Gauge control for sub-170-nm DRAM product features

As modern circuit architecture features steadily decrease in size, more accurate tools are needed to meaningfully measure critical dimensions (CD). As a general rule, a metrology tool should be able to measure 1/10 of the product tolerance. As CD's continue to shrink, gauge control becomes more relevant. The trend is illustrated in Table 1. The standard in-line critical dimension measurement tool is the top-down scanning electron microscope (SEM). An emergine technology for high speed, high accuracy CD measurement is scatterometry. This paper will compare the two technologies for in-line CD measurement for three applications: A product etch step (assessing gauge capability as well as trending), a product resist step (trending), and lithographic cell monitors (trending).