Abstract
Characterization of broadband noise of MOSFETs from room temperature down to 120 K in fine temperature steps is presented. A MOSFET is mounted on a reusable printed circuit board vehicle with a built-in low-noise amplifier, and the vehicle is loaded into a cryogenic chamber. The vehicle allows noise measurement in the frequency range from 50 kHz to 100 MHz. At low frequencies, it enables extraction of activation energies associated with electron trapping sites. At high frequencies, as has been suggested by noise figure measurements, the white noise of MOSFETs is shown to be dominated by the shot noise, which has much weaker temperature dependence than the thermal noise. The shot noise will be a problematic noise source in broadband RF CMOS circuits operating at cryogenic temperatures.
Highlights
Low temperature environment enhances performance of CMOS devices through the improvement of the carrier mobility, subthreshold slope, Cu wire resistance, and thermal noise [1,2,3]
We developed a reusable printed circuit board (PCB) vehicle for cryogenic measurements, on which a device under test (DUT) is mounted
SD at V! > 0 V remains higher than the thermal noise S$%, clearly demonstrating that shot noise becomes predominant at low temperatures
Summary
Low temperature environment enhances performance of CMOS devices through the improvement of the carrier mobility, subthreshold slope, Cu wire resistance, and thermal noise [1,2,3]. A proof-of-concept noise probe for on-wafer broadband noise characterization was demonstrated at room temperature, achieving noise measurement from 100 kHz up to 800 MHz [26,27]. This approach “quietly” listens to noise from a DUT as does a conventional low-frequency noise measurement system, and does not require a hot noise source. Low-frequency noise from a very small MOSFET can reveal individual trapping/detrapping of a single electron to/from a trapping site Using this capability, low-frequency noise measurement is commonly employed to characterize the quality of gate dielectrics [30]. We will look at the temperature dependence of white noise, especially shot noise, and the suppression of the latter compared to its theoretical maximum value (full shot noise), through the use of the so-called Fano factor or the shot-noise suppression factor
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