Backside Illumination for Electronic Chip Inspection

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Solution Overview

Problem

There is a need for a reliable method to inspect semiconductor wafers that have been singularized into electronic chips, as existing methods struggle to accurately determine the positioning, orientation, and spatial relationships between the chips, often leading to errors in the singularization and packaging processes.

Innovation Solution

An apparatus and method utilizing backside illumination with electromagnetic radiation to detect the chips from the opposing side, creating a dark-light pattern that allows for accurate identification of chip positions and gaps, thereby enabling reliable inspection and early detection of errors such as inappropriate singularization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional inspection methods are used to inspect singularized electronic chips, then the inspection process can be performed, but the accuracy of determining chip positioning, orientation, and spatial relationships is insufficient, leading to errors in singularization and packaging processes

Engineering Contradiction:

Improveaccuracy of chip positioning and orientation detectionVSAvoiderror rate in singularization and packaging processes

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies backside illumination instead of conventional frontside illumination. By illuminating the wafer from the backside and detecting light transmission through the frontside, the method creates a pronounced dark-light pattern where dark regions correspond to chip positions and light regions correspond to gaps. This inverted illumination approach eliminates interference from surface structures on the chip front side, thereby improving measurement precision of chip positioning and orientation.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent replaces conventional optical reflection-based inspection with light transmission detection. By using transmission measurement instead of reflection measurement, the system achieves better contrast and accuracy in detecting chip positions and spatial relationships, reducing errors in subsequent packaging processes.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If backside illumination is used to inspect singularized electronic chips, then reliable information on chip positioning and orientation can be obtained, but the inspection apparatus requires precise alignment of illumination and detection units

Engineering Contradiction:

Improveaccuracy of chip inspection informationVSAvoidalignment requirements of illumination and detection units

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The detection unit is designed to detect electromagnetic radiation from the front side of the wafer, which serves both as the illumination side and the detection side. This multi-functional design simplifies the overall system architecture by using the same side for both light entry and light detection, thereby reducing alignment complexity while maintaining reliable inspection accuracy.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Manufacturing precision

If structures on the chip surfaces are present, then the electronic chips can be fully formed, but these structures interfere with the inspection process

Engineering Contradiction:

Improvechip structure completenessVSAvoidinterference with inspection process

Core Design Contradiction:

Manufacturing precisionVSDifficulty of detecting and measuring

Solution Approach 1:

By inverting the illumination direction to illuminate from the backside of the wafer, the inspection light passes through the chip substrate rather than reflecting off the front surface structures. This allows fully formed chips with complete surface structures to be inspected without interference, as the light transmission method bypasses the interfering surface features.

Inventive Principle:

Principle #13The other way round (Inversion)

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 provides a simple and robust means to obtain reliable information on chip positioning and orientation, reducing errors in the singularization and packaging processes by enhancing the accuracy of the inspection and allowing for early compensation of errors, such as those caused by a broken saw blade.

Implementation Method 1

an electromagnetic radiation source arranged and configured for illuminating at least part of a first main surface of the singularized wafer with electromagnetic radiation

Methodology Applied

Scientific EffectElectromagnetic radiation emission: Light

Implementation Method 2

a detection unit configured for detecting electromagnetic radiation from a side facing a second main surface of the singularized wafer and opposing the first main surface

Methodology Applied

Scientific EffectElectromagnetic radiation detection: Photoelectric Effect

Data Source

PatentUS10388610B2Electronic chip inspection by backside illumination

Publication Date: 2019.08.20 INFINEON TECHNOLOGIES AG

AI summary

An apparatus for inspecting a plurality of electronic chips singularized from a wafer, wherein the apparatus comprises an electromagnetic radiation source arranged and configured for illuminating at least part of a first main surface of the singularized wafer with electromagnetic radiation, and a detection unit configured for detecting electromagnetic radiation from a side facing a second main surface of the singularized wafer and opposing the first main surface.