| 摘要 |
1489390 MOSFETs GENERAL INSTRUMENT CORP 23 Dec 1974 [2 Jan 1974] 44630/74 Heading H1K MOSFETs with different threshold voltages are formed in a single semi-conductor wafer of one conductivity type by first forming the source and drain regions of a number of devices by introduction of dopant characteristic of the opposite conductivity type into the channel regions of some but not other devices and dopant determinative of the opposite conductivity type into those of at least some of said other devices. As described four MOSFETs each having a different threshold voltage are formed at a 111 or 100 orientated face of a high resistivity P type silicon wafer by first diffusing atsenic from an arseno-silica film through apretures in a thermal oxide mask to form all the source and drain regions, reoxidizing to a thickness of 5000Œ50Š, implanting boron ions into the face with the channels of the first and second devices maked with photoresist, pyrolytically depositing a further 5000 Š of silica, etching to expose all the channels, forming gate oxide thereon, implanting phosphorus ions with the channels of the first and third devices masked, annealing, and providing aluminium source, drain and gate electrodes by conventional processing.
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