NF Fast PPMU Application Note

Transcription

1 NF 1208 Fast PPMU Application Note Change History Version Date Remarks Author/s Jan 2010 Initial release HC Hay

2 Table of Contents 1 Abstract Test setup NI PXI-4130 SMU Measurement Time T2IS NF1208 PMU Measurement Time NF 1208 Advanced Measurements Features Automatic Channel Scan Measurement Automatic Detection of Multiple NF Conclusion...6

3 1 Abstract This application note describes the fast PPMU (Per-pin Parametric Measurement Unit) features of NF 1208, with benchmark against National Instruments (NI) PXI-4130 Power SMU (Source Measurement Unit). Advanced measurement features of NF 1208 are introduced in Section 5. 2 Test setup Both PXI-4130 SMU and NF 1208 are set up in the same PXI chassis. The details of the set-up are as the following: PXI chassis: NI PXIe-1062Q 8-slot PXIe/PXI Hybrid Chassis PXI controller: NI Embedded PXIe-8106, Intel Core 2 Duo 2.16GHz CPU, 2GB RAM Operating System: Windows XP LabVIEW version: Instruments: NI PXI-4130 SMU, NI PXI-7952R FlexRIO FPGA Module and T2IS NF 1208 For the purpose of illustration and simplicity, a resistor (approximate value is 1.15 ~1.2kOhm) is connected to Channel 1 of NI PXI-4130 SMU when performing FVMI (force voltage measure current) test. The resistor is connected to one of the 8 channels of NF 1208 Digital Pin Card for doing FVMI test. Note that NF 1208 used in this benchmark test has not been fully calibrated. To know more about calibration and measurement accuracy of NF 1208, please refer to the relevant materials available at 3 NI PXI-4130 SMU Measurement Time The LabVIEW program front panel displays the current measurement time of NI PXI-4130 SMU. 100 iterations of measurements are performed and the total time lapsed is divided by 100 to obtain the measurement time per iteration. As can been seen from the result, it takes an average of 3.33 ms for the NI SMU to complete one current measurement when it forces 1.0V to the device. As the default value of the nidcpower Samples to Average property is 10 and the fixed sampling rate of PXI-4130 SMU is 3 ks/s, therefore; the fastest possible software measurement rate is 300 measurements per second (reference: The benchmark test of 3.33 ms correlates with theoretical calculation. The LabVIEW program block diagram used for calculating measurement time is shown in a snapshot below. As can be seen, the voltage output is enabled before the iterations begin. nidcpower Measure Multiple.vi is used to perform current measurement. Force voltage execution time and wait time for voltage output settling (minimum 1 ms on a Windows PC) is not included.

4 Note that NI PXI-4130 Power SMU has only 1 SMU channel (channel 1) and therefore the benchmark test is only performed on this channel. Channel 0 of PXI-4130 is a utility channel that can only source voltage (0 to +6V) or current (0 to +1A) and cannot be used to sink current. 4 T2IS NF1208 PMU Measurement Time The LabVIEW program front panel displays the current measurement time of NF 1208 Digital Pin Card. 100 iterations of measurements are performed and the total time lapsed is divided by 100 to obtain the measurement time per iteration. As can been seen from the result, it takes an average of 0.36 ms for NF 1208 to complete one channel of FVMI measurement. Note this measurement time includes the time taken for NF 1208 to force voltage plus the configurable waiting time (0.1 ms in this case) between force and measure which is necessary to allow the output and device to settle. NF 1208 performs an average of 32 samples in hardware. The configurable waiting time between force and measure is also implemented in hardware. This waiting time has a resolution of 25 ns, as compared to Windows software wait with a resolution of 1 ms.

