Mask inspection

About: Mask inspection is a research topic. Over the lifetime, 1072 publications have been published within this topic receiving 8696 citations.

Defect inspection strategy of LEEPL masks

Abstract: The process of inspection and repair for LEEPL masks is increasingly required. A stencil mask inspection system EBScanner (Tokyo Seimitsu), using transmission electron beam, was investigated defect inspection capability on LEEPL masks. We fabricated a defect standard mask (DSM) in which programmed defects were formed, to estimate the performance of the inspection system. We performed experiments on printability of the DSM and Area MEEF (Mask Error Enhancement Factor) of LEEPL. As a result, correlation between area of pattern on mask and that on wafer is excellent, and Area MEEF is 1.19. The killer defect was defined based on the printing result on wafer. The defect size is measured by pattern shape analysis tool MaskEXPRESS (Toppan Printing). We checked the detection rate of killer defects and the number of false or real defects other than programmed defects by optimizing sensitivity of EBScanner. In case that a lot of false defect and very small defect (not crucial) are detected due to the non-uniformity of the pattern size, it takes too much time for defect review and practical classification. For reducing this work, we studied some solutions. And thus, we will discuss the analysis of EBScanner’s inspection image, including the defect classification.

Through-pellicle imaging of extreme ultraviolet mask with extreme ultraviolet ptychography microscope

Abstract: Background: An extreme ultraviolet (EUV) pellicle is necessary to increase the process yield even though the declining throughput is a big concern. However, an EUV metrology/inspection tool for this pellicle has not been commercialized yet. Aim: The goal of this study is to verify the pellicle/mask inspection feasibility of EUV scanning lensless imaging (ESLI) and verify the impact of contaminants on pellicles depending on their size. Approach: Through-pellicle imaging was implemented by using ESLI, which uses a high-order harmonic generation EUV source and ptychography. Optical characteristics of various sizes of Fe-contaminated EUV pellicles were evaluated to verify their impact on wafer images. Results: Large size (∼10 μm) contaminants on the pellicle were found to contribute to the final wafer pattern loss. However, small size (2 to 3 μm) contaminants on the pellicle do not have substantial impact on the wafer image. Conclusions: The defect detection capability of ESLI for pellicle and mask was confirmed. Therefore, ESLI is useful in applications like pellicle qualification and EUV mask inspection metrology.

A new high-resolution photomask inspection system for contamination detection

Abstract: STARlight2+ TM (SL2+) is a new high-resolution contamination inspection system based upon the KLA-Tencor TerascanHR platform. Building upon the proven technology of STARlight TM (SL2), SL2+ uses transmitted and reflected images to detect potentially yield-limiting contamination defects on photomasks for wafer fabs and mask shops. It extends the contamination inspection capability to the 32nm logic/45nm Half Pitch (HP) technology nodes using the newly developed 72nm pixel image resolution as well as a significantly improved rendering model in the algorithm. In this paper, we present inspection results on a wide variety of photomasks, spanning the 32nm to 110nm technology nodes, in the recently concluded period of Alpha tests on the SL2+ system. The test results show that the sensitivity and the inspection capability of the new SL2+ system have been greatly improved. Such improvement enables wafer fabs and mask shops to inspect and qualify photomasks for 32nm node development and 45nm node production.

Photomask inspection method including separated steps of inspecting, reviewing and repairing patterns, and systems and reviewing system for using the same

Abstract: A photomask inspection method in which pattern inspection, a pattern checking and a pattern correction are separately performed is provided to improve productivity of a photomask by separately performing processes for inspecting, checking and correcting the pattern of a photomask. A photomask having an optical pattern on its one surface is fabricated(S10). The photomask is inspected by a first resolution in a photomask pattern inspecting system with the first resolution to extract the coordinates of the pattern defects of the photomask. The coordinates of the extracted defects are converted into coordinates data(S30). The coordinates data is transferred to a photomask pattern checking system with a second resolution better than the first resolution. In the photomask pattern checking system, the extracted defects are displayed on a monitor by the second resolution. The defects displayed on the monitor are classified according to their types(S40). Among the classified defects, defects that need to be corrected are converted into correction data. The correction data is transferred to a photomask pattern correcting system. The defects are corrected according to the correction data in the photomask pattern correcting system(S50). The corrected defects are checked in the photomask pattern checking system(S60). The photomask whose defects are corrected are finally inspected(S90).