Non-volatile memory cell having Si rich silicon nitride charge trapping layer
First Claim
1. A charge storage means for a memory cell comprising a layer of silicon-rich silicon nitride having an index of refraction between approximately 2.10 and 2.35, and a thickness of less than 90 nm, so that said layer of silicon-rich silicon nitride provides appreciable charge storage enhancement, without providing appreciable charge conductance enhancement, as compared to stoichimetric silicon nitride.
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Abstract
A non-volatile storage cell comprising a field effect transistor having source, gate, and drain electrodes. The gate electrode includes a gate stack having a dielectric layer, a charge storage structure comprising a layer of silicon-rich silicon nitride having sufficient excess silicon to provide appreciable charge storage enhancement, without providing appreciable charge conductance enhancement, as compared to stoichiometric silicon nitride, and a charge injection means. A control electrode is disposed on the gate stack for effecting charge transfer to and from the silicon-rich silicon nitride layer through the charge injection means. An array of these cells is formed by disposing the FETs within independently biased substrate portions. Thus the cells can be overwritten without an intervening erasure cycle.
466 Citations
24 Claims
- 1. A charge storage means for a memory cell comprising a layer of silicon-rich silicon nitride having an index of refraction between approximately 2.10 and 2.35, and a thickness of less than 90 nm, so that said layer of silicon-rich silicon nitride provides appreciable charge storage enhancement, without providing appreciable charge conductance enhancement, as compared to stoichimetric silicon nitride.
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3. An memory cell comprising a field effect transistor having source, gate, and drain electrodes, said gate electrode including a gate stack comprising:
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a dielectric structure deposited on the substrate between said source and drain electrodes; a first layer of silicon-rich silicon nitride disposed on said dielectric structure, said first layer of silicon-rich silicon nitride having an index of refraction of less than 2.35; a barrier structure disposed on said first layer of silicon-rich silicon nitride; a second layer of silicon-rich silicon nitride disposed on said barrier structure, said second layer of silicon-rich silicon nitride having an index of refraction of at least 2.35; and a control electrode disposed on said second silicon-rich silicon nitride layer. - View Dependent Claims (4, 5, 6)
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7. A memory cell formed on a semiconductor substrate, comprising:
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a gate stack, comprising a first dielectric structure formed on a first portion of the substrate, a first silicon-rich silicon nitride layer having an index of refraction of less than 2.35 disposed on said first dielectric structure, said first silicon-rich silicon nitride layer having sufficient excess silicon to provide appreciable charge storage enhancement, without providing appreciable charge conductance enhancement, as compared to stoichiometric silicon nitride, a second dielectric structure disposed on said first silicon-rich silicon nitride layer, a second layer of silicon-rich silicon nitride disposed on said second dielectric structure, said second silicon-rich silicon nitride layer having an index of refraction of at least 2.35, said second silicon-rich silicon nitride layer having sufficient excess silicon to provide appreciable charge injection enhancement as compared to stoichiometric silicon nitride; a control electrode disposed on said second layer of silicon-rich silicon nitride; first and second diffusion regions formed in portions of said substrate abutting said first portion of the substrate; first means for biasing said first diffusion region; and second means independent of said first means for biasing said second diffusion region. - View Dependent Claims (8, 9, 10, 11)
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12. An array of memory cells formed on a semiconductor substrate, comprising:
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isolation means formed in the substrate for defining discrete portions of the substrate that are isolated from remaining portions of the substrate; a plurality of cells being formed in each of said isolated discrete portions of the substrate, each of said cells comprising an FET having source and drain diffusions formed in the substrate and a gate electrode formed on a portion of the substrate between said source and drain diffusions, said gate electrode comprising a dielectric structure formed on the substrate, a first layer of silicon-rich silicon nitride having an index of refraction between approximately 2.10 and 2.30, said first layer of silicon-rich silicon nitride having sufficient excess silicon to provide appreciable charge storage enhancement, without providing appreciable charge conductance enhancement, as compared to stoichiometric silicon nitride, a barrier structure, and a control electrode; first means for biasing said source diffusions; second means for biasing said drain diffusions; and third means for biasing each of said isolated discrete portions of said substrate separately from others of said isolated discrete portions of said substrate. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification