Pattern defects and uninvited particles (residuals) probably appear on Mask and Wafer in any manufacturing process of integrated circuits (ICs) and impact the final yield of IC chips. To ensure a high yield, defect inspection of Mask and Wafer has been broadly adopted for monitoring many processes in high volume manufacturing (HVM) and shortening development cycle-times of critical processes in R&D. In HVM optical inspection tools have played a major role, and in R&D e-beam inspection tools have been a critical role. For the 7nm technology node and beyond, minimum size killer defects are going to be invisible for optical inspection tools, and e-beam inspection tools are too slow to capture smaller killer defects in an acceptable throughput. Accordingly, enhancing e-beam inspection tools in throughput has become an issue demanding prompt attention, and one promising solution is multi-beam inspection (MBI) technology. We are developing a MBI tool, which combines our cutting edge technologies in multi-beam electron optics, sample stage, scanning strategy and computational architecture. In this paper we will introduce MBI technology and development progress of our MBI tool, and will discuss future application of MBI technology.
EUV lithography has been adopted in most advanced semiconductor manufacture fabs, enabling the next step in design rule scaling. With this progress, minimum critical defect size has become smaller and harder to detect. Defect inspection equipment suppliers must therefore in parallel provide a significant step up in inspection sensitivity at a reasonable throughput. Optical inspection tools are facing an unprecedented challenge because defects less than 10nm are not optically visible. As an alternative, semiconductor manufacturers have turned toward e-beam inspection. E-beam inspection is widely used in R&D to shorten development cycle-time and selectively used in high volume manufacturing (HVM) for process monitoring, however currently it is not fast enough for large-scale replacement of optical inspection. Our approach to address this shortcoming is to combine cutting edge multiple-beam technology with a cutting edge positioning system/computation architecture to create a next generation e-beam inspection system capable of scanning with multiple electron beams at the same time. This paper reports on the progress in developing such a system as well as future multi-beam inspection applications.
On-product overlay requirements are becoming more challenging with every next technology node due to the continued decrease of the device dimensions and process tolerances. Therefore, current and future technology nodes require demanding metrology capabilities such as target designs that are robust towards process variations and high overlay measurement density (e.g. for higher order process corrections) to enable advanced process control solutions. The impact of advanced control solutions based on YieldStar overlay data is being presented in this paper. Multi patterning techniques are applied for critical layers and leading to additional overlay measurement demands. The use of 1D process steps results in the need of overlay measurements relative to more than one layer. Dealing with the increased number of overlay measurements while keeping the high measurement density and metrology accuracy at the same time presents a challenge for high volume manufacturing (HVM). These challenges are addressed by the capability to measure multi-layer targets with the recently introduced YieldStar metrology tool, YS350. On-product overlay results of such multi-layers and standard targets are presented including measurement stability performance.
Requirements for on-product overlay, focus and CD uniformity continue to tighten in order to support the demands of 10nm and 7nm nodes. This results in the need for simultaneously accurate, robust and dense metrology data as input for closed-loop control solutions thereby enabling wafer-level control and high order corrections. In addition the use of opaque materials and stringent design rules drive the need for expansion of the available measurement wavelengths and metrology target design space. <p> </p>Diffraction based optical metrology has been established as the leading methodology for integrated as well as standalone optical metrology for overlay, focus and CD monitoring and control in state of the art chip manufacturing. We are presenting the new approaches to diffraction based optical metrology designed to meet the ≤10nm node challenges. These approaches have been implemented in the latest addition to the YieldStar metrology platform, the YS350E introducing a new way of acquiring and processing diffraction based metrology signals.<p> </p> In this paper we will present the new detection principle and its impact on key performance characteristics of overlay and focus measurements. We will also describe the wide range of applications of a newly introduced increased measurement spot size, enabling significant improvements to accuracy and process robustness of overlay and focus measurements. <p> </p>With the YS350E the optical CD measurement capability is also extended, to 10x10μm<sup>2</sup> targets. We will discuss the performance and value of small targets in after-develop and after-etch applications.
