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X rays lithography

This document discusses x-ray photolithography, which uses x-rays to transfer geometric patterns from a mask to a resist on a substrate. It describes the lithographic process and sources of x-rays, including electron impact and synchrotron sources. The procedure of x-ray photolithography involves applying PMMA resist to a silicon wafer, exposing it to x-rays through an absorber/membrane mask, and developing the pattern. Key advantages are high resolution capability due to less diffraction effects and large depth of focus. Applications include fabrication of gigabit DRAM and MEMS technologies. Limitations include inability to focus x-rays through a lens and high costs of producing masks.

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X-Ray Photolithography
Contents Lithography  Lithographic Process X-Ray Photolithography Sources of X-Rays i) Electron Impact X-Ray Sources ii) Synchrotron X-ray source Procedure of X-Ray Photolithography Advantages Applications Limitations
Lithography is the process of printing patterns onto a thin film called resist, using localized interaction between this layer and the particle beam. What Is Lithography
G. D. Hutcheson, et al., Scientific American, 274, 54 (1996). Lithographic Process
X-Ray Photolithography is a process which uses X-rays to transfer a geometric pattern from a mask to the resist on the substrate. X-ray Photolithography
Sources of X-rays 1) Electron Impact X-Ray Sources E-beam accelerated at high energy by the metals anode. By striking the target x-rays are emitted. Fig1 Electron beam Impact X-Ray source
2) Synchrotron X-ray source Fig 2 Synchrotron X-ray source Sources of X-rays
Procedure of X-Ray Photolithography  PMMA is applied to the surface of silicon wafer  PMMA hardens when contacted with x- rays  X-ray mask is applied on top of silicon wafer before exposure  Absorber  Membrane  Synchrotron radiation (0.2 – 2 nm)  Gap between substrate and mask Fig 3: Procedures of X-Ray Lithography
Proximity mask Fig 4: X-Ray Lithography use only Proximity mask
Less diffraction effect High Resolution. Large Area (Large depth of focus ) Excellent resist profiles R. Waser (ed.), Nanoelectronics and Information Technology, Chapter 9 Advantages Fig 5: Patterns produced by x-ray photolithography
For febrication of gigabit DRAM. Applications Fig 6: Photograph of DRAM J. Zyss (Ed.): Photonique Mol´eculaire: Mat´eriaux, Physique et Composants, C.R. Physique 3, No. 4 (2002)
Used in the MEMS(micro-electro mechanical systems) technology. Fig 7: Photograph of MEMS Applications Sunney Xie, X., and Trautman, J.K.: Ann. Rev. Phys. Chem. 49, 441–480 (2008)
 Thin Lens Distortion in absorber Cannot be focused through lens Masks are expensive to produce Limitations
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