High-Energy SEM Overlay Measurement for Semiconductor Wafers
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Solution Overview
Problem
Current SEM systems are inadequate in accurately measuring overlay offsets between stacked circuit patterns in semiconductor wafers, particularly due to misalignment issues during manufacturing processes, which can lead to physical discrepancies between actual and optical overlay measurements.
Innovation Solution
A scanning electron microscope (SEM) system and method utilizing a high-energy electron beam to scan an in-cell region with a landing energy of at least 10 kV, detecting back-scattered and secondary electrons to generate images and measure overlay offsets between overlapping patterns, without relying on alignment marks, using image processing and overlay offset measurement devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SEM systems use low-energy electron beams to scan samples, then the system operation is simpler and less complex, but the measurement precision of overlay offsets deteriorates due to insufficient image clarity
Solution Approach 1:
The patent changes the energy parameter of the electron beam from conventional low energy to high energy (at least 10 kV landing energy). This parameter change enables the electron beam to penetrate through multiple layers of the semiconductor wafer and generate clear images of both lower and upper circuit patterns, thereby improving overlay offset measurement precision without requiring fundamental system redesign
Solution Approach 2:
The patent implements dynamic control of the electron beam energy during the scanning process. The system dynamically adjusts the beam energy to optimize penetration depth and image quality for different wafer structures, allowing flexible adaptation to various measurement scenarios while maintaining operational simplicity
2Measurement precision
If alignment marks in scribe lines are used for overlay measurement, then the measurement process is simpler, but the measurement precision deteriorates due to physical distance between actual circuit patterns and measurement patterns
Solution Approach 1:
The patent extracts the overlay measurement function from the conventional alignment mark-based approach and relocates it directly to the in-cell region containing actual circuit patterns. By removing the intermediary alignment marks and measuring directly on the stacked patterns, the system eliminates the physical distance error and achieves higher measurement precision
Solution Approach 2:
The patent uses the actual circuit patterns in the in-cell region as the measurement target, effectively copying the function of alignment marks directly onto the patterns of interest. This eliminates the need for separate alignment mark structures and their associated physical distance errors
3Measurement precision
If high-energy electron beams with landing energy of at least 10 kV are used to scan in-cell regions, then the image clarity and overlay offset measurement precision improve, but the energy consumption and system complexity increase
Solution Approach 1:
The patent applies high energy (at least 10 kV) only when and where needed - specifically during the scanning of in-cell regions for overlay offset measurement. The system uses conventional lower energy for other operations, thereby achieving the necessary measurement precision while minimizing overall energy consumption
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 enables precise measurement of overlay offsets, improving alignment accuracy and compensating for misalignment in semiconductor manufacturing by using high-energy electron beams to enhance image clarity and detectivity, thereby improving the precision of overlay offset determination.
Implementation Method 1
scanning an in-cell region, which includes a lower structure and an upper structure stacked in a sample, using a primary electron beam with a landing energy of at least 10 kV
Implementation Method 2
detecting electrons emitted from the scanned in-cell region; the detected electrons may be back-scattered electrons
Implementation Method 3
scanning an in-cell region... using a primary electron beam with a landing energy of at least 10 kV... measuring an overlay offset with respect to overlapping patterns included in the in-cell region
Data Source
AI summary
A method of measuring an overlay offset using a scanning electron microscope system includes: scanning an in-cell region, which includes a lower structure and an upper structure stacked in a sample, using a primary electron beam with a landing energy of at least 10 kV; detecting electrons emitted from the scanned in-cell region; and measuring an overlay offset with respect to overlapping patterns included in the in-cell region using an image of the in-cell region that is generated based on the detected electrons emitted from the scanned in-cell region.