Selective Deposition of Cu Interconnects by Prepatterned Ta Film

Abstract

A process of fabricating Cu layers by displacement reaction is demonstrated in this study. A prepatterned Ta film on a TaN layer was displaced by a redox reaction to form the copper top layer. The TaN layer was included to improve adhesion between the copper and the dielectric layers. The average electrical resistivity obtained from the Cu films was 2.02 ⍀ cm after thermal annealing. Reliability analysis showed that the activation energy of the copper interconnect was 0.94 eV, which was close to the result for Cu films grown by sputtering.For future ultralarge-scale integration, the ever-decreasing lateral dimensions of contacts and holes require new developments in metallization technology. Consequently, copper has been studied as an alternative metal for interconnections due to its lower resistivity, better mechanical properties, and electromigration resistance compared to aluminum. 1,2 For Cu metallization, an efficient diffusion barrier is required to prevent Cu atoms from penetrating into dielectrics or Si substrates. Since copper is highly diffusive and drifts into the surrounding dielectric layer even at low temperatures, 3,4 a highly conducting diffusion/drift barrier typically less than 20 nm thick is needed to separate the Cu from the dielectric layer. Refractory metals and their nitrides have been used and thoroughly investigated for interconnection applications. These materials are promising as diffusion barriers because of their good thermal stability at elevated temperatures. 5 Several methods have been proposed for depositing Cu on these diffusion barriers, e.g., physical vapor deposition, 6,7 chemical vapor deposition, 8,9 and electrochemical deposition ͑ECD͒. 10,11 However, since the substrate surface is generally not catalytic, a seeding treatment or surface modification must be invoked to initiate the deposition of an electroless barrier for Cu. Traditionally, predeposition of a catalyst is carried out by sensitizing and activating the surface in tin-palladium colloidal solutions or tin-free PdCl 2 acidic solutions, or by UV-induced copolymer-grafting molecular modification, thereby forming disjointed catalytic sites on the surface to be metallized. 12 Recently, a simple and fast displacement technique for Cu metallization has been proposed. It involves forming a seed layer of copper directly by displacement of Ta in the barrier layer. This technique is attractive in the microelectronics and semiconductor industries because of its low processing temperature, high step coverage, high selectivity, low cost, and no need for sensitization and activation. 13 Although direct electroless copper plating onto TiN, TaN, and WN does not require catalysis adsorption pretreatment, it is necessary to prepare complex solutions containing diamine-tetraacetic, glyoxylic acid as a reducing agent, polyethylene glycol as a surfactant, and 2,2Ј-bipyridine as stabilizers. 14 This study investigated a low-cost selective plating technique that does not require etching copper layers. The quality of the deposited Cu fil...

Advanced Cu chemical displacement technique for SiO2-based electrochemical metallization ReRAM application

“…Therefore, this study presents a Cu chemical displacement technique (CDT) for fabricating Cu/SiO 2 -stacked ReRAM devices in nonvolatile memory applications. Cu interconnects have already been fabricated by Cu CTD [ 14 ]. The simple Cu CDT process overcomes the difficulty of etching Cu into the required patterns and enables easy modulation of the interface between Cu and SiO 2 during Cu deposition.…”

Fabrication and Application of Copper Nano Doughnut with Electro-plating Method on Patterned Nickel Template

“…Two kinds of copper interconnect fabrications are extensively applied in interconnects and metal bumping: Cuelectroplating and Cu-electroless deposition, respectively. Cu-electroless deposition is a method to deposit Cu directly on the barrier layer such as Ta, TaN, Ti, TiN, W, NiB, or AlN (14)(15)(16)(17)(18)(19) by sensitization, activation, and a replacement process that possesses film characteristics analogous to Cu-electroplating; but its chemical and physical properties are still not superior to that of Cu-electroplating. Recently, a variety of liner materials as a conductive layer and barrier layer for direct Cu-electroplating were examined, including Pt, Pd, Ru, Os, and Ir, where the formation enthalpy of the metal oxide is smaller than that of Cu oxide (20-24) Among these materials, Ni bears low electrical resistivity and high thermal stability, and has a potential compatible with conventional silicon complementary metal oxide semiconductor (CMOS) manufacturing.…”

Fabrication and Application of Copper Sub-Microdoughnut with Electroplating Method on Patterned Nickel Template

“…Two kinds of copper interconnect fabrications are extensively applied in interconnects and metal bumping: Cu-electroplating and Cu-electroless deposition, respectively. Cu-electroless deposition is a method of depositing Cu directly on a barrier layer such as Ta, TaN, Ti, TiN, W, NiB, or AlN [14][15][16][17][18][19] by sensitization, activation, and a replacement process that possesses film characteristics analogous to Cu-electroplating, but its chemical and physical properties are still not superior to that of Cu-electroplating. Recently, a variety of liner materials as a conductive layer and barrier layer for direct Cu-electroplating was examined, including Pt, Pd, Ru, Os, and Ir, where the formation enthalpy of the metal oxide is smaller than that of Cu oxide.…”