Tim Brunner

Tim Brunner
ASML · Technology Development Center

PhD physics, MIT

About

135
Publications
21,698
Reads
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2,516
Citations
Citations since 2016
18 Research Items
364 Citations
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Introduction
My professional interest is in all aspects of microlithographic patterning for the manufacture of integrated circuits. Specific interests include high resolution imaging methods, simulation, metrology, overlay error, process control and process characterization.
Education
September 1975 - January 1980
September 1971 - May 1975
Carleton College
Field of study
  • Physics

Publications

Publications (135)
Article
The relationship between edge placement error (EPE), semiconductor design-rule determination, and predicted yield in the era of EUV lithography is examined, starting with the basics of EPE and then building up to design-rule calculations. The EPE definitions can be used as the building blocks for design-rule equations. Next the concept of "good fie...
Article
Vote-taking lithography is a method for mitigating mask defects, which has been applied in the 1980s to enhance yield. Vote-taking sums up N different mask images with identical content, each at 1 / N dose, to mitigate the defects on each individual mask. The fundamental assumption is that the mask defects do not correlate in position from mask to...
Article
As more aggressive EUV imaging techniques and resists with lower intrinsic roughness are developed for patterning at 7- and 5-nm technology nodes, EUV mask roughness will contribute an increasing portion of the total printed line-width roughness (LWR). We perform a comprehensive characterization of the EUV mask impacts on wafer LWR using actinic ae...
Article
The use of different illumination source shapes and multipatterning processes used to generate sub-40-nm images can create image placement errors level to level, resulting in significant intrafield overlay errors. These errors arise because of the impact of the different pupil shapes on lens aberrations resolving into image placement errors as well...
Conference Paper
Prime silicon wafers are ideal substrates for lithographic patterning, with tight flatness specifications for focus control. Process engineers are painfully aware that in-process product wafers can substantially depart from this ideal substrate. Wafer processing can induce non-flatness leading to focus problems, or distort the wafer leading to over...
Conference Paper
The use of extreme freeform illumination conditions and multi patterning processes used to generate sub 40nm images can result in significant intra-field overlay errors. When levels with differing illumination conditions are aligned to each other, these intra-field distortions can result in overlay errors which are uncorrectable using normal linear...
Article
Among the challenges with which lithographers are currently grappling, the issues of line-edge roughness (LER) and non-linear overlay errors intersect the concerns of ion implantation and thermal process engineers. LER, and the associated metric for contact holes, local critical dimension uniformity (LCDU), must be small to meet the requirements of...
Article
Full-text available
In optical lithography for microchip manufacturing, it is important that the focal ranges of all patterns in the layout be closely aligned in order to maximize a common process window. In practice, large pattern-dependent variations in the position of the best focus are observed, which have been traced back to phase errors induced on the image-form...
Patent
Full-text available
This invention relates to the manufacture of semiconductor substrates such as wafers and to a method for monitoring the state of polarization incident on a photomask in projection printing using a specially designed polarization monitoring reticle for high numerical aperture lithographic scanners. The reticle measures 25 locations across the slit a...
Conference Paper
Full-text available
Process-induced overlay errors are a growing problem in meeting the ever-tightening overlay requirements for integrated circuit production. While uniform process-induced stress is easily corrected, non-uniform stress across the wafer is much more problematic, often resulting in non-correctable overlay errors. Measurements of the wafer geometry of f...
Article
Process-induced overlay errors are a growing problem in meeting the ever-tightening overlay requirements for integrated circuit production. Although uniform process-induced stress is easily corrected, nonuniform stress across the wafer is much more problematic, often resulting in noncorrectable overlay errors. Measurements of the wafer geometry of...
Patent
Full-text available
A system and method is provided which predicts problematic areas for lithography in a circuit design, and more specifically, which uses modeling data from a modeling tool to accurately predict problematic lithographic areas. The method includes identifying surface heights of plurality of tiles of a modeled wafer, and mathematically mimicking a lith...
