Abstract or Demonstration Description: During RF measurement in production environments, the increased accuracy required for Known-Good-DUT requires RF calibration to the probe tip. This is due to the higher bandwidths and higher channel counts for semiconductors chips that are supporting 5G FR2 and as well as chips that are moving data in and out of large data centers. However, calibration substrates in general have not been designed to provide the best measurements possible due to the unique layouts of these devices. This can be attributed to the un-controlled RF state of the non-measured channels interacting with the channels that are being measured as well as the limitations due to the types of RF calibration algorithms that are available for HVM wafer test at RF. I will review some design methodologies for making the calibration substrates, as well as which RF calibration methods are best for the particular layout. In addition, I will present example RF measurements of these different situations that can be used for calibration verification prior to wafer test.