Automated handling of wafers
Robots moving components from A to B may sound like a routine procedure. It is a very different matter, however, when they are handling silicon wafers in the back end area, since at this stage, a single disk can be worth several thousand euros. SÜSS MicroTec has opted for the high-precision Stäubli TX60L CR (Cleanroom) robot to ensure ultra-safe handling of this precious cargo.
Asia effectively has a stranglehold on the semiconductor market, yet the SÜSS MicroTec Group is able to compete on the same level where wafer processing is concerned. One of the companies in the group is SÜSS MicroTec Lithography GmbH which, as the name suggests, specializes in the use of lithography for the processing of wafers in the back-end area and offers a comprehensive product range of coaters and developers.
Their complete mastery of the processes as well as the fast, precise and reliable handling of the wafers with negligible breakage rates in the ppm range are arguments that have persuaded customers all around the world. Another reason for their competitiveness in the Asian market is flexibility. The German specialist equipment manufacturer has an exceptionally high level of expertise with regard to customer-specific plant adaptation, whereas the focus of its Asian competitors is primarily on the construction of off-the-shelf systems.
Innovative coater and developer systems with robot handling
Even in standard configuration, the systems are designed to be highly flexible, as exemplified by the ACS 300 Gen2 modular coating and development cluster. The system can be used without mechanical modification for the processing of 200 mm and 300 mm wafers. The main application areas are in sophisticated coating processes, in wafer level packaging applications and in 3D integration. All handling tasks within the plant are carried out by the high-precision Stäubli cleanroom robot TX60L CR. In the back-end area, cleanroom specifications range from ISO 3 to ISO 4 and are easily fulfilled by the cleanroom version of the TX60L.
The SÜSS MicroTec systems are subject to very high demands in terms of reliability, repeatability, up-time and safe handling, because approximately 90 percent of the production steps have already been completed by this stage. It would therefore be catastrophic if one of the very expensive wafers were to break.
Compared to the three-link robots that are prevalent in the industry and which have freedom of movement in only three planes, the Stäubli six-axis is far more flexible. The TX60L in particular with its long arm is able to reach considerably further. The larger workspace allows a much more flexible arrangement of the modules within the system. In addition, the TX60L has higher placement accuracy and superior repeatability by comparison with three-link systems, which is a decisive criterion in wafer edge bead removal.
Maximum precision for maximum reliability
The robot has to be ultra-precise when placing wafers in the process modules. With the high-precision Stäubli TX60L, the stated goal of achieving an absolute placement accuracy of ± 50 microns in the modules has been realized. This is due in no small part to the patented JCM drive technology of the Stäubli robot.
The high path accuracy of the robot is also a major benefit when picking and inserting wafers. Without the slightest hint of a tremble, the robot handles the costly wafers with exemplary reliability. Wafer breakage is consequently unheard of. Cycle times for the system vary considerably depending on the task in hand. Module times are the limiting elements for certain sequences, while for other tasks, it is the cycle time of the robot itself that is the determining factor. In both cases, the plant benefits from the ultra-fast cycle times of the Stäubli industrial robot which works with the utmost precision despite high acceleration forces, safely avoiding damage to the wafer.
The fact that only 6-axis robots produced by Stäubli are now used in the innovative ACS300 Gen2 clusters built by SÜSS is no coincidence. The selection procedure involved close scrutiny of alternatives on the market. But in the quest for the optimum combination of range, speed, accuracy, and reliable handling; only the best robot for this application was ever going to secure approval.