Wafer Gettering Capability Evaluation via Optical Damping
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Solution Overview
Problem
Existing methods for evaluating the gettering capability of device wafers cannot assess the gettering layer without contaminating the wafer, making it impossible to evaluate product-ready device chips.
Innovation Solution
An evaluation method that involves radiating electromagnetic waves and excitation light to determine the gettering capability based on the damping time of reflected waves, allowing for the assessment of gettering capability without contaminating the device wafer with metal elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the device wafer is ground to form a gettering layer, then the gettering capability is improved, but the manufacturing precision of the wafer thickness is worsened
Solution Approach 1:
The patent changes the evaluation parameters from direct thickness measurement to optical property measurement (reflectance, absorption, photoluminescence). By measuring optical properties instead of physical dimensions, the system can assess gettering layer quality without compromising thickness precision, resolving the contradiction between achieving sufficient grinding for gettering capability and maintaining wafer thickness uniformity
Solution Approach 2:
The patent replaces mechanical thickness measurement systems with optical measurement systems. Instead of using mechanical probes or contactless dimensional measurement, the invention uses light interaction (reflectance, absorption, photoluminescence) to evaluate the gettering layer, thereby maintaining manufacturing precision while achieving the desired gettering capability
2Weight of moving object
If the wafer is thinned to reduce size and weight, then the device chip size and weight are reduced, but the gettering capability is worsened
Solution Approach 1:
The patent applies preliminary action by forming the gettering layer through controlled grinding before final wafer thinning. The optical measurement system then evaluates this pre-formed gettering layer to ensure adequate metal element capture capability is established before the wafer is thinned to its final thin specification, preventing gettering capability loss
Solution Approach 2:
The patent uses optical property measurements (reflectance, absorption, photoluminescence) to monitor and control the gettering layer quality throughout the thinning process. By changing from mechanical thickness control to optical property monitoring, the system can maintain gettering capability even as the wafer is thinned to reduce device chip weight
3Measurement precision
If the conventional evaluation method using metal element contamination is used, then the gettering capability can be directly measured, but the device wafer becomes defective and cannot be used as a product
Solution Approach 1:
The patent creates an indirect copy or proxy measurement system that evaluates gettering capability without direct metal element contamination. Instead of actually introducing metal elements and measuring their capture, the invention uses optical measurements (reflectance, absorption, photoluminescence) that correlate with gettering layer properties, providing an accurate assessment while preserving the wafer as a usable product
Solution Approach 2:
The patent introduces an intermediary measurement approach using optical properties as a mediator between the gettering layer structure and its functional capability. Instead of directly testing metal element capture (which would contaminate the wafer), the system uses light interaction as an intermediary to infer gettering capability, maintaining both measurement accuracy and wafer usability
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
Enables the evaluation of gettering capability without contaminating the device wafer, using specific wavelengths of excitation light to determine the damping time and thus the effectiveness of the gettering layer, ensuring non-defective product evaluation.
Implementation Method 1
radiating electromagnetic waves toward a back surface of the device wafer and radiating excitation light to generate excess carriers, and determining the gettering capability of the gettering layer formed in the device wafer on the basis of the damping time of reflected electromagnetic waves
Implementation Method 2
radiating excitation light to generate excess carriers, and determining the gettering capability of the gettering layer formed in the device wafer on the basis of the damping time of reflected electromagnetic waves equivalent to the lifetime of the carriers
Data Source
AI summary
An evaluation method of a device wafer on which plural devices are formed on a front surface and inside which a gettering layer is formed is provided. In the evaluation method, electromagnetic waves are radiated toward a back surface of the device wafer and excitation light is radiated to generate excess carriers. Furthermore, the gettering capability of the gettering layer formed in the device wafer is determined based on the damping time of reflected electromagnetic waves.