Methods for forming a silicon substrate with reduced grown-in nuclei for epitaxial defects and methods for forming an epitaxial wafer

Patent metadata

Field	Value
Publication number	US-11987901-B2
Application number	US-202217711691-A
Country	US
Kind code	B2
Filing date	Apr 1, 2022
Priority date	Nov 11, 2020
Publication date	May 21, 2024
Grant date	May 21, 2024

Abstract

Methods for preparing single crystal silicon substrates for epitaxial growth are disclosed. The methods may involve control of the (i) a growth velocity, v, and/or (ii) an axial temperature gradient, G, during the growth of an ingot segment such that v/G is less than a critical v/G and/or is less than a value of v/G that depends on the boron concentration of the ingot. Methods for preparing epitaxial wafers are also disclosed.

First claim

What is claimed is:

1. A method for forming a silicon substrate with reduced grown-in nuclei for epitaxial defects, the silicon substrate being boron doped, the method comprising:
adding an initial charge of polycrystalline silicon to a crucible;
heating the crucible comprising the initial charge of polycrystalline silicon to cause a silicon melt to form in the crucible;
adding boron to the crucible to produce a doped silicon melt;
contacting a silicon seed crystal with the doped silicon melt;
withdrawing the silicon seed crystal to grow a single crystal silicon ingot, the ingot having a constant diameter portion, wherein a segment of the constant diameter portion of the ingot has a boron concentration from 2.8×10 18 atoms/cm 3 to 5.4×10 18 atoms/cm 3 ;
controlling (i) a growth velocity, v, and/or (ii) an axial temperature gradient, G, during the growth of the segment such that v/G is less than 0.20 mm 2 /(min*K) and interstitials are the dominant intrinsic point defect in the segment;
cooling the segment of the constant diameter portion of the ingot from its solidification temperature to 950° C. or less, wherein the dwell time the segment of the constant diameter portion of the ingot is in the temperature range from 1150° C. to 950° C. is less than 160 minutes; and
slicing the substrate from the single crystal silicon ingot.

2. The method as set forth in claim 1 wherein the constant diameter portion has a length D, the length of the segment being at least 0.5*D.

3. The method as set forth in claim 1 wherein the dwell time the segment of the constant diameter portion of the ingot is in the temperature range from 1150° C. to 950° C. is less than 120 minutes.

4. The method as set forth in claim 1 wherein the melt is not doped with carbon.

5. The method as set forth in claim 1 wherein the length of the segment is the entire constant diameter portion of the ingot.

6. The method as set forth in claim 1 wherein the dwell time the segment of the constant diameter portion of the ingot is in the temperature range from 1150° C. to 950° C. is less than 60 minutes.

7. A method for preparing an epitaxial structure, the method comprising:
forming the silicon substrate by the method of claim 1 ; and
contacting a front surface of the silicon substrate with a silicon-containing gas, the silicon-containing gas decomposing to form an epitaxial silicon layer on the silicon substrate.

8. The method as set forth in claim 1 wherein a single dopant is added to the melt, the single dopant being boron.

9. A method for forming a silicon substrate with reduced grown-in nuclei for epitaxial defects, the silicon substrate being boron doped, the method comprising:
adding an initial charge of polycrystalline silicon to a crucible;
heating the crucible comprising the initial charge of polycrystalline silicon to cause a silicon melt to form in the crucible;
adding boron to the crucible to produce a doped silicon melt;
contacting a silicon seed crystal with the doped silicon melt;
withdrawing the silicon seed crystal to grow a single crystal silicon ingot, the ingot having a constant diameter portion, wherein a segment of the constant diameter portion of the ingot has a boron concentration from 5.4×10 18 atoms/cm 3 to 8.0×10 18 atoms/cm 3 ;
controlling (i) a growth velocity, v, and/or (ii) an axial temperature gradient, G, during the growth of the segment such that v/G is less than 0.25 mm 2 /(min*K) and interstitials are the dominant intrinsic point defect in the segment;
cooling the segment of the constant diameter portion of the ingot from its solidification temperature to 950° C. or less, wherein the dwell time the segment of the constant diameter portion of the ingot is in the temperature range from 1150° C. to 950° C. is less than 160 minutes; and
slicing the substrate from the single crystal silicon ingot.

10. The method as set forth in claim 9 wherein the constant diameter portion has a length D, the length of the segment being at least 0.5*D.

11. The method as set forth in claim 9 wherein the dwell time the segment of the constant diameter portion of the ingot is in the temperature range from 1150° C. to 950° C. is less than 120 minutes.

12. The method as set forth in claim 9 wherein the melt is not doped with carbon.

13. The method as set forth in claim 9 wherein the length of the segment is the entire constant diameter portion of the ingot.

14. The method as set forth in claim 9 wherein the dwell time the segment of the constant diameter portion of the ingot is in the temperature range from 1150° C. to 950° C. is less than 60 minutes.

15. A method for preparing an epitaxial structure, the method comprising:
forming the silicon substrate by the method of claim 9 ; and
contacting a front surface of the silicon substrate with a silicon-containing gas, the silicon-containing gas decomposing to form an epitaxial silicon layer on the silicon substrate.

16. The method as set forth in claim 9 wherein a single dopant is added to the melt, the single dopant being boron.

Assignees

• Globalwafers Co Ltd

Inventors

• Valcozzena Pietro
• Porrini Maria
• Duchini Januscia

Classifications

• C30B29/06 Primary

  Silicon · CPC title

• C30B15/007

  Pulling on a substrate · CPC title

• C30B15/04

  adding doping materials, e.g. for n-p-junction · CPC title

• C30B15/14

  Heating of the melt or the crystallised materials · CPC title

• C30B15/203 Primary

  the relationship of pull rate (v) to axial thermal gradient (G) · CPC title