JP2007087992A - Semiconductor device and its fabrication process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a III nitride semiconductor layer excellent in crystallinity with few crystal defects on an SiC buffer layer formed on a single crystal substrate, and to enhance light emission characteristics and high frequency characteristics. <P>SOLUTION: A semiconductor device 10 includes a substrate 101 of single crystal, a silicon carbide layer 102 provided on the surface of the single crystal substrate 101, and an intervention layer 103 of III nitride semiconductor provided on the surface of the silicon carbide layer 102 wherein the silicon carbide layer 102 comprises cubic crystal rich in silicon stoichiometrically and has a surface of rearrangement structure of (3×3). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides a semiconductor comprising a substrate made of a single crystal, a silicon carbide layer provided on the surface of the single crystal substrate, and an intervening layer made of a group III nitride semiconductor provided on the surface of the silicon carbide layer The present invention relates to an element and a semiconductor element manufacturing method.

Group III-V compounds such as gallium nitride (GaN) and aluminum nitride (AlN) are conventionally known as group III nitride semiconductors. These group III nitride semiconductor materials are used to construct semiconductor light emitting devices such as light emitting diodes (English abbreviation: LED) and laser diodes (abbreviation: LD) that emit visible light of short wavelengths such as blue or green. (See Patent Document 1 below). Further, it is used to construct electronic devices such as Schottky junction field effect transistors (English abbreviation: MESFET) that operate in a high frequency band (see Non-Patent Document 1 below).
Japanese Patent Publication No.54-3834 M.A. Khan et al., Applied Physics Letters (Appl. Phys. Lett.), (USA), 1993, 62, 1786.

A semiconductor element made of such a group III nitride semiconductor material includes a sapphire (α-Al ₂ O ₃ ) bulk single crystal (see Patent Document 3 below) or a cubic silicon carbide (SiC) bulk (bulk). ) A single crystal is used as a substrate (see Patent Document 4 below). For example, short wavelength visible LEDs have been manufactured using a laminated structure including a clad layer made of a group III nitride semiconductor material and a light emitting layer on a sapphire substrate (Patent Document 5 below) reference).
JP-A-6-151963 JP-A-6-326416 JP-A-6-151966

  However, sapphire commonly used as a substrate for a group III nitride semiconductor device does not have sufficiently good lattice matching with a group III nitride semiconductor material such as GaN. For this reason, even if sapphire is used as a substrate, there is a problem that a group III nitride semiconductor layer excellent in crystallinity with few crystal defects such as dislocations cannot be obtained stably. Further, if a silicon carbide bulk single crystal having excellent thermal conductivity is used as a substrate, it is convenient to construct, for example, an LED having excellent voltage resistance against static electricity or the like and an MESFET having excellent heat dissipation. However, a silicon carbide bulk single crystal having a moderately large diameter for use as a substrate is expensive, which is disadvantageous when manufacturing a low-cost general-purpose group III nitride semiconductor device.

  On the other hand, silicon single crystals (silicon) are originally excellent in thermal conductivity and well-developed large-diameter single crystals have already been mass-produced. Therefore, it is expected that if a highly conductive and large-diameter silicon is used as a substrate, an inexpensive general-purpose LED having high withstand voltage against static electricity or the like can be put into practical use. Moreover, if silicon having high resistance and high thermal conductivity is used as a substrate, it is expected that a MESFET for high-frequency band communication with low loss can be realized. However, the lattice constant (a) of silicon single crystal is 0.543 nm, and there is a large lattice mismatch with a group III nitride semiconductor such as hexagonal GaN (a-axis lattice constant = 0.319 nm). is there. Also, the mismatch with silicon is large even for cubic GaN (a = 0.451 nm). Therefore, it has been difficult to stably form a high-quality group III nitride semiconductor layer with few crystal defects on the silicon substrate.

In order to overcome this drawback, when providing a group III nitride semiconductor layer on a single crystal substrate having a large lattice mismatch, a buffer layer for relaxing the mismatch between both lattices is conventionally provided. It has become a general means. When forming a group III nitride semiconductor layer on a silicon substrate, a conventional technique for forming a group III nitride semiconductor layer through a thin film layer of cubic 3C-type silicon carbide (3C-SiC) is known. (See Non-Patent Document 2 below). However, since the crystallinity and the like of the upper group III nitride semiconductor layer are remarkably changed depending on the properties of the 3C—SiC thin film layer, there is a difficulty in stably forming a high-quality group III nitride semiconductor layer. Further, even when a buffer layer made of SiC is used, the group III nitride semiconductor layer formed thereon has a problem that the surface flatness is not necessarily excellent.
T. Kikuchi et al., J. Crystal Growth, (Netherlands), 2005, Vol. 275, No. 1-2, pages e1215 to e1221.

  In order to obtain a semiconductor device with excellent optical and electrical characteristics using silicon as a substrate, which has already been mass-produced with a single crystal with excellent conductivity and heat dissipation, it is preferable to relax the lattice mismatch with the silicon substrate. Thus, there is a need for a buffer layer having a configuration that can provide a good Group III nitride semiconductor layer. Longitudinal slabs, when forming a group III nitride semiconductor layer on a silicon substrate, even when a cubic SiC layer is used as a buffer layer, the lattice mismatch between the two materials is preferably alleviated and crystal defects Therefore, a SiC buffer layer having a configuration that enables the formation of a group III nitride semiconductor layer having a low density and excellent crystallinity and excellent surface flatness as an upper layer is required.

  The present invention has been made to overcome the above-mentioned problems of the prior art, and uses a SiC buffer layer on a single crystal substrate to form a group III nitride semiconductor layer having excellent crystallinity with few crystal defects thereon. It is an object of the present invention to provide a semiconductor element and a method for manufacturing a semiconductor element that can improve light emission characteristics and high-frequency characteristics.

  1) In order to achieve the above object, a first invention provides a substrate made of a single crystal, a silicon carbide layer provided on the surface of the single crystal substrate, and a group III provided on the surface of the silicon carbide layer. In a semiconductor device including an intervening layer made of a nitride semiconductor, the silicon carbide layer is made of a cubic crystal containing a stoichiometrically rich silicon and has a rearranged structure with a (3 × 3) structure on the surface. Is.

