Zhonghua Gu

Effects of mixed inhibitors in copper chemical mechanical polishing at a low down pressure

The individual and synergistic effects of benzotriazole and sodium dodecyl sulfonate on copper disc are investigated at a down pressure of 3.4 kpa. The corrosion rate is reduced by using benzotriazole, but the surface quality is poor owing to the slow formation rate of copper–benzotriazole protection film. For sodium dodecyl sulfonate, the corrosion rate is further reduced, but slight corrosions can be still observed due to the incomplete coverage of sodium dodecyl sulfonate molecules. The combination of sodium dodecyl sulfonate and benzotriazole leads to the maximum decrease of corrosion rate. Under the benzotriazole/sodium dodecyl sulfonate ratio of 1:3, the average roughness achieves as low as 1.025 nm owing to the soft and dense coverage of benzotriazole/sodium dodecyl sulfonate molecules. Besides, the trends of removal rate, roughness and friction coefficient are proved to be similar for copper discs and copper wafers in slurries with different inhibitors. Therefore, the results presented here are relevant for further developments in the area of low-pressure chemical mechanical planarization of copper lines overlying fragile low-k dielectrics in the new interconnect structures.

Effect of Modified Silica Abrasive Particles on Nanosized Particle Deposition in Final Polishing of Silicon Wafers

The silane coupling agent γ-aminopropyl triethoxysilane (APTS) and polyethylene oxide (PEO) are proposed to modify the SiO2 abrasive particles for final polishing of silicon wafers. The effects of the modified silica abrasive particles on nanosized particle deposition, roughness, and removal rate of the silicon wafer are explored in detail. PEO is proved to be a potential modifying agent for controlling deposition of large particles (∼410 nm diameter), leading to low roughness (Ra = 0.097 nm), and APTS is found to be effective in controlling deposition of both large and small particles (∼410 and ∼200 nm diameter, respectively), resulting in lower roughness (Ra = 0.054 nm).

Investigation on defect control for final chemical mechanical polishing of aluminum alloy

In acid final chemical mechanical polishing (CMP) of aluminum alloy, the addition of a small amount of nitric acid (HNO3) is proved to be the effective measure for reducing the orange peel defect due to the protective film produced by HNO3 on aluminum alloy; however, it makes point defects worse. The effect of hydrolyzed polymaleic anhydride (HPMA) on point defects is investigated. HPMA adsorbs on the surface of aluminum alloy first, and the composite film formed by both HPMA and HNO3 is proved to be efficient for controlling both the orange peel and point defects. When the aluminum alloy is polished by the acid original slurry with 0.7 wt% HNO3 and 0.1 wt% HPMA, the roughness of the aluminum alloy surface is low to 0.678 nm.