Drake Miller

Characterization of single electron effects in nanoscale MOSFETs

The future of mixed-signal, memory, and microprocessor technologies are dependent on ever increasing analog and digital integration and higher cell densities. However, device variability creates challenges at each new technology node which decreases yield, performance, and noise margins. At these device dimensions the low-frequency noise is dominated by the influence of one or more traps capturing and emitting charge in the oxide creating wide variations in noise from otherwise identical devices. Existing processes of record have been extended well beyond the ranges previously deemed feasible or reliable and single electron events and random telegraph noise signals become important.

Subthreshold Leakage Due to 1/F Noise and Rts(Random Telegraph Signals)

An analysis of subthreshold leakage predicts a Gaussian or Normal distribution on large devices but a distorted distribution is possible on small devices. 1/f noise due to RTS signals on large well behaved devices will have a Gaussian distribution and cause a Gaussian current distribution under normal and subthreshold operating conditions. Localized channels or percolation channels can cause a distortion of this distribution and large subthreshold leakage current pulses which are most obvious in small devices.

Low Capacitance Electrical Probe for Nanoscale Devices and Circuits

An electrical probe is constructed of a small capacitor in contact with the circuit node under test so as not to load this circuit node and cause distortion of the input signal. The small capacitor is then placed in series with the small input resistance of a terminated coaxial signal line. The voltage signal at the output of the coaxial line will be approxi- mately the product of the small capacitance, the resistance of the coaxial line and the derivative with respect to time of the input signal. Tungsten probe tips can be sharpened to 100nm or less, enabling measurements of nanoscale devices.

Ultra low capacitance high frequency IC probe

The high speed low capacitance probe presented here is a flexible / tailorable tool for internal node testing on Radio Frequency Integrated Circuits (RFIC). The probe utilizes the mutual capacitive coupling between two wires. In this case, a tungsten whisker and the inner conductor of a coaxial cable forms a capacitor, enabling extremely low probing (loading) capacitance. The mutual capacitance which can be modeled to the first order as a lumped element capacitor provides differentiating action. Viewing the derivative of the output signal, rise time and can be observed directly. Through the use of probe calibration and Fourier transforms the probed signal can be re-created. Probe calibration develops a transfer function enabling re-creation of time domain signals.

1/f Noise and RTS(Random Telegraph Signal) Errors in Sense Amplifiers

The modeling of noise in the frequency domain gives the mean square noise current of a transistor as a function of frequency. RTS in nanoscale devices is easiest modeled as an instantaneous fluctuation in threshold voltage due to the capture and emission of traps. The capture and emission of a single electron at an interface or oxide trap in a nanoscale NMOS transistor is equivalent to a discrete change in threshold voltage. There is a small-finite probability of a large threshold voltage change due the collective capture or emission of multiple active traps. Even in wide devices this noise can contribute a mismatch in sense amplifiers in CMOS integrated circuits which can lead to errors.