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E4727A Advanced Low-Frequency Noise Analyzer

Data Sheets

E4727A/E4727P3

Advanced Low-Frequency Noise Analyzer/Measurement Bundle Software

E4727E3

WGFMU Measurement Bundle Software

Introduction

Electrical noise is inherent in every circuit and may be caused by current flowing through a resistor or transistor, or even leakage current through a tantalum capacitor. As a classical limitation of electronics, this noise must be managed. A systems engineer must understand overall system sensitivity to noise, and then derive the key contributors. A typical key contributor might be a component like a semiconductor device, sensor or passive component. How do we quantify the noise of these constituent parts? The Keysight E4727A Advanced Low-Frequency Noise Analyzer (A-LFNA) enables a closer, deeper look at noise in components, individual devices and integrated circuits, both packaged and at the wafer level. A device modeling engineer may now leverage the A-LFNA’s rare combination of industry-leading noise sensitivity (–183 dBV2/Hz) to characterize devices at high voltages (to 200 V) and down to ultra-low frequencies (to 0.03 Hz). Thanks to seamless integration with WaferPro Express software, one may program and sequence high-speed DC, capacitance and RF measurements, all the while automating wafer prober control using Cascade Microtech’s software API.

The applications for wafer-level 1/f noise measurements are numerous; however, a few important ones are listed as follows.

  • Process design kit development. Semiconductor device foundries enable fabless design centers to design components such as transceivers for mobile phones, frequency synthesizers, analog-to-digital converters and much more. To make this possible, the foundries must provide Process Design Kits (PDK’s) with simulation models of the primitive devices. The simulation models must include noise effects on transistors (BJT, CMOS, etc.) and resistors. The noise models must be across all possible bias currents, temperatures and device geometries.
  • Manufacturing statistical process control and reliability. As an example, manufacturers of GaN devices may use noise measurements across their wafers as an early indicator of device reliability. Those devices that exhibit more noise are likely to fail sooner. Now we have a nondestructive way of assessing reliability, quite in contrast with standard accelerated life testing. Furthermore, for circuit applications where noise is a critical parameter, wafer level measurements may be used to track the evolution of noise performance across days, weeks and months of manufacturing.
  • IC noise specification. Integrated circuit manufacturers of operational amplifiers and linear voltage regulators often need to characterize input referred voltage noise as a critical specification in their datasheets. One wafer may contain 20,000 such circuits. To efficiently measure and map circuit performance across the wafer (and even across lots of wafers), the probe and signal conditioning circuitry must be placed close to the device under test to improve grounding and minimize external noise influences.

The resulting noise data may be used to develop device models with the help of state-of-theart device modeling tools like Model Builder Pro (MBP) and Integrated Circuit Characterization and Analysis Program (IC-CAP). These models can then be passed along to circuit designers, who may then push the envelope in low noise circuitry.

The E4727A hardware has been designed for both on-wafer and discrete device/circuit measurements, and consists of a series of modules paired with a PXI computer and digitizer. These modules are connected to a source measurement unit (SMU) such as the B1500A to enable both flexible and clean device biasing and noise signal conditioning.

An SMU is used to apply bias and measure DC operating points. However, when measuring noise, the noise contribution must be filtered out. The voltage noise taken from the device output is amplified and analyzed using a high-speed digitizer. One possible configuration of noise measurement is shown below, although many others are possible. The variable resistance, switching and filtering functions are included in the A-LFNA modules.

Different device types require different source and load impedance terminations. The E4727A is the only analyzer in the industry to offer 25 impedance values ranging from 0 ohms to 100 MΩ. The A-LFNA software is able to judiciously select RSource and RLoad based on device type (FET, diode, BJT, etc.) and measured DC characteristics.

The PXI chassis system controller comes equipped with the A-LFNA software integrated with WaferPro express, enabling fast and flexible instrument and prober control. Thus, the engineer may now automate multi-bias, multi-device DC and noise measurements. Measurement speed and accuracy may be adjusted by setting the degree of hardware averaging. The factory provided measurement routines offer a rich set of biasing schemes that can be copied and modified to suit specific needs.

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