Pattern transfer

FIG. 23 Schematic drawing of using microcontact printing for obtaining hydrophobic areas on a gold-coated substrate. After pattern transfer (a and b), incubation with an S-layer protein solution (c) leads to the formation of a protein monolayer on the hydrophobic areas only. 

One possibility to prepare regular dewetted patterns on rough substrates is by pattern transfer. A regular pattern is formed on mica, on which then another substrate is placed. The pattern is released from the mica and fixed on the other substrate at the original droplet positions [49]. 

The etching resistance of a resist is simply a function of how well the material withstands the pattern transfer processes used in device manufacturing. Its resistance must be sufficiently high to allow precise transfer of the resist image into the underlying substrate with < 10% linewidth change. This is not an easy... 

The incorporation of PDMSX into conventional novolac resins has produced potential bilevel resist materials. Adequate silicon contents necessary for O2 RIE resistance can be achieved without sacrificing aqueous TMAH solubility. Positive resist formulations using an o-cresol novolac-PDMSX (510 g/mole) copolymer with a diazonaphthoquinone dissolution inhibitor have demonstrated a resolution of coded 0.5 pm L/S patterns at a dose of 156 mJ/cm2 upon deep-UV irradiation. A 1 18 O2 etching selectivity versus hard-baked photoresist allows dry pattern transfer into the bilevel structure. 

Figure 7 Scanning electron microscope photographs of coded 0.5 (im line-space patterns obtained in the o-cresol novolac-PDMSX ( = 510 g/mole) based resist followed by O2 RIE pattern transfer.

Role of Bombardment in Pattern Transfer Regime. Gokan et al. [18] measured the relative 02 RIE rates of a series of polymers and found that the RIE rates scaled inversely with the mass density of carbon as in their IBE study (several materials deviated from the correlation). The relative RIE rates [18] varied by a factor of 3 and do not show the large variations characteristic of the radical-induced mechanism [10]. These results strongly suggest a bombardment-induced mechanism, but one can not directly apply the IBE results to RIE conditions because IBE neutral-to-ion flux ratios are orders of magnitude lower than under RIE conditions. 

Bombardment-induced Yields in Pattern Transfer Regime. Visser and de Vries [29] estimated the sheath acceleration voltages in their system, and... 

Two general types of multilayer process may be distinguished, depending on whether they use oxygen reactive ion etching (RIE) (4) or optical exposure (5-11) to transfer the pattern into the resist. Optical pattern transfer may suffer from some limitation due to substrate reflections, but has an advantage in the simplicity of the equipment compared to RIE. 

A central aspect of the PIE concept is that the dye and resist exposures should be completely separated (9,15) any departure from this condition makes the system more like CEL and lowers its performance. Further bleaching of the anthracene is of course eliminated simply by removing oxygen the bleaching reactions described above (e.g. Figure 8) are much lower in efficiency and therefore irrelevant insofar as pattern transfer is concerned. However, "antibleaching" due to the loss of oxygen from the anthracene peroxide upon DU V irradiation (47) is a concern it constitutes a dose-dependent loss of contrast. 

Fig. 6 Trilayer pattern transfer approach using nanoporous diblock copolymers. Reproduced from [24]...

Figure 13 Schematic representation of the bilevel resist process employing an oxygen reactive ion etching pattern transfer technique.

The development of that image to give a three-dimensional relief structure suitable for subsequent pattern transfer... 

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