Mask manufacturers are facing major reticle metrology challenges, driving the need for
cost‐effective solutions that provide tighter registration specifications and on‐device
E‐beam mask writers’ local registration error may have a critical impact on the error
contribution of the reticles to wafer overlay, as it is very local and most likely is not
revealed with standard quality control schemes and sampling. The reticle error
signatures are, of course, writing‐strategy‐dependent, but may also be caused by
residual deflector alignment issues, thus leading to a very local but potentially critical
non‐correctable overlay error on the wafer. Since the e‐beam writer strategy does not
differ significantly between ArFi masks and EUV masks, we expect a similar error
signature for both mask types.
We will present data which demonstrates local registration errors that can be correlated
to the writing swathes of state‐of‐the‐art e‐beam writers and multi‐pass strategies,
potentially leading to systematic device registration errors versus design of close to 2nm.
Furthermore, error signatures for local charging and process effects are indicated by
local registration measurements resulting in systematic error, also on the order of 2nm.
A unique measurement methodology, Local Registration Metrology, is presented that
allows for dense sampling of reticle dies to characterize the local e‐beam registration
error. Several thousand sites in a region of interest with length and width of a few
hundred microns are measured. LMS IPRO metrology algorithms enable parallel
registration measurement of all individual sites for fast and accurate metrology. High
throughput allows completion of Local Registration measurement within a few minutes
instead of exceeding a day of measurement time with conventional registration
metrology strategies. This capability enables mask users to add local registration quality
control to ensure the local wafer pattern placement error contribution by a mask is
within the acceptable tolerance.
In addition, based on the results of Local Registration Metrology, e‐beam mask writer
corrections via feed forward can now be developed to significantly reduce local overlay
error on wafer caused by the reticles.
Mask data are presented which demonstrate local registration errors that can be correlated to the writing swathes of stateof-the-art e-beam writers and multi-pass strategies, potentially leading to systematic device registration errors versus design of close to 2nm. Furthermore, error signatures for local charging and process effects are indicated by local registration measurements resulting in systematic error, also on the order of 2nm.
As EUV lithography moves towards high-volume manufacturing, standardized commercial EUV masks are becoming available. The overlay requirements for the technology nodes utilizing EUV lithography are very tight, therefore reliable and accurate reticle registration metrology—on target and especially on-device areas—is of great importance. We report investigations using the latest generation LMS IPRO system for reticle pattern placement measurements on EUV masks. High performance metrology is based on excellent optical imaging capabilities and consideration of the reticle optical properties for EUV mask-specific measurement setup. This enables highaccuracy, model-based measurement on the device. The die-to-database algorithm is optimized with respect to the mask pattern properties of EUV masks. Repeatability and accuracy results are presented. The cost effectiveness of LMS IPRO is demonstrated by comparing results of high-performance and high-throughput modes.
Mask registration data are presented, which demonstrate local errors that can be correlated to writing swathes of state-of-the-art e-beam writers and multi-pass strategies. A unique measurement methodology, Local Registration Metrology, allows for dense sampling of reticle dies to characterize the local e-beam registration error and enables e-beam corrections via feed forward.
SiN-based absorber materials are considered to be the new work horse for cutting-edge patterning using 193-nm
immersion lithography. The high robustness against cleaning procedures and the low susceptibility for haze
makes SiN an ideal material for phase-shift masks. Reliable metrology with high precision, on target as well as
on feature, is enabled by the LMS IPROTM metrology tool. This is achieved by taking into account the optical
properties of the novel materials and utilisation of the high-accuracy die-to-database algorithm. Simulation as
well as actual measurement results are presented. Cost effectiveness of the LMS IPRO is demonstrated by
comparison of high-performance mode results versus high-throughput results, confirming suitable metrology
performance for high-volume manufacturing.
Mask repair is an essential step in the mask manufacturing process as the extension of 193nm technology and the
insertion of EUV are drivers for mask complexity and cost. The ability to repair all types of defects on all mask blank
materials is crucial for the economic success of a mask shop operation. In the future mask repair is facing several
challenges. The mask minimum features sizes are shrinking and require a higher resolution repair tool. At the same time
mask blanks with different new mask materials are introduced to optimize optical performance and long term durability.
For EUV masks new classes of defects like multilayer and phase defects are entering the stage. In order to achieve a high
yield, mask repair has to cover etch and deposition capabilities and must not damage the mask. These challenges require
sophisticated technologies to bring mask repair to the next level. For high end masks ion-beam based and e-based repair
technologies are the obvious choice when it comes to the repair of small features. Both technologies have their pro and
cons. The scope of this paper is to review and compare the performance of ion-beam based mask repair to e-beam based
mask repair. We will analyze the limits of both technologies theoretically and experimentally and show mask repair
related performance data. Based on this data, we will give an outlook to future mask repair tools.
Drilling and surface processing of bone and tooth tissue belongs to standard medical procedures (bores and embeddings
for implants, trepanation etc.). Small circular bores can be generally quickly produced with mechanical drills. However
problems arise at angled drilling, the need to execute drilling procedures without damaging of sensitive soft tissue
structures underneath the bone or the attempt to mill small non-circular cavities in hard tissue with high precision. We
present investigations on laser hard tissue "milling", which can be advantageous for solving these problems.
The processing of bone is done with a CO2 laser (10.6 &mgr;m) with pulse durations of 50 - 100 &mgr;s, combined with a PC-controlled
fast galvanic laser beam scanner and a fine water-spray, which helps keeping the ablation process effective
and without thermal side-effects.
Laser "milling" of non-circular cavities with 1 - 4 mm width and about 10 mm depth can be especially interesting for
dental implantology. In ex-vivo investigations we found conditions for fast laser processing of these cavities without
thermal damage and with minimised tapering. It included the exploration of different filling patterns (concentric rings,
crosshatch, parallel lines, etc.), definition of maximal pulse duration, repetition rate and laser power, and optimal water
spray position. The optimised results give evidence for the applicability of pulsed CO2 lasers for biologically tolerable
effective processing of deep cavities in hard tissue.
Drilling of bone and tooth tissue belongs to recurrent medical procedures (screw- and pin-bores, bores for implant inserting, trepanation etc.). Small round bores can be in general quickly produced with mechanical drills. Problems arise however by angled drilling, by the necessity to fulfill the drilling without damaging of sensitive soft tissue beneath the bone, or by the attempt to mill precisely noncircular small cavities. We present investigations on laser hard tissue "milling", which can be advantageous for solving these problems.
The "milling" is done with a CO2 laser (10.6 &mgr;m) with pulse duration of 50 - 100 &mgr;s, combined with a PC-controlled galvanic beam scanner and with a fine water-spray, which helps to avoid thermal side-effects. The damaging of underlying soft tissue can be prevented through control of the optical or acoustical ablation signal. The ablation of hard tissue is accompanied with a strong glowing, which is absent during the laser beam action on soft tissue. The acoustic signals from the diverse tissue types exhibit distinct differences in the spectral composition. Also computer image analysis could be a useful tool to control the operation.
Laser "milling" of noncircular cavities with 1 - 4 mm width and about 10 mm depth is particularly interesting for dental implantology. In ex-vivo investigations we found conditions for fast laser "milling" of the cavities without thermal damage and with minimal tapering. It included exploration of different filling patterns (concentric rings, crosshatch, parallel lines and their combinations), definition of maximal pulse duration, repetition rate and laser power, optimal position of the spray. The optimized results give evidences for the applicability of the CO2 laser for biologically tolerable "milling" of deep cavities in the hard tissue.