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在阻挡层的化学机械平坦化(CMP)过程中,Cu与阻挡层去除速率的一致性是保证平坦化的关键问题之一。低k介质材料的引入要求阻挡层在低压力下用弱碱性抛光液进行CMP,这给抛光液对不同材料的选择性提出了新的挑战。研究了低压2 psi,(1 psi=6.89 kPa)CMP条件下,磷酸和酒石酸作为阻挡层抛光液pH调节剂对Cu和Ta的络合作用。实验结果表明,酒石酸对Cu和Ta有一定的络合作用,能够提高它们的去除速率;磷酸能提高Ta的去除速率,而对Cu的去除有抑制作用。最终在加入磷酸浓度为2×10-2mol/L,酒石酸浓度为1×10-2mol/L,H2O2体积分数为0.3%,pH=8.5时,Cu/Ta/SiO2介质的去除速率选择比达到了1∶1∶1,去除速率约为58 nm/min;同时,磷酸和酒石酸的加入能够有效改善Cu的表面状态。
The consistency of Cu with the barrier removal rate during chemical mechanical planarization (CMP) of the barrier layer is one of the key issues in ensuring planarization. The introduction of low-k dielectric materials requires the barrier layer to be CMP-treated with a weakly basic polishing solution at low pressures, which presents new challenges to the selectivity of different materials by the polishing solution. The complexation of Cu and Ta with phosphoric acid and tartaric acid as the pH adjusting agent for the barrier layer polishing solution was studied under low pressure 2 MPa, (1 psi = 6.89 kPa) CMP conditions. The experimental results show that tartaric acid has a certain complexation effect on Cu and Ta, which can increase their removal rate. Phosphoric acid can improve the removal rate of Ta and inhibit the removal of Cu. In the end, the removal rate selectivity of Cu / Ta / SiO2 media reached about 2 × 10-2mol / L, the concentration of tartaric acid was 1 × 10-2mol / L, the volume fraction of H2O2 was 0.3%, pH = 8.5 1: 1: 1, the removal rate is about 58 nm / min; Meanwhile, the addition of phosphoric acid and tartaric acid can effectively improve the surface state of Cu.