Epitaxial film forming method, sputtering apparatus, manufacturing method of semiconductor light-emitting element, semiconductor light-emitting element, and illumination device

Abstract

The present invention provides an epitaxial film forming method for epitaxially growing a high-quality group III nitride semiconductor thin film on an α—Al 2 O 3 substrate by a sputtering method. In the epitaxial film forming method according to an embodiment of the present invention, when an epitaxial film of a group III nitride semiconductor thin film is to be formed on the α—Al 2 O 3 substrate arranged on a substrate holder provided with a heater electrode and a bias electrode of a sputtering apparatus, in a state where the α—Al 2 O 3 substrate is maintained at a predetermined temperature by the heater electrode, high-frequency power is applied to a target electrode and high-frequency bias power is applied to a bias electrode and at that time, the powers are applied so that frequency interference between the high-frequency power and the high-frequency bias power does not occur.

1 . An epitaxial film forming method that uses a sputtering apparatus having a target electrode on which a target can be arranged and a substrate holder on which a substrate can be arranged toward the target electrode and provided with a heater electrode and a bias electrode, and that epitaxially grows a group III nitride semiconductor thin film by a sputtering method on an α—Al 2 O 3  substrate arranged on the substrate holder, the method comprising the steps of:
 arranging the α—Al 2 O 3  substrate on the substrate holder; and 
 forming an epitaxial film of the group III nitride semiconductor thin film immediately on the α—Al 2 O 3  substrate arranged on the substrate holder by applying high-frequency power to the target electrode and by applying high-frequency bias power to the bias electrode, 
 wherein the step of forming an epitaxial film of the group III nitride semiconductor thin film immediately on the α—Al 2 O 3  substrate; 
 maintains the α—Al 2 O 3  substrate at a predetermined temperature by the heater electrode; 
 emits a group III nitride molecule from the target arranged on the target electrode by applying the high-frequency power to the target electrode; and 
 applies high-frequency bias power to the bias electrode for generating an electric field in which polarization from a negative charge to a positive charge of the group III nitride molecule is oriented toward the α—Al 2 O 3  substrate arranged on the substrate holder, and 
 wherein the high-frequency power and the high-frequency bias power are applied so that frequency interference between the high-frequency power and the high-frequency bias power does not occur. 
 
     
     
         2 . The epitaxial film forming method according to  claim 1 , wherein for frequencies of the high-frequency power and the high-frequency bias power, different frequencies are selected. 
     
     
         3 . The epitaxial film forming method according to  claim 1 , wherein the high-frequency power and the high-frequency bias power, for which the same frequency is selected, are applied so that a phase difference becomes 180°. 
     
     
         4 . The epitaxial film forming method according to  claim 1 , wherein
 the bias electrode has a first electrode to which a DC voltage with one polarity is applied and a second electrode to which a DC voltage with the other polarity is applied,   in a state in which the DC voltage is applied to the first electrode and the second electrode, the α—Al 2 O 3  substrate is electrostatically adsorbed by the substrate holder, and also the high-frequency bias power is applied to the first electrode and the second electrode, and   an epitaxial film of the group III nitride semiconductor thin film is formed on the α—Al 2 O 3  substrate.   
     
     
         5 . The epitaxial film forming method according to  claim 1 , wherein the high-frequency bias power is applied after the high-frequency power is applied and before a film formation surface of the α—Al 2 O 3  substrate is covered by a crystal layer made of a group III nitride semiconductor. 
     
     
         6 . A manufacturing method of a semiconductor light-emitting element comprising the step of: forming a buffer layer of a semiconductor light-emitting element by the epitaxial film forming method according to  claim 1 . 
     
     
         7 - 8 . (canceled) 
     
     
         9 . A sputtering apparatus comprising:
 a target electrode on which a target can be arranged;   a substrate holder on which a substrate can be arranged toward the target electrode and provided with a heater electrode and a bias electrode;   frequency interference suppressing means for preventing frequency interference from occurring between the high-frequency power applied to the target electrode and the high-frequency bias power applied to the bias electrode when the step of forming an epitaxial film of the group III nitride semiconductor thin film according to  claim 1  is performed;   means for applying high-frequency power that is high-frequency power for emitting the group III nitride molecule from the target arranged on the target electrode to the target electrode; and   means for applying high-frequency bias power that is high-frequency bias power for generating the electric field in which polarization from a negative charge to a positive charge of the emitted group III nitride molecule is oriented toward the α—Al 2 O 3  substrate arranged on the substrate holder to the bias electrode.   
     
     
         10 . The sputtering apparatus according to  claim 9 , wherein when the step of forming an epitaxial film of the group III nitride semiconductor thin film according to  claim 1  is performed, for frequencies of the high-frequency power and the high-frequency bias power, different frequencies are selected. 
     
     
         11 . The sputtering apparatus according to  claim 9 , wherein when the step of forming an epitaxial film of the group III nitride semiconductor thin film according to  claim 1  is performed, the high-frequency power and the high-frequency bias power, for which the same frequency is selected, are applied so that a phase difference becomes 180°. 
     
     
         12 . The sputtering apparatus according to  claim 9 ,
 wherein the bias electrode has a first electrode to which a DC voltage with one polarity is applied and a second electrode to which a DC voltage with the other polarity is applied, and   wherein when the step of forming an epitaxial film of the group III nitride semiconductor thin film according to  claim 1  is performed, the DC voltage is applied to the first electrode and the second electrode, the α—Al 2 O 3  substrate is electrostatically adsorbed by the substrate holder, and also the high-frequency bias power is applied to the first electrode and the second electrode.   
     
     
         13 . The sputtering apparatus according to  claim 9 , wherein when the step of forming an epitaxial film of the group III nitride semiconductor thin film according to  claim 1  is performed, the high-frequency bias power is applied after the high-frequency power is applied to the bias electrode and before a film formation surface of the α—Al 2 O 3  substrate is covered by a crystal layer made of a group III nitride semiconductor.