Original URL: http://www.theregister.co.uk/2004/04/26/golden_3d_circuits/

Gold and laser key to 3D circuits

Auric Goldfinger would be delighted

By Lucy Sherriff

Posted in Science, 26th April 2004 15:56 GMT

Physicists in Shanghai have developed a revolutionary new technique for building three-dimensional micro-circuits, using gold oxide, chunks of glass and some high powered lasers to create a kind of 3D dot-matrix transistor-printer.

Taking circuit boards into 3D is a logical and neccessary next step: although chip makers are squeezing as much as they can on to circuit boards, going up as well as out would help enormously. In fact, finding an inexpensive and reliable way of creating a 3D circuit is something of a holy grail for scientists in the field.

Existing techniques include sequential fabrication. In this case, the circuit is built up layer by layer: one layer fabricated, then a layer of material is deposited on top, then another layer can be fabricated, and so on. The trouble with this is that the lower layers are 'cooked' too many times.

Another method involves stacking completed wafers on top on each other and somehow bonding them together. Still another involves literally soldering two chips on top of each other. All are basically variations on a theme of the traditional circuit board fab process.

The team from the Shanghai Institute of Optics and Fine Mechanics has approached the problem in a totally new way, according to Nature. It has found a way to draw circuits by firing a laser directly into glass blocks enriched with gold oxide at one part per 10,000.

They fire short laser pulses at the block to dislodge individual gold atoms. Once the block is heated to 550 ºC, the gold atoms coalesce into blobs inside the glass. So far the team has limited its efforts to sketching images in the blocks made up on millions of nanoscale golden globules.

The next step is to use a slightly higher concentration of gold oxide. This, the researchers hope, will help to complete the circuits, as the blobs of gold run into one another. The findings have been published in chemistry journal Angewandte Chemie.

According to Nature, the team has also suggested using the technique to store data: a dot in a 3D grid could represent a bit of data. However, it concedes that it may be some time before this is a commercially viable disk replacement technology. ®

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Original story on Nature

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