Method and apparatus for use in improving linearity of MOSFETs using an accumulated charge sink
First Claim
1. An accumulated charge control (ACC) NMOSFET (ACC NMOSFET), adapted to process RF signals, and adapted to control nonlinear response of RF signals processed by the ACC NMOSFET, comprising:
- a) an NMOSFET having a floating body, a gate, a source, a drain and a gate oxide layer between the gate and the body, wherein the NMOSFET is selectively biased to operate in an accumulated charge regime, and wherein, but for an accumulated charge control structure, accumulated charge accumulates within the body in a region proximate to the gate oxide when the NMOSFET is biased to operate in the accumulated charge regime; and
b) the accumulated charge control structure comprising an accumulated charge sink (ACS) coupled to the body of the NMOSFET, wherein when the NMOSFET is operated in the accumulated charge regime, an ACS bias voltage (VACS) is applied to the ACS to remove or otherwise control the accumulated charge;
wherein the VACS is sufficiently negative with respect to ground, the source, and the drain to cause removal of or otherwise control the accumulated charge.
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Abstract
A method and apparatus for use in improving the linearity characteristics of MOSFET devices using an accumulated charge sink (ACS) are disclosed. The method and apparatus are adapted to remove, reduce, or otherwise control accumulated charge in SOI MOSFETs, thereby yielding improvements in FET performance characteristics. In one exemplary embodiment, a circuit having at least one SOI MOSFET is configured to operate in an accumulated charge regime. An accumulated charge sink, operatively coupled to the body of the SOI MOSFET, eliminates, removes or otherwise controls accumulated charge when the FET is operated in the accumulated charge regime, thereby reducing the nonlinearity of the parasitic off-state source-to-drain capacitance of the SOI MOSFET. In RF switch circuits implemented with the improved SOI MOSFET devices, harmonic and intermodulation distortion is reduced by removing or otherwise controlling the accumulated charge when the SOI MOSFET operates in an accumulated charge regime.
426 Citations
51 Claims
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1. An accumulated charge control (ACC) NMOSFET (ACC NMOSFET), adapted to process RF signals, and adapted to control nonlinear response of RF signals processed by the ACC NMOSFET, comprising:
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a) an NMOSFET having a floating body, a gate, a source, a drain and a gate oxide layer between the gate and the body, wherein the NMOSFET is selectively biased to operate in an accumulated charge regime, and wherein, but for an accumulated charge control structure, accumulated charge accumulates within the body in a region proximate to the gate oxide when the NMOSFET is biased to operate in the accumulated charge regime; and b) the accumulated charge control structure comprising an accumulated charge sink (ACS) coupled to the body of the NMOSFET, wherein when the NMOSFET is operated in the accumulated charge regime, an ACS bias voltage (VACS) is applied to the ACS to remove or otherwise control the accumulated charge; wherein the VACS is sufficiently negative with respect to ground, the source, and the drain to cause removal of or otherwise control the accumulated charge. - 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, 49, 50)
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26. An accumulated charge control NMOSFET (ACC NMOSFET) adapted to switch RF signals and further adapted to control nonlinear response of RF signals switched by the ACC NMOSFET, comprising:
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a) an NMOSFET including a floating body, a gate, a drain, a source, and a gate oxide layer between the gate and the body, wherein the NMOSFET has a threshold voltage (Vth); and b) an accumulated charge sink (ACS) electrically coupled to the body of the NMOSFET, wherein the NMOSFET operates in an accumulated charge regime when the NMOSFET is biased by means of a gate control voltage (Vg) to operate in an off-state (non-conducting state), and wherein, but for the ACS, charge accumulates within the body in a region proximate the gate oxide, and wherein the NMOSFET has no source-to-drain DC voltage applied thereto; and
wherein an ACS bias voltage (VACS) is applied to the ACS and thereby substantially prevents accumulated charge from accumulating in the body, and wherein VACS is sufficiently negative with respect to ground, the source, the drain, and Vth to substantially prevent accumulated charge from accumulating in the body; andc) a silicon-on-insulator substrate having at least a silicon layer and an insulating layer; wherein the NMOSFET and ACS are fabricated in the silicon layer to form the ACC NMOSFET and wherein the NMOSFET body is situated between the source, the drain, the gate oxide, and the insulating layer, wherein the source and drain of the MOSFET extend through an entire thickness of the silicon layer and further down to the insulating layer. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48)
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51. An accumulated charge control (ACC) NMOSFET (ACC NMOSFET), adapted to process RF signals and to control nonlinear response of RF signals processed by the ACC NMOSFET, comprising:
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a) an NMOSFET having a floating body, a gate, a source, a drain and a gate oxide layer between the gate and the body; b) an accumulated charge sink (ACS) coupled to the body of the NMOSFET; wherein the NMOSFET is selectively biased to operate in an accumulated charge regime, and when so biased; (1) but for the ACS, accumulated charge accumulates within the body in a region proximate to the gate oxide; and (2) an ACS bias voltage (VACS) is applied to the ACS to remove or otherwise control the accumulated charge, wherein the VACS is sufficiently negative with respect to ground, the source, and the drain to cause removal of or otherwise control the accumulated charge; and c) a silicon-on-insulator substrate having at least a silicon layer and an insulating layer;
wherein the source and drain of the NMOSFET extend through an entire thickness of the silicon layer and further down to the insulating layer.
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Specification