Method of making floating-gate memory-cell array with digital logic transistors
First Claim
1. A nonvolatile, floating-gate memory with logic transistors, comprising:
- a semiconductor body having doping of a first conductivity-type;
at least first and second opposite-conductivity-type diffusion regions having a first depth in said semiconductor body, said opposite-conductivity-type diffusion regions having doping primarily of a second conductivity-type opposite said first conductivity-type;
at least first and second same-conductivity-type diffusion regions having a second depth in said semiconductor body, said first and second same-conductivity-type diffusion regions having doping primarily of said first conductivity-type, said first same-conductivity-type diffusion region encased by said first opposite conductivity-type diffusion region, said second same-conductivity-type diffusion region separated on said substrate from said first and second opposite-conductivity-type diffusion regions; and
at least one floating-gate memory cell in said first same-conductivity-type diffusion region, at least one high-voltage logic transistor in said second opposite-conductivity-type region, and at least one low-voltage logic transistor in said second same-conductivity-type region.
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Abstract
A nonvolatile memory array is encased in a P-well, and the P-well encased in a deep N-well, the two wells separating the memory array from the integrated circuit substrate and from the other circuitry of the integrated circuit. At the same time the deep N-well is formed for the nonvolatile memory array, deep N-wells are formed for the high-voltage P-channel transistors of the logic circuitry. At the same time the P-well is formed for the nonvolatile memory array, P-wells are formed for the low-voltage N-channel transistors. The memory array contains nonvolatile cells of the type used in ultra-violet erasable EPROMs. During erasure, the isolated-well formation allows the source, the drain and the channel of selected cells to be driven to a positive voltage. The isolated well is also driven to a positive voltage equal to, or slightly greater than, the positive voltage applied to the source and drain, thus eliminating the field-plate breakdown-voltage problem.
56 Citations
10 Claims
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1. A nonvolatile, floating-gate memory with logic transistors, comprising:
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a semiconductor body having doping of a first conductivity-type; at least first and second opposite-conductivity-type diffusion regions having a first depth in said semiconductor body, said opposite-conductivity-type diffusion regions having doping primarily of a second conductivity-type opposite said first conductivity-type; at least first and second same-conductivity-type diffusion regions having a second depth in said semiconductor body, said first and second same-conductivity-type diffusion regions having doping primarily of said first conductivity-type, said first same-conductivity-type diffusion region encased by said first opposite conductivity-type diffusion region, said second same-conductivity-type diffusion region separated on said substrate from said first and second opposite-conductivity-type diffusion regions; and at least one floating-gate memory cell in said first same-conductivity-type diffusion region, at least one high-voltage logic transistor in said second opposite-conductivity-type region, and at least one low-voltage logic transistor in said second same-conductivity-type region. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification