Peter Speckbacher

Qualification of HEIDENHAIN linear encoders for picometer resolution metrology in VTF Etalons

The Visible Tunable Filter (VTF) is a narrowband tunable instrument for imaging spectropolarimetry in the wavelength range between 520 and 870 nm. It is based on large-format Fabry Perots with a free aperture of 250 mm. The instrument will be one of the first-light instruments of the 4 m aperture Daniel K. Inoue Solar Telescope (DKIST) that is currently under construction on Maui (Hawaii). To provide stable and repeatable spectral scanning by tuning the air gap distance of the Etalons, a metrology system with 20 pm resolution and drift stability of better 100 pm per hour is needed. The integration of the metrology system must preserve the tight optical specifications of the Etalon plates. The HEIDENHAIN LIP 382 linear encoder system has a selected linear scale for low noise high signal interpolation. The signal period is 128nm and the interpolated signal from the sensor can be read out at 128 nm/ 14 bit = 7.8125 pm. To qualify the LIP 382 system for the VTF, we investigated the resolution and stability under nominal VTF operation conditions and verified a mounting concept for the sensor heads. We present results that demonstrate that the LIP 382 system fulfills the requirements for the VTF Etalons. We also present a design for the sensor head mounts.

Point spread function and total process function measured for a variable-shaped electron beam system

In the field of electron beam lithography, accurate exposure requires a precise proximity effect correction (PEC). The most common approaches for PEC such as dose modification, shape modification, and hybrid models require the evaluation of the point spread function (PSF) and, in view of real applications, the measurement of the total process function (TPF) considering both tool behavior and process effects. In contrast to research tools equipped with a Gaussian beam column, variable-shaped beam (VSB) systems are established in the commercial field, e.g., for mask fabrication. In this paper, the authors present an approach to measure PSF and TPF on a VSB lithography tool. This method is based on the well known point exposure distribution measurement technique early introduced for Gaussian beam systems by Rishton and Kern [J. Vac. Sci. Technol., B 5, 135 (1987)]. The approach is enhanced by application of specific features provided on a VSB system. The interpretation of the experiment was enabled by a comp...

Development and characterization of new CD mask standards: a status report

We report on the current status of a project on development and characterization of CD photomasks with 6025 format to be used as reference standards for different type of CD metrology instruments. The project consortium consists of mask suppliers, manufacturers of CD metrology instruments, users of such instruments and calibration laboratories. Different type of CD metrology instrumentation, namely optical CD microscopes, CD-SEM, and AFM will be applied for investigation and measurement of microstructures, additionally supported by AIMS tool. We will describe the basic design criteria of the mask standard and first measurement results gained with different metrology tools on the prototype mask standards.