A functional CMOS compatible MEMS pyroelectric detector using 12%-doped scandium aluminum nitride

Abstract

In this paper, we fabricate and demonstrate a functional complementary metal-oxide-semiconductor (CMOS) compatible pyroelectric uncooled thermal detector using 12% doped Scandium Aluminum Nitride (ScAlN) as the sensing layer. The ScAlN pyroelectric material is deposited at a temperature of ∼200 °C over an 8-in. wafer area. This detector has shown, in general, improved performance compared to AlN, with specific detectivity as high as ∼ 6.08×107 cm Hz/W and noise equivalent power as low as ∼ 8.85×10−10 W/Hz. The results show the specific detectivity of ScAlN-based pyroelectric detectors in the range of 107 cm Hz/W, which is an improvement compared to AlN-based pyroelectric detectors which report specific detectivity typically in the range of 105–106 cm Hz/W. This promising result opens up the opportunities for a CMOS compatible, 8-in. wafer-level manufacturable lead-free pyroelectric detector toward low cost and high throughput, allowing microelectromechanical systems (MEMS) and CMOS integration for increased applications in CMOS–MEMS integrated devices utilizing pyroelectric detectors.

Miniaturized CO2 Gas Sensor Using 20% ScAlN-Based Pyroelectric Detector

“…The pyroelectric coefficient of 20% ScAlN pyroelectric detector with AOGs calculated ranges from ∼11.4 to ∼18.7 μC/m 2 K, higher than what was previously reported for the 12% ScAlN pyroelectric detector. 27,44 This is, in general, in line with the expectation that higher Sc doping concentration gives higher pyroelectric coefficient, since it has previously been demonstrated 43 that the higher Sc doping concentration resulted in an increase in the piezoelectric response of ScAlN. The pyroelectric coefficients of AlN and Sc-doped AlN films reported so far with different Sc doping concentrations compared with the pyroelectric coefficient of our current 20% ScAlN are shown in Table S1.…”

“…In this work, we are using >20% Sc-doped AlN compared to the previously reported 3 12% Sc-doped AlN pyroelectric material. Our previous work 27 has shown that the specific detectivity of the detector increases when doped with 12% Sc, and we anticipate a further increase in specific detectivity as the Sc doping increases. Meanwhile, Akiyama et al 43 was examining the piezoelectric response of ScAlN and noted an increase in the piezoelectric response as the Sc doping concentration increases up to 43% Sc concentration.…”

“…The pyroelectric coefficient obtained is higher than that of 12% ScAlN previously reported. 27 We also note that as the set background temperature increases, the output current measured from the pyroelectric detector shows an increasing trend. This eventually corresponds to an increase in the calculated pyroelectric coefficient when measured at higher background temperature, ranging from ∼11.4 to ∼18.7 μC/m 2 K. The CO 2 gas sensing response is measured for this miniature CO 2 gas sensor together with its larger version.…”

“…We further estimate the pyroelectric coefficient (ρ) of this 20% ScAlN with AOGs based on the following equation: 27 where i is the current measured, A is the sensing area of the 20% ScAlN pyroelectric detector stack with AOGs which is ∼0.29 mm 2 , d T is the temperature change, and d t is the rise time of the detector when encountering the temperature change. Five readings of current output were taken at each temperature variation of ∼24–26 °C to ∼84–86 °C.…”

Compensation of the Stress Gradient in Physical Vapor Deposited Al1−xScxN Films for Microelectromechanical Systems with Low Out-of-Plane Bending

“…Al 1−x Sc x N with high Sc alloying is a promising piezoelectric material for MEMS radio frequency (RF) filtering [ 3 ], energy harvesting [ 4 ], and sensing [ 23 , 24 ] devices because of its demonstrated high figure of merit [ 2 ] for each of these application areas. Piezoelectric RF bulk acoustic wave (BAW) resonator filters can often be implemented as anchored plates with extremely high out-of-plane bending stiffness.…”