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Silicon-Rich "Haze" Elimination on Wafers by Wafer/Boat Modifications

IP.com Disclosure Number: IPCOM000036230D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Bassett, EE: AUTHOR [+3]

Abstract

When certain PECVD systems are utilized to deposit silicon nitride insulator material on wafers, a streak of silicon-rich silicon nitride "haze" (spots 5 mm ---> 8 mm in diameter) typically occurs across the face of a wafer. This "haze" cannot be seen with the unaided naked eye, but is easily seen with a bright light. An increase in pin hole density due to the "haze" can result in ionic passivation defects. Also, for double level metal FET and CMOS chip designs which have substantial nitride only passivation, an increase in pin hole density can result in shorts between metal levels.

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Silicon-Rich "Haze" Elimination on Wafers by Wafer/Boat Modifications

When certain PECVD systems are utilized to deposit silicon nitride insulator material on wafers, a streak of silicon-rich silicon nitride "haze" (spots 5 mm ---> 8 mm in diameter) typically occurs across the face of a wafer. This "haze" cannot be seen with the unaided naked eye, but is easily seen with a bright light. An increase in pin hole density due to the "haze" can result in ionic passivation defects. Also, for double level metal FET and CMOS chip designs which have substantial nitride only passivation, an increase in pin hole density can result in shorts between metal levels.

Wafers are held in contact with aluminum or graphite boats during deposition with tapered (conductive) graphite pins (see the figure). Referring to front view "AA", the "haze" is generated between some wafer support pin locations. By replacing all of the graphite support pins with either nonconductive ceramic pins or alternating nonconductive/conductive pins, the haze is completely eliminated. However, when only nonconductive ceramic pins are used, the thermal expansion differential between ceramic and aluminum or graphite causes the wafers to be pinched at the pin locations, resulting in wafer extraction problems post nitride deposition. By replacing only the leading edge graphite pins in the boat rails with nonconductive ceramic pins, both wafer pinching and "haze" is eliminated. It should be noted that opposing l...