Design of a setup to measure and adjust the height and tilt of an element of a microcope on the micron scale

Abstract

This report describes the design, build and verification of a setup to measure and adjust the Rx, Ry, and Z coordinates of an element within a microscope at ASML to improve the precision of a microscope. The required tolerance budget for the measurement and adjustment of these coordinates are $\pm 1~mrad$ in Rx and Ry and $0.1~mm$ in Z. The design is done by first finding different solutions for the sensor, the calibration approach and the adjustment. These different solutions are then combined to create different concepts for the setup. Subsequently, these concepts are traded off against each other using different selection criteria. The selected concept uses a lasertriangulator on an X and a Y directed stage that measures the height of a selection of preselected locations on a coplanar reference, which has the desired Rx, Ry, and Z coordinates. This set of data points is then used to make a plane fit from which the Rx, Ry, and Z coordinates of the reference can be retrieved. Subsequently, the same process is used to determine the Rx, Ry and Z coordinates of the element. The required adjustment of the element can then be calculated from the difference between the two sets of coordinates. After a 3D design is made for the setup, the different subsystems of the setup are elaborated and their tolerances are budgeted. To verify the setup, the setup is build in the cleanroom and the different subsystems are tested for their functionality and their performance. These results are then compared with the calculated tolerances. Since most of the tolerances are approximately the same as budgeted and the setup works as expected, it can be concluded that the selected design is suitable. This is however with the exception the tolerance due the stage wobble, which could not be measured as accurately as desired, and with the exception of the tolerance due to the heat generated by the stages, which was unexpected. In the end, recommendations are given on how to improve the setup. From these recommendations, changing the lasertriangulator for a sensor which preforms better on a reflective surface and implementing a solution for the tolerance due to the heat generated by the stages are the most important to alter the setup and make it a production ready design. If a sensor would be implemented that can measure reflective surfaces, the stage wobble, which is the last unknown tolerance contributor, could also be measured after which it can be fully concluded whether the setup works.