Patterning of 100 nm Features Using X-ray Lithography (original) (raw)
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Proceedings of The IEEE, 1993
The fundamentals of X-ray lithography are reviewed. Issues associated with resolution, wafer throughput, and process latitude are discussed. X-ray lithography is compared with other lithographic technologies; future advancements, such as X-ray projection lithography, are described. It is shown that the major barrier to the near-term success of X-ray lithography is the requirement for a defect-fvee one-to-one mask which satisfies the stringent image-placement needs of submicrometer patterning.
Design, Characterization, and Packaging for MEMS and Microelectronics, 1999
New developments for X-ray nanomachining include pattern transfer onto non-planar surfaces coated with electrodeposited resists using synchrotron radiation X-rays through extremely high-resolution masks made by chemically assisted focused ion beam lithography.
Extension of x-ray lithography to 50 nm with a harder spectrum
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1999
To be competitive with the next-generation lithography technologies, synchrotron-based proximity x-ray lithography ͑PXRL͒ must prove to be extendible to produce minimum feature sizes of 70 nm and below. We present here a relatively simple and practical method to improve the PXRL system performance for the replication of features down to 50 nm with reasonable process latitude at large (gϷ15) mask-wafer gaps. Contrary to previous conclusions indicating ϭ1 nm as the best operating region, we find that a significant improvement can be achieved by a modest decrease in the effective wavelength of present PXRL systems, and by the use of non-silicon-based materials in beamline filters and masks. The proposed PXRL system requires a synchrotron storage ring with slightly higher energy than older rings such as Aladdin, but well within the design parameters of the newer generation of synchrotrons, and some beamline modifications. In addition, a diamond mask substrate is also utilized to eliminate the x-ray absorption due to the Si-absorption edge at 1.75 keV.
Can proximity x-ray lithography print 35 nm features? Yes
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2001
We report on the results of our effort to extend proximity x-ray lithography ͑PXL͒ to 35 nm using a harder energy spectrum, and choosing the appropriate materials for the mask and the resist to match the transmission and absorption at higher energies. Previous studies ͓M.
An overview of x-ray lithography for use in semiconductor device preparation
Vacuum, 1991
Different aspects of X-ray lithography with a proven capability for the fabrication of 0.1 pm lines and 0.5 pm devices such as ULSI and multi-megabit memory are discussed. The technical, dimensional and economic features of modern X-ray sources such as synchrotron with classical, normal and superconducting storage rings, have been compared. Materials fully transparent or opaque to X-rays do not exist and so the choice of X-ray mask substrate and patterning of absorber on it are rather critical. EBL, FIBL, RIE, XRL and other techniques used for preparing submicron masks have been dealt with. The sensitivity and resolution of 76 positive and negative X-ray resists vis-2-vis specific sources and characteristic features of 7 XRL systems are compared. Alignment schemes using laser controlled stage and visible lights are discussed. R&D as well as commercial systems and results like quarter micron patterns, 0.5 pm CMOS, SAW BPF and large aspect ratio grooves are demonstrated.
Physical and technological limits in optical and x-ray lithography
Microelectronic Engineering, 1987
If we assume that optical steppers for deep UV lithography can be developed down to wavelengths of 248 nm, but not further, then the focus depth requirement of device manufacturing will restrict the minimum linewidth to 0.5 ~m for standard single layer resists and perhaps to 0.35 ~m for advanced complex resists systems. While optical lithography is resolution limited, an analysis of the overlay budget reveals that X-Ray synchrotron lithography is confined by overlay requirements. When a compensation mechanism for linear mask and wafer distortion can be realized, then minimum linewidths of 0.3 to 0.35 ~m with chip sizes up to 30 mm would be feasible with X-Rays. A comparison of the lithography performance with future DRAM demands indicates that optical lithography would meet the requirements down to 16M or 64M, and X-Ray lithography down to 256M.
Investigation of mask pattern proximity correction to reduce image shortening in X-ray lithography
Microelectronic Engineering, 1998
Previous experimental studies of proximity x-ray lithography for complex patterning at 75-125 nm linewidths have indicated that image shortening is significant at >10 ~m gaps . Simple serifs added to line ends have been shown to reduce line-end shortening for 75-125 nm ground-rule SRAM-like (static random access memories) patterns. However, line-end shortening is still >30 nm for 85 nm ground-rule patterns at 10-15 ~tm gaps. In this study, simulations are used to evaluate requirements on serif patterning to reduce line-end shortening. Initial experimental results using positive resist indicate that negative tone mask patterns may result in less line-end shortening.
Monte Carlo simulation of line edge profiles and linewidth control in x-ray lithography
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1985
X-ray lithography exposures of PMMA on silicon have been simulated with a Monte-Carlo method including the energy backscattering from the substrate. The line-edge acuity of the resist image has been modeled with experimentally determined x-ray spectra of various sources (aluminum, tungsten, and palladium) and various source diameters (0.1, 1.5, and 3 mm). The intrinsic line-edge degradation due to secondary electron exposure is derived from the point source images while the finite-source effect (penumbra) is extracted from the additional degradation at finite source diameters. The penumbra effect is found to be rather small in PMMA. Depth profiles of the energy absorbed in PMMA demonstrate the significance of the energy backscattering from the substrate for energetic x rays. This effect can be significantly reduced by an organic spacer layer. The extent of the geometric projection effect has been modeled with the aluminum source. The results show that a finite angle of incidence of the x rays causes a sizable enlargement of the mask shadow due to the finite absorber thickness ultimately restricting the usable field size. The resultant linewidth variation is more pronounced for a mask with vertical profiles than for one with 20' wall angle. It can be reduced by thinning the absorber although at the expense of the mask contrast. The angle of incidence is replicated in the resist profiles causing an increasing tilt of the lines further away from the center of the wafer. This also restricts the field size but can be controlled to some extent by the thickness of the imaging resist layer. FIG. I. X-ray lithography proximity scheme. The radial variation of the line-to-space ratio restricts the usable field size.