Optical Critical Dimension Module Selection for Polysilicon Layer Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current optical critical dimension measuring methods fail to accurately correlate theoretical and real curves for photoresist patterns due to the influence of underlying film layers, leading to inaccurate information about the photoresist pattern, especially when ion implantation and thermal processes alter the polysilicon layers.
Innovation Solution
The method involves constructing specific optical critical dimension modules based on the type of polysilicon layers and processes applied, such as ion implantation and thermal treatment, to select appropriate modules from a library for correlation, setting optical parameters and thickness at fixed or floating values to match real curves, using normal incidence or spectroscopic ellipsometry methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard optical critical dimension module is used with fixed optical parameters for polysilicon layers, then the measurement process is simple and fast, but the theoretical curve cannot accurately correlate with the real curve, leading to measurement inaccuracy
Solution Approach 1:
The patent segments the optical critical dimension module construction into multiple specific modules based on different polysilicon layer conditions (ion implantation status, thermal process history, amorphous layer presence). Each module is tailored to specific process conditions, allowing accurate correlation between theoretical and real curves by selecting the appropriate module for the measured structure.
Solution Approach 2:
The patent changes the optical parameters (refraction index, extinction coefficient) and layer structure parameters based on the specific process history of the polysilicon layer. By adjusting these parameters to match the actual physical state of the layer (crystalline vs. amorphous, doped vs. undoped), the theoretical curve accurately correlates with the real measurement curve.
2Ease of manufacture
If the optical parameters and layer thickness are set at fixed values in the module, then the module construction is straightforward, but the theoretical curve and real curve of the spectrum cannot correlate, resulting in inability to obtain accurate photoresist pattern information
Solution Approach 1:
The patent performs preliminary actions by pre-defining multiple specific modules in the library, each configured with appropriate optical parameters and layer structures for different polysilicon layer conditions. This preliminary preparation allows quick selection of the correct module during measurement without requiring complex real-time adjustments, maintaining ease of use while ensuring measurement accuracy.
3Productivity
If ion implantation and thermal processes are performed on polysilicon layers, then the semiconductor fabrication process is complete, but the polysilicon layer structure changes (amorphous layer formation, crystallization) which complicates the optical measurement model
Solution Approach 1:
The patent applies local quality by creating different module configurations for different local conditions of the polysilicon layer. Modules are specifically designed for: (1) polysilicon without ion implantation, (2) polysilicon with ion implantation but without thermal process, (3) polysilicon with ion implantation and thermal process. Each module has locally optimized parameters matching the specific physical state of the layer.
Solution Approach 2:
The patent introduces dynamics by making the module selection adaptive to the process history of the polysilicon layer. The measurement system dynamically selects the appropriate module based on whether ion implantation and thermal processes were performed, allowing the model to adapt to different physical states (crystalline, amorphous, partially crystallized) of the polysilicon layer.
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 allows for accurate measurement of photoresist patterns by generating theoretical curves that closely match real curves, providing better information about the pattern's critical dimensions and processes, enhancing the precision of semiconductor fabrication.
Implementation Method 1
the test key spectrum that corresponds to the photoresist pattern is being measured first to obtain the real curve
Implementation Method 2
When the polysilicon layer has been subjected to an ion implantation process and the surface of the polysilicon layer has been formed with an amorphous silicon layer
Implementation Method 3
when the amorphous layer is completely crystallized into the polysilicon layer
Data Source
AI summary
An optical critical dimension measuring method, applicable in measuring a pattern, that includes a plurality of polysilicon layers, of a device, is provided. The method includes obtaining a real curve corresponding to the to-be-measured device. Then, determining whether an ion implantation process has been performed on the polysilicon layers, a different module is selected. A correlation process is performed according to the selected module to generate a theoretical curve that correlates with the real curve to obtain a plurality of parameters corresponding to the theoretical curve.