MEMS applications of laser-induced ultra-shallow and ultraheavy boron-doping of silicon above the solid-solubility

Abstract

We investigate applications of laser-induced boron-doping of silicon as a new technology which offers number of unique and very promising applications to MEMS: (i) it is proven that doping levels up to 3.10/sup 21/ at/cm/sup 3/ can be produced, that is 10 times more than the maximum levels, which are usually limited by the solid solubility 3-6.10/sup 20/ at/cm/sup 3/) in conventional techniques; (ii) the measured doping profiles have also shown boxlike junctions with depths down to 20 nm; (iii) the high doping levels show high selectivity to TMAH and KOH etching solutions; (iv) the high doping levels also lead to very high mechanical tensile stress up to 3 GPa. Among the impact of these reported data on future MEMS developments, one can propose for instance to take advantage of the very high mechanical stress to manufacture high frequency resonators. Such resonators are expected to have high quality factors as well, due to the crystalline nature of silicon.