal in which In or B is grown at the same time is easily manufactured, the degree of freedom of the process is improved. Epitaxial layer) can be reliably formed.

According to the second semiconductor manufacturing method of the present invention, since ammonia gas is used as the nitrogen source, the quality of the GaN-based crystal is improved as compared with a commonly used nitrogen gas. Further, since the ammonia gas of the nitrogen source is supplied to the reaction vessel so as not to lower the degree of vacuum, the MBE method that requires a high vacuum in the reaction vessel can be reliably used.

According to the semiconductor manufacturing apparatus of the present invention, since the solenoid valve of the ammonia gas introducing means can open and close the valve within 0.1 second, the degree of vacuum in the reaction vessel decreases during the opening operation. In addition, even during the closing operation, the leak rate can be reliably suppressed to 1 × 10 ⁻⁵ cc / sec or less. This makes it possible to reliably improve the crystal quality of the semiconductor layer containing gallium and nitrogen even when using a difficult-to-handle ammonia gas, although the crystallinity is higher than the nitrogen gas as the nitrogen source.

In the semiconductor manufacturing apparatus of the present invention, if the reaction vessel is further provided with a nitrogen gas introducing means for introducing a plasma-converted nitrogen gas, the crystal growth rate of the semiconductor layer can be further increased, and the Al, In Alternatively, since the production of a ternary mixed crystal or a quaternary mixed crystal in which B or the like is grown at the same time is facilitated, the degree of freedom of the process is improved. Can be formed.

[Brief description of the drawings]

FIG. 1 shows a crystal structure of a GaSe crystal, which is a Van der Waals crystal used for a buffer layer in a method for manufacturing a semiconductor according to a first embodiment of the present invention, and (a) is a schematic diagram of a unit layer; (B) is a diagram showing a C plane,
(C)-(e) are schematic diagrams showing different crystal systems.

FIG. 2 is a schematic view illustrating a crystal structure of a semiconductor obtained by using the method for manufacturing a semiconductor according to the first embodiment of the present invention.

FIGS. 3A to 3C are schematic views showing respective crystal layers in the order of steps of the semiconductor manufacturing method according to the first embodiment of the present invention.

FIG. 4 is a schematic view illustrating a crystal structure of a semiconductor obtained by using a method for manufacturing a semiconductor according to a second embodiment of the present invention.

FIGS. 5A to 5C are schematic views showing respective crystal layers in the order of steps of a method for manufacturing a semiconductor according to a second embodiment of the present invention.

FIG. 6 is a schematic view showing a crystal growth mechanism of GaN in the MBE method using a nitrogen gas converted into RF plasma as a nitrogen source.

FIG. 7 is a front view showing a cross-sectional configuration of a semiconductor manufacturing apparatus according to a third embodiment of the present invention.

FIG. 8 is a schematic view illustrating a GaN crystal growth mechanism in a semiconductor manufacturing method according to a third embodiment of the present invention.

FIG. 9 shows an opening / closing sequence of each Knudsen cell and valve in the semiconductor manufacturing apparatus according to the third embodiment of the present invention, and FIG. 9 (a) is a diagram showing an opening / closing state of a nitrogen source cell or valve. (B) is a diagram showing the open / closed state of the group III element cell.

FIG. 10 is a sectional view illustrating a configuration of a short-wavelength semiconductor laser device according to a fourth embodiment of the present invention.

FIG. 11 is a sectional view showing a configuration of a high-breakdown-voltage electronic device according to a fifth embodiment of the present invention.

FIGS. 12A to 12D are plan views illustrating a method of manufacturing an optoelectronic integrated circuit device according to a sixth embodiment of the present invention in the order of steps.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Crystal lattice (C plane) 11 Substrate 12 Hydrogen atom layer 13 Buffer layer (Van der Waals crystal) 14 Semiconductor layer 23 Nitrogen substitution buffer layer 31 Substrate 32A N ₂ molecule 32B N atom 32C N ion 33 Ga atom 34 GaN 35 island 41 first reaction vessel 42 second reaction vessel 43 connecting pipe 44A first substrate holder 44B second substrate holder 45A first Knudsen cell 45B second Knudsen cell 45C third Knudsen cell Cell (gallium source supply means) 45D Fourth Knudsen cell 45E Fifth Knudsen cell 46 RF plasma cell (nitrogen gas introduction means) 47 Solenoid valve (ammonia gas introduction means) 48A First manual valve 48B 2 manual valve 49A first gate 49B second gate 51 substrate 52 NH ₃ molecule 53 Crystal layer 54 Ga atom 55 N atom 56 H atom 61 Substrate 62 Buffer layer (Van der Waals crystal) 63 First n-type cladding layer 64 Second n-type cladding layer 65 Light confinement layer 66 Multiple quantum well active layer 67 p-type cladding layer 68 contact layer 69 current confinement layer 70 p-type electrode 71 n-type electrode 81 substrate 82 buffer layer (Van der Waals crystal) 83 semiconductor layer 84 first barrier layer 85 channel layer 86 second barrier layer 87 Gate electrode 88 Source electrode 89 Drain electrode 91A Substrate 91B Photodiode 91C First MOS transistor circuit 91D Second MOS transistor circuit 92A First epitaxial layer 92B Semiconductor laser element 93A Second epitaxial layer 93B Transistor circuit

