JP5043363B2 - Method for forming gallium nitride crystal, substrate, and method for forming gallium nitride substrate - Google Patents

Description

  The present invention relates to a method for forming a gallium nitride crystal, a substrate, and a method for forming a gallium nitride substrate.

  Patent Document 1 describes a GaN light emitting diode with high luminance and high luminous efficiency. The light emitting diode includes a plurality of GaN nanorods. Each GaN nanorod consists of an n-type GaN nanorod, an InGaN quantum well structure, and a p-type GaN nanorod in this order in the longitudinal direction. An InGaN quantum well structure is provided in the pn junction region of the pn junction GaN nanorod. When a large number of such GaN nanorods are arranged in an array, an LED having higher luminance and higher luminous efficiency than a laminated film-like GaN LED is provided.

  Non-Patent Document 1 describes crystal growth on a silicon (111) plane substrate. In crystal growth on a silicon (111) plane substrate, different crystal morphology is exhibited under the nitrogen-rich condition and the gallium-rich condition. Under nitrogen-rich conditions, it shows columnar features. The diameter of the nanocolumn is, for example, about 60 nm.

Non-Patent Document 2 describes a GaN nanostructure (GaN nanocolumn) formed on a sapphire substrate. This nanocolumn is formed by molecular beam epitaxy using an RF radical source. The average diameter of the nanocolumn can be reduced to about 40 nm to 45 nm by adjusting the conditions.
JP 2005-228936 A Journal of Crystal Growth 183, (1998) pp.23-30 Journal of Crystal Growth 189/190, (1998) pp.138-141

  Non-Patent Documents 1 and 2 show that a fine columnar structure grows on a silicon substrate and a sapphire substrate. The average diameter is given in the above document. Gallium nitride based columnar structures formed under nitrogen-rich conditions are called “nanocolumns”. In Patent Document 1, a semiconductor device including a light emitting diode formed in each nanocolumn is manufactured, and a transparent insulator is provided between the nanocolumns. An n-electrode is provided on the gallium nitride buffer layer serving as a base for the nanocolumn, and a transparent electrode and a p-electrode are provided on the nanocolumn and the transparent insulator. The transparent electrode is provided so as to be directly connected to each of the nanocolumns.

  As described above, Non-Patent Documents 1 and 2 only describe the academic aspects of nanocolumns, and Patent Document 1 only describes light-emitting diodes (LEDs) formed in the nanocolumns. It is.

  On the other hand, in the field of gallium nitride based semiconductor devices, unlike other III-V compound semiconductors, it is required to provide a substrate for high-quality crystal growth for gallium nitride based semiconductor devices. In order to meet such a demand, the inventors conducted various studies.

  An object of the present invention is to provide a method of forming a gallium nitride based crystal for a substrate for crystal growth of a gallium nitride based semiconductor, and to provide a substrate for a gallium nitride based semiconductor device. A further object is to provide a method of forming a gallium nitride based substrate for a gallium nitride based semiconductor device.

One aspect of the present invention is a method of forming a gallium nitride based crystal for a gallium nitride based crystal growth substrate. The method includes (a) preparing a substrate that includes a semiconductor material different from a gallium nitride based semiconductor and growing the gallium nitride based semiconductor; and (b) forming the substrate in a first crystal. A step of growing on a substrate a nanocolumn region having a plurality of nanocolumns made of a gallium nitride based semiconductor after being disposed in a growth apparatus ; and (c) a dislocation density of 1 so as to bond the plurality of nanocolumns in the nanocolumn region to each other. A step of growing a gallium nitride based semiconductor film of 10 ⁵ cm ⁻² or less with the first crystal growth apparatus ; and (d) a step of removing the substrate after growing the gallium nitride based semiconductor film; e) After removing the substrate, a gallium nitride based semiconductor thick film is placed on the gallium nitride based semiconductor film in a second crystal growth apparatus different from the first crystal growth apparatus. And a step of growing by HVPE Te, the gallium nitride-based semiconductor film crystal growth method for growing Unlike HVPE method, conductivity type gallium nitride based semiconductor of the nano-columns region, conduction of the gallium nitride-based semiconductor film Same as type.

  According to this method, since the nanocolumn region is made of a single crystal having a very low dislocation density, the gallium nitride semiconductor film grown on the nanocolumn region is also made of a single crystal having a very low dislocation density. In addition, since the substrate includes a support made of a material different from that of the gallium nitride semiconductor, a gallium nitride semiconductor film can be obtained without using a substrate made of a gallium nitride semiconductor. Further, the size of the gallium nitride based semiconductor film can be made substantially the same as the size of the substrate.

  The method according to the present invention further comprises (d) a step of growing a gallium nitride based semiconductor thick film on the gallium nitride based semiconductor film by an HVPE method, and the crystal growth method for growing the gallium nitride based semiconductor film is an HVPE method. And can be different. According to this method, since the HVPE method is used for the growth of the gallium nitride semiconductor, a thick gallium nitride semiconductor with a low dislocation density can be obtained.

  In the method according to the present invention, the nanocolumn region and the gallium nitride based semiconductor film are preferably made of gallium nitride. According to this method, since it is a binary crystal, growth is easy.

  The method according to the present invention may further include a step of removing the substrate after growing the gallium nitride based semiconductor thick film. According to this method, since the gallium nitride semiconductor film is supported by the support in the substrate, the gallium nitride semiconductor thick film can be grown regardless of the film thickness of the gallium nitride semiconductor film. By removing the substrate, a crystal body substantially made of a gallium nitride based semiconductor can be obtained.

  The method according to the present invention may further include a step of removing the substrate after growing the gallium nitride based semiconductor film. According to this method, the gallium nitride based semiconductor film does not receive stress from the substrate.

  The method according to the present invention includes: (e) a step of removing the substrate after growing the gallium nitride semiconductor film; and (f) a gallium nitride based semiconductor on the gallium nitride based semiconductor film after removing the substrate. A crystal growth method for growing the gallium nitride based semiconductor film may be different from the HVPE method. According to this method, the growth of the gallium nitride-based semiconductor thick film does not receive stress from the substrate. In addition, a crystal body substantially made of a gallium nitride semiconductor can be obtained.

