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.

Method for repairing glass photomasks

Abstract: A method for repairing defects in the form of discontinuities in a photomask pattern in or on a glass substrate by means of electroless deposition of a nickel-containing coating on the surface of a glass substrate is disclosed.

Processing and modeling optimization for grayscale lithography

Abstract: Grayscale lithography is an extension of the conventional binary lithographic process for realization of arbitrary three-dimensional features in photoresist materials, with applications especially in micro-optics fabrication. The grayscale photomask possesses a spatially varying transmission that modulates the exposure dose received in the photoresist. By using a low contrast photoresist, such as those based on diazonaphthoquinone (DNQ), the material is only partially removed during development in proportion to the local exposure dose received. In this way, an arbitrary surface topography can be sculpted in the photoresist material. It is common practice in grayscale lithography to encode the transmission levels of the photomask by using the photoresist contrast curve to determine the exposure dose required for a given photoresist thickness at each lateral point in the pattern. This technique is adequate when the surface topography is slowly varying and the photoresist film is thin. However, it is inaccurate when these conditions are not met, because the technique essentially represents a one-dimensional approximation to the lithographic process where the isotropy of the development and the diffractive imaging of the photomask are neglected. Currently we are applying grayscale lithography to the fabrication of a fiber-to-waveguide coupler based on the parabolic reflector, where the efficiency of the device is quite sensitive to fabrication errors in the coupler geometry. In this case the thin photoresist and slowly varying topography conditions are not met, and we turn to more comprehensive process models to determine the appropriate transmission levels to encode in the photomask. We demonstrate that the photomask can be optimized, based on simulation of the lithography process, to produce the required three-dimensional photoresist pattern.

Photomask in-plane distortion induced during e-beam patterning

Abstract: As feature sizes decrease and the demand for throughput increases, the semiconductor industry must concentrate on pattern positioning accuracy and process efficiency. Thermomechanical distortions induced in the photomask during fabrication may act to constrain the desired range of operating conditions to meet the manufacturing requirements for pattern placement accuracy and throughput. 3D finite element heat transfer and structural models have been developed to determine the global in-plane distortions induced in the photomask during e-beam patterning. Results obtained from these models show that the thermal-induced distortions, caused by global heating, are significant. Whereas, distortions due to the mechanical loading, caused by resist in situ stress relief, are minimal and can be neglected.

Method of evaluating the exposure property of data to wafer

Abstract: A method of evaluating the exposure property of data to a wafer in which errors in the production of a photomask and the formation of patterns caused by defocus in the transfer of data to the wafer are considered. Accordingly, errors in the production of the photomask and deformation of patterns caused by defocus can be evaluated in the stage of design data. Oversize processing and undersize processing are given to pattern data of the object of the process by figure operation for the whole pattern data within errors of the production of the photomask according to the specification thereof, and simulation is used as a reference to the original pattern data of the object of the process, the oversize data in which oversize processing is given to the pattern data and the undersize data in which undersize processing is given to the pattern data, in which the wafer exposure simulation is carried out under the condition of zero focus, or under each exposure condition of zero focus, a given value minus defocus or a given value plus defocus. The exposure property of data to the wafer is evaluated from the results of the wafer exposure simulation.