C-Plane Sapphire Method
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.
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.