The Role of Mass Transfer in Removal of Cross-Linked Sacrificial Layers in 3DI Applications

Abstract

The demand for higher functionality in smaller form-factor electronic devices continues to grow. This growth is enabled in large part by wafer-scale packaging technologies for 2-D, 2.5-D, and 3-D integration. Solder bump, copper pillar, and TSV processes are key enablers for advanced packaging. Sacrificial polymer materials such as photoresist and polyimides are used for patterning and/or passivation steps [1,2]. Typical challenges in removing these materials include long process times, short bath life, corrosion, sludge formation, and filter clogging. This paper presents a novel tool design that addresses these issues by a high rate of hydrodynamic agitation that maintains a thin boundary layer at the wafer surface. The outcome is quick removal and breakdown of the sacrificial layer, independent of pitch and without all the negative side effects.

Fluid Flow and Defect Density Considerations when Drying Bumped Wafers Using Spin and Surface Tension Gradient Methods

“…Photoresist from wafers with tall bump features ranging from 30-90 um and pitches ranging from 74-200um were stripped, rinsed and dried in an experimental resist strip tool at TEL-NEXX in Billerica, MA. The tool processes eight wafers in a parallel single wafer geometry which allows batch processing but the uniformity and process control characteristic of single wafer tools [6]. After high-rate stripping using shear-plate TM agitation, wafers were rinsed with deionized water and dried using Marangoni drying in an IPA vapor STG module.…”

Cleaning and Particle Challenges in the Temporary Bonding and Debonding Process

“…In addition to the chemistry, tool-based processing parameters can also help increase the dissolution rate by increasing the collision factor (A). Providing agitation or physical force in the form of ultrasonics or sprays can increase mass transfer and accelerate liftoff, physical breakdown, and enhance solvation [13]. The use of sprays or agitation has been a common practice in the removal of thicker back-end-of-line (BEOL) photoresists [14].…”