Wafer Level Package Leak Detection via Acoustic Emission

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Solution Overview

Problem

Current methods for air tightness evaluation of semiconductor devices, particularly wafer level chip scale packages, are time-consuming and lack sufficient detection sensitivity, leading to reduced test accuracy.

Innovation Solution

A test method involving exposure to high moisture and cooling, followed by power supply to the semiconductor element to detect sound waves generated, allowing for non-destructive leak discrimination in airtight packages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If fine leak test with helium pressurization is used, then leak detection capability is achieved, but test time becomes several hours and productivity decreases

Engineering Contradiction:

Improveleak detection capabilityVSAvoidtest time

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent changes the test environment parameters from dry helium pressurization to high-temperature high-humidity conditions. This parameter change enables the use of acoustic emission detection instead of helium mass spectrometry, reducing test time from several hours to several minutes while maintaining leak detection capability through a different physical mechanism

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical/physical system of helium pressurization and mass spectrometry detection with an acoustic emission detection system. By applying power to the device under test in a high-temperature high-humidity environment, the system detects acoustic signals generated by leak-induced thermal expansion, substituting a complex pressurization system with a simpler acoustic detection approach

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If fine leak test with helium pressurization is used, then leak detection is possible, but device complexity and test setup complexity increase

Engineering Contradiction:

Improveleak detection capabilityVSAvoidtest setup complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the complex helium pressurization system and mass spectrometry detection equipment with a simpler acoustic emission detection system. The test setup only requires a standard acoustic sensor and a temperature-humidity chamber, eliminating the need for specialized helium handling equipment and complex vacuum systems

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The device under test serves its own function as the test object while simultaneously generating the acoustic signals needed for detection. By applying power to the device during testing, it autonomously generates thermal expansion effects that create acoustic emissions, eliminating the need for external pressurization equipment

Inventive Principle:

Principle #25Self-service

3Reliability

If conventional moisture resistance test with device operation in high temperature high moisture atmosphere is used, then moisture resistance evaluation is achieved, but test time becomes several days

Engineering Contradiction:

Improvemoisture resistance evaluationVSAvoidtest time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent performs preliminary exposure to high-temperature high-humidity conditions before the actual leak detection measurement. This preliminary action saturates any potential leak paths with moisture, so that subsequent acoustic emission detection can quickly identify leaks without requiring prolonged exposure times, reducing total test time from several days to several minutes

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the conventional method of evaluating moisture resistance through prolonged device operation and characteristic measurement with acoustic emission detection. This substitution enables rapid identification of leaks by detecting acoustic signals generated during thermal expansion, eliminating the need for multi-day exposure and complex electrical characteristic measurements

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables rapid and accurate leak testing of wafer level chip scale packages with high detection sensitivity, reducing testing time and improving accuracy.

Implementation Method 1

a test method comprises an applying water process in which the semiconductor device is exposed to high moisture atmosphere and cooled

Methodology Applied

Scientific EffectCondensation: Condensation

Implementation Method 2

power is supplied to the element which is formed on the substrate wafer and by detecting a sound wave which is generated by the semiconductor device

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS11499886B2Test method of a semiconductor device and manufacturing method of a semiconductor device

Publication Date: 2022.11.15 MITSUBISHI ELECTRIC CORP

AI summary

A test method for a semiconductor device having a package with airtight space, which is formed between a substrate wafer on which an element is formed and a cap wafer which is provided being opposite to the substrate wafer, comprises an applying water process in which the semiconductor device is exposed to high moisture atmosphere and cooled and a leak discrimination process in which power is supplied to the element which is formed on the substrate wafer and leak of the package is discriminated by detecting a sound wave which is generated by the semiconductor device.