Polymerization photoresists

Organic-based polymeric photoresists, whose contrasts are on the order of 2, require a value of (CMTF)resist of about 0.6. In order to achieve higher resolution, one would need to increase NA, decrease X or both. However such changes in the system NA or in the wavelength of the exposing radiation can be achieved only at the expense of defocus tolerance and increased lens complexity. An alternative approach would be to use a resist system with a contrast value substantially greater than that of conventional photoresists. 

CARS microscopy has emerged as a highly sensitive analytical tool for vibrational bioimaging, predominantly, of lipids in membrane model systems [69, 81-84], live unstained cells [85-95, 43], and both ex vivo and in vivo tissues [26, 96-103, 43]. Examples of CARS imaging applications in the physical and material sciences include the study of fracture dynamics in drying silica nanoparticle suspensions [104], patterned polymeric photoresist film [105], drug molecules in a polymer matrix [106], and liquid crystals [107, 108],... 

Fig. 4. Polynucleotide array fabrication processes using polymeric photoresists. Left. A single layer resist process. Right A bilayer process using a protective underlayer...

Microelectronic device fabrication currently relies primarily upon photoresist processing for integrated circuit pattern delineation. Adhesion of polymeric photoresist patterns, especially those of micron and submicron dimensions, to the required fabrication substrates is of paramount importance. Photoresist image adhesion problems encountered in device fabrication have been solved by chemical interfacial treatments. Current new trends in microelectronic adhesion technology will be described and discussed with emphasis upon the chemical nature of the interface involved as determined by ESCA. 

Before determining surface condition treatment effects, the surface sensitivity enhancement of angle resolved ESCA surface analysis is demonstrated in Fig. 2. The figure clearly shows the 0, Si, and C surface concentrations to be dramatically different than the respective bulk concentrations. The silicon concentration in the top surface layer measured at 5° ESCA take-off angle, for example, is approximately 2.5X less than that obtained at a 75 take-off angle, which represents an approximate depth of 50A from the surface. Most of the surface data presented here is at the low take-off angle of 5 to concentrate primarily upon the wafer surface condition in the first 2-3 atomic layers, and how it affects polymeric photoresist adhesion. 

Nanostructured materials can be synthesized from the so-called top down or bottom-up approach. In the first approach, features at the micron (or submicron) length scale are created on a substrate by masking and exposing selected regions of a radiation sensitive layer (typically a polymeric photoresist) to a UV source. This exposure is followed by various chemical treatments and mechanical steps to obtain the desired spatial pattern on a substrate. However, the feature sizes that can be obtained with this approach are limited to the length scale of the wavelength of the radiation employed. If features at the nanometer scale are desired, one must start from the bottom (i.e., use individual molecules or clusters) and assemble templates that will impart the nanostructure to the desired material. 

A printed circuit has many n-p-n junction transistors. Fig. 10.33 illustrates the formation of one transistor area. The chip begins as a thin wafer of silicon that has been doped with an n-type impurity. A protective layer of silicon dioxide is then produced on the wafer by exposing it in a furnace to an oxidizing atmosphere. The next step is to produce a p-type semiconductor. To do this, the surface of the oxide is covered by a polymeric photoresist, as shown in Fig. 10.33(a). A template that only allows light to shine... 

Photolithography. Passing light through a mask alters the properties of the polymeric photoresist, such that its solubility decreases (negative) or increases (positive). Treatment with solvent then reveals the pattern in the mask. In actual practice the situation may be more complex. For example, if the substrate is Si, there would likely be a layer of SiOi (an insulator) between the substrate and the photoresist. Treatment with solvent then reveals the Si02, which is then etched away in a subsequent step to reveal the Si surface. 

Polymeric materials are used as the basis of photoresists for making metal patterns on printed circuit boards, and also on the individual integrated circuit devices themselves. The circuit boards are made of various glass-fibre filled epoxides and polyesters, and are usually coated with other polymeric materials to prevent tarnishing and to improve solderability. The devices that are mounted on the completed printed circuit boards may have been manufactured using polymeric photoresists or have plastics such as polypropylene and polyester films in capacitors or epoxide resins in integrated circuits and transistors. The completed boards containing various devices are often then coated in another protective polymer. Finally, electrical connections are made... 

During the past few decades, processes based on the interaction of visible and ultraviolet (Vis/UV) light with polymers have become important for various technical applications. The latter include the use of polymeric photoresists in the production of computer chips, and the use of nonlinear optical polymeric materials as core materials for optical wave guides. Polymers are employed in... 

---