Proceedings Article | 28 August 2003
KEYWORDS: Inspection, Reticles, SRAF, Semiconducting wafers, Defect detection, Ultraviolet radiation, Databases, Lithography, 193nm lithography, Defect inspection
The implementation of low k1 193nm lithography for 90nm node IC production brings new challenges to reticle inspection systems. The inspection tools have to deal with new attenuating films, smaller and more complex features, and more aggressive OPC. In addition, low k1 lithography causes the mask error factor (MEEF) to increase, magnifying CD errors. This, in turn, makes reticle defect detection specifications more aggressive. Achieving high sensitivity, low false defect count, for a full plate inspection is a big challenge. Those three (high sensitivity, low false defect count, full plate inspection) are the three “legs” that must support real die-to-database inspection. In order to demonstrate inspection success, all three must be achieved. Without any of them, there is no die-to-database inspection solution. The capabilities described in this paper (the XPE die-to-database algorithm working with the KLA-Tencor TeraStar SLF87 system) were developed precisely because no tool in the industry was capable of meeting all of these requirements. The industry was in urgent need of a die-to-database system that is capable of inspecting reticles for the 90nm node at high sensitivity, with a low false defect count for a full plate inspection. XPE, the new die-to-database inspection algorithm for the TeraStar SLF87 (XPE-87), has been developed for the inspection of 193nm lithography reticles to be used for the 90nm node and beyond. XPE-87 uses new and improved methods for database rendering, defect detection and image contrast adjustment. The algorithm can accommodate the reticle characteritics, inspecting plates with complex features and addvanced Sub-Resolution Assist Features (SRAFs) at high sensitivity and low false defect count. Thanks to enhancements to system hardware and light calibration routines, the algorithm is very effective at inspecting 90 nm node ArF half-tone reticles. XPE-87 has been characterized with 193 nm and 248 nm EPSM versions of Spica, a new programmed defect test reticle. In the presence of complex OPC, results show a substantial improvement in sensitivity compared to previous die-to-database inspection algorithms. The new algorithm has also been used to inspect a variety of 193nmEPSM, 248 EPSM and chrome on glass production reticles. The results show significant improvement for the inspection of 90 nm node half-tone reticles including plates with SRAFs. Simulations were performed to verify the XPE-87 potential for defect detection. Evaluating changes in signal profile due to the presence of defects, a comparison was performed between the aerial profile of the XPE-87 at UV inspection aerial image and the wafer print aerial image at 193 nm. The results, show a larger signal for defects in small lines.
