We report on the capacitively coupled O2 plasma etching of PMMA and polycarbonate (PC) with a diffusion pump. Plasma process variables were process pressure and CCP power at 5 sccm O2 gas flow rate. Characterization was done in order to analyze etch rate, etch selectivity, surface roughness, and morphology using stylus surface profilometry and scanning electron microscopy. Self bias decreased with increase of process pressure in the range of 25~180 mTorr. We found an important result for optimum pressure for the highest etch rate of PMMA and PC, which was 60 mTorr. PMMA and PC had etch rates of 0.46 and 0.28 μm/min under pressure conditions, respectively. More specifically, etch rates of the materials increased when the pressure changed from 25 mTorr to 60 mTorr. However, they reduced when the pressure increased further after 60 mTorr. RMS roughnesses of the etched surfaces were in the range of 2.2~2.9 nm. Etch selectivity of PMMA to a photoresist was ~1.5:1 and that of PC was ~0.9:1. Etch rate constant was about 0.04 μm/minW and 0.02 μm/minW for PMMA and PC, respectively, with the CCP power change at 5 sccm O2 and 40 mTorr process pressure. PC had more erosion on the etched sidewall than PMMA did. The OES data showed that the intensity of the oxygen atomic peak (777.196 nm) proportionally increased with the CCP power.

This study investigates GaAs dry etching in capacitively coupled BCl3/N2 plasma at a low vacuum pressure (>100 mTorr). The applied etch process parameters were a RIE chuck power ranging from 100~200W on the electrodes and a N2 composition ranging from 0~100% in BCl3/N2 plasma mixtures. After the etch process, the etch rates, RMS roughness and etch selectivity of the GaAs over a photoresist was investigated. Surface profilometry and field emission-scanning electron microscopy were used to analyze the etch characteristics of the GaAs substrate. It was found that the highest etch rate of GaAs was 0.4μm/min at a 20 % N2 composition in BCl3/N2 (i.e., 16 sccm BCl3/4 sccm N2). It was also noted that the etch rate of GaAs was 0.22μm/min at 20 sccm BCl3 (100 % BCl3). Therefore, there was a clear catalytic effect of N2 during the BCl3/N2 plasma etching process. The RMS roughness of GaAs after etching was very low (~3nm) when the percentage of N2 was 20 %. However, the surface roughness became rougher with higher percentages of N2.

This study investigated dry etching of acrylic in capacitively coupled SF6, SF6/O2 and SF6/CH4 plasma under a low vacuum pressure. The process pressure was 100 mTorr and the total gas flow rate was fixed at 10 sccm. The process variables were the RIE chuck power and the plasma gas composition. The RIE chuck power varied in the range of 25~150 W. SF6/O2 plasma produced higher etch rates of acrylic than pure SF6 and O2 at a fixed total flow rate. 5 sccm SF6/5 sccm O2 provided 0.11μm/min and 1.16μm/min at 25W and 150W RIE of chuck power, respectively. The results were nearly 2.9 times higher compared to those at pure SF6 plasma etching. Additionally, mixed plasma of SF6/CH4 reduced the etch rate of acrylic. 5 sccm SF6/5 sccm CH4 plasma resulted in 0.02μm/min and 0.07μm/min at 25W and 150W RIE of chuck power. The etch selectivity of acrylic to photoresist was higher in SF6/O2 plasma than in pure SF6 or SF6/CH4 plasma. The maximum RMS roughness (7.6 nm) of an etched acrylic surface was found to be 50% O2 in SF6/O2 plasma. Besides the process regime, the RMS roughness of acrylic was approximately 3~4 nm at different percentages of O2 with a chuck power of 100W RIE in SF6/O2 plasma etching.

We investigated dry etching of acrylic (PMMA) in O2/N2 plasmas using a multi-layers electrode reactive ion etching (RIE) system. The multi-layers electrode RIE system had an electrode (or a chuck) consisted of 4 individual layers in a series. The diameter of the electrodes was 150 mm. The etch process parameters we studied were both applied RIE chuck power on the electrodes and % O2 composition in the N2/O2 plasma mixtures. In details, the RIE chuck power was changed from 75 to 200 W.% O2 in the plasmas was varied from 0 to 100% at the fixed total gas flow rates of 20 sccm. The etch results of acrylic in the multilayers electrode RIE system were characterized in terms of negatively induced dc bias on the electrode, etch rates and RMS surface roughness. Etch rate of acrylic was increased more than twice from about 0.2μm/min to over 0.4μm/min when RIE chuck power was changed from 75 to 200 W. 1 sigma uniformity of etch rate variation of acrylic on the 4 layers electrode was slightly increased from 2.3 to 3.2% when RIE chuck power was changed from 75 to 200 W at the fixed etch condition of 16 sccm O2/4 sccm N2 gas flow and 100 mTorr chamber pressure. Surface morphology was also investigated using both a surface profilometry and scanning electron microscopy (SEM). The RMS roughness of etched acrylic surface was strongly affected by % O2 composition in the O2/N2 plasmas. However, RIE chuck power changes hardly affected the roughness results in the range of 75-200 W. During etching experiment, Optical Emission Spectroscopy (OES) data was taken and we found both N2 peak (354.27 nm) and O2 peak (777.54 nm). The preliminarily overall results showed that the multi-layers electrode concept could be successfully utilized for high volume reactive ion etching of acrylic in the future.