AVS 60th International Symposium and Exhibition
    Plasma Science and Technology Monday Sessions
       Session PS-MoM

Paper PS-MoM6
Characterization of the Effects of Mildly Oxidizing Chemistries on Silicon Oxidation for Advanced Photoresist-Strip Applications

Monday, October 28, 2013, 10:00 am, Room 104 C

Session: Innovative Chemistries for Advanced Etch Processes
Presenter: B. Thedjoisworo, Lam Research
Authors: B. Thedjoisworo, Lam Research
B. Jacobs, Lam Research
I. Berry, Lam Research
D. Cheung, Lam Research
J. Park, Lam Research
Correspondent: Click to Email
For the advanced technology nodes, there is a need to strip photoresist quickly while meeting the stringent requirement of ultra-low oxidation and loss of the semiconductor substrate, silicon (Si). Two chemistries, NH3/O2 and H2/N2, have garnered attention for their ability to strip photoresist reasonably quickly while incurring low material loss. In this work, Si surfaces were exposed to either downstream NH3/O2 or H2/N2 plasmas, and the effects of these chemistries on Si oxidation were characterized and compared. For the NH3/O2 chemistry, Si oxidation was found to occur during the plasma-exposure step, while the extent of post-plasma oxidation was determined to be relatively minor. Accordingly, we evaluated the behaviors of Si oxidation as a function of plasma process parameters, and substrate temperature and NH3 concentration in the gas feed were determined to exert strong effects on Si oxidation. Specifically, oxidation decreases with increasing temperature and with increasing NH3 concentration. These process trends provide insight into the mechanism of the Si oxidation as well as to the nature of the radicals that induce the oxidation. Furthermore, the above finding demonstrated that Si oxidation can be controlled through judicious choice of the process parameters. When compared to the NH3/O2 (90% NH3) chemistry, the H2/N2 chemistry generally led to lower Si oxide growth. Although the H2/N2 chemistry gives rise to lower Si oxidation, the NH3/O2 could offer other advantages, such as higher ash rate and better photoresist-residue performance. Therefore, the desired trade-offs among ash rate, residue performance, and level of substrate oxidation will ultimately govern the choice between the two chemistries.