1973 · Projection Mask Aligner · Work 866 of 1,871
An exposure room in a chip factory under amber yellow light, a projection mask aligner, a light grey steel cabinet one metre high on a plinth painted blue, one side panel removed to show coiled blue air hoses, small valves and brass cylinders, at its left a black optics housing with a tilted binocular head and a narrow strip of plain dark grey push-buttons, a slit of bright light passing across a mirror-bright silicon wafer, on the work surface a white plastic cassette of wafers, an operator in a white clean- room coat and hood seen from behind with eyes at the eyepieces, a shelf of closed plain white cases behind.
What it was used for
In wafer fabs the Perkin-Elmer Micralign exposed whole wafers by scanning a narrow arc of light across mask and wafer together, at 1:1 and without the mask touching the wafer. Chris Mack's chronology of lithography tools gives 1973 for its introduction, more than 2,000 units sold, and a 1979 price of 170,000 dollars; according to Kato's chronology the Micralign 500, announced in 1981, was the first tool to reach 100 wafers per hour. According to chiphistory.org, scanning projection dominated production by the late 1970s, at 40 wafers per hour and a defect density of about 4 per square inch.
What was new
Before the Micralign there were only contact and proximity aligners, in which the mask touched the resist wholly or partly and wore out. According to chiphistory.org yield had been 10 or 20 percent, often nearer zero; word leaked out that Intel's new aligner yielded about 70 percent. The numerical aperture was 0.167 according to Atsuhiko Kato's chronology, which is low; the gain lay not in resolution but in the mask no longer touching the wafer. The barb: chiphistory.org writes that Perkin-Elmer responded too late to the stepper threat; by Kato's figures the company's share of the Japanese projection-aligner market fell from 60 to under 20 percent between 1981 and 1983, and in 1986 Canon held 90 percent of it.
What the sources leave open: The yield of about 70 percent is given by chiphistory.org explicitly as word that leaked out about Intel, not as a measured value; the 10 to 20 percent it states generally for the older aligners. Price and unit count come from Mack's compilation, not from a Perkin-Elmer source.
Connections
Every connection names its kind. “Forerunner” on its own would be a claim.