Mass spectrometer characterization of reactions in photoresists exposed to extreme ultraviolet radiation

Abstract

The development of resists that meet the requirements for resolution, line edge roughness and sensitivity remains one of the challenges for extreme ultraviolet (EUV) lithography. Two important processes that contribute to the lithographic performance of EUV resists involve the efficient decomposition of a photoacid generator (PAG) to yield a catalytic acid and the subsequent deprotection of the polymer in the resist film. We investigate these processes by monitoring the trends produced by specific masses outgassing from resists following EUV exposure and present our initial results. The resists tested are based on ESCAP polymer and either bis(4-tert-butylphenyl)iodonium perfluoro-1-butanesulfonate or bis(4-tert-butylphenyl)iodonium triflate. The components originating from the PAG were monitored at various EUV exposure doses while the deprotection of the polymer was monitored by baking the resist in vacuum and detecting the cleaved by-product from the polymer with an Extrel quadruple mass spectrometer.

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 .…”

“…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.…”

“…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. 20 Semiconductor Leading Edge Technologies, Inc. and the University of Hyogo in Japan have a stand-alone and a synchrotron radiation-based EUV outgassing evaluation system, respectively. [21][22][23][24] They qualitatively rationalized resist outgassing from forty-two R&D resists and found that the common outgassed species were isobutene or adamantane derivatives from deprotection groups, and benzene and biphenyl or biphenyl sulfides from the PAGs.…”

Reactivity of metal-oxalate EUV resists as a function of the central metal

“…The oxalate ligand will decompose readily when detached from the metal center and produce carbon dioxide in the process. The rate of CO2 production can be monitored using in situ mass spectrometry measurements [29][30][31][32] . [24][25][26][27][28] .…”