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Measuring 5nm Particles In-Line

By Ed Korczynski, Sr. Technical Editor

Industrial Technology Research Institute (ITRI) (https://www.itri.org.tw/) worked with TSMC (http://www.tsmc.com) in Taiwan on a clever in-line monitor technology that transforms liquids and automatically-diluted-slurries into aerosols for subsequent airborn measurements. They call this “SuperSizer” technology, and claim that tests have shown resolution over the astounding range of 5nm to 1 micron, and with ability to accurately represent size distributions over that range. Any dissolved gas bubbles in the liquid are lost in the aerosol process, which allows the tool to unambiguously count solid impurities. The Figure shows the compact components within the tool that produce the aerosol.

Aerosol sub-system inside “SuperSizer” in-line particle sizing tool co-developed by ITRI/TSMC. (Source: ITRI)

Semiconductor fabrication (fab) lines require in-line measurement and control of particles in critical liquids and slurries. With the exception of those carefully added to chemical-mechanical planarization (CMP) slurries, most particles in fabs are accidental yield-killers that must be kept to an absolute minimum to ensure proper yield in IC fabs, and ever decreasing IC device feature sizes result in ever smaller particles that can kill a chip. Standard in-line tools to monitor particles rely on laser scattering through the liquid, and such technology allows for resolution of particle sizes as small as 40nm. Since we cannot control what we cannot measure, the IC fab industry needs this new ability to measure particles as small as 5nm for next-generation manufacturing.

There are two actual measurement technologies used downstream of the SuperSizer aerosol module:  a differential mobility analyzer (DMA), and a condensation particle counter (CPC). The aerosol first moves through the DMA column, where particle sizes are measured based on the force balance between air flow speed in the axial direction and an electric field in the radial direction. The subsequent CPC then provides particle concentration data.

Combining both data streams properly allows for automated output of information on particle sizes down to 5nm, size distributions, and impurity concentrations in liquids. Since the tool is intended for monitoring semiconductor high-volume manufacturing (HVM), the measurement data is automatically categorized, analyzed, and reported according to the needs of the fab’s automated yield management system. Users can edit the measurement sequences or recipes to monitor different chemicals or slurries under different conditions and schedules.

When used to control a CMP process, the SuperSizer can be configured to measure not just impurities but also the essential slurry particles themselves. During dilution and homogeneous mixing of the slurry prior to aerosolization, mechanical agitation needs to be avoided so as to prevent particle agglomeration which causes scratch defects. This new tool uses pressured gas as the driving force for solution transporting and mixing, so that any measured agglomeration in the slurry can be assigned to a source somewhere else in the fab.

TSMC has been using this tool since 2014 to measure particles in solutions including slurries, chemicals, and ultra-pure water. ITRI, which owns the technology and related patents, can now take orders to manufacture the product, but the research organization plans to license the technology to a company in Taiwan for volume manufacturing. EETimes reports (http://www.eetimes.com/document.asp?doc_id=1328283) that the current list price for a tool capable of monitoring ultra-pure water is ~US$450k, while a fully-configured tool for CMP monitoring would cost over US$700k.

—E.K.

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