We propose a construction and calibration method of an absolute coordinate system for lithography tools. In the conventional overlay control system, subsequent layers are overlaid on the 1st layer that could have unknown wafer distortion. This is inefficient, because the distortion of the 1st layer may be large. A high-level overlay control can be realized with the absolute coordinate system by correcting the 1st layer to zero distortion. This can be possible by using absolute alignment metrology system. In order to confirm our theory, we report experimental results of the absolute grid construction and matching accuracy among multiple lithography tools.
A standalone alignment technology was developed as a fundamental solution to improve on-product overlay (OPO). It enables high performance alignment measurements, and delivers state-of-the-art feed forward corrections to exposure scanner. Dense alignment sampling and high-order field distortion correction is effective for scanner fingerprint matching and for heat related field distortions. A modeling and sampling optimization software is a powerful tool for dense sampling and high-order overlay correction with minimal throughput loss. We performed an overlay experiment using the standalone alignment technology coupled with a modeling and sampling optimization software, which demonstrates on-product overlay improvement potential for next generation manufacturing accuracy and productivity challenges.
Due to the importance of errors in lithography scanners, masks, and computational lithography in low-k1 lithography,
application software is used to simultaneously reduce them. We have developed “Masters” application software, which is
all-inclusive term of critical dimension uniformity (CDU), optical proximity effect (OPE), overlay (OVL), lens control
(LNS), tool maintenance (MNT) and source optimization for wide process window (SO), for compensation of the issues
on imaging and overlay.
In this paper, we describe the more accurate and comprehensive solution of OPE-Master, LNS-Master and SO-Master
with functions of analysis, prediction and optimization. Since OPE-Master employed a rigorous simulation, a root cause
of error in OPE matching was found out. From the analysis, we had developed an additional knob and evaluated a proof-of-
concept for the improvement. Influence of thermal issues on projection optics is evaluated with a heating prediction,
and an optimization with scanner knobs on an optimized source taken into account mask 3D effect for obtaining usable
process window. Furthermore, we discuss a possibility of correction for reticle expansion by heating comparing
calculation and measurement.
Current technology nodes, as well as subsequent generations necessitate ongoing improvements to the mix-and-match overlay (MMO) capabilities of lithography scanners. This work will introduce newly developed scanner solutions to address this requirement, and performance data from the latest generation immersion scanner, the NSR-S622D, will be introduced. Enhanced MMO accuracy is imperative for the 22 nm half-pitch and future technology nodes. In order for the matched overlay accuracy to approach single machine overlay (SMO) capabilities, MMO errors must be reduced further. The dominant MMO error sources can be divided into three main areas: SMO, lens distortion matching and wafer grid matching. Nikon continues to decrease these matching error contributors over time, and the latest generation NSRS622D immersion scanner provides a number of innovative solutions to satisfy the most demanding overlay matching requirements ; as a result MMO performance within 3nm is achieved on S622D. Moreover, overlay master system is developed for further product overlay accuracy and stability improvement.
KEYWORDS: Optical alignment, System on a chip, Lithography, Semiconducting wafers, Image processing, Optical lithography, Scanning electron microscopy, Scanners, Signal processing, Photoresist processing
Self Aligned Double Patterning (SADP) is now widely accepted as a viable technology for the further extension of
193nm immersion lithography towards the 22nm /18nm technology nodes. SADP was primary introduced for the
manufacturing of flash memory due to its 1D design geometry. However, SADP is now becoming a main stream
technology for advanced technology nodes for logic product.
SADP results in alignment marks with reduced image contrast after completion of spacer patterning.
Consequently there is an elevated risk that the alignment performance of the cut lithography layer on the spacer [1]
may be negatively impacted. Initial studies indicate that it may be necessary to consider new mark designs. In this
paper, we will evaluate different types of SADP processes with the alignment system of the Nikon S620D and
S621D immersion scanner. We will discuss the performances and the differences observed due to the SADP
materials.
Included in this study is an intensive characterization of the morphology of the spacer after SADP process. We
will use for this a 3D-AFM from Insight, and characterize the spacer profile of the spacer. Using a standard AFM
microscope, we can characterize the surface roughness in the inner and the outer part of the wafer. The self aligned
spacer process results in asymmetric spacers. Two types of surface (inside and outside) of the spacer are formed.
The impact of this asymmetry is also assessed. The roughness difference, between the two parts, will play an
important roll in the alignment contrast.
Double patterning (DP) is widely regarded as the lithography solution for 32 nm half pitch semiconductor manufacturing,
and DP will be the most likely litho technology for the 22 nm node [1]. When using the DP technique, overlay accuracy
and CD control are of critical importance [2]. We previously introduced the NSR-S620D immersion scanner, which
provides 2 nm overlay capabilities. In the case of the latest generation NSR-S621D system, improvements have been
developed for further overlay accuracy enhancement.
In this paper, we will show the overlay accuracy and Mix-and-Match performance of the NSR-S621D. Further, the
marked improvement in product overlay and the overlay result in Spacer DP as a result of enhanced alignment accuracy
will also be shown.
Double patterning with Spacer (DPS) is now widely accepted as a viable technology for the further extension of
193nm lithography towards the 22nm /18nm technology nodes. DPS was primary introduced for the manufacturing
of flash memory due to its 1D design geometry. However, DPS is now becoming a main stream technology for
advanced technology nodes for logic product.
DPS results in alignment and overlay marks with reduced image contrast after completion of spacer patterning.
Consequently there is an elevated risk that the overlay performance of the cut lithography layer on the spacer [1]
may be negatively impacted. Initial studies indicate that it may be necessary to consider new mark designs. In this
paper, we discuss the basic design of the Nikon alignment marks and make a statistical assessment of their relative
performance.
The self aligned spacer process results in asymmetric spacers. That are two types of surface (inside and outside)
of the spacer are formed. The impact of this asymmetry is also being assessed. Mark geometries are characterized
with 3D-AFM measurement and alignment / overlay performance analysis.
Traditional "matching matrix" methods for characterizing scanner matching assume that the scanner distortion
performance is static. The latest scanner models can adjust the distortion performance dynamically, at run-time. The
Scanner Match Maker (SMM) system facilitates calculation and application of these run-time adjustments, improving
effective overlay performance of the scanner fleet, allowing more flexibility for mix-and-match exposure. The overlay
|mean|+3s performance was improved significantly for a layer pair that is currently allowed mix-and-match pairing.
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