Claims (18)

[Claims] 1. A buffer layer forming step of forming a buffer layer made of a Van der Waals crystal on a substrate having a crystal structure, and a semiconductor layer forming a semiconductor layer containing gallium and nitrogen on the buffer layer. And a semiconductor manufacturing method. 2. The method according to claim 1, wherein the crystal structure of the substrate is cubic. 3. The method according to claim 2, wherein a plane orientation of a main surface of the substrate is a (111) plane. 4. The buffer layer comprises gallium selenide,
Gallium sulfide, indium selenide, indium sulfide,
2. The method for manufacturing a semiconductor according to claim 1, comprising molybdenum selenide or molybdenum sulfide. 5. The method according to claim 1, further comprising, between the buffer layer forming step and the semiconductor layer forming step, a step of replacing atoms exposed on the surface of the buffer layer with Group V atoms. Item 2. A method for manufacturing a semiconductor according to Item 1. 6. The method according to claim 5, wherein the group V atom is a nitrogen atom. 7. The method according to claim 1, wherein the buffer layer forming step uses an atomic layer controlled epitaxy method or a migration enhanced epitaxy method. 8. A reaction vessel for growing a buffer layer for forming the buffer layer in the step of forming a buffer layer, and a reaction vessel for growing a semiconductor layer for forming the semiconductor layer in the step of forming a semiconductor layer, The method according to claim 1, wherein the containers are different from each other. 9. The semiconductor layer forming step includes a step of supplying a gallium source and a step of supplying a nitrogen source to a reaction vessel for growing a crystal layer on the substrate, and supplying the nitrogen source. The method according to claim 1, wherein in the step, the ammonia gas is supplied to the reaction container in an amount necessary for growing the semiconductor layer and so as not to lower the degree of vacuum of the reaction container. . 10. The semiconductor layer forming step, wherein: a substrate accommodating step of accommodating the substrate on which the buffer layer is formed in a reaction vessel; a gallium supplying step of supplying gallium as a molecular beam on the buffer layer; 2. The method of manufacturing a semiconductor according to claim 1, further comprising an ammonia gas supplying step of supplying ammonia gas onto the buffer layer via an electromagnetic valve provided in the reaction vessel. 11. The method according to claim 10, wherein a time interval is provided between the gallium supply step and the ammonia gas supply step. 12. The semiconductor manufacturing method according to claim 9, wherein said semiconductor layer forming step includes a nitrogen gas supplying step of supplying a plasma-converted nitrogen gas as a nitrogen source to said reaction vessel. Method. 13. A gallium source and a nitrogen source are supplied onto a substrate housed in a reaction vessel, and the gallium source and the nitrogen source are reacted on the substrate while containing gallium and nitrogen. A method for manufacturing a semiconductor for forming a semiconductor layer, comprising supplying an ammonia gas serving as the nitrogen source to the reaction vessel in an amount necessary for growing the semiconductor layer and without lowering the degree of vacuum of the reaction vessel. A method for manufacturing a semiconductor, comprising a semiconductor layer forming step. 14. The semiconductor layer forming step, wherein: a substrate accommodating step of accommodating the substrate in a reaction vessel; and a gallium supplying step of supplying gallium serving as the gallium source as a molecular beam on a main surface of the substrate; 14. The method for manufacturing a semiconductor according to claim 13, further comprising an ammonia gas supply step of supplying the ammonia gas on a main surface of the substrate via an electromagnetic valve provided in the reaction vessel. 15. The method according to claim 14, wherein a time interval is provided between the gallium supply step and the ammonia gas supply step. 16. The method according to claim 14, wherein the semiconductor layer forming step includes a nitrogen gas supply step of supplying a plasma-formed nitrogen gas as a nitrogen source to the reaction vessel. 17. Supplying at least a gallium source and a nitrogen source onto a substrate housed in a reaction vessel, and containing gallium and nitrogen while reacting the supplied gallium source and nitrogen source on the substrate. An apparatus for manufacturing a semiconductor for forming a semiconductor layer, wherein the reaction vessel includes a gallium source supply unit that supplies a gallium source and an ammonia gas introduction unit that introduces ammonia gas, and the ammonia gas introduction unit introduces the gallium source. An apparatus for manufacturing a semiconductor, comprising an electromagnetic valve for intermittently controlling the flow of ammonia gas. 18. The semiconductor manufacturing apparatus according to claim 17, wherein said reaction vessel further comprises a nitrogen gas introducing means for introducing a plasma-converted nitrogen gas.