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Scatterometry is an investigation method that is gaining in importance in semiconductor industry. As an optical method it has distinct advantages that its competitor-methods do not possess: the ability for a quick and non-destructive measurement of fine features fabricated by modern generations of lithography machines. Scatterometry is very distinct from other measurement techniques also in this respect that it is a model-based method. As such it relies heavily on simulation and is essentially solving an inverse problem. In a forward optical measurement an imaging system processes the object information losing some fraction of information in the process. The measurement process in scatterometry follows the same pattern. The measurement result however is now compared against multiple simulated direct problems. The best fit between the simulation and the measurement is assumed to reconstruct the measured object. [ABSTRACT FROM AUTHOR]

International Technology Roadmap for Semiconductors (ITRS) report proposes extreme ultraviolet (EUV) lithography to be the key candidate of lithography tools to manufacture devices at the 22nm node and beyond. The image effects on wafer critical dimensions (CDs) in the EUV lithography are different from the effects in the conventional lithography caused by the off-axis illumination and refelective optics design. This research investigates process windows of line/space (L/S) with the target CD 22nm and contact hole (CH) features with the target CD 35nm illuminated by the conventional, annular, dipole, and quasor source shapes. The diffraction amplitudes by the EUV mask are summarized. The research suggests that the dipole is the better illumination source shape to print L/S features and the quasor is the better one for CH features. In addition, the research reports the best dipole illumination setting for the L/S features and the best quasor illumination setting for the CH features. The exposure latitude and depth of focus (DOF) for L/S feature illuminated by the dipole to print the target CD 22nm are 4% and 100nm respectively. The exposure latitude and DOF for CH feature illuminated by the quasor to print the target CD 35nm are 24% and 300nm respectively. Full field analysis of CH CDs displays the minimized CD error through slit due to the quasor illumination in the EUV lithography. [ABSTRACT FROM PUBLISHER]

The paper presents a novel hardware-measurement based methodology to extract within-product-array variability as opposed to kerf. The methodology was applied to a 45nm 2.4Mb SRAM design with emphasis on critical dimension measurements. Local mismatch and spatial variations, LER effects and backend effects were measured. Lithographic models were tuned to the 45nm process. Statistically measured variability in critical process units along with extracted long-range CD variation through lithography simulations were then fed to a newly developed statistical engine to predict design yield, leakage and performance. The predicted yield results were then corroborated with the hardware providing feedback for process tuning. In addition to monitoring mature processes, such hardware measurement techniques can also be used to monitor or decipher yield-detractor defects. [ABSTRACT FROM PUBLISHER]

Microwire makes good sensors because their small dimensions which enhance their sensitivity. To be useful, microelectrode sensors must be integrated with electronic capable of processing those signal. In this research, we demonstrated a method to fabricated and characterize metal microwire device for biosensing application. Using conventional photolithography technique and other experimental techniques, we developed a reliable procedure for producing aluminium wires with micron-scale features. Significantly, in micro fabrication the critical dimension (CD) of wafers in photolithography is the most important parameter that determines the final performance of devices. Hence, it is paramount to have high resolution, high sensitivity and precise alignment to successfully transfer the original pattern to wafer. The process was optimized by control the spin speed for photoresist (PR) coating, spin time, post exposure bake time, developer concentration ratio, hard bake and aluminium etch time so as to achieve the possible fabrication process and get the expected microwire size. The process begins with the photoresists coating and spinning at 3000 rpm to form a thin and uniform layer. Subsequently, the PR coated substrates were exposed to UV light for 10s. After the alignment and exposure, the substrate were developed using the resists developer with 25:10 ratio in which 25 parts of developer and 10 parts of deionized water. Eventually, the post exposure bake and hard bake time were optimized for a better throughput on the pattern transfer process. The aluminium microwire has been successfully fabricated with the contact pads. The wires range in thickness from 1 μm-4μm to achieve a resistivity as low as possible for nano range limit of detection. This microelectrodes transducer will be eventually used as biomolecule detection kit. The fabricated microwire was morphologically characterized using Atomic force microscope (AFM), Scanning electron microscope (SEM), High power microscope (HPM). Besides that, the electrical properties of the fabricated aluminium microwire were studied using source meter. [ABSTRACT FROM PUBLISHER]

