Advanced analysis and modeling of process overlay and registration data.
(Imports any metrology data)
A seventh-generation overlay & registration tool from TEA Systems with unique tools for Double Patterning and Feature Design Verification
An engineering workbench for setup, tuning, characterization and control.
Any Vector Raptor TM analysis can be encapsulated into macros &
production automated with trend charts using Weir DMA
Overlay and registration data analysis has been used extensively since the early 1980's when automated metrology was first introduced. There have been many overlay software packages provided over the years and every metrology tool and some exposure tools come with their own software. So why a new software package for overlay and registration analysis?
Quite recently classic overlay metrology methods based on automated optical microscopes have been joined by ellipsometer and scattering techniques that simultaneously measure both overlay and feature profile characteristics. Process control efforts therefore need a device-independent means of reading in data from any source to calibrate and understand the metrology response to subtle changes in test pattern design. New methods of comparison, correlation and calibration are also needed to tune these tools for process yield control.
Recent device-design nodes enjoyed the presence of process margins that had been improved to the point that most of the overlay error was within the capabilities of a properly tuned exposure tool ("Scanner"). However this safety margin was eliminated as recent radical changes in the approach to semiconductor manufacturing lithography were altered by a drastic change in direction of the technology roadmap into "Double Patterning".
"Double Patterning" (DP) is the selected method of extending the current proven "i193" technology to smaller feature sizes by splitting the most complex layers of new designs into two to five imaging levels. Each split level requires sequential exposure and development of different resist films and multiple etch steps to transfer the pattern-mask into the substrate. The intent of this technique is to allow the level of reticle enhancement to remain at present levels while continuing chip-design progress a few more nanometers (nm) down the design-node slope.
Classic overlay control techniques have been developed to optimize layer-to-layer pattern registration. Reticle manufacturing problems such as alignment-mark to device-pattern registration were easily controlled as a simple offset and rotation of the wafer exposure. Reticle-manufacturing process variations were acceptable as long as the feature size distribution feel within production tolerance. These levels of control are no longer sufficient for the needs of sub-45 nm designs.
The complexity of Double Patterning technology is raised by increased within-layer pattern-to-pattern registration demands to the mask-maker as well as the device manufacturer. The DP methodology presents a need for some very clever pattern-splitting algorithms in chip design to minimize the number of exposures required to piece together these critical layers. For the lithographer, these splits mean that the demands on process control will spiral upward with the additional need to control multiple reticle pattern shifts, rotation and even the effective critical feature size that are now occurring within a single lithographic device layer and will eventually still be subject to the same intra-layer requirements.
For the first time the overlay and even feature size uniformity of the most critical layers of the process will be registration and feature-size sensitive to whole-wafer process and exposure tool systematic drift whose errors are now derived from both reticle and wafer fabrication steps. Small changes in reticle alignment mark to pattern placement result not only in single-field registration errors but also in a reduction in feature size uniformity. Small variations in across-plate reticle process uniformity from etch or film variation compound to increase the across-field and across wafer uniformity of critical features and single-layer registration that in-turn complicates the overlay task of alignment to it's reference layer.
So with a device-layer now exposed by two to five reticles, how does the lithographer quantify and correct for errors created by the individual mask, wafer-process or exposure tool?
Vector Raptor provides the tools needed to extract the individual contributions of metrology, reticle, process and exposure tool. These new tools are enhanced by:
Vector Raptor loads data from Weir Standard Format storage that uses Microsoft Excel © workbooks. After the first import, this workbook is retained and loaded directly into the software from this user-friendly format. All data, analysis reports and Vector-Raptor derived response data sets are always available and open to the user. Weir workbook entered data and reports are summarized in a hyper-linked "Index" for rapid access and can be saved to any html-format site.
Data from ANY metrology tool is easily imported into the Weir Workbook for analysis. There is never a charge for updates or additions to the metrology library as long as the data is a standard metrology format or is intensively used by the customer.
Vector Raptor automatically imports and formats data from SEM’s, scatterometry, simulations, ELM, Optical and any tool measuring registration or overlay. Automated and manual mouse- interactive data culling methods are employed. Software can be used as an Advanced Process Control (APC) or tool tuning module. Output can be paper or binary media with control element output to optimize tool settings.
Data import is set up using a simple windows-graphic controls. The system is an “open” tool with data stored and easily accessed using Microsoft Excel Spreadsheets. Worksheet macros are not used but can be user-added if desired.
TEA Systems Vector Raptor TM is a compiled application with a full object oriented, mouse-interactive interface. Drill down graphics and spreadsheet analysis supported. Functional on Windows 2000, XP etc.. Microsoft Excel© is required.
Data subset viewing and graphic generation selected by the mouse.
|Vector Raptor, Weir, Weir PW and Weir PSFM are trademarks of TEA Systems Corp.|
ASML and FOCAL are trademarks of ASM Lithography.
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