Impedance Standard Substrate Research Articles

An Improved Thru-Line De-Embedding Technique up to 80 GHz

With the rapid increase of high-speed communications, the frequency range of integrated circuits enters the field of millimeter wave, and the size of devices has become smaller and smaller. In the measurement of microwave devices, the probe cannot contact the device directly. The actual device under test (DUT) is surrounded by metal traces called leads, which provide the interface between the probing pads on the wafer and the DUT itself. The probes are pressed on the pads at both ends of the DUT. The parasitic effect of pads and transmission lines is significant at high frequency. The established technique such as Short-Open-Load-Thru (SOLT) and Line-Reflect-Reflect-Match (LRRM) move the reference plane up to the tip of the probes by means of Cascade Microtech impedance standard substrate (ISS). To obtain accurate parameters of DUT, a deembedding method must be implemented to eliminate the influence of pads and interconnect transmission lines.

A Study on the Radiation Characteristics of Microelectronic Probes

Microelectronic probes with the ground-signal-ground (GSG) tips have been widely used in testing integrated circuits and antennas. Yet, the radiation from probes has been rarely studied, which has been found to degrade the testing accuracy of the radiation from an antenna. In this paper, a typical ACP40-GSG-100 probe is studied from both simulation and measurement. It is confirmed that the probe radiation is caused by current on its tips, the metal probe shell strongly affects the radiated power distribution, and the ignorance of probe radiation causes error to the realized gain calculation. It is found that the probe shows a symmetrical radiation pattern for its symmetrical current distribution on the tips, the matched probe has larger realized gain than the open-ended one for about 4.8 dB because of stronger current, and the different contact positions on an impedance standard substrate (ISS) make the radiation distribution be different but hardly affect the realized gain. The strongest radiation of the probe basically locates within a narrow region near the symmetry plane of the probe, which makes it easier and faster to find the peak gain. A simple mathematical model is given to explain why low-gain probes are preferred in antenna radiation tests.

Electrooptic Measurements to Assess the Quality of Calibration Kit Design

Electromagnetic coupling between planar devices can degrade microwave calibrations and, consequently, the accuracy of a measurement. This letter describes measurement-based methods that can identify, assess, and visualize the electric field coupled between the adjacent planar calibration structures. The coupling within a printed circuit board (PCB)-based and an on-wafer impedance standard substrate is successfully demonstrated and analyzed up to 4 and 20 GHz, respectively, through S-parameter and electric-field measurements obtained using an electrooptic probing system.

Comparison of On-Wafer TRL Calibration to ISS SOLT Calibration With Open-Short De-Embedding up to 500 GHz

Sub-mm circuit design requires accurate on-wafer characterization of passive and active devices. In industry, characterization of these devices is often performed with off-wafer short-open-load-thru (SOLT) calibration. In this paper, the validity of this characterization procedure above 110 GHz is investigated by an exhaustive study of on-wafer and alumina off-wafer calibration using measurement and electromagnetic (EM) simulation up to 500 GHz. The EM simulation is performed at two different levels, first at the intrinsic level of the devices under test for reference and afterward up to the probe level to simulate different standards used in the off-wafer calibration or in the on-wafer calibration in the presence of the probe. Furthermore, EM simulation data are calibrated with the same procedures and tools that are used in the measurement; therefore, it includes the probe-to-substrate coupling. In addition, precise EM model of a commercial impedance standard substrate is developed and used to perform the SOLT calibration. A good agreement is observed between measurement and EM modeling for the off-wafer calibration as well as for the on-wafer calibration. Results clearly highlight a limitation of alumina off-wafer methodology above 200 GHz for characterization of silicon-based technologies. Finally, a discussion is given on the pros and cons of the off-wafer and on-wafer methodologies.

Realization of Accurate On-Wafer Measurement Using Precision Probing Technique at Millimeter-Wave Frequency

This paper demonstrates a novel measurement technique that can be utilized in on-wafer calibration and device evaluation procedures. This technique can realize a repeatable determination of the distance between probes thorough RF signal detection. The measured S-parameters are analyzed to determine the origin coordinates of probes. As these procedures are automated, operator dependence in the alignment of the probe position and resolution of the microscope is eliminated. A fully automatic probe station is constructed, and an impedance standard substrate (ISS) with special alignment patterns is fabricated for realizing this technique. The origin coordinates of two probes are determined at a certain position above the alignment patterns. The obtained variation in the distance between the probes is a few micrometers, which is less than that in conventional manual probing. Measurement reproducibility is investigated by evaluating the standard deviations of the measured S-parameters of a matched transmission line on the ISS. The proposed technique exhibits lower standard deviations compared to those of conventional manual probing.

