Influence of chemical-mechanical polishing on the surface roughness of microchannel plate

Microchannel plate (MCP) is an important charged-particle electronic multiplier, whose surface roughness is one of the vital factors of high-performance multiplication. A chemical-mechanical polishing (CMP) is a planarization process assisted by chemical reactions to remove surface materials and improve surface smoothness. In this paper, atomic force microscopy (AFM) was applied to investigate the surface roughness of the MCP wafers by chemical-mechanical polishing. After chemical-mechanical polishing, the global surface roughness increased from 8.33 nm into 9.01 nm, which was contrary to the conventional chemical-mechanical polishing results. Using the surface partitioning analysis, we confirmed that the escalated global surface roughness was related to the raised surface roughness of the acid-soluble core glass (from 2.35 nm rise to 3.07 nm after CMP), which occupied more than 60% area of the MCP wafer. Moreover, the surface roughness of the etching-resistance cladding glass was notably dropped after CMP (from 6.48 nm decreased to 4.84 nm). Thus, CMP was a benefit to improve the surface finishing of the MCP multiplier despite the global surface roughness increasing after that.