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Standalone Pushes Optical CD Boundaries
July 14, 2008
Semiconductor manufacturers face tough process and business challenges. On one hand they are required to increase metrology sampling to cope with shrinking process windows, new materials and new architectures, and on the other they are required to reduce cost to maintain profitability. In the case of litho- or etch-based, 32-nm double patterning, for example, there is an increasing need for increased metrology sampling. Shrinking process windows dictate better understanding of metrology uncertainty factors. The 2007 International Technology Roadmap for Semiconductors (ITRS) replaced single term precision, representing variability of a single tool over time, with uncertainty, consisting of three different factors: single tool measurement-to-measurement variability, tool-to-tool variability and sample-to-sample variability.
Nova Measuring Instruments Ltd. (Rehovot, Israel) has introduced a new high throughput high accuracy standalone optical CD platform, designed to be a cost-effective alternative to the CD-SEM in lithography and other applications. The Nova T500 follows the company’s NovaScan 3090Next metrology tool, and offers a 250 wph throughput (13 measurement sites) and its redesigned optics provide a 30% improvement in precision over the 3090Next.
Based on the company’s proprietary normal incidence spectral reflectometry, the platform allows up to three measurement units (MUs) to be installed on it, providing a straightforward upgrade path, and will also be compatible with other future metrology capabilities as they become available. The tool uses the NovaMARS application development software and can measure fine profile parameters on complex 3-D test structures as well as in the device itself. As process windows shrink, the correlation between solid or 2-D test structures and the actual device diminishes. The platform’s hardware and software provide the capability to measure complex 3D profile parameters on test structures as well as in the device.
The tool’s improved spectral accuracy enables 32-nm FEOL applications. The system provides configurable throughput capabilities of 135 wph with one MU and 250 wph (both on 13 sites) with a second MU. A third MU can be added for sampling rates of 40 or more sites per wafer for applications such as scanner qualification and monitoring. The system should meet ITRS requirements down to the 22-nm node.
The system’s GUI conforms to SEMI standard E-95, controlling all tool operations including recipe creation, measurement, result plotting and analysis, troubleshooting, preventive maintenance and more. An error logging, diagnostic, handling and recovery module constantly analyzes the tool’s health, handling errors when they occur and increasing the mean time between interrupts. A “rights management” module supports simple as well as complex viewing and editing rights, management schemes preventing unwanted recipe change, and information leak to unauthorized personnel.
Posted by Alexander E. Braun on July 14, 2008 | Comments (4)