  In the method according to the present invention, the nanocolumn region, the gallium nitride based semiconductor film, and the gallium nitride based semiconductor thick film are preferably made of gallium nitride having the same conductivity type. According to this method, an n-type, i-type or p-type gallium nitride single crystal having a very low dislocation density can be obtained.

In the method according to the present invention, the gallium-based semiconductor thick film may be made of _{In X Al Y Ga 1-X} -Y N (0 ≦ X ≦ 1,0 ≦ Y ≦ 1). According to this method, single crystals of GaN, InGaN, AlGaN, and InAlGaN having a very low dislocation density can be obtained.

  In the method according to the present invention, the conductivity type of the nanocolumn region and the gallium nitride based semiconductor film is p-type. According to this method, a single crystal made of a p-type gallium nitride semiconductor can be obtained.

  In the method according to the present invention, the substrate may include a silicon support. According to this method, a single crystal made of a gallium nitride-based semiconductor having a very low dislocation density can be obtained by using an easily available large-diameter, low-cost silicon support.

  In the method according to the invention, the substrate preferably comprises a GaAs support. According to this method, a single crystal made of a gallium nitride semiconductor having a very low dislocation density can be obtained by using an easily available GaAs support.

  The product produced by the above method can be used as a gallium nitride crystal growth substrate. Alternatively, the product produced by this method can be used as a crystal for producing a gallium nitride-based substrate.

  Another aspect of the present invention is a substrate for a gallium nitride based semiconductor device. The substrate has (a) a nanocolumn region having a plurality of nanocolumns made of gallium nitride, and (b) a main surface connected to one end of each of the plurality of nanocolumns to form a gallium nitride based semiconductor device. A gallium nitride semiconductor film; and (c) a support made of a material different from gallium nitride, and a support base supporting the other ends of the plurality of nanocolumns, wherein the conductivity type of gallium nitride in the nanocolumn region is the nitride It is the same as the conductivity type of the gallium semiconductor film.

  According to this substrate, since the nanocolumn region is made of a crystal having a very low dislocation density, the gallium nitride based semiconductor film grown on the nanocolumn region is also made of a crystal having a very low dislocation density. In addition, since the nanocolumn is formed using a substrate made of a material different from that of the gallium nitride semiconductor, a gallium nitride semiconductor film can be obtained without using a substrate made of the gallium nitride semiconductor. Further, the size of the gallium nitride based semiconductor film can be made substantially the same as the size of the substrate.

  In the substrate according to the present invention, the support base may include a support made of either silicon or GaAs. Preferably, silicon and GaAs exhibit the desired conductivity.

  Another aspect of the present invention is a substrate for a gallium nitride based semiconductor device. The substrate has (a) a nanocolumn region having a plurality of nanocolumns made of gallium nitride, and (b) a main surface connected to one end of each of the plurality of nanocolumns to form a gallium nitride based semiconductor device. A conductivity type of the gallium nitride in the nanocolumn region is the same as the conductivity type of the gallium nitride semiconductor film.

  According to this substrate, since the nanocolumn region is made of a crystal having a very low dislocation density, the gallium nitride based semiconductor film grown on the nanocolumn region is also an n-type, i-type, or p-type having a very low dislocation density. It consists of a semiconductor crystal. In addition, since the nanocolumn is formed using a substrate made of a material different from that of the gallium nitride semiconductor, a gallium nitride semiconductor film can be obtained without using a substrate made of the gallium nitride semiconductor. Further, the size of the gallium nitride based semiconductor film can be made substantially the same as the size of the substrate. Further, since the other end of the nanocolumn region is not supported by the support base, the gallium nitride crystal is not subjected to stress from the support base. Therefore, the warpage of the substrate is small.

  In the substrate according to the present invention, the support base may include a support made of any one of silicon, GaAs, and sapphire. Preferably, silicon and GaAs exhibit the desired conductivity.

  In the substrate according to another aspect of the present invention, the nanocolumn region and the gallium nitride semiconductor film may have a p-type conductivity. This substrate can be used as a p-type gallium nitride semiconductor substrate.

Yet another aspect of the present invention is a method of forming a gallium nitride based substrate. The method includes (a) preparing a substrate including a support made of a material different from a gallium nitride based semiconductor and growing a gallium nitride based semiconductor; and (b) a plurality of gallium nitride based semiconductors. Growing a nanocolumn region having nanocolumns on the substrate; (c) coupling one end of the plurality of nanocolumns of the nanocolumn region to each other while growing a gallium nitride-based semiconductor; and (d) the plurality of the plurality of nanocolumns. A step of growing a gallium nitride based semiconductor film after bonding one ends of the nanocolumns; and (e) after growing the gallium nitride based semiconductor film, removing the substrate and the nanocolumn region to form a gallium nitride based crystalline body. And (f) a step of forming one or a plurality of gallium nitride semiconductor slices from the gallium nitride crystal. That.

  According to this method, since the nanocolumn region is made of a crystal having a very low dislocation density, the gallium nitride semiconductor grown on the nanocolumn region is also made of a crystal having a very low dislocation density. The size of the gallium nitride based semiconductor slice can be substantially the same as the size of the substrate. Therefore, an n-type, i-type or p-type gallium nitride semiconductor single crystal slice having a very low dislocation density can be formed.

Yet another aspect of the present invention is a method of forming a gallium nitride based substrate. The method includes (a) preparing a substrate including a support made of a material different from the gallium nitride based semiconductor and growing the gallium nitride based semiconductor; and (b) growing the substrate through a first crystal growth. A step of growing on the substrate a nanocolumn region having a plurality of nanocolumns made of a gallium nitride based semiconductor after being placed in the device ; and (c) while growing the gallium nitride based semiconductor in the first crystal growth device, A step of bonding one end of the plurality of nanocolumns in the nanocolumn region to each other; and (d) a dislocation having the same conductivity type as that of the gallium nitride-based semiconductor in the nanocolumn region after bonding one end of the plurality of nanocolumns to each other a step of growing a density 1 × 10 ⁵ cm ^-2 or less of gallium nitride-based semiconductor film, after growing the (e) the gallium nitride based semiconductor film, the group Removing the, (f) after removing the substrate, the gallium nitride-based semiconductor film on said first crystal growth apparatus different from the second gallium nitride semiconductor thick film by the HVPE method in the crystal growing apparatus (G) after growing the gallium nitride semiconductor thick film, removing the nanocolumn region to produce a gallium nitride crystal, and (h) one from the gallium nitride crystal. Or forming a plurality of gallium nitride based semiconductor slices.

