Low-k dielectric obtained by noble gas implantation in silicon oxide

Thermally-grown 220nm-thick silicon oxide layers were implanted at room temperature with 300keV Xe at doses ranging from 0.5 to 5×10 ¹⁶Xe/cm². As-implanted samples exhibit bubbles in silicon oxide for all doses. Annealing at T≥400°C results in the disappearance of bubbles from SiO₂ layer for the dose of 1×10 ¹⁶Xe/cm². But for the higher doses of 3.5 and 5×10¹⁶Xe/cm², the bubbles are very stable and remain in the sample even after very high thermal annealing. Capacitance measurements show a strong decrease in the dielectric constant k of the implanted SiO ₂ sample from 4 (reference sample) to 1.5.