A new life for a 10-year old MueTec2010, CD measurement system: the ultimate precision upgrade, with additional film thickness measurement capability

Abstract:
A 10-year old MueTec2010, white light CD measurement system, installed at DNP Photomask Europe and previously owned by STMicroelectronics, has been upgraded to fulfill the high-end optical CD measurement requirements, and to add the film thickness measurement capability. That is the ultimate upgrade, consisting of two new computers with WINDOWS 2000 operating system, a new 150X measurement objective, a new 16-bit CCD digital camera, a new tube lens for the old Leica Ergoplan microscope, and the NanoStar software with the pattern recognition option. The upgrade yielded an average 45% repeatability improvement for isolated and dense lines and spaces, with 1.2nm average repeatability in a 0.3-10micrometer CD nominal range. Contact holes report an average 50% repeatability improvement, with 2.5nm average repeatability. The improved precision allows a ±2-nm CD calibration and correlation down to 0.4micrometer CD nominal. Overall, the upgraded MueTec2010 shows same or better performance than the already installed Leica LWM250UV CD measurement system, despite the longer illumination wavelength of the former. The improved short and long term repeatability reduced the Gauge R&R figure from 24% to 11% at ±20nm tolerance, which qualifies the system for high-end binary mask down to 0.5micrometer CD nominal. The feasibility to calibrate the system for 248nm Molybdenum Silicide Phase Shifting Masks is currently being investigated. In addition to that, the new measurement algorithms, the capability to take multiple measurements within the FOV, and the pattern recognition capability included in the NanoStar software gave a 75% throughput boost to the fully automated macros for the weekly calibration tests of the laser writing tools, compared to the LWM250UV run time. With little additional hardware and software, the system has also been upgraded to include the film thickness measurement capability for the PSM resist coating process (2nd exposure), without the need for a dedicated, more expensive system. Two years ago, this 10-year old MueTec2010 system was about to be deinstalled. Today, thanks to creative thinking at DNP Photomask Europe and to the enthusiastic and cooperative MueTec approach, it is ready for another 10 years of honored service with up-to-date performance and with the additional film thickness measurement capability. This upgrade has by far exceeded the technical and return-on-investment expectations.