HK1094623B - Growth process of a crystalline gallium nitride based compound and semiconductor device including gallium nitride based compound - Google Patents

Description

Method for growing crystalline gallium nitride-based compound and semiconductor device comprising gallium nitride-based compound

Technical Field

The present invention relates generally to the fabrication of crystalline gallium nitride (GaN) -based semiconductor devices, and more particularly to methods of forming crystalline gallium nitride-based compounds and semiconductor devices including the same.

Background

Electronic devices of gallium nitride-based semiconductor compounds, such as light emitting devices or transistor devices, have been widely researched and developed in the field of the electronics industry. For gallium nitride-based transistor devices, the gallium nitride-based semiconductor compound is advantageously characterized by high electron mobility and high saturation velocity (about 2.5 × 10)⁷cm/s) and high breakdown electric field (about 5X 10)⁶V/cm) which allows gallium nitride based transistors to operate at high current densities. Therefore, gan transistor devices are particularly advantageous for high power and high temperature applications.

In the light emitting device, the multilayer structure is generally formed of a gallium nitride-based compound such as gallium nitride (GaN), aluminum gallium nitride (AlGaN), gallium indium nitride (GaInN), and the like, and the formed multilayer structure includes a light emitting layer sandwiched between an n-type clad layer and a p-type clad layer.

Regardless of the implementation of the transistor or light emitting device, the gallium nitride based compound is typically deposited on the substrate in the form of an epitaxial layer. During this deposition process, the crystalline quality of the gallium nitride epitaxial layer determines the electron mobility and is therefore a determining factor in the performance of the semiconductor device. In this case, many such studies have been made in the prior art.

Vapor phase epitaxial growth methods are known for forming gallium nitride based layers on a substrate, however commonly used substrate materials have a crystalline structure that does not match the lattice structure of the gallium nitride based layer, or have a high density of dislocations. To solve this problem, a known technique is to deposit a buffer layer composed of aluminum nitride (AlN) or aluminum gallium nitride (aigan) on a substrate made of sapphire or the like at a low temperature of 900 ℃ or a temperature lower than 900 ℃, and then grow a gallium nitride-based layer on the buffer layer. This technique is described in Japanese patent laid-open publication No. 63-188938, the disclosure of which is incorporated herein by reference. The inserted buffer layer can reduce dislocation caused by mismatching of the substrate and the gallium nitride-based compound, so that the crystallinity and the form of the gallium nitride-based compound are improved.

Another known solution is to deposit a first gallium nitride-based layer on the substrate and then to selectively cover the surface of the gallium nitride-based layer with a protective film, such as silicon oxide or silicon nitride. Then, a second gallium nitride-based layer is grown on the region of the first gallium nitride-based layer not covered by the protective film. The protective film prevents threading dislocations from extending in a direction perpendicular to the substrate interface. This technique is described in Japanese patent laid-open publication No. 10-312971, the disclosure of which is incorporated herein by reference.

In certain aspects, the aforementioned techniques do not provide satisfactory results, especially when implementing light emitting devices, where the buffer layer between the gallium nitride based layer and the substrate may absorb too much uv light. In addition, the insertion of silicon nitride or silicon oxide may affect the electrical performance of the semiconductor device.

Therefore, there is a need for a method of growing crystalline gallium nitride-based materials that compensates for lattice mismatch with the substrate while having improved characteristics, such as reduced uv absorption.

Disclosure of Invention

A method of forming a crystalline gallium nitride-based compound and a semiconductor device including a gallium nitride-based compound are described.

In one embodiment, a method of forming a crystalline gallium nitride-based compound includes forming a first nucleation layer on a substrate at a first processing temperature; forming a second nucleation layer on the first nucleation layer at a second processing temperature, the second processing temperature being different from the first processing temperature; and forming a gallium nitride-based epitaxial layer on the second nucleation layer.

In one embodiment, the first treatment temperature is between about 1000 ℃ and 1200 ℃. In another embodiment, the second treatment temperature is between about 400 ℃ and 1000 ℃. In some embodiments, the first nucleation layer has a thickness between about 10 angstroms and 100 angstroms. In other embodiments, the second nucleation layer has a thickness between about 300 and 2000 angstroms.

