Tektronix announced the availability of two new source measure unit (SMU) modules for the Keithley 4200A-SCS Parameter Analyzer that can perform low-current measurements even in the presence of high load capacitance due to long cables and complex test setups. Among the notable test applications facing this challenge are LCD display manufacturing and nano FET device testing on a chuck.
The new 4201-SMU and 4211-SMU are designed specifically for test setups with long cables, switch matrices, gate contacts to the chuck, and other fixturing. Such test setups, which are required in a number of low current measurement applications, can increase the capacitance seen at the output of the SMU, even though the device under test itself has very low capacitance. When the test connection capacitance is too high, the resulting low current measurements can become unstable.
At the lowest supported current measurement range, the 4201-SMU and 4211-SMU can source into and measure a system that is 1,000 times more capacitive than what's possible today. For example, if the current level is between 1 to 100 pA (picoamp), the new Keithley modules can be stable with as much as 1 µF (microfarad) of load capacitance. In contrast, the maximum load capacitance competitive units can tolerate before measurement stability degrades is just 1,000 pF (picofarad), or 1,000 times worse (more info).