MELT FIXTURE INCLUDING THERMAL SHIELDS HAVING A STEPPED CONFIGURATION AND A METHODS OF USING THE SAME

• US 20120145069A1
• Filed: 02/14/2012
• Published: 06/14/2012
• Est. Priority Date: 04/08/2004
• Status: Active Grant

• Current Assignee: Luxium Solutions LLC
• Original Assignee: Saint-Gobain Ceramics & Plastics Incorporated (Compagnie De Saint-Gobain)
• Inventors: Locher, John Walter, Zanella, Steven Anthony, MacLean, Ralph Lampson Jr., Bates, Herbert Ellsworth
• Granted Patent: US 8,685,161 B2
• Time in Patent Office: Days
• US Class Current: 117/26
• CPC Class Codes: C30B 15/30 Mechanisms for rotating or moving either the melt or the crystal flotation methods C30B15/28
• CPC Class Codes: C30B 15/34 Edge-defined film-fed crystal-growth using dies or slits
• CPC Class Codes: C30B 29/20 Aluminium oxides
• CPC Class Codes: Y10T 117/1044 including means forming a flat shape [e.g., ribbon]
• CPC Class Codes: Y10T 428/2495 Thickness [relative or absolute]
• CPC Class Codes: Y10T 428/26 Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension

Abstract

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.

Claims

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. A method of forming a sapphire single crystal comprising:

providing 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;

forming a melt in the crucible; and

drawing an as-formed sapphire single crystal sheet from the die.

6. The method of claim 5, 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.

7. The method of claim 6, wherein each of the first and second shield sets is generally symmetrical about a vertical central axis corresponding to the midpoint of the die.

8. The method of claim 5, wherein from a side view, the thermal shields have an overall shape that is generally trapezoidal.

9. The method of claim 5, wherein thermal shields are substantially parallel to one another.

10. The method of claim 9, further comprising shield pins to hold the thermal shields in place.

11. The method of claim 5, wherein the thermal shields provide a static temperature gradient along the die.

12. The method of claim 11, 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.

13. The method of claim 5, wherein the as-grown single crystal sheet has a neck and a main body that defines first and second opposite lateral sides that are generally parallel to each other, a transition of the neck to the main body portion is defined by respective first and second transition points of the first and second opposite lateral sides, and the single crystal has a Δ

_T not greater than 4.0 cm, wherein Δ

_T is the distance by which the respective first and second transition points are spaced apart as projected along a length segment of the single crystal sheet.

14. The method of claim 5, wherein the sapphire single crystal sheet has a length, width and thickness, wherein length>

width>

thickness, the width is not less than about 28 cm, and the thickness is not less than about 0.5 cm.

15. The method of claim 14, wherein the width is not less than about 30 cm.

16. The method of claim 14, wherein the sapphire single crystal sheet has a variation in thickness is not greater than 0.2 cm.

17. The method of claim 5, further comprising pulling the single crystal upward from the die and into an afterheater having a lower compartment and an upper compartment separated from each other by an isolation structure.

18. The method of claim 17, further comprising cooling the single crystal in the upper compartment of the afterheater, the single crystal cooling at a rate not greater than about 300°

C./hr.

19. The method of claim 17, wherein the single crystal is a generally planar sheet having a mass greater than about 4 kg.

20. The method of claim 19, wherein the isolation structure comprises isolation doors, and wherein the method further comprises closing the isolation doors after the crystal passes into the upper compartment.