Multi-Spot Inspection Illumination Power Control for Wafer Thermal Protection

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Solution Overview

Problem

Multi-spot inspection systems face challenges in detecting large particles on semiconductor wafers without causing thermal damage, as high power density illumination can lead to particle explosion and contamination during surface inspection scans.

Innovation Solution

The system adjusts illumination power density by using secondary low-power illumination spots to detect large particles, reducing the power of primary illumination spots before they reach the particles, thereby preventing thermal damage and contamination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If high power density illumination is used in multi-spot inspection systems, then inspection speed and detection capability are improved, but thermal damage to large particles and wafer surface occurs

Engineering Contradiction:

Improveinspection speedVSAvoidthermal damage

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary detection using low-power secondary illumination spots before the high-power primary illumination spots reach the particle location. This advance detection allows the control system to reduce power density of primary spots before they encounter large particles, preventing thermal damage while maintaining high-speed inspection capability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Low-power secondary illumination spots act as intermediary detection elements that precede the high-power primary illumination spots. These secondary spots detect large particles without causing thermal damage, and their detection signals trigger power reduction of primary spots, serving as a protective intermediary mechanism.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If high power density illumination is used, then detection range and inspection accuracy are improved, but particle explosion and contamination occur

Engineering Contradiction:

Improveinspection accuracyVSAvoidparticle explosion

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system applies preliminary anti-action by detecting particles with low-power secondary spots and preemptively reducing the power of primary spots before they can cause harmful effects. This counter-measure prevents particle explosion and contamination before they can occur.

Inventive Principle:

Principle #9Preliminary anti-action

3Object-affected harmful factors

If secondary illumination spots are added for particle detection, then thermal damage is prevented, but system complexity increases

Engineering Contradiction:

Improvethermal damageVSAvoidsystem complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The system merges the functions of detection and protection by having secondary illumination spots and primary illumination spots work in coordination. The secondary spots detect particles while the primary spots provide high-power inspection, and their combined operation through the control system achieves both detection and thermal protection without requiring entirely separate systems.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The illumination system achieves multi-functionality by using secondary spots for both detection and as triggers for power modulation of primary spots. The same optical path and detector serve multiple purposes: detecting particles, determining their size, and triggering appropriate power reduction responses.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 reduces thermal damage and extends the detection range by accurately identifying and mitigating the impact of large particles on the wafer surface during inspection, ensuring higher inspection accuracy and yield.

Implementation Method 1

Light scattered from the secondary illumination spot is collected and imaged onto one or more detectors

Methodology Applied

Scientific EffectLight scattering: Scattering

Data Source

PatentUS8755044B2Large particle detection for multi-spot surface scanning inspection systems

Publication Date: 2014.06.17 KLA CORP

AI summary

The illumination power density of a multi-spot inspection system is adjusted in response to detecting a large particle in the inspection path of an array of primary illumination spots. At least one low power, secondary illumination spot is located in the inspection path of an array of relatively high power primary illumination spots. Light scattered from the secondary illumination spot is collected and imaged onto one or more detectors without overheating the particle and damaging the wafer. Various embodiments and methods are presented to distinguish light scattered from secondary illumination spots. In response to determining the presence of a large particle in the inspection path of a primary illumination spot, a command is transmitted to an illumination power density attenuator to reduce the illumination power density of the primary illumination spot to a safe level before the primary illumination spot reaches the large particle.