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Browse Prior Art Database

DEFECTIVITY REDUCTION ON LITHOGRAPHY EXPOWRE SYSTEMS

IP.com Disclosure Number: IPCOM000008760D
Original Publication Date: 1998-Jun-01
Included in the Prior Art Database: 2002-Jul-10
Document File: 3 page(s) / 227K

Publishing Venue

Motorola

Related People

Karl E. Mautz: AUTHOR [+2]

Abstract

A technique to reduce printing defects on litho- graphy wafers has been developed. This involves the use of an automated system to diagnose and remove particles or contamination from the litho- graphic exposure tool chuck surface.

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MOTOROLA Technical Devrlopment.~

DEFECTIVITY REDUCTION ON LITHOGRAPHY EXPOWRE SYSTEMS

by Karl E. Mautz anct Mark ptfapt

ABSTRACT

  A technique to reduce printing defects on litho- graphy wafers has been developed. This involves the use of an automated system to diagnose and remove particles or contamination from the litho- graphic exposure tool chuck surface.

PROBLEM STATEMENT

  Exposure tool chucks frequently become con- taminated from wafer backside defectivity (which consists of inorganic particles from various sources and organic residues from the photoresist coating operations) being transferred from the wafer to the exposure tool chuck, and this can result in printing defects during the exposure operation. Periodic manual maintenance is performed on the exposure chucks to remove particles or contamination. This is a manual-intensive and time-consuming task requiring Ihe system to discontinue processing until completed.

INTRODUCTION

  Defectivity, consisting of particles or other con- tamination on the wafer backside or an exposure tool chuck during lithographic processing, affects the wafer flatness and reduces the ability to resolve printed features and control critical dimensions on wafers or other substrates. The exposure tool's chuck surface can become contaminated with parti- cles from metals, plastics, ceramics, and silicon or organics from masking materials and solvent residues, transported by the wafer backside. Currently exposure tools do not have the ability to diagnose these defects or remove them. On advanced exposure tools, these defects cause the system to compensate for the site flatness deviation due to wafer non-planarity, and in some cases the adjustment required may be beyond the corrective ability of the tool, and this results in printing

defects. Because exposure tool chucks frequently become contaminated to the magnitude of causing printing defects, periodic manual preventative maintenance (PMs) is done on these systems. This requires taking the exposure system off-line, commanding the system to move the chuck stage away from the optical column to prevent damage to the optics and to access the chuck, and manually wiping the chuck surface with a solvent-soaked lint- free cloth. Manual wipedowns of exposure tool chucks are done as preventative maintenance requiring approximately l/4-1/2 hour per system at periodic intervals depending on the required tool performance or printing defect susceptibility. This procedure is typicaiIy done: 1) at the beginning of each shit? on every exposure tool, 2) after a pre- determined number of lots, or 3) before a critical layer or lot is run. These procedures are performed whether the defects are present or not (no chuck surface defect determination is done), and obtaining confirmation that the defects have been removed or reduced is dificuh, until test or product wafers are exposed on the system and inspected for the quality of the printed features. The disadvantages of t...