Overcoming Etch Challenges on a 6″ Hg1−x Cd x Te MBE on Si Wafer

Abstract

The effect of increasing photoresist (PR) thickness on the inductively coupled plasma (ICP) dry etched characteristics of a 6″ (c.15 cm) molecular beam epitaxy Hg1−x Cd x Te/Si wafer is investigated. It is determined that the Hg1−x Cd x Te etch rate (ER) does not vary significantly with a change in the PR thickness. Also, the vertical ER of the PR is seen to be independent of the PR thickness, but the lateral ER is seen to reduce significantly with increased PR thickness. Indeed, very little reduction in the pixel mesa area post-dry etch is seen for the thicker PR. Consequently, the trench sidewall angle is also seen to vary as a function of the PR thickness. Since ICP is the more attractive choice for dry etching Hg1−x Cd x Te, this simple, cost-effective way to extend the capabilities of dry etching (larger mesa top area post-dry etch, ability to create tailor-made trench sidewall angles for optimal conformal passivation deposition, and potential for reduced dry etch damage) described here would allow for the fabrication of next generation infrared detectors with increased yield and reduced cost. Although similar results have been presented using the electron cyclotron resonance system to dry etch Hg1−x Cd x Te, to the best of our knowledge, this is the first time that such results have been presented using an ICP system.