BARC1 tested in this experiment is also an acrylate polymer. Figure 2 shows the etch rate of BARC1 and its etch selectivity to the resist. The etch rate of BARC1 in Figure 2a followed the same trend as the resist did because they are same type of polymer. The more O2 in the etch recipe, the faster the etch rate. The selectivity of BARC1 to the resist in Figure 2b is not very high; in this case, the highest selectivity is only 1.15.