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Method for the Production of Self-Aligned Bump Tape for Tape Automated Bonding

IP.com Disclosure Number: IPCOM000039632D
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 38K

Publishing Venue

IBM

Related People

Eastman, DE: AUTHOR [+7]

Abstract

The article describes a method for the production of self-aligned bump tape for tape automated bonding (TAB) employing the single expose double develop (SEDD) process. Tape automated bonding is a process for first level silicon device packaging using, for example, 35 mm tape on which the progressive operations of chip bonding, testing, encapsulation, and carriage to the card/board bonding location, etc. are performed. This packaging technique is currently used by many manufacturers. Preparation of bumped metallization on tape automated bonding materials has required separate lithographic procedures to allow etching of the beam patterns and etching of the bump structures.

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Method for the Production of Self-Aligned Bump Tape for Tape Automated Bonding

The article describes a method for the production of self-aligned bump tape for tape automated bonding (TAB) employing the single expose double develop (SEDD) process. Tape automated bonding is a process for first level silicon device packaging using, for example, 35 mm tape on which the progressive operations of chip bonding, testing, encapsulation, and carriage to the card/board bonding location, etc. are performed. This packaging technique is currently used by many manufacturers. Preparation of bumped metallization on tape automated bonding materials has required separate lithographic procedures to allow etching of the beam patterns and etching of the bump structures. The manufacturing complication to be avoided here is the necessary realignment of the first-pass etched pattern to the mask pattern for the second

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lithographic exposure, it being a costly and difficult procedure. Furthermore, an improved tape structure having a plated soft bump on a supporting hard beam is greatly facilitated by the process described below. The importance of having a soft bump (gold, for example) plated on the end of a hard copper beam has been demonstrated by as a structure which statistically results in superior bonds. The SEDD process uses positive photoresist and a glass mask with patterned areas of chromium (high optical density) and areas of INCONEL* (intermediate optical density) to enable two exposures to be made simultaneously. Since the photoresist development rate is proportional to the amount of exposure and multiple development cycles are possible, two separate photoresist stencils can be created at different times with this mask. An overall exposure through the chrome/glass/INCONEL mask onto the positive photoresist will produce three defined patterns. Clear areas of the mask will allow maximum photoresist exposure. These areas will be fully developed during the first develop, leaving the underlying substrate exposed for subsequent etching or plating. The INCONEL areas on the mask attenuate the exposing radiation and partially expose the photoresist. The first develop does not open these areas for etching. It is after the second develop that the INCONEL-exposed photoresist is fully developed, leaving the underlying substrate open for processing. The chrome areas of the mask are essentially opaque and do not expose the photoresist. These areas are not developed by either the first or second develop.

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The developers used are aqueous-based, usually a solution of sodium metasilicate. Exposure can be accomplished with contact, projection, or proximity printing using a wavelength region between 365 nm to 435 nm. The only size limitation, imposed for control of the process, is that the size of the INCONEL-exposed areas should be substantially larger than the...