Epi-Diffraction Phase Microscopy for Nanoscale Etching Control
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Solution Overview
Problem
Current semiconductor fabrication processes face challenges in achieving accurate, non-destructive, real-time monitoring of dynamic processes, particularly in nanoscale precision, due to system drift and vibrations, which hinder effective control of feature size and etching rates in high-aspect-ratio structures.
Innovation Solution
The method involves using epi-diffraction phase microscopy to characterize a scattering surface's height profile by illuminating it with spatially coherent light, dispersing and filtering the scattered light to generate an interferogram, and transforming it into quantitative phase and amplitude images, enabling precise monitoring and control of semiconductor processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single-point or imaging optical measurement methods are used to monitor semiconductor fabrication processes, then non-destructive real-time monitoring is achieved, but measurement precision deteriorates due to vibrations and drift in the sample
Solution Approach 1:
The patent introduces a reference beam as an intermediary element in the interferometric measurement system. This reference beam serves as a stable comparator against which the sample beam is measured, allowing the system to distinguish between actual sample changes and spurious movements caused by vibrations or drift. The reference beam acts as a mediator that enables precise measurement despite environmental disturbances.
Solution Approach 2:
The patent implements real-time feedback through continuous interferometric monitoring during the fabrication process. The measurement system provides immediate feedback on feature dimensions, allowing the etching process to be dynamically adjusted to maintain nanoscale precision. This closed-loop feedback mechanism compensates for vibrations and drift by continuously correcting measurement readings.
2Manufacturing precision
If iterative calibration runs are performed on dummy wafers to control feature size, then manufacturing precision is improved, but productivity deteriorates due to added time and cost of duplicate runs
Solution Approach 1:
The patent performs preliminary characterization of the etching process using the interferometric measurement system before full production fabrication. By obtaining accurate etch rate data and process parameters in advance through real-time monitoring of a test structure, the system enables direct transfer of these parameters to production wafers without requiring iterative calibration runs, thus maintaining precision while improving productivity.
Solution Approach 2:
The patent implements real-time feedback monitoring during the actual fabrication process, allowing immediate detection and correction of process deviations. This eliminates the need for post-process measurements and iterative calibration on separate dummy wafers, as the system continuously monitors and maintains feature dimensions within specifications during production runs.
3Manufacturing precision
If post-process measurements are used to determine etching rates, then manufacturing precision is improved, but loss of time occurs due to iterative calibration and duplicate measurement runs
Solution Approach 1:
The patent implements continuous interferometric monitoring throughout the etching process, eliminating the interruption caused by stopping for post-process measurements. The measurement system operates continuously alongside the fabrication process, providing real-time etch rate data without requiring process interruption or separate measurement steps, thus maintaining precision while eliminating time loss.
Solution Approach 2:
The patent uses optical interferometry as an intermediary measurement technique that can operate in-situ during the etching process. This intermediary method provides continuous real-time measurement of feature dimensions and etch rates without requiring process interruption or physical contact with the sample, enabling accurate determination of etching rates during production rather than after completion.
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 provides accurate, nanoscale monitoring of dynamic processes, reducing spatial and temporal noise, and allowing for adaptive control of etching processes, enhancing precision and reducing the need for iterative calibration runs.
Implementation Method 1
interfering the zeroth- and first-order beams at a focal plane detector to generate an interferogram
Implementation Method 2
dispersing the scattered light into zeroth- and first-order beams
Data Source
AI summary
Methods and apparatus for method for characterizing a height profile of a scattering surface relative to a fiducial plane. The scattering surface, which may be an interface between distinct solid, liquid, gaseous or plasma phases, is illuminated with substantially spatially coherent light, and light scattered by the scattering surface is collected and dispersed, such as by a grating, into zeroth- and first-order beams. A spatial Fourier transform of the zeroth- and first-order beams is created, and one of the beams is low-pass filtered. The beams are interfered at a focal plane detector to generate an interferogram, which is transformed to retrieve a spatially resolved quantitative phase image and/or an amplitude image of the scattering surface. Imaging may be performed during an etching process, and may be used to adaptively control a photoetching process in a feedback loop.