Optimization Of Thin Metal Layer Etch Process For Hems/Sensor Application

In this work, CMOS thin barrier metal Ti\TiN was used as electrode layer to define the sensing material resistor for MEMs/Sensor application. APM (ammonia peroxide mixture) based wet etch process was introduced in electrode layer patterning process with no process loss of Si based sensing material. It was found sidewall recess problem at bottom Ti layer after electrode layer wet etch process due to faster horizontal wet etch rate of Ti than that of TiN. Optimized process scheme were introduced to solve this problem, including Ti layer thinning, surface nitridation of Ti layer and optimized TiN layer instead of Ti\TiN bilayer. After process evaluation, best option was selected with dimension of electrode layer sidewall recess less than 20nm after about 50% overetch time, which can greatly improve the CD (critical dimension) uniformity control of sensing resistor.