As transistor dimensions shrinks, the requirement for wafer critical dimensions control is becoming increasingly
challenging. The intra-field critical dimension uniformity (CDU) of the features on the reticle is one of the many
sources of wafer CD variation. In this paper, we study how the CDU on the reticle can be obtained by using the
intensity information collected during reticle inspection (iCDUTM) on the KLA-Tencor TeraScan reticle inspection
tool. The collected CDU information of the reticle is then applied as an intra-field dose correction function to
improve wafer intra-field CD uniformity.
Using this method of extracting the reticle CDU from the intensity information allows for simple integration into a
high-volume production environment and an improved capability for intra-field CDU correction without the need to
expose any wafers for CD measurement nor any GDS design information. The ability to apply iCDU on prototype
devices on first pass run can also accelerate device development.
In advanced IC manufacturing reticle contamination through crystal growth causing printed defects¹ is a major source of yield
loss. This crystal growth requires frequent inspection to ensure reticles are free from such contamination (reticle requalification).
STARlight is the industry accepted method for mask inspection in wafer fabs for reticle re-qualification (requal)
². The principal focus of this paper is a study correlating the detection of contamination (crystal growth) on logic product
masks found with STARlight to defects that can be found on a print-check wafer (a photo-resist test wafer). A critical
component in this study was the translation of reticle coordinates to wafer coordinates and integrating the results between
high-resolution broadband DUV BrightField inspection (BF) and scanning electron microscope (SEM) review. All of the
STARlight defect locations were reviewed using the SEM regardless if the defect was found on opaque or on clear surfaces of
the mask. As such defects being SEM reviewed were classified as either 'printing', 'early-warning' or 'non-printing'. BF defect
inspection results after repeater analysis were compared with STARlight results to determine the correlations. SEM Defect
Review was performed on STARlight inspection results and the resulting classified data was correlated to the BF defect
inspection results.
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