Introduction to Nano by Amretashis Sengupta & Chandan Kumar Sarkar

Author:Amretashis Sengupta & Chandan Kumar Sarkar
Language: eng
Format: epub
Publisher: Springer Berlin Heidelberg, Berlin, Heidelberg

1.3.1 X-ray Lithography

X-ray lithography is one of the modern lithographic techniques that is being widely used in recent time to transfers the geometric patterns from a mask to the surface of the wafer (mainly Si). International Business Machines (IBM) first developed X-ray lithographic technique in the year 1969 and generated metal structure ~20 μm. In this lithographic technique, X-ray from synchrotron radiation is used to generate the pattern [17]. Similar to photolithography, the first step, involved in this lithographic technique, is the exposure of thick layer of resist via patterned mask to highly intensed X-ray beam. The pattern is then exposed to X-ray such that it gets etching into the resist substrate that results negative replica of the mask pattern. In order to remove unwanted material and resist materials (in case of free standing material), chemical treatment is carried out. The mask materials, generally used in X-ray lithography, are made of materials with low atomic mass (polymethyl methacrylate (PMMA) is used as resist material). In this context, it has to be mentioned that the mask materials with high atomic number can’t be used due to attenuation of X-ray. Primarily the requirement of choosing substrate is that it should be conducting in nature. Resolution of X-ray lithography is increased by decreasing wavelength of the X-ray. But the major problem that is inherent in this lithographic technique is the proper alignment of the mask with resist, since no visible light can penetrate through X-ray membrane.

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