Effects of Coating Thickness on Particle Adhesion in Microelectronics-Based Systems

Abstract

The effects of coating thickness on the adhesion between a particle and surface were investigated using a pre-manufactured silicon nitride AFM cantilever probe with radius of curvature ∼15 nm and a silicon substrate coated with ALD alumina films of 5.5, 11, 20.6, 27.8, 34.5, or 39.6 nm thickness. The adhesion was measured using contact mode atomic force microscopy. For small alumina thicknesses, the probe-substrate adhesion was relatively unaffected, while for large thicknesses, it was dominated by the alumina. Particle removal efficiency (PRE) experiments were performed on 300-mm silicon dioxide-on-silicon wafers coated with 5, 10, 15, or 20 nm of titanium nitride. Dry-deposited silica challenge particles with diameter distributions centered at 55 or 110 nm were used. Wafers were cleaned using a commercially available argon/nitrogen cryogenic aerosol process. Silica PRE transitioned smoothly as nitride film thickness increased, reflecting that the silica particles adhered less strongly to the titanium nitride than to the underlying silicon dioxide. This result was consistent with the expectation from the idealized studies performed with the atomic force microscope, suggesting that the phenomenon is generalized.