Masato Hamatani

Portable phase measuring interferometer using Shack-Hartmann method

A real-time inspection is useful and effective to optimize lens aberrations of excimer-exposure sytem, which can expose patterns less than 100 nm. We have developed a portable i.e., compact and lightweight phase measuring interferometer (P-PMI), which can be attached to a stage of the exposure system during real-time monitoring the aberration of the projection lens mounted on the exposure system. Measured repeatability of the wavefront measurement is ab out 0.1 mλ and tool-to-tool difference is 0.6mλ. Measured wavefront during adjusting a projection lens agree dwell with a simulated result. LWA was successfully optimized using P-PMI data.

Self-calibration of wafer scanners using an aerial image sensor

To improve both the versatility and stability of leading edge wafer scanners, the functionality of an integrated aerial image sensor has been expanded. The system performance of current wafer scanners is a strong function of the quality of image formation of the projection lens. Current wafer scanners use aerial image sensors for best image plane calibration, illumination telecentricity calibration, coma aberration calibration, and distortion calibration. The aerial image sensor is used not only for a scanners self-calibration but also during the projection lens manufacturing purposes. The slit-scan type aerial image sensor is used for measurement of the intensity distribution of the aerial images. This type of the image sensor can detect the intensity distribution of the aerial image from 110nm L/ S to 6micrometers L/ S. Therefore this aerial image sensor covers most aerial image measurement requirements. In this paper we will focus on the aerial image measurement for self-calibration purposes and their actual performances. We evaluate the actual performance of illumination telecentricity and coma aberration measurement. Evaluation is based upon not only measurement repeatability but also its agreement with resist image measurement results.

Latest performance of immersion scanner S620D with the Streamlign platform for the double patterning generation

Currently, it is considered that one of the most favorable options for the 32 nm HP node is pitch-splitting double patterning, which requires the lithography tool to achieve high productivity and high overlay accuracy simultaneously. In the previous work [1], we described the concepts and the technical features of Nikons immersion scanner based on our newly developed platform, Streamlign, designed for 2nm overlay, 200wph throughput, and short setup time. In this paper, we present the latest actual performance of S620D with the Streamlign platform. Owing to the high repeatability of our new encoder metrology system, Birds Eye Control, and Stream Alignment, S620D achieves less than 2 nm overlay accuracy, less than 15nm focus accuracy, and successful 32 and 22 nm L/S pitchsplitting double patterning exposures. Furthermore, the results at high scanning speed up to 700 mm/s are fine and we have successfully demonstrated over 4,000 wpd throughput, which confirms the potential for high productivity. Nikon has developed this Streamlign as an optimized long life platform based on the upgradable Modular2 structure for upcoming generations. The performance of S620D indicates the possibility of immersion extension down through the 22 nm HP node and beyond.

Mass production level ArF immersion exposure tool

VLSI chips are becoming denser and the industry is now moving to the development of devices at the 65nm node. While Nikon is working toward the development of next-generation lithography tools, we are also making efforts to extend the life of DUV excimer steppers by continuing reductions in feature size without any major changes to the conventional process. Nikons new model, the ArF Immersion Scanner NSR-S609B, utilizes immersion lithography in which the space between the projection lens and the wafer is filled with ultra pure water with a refractive index of 1.44. This immersion technology enables the NSR-S609B to break through the N.A. 1.0 barrier to achieve the worlds highest N.A. of 1.07, an impossible feat by a conventional lithography or dry exposure. This system will contribute to the production of advanced 55nm and smaller devices. Latest evaluation results of the immersion imaging system and the new stage system are presented.

Wafer edge-shot algorithm for wafer scanners

The requirement for the higher resolution is pushing up the NA of the projection lens, so the DOF becomes shallower and the focus budget becomes tight. On the other hand, the requirement for the higher through-put is still demanding. To achieve the best throughput, the alternate scanning exposure sequence is inevitable to current wafer scanners. To realize the alternative scanning exposure, it is necessary to perform precise focusing control even at the partial shot on the wafer edge region. A wafer edge stepwise focusing algorithm is developed. This algorithm utilizes multi-points focusing sensors and dynamically switches the focusing sensors during alternating scan exposure of the partial site on the wafer edge region. Thus the amount of the defocus on the wafer edge region is minimized. The actual performance of the wafer edge stepwise focusing algorithm is discussed. This algorithm can be used with or without pitching motion control of the wafer leveling stage. The influence of the pitching motion control to the focusing performance is also discussed.

