The effect of conditioner aggressiveness is investigated in interlayer dielectric polishing on three types of pad. A method using confocal microscopy is used to analyze the effect of conditioner aggressiveness on pad–wafer contact. Results show that a more aggressive conditioner produces a higher interlayer dielectric polishing rate while at the same time a pad surface with fewer contacting summits and less contact area. It is found that the ratio of the contacting summit density to the contact area fraction is more important than either parameter measured separately since the ratio determines the mean real contact pressure. Modeling results based on contact area measurements agree well with experimental results. Moreover, it is found that a more aggressive disc also generates a thicker slurry film at the pad–wafer interface. This is in agreement with our general findings regarding pad asperity height distribution obtained using confocal microscopy.
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.Chemical mechanical planarization (CMP) has been widely used in the semiconductor industry to achieve local and global surface planarity through combined chemical and mechanical means. During polishing, as the pad directly contacts the wafer surface under an applied pressure to mechanically remove the chemically modified wafer surface layer, it has significant impacts on the material removal rate, planarization efficiency and defects. Recently, laser confocal microcopy has been used to measure pad surface contact area and topography to gain insight into the mechanical interaction between pad asperities and wafer surface. 1-4 For example, Sun et al. used laser confocal microscopy to measure pad-wafer contact area as well as pad surface topography and investigated the relation between contact area and contact summit density under different pressures. 3 While pad surface contact area and topography have been successfully characterized in the above studies, their impacts on the CMP process performance such as material removal rate have not been fully examined and understood. In this study, two different diamond discs were used to condition an IC1010 M-groove pad, on which 200-mm blanket copper wafers were polished. Pad surface contact area and topography were analyzed using laser confocal microscopy and scanning electron microscopy (SEM) to illustrate how the pad surface micro-texture affects copper removal rate, as well as the frictional force generated among pad asperities, slurry abrasives and wafer surface during polishing. ExperimentalIn this study, 200-mm blanket copper wafers were polished on a 20-in. IC1010 M-groove pad with Suba IV sub-pad using an Araca APD-500 polisher. The polisher was capable of measuring frictional force generated among pad asperities, slurry abrasives, and wafer surface in real-time during wafer polishing. Hitachi Chemical HS 2H635-12 slurry was used and the slurry flow rate was 150 ml/min. Two diamond disc conditioners, 3M A2810 disc and Mitsubishi Materials Corporation (MMC) 100-grit disc with triple ring dot (TRD) design as shown in Fig. 1, were used to condition the pad under the conditioning force of 26.7 N (6 lb) during wafer polishing. The conditioners rotated at 95 rpm and swept 10 times/min across the pad during pad conditioning. For each conditioner, eight new blanket monitor copper wafers were polished for 1 min at 10.3 KPa (1.5 psi) and 1....