  2) According to a second invention, in the structure of the invention described in the above item 1), the substrate is made of a silicon single crystal.

  3) According to a third invention, in the structure of the invention described in the above item 1) or 2), the substrate is made of a {111} silicon single crystal having a {111} crystal plane as a surface.

  4) A fourth aspect of the present invention is the structure according to any one of the above items 1) to 3), wherein the surface of the substrate has a (7 × 7) rearrangement structure.

  5) A fifth aspect of the present invention is the structure according to any one of the above items 1) to 4), wherein the intervening layer contains aluminum as a group III element.

6) A sixth aspect of the present invention is the structure of the invention described in the above item 5), wherein the intervening layer is formed of hexagonal wurtzite crystal type aluminum gallium nitride (compositional formula Al _x Ga _1-x N: 0 ≦ X ≦ 1).

  7) A seventh invention is the above-described structure according to any one of items 1) to 6), wherein a group III nitride semiconductor layer is provided on the intervening layer.

  8) According to an eighth invention, a substrate made of a single crystal, a silicon carbide layer provided on the surface of the single crystal substrate, and an intervening layer made of a group III nitride semiconductor provided on the surface of the silicon carbide layer, In a semiconductor device manufacturing method for manufacturing a semiconductor device comprising: a first step of spraying a hydrocarbon gas onto the surface of the substrate to adsorb hydrocarbons, and irradiating the surface of the substrate on which the hydrocarbons are adsorbed with electrons However, by heating the substrate to a temperature equal to or higher than the temperature at which the hydrocarbons were adsorbed, a silicon carbide layer having a (3 × 3) rearrangement structure made of cubic crystals that are stoichiometrically rich in silicon is formed. A second step of forming, and a gas source containing nitrogen and a gas source containing a group III element are supplied to the surface of the silicon carbide layer to form the intervening layer made of a group III nitride semiconductor. And a third step.

  9) According to a ninth invention, in the configuration of the invention described in the above item 8), in the third step, the gaseous raw material containing the Group III element is temporally preceded by the gaseous raw material containing nitrogen. It supplies and forms the said intervening layer.

  10) The tenth invention is the structure of the invention described in the above item 8), wherein in the third step, a gaseous raw material containing aluminum is first supplied temporally, and then a group III element other than aluminum Then, a gas material containing nitrogen is supplied, and then a gas material containing nitrogen is supplied to form the intervening layer made of a group III nitride semiconductor layer containing aluminum.

  11) The eleventh aspect of the invention is the structure of the invention according to any one of paragraphs 8) to 10), wherein, in the first step, a hydrocarbon gas is blown onto the surface of the substrate and electrons are emitted. While irradiating, the hydrocarbon is adsorbed on the surface of the substrate.

  According to the present invention, a substrate made of a single crystal, a silicon carbide layer provided on the surface of the single crystal substrate, and an intervening layer made of a group III nitride semiconductor provided on the surface of the silicon carbide layer are provided. In the semiconductor device, since the silicon carbide layer is made of a cubic crystal containing a stoichiometrically rich silicon and the surface has a rearranged structure of (3 × 3) structure, the silicon carbide layer is formed on the silicon carbide layer. An intervening layer made of a group III nitride semiconductor having few crystal defects and excellent crystallinity can be formed. Therefore, the high-quality intervening layer can be used to improve the light emission characteristics and high-frequency characteristics as a semiconductor element. it can.

  According to the present invention, the substrate is composed of {111} silicon single crystal having the {111} crystal plane as the surface, and the intervening layer composed of the silicon carbide layer and the group III nitride semiconductor is provided thereon. A good quality intervening layer having few grain boundaries and particularly excellent crystallinity can be provided.

  According to the present invention, since the surface of the substrate has a (7 × 7) rearrangement structure, a cubic silicon carbide layer having a (3 × 3) rearrangement structure is efficiently and stably formed thereon. be able to.

  According to the present invention, since the group III nitride semiconductor constituting the intervening layer contains aluminum as a group III element, the silicon carbide layer provides a buffering action for lattice mismatch between the substrate and the group III nitride semiconductor. Together, it is possible to form an interstitial layer made of a group III nitride semiconductor having few crystal defects and excellent crystallinity. Therefore, an LED having excellent optical and electrical characteristics by using the good interstitial layer. It is effective to bring about semiconductor elements such as.

According to the present invention, a group III nitride semiconductor constituting an intervening layer is formed from a hexagonal wurtzite crystal type aluminum gallium nitride (compositional formula Al _x Ga _1-x N: 0 ≦ X ≦ 1) layer. Since it is constituted, the intervening layer can be made of silicon carbide having a high quality with few twin crystal grain boundaries and excellent crystallinity.

  According to the present invention, since the group III nitride semiconductor layer is provided on the intervening layer, the group III nitride semiconductor layer can be excellent in crystallinity with few crystal defects, and its high quality. By using such a group III nitride semiconductor layer, it is possible to provide a compound semiconductor light emitting device having high luminance and excellent electrical characteristics such as reverse voltage. Moreover, if the hexagonal group III nitride semiconductor layer is used as an electron transit layer (channel layer), a Schottky junction field effect transistor (FET) can be formed, and high electron mobility can be expressed. An FET having excellent high frequency characteristics can be obtained.

  According to the present invention, a substrate made of a single crystal, a silicon carbide layer provided on the surface of the single crystal substrate, and an intervening layer made of a group III nitride semiconductor provided on the surface of the silicon carbide layer are provided. In the semiconductor device manufacturing method for manufacturing a semiconductor device, a first step of adsorbing hydrocarbons by blowing a hydrocarbon gas onto the surface of the substrate, and irradiating the surface of the substrate on which the hydrocarbons are adsorbed with electrons, First, the substrate is heated to a temperature equal to or higher than the temperature at which the hydrocarbon is adsorbed to form a silicon carbide layer having a (3 × 3) rearrangement structure composed of cubically rich silicon stoichiometrically. And a third step of forming an intervening layer made of a group III nitride semiconductor by supplying a gas source containing nitrogen and a gas source containing a group III element to the surface of the silicon carbide layer. (3x3) rearrangement structure It is possible to easily and stably form a cubic silicon carbide layer having a surface, and to form an intervening layer made of a group III nitride semiconductor having few crystal defects and excellent crystallinity on the silicon carbide layer. Therefore, it is possible to improve the light emission characteristics and the high frequency characteristics as a semiconductor element by using the high-quality intervening layer.

