Photomasks

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. 

Photomask SubstratesJorMicrolithographj, Corning Glass Works, Coming, New York, 1980. 

S. S. H. Naqvi, S. M. Caspar, K. C. Hickman, and J. R, McNeil. A Simple Technique for Linewidth Measurement of Gratings on Photomasks. Proc. SPIE. 1261, 495, 1990. K.P. Bishop, S.M. Caspar, L.M. Milner, S.S.H. Naqvi, and J.R, McNeil, rasterization using Scatterometry. Proc. SPIE. 1545, 64, 1991. These papers discusses a simple application of scattering from surhices that are intentionally patterned. 

In practice, the stepper consists of a machine incorporating a light source, a photomask holder and a lens for focusing the pattern on the photoresist layer on the silicon wafer. The pattern is repeated clear across the wafer, step by step, hence the name. The lens system must be of highest quality so that definition of lines and areas remain accurate and do not overlap each other. 

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... 

Sci. in press). In these studies, the PIQ (2.0 ym thick) was used as an underlayer. Thus, the film consisting of the polymer 11 and PIQ prepared on a silicon wafer was exposed to deep UV-light with the use of Canon contact aligner PLA-521 through a photomask for 5 to 6 s (UV intensity 72 mV/cm2 at 254 nm). The resulting film was then developed with a 1 5 mixture of toluene and isopropyl alcohol for 15 s and rinsed with isopropyl alcohol for 15 s. A positive resist pattern was obtained after treatment of the film pattern with 02 RIE under the condition of 0.64 W/cm2 (RF power 7 MHz, 02 pressure 3 mtorr). 

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. 

C The Epoxy Resists. The first negative tone electron beam resist materials with useful sensitivity were based on utilizing the radiation chemistry of the oxirane or epoxy moiety. The most widely used of these materials, COP (Figure 32) is a copolymer of glycidyl methacrylate and ethyl acrylate and was developed at Bell Laboratories (43,44). COP has found wide applicability in the manufacturing of photomasks. The active element... 

Patterned exposure, (twin laser beams for holograms and photomasks for... 

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