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STRUCTURE AND METHOD FOR ETCH MONITORING THROUGH ELECTRON CHARGING

IP.com Disclosure Number: IPCOM000006781D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2002-Jan-31
Document File: 3 page(s) / 124K

Publishing Venue

Motorola

Related People

Marco Racanelli: AUTHOR [+3]

Abstract

A sidewall spacer is used to define deep-submicron features in "slot" processes for many advanced technologies [l-3]. Optical techniques cannot be used to endpoint etches that open these narrow spaces because of the small open area. For the same reason, conven- tional inspection techniques cannot be used. A technique and structure have been developed for the nondestructive evaluation of etches that open deep-submicron spaces. Our approach allows detection of the successful com- pletion ofa slot etch through the use ofelectron charging.

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MO-LA INC. Technical Developments Volume 18 March 1993

STRUCTURE AND METHOD FOR ETCH MONITORING THROUGH ELECTRON CHARGING

by Marco Racanelli, Clifford I. Drowley and Lisa K Garling

  A sidewall spacer is used to define deep-submicron features in "slot" processes for many advanced technologies [l-3]. Optical techniques cannot be used to endpoint etches that open these narrow spaces because of the small open area. For the same reason, conven- tional inspection techniques cannot be used. A technique and structure have been developed for the nondestructive evaluation of etches that open deep-submicron spaces. Our approach allows detection of the successful com- pletion ofa slot etch through the use ofelectron charging.

  The approach described in this paper relies on the structure described in Figure 1. In Figure 1, region A is a region being etched while region B is a region that is electrically isolated from the rest of the wafer by the successtid completion of the etch. When electrons are directed toward the wafer, isolated regions charge (Fig- ure 2a) while regions that are not isolated do not charge (Figure 2b). By detecting this charging, a determination can be made of whether the etch is complete. Several approaches can be taken to the detection of electron charging such as detecting changes in secondary emis- sion characteristics, electron beam induced currents or changes in the reflected electrons.

  We have used the above approach to investigate the Mosaic 5 and 0.5 pm BiCMOS slot modules [l]. We used a scanning electron microscope (SEM) to direct electrons at the wafer and collect secondary electrons. Charging is detected by a change in the intensity of sec-

ondary electrons collected by the SEM. Figure 3 shows an array of Mosaic 5 transistors (ovals) immediately after a slot was cut along the perimeter (CO.1 pm, not visible in Figure 3). Transistors with a complete slot are charg- ing and seen as dark ovals while transistors with an incomplete slot are not charging and s...