Optical Scatterometry for Semiconductor Strain Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor manufacturing processes face challenges in accurately measuring strain in semiconductor devices during the fabrication process, leading to increased costs and delays, as strain is typically measured indirectly after the device is completed.
Innovation Solution
The implementation of optical scatterometry methods to measure uniaxial strain in semiconductor channels by analyzing differences in optical properties along and across the channel, using metrology targets that mimic partially manufactured device structures, and correlating these measurements with electrical test results to predict device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain is measured indirectly after device completion, then measurement can be performed with existing tools, but measurement time is delayed and production costs increase
Solution Approach 1:
The patent performs strain measurements at an intermediate fabrication stage (after epitaxial growth but before device completion) rather than waiting until the end. This preliminary measurement allows for early detection and correction of strain issues, reducing both time loss and production costs while maintaining measurement accuracy through scatterometry techniques
Solution Approach 2:
The patent introduces scatterometry as an intermediary measurement technique that can non-destructively measure strain in partially fabricated devices. This intermediary approach enables measurement at intermediate stages without requiring device completion, thereby reducing time delay while maintaining measurement capability
2Productivity
If optical scatterometry is used to measure strain early in fabrication, then production time and costs are reduced, but measurement complexity increases
Solution Approach 1:
The patent employs optical scatterometry, a universal measurement technique already widely used in semiconductor manufacturing for other purposes. By leveraging this existing multi-functional tool for strain measurement, the patent avoids introducing entirely new complex equipment while enabling early strain assessment to improve productivity
Solution Approach 2:
The patent measures changes in optical parameters (reflectivity, scattering patterns) of the semiconductor structure at different fabrication stages. By monitoring parameter changes rather than introducing new measurement dimensions, the patent maintains relative measurement simplicity while enabling early strain detection to boost productivity
3Reliability
If strain measurements are performed at intermediate fabrication stages, then process optimization is improved, but measurement accuracy may be compromised due to incomplete device structure
Solution Approach 1:
The patent performs preliminary strain measurements at an intermediate stage (after epitaxial growth) when the strain-inducing structure is already formed. This timing allows accurate strain measurement of the critical component while enabling process optimization before subsequent fabrication steps, maintaining both reliability and precision
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
Enables early detection and refinement of epitaxial growth processes, allowing for immediate monitoring and optimization of semiconductor fabrication, reducing production costs and time by providing accurate strain measurements before device completion.
Implementation Method 1
optical scatterometry methods to measure uniaxial strain in semiconductor channels by analyzing differences in optical properties along and across the channel
Data Source
AI summary
Methods and systems for measuring optical properties of transistor channel structures and linking the optical properties to the state of strain are presented herein. Optical scatterometry measurements of strain are performed on metrology targets that closely mimic partially manufactured, real device structures. In one aspect, optical scatterometry is employed to measure uniaxial strain in a semiconductor channel based on differences in measured spectra along and across the semiconductor channel. In a further aspect, the effect of strain on measured spectra is decorrelated from other contributors, such as the geometry and material properties of structures captured in the measurement. In another aspect, measurements are performed on a metrology target pair including a strained metrology target and a corresponding unstrained metrology target to resolve the geometry of the metrology target under measurement and to provide a reference for the estimation of the absolute value of strain.