Silicon film with improved thickness control

• US 5,256,581 A
• Filed: 08/28/1991
• Issued: 10/26/1993
• Est. Priority Date: 08/28/1991
• Status: Expired due to Fees

• Current Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: D'Aragona, Frank S., Foerstner, Juergen A., Hughes, Henry G.
• Primary Examiner(s): Chaudhuri, Olik
• Assistant Examiner(s): OJAN, OURMAZD
• Application Number:
  US07/751,001
• Time in Patent Office: 790 Days
• Field of Search: 437/24, 437/61, 437/974, 148/DIG. 135
• US Class Current: 438/459
• CPC Class Codes: H01L 21/2007 Bonding of semiconductor wafers to insulating substrates or to semiconducting substrates using an intermediate insulating layer H01L21/2011 takes precedence; bonding of semiconductor wafers to semiconductor wafers for junction formation H01L21/187
• CPC Class Codes: H01L 21/76251 using bonding techniques

Abstract

A method of fabricating a silicon film with improved thickness control and low defect density. The method comprises implanting a silicon wafer (19) with hydrogen ions to produce a layer of n-type silicon (18) having a precisely controlled thickness. Bonding the n-type silicon layer (18) to an oxidized surface (17) of a handle wafer (21) while using a temperature of 200 degrees Celsius. Etching the silicon wafer (19) to the boundary of the n-type layer (18). Annealing the silicon to drive out the hydrogen ions, leaving a silicon film (18) with a precisely controlled thickness and of the same type as the original silicon wafer (19).

Claims

1. A method of fabricating a silicon film with improved thickness control, comprising:

providing an active wafer of silicon material;

implanting the active wafer with hydrogen ions to produce a layer of n-type silicon having a precisely controlled thickness;

providing a handle wafer having at least one oxidized surface;

bonding the n-type silicon layer to the oxidized surface of the handle wafer using a temperature of 200 degrees Celsius;

etching the active wafer to the boundary of the n-type layer; and

annealing the n-type silicon layer to drive out the hydrogen ions, leaving a silicon film on top of a silicon dioxide insulating layer.

2. The method of claim 1 wherein etching of the active wafer is preceded by mechanically grinding away excess silicon to a thickness.

3. The method of claim 1 wherein providing the active wafer comprises providing a p-type silicon wafer, and etching is an electrochemical etch using an etchant which selectively etches the p-type material such that etching stops at a p-n junction.

4. The method of claim 1 further comprising:

providing a tungsten silicide electrode attached to the handle wafer which electrically couples the handle wafer to the implanted n-type silicon layer after the active wafer and the handle wafer are bonded together; and

mechanically polishing both the tungsten silicide electrode and the oxidized surface of the handle wafer to provide a uniform surface for bonding.

5. A method of fabricating a silicon film with improved thickness control, comprising:

providing an active wafer;

implanting the active wafer with hydrogen ions to produce a layer of n-type silicon having a precisely controlled thickness;

providing a handle wafer having an oxidized layer with an upper surface;

forming a conductive plug through the oxidized layer, the conductive slug being polished flush with the upper surface of the oxidized layer;

bonding the n-type silicon layer to the oxidized handle wafer to produce a composite wafer;

etching the composite wafer to the boundary of the n-type layer; and

annealing the composite wafer to drive out the hydrogen ions, leaving a silicon film having a precisely controlled thickness.

6. A method of fabricating a silicon film with improved thickness control, comprising:

providing an active wafer having p-type doping;

implanting the active wafer with hydrogen ions to produce a layer of n-type silicon having a precisely controlled thickness and forming a p-n junction;

etching a hole in an oxidized surface of an oxidized handle wafer having a desired position and shape;

depositing tungsten silicide onto the oxidized surface and into the hole;

polishing the tungsten silicide and the oxidized surface to produce a smooth surface for bonding;

bonding the n-type silicon layer to the oxidized handle wafer using a temperature of less than 200 degrees Celsius to produce a composite wafer;

mechanically grinding the surplus silicon from the active wafer to leave a predetermined thickness of silicon above the n-type silicon film;

electrochemically etching the composite wafer using an etchant which selectively etches the p-type material such that etching stops at the p-n junction; and

annealing the composite wafer to drive out the hydrogen ions, leaving a p-type silicon film having a precisely controlled thickness.

7. A method of fabricating a silicon film with improved thickness control, comprising:

providing an active wafer;

epitaxially depositing an n-type layer of silicon onto the surface of the active wafer;

providing a handle wafer having an oxidized layer with a conductive plug through the oxidized layer and which is polished to be flush with a surface of the oxidized layer;

bonding the n-type silicon layer of the active wafer to the oxidized layer of the handle wafer to produce a composite wafer;

removing silicon from the active wafer by mechanical means to a predetermined thickness above the n-type silicon film;

etching the composite wafer until only the n-type silicon layer remains; and

annealing the composite wafer.