Development of a Modular Ellipsometry System

Abstract

This work presents a framework for the development of new hard- and software for ellipsometry. It does this by analysing existing instrumentation to specify the requirements for a modular hardware system and the corresponding control software. By following a rigorous modular approach, the system can be used to implement different types of ellipsometers based on a standard set of components. Improvements and new developments can be accommodated by extending the feature set through well-defined interfaces. The modular design encompasses both hardware and software. Two types of ellipsometers have been implemented: a single-beam phase-modulated ellipsometer, working both in single-wavelength and spectroscopic mode, and an imaging ellipsometer. These instruments are discussed in the first part of the thesis. A comparison of different types of ellipsometers is used to identify common components, which form the basis of the modular architecture. The important aspects of the different instrument configurations are discussed in detail. These include the theory of the signal detection and calibration; the design of the optical path and illumination systems; and the design of the mechanical and electronic hardware. Examples of applications are given in which different configurations of the modular ellipsometer system were used. A key role in the modular ellipsometer is played by a newly developed universal measurement control system, called the Measurement Controller. The architecture of the Measurement Controller's hardware and software is the topic of the second part of the thesis. The system requirements are defined based on an analysis of different measurement and control procedures in computerised laboratory environments. Particular emphasis is placed on the real-time performance of the Measurement Controller. To achieve reliable operation, the real-time and non-real-time parts of the system are implemented separately. A simple, yet efficient real-time scheduling approach is developed and discussed in the context of scheduling theory. The performance of the scheduler is measured and compared to that of real-time operating systems. The modular design of the ellipsometer hardware is reflected in the structure of the Measurement Controller's software. It uses the concept of device drivers to implement configurable hardware control and measurement systems. Details on the object-oriented software implementation of the Measurement Controller are given in the companion volume. The class structures, interfaces, execution sequences, and object collaborations are visualised using the Unified Modeling Language (UML). This documentation shows how the modular software structure is used to control the instrument hardware, and how the software can be extended and developed further.