In one aspect, the present invention is a sensor unit for sensing process parameters of a process to manufacture an integrated circuit using integrated circuit processing equipment. A dielectric capping layer having residual compressive stress is formed on the salicide layer by depositing a plurality of PECVD dielectric sublayers and plasma-treating each sublayer. The support members lie on a support surface in a spaced-apart arrangement, and the sheet rests on the support members substantially parallel to and offset vertically above the support surface and defines with the support surface a containment space for receiving fluid spilled on the upper surface of the sheet that flows through the fluid channels. The filter media may be replaced when the filter media becomes too dirty to effectively filter air. A large shift in the threshold voltage of the p-channel MOSFET results.