Digital Etching Using KrF Excimer Laser: Approach to Atomic-Order-Controlled Etching by Photo Induced Reaction

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Abstract
Cl2-based digital etching of GaAs has been studied using a 248 nm KrF excimer laser, which allowed a self-limited etching reaction. A threshold fluence for etching of 13 mJ/cm2 was found, above which the etch rate abruptly increases and finally saturates at around 0.2 nm/cycle from 20 to 33 mJ/cm2. The self-limiting etching characteristics can be explained assuming the etching reaction to be limited by the amount of adsorbed Cl2. The etched depth is proportional to the number of digital etching cycles, and atomic-order-controlled etching is achieved.