| Method of manufacturing group iii nitride substrate and semiconductor device -> Monitor Keywords |
|
|
  Method of manufacturing group iii nitride substrate and semiconductor deviceUSPTO Application #: 20070187700Title: Method of manufacturing group iii nitride substrate and semiconductor device Abstract: The present invention provides a method of manufacturing a Group III nitride substrate that has less variations in in-plane carrier concentration and includes crystals grown at a high growth rate. The manufacturing method of the present invention includes: (i) forming a semiconductor layer (a seed layer 12) on a substrate, with the semiconductor layer being formed of a semiconductor expressed by a composition formula of AluGavIn1−u−vN (wherein 0≦u≦1 and 0≦v≦1) and having a (0001) plane present at its surface; (ii) processing the surface of the semiconductor layer so that the surface becomes a plane sloped with respect to the (0001) plane of the semiconductor layer; and (iii) bringing the surface of the semiconductor layer into contact with a melt containing a solvent and at least one Group III element selected from gallium, aluminum, and indium, in an atmosphere containing nitrogen, to make the at least one Group III element and the nitrogen react with each other to grow Group III nitride crystals (GaN single crystals 13) on the semiconductor layer. (end of abstract)
Agent: Hamre, Schumann, Mueller & Larson P.C. - Minneapolis, MN, US Inventors: Yasuo Kitaoka, Hisashi Minemoto, Isao Kidoguchi, Akihiko Ishibashi USPTO Applicaton #: 20070187700 - Class: 257079000 (USPTO) Related Patent Categories: Active Solid-state Devices (e.g., Transistors, Solid-state Diodes), Incoherent Light Emitter Structure The Patent Description & Claims data below is from USPTO Patent Application 20070187700. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a Division of application Ser. No. 10/757,864, filed Jan. 15, 2004, which application is incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates generally to a Group III nitride substrate (a substrate containing Group III nitride crystals), a method of manufacturing the same, and a semiconductor device. [0004] 2. Related Background Art [0005] A Group III nitride compound semiconductor such as, for instance, gallium nitride (GaN) (hereinafter also referred to as a "Group III nitride semiconductor" or a "GaN-based semiconductor") has been gaining attention as a material for semiconductor elements that emit blue or ultraviolet light. A blue laser diode (LD) is used for high-density optical disk devices or displays while a blue light emitting diode (LED) is used for displays, lighting, etc. It is expected to use an ultraviolet LD in the field of biotechnology or the like and to use an ultraviolet LED as an ultraviolet source for a fluorescent lamp. [0006] Generally, substrates of a Group III nitride semiconductor (for example, GaN) that are used for LDs or LEDs are formed through vapor phase epitaxy. For instance, substrates have been used that are obtained through heteroepitaxial growth of Group III nitride crystals on a sapphire substrate. However, the sapphire substrate and GaN crystals are different from each other in lattice constant by 13.8% and in coefficient of linear expansion by 25.8%. Hence, a sufficiently high crystallinity cannot be obtained in the GaN thin film obtained through the vapor phase epitaxy. Generally, crystals obtained by this method have a dislocation density of 10.sup.8 cm.sup.-2 to 10.sup.9 cm.sup.-2 and thus the reduction in dislocation density has been an important issue. In order to resolve this issue, efforts have been made to reduce the dislocation density and thereby, for example, an epitaxial lateral overgrowth (ELOG) method has been developed. With this method, the dislocation density can be reduced to around 10.sup.5 cm.sup.-2 to 10.sup.6 cm.sup.-2, but its manufacturing process is complicated. [0007] On the other hand, besides the vapor phase epitaxy, a method of carrying out crystal growth from the liquid phase also has been studied. However, since the equilibrium vapor pressure of nitrogen is at least 10000 atm at a melting point of a Group III nitride single crystal such as, for instance, GaN or AlN, conventionally it has been understood that a condition of 8000 atm at 1200.degree. C. is required for growing GaN from liquid phase. In this connection, recently, it was made clear that GaN was able to be synthesized at relatively low temperature and pressure, specifically, 750.degree. C. and 50 atm, by using a Na flux. [0008] Recently, single crystals with the maximum crystal size of about 1.2 mm are obtained by a method in which a mixture of Ga and Na is melted in a nitrogen gas atmosphere containing ammonia at 800.degree. C. and 50 atm, and then the single crystals are grown for 96 hours using the melt (for instance, JP2002-293696A). [0009] Furthermore, another method also has been reported in which after a GaN crystal layer is formed on a sapphire substrate by a metal organic chemical vapor deposition (MOCVD) method, single crystals are grown by a liquid phase epitaxy (LPE) method. [0010] However, in order to manufacture semiconductor devices with excellent characteristics at low cost, it has been required to provide a method of manufacturing a Group III nitride substrate with