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. Year 2000, 2001, 2002, 2004, Lithography Requirements similar to 175 nm, similar to 150 nm, similar to 130 nm, similar to 110 nm CD Tolerance 17.5 nm, 15 nm, 13 nm, 11 nm Gauge Control 1.8 nm, 1.5 nm, 1.3 nm, 1.1 nm Table 1. Lithographic Road Map(1) The standard in-line critical dimension measurement tool is the top-down scanning electron microscope (SEM). An emerging 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).