  According to the present invention, when the intervening layer is formed in the third step, the intervening layer is formed by supplying the gas raw material containing the Group III element earlier than the gaseous raw material containing nitrogen. Therefore, it is effective to form an intervening layer made of a group III nitride semiconductor having excellent crystallinity without eliminating the rearrangement structure of the (3 × 3) structure formed on the surface of the silicon carbide layer. .

  According to the present invention, when forming the intervening layer in the third step, the gaseous raw material containing aluminum is first supplied temporally, and then the gaseous raw material containing a group III element other than aluminum is supplied, Next, a gaseous material containing nitrogen was supplied to form an intervening layer made of a group III nitride semiconductor layer containing aluminum, so that the (3 × 3) structure formed on the surface of the silicon carbide layer was regenerated. An intervening layer made of a group III nitride semiconductor containing aluminum having excellent crystallinity can be formed without eliminating the array structure.

  According to the present invention, in the first step, hydrocarbon gas is blown onto the surface of the substrate and electrons are irradiated while adsorbing hydrocarbons on the surface of the substrate. Therefore, a silicon carbide layer stoichiometrically rich in silicon having a homogeneous (3 × 3) rearrangement structure on the surface of the single crystal substrate can be adsorbed on the surface of the single crystal substrate. Contributes to uniform formation.

  The present invention provides a semiconductor comprising a substrate made of a single crystal, a silicon carbide layer provided on the surface of the single crystal substrate, and an intervening layer made of a group III nitride semiconductor provided on the surface of the silicon carbide layer In the device, the silicon carbide layer is made of a cubic crystal containing a stoichiometrically rich silicon, and the surface thereof has a rearranged structure of (3 × 3) structure.

  As a substrate used for forming a silicon carbide layer having a (3 × 3) structure rearrangement structure and containing a stoichiometrically rich silicon according to the present invention, a {111} crystal plane is the surface. A {111} silicon single crystal is preferred. Silicon having a crystal plane inclined by several degrees from the {111} crystal plane as a surface can also be sufficiently used as a substrate. The conductivity type of silicon used as the substrate is not limited. Either the p-type or n-type conductivity type can be used as the substrate. In particular, highly conductive silicon having a low resistivity (specific resistance) can be used as a substrate suitable for manufacturing semiconductor light emitting devices such as LEDs and LDs. In addition, high-resistance silicon is suitably used as a substrate for manufacturing electronic devices such as MESFETs that need to reduce leakage to the substrate side of current for operating the element (element operating current). it can.

The silicon carbide layer having a (3 × 3) rearranged structure and containing a stoichiometrically rich silicon has a 3C crystal structure (edited by the Japan Society for the Promotion of Science High Temperature Ceramic Materials No. 124, “ It is preferably a cubic crystal layer having a new SiC-based ceramic material-recent developments ", February 28, 2001, published by Uchida Otsukuru, 1st edition, pages 13-16. . The 3C-type silicon carbide (3C—SiC) layer is formed using, for example, hydrocarbon molecules adsorbed on the surface of a silicon substrate. Hydrocarbon molecules adsorbed to form a 3C-SiC layer include saturated aliphatic hydrocarbon molecules such as methane (molecular formula CH ₃ ), ethane (molecular formula C ₂ H ₆ ), and propane (molecular formula C ₃ H ₈ ). And an unsaturated hydrocarbon molecule such as acetylene (molecular formula C ₂ H ₂ ). In addition, although there are molecules of aromatic hydrocarbons or alicyclic hydrocarbons, acetylene which is easily decomposed and reacts with silicon (Si) is most preferably used.

  For example, the temperature at which acetylene molecules are adsorbed on the {111} crystal plane forming the surface of {111} silicon is preferably 400 ° C. to 600 ° C. After the hydrocarbon is adsorbed on the crystal surface forming the surface of the silicon substrate, the adsorbed hydrocarbon reacts with the silicon (Si) atoms forming the silicon substrate crystal by heating the silicon substrate, and the 3C-SiC layer Form. At this time, heating the silicon substrate to 500 ° C. to 700 ° C. is convenient for forming a 3C—SiC layer stoichiometrically rich in silicon. The higher the temperature at which the silicon substrate on which the hydrocarbons are adsorbed is heated, the shorter the time can be, the shorter the stoichiometric 3C-SiC layer can be formed.

  In the 3C-SiC layer having a non-stoichiometric composition, the degree of richness of silicon (Si) compared to carbon (C) is reflected in the lattice constant of the 3C-SiC layer. In 3C-SiC having a non-stoichiometric composition, the lattice constant increases as the silicon composition becomes richer. While the lattice constant of 3C-SiC having a chemical equivalent composition is 0.436 nm (see "SiC-based ceramic new material-recent development" above, page 340, Table 5.1.1.), In the present invention, a 3C—SiC layer having a lattice constant exceeding 0.436 nm, for example, 0.450 nm is used. Confirmation that the SiC layer to be used is a 3C-type crystal and confirmation of its lattice constant can be performed using, for example, electron diffraction analysis.

  A 3C-SiC layer having a non-stoichiometric composition containing abundant silicon as described above and having a (3 × 3) rearrangement structure on the surface is formed on the surface of the silicon substrate. After creating an atomic rearrangement structure, it can be easily formed by means of adsorbing hydrocarbon molecules such as acetylene. For example, after a (7 × 7) rearrangement structure appears on the surface of {111} silicon substrate consisting of {111} crystal planes, a hydrocarbon molecule is adsorbed and a (3 × 3) rearrangement structure is simply formed. The 3C-SiC layer can be formed.

