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Scanning Electron Beam Facilitated Identification/Repair of Open Conductors in Trench Capacitor Technology

IP.com Disclosure Number: IPCOM000040326D
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Cain, OJ: AUTHOR [+3]

Abstract

A method is reported for in-line testing of trench strap integrity using scanning electron microscope (SEM) image enhancement of unstrapped trenches in conjunction with molecular beam deposition of conductor material or laser spot annealing to repair partially good semiconductor chips. In certain CMOS (complementary metal-oxide semiconductor) memory arrays, enhanced storage capacitor storage is provided by trenches etched in silicon. The trench walls are coated with a dielectric, and the trench is filled with polysilicon, as shown in the figure. Contact to the "upper plate" of the capacitor storage node is made through a conductive strap leading from the storage node source/drain to the trench. If the strap does not form, storage capacitance is insufficient to store readable information.

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Scanning Electron Beam Facilitated Identification/Repair of Open Conductors in Trench Capacitor Technology

A method is reported for in-line testing of trench strap integrity using scanning electron microscope (SEM) image enhancement of unstrapped trenches in conjunction with molecular beam deposition of conductor material or laser spot annealing to repair partially good semiconductor chips. In certain CMOS (complementary metal-oxide semiconductor) memory arrays, enhanced storage capacitor storage is provided by trenches etched in silicon. The trench walls are coated with a dielectric, and the trench is filled with polysilicon, as shown in the figure. Contact to the "upper plate" of the capacitor storage node is made through a conductive strap leading from the storage node source/drain to the trench. If the strap does not form, storage capacitance is insufficient to store readable information. Locating failed straps to confirm the cause of electrical fails for analysis and repair has been a problem. By taking advantage of enhanced SEM image brightness produced by charging electrically isolated elements (capacitors) in the midst of an array of non-isolated elements with the SEM electron beam, an electron micrograph recording of the image will identify strap formation failures in the array. The procedure is non-destructive and applicable to in-line monitoring after the silicide formation and prior to the deposition of borophosphosilicate glass (BPSG). Once the unstr...