Numerical analysis and experimental research on the removal of CuO particles from monocrystalline silicon surfaces by picosecond laser

Abstract

CuO particles on the surface of silicon wafers can seriously affect integrated circuits performance and service life. This paper carries out numerical calculations and experimental research on the removal of CuO particles from silicon substrates surfaces by picosecond laser. A thermal-stress coupled finite element model is established to simulate the changes in the temperature of silicon substrates and the thermal stress of CuO particles with laser action time and energy density, to predict the cleaning threshold of the particles and the damage threshold of the silicon substrates. The results show that the cleaning threshold for CuO particles with a particle size of 10 μm is 0.029 J/cm2 and the damage threshold for the silicon substrate is 0.512 J/cm2. As the laser energy density increases, the CuO particles removal rate on the silicon surface increases first and then decreases, and the silicon substrate roughness decreases first and then increases. When the laser energy density is 0.429J/cm2, the CuO particle removal rate reaches 93.42 %, the wafer surface is undamaged, and the roughness is as low as 1.33 nm. The ratio of Cu and Si elements on the cleaned silicon substrate surface is close to that on the silicon substrate surface before the sample was made.