Ultra-precision geometrical measurement technique based on a statistical random phase clock combined with acoustic-optical deflection

Abstract

Mask writers and large area measurements systems are key systems for production of large liquid crystal displays (LCD) and image devices. With position tolerances in the sub-μm range over square meter sized masks, the metrology challenges are indeed demanding. Most systems used for this type of measurement rely on a microscope camera imaging system, provided with a charge coupled device, a complementary metal-oxide-semiconductor sensor or a time delay and integration sensor to transform the optical image to a digital gray-level image. From this image, processing algorithms are used to extract information such as location of edges. The drawback of this technique is the vast amount of data captured but never used. This paper presents a new approach for ultra-high-precision lateral measurement at nm-levels of chrome/glass patterns separated by centimeters, so called registration marks, on masks used for the LCD manufacturing. Registration specifications demand a positioning accuracy <200 nm and critical dimensions, i.e. chrome line widths, which need to be accurate in the 80 nm range. This accuracy has to be achieved on glass masks of 2.4 × 1.6 m 2 size. Our new measurement method is based on nm-precise lateral scanning of a focused laser beam combined with statistical random phase sampling of the reflected signal. The precise scanning is based on an extremely accurate time measuring device controlling an acousto optic deflector crystal. The method has been successfully applied in measuring the 4 μm pitch of reference gratings at standard deviations σ of 0.5 nm and registration marks separated by several cm at standard deviations of 23 nm.

Towards an European Approach for Characterisation of Multimaterial Micromanufacturing Process Capabilities

“…A number of artefacts have been machined in JRA3.1 and will in early 2011 be analyzed by KTH using high performance metrology systems. [10]. As an example, in the accomplished measurements we have found cases where machine accuracy was off by an order of magnitude.…”

No Evidence That Homologs of Key Circadian Clock Genes Direct Circadian Programs of Development or mRNA Abundance in Verticillium dahliae

“…Indeed, there is little evidence to support circadian gene transcription/expression in gymnosperms (Oberschmidt et al, 1995;Piechulla et al, 2001). Nevertheless, night break experiments indicate that a circadian rather than an hour-glass clock is used in photoperiodism (Clapham et al, 2001;Ekberg et al, 2010;Pokhilko et al, 2012). The second circumstance is in an environment where the absence of a circadian clock reduces the organism's ability to anticipate and respond to a changing environment but this has no adverse effect.…”

Measurement technologies for precision positioning

“…Shown are the measured deviations from a linear regression line (black curve) and a fitted sinusoidal function with a period of 133 nm and an amplitude of 4.8 pm (red curve). Advanced precision 2D measurement systems for 152 mm (6 00 ) photomask metrology [8,56] and for calibration of larger 2D substrates like liquid crystal display (LCD) substrates [40] were described recently. Alternative approaches for calibrations of 2D (masks, ball plates, hole plates) as well as 3D standards use trilateration or multilateration methods, i.e.…”