Journal of Micro-nanolithography Mems and Moems 

About: Journal of Micro-nanolithography Mems and Moems is an academic journal. The journal publishes majorly in the area(s): Lithography & Extreme ultraviolet lithography. It has an ISSN identifier of 1932-5150. Over the lifetime, 1578 publications have been published receiving 16302 citations.

Optimum mask and source patterns to print a given shape

Abstract: New degrees of freedom can be optimized in mask shapes when the source is also adjustable, because required image symmetries can be provided by the source rather than the collected wave front. The optimized mask will often consist of novel sets of shapes that are quite different in layout from the target integrated circuit patterns. This implies that the optimization algorithm should have good global convergence properties, since the target patterns may not be a suitable starting solution. We have developed an algorithm that can optimize mask and source without using a starting design. Examples are shown where the process window obtained is between two and six times larger than that achieved with standard reticle enhancement techniques (RET). The optimized masks require phase shift, but no trim mask is used. Thus far we can only optimize two-dimensional patterns over small fields (periodicities of ;1 mm or less), though patterns in two separate fields can be jointly optimized for maximum common window under a single source. We also discuss mask optimization with fixed source, source optimization with fixed mask, and the retargeting of designs in different mask regions to provide a common exposure level.

Optical properties of Teflon ® AF amorphous fluoropolymers

Abstract: The optical properties of three grades of Teflon ® AF— AF1300, AF1601, and AF2400—were investigated using a J.A. Woollam VUV-VASE spectroscopic ellipsometry system. The refractive indices for each grade were obtained from multiple measurements with different film thicknesses on Si substrates. The absorbances of Teflon ® AF films were determined by measuring the transmission intensity of Teflon ® AF films on CaF2 substrates. In addition to the refractive index and absorbance per cm base 10, the extinction coefficient k, and absorption coefficient per cm base e, Urbach parameters of absorption edge position and edge width, and two-pole Sellmeier parameters were determined for the three grades of Teflon ® AF. We found that the optical properties of the three grades of Teflon ® AF varied systematically with the AF TFE/PDD composition. The indices of refraction, extinction coefficient k, absorp- tion coefficient , and absorbance A increased, as did the TFE con- tent, while the PDD content decreased. In addition, the Urbach edge position moved to a longer wavelength, and the Urbach edge width became wider. © 2008 Society of Photo-Optical Instrumentation Engineers.

Source optimization for image fidelity and throughput

Abstract: A system and method for optimizing an illumination source to print a desired pattern of features dividing a light source into pixels and determining an optimum intensity for each pixel such that when the pixels are simultaneously illuminated, the error in a printed pattern of features is minimized. In one embodiment, pixel solutions are constrained from solutions that are bright, continuous, and smooth. In another embodiment, the light source optimization and resolution enhancement technique(s) are iteratively performed to minimize errors in a printed pattern of features.

True process variation aware optical proximity correction with variational lithography modeling and model calibration

Abstract: Optical proximity correction (OPC) is one of the most widely used resolution enhancement techniques (RET) in nanometer designs to improve subwavelength printability. Conventional model-based OPC assumes nominal process conditions without considering process variations because of the lack of variational lithography models. A simple method to improve OPC results under process variations is to sample multiple process conditions across the process window, which requires long run times. We derive a variational lithography model (VLIM) that can simulate across the process window without much run-time overhead compared to the conventional lithography models. To match the model to experimental data, we demonstrate a VLIM calibration method. The calibrated model has accuracy comparable to nonvariational models, but has the advantage of taking process variations into consideration. We introduce the variational edge placement error (VEPE) metrics based on the model, a natural extension to the edge placement error (EPE) used in conventional OPC algorithms. A true process-variation aware OPC (PVOPC) framework is proposed used the VEPE metric. Due to the analytical nature of VLIM, our PVOPC is only about 2 to 3× slower than the conventional OPC, but it explicitly considers the two main sources of process variations (exposure dose and focus variations) during OPC. Thus our post-PVOPC results are much more robust than the conventional OPC ones, in terms of both geometric printability and electrical characterization under process variations.

The k3 coefficient in non-paraxial (lambda)/NA scaling equations for resolution, depth of focus, and immersion lithography

Abstract: The Rayleigh's equations for resolution and depth of focus(DOF) have been the two pillars of optical lithography, defining the dependency of resolution and DOF to wavelength and to the numerical aperture (NA) of the imaging system. Scaling of resolution and DOF as well as determination of k 1 and k 2 have been depending on these two equations. However, the equation for DOF is a paraxial approximation. Rigorously solving the optical path difference as a function of wavelength and NA produces a DOF depending on the inverse of the square of the numerical half aperture instead of the numerical full aperture. Using this new DOF scaling equation and a new coefficient of DOF k 3 , the previously determined DOF have been shown to be overestimated by 10%-20% at NA of 0.6 and 0.8, respectively. The equation for resolution does not suffer from paraxial approximation but both new equations remove an ambiguity when the refractive index in the imaging medium is larger than unity. Application to immersion lithography using these equations is included.