Accurate and Efficient Self-Calibration Algorithm of Broadband On-Wafer Scattering-Parameter Measurements for Production Test Applications Up to 110 GHz

This paper presents an accurate and efficient on-wafer calibration algorithm of broadband scattering-parameter measurements for radio-frequency integrated circuit production test applications. Three on-chip calibration standards with the same probe positions as those of the devices under test (DUTs) were designed to take advantage of fixed probe heads in the x–y directions during calibration and measurements. In addition, three on-chip standards—a series resistor and a shunt resistor (both of which have an offset line segment) as well as a transmission line (TL)—do not have to be characterized in advance, and the measurement reference impedance can be acquired further though self-calibration without an impedance-standard substrate (ISS). Simulation studies and experimental confirmation were conducted on GaAs substrates, from 2 to 110 GHz, in addition to comparisons of the multiline thru-reflect-line (TRL) calibration results.

Applying line-series-shunt calibration to one-tier on-wafer device de-embedding up to millimeter waves

In this article, a one-tier on-wafer device de-embedding methodology up to millimeter wave regions is presented by using the line-series-shunt calibration technique. All the calibration and de-embedding processes are accomplished without the needs of impedance-standard-substrate (ISS), which defines the reference impedance in the conventional on-wafer measurements. Three on-chip standards, namely a section of transmission line (TL), a series resistor, and a shunt resistor, are utilized to perform the calibration where the characteristics of the standards need not to be known in advance and can be evaluated through the self-calibration procedure. The proposed method is examined by the GaAs 0.15 μm pseudomorphic high electron mobility transistor (pHEMT) device in the measured frequencies from 2 GHz to 90 GHz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:744–747, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27445

A General 4-Port Solution for 110 GHz On-Wafer Transistor Measurements With or Without Impedance Standard Substrate (ISS) Calibration

This paper presents a general 4-port algorithm that can remove on-wafer parasitics from on-wafer measurements after impedance standard substrate (ISS) calibration of system errors, or remove both system errors and on-wafer parasitics in a single step without ISS calibration. On-wafer standards are fabricated on a 0.13 RF CMOS process, and experimental data are measured from 2 to 110 GHz using an HP 8510XF system. The impact of nonideal on-wafer load standards is examined using the deembedded transistor-parameters and the extracted small signal parameters. The errors remaining after the traditional open-short deembedding are numerically evaluated, which become significant above 50 GHz. The solved 4-port network for on-wafer parasitics is indeed reciprocal despite the assumptions of ideal OPEN and SHORT, thus allowing a mathematically simpler reciprocal 4-port solution. The general 4-port solution can also be directly applied to the measured raw S-parameters to remove both system errors and on-wafer parasitics in a single step. Single-step calibration leads to reasonably accurate transistor -parameters, despite the less accurate on-wafer standards compared to precision ISS standards.

A potentially significant on-wafer high-frequency measurement calibration error

High accuracy radio-frequency (RF) measurements typically require a calibration to remove the undesired effects of the measurement apparatus. The calibration consists of measuring some combination of known standards such as short, open, load, through, and delay. When measurements are performed on-wafer for silicon RF integrated circuits (RFICs), a two-step calibration/de-embedding technique is typically used. First, the measurement system is calibrated to a reference plane located at the probe tips through measurement of calibration standards fabricated on an impedance-standard substrate. Second, on-wafer de-embedding standards are measured in an attempt to shift the reference plane to the terminals of the device under test (DUT). While significant effort has gone into the development of improved on-wafer de-embedding schemes, discrepancies between actual and de-embedded data still exist. In this article, we first discuss a specific case (a spiral inductor on silicon) for which there was a significant discrepancy between measurement and analysis. The problem is found to be with the measurement. This problem is detailed, and a technique we call "synthetic calibration" is described that can be used with any electromagnetic (EM) analysis to quantify calibration error for any proposed set of calibration standards. Due to the high expense and time required for wafer fabrication, it is important to successfully complete such a calibration validation prior to tape-out.

An Improved On-Wafer Measurement Method for PHEMT Modeling for Millimeter Wave Application

An improved on-wafer measurement method by using coaxial calibration instead of on-wafer calibration for PHEMT modeling is proposed in this paper. The advantage is that S-parameters of PHEMT device can be measured on wafer without impedance standard substrate (ISS) after the S-parameters of the microprobes have been determined. Excellent agreement is obtained between on-wafer calibration measurement and coaxial calibration measurements, respectively.

Results of a multi-site round-robin to examine probed measurements of an impedance standard substrate

The results from a round-robin measurement using microwave coplanar waveguide probes are presented. The round robin was initiated and coordinated by the TRW Equipment Management Center's Measurement Engineering Department (MED). Ten probe sites, within and outside of TRW, participated in the round-robin. Each participant used the same Cascade Microtech impedance standard substrate, the same measurement and calibration structures, the same calibration method, and the same network analyzer conditions. S-parameter measurements were performed over the frequency range of 0.045-26.5 GHz on a 10-dB attenuator and a 20-dB attenuator. In addition to the data comparison between the various probe sites, measurement repeatability results obtained by TRW are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>