Lithographic masks

Douglas and coworkers were the first one that described a bottom-up approach based on S-layers as templates for the formation of perfectly ordered arrays of nanoparticles [128]. The S-layer lattice was used primarily to generate a nanometric lithographic mask for the subsequent deposition of metals. In this approach a thin Ta-W film was deposited... 

Two-level glass etch was also performed first over photoresist for shallow etch (10 pm), and then over black lithographical masking tape for deep etch [117]. 

Potential applications of peptide-polymer conjugates include drug delivery materials, optoelectronics, biosensors, tissue scaffolds, tissue replacement materials, hydrogels, adhesives, biomimetic polymers, lithographic masks, and templates for metallic or silica nanostructures. 

Figures 23-28 show the process of producing basic circuit elements of vertically stacked circuits. The use of the three lithographic masking techniques mentioned results in very low loss transitions between optical circuits in different vertical stacks. These techniques can also be used to fabricate the low loss electro-optic modulator configuration shown in Figs. 29 and 30.

The etching procedure using a negative photoresist is identical except that the lithographic mask must be opaque in the regions where metal is to be removed — this is known as a dark-field mask. Exposure of negative resist to UV light makes it insoluble in its developer. 

The imaging properties of PVTMSK were studied by spin coating 350-nm-thick films on silicon wafers or on silicon wafers precoated with a 1.5-(xm-thick layer of hard-baked photoresist, exposing them to mid- or deep-UV radiation through a chromium-on-quartz lithographic mask, and developing the pattern as described earlier. This scheme was used to test the intended application of PVTMSK as an imaging material for two-layer resist applications. The densest patterns resolved were composed of l-(xm coded lines and spaces. 

Brault, R.G. Graft Polymerized Si02 Lithographic Masks. PCT Patent WO 85/02030, May 5, 1985. 

Today, these theories of solutions and of electrolytic solutions are used in the analysis of the solvent development of exposed resists, lithographic mask degradation due to corrosion, electromigration of chromium ions, etc. 

The fabrication of a lithographic mask involves the transformation of computer-aided designs of an IC into a physical layout to create a geometrical pattern of the mask. Coordinates of the IC layout are digitized and stored in appropriate electronic storage media such as tapes. The pattern is then transferred onto the surface of chrome-quartz plates or appropriate substrates, depending on the mask type. ... 

Mechanism of lithographic mask chrome structure oxidation... 

A possible fabrication process flow for a single 90-nm technology node microprocessor CMOS inverter, consisting of two transistors— nMOS and pMOS—is presented in this section. Cross-sectional views of the inverter are provided for each major operation, with the operations involving lithographic masking called out with thicker lines, where possible. It must be noted that the illustration is for only a small microscopic area of a microprocessor that is one of hundreds of microprocessors that may populate a given 300-mm wafer at the end of the fabrication process. 

Figure 16.5 Process sequence for n-well formation (a) p silicon substrate, (b) expitaxial growth, (c) initial oxide growth, (d) n-well lithographic masking that defines the area to be implanted, (e) n-well implantation with phosphorus ions, (f) resist stripping and cleaning, and (g) annealing of the implanted wafer.

Figure 16.6 shows the process sequence executed in p-well formation. The lithographic masking step (involving mask 2) is the same as that for the u-well implant mask. It defines the area of the inverter to be implanted to form the p-wells for the nMOS transistors. A boron implantation is performed, followed by resist stripping and cleaning. Annealing is done in basically the same manner as described above for the u-well. 

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