The (7 × 7) rearrangement structure of silicon is, for example, that the {111} crystal plane forming the surface of a {111} silicon substrate is formed in a high vacuum environment of about 10 ⁻⁶ Pascal (pressure unit: Pa), It can be formed by performing a heat treatment at 750 ° C. to 850 ° C. in a chamber for line epitaxial (abbreviation: MBE) growth. The appearance of the (7 × 7) rearrangement structure of silicon can be confirmed by electron diffraction analysis means such as high-speed reflection electron diffraction (abbreviation: RHEED).

  When the silicon carbide layer is formed on the surface of the silicon substrate, when hydrocarbon molecules are sprayed on the surface of the substrate while irradiating electrons, the hydrocarbon can be uniformly adsorbed on the surface of the silicon substrate. As the electrons to be irradiated, for example, thermal electrons emitted from a metal heated in a vacuum are used. In order to uniformly adsorb hydrocarbon molecules on the surface of the single crystal substrate, it is preferable to irradiate electrons with a uniform density on the surface of the substrate. The electrons are preferably irradiated at a lower angle than the angle at which the hydrocarbon molecules are sprayed onto the surface of the single crystal substrate. By making the electrons incident at a low angle, the atoms constituting the single crystal in the region near the surface of the single crystal substrate are activated so that the hydrocarbon molecules can be easily trapped. This is to prevent electrons from entering deeply into the interior and suppress the occurrence of crystal defects in the deep portion of the single crystal substrate. For example, while hydrocarbon molecules are sprayed from a substantially vertical direction of the surface of the single crystal substrate, electrons are irradiated from an angle of 30 °, for example, at an elevation angle with respect to the substrate surface, which is a lower angle than that.

As the electron irradiation density, 1 × 10 ^{12 to} 5 × 10 ¹³ cm ⁻² is suitable. If the acceleration energy of the irradiated electrons is less than about 100 electron volts (unit: eV), hydrocarbon molecules cannot be uniformly adsorbed on the surface of the single crystal substrate, which is inconvenient. Irradiation with electrons having acceleration energy exceeding 500 eV is disadvantageous because decomposition and desorption of hydrocarbon molecules are promoted, and the hydrocarbon molecules are not uniformly adsorbed on the surface of the substrate. Therefore, the potential difference between an electron generation source, for example, a tungsten (W) filament and a single crystal substrate which is an object to be irradiated is preferably 100 volts (V) or more and 500 V or less.

In addition, when a silicon substrate having hydrocarbons adsorbed on the surface is heated to form a 3C-SiC layer on the surface of the substrate, when electrons are irradiated toward the surface of the substrate, (3 × 3) A 3C-SiC layer having a rearranged structure can be stably formed. This is presumably because the irradiating electrons give the silicon atoms forming the surface of the silicon substrate favorable energy for inducing the rearrangement structure. As the electron irradiation density, 1 × 10 ^{12 to} 5 × 10 ¹³ cm ⁻² is suitable. Further, the acceleration energy of the irradiated electrons is suitably 100 eV to 500 eV. By irradiation with electrons under such a suitable condition, a 3C—SiC layer having excellent crystallinity with a small crystal defect density such as twins and stacking faults can be formed.

An intervening layer made of a group III nitride semiconductor is provided on the surface having a (3 × 3) rearrangement structure of the 3C—SiC layer having a non-stoichiometric composition. As this group III nitride semiconductor, for example, Al _X Ga _Y In _Z N _1-α M _α (0 ≦ X, Y, Z ≦ 1, X + Y + Z = 1. Symbol M is a group V element other than nitrogen (N) And 0 ≦ α <1.) Al _X Ga _Y In _Z N _1-α M _α forming this intervening layer is, for example, aluminum nitride / gallium (Al _X Ga _Y N: 0 ≦ X, Y ≦ 1, X + Y = 1), gallium nitride / indium ( Ga _Y In _Z N: 0 ≦ Y, Z ≦ 1, Y + Z = 1), aluminum nitride phosphide (AlN _1-α P _α : 0 ≦ α <1).

  In particular, the intervening layer is preferably made of a group III nitride semiconductor material having a low degree of lattice mismatch with the 3C—SiC layer. For example, a 3C-SiC layer having a non-stoichiometric composition with a lattice constant of 0.451 nm is joined with a cubic and zinc blende-type GaN layer (lattice constant = 0.451 nm). It is preferable to provide it. Further, for example, a 3C-SiC layer having a non-stoichiometric composition with a lattice constant of 0.438 nm is joined with a layer of cubic and zinc blende-type AlN (lattice constant = 0.438 nm). It is preferable to provide them.

  In addition, a layer formed of a wurtzite crystal type hexagonal group III nitride semiconductor having an a-axis lattice constant that matches the spacing of the (110) crystal plane of the 3C-SiC layer of a non-stoichiometric composition is an intervening layer. It is convenient to provide as. For example, a 3C-SiC layer having a non-stoichiometric composition in which the spacing of (110) crystal planes is in the range of 0.308 nm to 0.325 nm may include hexagonal wurtzite having an a-axis lattice constant in that range. Crystalline AlN (a = 0.111 nm) or GaN (a = 0.319 nm) can be suitably bonded and provided.

  The lattice constant of the 3C—SiC layer having a non-stoichiometric composition is also changed by the temperature at which hydrocarbon molecules are adsorbed on the surface of the single crystal substrate to form the layer. The higher the temperature at which the hydrocarbon molecules are adsorbed, the more the 3C—SiC layer containing silicon (Si) can be made richer. Therefore, the 3C—SiC layer having a larger lattice constant can be formed. Further, after the hydrocarbon molecules are adsorbed on the single crystal substrate, when the single crystal substrate is heated, a 3C-SiC layer containing silicon (Si) richly when heated while supplying a gas containing silicon (Si). Can be formed. A silicon (Si) rich in lattice constant exceeding 0.436 nm and 0.460 nm or less can be suitably used to form the intervening layer made of the above cubic or hexagonal group III nitride semiconductor. 3C-SiC layer having a non-stoichiometric composition.

