SiO2 Etching Employing Inductively Coupled Plasma with Hot Inner Wall

The selective etching of SiO2 on Si employing C4F8/H2 inductively coupled plasma (ICP) was studied based on measurements of radical and ion densities, flow rate and wall temperature. Since polymer films were not deposited when the reacter wall was heated to temperatures above 200° C, CF1 radical density at 200° C was one order higher than that at the wall temperature of 30° C. Thus both Si and SiO2 etch rates decreased rapidly with increasing H2 concentration in C4F8, and Si etching stopped at 15% H2. The etch stop was attributed to insufficient removal of polymer with a reduced amount of ions and was suppressed considerably by increasing the RF power to generate a large amount of ions. The use of poly-Si masks reduced the microloading effect in comparison to resist masks and a contact hole feature with 0.2 µ m size and aspect ratio of 6 was successfully obtained.