One of the delicate processes in semiconductor microfabrication is the photolithography. It is the process that sets the design dimensions on various parts of the device. In order to complete this process, two requirements need to be satisfied. First is to create, the exact dimensions and pattern as established in design phase, which in other word can be referred as the resolution of the images on the wafer. The second is the correct placement of the device pattern on the wafer relative to the crystal orientation of the wafer substrate. This is called alignment or registration of patterns in correct position. This registration requirement is similar to the correct alignment of the different floors of a building. It is easy to visualize that misalignment of elevator shafts and stair wells would render the building useless. In a circuit, the effects of misaligned mask layers can cause the entire circuit to fail. In this paper we have reported a couple of results that leads to photoresist development and optimization technique as a standard manufacturing process to form 1μm microbridge for later process of size reduction to form nanogap. Therefore, at the final stage of fabrication, a nano-diagnostic biochip device is developed to use it as a biomolecule detection biosensor. The development of biosensors is still an open field and much remains to be done before many of these bioelectronic devices become commercialized. In this research, the key factors such as resist thickness, post-exposure bake (PEB) time and developer concentration are taken into account to study the optimum measurements and process. The thickness of resist will affect the resolution of image transferred and developing time. Both PEB and developer concentration also has the tendency to affect the device pattern and developing time. As the result, the photoresist thickness is optimized at 1500nm, the developer RD6 concentration diluted at 10:25 (DI water: RD6) and PEB time optimized at 65s. [ABSTRACT FROM PUBLISHER]

The swing curve is depending on the rotation speed of the spinner and the thickness of the photoresist. The thickness should be thick enough to prevent the unexposed area from being etched. It is also need to be uniform so that the image of the pattern to be developed later is in focus at all points on the resist surface. The variation of the photoresist thickness will impact the overall yield of the devices. In this respect, the photoresist thickness needs to be characterized carefully. Therefore, an experiment was set up to determine the right thickness and exposure time to control the critical dimension of the pattern. Photoresist coater and stepper are the main equipment used in this experiment. Positive photoresist is utilized as a pattern transfer medium and elipsometer is employed for film thickness measurement. 24 wafers are used in this experiment. The wafers are separated into 2 sets, each set which consists of 12 wafers have all the thickness variation. This to test the effect of standing resist before exposure and development to the dose-to-clear. The first set is coated, exposed and development. However, the second set is exposed and developed two days after being coated. After the wafer went through the standard cleaning procedure, the wafers were then coated using standard recipes which the spin speed ranging from 6500 to 7600 rpm in 100 rpm incremental with the designated rpm fro 1.2 μm photoresist thicknesses is in the middle. Subsequently, the photoresist thickness of each wafer is measured using elipsometer. Then, the exposure process is done by creating job that will expose the wafers in 20 by 10 arrays of small squares of open field with size 2×2 mm. The exposure is done in such a way where the exposure time will step up to the right and step down to the left from the center after each column. The center of the exposure energy time/step is 240/5. Then the graph is plotted to see the different. From the results we obtained that the minima for the dose-to-clear is at 7200 rpm where the thickness is 1.22 μm. whereby the first set and the second set of wafers produce a slight variation in clearing point. [ABSTRACT FROM PUBLISHER]

In fabrication of Nanowire alignment and exposure are the most critical steps in photolithography process, the resolution requirements and precise alignment are vital, each mask needs to be precisely aligned with original alignment mark. Otherwise, it can't successfully transfer the original pattern to the wafer surface causing device and circuit failure. Precise transfer of pattern transfer means guarantee in high repeatability and reliability, high throughput and low cost of ownership. By improving this resolution and alignment precision the minimum size can be further reduced to 1nm and beyond. The other important aspect of achieving minimum precised size is, the photo resist must be very sensitive to the exposure light to achieve reasonable throughput. However, if the sensitivity is too high, other photoresist characteristics can be affected, including the resolution. Thus, the paper present a preliminary study on fundamentals of resist exposure and development mechanisms for fabrication of Nanowire, We demonstrated significance of considering process parameters such as quality of resist, soft bake, exposure time and intensity, and development time. [ABSTRACT FROM PUBLISHER]