Conference Paper
Immersion lithography is being extended to below 20-nm and the lithography performance requirements need to be tightened further to enable this shrink. With depth of focus control requirements of the scanner going down to 60 nm and below, high quality metrology data is needed to quantify the disturbance of the exposed image. In this paper we presen...
Conference Paper
This paper describes the joint development and optimization of an advanced critical dimension (CD) control methodology at IBM’s 300 mm semiconductor facility. The work is initially based on 22 nm critical level gate CD control, but the methodology is designed to support both the lithography equipment (1.35 NA scanners) and processes for 22, 20, 18,...
Article
Full-text available
A dose-focus monitoring technique using a critical-dimension scanning electron microscope (CD-SEM) is studied for applications on product wafers. Our technique uses two target structures: one is a dense grating structure for dose determination, and the other is a relatively isolated line grating for focus determination. These targets are less than...
Article
A dose-focus monitoring technique using critical dimension scanning electron microscope (CD-SEM) is studied for onproduct applications. Our technique uses two target structures; one is a dense grating structure with iso-focal pitch for dose determination, and the other is a relatively isolated line grating with no assists for focus determination. T...
Article
The first use of extreme ultraviolet (EUV) lithography in logic manufacturing is targeted for the 14 nm node, with possible earlier application to 20-nm node logic device back-end layers to demonstrate the technology. Use of EUV lithography to pattern the via-levels will allow the use of dark-field EUV masks with low pattern densities and will post...
Article
Negative tone development (NTD) processes have been widely explored as a way to enhance the printability of dark field features such as contact holes and trenches. A key consequence of implementing NTD processes and subsequent tone reversal of dark field reticles is the significantly higher transmission of bright field masks and thus higher light i...
Article
Full-text available
Mask topography is only one of the challenges for extending 193nm immersion lithography to 22nm and beyond. Migration to binary but thinner mask absorbers, from the previously employed attenuated phase-shift mask (attnPSM) technology, traded a tolerable loss in contrast for better mask making performance and reduced electromagnetic field (EMF) impa...
Article
Optical properties (n&k) of the material films under measurement are commonly assumed invariant and fixed in scatterometry modeling. This assumption keeps the modeling simple by limiting the number of floating parameters in the model. Such scatterometry measurement has the potential to measure with high precision some of the profile parameters (CD,...
Article
Advanced 193 nm lithographic processes will require defocus control for product wafers in order to meet CD and profile requirements in the future. Dose control is already required. The interaction of product wafer materials with lithography requires additional controls beyond tool monitoring. While scatterometry has demonstrated excellent ability t...
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
Continued lithographic pattern density scaling depends on aggressive overlay error reduction.1,2 Double patterning processes planned for the 22nm node require overlay tolerances below 5 nm; at which point even sub-nanometer contributions must be considered. In this paper we highlight the need to characterize and control the single-layer matching am...
Article
Many factors are driving a significant tightening of the overlay budget for advanced technology nodes, e.g. 6nm [mean + 3sigma] for 22nm node. Exposure tools will be challenged to support this goal, even with tool dedication. However, tool dedication has adverse impact on cycle time reduction, line productivity and cost issues. There is a strong de...
Article
Full-text available
We discuss the lithographic qualification of a new type of binary mask blank consisting of an opaque layer of MoSi on a glass substrate, referred to simply as OMOG. First, OMOG lithographic performance will be compared to a previous chrome/MoSi/glass binary intensity mask (BIM) blank. Standard 70-nm chrome on class (COG) was not considered, as it f...
Article
Full-text available
The process window for state of the art chip manufacturing continues to decrease, driven by higher NA exposure tools and lower k1 values. The benefits of immersion lithography for Depth of Focus (DoF) are well known. Yet even with this immersion boost, NA=1.35 tools can push DoF into sub-100nm territory. In addition, immersion processes are subject...
Article
Full-text available
Focus and dose control of lithography tools for leading edge semiconductor manufacturing are critical to obtaining acceptable process yields and device performance. The need for these controls is increasing due to the apparent limitation of optical water immersion lithography at NA values of approximately 1.35 and the need to use the same equipment...
