Dual-Frequency Comb Metrology for Intra-Field Overlay Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Overlay metrology in semiconductor manufacturing requires more sites per wafer for higher order model corrections, necessitating improved systems and methods for intra-field target measurements, particularly for Correction Per Exposure (CPE), which is challenging due to the need for on-product target measurements.
Innovation Solution
A metrology system utilizing a dual frequency comb illumination beam with different repetition rates, incorporating an illumination and collection sub-system with optical elements like polarizers and phase plates, generates spectral measurements through a detector, enabling metrology measurements such as overlay, tilt, and critical dimension analysis by reconstructing Mueller matrix elements from radio-frequency signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If more sites per wafer are required for overlay monitoring and control, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The dual frequency comb source performs multiple metrology functions (overlay, critical dimension, line edge roughness, surface roughness) simultaneously using a single integrated system, eliminating the need for separate measurement systems for each parameter and enabling comprehensive wafer-level monitoring without proportionally increasing system complexity
Solution Approach 2:
The system varies the repetition rates of the two frequency combs to encode different spectral information, allowing extraction of multiple metrology parameters from a single measurement sequence. By changing the comb parameters dynamically, the system achieves multi-parameter measurement capability without requiring multiple physical measurement systems
2Manufacturing precision
If intra field target measurements are implemented for Correction Per Exposure, then manufacturing precision is improved, but measurement precision requirements increase
Solution Approach 1:
The dual frequency comb source acts as an intermediary that transforms optical spectral information into radio-frequency beat signals through heterodyne detection. This frequency conversion process preserves spectral information while enabling high-precision measurements through electronic signal processing, which offers superior precision compared to direct optical detection methods
Solution Approach 2:
The system replaces direct optical spectrum analysis with radio-frequency heterodyne detection. By converting optical frequency differences into measurable RF beat frequencies, the system achieves higher measurement precision through electronic detection methods rather than optical spectroscopy, enabling precise intra-field target measurements for CPE
3Productivity
If dual frequency comb illumination is used, then productivity is improved, but device complexity increases
Solution Approach 1:
The system uses two frequency combs with different repetition rates to create periodic beat signals at radio frequencies. This periodic modulation of the illumination enables time-multiplexed measurement of multiple spectral components, allowing comprehensive metrology data acquisition in a single illumination cycle and significantly improving measurement throughput
Solution Approach 2:
The dual frequency comb source merges two independent frequency combs into a single illumination beam that contains encoded spectral information for multiple measurements. By combining the combs in the optical domain and using heterodyne detection, the system achieves multi-parameter measurement capability in a single integrated illumination path, improving productivity without requiring separate measurement systems
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
The system provides accurate and efficient metrology measurements, supporting in-die and on-target assessments with high numerical aperture and fast throughput, overcoming limitations of existing techniques by offering small spot sizes and rich spectral and phase information for advanced imaging and scatterometry overlay targets.
Implementation Method 1
receiving a radio-frequency signal from a detector associated with illumination of a sample with a dual frequency comb illumination beam
Implementation Method 2
at least a portion of the radio-frequency signal is associated with zero-order diffraction from the sample
Implementation Method 3
illumination of a sample with a dual frequency comb illumination beam through an objective lens
Data Source
AI summary
A metrology system may include a dual frequency comb source providing a first comb beam with a first repetition rate and a second comb beam with a second repetition rate, a beamsplitter to generate one or more dual frequency comb illumination beams from the first comb beam and the second comb beam, and a beam combiner to form a dual frequency comb illumination beam from the first comb beam and the second comb beam. The system may further include an illumination sub-system to illuminate a sample with the dual frequency comb illumination beam through an objective lens, a collection sub-system to collect sample light from the sample with the objective lens, and a detector to capture a radio-frequency signal based on the sample light. The system may further extract spectral measurement data associated with the sample from the radio-frequency signal and generate metrology measurements based on the spectral measurement data.