Processing efficiency of elastic emission machining for low‐thermal‐expansion material

Abstract

Extreme ultraviolet (EUV) lithography is currently being developed as a next-generation lithography system. In this system, light at a wavelength of 13.4 nm is used, allowing the patterning of lines with dimensions of less than 40 nm. To focus the light, high-precision optical mirrors are required with a surface roughness of 0.1 nm. In addition, mirror substrates must be low-thermal-expansion materials because EUV light is easily absorbed in matter, accordingly converted to heat. ULE (Corning Inc.) and Zerodur (SCHOTT AG) are well-known examples of such materials. To achieve these requirements for EUV lithography, a high-performance machining method is needed. In previous studies, the machining performance of elastic emission machining (EEM) for the above materials was examined from the viewpoint of roughness improvement. As a result, we considered that EEM has sufficient figuring and smoothing capability for the fabrication of EUV optics. We next evaluate the processing efficiency of EEM. In this study, the processing efficiency of EEM for a low-thermal-expansion material was examined from the viewpoint of the removal rate. As a result of this investigation, the conditions under which the efficiency of EEM is increased were clarified. We analyzed and discussed these conditions.

Effect on surface roughness of zerodur material in atmospheric pressure plasma jet processing

“…To solve these damage problems, some non-contact abrasive based machining methods have been developed, such as float polishing and EEM (Elastic Emission Machining). Using float polishing for zerodur material, surface with roughness less than 2nm RMS can be obtained [4][5] , while using EEM, it is possible to obtain a surfaces with roughness less than 0.2nm Ra [6][7][8] . However, both of them have extremely low efficiency.…”

Polishing Approaches at Atomic and Close-to-Atomic Scale

“…For a hard X-ray system, 0.2 nm in RMS is required for mirrors [ 27 , 28 ]. In the field of ultraviolet lithography, 0.3 nm in RMS [ 29 ] and 0.15 nm in RMS [ 30 , 31 ] are needed by the lens. The roughness of a PC hard disc must be less than 0.05 nm in Ra to achieve a storage density larger than 500~1000 Gb/in 2 [ 32 ], as shown in Figure 2 .…”

Dual-rotor tool path generation and removal error analysis in active feed polishing

“…Modern science and technique put forward a higher requirement for optical surface quality, so ultrasmooth fabrication technology becomes an important research direction because it can get extremely low surface roughness. At present, the common ultrasmooth processing methods include float polishing (FP) [1,2], bowl polishing [3], elastic emission machining (EEM) [4][5][6], chemical mechanical polishing [7,8], and plasma-assisted chemical etching [9]. However, most of these methods process the whole surface simultaneously, so that it is difficult for them to balance the surface figure.…”