  According to this method, since the nanocolumn region is made of a crystal having a very low dislocation density, the gallium nitride semiconductor film grown on the nanocolumn region is also made of a crystal having a very low dislocation density. Further, since the substrate is removed, a gallium nitride based semiconductor thick film is grown without stress from the substrate. Further, the size of the gallium nitride based semiconductor slice can be substantially the same as the size of the substrate. Therefore, a gallium nitride based semiconductor single crystal slice with a very low dislocation density can be formed.

  In the method according to still another aspect of the present invention, the nanocolumn region, the gallium nitride based semiconductor film, and the gallium nitride based semiconductor thick film are preferably made of gallium nitride having the same conductivity type. According to this method, an n-type, i-type or p-type gallium nitride single crystal is obtained.

  In the method according to still another aspect of the present invention, the gallium nitride based semiconductor slice is preferably made of a p-conductivity type gallium nitride semiconductor. According to this method, a slice is provided for a p-type gallium nitride semiconductor substrate.

In the method according to still another aspect of the present invention, the gallium nitride based semiconductor thick film may be made of In _X Al _Y Ga _1- XYN (0 ≦ X ≦ 1, 0 ≦ Y ≦ 1). it can. According to this method, a single crystal slice of GaN, InGaN, AlGaN, or InAlGaN having a very low dislocation density can be formed.

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  As described above, according to the present invention, a method of forming a gallium nitride based crystal for a substrate for crystal growth of a gallium nitride based semiconductor is provided. The invention also provides a substrate for a gallium nitride based semiconductor device. Furthermore, the present invention provides a method of forming a gallium nitride based substrate for a gallium nitride based semiconductor device.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, embodiments of the method for forming a gallium nitride crystal, the substrate, and the method for forming a gallium nitride substrate of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.

(First embodiment)
FIG. 1A schematically shows a substrate for a gallium nitride based semiconductor device. The substrate 11 a includes a nanocolumn region 13, a gallium nitride semiconductor film 15, and a support base 17. The nanocolumn region 13 has a plurality of nanocolumns 13a made of gallium nitride. The gallium nitride semiconductor film 15 is connected to each of the one ends 19 a of the plurality of nanocolumns 19. The conductivity type of the gallium nitride semiconductor film 15 is the same as the conductivity type of gallium nitride in the nanocolumn region 13. The gallium nitride semiconductor film 15 has a main surface 15a. The main surface 15a is provided for depositing a semiconductor film for forming a gallium nitride based semiconductor device. The support base 17 supports the other ends 19b of the plurality of nanocolumns 19 and includes a support 21 made of a material different from gallium nitride. The support 21 can be made of, for example, silicon, GaAs, or the like. Silicon and GaAs preferably exhibit the desired conductivity. The silicon substrate has a main surface made of, for example, a (111) surface, and the support base 17 including the silicon substrate includes a thin buffer film 23 provided on the silicon (111) surface. Includes AlN film. The AlN film has a wurtzite crystal structure. The support 21 can be made of, for example, sapphire. The sapphire substrate has a main surface made of, for example, a (0001) surface, and the support base 17 including the sapphire substrate includes a thin buffer film 23 provided on the sapphire (0001) surface. Including GaN film or AlN film. The GaN film or AlN film has a wurtzite crystal structure.

  According to this substrate 11a, since the nanocolumn region 13 is made of a crystal having a very low dislocation density, the gallium nitride based semiconductor film 15 grown on the nanocolumn region 13 is also made of a crystal having a very low dislocation density. Further, since the substrate 17 includes the support 21 made of a material different from that of the gallium nitride semiconductor, the gallium nitride semiconductor film 15 can be obtained without using the gallium nitride semiconductor substrate. Furthermore, the size of the gallium nitride based semiconductor film 15 can be made substantially the same as the size of the support base 17.

  Each nanocolumn 19 extends along an axis orthogonal to the main surface 17a of the substrate 17, and as described above, one end 19a of the nanocolumn 19 is connected to the gallium nitride semiconductor film 15, and The end 19 b is connected to the support base 17. Each nanocolumn 19 is made of a gallium nitride single crystal, and its growth axis is defined by the plane orientation of the underlying substrate 17. Further, the gallium nitride semiconductor film 15 has a region that transitions from each nanocolumn 19 to an integral gallium nitride single crystal.

  When the support 21 of the support base 17 is made of silicon, the size of the support base 17 is the size of a silicon wafer on the market, for example, about 2 inches to 12 inches. The support 21 can be made of GaAs. When the support body 21 of the support base 17 is made of sapphire, the size of the support base 17 is the size of a sapphire substrate distributed in the market, for example, about 2 inches to 6 inches.

  The thickness D1 of the nanocolumn region 13 is preferably 0.5 micrometers or more, for example. If the thickness D1 of the nanocolumn region 13 is 0.5 micrometers or more, there is an advantage that a nanocolumn with improved crystallinity can be obtained in order to produce a gallium nitride crystal for a substrate. The thickness D1 of the nanocolumn region 13 is preferably 1 micrometer or more, for example. If the thickness D1 of the nanocolumn region 13 is 1 micrometer or more, there is an advantage that a nanocolumn having a low dislocation can be obtained in order to produce a gallium nitride crystal for a substrate.

  The thickness D2 of the gallium nitride semiconductor film 15 is preferably not less than 0.5 micrometers, for example. If thickness D2 is 0.5 micrometer or more, there exists an advantage of surface smoothness in order to produce the gallium nitride type crystal for substrates. The thickness D2 of the gallium nitride semiconductor film 15 is preferably 3 micrometers or more, for example. When the thickness D2 is 3 micrometers or more, there is an advantage that the current spreads in the lateral direction with a low resistance when the crystallinity is high and conductivity is added in order to produce a gallium nitride crystal for a substrate.

