Lithium tantalate substrate and method of manufacturing same

Abstract

In a process for manufacturing a LT substrate from a LT crystal, after growing the crystal, a LT substrate in ingot form is imbedded in carbon power, or is place in a carbon vessel, and heat treated is conducted at a maintained temperature of between 650° C. and 1650° C. for at least 4 hours, whereby in a lithium tantalate (LT) substrate, sparks are prevented from being generated by the charge up of an electric charge on the substrate surface, and thereby destruction of a comb pattern formed on the substrate surface and breaks or the like in the LT substrate are prevented.

What is claimed is:  
     
         1 . A lithium tantalate substrate having a thermal history of heat treatment wherein lithium tantalate in ingot form is maintained at a temperature of between 650° C. and 1650° C., while embedded in a carbon powder, or in a carbon vessel.  
     
     
         2 . A lithium tantalate substrate having a thermal history of heat treatment wherein lithium tantalate in ingot form is maintained at a temperature of between 650° C. and 1400° C., while embedded in a Si powder, or in a Si vessel.  
     
     
         3 . A lithium tantalate substrate having a thermal history of heat treatment wherein lithium tantalite in wafer form is maintained at a temperature of between 350° C. and 600° C., while embedded in a metal powder selected from a group consisting of Ca, Al, Ti, and Si.  
     
     
         4 . A lithium tantalate substrate having a thermal history of heat treatment wherein lithium tantalite in wafer form is maintained at a temperature of 350° C. or higher and below the melting point of Zn, while embedded in a Zn powder.  
     
     
         5 . A lithium tantalate substrate according to any one of  claim 1  through  claim 4 , wherein the heat treatment lasts 4 hours or longer.  
     
     
         6 . A lithium tantalate substrate which is blackened by the heat treatment according to any one of  claim 1  through  claim 5 .  
     
     
         7 . A method of manufacturing a lithium tantalate substrate using a lithium tantalate crystal grown using the Czochralski method, comprising the step of heat treating the lithium tantalate crystal in ingot form, which is embedded in carbon powder or in a carbon vessel, at a maintained temperature of between 650° C. and 1650° C.  
     
     
         8 . A method of manufacturing a lithium tantalate substrate using a lithium tantalate crystal grown using the Czochralski method, comprising the step of heat treating the lithium tantalate crystal in ingot form, which is embedded in Si powder or in a Si vessel, at a maintained temperature of between 650° C. and 1400° C.  
     
     
         9 . A method of manufacturing a lithium tantalate substrate using a lithium tantalate crystal grown using the Czochralski method, comprising the step of heat treating the lithium tantalate crystal in wafer form, which is embedded in a metal powder selected from a group consisting of Ca, Al, Ti, and Si, at a maintained temperature of between 350° C. and 600° C.  
     
     
         10 . A method of manufacturing a lithium tantalate substrate using a lithium tantalate crystal grown using the Czochralski method, comprising the step of heat treating the lithium tantalate crystal in wafer form, which is embedded in a Zn powder, at a maintained temperature of 350° C. or higher and below the melting point of Zn.  
     
     
         11 . A method of manufacturing a lithium tantalate substrate according to any one of  claim 7  through  claim 10 , wherein the heat treatment lasts 4 hours or longer.