Process for etching a transparent workpiece including backside endpoint detection steps

• Main Authors: BIVENS DARIN, KUMAR AJAY, GRIMBERGEN MICHAEL N, LEWINGTON RICHARD, NGUYEN KHIEM K, CHANDRACHOOD MADHAVI R
• Format: Patent
• Language: English
• Published: 01.05.2008
• Subjects: APPARATUS SPECIALLY ADAPTED THEREFOR; BASIC ELECTRIC ELEMENTS; CHEMICAL SURFACE TREATMENT; CHEMISTRY; CINEMATOGRAPHY; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; DIFFUSION TREATMENT OF METALLIC MATERIAL; ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS; ELECTRICITY; ELECTROGRAPHY; HOLOGRAPHY; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; MATERIALS THEREFOR; METALLURGY; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLICMATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASSC23 AND AT LEAST ONEPROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25; NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; ORIGINALS THEREFOR; PHOTOGRAPHY; PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES,e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTORDEVICES; PHYSICS

A method is provided for defining a pattern on a workpiece such as a transparent substrate or mask or a workpiece that is at least transparent within a range of optical wavelengths. The method includes defining a photoresist pattern on the top surface of the mask, the pattern including a periodic structure having a periodic spacing between elements of the structure. The method further includes placing the mask on a support pedestal in a plasma reactor chamber and generating a plasma in the chamber to etch the top surface of the mask through openings in the photoresist pattern. The method also includes transmitting light through the pedestal and through the bottom surface of the mask, while viewing through the support pedestal light reflected from the periodic structure and detecting an interference pattern in the reflected light. The method further includes determining from the interference pattern a depth to which periodic structure has been etched in the top surface.