Parasitic Channel Induced by Spin‐On‐Glass in a Double‐Level Metallization Complimentary Metal Oxide Semiconductor Process: Its Formation and Method of Suppression

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Abstract
We studied the degradation mechanism and the suppression method for parasitic channel formation by inorganic spin‐on‐glass (SOG) in complimentary metal oxide semiconductor (CMOS) devices with double‐level metallization using test structures and a high frequency C‐V technique. The positive charge induced near the interface in the field isolation region caused the parasitic channel. We propose a new mechanism that atomic hydrogen created by the SOG film diffuses to the interfacial region and generates the positive charge. There are two distinct mechanisms for the creation of the atomic hydrogen by the SOG films with different cap oxide. In cap which is nondoped silicon oxide deposited by PECVD, Si—OH bonds in the SOG film are broken during the cap deposition and create the atomic hydrogen. In nondoped silicate glass (NSG) cap which is nondoped silicate glass deposited by atmospheric pressure chemical vapor deposition (APCVD), water desorbed from the SOG film reacts with the aluminum electrode and creates the atomic hydrogen. Furthermore, film with higher dangling bond density exhibited a capability to reduce the density of the SOG‐related positive charge. Especially, the bottom film under the SOG film was more effective for reducing the positive charge density compared with the cap film on the SOG film. The improvement is attributed to trapping of SOG‐related atomic hydrogen by the dangling bond in the film. These experimental results are qualitatively explained well with the trapping model introducing the dangling bond as the trap center in the cap and bottom films.

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