Semiconductor Probe Station
Upgraded HP4145A semiconductor peramater analyzer with a probe station for semiconductor device characterization.
Post-fabrication testing is crucial for assessing the performance and properties of devices. Semiconductor parameter analyzers are employed to characterize these devices, particularly focusing on DC parameters. However, these analyzers can be prohibitively expensive, with prices often exceeding $100,000.
The HP4145, a semiconductor parameter analyzer dating back to 1986, retains the functionality to perform most of the key tasks of a newer unit. Notable differences encompass the resolution of data points and a higher noise floor at a pA level as opposed to the fA range. These units can be acquired affordably online or through auctions, often for just a few hundred dollars. I procured this unit from an auction during OnSemi's relocation. Despite their age, these units are robustly built, with the primary point of failure being the disk drives. The HP4145A, my unit, utilizes a 5 and 1/2" floppy drive, while the HP4145B model employs a 3 and 1/2" floppy drive. Encountering issues with the drive in my unit, I opted to replace it with a solid-state alternative—installing an HxC floppy emulator in place of the old floppy drive. The drive's contents were customized and transferred to an SD card for the emulator, followed by designing a 3D printed faceplate to cover the original drive housing.
For data extraction and remote control, the unit is equipped with an HPIB port, which is then integrated with a National Instruments HPIB to USB adapter. Through Labview and National Instruments, custom code enables control over the machine.
With the updates to the machine and code, the HP4145A semiconductor parameter analyzer is primed for device characterization. An interfacing probe station is essential for connecting the parameter analyzer to the semiconductor device. This station comprises a vacuum chuck, micromanipulators (or a probe card), and a microscope. The micromanipulators, bearing fine tungsten tips, are manually positioned to contact the semiconductor devices.
A compact probe station, along with micromanipulators, was acquired; the micromanipulators are connected to the HP4145A to apply and record voltages/current. One of the devices tested was a basic Silicon diode I had fabricated back in high school, a process involving spin-on dopant and diffusion through an oxide mask. The recorded IV results clearly demonstrate the diode functionality of the device. This setup is conducive for further device characterizations, including but not limited to, MOSFETs, LEDs, etc.
Future plans for this system include homebrew transistor fabrication and research on wide band-gap materials.