We have studied the photolysis of tin clusters of the type [(RSn) 12 O 14 (OH) 6 ] X 2 using extreme ultraviolet (EUV, 13.5 nm) light, and developed these clusters into novel high-resolution photoresists. A thin film of [(BuSn) 12 O 14 (OH) 6 ][p-toluenesulfonate] 2 (1) was prepared by spin coating a solution of (1) in 2-butanone onto a silicon wafer. Exposure to EUV light caused the compound (1) to be converted into a substance that was markedly less soluble in aqueous isopropanol. To optimize the EUV lithographic performance of resists using tin-oxo clusters, and to gain insight into the mechanism of their photochemical reactions, we prepared several compounds based on [(RSn) 12 O 14 (OH) 6 ] X 2. The sensitivity of tin-oxide films to EUV light were studied as a function of variations in the structure of the counter-anions (X, primarily carboxylates) and organic ligands bound to tin (R). Correlations were sought between the EUV sensitivity of these complexes vs. the strength of the carbon-carboxylate bonds in the counteranions and vs. the strength of the carbon-tin bonds. No correlation was observed between the strength of the carboncarboxylate bonds in the counter-anions (X) and the EUV photosensitivity. However, the EUV sensitivity of the tinoxide films appears to be well-correlated with the strength of the carbon-tin bonds. We hypothesize this correlation indicates a mechanism of carbon-tin bond homolysis during exposure. Using these tin clusters, 18-nm lines were printed showcasing the high resolution capabilities of these materials as photoresists for EUV lithography.
We present the synthesis and preliminary lithographic evaluation of Molecular Organometallic Resists for EUV (MORE) that contain post-transition metals. These elements have high EUV optical density so they can utilize a large fraction of the incident photons. We will describe two technical approaches for EUV resist platforms that contain bismuth. Approach 1: Combination of organometallic compounds with photoacid generators. Approach 2: Combination of high-oxidation state metal-center oligomers that utilize carboxylate anions bound to the metal centers.
We present the synthesis and preliminary lithographic evaluation of Molecular Organometallic Resists for EUV (MORE) that contain post transition metals. These post transition metal nuclei have high EUV optical density so they can utilize a high fraction of the incident photons. We will describe two technical approaches for EUV resist platforms that contain bismuth. Approach 1: Combination of organometallic compounds with photoacid generators. Approach 2: Combination of high-oxidation state metal-center oligomers that utilize carboxylate anions bound to the metal centers. I. Introduction.As the microelectronics industry continues to follow Moore's law, increasing strain has been placed on today's photoresists systems. With 22-nm gate-lengths currently in production, many chip manufacturers are looking for ways to implement the 16 and 10-nm lithography nodes. Chip manufacturers currently use 193-nm scanners for printing these features, however, these systems have already surpassed their resolution capabilities and imaging is only made possible by multiple patterning. Extreme ultraviolet (EUV, 13.5-nm wavelength) lithography is thought to be the next imaging technology for fabricating microelectronic devices, however, there are still many obstacles that must be overcome. The traditional, chemically-amplified photoresist systems which have been successful in lithography since the 1980's are finally encountering extremely challenging 1 hurdles: poor photon absorption in thin-films, 2 moderate etch selectivity 2,3 and limited gains in resolution. 4,5 Recently, two novel resist systems have been developed based on hafnium-oxide nanoparticles. 6 Researchers at Inpria Co., have demonstrated high resolution EUV resists capable of 8 nm dense line and space patterns at 200 mJ/cm 2 . Christopher Ober's group at Cornell have demonstrated good sensitivity of 12 mJ/cm 2 at modest resolution of 36 nm. This pioneering work has demonstrated the great potential of inorganic systems as photoresists.In this paper, we present on a subset of Molecular Organometallic Resists for EUV (MORE) that are comprised of organometallic compounds containing main group metals. The MORE approach utilises high EUV optical density metals to increase the photon absorbance of thin resist films. James Thackeray in his 2011 SPIE plenary presentation stated that the target absorption for EUV resist films is 50%. To print 10-nm lines with an aspect ratio of 2:1, film thickness must be around 20 nm. Polyhydroxystyrene at this thickness will stop only ~10% of the light (T ≅ 0.90). 7 Loading organic polymers with fluorine will have limited impact. Teflon ((C 2 F 4 ) n ) probably contains the most fluorine possible in an organic polymer,
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