On-Wafer SOLT Calibration Using 4-port PNA-L Network Analyzers (N5230A Options x4x)

Table of Contents

• Introduction
• Equipment used
• Implementation
• Step 1. Create a new calibration kit for probing
• Step 2. Perform the SOLT (Short-Open-Load-Thru) calibration
• Conclusion

Introduction

This application note is intended for on-wafer applications using the 4-port, PNA-L network analyzers with two dual probes to achieve full 4-port on-wafer calibrations manually. 4-port PNA-L network analyzers are available in 13.5 or 20 GHz models. PNA-L firmware revision must be 6.03 or higher.

This document provides step-by-step instructions needed to set up a calibration kit before a 4-port SOLT (Short-Open-Load-Thru) calibration can be performed. The steps outlined here can be applied toward nearly any kind of non-coaxial application, of which on-wafer is one.

Equipment used

• 4-port PNA-L, N5230A with Option x4x (referred throughout this document as PNA-L)
• Option 140, 300 kHz to 13.5 GHz, 4-port with the standard test set
• Option 145, 300 kHz to 13.5 GHz, 4-port with the configurable test set
• Option 146, 300 kHz to 13.5 GHz, 4-port with configurable test set and internal second source
• Option 240, 300 kHz to 20 GHz, 4-port with the standard test set
• Option 245, 300 kHz to 20 GHz, 4-port with the configurable test set
• Option 246, 300 kHz to 20 GHz, 4-port with configurable test set and internal second source
• Dual probes and associated ISS (Impedance Standard Substrate)

Implementation

Although a total of six thru paths are present for any 4-port measurement setup, a minimum of only three thru paths are required with the PNA-L to yield a full 4-port SOLT calibration. (If desired, the user can choose to apply all six thru paths; but measuring more paths will take more time and will cause more wear-and-tear of the calibration standards).

The PNA-L performs 4-port calibrations using either SmartCal (Guided calibration) or an Electronic Calibration (ECal) module. With Guided calibration, the process chooses the standards to apply from the calibration kit based on how they were defined. For on-wafer 4-port calibration, only SmartCal is applicable.

Given that most 4-port on-wafer setups tend to have one dual-probe on the left and one on the right, we can assume the ports on the left are 1 and 2, and the ones on the right are 3 and 4, see Figure 3. As can be seen from this illustration, performing on-wafer 4-port calibration using dual probes would require the need to measure thru standards of different lengths because more than one thru configuration must be used during the calibration. Three of the most common configurations are “straight thru,” “loop-back thru,” and “cross-thru,” as shown in Figure 4.

With the PNA-L, the unknown thru calibration method is available and can be applied whenever standards are not perfect. Since loop-back and cross-throughs are in general not perfect, as compared to straight-throughs, the unknown thru calibration method provides a much more accurate calibration. This approach is preferred because, with the unknown thru the method, the through standard does not need to be perfect.

Two major steps are needed to complete a 4-port on-wafer calibration manually using the PNA-L. The details in these steps describe how to properly define a calibration kit and then how to perform the actual calibration.