Vision enabled mobile robot revolutionises semiconductor manufacturing

Using robotics, individual production steps can be automated very well and to a high-quality standard. However, up until now, robotics have not been used to transporting semiconductor substrates (wafers) from one workstation to the next. Ideally, semi-conductor manufacturers would prefer end-to-end automation, because pristine cleanroom conditions can be much better achieved with ‘unmanned production’. Until now, however, this aspect of the process was untenable due to the lack of precision with which mobile robots move and grasp.

Kuka has now developed the world's first single-source solution for the automated transport and handling of semiconductor cassettes: the ‘Semi Mobility Solution’. In this instance, a lightweight robot from Kuka’s LBR iiwa series is mounted on a KMR 200 CR autonomous automated guided vehicle (AGV). The AGV can manoeuvre in the smallest of spaces and KUKA's engineers have developed a sophisticated gripper system for the handling.

The Semi Mobility Solution goes to a handover point where wafer transport boxes are located. When the AGV has reached its destination, the robot arm is in place to precisely determine its position with the help of an integrated image processing sensor and performs a fine calibration.

This moves the robot into the position to grasp the transport box with a high degree of accuracy and deposit the sensitive wafers without any vibrations in a storage space on the AGV platform. Using this approach, the robot can pick up and transport two different sizes of boxes for wafers with a diameter of 200 or 300 mm. Once it has reached its destination, the robot puts down the transport boxes on the respective processing line.

The Semi Mobility Solution moves around the room on the basis of stored destinations but chooses the route there itself. The navigational capacity of the LBR iiwa platform enables it to move autonomously in a safe and sensitive way. Environment tracking is supported by laser scanners. They perceive the environment in real time, thus preventing collisions.

The safety-oriented environment recognition also creates the preconditions for being able to use the platform as a cobot (collaborative robot) without a safety fence near the operators. The gripping process itself is guided by image processing. Extremely high precision and reliability are essential in this process, because the wafers are sensitive. Vibrations must be avoided.

When selecting the image processing system to guide the robot, Kuka’s developers chose Cognex’s In-Sight 2000 sensors. These sensors combine the performance of image processing systems with the ease and low cost of an industrial sensor. They also offer maximum flexibility when mounting in space-constrained environments. This attribute was highly desired in this application because the IP sensor travels on the robot arm. Minimizing wiring requirements was also a key criterion and the In-Sight 2000 provided easy integration via Ethernet and PoE connections, which was another factor behind the decision.

In addition, Kuka’s engineers appreciate the fact that with In-Sight 2000 the logic circuit is integrated into the device and the image processing quite simply lets itself be taught. Ralf Ziegler, business development manager for electronics at Kuka, said: “The extensive communication possibilities that the sensor offers, its ‘built-in’ intelligence and the good programmability are also advantageous.”

The In-Sight 2000’s patent-pending integrated LED lighting provides uniform illumination over the whole image, regardless of the prevailing lighting conditions. This is particularly important in mobile applications because there is not the same lighting everywhere and even the time of day or the season can affect the image quality.

In practice, the Semi Mobility Solution first drives the robot gripper up to the transport box. At this point, the image processing is activated. It recognises the offset from the destination point stored in the control system and on this basis references the position of the gripper, which can subsequently grasp the respective transport box with the required high degree of millimetric precision. An integrated calibration function guarantees consistently accurate positioning.

Kuka has already delivered the first Semi Mobility Solutions to international semiconductor manufacturers. The mobile robots work under cleanroom conditions and are certified in accordance with ISO Class 3 (IPA), UL 1740 and UL 1998. They can also be used in a fleet and using Cognex’s state-of-the-are image processing grasp the boxes with the highly sensitive wafers both reliably and accurately. This innovative solution marks an important automation step in the microprocessor production chain.