Profiles of trenches in silicon were calculated by fitting measured polarized reflectance spectra with theoretically calculated RCWA (rigorous coupled wave analysis) models. The agreement of trench geometry from optical measurements with SEM cross-sections was good. The contact-free optical measurement on productive wafers constitutes a serious alternative to the time consuming and destructive cross-section analyses. Critical dimensions (CD) of gratings of resist lines were obtained from RCWA modeling of optical spectra. An i-line resist with lines of larger spacing and a UV resist with lines of smaller pitch were investigated. In both cases the top and bottom CDs varied over a wide range due to the change in exposure dose across the wafer. The good agreement between optically obtained CD values, in-line CD SEM data and cross-section SEM data makes the optical method an ideal tool for process control. [ABSTRACT FROM PUBLISHER]

Novel process control methodologies are required for SiGe gate recess structures that are used in IC manufacturing to enhance device performance. Metrology measurements of 28nm SiGe after-etch inspection U-sigma shaped and V-sigma shaped gate structures must be able to track subtle variations for several critical parameters, including SiGe-to-gate width, tip-to-gate width, sigma depth and recess depth. For production process control of these structures, a metrology tool must utilize a nondestructive measurement technique, and have high sensitivity, precision and throughput. This paper explores the capabilities of a new-generation scatterometry critical dimension (SCD) metrology tool to measure critical parameters and serve as a production process monitor for 28nm and beyond complex gate structures. [ABSTRACT FROM PUBLISHER]

Real-time control is the trend for photoresist processing in the advanced lithography. In this paper we develop an in-situ ellipsometer integrated with a programmable thermal heating system, which could perform real-time monitoring and control for critical dimension (CD) latent image through the entire post-exposure bake (PEB) process. The inline ellipsometry measurements are fitted into an electromagnetic wave model built on the rigorous coupled-wave analysis (RCWA) theory for CD latent image characterization. Thereafter a real-time control scheme is proposed by applying the programmable thermal bake-plate. The experimental outcome demonstrates a significant improvement on the final CD result comparing to the conventional baking method. [ABSTRACT FROM PUBLISHER]

Critical dimension is the minimum number of features that is required to ensure the performance of a learning machine to be “high”. This critical dimension is usually unique to the learning machine and the ranking algorithm combination. Medical- and bio-informatics datasets are different from most other datasets in that there is an imbalance in most of these datasets and a high prediction accuracy often depends upon not just the overall accuracy but also the true positive and the false negative rates. To find a medically and bio-informatically accurate critical dimension and for better analysis of such datasets we develop two evaluation models, one using all features and the other using critical number of features. The performance measurements such as accuracy, specificity, sensitivity, area under the curve, F-score and kappa values are compared. This paper shows that at the critical dimension the evaluation model shows good results for all performance measurements measured on most datasets studied. The difference in performance measurements obtained using only critical number and using all features is significantly less, i.e., there is not much difference in sensitivity, specificity and other measurements calculated. [ABSTRACT FROM PUBLISHER]

Precise transfer of pattern means guarantee in high repeatability and reliability, high throughput and low cost of ownership. By improving this resolution and alignment precision the minimum size can be further reduced to 1nm and beyond. The other important aspect of achieving minimum precised size is the photo resist must be very sensitive to the exposure light to achieve reasonable throughput. However, if the sensitivity is too high, other photoresist characteristics can be affected, including the resolution. Thus, the paper present a preliminary study on fundamentals of resist exposure and development mechanisms for fabrication of Micro- Nanowire formation, We demonstrated significance of considering process parameters such as quality of resist, soft bake, exposure time and intensity, and development time. [ABSTRACT FROM PUBLISHER]

