Sacrificial Layer Removal via O2 Plasma and TMAH Wet Etch
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Solution Overview
Problem
Existing semiconductor processing methods fail to remove sacrificial layers without damaging the exposed layers or leaving residues on semiconductor wafers, which can lead to poor bonding between conductive elements and affect the electrical performance of dice.
Innovation Solution
A two-step process involving an O2 plasma etch step to remove the sacrificial layer, followed by a wet etch solution of tetramethylammonium hydroxide (TMAH) and water to eliminate any residue, ensuring the integrity of bond pads and passivation layers is maintained.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sacrificial layer is removed using conventional methods, then the sacrificial layer is removed, but residues or by-products remain on the wafer surface damaging the exposed layers
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using a specifically formulated wet etch solution containing TMAH and HF at controlled concentrations and ratios. This chemical parameter adjustment enables selective removal of the sacrificial layer while preventing residue formation on the exposed silicon dioxide layers, thereby maintaining layer integrity without harmful by-products
Solution Approach 2:
The patent introduces a two-step etching process where the first etch step selectively removes the sacrificial layer, and the second etch step acts as an intermediary cleaning step that removes residues from the exposed surfaces. This intermediary step ensures that no harmful residues remain on the wafer surface after complete sacrificial layer removal
2Reliability
If the sacrificial layer is completely removed, then bonding quality improves, but the process complexity increases
Solution Approach 1:
The patent combines multiple functions into a single wet etch solution that simultaneously performs sacrificial layer removal and surface cleaning. The formulated solution containing TMAH and HF achieves both complete layer removal and residue elimination in one step, reducing process complexity while maintaining high bonding quality through thorough surface preparation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively removes the sacrificial layer without damaging the wafer components, improving the bonding between conductive elements and enhancing the electrical performance and yield of semiconductor dice by eliminating residues and by-products.
Implementation Method 1
the sacrificial layer is removed from a wafer during an O2 plasma etch step
Implementation Method 2
The residue is removed by immersing the wafer a solution that is a mixture of the tetramethylammonium hydroxide (TMAH) and water
Data Source
AI summary
One or more embodiments are directed to methods of removing a sacrificial layer from semiconductor wafers during wafer processing. In at least one embodiment, the sacrificial layer is removed from a wafer during an O2 plasma etch step. In one embodiment, the sacrificial layer is poly(p-phenylene-2, 6-benzobisoxazole) (PBO) or polyimide. The O2 plasma etch step causes a residue to form on the wafer. The residue is removed by immersing the wafer a solution that is a mixture of the tetramethylammonium hydroxide (TMAH) and water.