a lower dislocation density than that of conventional one and a method of manufacturing a Group III nitride substrate at lower cost. A method of growing nitride crystals from liquid phase is expected to be a method that allows a Group III nitride substrate with less defects to be obtained. However, considerable variations in crystallinity are caused depending on a seed crystal to be used and on in-plane carrier concentration of the nitride substrate. Furthermore, the growth rate is not so high, which has been a problem. SUMMARY OF THE INVENTION [0011] With such a situation in mind, the present invention is intended to provide a Group III nitride substrate that has less variations in in-plane carrier concentration and includes Group III nitride crystals grown at a high growth rate, and to a method of manufacturing the same. [0012] In order to achieve the aforementioned object, a Group III nitride substrate of the present invention includes: a substrate; a semiconductor layer formed on the substrate; and Group III nitride crystals formed on the semiconductor layer, wherein the semiconductor layer is formed of a semiconductor expressed by a composition formula of Al.sub.uGa.sub.vIn.sub.1-u-vN (wherein 0.ltoreq.u.ltoreq.1 and 0.ltoreq.v.ltoreq.1). A surface of the semiconductor layer is a plane that is sloped in one direction and includes steps of (0001) planes arranged step-wise. The plane sloped in one direction and the (0001) planes form an angle of at least 0.05.degree. therebetween, and the Group III nitride crystals formed on the semiconductor layer have variations in in-plane carrier concentration that are within a range of one fifth to five times a carrier concentration mean value. [0013] In the present invention, the "Group III nitride" denotes a semiconductor expressed by a composition formula of Al.sub.xGa.sub.yIn.sub.1-x-yN (wherein 0.ltoreq.x.ltoreq.1 and 0.ltoreq.y.ltoreq.1) unless otherwise specified. In this connection, it is understood that a formula of 0.ltoreq.1-x-y.ltoreq.1 is satisfied since the composition ratio can never be a negative value (the same applies to other composition formulae). [0014] A manufacturing method of the present invention includes the steps of: (i) forming a semiconductor layer on a substrate, with the semiconductor layer being formed of a semiconductor expressed by a composition formula of Al.sub.uGa.sub.vIn.sub.1-u-vN (wherein 0.ltoreq.u.ltoreq.1 and 0.ltoreq.v.ltoreq.1) and having a (0001) plane present at its surface; (ii) processing the surface of the semiconductor layer so that the surface becomes a plane sloped with respect to the (0001) plane of the semiconductor layer; and (iii) bringing the surface of the semiconductor layer into contact with a melt containing a solvent and at least one Group III element selected from gallium, aluminum, and indium, in an atmosphere containing nitrogen, to make the at least one Group III element and the nitrogen react with each other to grow Group III nitride crystals on the semiconductor layer. [0015] A semiconductor device of the present invention includes: a substrate; and a semiconductor element formed on the substrate, wherein the substrate is a Group III nitride substrate manufactured by the above-mentioned manufacturing method of the present invention. The semiconductor element may be a laser diode or a light emitting diode. [0016] The Group III nitride substrate of the present invention has less variations in carrier concentration, includes Group III nitride crystals grown at a high growth rate, and thus can be manufactured efficiently. BRIEF DESCRIPTION OF THE DRAWINGS [0017] FIGS. 1A (surface) and 1B (cross section) show conventional crystal growth; and FIGS. 1C and 1D show crystal growth according to an example of a manufacturing method according to the present invention. [0018] FIG. 2 includes a cross-sectional view showing another example of a manufacturing method according to the present invention and an enlarged schematic view showing a surface structure obtained by the method. [0019] FIGS. 3A to 3C are cross-sectional views illustrating steps of still another example of a manufacturing method according to the present invention. [0020] FIG. 4 is a schematic view showing an example of a manufacturing apparatus used in the manufacturing method of the present invention. Continue reading... Full patent description for Method of manufacturing group iii nitride substrate and semiconductor device Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method of manufacturing group iii nitride substrate and semiconductor device patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Method of manufacturing group iii nitride substrate and semiconductor device or other areas of interest. ### Previous Patent Application: Semiconductor device and method of forming the same Next Patent Application: Nitride based mqw light emitting diode having carrier supply layer Industry Class: Active solid-state devices (e.g., transistors, solid-state diodes) ### FreshPatents.com Support Thank you for viewing the Method of manufacturing group iii nitride substrate and semiconductor device patent info. IP-related news and info Results in 7.28483 seconds Other interesting Feshpatents.com categories: Computers: Graphics , I/O , Processors , Dyn. Storage , Static Storage , Printers |
||
