Quantitative measurement of EUV resist outgassing

Abstract

The Mo/Si multilayer mirrors used for extreme ultraviolet (EUV) lithography can become contaminated during exposure in the presence of some hydrocarbons [1][2][3]. Because this leads to a loss in the reflectivity of the optics and throughput of the exposure tools, it needs to be avoided. Since photoresists are known to outgas during exposure to EUV radiation in a vacuum environment, the careful choice of materials is important to preserving the EUV optics. Work therefore has been performed to measure the species and quantities of molecules that outgas from EUV resists when exposed to EUV radiation [4][5][6][7].

Film Quantum Yields of Ultrahigh PAG EUV Photoresists

“…[20] The typical procedure is to expose resist films to 2.5x the clearing dose (Eo). Surprisingly, all resists passed the SEMATECH limit of 6.5 x 10 14 molecules/cm 2 , even when the resists 3.…”

Outgassing and photochemical studies of photosensitive films upon irradiation at 13.5 nm

“…IMEC determined outgassing rates in the m/z ¼ 45-200 range under an irradiance of 10 mW cm À2 , 7-10 whereas CNSE/SEMATECH counted them in the m/z ¼ 35-200 range (excluding 44) under an irradiance of 15 mW cm À2 . [17][18][19][20] The deviation of assessing outgassing rates with different irradiances can be calculated according to the first-order integrated rate law as (1 -exp(-Dill's C parameter  irradiance)]/irradiance, where Dill's C parameter was approximated 4  10 À3 mJ À1 cm 2 from our previous CH 3 þ outgassing results. 28 The outgassing rates determined with an actual irradiance of 10 or 15 mW cm À2 differed by approximately 6% or 5%, respectively, from the results obtained with an actual irradiance of 38 mW cm À2 and scaled to a value of either 10 or 15 mW cm À2 .…”

“…The features of the neutral outgassing are identical to those reported by Denbeaux and co-workers, and by Dentinger in an early EUV outgassing study. 18,31 The outgassed species in order of abundance were as follows (m/z values are presented in parentheses): CO (28) Figures 2(b) and 2(c) illustrate the differences in the outgassing rates from the 80 and 100 nm films relative to the 125 nm film, respectively. The solid blocks in these figures represent the differences in the major outgassed species, with the differences occurring mostly within 620% of each other with no significant dependence on film thickness.…”

“…Prior to the development of the witness-plate method, new EUV photosensitive samples had to pass certain preset outgassing criteria before they could be exposed under an EUV exposure tool. [7][8][9][10][16][17][18][19][20][21][22][23][24][25][26] Although the characterization of outgassed species and the quantification of outgassing are no longer used for resist a) Author to whom correspondence should be addressed; electronic mail: graceho@nuk.edu.tw qualification by the majority of the EUVL community, these techniques can provide useful information for understanding the photochemical mechanisms of outgassing, which can help in the design of new photosensitive materials. Semiconductor Manufacturing Technology (SEMATECH) organized a roundrobin resist test to measure the absolute outgassing rates from an EUV model photoresist at eight measurement sites and reported that the absolute values varied over 4 orders of magnitude.…”

“…In the United States, a SEMATECH-supported Resist Outgassing and eXposure (ROX) tool with a stand-alone EUV source and a newly installed electron beam is based at the College of Nanoscale Science and Engineering (CNSE) at the University of Albany. [17][18][19][20] The CNSE team recently measured tert-butylbenzene outgassing to derive the relative acid yields from the two photoacid generators (PAGs), di(tert-butylphenyl)iodonium 1-perfluorobutanesulfonate and di(tert-butylphenyl)iodonium triflate. They also measured isobutene outgassing from the deprotection groups of polymers and established a linear correlation between the absolute number of isobutene outgassing and the relative thickness loss after development.…”