  In forming an intervening layer made of a group III nitride semiconductor on a 3C-SiC layer having a non-stoichiometric composition, before supplying a raw material of a group V constituent element constituting the intervening layer, III According to the method of supplying the group constituent element raw material, an intervening layer having a uniform orientation can be efficiently formed. For example, when forming a hexagonal GaN layer as an intervening layer on the surface of the {111} crystal plane of a 3C-SiC layer having a (3 × 3) rearrangement structure, a gallium (Ga) source material is used as a nitrogen source material. If it is supplied earlier in time, a group III nitride semiconductor layer can be formed in which the orientation relationship is uniform with <110> -3C—SiC‖a-axis—GaN. Here, the symbol “‖” means that both crystal planes are parallel to each other.

  In the case where an interstitial layer made of a group III nitride semiconductor material containing aluminum (Al) is provided on a 3C-SiC layer having a non-stoichiometric composition, first, in terms of time, the aluminum (Al) It is preferable to start supplying the raw material, then supply a raw material of a group III constituent element other than Al, and then supply a raw material of a group V constituent element such as nitrogen. By supplying the Al raw material first in time, an intervening layer in which the crystal system is uniformly unified can be formed in both orientation relations.

  The intervening layer made of a group III nitride semiconductor is, for example, a metal organic chemical vapor deposition method (English abbreviation: MOCVD), a halogen or hydride chemical vapor deposition (CVD) method, an MBE method, It can be formed using a growth means such as a chemical beam growth method (English abbreviation: CBE). In such a growth means, (a) the surface of the silicon substrate is cleaned and (7 × 7) a rearranged structure appears, and (b) hydrocarbon molecules are adsorbed on the cleaned surface of the silicon substrate. (C) using the adsorbed hydrocarbon molecules to form a 3C-SiC layer, and (d) forming the intervening layer on the 3C-SiC layer in the order listed. If the same means is used, it is advantageous to manufacture a semiconductor device easily.

  By means of growing under a high vacuum environment such as MBE method or CBE method, a (7 × 7) rearrangement structure can easily appear on the surface of the (111) silicon substrate made of the (111) crystal plane. The hydrocarbon molecules were adsorbed on the surface of the silicon substrate while maintaining a high vacuum environment convenient for maintaining the rearrangement structure, and a 3C-SiC layer was formed using the adsorbed hydrocarbon molecules. After that, the process of forming an intervening layer made of a group III nitride semiconductor on the surface having the (3 × 3) rearrangement structure of the 3C—SiC layer can be carried out consistently and continuously, and the semiconductor can be simplified. An element can be manufactured.

  In addition, if a means for performing growth using a high vacuum environment is used, when hydrocarbon molecules are adsorbed on the surface of the silicon substrate, electrons can be easily irradiated toward the surface of the silicon substrate. . In addition, when a 3C-SiC layer having a (3 × 3) rearrangement structure is formed using adsorbed hydrocarbon molecules, it is also possible to irradiate electrons toward the surface of the silicon substrate in a high vacuum environment. There is an advantage that it can be easily performed because it is a growth means utilizing the above.

  The intervening layer made of a group III nitride semiconductor provided bonded to the surface of the 3C—SiC layer having the (3 × 3) rearrangement structure is a growth layer having excellent surface flatness. In addition, for example, a group III nitride semiconductor layer formed using an intervening layer having a flat surface as a base also inherits the flatness of the surface of the base and has excellent flatness of the surface. Therefore, if such a group III nitride semiconductor layer having excellent flatness or a growth layer formed using it as an underlayer is used as an active layer (active layer), a semiconductor element having excellent optical or electrical characteristics can be configured.

  An intervening layer made of a hexagonal group III nitride semiconductor with a flat surface formed on the surface of a (3 × 3) rearrangement structure of 3C—SiC, or a flat surface formed using the intervening layer as a base If a high-purity group III nitride semiconductor layer is used as, for example, an electron transit layer (channel layer) or an electron supply layer, a flat heterojunction that has an advantage in high-speed travel and movement of two-dimensional electrons. A junction interface can be formed, which is advantageous for manufacturing a high mobility group III nitride semiconductor FET. That is, coupled with the expression of the piezo effect by the hexagonal group III nitride semiconductor material, high-speed operation with a flat junction interface capable of efficiently storing high-mobility two-dimensional electrons is possible. MESFET can be produced stably.

  In addition, an intervening layer made of a hexagonal group III nitride semiconductor having a flat surface formed on the surface of a 3C-SiC (3 × 3) most aligned structure, or a surface formed using it as a base is flat. If such a high-purity group III nitride semiconductor layer is used as, for example, a barrier layer such as a clad layer for a light-emitting device or a light-emitting layer, a light-emitting device such as a high-intensity LED can be formed. In particular, a group III nitride semiconductor layer having a uniform orientation can be formed on the surface of 3C-SiC having a (3 × 3) top-aligned structure. Since the group III nitride semiconductor layer has a low density of crystal grain boundaries due to the difference in orientation, it is useful as a light-emitting layer for providing high-intensity light emission.

  (Example 1) In Example 1, a hexagonal crystal formed via a non-stoichiometric cubic silicon carbide layer provided on a (111) silicon substrate having a (111) crystal plane as a surface. The present invention will be specifically described by taking as an example the case of producing a group III nitride semiconductor LED from a laminated structure having an intervening layer made of a group III nitride semiconductor.

  A vertical cross-sectional structure of the LED 10 produced in Example 1 is schematically shown in FIG. FIG. 2 schematically shows a planar structure of the LED 10 shown in FIG.

For manufacturing the LED 10, p-type silicon having a (111) crystal plane as a surface and doped with boron (element symbol: B) was used as the substrate 101. First, after the substrate 101 was transferred into a growth chamber for MBE growth, the substrate 101 was heated to 850 ° C. in a high vacuum of about 5 × 10 ⁻⁷ Pascal (Pa). When heating the silicon substrate 101, electrons were also irradiated toward the surface of the substrate 101. The density of the irradiated electrons was 1 × 10 ¹² cm ⁻² and the acceleration voltage was 100V. While monitoring the RHEED pattern, heating was performed while irradiating electrons continuously at the same temperature until a (7 × 7) rearrangement structure appeared on the (111) crystal plane forming the surface of the substrate 101.

