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The Challenges of 300 mm CMP Brian Stephenson, Ebara Technologies Inc.
The transition from 200 mm to 300 mm presents many challenges for semiconductor manufacturers throughout the entire processing flow. From raw silicon to packaging operations, processes and processing equipment must meet the strictest speci fications at ever increasing chip complexity and shrinking design rules. Throw in rapid moves to advanced technologies such as low- dielectric and copper metallization converging at the same time, and the 300 mm transition is even more challenging.
Past transitions from 125 mm to 150 mm, and 150 mm to 200 mm, were considered to be incremental changes, the transition from 150 mm to 200 mm being the most significant as far as equipment goes. For most of these transitions, the industry was not near the processing limits for the linewidths being transitioned. Only recently has IC manufacturing began to push the limits of optical lithography as gate lengths are rapidly dropping below the 0.18 µm level, to 0.13 µm and now sub-0.1 µm levels. Also, front-end and back-end processes and materials have been, up to now, virtually unchanged or experienced relatively slow migration into advancing technologies as the industry transitioned to larger wafer sizes. With the advent of 300 mm, this past model does not appear to be holding any longer. The manufacturers taking the risk now to introduce 300 mm lines are not simply putting in proven, stable technology to ramp up a fab. There appears to be a push to put in the most advanced processes (low-κ, copper, sub-0.13 µm linewidths) at the initial stages to allow faster return on investment: faster chips with higher ASP, and smaller chips on twice the silicon real estate. However, if device and line yields are poor, this strategy is all for naught. Therefore, chipmakers are putting large 16
Spring 2001
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pressures on the capital equipment makers to produce equipment with unprecedented levels of integration, process flexibility, automation, and reliability. So, with all of these advanced technologies converging at the 300 mm node, where does that leave CMP? Is it drastically different than the 200 mm processes your familiar with? Well, as it turns out, not really. 300 mm CMP—Is it ready?
The short answer is “yes” with regards to process capabilities. The major CMP players in the market today have demonstrated capability at 300 mm across the board from STI to copper polishing. Companies such as Ebara even have second-generation equipment out in the field being started up in pilot and production lines around the world. So from the process standpoint, there doesn’t appear to be any major hurdles in the transition. However, increasingly tight specifications on uniformity and planarization efficiency will drive further design improvements in 300 mm tools moving forward. This reality, plus a host of new requirements for 300 mm manufacturing equipment, provides the greatest challenges to CMP. Transitioning CMP—The challenges
CMP is already a major process module for most 200 mm manufacturers, with advanced logic manufacturers utilizing CMP for 12 to 15 layers (see Figure 1). For 200 mm, the bulk of CMP is utilized for three process steps: shallow trench isolation, intermetal dielectric