Serge Demidenko - RMIT International University Vietnam
Moi-Tin Chew - RMIT International University Vietnam
Nhat Minh Doung - RMIT International University Vietnam
Ye Chow Kuang - Monash University Sunway Campus
Melanie Ooi - Monash University Sunway Campus
Test technology is a critical component in electronic engineering education. The main difficulty in incorporating it in university curricula is the extremely high cost of industrial-grade automated test equipment. To address this problem, we used NI LabVIEW and NI ELVIS II to create a low-cost, programmable electronic test system for functional and DC parametric testing of simple logic ICs. The system includes a simple, plug-and-play, custom-made IC testing board and application software. We can further extend it to include other test types, such as AC parametric, structural, and current (so-called DDQ testing, where current is measured at VDD terminal of CMOS integrated circuit in a quiescent state).
Semiconductor Test and Training Needs
Testing is extremely important in IC fabrication. Its complexity is growing faster than overall progress in semiconductor fabrication. Testing determines the functionality, electrical, and performance parameters of the fabricated ICs and checks for defects.
The spectacular growth of IC technology is only economically viable with high-quality, cost-effective automatic test equipment manned by qualified engineering personnel to test chips in a reasonable time and at a reasonable cost. Verification and production testing routinely represent 50 to 60 percent or more of the total cost and time of IC manufacturing. This makes testing the biggest single expense of the chip fabrication process.
There is a serious shortage of qualified test specialists in the industry. Testing and failure analysis are specialty areas requiring knowledge and skills in different general disciplines as well as discipline-specific domains. As a result, we cannot address the staff shortage problem by just using more fresh graduates or engineers from other sectors of the industry. The industry usually requires new staff to undergo substantial retraining for testing and failure analysis, leading to high costs, long learning curves, and smaller pools of test and failure analysis engineers available for employment. In addition, such an approach does not contribute to the employability of university graduates.
The main goal of our proposed test system was to contribute to skills development and the employability of engineering students at RMIT International University Vietnam and Monash University Sunway by enhancing the laboratory experiment part of electronic testing courses. The laboratory section of the course gives students practical experience in test technology without requiring the use of multimillion-dollar production testers.
We built the system around three major parts (see Figure 1):
- A PC equipped with LabVIEW and application-specific software
- The NI ELVIS II development and prototyping platform
- A custom-designed IC testing (load) board
Test System Software
We wrote the software of the IC parametric test system using LabVIEW graphical programming software, which gave us visual interaction with the tester for setting various test conditions and signal parameters as well as displaying user-friendly test results (see Figure 2).
We developed the software with a modular structure for expanded functionality (for example, for the addition of new test types) where required. In addition, the software provided to students for the laboratory experiment was a template with some deliberately removed portions. Students used these reduced software shells as guides in their lab work and miniproject development to create their own test procedures and integrate the software into the system to work with the hardware resources. This provided significant benefits to student learning and understanding of the test technology and virtual instrumentation, programming, and interfacing.
After we developed the system, we integrated the testing procedures. Before actual IC testing began, a student configured the system to provide appropriate conditions for the specific test by following outlined steps. For example, when testing of a voltage at an output pin of IC, which is in “High” state – so-called VOH parametric DC test) corresponding with Figure 2, the test measured a voltage level at the output pin of the gate under test when it was in a logic “1” signal state and while a specified current (0.4 mA) was drawn out (sunk) from this pin. To achieve the high state of the output pin, two input pins of this gate were pulled down to the logic “0” level (0.8 V). For the gate to pass this test, its output could not be less than 2.4 V. To configure the system, the user had to follow these steps:
- Select the appropriate socket with IC under test
- Select the type of IC to test (when an IC is selected, the image containing its structure displays on the screen)
- Select the DC parametric test to run (connection between gate inputs and output of tested IC and stimulated signals displays on the connection information frame according to the type of IC parametric test, illustrating the concept of configuring test signals)
- Adjust the values of the power supply voltage(VCC) and voltage of the IC input pins
- Select the value and type (sourcing or sinking) of the current sources based on the test requirements
After completing the configuration setting, when the user pressed the test button, the system automatically began to test the IC gate by gate. The system captured results and displayed them next to the corresponding IC pins. The results could be either voltages or currents, depending on the test type. After finishing the test, the system waited for the next test command to start testing a new IC. When the user pressed the stop button, the system stopped the test program.
We used NI DAQ hardware and LabVIEW SignalExpress to control the system. With DAQ, users could quickly and accurately capture and process data. IC testing was an application that required data capture procedures and data processing. In the tester we developed, the DAQ assist function read and wrote signals to and from input and output channels. This was useful in creating tasks with simple configurations. To measure currents, the system used the differential mode while the referenced single-ended (RSE) mode measured voltages. With LabVIEW SignalExpress, the user could configure settings for each part of NI ELVIS II through LabVIEW.
The IC test system captured 100 measured samples with a frequency of 1 kHz per measurement. The more measured samples captured, the more reliable the measurement result. However, high sample numbers could slow down the system. We used NI ELVISmx digital reader and writer palettes to write digital values to the digital I/O (DIO) pins of NI ELVIS II, an NI ELVISmx digital multimeter (DMM) to read current values from the NI ELVIS DMM, and NI ELVISmx variable power supplies to supply VCC voltage to the IC under test.
IC Tester Hardware
We used NI ELVIS II to generate required conditions and signals for the device under test on the IC testing load board, such as currents, voltages, power levels, and control signals (see Figure 3).
We used the following NI ELVIS II modules in the test system (see Figure 4): breadboard for connections between NI ELVIS II and the testing board; DIO signal rows for control signals; analog input for capturing and measuring the voltage/current levels of pins of the IC under test; analog output for providing voltage levels to appropriate IC under test pins to create the required test conditions; DMM and banana jack connectors to measure the current of current sources; a DC power supply to provide voltage to the modules of the testing board; and a power supply to provide the appropriate voltage to the VCC pin of the IC under test.
A custom-designed IC testing load board (see Figure 5) offers the following functions and test resources:
- Device sockets to connect to the ICs under test of small- to medium-scale integration levels
- Connectors to interface with NI ELVIS II
- Electronic and measurement tools to perform functions such as digital and analog test signal generation (amplification, level generation, and buffering)
- Hardware for sensing and controlling the applied test signals to ensure correct voltage and current levels and correction when required
- Circuitry for test response signal acquisition and transferring to NI ELVIS II (from there, test results are transferred to the host PC for final storage, visualization, and processing when required)
Enhancing Engineering Education
We used NI LabVIEW and NI ELVIS to successfully create a desktop IC parametric and functional tester. The NI tools helped us significantly enhance the laboratory portion of our award-winning electronic test technology course (2012 IEEE Instrumentation and Measurement Society Course Development Award). The multidisciplinary system has been well-received by students and is a valuable tool for developing skills in test technology as well as data acquisition, graphical programming, measurement and instrumentation, and electronics.
RMIT International University Vietnam
702 Nguyen Van Linh Blvd, Dist. 7
Tel: 84 08 37761322
Fax: 84 08 3776 1399