In a specific embodiment, a gallium nitride-based semiconductor device includes a substrate, a crystalline gallium nitride-based layer, and at least two nucleation layers interposed between the substrate and the crystalline gallium nitride-based layer. In some embodiments, the two nucleation layers are formed at different temperatures. In some embodiments, one of the two nucleation layers has a thickness of between about 300 angstroms and 2000 angstroms and the other layer has a thickness of between about 10 angstroms and 100 angstroms. In some embodiments, at least one of the two nucleation layers comprises Al_xIn_yGa_(1-x-y)N, wherein x, y and (1-x-y) are in [0, 1 ]]Within the range of (1).

The invention relates to a method of forming a gallium nitride based layer, comprising:

forming a plurality of nucleation layers on a substrate, wherein the plurality of nucleation layers includes at least two nucleation layers formed at different temperatures; and

an epitaxial gallium nitride-based layer is formed on top of one of the plurality of nucleation layers.

The nucleation layers preferably comprise Al_xIn_yGa_(1-x-y)At least one nucleation layer of N, wherein x, y and (1-x-y) are in [0, 1%]Within the range of (1). One or more of the plurality of nucleation layers are preferably formed by vapor phase epitaxial deposition. The step of forming the plurality of nucleation layers preferably comprises forming the first nucleation layer at a temperature between 1000 ℃ and 1200 ℃. The first nucleation layer preferably has a thickness of between 10 angstroms and 100 angstroms. The step of forming the plurality of nucleation layers preferably comprises forming the second nucleation layer at a temperature between 400 ℃ and 1000 ℃. The second nucleation layer preferably has a thickness between 300 and 2000 angstroms.

The foregoing is a summary and is not intended to limit the scope of the patent application, which is disclosed herein, but is capable of other embodiments and of changes and modifications that can be made without departing from the invention and its broader aspects. The features and advantages of the invention, on the other hand, are defined by the claims and are described in the following non-limiting detailed description.

Drawings

Fig. 1 is a schematic diagram of an organometallic vapor phase crystallization reactor used in forming a crystalline gallium nitride-based compound according to an embodiment of the invention.

Figure 2A is a schematic diagram illustrating an initial thermal cleaning process performed on a substrate in accordance with one embodiment of the present invention.

FIG. 2B is a schematic illustration of the formation of a first nucleation layer on a substrate according to one embodiment of the present invention.

Figure 2C is a schematic illustration of the formation of a second nucleation layer on the first nucleation layer, according to one embodiment of the present invention.

Figure 2D is a schematic diagram illustrating the epitaxial formation of a gallium nitride-based layer on a second nucleation layer, in accordance with one embodiment of the present invention.

Detailed Description

The present invention describes a method for growing crystalline gallium nitride-based compounds comprising at least three deposition steps. First forming a first nucleation layer on a base substrate at a first temperature and then forming a second nucleation layer at a second temperature different from the first temperature, wherein the first and second nucleation layers comprise Al of the formula_xIn_yGa_(1-x-y)And N represents a compound. Then, a crystalline gallium nitride-based compound is epitaxially grown on the second nucleation layer.

"gallium nitride-based compound or layer" means any composition comprising gallium nitride (GaN), aluminum gallium nitride (AlGaN), indium gallium nitride (InGaN), aluminum indium gallium nitride (AlInGaN), and aluminum, indium, and gallium with nitrogen. Methods suitable for forming the first and second nucleation layers and the gallium nitride-based compound include various vapor deposition growth processes such as Metal Organic Vapor Phase Epitaxy (MOVPE) growth deposition, Molecular Beam Epitaxy (MBE) growth deposition, Hydride Vapor Phase Epitaxy (HVPE) growth deposition, and the like.

Fig. 1 is a schematic diagram of an organometallic vapor phase crystallization reactor used in a process for forming a crystalline gallium nitride-based compound according to an embodiment of the invention. The reactor 100 includes a reaction chamber 102 in which a substrate 104 is placed on a susceptor (susceptor)106 to perform a deposition process. A heating device 108 is mounted on the pedestal 106 to heat the substrate 104. The gas-phase chemical reagent is introduced into the reaction chamber 102 through a plurality of inlet pipes 110 respectively connected to a plurality of containers 112. The mechanical pump 114 is operable to exhaust gases from the reaction chamber 102 through an outlet line 116. In addition, a control and regulation mechanism 118 is connected to the mechanical pump 114 to regulate the pressure in the reaction chamber 102.

