Browse Prior Art Database

Plastic Package Compatible Back End of the Line Process

IP.com Disclosure Number: IPCOM000037792D
Original Publication Date: 1989-Jul-01
Included in the Prior Art Database: 2005-Jan-30
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Akiki, G: AUTHOR [+4]

Abstract

A process which improves the long term reliability of a plastic package for a high density semiconductor chip is reported.

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This is the abbreviated version, containing approximately 69% of the total text.

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Plastic Package Compatible Back End of the Line Process

A process which improves the long term reliability of a plastic package for a high density semiconductor chip is reported.

Metal land corrosion due to phosphorous/metal interaction, severe chip passivation damage and metal cracking due to mechanical stress are a few typical problems encountered when utilizing an inexpensive plastic package for semiconductor chips.

The main concerns with a plastic package are long term reliability under stress conditions and corrosion due to the non-hermiticity of the passivation material. To assure a reliable device, two process parameters are important: 1) The amount of phosphorous allowed to contact the device. (Water and phosphorous combine to form phosphoric acid, an effective metal etch.) 2) The integrity of the final device passivation. (Moisture reaching a device is limited.)

To smooth out the severe chip topography created early in the chip fabrication process, an extensive reflow of a phosphosilicateglass (PSG) film deposited late in the process is required. The higher the phosphorus content in the PSG, the more extensive (planar) will be the reflow. However, the danger of corrosion limits the amount of PSG phosphorous which can safely be used. The upper bound of PSG phosphorous content in plastic considered prudent was thought to be between 7.0 - 7.5% by weight as-deposited, which is a trade off between the reflow angle and a lower phosphorous content. By utilizing...