Bernhard Liegl's scientific contributions

Publications (8)

Article
This work describes the implementation and performance of AGILE focus corrections for advanced photo lithography in volume production as well as advanced development in IBM's 300mm facility. In particular, a logic hierarchy that manages the air gage sub-system corrections to optimize tool productivity while sampling with sufficient frequency to ens...
Article
More sophisticated corrections of overlay error are required because of the challenge caused by technology scaling faster than fundamental tool improvements. Starting at the 45 nm node, the gap between the matchedmachine- overlay error (MMO) and technology requirement has decreased to the point where additional overlay correction methods are needed...
Article
The ever shrinking lithography process window requires us to maximize our process window and minimize tool-induced process variation, and also to quantify the disturbances to an imaging process caused upstream of the imaging step. Relevant factors include across-wafer and wafer-to-wafer film thickness variation, wafer flatness, wafer edge effects,...
Article
Full-text available
Depth of Focus (DOF) and exposure latitude requirements have long been ambiguous. Techniques range from scaling values from previous generations to summing individual components from the scanner. Even more ambiguous is what critical dimension (CD) variation can be allowed to originate from dose and focus variation. In this paper we discuss a compre...
Article
Full-text available
As the Rayleigh equations already tell us, improvements in imaging resolution often come at the price of a depth-offocus loss. Often we balance the resolution versus DoF dilemma without regard of the imaging layers location in the overall film stack. E.g. often several via or metal layers are processed with the same optical settings despite facing...
Article
Our case study experimentally gauges the defocus component induced by a step in the exposure field substrate, with the edge of the step aligned parallel to the scanning slit. Such steps frequently occur at the border of different chiplets or process monitors within one exposure field. A common assumption is that a step-and-scan imaging system can c...
Article
Two full-chip OPC approaches, a traditional rule-based approach and a more recent model-based approach are compared on DRAM applications using both ArF and KrF lithography, with off-axis illumination and phase shift masks. The similarities and differences between these two OPC approaches are compared in detail with selected one- and two-dimensional...
Article
The continued downscaling of semiconductor fabrication ground rule has imposed increasingly tighter overlay tolerances, which becomes very challenging at the 100 nm lithographic node. Such tight tolerances will require very high performance in alignment. Past experiences indicate that good alignment depends largely on alignment signal quality, whic...

Citations

... La problématique de la topologie du wafer n'est pas récente [49] Pour s'assurer que la mesure donne une valeur correcte de la topographie du wafer, un second capteur pneumatique (non impacté par ces effets), nommé AGILE [52] pour « Air Gauge Improved Leveling » (ou mise à niveau améliorée par capteur pneumatique), a été installé dans les scanners de lithographie ASML. AGILE mesure une différence de pression entre deux jets d'air : une référence et le capteur. ...
... Since the length of an exposure slit along the scan axis is generally several millimeters in size, there is little benefit of the detection system probing topography with sub-millimeter lateral resolution. This is sufficient for the operation of the exposure tool, but may hide short-range topography and limit our understanding of the wafer topography [2] . Further, we have learned that changes in substrate composition can alter the response of the optical leveling system and be interpreted as apparent false topography (Fig. 2). ...
... Recent research by Yin [101] and Wu [97] has used TEMPEST to simulate the scattering from alignment mark topographies, to discover what are the critical parameters affecting signal contrast and to optimize the topography for performance. ...