The introduction of porous low-k dielectric materials into semiconductor devices requires the development of low downforce Cu chemical mechanical planarization ͑CMP͒. An alternative passivation agent, 5-phenyl-1H-tetrazole ͑PTA͒, is proposed here that is effective at lower pH than the traditional CMP passivation agent, benzotriazole ͑BTA͒. PTA has previously been reported as a low-pH Cu corrosion inhibitor, but has not been explored for Cu CMP. Cu CMP removal rates and Cu static etch rates are measured for slurries containing 3 wt % H 2 O 2 , 1 wt % glycine, 3 wt % colloidal silica, and PTA concentrations ranging from 0.5 to 3 mM. At pH 3 and PTA concentrations of 0.5-2 mM, PTA provides both effective passivation and Cu removal rates of Ͼ1400 nm/min. Fourier transform-infrared and electrochemical studies are consistent with the formation of an effective passivation layer on Cu in CMP slurries containing PTA concentrations ranging from 0.5 to 2 mM, with the effectiveness of passivation increasing with PTA concentration. The improved low-pH passive film formation for PTA in Cu CMP slurries relative to BTA is most likely due to its much lower pKa ͑4.3͒, with a much larger fraction of PTA in the anionic form at low pH.

Copper chemical-mechanical planarization (Cu CMP) is a rapidly growing segment in the fabrication process of today's semiconductor devices [1]. Copper CMP slurry typically contains an oxidizer that chemically converts the metal film for easy removal, abrasive particles that enhance the abrasiveness of the pad, a complexing agent that enhances the solubility of the abraded metal/ metal oxide, a passivating agent that protects the lower lying areas, a pH regulating agent, and a surfactant [2]. The main function of the passivating agent is to protect the copper film from aggressive chemical attack that may lead to isotropic dissolution of the copper film. With the protection of such passivating agent, ideally, only the copper film in the protruded area is selectively removed by mechanical force, thus yielding a step height reduction. It is commonly observed that a passivating agent in a Cu CMP slurry will lower not only the static etch rate but also the removal rate. As a strong corrosion inhibitor, benzotriazole (BTA) is the most commonly used passivating agent in Cu CMP slurry. A vast number of publications and reports have been devoted to the use of BTA in metal CMP slurry [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The study of BTA analogs for CMP application, however, has been relatively limited in open literature. In this chapter, the role of corrosion inhibitor in Cu CMP slurry is first described. As a case study, the relative effectiveness of some tetrazoles such as 5-aminotetrazole monohydrate (ATA), 5-phenyl-1H-tetrazole (PTA), and 1-phenyl-1H-tetrazole-5-thiol (PTT) as corrosion inhibitor in Cu CMP slurry will be discussed.