Chloropentafluoroethane plasma chemistry and its effects on the etch rates of silicon germanium and silicon dioxide

Shannon Chen, Purdue University

Abstract

This work applied surface response methodology (RSM) and phenomenological surface methodology (PSM) to identify the unknown C2ClF5 plasma etch chemistry of SiO2 (RSM only) and Si1−xGe x (0.01 ≤ x ≤ 0.22) (RSM and PSM) in a nanometer scale. For the RSM, C2ClF5 flow rate, radiofrequency (rf) power input, and reactor camber pressure were used to construct the three facto' Box-Behnken second-order response surface. For the PSM, particle mass and energy balances, along with the Langmuir-Hinshelwood bimolecular Cl and Cl+ kinetics were used to model the etch rates (ER) of Si1−xGe x (0.01 ≤ x ≤ 0.22). The experiments were performed in a Semi-Group 1000TP parallel plate reactor that was operated at 13.56 MHz. The plasma flow was tested at 12–31.2 sccm. The rf power was set at 40–120 W. Lastly the chamber pressure was arranged at 50–110 mtorr. The Si 1−xGex layer, with a thickness of 75–105 nm, was grown on top of a (100) Si n-type substrate by a low-pressure chemical vapor deposition (LPCVD) method. Our experimental results showed that an anisotropic Si0.99Ge0.01SiO2 etch ratio, ranged 2–16, followed an Arrhenius contour curve. From the RSM analyses, three significant reactions, including a first order [Cl] chemical etch, a zero order ion-enhanced etch, and a second order Cl–Cl homogeneous recombination reaction (Cl loss on the electrode), were observed to control the etch rates. From the PSM analyses, the etching responses followed a second order Cl and Cl + Langmuir-Hinshelwood mechanism. Overall, for the very first time, the C2ClF5 plasma etching chemistry was identified and showed a very close agreement with the experimental etching observations.

Degree

Ph.D.

Advisors

Takoudis, Purdue University.

Subject Area

Chemical engineering|Electrical engineering

COinS