The effect of fluorocarbon polymer buildup on oxide etching was investigated by monitoring the reactor chamber under an 0,/Ar plasma. Its effect on contact etching was also investigated by employing a CF4/CHF,/Ar plasma. It was determined that the 0,/Ar plasma was very useful for confirming polymer buildup on the inner chamber surface. This is because of an increased oxide etch rate by fluorine radicals, formed by the dissociation of the fluorocarbon polymer.Meanwhile, contact etching in a CF4/CHF,/Ar plasma with a high CHF4/CF4 ratio caused a reduction in etch rate near the edge of the wafer (in some cases even an etch stop), a considerable loss of critical dimension, and higher etch selectivity to polysilicon. These various etch behaviors are attributed to the polymer buildup on the inner surface of the chamber.CF4/O, plasma after the contact etching. On the other hand, the resist etch rate in the chamber was a little lower than that in the TLR chamber, seemingly due to the role of carbon as a scavenger of oxygen radicals in the fluorocarbon polymer. This implies that the oxygen selectivity to the resist can be increased greatly by the polymer buildup.An investigation of the effects of process parameters on the oxide etch rate in the 0,/Ar plasma confirmed that the increased oxide etch rate in the oxide chamber was primarily due to the polymer buildup. Figure 2 shows a significant increase in the etch rate with the RF power in the oxide chamber and its relatively low value of 2 nm/mm in the TLR chamber. When changing the gas mixture from 20 sccm 0, and 5 sccm Ar to 25 sccm Ar, the etch rate in the oxide chamber decreased from 72 to 10 nm/mm. This means that adding oxygen is effective for removing the polymer built on the inner chamber surface. This also sug-