(/* Nanostructure Array Fabrication with a Size-Controllable Natural LithographyHaginoya, Chiseki, Masayoshi Ishibashi, and Kazuyuki Koike. “Nanostructure Array Fabrication with a Size-Controllable Natural Lithography.” Applied Physics Letters 71, no.) |
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* ''the author summarized an empirical equation to show the diameter of the hole is in relation with the etching time of the beads, d = d<sub>0</sub>cos[arcsin(kt/2d<sub>0</sub>)], d is the diameter of the hole(equivalent to the diameter of the beads after etch), d<sub>0</sub> is the initial diameter of the beads, k is a constant, depending on etching conditions and t is the bead etching time.'' | * ''the author summarized an empirical equation to show the diameter of the hole is in relation with the etching time of the beads, d = d<sub>0</sub>cos[arcsin(kt/2d<sub>0</sub>)], d is the diameter of the hole(equivalent to the diameter of the beads after etch), d<sub>0</sub> is the initial diameter of the beads, k is a constant, depending on etching conditions and t is the bead etching time.'' | ||
* ''the authors said in summary that the hole diameter being tested falls in the range of 87nm to 157nm with a pitch depth of 200nm'' | * ''the authors said in summary that the hole diameter being tested falls in the range of 87nm to 157nm with a pitch depth of 200nm'' | ||
====[http://stacks.iop.org/0957-4484/17/i=5/a=028?key=crossref.7384ee986825c9c53df049d6aefcc074 Fabrication of Nanopillars by Nanosphere Lithography<ref name="Cheung">Cheung, C L, R J Nikolić, C E Reinhardt, and T F Wang. “Fabrication of Nanopillars by Nanosphere Lithography.” Nanotechnology 17, no. 5 (March 14, 2006): 1339–1343. doi:10.1088/0957-4484/17/5/028.</ref>]==== | |||
'''Abstract''': A low cost nanosphere lithography method for patterning and generation of semiconductor nanostructures provides a potential alternative to the conventional top-down fabrication techniques. Forests of silicon pillars of sub-500 nm diameter and with an aspect ratio up to 10 were fabricated using a combination of the nanosphere lithography and deep reactive ion etching techniques. The nanosphere etch mask coated silicon substrates were etched using oxygen plasma and a time-multiplexed ‘Bosch’ process to produce nanopillars of different length, diameter and separation. Scanning electron microscopy data indicate that the silicon etch rates with the nanoscale etch | |||
masks decrease linearly with increasing aspect ratio of the resulting etch structures. | |||
* ''The general purpose of the paper is to use the nanosphere lithography to produce nano pillars and they demonstrate that not only the size but also the packing density resist the etching so the time of etching needed to be precisely controlled to yield distance-specified separation''. | |||
* ''experiment briefs: 2 by 2 cm Si wafer goes through RCA clean at 70 Celsius for 30min followed by DI cleaning and N2 flow drying. 350ul of PS beads with diameter 500nm was diluted with a mixed solution(50ul Triton X-100 in methanol by 1:400), the solution was SPIN-COATED on the samples with a spin coater, the spin program consists three parts:1) 400rpm 10s to spread the solution evenly; 2) 800rpm for 2min to spin away the excess bead solution; 3) 1400rpm 10 s to spin off the excess materials from the edges. the samples were then tailored by a parallel plate RIE etcher with 200sccm of oxygen and 8.4 sccm of tetrafluoromethane at a pressure of 200mTorr and RF power of 100W'' | |||
* ''Nano pillar fab: alternative cycles of RIE in a flow of SF<sub>6</sub> (12 sccm 12 sec) and passivation in a flow of C<sub>4</sub>F<sub>8</sub>( 85 sccm 9 sec) were used to etch the unprotected areas and to deposite fluorinated polymer to protect the side walls of the resulting etched structures. RF power = 600W, pressure = 4.5 mTorr, temperature = 25 C.'' | |||
* ''the spin-coating was a more controllable process than the traditional dip-drying process in spreading the beads on the sample surface, especially for patterning a monolayer of beads.'' | |||
* ''During the fab of nano pillars from the bead mask, the reactive ions preferentially attack the bottom of the pitch. The side walls were etched only minimally due to the parallel directionality of the ions to the side walls and the protection of deposited fluorinated polymers.'' | |||
* ''This is likely to say: without the alternative etching cycles, the side walls may be attenuated from top to bottom, resulting in a spike-like nano pillar. For pillars with high aspect ratio this etching process is crucial but for pillars that is very shallow the prectetion of the polymer is not further demonstrated to be necessary'' | |||
* ''the difference between this paper and the previous one is that in the first paper it is the areas that covered by beads being 'etched', this one etched the unprotected areas which are the areas without beads on them!'' | |||
* ''silicon etch rate drops as the aspect ratio goes higher, beads mask was degraded in prelonged silicon etch period'' | |||
==References== | ==References== | ||
Revision as of 21:47, 26 January 2014
This page is the literature review of large scale plasmonic cell fabrication and severs as part of my PhD project at Michigan Tech under supervision of Dr. Pearce.
Controlled distance nanosphere lithography literature reviews
Nanostructure Array Fabrication with a Size-Controllable Natural Lithography[1]
Abstract: A simple technique for size-controllable nanostructure array formation has been developed, using self-assembled polystyrene beads whose diameters can be arbitrarily reduced by reactive ion etching. We have produced a hole array of 83 and 157 nm diameter with 200 nm pitch on Si substrate. This technique can find potential applications in many areas of science and technology.
