The images on this page show an IC-testing instrument designed as a "specimen substage" with six motorized manipulators for the prober needles. The instrument is shaped in such a way, that it makes optimum use of the available space inside the chamber of the "LEO 1455" FIB. The very low height of the crosstables was made possible by using new, miniaturized motors. The Standard Version provides positioning accuracy of <1µm under visual observation.

Abb.1: 6-Stationen Prober-Modul

Three motorized manipulators per crosstable allow strictly orthogonal tip movement in X, Y, and Z, covering 20 mm × 20 mm × 4 mm. Piloting is done from a small, easy to operate desktop controller. The needles can be pre-set before inserting the prober module into the chamber, so that larger areas can also be investigated. Piezo-controlled touchdown is extremely gentle, much superior to any mechanical downward driving.

The whole prober-module rests on a base-plate that serves as an adapter to fit the assembly to the SEM specimen stage.

The LEO 1455 stage allows to tilt the module to about 20° inside the chamber and under the lens, so that the touchdown process can be observed slightly from the side. This makes work quite comfortable.

Specifications

Prober-Module with 6 Needles for the LEO 1455. Substage with six Prober Tips, Piezo Controlled High Precision Touchdown

Coverage

The here described prober may be used to take measurement from individual chips held in small clamps, or from packaged ICs. The specimens are placed on the rotational sample holder of the module. Therefore they can rotate +/- 45°. The prober's X-Y coverage is 20 mm × 20 mm, and 4 mm in Z. Motorized and Piezo drives are oriented orthogonally for the sake of intuitive and fatigueless operation. Before chamber evacuating, the needle holders can be lined up manually to center them inside the area of interest.

Changing the voltage at the integrated Z-piezo actuator moves the needle tips down with ultimate precision. This movement is magnitudes finer than anything a standard mechanical guide mechanism will ever reach. There is absolutely no mechanical hysteresis in this movement (unwanted lateral shifting when reversing the movement). Motor driven vertical movement can be done very slowly. Many users find, that the motorized "semi-fine" movement is already so accurate, that they use the Z-piezo very seldomly and only for critical operations. A "Panic"-key moves all 6 needles up (away from the sample surface), to avoid unwanted touchdown. In the event of a power failure, all Piezo actuators return to their relaxed position, and the tips will lift up to a safe position.

Controllers

The simplest form of a controller is a digital manual controller which drives the miniaturized motors of the manipulator crosstables. A potentiometer provides motor speeds from 1.5 mm/sec down to 0.2 µm/sec. The "Panic"-button lifts up all prober tips when touched. The controller is a small footprint unit, that will easily find room on the operator's console. It is connected to the micro-processor controller placed behind the SEM or FIB. It should be connected to the same power phase as the SEM or FIB, using a connector at the rear of the host instrument. Alternatively there is a PC operated controller available, that will run with the software package "TouchDown".

Setting-up

The here described prober-module fits to the base plate of the LEO 1455 SEM specimen stage. Therefore, the needles can remain in touch with the IC surface, while the prober-module moves "piggyback" in X, Y, and Z on top of the main SEM stage. The size of the specimen chamber allows to tilt the stage with the module a small amount (approximately 20°) to the left. Multi-purpose needle holders take the needle shafts at right angles, 45°, or straight out of the shaft. Highly flexible, shielded cables take the signal to the prober tips. There is a vacuum feedthrough flange with high-frequency compatible connectors, that fits the entry port at the side of the vacuum chamber or stage door. If required, this signal line can be equipped with "Triax" cables.

Six small standoffs help when using the module at air, such as under a light-microscope.

Options for the Prober-Module

• Heating from Room Temperature to +300°C
• Partial rotation (+/- 45°) for the exact lining up under vacuum
• Software "TouchDown" with many useful sub-routines, such as easy re-visiting of previously saved positions, needle arrangement patterns and many other features.

Further Products in this Field

• "Electrostatic "Beam Blanking" with pulses in the Picosecond range
• Wafer-Prober-Stage
• Cryo-stages and modules (liquid Nitrogen or Helium). The Cryo-systems can be combined with fixed or detachable probing devices.
• There is a number of Variatons of different SEM and FIB adaptable prober-modules available, with one, two, three and more needles, with or without high precision Piezo translators (10 nm positioning resolution).