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Method for removing small particles from EUV photomasks

IP.com Disclosure Number: IPCOM000030169D
Publication Date: 2004-Jul-30
Document File: 3 page(s) / 28K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for removing small particles from extreme ultraviolet (EUV) photomasks. Benefits include improved functionality, improved performance, and improved power performance.

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Method for removing small particles from EUV photomasks

Disclosed is a method for removing small particles from extreme ultraviolet (EUV) photomasks. Benefits include improved functionality, improved performance, and improved power performance.

Background

              Scientists are developing electronic devices with thicknesses of a few nanometers and lines with picometer separation. Most of the fabrication takes place in a vacuum or contamination-free inert atmosphere. To produce very high-density electronic devices, a cleaner environment with more carefully designed procedures is required.

              Laser-induced airborne plasma shock waves initiated above the surface of a substrate is one of the most promising ways to remove submicron particles from the surface of high-density electronic devices. However, this technique is limited for removing nanometer-size particles from a pattern area. Experimental results suggests two effective ways for removing small particles, using a higher power laser to provide a stronger shock wave and decreasing the distance between the laser’s focus point with the device surface. In both approaches, the pattern section of the device is significantly damaged if the gap between the focused laser beam and the substrate surface becomes very small (see Figures 1 and 2).

              Conventionally, a high power laser beam, such as 1012 W/cm2 for 10-ns pulses, is used.

              An effective cleaning procedure is required that enhances the cleaning efficiency by removing very small particles and does not cause any damage to the surface of the substrate.

General description

              The disclosed method creates a laser shock wave in dynamic pressurized inert gas. The combination of the laser shock wave with UV light in a pressurized inert gas eliminates the formation of photochemical reactions during UV exposure. The method eliminates the formation of ions during the laser shock wave to prevent reaction with the device surface. The combination of dynamic inert gas flow with the laser shockwave removes particles faster after each laser pulse.

Advantages

              The disclosed method provides advantages, including:
•             Improved functionality due to creating a laser shock wave in dynamic pressurized inert gas
•             Improved functionality due to combining a laser shock wave with UV light in a pressurized inert gas

•             Impr...