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An attenuated phase shift mask (PSM) (half-tone PSM) is an effective and common technique for resolution enhancement and for forming specific patterns. When an ArF-attenuated PSM with hole- or space-type patterns is used under a KrF light source scanner, the original hole or space patterns are changed to island or bar patterns. In other words, reverse patterns are obtained from the original patterns. This phenomenon is explained by the transmittance change in the attenuated PSM due to the change in the light source. The wavelength of the original light source is extended when the light source is changed, and consequently, the dark field transmittance of this attenuated PSM becomes greater than the original transmittance. Thus, the final pattern becomes the inverse of the original pattern.

We have investigated the characteristics of Ar/O"2 plasmas in terms of the photoresist (PR) and low-k material etching using a ferrite-core inductively coupled plasma (ICP) etcher. We found that the O"2/(O"2+Ar) gas flow ratio significantly affected the PR etching rate and the PR to low-k material etch selectivity. Fourier transform infrared spectroscopy (FTIR) and HF dipping test indicated that the etching damage to the low-k material decreased with decreasing O"2/(O"2+Ar) gas flow ratio.

We have investigated the characteristics of etching processes involved in the fabrication of the stack-type DRAM capacitor. The 4000-A high Ru electrode and the SiO2 hard mask with a critical dimension of 0.15 kHz were employed. The Ru etch rate and the Ru to SiO2 mask etch selectivity increased by increasing pressure, total gas flow rate, and by addition of C12 gas. We have removed the SiO2 mask residues using Ar/CHF3 plasmas, revealing that high RF power helps to remove the residue efficiently.

We have developed a concave-type Pt electrode capacitor to overcome the limitations of the conventional stack-type capacitor in a small critical dimension pattern. We deposited a Pt layer on the concave-type structure made by the patterning of SiO2 and subsequently separated the adjacent nodes by the etch-back process with a photoresist as a protecting layer. We summarize the issues regarding patterning in the reactive ion etching system for fabrication of a concave-type capacitor.

We have studied the characteristics of Ru etching using O2/Cl2 plasmas in an inductively coupled plasma (ICP) etcher. The changes of Ru etch rates and Ru electrode etching slopes by varying Cl2/(O2 + Cl2) gas flow ratio, total flow rate, source power, bias power, and pressure were investigated. A high Ru etch rate of > 1400 A/min with a high etching slope of > 85° was demonstrated using 0.15 µm critical dimension (CD) patterned wafers. The mechanism of high-rate Ru etching is studied.

We have developed a high temperature Pt etching by using a titanium (Ti) mask layer in oxygen (O2)-containing plasma. The high temperature Pt etching technique has been employed to fabricate a stacked capacitor with a critical dimension (CD) of 0.15 µm. Due to reactive ion etching (RIE) lag, the Pt etch rate decreased drastically below the CD of 0.20 µm and, thus, the storage node electrode with the CD of 0.15 µm could not be fabricated. Accordingly, we have proposed novel techniques to surmount the above difficulties.