Ability to predict process behavior under defocus has until now relied on explicit calculations, which while accurate, cannot be realistically used in full-chip optical and process correction strategies due to the long run times. In this work, we have applied a vector model for the optics, and a compact model for the resist development process. Simulations with these models are fast enough to be the basis of full-chip OPC. We verify this strategy with an independent set of measurements, and compare it to current lithographic process fitting strategies. The results indicate that by describing optical processes as accurately as possible, the model accuracy improves over a wider range of defocus conditions when compared to the traditional calibration method.As long as the calibration process successfully decouples optical and resist effects, relatively simple resist models deliver excellent accuracy within the noise level of the metrology measurements. Our data are based on onedimensional and two-dimensional results using a 193nm system using 0.75 NA and off axis illumination with 6% attenuated phase shift mask. In all cases, a wide variety of sub-resolution assist feature rules were used in order to further test the ability of the models to predict various optical and resist environments.

A major problem in form reading applications is that form fields can not be located exactly because of nonlinear distortions on the form images. Such nohlinear distortions appear f o r example on photocopied forms or on forms transmitted by fax. One way to solve this problem is to determine the form fields by considering the positions of the form lines. This paper describes a new method to find pairs of corresponding form-lines on a reference form and a filled form. The advantage of this method is that the corresponding line-pairs can be used to map any pixel of the filled form and the reference form without any assumption about the kind of distortion. The core of this method is an algorithm that is based on the A *-search-algorithm. Given two sets of horizontal or vertical lines, one from the reference form and one from the filled form, it is searched for pairs of corresponding lines. The algorithm's runtime keeps low and nonlinear distortions of the form-images hardly influence its results. With increasing complexity -i.e. increasing number of lines or decreasing image quality -the number of rejected form-lines grows, but the error-rate stays low.

Two fundamentally different approaches for chemical ArF resist shrinkage are evaluated and integrated into process flows for 90 nm technology node. The chemical shrin k and the corresponding gain in process window is studied in detail for different resist types with respect to CD uniformity through pitch, linearity and resist profiles. For both, SAFIER and RELACS material, the sensitivity of the shrink process with respect to the baking temperature is characterized by a temperature matrix to check process stability, and optimized conditions are found offering an acceptable amount of shrinkage at contact and trench levels. For the SAFIER material, thermal flow contributes to the chemical shrink which is a function of the photoresist chemistry and its hydrodynamic properties depending on the resists' glass transition temperature (Tg) and the baking temperature: at baking temperatures close to Tg, a proximity and pattern dependent shrink is observed. For a given resist, line-space patterns and contact holes shrink differently, and their resist profiles are affected significantly. Additionally, the chemical shrinkage depends on the size of contact holes and resist profile prior to the application of the SAFIER process. At baking temperatures below Tg some resists exhibit no shrink at all. The RELACS technique offers a constant shrink for contacts at various pitches and sizes. This shrink can be moderately adjusted and controlled by varying the mixing bake temperature which is generally and preferably below the glass transistion temperature of the resist, therefore no resist profile degradation is observed. A manufacturable process with a shrink of 20nm using RELACS at the contact layer is demonstrated. Utilizing an increased reticle bias in combination with an increased CD target prior to the chemical shrink, the common lithography process window at contact layer was increased by 0.15um. The results also indicate a possibility for an extension of the shrink to greater than 50nm for more advanced processes.

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