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SU-8  정리 2

　

　

High performance thin film transistor with Su8 gate insulators LiuXiang, Emmanuel Jacques, Tayeb Mohammed-Brahin Université de Rennes1- IETR/ Département Microélectronique et Microcapteurs Campus Beaulieu - Bat 11B 35042 Rennes Cedex, France , 2016
　 　
we reported a possible solution to combine the low temperature and feasible organic Su8 insulator with the inorganic silicon active layer. This solid-state device demonstrated the possibility to employ the organic insulator with the inorganic active layer which will benefit the future application in flexible devices, such as the flexible on-chip circuits and display device.
The detailed process parameter is 2500rpm and 3000rpm/s for the spin-coating process to form the 400nm Su8 insulator which is illustrated in figure 2 (b). 　
With series of low-temperature processes (below 120℃), a high performance TFT with Su8 insulator and 15nm thin film interface improving SiO2 layer was fabricated to achieve high on/off ratio (~ 105 ), high mobility, excellent stability and reproducibility. 　
　 　
08 JAP Gate bias stress effects due to polymer gate dielectrics in organic thin-film transistors
　 　
Polymer insulators are desirable as the gate dielectrics in organic thin-film transistors OTFTs to enable electronic devices that are printable and mechanically flexible.1,2 1. K. Jain, M. Klosner, M. Zemel, and S. Raghunandan, Proc. IEEE 93, 1500
2005 .
2. Y. Noguchi, T. Sekitani, and T. Someya, Appl. Phys. Lett. 89, 253507
2006 .
Since bias stress is influenced by the composition of the gate insulator17,18 and because there is a wide range of polymer insulators available, it is important to understand the origins of device instability in order to choose the appropriate materials and to control the processing conditions. 17 S. Lee, B. Koo, J. Shin, E. Lee, H. Park, and H. Kim, Appl. Phys. Lett. 88, 162109 2006 .
18 S. C. Lim, S. H. Kim, J. B. Koo, J. H. Lee, C. H. Ku, Y. S. Yang, and T. Zyung, Appl. Phys. Lett. 90, 173512 2007.
For OTFTs with polymer gate insulators, changes in device characteristics during operation have been attributed
to surface polarization,19 ion migration,20,21 and charge injection and trapping inside the gate dielectric,22 in addition to the typical mechanism of charge trapping at the semiconductor-dielectric interface.		 Here we examine the hysteresis mechanisms in OTFTs with bilayer polymer dielectrics, in which the top layer next to the semiconductor remains unchanged and only the bottom layer is varied.
Alternatively, it has been shown in Refs. 25 and 26 that use of a layer of poly methylsilsesquioxane pMSSQ coated onto PMMA and PVP also improves the carrier mobility of polythiophene OTFTs by creating a hydrophobic, cross-linked layer on the dielectric. To investigate how such a bilayer dielectric affects electrical stability of OTFTs, we fabricated the dielectric with a top layer of pMSSQ and with a bottom layer of PVP or epoxy resin SU-8.
After 1 h, the moisture content in pMSSQ/ PVP was approximately five times higher than in pMSSQ/SU-8 Fig. 4 , which may be due to more extensive cross-linking18 in SU-8. 　
　 　
In our OTFTs, the SU-8 polymer serves as a better gate insulator than PVP because SU-8 has low hygroscopicity and does not permit charge injection into the dielectric. The extent of cross-linking in the polymers may influence both water absorptionand charge injection and should be further investigated.17,18
　 　
16 ICST Highly sensitive visible and near-infrared photo-FET based on PbS quantum dots embedded in the gate insulator
Uncrosslinked Su-8 2000 series photoresist (Bisphenol A Novolak epoxy) is used as organic gate insulator. Indeed, Su-8emerged recently as an efficient gate insulator for organic TFTs [7]. E. Jacques, M. Romain, A. Yassin, S. Bebiche, M. Harnois, T. Mohammed-Brahim, J. Rault-Berthelot, C. Poriel, “An electron deficient dicyanovinylene-ladder-type pentaphenylene derivative for n-type organic field effect transistors” J. Mater. Chem. C 2 (17), pp.3292-3302.
(2014)
The QDs-SU8 mixed solution is spin-coated at 2500rpm during 30s, then soft-baked at 95°C during 90s, exposed during 70s to UV light and finally baked at 95°C during 90s. The final thickness of the formed film is 400nm 　
　 　
13 JMC An electron deficient dicyanovinylene-ladder-type pentaphenylene derivative for n-type organic field effect transistors
　 　
Indeed, the potential at which an n-type doped molecule can be oxidized should be higher than -0.658 V (vs SCE) in order to be stable towards water reduction (2H2O+2e- →H2 +2OH- ).4, 5* 4 D. M. de Leeuw, M. M. J. Simenon, A. R. Brown, R. E. F. Einerhand, Synth. Met. 1997, 87, 53.

5 H. Usta, C. Risko, Z. Wang, H. Huang, M. K. Deliomeroglu, A. Zhukhovitskiy, A. Facchetti, T. J. Marks, J. Am. Chem. Soc. 2009, 131, 5586.
It is hence usually accepted that molecules with a lowest unoccupied molecular orbital (LUMO) lower than -4 eV may lead to air stable n-type OFET.2 2 H. Usta, A. Facchetti, T. J. Marks, Acc. Chem. Res. 2011, 44, 501.
A 100 nm thick aluminum layer is thermally evaporated on previously cleaned glass substrate. This layer was wet etched to define the gate contact. The insulator (SU-8 photoresist 2000.5 from Microchem) was spin-coated and annealed. The final thickness of this SU-8 layer is about 300 nm. 　
　 　
16 AEM Highly Effi cient All-Solution-Processed Low-Voltage Organic Transistor with a Micrometer-Thick Low- k Polymer Gate Dielectric Layer
　 　
16 OE Development, characterization, and processing of thin and thick inkjet-printed dielectric films
. SU-8 polymer chains have two advantages for inkjet printing fabrication: low-temperature UV cross-linking (compared for instance to dielectric ceramics [13]) and high polymer content by weight while still maintaining a relatively low viscosity [13] M. Mikolajek, A. Friederich, C. Kohler, M. Rosen, A. Rathjen, K. Krger, J.R. Binder, Direct inkjet printing of dielectric ceramic/polymer composite thick films, Adv. Eng. Mater. 17 (9) (2015) 1294e1301.
The SU-8 thick film dielectric ink is formulated using photoresists from the SU-8 2000 polymer series provided by MicroChem (MicroChem, Newton, MA, USA).The SU-8 polymer is typically used as a photo-resist in cleanroom photolithographic processes with its inclusion of Triaryl salt (SbF6) for near-UV cross-linking A cyclopentanone solvent (C5 H8 O) is also included in order to improve coating and adhesion properties upon deposition while also helping to increase the viscosity of the SU-8 polymer to that of the printable range.
In order to ensure printability with the Dimatix DMP-2800 inkjet printing platform, an ink viscosity within the range of 8e16 cP is desired. 　
Once a layer is deposited, the sample is steadily heated from 60 to 120 C over a time of 10 min. Following the pre-exposure bake, the sample is exposed to 170 mJ/cm2 of 365 nm ultraviolet (UV) light using a UVP CL-1000 Ultraviolet Crosslinker (UVP LLC, Upland, CA, USA) . This UV dosage is derived from the recommended exposure for the deposited SU-8 thickness on a glass substrate. Finally, the sample is given a post-exposure bake at 100 C for 7 min