Probe station

From the fabrication of the capacitor we run into the problem of contacting the capacitor, which can mostly be done in two ways. The easiest way is to contact by standard metal needle probes on a probe station, however, this requires large contact areas larger than 3x3 nm2. But this also requires fully structured top and bottom electrodes as in Figure 17.6, or integrated devices, which are much more difficult to manufacture, especially for sub-micron capacitors. 

Figure 17.6 Structured Pt top and bottom electrodes for probe station probing...

To circumvent these difficulties in testing integrated structures whose cell capacitor size moved into the dimension of 500 nm x 500 nm and below [7], contact pads with a size of a few hundred /im2 at the word line, bit line and plate line are used as shown above in Figure 17.2. These pads can be used for simple probing in an automated probing station. 

However, by far most sensors convert nonelectrical (primary) input signals into electrical output. At first sight, the adoption of automated probe stations seems to be limited to purely electrical networks on sensor elements. However, electrical stimuli provided by the probe station may replace the nonelectrical primary input signals to the sensor transducer element, if a built-in self-test function (BITE) can be incorporated into the sensor design, allowing transducer-related (i.e., sensitivity-related) fundamental functional parameters to be tested. 

Ideally, all of the transistors (even those of different length and width) will have the bond pads in the same location. This simplifies testing of arrays on most probe stations by lifting the platen, moving the sample, and dropping it without moving the probes. A probe card can also be used to increase efficiency. 

The fuel cell seal samples were tested using the Microtech Model 44 Probe Station. A block diagram of the TDR measurement system is shown in Figure 4-5. The sample is mounted on the wafer chuck, and both ends of the transmission line embedded in the sample are connected to the TDR sampling head. 

For illustration, consider the circuit schematic of a simple functional model of an analog integrator depicted in Fig. 4.26. In reality, an integrated operational amplifier is built by means of a number of transistors. The macro-model in Fig. 4.26 reproduces the input-output behaviour of an operational amplifier. It is sufficiently accurate for low frequencies. Its parameters that can be tuned are the gain. A, the input resistance Ri, and the output resistance Ro- The measurement at internal nodes of a real integrated circuit requires special equipment such as a probe station. The output voltage Vo of a bonded and packaged operational amplifier chip can be measured at one of its pins and may be used for the detection of possible failures in the circuit [36]. 

The probe station should have some means for holding down the device under test. A common approach is to use vacuum hold down, but many probe stations have platens with vacuum ports spaced to hold down whole wafers rather than diced parts. It is possible to block some of the outlying vacuum ports with tape so that sufficient vacuum can be developed in the inner vacuum ports to hold down the die. Alternatively, the die can be held in place with double-sided sticky tape, but this tape can leave a residue on the probe station platen and the back of the part under test. 

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