Electrochemical Polishing of Copper for Microelectronic Applications

Abstract

Electrochemical polishing (ECP) of copper using hydroxyethylidenediphosphonic acid (HEDP) has been investigated as an alternative to chemical mechanical polishing (CMP) for integration of low-k dialectrics in microelectronic devices. An optimal copper ECP process produces smooth polishing and a fast removal rate. For this investigation copper anodic polarisation curves in HEDP -phosphoric acid solutions were measured and copper ECP effects in various HEDP -phosphoric acid solutions were examined. Copper surface smoothing effects in various HEDP -phosphoric acid solutions were evaluated with atomic force microscopy. It was shown that HEDP and HEDP -phosphoric acid solutions have polarisation curves with a limited current plateau characteristic of ECP. Twenty to forty per cent of HEDP solutions had a maximum limiting current density of~80 A cm 2 2 . Adding phosphoric acid to HEDP solutions increased the limiting current to a maximum, beyond which further addition caused a decrease. An optimal ECP effect (removal rate1 . 8 mm min 2 1 , 80% reduction in mean roughness) was achieved with a solution of 30HEDPz30H 3 PO 4 z 40H 2 O (vol.-%). A higher removal rate was achieved by decreasing the concentration of phosphoric acid, but this resulted in a reduction of the smoothing effect. SE/455 J. Huo (huoj@ece.ogi.edu) and R. Solanki (solanki@ ece.ogi.edu) are in the

Why is copper locally etched by scanning electrochemical microscopy?

“…Microelectrodes were characterized by cyclic voltammetry (CV) using a solution of 1 mM Ru(NH 3 ) 6 3+ in 0.1 M K 2 SO 4 . Cu substrates for SECM experiments were electropolished by applying a constant current of 1.5 mA cm À2 in 0.85% (v/v) H 3 PO 4 aqueous solution at room temperature for different durations [28,29]. The thickness of the copper was determined immediately after this process by profilometry, which scanned across a notch made on the surface using a sharpened wooden stick.…”

Electrochemical planarization of interconnect metallization

“…Thus, according to Equations (8) and (9), the replacement of the NaCl with a 4.0-M FeCl 2 electrolyte should lead to roughly an order of magnitude decrease in limiting-current density. This indeed occurs, helping to validate the salt-film hypothesis.…”

“…In a related study, Huo et al [8] measured the polarization behavior of copper oxidation in HEDP/ phosphoric-acid mixtures. The resulting surface finish of blanket copper films, as measured by atomic force microscopy, was reported.…”

“…Alternative metal-removal methods should enable high dissolution rates without subjecting the substrate to excessively large pressures. Electrochemical dissolution methods, either as a CMP replacement or a complement to CMP, have received a fair amount of recent attention [8][9][10][11][12][13][14][15][16].…”

Uso de eletrodos de cobre e eletrodos modificados como sensores eletroquímicos

“…O estudo do comportamento eletroquímico do cobre em soluções contendo íons fosfato foi direcionado fundamentalmente ao processo de eletropolimento em soluções concentradas de ácido fosfórico [112,[114][115][116][117]. Apesar da utilização do ácido fosfórico em vários processos em meio aquoso, ainda há controvérsias quanto à identidade das espécies formadas e mecanismos de reação [94,112,[115][116] Estes resultados podem ser explicados em função da formação de espécies solúveis de cobre e da passivação causada pelo crescimento do filme anódico [37,94,105,[136][137][138].…”