Photomask fabrication

Electron Beam Lithography. LB PMMA films with thicknesses of 6.3 nm (7 layers) are sufficient for patterning a Cr film suitable for photomask fabrication. For ultrathin PMMA films the resolution (see Fig. 1) is limited by the smallest spot diameter available on MEBES I (1/8 pm). However, it is not possible to obtain this resolution if a thicker resist (>100 nm) is used under the same exposure and development conditions, which demonstrates that ultrathin resists are able to minimize the proximity effect. Also, since the radius of gyration of 188,100 Mw PMMA is about 10 nm in the bulk, and the thickness of the 7 layer film (6.3 nm) is less than 10 nm, it is reasonable to assume there must be an alteration of chain configuration in the ultrathin films. This will be particularly true when the post-deposition baking temperature of the multilayer films is less than the glass transition temperature (115°C), as is the case for the present experiments. In such a case, interdiffusion of PMMA chains between the deposited layers may not result in chain configurations characteristic of the bulk. 

Exposure of the photosensitive article. The exposure step photographically transfers a pattern from a reticle or photomask to the photoresist coated on the wafer surface. Photomasks are glass plates with patterns made of opaque and transparent areas. A photomask will typically have the pattern for a few dice and will be stepped across the wafer exposing the pattern after each step. In order to ease a task of a photomask fabrication and make the process less defect sensitive, photomask patterns are either 5x or 4x, the size of the desired feature on the wafer, and the photomask pattern is optically shrunk before reaching the wafer. 

Kurihara, M. Segawa, T. Okuno, D. Hayashi, N. Sano, H. Performance of a chemically amplified positive resist for next-generation photomask fabrication. Proc. SPIE 1998, 3412, 279-291. 

Items Photomask Fabrication Direct Wafer-writing... 

Chromium is the most widely sputtered material for photomask fabrication. It sputters easily and it adheres well to glass. This high level of adhesion can be attributed to its alfility to form a metal suboxide interface layer oti glass. The exposed surface of the chromium is often oxidized to reduce... 

The market for fused siUca started ia 1906 with the sale of siUca muffles and pipes. That same year resulted ia the iacorporatioa of the Thermal Syadicate Ltd. Siace that time, worldwide sale of vitreous siUca material and fabricated products has continued to grow. The sales of vitreous siUca iagots, tubes, rods, plates, fabricated products, photomask blanks, cmcibles, and optics was estimated to be between 800 million to 1 biUion ia 1995. These figures do aot, however, take iato accouat the optical waveguide market based oa fused siUca technology. 

The process of lithographic patterning determines the geometric features specified by the layout and patterning as the integrated circuit is fabricated layer by layer. A photomask, containing pattern information in... 

Arrayed microlenses are widely used in a variety of applications that involve miniaturized optical components.172 For example, they can be found at the heart of optical communication systems, facsimile machines, laser printers, and many other kinds of digital information storage or processing devices. In all these applications, the arrayed microlenses simply serve as diode laser correctors, fiber-optic couplers or connectors, and optical scanners. In a set of recent publications, Whitesides and coworkers have also demonstrated that arrayed microlenses could be used as a new platform for photolithography, through which submicrometer-sized structures could be conveniently fabricated as patterned arrays by reducing mm to cm scale features on a photomask.157... 

FIGURE 2.3 Sequence for fabrication of the glass microfluidic chip, (a) Cr and Au masked glass plate coated with photoresist (b) sample exposed to UV light through a photomask (c) photoresist developed (d) exposed metal mask etched (e) exposed glass etched (f) resist and metal stripped (g) glass cover plate bonded to form sealed capillary [102]. Reprinted with permission from American Chemical Society. 

FIGURE 2.14 Electron micrograph of a turn in the channel fabricated in a PDMS chip, created by casting the polymer against a positive relief, which is made of photoresist patterned on a glass substrate. The roughness in the side wall arises from the limited resolution of the transparency used as a photomask in photolithography [1033]. Reprinted with permission from the American Chemical Society. 

Liquid-phase photopolymerization was used to fabricate plastic chips [218, 219]. To create a microchannel, a UV photomask was used so that the masked channel areas were prevented from polymerization, while the exposed areas were photopo-lymerized. Subsequent suction and flushing removed the unexposed monomer mixtures [218]. 

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