Excimer laser induced chlorine etching of Si patterns for microelectronics

The laser-induced etching process of Si(100) and Si(111) surfaces in static chlorine atmosphere (10−6–10 mbar) has been investigated using an excimer laser at 248 nm varying the energy fluence Φ from 0.1 to 1 J/cm2. According to energy fluence the etching behaviour can be divided into three regions: At Φ > 0.65 J/cm2 the etch rate increases linearly with Cl2 pressure and saturates at about 0.55 Å/pulse. For 0.4–0.65 J/cm2 the etching process is only detectable at chlorine pressures above 0.1 mbar with an etch rate R ∼ p2(Cl2). Below 0.4 J/cm2 etching only occurs for chlorine pressures above 10 mbar. The etching mechanism in all regions can be described by laser-induced thermal desorption of chlorinated species. Based on our investigation of surface morphology and process induced defects, the parameters laser fluence and Cl2 pressure can be optimised for an application in microelectronics technology.