The effect of He plasma treatment on properties of organosilicate glass low-k films

The effect of low-pressure He plasma on properties of nanoporous organosilicate glasses low-k films with 24% and 33% open porosity is studied. The influence of ions, VUV radiation, and metastable atoms are extracted separately using a special experimental system designed for this purpose. The low-k films treated in He plasma were exposed to O or H atoms in the downstream of high-pressure O-2 or H-2 rf discharge. The changes in chemical composition and structure occurring in low-k films were measured before and after all treatments. The loss probabilities of oxygen and hydrogen atoms on the low-k film surface were measured for both treated and pristine films. It is shown that the film pretreatment in He plasma leads to the noticeable densification of the top surface layer up to complete sealing all the films studied. The sealing layer prevents O atoms from deep penetration to the film bulk and carbon extraction. The sealing mechanism related to the joint impact of low-energy ions and VUV photons with metastable atoms in He plasma is discussed in detail. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3549733]