- X-ray, e-beam and ion beam have many advantages but they are large, expensive and not easy to handle; natural lithography which relies on small structure self-organization is a relative simple and inexpensive way for large scale manufactory.
- polystyrene beads size is controlled by subsequent RIE, the array pitch is determined by the size of the sphere thus also subjected to the etch of the beads. The experiment is conducted on Si(100) with polystyrene beads with initial size of 200nm
- obtain the polystyrene beads array: Si(100) wafer rinsed in acetone then ultrasonic for 1h, the cleaned wafer was preserved in pure water to keep a hydrophilic surface. To form the array, wafer was taken out from pure water and tilted and suspension of beads diluted pure water was dropped onto it, the substrate was kept still until all the water was evaporated
- styrene beads were attenuated by oxygen RIE, the silicon wafer was not affected because the etch rate for silicon in oxygen is much smaller than the rate of the beads.
- Masking(this process can also be used for some plasmonic metal masking): The Pt-Pd mask was deposited using sputtering for about 5nm in thickness, the polystyrene beads with Pt-Pd on top were removed by rubbing the surface with acetone-soaked cotton bud.
- Lithography: The sample was etched by RIE using a mixture of oxygen and carbon fluoride(CF4:O2=9:1), since Pt-Pd mask has a much higher resistance than Si does, the Si wafer is etched and an array of Si holes formed.
- Structure nonuniformity was found in the hole size, position and shape, ascribed to the initial nonuniform bead size, rate of RIE and the non uniformity of the self-organization, however, the overall array, seeing from the SEM images attached, is quite uniform and conformal.
- By changing the RIE time for the beads, different hole diameters were obtained, by changing the time of Si etching, the pitch depth can be adjusted.
- the author summarized an empirical equation to show the diameter of the hole is in relation with the etching time of the beads, d = d0cos[arcsin(kt/2d0)], d is the diameter of the hole(equivalent to the diameter of the beads after etch), d0 is the initial diameter of the beads, k is a constant, depending on etching conditions and t is the bead etching time.
- the authors said in summary that the hole diameter being tested falls in the range of 87nm to 157nm with a pitch depth of 200nm
Fabrication of Nanopillars by Nanosphere Lithography[2]
Abstract: A low cost nanosphere lithography method for patterning and generation of semiconductor nanostructures provides a potential alternative to the conventional top-down fabrication techniques. Forests of silicon pillars of sub-500 nm diameter and with an aspect ratio up to 10 were fabricated using a combination of the nanosphere lithography and deep reactive ion etching techniques. The nanosphere etch mask coated silicon substrates were etched using oxygen plasma and a time-multiplexed ‘Bosch’ process to produce nanopillars of different length, diameter and separation. Scanning electron microscopy data indicate that the silicon etch rates with the nanoscale etch masks decrease linearly with increasing aspect ratio of the resulting etch structures.
- The general purpose of the paper is to use the nanosphere lithography to produce nano pillars and they demonstrate that not only the size but also the packing density resist the etching so the time of etching needed to be precisely controlled to yield distance-specified separation.
- experiment briefs: 2 by 2 cm Si wafer goes through RCA clean at 70 Celsius for 30min followed by DI cleaning and N2 flow drying. 350ul of PS beads with diameter 500nm was diluted with a mixed solution(50ul Triton X-100 in methanol by 1:400), the solution was SPIN-COATED on the samples with a spin coater, the spin program consists three parts:1) 400rpm 10s to spread the solution evenly; 2) 800rpm for 2min to spin away the excess bead solution; 3) 1400rpm 10 s to spin off the excess materials from the edges. the samples were then tailored by a parallel plate RIE etcher with 200sccm of oxygen and 8.4 sccm of tetrafluoromethane at a pressure of 200mTorr and RF power of 100W
- Nano pillar fab: alternative cycles of RIE in a flow of SF6 (12 sccm 12 sec) and passivation in a flow of C4F8( 85 sccm 9 sec) were used to etch the unprotected areas and to deposite fluorinated polymer to protect the side walls of the resulting etched structures. RF power = 600W, pressure = 4.5 mTorr, temperature = 25 C.
- the spin-coating was a more controllable process than the traditional dip-drying process in spreading the beads on the sample surface, especially for patterning a monolayer of beads.
- During the fab of nano pillars from the bead mask, the reactive ions preferentially attack the bottom of the pitch. The side walls were etched only minimally due to the parallel directionality of the ions to the side walls and the protection of deposited fluorinated polymers.
- This is likely to say: without the alternative etching cycles, the side walls may be attenuated from top to bottom, resulting in a spike-like nano pillar. For pillars with high aspect ratio this etching process is crucial but for pillars that is very shallow the prectetion of the polymer is not further demonstrated to be necessary
- the difference between this paper and the previous one is that in the first paper it is the areas that covered by beads being 'etched', this one etched the unprotected areas which are the areas without beads on them!
- silicon etch rate drops as the aspect ratio goes higher, beads mask was degraded in prelonged silicon etch period
References
- ↑ Haginoya, Chiseki, Masayoshi Ishibashi, and Kazuyuki Koike. “Nanostructure Array Fabrication with a Size-Controllable Natural Lithography.” Applied Physics Letters 71, no. 20 (1997): 2934. doi:10.1063/1.120220.
- ↑ Cheung, C L, R J Nikolić, C E Reinhardt, and T F Wang. “Fabrication of Nanopillars by Nanosphere Lithography.” Nanotechnology 17, no. 5 (March 14, 2006): 1339–1343. doi:10.1088/0957-4484/17/5/028.