What are the VNA On-Wafer Calibration Coefficients for my ISS?

Impedance Standard SubstrateA simple answer is in the table below, however, a more advanced answer follows. This question may indicate a basic misunderstanding of on-wafer calibration. So, let's try to correct it.

In coaxial calibrations the standards are unique devices and since they have a unique connector can have only a single electrical characteristic. In on-wafer probing the electrical behavior of the standards are dependent upon the probe and how it is placed.

The shape and configuration of the standard will also be important. We make a variety of impedance standard substrates (ISS's). There are versions for probes with standard or wide pitch with choices for ground-signal or ground-signal-ground tip configurations. In addition there are general purpose, specialty, and custom configurations supporting a wide variety of applications.

What all of this boils down to is that the on-wafer calibration coefficients are supplied with the probe, not with the impedance standard substrate. For air coplanar (ACP) probes, refer to the lid of the box for a table. When used with the designated ISS the calibration coefficients for a specific probe are found by selecting the tip configuration and pitch entry in the table. For 250 um pitch probes either the standard pitch or the wide-pitch ISS may be used. The calibration coefficients that are normally supplied correspond to the standard pitch ISS. The values will be somewhat different when using the wide pitch ISS.

The only on-wafer calibration term not supplied with the probe is the Thru standard delay. For standard pitch probes with proper alignment of probe separation using the alignment marks provided on the ISS, the Thru delay will be 1 ps. For wide-pitch ISS's the Thru delay is 4 ps.

What are the VNA On-Wafer Calibration Coefficients for my Impedance Standard Substrate?

Air-Coplanar Probe (ACP) on-wafer calibration coefficients table above. Coefficients for VNA on-wafer calibration depend on the style and pitch of the probe, as well as the ISS used. The wide-pitch ISS's (106-682 and 106-683) use a 4 ps long Thru line while the standard-pitch ISS's (101-190 and 103-726) have a 1 ps Thru line.

If you have questions about the chart above or need additional assistance determining your VNA on-wafer calibration coefficients, drop a comment in the comment field below. We'll be sure to get back to you with the information you need.


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