Lars Johnsen

Next-generation test equipment for micro-production

The paper introduces different approaches to overcome the large ratio between wafer size and feature size in the testing step of micro production. For the inspection of Micro(Opto)ElectroMechanicalSystems (M(O)EMS) a priori information are available to optimise the inspection process. The EU-project SMARTIEHS develops a new concept for high volume M(O)EMS testing. The design of the test station and the fabrication of the first components are presented and the advancements compared to the state of the art are introduced within the following fields: micro-optical interferometer design, micro-optical production, smart-pixel camera and mechanical design. Furthermore the first demonstrators are introduced and experimental results are presented.

Inspection of processes during silicon wafer sawing using low coherence interferometry in the near infrared wavelength region

Multi-wire sawing of silicon wafers is a tribological process. Slurry consisting of small silicon carbide particles embedded in polyethyleneglycol carries out the abrasive material removal process. During this process small silicon chips are removed from the bulk material. Low coherence interferometry (LCI) is widely used for high accuracy surface topography measurements of materials. This paper presents an application of LCI where the surface of a material (silicon) is inspected from the inside. Light in the near infrared (NIR) wavelength region is used. High spatial resolution is necessary to be able to observe the processes on the micro scale. Therefore a modified solid immersion approach is suggested. That makes it possible to reach a spatial resolution in the range of the illumination wavelength. The topography changes produced by the chippings are in the range of some micrometers. To be able to estimate the volumes of the Si chippings interferometric phase measurements are applied.

Practical fiber optic sensor for measuring large mechanical deformations

A fiber-optic sensor for measuring large mechanical deformations based on a digital use of fringes in a polarimeter was developed and tested in the laboratory. Two sensors were mounted on an air cushion catamaran and used for measuring strain in the fiberglass laminates and thereby also the relative movement of the two hulls. The data were logged together with other ship movement data and provided useful information on the craft performance.