Enhanced silicon oxidation by a hyperthermal beam obtained from laser evaporation of solid ozone

A new oxidation method for gate oxide applications using a collimated neutral hyperthermal ozone beam produced by pulsed laser evaporation of solidified ozone is demonstrated. This method enables ozone molecules, together with oxygen molecules and oxygen atoms, in an electronically excited state, O(¹D), with a translational energy of around 1 eV to be intermittently supplied to silicon just after each laser shot, so that the silicon dioxide (SiO₂) film thickness can be accurately controlled by the number of laser shots. The effect of ozone having this translational energy was clearly apparent from the temperature-independent initially high oxidation rate. which enabled the oxidation to be shorter and with a lower temperature process. Compared to oxidation by the conventional method using thermal ozone gas, higher efficiency was achieved in the sense that a thicker SiO₂ film could be obtained with a smaller number of ozone molecules as long as the oxidized area was localized. Further enhanced oxidation was enabled by using a hyperthermal beam rich in O(¹D) that had been obtained at a high laser fluence irradiation, demonstrating the high reactivity of O(¹D) compared to the ground-state oxygen atom, O(³P).