Threshold voltage roll-off compensation using back-gated MOSFET devices for system high-performance and low standby power

Abstract

A method for compensating the threshold voltage roll-off using transistors containing back-gates or body nodes is provided. The method includes designing a semiconductor system or chip having a plurality of transistors with a channel length of Lnom. For the present invention, it is assumed that the channel length of these transistors at the completion of chip manufacturing is Lmax. This enables one to set the off-current to the maximum value of I-offmax which is done by setting the threshold voltage value to Vtmin. The Vtmin for these transistors is obtained during processing by using the proper implant dose. After manufacturing, the transistors are then tested to determine the off-current thereof. Some transistors within the system or chip will have an off-current value that meets a current specification. For those transistor devices, no further compensation is required. For other transistors within the system or chip, the off-current is not within the predetermined specification. For those transistors, threshold voltage roll-off has occurred since they are transistors that have a channel length that is less than nominal. For such short channel transistors, the threshold voltage is low, even lower than Vtmin, and the off-current is high, even higher than I-offmax. Compensation of the short channel transistors is achieved in the present invention by biasing the back-gate or body node to give increased threshold voltage about equal to Vtmin and hence an off-current that meets the predetermined specification, which is about equal to I-offmax.

Dependencies are inferred from the claim text.