Chemical mechanical polishing: future processes require CMP tool flexibility

Abstract

Development of Chemical Mechanical Polishing (CMP) tools and CMP processes are proceeding in parallel, but are not independent. Advanced processes require more flexibility and high throughput than available on present production CMP tools. This paper illustrates the development of a new CMP tool where both maximum flexibility and highest throughput are being designed in from the very beginning conceptual design. The tool includes capability to meet the predicted future need for copper/low-k dielectric CMP as one primary process model. This specification has led to a four-spindle, three-table tool with multi-step capability on each table. This flexibility allows (for example) for optimized copper CMP on table one, tantalum barrier CMP on table two, and a cleanup buff on table three before passing off to on-board metrology then to the post-CMP cleaner. Independent motions allow for high throughput even when the three process steps are of different time durations. The multitude of CMP processes development and chemistry requirements translate into complex control software and hardware solutions. The paper will describe how meeting these requirements for such flexibility and complexity add cost and delay the tool development process, but lead to a tool which is expected to better serve the microelectronics industry needs for CMP on larger wafer sizes (300 mm), smaller critical dimensions (less than 0.18 micron), and new materials (like Cu). The tool described to illustrate these principles is the Symphony-CMP by Strasbaugh.