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Cascade Microtech’s WinCal XE Adds 16-term Calibration to Enhance RF Device Model Accuracy

Cascade Microtech added an important new capability, a 16-term calibration technique, to its WinCal XE calibration software to help semiconductor labs reduce design cycles and time to market. Using WinCal XE for on-wafer measurement helps semiconductor manufacturers create more accurate high frequency RF device models. With the explosion of wireless devices, semiconductor companies are under pressure to get their high speed products to market faster than ever before. The 16-term calibration eliminates certain undesired measurement parasitic effects, thus enabling more accurate device models and shorter design cycle times.

The new WinCal XE 16-term calibration was implemented with the assistance of researchers from Auburn University, Auburn, AL, who will present a technical paper demonstrating superior transistor model accuracy using the technique. The paper will be presented June 7, 2007 at the International Microwave Symposium (IMS) in Honolulu, HI.

WinCal XE’s open architecture easily adopts 16-term calibration

WinCal XE’s highly flexible design and open architecture allows new innovations and capabilities to be added quickly to the software. In cooperation with Auburn University, Cascade Microtech was able to add the new feature seamlessly, making it available to all customers who need advanced capability for high frequency measurements.

High frequency transistor measurement begins by calibrating the test system to the wafer probe tips using known test standards. Next, to eliminate undesired parasitic effects of transistor probing pads, wafer “dummy” pad structures are measured, de-embedding their loading and crosstalk effects on the “intrinsic” transistor. The accuracy of this approach is limited at extremely high frequencies due to necessary lumped element behavior assumptions that are no longer valid. A calibration-like approach with dedicated on-wafer standards for de-embedding makes no such assumptions and will overcome the high frequency limitations.

Past attempts to use traditional 12-term error model calibration for de-embedding have been incomplete and were not capable of characterizing the device-dependent coupling present in the pad structures. Only the complete 16-term error model can handle the complete behavior of device pads while providing improved transistor model parameter extraction. This approach is particularly valuable when a single-step calibration to the intrinsic transistor is desired and proper correction for device-dependent coupling is necessary. For more detailed information, see IMS session TH2D-04, June 7, 2007, “Singular Value Decomposition-based Four-port De-embedding and Single-Step Error Calibration for On-Chip Measurement,” by X. Wei and G. Niu, Auburn University.

Other new capabilities for WinCal XE

WinCal XE calibration software is designed to reduce the complexity of making accurate wafer-level measurements at ever-higher frequencies and obtaining fast-turn data to reduce time to market. WinCal XE’s open architecture allows new innovations and capabilities to be added quickly. It provides easy access to advanced features to refine RF measurements that are accurate, repeatable and reliable.

In addition to the new 16-term calibration, WinCal XE also includes new and recently added features, including:

• Unique hybrid calibrations, SOLT-SOLR and LRRM-SOLR, enable more accurate multi-port measurements;

• Advanced data post-processing of S-parameters with flexible viewing, customizable data manipulation and simple creation and sharing of display templates to increase lab productivity;

• Management and automation of all calibration methods—whether it is SOLT, SOLR, multi-line TRL, LRM, LRRM or hybrid: and for 1-, 2-, 3-, or 4-ports—enable shorter setup times;

• System validation tools, including a calibration comparison and advanced statistical reporting tools, to increase data accuracy;

• For faster measurement verification, the vector network analyzer (VNA) error set manager allows you to post-correct measured or stored data and make fast and simple calibration comparisons or augmentations.

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