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The Moisture Event Solution for Semiconductor and UHP Gas Applications

13 February 2008

Michell Instruments is delighted to announce the launch of their trace moisture event sensor, PURA plus.

The PURA plus is an on-line trace moisture event sensor designed for UHP inert gas applications in semiconductor fabs to allow installation at multiple locations at the final point of entry to the process tool. Installed in the gas distribution system the PURA plus provides rapid indication (less than 1 minute) of a moisture event as low as 20 ppb at 1 ppb baseline.

To achieve this high speed of response while maintaining the extreme sensitivity Michell have invented a unique detection algorithm and combined it with a new developed UHP suitable ceramic sensor design. Besides other benefits it allows the PURA plus to meet the particulate shedding performance required by the semiconductor industry.

The PURA plus meets the highest quality standards for material and surface finish. It is assembled and packed in a class 100 clean room environment. Prior to packaging Michell leak tests PURA plus do 10-9 bar / sec Pura Plus is designed to operate reliably and without any maintenance for a minimum of 2 years. Information is output via MODBUS, with warning and alarm status being indicated with a “Traffic Light” status indicator LEDS. Further development will add a 4-20 mA output to the instrument.

The new sensor is Michell Instruments’ response to the latest changes in the wafer fabrication industry requirements for device size and specification. The wafer fabrication industry is continuing to push the technical boundaries in terms of device size and packing density. New, larger wafers as well as high $ value per wafer put pressure on wafer fabrication plants to increase yield by reducing wastage caused by contamination.

The current specification for moisture contaminant level in bulk inert gases e.g. N2, Ar is less than 10 ppb while there is a pressure on in the industry to reduce this specification to less than 1 ppb.

Bulk gas supplies are normally monitored for moisture contamination with large, complicated high-cost instruments with low speed of response at the point of entry to the fab. The moisture contamination from the bulk gas supply is a very rare event. In contrast to this in the complex distribution system of a fab involving many branches, joints and points of use moisture ingress often takes place downstream of the conventional moisture monitoring point through small leaks, imperfect system design, component failure or via procedural failures.

The small size and innovative concept of the PURA plus makes multiple location installations at point of use a realistic and cost effective proposition to effectively protect the wafer manufacturing process.

If you would like more information about PURA plus, please contact:

  • Process Sensing Technologies PST GmbH
    Max-Planck-Straße 14
    61381 Friedrichsdorf
    Germany / Europe
    Tel.:+49 (0)6172 5917-0
    Fax:+49 (0)6172 5917-99
    Web :
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