After confirming the appearance of the (7 × 7) rearrangement structure on the RHEED pattern, the temperature was lowered to 600 ° C. while the substrate 101 was housed in the MBE growth chamber. Next, acetylene gas was sprayed to irradiate the surface of the substrate 101 with electrons, and acetylene molecules were adsorbed on the surface. The density of the irradiated electrons was 1 × 10 ¹³ cm ⁻² and the acceleration voltage was 300V. The acetylene gas was continuously blown on the RHEED pattern until the electron diffraction spots caused by the (7 × 7) rearrangement structure on the surface of the substrate 101 almost disappeared. When the (7 × 7) rearrangement structure appeared, the irradiation of electrons toward the silicon substrate 101 was stopped as the acetylene gas blowing in the high vacuum was finished.

After stopping the blowing of acetylene gas to the surface of the substrate 101 and electron irradiation, the substrate 101 was heated to 700 ° C. Again, irradiation of electrons was started toward the surface of the silicon substrate 101 on which acetylene molecules were adsorbed. The density of the irradiated electrons was 5 × 10 ¹³ cm ⁻² and the acceleration voltage was 350V. Streaks (light stripes) appear in the RHEED pattern, and a cubic 3C-type silicon carbide (3C-SiC) layer 102 is formed by a reaction between the adsorbed acetylene molecules and silicon (Si) atoms near the surface of the silicon substrate 101. The electron irradiation was continued while the silicon substrate 101 was held at 700 ° C. until it was recognized that this was done.

  Based on the lattice constant of (111) silicon at the temperature at which the 3C-SiC layer 102 was formed on the surface of the silicon substrate 101, the lattice constant of the 3C-SiC layer 102 was calculated to be 0.450 nm. The lattice constant of the 3C—SiC layer 102 was determined not to be due to strain affected by the silicon substrate 101 but to be rich in chemical equivalents of silicon. The surface was a (111) crystal plane. Moreover, it was certain from the RHEED pattern that a (3 × 3) rearrangement structure appeared on the surface.

  Even if the incident position of the electron beam incident on the surface of the 3C-SiC layer 102 is changed in order to obtain the RHEED pattern, the (3 × 3) rearrangement structure is uniformly formed from the surface of the 3C-SiC layer 102. An RHEED pattern showing was obtained. Therefore, if the 3C-SiC layer is formed while irradiating electrons, it can be effective to form a (3 × 3) rearrangement structure uniformly on the entire surface of the silicon substrate 101. Indicated. The layer thickness of the 3C—SiC layer 102 was about 2 nm over substantially the entire surface of the silicon substrate 101.

On the surface having a (3 × 3) rearrangement structure of the 3C-SiC layer 102 having a non-stoichiometric composition rich in silicon, a wurtzite crystal type is formed by a high frequency plasma MBE method using nitrogen plasma as a nitrogen source. The hexagonal aluminum nitride / gallium mixed crystal (Al _0.75 Ga _0.25 N) layer 103 was formed as an intervening layer made of a group III nitride semiconductor. The Al _0.75 Ga _0.25 N layer 103 was formed at a temperature of the silicon substrate 101 of 720 ° C.

When the Al _0.75 Ga _0.25 N layer 103 is formed, the aluminum (Al) beam is rearranged (3 × 3) of the 3C—SiC layer 102 in time before the nitrogen source. The surface of the structure was irradiated. The nitrogen source started to irradiate the surface of the (3 × 3) rearranged structure 5 seconds after the start of irradiation with the aluminum beam.

The layer thickness of the n-type Al _0.75 Ga _0.25 N layer 103 was about 50 nm, and the surface was a {0001} crystal plane. In addition, the Al _0.75 Ga _0.25 N layer 103 was formed with a uniform (3 × 3) rearranged 3C—SiC layer 102 as an underlayer, and thus became a layer particularly excellent in orientation. The orientation relationship obtained from the electron diffraction pattern is <110> -3C-SiC‖ <1. -2.1.0. It was> (a-axis) -Al _0.75 Ga _0.25 N. Further, according to observation of the surface using a general atomic force microscope (abbreviation: AFM), the height difference of the surface of the Al _0.75 Ga _0.25 N layer 103 is about 1 nm at the maximum, and the flatness is excellent. It was shown to be a thing.

A hexagonal n-type gallium nitride (GaN) layer 104 was formed on a hexagonal wurtzite crystal Al _0.75 Ga _0.25 N layer 103 by a high-frequency plasma MBE method at 720 ° C. as described above. . The layer thickness of the n-type GaN layer 104 was about 3200 nm. When growing the n-type GaN layer 104, a gallium (Ga) beam and a nitrogen source were simultaneously irradiated onto the surface of the Al _0.75 Ga _0.25 N layer 103 at the same time.

Since the n-type GaN layer 104 is formed with the uniform orientation Al _0.75 Ga _0.25 N layer 103 as a base, it becomes a single crystal layer with uniform orientation and excellent crystallinity. Used as the lower cladding layer.

On the lower cladding layer 104, one cycle of a barrier layer made of n-type GaN and a well layer made of n-type gallium nitride / indium mixed crystal (Ga _0.85 In _0.15 N) is formed by the same high frequency MBE method as described above. A light emitting layer 105 having a multiple quantum well (English abbreviation: MQW) structure formed by stacking them over 5 periods was formed. An upper cladding layer 106 made of p-type Al _0.10 Ga _0.90 N (layer thickness: about 45 nm) was formed on the light emitting layer 105. Thus, a light emitting portion having a pn junction type double hetero (DH) junction structure was constituted by the n type clad layer 104, the n type light emitting layer 105, and the p type upper clad layer 106. A contact layer 107 made of p-type GaN (layer thickness: about 90 nm) was further provided on the p-type upper clad layer 106 forming the light emitting portion to form a laminated structure 100 for LED 10 use.

