Browse Prior Art Database

SILICON POLYGON FABRICATION

IP.com Disclosure Number: IPCOM000026115D
Original Publication Date: 1990-Jun-30
Included in the Prior Art Database: 2004-Apr-05
Document File: 4 page(s) / 203K

Publishing Venue

Xerox Disclosure Journal

Abstract

Present polygon fabrication for raster output scanners (ROS) is a very difficult, complex, and costly process. The base material is aluminum which is diamond machined. It has been estimated that a diamond machining set-up cost for the fabrication of polygons is about $400,00O/machine with a usable lifetime of about 3 years. Diamond cutting bits are expensive (about $500 each) and are very sensitive to material composition. A slight change of impurities in the base material could affect machining operation. As a result, cutting bits are only good 50% of the time.

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XEROX DISCLOSURE JOURNAL

SILICON POLYGON FABRICATION Proposed Classification Michael R. Campanelli U.S. C1.350/006.8 Peter J. John Int. C1. G02b 27/17

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FIG. I

XEROX DISCLOSURE JOURNAL - Vol. 15, No. 3 May/June 1990 143

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SILICON POLYGON FABRICATION(Cont'd)

Present polygon fabrication for raster output scanners (ROS) is a very difficult, complex, and costly process. The base material is aluminum which is diamond machined. It has been estimated that a diamond machining set-up cost for the fabrication of polygons is about $400,00O/machine with a usable lifetime of about 3 years. Diamond cutting bits are expensive (about $500 each) and are very sensitive to material composition. A slight change of impurities in the base material could affect machining operation. As a result, cutting bits are only good 50% of the time.

Standard polygon sizes range from 2-3+" with thicknesses ranging from 1/8" to l/2". The extreme thickness is strictly required to address materials handling issues. The facet flatness requirement is 0.llpm with top to bottom parallelism to 1.5pm.

Surface roughness, reflectivity, facet angle error, and draft angle error add to the complexity of and already difficult manufacturing process. For example, an 8 facet polygon 2.64"diameter in quantities of $50,00O/year is $18.14 each.

A cost reduction is obtained by the fabrication of polygons using silicon as the base material. The immediate advantage to using silicon is that machining equipment already exists and is well established in the semiconductor industry. Silicon polygons would have low mass, good thermal conductivity, and low stress machinability. Wafer grinding machines exist which typically achieve parallelism and flatness within 3.8ym over a 4" wafer (Disco Wafer Grinder). The surface roughness on the same machine typically ranges from
0.05 - lp rms. Another machine typically used in the industry is a dicing saw. The unique feature here is the rotational stage. The minimum index step is 0.0022" or 8 arc seconds. The final piece of equipment necessary to complete the process is the orientation flat grinder. This machine supports a silicon ingot to grind in, at various depths, the orientation flat. A hybrid of these three machines would allow fine grinding with precise rotational accuracy.

One fabrication procedure shown in Figures 1 and 2, utilizes high purity single crystalline 3" diameter x 0.1" thick silicon wafers 10. Seven 8 faceted, 0.8" diameter polygons 12 were fabricated from 1 wafer via a dicing saw by dicing along vertical and horizontal cut lines 16, s...