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TU Berlin

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The institute performed considerable research in the field of circuit edit using a state-of-the-art "Opti-Fib" focused ion beam tool from DCG Systems. We have been successfully offering circuit edit to commercial customers using our and commercially available techniques. We typically have a short turn-around time due to very flexible tool availability. Our staff consists of highly qualified people who develop edit procedures and are able to provide useful information on the best implementation of the desired FIB modification. Prior to an edit the customers proposal is reviewed and sometimes an electrically equivalent but more effective procedure is suggested.

** Picture OptiFIB**

Besides standard modification from the front-side of circuits with aluminum back-end, we are able to edit Cu-back-end ICs. Further we are specialized in performing back-side edits including the sample preparation which allows to access devices in circuits with many metal layers or in flip-chip packages. In both cases we can use gdsII layout information for precise navigation.
For analog and mixed-signal applications we offer a low-ohmic long distance connection with bond-wires which has been successfully applied.

** Picture Bondpad**

Our DCG-Systems Cu2 chemistry effectively employs a triple effect to enable large area (power plane opening) and within high aspect ration hole copper removal. The Cu2 etch option allows to simultaneously etch inter level dielectric (including low-k) and copper lines which effectively prevents topology creation (for example from dummy fill) and associated collateral damage.
Ion channeling in differently oriented copper grains lead to grain orientation dependent etch rate which creates major damage in underlying layers. The chemistry largely prevents ion-beam channeling and ensures a planar removal.
Deeply lying copper lines need to be accessed through high aspect ration holes. During copper removal a redeposition on the sidewall of the access hole takes place leading to conductive paths (shorts). With Cu2 the redeposited Cu is chemically modified and becomes non-conductive.
See a front side modification through multiple layers with various dummy fill patterns.

** Picture Edit**

The OptiFib features a columnar infrared optical microscope for front side alignment of fully planarized integrated circuits and through silicon backside navigation (see Poster FIB technique). In backside editing the chip is opened from the backside (Link UltraTec) and locally polished down to a thickness of ~ 50 µm. Starting from there a FIB trench window is opened with the OptiFib. The columnar microscope offers a unique live image feature which is used in our backside edit procedure to control trench floor planarity. The trenching is stopped close to device level yet far enough to prevent damage. Starting from the trench floor minimum size edits are performed.

** Trench window, n-well level, Optical image with fringes, STI level, Post edit **

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Once a circuit exhibits a non-conforming behavior which cannot be identified by electrical means, physical methods need to be employed. One simple and successful method for active devices is to detect abnormal light emission in the visible to near-infrared range and overlay the emission image with the layout. Vice versa metalization defects do not emit light but are very often temperature sensitive. Therefore a distinct thermal stimulation of the metalization with focused near-infrared laser light can be detected electrically. A mapping of the electrical stimulation intensity at the corresponding laser position onto the layout or optical image locates the defect. (see Poster). We cooperate with Hamamatsu (Phemos 1000) as the leading supplier of such equipment.
We conduct research in the analysis of dynamic failures in conjunction with emission and stimulation.

Upon localization further analysis maybe performed in the DualBeam system or the circuit can be modified to verify the analysis (probe pads, bypass).

** Foto Phemos, Photoemission, Laserstimulation **

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Our FEI830 200mm Wafer stage dual beam system allows to quickly cross section parts with an ion beam similar to the OptiFib while simultaneously watching the milling procedure with a high resolution SEM. The low voltage capabilities of the SEM supersede delineation etch and subsequent metal coating.

** Foto Dual Beam **

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Electrical Characterization

Our Lab is equipped with a five channel Keithley 2600-SCS characterization system for very accurate pA-level DC characterization. An Agilent E4980A LCR meter complements the device characterization equipment. High power/high voltage can be applied and measured with our Tektronix 370/371 curve tracers.
Time dependent analysis is enabled with an Agilent 83000 mixed signal tester, and for high frequency analysis a digital full bandwidth 6GHz Oscilloscope from LeCroy is available.

All equipment can be connected to an automated SUSS probe-station.

** Foto Rack, Tester **

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  • Device preparation for analysis through chip backside. Mechanical decapsulation of semiconductor chips, including ceramic packages on a specialized system.
  • Failure localisation using Photo Emission Microscopy and Laser Stimulation through front- and backside (Hamamatsu Phemos 1000, Parameter Analyzer, Tester Agilent 83000).
  • Sample preparation and device / circuit edit using a Focused Ion Beam (FIB) system featuring a coaxial optical microscope for in-situ control. The OptiFIB tool from DCG Systems (ex Credence, ex np-test, ex Schlumberger) is used for the procedure.
  • Analytics of solar cells and modules, in particular thin film systems, at the Competence Centre Thin-Film and Nanotechnology for Photovoltaics Berlin (PVcomB). We offer standard characterization methods like I-V-curves or EQE as well as advanced analytics like FIB cross sections, thermography, electroluminescence or light induced degradation.


DCG Systems

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