Effects of Film Stress on the Chemical Mechanical Polishing Process

Abstract

A theoretical model is constructed to simulate the pressure distribution arising from wafer curvature (film stress) during chemical mechanical polishing (CMP), based on theories of elastic contact stress. Results from oxide CMP experiments suggest that the wafer curvature results in a nonuniform polish rate distribution across the wafer, in agreement with the simulation based on the model. This stress-dependent polish nonuniformity is attributed to the nonuniform pressure distribution across the wafer, induced by the wafer radius of curvature (film stress). Also, it was found that the magnitude of oxide film stress itself has little effect on removal rate. Oxides with tensile stress tend to have a weakened bond structure and enhanced chemical reactivity, both of which result in slightly higher removal rates. The reverse is true for oxides with compressive stress. Deviations from the model prediction may result from the stress induced by slurry flow, local variations in wafer shape and form, and pad surface properties.

Mechanical effect of process condition and abrasive concentration on material removal rate profile in copper chemical mechanical planarization

“…In this experiment, pressure effects on material removal profile were considered. Tseng et al (1999) simulated the pressure distribution at the wafer level during CMP. Their results revealed that the pressures at the wafer edge are larger than those at the wafer center, and the pressure-high edge profile determines the MRR profile.…”

Influence of a Retaining Ring on Strain and Stress in the Chemical Mechanical Polishing Process

“…These values were incorporated into Eq. (8) to obtain the wafer's nonuniformity, R, which equals to 5.33. However, the simulated c and max from the CMP model with a retaining ring were 5 80 * 10 −2 MPa and 1 76 * 10 −1 MPa, respectively.…”

“…The profile of the stress distribution is similar to that in Wang et al [6], but the site of peak stress is somewhat different. Tseng et al [8] constructed a theoretical model based on Hertzian contact theory to simulate the pressure distribution along the pad/wafer interface arising from wafer curvature during the CMP process. They found that the film stress does not bring about a significant change in removal rate, but it induces a redistribution of pressure profile.…”

Modified nanoparticle oxides for final polishing of metals

“…Модель химико-механического полирования и концепция молекулярного воздействия абразивных частиц суспензии на поверхность полируемой поверхности с учетом окисляю-щей способности компонентов и образования тонких оксидных пленок рассмотрена в [17][18][19]. В связи с этим развивается теория молекулярно-атомного воздействия абразивного материала на полируемую поверхность [20,21].…”