Researcher in the Spotlight: Clarisse Pétua Bosman Barros
My goal is to demonstrate the feasibility of high-speed sub-nanometer accuracy positioning systems using piezo-electric actuators.
I’m Clarisse Pétua Bosman Barros and I’m working in the Control Systems group of the Department of Electrical Engineering. The goal of my project is to demonstrate the feasibility of high-speed sub-nanometer accuracy positioning systems using piezo-electric actuators. Direct applications include lithographic machines and electron-beam metrology systems, but roadmaps like printing, advanced instrumentation, healthcare, smart industry and high-tech materials can also benefit.
Regarding the lithographic systems, the feasibility demonstrations followed by the construction of this new type of positioning systems should allow the production of smaller chips with more efficiency and lower power consumption, reducing the production costs and making electronics even more accessible to the general public. Additionally, smaller electronics are generally faster because the signals do not have to travel as far within the device. Greater density means the possibility of integrating more functionalities into same-sized devices.
The reasons for using piezo-electric materials in these challenging applications are their effectively infinite resolution, excellent operating bandwidth, generation of large mechanical forces for small amounts of power in compact designs, capability of operating at cryogenic temperatures, compatibility with vacuum and clean room environments, and lack of magnetic fields.
The piezo-electric effect
First, the piezo-electric actuator is investigated and modeled. Piezo-electric materials can convert mechanical energy into electric energy and vice-versa: the direct and the inverse (or converse) piezo-electric effect. The first is the conversion from mechanical to electric energy due to mechanical pressure and the second is the conversion from electric to mechanical energy due to the application of an electric field. These effects form a basis for piezo-electric sensors and actuators, simultaneously. Secondly, the optical lithography application is investigated and its main limitations and specifications are defined. Lithography machines are used by the semiconductor industry to fabricate chips and to provide accuracy in the order of one nanometer (10-9 m). Finally, the control architecture is explored – the types of sensors and their locations, the quantity and locations of the actuators and the amplifier specifications. In parallel, different methodologies for controller design are analyzed and tested.
An extra level of accuracy
For optical lithography and e-beam metrology applications, high-accuracy motion stages are equipped with a dual-stage actuator. A long-range mover, which may contain multiple linear motors or have a planar architecture, is able to move the stage over a relatively large range of 500 mm with an accuracy of 10 mm. To improve accuracy at the nanometer level, a short stroke stage is added. When using a piezo short-range actuator, the high inherent stiffness creates a dynamic coupling between long-range and short-range stages, causing the long-range stage vibrations to directly act on the short-range system. To compensate for these vibrations, new control techniques are required.
Given the complexity of a test set-up, there are no experimental results yet. The first experiments are expected in the first semester of 2020. We already have a one-dimensional model of the system, initial analysis of the possible control architectures and potential controller tuning methods, but the focus is on addressing the coupling and vibration problem. The idea is to demonstrate what can be achieved when considering only one degree of freedom with linear behavior and testing this in the real set-up.
The importance of collaboration
Feasibility demonstrations should allow the production of smaller chips with more efficiency and lower power consumption, reducing the production costs and making electronics even more accessible to the general public. Additionally, smaller electronics are generally faster because the signals do not have to travel as far within the device. Greater density means the possibility of integrating more functionalities into same-sized devices.
The work in this project is carried out by PhD students in various groups at Eindhoven University of Technology. High Tech Systems Center and ASML were the initiators of this project, which has since been incorporated as a founding venture of the Eindhoven Engine. Co-location is one of the Engine’s guiding principles: once a week, all of the PhD students are based in a joint project room at the TU/e campus’ Multimedia Paviljoen building, where they present their main results and challenges and discuss similar challenges and solutions from the other areas. Given the complexity of the objective, this kind of strong collaboration is considered key to success.