5 5 NF 1208 Advanced Measurements Features 5.1 Automatic Channel Scan Measurement NF 1208 also supports automatic channel scan measurement mode. In below LabVIEW program front panel, 0-7 is entered as the channel parameter, since every NF 1208 Digital Pin Card has 8 channels. With this parameter setting, NF 1208 instrument driver automatically does FVMI or FIMV measurements across all the channels. When a particular channel is to be forced and measured, all other channels are automatically forced to ground. In the example below, Force Current Measure Voltage (FIMV) test is performed. The test resistor is only connected to Channel 5 of NF Therefore, measurement result is displayed as the 5th number in the row. All other channels are left open. And therefore their measurement values are 3V which is the clamp value set on the GUI (VCH). 100 iterations are performed. For each iteration, all channels are scanned through with FIMV measurements. Time per iteration is obtained by way of dividing the total time by the number of Iterations. Note that the per-iteration time of 2.27 ms is the total time required to perform 8 channels of FIMV. For each FIMV channel, all other channels are forced to ground. There is also a waiting time of 0.1 ms configured between each force and measure. A total of 0.8 ms waiting time forms part of the 2.27 ms total time.

6 5.2 Automatic Detection of Multiple NF 1208 When there are multiple PXI FlexRIO FPGA modules with NF 1208 inserted in the same PXI chassis, NF 1208 instrument driver automatically detects all of them and assigns channel numbers according to their slot number sequence. For example, if a PXI-7954R with NF 1208 is inserted in slot 5 and another PXI-7952R with NF 1208 is inserted in Slot 8, the 8 channels on the slot 5 NF1208 will be automatically assigned Channel 0 to 7. The 8 channels on the Slot 8 module will be automatically assigned Channel 8 to 15. Therefore, if a user wants to perform FVMI or FIMV using all the 16 channels of both NF 1208 cards, he only needs to do the following using NF 1208 instrument driver: Force Channel 8-15 to ground (i.e. the 8 channels of Card 2). Enter 0-7 for the Channel Number parameter before measurement. The instrument driver will automatically scan through channel 0 to 7 for force and measurement. Keep in mind that when one of the 8 channels is being forced and measured, the remaining 7 channels are automatically forced to ground. Force Channel 0-7 to ground (i.e. the 8 channels of Card 1). Enter 8-15 for the Channel Number parameter before measurement. The instrument driver will automatically scan through channel 8 to 15 for force and measurement The approach above provides a very efficient way of performing open/short and leakage test on semiconductor device pins, without the need to program additional switching matrix and relays. Neither does the user need to worry about hardware device names of each individual NF 1208 card. The LabVIEW example below illustrates the automatic detection of multiple FlexRIO FPGA and NF 1208 modules. 6 Conclusion As seen from the benchmark test results in Chapter 3 and Chapter 4, T2IS NF 1208 Digital I/O Module delivers approximately 10x faster PMU measurement time than NI PXI-4130 SMU (0.36 ms for both force and measure versus 3.33 ms for measurement only). When doing PMU measurements on multiple pins of a semiconductor device, NF 1208 s Per-pin PMU architecture eliminates the need of an additional switching matrix and simplifies device pin connections. Each channel of NF 1208 can be directly connected to the device pin. If a singlechannel SMU is used, switching matrix or relays on the DUT board becomes necessary and this inevitably introduces additional delay due to matrix and relay switching and settling time. Besides,

7 when writing test software for single-channel SMU, iteration is needed to iterate through all DUT pins one pin at a time (reference: T2IS NF 1208 features advanced automatic channel scan measurement mode. In this mode, a user no longer has to write iterative test steps to perform PMU measurements on all device pins with one pin at a time. NF 1208 instrument driver automatically takes care of the scanning of all device pins on a per card basis while forcing all other non-measurement pins of the card to ground. This feature is especially useful for doing open/short and leakage test on devices pins. NI PXI-4130 SMU is a Power SMU that is suitable for high power applications. It has a single SMU channel that features ±20V and up to 2A isolated output. It has current range of 2A to 200µA, with 1nA measurement resolution and 0.02µA accuracy on the 200µA range. NF 1208 has 8 channels Per-pin PMU. Each PMU has a force voltage range of -2.0 V to +6.0 V and up to ±100mA. There are 5 current ranges: 25mA, 2mA, 200µA, 20µA, 2µA. On its smallest current range, measurement accuracy is 0.02µA. NF 1208 also has a DUTGND sense pin that is similar to the power sense lines found on the NI PXI-4130 SMU. In addition to Per-pin PMU, NF 1208 s 8 digital I/O channels support 100MHz digital vector rate with advanced digital timing format, which makes it ideal for digital stimulus-response applications.