Overlay accuracy is a key element of lithography performance that can be improved by applying a variety of packages and techniques.
Stage accuracy and stability are directly related to overlay performance and both can be improved through the XY Stage Optimization Package from Canon Applications Services. During XY stage optimization, Canon Engineers perform a series of advanced stage tests to identify and correct a variety of stage drive and laser interferometer errors.
The Alignment Parameter Optimization Package requires Canon Engineers to perform a series of tests and experiments to determine optimal alignment mark and alignment process parameters for your most challenging layers.
In the Advanced Lens Heating Compensation Package, Canon Engineers perform advanced exposure tests, simulations and offsets to minimize intra-field overlay errors due to magnification change. This package compensates for lens heating aberrations experienced during heavy exposure loads, and when utilizing non-standard illumination modes (ex. micro-sigma).
Through the Distortion Matching Package, image fields of all steppers and scanners in a facility are matched, reducing machine-to-machine overlay differences. Canon Engineers expose a series of test wafers and collect data that characterizes the distortion characteristics of a particular projection lens. Advanced lens compensation is performed to match the tools exposure field characteristics to all of the other image fields in the fab.
Many Applications Services packages may be combined to amplify their individual effects and the following scenario illustrates the benefits to be gained with Canon Overlay Improvement Packages.
In the case of a layer with a 40nm overlay tolerance and a process overlay 3-Sigma of 40nm, what can be gained by improving overlay performance so that 35nm or 30nm overlay could be maintained?
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Estimating the lost revenue due to defects for 90 days of production shows the merit of investing in overlay performance improvements. With a 40nm 3-Sigma process, approximately 0.27% of all chips will be defective (>40nm), potentially costing hundreds of thousands of dollars.
Overlay Improvement Packages can reduce overlay accuracy to 30nm, ensuring that nearly all products (.006% chance of failure) will fall within the product specification. Product defects and costs due to overlay error are virtually eliminated.
Canon Throughput Enhancement and Overlay Improvement Packages essentially pay for themselves as you optimize and control your critical processes to increase productivity and drive down overlay error. For more information about Overlay Enhancement or any other Canon Applications Services,
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