Die-to-die reticle inspections are among the simplest and most sensitive reticle inspections because of the use of an identical-design neighboring-die for the reference image. However, this inspection mode can have two key disadvantages: (1) The location of the defect is indeterminate because it is unclear to the inspector whether the test or reference image is defective; and (2) nuisance and false defects from mask manufacturing noise and tool optical variation can limit the usable sensitivity. The use of a new sequencing approach for a die-to-die inspection can resolve these issues without any additional scan time, without sacrifice in sensitivity requirement, and with a manageable increase in computation load.
In this paper we explore another approach for die-to-die inspections using a new method of defect processing and sequencing. Utilizing die-to-die double arbitration during defect detection has been proven through extensive testing to generate accurate placement of the defect in the correct die to ensure efficient defect disposition at the AIMS step. The use of this method maintained the required inspection sensitivity for mask quality as verified with programmed-defectmask qualification and then further validated with production masks comparing the current inspection approach to the new method. Furthermore, this approach can significantly reduce the total number of defects that need to be reviewed by essentially eliminating the nuisance and false defects that can result from a die-to-die inspection. This "double-win" will significantly reduce the effort in classifying a die-to-die inspection result and will lead to improved cycle times.
Data and simulation results characterizing the capability of a DUV system to inspect EUV mask blanks and substrates
are reported. Phase defects and particles on multilayer (ML) surfaces, ARC-coated absorber, and substrate material are
considered. Phase defects on a quartz substrate surface are shown. The principle of phase detection is described.
Results demonstrating the Teron 600's readiness for meeting 32nm hp requirements for bump / pit phase defect detection
are shown. Simulations show that the 22-nm node requirement for phase defect detection should be met, assuming a
reduction in the multilayer roughness. Preliminary data on the sensitivity of SiO2 sphere detection on ML and quartz are
reported. Simulation results show relative sensitivities for detecting SiO2 spheres of different diameters on various EUV
materials.
KEYWORDS: Inspection, Extreme ultraviolet, Optical spheres, Particles, Quartz, Photomasks, Silica, Deep ultraviolet, Defect detection, Signal to noise ratio
Data and simulation results characterizing the capability of a DUV system to inspect EUV mask blanks and substrates
are reported. Phase defects and particles on multilayer (ML) surfaces, ARC-coated absorber, and substrate material are
considered. In addition to the previously reported results of inspecting phase defects on multilayer surfaces, phase
defects on a quartz substrate surface are shown. The principle of phase detection is described. Simulations show that the
22-nm node requirement for phase defect detection should be met, assuming a reduction in the multilayer roughness.
Initial inspections of deposited SiO2 spheres show sensitivities of at least 40 nm on ML and quartz; however, the
availability of calibrated spheres of smaller diameters has limited testing below this value. Simulation results show
relative sensitivities for detecting SiO2 spheres of different diameters on various EUV materials.
Programmed defect test masks serve the useful purpose of evaluating inspection system sensitivity and capability. It is
widely recognized that when evaluating inspection system capability, it is important to understand the actual sensitivity
of the inspection system in production; yet unfortunately we have observed that many test masks are a more accurate
judge of theoretical sensitivity rather than real-world usable capability. Use of ineffective test masks leave the purchaser
of inspection equipment open to the risks of over-estimating the capability of their inspection solution and overspecifying
defect sensitivity to their customers. This can result in catastrophic yield loss for device makers. In this paper
we examine some of the lithography-related technology advances which place an increasing burden on mask inspection
complexity, such as MEEF, defect printability estimation, aggressive OPC, double patterning, and OPC jogs. We
evaluate the key inspection system component contributors to successful mask inspection, including what can "go
wrong" with these components. We designed and fabricated a test mask which both (a) more faithfully represents actual
production use cases; and (b) stresses the key components of the inspection system. This mask's patterns represent
32nm, 36nm, and 45nm logic and memory technology including metal and poly like background patterns with
programmed defects.
This test mask takes into consideration requirements of advanced lithography, such as MEEF, defect printability, assist
features, nearly-repetitive patterns, and data preparation. This mask uses patterns representative of 32nm, 36nm, and
45nm logic, flash, and DRAM technology. It is specifically designed to have metal and poly like background patterns
with programmed defects. The mask is complex tritone and was designed for annular immersion lithography.
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