Light Modulated Electron Source for Semiconductor Inspection

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current electron sources for semiconductor inspection and review, such as thermionic and field emission sources, face limitations including inefficient power consumption, short lifetime, and instability due to contamination and oxidation issues, which hinder high-speed and high-resolution inspections.

Innovation Solution

A light modulated electron source utilizing a silicon-type field emitter cathode with a photon beam to enhance electron emission current, where a p- or n-doped silicon substrate is etched to form a protrusion and coated with antioxidation layers, and a photon beam with energy greater than the silicon bandgap is directed onto the emitter to increase electron emission, with a control circuit modulating the photon beam intensity to stabilize and control the emission current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If thermionic emission is used to generate electron beam, then electron source can be operated continuously, but power consumption is high and lifetime is short due to high temperature operation

Engineering Contradiction:

Improveelectron source lifetimeVSAvoidpower consumption

Core Design Contradiction:

Duration of action of stationary objectVSUse of energy by moving object

Solution Approach 1:

The patent utilizes field emission instead of thermionic emission, transitioning from a thermal process to a quantum mechanical tunneling process. This eliminates the need for high temperature operation, thereby reducing power consumption and extending the electron source lifetime without requiring phase change materials or processes.

Inventive Principle:

Principle #36Phase transitions

Solution Approach 2:

The patent replaces the thermal field emission mechanism with a cold field emission mechanism based on quantum tunneling. This substitution eliminates the mechanical/thermal heating process, reducing power consumption and extending component lifetime by avoiding thermal degradation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Use of energy by moving object

If field emission source is used to reduce power consumption, then electron emission can be achieved at low temperature, but emission current is unstable due to contamination and oxidation

Engineering Contradiction:

Improvepower consumptionVSAvoidemission current stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent operates the field emission source in a vacuum environment, which serves as an inert atmosphere that prevents oxidation and contamination of the emitter surface. This maintains emission current stability while preserving the low power consumption advantage of field emission.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

Solution Approach 2:

The patent modifies the operational parameters by maintaining a high vacuum environment and controlling the electric field strength to optimize emission current stability. This allows the field emission source to operate reliably at low temperatures without suffering from contamination and oxidation issues.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If high current density is required for fast inspection, then inspection speed increases, but electron source brightness is limited and energy spread is wide

Engineering Contradiction:

Improveinspection speedVSAvoidelectron source brightness

Core Design Contradiction:

ProductivityVSIllumination intensity

Solution Approach 1:

The patent changes the fundamental emission mechanism from thermionic to field emission, which enables higher current density with simultaneously improved brightness and reduced energy spread. The quantum tunneling process inherent in field emission produces a more monochromatic electron beam with higher radiance, satisfying the requirements for both fast inspection and high image quality.

Inventive Principle:

Principle #35Parameter changes

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 solution provides a stable, high-brightness, and long-lasting electron source with improved current density and reduced contamination issues, enabling faster and more reliable semiconductor inspections and lithography processes.

Implementation Method 1

a photon beam with energy greater than the silicon bandgap is directed onto the emitter to increase electron emission

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

silicon-type field emitter cathode with a photon beam to enhance electron emission current

Methodology Applied

Scientific EffectField emission: Electron Beam

Data Source

PatentUS11715615B2Light modulated electron source

Publication Date: 2023.08.01 KLA CORP

AI summary

A light modulated electron source utilizes a photon-beam source to modulate the emission current of an electron beam emitted from a silicon-based field emitter. The field emitter's cathode includes a protrusion fabricated on a silicon substrate and having an emission tip covered by a coating layer. An extractor generates an electric field that attracts free electrons toward the emission tip for emission as part of the electron beam. The photon-beam source generates a photon beam including photons having an energy greater than the bandgap of silicon, and includes optics that direct the photon beam onto the emission tip, whereby each absorbed photon creates a photo-electron that combines with the free electrons to enhance the electron beam's emission current. A controller modulates the emission current by controlling the intensity of the photon beam applied to the emission tip. A monitor measures the electron beam and provides feedback to the controller.