Mirror Electron Inspection Apparatus for High-Resolution Semiconductor Defect Detection
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Solution Overview
Problem
Conventional semiconductor inspection apparatuses face challenges with insufficient resolution and throughput, particularly in detecting small foreign matters and irregularities on surfaces with high contrast, due to limitations in pixel size, aberration, and energy width of irradiation current.
Innovation Solution
An inspection apparatus that generates charged particles or electromagnetic waves, with a primary optical system for irradiating the object and a secondary optical system for detecting secondary charged particles, utilizing mirror electrons emitted under specific energy conditions, and adjusting the numerical aperture for high-contrast imaging, along with focus and shading correction techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is reduced to improve resolution, then measurement precision is improved, but productivity deteriorates due to increased inspection time
Solution Approach 1:
The patent changes the imaging parameter from conventional secondary electron detection to mirror electron detection, which fundamentally alters the detection mechanism. Mirror electrons provide superior depth of field and resolution without requiring smaller pixel sizes, thus maintaining high throughput while achieving the required 5-30 nm design rule inspection capability
Solution Approach 2:
The patent employs dynamic focus adjustment and numerical aperture optimization specifically tuned for mirror electron detection. The system dynamically adapts imaging conditions to maximize both resolution and throughput by optimizing the balance between depth of field and signal intensity for mirror electrons
2Measurement precision
If aberration is reduced to improve resolution, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts and utilizes mirror electrons specifically, separating them from other secondary electrons. This selective detection approach simplifies the optical system requirements because mirror electrons inherently provide the needed resolution and depth of field without requiring complex aberration correction systems
Solution Approach 2:
The patent introduces a specialized detector configured for mirror electron detection as an intermediary between the sample and the imaging system. This detector acts as a mediator that converts mirror electron signals into usable image data with high resolution while keeping the overall optical system relatively simple
3Measurement precision
If energy width of irradiation current is reduced to improve resolution, then measurement precision is improved, but use of energy increases
Solution Approach 1:
The patent changes the detection parameter from conventional secondary electron detection to mirror electron detection, which allows using broader energy width irradiation current while still achieving high resolution. Mirror electrons are less sensitive to energy width variations, enabling higher throughput without sacrificing measurement precision
4Measurement precision
If smaller pixel size is used to improve resolution, then measurement precision is improved, but productivity deteriorates due to increased inspection time
Solution Approach 1:
The patent fundamentally changes the detection parameter from conventional secondary electrons to mirror electrons, which provide superior depth of field and resolution characteristics. This parameter change allows using larger pixel sizes while maintaining the required resolution for 5-30 nm design rules, thereby reducing inspection time and improving throughput
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 high-contrast inspection of surface irregularities and detection of small foreign matters, improving resolution and throughput by aligning mirror electron crossovers with the numerical aperture and using shading corrections to emphasize defect signals.
Implementation Method 1
beam generation means that generates any of charged particles and electromagnetic waves as a beam
Implementation Method 2
secondary charged particles occurring from the inspection object due to the beam irradiation
Implementation Method 3
a lens that forms an image of the secondary charged particles that have passed through the numerical aperture on an image surface of the camera
Data Source
AI summary
An inspection apparatus includes beam generation means, a primary optical system, a secondary optical system and an image processing system. Irradiation energy of the beam is set in an energy region where mirror electrons are emitted from the inspection object as the secondary charged particles due to the beam irradiation. The secondary optical system includes a camera for detecting the secondary charged particles, a numerical aperture whose position is adjustable along an optical axis direction and a lens that forms an image of the secondary charged particles that have passed through the numerical aperture on an image surface of the camera. In the image processing system, the image is formed under an aperture imaging condition where the position of the numerical aperture is located on an object surface to acquire an image.