A Four-Step Method for De-Embedding Gigahertz On-Wafer CMOS Measurements

In this paper, a de-embedding method is proposed for conducting accurate on-wafer device measurements in the gigahertz range. The method addresses issues of substrate coupling and contact effects and is therefore suitable for measurements with lossy technologies such as CMOS. The method assumes a probe-tip two-port calibration performed with well-known techniques and impedance substrates. By employing a physical interpretation of the test-fixture, the method alleviates a number of known problems with common de-embedding procedures. Four distinct mathematical steps are suggested to de-embed parasitics for the test-fixture to give an accurate measurement of the device under test. By introducing a simple compensation factor for in-fixture standard imperfections, the proposed method allows large devices to be measured with high accuracy. The applicability of the method is demonstrated with measurements up to 12 GHz.