As leading edge lithography is moving to 2x-nm design rules, lithography control
complements resolution as one of the main drivers and enablers to meet the very
stringent overlay, focus and CD requirements. As part of ASML's holistic
lithography roadmap, ASML is developing several application-specific
optimization and control applications, such as LithoTuner Pattern Matcher and
These applications are all explicitly designed to improve the scanner process
window (overlay, focus, CDU and matching). All these applications have in
common that they require vast amounts of precise, accurate and process robust
wafer data (either taken on product stacks or on so-called monitor wafers).
To provide such essential data in a cost-effective manner, ASML developed a
metrology platform, called YieldStar. This platform is based on an angle-resolved
high-NA scatterometer. It is versatile, as YieldStar's sensor can measure overlay,
CD and focus in a single measurement. Thanks to its high speed, large amounts
of measurements can be quickly collected.
In this paper the latest generation YieldStar is presented, the so-called 200
platform. This YieldStar 200 can be used in a stand-alone configuration (S-200)
or as an integrated module in a lithography track (T-200). First overlay results
show good TMU results without comprising speed. Furthermore, data is shown
that demonstrate YieldStar's capability to reconstruct 3D CD patterns as well.
As leading edge lithography moves to 22-nm design rules, low k1 technologies like double patterning are the new
resolution enablers, and system control and setup are the new drivers to meet remarkably tight process requirements. The
way of thinking and executing setup and control of lithography scanners is changing in four ways.
First, unusually tight process tolerances call for very dense sampling , which in effect means measurements at high
throughput combined with high order modeling and corrections to compensate for wafer spatial fingerprint.
Second, complex interactions between scanner and process no longer allow separation of error sources through
traditional metrology approaches, which are based on using one set of metrology tools and methods for setup and
another for scanner performance control. Moreover, setup and control of overlay is done independently from CD
uniformity, which in effect leads to independent and conflicting adjustments for the scanner.
Third, traditional CD setup and control is based on the focus and dose calculated from their CD response and not from
measurement of their effect on pattern profile, which allows a clean and orthogonal de-convolution of focus and dose
variations across the wafer.
Fourth, scanner setup and control has to take into consideration the final goal of lithography, which is the accurate
printing of a complex pattern describing a real device layout. To this end we introduce a new setup and control
metrology step: measuring-to-match scanner 1D and 2D proximity.
In this paper we will describe the strategy for setup and control of overlay, focus, CD and proximity based on the
YieldStar<sup>TM</sup> metrology tool and present the resulting performance. YieldStar-200 is a new, high throughput metrology
tool based on a high numerical aperture scatterometer concept. The tool can be used stand-alone as well as integrated in a
processing track. It is suitable for determining process offsets in X,Y and Z directions through Overlay and Focus
measurements respectively. In addition CD profile information can be measured enabling proximity matching
By using a technique  to de-convolve dose and focus based on the profile measurement of a well-characterized
process monitor target, we show that the dose and focus signature of a high NA 193nm immersion scanner can be
effectively measured and corrected. A similar approach was also taken to address overlay errors using the diffraction
based overlay capability  of the same metrology tool. We demonstrate the advantage of having a single metrology tool
solution, which enables us to reduce dose, focus and overlay variability to their minimum non-correctable signatures.
This technique makes use of the high accuracy and repeatability of the YieldStar tool and provides a common reference
of scanner setup and user process. Using ASML's YieldStar in combination with ASML scanners, and control solutions
allows for a direct link from the metrology tool to the system settings, ensuring that the appropriate system settings can
be easily and directly updated.
Holistic lithography is needed to cope with decreasing process windows and is built on three pillars: Scanner Tuning,
Computational Lithography and Metrology & Control. The relative importance of stability to the overall manufacturing
process latitude increases. Overlay and focus stability control applications are important elements in improving stability
of the lithographic process. The control applications rely on advanced control algorithms and fast and precise metrology.
To address the metrology needs at the 32 nm node and beyond, an optical scatterometry tool was developed capable of
measuring CD, focus-dose as well as overlay. Besides stability and control of lithographic performance also scanner
matching is a critical enabler where application development and metrology performance are key. In this paper we
discuss the design and performance of the metrology tool, the focus and overlay control application and the application
of scatterometry in scanner matching solutions.