Layer-Aware Charged-Particle Scanning for Accurate Overlay Measurement
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Solution Overview
Problem
Existing optical-based overlay measurement techniques face challenges such as weak signal strength with decreasing pitch and increasing separation between pattern layers, complexity in selecting wavelengths, and sensitivity to target tilt, leading to inaccurate overlay measurements in semiconductor manufacturing.
Innovation Solution
Utilizing a scanning charged-particle microscope to measure overlay by injecting a charged-particle beam onto targets with patterned layers, detecting secondary and backscattered electrons, and applying a model that accounts for the properties of each pattern layer to determine overlay accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical-based overlay measurement techniques are used, then measurement can be performed, but signal strength becomes weak with decreasing pitch and increasing separation between pattern layers
Solution Approach 1:
The patent replaces optical-based measurement techniques with charged-particle beam inspection apparatus. Instead of using light to detect overlay, the system uses charged particles (electrons or ions) to scan the sample and detect signals from pattern layers, thereby overcoming the signal strength limitations of optical methods at small pitches and large separations
Solution Approach 2:
The patent changes the fundamental detection parameter from optical wavelength to charged-particle beam energy and detection signal intensity. By using charged particles instead of light, the system can achieve sufficient signal strength even when pitch decreases and layer separation increases, as the charged particles interact directly with the material layers to generate detectable signals
2Measurement precision
If optical-based overlay measurement techniques are used, then measurement can be performed, but complexity increases in selecting wavelengths
Solution Approach 1:
The patent eliminates the need for wavelength selection by replacing optical systems with charged-particle beam systems. Instead of choosing specific wavelengths to optimize measurement, the system uses charged particles with controlled energy, simplifying the overall device complexity while maintaining measurement capability
3Measurement precision
If optical-based overlay measurement techniques are used, then measurement can be performed, but sensitivity to target tilt increases leading to inaccurate measurements
Solution Approach 1:
The patent replaces optical detection with charged-particle beam detection that is less sensitive to target tilt. The charged particle beam can scan through tilted samples more effectively than optical light, reducing the harmful effect of tilt on measurement accuracy and enabling reliable overlay measurement even when the sample is not perfectly aligned
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
Improves overlay measurement accuracy by addressing the limitations of optical methods, providing precise alignment data for semiconductor manufacturing.
Implementation Method 1
a charged-particle beam inspection apparatus configured to scan a sample that comprises a target with a plurality of pattern layers
Implementation Method 2
detecting particles (e.g., photons, secondary electrons, backscattered electrons, mirror electrons, or other kinds of electrons) from a surface of a wafer substrate upon impingement by a beam
Implementation Method 3
detecting particles (e.g., photons, secondary electrons, backscattered electrons, mirror electrons, or other kinds of electrons) from a surface of a wafer substrate upon impingement by a beam
Data Source
AI summary
A system, including: a charged-particle beam inspection apparatus configured to scan a sample that includes a target with a plurality of pattern layers; and a controller including circuitry, configured to: obtain detection data in response to a scan of the target; and determine one or more characteristics of the sample in dependence on the obtained detection data and a model, wherein, for each of the plurality of pattern layers of the target, the model has a term that is dependent on the properties of the pattern layer.