While developing the etch process for PMMA:HSQ bilayer, we decided to use those samples to also characterize the etch rate of SiO2 and HSQ. This experiment is designed to confirm the etch rate of SiO2 that was developed earlier and learn how the ICP power affects etch rate.
Characterize the etch rate of SiO2 and HSQ for an oxide etch process. Determine how ICP power influences etch rate of SiO2.
The experiment is described below:
|ICP Power||[W]||200 to 1500|
Figure 1 is a graph of the etch rates for SiO2 and HSQ at various ICP power. After realizing that the etch rates for both SiO2 and HSQ is the same at an ICP power of 200 W, we decided to run the experiment again to confirm our results. From the second set, we confirmed that the data results at an ICP power of 200 watts is repeatable and therefore real. It will be interesting to perform another experiment in the future to determine what the etch rates at ICP power between 0 and 350 watts.
Figure 1: The etch rate increases monotonically with ICP power and the two sets of measurements are in agreement.
Figure 2 is a graph of the etch selectivity of SiO2 and HSQ. At 350W and above the selectivity of SiO2 to HSQ is approximately 0.6 to 1. An anomaly occurs at an ICP power of 200 W, where the selectivity is almost 1 to 1.
Figure 2: The etch selectivity of SiO2 and HSQ is approximately 0.6 for all ICP power values except 200 W.
Figure 3 is a graph of the DC bias that is observed at each etch process. Normally, the DC bias is deliberately decreased to increase selectivity. In this case, we have the highest selectivity at the highest DC bias. What is going on?
Figure 3: The etch rate increases monotonically with ICP power and the two sets of measurements are in agreement.