  The nanocolumn region 13 and the gallium nitride based semiconductor film 15 are preferably made of gallium nitride having the same conductivity type. According to this method, an n-type, i-type or p-type gallium nitride single crystal is obtained.

Example 1
A silicon wafer having a (111) plane is RCA cleaned and then placed in the MBE chamber. In the MBE chamber, after evacuation, the wafer is heated at a temperature in the range of 850 degrees Celsius to 950 degrees Celsius. The heating time is preferably 10 minutes or more and 40 minutes or less, for example. With this heating, the natural oxide film on the silicon wafer is removed. After an AlN buffer layer is grown on this silicon wafer, GaN nanocolumns are fabricated under nitrogen-rich conditions. Thereafter, the amount of Ga flux is increased to bond individual GaN nanocolumns. After bonding, a GaN crystal is subsequently grown. As a result, a structure consisting of GaN film / GaN nanocolumn / buffer layer / wafer is obtained. During the growth of gallium nitride, if a dopant is not added when depositing GaN nanocolumns and GaN films, gallium nitride exhibiting insulating properties is produced. Moreover, if a dopant is added, gallium nitride which shows electroconductivity will be produced. For example, if GaN is grown while adding a p-type dopant such as Mg, a p-type gallium nitride substrate can be obtained. The dislocation density of the GaN film is, for example, 1 × 10 ⁵ cm ⁻² or less. The dislocation density was measured by cathodoluminescence.

(Second Embodiment)
FIG. 1B schematically shows a substrate for a gallium nitride based semiconductor device. The substrate 11 b includes a nanocolumn region 25 and a gallium nitride semiconductor film 27. The nanocolumn region 25 has a plurality of nanocolumns 29 made of gallium nitride. The gallium nitride semiconductor film 27 is connected to each one end 29a of the plurality of nanocolumns 29, and has a main surface 27a for forming a gallium nitride based semiconductor device. The conductivity type of gallium nitride in the nanocolumn region 25 is the same as the conductivity type of the gallium nitride semiconductor film 27.

  According to this substrate 11b, since the nanocolumn region 25 is made of a crystal having a very low dislocation density, the gallium nitride based semiconductor film 27 grown on the nanocolumn region 25 also has an n-type or i-type having a very low dislocation density. Or it consists of a p-type semiconductor crystal. Further, since the other end 29b of the nanocolumn 29 is not supported by the support base, the gallium nitride crystal is not subjected to stress from the support base. Therefore, the warpage of the substrate is small.

  Since the nanocolumns 29 are formed using a substrate made of a material different from that of the gallium nitride semiconductor, the large-diameter gallium nitride semiconductor film 27 can be obtained without using a substrate made of the gallium nitride semiconductor. Furthermore, the size of the gallium nitride based semiconductor film 27 can be made substantially the same as the size of the substrate. The other end 29b of the nanocolumn 29 may include a buffer layer. This buffer layer may include, for example, an AlN layer. This AlN layer has a wurtzite crystal structure. The crystal axis of each nanocolumn 29 is defined by this wurtzite crystal structure.

  Each nanocolumn 29 extends along an axis orthogonal to the main surface 27a of the gallium nitride semiconductor film 27. As already described, one end 29a of the nanocolumn 29 is connected to the gallium nitride semiconductor film 27, and the nanocolumn The other end 29b of 29 is open. Each nanocolumn 29 is made of a gallium nitride single crystal, and its growth axis is defined by the plane orientation of the underlying growth substrate. Further, the gallium nitride semiconductor film 27 has a region that transitions from each nanocolumn 29 to an integral gallium nitride single crystal.

  The thickness D3 of the nanocolumn region 27 is preferably about 0.5 to 1 micrometer, for example. If the thickness D3 of the nanocolumn region 27 is 0.5 micrometers or more, there is an advantage that a nanocolumn having improved crystallinity can be obtained in order to produce a gallium nitride crystal for a substrate. Further, when the thickness D3 of the nanocolumn region 27 is 1 micrometer or more, there is an advantage that a low-dislocation nanocolumn can be obtained in order to produce a gallium nitride crystal for a substrate.

  Further, the thickness D4 of the gallium nitride semiconductor film 27 is preferably, for example, not less than 0.5 micrometers. If the thickness D4 is 0.5 micrometers or more, in order to produce a gallium nitride based crystal for a substrate, a base (nanocolumn region) is formed on the surface of the gallium nitride semiconductor film 27 to which a number of columnar nanocolumn regions are connected. ) Has an advantage that it is smooth) to the extent that the effect of The thickness D4 of the gallium nitride semiconductor film 27 is preferably, for example, 3 micrometers or more. If the thickness D4 is 3 micrometers or more, there is an advantage that the current spreads in the lateral direction with a low resistance when the crystallinity is high and conductivity is added to produce a gallium nitride crystal for a substrate.

The substrate 11b is obtained by removing a support for the substrate 11a, for example, a silicon wafer. Wet etching can be used to remove the silicon wafer. As the etchant, it is possible to use, for example, HF + HNO ₃ , etc. in which silicon is etched but a gallium nitride based semiconductor is not etched. If a wafer made of a material different from the gallium nitride material is removed, the influence of the potential barrier and interface state due to, for example, a heterojunction (for example, a junction between silicon and aluminum nitride) is eliminated. Further, by this removal, the warpage of the substrate 11b becomes smaller than the warpage of the substrate 11a.

  As described above, according to the first and second embodiments, a substrate for a gallium nitride based semiconductor device is provided. The dislocation density of the main surfaces 15a and 27a of the gallium nitride semiconductor films 15 and 27 is low, and the sizes of the main surfaces 15a and 27a are almost equal to the size of the base substrate used for the fabrication of the nanocolumns. A large-diameter substrate for a gallium nitride based semiconductor device is provided without using a gallium nitride substrate.

(Third embodiment)
FIGS. 2A, 2B and 3 are schematic views showing main steps of a method of forming a gallium nitride based substrate for a gallium nitride based semiconductor device.

