O2 reactive-ion etching

All future alternatives will require new resists and processes, and for the first time, manufacturing lines will be using at least two different resists. These new materials must have satisfactory sensitivity, resolution, and process latitude. In addition, the deep-UV tools will have limited depth of focus (1-2 (xm) and will be useful only with relatively planar surfaces. Multilayer-resist schemes have been proposed to overcome these limitations, and the simplest is the bilevel scheme that requires a resist that can be converted, after development, to a mask resistant to O2 reactive ion etching (RIE). Resistance to O2 RIE can be achieved by incorporating an element into the resist structure that easily forms a refractory oxide. Silicon performs this function very well and is relatively easy to include in a wide variety of polymer structures. 

Step 4. O2 reactive-ion etching pattern transfer to underlying substrate... 

Fig. 2 SEM image of a patterned silicon substrate. Lines of poly(ferrocenylmethylphen)4-silane) were introduced by capillary force lithography, foUowed by CF4/O2 reactive ion etching (10 min). The polymer mask was subsequently removed using nitric acid...

Fig. 8. Schematic of the procedure used for fabrication of nanoscale molecular-switch devices by imprint lithography [62]. (a) Deposition of a molecular film on Ti/Pt nanowires and their micron-scale connections to contact pads, (b) Blanket evaporation of a 7.5 nm Ti protective layer, (c) Imprinting of 10 nm Pt layers with a mold that was oriented perpendicular to the bottom electrodes and aligned to ensure that the top and bottom nanowires crossed, (d) Reactive ion etching with CF4 and O2 (4 1) to remove the blanket Ti protective layer.

Reactive-ion etch resistance was evaluated using a Cook Vacuum Products RIE system. Model C71-3 operating at 13.56 MHz. The etch resistance was determined for a two-layer configuration in which the resist was spun on 1.5 m of a polyester planarizing layer (PC-1) supplied by Futurrex Inc. The latter etches approx. 30-50% faster than HPR-204 ( 1500 A/min compared to 1000 A/min for HPR). The etching conditions were Power 0.16 W/cm Bias —350 V Pressure, 20 mTorr O2 Flow rate 15 seem O2. 

Etch resistance for 12 organosilicon polymers has been studied under oxygen ion-beam etching (O2-IBE) and oxygen reactive ion etching (02-RIE) conditions. Under O2-IBE conditions, the etching rate for organosilicon polymers is found to be proportional to N/Nsi, where N and Nsi denote the number of total atoms in a monomer unit and the number of silicon atoms in a monomer unit, respectively. This means... 

Oxygen reactive-ion etching (O2 RIE) was carried out with a Cooke Vacuum Products (model C71-3) parallel-plate RIE reactor operating at 13.56 MHz. Oxygen pressure and flow rate were 2 Pa and 10 seem (standard cubic centimeters per minute), respectively, and the RF (radio frequency) power density and self-bias were 0.15 W/cm and -350 V, respectively. 

It is well known that insertion of silicon-containing groups into a polymer enhances its plasma resistance greatly. The rate of a reactive ion etching in oxygen (RIE in O2) in the stationary state, P, is proportional to the ratio of the silicon atom mass densities in the polymer, ppoi., and in Si02, Poxide ... 

Figure 10.6 Procedure for polymer nanowire fabrication. An aqueous PEDOTtPSS solution was spin-coated on a substrate patterned with a 1.3 ym period grating, then coated with a thin Si02 layer and a PDMS homopolymer brush. A PS-PDMS block-copolymer thin film was then spin-coated and solvent-annealed. The self-assembled block-copolymer patterns were transferred into the underlying PEDOT-.PSS film through a series of reactive ion etching steps employing CF4 and O2 plasmas. (Reprinted with permission from Nano Letters, Nanowire Conductive Polymer Gas Sensor Patterned Using Self-Assembled Block Copolymer Lithography by Y. S. Jung et al., 8, 11. Copyright (2008) American Chemical Society)...

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