Improvement of high temperature water rinsing and drying for HF-last wafer cleaning

The reactions on HF cleaned (100)Si surfaces in high temperature water solutions are investigated by multiple internal reflection, Fourier transform infrared spectroscopy, atomic force microscopy, contact angle, and light scattering measurements. The hot water immersion causes a fast reoxidation, while a prolonged boiling water treatment results in an oxide-free Si surface. It is found that the continuous H2O gas bubbling can effectively drive the dissolved oxygen out of the boiling water. Comparing with the room temperature water rinsing, the boiling water treatment enhances the anisotropic etching on the HF cleaned bare silicon surface; and thus increases the microroughness on the Si(100) surface. The increased OH- concentration in boiling water is found to be the main cause of the surface etching. So, the etching reaction can be effectively suppressed by adding HCl to control the OH- concentration.