Characterization of doping via laser chemical processing (LCP)

Laser Chemical Processing (LCP) is a laser-assisted technique that allows for various applications within solar cell fabrication. With appropriate chemicals as dopant media, the LCP process can be used for local doping of silicon wafers. With n-type LCP selective emitters efficiencies exceeding 20% have been achieved. However for further optimization and understanding of the process, a detailed characterization has to be performed. But appropriate methods for such a characterization are not available, yet. This paper presents a test structure that allows to measure the average sheet resistance of single LCP grooves and the specific contact resistance of contacts to LCP grooves. It is used here to study the impact of laser pulse energy on sheet and contact resistance. With phosphoric acid (85 wt%) as dopant a minimum sheet resistance of 13 ?/ and a minimum specific contact resistance of 2 x 10-5 ?cm² for evaporated contacts have been achieved in the low pulse energy range between 20 ?J and 30 ?J. The proposed test structure can be used for future characterization of the LCP process focusing on new doping chemicals and for studying the influence of other process parameters