Alternative NH4F/HCl solution for ultraclean Si(001) surface

Ultraclean silicon surface after wet cleaning is extremely crucial in critical steps such as pregate clean in the next generation of electronic devices. Metallic contamination has an adverse effect on device characteristics and must be controlled as low as possible, typically less than 10(10) atoms/cm(2) A new solution was developed for wet chemical cleaning of silicon, which was investigated by using scanning tunneling microscope, inductively coupled plasma mass spectrometer and total reflection x-ray fluorescence spectrometry. It was found that NH4F with HCl diluted with deionized water resulted in the least surface roughness (0.16+/-0.02 nm) on silicon and metallic impurities adhered to the silicon surface compared to diluted HF. With the new solution, Cu impurity, the major metallic contamination, was suppressed to less than 2x10(9) atoms/cm(2). Other metallic impurities such as Ca, Fe, Zn, and Ti on the silicon surface were at level of 10(10) atoms/cm(2), which were lower than that treated by diluted HF. The results suggest that the complex reactions between chloride and metal ions result in less metal deposition on silicon surfaces. (C) 2000 American Vacuum Society. [S0734-2101(00)02905-5].