A new general approach for solving the self-calibration problem on large area 2D ultra-precision coordinate measurement machines

Abstract

The manufacturing of flat panel displays requires a number of photomasks for the placement of pixel patterns and supporting transistor arrays. For large area photomasks, dedicated ultra-precision writers have been developed for the production of these chromium patterns on glass or quartz plates. The dimensional tolerances in X and Y for absolute pattern placement on these plates, with areas measured in square meters, are in the range of 200–300 nm (3σ). To verify these photomasks, 2D ultra-precision coordinate measurement machines are used having even tighter tolerance requirements. This paper will present how the world standard metrology tool used for verifying large masks, the Micronic Mydata MMS15000, is calibrated without any other references than the wavelength of the interferometers in an extremely well-controlled temperature environment. This process is called self-calibration and is the only way to calibrate the metrology tool, as no square-meter-sized large area 2D traceable artifact is available. The only parameter that cannot be found using self-calibration is the absolute length scale. To make the MMS15000 traceable, a 1D reference rod, calibrated at a national metrology lab, is used. The reference plates used in the calibration of the MMS15000 may have sizes up to 1 m2 and a weight of 50 kg. Therefore, standard methods for self-calibration on a small scale with exact placements cannot be used in the large area case. A new, more general method had to be developed for the purpose of calibrating the MMS15000. Using this method, it is possible to calibrate the measurement tool down to an uncertainty level of <90 nm (3σ) over an area of (0.8 × 0.8) m2. The method used, which is based on the concept of iteration, does not introduce any more noise than the random noise introduced by the measurements, resulting in the lowest possible noise level that can be achieved by any self-calibration method.

A double shift self-calibration method for micro XY stages

“…The proposed result is an analytical solution, which, in the absence of random measurement errors, decompose the measurement results into the plate deviations from the nominal geometry and the systematic stage errors. Several evolutions and inspired approaches have been proposed [8,9,10,11,12,13,14,15,16,17], including approaches dealing with coordinate measuring machines [9,13], rotary stages [14], and XY θ z stages [11].…”

Geometrical Characterisation of a 2D Laser System and Calibration of a Cross-Grid Encoder by Means of a Self-Calibration Methodology

“…The only calibrated pattern required is a 1D-length scale to correct the scale factor of the system to be calibrated [ 9 ]. To address this inconvenience, other authors have proposed a calibrated reference rod [ 16 ]. In the case of this study, the wavelength of the laser beam has already been calibrated by the manufacturer.…”

Precise fabrication of large-area microstructures by digital oblique scanning lithography strategy and stage self-calibration technique

“…As the measurement error is composed of motion stage systematic errors, random measurement errors, marking plate errors and coordinate system errors. 30) Thus, it is very important to isolate the stage systematic error efficiently and compensate it to improve the motion positional accuracy. Here, a 2D self-calibration technique is studied, which can avoid some shortcomings of the existing self-calibration algorithms, 31) such as complex model solving or incomplete model building.…”