Retaining rings made of poly͑phenylene sulfide͒ ͑PPS͒ and polyetheretherketone ͑PEEK͒ with two different slot designs were subjected to a 4 h wear test. During the chemical mechanical planarization ͑CMP͒ process, the PPS retaining ring induced a higher coefficient of friction ͑COF͒ by ϳ0.1 than the PEEK retaining rings. In addition, the PPS retaining ring exhibited a higher wear rate than the PEEK retaining rings by ϳ28%. Although the retaining ring slot design did not significantly affect the COF and wear rate, retaining rings with sharp slot edges resulted in higher pad surface abruptness.During chemical mechanical planarization ͑CMP͒ processes, retaining rings are used to secure wafers from slipping out of the wafer carrier head. For a typical polishing platform, such as Applied Materials Mirra and Reflexion polishers, the retaining ring is pressed against the pad surface at a pressure normally higher than the wafer polishing pressure. As a result, frictional force is generated among the retaining ring, slurry, and pad surface, leading to an increase in the pad temperature, which in turn impacts material removal rate and nonuniformity. In recent years, advanced engineering plastics have become materials of choice for constructing retaining rings because they can be easily modified to withstand various chemicals in CMP slurries while maintaining dimensional stability over a wide range of temperatures and pressures and extending the service life of retaining rings. Furthermore, compared with metal and ceramics, advanced engineering plastics can be formulated to have a very low level of ionic impurities and inorganic element contamination.There are several patents and publications associated with retaining rings and their applications. For example, Chen and Zuniga and Chen et al. showed new retaining ring slot designs in 2005. 1,2 Zuniga et al. invented a multilayer retaining ring and Wang and Zuniga improved the design afterward. 3,4 Chen et al. invented a specific retaining ring consisting of two different parts. 5 Hoffman compared the thermal, chemical, and mechanical properties of several commercially advanced machinable plastics. 6 In that study, the wear results were simulated without any experimental confirmation. Moussa and Quartapella and Gitis et al. performed wear tests on three materials commonly used for CMP retaining rings ͓poly͑phe-nylene sulfide͒ ͑PPS͒, polyetheretherketone ͑PEEK͒, and polycarbonate͔ and reported coefficient of friction ͑COF͒ and wear rates. 7,8 However, the wear tests were conducted using a small piece of substrate that was substantially different in size and design compared to the actual retaining rings used in the semiconductor industry.In this study, three retaining rings designed for 200 mm wafer polishing were subjected to a 4 h wear test. The retaining rings were made of two different materials ͑PPS and PEEK͒ with two different slot designs. Frictional force generated among the retaining ring, slurry, and pad surface was measured in real-time during the wear test. Pad surfa...
Diamond disk substrate wear and diamond microwear in the copper chemical mechanical planarization process were investigated in this study. Three types of disks (D1, D2, and D3) made by three different manufacturers were analyzed. For each type of disk, 24 h static etch tests were performed with Fujimi PL-7103 and Cabot Microelectronics Corporation iCue 600Y75 slurries at 25 and 50°C . Scanning electron microscopy (SEM) analysis showed that there was no appreciable microwear on the diamond after the static etch tests for all three types of disks. Disks D1 and D3 showed no appreciable corrosion on the diamond disk substrate for both slurries at both temperatures. In comparison, disk D2 showed apparent surface corrosion using the Fujimi PL-7103 slurry at 25 and 50°C and the Cabot Microelectronics Corporation iCue 600Y75 slurry at 50°C . Inductively coupled plasma-mass spectroscopy (ICPMS) analysis was performed before and after the static etch tests to investigate metal concentration increases in the slurry due to diamond disk substrate corrosion. The ICPMS analysis was consistent with the SEM images, showing a significant Ni concentration increase in the slurry for disk D2 with the Fujimi PL-7103 slurry at 25 and 50°C and the Cabot Microelectronics Corporation iCue 600Y75 slurry at 50°C . In addition to the above static etch tests, 24 h wear tests were performed on each type of diamond disks with Fujimi PL-7103 and Cabot Microelectronics Corporation iCue 600Y75 slurries at two different platen temperatures (25 and 50°C ). SEM analysis was performed on selected aggressive and inactive diamonds as well as on the surrounding disk substrate before and after the wear tests. SEM images showed that there was microwear on the cutting edges of the aggressive diamonds for disks D1 and D3 with both slurries at 25 and 50°C . For disk D2, there was microwear on the cutting edges of the aggressive diamond with the Fujimi PL-7103 slurry at 25°C and with the Cabot Microelectronics Corporation iCue 600Y75 slurry at 25 and 50°C , and the aggressive diamond broke off from the disk substrate with the Fujimi PL-7103 slurry at 50°C . The SEM images also showed that there was no microwear on the inactive diamond for all three types of disks with both slurries at 25 and 50°C , confirming that the inactive diamonds did not participate in regenerating pad asperities during conditioning. The pad thickness profile was measured after the wear tests, and the effect of platen temperature on pad wear rate was investigated.
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