In this paper, we discuss the lithographic qualification of high transmission (High T) mask for Via and contact hole applications in 10nm node and beyond. First, the simulated MEEF and depth of focus (DoF) data are compared between the 6% and High T attnPSM masks with the transmission of High T mask blank varying from 12% to 20%. The 12% High T blank shows significantly better MEEF and larger DoF than those of 6% attnPSM mask blank, which are consistent with our wafer data. However, the simulations show no obvious advantage in MEEF and DoF when the blank transmittance is larger than 12%. From our wafer data, it has been seen that the common process window from High T mask is 40nm bigger than that from the 6% attnPSM mask. In the elongated bar structure with smaller aspect ratio, 1.26, the 12% High T mask shows significantly less develop CD pull back in the major direction. Compared to the High T mask, the optimized new illumination condition for 6% attnPSM shows limited improvement in MEEF and the DoF through pitch. In addition, by using the High T mask blank, we have also investigated the SRAF printing, side lobe printing and the resist profile through cross sections, and no patterning risk has been found for manufacturing. As part of this work new 12% High T mask blank materials and processes were developed, and a brief overview of key mask technology development results have been shared. Overall, it is concluded that the High T mask, 12% transmission, provides the most robust and extendable lithographic solution for 10nm node and beyond.
In this paper, we demonstrate a new methodology for post-etch OPC modeling to compensate for effects of
underlayer seen on product wafers. Current resist-only OPC models based on data from flopdown wafers
are not always accurate enough to deliver patterning solutions with stringent critical dimension
requirements in 45/32nm technology node. Therefore it is necessary to include an etch model into the OPC
correction. Both litho and etch model were built using flopdown and integrated wafers to compensate for
topography, differential etch due to different underlayer substrate based on local geometry and local
loading. The wafer data based on such OPC keyword show significant decrease of critical dimensions
offsets of device macros from long poly-line nested structures for gate level. We will compare wafer data
from two different OPC model versions built from flopdown and integrated wafer. We will also discuss
modeling options in terms of two layer test masks for future technologies.
Optical Proximity Correction (OPC) Model Calibration has required an increasing number of measurements as the
critical dimension tolerances have gotten smaller. Measurement of two dimensional features have been increasing at a
faster rate than features with one dimensional character as the technologies require better accuracy in the OPC models
for line-end pull-back and corner rounding. New techniques are becoming available from metrology tool manufacturers
to produce GDSII contours of shapes from wafers and modeling software has been improved to use these contours.
The challenges of implementing contour generation from the SEM tools will be discussed including calibration methods,
physical dimensions, algorithm derivations, and contour registration, resolution, scan direction, and parameter space
Optical and Process Correction in the 45nm node is requiring an ever higher level of characterization. The greater
complexity drives a need for automation of the metrology process allowing more efficient, accurate and effective use of
the engineering resources and metrology tool time in the fab, helping to satisfy what seems an insatiable appetite for data
by lithographers and modelers charged with development of 45nm and 32nm processes. The scope of the work
referenced here is a 45nm design cycle "full-loop automation", starting with gds formatted target design layout and
ending with the necessary feedback of one and two dimensional printed wafer metrology.
In this paper the authors consider the key elements of software, algorithmic framework and Critical Dimension Scanning
Electron Microscope (CDSEM) functionality necessary to automate its recipe creation. We evaluate specific problems with the methodology of the former art, "on-tool on-wafer" recipe construction, and discuss how the implementation of the design based recipe generation improves upon the overall metrology process. Individual target-by-target construction, use of a one pattern recognition template fits all approach, a blind navigation to the desired measurement
feature, lengthy sessions on tool to construct recipes and limited ability to determine measurement quality in the resultant
data set are each discussed as to how the state of the art Design Based Metrology (DBM) approach is implemented.
The offline created recipes have shown pattern recognition success rates of up to 100% and measurement success rates of
up to 93% for line/space as well as for 2D Minimum/Maximum measurements without manual assists during measurement.
Optimal Proximity Correction (OPC) models are calibrated with Scanning Electron Microscope (SEM) data where the measurement uncertainty vary among pattern types (i.e., line versus space, 1D versus 2D and small versus large). The quality of the SEM measurement uncertainty's impact on OPC model integrity is mitigated through a weighting scheme. Statistical methods such as relating the weight to the SEM measurements standard deviation require more measurements per calibration structure than economically feasible. Similarly, the use of experience and engineering judgment requires many iterations before some reasonable weighting scale is determined. In this paper we present the results of OPC model fitness statistics associated with metrology based weights (MtBW) versus model based weights (MBW). The motivation for the latter approach is the promise for an unbiased, consistent, and efficient estimate of the model parameters.
Performing model based optical proximity correction (MB-OPC) is an essential step in the production of advanced integrated circuits that are manufactured with optical lithography technology. The accuracy of these models depends highly on the experimental data used in the model development (model calibration) process. The calibration features are weighted relative to each other depending on many aspects, this weighting plays an important role in the accuracy of the developed models.
In this paper, the effect of the feature weighting on OPC models is studied. Different weighting schemes are introduced and the effect on both the optical and resist models (specifically the resist model coefficients) is presented and compared. The effect of the weighting on the overall model fitting was also investigated.
The formation of photoinduced crystals and haze has become a challenge for 193nm photolithography high volume manufacturing (1-6). Extensive work has been performed to develop alternative to piranha chemistry for photomask cleaning processes in an attempt to eliminate the incidence of clean induced ammonium sulfate crystal formation (9-13). However, additional factors are impacting 193nm reticle optical quality. Sources of molecular contaminants such as environmental factors, outgasing from pellicle and reticle storage material can generate varieties of photoinduced crystals over the reticle useable lifetime (5-6). This paper will quantify and rank contributing factors for crystals generated under high energy UV exposure. A broad range of analytical and metrology techniques (FTIR, IC, TD-GC/MS, Inorganics impinger, AIMSTM, KLA Starlight, UV 172nm) and improvements in technique sensitivity were developed in order to identify crystal structure, quantify photogenerated contaminants levels and assess wafer printability impact. Engineering systems aimed at minimizing organic and inorganic molecular contaminants levels will be suggested.