1 July 1994 Semiconductor process control
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Abstract
Control of critical dimensions, overlay, and defects are required for lithography processes to be effective. Each area of concern requires appropriate metrology methods for measuring critical parameters. For measuring linewidths, there are optical, electrical, and scanning electron methods. The optimum operating point for the process must be determined for dimensional control, and individual process parameters need to be controlled as well. Similarly for overlay and defects, appropriate metrology methods must be established. Lithography is a situation in which conventional statistical process control techniques cannot be applied naively, and suitable statistical methods must be used.

The photolithography process consists of transferring a pattern optically from a chrome on quartz reticle onto a partially processed wafer that has been coated with photoresist. The image is transferred onto an underlying blanket of material after developing the resist by some sort of chemical and/or thermal step (etch, sinter, implant, growth, dope, etc.). This is repeated about 15 to 20 times, with each step seeing different pattern transfer steps, using different equipment. These steps may distort the wafer and its patterns, causing differences between wafers and lots. Despite this variance, each new step must precisely align to the previous layers. To accomplish this, each step of the process and every piece of equipment must be characterized. In this paper, the primary parameters and data analysis techniques that are most commonly tracked and used by photolithography engineers are reviewed.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Lynda C. Hannemann-Mantalas, Harry J. Levinson, "Semiconductor process control", Proc. SPIE 10274, Handbook of Critical Dimension Metrology and Process Control: A Critical Review, 102740E (1 July 1994); doi: 10.1117/12.187456; https://doi.org/10.1117/12.187456
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