  As shown in FIG. 2A, a substrate 31 for growing a gallium nitride based semiconductor is prepared. The substrate 31 includes a support 33 made of a material different from that of the gallium nitride semiconductor, and a buffer film 35 formed on the support 33. The substrate 31 is prepared as follows, for example. The support 33 is placed in the crystal growth apparatus 37. In the present embodiment, an RF-MBE apparatus is used as the crystal growth apparatus 37, but HVPE or the like can be used without being limited thereto. As the support 33, for example, a (111) plane silicon wafer or a GaAs wafer, a (0001) plane sapphire substrate, or the like can be used. A buffer film 35 is deposited on the support 33. When the (111) plane silicon substrate is used, the buffer film 35 can include, for example, a GaN film or an AlN film. In this case, the thickness of the buffer film 35 is preferably 3 nm or more and 5 nm or less, for example. When a (0001) plane sapphire substrate is used, the buffer film 35 can include, for example, an AlN film. In this case, the thickness of the buffer film 35 is preferably 3 nm or more and 5 nm or less, for example. If necessary, the surface 33a of the support 33 can be thermally cleaned prior to the growth of the buffer film.

(Example 2)
Example of growth of AlN buffer layer (1) A 6-inch wafer having a silicon (111) surface is RCA cleaned and then placed in an MBE chamber. In an MBE chamber, after evacuation, heat at a temperature in the range of 850 degrees Celsius to 950 degrees Celsius. The heating time is preferably 10 minutes or more and 40 minutes or less, for example. By this heating, the natural oxide film of the silicon 6 inch wafer is removed. Next, at 500 degrees Celsius, 1 to 3 monolayers of aluminum are deposited and active nitrogen is supplied using an RF radical gun to obtain an AlN buffer layer.

(2) A titanium film is deposited on the back surface of a 4-inch substrate with a sapphire (0001) surface. The titanium film is, for example, 200 nm. After the formation of the titanium film, the sapphire substrate is placed in the MBE chamber. In an MBE chamber, after evacuation, heat at a temperature in the range of 850 degrees Celsius to 950 degrees Celsius. Thereafter, active nitrogen is supplied from an RF radical gun at 500 degrees Celsius to nitride the surface of the sapphire substrate. Subsequently, active nitrogen is supplied from an RF radical gun, and Al flux is supplied to form an AlN film of 1 to 5 nm.

Example of growth of GaN buffer layer A titanium film is deposited on the back surface of a 4-inch substrate of sapphire (0001) plane. The titanium film is, for example, 200 nm. After the formation of the titanium film, the sapphire substrate is placed in the MBE chamber. In an MBE chamber, after evacuation, heat at a temperature in the range of 850 degrees Celsius to 950 degrees Celsius. Thereafter, active nitrogen is supplied from an RF radical gun at 500 degrees Celsius to nitride the surface of the sapphire substrate. Subsequently, active nitrogen is supplied from an RF radical gun at 500 degrees Celsius, and Ga flux is supplied to form a GaN film of 1 to 5 nm.

As shown in FIG. 2B, the nanocolumn region 39 is formed on the substrate 31. The nanocolumn region 39 includes a plurality of nanocolumns 41 made of a gallium nitride semiconductor. The shape of the nanocolumn changes depending on the ratio of the number of moles of the Group V material supplied to the number of moles of the Group III material supplied (hereinafter referred to as “V / III”). Nanocolumns are grown under nitrogen-rich conditions. The nanocolumn is formed on the buffer film having the wurtzite structure and extends in the direction of the (0001) axis of the buffer film. The nanocolumn density in the nanocolumn region varies depending on, for example, the type of material of the buffer layer, its film thickness, and its growth conditions. The nanocolumn density can be changed, for example, in the range of about 1 × 10 ⁹ cm ^{−2 to} 5 × 10 ¹⁰ cm ⁻² . Under nitrogen-rich conditions, gallium nucleation and gallium migration are limited, so that columnar crystals grow rather than crystal film formation.

(Example 3)
An example of GaN nanocolumn growth uses an MBE growth apparatus. A K cell is used to provide a 7N gallium source and a 7N aluminum source, and an RF radical gun is used to provide a 6N N ₂ gas and a nitrogen source. The growth temperature is in the range of 750 degrees Celsius to 850 degrees Celsius. Supply gallium source and active nitrogen.
Example V / III ratio: nanocolumn growth (nitrogen rich condition rather than smooth GaN growth)
It is. The distortion of the nanocolumn is relaxed, and the nanocolumn region is a very high quality crystal. The growth surface includes facet planes, and dislocations are bent with growth, resulting in low dislocations in the nanocolumn region. The diameter of the nanocolumn varies depending on the growth temperature, growth rate, and V / III ratio, and is controlled, for example, in the range of about 30 nm to 200 nm. In particular, the diameter of the nanocolumn is highly dependent on the gallium supply. This is due to the fact that nanocolumn growth regulates gallium migration under nitrogen-rich conditions. The thickness of the nanocolumn region is changed according to the growth time. In order to obtain a high-quality nanocolumn, if this thickness is 0.5 micrometers or more, there is a technical advantage of improving crystallinity. If this thickness is about 3 micrometers, there is a technical advantage of low dislocation.

  As shown in FIG. 3, a gallium nitride based semiconductor film 43 is grown so that a plurality of nanocolumns 41 in the nanocolumn region 39 are coupled to each other. First, a gallium nitride based semiconductor region 45 that connects the plurality of nanocolumns 41 in the nanocolumn region 39 to each other is grown. A gallium material larger than the gallium supply amount in the growth condition of the nanocolumn region 39 is supplied. Increased gallium source promotes gallium nucleation and gallium migration. As a result, the plurality of nanocolumns 41 are coupled to each other, and a transition region 45 is formed.

Example 4
A transition region 45 is formed. Next, a gallium nitride single crystal region 47 is deposited on the gallium nitride based semiconductor region 45. Thereby, a gallium nitride based semiconductor film 43 is obtained. The conductivity type of the gallium nitride semiconductor in the nanocolumn region 39 is the same as that of the gallium nitride semiconductor film 43.

