A Wireless Sensor Network for Machine Dynamics Performance Monitoring

The availability of photolithography machines is key in the semiconductor industry, as downtime generally incurs in immense economic loss. Time to market is also very important for suppliers of photolithography systems, such as ASML. Photolithography machines include numerous measurement systems that are frequently used for qualification and troubleshooting, most of which are required during normal operation. Due to increased costs and complexity, it would not be practical to include dedicated sensors for every machine performance parameter relevant for diagnosis, therefore many parameters regarded as non-critical are not monitored. However, in some cases the information about the behaviour of these parameters can be very valuable to find the root cause of a failure or defect promptly. In these cases, a Wireless Sensor Network (WSN) would allow for a temporary installation of a measurement system to monitor such parameters.This work presents the design of a WSN for monitoring the dynamics performance of the WaferHandler (WH), which is one of the major subsystems of a photolithography machine. The scope of the project includes:• The selection of a radio technology on which the network is based on.• The hardware design of a wireless sensor node for measuring acceleration, based on commercial off-the-shelf (COTS) components.• The identification and firmware implementation of key principles in which the communication protocol should be based on according to the requirements of the application.• The estimation of the power consumption and lifetime of the network.• The design and execution of experiments to assess the reliability of the proposed solution.Among the requirements of the system, the size of the sensor nodes, the network synchronization accuracy, and the maximum power dissipation stand out as the main challenges. As the available space inside the WH is very scarce, the sensor nodes must have a compact form factor to fit in the locations where they are meant to be installed. The reliability of the system is greatly determined by its capacity to remain synchronized with relatively high accuracy during a measurement. This can be difficult to achieve in a harsh environment such as the inside of a machine, where interference and signal fading are expected to recurrently cause the loss of packets used for network synchronization.Packet re-transmission should not be abused to alleviate the problem, as the sensor nodes are required to operate in vacuum and overheating can become a problem