Small Angle X-ray Scattering (SAXS) is a possible candidate to complement and, in a longer term, to replace existing methods like CD-SEM and OCD for measurements of CD profiles. Previously reported CD-SAXS results were very promising; however as obtained using bulky sources as synchrotron, they are most often restricted to research rather than production control. We have designed a pilot set-up (XCD™) around μ-focus X-tube, high-luminosity focusing mirror-monochromator and pixilated detector, having in mind that after further optimization of the components, the tool will have a suitable footprint and acceptable throughput. The system operates on MoKα (17.4 keV) beam shining through the wafer, from below. The measurement spot size is 100 μ. The angular resolution allows to measure structures with a pitch 100 nm and below. A software package was developed to simulate and process XCD spectra, taking into account all the components contributing to the instrumental function of the system. A special technique was developed for alignment. For the purpose of the feasibility study a special CD structure was prepared. It consists of Si trenches with 50 nm pitch. It was found that in a relatively short time, pitch and width can be extracted with a precision on the level 1% RSD. The depth of the trenches was measured using another independent X-ray channel (fast XRR) operating on the CuKα line (8 keV) at the grazing angle, striking normally to the trenches direction. [ABSTRACT FROM AUTHOR]

Interference microscopy satisfies many of the dimensional metrology requirements for semiconductor device interconnects manufacturing by providing 3D topography maps of patterned structures with sub-nm vertical reproducibility. Analysis of topography maps and intensity images with pattern recognition software extends the metrology capability for CD, overlay and registration. This functionality is used in a flexible, multi-purpose, inline process control tool for pre- and post-metallization metrology on BEOL via and bump layers. Through Silicon Vias is another promising field of application, as demonstrated by the strong correlation of optical profiler results to cross-section SEM reference metrology. [ABSTRACT FROM AUTHOR]

This project focuses on five different gate lengths; 0.35 μm, 0.25 μm, 0.18 μm, 0.13 μm and 0.09 μm. These gate lengths were determined by changing the etch location of polysilicon during the fabrication process of NMOS. The electrical characteristics that investigated were threshold voltage (Vth) and current maximum (Idmax). The investigation process was performed by analyzing boron doping concentration in the plysilicon doping, altering impurity in polysilicon doping and also changing arsenic doping concentration in source/drain annealing. The doping concentration was varied properly to gain an optimum property of the transistor. SILVACO TCAD tools were used to obtain electrical characteristics of NMOS structure. In summary, smaller gate length 0.09 μm have optimum voltage and highest current compared to others with Vth = 0.0225 V and Id max = 972.465 μA for device performance. [ABSTRACT FROM AUTHOR]

The MIRAI project has been improving the precision of critical dimension measurements with atomic force microscopy (AFM) by implementing modularized laser interferometers to meet requirements for dimensional measurement at the 45 nm technology node. Recent advances in semiconductor process technologies require a breakthrough in nanometer-pattern dimensional measurement on large wafers such as linewidth, hole diameter, and depth. AFM is promising method to meet this need because of its spatial atomic-level resolution along three axes. The higher the resolution is, the better we can know geometrical shape of a target pattern. We discuss the design of a high-resolution homodyne interferometer modularized and installed in a critical-dimension AFM (CD-AFM) prototype. The symmetrical optical path layout of the homodyne interferometer makes measurement of the mechanical displacements of an AFM scanner highly stable. The stability of the cross-sectional AFM profile for a pattern with a rectangular cross-section was greatly improved by optimizing interferometer linearity and resolution with DSP signal processing and reducing the angular motion and mechanical vibration of the monolithic three-dimensional probe scanner with a unique parallel spring mechanism. Repeated measurement of a nominal 100 nm linewidth along the same scanned line showed a standard deviation of 0.5–1.0 nm (3 sigma). This shows AFM to be one of the most promising metrological tools for next-generation nanodevice fabrication processes. We detail instrumentation, performance, and measurement results. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The continuing progress of sub-65 nm patterning technologies highlights the critical need for high precision metrologies capable of characterizing dense, high aspect ratio patterns. We present data from small angle x-ray scattering measurements of critical dimension and average pattern cross section of photoresist line/space patterns. The technique is non-destructive and capable of sub-nm precision in characterizing dimensions and sub-degree precision in sidewall angle of patterns with regular periodicity. Moreover, the information enabling linewidth, pitch and sidewall angle determination are decoupled. Efforts to probe line edge roughness are also discussed. The technique is applicable to dense structures of arbitrary composition with dimensions of (10 to 500) nm, including lines, vias and contact holes and buried structures. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]