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Bonding Together Surfaces Coated With Silicon Dioxide

IP.com Disclosure Number: IPCOM000087212D
Original Publication Date: 1976-Dec-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 37K

Publishing Venue

IBM

Related People

Bassous, E: AUTHOR

Abstract

A simple fabrication procedure is disclosed for cementing two surfaces together while maintaining their topographical features. The two surfaces are coated with silicon dioxide (SiO(2)) and are bonded together by converting the oxide surface into a glass whose melting point is lower than SiO(2). When the surfaces are brought in intimate contact and pressure is applied while simultaneously raising the temperature above the melting point of the glass, the two surfaces will fuse and adhere strongly together. This technique has been applied to bond together two silicon wafers having glass films on their surface less than 1 Micron thick. An excellent bond will form only in those areas where the surfaces are in contact.

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Bonding Together Surfaces Coated With Silicon Dioxide

A simple fabrication procedure is disclosed for cementing two surfaces together while maintaining their topographical features.

The two surfaces are coated with silicon dioxide (SiO(2)) and are bonded together by converting the oxide surface into a glass whose melting point is lower than SiO(2). When the surfaces are brought in intimate contact and pressure is applied while simultaneously raising the temperature above the melting point of the glass, the two surfaces will fuse and adhere strongly together. This technique has been applied to bond together two silicon wafers having glass films on their surface less than 1 Micron thick. An excellent bond will form only in those areas where the surfaces are in contact.

The silicon wafers which were used to demonstrate this method of bonding were 1.25 in. diameter, 8 mils thick. Such wafers possess flat, smooth surfaces requiring only thin layers of glass to form a uniform bond. Because bonding takes place only in those regions where the surfaces are in contact, any irregularities introduced into the surfaces, deliberately or otherwise, will reproduce very clearly.

As shown in the figure, wafer 1, which has a set of parallel trenches etched into the surface, is bonded to plane wafer 3, via glass film 5, resulting in a structure whose cross-section clearly shows the profile of these trenches.

Such a bonding technique is very useful in fabricating structures in silicon or other materials which can be coated with silicon dioxide and are capable of withstanding elevated temperatures. This method can also be applied in packaging and in the fabrication of arrays of tunnels or tubulations, guides for acoustic waves and electromagnetic radiation, filters, shower heads for fluids, precise alignment tools, etc.

Conventional methods used in silicon technology were applied to demonstrate the principles of the bonding technique described here. The silicon wafers were thermally oxidized at 1000 degrees C to produce a film of SiO(2) ~ 1 Micron thick. The wafers were then coated with a layer of phosphorus pentoxide (P(2)O(5)) by heating the wafers at 870 degrees in the presence of phosphorus oxychloride (POCl(3)) vapor and oxygen. A layer of phosphosilicate glass (PSG) immediately f...