US 9,541,521 B1Granted

Enhanced sensitivity ion sensing devices

AssigneeNXP USA, Inc.

InventorsMd M. Hoque, Weize Chen, Patrice M. Parris

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Abstract

A mechanism is provided for enhancing the sensitivity of an ion-sensitive semiconductor device by creating a second gate coupled to a sense plate that can improve the amount of charge brought to the ion-sensitive semiconductor device conductivity modulated region (e.g., a channel region of an ISFET). This is accomplished by utilizing a buried dielectric layer associated with the ion-sensitive semiconductor device conductivity modulated region as the second gate dielectric. The buried dielectric layer is coupled to the sense plate using an isolated well region as a conductor that is coupled to metal layers extending to the sense plate. Some embodiments further use the buried dielectric layer as the sole gate dielectric for the semiconductor device, thereby allowing the traditional gate dielectric region to be coupled to a protection diode. This protection diode then protects the gate dielectric from plasma induced damage and electrostatic discharge.

Claims20

Dependent claims

An ion sensitive semiconductor device comprising:

a substrate comprising a surface;
a semiconductor device layer, formed within the surface of the substrate, and comprising a conductivity modulated region, a first doped region disposed laterally adjacent to the conductivity modulated region, and a second doped region disposed laterally adjacent to the conductivity modulated region;
a gate stack formed on the surface of the substrate and over a first surface of the conductivity modulated region;
a buried dielectric layer formed within the substrate and adjacent to a second surface of the conductivity modulated region, wherein the second surface is opposite to the first surface;
a conductive well region formed within the substrate beneath and adjacent to the buried dielectric layer, wherein the conductive well region is electrically isolated from the remainder of the substrate;
multiple conductive structures overlying the surface of the substrate, wherein the multiple conductive structures comprise
a first conductor formed in first metal layer electrically coupled to the conductive well region by a first conductive via, and
an ion-sensitive sense plate structure electrically coupled to the first conductor and configured to sense a concentration of a target ion or molecule in a fluid adjacent to a portion of the ion-sensitive sense plate structure.

5 more elements

A method of forming an ion sensitive semiconductor device structure, the method comprising:

forming a first well region of a first conductivity type in a substrate of a second conductivity type;
forming a second well region of a second conductivity type within the first well region;
forming a buried dielectric layer within the second well region;
forming a semiconductor device layer within the substrate, wherein
the semiconductor device layer comprises a conductivity modulated region, a first doped region disposed laterally adjacent to the conductivity modulated region, and a second doped region disposed laterally adjacent to the conductivity modulated region,
the semiconductor device layer is disposed above each of the first well region, the second well region, and the buried dielectric layer, and
the conductivity modulated region is disposed above and adjacent to the buried dielectric layer;
electrically isolating the second doped region from the remainder of the semiconductor device layer by forming a second trench extending from the surface of the semiconductor device layer to a depth within the second well region, but not extending to the first well region;
and
electrically coupling the second doped region to an ion-sensitive sense plate structure that is configured to sense a concentration of a target ion or molecule in a fluid adjacent to a portion of the ion-sensitive sense plate structure.

7 more elements

Dependencies are inferred from the claim text.