LASER-BASED AFTERHEATING FOR CRYSTAL GROWTH

Abstract

A crystal-growth apparatus (10, 10’,10”) and a crystal-growth method for growing a crystal (21) from a molten feed material (23) are presented, where in addition to a molten-zone heater, at least one afterheater laser (5) is arranged to heat an extended afterheater zone (50), the afterheater zone (50) at least partly overlapping a solidification zone (210) adjacent to the molten zone (230). The crystal-growth apparatus (10, 10’,10”) and the crystal-growth method may be used for thermal treatment to reduce crack formation or thermal stress in grown crystals (21).

Description

Claims

1. A crystal-growth apparatus (10, 10’,10”) for growing a crystal (21) from a molten feed material (23), comprising a molten-zone heater to melt the feed material in a molten zone (230);at least one afterheater laser (5) arranged to emit an afterheater laser beam (51) to heat an extended afterheater zone (50), the afterheater zone (50) at least partly overlapping a solidification zone (210) adjacent to the molten zone (230).

2. The crystal-growth apparatus (10, 10’,10”) according to claim 1, further comprising irradiation-area adjustment means to adjust the irradiation area of the afterheater laser beam (51).

3. The crystal-growth apparatus (10, 10’,10”) according to claim 2, wherein the irradiation-area adjustment means comprise at least one adjustable defocusing means.

4. The crystal-growth apparatus (10, 10’,10”) according to claim 2, wherein the irradiation-area adjustment means comprise at least one movable lens.

5. The crystal-growth apparatus (10, 10’,10”) according to claim 1, wherein the at least one afterheater laser is a diode laser (5) with or without adjustable output power.

6. The crystal-growth apparatus (10″) according to claim 1, wherein the crystal-growth apparatus (10″) comprises an odd number N of afterheater lasers (5) with N > 1, the afterheater lasers (5) circumferentially surrounding the afterheater zone (50).

7. The crystal-growth apparatus (10′) according to claim 1, wherein the crystal-growth apparatus (10′) comprises several afterheater lasers (5) arranged to have variable and/or superimposable irradiation areas and/or arranged to regulate the temperature profile (4′) of the afterheater zone (50).

8. The crystal-growth apparatus (10, 10′, 10″) according to claim 1, wherein the at least one afterheater laser (5) is arranged to heat an afterheater zone (50) which is directly adjacent to the molten zone (230) and/or at least partly overlaps the molten zone (230).

9. The crystal-growth apparatus (10, 10,10”) according to claim 1, wherein the afterheater laser (5) is arranged to heat an afterheater zone (50) overlapping at least partly with the solidification zone (210) and the zone of the feed material (220) which is adjacent to the molten zone (230).

10. A crystal-growth method for growing a crystal (21) from a molten feed material (23), wherein in addition to heating the molten zone (230), an extended afterheater zone (50) which partly overlaps a solidification zone (210) adjacent to the molten zone (230), is heated by at least one afterheater laser beam (51) emitted by at least one afterheater laser (5).

11. The crystal-growth method of claim 10, wherein the irradiation area of the afterheater laser beam (51) emitted by the afterheater laser (5) is adjustable by irradiation-area adjustment means.

12. The crystal-growth method according to claim 10, wherein the temperature profile (4′) of the afterheater zone (50) is adjustable.

13. The crystal-growth method according to claim 10, wherein the afterheater zone (50) is directly adjacent to the molten zone (230) or at least partly overlaps the molten zone (230).

14. The crystal-growth method according to claim 10, wherein the afterheater zone (50) at least partly overlaps the solidification zone (210) and the zone of the feed material (220) which is adjacent to the molten zone (230).

15. A zone-melting-type or a Czochralski-type or a Bridgman-type apparatus comprising the crystal-growth apparatus according to claim 1.

16. A method for thermal treatment to reduce crack formation or thermal stress in crystals (21) grown from a molten feed material (23) and/or for facilitating the melting process of the feed material (23), said method comprising performing the method according to claim 10.

17. The crystal-growth apparatus (10, 10’,10”) according to claim 3, wherein the irradiation-area adjustment means comprise at least one movable lens.

18. The crystal-growth apparatus (10, 10’,10”) according to claim 17, wherein: the at least one afterheater laser is a diode laser (5) with or without adjustable output power.

19. The crystal-growth apparatus (10″) according to claim 18, wherein the crystal-growth apparatus (10″) comprises an odd number N of afterheater lasers (5) with N > 1, the afterheater lasers (5) circumferentially surrounding the afterheater zone (50).

20. The crystal-growth apparatus (10′) according to claim 19, wherein the crystal-growth apparatus (10′) comprises several afterheater lasers (5) arranged to have variable and/or superimposable irradiation areas and/or arranged to regulate the temperature profile (4′) of the afterheater zone (50).