Memory device with improved charge storage barrier structure
First Claim
1. A memory device comprising a path for charge carriers, a node for storing charge to produce a field which alters the conductivity of the path, an electrode structure, and a tunnel barrier configuration through which charge carriers tunnel from the electrode structure to the node and vice versa in response to given voltages so as to become stored on and discharged from the node, the tunnel barrier configuration exhibiting an energy band profile that comprises a dimensionally relatively wide barrier component with a relatively low barrier height, and at least one dimensionally relatively narrow barrier component with a relatively high barrier height.
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Abstract
A memory device includes a memory node (1) to which charge is written through a tunnel barrier configuration (2) from a control electrode (9). The stored charge effects the conductivity of a source/drain path (4) and data is read by monitoring the conductivity of the path. The charge barrier configuration comprises a multiple tunnel barrier configuration, which may comprise alternating layers (16) of polysilicon of 3 nm thickness and layers (15) of Si3 N4 of 1 nm thickness, overlying polycrystalline layer of silicon (1) which forms the memory node. Alternative barrier configurations (2) are described, including a Schottky barrier configuration, and conductive nanometre scale conductive islands (30, 36, 44), which act as the memory node, distributed in an electrically insulating matrix.
249 Citations
63 Claims
- 1. A memory device comprising a path for charge carriers, a node for storing charge to produce a field which alters the conductivity of the path, an electrode structure, and a tunnel barrier configuration through which charge carriers tunnel from the electrode structure to the node and vice versa in response to given voltages so as to become stored on and discharged from the node, the tunnel barrier configuration exhibiting an energy band profile that comprises a dimensionally relatively wide barrier component with a relatively low barrier height, and at least one dimensionally relatively narrow barrier component with a relatively high barrier height.
- 44. A method of fabricating a memory device which includes a path for charge carriers, a node for storing charge that alters the conductivity of the path, an electrode structure and a tunnel barrier configuration through which charge carriers tunnel from the electrode structure to the node and vice versa in response to given voltages so as to become stored on and discharged from the node, the method including forming the tunnel barrier configuration such that it exhibits an energy band profile that comprises a dimensionally relatively wide barrier component with a relatively low barrier height, and at least one dimensionally relatively narrow barrier component with a relatively high barrier height.
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62. A memory device comprising a path for charge carriers, a node for storing charge to produce a field which alters the conductivity of the path, and a tunnel barrier configuration through which charge carriers tunnel in response to a given voltage so as to become stored on the node, the tunnel barrier configuration exhibiting an energy band profile that comprises a dimensionally relatively wide barrier component with a relatively low barrier height, and at least one dimensionally relatively narrow barrier height, wherein the charge storage nodes comprises a plurality of conductive islands distributed in the barrier configuration.
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63. A memory device comprising:
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a source-drain path for charge carriers, a node for storing charge to produce a field which alters the conductivity of the source-drain path, an electrode structure overlying the node, and a tunnel barrier configuration between the node and the electrode structure through which charge carriers tunnel between the electrode structure and the node in response to given voltages so as to become stored on and discharged from the node, the tunnel barrier configuration comprising a layer of relatively conductive polysilicon material, a first layer of relatively non-conductive silicon nitride between the polysilicon layer and the node, and a second layer of relatively non-conductive silicon nitride between the polysilicon layer and the electrode structure, the tunnel barrier configuration exhibiting an energy band profile that comprises a dimensionally relatively wide barrier component with a relatively low barrier height, and at least one dimensionally relatively narrow barrier component with a relatively high barrier height.
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Specification