A p-type ohmic electrode 108 made of gold (Au) and nickel (Ni) oxide was formed on the surface of the p-type contact layer 107 that is the outermost layer of the multilayer structure 100. One n-type ohmic electrode 109 is exposed by removing the lower cladding layer 104, the light emitting layer 105, the upper cladding layer 106, and the contact layer 107 in the region where the electrode 109 is provided by a general dry etching means. The Al _0.75 Ga _0.25 N layer 103 was provided on the surface. The n-type ohmic electrode 109 was composed of a titanium (Ti) film formed by a general electron beam evaporation method.

  The device operating current was passed between the p-type and n-type ohmic electrodes 108 and 109 of the LED chip 10 manufactured as described above, and the optical and electrical characteristics were investigated. When a current was passed through the LED 10 in the forward direction, blue light having a dominant wavelength of 460 nm was emitted. The light emission output when the forward current was 20 mA was a high value of about 2.3 milliwatts (mW). The forward voltage (Vf) when a current of 20 mA was passed in the forward direction was about 3.6V.

  In addition, the surface of the (3 × 3) rearrangement structure of the 3C—SiC layer 102 of the non-stoichiometric composition containing abundant silicon (Si) and carbon (C) is uniform. When the reverse current was set to 10 μA, the light emitting part was composed of a group III nitride semiconductor layer having excellent crystallinity and an excellent crystallinity formed through an intervening layer made of a group III nitride semiconductor having excellent crystallinity. The reverse voltage was 15V. Moreover, the LED which was excellent in the reverse withstand voltage property with almost no local withstand voltage breakdown (local breakdown) was brought about.

  (Example 2) In this Example 2, hexagonal crystal formed through a cubic silicon carbide layer having a non-stoichiometric composition provided on a (111) silicon substrate having a (111) crystal plane as a surface. The present invention will be specifically described by taking as an example the case of producing a group III nitride semiconductor MESFET from a laminated structure having an intervening layer made of a group III nitride semiconductor.

  FIG. 3 schematically shows a longitudinal sectional structure of the MESFET 20 according to the second embodiment.

For manufacturing the MESFET 20, high resistance silicon having a (111) crystal plane as a surface and added with phosphorus (element symbol: P) was used as the substrate 201. After the silicon substrate 201 was transferred into a growth chamber for MBE growth, the substrate 201 was heated to 800 ° C. in a high vacuum of about 5 × 10 ⁻⁷ Pascal (Pa). While monitoring the RHEED pattern, heating was continued at the same temperature until a (7 × 7) rearranged structure appeared on the (111) crystal plane forming the surface of the silicon substrate 201.

  After confirming the appearance of the (7 × 7) rearrangement structure, the temperature was lowered to 400 ° C. while the silicon substrate 201 was housed in the MBE growth chamber. Next, acetylene gas was sprayed on the surface of the silicon substrate 201 to adsorb acetylene molecules on the surface. Acetylene gas was continuously supplied on the RHEED pattern until the electron diffraction spots derived from the (7 × 7) rearrangement structure on the surface of the substrate 201 almost disappeared.

Thereafter, the temperature of the silicon substrate 201 was raised to 500 ° C. When the temperature of the substrate 201 was stabilized at 500 ° C., irradiation of electrons toward the surface of the silicon substrate 201 began. Electrons were generated by energizing and heating a tungsten (element symbol: W) filament disposed in a growth chamber maintained in a high vacuum. The acceleration voltage for electron irradiation was 500 V, and the irradiation density was 5 × 10 ¹³ cm ⁻² . The surface of the substrate 201 was continuously irradiated with electrons until a streak due to the (3 × 3) rearrangement structure of 3C—SiC appeared in the RHEED pattern.

  At 500 ° C., the lattice constant of the formed 3C—SiC layer 202 was calculated based on the lattice constant of silicon obtained from the RHEED pattern of (111) silicon. The lattice constant of the 3C—SiC layer 202 was calculated to be 0.438 nm. The reason why the lattice constant is smaller than that of the 3C-SiC layer 102 described in Example 1 is that the temperature for heating the silicon substrate after adsorbing acetylene molecules is lower than that in Example 1 above. It was interpreted. Further, in the RHEED pattern of the 3C—SiC layer 202, abnormal diffraction due to twins and stacking faults was not observed. The layer thickness of the 3C—SiC layer 202 was about 2 nm.

A hexagonal wurtzite crystal-type aluminum nitride (AlN) layer 203 is formed on the 3C-SiC layer 202 having a non-stoichiometric composition rich in silicon as compared with carbon by MBE using nitrogen plasma as a nitrogen source. Was formed as an intervening layer. The undoped AlN layer 203 forming the intervening layer was formed at a temperature of 780 ° C. while maintaining the pressure in the MBE growth chamber at a high vacuum of about 1 × 10 ⁻⁶ Pa. The nitrogen plasma was generated using an electron cyclotron resonance (ECR) type apparatus that applies a high frequency of 13.56 MHz and a magnetic field to high purity nitrogen gas.

  When the AlN layer 203 forming the intervening layer was grown, an aluminum (Al) beam was first supplied to the surface of the (3 × 3) rearranged structure of the 3C—SiC layer 202 in time. Nitrogen plasma was irradiated toward the surface of the 3C—SiC layer 202 3 seconds after the start of irradiation with the aluminum beam.

  Since the AlN layer 203 was provided by being bonded to the surface of the 3C—SiC layer 202 having the (3 × 3) rearrangement structure, it became a single crystal layer having a uniform orientation. The orientation relationship obtained from the electron diffraction pattern is <110> -3C-SiC‖ <1. -2.1.0. > (A-axis) -AlN. The AlN layer 203 was a high resistance layer, and the layer thickness was about 8 nm. In addition, observation of the surface using a general atomic force microscope showed that the surface of the AlN layer 203 was excellent in flatness with a maximum height difference of about 1 nm.

