Fishing – trapping – and vermin destroying
Patent
1992-12-07
1994-08-09
Chaudhuri, Olik
Fishing, trapping, and vermin destroying
437 8, 437 34, 437913, 437 45, H01L 21265
Patent
active
053366247
ABSTRACT:
Focussed ion beam (FIB) implants (38,40) are used to set the threshold voltages of metal-oxide-semiconductor field-effect transistors (MOSFETs) in a selected logic gate (34,36) in a microelectronic integrated digital logic circuit (31) such that the direct current (DC) transfer function and logic thresholds are essentially the same as for another logic gate (30,32) which is not altered by FIB implants, but the switching speed is greatly reduced. This causes the altered gate (34,36) to switch in an apparently normal manner when tested under DC or low speed conditions, but to not switch at normal operating speed. The altered or disguised gate (34,36) is thereby always on or always off at the normal operating speed, whereas the unaltered gate (30,32) switches in the normal manner. This impedes attempts at reverse engineering since the circuit (31) operates differently under test and operating conditions, and the true logic functions of the gate (34,36) cannot be determined by known low speed test procedures.
REFERENCES:
patent: 4409434 (1983-10-01), Basset et al.
patent: 4472871 (1984-09-01), Green et al.
patent: 4530150 (1985-07-01), Shirato
patent: 4583011 (1986-04-01), Pechar
patent: 4766516 (1988-08-01), Ozdemir et al.
patent: 4922136 (1990-05-01), Ueda
patent: 4952824 (1990-08-01), Kamuro
patent: 5015594 (1991-05-01), Chu et al.
patent: 5021356 (1991-06-01), Hendersen et al.
Patent Abstracts of Japan, vol. 014, No. 463 (E-988) Oct. 8, 1990 & JP-A-21 88 944 (Sharp K.K.) Jul. 25, 1990.
Chaudhuri Olik
Denson-Low W. K.
Duraiswamy V. D.
Hughes Aircraft Company
Tsai H Jey
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