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Hybrid doping prototype for photodetectors

29/07/2015

By Optitec

Plasma immersion and laser annealing to improve photodetector performance and sensitivity

The project seeks to create a second-generation hybrid (plasma immersion/laser annealing) doping prototype. It will be used to create and optimise new generations of active (UV, visible and infrared) and passive (photovoltaic) photodetectors with greater versatility in choice of dopants and improved control of junction characteristics thanks to an in-situ transient reflectivity characterisation system. This cluster-type device is not designed to be used in final production, but nonetheless represents an essential step in transferring its technologies to industrial applications.

A project aiming to deal with the problems inherent in implanting dopants and their activation for sensors with increasingly small pixels and junctions hard to control when implanting dopants.

Plasma immersion enables low-energy implantation with major versatility in choice of dopants, as well as satisfactory implants on 3D and textured surfaces.

Laser treatment creates activation annealing with a low “thermal budget”, so enabling obtainment of junctions sensitive enough for photodetection (as thermal diffusion can be restricted to a few nanometres, or annealing of components on a plastic substrate, or annealing on the rear face without raising front-face temperature). Of particular interest to the astronomy and space sectors, which require detectors with high UV sensitivity.

Implantation of dopants by plasma immersion followed by excimer laser annealing currently represents a highly promising combination for creation of increasingly high-performance photodetectors. The first-generation hybrid doping prototype developed at IBS in collaboration with LP3 has enabled creation of ultrathin junctions (<30 nm, abrupt profile of 2.5 nm/dec and a per-square resistance lower than 500 Ω/sq) on 8-inch wafers at a rate of over 1 wafer/minute), along with a preliminary study on UV photodetectors that has aroused the interest of several of the field’s leading industrial concerns.

The project is being carried out at the CNRS, Laboratory LP3 UMR7341 at Aix Marseille University by Thierry Sarnet – sarnet@free.fr – CNRS Researcher; LP3 laboratory website: www.lp3.univ-mrs.fr