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Method for High Temperature Bonding of a Thin Glass Plate or Glass Wafer to a Carrier Disclosure Number: IPCOM000241722D
Publication Date: 2015-May-26
Document File: 2 page(s) / 45K

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Disclosed is a method for high temperature bonding of a thin glass plate or glass wafer to a carrier in order to implement glass interposers for high performance semiconductor packaging.

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Method for High Temperature Bonding of a Thin Glass Plate or Glass Wafer to a Carrier

The ideal range of thickness for glass interposers for high performance semiconductor packaging is in the range of 25 - 100um in final form. However, because a thin piece of glass is impossible to process through a semiconductor fab without fracturing and does not work with any standard semiconductor equipment automation, glass interposer substrates must first be joined to a thicker handler of glass or silicon. Once it is attached to this handler, it can be sputtered, Reactive Ion Etched (RIE'ed), plated, exposed, reflowed, and metallized, in order to create through-vias, redistribution lines, capture pads, and interconnect solder bumps. The handler can be of a thickness that when combined with thin glass interposer substrate, yields a total thickness that is similar to a Silicon (Si) semiconductor wafer, (approximately 775um for a 300mm diameter wafer) making it not only robust, but also easily processed through semiconductor fab equipment.

However, joining a very thin piece of glass that is 25 to 100 um in thickness to a handler made of glass or Si is not easy. The thinned glass tends to curl and easily warps at a thickness up to 500 um. When it is placed on a hot bonding chuck or hot plate, the glass warps further, making it impossible to hold with vacuum chucking or electro-static chuck (ESC). It is also impossible to use a Front Opening Unified Pod (FOUP) or a typical robotics system to move this piece of glass inside of a tool such as a bonder. When glass is thin, it tends to sag wherever it is not physically supported.

Because glass is a thermal insulator, a thin 300 mm glass wafer never flattens on a hot chuck or hot plate. Bending for a 100 to 300 um thick glass plate with a Coefficient of Thermal Expansion (CTE) of 3 ppm/C will be greater than 1 mm on a 250C hot plate. For some of the higher CTE glasses under consideration for glass interposers (...