Plasma Discharge Hermetic Seal Verification
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Solution Overview
Problem
Existing hermetic seal verification methods in the semiconductor industry face challenges such as compromised seals during manufacturing, difficulty in detecting leaks in high-volume testing, and the need for additional processing steps, which increase costs and complexity, especially with shrinking device sizes and the limitations of using unpassivated junction diodes.
Innovation Solution
A plasma discharge method and structure using electrodes within the sealed cavity to verify the integrity of the hermetic seal by measuring the electrical characteristics of the plasma, distinguishing between sealed and unsealed devices based on breakdown voltage and current responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If water soak is used to force liquid water into improperly sealed devices, then leak detection sensitivity is improved, but device complexity and processing time increase
Solution Approach 1:
The patent extracts the water soak step from the testing process by using a plasma discharge method that directly detects seal integrity without requiring external liquid water introduction. The plasma discharge is applied directly to the device under test, eliminating the need for separate water soak chambers and associated handling procedures.
Solution Approach 2:
The patent replaces the mechanical/chemical water soak process with a plasma discharge method. Instead of forcing liquid water into devices through physical soaking, the invention uses plasma - an ionized gas state - to detect seal integrity through electrical characteristics, substituting a physical-chemical process with a plasma-based electrical measurement.
2Productivity
If device size is reduced to increase volume, then productivity is improved, but leak detection reliability deteriorates due to shorter water retention time
Solution Approach 1:
The patent replaces the water-based detection mechanism with plasma discharge. Since plasma detection does not rely on water retention time within the device cavity, smaller devices can be tested with the same reliability as larger devices. The plasma discharge method provides immediate detection based on electrical characteristics rather than requiring prolonged exposure to liquid water.
Solution Approach 2:
The plasma discharge method is self-contained and does not require external water introduction or retention. The plasma is generated directly in the testing environment and interacts with the device seal independently of the device's internal volume, allowing consistent detection across different device sizes without modification.
3Measurement precision
If additional inspection processes are implemented to contain devices with large holes, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The plasma discharge method serves as a universal testing approach that handles all seal defect types - including large holes - through a single process. The plasma discharge characteristics change detectably regardless of the specific defect type or size, eliminating the need for separate inspection processes for different defect categories.
Solution Approach 2:
The patent extracts the need for multiple inspection processes by implementing a single plasma discharge test that replaces water soak, additional inspections, and handling procedures. This consolidation maintains high detection accuracy while improving throughput by eliminating redundant testing steps.
4Productivity
If wafer test time is extended to test more devices, then productivity is improved, but water evaporation increases causing false negatives
Solution Approach 1:
The patent substitutes the water-based detection system with plasma discharge. Since plasma detection does not depend on liquid water presence within the device, extended testing times do not lead to evaporation-related false negatives. The plasma method provides stable, time-independent detection across the entire testing duration.
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 method eliminates the need for external stimulants and additional processing, provides robust seal verification, and is applicable to both wafer and package levels, reducing the risk of misidentifying seal quality and enhancing the detection of seal integrity without damaging the device.
Implementation Method 1
A plasma discharge method and structure using electrodes within the sealed cavity to verify the integrity of the hermetic seal by measuring the electrical characteristics of the plasma
Implementation Method 2
The reverse diode characteristics of a junction diode of proper size become unstable when moisture or liquid water is present
Data Source
AI summary
A method and structure use characteristics of a plasma discharge for verifying a hermetic seal. The plasma discharge is created in a hermetically sealed cavity by a pair of spaced electrodes that extend from tips inside the hermetically sealed cavity to contacts outside the sealed cavity. An electrical bias is applied to the contacts that is sufficient to create a plasma discharge in a properly hermetically sealed cavity but not in an unsealed cavity.