Illumination System Of An Excimer Laser Stepper

An illumination system suitable for an excimer laser stepper has been investigated. Unnecessary interference pattern(speckel) is reduced effectively by scanning the laser beam. We report spatial coherence of the lasers with different spectral line width, illumination system of the stepper, appearance of the interference pattern,its spacing and contrust and their relation to the illumination system and to the coherence of the laser. Then we report reduction of this pattern together with a simple method to measure its contrast.

New advanced lithography tools with mix-and-match strategy

Nikon has developed cutting-edge lithography tools, and its product lineup encompasses all exposure wavelengths. They are: the NSR-S307E ArF scanner for the 90nm node; the NSR-S207D KrF scanner for the 110nm node; the NSR-SF130 i-line stepper for the middle layer and the new concept NSR-SF200 KrF stepper, which offers unparalleled productivity and cost performance. In addition, a powerful support system is provided, the Lithography Equipment Engineering System, which will allow its customers to use all of these exposure tools simultaneously and derive the maximum benefit of the mix-and-match strategy. The use of this system will increase the uptime and enable their combined performance to exceed that of a stand-alone tool.Latest actual performance data from each of the tools and the result of the optimization performed using application software will be reported.

Progressive ArF exposure tool for 65nm node lithography

To meet shrinkage demands of device pattern size, a new platform ArF exposure tool , NSR-S308F, has been developed with an extremely high NA projection lens. This equipment has been developed not only for ensuring better imaging of dry ArF, but also for achieving imaging enhancement of immersion ArF. To satisfy imaging and overlay accuracy requirements for 65nm node lithography, the heat management, body stiffness, and reaction force canceling system have been drastically improved. Optimized illumination conditions and polarized illumination1 have been developed to expand the severe process margin for ArF dry exposure tools. In addition, some applications support: the maximization of imaging performance of S308F; the aerial image measurement function2 to correct aberration of projection lens; the optimization software of lens aberration in a specific device pattern, and special software to realize excellent mix and match accuracy. Latest evaluation results and the improvement items of S308F will be presented.

Effect of azimuthally polarized illumination imaging on device patterns beyond 45nm node

For an ultra-high numerical aperture (NA), such as that exceeding 0.9, the p-polarized component of light that has passed through a region at the limit of the NA of a high-NA lithography tool, degrades contrast because of the so-called vector imaging effect, and is therefore detrimental to the formation of optical images. Polarized illumination removes the effect of the p-polarized light component and provides illumination light composed of s-polarized light. The higher the NA, the greater are the benefits of polarized illumination. Therefore, in lithography at the 45-nm node and below, polarized illumination is viewed as an indispensable technology. We explore the applicability of polarized illumination to device manufacturing processes at the 45-nm node and beyond, with a focus on the utilization of azimuthally polarized illumination, which enables one mask exposure. The data used in this research were obtained through imaging simulations and experiments using a dry lithography tool equipped with a 0.92-NA projection lens. In imaging simulations using a lithography simulator, the application of azimuthally polarized illumination improved image contrast in resists by approximately 20% for half pitch (HP) 65-nm dense patterns. As a result, device patterns showed enhanced robustness with respect to exposure dose error; extended process windows; and reduced mask error enhancement factor (MEEF), line edge roughness (LER), and line end shortening (LES). This paper examines the results of experiments conducted using imaging simulations and lithography tools on other product device like patterns (besides special patterns in which benefits can clearly be expected, including dense (L/S) patterns), and reports the results.

Latest results from the Nikon NSR-S620 double patterning immersion scanner

Double patterning (DP), an extension of immersion, is the leading contender for the manufacturing of 32 nm half pitch node devices. For DP, substantial improvement in overlay accuracy is required to meet the CDU requirements for the 32 nm node, and substantial increase in throughput is required to meet the cost requirements. To meet these challenges, Nikon introduced the NSR-S620. The S620 is based on the Streamlign platform, which is characterized by three innovations: Birds Eye Control, Stream Alignment, and Modular2 Structure. In addition, many of the current systems and techniques have been refined to meet the requirements for DP. This presentation will discuss these technological improvements and show the latest technical results.