DUV Mask Review Station "MRS248"

Along with the pursuit for ever-finer design rule, mask pattern is becoming ever finer and the structure is becoming more complex at the same time. Also, the defect size acceptable on photomasks is becoming smaller. Under such circumstance, the performance requirements for mask review equipment are more and more intense.

In the conventional mask production process, mask production process flow such as quality checking, repair and cleaning processes has been determined and established by observing detected defects by a review function mask defect inspection system that had been used for a defect inspection procedure. However, under the situation that the price of mask inspection system rapidly increases as a result of higher system sensitivity for a defect detection, there is a increasing need that pursues total cost reduction by virtually improving throughput of the inspection system by using the defect inspection system only for defect inspection and performing defect observation by a defect review system solely designed for the review function.

To satisfy this kind of new need, there have been attempts such as using a mask review station equipped with an ordinary optical microscope, which is becoming impractical due to the lack of enough resolution, and using SEM that requires mask cleaning after review due to unsolved problem of mask contamination during observation. Furthermore, along with popularization of phase shift masks with complicated structures, not only information on horizontal structure of masks but also information on vertical structure is becoming necessary, which may require an AFM observation. However, it is not an efficient way to review all the detected defects by an AFM because the throughput of the AFM is extremely low.

Our new product, the DUV Mask Review Station, has realized horizontal resolution of 0.1μm or higher by employing a DUV irradiation light source of 248nm with the combination of high aperture ratio and confocal optics. As a result, the new system provides higher resolution than the current defect inspection system, which makes possible to provide very efficient defect review functions. Also, the new system possesses very high operationality in the same manner as performing defect reviewing by the current defect inspection system, because the new system provides highlighted defect display after detecting a defective part automatically. In addition, confocal optics makes it possible to display defects by taking in three-dimensional feature information, which provides very effective defect analysis. Remarkable reduction of total mask production cost can be achieved due to a more efficient process management that results from replacement of review function tool from defect inspection system to our new Mask Review Station. Finally, when an AFM that can be equipped as an option is used simultaneously, defects can be observed with higher resolution, which can be utilized for the three-dimensional feature measurement of the defective parts necessary for determining correction condition of phase shifter defects in Levenson type phase shift masks.

• A new mask review station most suitable for defect observation after defect inspection in the photomask production for semiconductor devices
• Reflected images and Transmitted image on masks with pellicle can be observed with high resolution.
• Three-dimensional features can be measured by a reflective mode confocal optics.
• In case higher resolution is necessary, an AFM (option) may be utilized.
• The system price is as low as just a fraction of the mask inspection system price.
• The system is very compact not requiring large area and installation is very easy by just connecting the system to a power source and dry air.-- Running cost is very low as a total.

• Light source is a lamp with wavelength of 248nm.
• Objective lens of high N.A. is used.
• A confocal optics that provides higher resolution than conventional microscope is utilized.
• Phase image of reflected light is available and concavity/convexity determination of defect parts is easily conducted.
• Automatically moves to a defect coordinate that is output from defect inspection tools.
• Automatically detect the defect part in the view and provides highlighted display.
• Mask is handled automatically because mask cassettes such as RSP can be equipped.
• Measurement is easy because the system operationality is high.

Main body and control unit

Horizontal resolution : 0.1μm
Frame Rate : 11fps
Mask Size : 6025
Outer dimension : Main body W:1100 D:1600 H:2000 mm
Control unit W:600 D:900 H:550 mm
Weight : About 1t

Please review product page for any further information.