Renishao provides customized laser ruler solutions for ASML

Renishao collaborated with ASML to meet a range of strict manufacturing and performance requirements and developed a differential interferometer system for providing direct position feedback in metrology applications. Customized encoder solutions can achieve step wise improvements in speed and throughput.

Modern semiconductor technology relies on precise control of various processes used in integrated circuit production. Semiconductor wafers are inspected after each processing step to detect issues as soon as possible. This detection requires rapid scanning of the entire wafer or mask area to maintain a high level of production throughput.

The moving components of a measuring machine include a wafer motion platform, a detector, and signal optical devices. The motion control system relies on high-quality position encoder feedback to provide excellent positioning accuracy.

In 2018, ASML and Renishao contacted each other regarding the wafer platform design for their next-generation detection system. Due to its multiple degrees of freedom, the stage has complex metrological requirements. ASML designed the hardware specifications of the position encoder based on the RLE20 dual axis laser interferometer encoder.

The RLE20 system is known for its high precision and is a laser position encoder designed specifically for linear position feedback. It consists of a laser unit and a detection head, which interact with a reference mirror and a position measurement mirror. The differential interferometer head is directly installed on the outer wall of the process chamber, which has the characteristics of low cyclic error and high accuracy. Some interface configurations can provide an output resolution of up to 38.6 picometers. The system has multiple configurations to choose from to meet different optical arrangements and applications, including angle measurement. The standard application of encoders is for XY motion control of measuring machines.

ASML has special requirements for its application, and the standard RLE20 system cannot fully meet these requirements. Detailed information on hardware and performance requirements is shared with us in a comprehensive specification document. This project requires a customized laser encoder solution that can be delivered on time before the start of production of the ASML new detection system.

Renishao has established a dedicated project team to ensure that the new laser ruler is ready in a timely manner. In the following months, teams from both companies worked together to develop an achievable product specification to meet stage performance requirements and urgent timelines. This includes several face-to-face group meetings held at Renishaw headquarters in Gloucestershire, UK and ASML headquarters in Feldhofen, Netherlands.

Technical cooperation relies on close working relationships, including disclosure and discussion of commercially sensitive details. According to the confidentiality agreement, we have learned about the novel aspects of motion platform design, and ASML can gain a deeper understanding of the metrological aspects of laser interferometer systems. Through close and transparent collaboration with ASML, we have gained valuable insights into their specific needs and challenges. This enables us to design and deliver encoders that meet their high standards and are seamlessly integrated into their systems.

The Renishao project team began developing and validating solutions that meet ASML performance requirements, and began delivering the first batch of products to ASML in 2019. Having overcome significant technical challenges, our team has adjusted the current RLE20 design and created a new RLE21 encoder.

The development of the RLE21 system involves several key changes. This includes verifying the extended optical angle range, which is crucial for ensuring the signal strength of the laser system within a wider range of angle misalignment. This enables ASML to design more complex motion systems and precisely control each additional degree of freedom of the motion platform. Accurate angle measurement can also be performed; The difference in path length of these beams comes from the optical path difference between two measuring beams at different points of interest on the same reflector, as it is skewed or tilted.

In addition, each RLE21 system comes with a differential interferometer head with an improved beam steering mechanism. These allow for more precise pitch and yaw adjustments during the setup process. This in turn improves the alignment process.

ASML has also gained access to diagnostic software within the RLE21 system. This involves the electronic redesign of laser units and the definition of communication protocols they can use in front-end software. This software has improved system settings and supports remote access to encoder system diagnostics.

A new electronic solution has been developed for plug and play functionality, with improved offset and gain settings. Therefore, the RLD detection head can be paired with any RLE21 laser unit without the need for a system matching process. This has several advantages, including reducing maintenance downtime.

ASML requires additional product testing at our production site to demonstrate that each encoder meets enhanced specifications. To ensure delivery acceptance, further requirements have been jointly developed, including product identification labels, ISO level 4 cleanroom products and packaging compatibility, and transportation packaging. To achieve this goal, we have invested in new equipment and processes. As part of qualification certification and introduction of new suppliers, ASML has implemented a detailed long-term supply agreement, which is a binding RLE21 encoder supply contract.

The RLE21 laser encoder is designed to meet the urgent needs of ASML, address multiple technical challenges, and improve the convenience of grating system installation and setup. This project enables Renishao to develop new manufacturing processes and internal expertise for future ASML specific product collaborations. Many design improvements of the RLE21 grating project are being integrated into future products for our interference laser grating series.

Source: Laser Net