The authors will explore the possible contact hole lithography solutions for the future technology nodes, from 90 nm
down to 32 nm half-pitch (HP) in this paper. The special emphasis will be on the logic application because of the lack of
a strong resolution enhancement technique (RET) for the random hole layouts. The use of illumination optimization,
focus drilling can extend the projection optical lithography down to near 60 nm HP. The adoption of pitch split double
exposure technique is needed to provide a robust manufacturing process window to further extend to around 50 nm HP.
To further shrinking the design rule, a double patterning is need after the pitch split. The pitch split double patterning
technique reaches its limit around 40 - 45 nm HP. The desire to not limit the integrated circuit (IC) design requires the
lithography process k1 to be as high as possible. The random logic contact hole application is well suited for EUV
lithography for 35 nm HP and below because of the high k1 process and a potential for high productivity of a mask based
lithography. The pattern density of contact hole masks would not require a stringent mask defect requirement, and
moreover, the EUV's relatively higher system flare does not have a significant impact on imaging. Actual EUV data and
calibrated simulations will be used to demonstrate that EUV can provide a robust process window.
This paper presents lithographic performance results obtained from the newest member of ASML's TWINSCAN platform-based step & scan systems, the TWINSCAN XT:1400. The system has been designed to meet the semiconductor industry's aggressive requirements on CD control, overlay and productivity at and below the 65 nm node. This dual stage 193 nm lithographic system combines the worlds highest NA, with excellent overlay and CD control at high throughput on both 200 and 300 mm wafers and is intended for use in volume production environments. Advances in stage technology have enabled further extension of stage scan speeds and an associated increase in tool productivity. However, maximizing the number of yielding die per day also requires stringent overlay and Critical Dimension (CD) control. Tight CD control at improved resolution is supported by the Starlith 1400 projection lens and the extended sigma capabilities of the new AERIAL-E illumination system. Focus control is improved in line with the stringent requirements posed by low-k1 imaging applications, taking full advantage of the unique dual-stage TWINSCAN system architecture.
Current roadmaps show that the semiconductor industry continues to drive the usable Rayleigh resolution towards the fundamental limit (for 50% duty cycle lines) at k1=0.25. This is being accomplished through use of various resolution enhancement technologies (RETs), extremely low aberration optics with stable platforms, and resists processes that have ever-increasing dissolution contrast and smaller diffusion lengths. This talk will give an overview of the latest optical mechanisms that can be used to improve the imaging system for low k1 resolutions. We show 3 non-photoresist techniques to measure the optical parameters of a scanner: 1) a new fast phase measurement interferometer to measure aberrations is presented with an accuracy and repeatability of <3mλ, 2) we introduce a method to measure the illumination profile of the exposing source, and 3) a measurement system to monitor scattered light is presented with correlation to other techniques using a salted pellicle experiment to create controlled scattered light. The optimization of illumination and exposure dose is presented. We show the mechanism for customizing illumination based on specific mask layers. We show how this is done and compare process windows to other more conventional modes such as annular illumination or QUASAR. The optimum design is then implemented into hardware that can give extremely high optical efficiency. We also show how system level control mechanisms can be used to field-to-field and across-field exposure to compensate for lithography errors. Examples of these errors can include reticle CD deviations, wavefront aberrations, and across-field illumination uniformity errors. CD maps, facilitated by SEM and ELM, can give the prescribed changes necessary. We present a system that interfaces to new hardware to compensate these effects by active scanner corrections.
Aberrations, aberrations, here there everywhere but how do we collect useful data that can be incorporated into our simulators? Over the past year there have no less than 18 papers published in the literature discussing how to measure aberrations to answering the question if Zernikes are really enough. The ability to accurately measure a Zernike coefficient in a timely cost effective manner can be priceless to device manufacturers. Exposure tool and lens manufacturers are reluctant to provide this information for a host of reasons, however, device manufacturers can use this data to better utilize each tool depending on the level and the type of semiconductors they produce. Dirksen et al. first discussed the ring test as an effective method of determining lens aberrations in a step and repeat system, later in a scanning system. The method is based on two elements; the linear response to the ring test to aberrations and the use of multiple imaging conditions. The authors have been working to further enhance the capability on the test on the first small field 157 nm exposure system at International SEMATECH. This data was generated and analyzed through previously discussed methods for Z5 through Z25 and correlated back to PMI data. Since no 157nm interferemetric systems exist the lens system PMI data was collected at 248nm. Correlation studies have isolated the possible existence of birefringence in the lens systems via the 3-foil aberration which was not seen at 248nm. Imaging experiments have been conducted for various geometry's and structures for critical dimensions ranging from 0.13micrometers down to 0.10micrometers with binary and 0.07micrometers with alternating phase shift mask. The authors will review the results of these experiments and the correlation to imaging data and PMI data.
