X-ray lithography produces next-generation probe

Using novel X-ray lithographic micromachining technology, Sumitomo Electric Industries has developed a compact contact probe that can be used to test next-generation high-frequency ICs.

Using novel X-ray lithographic micromachining technology, Sumitomo Electric Industries has developed a compact contact probe that can be used to test next-generation high-frequency integrated circuits.

Contact probes work by coming into contact with IC pads and then passing electrical test signals into and out of the pad.

As ICs become more integrated and of higher frequencies more advanced testing technology is required.

IC pad pitches are getting smaller, with pad pitches for memory devices seen narrowing from 120-150um at the moment to 100um or less in the future.

However, with conventional machining methods, contact probe size cannot be made smaller than a certain limit.

Conventional probes are unsuitable for testing high-frequency ICs that operate in the region of 200 to 500MHz or more because they are too long and the resulting crosstalk is too large.

Using its own technology of X-ray lithographic micromachining, Sumitomo Electric has developed a contact probe that is sufficiently compact which can be used for narrow IC pad pitches and high-frequency ranges.

The new contact probe is 30um square and less than 2mm long.

Lithography using X-rays carry certain advantages over lithography using ultraviolet light, allowing thicker microstructures, sharper edges, and improved accuracy.

The main material of the developed contact probe is nickel and by adding manganese to it, Sumitomo Electric has achieved heat resistance of 150C or more.

By miniaturising normally 0.5-1um nickel crystals into 50nm and by arranging crystal orientation to the same direction, Sumitomo succeeded in developing a material that is extremely high in Young's modulus and in elastic limit.

As the contact probe has an extremely minute microstructure, material control at a nano level is an issue of great importance.

To solve this issue and enable stable fabrication of the material, Sumitomo Electric has devised the plating process and other procedures.

The market for next-generation contact probes is forecasted to grow to about 20 billion yen in 2005.

Sumitomo Electric therefore plans to commercialise the new contact probe some time in 2002.

Moreover, Sumitomo Electric aims to apply this fabrication technology to fields other than contact probes.

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