Lithography beamline at Indus-2

• Introduction
• Optical design
• Mechanical layout
• Specifications
• Present Status

Introduction

Synchrotron radiation sources, with their high brightness and high photon flux, are attractive to achieve higher lithographic resolution. They are used for deep X-ray lithography, also known as LIGA ( LIthography, Galvanoformung (electroplating) and Abformung (molding)), for producing high aspect ratio three-dimensional structures that opens a wide variety of potential applications like micro-electro-mechanical-system (MEMS). Lithography at the soft X-ray range (photon energies from 1 to 3 keV) achieves the highest lithographic resolution (< 100nm). On the other hand, with lithography done in hard X-ray region (> 4 keV), sensitive materials of thickness, tens of microns, can be exposed. In addition to the traditional application of manufacturing microelectronic semiconductor devices using lithography, many new applications of synchrotron radiation based lithography can be envisaged using hard and soft X-rays. Microstructures with high aspect ratio (100-1000) are widely applied to the various field such as micro mechanics, micro-optics, sensor and actuator technology, and biological, medical and chemical engineering.

During the last one and half decade there has been a rapid development in microfabrication technology driven by the need of low-cost micro-components and microsystems. If the recent development in the field of micro optics, micromechanical engineering and biochemical engineering are projected forward, it is obvious that micro-technology will be one of the outstanding key technologies of the 21st century.

Taking into consideration the view about microsystem technologies prevalent worldwide, a dedicated beamline is required for the fabrication of (i) structures with micro and nano resolutions using soft x-ray lithography (SXRL) and (ii) high aspect ratio in 3-dimension structures (LIGA) using deep x-ray lithography (DXRL). The proposed lithography beamline on Indus-2 is combination of soft and deep x-ray lithography (SDXRL) beamline.

Optical layout

The lithography beamline would be set up on a bending magnet source of Indus-2 and would have a wide lithographic window without the use of any monochromator. The main design consideration for a lithography beamline is to produce a radiation at the sample position having both a high flux in the appropriate x-ray range and a high degree of homogeneity with respect to the intensity profile in horizontal plane. The optical layout of the beamline is shown in figure 1. The selection of soft- and hard x-ray energy domains is achieved with combination of high-pass filters (Be-windows and absorption edge filter) and low-pass filters (mirrors at increasing angles of incidence). The beamline design allows continuous change of spectral range of interest from soft to hard X-ray region. In order to vary the cut off energy of the spectrum, the grazing incidence angle of the mirror is varied. Using mirrors at grazing incidence and Be-windows, energy spectrum between 1-18 keV can be tuned as shown in figure 2.

Mechanical layout

Beamline specifications

Present status

• The beamline is under construction phase and being installed on bending magnet port no 7 of Indus-2.
• The heart of the beamline, two mirror system is installed on the beamline. Frontend of the beamline is under UHV environment and being in commissioning phase.
• The mechanical fabrications of other sub-components are under process. The delivery of slit system is due in February 2010 and purchase of endstation of the beamline is in final phase.

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