Semiconductor Package Leak Testing via Infrared Moisture Absorption
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Solution Overview
Problem
Current air tightness evaluation methods for semiconductor devices, particularly wafer level chip scale packages, are time-consuming and lack sufficient detection sensitivity, leading to reduced test accuracy and the need for multiple tests.
Innovation Solution
A method involving exposure to a high moisture atmosphere and the use of infrared detection to identify leaks based on water absorption, utilizing materials like GaAs that transmit infrared rays, allowing for rapid and accurate leak discrimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fine leak test using helium pressurization is used, then leak detection capability is improved, but test time becomes excessively long (several hours) and individual device evaluation becomes difficult
Solution Approach 1:
The patent replaces the mechanical helium pressurization and detection system with an optical system. Instead of using helium gas pressurization and mass spectrometry detection, the invention uses infrared light transmission through the device package to detect water molecules that have entered through leaks. This substitution of mechanical/gas-based detection with optical detection enables rapid testing while maintaining leak detection capability.
Solution Approach 2:
The patent changes the detection parameter from helium gas concentration to infrared light absorption by water molecules. By measuring the absorption of infrared light at specific wavelengths where water molecules absorb energy, the system can quickly determine whether water has entered the device through package leaks, eliminating the time-consuming helium pressurization process.
2Measurement precision
If conventional fine leak test methods are applied to wafer level chip scale packages, then leak detection is attempted, but detection sensitivity is insufficient due to the small volume and small amount of helium that can be injected
Solution Approach 1:
The patent replaces the volume-dependent helium injection method with an optical absorption method. Instead of relying on the amount of helium that can be injected into the small device volume, the invention uses infrared light transmission to detect water molecules. This optical method is not limited by the small device volume and can achieve high detection sensitivity even in wafer level chip scale packages with very small internal volumes.
3Reliability
If a high temperature high moisture atmosphere test method is used, then moisture resistance can be evaluated, but the test requires more than several days and uses complicated evaluation devices
Solution Approach 1:
The patent performs preliminary exposure to high temperature high moisture atmosphere to accelerate water ingress through any leaks, then quickly detects the presence of water using infrared absorption. This preliminary exposure step (typically minutes to hours rather than days) is sufficient to allow water to enter through leaks, after which the rapid optical detection can immediately identify the leak, eliminating the need for multi-day conventional testing.
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 enables a quick and accurate leak test for wafer level chip scale packages, reducing testing time and improving sensitivity, thus enhancing overall test accuracy.
Implementation Method 1
a cap wafer, which is made of a material that can transmit an infrared ray and is provided opposite to the substrate wafer
Implementation Method 2
an infrared ray from the semiconductor device is detected. A leak of the package is discriminated based on absorption of the infrared ray by water molecules
Data Source
AI summary
A test method for a semiconductor device comprising a substrate wafer (1), in which an element is formed and a material through which an infrared ray can be transmitted, and a package having an airtight space (7) between a cap wafer (3), which is provided opposite to the substrate wafer (1); and which includes a water applying process in which the semiconductor device is exposed to a high moisture atmosphere and a leak discrimination process in which an infrared ray from the semiconductor device is detected and a leak of the package is discriminated based on absorption of the infrared ray by water molecules.