Plasma resistant glass (PRG) for reducing particulate contamination during plasma etching in semiconductor manufacturing: A review

Abstract

Plasma resistant glass (PRG) is used to reduce particulate contamination in semiconductor etching processes. This article reviews previous studies on PRG, and proposes its new application as a material for semiconductor etching. For semiconductor wafer patterning, dry etching is performed by applying CF4, O2, and Ar mixed gases due to the excellent selectivity of inductively coupled plasma-reactive ion etching (ICP-RIE). At this point, the ceramic parts comprising the etching chamber are degraded due to inevitable internal defects such as nanopores, and grain-boundaries as a function of plasma etching exposure time regardless of composition. Consequently, surface craters are enlarged, and the amount of particulate contamination increases. In contrast, the PRG etched by plasma shows a lower etching rate than single-crystalline sapphire, and maintains non-deteriorated smooth surface microstructure, and roughness. Until now, glass for semiconductor apparatus has been researched mainly based on quartz glass, and examples compile quartz glass doped with non-volatile elements (Al, Y, lanthanoid series), RE-Al-Si-O (RE: Y, La, Gd), and R-Al-Si-O (R: Mg, Ca, Sr, Ba). SiF4, which is formed by the reaction of Si, SiO2 with F* during plasma etching, is vaporized, and AlF3, CaF2, and MgF2, which remain on the surface contribute to the reduction in the etching rate due to improved resistance to positive ion bombardment. This is considered highly related to the sublimation enthalpy of fluorinated compounds. Therefore, for PRG to have excellent plasma resistance, it is necessary to (1) stable glass phase, (2) have a high sublimation enthalpy when the constituent cations are fluoridated, and (3) maintain a uniform surface.