Takahisa Yamaha

Influence of Retarding Hydrogen Diffusion in Boron Phosphosilicate Glass on Annealing Damage of Metal‐Oxide Semiconductor Transistors

This paper reports results on an investigation of the influence of titanium film in interconnects on incomplete transistor annealing. Annealing damage may be impeded when titanium directly overlays transistors. This may be due to not only gettering of hydrogen by titanium films but also to retarding hydrogen diffusion of the interlayer between the gate electrode of transistors and the titanium‐containing interconnects in boron phosphosilicate glass. The hydrogen diffusion coefficient in the boron phosphosilicate glass film was approximately at 400°C, which is three orders of magnitude smaller than that in the thermal oxide.

Electromigration Characteristics of Sputtered TiN/Ti/AlSiCu/TiON/Ti Interconnects with Aluminum Reflow

Electromigration-induced failures in sputtered TiN/Ti/AlSiCu/TiON/Ti interconnects with aluminum (Al) reflow treatment have been studied in terms of aluminum microstructure and stress relaxation between the AlSiCu and TiON barrier metal. The sputtered interconnects with Al reflow treatment have an electromigration lifetime three times longer than the sputtered interconnects without Al reflow treatment. Furthermore, electromigration-induced voids in sputtered interconnects without Al reflow treatment are generated at the interface between the AlSiCu and TiON. Voids in sputtered interconnects with Al reflow treatment are seldom generated at the interface between the AlSiCu and TiON. The difference in electromigration performance between the two metallizations cannot be explained merely by the orientations of aluminum crystallites and the grain size of the aluminum. We conclude that the most effective factor in electromigration performance is the stress relaxation between AlSiCu and TiON during reflow annealing. The negligible residual compressive strain has little influence on the electromigration resistance of sputtered interconnects with Al reflow treatment. On the contrary, the residual compressive strain lowers the electromigration resistance in sputtered interconnects without Al reflow treatment.

Enhanced Hot‐Carrier Degradation Due to Water‐Related Species in Plasma‐Enhanced Tetraethoxysilane Oxide

Hot-carrier (HC) degradation was compared in three kinds of intermetal oxide structures : in a single layer of tetraethoxysilane (TEOS) based plasma-enhanced silicon dioxide (PETEOS) structures, in PETEOS-based spin-on glass (SOG) etchback structures, and in PETEOS-based SOG nonetchback structures. HC degradation was found to be enhanced in SOG nonetchback structures rather than in SOG etchback structures. HC degradation in SOG etchback structures is almost the same as in a single layer of PETEOS even though SOG remains over the gate of the transistor measured. Next, the influence of water-related species in intermetal oxides on HC degradation was investigated. The PETEOS is blocking H 2 O which diffuses from the SOG in the SOG etchback structure. However, H 2 O diffuses through the PETEOS in the SOG nonetchback structure with a large amount of SOG. Moreover, we understand that a little OH - released from PETEOS in the final annealing most likely enhances HC degradation.

Three kinds of via electromigration failure mode in multilevel interconnections

The via electromigration performance of four metallization systems has been investigated for via chains of 1500-4400 vias of 1.0 mu m diameter. AL(AL/Ti), (Al/Ti)AL, and AL/(WSi/AL) metallization systems have longer electromigration lifetime than AL/AL. The via failures have been analyzed by the contrast scanning ion microscope technique. Further failure analysis by focused ion beam milling on the opened via has revealed that at least three kinds of failure modes exist for via electromigration. Models for the failure mechanism in each metallization system are discussed.<<ETX>>

Roles of Cap‐Metal on Via Electromigration Resistance in Aluminum‐Based Interconnections

Cap-metal of the lower metal can be partially etched at shallow via contacts in actual LSI devices. Influence of the cap-metal which partially remains in via contacts on via electromigration (EM) was investigated in cases where the cap-metal was WSi and TiN/Ti. The EM lifetime of via contacts where cap-metal remains is longer than that of via contacts where cap-metal is partially etched when using WSi cap-metal. However, the EM lifetime of via contacts where cap-metal is etched partially is longer than that of via contacts where cap-metal remains when using the TiN/Ti cap-metal. These mechanisms are discussed. Furthermore, EM characteristics of via contacts where aluminum and aluminum are connected directly are reinvestigated and also discussed.

Field Inversion Induced by Water from Outside in a Spin‐on‐Glass Nonetchback Complementary Metal Oxide Semiconductor Process

N-channel field inversion has been investigated in large scale integrated chips fabricated by 0.65 μm complementary metal oxide semiconductor double metal process in which spin-on-glass (SOG) is not etched back. Three kinds of organic SOG and two kinds of inorganic SOG were compared. Though n-channel field inversion is never observed in all structures at wafer completion, contrary to previous investigations, the inversion is observed only in organic SOG after storage under 140°C/85% RH. H 2 O permeates the field oxide through organic SOG from chip sidewalls without sealing rings. Strained Si-O-Si bonds in the field oxide are most likely broken there by H 2 O yielding positive charges. The H 2 O also causes threshold voltage (V t ) shift of active transistors. Further, the H 2 O enhances transconductance degradation rather than H + in inorganic SOG.

Aluminum reflow and electromigration characteristics of sputtered TiN/Ti/AlSiCu/TiON/Ti interconnects

Aluminum (Al) reflow is suppressed in TiN/Ti/AlSiCu/Ti/TiON/Ti interconnects because the interfacial AlxTi layer hinders the migration of Al atoms during reflow annealing. Therefore, electromigration (EM) characteristics of sputtered TiN/Ti/AlSiCu/TiON/Ti interconnects with Al reflow were investigated. The sputtered interconnects with Al reflow treatment have a three times longer electromigration lifetime than the sputtered interconnects without Al reflow treatment. The difference in EM performance between the two metallizations cannot be explained merely by 〈111〉 orientation of Al crystallites and the grain size of Al. We verify that the most effective factor in electromigration performance is the stress relaxation between AlSiCu and TiON during reflow annealing. The negligible residual compressive strain has little influence on EM resistance of sputtered interconnects with Al reflow treatment. On the contrary, the residual compressive strain lowers the EM resistance in sputtered interconnects without Al...