Scatterfield Microscopy Using Optical Switching Array
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Solution Overview
Problem
Conventional optical microscopes are insufficient for measuring surface structures in advanced semiconductor processing due to feature sizes smaller than the optical diffraction limit, requiring precise mechanical control and complex system modeling in existing scatterometers and interference microscopes.
Innovation Solution
An apparatus using an optical switching array device to control incident light at different angles for scatterfield microscopical measurement, simplifying the system and reducing mechanical actuation inaccuracies, comprising a light source module, optical switching array device, beam splitting unit, objective lens with a back focal plane, and array-type detection device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical microscopes are used for surface structure measurement, then the system structure is simple, but the measurement precision is insufficient due to feature sizes smaller than the optical diffraction limit
Solution Approach 1:
The patent replaces mechanical mask movement systems with an optical switching array device that electronically controls incident light angles. This substitution eliminates mechanical actuation inaccuracies while maintaining the scatterometer's measurement capability for sub-diffraction-limit features, thereby improving measurement precision without proportionally increasing system complexity
Solution Approach 2:
The patent integrates the scatterometer and bright-field microscope into a unified measurement system that can perform both scatterfield measurements and conventional optical imaging. This multi-functional approach allows the system to handle various measurement requirements (surface structure analysis and general imaging) with a single apparatus, improving measurement precision for advanced semiconductor features while managing system complexity through functional integration
2Measurement precision
If a scatterometer is used to measure sub-diffraction-limit features, then the measurement precision improves, but the device complexity increases due to precise mechanical control requirements
Solution Approach 1:
The patent replaces the mechanical mask translation system with an optical switching array device that uses electronic control to vary incident light angles. This eliminates the need for precise mechanical actuation while maintaining the ability to perform scatterfield measurements on sub-diffraction-limit features, thereby improving measurement precision while reducing mechanical control complexity
Solution Approach 2:
The patent implements dynamic control of incident light angles through the optical switching array device, which can rapidly switch between different illumination configurations without mechanical movement. This dynamic optical control system maintains measurement precision for advanced semiconductor features while eliminating mechanical complexity
3Measurement precision
If an interference microscope is used to select incident light by position variation, then the measurement precision improves, but the device complexity increases and system modeling becomes more complicated
Solution Approach 1:
The patent replaces the mechanical position variation system of the interference microscope with an optical switching array device that electronically selects incident light angles. This substitution maintains precise incident light selection capability while simplifying the overall system structure and reducing modeling complexity, as the optical switching device has fewer moving parts and simpler control requirements
4Measurement precision
If precise mechanical actuation is used to control incident angles, then the measurement precision improves, but the reliability decreases due to mechanical actuation inaccuracies
Solution Approach 1:
The patent replaces mechanical actuation systems with an optical switching array device that uses electronic control to precise incident light angles. This eliminates mechanical play, friction, and actuation inaccuracies, thereby improving measurement reliability while maintaining precise incident angle control for scatterfield measurements
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 solution provides accurate and reliable scatterfield microscopical measurements by generating and focusing detection beams on a back focal plane, simplifying system integration and reducing mechanical precision requirements, thus addressing the limitations of conventional optical microscopes and interference microscopes.
Implementation Method 1
an objective lens set with a back focal plane, capable of generating an optical signal by projecting the detection beam passing through the beam splitting unit onto an object under test to generate a scattered light and focus the scattered light on the back focal plane
Implementation Method 2
an optical switching array device, capable of adjusting the intensity of the uniform light to generate a detection beam
Implementation Method 3
focusing zero or higher order diffraction beams resulting from the detection beam illuminating on an object under test
Data Source
AI summary
A method and an apparatus are disclosed for scatterfield microscopical measurement. The method integrates a scatterometer and a bright-field microscope for enabling the measurement precision to be better than the optical diffraction limit. With the aforesaid method and apparatus, a detection beam is generated by performing a process on a uniform light using an LCoS (liquid crystal on silicon) or a DMD (digital micro-mirror device) which is to directed to image on the back focal plane of an object to be measured, and then scattered beams resulting from the detection beam on the object's surface are focused on a plane to form an optical signal which is to be detected by an array-type detection device. The detection beam can be oriented by the modulation device to illuminate on the object at a number of different angles, by which zero order or higher order diffraction intensities at different positions of the plane at different incident angles can be collected.