Xiaoyan Liao

Effect of Pad Surface Micro-Texture on Coefficient of Friction and Removal Rate during Copper CMP Process

In this study, 200-mm blanket copper wafers were polished on an IC1010 M-groove pad, which was conditioned by a 3M A2810 disc and Mitsubishi Materials Corporation (MMC) TRD disc. Pad surface contact area and topography were analyzed using laser confocal microscopy and scanning electron microscopy. The MMC TRD disc generated a lot of large near contact areas corresponding to fractured and collapsed pore walls. The fractured and collapsed pore walls partly covered the adjacent pores, making the pad surface more lubricated during wafer polishing and rendering significantly lower coefficient of friction and removal rate than the 3M A2810 disc.

Effect of Pad Surface Micro-Texture on Removal Rate during Interlayer Dielectric Chemical Mechanical Planarization Process

The effect of pad surface micro-texture on removal rate in interlayer dielectric chemical mechanical planarization was investigated. Blanket 200-mm oxide wafers were polished on a Dow® IC1000TM K-groove pad conditioned at two different conditioning forces. The coefficient of friction increased slightly (by 7%) while removal rate increased dramatically (by 65%) when conditioning force was increased from 26.7 to 44.5 N. Pad surface micro-texture analysis results showed that pad surface contact area decreased dramatically (by 71%) at the conditioning force of 44.5 N, leading to a sharp increase in the local contact pressure and resulting in a significantly higher removal rate.

Tribological, thermal, and kinetic attributes of 300 vs. 450 mm chemical mechanical planarization processes

An existing 300 mm CMP tool has been modified to polish 450 mm wafers in order to demonstrate experimentally whether any differences exist in the tribological and thermal characteristics of the two processes, and from that, to infer whether one can expect any removal rate differences between the two systems. Results suggest that, within the ranges of parameter investigated, the two systems behave similarly in terms of their coefficients of friction and lubrication regimes. Additionally, it is shown that the 450 mm process, once adjusted for its platen velocity, runs only slightly warmer (by 1 to 2°C) than its 300 mm counterpart. Experimental data, coupled with copper removal rate simulations show that the wafer surface reaction temperatures of the 450 mm adjusted process are higher (by 2 to 3°C) than the 300 mm process. Consequently, simulated copper removal rates for the 450 mm adjusted process are higher (by 8 to 31%) than those of the 300 mm process.

Effect of Pad Micro-Texture on Frictional Force, Removal Rate, and Wafer Topography during Copper CMP Process

In this study, the effect of pad micro-texture on frictional force, removal rate, and wafer topography during ILD/STI CMP processes was investigated. Blanket 200-mm TEOS wafers and SKW3-2 patterned STI wafers were polished on an Araca APD-500 polisher and frictional force was measured in real-time during polishing. Two diamond discs (3M A2810 diamond disc and Mitsubishi Materials Corporation (MMC) diamond disc with triple ring dot (TRD) design) were used to condition an IC1000 K-groove pad with Suba IV sub-pad during wafer polishing. For each diamond disc, two conditioning forces (6 and 10 lb) were used. Under each conditioning force, five blanket TEOS wafers and three SKW3-2 STI wafers were polished at 4 PSI and 1.2 m/s. Pad samples were taken after blanket TEOS wafer polishing, as well as after patterned STI wafer polishing. Pad contact area and surface topography were analyzed using laser confocal microscopy. Pad contact area, pad surface abruptness, and pad summit curvature were obtained. When the conditioning force increased from 6 to 10 lb, the COF and removal rate increased for both diamond discs while the pad contact area decreased from 0.053% to 0.036% and from 0.040% to 0.011% for the 3M A2810 disc and MMC TRD disc, respectively. The contact area during patterned wafer polishing was larger than that during blanket wafer polishing for both diamond discs at 6 and 10 lb conditioning forces. In addition, the pad surface was less abrupt and the mean summit curvature was smaller during patterned wafer polishing than that during blanket wafer polishing for both diamond discs at 6 and 10 lb conditioning forces. Dishing and erosion analyses were performed on 100-micron pitches on the wafer center with different pattern densities. The MMC TRD disc generated higher dishing and erosion than the 3M A2810 disc under both 6 and 10 lb conditioning forces. The mean summit curvature of the MMC TRD disc was larger than that of the 3M A2810 disc at both 6 and 10 lb conditioning forces during patterned wafer polishing, indicating sharper pad summits contributed to higher dishing and erosion for the MMC TRD disc.