Effect of fabrication temperature on the manufacturability of lateral ZnO nanowire array UV sensor

Abstract

Fabrication temperature is an important factor affecting the manufacturability of electronic devices, especially for the bottom-up self-assembled nano-device. In this study, we used a lateral-bridged zinc oxide (ZnO) nanowire array UV sensor as a model to investigate the influence of temperature on device performance over the entire manufacturing process, from sensor fabrication to packaging. We found that annealing of the SiO₂ substrate would make ZnO seed layer on top of it more compact and uniform, and hence improve the lateral orientation and uniformity of ZnO nanowires grown from the seed layer. With the annealed substrate, the light-to-dark current ratio increased by two orders of magnitude. On the contrary, annealing the ZnO seed layer would deteriorate the light-to-dark current ratio of the sensor, because annealing caused most of the grains in the seed layer to become vertically aligned, which in turn affected the lateral growth of ZnO nanowire arrays. During the packaging process, the surface structure of ZnO nanowires would change if the chip welded at a temperature of 230°C for 2 min, resulting in a decrease of light-to-dark current ratio by three orders of magnitude.