Fabrication of the X-Ray Mask using the Silicon Dry Etching (original) (raw)
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Japanese Journal of Applied Physics, 2002
In order to meet the long term goals of the International Technology Roadmap for Semiconductors, it is important to demonstrate that X-ray masks can be fabricated at resolutions well below the 100 nm barrier. This paper presents results on the use of conventional electron-sensitive resists and the silicide direct write electron beam lithography process (SiDWEL) for the fabrication of X-ray masks with sub-100 nm resolution. By optimizing the deposition of the thin films using conventional evaporators, the SiDWEL process was able to achieve linewidths of less than 40 nm and line spacing of less than 100 nm. The silicide patterns formed by the SiDWEL process are sufficiently resistant to plasma etching to directly transfer the patterns to the tantalum absorber. To improve the turnover time for mask fabrication, different writing schemes were studied, including combining the SiDWEL process with QSR-4, a novel negative resist designed specifically for this application.
High resolution x-ray masks for high aspect ratio microelectromechanical systems (HARMS)
Micromachining and Microfabrication Process Technology VIII, 2003
X-ray lithography is commonly used to build high aspect ratio microstructures (HARMS) in a 1:1 proximity printing process. HARMS fabrication requires high energy X-rays to pattern thick resist layers; therefore the absorber thickness of the working X-ray mask needs to be 10-50 µm in order to provide high contrast. To realize high resolution working X-ray masks, it is necessary to use intermediate X-ray masks which have been fabricated using e-beam or laser lithographic techniques. The intermediate masks are characterized by submicron resolution critical dimensions (CD) but comparatively lower structural heights (~2 µm). This paper mainly focuses on the fabrication of high resolution X-ray intermediate masks. A three-step approach is used to build the high resolution X-ray masks. First, a so called initial mask with sub-micron absorber thickness is fabricated on a 1 µm thick silicon nitride membrane using a 50KeV e-beam writer and gold electroplating. The initial X-ray mask has a gold thickness of 0.56 µm and a maximum aspect ratio of 4:1. Soft X-ray lithography and gold electroplating processes are used to copy the initial mask to form an intermediate mask with 1 µm of gold. The intermediate mask can be used to fabricate a working X-ray mask by following a similar set of procedures outlined above.
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.
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.
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.
Masks for X-Ray-Lithography with a Point-Source Stepper
Journal of Vacuum Science & Technology B, 1992
We describe some key aspects of proximity x-ray technology currently being developed at AT&T, from mask fabrication to wafer patterning. The masks are primarily based on polycrystalline Si membranes, 1 J.tffi thick, which are formed directly on optically flat glass disks. A tungsten absorber layer is deposited on the membranes by radio-frequency diode sputtering, with in situ stress control in the deposition chamber so that stresses < 10 MPa are routinely achieved. Patterns are defined in an organosilicon negative resist, P(SI-CMS), using an electron beam writing tool and a neural network based proximity correction algorithm. The patterns are transferred into metallic absorber layers by reactive ion etching in a parallel plate plasma system. Using the above procedure, we have fabricated masks with 0.25 f.lm features and also some test patterns with lines and spaces as small as 0.1 ,urn. X-ray exposures were done with a Hampshire 5000P point source stepper, using AZ PF-114 resist from Hoechst-Ce1anese.
Mask technologies for soft-x-ray projection lithography at 13 nm
Applied Optics, 1993
We describe a variety of technologies for patterning transmissive and reflective soft x-ray projection lithography masks containing features as small as 0.1 pLm. The transmission masks fabricated for use at 13 nm are of one type, a Ge-absorbing layer patterned on a boron-doped Si membrane. Reflective masks were patterned by various methods that included absorbing layers formed on top of multilayer reflectors, multilayer-reflector-coating removal by reactive ion etching, and ion damage of multilayer regions by ion implantation. For the first time, we believe, a process for absorber repair that does not significantly damage the reflectance of the multilayer coating on the reflection mask is demonstrated.