Article
The performance of a 0.25NA full-field EUV exposure tool is characterized in terms of CD uniformity, focus and overlay control, as well as dose uniformity. In addition to the characterization of the scanner, we explore the use of scatterometry techniques for the measurements of extremely fine resolution features, with critical dimensions below 40 n...
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
Despite the increasing use of advanced imaging methods to pattern chip features, process windows continue to shrink with decreasing critical dimensions. Controlling the manufacturing process within these shrinking windows requires monitor structures designed to maximize both sensitivity and robustness. In particular, monitor structures must exhibit...
Article
We derive a physical model to describe the dependence of pattern dimensions on dose, defocus and blur. The coefficients of our model are constants of a given lithographic process. Model inversion applied to dimensional measurements then determines effective dose, defocus and blur for wafers patterned with the same process. In practice, our approach...
Article
The back-end-of-line metallization of a state-of-the-art CMOS process is the most critical level regarding the final density of the chip. While the gate level requires the most emphasis on linewidth control and critical dimension uniformity (CDU) of all lithography steps, the smallest pitch in the process is typically printed on the first metalliza...
Article
Full-text available
It is generally assumed that achieving a narrow distribution of physical gate length (Lpoly) for the poly conductor layer helps improve power performance metrics of modern integrated circuits. However, in advanced 90 nm technologies, there are other drivers of chip performance. In this paper we show that a global optimization of all variables is ne...
Article
Despite the increasing use of advanced imaging methods to pattern chip features, process windows continue to shrink with decreasing critical dimensions. Controlling the manufacturing process within these shrinking windows requires monitor structures designed to maximize both sensitivity and robustness. In particular, monitor structures must exhibit...
Chapter
IntroductionTheoryPower-Law FitsNon-Power-Law SystemsSummary, Conclusions, and the Future
Conference Paper
Full-text available
Contact holes represent one of the biggest critical dimension (CD) mask metrology challenges for 45nm technology mask development. The challenge is a consequence of both wafer and mask sensitivities. Large mask error factors and the small process windows found when contact holes are imaged on wafers impose very tight mask specifications for CD unif...
Conference Paper
Despite the increasing use of advanced imaging methods to pattern chip features, process windows continue to shrink with decreasing critical dimensions. Controlling the manufacturing process within these shrinking windows requires monitor structures designed to maximize both sensitivity and robustness. In particular, monitor structures must exhibit...
Article
It is well known that the refractive optics used in today’s exposure tools are highly chromatic, meaning that small wavelength shifts will cause large focus shifts. Even a line-narrowed excimer laser has a large enough range of wavelengths that we can no longer think of an infinitely thin image plane. The concept of “focus blur” can be generalized...
Article
It is well known that the refractive optics used in today's exposure tools are highly chromatic, meaning that small wavelength shifts will cause large focus shifts. Even a line-narrowed excimer laser has a large enough range of wavelengths that we can no longer think of an infinitely thin image plane. The concept of "focus blur" can be generalized...
Article
As metrology tolerances for photomasks become increasingly tight, the issues of measurement methods and calibration standards become more and more important. This is as true for optical phase metrology as it is for dimensional metrology. To first order, an optical phase standard can be defined by etching a step or trench into a transparent medium l...
Article
We present a systematic analysis of the imaging performance for a 0.93 numerical aperture (NA) state-of-the-art immersion lithography scanner and we compare this performance to its dry NA=0.93 counterpart. The increased depth of focus (DOF) enabled by immersion lithography presents a set of advantages for semiconductor manufacturing which we explor...
Article
Anomalous linewidth variations of tens of nanometers have been observed for certain chemically amplified resist processes, a phenomenon we call chemical flare. These variations are highly undesirable, since they fall outside the scope of normal OPC corrective action. Experimental data is presented which clarifies the magnitude and range of chemical...
Article
Immersion lithography has emerged as the leading solution for semiconductor manufacturing for the 45nm node, in spite of a continuing concern about defects. Fully functional 90nm PowerPC microprocessors have now been fabricated using immersion lithography for one litho-critical via level, allaying that concern.
