Selectively doped electrostatic discharge layer for an integrated circuit sensor
First Claim
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1. A method for fabricating an electrostatic discharge protection circuit for an integrated sensor comprising:
- forming sensor circuitry that partially covers a substrate;
depositing an insulating layer over the substrate;
depositing a discharge layer over the insulating layer; and
doping portions of the discharge layer that are not over the sensor circuitry.
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Abstract
A structure and method for creating an integrated circuit passivation structure including, a circuit, a dielectric, and metal plates over which an insulating layer is disposed that electrically isolates the circuit, and a discharge layer that is deposited to form the passivation structure that protects the circuit from electrostatic discharges caused by, e.g., a finger, is disclosed. The discharge layer additionally contains dopants selectively deposited to increase electrostatic discharge carrying capacity while maintaining overall sensing resolution.
73 Citations
22 Claims
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1. A method for fabricating an electrostatic discharge protection circuit for an integrated sensor comprising:
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forming sensor circuitry that partially covers a substrate;
depositing an insulating layer over the substrate;
depositing a discharge layer over the insulating layer; and
doping portions of the discharge layer that are not over the sensor circuitry. - View Dependent Claims (2, 4, 5, 6, 7)
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3. The method of 1, further including coupling the doped portions of the discharge layer to a system ground.
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8. A method for fabricating an electrostatic discharge circuit for an integrated circuit, the method comprising:
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forming a plurality of sensor circuits in an array partially covering a substrate, the circuits mutually offset by intervening offset areas;
depositing a passivation structure over the circuits and intervening offset areas, the passivation structure including;
a dielectric insulation layer deposited adjacent to the circuits and intervening offset areas; and
a discharge layer separated from the circuits and offset areas by the dielectric insulation layer, a portion of the discharge layer over the intervening offset areas having a doping concentration that is high relative to a doping concentration of a portion of the discharge layer over the circuits. - View Dependent Claims (9, 10, 11, 12, 13, 14)
forming a ground pad on the substrate; and
electrically coupling the portion of the discharge layer having a relatively high doping concentration to the ground pad.
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10. The method according to claim 9, wherein the discharge layer comprises SiCx, wherein X determines hardness and conductivity parameters of the discharge layer.
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11. The method according to claim 10, further comprising depositing a mechanical protection layer over the insulation layer;
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wherein the discharge layer is deposited over the mechanical protection layer.
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12. The method according to claim 10, further comprising depositing a mechanical protection layer over the discharge layer.
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13. The method according to claim 10, wherein the discharge layer is deposited concurrently with a mechanical protection layer.
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14. The method according to claim 13, wherein deposition of the concurrently deposited discharge and mechanical protection layers comprises depositing silicon and carbon in a varying ratio to form the discharge and mechanical protection layers.
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15. A method for fabricating an electrostatic discharge circuit for a fingerprint sensor on an integrated circuit, the method comprising:
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forming a plurality of fingerprint sensor circuits on a substrate in an array sized to receive a fingerprint, the circuits separated by non-circuit areas intervening therebetween;
forming a plurality of ground pads on the substrate;
depositing a dielectric insulation layer over the circuits and non-circuit areas;
depositing a discharge layer over the dielectric insulation layer, selectively doping portions of the discharge layer over the non-circuit areas; and
electrically coupling the portions of the discharge layer over the non-circuit areas to the ground pads. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22)
doping portions of the discharge layer over the circuits and over the non-circuit areas; and
wherein selectively doping portions of the discharge layer over the non-circuit areas comprises doping the portions of the discharge layer over the non-circuit areas heavily than the portions over the circuits.
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19. The method according to claim 18, wherein selectively doping portions of the discharge layer over the non-circuit areas further comprises partially masking the portions of the discharge layer over the circuit areas.
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20. The method according to claim 19, further comprising depositing a mechanical protection layer over the discharge layer.
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21. The method according to claim 19, further comprising depositing a mechanical protection layer over the insulation layer and under discharge layer.
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22. The method according to claim 19, further comprising forming a mechanical protection layer in combination with the discharge layer, wherein a difference in stoichiometric ratios of silicon and carbon differentiates the mechanical protection and discharge layers.
Specification