{0.0.0.1. Of the surface of the AlN layer 203. } On the crystal plane, an undoped n-type gallium nitride (GaN) layer was formed as an electron transit layer 204 at 750 ° C. by the same MBE method as described above. The n-type GaN layer 204 forming the electron transit layer 204 has a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ and a layer thickness of about 25 nm. On the electron transit layer 204, an electron supply layer 205 made of an n-type hexagonal Al _0.25 Ga _0.75 N mixed crystal having a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ and a layer thickness of about 25 nm was formed. On the electron supply layer 205, there is further provided a contact layer 206 made of hexagonal n-type GaN having a carrier concentration of 3 × 10 ¹⁸ cm ⁻³ and a layer thickness of about 50 nm. A body 200 was formed.

  As described above, the n-type GaN layer constituting the electron transit layer 204 is an intervening layer made of a group III nitride semiconductor (AlN layer) formed on the surface of the 3C—SiC layer 202 having a (3 × 3) rearrangement structure. 203), a layer having excellent surface flatness was obtained. Therefore, it was confirmed from observation of a lattice image using a high-resolution transmission electron microscope (English abbreviation: HRTEM) that a heterojunction having a flat junction interface was formed with the electron supply layer 205.

In addition, since a heterojunction interface having excellent flatness is formed by the electron transit layer 204 and the electron supply layer 205, the stacked structure 200 having the structure of the present invention has a high hole of about 1500 cm ² / V · s at room temperature. (Hall) Mobility was revealed. Using this high electron mobility, MESFET 20 capable of expressing high mutual conductance (gm) was produced.

  In manufacturing the MESFET 20, the region where the Schottky contact gate electrode 207 is provided and the contact layer 206 in the vicinity thereof were removed by a general dry etching method. Next, a metal gate electrode 207 was formed on the surface of the electron supply layer 205 exposed in the recess region formed by the etching. By providing the source electrode 208 and the drain electrode 209 on the surface of the contact layer 206 left facing both sides of the recess region, the MESFET 20 capable of expressing high gm was configured.

  In addition, the MESFET 20 is provided as a base of the electron transit layer 204 by being bonded to the 3C-SiC layer 202 having a (3 × 3) rearrangement structure, and is a group III nitride semiconductor layer (highly oriented and excellent in crystallinity). Since the resistor AlN layer 203 is arranged, the pin-off characteristic of the source-drain current (so-called Ids) is excellent.

It is a longitudinal cross-sectional schematic diagram of LED as described in Example 1 of this invention. It is a plane schematic diagram of LED described in FIG. It is a longitudinal cross-sectional schematic diagram of MESFET as described in Example 2 of this invention.

Explanation of symbols

10 LED
DESCRIPTION OF SYMBOLS 100 LED use laminated structure 101 (111) Silicon substrate 102 Cubic 3C type silicon carbide layer 103 of non-stoichiometric composition 103 Interposition layer (n-type AlGaN layer)
104 Group III nitride semiconductor lower cladding layer 105 Group III nitride semiconductor light emitting layer 106 Group III nitride semiconductor upper cladding layer 107 Group III nitride semiconductor p-type contact layer 108 p-type ohmic electrode 109 n-type ohmic electrode 20 MESFET
200 MESFET Use Laminated Structure 201 (111) Silicon Substrate 202 Non-stoichiometric Cubic 3C Type Silicon Carbide Layer 203 Intervening Layer (High Resistance AlN Layer)
204 Group III nitride semiconductor electron transit layer 205 Group III nitride semiconductor electron supply layer 206 Group III nitride semiconductor n-type contact layer 207 Gate electrode 208 Source electrode 209 Drain electrode

Claims (11)

In a semiconductor element comprising a substrate made of a single crystal, a silicon carbide layer provided on the surface of the single crystal substrate, and an intervening layer made of a group III nitride semiconductor provided on the surface of the silicon carbide layer,
The silicon carbide layer is made of a cubic crystal containing a stoichiometrically rich silicon, and the surface has a rearranged structure having a (3 × 3) structure.
The semiconductor element characterized by the above-mentioned.   The semiconductor element according to claim 1, wherein the substrate is made of a silicon single crystal.   The semiconductor element according to claim 1, wherein the substrate is made of a {111} silicon single crystal having a {111} crystal plane as a surface.   The semiconductor element according to claim 3, wherein a surface of the substrate has a (7 × 7) rearrangement structure.   5. The semiconductor element according to claim 1, wherein the intervening layer contains aluminum as a group III element. The semiconductor element according to claim 5, wherein the intervening layer is a layer made of hexagonal wurtzite crystal type aluminum nitride gallium (compositional formula Al _X Ga _{1 -X} N: 0 ≦ X ≦ 1).   The semiconductor element according to claim 1, wherein a group III nitride semiconductor layer is provided on the intervening layer. Manufacturing a semiconductor element comprising a substrate made of a single crystal, a silicon carbide layer provided on the surface of the single crystal substrate, and an intervening layer made of a group III nitride semiconductor provided on the surface of the silicon carbide layer In the semiconductor element manufacturing method,
A first step of spraying hydrocarbon gas on the surface of the substrate to adsorb hydrocarbons;
While irradiating electrons onto the surface of the substrate on which the hydrocarbon is adsorbed, the substrate is heated to a temperature equal to or higher than the temperature on which the hydrocarbon is adsorbed, and the surface is made of a cubic crystal that is stoichiometrically rich in silicon. A second step of forming a silicon carbide layer having a (3 × 3) rearrangement structure;
Including a third step of forming a gas source containing nitrogen and a gas source containing a Group III element on the surface of the silicon carbide layer to form the intermediate layer made of a Group III nitride semiconductor.
A method of manufacturing a semiconductor device.   The semiconductor element manufacturing method according to claim 8, wherein in the third step, the intervening layer is formed by supplying a gas source containing a Group III element earlier in time than a gas source containing nitrogen.   In the third step, the gaseous raw material containing aluminum is first supplied temporally, then the gaseous raw material containing a group III element other than aluminum is supplied, and then the gaseous raw material containing nitrogen is supplied, 9. The method of manufacturing a semiconductor element according to claim 8, wherein the intervening layer made of a group III nitride semiconductor layer containing aluminum is formed.   11. The semiconductor element manufacturing according to claim 8, wherein in the first step, hydrocarbon gas is sprayed onto the surface of the substrate and hydrocarbons are adsorbed on the surface of the substrate while irradiating electrons. Method.

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