  According to this method, since the nanocolumn region 39 is made of a crystal having a very low dislocation density, the gallium nitride based semiconductor film 43 grown on the nanocolumn region 39 is also made of a crystal having a very low dislocation density. Further, since the substrate 31 includes the support 33 made of a material different from that of the gallium nitride semiconductor, the gallium nitride semiconductor film 43 can be obtained without using a substrate made of the gallium nitride semiconductor. Further, the size of the gallium nitride based semiconductor film 43 can be made substantially the same as the size of the substrate 31. Thereby, a substrate product 49 was obtained. A substrate product 49 for a gallium nitride based substrate includes a substrate 31 and a gallium nitride based region 51 grown thereon.

  Although the main steps have been described above, these steps provide a method for forming a gallium nitride based substrate for a gallium nitride based semiconductor device.

  If necessary, a substrate product 49 is prepared as shown in FIG. The substrate product 49 is placed in the crystal growth apparatus 57. As shown in FIG. 4B, a gallium nitride based semiconductor thick film 53 can be grown on the gallium nitride based semiconductor film 43 of the substrate product 49. This growth is performed using, for example, the HVPE method. The conductivity type of the gallium nitride based semiconductor thick film 53 is the same as the conductivity type of the gallium nitride based semiconductor 43 and the nanocolumn region 39. Thereby, the substrate product 55 was obtained. A substrate product 55 for a gallium nitride based substrate includes a substrate 31 and a gallium nitride based region 59 grown thereon.

(Example 5)
The HVPE method is used for the growth of the thick film. A 6N gallium source, a 5N hydrogen chloride source, and a 6N ammonia source are used, and these are supplied to the HVPE growth reactor. H ₂ is used as a carrier gas. In this growth reactor, HCl is supplied to Ga metal to produce gallium chloride. The gallium chloride and ammonia react on the surface of the underlying gallium nitride film to deposit gallium nitride. The substrate temperature is, for example, 900 degrees Celsius to 1050 degrees Celsius. Growth is performed at normal pressure. The growth rate is, for example, about 20-300 micrometers / hr. Depending on this growth rate, a gallium nitride film of about 4 mm to 8 mm can be grown in a practical time.

Gallium nitride semiconductor thick film 53 may be made of _{In X Al Y Ga 1-X} -Y N (0 ≦ X ≦ 1,0 ≦ Y ≦ 1). According to this method, single crystals of GaN, InGaN, AlGaN, and InAlGaN having a very low dislocation density can be obtained.

  The conductivity type of the nanocolumn region 39 and the gallium nitride based semiconductor film 43 can be p-type. The conductivity type of the gallium nitride based semiconductor thick film 53 can be p-type. According to this method, a single crystal made of a p-type gallium nitride semiconductor can be obtained. A p-type gallium nitride semiconductor substrate is provided using this single crystal.

  As a result, a method for forming a gallium nitride based substrate for a gallium nitride based semiconductor device is provided. These steps also provide a method of forming a gallium nitride crystal for a gallium nitride semiconductor crystal growth substrate.

(Fourth embodiment)
5A and 5B illustrate a method for forming a gallium nitride based substrate for a gallium nitride based semiconductor device and a method for forming a gallium nitride based crystal for a gallium nitride based crystal growth substrate. It is drawing which shows the main processes roughly. In the present embodiment, the support 33 is made of a material that can be removed by etching. For example, the support 33 is made of silicon or GaAs.

As shown in FIG. 5A, the product 49 (or 59) is placed in the etching apparatus 61. The etching apparatus 61 is used for selectively removing the support 33. For example, in order to remove silicon by etching, for example, HF + HNO ₃ can be used.

  FIG. 5B shows the product 63 from which the support 33 is selectively removed by the etching apparatus 61. The product 63 substantially consists of a gallium nitride-based region 51a (59a). The gallium nitride-based region 51a (59a) includes the nanocolumn region 39. In each of the nanocolumns 41 in the nanocolumn region 39, the buffer layer 35a remains at one end 41a without being etched. If necessary, the remaining buffer layer 35a is removed. Thereby, the substrate product 63 was obtained. The substrate product 63 for the gallium nitride based substrate includes a gallium nitride based region 51a (59a). The gallium nitride based region 51a (59a) includes a nanocolumn region 39 and a gallium nitride based semiconductor film 43 (43, 53) grown thereon.

  Although the main steps have been described above, these steps provide a method for forming a gallium nitride based substrate for a gallium nitride based semiconductor device. These steps also provide a method of forming a gallium nitride crystal for a gallium nitride semiconductor crystal growth substrate.

(Fifth embodiment)
6A and 6B show a method of forming a gallium nitride based substrate for a gallium nitride based semiconductor device and a method of forming a gallium nitride based crystal for a gallium nitride based crystal growth substrate. It is drawing which shows the main processes roughly. In the present embodiment, the support 33 is made of a material that can be removed by etching. The support 33 is made of, for example, silicon or GaAs.

  As shown in FIG. 6A, a substrate product 63 is prepared. The substrate product 63 is placed in the crystal growth apparatus 57. As shown in FIG. 6B, a gallium nitride based semiconductor thick film 65 can be grown on the gallium nitride based semiconductor film of the substrate product 63. This growth is performed using, for example, the HVPE method. The conductivity type of the gallium nitride based semiconductor 51a of the substrate product 63 is the same as the conductivity type of the gallium nitride based semiconductor thick film 63. Thereby, a substrate product 67 was obtained. A substrate product 67 for a gallium nitride based substrate includes a gallium nitride based region 51a and a gallium nitride based semiconductor thick film 63 grown thereon. The thick film 63 can be grown in the same manner as in the fifth embodiment, for example.

  As a result, a method for forming a gallium nitride based substrate for a gallium nitride based semiconductor device is provided. These steps also provide a method of forming a gallium nitride crystal for a gallium nitride semiconductor crystal growth substrate.

(Sixth embodiment)
7A and 7B show a method of forming a gallium nitride based substrate for a gallium nitride based semiconductor device and a method of forming a gallium nitride based crystal for a gallium nitride based crystal growth substrate. It is drawing which shows the main processes roughly. In the present embodiment, the support 33 is made of a material that can be removed by etching. The support 33 is made of, for example, silicon or GaAs.

As shown in FIG. 7A, the product 55 is placed in the etching apparatus 61. The etching apparatus 61 is used for selectively removing the support 33. For example, in order to remove silicon by etching, for example, HF + HNO ₃ can be used.

