Enhancement of metal coil quality on selective p-silicon based planar electromagnetic coil by thermal annealing process

In this paper we report an optimization of metal quality of planar MEMS electromagnetic coil through thermal annealing process. The study aims to see the effects of annealing process on the quality of metal layer deposited on localized p-type silicon regions. Two annealing process parameters namely isothermal (annealing under time variations in constant temperature) and isochronal (annealing under temperature variations at constant time) were performed on metal contact on highly doped Si substrate and characterized using transfer length method method by measuring the specific contact resistance ρ _C of the metal traces. The measurement results showed that the annealing process have significant influence on physical and electrical characteristics of the metal layer. Analysis showed that the quality of metal layer was significantly improved through the annealing process after treatment at temperature variations between 425–550 °C. An optimum annealing at 525 °C for 15 min was observed and the contact resistance can be reduced significantly up to 400 %. The results also showed that the surface roughness improves while metal contact resistance decreases 40 times when the metal is annealed for more than 10 min. The planar coil structure was designed to reduce the device density of a compact magnetic micro-sensor system.