03/12/2019

How to define wafer and MEMS quality in manufacturing process

Microelectronic components and semiconductors are manufactured on round thin discs, so called wafers. Wafers usually consist of silicon, sapphire or glass with a diameter of 150, 200 or 300 mm.

The manufacturing process

The blank wafers are subjected to various etching, grinding and polishing processes in the manufacturing process. The components and structures are produced by a repeated sequence of additional structuring and deposition processes.

The perfect wafer

The surface finish of the 'round disc' is characterized by its flatness. The flatter the surface, the more perfect.

But the thickness variations of the wafer are also decisive.

The point here is to determine the maximum difference between the thickest and thinnest point, the so-called Total Thickness Variation (TTV).

This value is so important because every structuring, etching and deposition process affects the TTV again. The thickness variation is then only in the range of a few micrometers. The TTV is therefore the most important parameter to be measured alongside the surface quality.

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Simultaneous measurement of roughness and TTV

Measuring both the roughness and the TTV with very high resolution simultaneously: this is possible with the MicroProf® surface measuring tool and the corresponding application.

This multi-sensor measuring tool can measure the complete wafer surface and determine TTV, flatness or waviness. In addition, high-resolution topography and roughness measurements or profiles can be recorded over the entire surface. The optical sensors are fast and very accurate. In addition, the system can be equipped with AFM. The system can perform the following metrological measurement tasks automatically:

-      sample thickness,

-      TTV, bow, warp,

-      roll-off amount,

-      stress,

-      parallelism,

-      flatness,

-      roughness,

-      layer thickness of coatings,

-      step heights,

-      pitch,

-      bumps,

-      profile,

-      contour,

-      radius of curvature,

-      edge structures,

-      vias and trenches,

-      topography,

-      geometry,

-      coplanarity,

-      critical dimensions and flank angle, as well as

-      overlay.

Hybrid measurement technology

The MicroProf® enables the measurement of wafers in different process steps. A hybrid measuring concept increases the precision of measurements on samples for which a single sensor or a single measuring principle is simply not enough. Depending on the task, it can include measurements with different topography and (layer) thickness sensors, which are fully automated by a single recipe. Controlled by FRT's own software, these sensors automatically combine different information to create new information that is not directly accessible.

Possible equipment of the MicroProf®

The MicroProf® can be equipped with a wafer handling system according to customer requirements. With its high throughput it is perfect for every high-volume manufacturing of microelectronics and wafer.

As an option, the MicroProf® can be equipped with filter fan units (FFU) that ensure ISO Class 3 clean room conditions within the unit. Further options are the handling of thin wafers and an ionizer bar. The tool is operated by the SEMI compliant Acquire Automation XT software. This software enables recipe-based measurement and data analysis of structured and unstructured wafers. 

The software

Select from a variety of packages the measurement and evaluation routine suitable for your measurement task. For recurring structures, a layout wizard with a graphical user interface (GUI) can help you to teach in the measuring positions. In addition, a fine alignment of the samples is available via pattern recognition.

This software offers comprehensive possibilities, from manual measurement on the tool to fully automatic measurement with one-button operation and integration into production control systems, e.g. via a SECS/GEM interface. The measuring tasks are then triggered by the host and the measuring results are automatically transferred to the Fab control.

You can configure different measurement tasks with different sensors so that they run in series within a measurement sequence. This includes performing measurements, processing and analysis with intelligent algorithms, outputting and visualizing the results in the form of reports, and exporting the results to various data formats.

Looking for more information? You can find them here

Do you have any further questions or comments? Then contact us! Our experts will be happy to help you solve your measuring tasks.

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