Method for producing a silicon ingot having symmetrical grain boundaries

Patent metadata

Field	Value
Publication number	US-10131999-B2
Application number	US-201414894380-A
Country	US
Kind code	B2
Filing date	May 26, 2014
Priority date	May 27, 2013
Publication date	Nov 20, 2018
Grant date	Nov 20, 2018

Abstract

A method for producing a silicon ingot, provided with symmetrical grain boundaries, including at least steps made of: (i) providing crucible with longitudinal axis, bottom of which includes a paving formed from monocrystalline cuboid silicon seeds with a square or rectangular base and arranged contiguously, the paving, when viewed according to axis, being in shape of a grid of orthogonal directions (x) and (y) parallel to edges of seeds; and (ii) proceeding with controlled solidification of silicon by growth on seeds in a growth direction collinear to axis; wherein paving in step (i) is produced from identical silicon seeds, with two seeds contiguous in direction (x) being images of each other by turning axis (y) and two seeds contiguous in direction (y) being images of each other by turning axis (x), and misorientation 2θ between crystalline arrays of two contiguous seeds being greater than 4°.

First claim

The invention claimed is:

1. A process for manufacturing a silicon ingot, having symmetrical grain boundaries, comprising at least the steps consisting of:
(i) providing a crucible of longitudinal axis (Z), the bottom of which comprises a tiling formed from monocrystalline silicon seeds of square- or rectangular-based straight block shape, said monocrystalline silicon seeds being positioned contiguously, said tiling seen along the axis (Z) being in the form of a grid having orthogonal directions (x) and (y) parallel to the edges of the seeds; and
(ii) carrying out the directional solidification of silicon by seeded regrowth in a growth direction collinear to the axis (Z);

characterized in that the tiling in step (i) is produced from identical silicon seeds, with two adjacent seeds along the direction (x) being images of one another by a turning over in axis (y) and two adjacent seeds along the direction (y) being images of one another by a turning over in axis (x), and the disorientation 2θ between the crystal lattices of two adjacent seeds being greater than 4°.

2. The process as claimed in claim 1 , wherein the thickness (e) of the seeds along the axis (Z) are greater than or equal to 5 mm.

3. The process as claimed in claim 1 , wherein the disorientation 2θ between the crystal lattices of two adjacent seeds is greater than or equal to 5°.

4. The process as claimed in claim 1 , wherein the crystal lattice of a seed has a direction collinear to the axis (Z).

5. The process as claimed in claim 1 , wherein the crystal lattice of a seed has a <100> direction collinear to the axis (Z).

6. The process as claimed in claim 1 , wherein the seeds are derived from a Cz silicon lingot; or from the recycling of an ingot formed according to the process as claimed in claim 1 .

7. A silicon ingot having symmetrical grain boundaries, obtained according to the process of claim 1 .

8. The ingot as claimed in claim 6 , having a height measured along the growth axis (Z) of greater than or equal to 100 mm.

9. A process for manufacturing monocrystalline silicon wafers free of grain boundaries, comprising a step (iii) of cutting a silicon ingot as defined in claim 6 , into bricks, by cutting along the planes P.

10. The process as claimed in claim 9 , wherein the cutting are carried out using a cutting wire or a bandsaw.

Assignees

• Commissariat Energie Atomique
• Commissariat A Lenergle Atomique Et Aux Energies Alternatives

Inventors

• Fortin Gautier
• Amaral De Oliveira Vanessa
• Camel Denis
• Pihan Etienne

Classifications

• C30B11/002

  Crucibles or containers for supporting the melt · CPC title

• B28D5/045

  by cutting with wires or closed-loop blades (B28D5/042 takes precedence) · CPC title

• C30B11/14 Primary

  characterised by the seed, e.g. its crystallographic orientation · CPC title

• B28D5/04

  by tools other than rotary type, e.g. reciprocating tools {(B28D5/0005 takes precedence)} · CPC title

• C30B15/00

  Single-crystal growth by pulling from a melt, e.g. Czochralski method (under a protective fluid C30B27/00) · CPC title