Customer SolutionsResearch Group Creates Flexible, High-Speed, Mixed-Signal System for On-Wafer Function and Performance Testing
Author(s):Bart De Wachter, Interuniversity Microelectronics Centre; Axel Nackaerts, Interuniversity Microelectronics Centre
Industry:Semiconductor, University/Education
Product:LabVIEW, PXI/CompactPCI
The Challenge:Developing a custom mixed-signal measurement platform that can accommodate multiple power supplies and high-speed digital and analog signals for on-wafer measurement of devices and prototype circuits.
The Solution:Creating a flexible test system using National Instruments PXI hardware and a custom interface to a wafer prober system.
In a research consortium such as the Interuniversity Microelectronics Centre (IMEC), a large number of projects are running in parallel with a wide variety of devices under test (DUTs). DUTs can be simple passive components, transistors, memory cells, or sizeable memories and microprocessor cores. Large automated batch tools handle device parametric testing and testing of simple circuits (such as static RAM cells or ring oscillators). However, it is not cost-effective to implement different test procedures for more complex circuits on these systems. We required a flexible platform that would help researchers set up and execute their own test procedures quickly. Furthermore, the platform had to replace an aging industrial ASIC test system while maintaining the same functionality. Key system requirements included: We selected a National Instruments PXI-1044 14-slot chassis with four NI PXI-6551 high-speed 20-channel digital I/O modules, an NI PXI-5124 2-channel 200 MS/s high-speed digitizer, an NI PXI-6259 multipurpose data acquisition module, two NI PXI-4110 power supplies, and an NI PXI-4072 6½-digit LCR meter. Future expansion of the system is possible by adding more PXI modules or another chassis. The interface between the probe card (300 pins) and the data acquisition and generation system had to be flexible enough to accommodate the different circuit pinouts but also reconfigurable in a few minutes. Any probe card pin had to be connectable to any I/O pin. The large number of pins and the high-frequency signal content excluded the use of a large switch matrix, so we designed an impedance-matched interface board with two backplane buses and a plug-in interconnection daughterboard. One backplane bus connects to every possible probe card pin, while the other bus connects to every digital or analog I/O of the measurement system. The daughterboard contains the probe-to-I/O mapping. Two variants of the daughterboard were designed: a development board where the two backplane buses are expanded into connectors, so researchers can wire wrap manual connections, and a second variant with hardwired interconnections for production testing. Direct connections to the probe card pins are also possible. All data generation and acquisition is controlled with virtual instruments created in the National Instruments LabVIEW graphical development environment. With this system installed, researchers can now develop a measurement application at their desk and prewire a development daughterboard for their specific circuit. Running the measurements on a wafer now requires only loading and aligning the wafer, plugging in the prewired interconnection daughterboard, and loading the NI LabVIEW application. Researchers can perform these (on-tool) operations in less than 30 minutes, compared to several hours with the previously used system. By using National Instruments PXI modular instruments and LabVIEW as the programming interface, the measurement throughput has increased by a factor of four, while the total cost of ownership was reduced by 60 percent. Additionally, we can easily modify the system for additional functionality. For more information, contact: Phone: +32 16 28 87 54
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