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.

1. X-Ray
Photolithography

2. 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

3. 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

4. G. D. Hutcheson, et al., Scientific American, 274, 54 (1996).
Lithographic Process

5. 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

6. 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

7. 2) Synchrotron X-ray source
Fig 2 Synchrotron X-ray source
Sources of X-rays

8. 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

9. Proximity mask
Fig 4: X-Ray Lithography use only Proximity mask

10. 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

11. 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)

12. 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)

13.  Thin Lens
Distortion in absorber
Cannot be focused through lens
Masks are expensive to produce
Limitations

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