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Spindle Etching Polysilicon with Motion

IP.com Disclosure Number: IPCOM000086426D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Lounsbury, JB: AUTHOR [+2]

Abstract

Improvement in etch bias and tolerance when etching polysilicon in 7:4:1 (nitric acid: water: (5:1) buffered HF) using spindle etching is obtained with a moving baffle.

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Spindle Etching Polysilicon with Motion

Improvement in etch bias and tolerance when etching polysilicon in 7:4:1 (nitric acid: water: (5:1) buffered HF) using spindle etching is obtained with a moving baffle.

In spindle etching, a wafer is held by vacuum on a spindle and a puddle of etchant is applied to the wafer surface. Etching polysilicon in this manner with 7:4:1 etchant gives 18-24 microinches bias and +/= 13 microinches tolerance per edge. To improve the etch bias and tolerance, a baffle such as a disk of a suitable material, for example plastic, is brought into contact with the puddle of etchant. Surface tension holds the etchant between the wafer and baffle. The baffle is moved vertically through an amplitude of 1-2 mm of a frequency of 1-10 HZ.

Etch end-point detect (EEPD) is provided in one of two ways:
1. Shining the light beam through the moving plate and

eliminating any signal oscillations due to the plate

electronically (filter).
2. Mounting the fiber bundle from the EEPD in the plate

and eliminating the signal oscillations electronically.

Motion of the baffle of the necessary amplitude is created mechanically with a vibrator, solenoid, or motor, acoustically with an audio speaker or transducer, or piezoelectric elements.

The same technique (a baffle in contact with the solution puddle) can further be used to add ultrasonic agitation to the process by attaching a suitable transducer to the baffle.

Finally, the baffle, if it contains heating or cool...