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As lithographic technology nodes advance beyond the 193 nm generation, the optical absorption of organic materials will require the use of thin layer imaging (TLI) techniques. Of the techniques under consideration, the use of ultra-thin resist (UTR) over a hardmask is the most desirable because of its simplicity and close similarity to standard single layer resist processes. Prior work has demonstrated that the UTR process is capable of pattern transfer to poly silicon device layers with as little as 1000 Angstrom of resist on flat wafers using 248 nm lithography. This was achieved with defect levels comparable to a conventional 5000 Angstrom resist process. In this work, we demonstrate 'proof of concept' by integrating the UTR process into the transistor gate module of a production device using 248 nm lithography. In doing so we focus on three key areas for manufacturability: inherent defectivity of UTR films, sensitivity of thin resist to topography, and quality of pattern transfer. We find that pinhole defects are of little concern in the UTR process after SEM review of defects on un-patterned UTR films. We show that the UTR process is sensitive to wafer topography, since it does not provide a completely planar surface over the underlying device features. Finally, we demonstrate that the UTR process is capable of reliable pattern transfer on a production device with defect levels comparable to the thicker baseline single layer resist process.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Resolution, R, in optical lithography is often described by the Rayleigh equation: R equals k1(lambda) /NA. Since the 0.25 um generation there has been a trend of aggressive gate length reduction for high performance devices. Leading edge logic technologies require gate CDs equal to ½to 2/3 the wavelength of the exposure system. Even with high NA steppers and scanners low k1 patterning is a requirement. Development of processes utilizing OPC and PSM technology is critical to achieving adequate process latitude and CD control. As k1 factor falls below 0.5 the image quality and contrast degrades substantially. One result of low contrast images is that the CD variation in the photomask gives rise to larger than expected printed CD changes: the so-called MEEF. The MEEF can be simply defined as the ratio of the change of the resist feature width to the change in the mask feature width, assuming constant process and illumination conditions. For a 4x mask the MEEF can be calculated.

Extreme UV Lithography (EUVL) is one of the leading candidates for the next generation lithography, which will decrease critical feature size to below 100 nm within 5 years. EUVL uses 10-14 nm light as envisioned by the EUV Limited Liability Company, a consortium formed by Intel and supported by Motorola and AMD to perform R and D work at three national laboratories. Much work has already taken place, with the first prototypical cameras operational at 13.4 nm using low energy laser plasma EUV light sources to investigate issues including the source, camera, electro- mechanical and system issues, photoresists, and of course the masks. EUV lithograph masks are fundamentally different than conventional photolithographic masks as they are reflective instead of transmissive. EUV light at 13.4 nm is rapidly absorbed by most materials, thus all light transmission within the EUVL system from source to silicon wafer, including EUV reflected from the mask, is performed by multilayer mirrors in vacuum.

A laboratory extreme ultraviolet lithography tool (EUVL) has been assembled atSandia National Laboratories [1]. Its major components include a Schwarzschildcamera with 0.1 jim resolution integrated with a laser plasma source (LPS) and amagnetically levitated stage. Other subsystems are a grazing-incidence optical system to maintain focus, and a through-the-lens Moire alignment system for overlay. This exposure tool is being used to study integration issues for EUVL.Experiments have been performed to characterize the alignment system's performance. The measured sensitivity of the alignment system is 15 nm 3. 1. INTRODUCTION A laboratory extreme ultraviolet lithography tool (EUVL) has been assembled atSandia National Laboratories' . Its major components include a Schwarzschild camera with 0.1 jim resolution integrated with a laser plasma source (LPS) and a magnetically levitated stage. Other subsystems include a grazing-incidence opticalsystem to maintain focus and an alignment system for overlay. This exposure toolis being used to study integration issues for EUVL. In order to demonstrate thesuccessful integration of the system, microelectronic devices and circuits will befabricated with at least one lithography step performed with EUVL.In this paper, we will describe in detail the EUVL tool and its capabilities. We willalso report results from recent experiments performed to characterize theperformance of the visible through-the-lens (TTL) Moire alignment system.

A study was conducted to explore the manufacturability of ultrathin resist by focusing on two key issues, defects and etch resistance. Defects in ultrathin resist were characterized by optical inspection and scanning electron microscopy reviews. A number of representative defect types in the ultrathin resist/hardmask process were identified. With process optimization, defect density in ultrathin resist was reduced to levels that are comparable to that of a baseline 0.5 μm thick resist process on nontopographic wafers. Etch resistance sufficient for patterning metal–oxide–semiconductor transistor gate film stacks was demonstrated for a 100–150 nm thick resist layer.

Extreme ultraviolet lithography (EUVL) is a candidate for high‐volume production of integrated circuits with 0.1 μm design rules. As a reduction imaging technique with robust mask substrates, EUVL reduces the mask contribution to the critical dimension (CD) error budget. However, the ability to manufacture EUVL mask blanks that are free of printable defects remains an important challenge. Electromagnetic simulations and imaging experiments have suggested that defects in the substrates and reflective coatings, in particular, may be highly printable and difficult to detect. A defect printability study using programmed defects was performed in order to determine the printing behavior of mask defects of different sizes and locations with respect to absorber features. Imaging was performed using a 10× Schwarzschild camera operating at 13.4 nm with a numerical aperture of 0.08, corresponding to a Rayleigh resolution of 0.1 μm. This system has an effective exposure field of 0.4 mm diam. Measurements of the defec...

We report experimental and theoretical studies of the resist sidewall angles produced using extreme ultraviolet lithography at exposure wavelengths of 37.5, 13.9, and 6.8 nm. We show that high resist absorption in this wavelength region leads to a significant degradation in pattern sidewall angle. Because steep resist profiles are needed in semiconductor manufacturing to ensure adequate linewidth control it seems unlikely that a single‐layer resist process can be used in extreme ultraviolet lithography except at the shortest wavelength.