Fig. 2A to 2D are schematic diagrams illustrating a process of forming a crystalline gallium nitride-based compound according to an embodiment of the present invention. In one embodiment, the crystalline gallium nitride-based compound is a gallium nitride layer formed on a sapphire base substrate; however, one skilled in the art will appreciate that the gallium nitride layer may be formed on a different material, such as a silicon substrate, a silicon carbide (SiC) substrate, or the like, or on a substrate on which a different material layer has been formed.

Figure 2A is a schematic diagram illustrating an initial thermal cleaning process performed on a substrate in accordance with one embodiment of the present invention. Sapphire substrate 202 has a carbon plane as a major plane and a thermal cleaning process is started. According to one embodiment, the thermal cleaning process includes heating the substrate 202 to a temperature above 1000 ℃ while maintaining a pressure environment of about 1000mbar and introducing hydrogen gas (H) at a flow rate of about 5slm (standard liters per minute)₂) And/or nitrogen (N)₂)。

FIG. 2B is a schematic diagram of MOVPE growth of a first nucleation layer 204 on a substrate 202 using MOVPE according to one embodiment of the present invention, wherein the first nucleation layer 204 is formed from Al_xIn_yGa_(1-x-y)N is composed of (1-x-y) and (x, y) is in [0, 1 ]]Within the range of (1). Although the embodiment is described with the AlGaN as the nucleation layer 204, one skilled in the art will appreciate that the composition of the nucleation layer can be adjusted by changing the values of x and y. The substrate 202 is cleaned and then heated to a temperature in the range of 1000 ℃ to 1200 ℃, and ammonia (NH) gas is then introduced₃) Injection was carried out at a flow rate of approximately 5000sccm, while trimethylgallium (TMGa) and trimethylaluminum (TMAl) were introduced into the reaction chamber at a flow rate of 2.5sccm and 7.5sccm, respectively, and maintained at a pressure of 110 mbar. A first nucleation layer 204 comprised of AlGaN is thereby grown on sapphire substrate 202 to a thickness of between about 10 angstroms and 100 angstroms. One skilled in the art will appreciate that suitable sources of gallium and aluminum, in addition to trimethylgallium (TMGa) and trimethylaluminum (TMAl), may include other metal alkyls, such as triethylgallium (TEGa), triethylaluminum (TEAl), or the like.

Figure 2C is a schematic diagram illustrating MOVPE growth of a second nucleation layer 206 on the first nucleation layer 204, wherein the second nucleation layer 206 is made of Al, according to an embodiment of the present invention_xIn_yGa_(1-x-y)And N is used for preparing the composition. In this embodiment, the second nucleation layer206 may also be AlGaN. The ammonia supply is maintained at 5000sccm and the temperature of the substrate 202 is set between about 400 ℃ and 1000 ℃. Trimethylgallium (TMGa) and trimethylaluminum (TMAl) are introduced into the reaction chamber at a pressure of 200mbar at a flow rate of 0.5sccm and 37.5sccm, respectively. A second nucleation layer 206 composed of gallium aluminum nitride (AlGaN) is thus formed on the first nucleation layer 204. The thickness of the second nucleation layer 206 is between about 300 angstroms and 2000 angstroms and the aluminum composition ranges between about 0 and 1.

Figure 2D is a schematic diagram illustrating a crystalline gallium nitride-based compound layer 208 epitaxially grown on a second nucleation layer 206, according to an embodiment of the present invention. The gallium nitride-based compound layer 208 may be composed of any combination of aluminum, indium, and gallium with nitrogen elements, and depends on the particular characteristics desired for the device intended to be formed.

In implementing a light emitting device or a gallium nitride transistor, the gallium nitride based layer 208 is, for example, a layer of doped gallium nitride grown on a substrate. In the light emitting device, the gallium nitride layer may be configured as a first cladding layer on which multiple structure layers and a second cladding layer are respectively stacked. In implementing a gallium nitride transistor, the gallium nitride layer may be configured as an active region in which electrons and small hole tunneling occur during operation of the transistor semiconductor device.

