MELT FIXTURE INCLUDING THERMAL SHIELDS HAVING A STEPPED CONFIGURATION
Various single crystals are disclosed including sapphire. The single crystals have desirable geometric properties, including a width not less than about 15 cm and the thickness is not less than about 0.5 cm. The single crystal may also have other features, such as a maximum thickness variation, and as-formed crystals may have a generally symmetrical neck portion, particularly related to the transition from the neck to the main body of the crystal. Methods and for forming such crystals and an apparatus for carrying out the methods are disclosed as well.
1 . A melt fixture comprising:
a crucible;
a die open to and extending along a length of the crucible; and
a plurality of thermal shields overlying the crucible and adjacent to the die, the thermal shields having a stepped configuration.
2 . The melt fixture of claim 1 , wherein thermal shields include a first shield set positioned along a first lateral side of the die, and a second shield set positioned along an opposite, second lateral side the die.
3 . The melt fixture of claim 2 , wherein each of the first and second shield sets is generally symmetrical about a vertical central axis corresponding to midpoint of the die.
4 . The melt fixture of claim 1 , further comprising an afterheater disposed above the die and configured to receive an as-formed crystal sheet, wherein the afterheater has a lower compartment and an upper compartment separated from each other by an isolation structure.
5 . The melt fixture of claim 1 , wherein thermal shields are substantially parallel to one another.
6 . The melt fixture of claim 5 , further comprising shield pins to hold the thermal shields in place.
7 . The melt fixture of claim 1 , wherein the thermal shields provide a static temperature gradient along the die.
8 . The melt fixture of claim 7 , wherein the thermal shields provide a temperature profile along the length of the die such that the temperature profile has a maximum temperature at about a midpoint of the die.
9 . The melt fixture of claim 1 , wherein the die has an opening with a length that is not less than about 28 cm.
10 . The melt fixture of claim 9 , wherein the opening of the die has a width that is not less than about 0.5 cm.
11 . The melt fixture of claim 10 , wherein the length of the opening is not less than about 30 cm.
12 . The melt fixture of claim 1 , further comprising an afterheater having a lower compartment and an upper compartment separated from each other by an isolation structure.
13 . The method of claim 12 , wherein the isolation structure comprises isolation doors, between the lower compartment and the upper compartment.