Enhancement layer

To date, we have exercised these materials in basically three types of multilayer lithographic applications (1) as short wavelength contrast enhancing layers, (2) as imagable 02-RIE resistant materials in bilayer processes and (3) as radiation sensitive materials for multilayer, e-beam processes. 

Contrast enhancement lithography is a clever procedure which uses a bleachable contrast enhancing layer to restore the distorted aerial image of the mask which has been blurred by diffraction effects into a sharp image at the underlying photoresist surface. The process is too complicated to explain in detail here and the interested reader is referred to the cited literature (60,61). Suffice it to say that the large extinction coefficients of most polysilane derivatives coupled with their ready bleachability make them ideally suited for such purposes and we have demonstrated this application at 313 nm (16,18). 

A rapidly increasing number of publications on polysilanes documents current interest in these polymers (JJ. Polysilanes are potentially applicable in microlithography as high resolution UV-resists (2J, imageable etch barriers ), or contrast enhancement layers (4). They have been successfully used as precursors to Si-C fibers (5J and ceramic reinforcing agents ((L). Polysilanes have also initiated polymerization of vinyl monomers (J ). Doping of polysilanes have increased their conductivity to the level of semiconductors (8). Very recently polysilanes were used as photoconductors (9) and non-linear optical materials (10b... 

A number of a-aryl-A-alkyl nitrones and contrast enhancement compositions, which can be used to make contrast enhancement layer photoresist composites (230, 231), and inhibitors of free radical polymerization of monomers in nonexposed regions of the photoresist layer at selective actinic radiation (232). Histidine was used as a catalyst in the synthesis of a, A-diaryl nitrones in situ (233). To study diphenylborate chelates with mono- and bidentate ligands, a series of hydroxyl-containing nitrones have been synthesized (Fig. 2.7) (234-237). 

West PR, Davis GC, Regh KA. Contrast Enhancement Layer Compositions, Alkyl-nitrones, and Use, US Patent No. 5106723, April 21, 1992. 

Zhang, Advani, and Prasad [51,52] also used microfabrication techniques in order to develop a thin, perforated copper foil and use it as a cathode DL in a PEMLC. In addition to the metal DL, an "enhancement" layer was used that consisted of a porous material locafed befween the perforated copper foil and fhe LF plate (CLP was used in fhis study). This layer improved the overall short-term performance and wafer managemenf of fhe cell. Flowever, the authors did not discuss any possible long-term issues related to contaminahon of the membrane due to the use of a copper DL. 

Contrast-Enhanced Lithography. Contrast-enhanced lithography is a clever technique that uses a thin layer of a bleachable contrast-enhancing layer coated over a conventional photoresist to sharpen the mask image. 

An effective contrast-enhancing layer must possess certain essential characteristics It must be thermally stable, soluble in solvents that permit casting on photoresist layers with no mixing at the interface, strongly absorbing in the desired spectral region, and bleachable upon exposure. In addition, removal of this layer from the exposed photoresist prior to image development is desirable. 

The EL spectrum of the color-variable device under reverse bias are similar to those of the single-layer PPyVPV and PTP devices, implying that the light is generated either in the bulk of the emitting polymer or at the EB interface. The EB layer functions as a charge-injection enhancement layer, playing a similar role to that in SCALE devices reported earlier.8 Under reverse bias, the SPAN layer on the cathode side plays a similar role. 

Fig. 6.9 Schematic diagrams of enhanced layer velocity sensor. ...

Major Applications Electrphoresis display device, image contrast-enhancing layer,3 photogra-phy,4 Photoelectrographic imaging,5 inks," pamts, toys ... 

Ru and Ru alloys have also been proposed as a seed enhancement layer. Ru by... 

Figure 19.10 Novel nanocomposites extruded in film form with silica platelets both oriented and localized in numerous internal layers to give plastics with low permeability and other property enhancements. (Layers of matrix polymer separate both the platelets and platelet-rich layers. Internal layers and platelets are optimally oriented parallel to the film surface.)...

Lai WF, Lawn F, Clinton HWD, McHenry JA, Washington NJ, Verduijn JP, et al. Supported zeolite membranes with foreign patent documents controlled crystal width and preferred orientation grown on a growth enhancing layer. Patent Number 5,871,650, Application Number US005871650A Feb 16,1999. 

The concept of a contrast enhancement layer (CEL) is straightforward. All exposure equipment... 

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