These nucleation layers formed at different temperatures can be grown under cost-effective conditions with a significant reduction in dislocations between the substrate and the epitaxial gallium nitride-based compound. By the crystalline structure of these nucleation layers, dislocations between the substrate and the epitaxial gallium nitride-based compound are mitigated. In addition, the observation of the use of the light emitting device shows that the layer structure formed during the growth process can prevent adverse ultraviolet absorption, and can significantly increase the luminance of the light emitting device. The degree of lattice mismatch and uv absorption reduction may be tuned by the composition of the nucleation layer (i.e., by adjusting the values x and y) according to the desired gallium nitride-based layer to be formed.

While the invention will be understood from the foregoing description of certain specific embodiments, these embodiments are provided for purposes of illustration and not limitation. Those skilled in the art will appreciate that the invention is susceptible to variations, modifications, additions and improvements. Thus, the example of multiple devices is only a single example, and structures and functions presented in separate devices in the example may be implemented in a combined structure or device. These and other variations, modifications, additions, and improvements may fall within the scope of the following claims.

Description of the symbols

100 reactor

102 reaction chamber

104 base material

106 base

108 heating device

110 inlet pipe

112 container

114 mechanical pump

116 out of the tube

118 adjustment mechanism

202 sapphire substrate

204 first nucleation layer

206 second nucleation layer

208 gallium nitride based layer

Claims (17)

1. A method of forming a crystalline gallium nitride (GaN) based layer, comprising:

forming a first nucleation layer on a substrate at a first processing temperature;

forming a second nucleation layer on the first nucleation layer at a second processing temperature lower than the first processing temperature, at least one of the first and second nucleation layers comprising Al_xIn_yGa_(1-x-y)N, wherein x, y and (1-x-y) are in [0, 1 ]]But x and y are not both 0; and

an epitaxial gallium nitride-based layer is formed on the second nucleation layer.

2. The method of claim 1, wherein the first processing temperature is between 1000 ℃ and 1200 ℃.

3. The method of claim 1, wherein the first nucleation layer has a thickness of between 10 a and 100 a.

4. The method of claim 1, wherein the second processing temperature is between 400 ℃ and 1000 ℃.

5. The method of claim 1, wherein the second nucleation layer has a thickness between 300 a and 2000 a.

6. The method of claim 1, wherein forming the first nucleation layer and the second nucleation layer comprises performing a vapor phase epitaxial growth process.

7. A method of forming a gallium nitride-based layer, comprising:

forming a plurality of nucleation layers on a substrate, wherein the plurality of nucleation layers includes at least two nucleation layers formed at different temperatures, and the plurality of nucleation layers comprises Al_xIn_yGa_(1-x-y)At least one nucleation layer of N, wherein x, y and (1-x-y) are in [0, 1%]But x and y are not both 0; and

an epitaxial gallium nitride-based layer is formed on top of one of the plurality of nucleation layers.

8. The method of claim 7, wherein one or more of the plurality of nucleation layers are formed by vapor phase epitaxial deposition.

9. The method of claim 7, wherein forming a plurality of nucleation layers comprises forming a first nucleation layer at a temperature between 1000 ℃ and 1200 ℃.

10. The method of claim 9, wherein the first nucleation layer has a thickness between 10 a and 100 a.

11. The method of claim 7, wherein forming a plurality of nucleation layers comprises forming a second nucleation layer at a temperature between 400 ℃ and 1000 ℃.

12. The process of claim 11, wherein said second nucleation layer has a thickness between 300 a and 2000 a.

13. A gallium nitride-based semiconductor device comprising:

a substrate;

a crystalline gallium nitride-based layer; and

at least two nucleation layers interposed between the substrate and the gallium nitride-based layer, at least one of the at least two nucleation layers comprising Al_xIn_yGa_(1-x-y)N, wherein x, y and (1-x-y) are in [0, 1 ]]But x and y are not simultaneously 0.

14. The semiconductor device of claim 13, wherein the substrate comprises a sapphire substrate.

15. The semiconductor device of claim 13, wherein the at least two nucleation layers are formed at different temperatures.

16. The semiconductor device of claim 15, wherein the at least two nucleation layers comprise a first nucleation layer formed at a temperature between 1000 ℃ and 1200 ℃.

17. The semiconductor device of claim 15, wherein the at least two nucleation layers comprise a second nucleation layer formed at a temperature between 400 ℃ and 1000 ℃.