  FIG. 7B shows the product 71 from which the support 33 is selectively removed by the etching apparatus 61. The product 71 substantially consists of a gallium nitride-based region 59b. The gallium nitride-based region 59 b includes the nanocolumn region 39. In each of the nanocolumns 41 in the nanocolumn region 39, the buffer layer 35a remains at one end 41a without being etched. If necessary, the remaining buffer layer 35a is removed. Thereby, a substrate product 71 was obtained. A substrate product 71 for a gallium nitride based substrate includes a gallium nitride based region 59b. The gallium nitride-based region 59b includes a nanocolumn region 39 and gallium nitride-based semiconductor films 43 and 53 grown thereon.

  Although the main steps have been described above, these steps provide a method for forming a gallium nitride based substrate for a gallium nitride based semiconductor device. These steps also provide a method of forming a gallium nitride crystal for a gallium nitride semiconductor crystal growth substrate.

(Seventh embodiment)
8A, FIG. 8B, FIG. 8C, FIG. 9A, FIG. 9B, and FIG. 9C show a gallium nitride based substrate for a gallium nitride based semiconductor device. It is drawing which shows the main processes of the method to form.

  First, as shown in FIG. 8A, a substrate 75 for growing a gallium nitride based semiconductor is prepared. The substrate 75 is made of a material different from that of the gallium nitride based semiconductor. The substrate 75 includes a support 77 and a buffer layer 79 provided on the support 77. A buffer layer is grown on the support 77.

  As shown in FIG. 8B, the nanocolumn region 81 is formed on the substrate 75. The nanocolumn region 81 has a plurality of nanocolumns made of a gallium nitride based semiconductor.

  As shown in FIG. 8C, while growing the gallium nitride semiconductor, the ends of the plurality of nanocolumns in the nanocolumn region 81 are coupled to each other, and the ends of the plurality of nanocolumns are coupled to each other, and then the gallium nitride based semiconductor is coupled. A film 83 is grown.

  As shown in FIG. 9A, after the gallium nitride based semiconductor film 83 is grown, the substrate 77 and the nanocolumn region 81 are removed to produce a gallium nitride based crystal body 85. The removal of the substrate 77 is performed by etching as already described. In addition, for example, polishing can be used to remove the nanocolumn region 81.

  As shown in FIG. 9B, one or a plurality of gallium nitride based semiconductor slices 87a to 87d are formed from the gallium nitride based crystal body 85.

  As shown in FIG. 9C, when necessary processing such as polishing is completed, a gallium nitride based semiconductor wafer 89 is completed. The gallium nitride based semiconductor wafer 89 has a main surface 89a for crystal growth.

  According to this method, since the nanocolumn region 81 is made of a crystal having a very low dislocation density, the gallium nitride-based semiconductor film 83 grown on the nanocolumn region 81 is also made of a crystal having a very low dislocation density. The size of the gallium nitride based semiconductor slices 87a to 87d can be substantially the same as the size of the substrate 75. Therefore, n-type, i-type or p-type gallium nitride semiconductor single crystal slices 87a to 87d having a very low dislocation density can be formed.

  According to one variation, the substrate 75 is removed after the gallium nitride based semiconductor is grown to bond the individual nanocolumns. After removing the substrate 85, a gallium nitride semiconductor thick film is grown on the gallium nitride semiconductor by HVPE. After the gallium nitride semiconductor thick film is grown, the nanocolumn region 81 is removed to produce a gallium nitride crystal 85. According to this method, since the nanocolumn region 81 is made of a crystal having a very low dislocation density, the gallium nitride-based semiconductor film 83 grown on the nanocolumn region 81 is also made of a crystal having a very low dislocation density. Further, since the substrate 75 is removed, the gallium nitride based semiconductor thick film is grown without stress from the substrate 75. Furthermore, the size of the gallium nitride based semiconductor slices 87a to 87d can be made substantially the same as the size of the substrate 75. Therefore, the gallium nitride based semiconductor single crystal slices 87a to 87d having a very low dislocation density can be formed. In another modification, the gallium nitride based semiconductor thick film may be grown after the nanocolumn region 81 is removed.

(Example 6)
A gallium nitride crystal is cut parallel to the (0001) plane using an inner peripheral slicer to produce a gallium nitride slice. Thereafter, processing such as polishing is performed to obtain a gallium nitride wafer from which the altered layer on the slice surface has been removed. This wafer can be used to fabricate semiconductor devices. Further, the warpage of the wafer is very small.

  The nanocolumn region 81 and the gallium nitride based semiconductor film 83 are preferably made of gallium nitride having the same conductivity type. According to this method, an n-type, i-type or p-type gallium nitride single crystal 85 is obtained.

  The gallium nitride based crystal body 85 is preferably made of a p-conductivity type gallium nitride semiconductor. According to this method, slices 87a-87d are provided for the p-type gallium nitride semiconductor substrate.

Gallium-based semiconductor thick film may be made of _{In X Al Y Ga 1-X} -Y N (0 ≦ X ≦ 1,0 ≦ Y ≦ 1). According to this method, a single crystal slice of GaN, InGaN, AlGaN, or InAlGaN having a very low dislocation density can be formed.

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configuration disclosed in the present embodiment. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

FIG. 1A schematically shows a substrate for a gallium nitride based semiconductor device. FIG. 1B schematically shows a substrate for a gallium nitride based semiconductor device. FIGS. 2A and 2B are schematic views showing main steps of a method of forming a gallium nitride-based substrate for a gallium nitride-based semiconductor device. FIG. 3 is a drawing schematically showing main steps of a method of forming a gallium nitride based substrate for a gallium nitride based semiconductor device. 4A and 4B show a method of forming a gallium nitride based substrate for a gallium nitride based semiconductor device and a gallium nitride based crystal for a substrate for crystal growth of the gallium nitride based semiconductor. It is drawing which shows a method. 5A and 5B illustrate a method of forming a gallium nitride based substrate for a gallium nitride based semiconductor device and a method of forming a gallium nitride based crystal for a gallium nitride based crystal growth substrate. It is drawing which shows the main processes roughly. 6A and 6B show a method for forming a gallium nitride based substrate for a gallium nitride based semiconductor device and a method for forming a gallium nitride based crystal for a gallium nitride based crystal growth substrate. It is drawing which shows the main processes roughly. 7A and 7B show a method of forming a gallium nitride based substrate for a gallium nitride based semiconductor device and a method of forming a gallium nitride based crystal for a gallium nitride based crystal growth substrate. It is drawing which shows the main processes roughly. FIGS. 8A, 8B, and 8C are diagrams illustrating main steps of a method of forming a gallium nitride-based substrate for a gallium nitride-based semiconductor device. FIGS. 9A, 9B, and 9C are drawings showing main steps of a method of forming a gallium nitride-based substrate for a gallium nitride-based semiconductor device.

