Photomask

About: Photomask is a research topic. Over the lifetime, 7917 publications have been published within this topic receiving 54524 citations. The topic is also known as: photoreticle & reticle.

Systems, masks, and methods for photolithography

Abstract: Photomask patterns are represented using contours defined by mask functions. Given target pattern, contours are optimized such that defined photomask, when used in photolithographic process, prints wafer pattern faithful to target pattern. Optimization utilizes 'merit function' for encoding aspects of photolithographic process, preferences relating to resulting pattern (e.g. restriction to rectilinear patterns), robustness against process variations, as well as restrictions imposed relating to practical and economic manufacturability of photomasks.

Halftone phase shift photomask, halftone phase shift photomask blank, and methods of producing the same

Abstract: A halftone phase shift photomask designed so that it is possible to shorten the photoengraving process, use a production line for a conventional photomask, prevent lowering of the contract between the transparent and semitransparent regions at a long wavelength in the visible region, which is used for inspection and measurement, and also prevent charge-up during electron beam exposure, and that ordinary physical cleaning process can be used for the halftone phase shift photomask. The halftone phase shift photomask has on a transparent substrate (1) a region which is semitransparent to exposure light and a region which is transparent to the exposure light so that the phase difference between light passing through the transparent region and light passing through the semitransparent region is substantially π radians. A semitransparent film that constitutes the semitransparent region is arranged in the form of a multilayer film including layers (3, 4) of chromium or a chromium compound. For example, the layer (3) is formed of chromium oxide, chromium oxide nitride, chromium oxide carbide, or chromium oxide nitride carbide, and the layer (4) is formed of chromium or chromium nitride. The layer (3) mainly serves as a phase shift layer, while the layer (4) mainly serves as a transmittance control layer that suppresses the rise of transmittance at the long wavelength side. The semitransparent film is formed by physical vapor deposition.

Materials issues for optical components and photomasks in 157 nm lithography

Abstract: Photolithography using 157 nm pulsed fluorine lasers has emerged as the leading candidate technology for the post-193-nm generation. Preliminary data have indicated that at 157 nm there are optical materials transparent enough to enable the fabrication of refractive elements, both in the projection and illumination part of the optical train. However, a number of critical issues still remain. Optical materials must show no appreciable degradation with laser irradiation. The availability of transparent photomask substrates must be ascertained. Optical coatings must be developed and qualified. At this short wavelength, interface effects, subsurface damage, and adsorbate effects become increasingly prominent. We present recent experimental results on the durability tests of calcium fluoride, modified fused silica, and optical coatings for 157 nm applications. Our initial assessment of several grades of modified fused silica demonstrates that at least one grade already meets transparency and durability requirements for reticle substrates for 157 nm applications. For both bulk calcium fluoride and antireflectance coatings our tests to date show no degradation for 300 million pulses at fluences up to 3 mJ/cm2/pulse. We do observe degradation of beam steering mirrors in our experimental setup. Detailed damage analysis of these coatings is presented.

Using microcontact printing to generate amplitude photomasks on the surfaces of optical fibers: A method for producing in-fiber gratings

Abstract: This letter describes a method for producing in-fiber gratings that reduces the effects of mechanical and optical instabilities limiting other methods. In this technique, opaque lines formed on the outside of the fiber using a procedure known as microcontact printing, serve as an amplitude photomask for exposure to ultraviolet light. Long-period fiber optic attenuators formed by ths technique demonstrate its advantages.

Diode-based additive manufacturing of metals using an optically-addressable light valve

Abstract: Selective Laser Melting (SLM) of metal powder bed layers, whereby 3D metal objects can be printed from a digital file with unprecedented design flexibility, is spurring manufacturing innovations in medical, automotive, aerospace and textile industries. Because SLM is based on raster-scanning a laser beam over each layer, the process is relatively slow compared to most traditional manufacturing methods (hours to days), thus limiting wider spread use. Here we demonstrate the use of a large area, photolithographic method for 3D metal printing, using an optically-addressable light valve (OALV) as the photomask, to print entire layers of metal powder at once. An optical sheet of multiplexed ~5 kW, 20 ms laser diode and ~1 MW, 7 ns Q-switched laser pulses are used to selectively melt each layer. The patterning of near infrared light is accomplished by imaging 470 nm light onto the transmissive OALV, which consists of polarization-selective nematic liquid crystal sandwiched between a photoconductor and transparent conductor for switching.