Diffracting Structure Measurement Using Film Thickness Pre-estimation
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Solution Overview
Problem
Conventional spectroscopic scatterometry methods for measuring dimensions and profiles of structures in semiconductor wafers are time-consuming due to the need to calculate multiple model parameters, and often require separate measurements from neighboring areas which may not be available or have different thickness characteristics.
Innovation Solution
Obtaining film thickness information from the same area as the target diffracting structures using a film model, allowing for the derivation of structure parameters from a single measurement, and using this thickness value in the structure model to reduce the number of model parameters and simplify calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional spectroscopic scatterometry is used to measure multiple model parameters (height, width, diameter, wall angle) simultaneously, then comprehensive structure characterization is achieved, but measurement time becomes too long for real-time applications
Solution Approach 1:
The patent applies preliminary action by first measuring the film thickness in a neighboring area before performing the main structure parameter measurement. This pre-obtained thickness information is then used as a known parameter in the scatterometry model, eliminating the need to calculate it simultaneously with other structure parameters, thereby reducing overall measurement and calculation time while maintaining measurement comprehensiveness
Solution Approach 2:
The measurement process is segmented into separate steps: first measuring film thickness in a neighboring area, then using that information to measure structure parameters (height, width, diameter, wall angle) in the target area. This segmentation allows each measurement to focus on specific parameters with optimized calculation, reducing total computation time compared to simultaneous multi-parameter measurement
2Device complexity
If separate measurements are performed on neighboring areas to obtain thickness information, then modeling complexity is reduced, but measurement reliability decreases when neighboring areas are unavailable or have different thickness characteristics
Solution Approach 1:
The patent applies local quality by performing the thickness measurement specifically in a neighboring area that is selected to have similar film characteristics to the target area. This localized approach ensures that the pre-measured thickness is relevant and accurate for the subsequent structure parameter measurement, maintaining reliability while reducing modeling complexity
Solution Approach 2:
By performing preliminary thickness measurement in a carefully selected neighboring area, the system establishes a reliable baseline parameter that can be confidently used in the main measurement. This preliminary action in a suitable location ensures both reduced modeling complexity and maintained measurement reliability
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 simplifies the measurement process by allowing for real-time calculations without the need for separate thickness measurements, improving efficiency and accuracy in determining parameters like pitch, critical dimension, and wall angle of diffracting structures.
Implementation Method 1
a periodic diffracting structure... The diffraction of the beam is detected... using the calculated position of a known diffraction order
Data Source
AI summary
To measure the critical dimensions and other parameters of a one- or two-dimensional diffracting structure of a film, the calculation may be simplified by first performing a measurement of the thickness of the film, employing a film model that does not vary the critical dimension or parameters related to other characteristics of the structure. The thickness of the film may be estimated using the film model sufficiently accurately so that such estimate may be employed to simplify the structure model for deriving the critical dimension and other parameters related to the two-dimensional diffracting structure.