Soluble Protective Coating for Wafer Bond Pad Integrity
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Solution Overview
Problem
Semiconductor bond pads are vulnerable to damage from contaminants and corrosion during wafer grinding and saw-to-reveal processes, and exposure to oxidizing environments, which can lead to reduced device yield and manufacturability.
Innovation Solution
A soluble protective coating is applied to the bond pads and bond shelf after wafer bonding, protecting them from contaminants and corrosion, and can be easily removed after processing without requiring additional operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wafer grinding and saw-to-reveal processes are performed to expose bond pads, then device manufacturability is improved, but bond pads are exposed to contaminants and corrosion that reduce device yield
Solution Approach 1:
A protective coating is applied to the bond pads before the wafer grinding and saw-to-reveal processes. This preliminary protective action prevents contaminants and corrosion from damaging the bond pads during manufacturing operations, thereby maintaining both manufacturability and device yield
Solution Approach 2:
A protective coating material serves as an intermediary between the bond pads and the harmful environment (contaminants, moisture, oxidizing agents) during grinding and sawing operations. This intermediary layer allows the manufacturing processes to proceed while protecting the underlying bond pads, resolving the contradiction between manufacturability and reliability
2Ease of operation
If bond pads are exposed during processing, then subsequent operations can be performed, but the bond pads become vulnerable to debris, water, and atmospheric corrosion
Solution Approach 1:
A thin protective coating film is applied over the bond pads, providing a barrier against contaminants, water, and atmospheric corrosion while allowing subsequent processing operations to access and work on the bond pads as needed. The thin film nature ensures it does not interfere with processing accessibility
Solution Approach 2:
The protective coating is applied in advance to counteract the harmful effects of contaminants and corrosion before they can damage the bond pads during processing operations. This preliminary protective action enables both processing accessibility and protection from harmful factors
3Reliability
If traditional protection methods are used during wafer processing, then bond pads are protected, but additional removal operations are required that increase process complexity
Solution Approach 1:
The protective coating is designed as a temporary, disposable layer that provides protection during critical processing operations and then can be easily removed or degraded without requiring complex removal equipment or additional processing steps. This disposable nature reduces overall process complexity while maintaining bond pad protection
Solution Approach 2:
The protective coating utilizes changes in physical or chemical parameters (such as solubility, temperature sensitivity, or chemical reactivity) to enable easy removal after serving its protective function. This parameter-based removal mechanism simplifies the overall process by eliminating the need for complex removal operations
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 protective coating effectively prevents damage and corrosion, improving device yield and manufacturability by safeguarding bond pads from debris, water, and atmospheric corrosion, and can be cost-effectively integrated into existing fabrication processes.
Implementation Method 1
protecting them from contaminants and corrosion... safeguarding bond pads from debris, water, and atmospheric corrosion
Implementation Method 2
A soluble protective coating is applied to the bond pads and bond shelf... can be easily removed after processing
Data Source
AI summary
A method for protecting terminal elements on a wafer during wafer level fabrication processes entails applying a protective coating to the terminal elements prior to further processing operations. These processing operations may include back side grinding of the wafer and/or saw-to-reveal operations to expose the terminal elements from a cap wafer of a wafer structure. The protective coating can protect the terminal elements from potentially damaging contaminants, such as debris from the grinding or saw-to-reveal operations. Furthermore, the protective coating can protect the bond pads from coming into contact with a rapidly oxidizing environment when exposed to water. The protective coating may be a hot-water soluble thermoplastic material the melts from a solid form to a liquid form at a relatively low temperature to enable application of the protective coating in liquid form onto the terminal elements and clean removal of the protective coating from the terminal elements.