Evaluation of 172-nm wavelength as a possible candidate for 22-nm and below

The lithography industry has been working to extend 193 nm immersion with double patterning and complex computational lithographic techniques for 32 nm and below. Also extreme ultraviolet lithography (EUV) are used to make the 22 nm half-pitch and below. However, technical challenges remain to be addressed, as well as the high cost of the manufacturing tool. There was a report that a new wavelength, 172 or 175 nm, can be used for next generation lithography system. 172 nm lithography, although, has higher absorbance than 193 nm, it has much higher transmission than 157 nm in high refractive index liquid. Compared with 193 nm immersion lithography that has the resolution limit of 35.7 nm by using maximum numerical aperture (NA) of 1.35, 172 nm immersion lithography can be used for possible resolution limit of 27.4 nm by using maximum NA of 1.57. In this paper, we evaluated the 172 nm immersion lithography using commercial lithography simulation for 28 nm node by single exposure. We also checked the patterning possibility of 22 and 16 nm node by using 172 nm and double patterning because a totally new wavelength should show the possible extension to multiple generations.