# Contact-Area-Changeable CMP Conditioning for Enhancing Pad Lifetime
## 2 Experimental Set-Up
### CMP Experiment and Pad Profile Measurement  
In this study, CMP experiments with SiO\({}_{2}\)-deposited (1.5 \(\upmu\)m thick) Si wafers (200 mm in diameter) were conducted to verify the pad lifetime after pad conditioning. The pad lifetime was defined as the usage duration of the polishing pad until the groove of the polishing pad had worn out, or when an abrupt change in the MRR and WIWNU occurred.  
An R&D CMP machine (POLI-762, G&P Technology Inc., Busan, Korea) was used for the CMP experiments. A hard polyurethane pad (KONI pad from KPX Chemical, Seoul, Korea) and a silica slurry (TSO-12, Soulbrain Co., Ltd., Seongnam, Korea) were prepared. During CMP, the location of the wafer center was fixed at 230 mm from the center of the polishing pad. Hence, the wafer contacted the polishing pad from 150 to 350 mm in the radial direction from the center of the polishing pad. The wafer and retaining-ring pressures were 34.3 and 44.1 kPa, respectively. The rotational speeds of the polishing head and platen were 87 and 93 rpm, respectively. The CMP experimental conditions are listed in Table 4.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Condition** & **Value** \\ \hline Rotational speed of polishing head & 87 rpm \\ Rotational speed of platen & 93 rpm \\ Wafer pressure & 34.3 kPa \\ Retaining-ring pressure & 44.1 kPa \\ Slurry flow rate & 150 mL/min \\ Polishing time & 60 s \\ Polishing pad & KONI pad \\ Slurry & TSO-12 \\ Wafer & SiO\({}_{2}\) wafer (200 mm) \\ \hline \hline \end{tabular}
\end{table}
Table 4: CMP experimental conditions.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Conditioning Zone** & **1** & **2** & **3** & **4** & **5** \\ \hline Case I (reference) & Full contact & Full contact & Full contact & Full contact & Full contact \\ Case II & Full contact & Inner & Inner & Inner & Inner \\ Case III & Inner & Outer ring & Inner & Outer ring & Inner \\ Case IV & Outer ring & Inner & Outer ring & Inner & Outer ring \\ \hline \hline \end{tabular} Full contact: Inner conditioner + outer ring-type conditioner.  
\end{table}
Table 3: Conditioning cases considered in this study.  
The thickness of the SiO\({}_{2}\) film was measured using a reflectometer (ST5030-SL, K-Mac, Daejeon, Korea, Measurement range: 10 nm\(\sim\)35 \(\upmu\)m). The MRRs of the SiO\({}_{2}\) films were measured at 39 points in the radial direction of the wafers. The edge exclusion in the measurement of the MRR was 7 mm.  
After pad conditioning, the pad profile was measured using a pad measurement system (PMS, G&P Technology, Busan, Korea, Resolution: 0.1 \(\upmu\)m, Repeatability <2% (1\(\sigma\))) (Figure 5). The PMS uses an active displacement sensor and transports the sensor using a linear motion guide and servo motor. To measure the deviation in the thickness of the polishing pad, the PMS measured the profile of the platen first and used it as a reference. The pad profile was measured from the center to the edge of the polishing pad, and the signal (thickness of pad) from the sensor was transmitted to the computer with information regarding the radial position of the pad. The pad cut rate distribution was obtained from the pad thickness profiles before and after conditioning.  
Figure 6 shows the procedure of the experiment. First, the polishing pad was attached to the platen and the initial pad profile was measured with the pad measurement system. The first conditioning was performed for 1 h, and the first CMP experiment using SiO\({}_{2}\) wafer was conducted after conditioning. After the first CMP, CMP experiments were performed after 1, 2, or 3 h of conditioning. The experiment was conducted for up to 20 h of cumulative conditioning time, but the experiment was stopped when the wafer was broken due to excessive pad wear.