Parametric study of InP backside processing using high density plasma etching

In this paper, the characterization of InP via hole etching under various electron cyclotron resonance (ECR) conditions at room temperature was carried out. A mixture of Cl₂/Ar plasma was used in the experiments. Etches were characterized in terms of the etch rate and via profile. The etch rates of InP were found to be able to greatly enhance by increasing Cl₂ percentage in the Cl₂ /Ar mixture, RF power or microwave power, but decreased by increasing process pressure. A 100 μm deep tapered profile has been achieved using a ~4 μm/min process without intentionally heating up the electrode. The gradient of the via was about 77° and is suitable for the via hole fabrication for monolithic microwave integrated circuits (MMIC) applications. To the best of our knowledge, this is the highest etch rate ever reported in InP substrate for via hole applications