Dummy-feature placement for chemical-mechanical polishing uniformity in a shallow-trench isolation process

• Published in: IEEE transactions on computer-aided design of integrated circuits and systems Vol. 21; no. 1; pp. 63 - 71
• Main Authors: Ruiqi Tian, Xiaoping Tang, Wong, M.D.F.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.01.2002; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Chemical processes; Chemical-mechanical polishing; Compressing; Density; Design engineering; Etching; Iterative methods; Manufacturing; Mathematical models; Placement; Process design; Production; Silicon; Strips; Surfaces; Topography; Variability; Very large scale integration
• ISSN: 0278-0070; 1937-4151
• DOI: 10.1109/43.974138

Manufacturability of a design that is processed with shallow-trench isolation (STI) depends on the uniformity of the chemical-mechanical polishing (CMP) step in STI. The CMP step in STI is a dual-material polish for which all previous studies on dummy-feature placement for single-material polish by Kahng et al. (1999), Tian et al. (2000), and Chen et al. (2000) are not applicable. Based on recent semiphysical models of polish-pad bending by Ouma et al (1998), local polish-pad compression by Grillaert (1999) and Smith (1999), and different polish rates for materials present in a dual-material polish by Grillaert (1999) and Tugbawa et al. (1999), this paper derives a time-dependent relation between post-CMP topography and layout pattern density for CMP in STI. Using the dependencies derived, the first formulation of dummy-feature placement for CMP in STI is given as a nonlinear-programming problem. An iterative approach is proposed to solve the dummy-feature placement problem. Computational experience on four layouts from Motorola is given.