Advanced materials for 193 nm immersion lithography

Abstract

Recently 193 nm immersion lithography is considered the most promising next generation technology which will enable a 45 nm and below node device to be manufactured. This will lead to not only depth of focus (DOF) enlargement, but immersion lithography enables the use of a hyper numerical aperture (NA) larger than 1.0 and achieve higher resolution capability. For 193 nm lithography, water is an ideal immersion fluid, providing suitable refractive index and transmission properties. Furthermore the higher refractive index fluid is expected to provide a potential extension of optical lithography to the 32 nm node. This paper describes the critical issues of the water immersion lithography process, such as photoresist component leaching into water, defectivity etc. Leaching materials were analyzed by liquid chromatography‐mass spectrometry (LC‐MS) and were found to be composed of the photoacid generator (PAG) and its decomposed chemicals. The leaching amount is in the order of 10−12 mol/cm2 with a normal 193 nm photoresist. An other issue to be studied is the water‐mark defect caused by small waters droplets left on the exposed wafer. These undesirable phenomenons could be prevented by applying a topcoat material onto the photoresist film. Material design for the topcoat material and its physical and lithographic properties are discussed in detail. Development of a high refractive index fluid is also discussed in this paper. A promising high refractive index fluid HIL‐001 was developed which has a higher refractive index (n = 1.64) than water and high transparency (98%/mm) at 193 nm wavelength. Immersion exposure experiments using high refractive index fluid with and without topcoat material was carried out and 32 nm L/S imaging capability was demonstrated by using a two‐beam interferometric exposure tool. Copyright © 2006 John Wiley & Sons, Ltd.

Compound redistribution due to droplet evaporation on a thin polymeric film: Theory

“…We combine Eqs. (26) and (28) into an expression for the full deposit stain profile h(r), deposit stain, with a pronounced edge and a decrease towards the centre, are qualitatively similar to experimental findings of Belmiloud et al 6 on the topology of a watermark on a hydrophobic Si wafer. Note that the expressions presented above are valid as long as the back-diffusion of material from the droplet into the thin film is neglected.…”

“…For the film this is the film thickness, whilst that for the droplet is the initial droplet radius. Typical film thicknesses in semiconductor photolithography are in the order of 100 nm and initial droplet sizes are in the range of tens to hundreds of micrometres 17,26,27 , so the timescales differ by four to six orders of magnitude, and our assumption is reasonable.…”

Immersion Lithography: Photomask and Wafer-Level Materials

“…Many topcoats incorporate fluorinecontaining functional groups for their increased hydrophobicity, as well as the same compound 112 French · Tran types used effectively for absorbance reduction in 157-nm technology (88,(96)(97)(98)(99)(100)(101). These fluoropolymers have also been used in water immersion resist materials-either as additives to current 193-nm materials or as block copolymers (102)(103)(104). These systems are designed so that a topcoat is not necessary, but instead incorporate the topcoat's hydrophobic properties directly into the photoresist, eliminating an extra topcoat spinning step.…”

Photoimaging and Lithographic Processes in Polymers

“…Resolution enhancement techniques (RET) allowed engineers to push the limits for which 193 nm is used, from 120 nm node down to 45 and 32 nm nowadays, and most likely for 22 nm as well. Double exposure, immersion lithography in a liquid with high refractive index, and optical proximity correction (OPC) have been employed so far [50][51][52]. Immersion lithography in water, which has a refractive index of 1.44, is the current technology employed [52].…”