Method for manufacturing a silicon cylinder by growth on seeds in a directed solidification furnace

Patent metadata

Field	Value
Publication number	US-10125430-B2
Application number	US-201414894385-A
Country	US
Kind code	B2
Filing date	May 26, 2014
Priority date	May 27, 2013
Publication date	Nov 13, 2018
Grant date	Nov 13, 2018

Abstract

A method for manufacturing a silicon cylinder by growth on seeds in a directed solidification furnace, including at least the following steps: (i) providing a crucible having a longitudinal axis (Z), in which the bottom is covered with a layer of seeds of monocrystalline silicon in a right prism shape; and (ii) proceeding with directed solidification of silicon by growth on seeds, in a direction of growth that is co-linear with the axis (Z) and with a concave solidification front, spatially or temporally; characterized in that the layer in step (i) of: one or more central seeds G c ; and one or more peripheral seeds G p contiguous to the seed(s) G c , the peripheral seeds G p having a specific size.

First claim

The invention claimed is:

1. A process for manufacturing a silicon ingot by seeded regrowth in a directional solidification furnace, comprising at least the steps consisting of:
(i) providing a crucible of longitudinal axis (Z), the bottom of which comprises a tiling of monocrystalline silicon seeds of straight prism shape; and
(ii) carrying out the directional solidification of silicon by seeded regrowth, in a growth direction collinear to the axis (Z) and with a spatially or temporally concave solidification front;

wherein the tiling in step (i) is formed:
from one or more central seeds G c ; and
from one or more peripheral seeds G p , adjacent to the seed(s) G c ,
a seed Gp having a crystal lattice symmetrical to the crystal lattice of the adjacent seed G c , relative to the plane P defined by the boundary between said seeds G p and Gc;
said seed(s) G p having, in a vertical cutting plane, a width (l p ) strictly smaller than the total width (l u ) of said central seed(s); and
the peripheral seeds G p being sized so that:
l p =d−b

with:
d satisfying: d≥H·tan θ max , wherein θ max is the maximum value of the angle θ of the solidification front of the furnace used, and H is the desired height, measured along the axis (Z), of the silicon ingot; and
b=0 for a crucible with right angles, and b=R internal crucible, wherein R internal crucible is the size of the bevel for a crucible with rounded edges.

2. The process as claimed in claim 1 , wherein the value θ max is determined at the end of a directional solidification test, in the same crucible, of a silicon ingot having a height H test similar to the height H of the desired ingot, obtained by seeded regrowth.

3. The process as claimed in claim 2 , wherein the value θ max is calculated, at the end of the directional solidification test, by the following formula: tan θ max =d test /H test , wherein d test is the distance furthest away from the edge of the crucible where the multicrystalline zone lies for the ingot of height H test obtained during the test.

4. The process as claimed in claim 1 , wherein the seeds G c and G p are derived from a C z silicon ingot; or from the recycling of an ingot produced during a previous directional solidification by removing a horizontal slice of the ingot formed.

5. The process as claimed in claim 1 , wherein the seeds G c and G p have a thickness (e) along the axis (Z) of greater than or equal to 5 mm.

6. The process as claimed in claim 1 , wherein said seed(s) G p have, in a vertical cutting plane, a width (l p ) of less than or equal to 157 mm.

7. The process as claimed in claim 1 , wherein said seed(s) G c have, in a vertical cutting plane, a width (l c ) of between 110 mm and l u /n wherein n is the number of central seeds placed side-by-side.

8. The process as claimed in claim 1 , wherein the seeds G c have the shape of a square- or rectangular-based straight block.

9. The process as claimed in claim 1 , wherein the crucible has right angles, the seed G p being placed next to the side wall of the crucible.

10. The process as claimed in claim 1 , wherein the crucible has rounded edges, the seed G p being spaced away from the side wall of the crucible by a distance (b) equal to the size of the bevel of the crucible R internal crucible.

11. The process as claimed in claim 1 , wherein the crucible is sized as a function of the previously determined width (l p ) of the peripheral seeds and of the desired width (l u ).

12. The process as claimed in claim 1 , wherein each seed G c has a crystal lattice symmetrical to the crystal lattice of the seed G c which is adjacent thereto, relative to the plane defined by the boundary between the two adjacent seeds G c .

13. The process as claimed in claim 1 , wherein a peripheral seed G p has a crystallographic orientation different from the adjacent central seed G c .

14. The process as claimed in any one of the preceding claims, wherein the total disorientation 2φ between the symmetrical crystal lattices of a seed G p and of an adjacent seed G c is greater than or equal to 4°.

15. A silicon ingot, having a monocrystalline core separated by substantially vertical grain boundaries from a peripheral multicrystalline zone, obtained as claimed in the process of claim 1 .

16. A process for manufacturing a monocrystalline silicon ingot, comprising at least a step (iii) of cutting the ingot as defined in claim 15 , along planes P defined by the interface between two adjacent seeds G c and G p , so as to eliminate the multicrystalline zones formed directly above the seeds G p .

17. The process as claimed in claim 16 , wherein the monocrystalline silicon ingot isolated at the end of step (iii) has a multicrystalline part of less than 5% of its total volume.

Assignees

• Commissariat Energie Atomique
• Commissariat Energie Atomique

Inventors

• Pihan Etienne
• Amaral De Oliveira Vanessa
• Camel Denis
• Chavrier Denis
• Fortin Gautier
• Jouini Anis
• Marie Benoit
• Plassat Nelly

Classifications

• B28D5/045

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

• B28D5/00

  Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor (working by grinding or polishing B24; for artistic purposes B44B) · CPC title

• C30B11/02

  without using solvents (C30B11/06 takes precedence) · CPC title

• C30B11/002

  Crucibles or containers for supporting the melt · CPC title

• C30B15/00

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