Development of 6DoF magnetically levitated stage

A customer needed to make a significant step in machine performance without drastically changing their machine architecture. Philips Engineering Solutions was contacted to assist in the definition of the improved machine concept. This led to the development of a precision motion stage with a scanning accuracy of few nanometer and design proposals of other performance-critical machine parts. After successful delivery, integration and test of the stage, the design was transferred to a series manufacturer.

Introduction

An overseas customer contacted Philips Engineering Solutions to support them in improving the performance of their machines. To serve the future market needs, the stage scanning accuracy should be a few nanometer, which is at least a factor of 10 better than their current systems. To save on development and implementation effort, they wanted to stay close to their current machine architecture.

In a combined effort, several potential improvements were identified and – within the constraints of performance and costs – the best machine improvements were selected.

The Philips Engineering Solutions contribution to the improvements included a 6 Degree of Freedom (DoF) magnetically levitated motion stage including drive electronics, motion control software and system advise on critical parts as the 6 DoF sensor system and vibration isolation systems to allow nm performance.

Approach

After definition of the improvements, the detailed scope and requirements were agreed. Having a well-defined project ensured an efficient design phase. Besides the stage development, also motion control software and drive electronics were included. For motion control, a platform was selected that was already developed at Philips Engineering Solutions and had been successfully applied in past projects. In addition, the passively damped vibration isolation system of the metrology frame, which was a critical element for performance, was also in scope of the project. The customer made the required adaptations to other parts, comprising the process part of the machine, the vacuum system and floor vibration isolation system.

For the stage concept, magnetic levitation was chosen, actuator building blocks with integrated magnetic gravity compensation from earlier developments within Philips Engineering Solutions were adapted to the customer needs (see concept layout in figure 1). Dynamic FEA models were used to predict the stage performance and to give guidance to the design team. Software modules were developed that could interface between the customer-specific hardware and the motion control software. Motion drive electronics were selected to match the requirements and interfaces with customer equipment.

Integration and delivery

After integration, the complete stage was evaluated on all performance aspects in a Philips Engineering Solutions cleanroom, before being shipped to the customer. The successful integration at the customer (performance indicated in figure 2) was combined with training the customer staff on mechanics, motion control software and servo control.

To ensure a smooth transition to the series production manufacturer, Philips Engineering Solutions was involved in the build of the first 3 stages. The first stage was used to validate the design and to verify performance. The second stage was used to train the staff of the series production manufacturer and to guide the customer staff on test and integration. The third stage was integrated and tested by the series manufacturer and customer staff themselves under supervision of Philips Engineering Solutions. Automated test software was integrated in the motion control platform to allow regular performance checks.

Figure 1: 2-stage concept with a 6 DoF magnetically levitated precise stage (stage 2) on top of a coarse stage (stage 1)

Figure 2: Stage performance at customer, showing that both low-frequency performance (MA) and high frequency performance targets (MSD) were met

Result

This development project provided the following results:

• Improvements defined that fit in the existing machine architecture.
• High precision magnetically levitated 6 DoF stage that met the required nm-performance.
• Delivery of dedicated motion control software. This could be done cost efficiently as Philips Engineering Solutions already developed a motion platform.
• Delivery of motion electronics for the full machine.
• Advise on all critical system aspects.
• Series manufacturer trained for supplying more modules.
• Customer staff trained for system tests and quick debugging via automated software environment.
• Satisfied customer.