Methods of thinning a silicon wafer using HF and ozone

• US 7,404,863 B2
• Filed: 07/30/2003
• Issued: 07/29/2008
• Est. Priority Date: 05/09/1997
• Status: Expired due to Fees

• Current Assignee: OEM Group, LLC
• Original Assignee: Semitool Incorporated (Applied Materials Incorporated)
• Inventors: Bergman, Eric J.
• Primary Examiner(s): EL ARINI, ZEINAB
• Application Number:
  US10/631,376
• Publication Number:
  US 20040020513A1
• Time in Patent Office: 1,826 Days
• Field of Search: 134/2, 134/3, 134/21, 134/25.4, 134/30, 134/31, 134/33, 134/36, 134/902
• US Class Current: 134/3
• CPC Class Codes: B08B 2203/005 the liquid being ozonated
• CPC Class Codes: B08B 2203/007 Heating the liquid
• CPC Class Codes: B08B 2230/01 Cleaning with steam
• CPC Class Codes: B08B 3/00 Cleaning by methods involving the use or presence of liquid or steam B08B9/00 takes precedence
• CPC Class Codes: B08B 3/02 Cleaning by the force of jets or sprays
• CPC Class Codes: B08B 3/044 using agitated containers in which the liquid and articles or material are placed by means of ultrasonic vibrations B08B3/12; cleaning casks or barrels by agitating B08B9/0817; mixers with shaking, oscillating or vibrating mechanisms B01F31/00
• CPC Class Codes: B08B 3/08 the liquid having chemical or dissolving effect substances used, see the relevant classes
• CPC Class Codes: B08B 7/00 Cleaning by methods not provided for in a single other subclass or a single group in this subclass
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/6704 for wet cleaning or washing
• CPC Class Codes: H01L 21/67051 using mainly spraying means, e.g. nozzles
• CPC Class Codes: H01L 21/6708 using mainly spraying means, e.g. nozzles
• CPC Class Codes: H01L 23/49582 Metallic layers on lead frames
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H05K 3/3426 characterised by the leads
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10S 134/902 Semiconductor wafer

Abstract

A method of thinning a silicon wafer in a controllable cost-effective manner with minimal chemical consumption. The wafer is placed into a process chamber, after which ozone gas and HF vapor are delivered into the process chamber to react with a silicon surface of the wafer. The ozone and HF vapor may be delivered sequentially, or may be mixed with one another before entering the process chamber. The ozone oxidizes the silicon surface of the wafer, while the HF vapor etches the oxidized silicon away from the wafer. The etched oxidized silicon is then removed from the process chamber. As a result, the wafer is thinned, which aids in preventing heat build-up in the wafer, and also makes the wafer easier to handle and cheaper to package. In alternative embodiments, HF may be delivered into the process chamber as an anhydrous gas or in aqueous form.

Claims

1. A method of thinning at least one silicon wafer, comprising:

placing the wafer into a process chamber;

spinning the wafer;

spraying a liquid including water onto the spinning wafer, with the liquid forming a substantially uniform liquid layer on the wafer;

controlling a thickness of the liquid layer;

providing hydrofluoric acid in an aqueous form in the process chamber, with the hydrofluoric acid etching a silicon dioxide layer on a surface of the wafer; and

providing ozone gas in the process chamber, with the ozone gas oxidizing a silicon surface of the wafer exposed by etching the silicon dioxide layer, and with the HF etching the oxidized silicon surface until the wafer is thinned to approximately 5 to 20% of its initial thickness.

2. The method of claim 1 with the HF etching the silicon at a rate over 1000 angstroms/minute.

3. The method of claim 2 with the HF etching the silicon at a rate of 5000-10000 angstroms/minute.

4. The method of claim 1 with the wafer thinned to a thickness of 50-100 microns.

5. The method of claim 1 further comprising continuously supplying fresh ozone gas into the process chamber to continually oxidize the exposed silicon surface.

6. The method of claim 1 wherein the oxidized silicon is removed as SiF₄ in vapor form from the process chamber.