The effect of dicarboxylic acid stabilizers on tungsten chemical mechanical planarization process

The effects of dicarboxylic acids (oxalic acid, malonic acid and succinic acid) on the H 2 O 2 stability during tungsten (W) chemical mechanical planarization (CMP) process were studied for the first time. The dicarboxylic acids can coordinate with Fe 3+ in the slurry and impact the reaction process by blocking the interaction between H 2 O 2 molecule and Fe 3+ , decreasing the Fe-complex redox potential and promoting the reduction of Fe 3+ to Fe 2+ . Among the three dicarboxylic acids, oxalic acid shows the superior coordination ability with Fe 3+ , resulting in a significant improvement of H 2 O 2 stability in the slurry. Appropriate amount of oxalic acid can improve the wafer surface quality (Ra=1.435 nm) while keeping the high material removal rate (MRR = 917 Å/min) at the same time. An increasing amount of dicarboxylic acids can result in a high degree of coordination between Fe 3+ and dicarboxylic acid in the slurry. The results also indicate that the main reaction path from Fe 3+ to Fe 2+ in this system is the reaction between Fe 3+ and H 2 O 2 . Meanwhile, the MRR keeps almost unchanged after one-week storage with the 2:1 mol ratio of oxalic acid to Fe 3+ .