Process for etching silicon with selectivity to silicon-germanium

• US 8,389,416 B2
• Filed: 11/22/2010
• Issued: 03/05/2013
• Est. Priority Date: 11/22/2010
• Status: Active Grant

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Luong, Vinh Hoang
• Primary Examiner(s): Ahmed, Shamim
• Assistant Examiner(s): GATES, BRADFORD M
• Application Number:
  US12/951,691
• Publication Number:
  US 20120129354A1
• Time in Patent Office: 834 Days
• Field of Search: None
• US Class Current: 438/714
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/3266 Magnetic control means
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/6831 using electrostatic chucks
• CPC Class Codes: H01L 29/0673 oriented parallel to a substrate

Abstract

A method for performing a selective etching process is described. The method includes preparing a substrate having a silicon layer (Si) and a silicon-germanium (SiGe_x) layer, and selectively etching the silicon layer relative to the silicon-germanium layer using a dry plasma etching process.

Claims

1. A method for performing a selective etching process, comprising:

preparing a substrate having a silicon layer (Si) and a silicon-germanium (SiGe.sub.x) layer; and

selectively etching an exposed surface of said silicon layer relative to an exposed surface of said silicon-germanium layer using a dry plasma etching process having a process composition containing as incipient ingredients HBr and an optional noble gas,

wherein said dry plasma etching process achieves an etch selectivity between said silicon layer and said silicon-germanium layer greater than or equal to 2.

2. The method of claim 1, wherein said process composition consists of HBr and He.

3. The method of claim 1, wherein said process composition further contains as incipient ingredients a halogen-containing gas, a fluorocarbon-containing gas, a hydrocarbon-containing gas, O₂, N₂, H₂, CO, CO₂, NO, NO₂, N₂O, or NH₃, or any combination of two or more thereof.

4. The method of claim 1, wherein said dry plasma etching process includes setting a gas pressure in a plasma etching system ranging up to 200 mTorr.

5. The method of claim 1, wherein said dry plasma etching process excludes coupling radio frequency (RF) power to a substrate holder upon which said substrate rests.

6. The method of claim 1, wherein said dry plasma etching process includes optionally coupling first radio frequency (RF) power at a first frequency to a substrate holder upon which said substrate rests in a plasma etching system, and coupling second radio frequency (RF) power at a second frequency to an upper electrode opposing said substrate on said substrate holder.

7. The method of claim 6, wherein said dry plasma etching process excludes coupling said first RF power to said substrate holder.

8. The method of claim 2, wherein a ratio between a flow rate of HBr and a flow rate of He ranges from 1:

1 to 4;

1.

9. The method of claim 2, wherein a ratio between a flow rate of HBr and a flow rate of He ranges from 1.5:

1 to 2.5;

1.

10. The method of claim 1, further comprising:

optionally introducing an additive gas to said process composition; and

adjusting one or more process parameters in said dry plasma etching process to change a polarity of an etch selectivity between said silicon layer and said silicon-germanium layer.

11. The method of claim 10, wherein said one or more process parameters includes a gas pressure, a RF power, a direct current (DC) power, a HBr flow rate, a He flow rate, a flow rate of said additive gas, or a temperature, or any combination of two or more thereof.

12. The method of claim 1, wherein said substrate rest on a temperature controlled substrate holder in a plasma etching system, said temperature controlled substrate holder comprises:

a support base having fluid channels to circulate a temperature controlled thermal fluid in said support base; and

a substrate support coupled via a thermal insulator to an upper portion of said support base, said substrate support comprising;

one or more heating elements embedded within said substrate support,

an upper surface to support said substrate by contact between said upper surface and a backside of said substrate, and

an electrostatic clamp electrode to hold said substrate on said upper surface of said substrate support.

13. The method of claim 12, wherein said temperature controlled substrate holder further comprises:

a backside gas supply system configured to supply a heat transfer gas to the backside of said substrate through at least one of a plurality of orifices or channels disposed on said upper surface of said substrate support, wherein said plurality of orifices of said backside gas supply system are arranged in a plurality of zones on said upper surface of said substrate support to vary a backside pressure in a radial direction between a substantially central region of the backside of said substrate and a substantially edge region of the backside of said substrate.

14. A method for preparing a silicon-germanium nano-wire, comprising:

preparing a film stack on a substrate having alternating layers of silicon (Si) and silicon-germanium (SiGe.sub.x);

transferring a pattern through a silicon (Si) layer in said alternating layers of silicon (Si) and silicon-germanium (SiGe.sub.x) to expose a sidewall of said silicon (Si) layer;

transferring said pattern through a silicon-germanium (SiGe.sub.x) layer in said alternating layers of silicon (Si) and silicon-germanium (SiGe.sub.x) to expose a sidewall of said silicon-germanium (SiGe.sub.x) layer; and

laterally etching said sidewall of said silicon (Si) layer by exposing said film stack to a dry plasma etching process having a process composition containing as incipient ingredients HBr and optionally He,

wherein said dry plasma etching process achieves an etch selectivity between said silicon (Si) layer and said silicon-germanium (SiGe.sub.x) layer greater than or equal to two.

15. The method of claim 14, wherein said process composition contains HBr and He.

16. The method of claim 14, wherein said process composition consists of HBr and He.

17. The method of claim 14, wherein said transferring said pattern through said silicon (Si) layer and said silicon-germanium (SiGe_x) layer creates a fin structure extending between opposing buttress structures located at distal ends of said fin structure.

18. The method of claim 17, wherein said laterally etching said silicon (Si) layer removes said silicon (Si) layer from said fin structure and releases a silicon-germanium (SiGe_x) layer bridge.