Why using an Electron Microscope?

The actual small wafer structures cannot be observed in a light microscope anymore. Every institution that investigates in semiconductor structure development has to overcome this problem, sooner or later. Therefore only two instruments can be used: the AFM expanded to a Wafer Prober or the SEM equipped with Wafer Prober. The AFM cannot resolve structures that are only 2-dimensional. This is a limitation for a lot of structures. And an AFM has a typical maximum scanning range of about 20x20 um². It can take hours to find a certain sample position with this slow device. The Electron Microscope can zoom from cm² sized areas into a few 10 nm² sized areas within a few seconds. And any kind of structures are visible in a SEM, independent if they are flat or not. Therefore Wafer Probing in a SEM is the best solution. A high-end SEM is not required, any (elder) SEM can be used for this application.

Measurement examples made by the Taiwanese semiconductor company TSMC are described in a paper (download area on the right) and here.

What's necessary?

• Cartesian manipulators with single nm resolution at stationary assembly
• Very sharp and robust conductive tips, well defined in shape and visible
• A secure tip approach
• Voltage support and current measurement, diagram features
• For automatic systems: a precise sample stage and a vision system for the automatic alignment of wafer structure and probe tip.
• Probe tips for Marking
• Software for manual control, current diagrams, up to the automatic process control of a programmed sequence.

Klocke Nanotechnik offers a complete series of Wafer Probing products, from single manipulators over sets of manipulators, different levels of automation and software - up to complete automatic systems including pattern recognition software. The manipulators resolution of 2 nm is by far enough to hit any existing wafer structure, also in the next years.
Depending on the space available in the vacuum chamber up to six Nanorobotics manipulators can be assembled for Wafer Probing. Our high resolution sample stages can easily be added in a SEM, driven by the same electronics and software, to increase the options for this application.

Depending on the Electron Microscope that shall be used individual Nanorobotics manipulators are configured, including development of the complete chamber assembly.
Special NanoProbing tips available from Klocke Nanotechnik are connected over a special preamplifier with our Network Controller to measure the current between probe tip and sample. This closed loop allows a secure approach of the tip towards a conductive sample. The following picture shows the tip of a cantilever during approach beside a sample:

Tip approach with a conductive cantilever

Details about different probe tips and tools for a secure tip approach towards all kind of samples are described at Accessory.

After the tip reached the sample:

Depending on the amount of manipulators used different current/voltage diagrams can be measured, e.g. between the three pads of a FET. Software modules show and store these diagrams:

Menu for defining of I/V parameters and input channels, Diagram of a Z-diode

Measurement of a transistor

Using our process control sequencer the following sequence can be executed completely automatically: Movement of the probe tips to certain sample areas (e.g. with the help of our vision system and pattern recognition), tip approach, measurement and storage of an I/V diagram, tip removal, ... if necessary on an array of sample positions.