Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1981-07-13
1983-09-27
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
250561, 356400, G01B 1100
Patent
active
044069499
ABSTRACT:
A method and apparatus are disclosed for aligning an integrated circuit die (110) by use of a machine which directs a laser beam (32) downward on a wafer containing the die (110). Each die (110) is provided with one or more targets (52, 64, 78). A target (52) comprises an N+ region (56) within the target (52) and a layer of polysilicon (56) over an oxide layer (70). A laser beam (32) is scanned across the target (52) to detect a transition across an edge of a polysilicon layer (68). The transition is detected by the generation of charge carriers (36) within the region (34). The region (34) has an opposite conductivity type from that of the substrate (10) thus forming a PN junction. The PN junction is reversed biased by a voltage source (38) which is connected in series with a resistor (40) between the substrate (10) and the region (34). A center point is determined by calculating the midpoint between transitions. The establishment of a center of the target (52) establishes a reference point. The establishment of two such reference points determines a scaling factor and an angular orientation factor for the die (110) such that any other point on the die (110) can be accurately located.
REFERENCES:
patent: 3885877 (1975-05-01), Horwath et al.
patent: 4213117 (1980-07-01), Kembo et al.
patent: 4266876 (1981-05-01), Nakazawa et al.
patent: 4315201 (1982-02-01), Suzuki et al.
Mostek Corporation
Nelms David C.
Westin Edward P.
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