C-Plane Sapphire Method

Abstract

A method and apparatus for the production of C-plane single crystal sapphire is disclosed. The method and apparatus may use edge defined film-fed growth techniques for the production of single crystal material exhibiting low polycrystallinity and/or low dislocation density.

What is claimed is: 
     
         1 . A method of forming single crystal C-plane sapphire material comprising:
 seeding a melt fixture with a seed having a C-axis orientation perpendicular to a longitudinal axis of a die opening;   crystallizing single crystal sapphire above the die, the single crystal sapphire exhibiting a C-axis orientation perpendicular to the sapphire's major surface;   passing the sapphire through a first region exhibiting a first thermal gradient, the sapphire being at a temperature greater than 1850° C.;   subsequently passing the sapphire through a second region exhibiting a second thermal gradient that is less than the first thermal gradient, the sapphire being at a temperature greater than 1850° C.; and   cooling the C-plane sapphire to produce the single crystal C-plane sapphire material.   
     
     
         2 . The method of  claim 1 , wherein the single crystal C-plane sapphire material exhibits fewer than 10,000 dislocations/cm 2 , when measured through a thickness of the single crystal C-plane sapphire material using transmission X-ray diffraction topography based on Bragg diffraction. 
     
     
         3 . The method of  claim 1 , wherein the single crystal C-plane sapphire material exhibits fewer than 1000 dislocations/cm 2 , when measured through a thickness of the single crystal C-plane sapphire material using transmission X-ray diffraction topography based on Bragg diffraction. 
     
     
         4 . The method of  claim 1 , wherein the single crystal C-plane sapphire material exhibits fewer than 500 dislocations/cm 2 , when measured through a thickness of the single crystal C-plane sapphire material using transmission X-ray diffraction topography based on Bragg diffraction. 
     
     
         5 . The method of  claim 1 , wherein the single crystal C-plane sapphire material exhibits fewer than 250 dislocations/cm 2 , when measured through a thickness of the single crystal C-plane sapphire material using transmission X-ray diffraction topography based on Bragg diffraction. 
     
     
         6 . The method of  claim 1 , wherein the single crystal C-plane sapphire material exhibits fewer than 100 dislocations/cm 2 , when measured through a thickness of the single crystal C-plane sapphire material using transmission X-ray diffraction topography based on Bragg diffraction. 
     
     
         7 . The method of  claim 1 , wherein the first thermal gradient is at least 10° C./cm greater than the second thermal gradient. 
     
     
         8 . The method of  claims 7 , wherein the first thermal gradient is in a range of 20° C./cm to 60° C./cm. 
     
     
         9 . The method of  claims 8 , wherein the second thermal gradient is in a range of 3° C./cm to 15° C./cm. 
     
     
         10 . The method of  claims 7 , wherein the first thermal gradient is in a range of 20° C./cm to 60° C./cm, and the second thermal gradient is in a range of 3° C./cm to 15° C./cm. 
     
     
         11 . The method of  claim 1 , comprising drawing the single crystal sapphire at a rate of greater than 2.5 cm/hr. 
     
     
         12 . The method of  claim 1 , comprising producing a sapphire plate having a length of greater than or equal to 30 cm. 
     
     
         13 . The method of  claim 1 , wherein the first region encompasses a portion of sapphire having a length of greater than or equal to 1 cm. 
     
     
         14 . The method of  claim 1 , wherein the second region encompasses a portion of sapphire having a length of greater than or equal to 1 cm. 
     
     
         15 . The method of any one of the preceding claims, wherein the single crystal C-plane sapphire material has a dimension that is greater than or equal to 7.5 cm. 
     
     
         16 . The method of  claim 8 , wherein the dimension is a diameter. 
     
     
         17 . The method of  claims 8 , wherein the dimension is a width, and the single crystal C-plane sapphire material has a length that is greater than 10 cm. 
     
     
         18 . The method of  claim 8 , wherein the thickness is 0.15 cm when measuring the single crystal C-plane sapphire material using transmission X-ray diffraction topography based on Bragg diffraction. 
     
     
         19 . A method of forming single crystal C-plane sapphire material comprising:
 seeding a melt fixture with a seed having a C-axis orientation perpendicular to a longitudinal axis of a die opening;   crystallizing single crystal sapphire above the die, the single crystal sapphire exhibiting a C-axis orientation perpendicular to the sapphire's major surface;   passing the sapphire through a first region exhibiting a first thermal gradient, wherein the sapphire is at a temperature greater than 1850° C., and the first thermal gradient is in a range of 20° C./cm to 60° C./cm;   subsequently passing the sapphire through a second region exhibiting a second thermal gradient that is less than the first thermal gradient, wherein the sapphire is at a temperature greater than 1850° C., and the second thermal gradient is in a range of 3° C./cm to 15° C./cm; and   cooling the C-plane sapphire to produce the single crystal C-plane sapphire material exhibiting fewer than 500 dislocations/cm 2 , when measured through a thickness of the single crystal C-plane sapphire material using transmission X-ray diffraction topography based on Bragg diffraction.   
     
     
         20 . The method of  claim 20 , wherein the first region encompasses a portion of sapphire having a length of greater than or equal to 1 cm, and the second region encompasses a portion of sapphire having a length of greater than or equal to 1 cm.