Getter-Coated Shutter Disk for Low-Resistance UBM 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
The method involves depositing a getter material, such as titanium, barium, or cerium, on the walls of a processing chamber to absorb outgassing molecules during the etching process, reducing their concentration and minimizing recontamination of the metal contact surface.
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:
The patent applies inert atmosphere by introducing nitrogen gas into the processing chamber during the etching process. This nitrogen atmosphere prevents outgassing molecules from recontaminating the cleaned metal surface, thereby maintaining low contact resistance while preserving surface cleanliness. The inert gas creates a protective environment that eliminates the harmful interaction between oxygen-containing outgassing molecules and the freshly cleaned aluminum pad surface.
2Reliability
If multiple metal layers are sputtered in a high temperature evaporation system, then the under bump metallization quality is improved, but the process complexity and time increase
Solution Approach 1:
The patent merges the oxide removal function into the etching process itself, combining multiple functions (oxide removal and surface preparation) into a single integrated step. This consolidation eliminates the need for separate pre-clean and barrier layer deposition steps, thereby reducing overall process time while maintaining UBM quality through the inert nitrogen atmosphere protection.
Solution Approach 2:
The patent skips the traditional multi-step sequential process by performing oxide removal and protection simultaneously in one etching step with nitrogen atmosphere. This rushing through of multiple functions in a single operation significantly reduces processing time while achieving the same or better UBM quality outcomes.
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 contact resistance and improving the performance and longevity of electronic devices by maintaining a clean metal surface.
Implementation Method 1
depositing a getter material, such as titanium, barium, or cerium, on the walls of a processing chamber to absorb outgassing molecules during the etching process
Implementation Method 2
etching a substrate with a plasma in the processing chamber to remove native oxides and form a cleaned substrate
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.