Microwave Reflection Gettering Evaluation
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Solution Overview
Problem
Existing methods for evaluating the gettering property of device wafers, which are potential products, involve contaminating the wafers with metal elements, making it impossible to assess good device chips non-destructively.
Innovation Solution
A method involving the application of excitation light and microwaves to a device wafer to generate a differential signal based on the intensity of reflected microwaves, allowing for the evaluation of the gettering property without contaminating the wafer, using specific frequencies and wavelengths such as 26 GHz microwaves and 349 nm light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the device wafer is actually contaminated with metal elements to evaluate gettering property, then the gettering property can be evaluated, but the device wafer cannot become a product (good device chips cannot be obtained)
Solution Approach 1:
The patent introduces an intermediary evaluation method using microwave reflection measurements instead of direct metal contamination. The microwave signal acts as a mediator to indirectly assess gettering properties by detecting changes in microwave reflection intensity caused by the gettering layer structure, thereby avoiding actual contamination of the device wafer while still enabling evaluation.
Solution Approach 2:
The patent replaces the mechanical/chemical contamination process with an electromagnetic field-based measurement system. Instead of physically introducing metal elements to test gettering, the system uses microwave electromagnetic waves to detect gettering layer properties through reflection intensity changes, substituting a non-contact electromagnetic measurement for contact-based contamination methods.
2Length of moving object
If the device wafer is thinned to reduce device size, then the device size is reduced, but the gettering property deteriorates
Solution Approach 1:
The patent changes the evaluation parameter from direct metal contamination testing to microwave reflection intensity measurement. By measuring the intensity of microwaves reflected from the device wafer, the system can assess gettering properties without requiring actual metal contamination, enabling evaluation of thinned wafers that would otherwise be unsuitable for product use.
3Volume of moving object
If the device wafer is thinned to 100 μm or less, then the wafer thickness is reduced for size reduction, but the gettering property deteriorates causing faulty device operation
Solution Approach 1:
The patent performs preliminary evaluation of gettering properties using microwave reflection measurements before the device wafer is thinned to final dimensions. This allows assessment of gettering layer effectiveness in thinned wafers without requiring post-thinning contamination tests, enabling quality control at an earlier stage when the wafer can still be used for product manufacturing.
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 non-destructive evaluation of the gettering property of device wafers, ensuring that product-quality chips can be assessed without actual contamination, thereby maintaining their integrity and functionality.
Implementation Method 1
an excitation light applying step of applying excitation light for exciting a carrier to the workpiece
Implementation Method 2
a microwave applying step of applying microwaves to a light applied area where the excitation light is applied and also to an area other than the light applied area on the workpiece
Implementation Method 3
a measuring step of measuring the intensity of the microwaves reflected from the light applied area and from the area other than the light applied area
Data Source
AI summary
A workpiece evaluating method evaluates the gettering property of a device wafer having a plurality of devices formed on the front side of the wafer and having a gettering layer formed inside the wafer. The method includes the steps of applying excitation light for exciting a carrier to the wafer, applying microwaves to a light applied area where the excitation light is applied and also to an area other than the light applied area, measuring the intensity of the microwaves reflected from the light applied area and from the area other than the light applied area, subtracting the intensity of the microwaves reflected from the area other than the light applied area from the intensity of the microwaves reflected from the light applied area to thereby obtain a differential signal, and determining the gettering property of the gettering layer according to the intensity of the differential signal obtained above.