Explanation of symbols

11a, 11b ... substrate, 13 ... nanocolumn region, 15 ... gallium nitride semiconductor film, 17 ... support base, 19 ... nanocolumn, 21 ... support, 23 ... buffer film, D1 ...
The thickness of the nanocolumn region, D2 ... the thickness of the gallium nitride semiconductor film, 25 ... the nanocolumn region, 27 ... the gallium nitride semiconductor film, 29 ... nanocolumn, D3 ... the thickness of the nanocolumn region, D4 ... the thickness of the gallium nitride semiconductor film, DESCRIPTION OF SYMBOLS 31 ... Substrate, 33 ... Support, 35 ... Buffer film, 37 ... Crystal growth apparatus, 39 ... Nano column region, 41 ... Nano column, 43 ... Gallium nitride semiconductor system film, 45 ... Gallium nitride semiconductor region or transition region, 47 ... Gallium nitride single crystal region, 49 ... substrate product, 51 ... gallium nitride based region, 51a ... gallium nitride based semiconductor, 53 ... gallium nitride based semiconductor thick film, 55 ... substrate product, 57 ... crystal growth apparatus, 59 ... nitriding Gallium-based region, 59a ... gallium nitride-based region, 59b ... gallium nitride-based region, 61 ... etching apparatus, 63 ... substrate product, 67 Substrate product, 71 ... substrate product, 75 ... substrate, 77 ... support, 79 ... buffer layer, 81 ... nanocolumn region, 83 ... gallium nitride semiconductor film, 85 ... gallium nitride crystal, 87a to 87d ... nitride Gallium based semiconductor slice, 89 ... Gallium nitride based semiconductor wafer

Claims (12)

A method of forming a gallium nitride based crystal for a gallium nitride based crystal growth substrate, comprising:
Preparing a substrate for growing a gallium nitride based semiconductor, comprising a support made of a semiconductor material different from the gallium nitride based semiconductor;
Growing a nanocolumn region having a plurality of nanocolumns made of a gallium nitride based semiconductor on the substrate after the substrate is disposed in the first crystal growth apparatus ;
Growing a gallium nitride-based semiconductor film having a dislocation density of 1 × 10 ⁵ cm ⁻² or less with the first crystal growth apparatus so that one ends of the plurality of nanocolumns in the nanocolumn region are coupled to each other ;
Removing the substrate after growing the gallium nitride based semiconductor film;
After removing the substrate, growing a gallium nitride based semiconductor thick film on the gallium nitride based semiconductor film by a HVPE method in a second crystal growth apparatus different from the first crystal growth apparatus;
With
The crystal growth method for growing the gallium nitride based semiconductor film is different from the HVPE method,
The conductivity type of the gallium nitride based semiconductor in the nanocolumn region is the same as the conductivity type of the gallium nitride based semiconductor film.   The method according to claim 1, wherein the nanocolumn region and the gallium nitride based semiconductor film are made of gallium nitride. The nanocolumn region, the gallium-based semiconductor film and the gallium-based semiconductor thick film nitride gallium nitride having the same conductivity type, the method described in claim 1 or claim 2, characterized in that. The gallium-based semiconductor thick film is made of _{In X Al Y Ga 1-X} -Y N (0 ≦ X ≦ 1,0 ≦ Y ≦ 1), any one of claims 1 to 3, characterized in that The method according to one item. The method according to claim 1, wherein a conductivity type of the nanocolumn region and the gallium nitride based semiconductor film is p-type. 6. A method as claimed in any preceding claim , wherein the substrate comprises a silicon support. The substrate method as claimed in any one of claims 1 to 5, characterized in that, comprising a support consisting of GaAs. A method of forming a gallium nitride-based substrate,
Preparing a substrate for growing a gallium nitride based semiconductor comprising a support made of a material different from the gallium nitride based semiconductor;
Growing a nanocolumn region having a plurality of nanocolumns made of a gallium nitride based semiconductor on the substrate after the substrate is disposed in the first crystal growth apparatus ;
Bonding one end of the plurality of nanocolumns in the nanocolumn region to each other while growing a gallium nitride based semiconductor in the first crystal growth apparatus ;
A step of growing a gallium nitride based semiconductor film having the same conductivity type as that of the gallium nitride based semiconductor in the nanocolumn region and having a dislocation density of 1 × 10 ⁵ cm ⁻² or less after bonding one ends of the plurality of nanocolumns to each other; When,
Removing the substrate after growing the gallium nitride based semiconductor film;
After removing the substrate, growing a gallium nitride based semiconductor thick film on the gallium nitride based semiconductor film by a HVPE method in a second crystal growth apparatus different from the first crystal growth apparatus ;
After growing the gallium nitride based semiconductor thick film, removing the nanocolumn region to produce a gallium nitride based crystal;
Forming one or more gallium nitride based semiconductor slices from the gallium nitride based crystal. 9. The method according to claim 8 , wherein the nanocolumn region, the gallium nitride based semiconductor film, and the gallium nitride based semiconductor thick film are made of gallium nitride having the same conductivity type. The gallium-based semiconductor thick film _is described _{In X Al Y Ga 1-X} -Y N (0 ≦ X ≦ 1,0 ≦ Y ≦ 1) consists, according to claim 8 or claim 9, characterized in that Way. The method according to any one of claims 8 to 10 , wherein the gallium nitride based semiconductor slice is made of a p-conductivity type gallium nitride semiconductor. The method according to any one of claims 8 to 11 , further comprising a step of processing the gallium nitride based semiconductor slice to form a gallium nitride based substrate.

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