Measurement of the 1/f noise of lateral actuated MEMS with sidewall piezoresistors

Abstract

Measurement of the 1/f noise of MEMS devices with sidewall embedded piezoresistors, prototyped for the current study, are described in the present paper. A modified sample conditioning and pre-amplification setup was employed and the complete arrangement was kept at 30°C. The 1/f and the 1/Δf noise signals are fully correlated as the underlying mechanism is the same for both phenomena. The bias voltage of each resistor ranges from zero to V pp and the device currents contain 1/f noise due to the DC bias in conjunction with conductivity fluctuations. Accordingly, the AC bias results in 1/Δf noise centred about the frequency of the sinusoidal. The spectrally resolved analysis of the 1/f and downconverted 1/Δf noise signals was then established with two instances of a digital lock-in amplifier capable of mHz operation. As both lock-in amplifiers have been locked to a common reference signal, the spectral analyser keeps any correlation between the two channels. Measurements of the current noise were done over the frequency range 0.0625 Hz to 2.048 kHz and measurement resolution of about 10 -18 V 2 /Hz is determined by the selected correlator averaging period in conjunction with the total noise of the instrumentation channels. For a direct comparison with metal-film resistor technology, sidewall piezoresistors have been replaced by 1 kΩ metal-film resistors for dedicated measurements. The crossover of the 1/f noise of a full bridge of piezoresistors and their thermal noise will appear below 10 Hz for a bias voltage smaller than 1V. This is, to our best knowledge, among the best 1/f noise performances for piezoresistors.