DNA Microarray Based On Amorphous Silicon Ultraviolet Sensor

Thin film detectors and arrays are receiving growing attention in DNA recognition. Recently, authors have demonstrated a 'label-free' detection of DNA hybridization based on the absorption variation in the ultra-violet (UV) range using hydrogenated amorphous silicon (a-Si:H)/amorphous silicon carbide (a-SiC:H) UV sensor. To increase the throughtput of the biochemical analysis, in this work we present the design and fabrication of a 16x16 UV sensor array, deposited by Plasma Enhanced Chemical Vapor Deposition on a glass substrate. Each pixel is constituted by two back-to-back series connected coplanar n-i-p diodes. One n-i-p diode acts as UV sensor (with 1.4x1.8 mm2 area) and the other as switching diode (with 200x200 m2 area). The whole structure is the following: glass substrate/metal/n-type a-Si:H/intrinsic a-Si:H/p-type a-SiC:H/metal. The top electrode is a grid metal layer to allow transmission of the incident radiation into the active layer of the device. The array performances have been enhanced taking advantage of the optical and electrical properties of different thin film materials. The sensor UV sensitivity has been improved by a chromium silicide (CrSi) window layer formed, at room temperature, on top of the p-doped layer. In particular, the (CrSi) film enhances the surface conductivity reducing the effect of the self-forward bias, which occurs in the device due to the high resistivity of the p-doped layer.