Effects of HgCdTe on the Optical Emission of Inductively Coupled Plasmas

Inductively coupled plasmas (ICP) are the high-density plasmas of choice for processing HgCdTe and related compounds. Real-time examination of the ICP plasmas used to process HgCdTe would be desirable. In this preliminary study, the feasibility of using optical emission spectroscopy (OES) of ICP plasma used for processing HgCdTe has been examined. We have examined the utility of OES as a real-time diagnostic tool for HgCdTe device fabrication. In this preliminary study it has been found that mercury and cadmium can be detected but are dependent on several factors: sample area, material composition, etch rate, sample temperature, photoresist area, and plasma power. Furthermore, we found strong correlation between the amount of hydrogen detected by OES for samples with photoresist versus samples without photoresist while processing with hydrogen-based plasma. Hydrogen emission intensity decreased dramatically in samples with photoresist, contrary to the theory that photoresist adds hydrogen to the plasma effluent. It appears that hydrogen complexes with photoresist, reducing the global amount of hydrogen during the process. Furthermore, this phenomena may help to explain macroloading issues whereby additional photoresist area slowed HgCdTe, CdTe, and photoresist etch rates.