The growing complexity of reticles and continual tightening of defect specifications causes the reticle defect disposition
function to become increasingly difficult. No longer can defect specifications be distilled to a single number, nor can
past simple classification rules be employed due to the effects of MEEF on actual printing behavior. The mask maker
now requires lithography-based rules and capabilities for making these go/no-go decisions at the reticle inspection step.
We have evaluated an automated system that predicts the lithographic significance of reticle defects using PROLITHTM
technology. This printability prediction tool was evaluated and tested in a production environment using both standard
test reticles and production samples in an advanced reticle manufacturing environment. Reference measurements on
Zeiss AIMSTM systems were used to assess the accuracy of predicted results.
The application, called the Automated Mask Defect Disposition System, or AMDD, models defective and non-defective
test and reference images generated by a high-resolution inspection system. The results were calculated according to the
wafer exposure conditions given at setup such that the reticle could be judged for its 'fitness-for-use' from a lithographic
standpoint rather than from a simple physical measurement of the film materials.
We present the methods and empirical results comparing 1D and 2D Intensity Difference Metrics (IDMs) with respect to
AIMS and discuss the results of usability and productivity studies as they apply to manufacturing environments.
Repair and printability of 193nm alternating aperture phase shift masks have been studied in detail in an effort to understand the overall production capability of these masks for wafer production at the 100nm node and below.
Many inspection tools generate massive false defects in the presence of radical OPC decorations or sub spec line widths causing system aborts and retries. We have defined the inspectivity (or runability) of a tool as the ability to complete inspections in the presence of challenging geometry, while still maintaining high defect sensitivity. A new UV wavelength multiple beam reticle inspection tool has been designed to dramatically reduce inspection time with improved inspectivity. Comprehensive inspection system capability evaluation should include both sensitivity and runability (i.e., ability to inspect various pattern types and sizes). An integrated reference mask was designed previously in order to quantify runability. The mask contains several typical industry feature types at multiple technology nodes. Detailed sensitivity and runability information for two inspection systems has been analyzed and is presented here. The test results provide direction for future improvements by identifying the strengths and weaknesses of inspection systems and their algorithms. In this study we have compared the sensitivity and runability of the KLA-Tencor 365UV-HR to that of the new TeraSTAR™ multiple beam inspection tool.
In this study, After Develop Inspection was used to inspect Cr photomasks incorporating iP3600 and ZEP7000 resists at several thicknesses. The detected defects were analyzed and compared to defects found after etch. A test mask with programmed defects was also created and tested to characterize the sensitivity of this new capability.
Decreasing feature sizes combined with high mask error enhancement factors (MEEF) are rapidly causing tighter defect and CD uniformity specifications on photomasks. In general, dry etching photomasks improves feature fidelity but also tends to increase defectivity. Since the first automated mask defect inspection usually occurs after chrome etch, it is difficult to determine if a defect originated with the photoblank or during one of the mask patterning steps (write, develop, and etch). To understand and optimize the dry etch process, After Develop Inspection (ADI) has been developed to isolate the cause of photomask defects. In this study, ADI was used to inspect Cr photomasks incorporating iP3600 and ZEP7000 resists at several thicknesses. The detected defects were analyzed and compared to defects found after etch. A test mask with programmed defects was also created and tested to characterize the sensitivity of this new capability.
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