Three-dimensional vertical NOR Flash Thin-Film Transistor Strings
First Claim
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1. A memory structure, comprising:
- a semiconductor substrate having a substantially planar surface and including circuitry formed therein for memory circuit operation;
a plurality of active columns of semiconducting material formed above the semiconductor substrate, each active column extending along a first direction orthogonal to the planar surface of semiconductor substrate and including a first heavily doped region, a second heavily doped region, and one or more lightly doped regions each adjacent both the first and second heavily doped regions, wherein the active columns are arranged in a two-dimensional array having rows of active columns extending along a second direction and rows of active columns extending along a third direction, the second direction and the third direction each being parallel to the planar surface of the semiconductor substrate;
charge-trapping material provided over one or more surfaces of each active columns; and
a plurality of word line conductors that are electrically isolated from each other provided between the active columns in a plurality of stacks, each stack extending lengthwise along the third direction, wherein the active columns, the charge-trapping material and the word line conductors together form a plurality of variable-threshold thin-film transistors, each variable-threshold thin-film transistor comprising an associated one of the word line conductors, a portion of the lightly doped region of an active column, the charge-trapping material between the portion of the lightly doped region and the word line conductor, and the first and second heavily doped regions;
first and second pluralities of interconnection conductors running lengthwise along the second direction above and beneath the active columns, respectively, wherein (i) the first heavily doped region forms a local bit line and serves as a first drain or source terminal of the variable-threshold thin-film transistor, the local bit line being selectably connected to an associated one of the second plurality of interconnection conductors, (ii) the associated word line conductor serves as a gate terminal to provide a control voltage to the variable-threshold thin-film transistor; and
(iii) the second heavily doped region forms a local source line and serves as a second drain or source terminal of the variable-threshold thin-film transistor, the local source line being connected to an associated one of the first plurality of interconnection conductors.
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Abstract
A memory structure, includes active columns of polysilicon formed above a semiconductor substrate, each active column includes one or more vertical NOR strings, with each NOR string having thin-film storage transistors sharing a local source line and a local bit line, the local bit line is connected by one segment of a segmented global bit line to a sense amplifier provided in the semiconductor substrate.
57 Citations
33 Claims
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1. A memory structure, comprising:
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a semiconductor substrate having a substantially planar surface and including circuitry formed therein for memory circuit operation; a plurality of active columns of semiconducting material formed above the semiconductor substrate, each active column extending along a first direction orthogonal to the planar surface of semiconductor substrate and including a first heavily doped region, a second heavily doped region, and one or more lightly doped regions each adjacent both the first and second heavily doped regions, wherein the active columns are arranged in a two-dimensional array having rows of active columns extending along a second direction and rows of active columns extending along a third direction, the second direction and the third direction each being parallel to the planar surface of the semiconductor substrate; charge-trapping material provided over one or more surfaces of each active columns; and a plurality of word line conductors that are electrically isolated from each other provided between the active columns in a plurality of stacks, each stack extending lengthwise along the third direction, wherein the active columns, the charge-trapping material and the word line conductors together form a plurality of variable-threshold thin-film transistors, each variable-threshold thin-film transistor comprising an associated one of the word line conductors, a portion of the lightly doped region of an active column, the charge-trapping material between the portion of the lightly doped region and the word line conductor, and the first and second heavily doped regions; first and second pluralities of interconnection conductors running lengthwise along the second direction above and beneath the active columns, respectively, wherein (i) the first heavily doped region forms a local bit line and serves as a first drain or source terminal of the variable-threshold thin-film transistor, the local bit line being selectably connected to an associated one of the second plurality of interconnection conductors, (ii) the associated word line conductor serves as a gate terminal to provide a control voltage to the variable-threshold thin-film transistor; and
(iii) the second heavily doped region forms a local source line and serves as a second drain or source terminal of the variable-threshold thin-film transistor, the local source line being connected to an associated one of the first plurality of interconnection conductors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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Specification