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TECHNIQUE TO UNIQUELY MONITOR PHOTOLITHOGRAPHY DEFECTIVITY

IP.com Disclosure Number: IPCOM000006104D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2001-Dec-04
Document File: 2 page(s) / 93K

Publishing Venue

Motorola

Related People

Syd R. Wilson: AUTHOR [+3]

Abstract

Defects due to particles tend to be the major source of yield loss in integrated circuits. The early detection and elimination of any source of particles can result in substantial increases in die yield. One area that is highly prone to this type of particle/defect related yield loss is the patterning of metal lines. This type of defect can cause opens or shorts in metal lines. In addition, any lithography related defect can impact many portions of the process since wafers are subjected to a lithography step more than any other step in the total flow.

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MOIOROLA INC. Technical Developments Volume 12 April 1991

TECHNIQUE TO UNIQUELY MONITOR PHOTOLITHOGRAPHY DEFECTIVITY

by Syd R. Wilson, Sandeep Malhotra and Donald F. Weston

  Defects due to particles tend to be the major source of yield loss in integrated circuits. The early detection and elimination of any source of particles can result in substantial increases in die yield. One area that is highly prone to this type of particle/defect related yield loss is the patterning of metal lines. This type of defect can cause opens or shorts in metal lines. In addition, any lithography related defect can impact many portions of the process since wafers are subjected to a lithography step more than any other step in the total flow.

  To detect these particles, many wafer fabs use a simple and easily testable pattern composed of a single metal line meandering between two metal comb structures. See Fig. 1. The metal is deposited on an insulating film. The pattern is created using standard metal deposition, photolithography and dry etching techniques. The line can be tested from one end to the other for electrical continuity to detect sources of opens. The resistance between the line and each comb can be measured to detect sources of shorts. After electrical testing confirms the presence of a defect, the wafers must be manually inspected to try and determine the location and source of the defect. Although this technique is used extensively, it has some inherent limitations. It is almost impossible to determine if the defects are caused by the metal deposition, the photolithography or the dry etch process. This is due to particles that were in the resist being removed during the resist strip or the dry etch removing particle that acts as micromasks. The delays associated with sorting out the source of particles will result in either a line down situation or in material being processed with a high defect level while waiting to resolve the problem. Efforts have been made in the past to monitor the photolithography process by patterning photoresist and performing a vis...