Getter Shutter Disk for Clean Aluminum Pad Plasma Etching
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Solution Overview
Problem
The existing under bump metallization (UBM) processes face challenges in removing native oxide layers from aluminum IC pads, leading to high contact resistance due to outgassing molecules recontaminating the metal surface, which affects the reliability and performance of electronic devices.
Innovation Solution
A processing method involving the deposition of a getter material, such as titanium, barium, or cerium, on the walls of a processing chamber to absorb outgassing molecules during plasma etching, minimizing recontamination and reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a pre-clean step is used to remove native oxide from aluminum IC pads, then the metal surface cleanliness is improved, but outgassing molecules recontaminate the surface causing high contact resistance
Solution Approach 1:
A getter material is deposited on the chamber walls before the pre-clean etching process. This preliminary action prepares the chamber environment to capture outgassing molecules during subsequent cleaning operations, preventing recontamination of the freshly cleaned metal surface.
Solution Approach 2:
The getter material acts as an intermediary substance between the outgassing molecules and the cleaned metal surface. It captures and holds the outgassing molecules that would otherwise recontaminate the surface, thereby maintaining surface cleanliness and low contact resistance.
2Productivity
If plasma etching is performed to remove native oxides, then the oxide removal efficiency is improved, but outgassing molecules are released causing recontamination
Solution Approach 1:
The outgassing molecules released during plasma etching, which would normally be harmful causes of recontamination, are converted into a beneficial situation by having them captured by the getter material. The harmful outgassing is thus transformed into a controlled process where the molecules are safely sequestered.
Solution Approach 2:
The getter material serves as an intermediary that intercepts outgassing molecules released during plasma etching. This allows the plasma etching process to proceed at full efficiency while the getter material manages the harmful byproducts, preventing them from affecting the substrate.
3Reliability
If multiple metal layers are sputtered in high temperature evaporation system, then the under bump metallization quality is improved, but the process complexity and time increase
Solution Approach 1:
The patent combines the pre-clean etching step and the UBM deposition process into a single integrated process sequence within the same chamber environment. The getter material enables this merging by protecting against recontamination during the transition between steps, reducing overall process complexity while maintaining UBM quality.
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
This approach significantly reduces outgassing molecule concentration by at least two orders of magnitude, minimizing recontamination and improving the performance and longevity of electronic devices by maintaining low contact resistance.
Implementation Method 1
depositing a getter material on walls of a processing chamber; and etching a substrate with a plasma in the processing chamber to remove native oxides and form a cleaned substrate, wherein etching the substrate releases outgassing molecules which are chemically bound to the getter material
Implementation Method 2
etching a substrate with a plasma in the processing chamber to remove native oxides
Implementation Method 3
outgassing molecules which are chemically bound to the getter material
Data Source
AI summary
Describes are shutter disks comprising one or more of titanium (Ti), barium (Ba), or cerium (Ce) for physical vapor deposition (PVD) that allows pasting to minimize outgassing and control defects during etching of a substrate. The shutter disks incorporate getter materials that are highly selective to reactive gas molecules, including O2, CO, CO2, and water.