Dry chlorinated oxide is a refinement of dry thermal oxidation in which a small, carefully controlled amount of a chlorine source is added to the oxygen ambient inside the furnace. The chlorine is incorporated near the silicon-to-oxide interface as the film grows, where it improves the electrical quality, cleanliness, and long-term reliability of the oxide. Rogue Valley Microdevices uses Trans-LC as the chlorine source for this process. The chlorine performs two related functions. It getters mobile ionic contamination, particularly sodium, that would otherwise drift through the oxide and shift device threshold voltages, and it traps heavy metals such as iron, chromium, and nickel before they can degrade the interface. The same chemistry continuously cleans the furnace tube by converting metallic residue into volatile chlorides that are carried away in the gas flow. Compared with standard dry oxidation, a chlorinated oxide provides: - Higher dielectric breakdown strength and lower leakage current - Lower fixed oxide charge and interface trap density - Reduced oxidation-induced stacking faults - Improved minority carrier lifetime - Effective gettering of mobile ions and heavy metal contamination - A slightly higher oxidation rate than chlorine-free dry oxidation Trans-LC is a liquid chlorine source based on trans-1,2-dichloroethylene (trans-DCE). It is metered into the furnace as a vapor carried in the oxygen flow during oxidation. Trans-LC replaced earlier chlorine sources such as TCA (1,1,1-trichloroethane) and TCE, which are restricted as ozone-depleting compounds under the Montreal Protocol, and it is preferred over corrosive anhydrous HCl gas. It carries a low toxicity hazard rating, is not regulated as an ozone-depleting chemical, and decomposes at a relatively low temperature, which gives consistent, repeatable results across the dry oxidation temperature range. Dry chlorinated oxide is selected wherever oxide integrity and device reliability are critical and mobile ion control matters most, including gate dielectrics, high-reliability MEMS, and sensor devices.