ARTEMISTM (Aberration Ring Test Exposed at Multiple Illumination Settings) is a technique to determine in-situ, full-field, low and high order lens aberrations. In this paper we are analyzing the ARTEMISTM data of PAS5500/750TM DUV Step & Scan systems and its use as a lithographic prediction tool. ARTEMISTM is capable of determining Zernike coefficients up to Z25 with a 3(sigma) reproducibility range from 1.5 to 4.5 nm depending on the aberration type. 3D electric field simulations, that take the extended geometry of the phase shift feature into account, have been used for an improved treatment of the extraction of the spherical Zernike coefficients. Knowledge of the extracted Zernike coefficients allows an accurate prediction of the lithographic performance of the scanner system. This ability is demonstrated for a two bar pattern and an isolation pattern. The RMS difference between the ARTEMISTM-based lithographic prediction and the lithographic measurement is 2.5 nm for the two bar pattern and 3 nm for the isolation pattern. The 3(sigma) reproducibility of the prediction for the two bar pattern is 2.5 nm and 1 nm for the isolation pattern. This is better than the reproducibility of the lithographic measurements themselves.
This paper presents an evaluation on the 0.15 micrometers and 0.13 micrometers lithographic patterning alternatives for semiconductor devices. Baseline for the evaluation is a first generation ArF step and scan exposure system with 0.63 NA projection optics. The system layout is discussed and main performance data on imaging, overlay and throughput are presented. Binary masks, and various advanced 193 nm resist system are used to evalute process latitudes of dense lines, isolated lines and contact holes. The manufacturing economics, expressed in Cost Of Ownership, are evaluated for an ArF based production technology, and compared to critical layer KrF.
KEYWORDS: Luminescence, Near field scanning optical microscopy, Polarization, Near field optics, Glasses, Reflection, Polymers, Optical microscopy, Aluminum, Absorption
A Fluorescence Scanning Near-Field Optical Microscope operated in reflection is presented. A pulled optical fiber is used both as an emitter for the exciting light and a collector for the generated fluorescence. The advantage of this set-up is the use of the fiber tip as an emitter and a collector. The sample is locally illuminated and no extra optical elements are needed for the detection. We will describe the shear force set-up which is used to control the tip to surface distance. Direct correlation between force map and optical signal is thus possible. Fluorescence images have been obtained on Langmuir-Blodgett films where we estimate the resolution at 200 nm. Moreover the anisotropic property of the monolayer allows polarization contrast measurements. Thus, we show true optical contrast due to fluorescence and polarization is applicable to this configuration. Artifacts in LB films shear force image are discussed. Shear force approach curves obtained on glass and polymer domains are presented to explain the chemical origin of the phenomenon.
KEYWORDS: Luminescence, Near field scanning optical microscopy, Near field optics, Near field, Optical fibers, Image filtering, Diffraction, Optical microscopy, Microscopy, Biomedical optics
Near-field Scanning Optical Microscopy (NSOM) is a true optical microscopic technique allowing fluorescence, absorption, reflection and polarization contrast with the additional advantage of nanometer lateral resolution, unlimited by diffraction and operation at ambient conditions. NSOM based on metal coated adiabatically tapered fibers, combined with shear force feedback and operated in illumination mode, has proven to be the most powerful NSOM arrangement, because of its true localization of the optical interaction, its various optical contrast possibilities and its sensitivity down to the single molecular level. In this paper applications of `aperture' NSOM to Fluorescence In Situ Hybridization of human metaphase chromosomes are presented, where the localized fluorescence allows to identify specific DNA sequences. All images are accompanied by the simultaneously acquired force image, enabling direct comparison of the optical contrast with the sample topography on nanometer scale, far beyond the diffraction limit. Thus the unique combination of high resolution, specific optical contrast and ambient operation offers many new direction possibilities in biological studies.
A `stand-alone' Photon Scanning Tunneling Microscope combined with an Atomic force Microscope, using a micro-fabricated silicon-nitride probe, is applied to the imaging of field distribution in integrated optical ridge waveguides. The electric field on the waveguide is locally probed by coupling to the evanescent wave. Application to direct observation of TM and TE modal field distributions, both in lateral and vertical direction, mode beating between low and higher order modes, and behavior of a Y-junction wavelength (de)multiplexer is demonstrated.
KEYWORDS: Near field scanning optical microscopy, Microscopes, Near field optics, Atomic force microscopy, Reflection, Optical microscopes, Scanning probe microscopy, Compact discs, Semiconductor lasers, Image resolution
Images obtained with a scanning near field optical microscope (SNOM) operating in reflection are presented. We have obtained the first results with a SiN tip as optical probe. The instrument is simultaneously operated as a scanning force microscope (SFM). Moreover, the instrument incorporates an inverted light microscope (LM) for preselection of a scan area. The SiN probe is operated in the contact regime causing a highly improved lateral resolution in the optical image compared to an alternative set-up using a fiber probe, which is also presented. The combined microscope is operated either in open loop or as a force regulated SNOM. Near field optical images can be directly compared with the topography displayed in the simultaneously recorded SFM image.
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