Top RDL Inspection via UV Absorption Contrast

Solution Overview

Problem

In redistribution layer (RDL) inspection, it is challenging to distinguish between the top RDL and lower RDLs due to the transparency of dielectric polymer layers in the visible spectral range, leading to difficulties in defect detection and potential false calls.

Innovation Solution

A method involving illumination with radiation where the top RDL is positioned above lower RDLs and dielectric layers that absorb the radiation, generating detection signals, and processing these signals to differentiate between the top and lower RDLs based on signal strength, utilizing a selected spectral range determined by the absorption properties of the dielectric layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If visible light is used for illumination, then the inspection system can operate with standard visible spectral range equipment, but the dielectric polymer layers are transparent causing inability to distinguish between top RDL and lower RDLs

Engineering Contradiction:

Improvespectral range compatibilityVSAvoidRDL distinction capability

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent changes the spectral parameter of the illumination radiation from visible light to ultraviolet radiation. The dielectric polymer layers have high absorption coefficients in the UV spectral range, which causes them to appear dark and opaque. This spectral parameter change enables the inspection system to distinguish the top RDL from lower RDLs by blocking the radiation from reaching and reflecting off the lower layers, thereby resolving the transparency issue while maintaining equipment adaptability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful effect of radiation absorption (which normally reduces signal strength) into a beneficial effect for distinction. By selecting UV radiation that is strongly absorbed by the dielectric layers, the absorption prevents radiation from reaching lower RDLs, thereby eliminating false signals from lower layers and improving the precision of top RDL inspection.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Measurement precision

If radiation that is significantly absorbed by dielectric layers is used, then the contrast between top RDL and lower RDLs is enhanced, but the radiation intensity reaching the detector is reduced

Engineering Contradiction:

ImproveRDL contrast and distinctionVSAvoidradiation intensity utilization

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent changes the spectral parameter of the illumination radiation from visible light to ultraviolet radiation. The dielectric polymer layers have high absorption coefficients in the UV spectral range, which causes them to appear dark and opaque. This spectral parameter change enables the inspection system to distinguish the top RDL from lower RDLs by blocking the radiation from reaching and reflecting off the lower layers, thereby resolving the transparency issue while maintaining equipment adaptability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful effect of radiation absorption (which normally reduces signal strength) into a beneficial effect for distinction. By selecting UV radiation that is strongly absorbed by the dielectric layers, the absorption prevents radiation from reaching lower RDLs, thereby eliminating false signals from lower layers and improving the precision of top RDL inspection.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 effectively enhances the contrast between the top RDL and lower RDLs, allowing for accurate defect inspection by selecting a spectral range that significantly attenuates lower dielectric layers, thereby improving defect detection accuracy.

Implementation Method 1

wherein the at least one lower dielectric layer significantly absorbs the radiation

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 2

generating, by a detector, detection signals that represent radiation reflected from the object

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS11682584B2Measuring buried layers

Publication Date: 2023.06.20 CAMTEK LTD

AI summary

There may be provided a method for inspecting a top redistribution layer conductors of an object. The top redistribution layer (RDL) is positioned above at least one lower RDL and above at least one other dielectric layer. The method may include (i) illuminating the object with radiation, the at least one lower dielectric layer significantly absorbs the radiation; (ii) generating, by a detector, detection signals that represent radiation reflected from the object, and (iii) processing, by a processor, the detection signal to provide information about the top RDL. The processing may include distinguishing detection signals related to the top RDL from detection signals related to the at least one lower RDL.