Article
Immersion lithography has recently emerged as the preferred lithography solution for manufacturing the next generation of semiconductor devices (likely to address the 65, 45, and possibly the 32 nm nodes). Full-field immersion scanners operating at λ=193 nm with de-ionized water as the immersion fluid have been recently demonstrated. In this articl...
Article
This paper will consider the basic concepts of resist blur in a chemically amplified resist process, and the implications of this blur to lithography. In particular, use of a double Gaussian form for the resist blur will be explored. A simple lithographic model utilizing a double Gaussian resist blur was developed and applied to the rapid calculati...
Article
This paper will consider the basic concepts of resist blur in a chemically amplified resist process, and the implications of this blur to lithography. In particular, use of a double Gaussian form for the resist blur will be explored. A simple lithographic model utilizing a double Gaussian resist blur was developed and applied to the rapid calculati...
Article
157 nm has been explored as a lithographic technology for several years on small field imaging tools with encouraging results. Significant progress has occurred in tool platform design, resist performance, and optical material quality. However, a major test of a new lithography comes when full field, scanned images can be produced as this becomes a...
Article
Much has been made of the term 'subwavelength' in the lithography community in recent years, referring to the smaller feature sizes that the International Technology Roadmap for Semiconductors (ITRS) demands. This term, however, has additional meaning when the features on the reticle, rather than on the wafer, are smaller than the wavelength. In th...
Article
Full-text available
A lithographic process capable of manufacturing state of the art chips faces many difficult challenges. Not only must the process resolve the minimum feature size but overlay errors must be held to tight tolerances, exquisitely complex patterns must be printed with high yield, and the overall cost of the process must be acceptable. Achieving accept...
Article
As the 193 nm generation of steppers reaches the limit of its capability, alternating aperture phase shift masks (altPSMs) are necessary to extend the lifetime of these tools. The fabrication of a production-worthy altPSM requires that the quartz dry etch satisfy many conditions. The etched quartz features must not only show excellent phase uniform...
Article
The importance of hardmask technology is becoming increasingly evident as the demand for high-resolution imaging dictates the use of ever-thinner resist films. An appropriately designed etch resistant hardmask used in conjunction with a thin resist can provide the combined lithographic and etch performance needed for sub-100 nm device fabrication....
Article
Recent advances have enabled exposure tool manufacturers to ship tools with numerical aperture (NA)=0.8, and to envision optics with even larger NA. Thus the lithography community must grapple with images formed by oblique waves close to the Brewster angle. (For a typical chemically amplified resist with index of refraction n=1.7, the Brewster angl...
Article
Recent advances have enabled exposure tool manufacturers to ship tools with Numerical Aperture (NA) equals 0.8, and to envision optics with even larger NA. Thus the lithography community must grapple with images formed by oblique waves close to Brewster's angle. (For a typical chemically amplified resist with index of refraction n equals 1.7, Brews...
Article
We have extended the recent work on high numerical aperture (NA) effects in novolac photoresists to investigate the influences of s- and p-polarization at Brewster's angle on the final developable image of a chemically amplified (CA) resist. Using our interferometric lithography tool, resist films (Shipley UVII-HS) were exposed using either s- or p...
Article
A methodology to study the bias and phase correction of strong phase-shifting masks is introduced. Isolated apertures are simulated to investigate the influence of aperture size, undercut etch, and quartz sidewall angle on aperture transmission. The simulations match well with experimental results that are measured with an ArF microlithography simu...
Article
Characterization of linewidth variation by a three-step methodology is presented. Via electrical linewidth measurement, sources of lnewidth variation with distinct spatial signatures are first isolated by spatial analysis. Causes with similar spatial signatures are then separated by contributor-specific measurements. Unanticipated components are la...
Article
The periodic variations of dose-to-clear, reflection and CD with resist thickness are well known phenomena commonly known as swing curves. Proper process control dictates that the resist thickness is chosen at a swing extreme, so as to reduce dose variation. Swing curves are commonly calculated for normal incidence waves. The recent trends toward h...