Correlation between film properties and anhydrous HF vapor etching behavior of silicon oxide deposited by CVD methods

The anhydrous HF vapor etching of sacrificial silicon dioxide films grown by plasma-enhanced and low-pressure chemical vapor deposition (PECVD and LPCVD) methods was studied. The film compositions and etch residue were analyzed as part of the study. The effects of the oxide deposition method, precursors, annealing and oxide composition on the etch rate are discussed. Annealing decreases the etch rate and removes water and other hydrogen-containing residue from the films. Films grown using a tetraethoxysilane (TEOS) precursor etch fast, unannealed films even 30 times faster than thermal oxide and they also contain more OH–species than films from SiH₄ precursors even after annealing. The etch rate of all CVD films is close to that of thermal oxide after annealing at 1000 °C, around 0.1 µm/min. Etch rate differences between CVD films are much larger than those observed during wet HF etching.