Fishing – trapping – and vermin destroying
Patent
1996-03-18
1998-12-01
Chaudhari, Chandra
Fishing, trapping, and vermin destroying
437 48, 437924, H01L 21266
Patent
active
058437975
ABSTRACT:
Programming of a plurality of mask ROMs having a common structure and formed on a semiconductor wafer is effected by an ion implantation for adjusting the threshold voltage of the memory transistors. The mask ROMs on the wafer is grouped in a plurality of groups arranged in point-symmetry or axisymmetry. During forming a photoresist pattern for each of the mask ROMs, a common alignment offset is assigned to the photoresist patterns of the mask ROMs in each group in the location of opening for ion implantation. Ion implantation is effected to the mask ROMs by using the photoresist patterns having respective alignment offsets in openings. During the ion implantation, the difference in incident angle of an ion beam between the positions on the wafer is compensated by the alignment offsets in the opening of the photoresist patterns.
REFERENCES:
patent: 4910162 (1990-03-01), Yasaka et al.
patent: 5350703 (1994-09-01), Lee
patent: 5372961 (1994-12-01), Noda
"Mask ROM, Reduction in delivery time to half by writing data after formation of interconnections", Nikkei Microdevices, Dec., 1991, pp. 104-109.
Chaudhari Chandra
NEC Corporation
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