Smoothing method for cleaved films made using a release layer

• US 20030008477A1
• Filed: 05/17/2002
• Published: 01/09/2003
• Est. Priority Date: 04/21/1999
• Status: Active Grant

• Current Assignee: Silicon Genesis
• Original Assignee: Silicon Genesis
• Inventors: Malik, Igor J., Kang, Sien G.
• Granted Patent: US 6,881,644 B2
• Time in Patent Office: Days
• US Class Current: 438/458
• CPC Class Codes: H01L 21/304 Mechanical treatment, e.g. grinding, polishing, cutting H01L21/30625 takes precedence
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/76254 with separation/delamination along an ion implanted layer, e.g. Smart-cut, Unibond
• CPC Class Codes: H01L 21/76259 with separation/delamination along a porous layer
• CPC Class Codes: Y10S 438/96 Porous semiconductor
• CPC Class Codes: Y10S 438/977 Thinning or removal of substrate

Abstract

A method for treating a film of material, which can be defined on a substrate, e.g., silicon. The method includes providing a substrate comprising a cleaved surface, which had a porous silicon layer thereon. The substrate may have a distribution of hydrogen bearing particles defined from the cleaved surface to a region underlying said cleaved surface. The method also includes increasing a temperature of the cleaved surface to greater than about 1,000 Degrees Celsius while maintaining the cleaved surface in a etchant bearing environment to reduce a surface roughness value by about fifty percent and greater. Preferably, the value can be reduced by about eighty or ninety percent and greater, depending upon the embodiment.

Claims

1. A semiconductor substrate producing method comprising:

forming a first porous silicon layer on at least one surface of a silicon substrate; and

forming a second layer having a larger porosity than the first porous silicon layer at a constant depth from a surface of said porous silicon in said first porous silicon layer, said second layer forming step comprising implanting ions into said first porous silicon layer with a given projection range;

bonding said non-porous layer and a support substrate together;

separating said silicon substrate into two portions at said second layer to remove the porous silicon layer exposed on a surface of said support substrate and exposing said non-porous layer; and

smoothing the non-porous layer by subjecting surfaces of the non-porous layer using an etchant species and thermal treatment.

2. The semiconductor substrate producing method according to claim 1 further comprising a non-porous layer forming step for forming a non-porous layer on a surface of said first porous layer before said ion implanting step.

3. The semiconductor substrate producing method according to claim 1 wherein said ions comprise at least one kind of noble gas, hydrogen and nitrogen.

4. The semiconductor substrate producing method according to claim 2 wherein said separating step is performed by heat-treating said silicon substrate.

5. The semiconductor substrate producing method according to claim 1 wherein said separating step is performed by pressurizing said silicon substrate in a direction perpendicular to a surface thereof.

6. The semiconductor substrate producing method according to claim 1 wherein said separating step is performed by drawing said silicon substrate in a direction perpendicular to a surface thereof.

7. The semiconductor substrate producing method according to claim 1 wherein said separating step is performed by applying a shearing force to said silicon substrate.

8. The semiconductor substrate producing method according to claim 1 wherein said non-porous layer is made of single-crystal Si.

9. The semiconductor substrate producing method according to claim 1 wherein said non-porous layer is made of single-crystal silicon having an oxidized silicon layer on a surface to be bonded.

10. A semiconductor substrate producing method comprising:

forming on a surface of a silicon substrate a first porous silicon layer, a second porous silicon layer and a third porous silicon layer, wherein the second porous silicon layer is located under the first porous silicon layer and has a porosity higher than the first porous silicon layer, and the third porous silicon layer is located under the second porous silicon layer and has a porosity lower than the second porous silicon layer;

forming a non-porous monocrystalline semiconductor layer on the first porous silicon layer;

bonding the non-porous monocrystalline semiconductor layer located on the silicon substrate to another substrate; and

separating the silicon substrate and the other substrate at the second porous silicon layer so that the non-porous monocrystalline semiconductor layer remains on the other substrate; and

removing the first porous silicon layer from the non-porous monocrystalline semiconductor layer; and

subjecting a surface of the non-porous monocrystalline semiconductor layer with thermal energy and an etchant to remove a surface roughness from a first value to a second predetermined value.

11. The semiconductor substrate producing method according to claim 10 wherein said forming step for forming said first, second and third porous silicon layers comprises a step for turning a surface portion of said silicon substrate porous.

12. The semiconductor substrate producing method according to claim 11 wherein said second porous silicon layer is formed by means of ion implantation.

13. The semiconductor substrate producing method according to claim 12 wherein said non-porous monocrystalline semiconductor layer is formed by epitaxial growth.

15. The method of claim 15 wherein the thermal treatment increases a temperature of the to about 1,000 Degrees Celsius and greater.

16. The method of claim 15 wherein the temperature increases is about 10 Degrees Celsius per second and greater.

17. The method of claim 15 wherein said temperature increases is about 20 Degrees Celsius per second and greater.

18. The method of claim 14 wherein said predetermined value is less than about two nanometers root mean square.

19. The method of claim 14 wherein said etchant comprises a hydrogen bearing compound.

20. The method of claim 19 wherein said etchant comprising a halogen bearing compound is selected from at least Cl₂, HCl, HBr, HI, and HF.

21. The method of claim 14 wherein said etchant comprises a fluorine bearing compound.

22. The method of claim 21 wherein said fluorine bearing compound is selected from SF₆, CF₄, NF₃, and CCl₂F₂.

14. A semiconductor substrate producing method comprising:

forming on a surface of a silicon substrate a first porous silicon layer;

implanting ions into the first porous silicon layer to form a second porous silicon layer having a porosity higher than the first porous silicon layer at a constant depth from a surface of the first porous silicon layer;

forming a non-porous monocrystalline semiconductor layer on the first porous silicon layer;

bonding the non-porous monocrystalline semiconductor layer located on the silicon substrate to another substrate; and

separating the silicon substrate and the other substrate at the second porous silicon layer so that the non-porous monocrystalline semiconductor layer remains on the other substrate; and

applying a combination of thermal treatment and an etchant to a surface of the non-porous monocrystalline semiconductor layer to reduce a surface roughness to a predetermined value.