Deep dishing and erosion are serious problems in conventional chemical mechanical planarization ͑CMP͒ of copper/barrier layer, specifically when a hard barrier layer is used as the polishing stopper. This paper describes the reduction of the dishing in the CMP with lower removal rate ratio. This CMP can be achieved by following procedures. ͑i͒ Increase of removal rate in barrier layer; removal rate is 1.5 nm/min in polycrystalline tantalum nitride barrier layer. This rate increases to 77 nm/min in TaSiN barrier layer when polished by MnO 2 slurry with hard pad. ͑ii͒ Reduction of the removal rate of copper layer; removal rate of electroplated copper layer decreases to 210 nm/min by MnO 2 slurry. This rate decreases to 77 nm/min when additive is doped into this slurry by 10%. Because thin antioxide layer is formed at the copper surface during the polishing by this additive, removal rate ratio of Cu/barrier layer reduces to unity by this doping. Dishing free CMP can be developed by this process.

Polishing and the polishing mechanism are studied for low dielectric constant SiOC layer deposited by plasma-enhanced chemical vapor deposition ͑PECVD͒. Hardness changed from 4.6 to 13.4 GPa with varying carbon content from 0.35 to 0.50. Good barrier performance was attained for the copper diffusion in layers with carbon contents above 0.35 when annealed at 400°C. Removal rate in mechanical polishing decreased, inversely proportional to the hardness as given theoretically. However, removal rate was weakly dependent on the hardness in the chemical polishing by the MnO 2 slurry. Higher removal rate is fulfilled by this chemical polishing.The reduction of CR time constant in multilayer interconnections can be fulfilled by employing low dielectric constant interlayers. Therefore, development of advanced low dielectric constant interlayers has become more important. A plasma-enhanced chemical vapor deposition ͑PECVD͒ SiOC layer is a promising low dielectric constant interlayer because the conformal layer can be deposited by conventional PECVD reactor. However, few papers have reported the deposition and properties of this interlayer. Chemical mechanical planarization ͑CMP͒ processing has been extensively used for planarization in the Cu/low dielectric layer damascene process. A polishing stopper of CVD Si 3 N 4 layer was applied during CMP. Hardness was as high as 15.0 GPa and lower removal rate was accomplished by Si 3 N 4 layer. Development of lower dielectric constant polishing stopper is required for the reduction of CR time constant in the copper interconnection. 1 This layer is also likely to be a good diffusion barrier layer for the copper diffusion.To establish a CMP process for these layers, the polishing mechanism for CVD SiOC layer must be studied. However, polishing of this layer has not been reported. This paper describes the polishing mechanism in mechanical and chemical polishings in CVD SiOC layer with different carbon contents. Hardness and removal rate in the mechanical polishing varied with this change of carbon content. ExperimentalLow dielectric constant SiOC interlayer 500 nm thick was deposited on p-Si͑100͒ wafers at 375°C, where dual-frequency plasmas ͑13.56 MHz and 380 kHz͒ were used in the deposition by PECVD. Hexamethyldisiloxane ͑HMDSO͒ and CH 4 gas were used as the source gas. The carbon content of the SiOC layer was controlled by varying the CH 4 flow rate from 0 to 300 sccm, while the flow rate of HMDSO was held at 50 sccm. The layers were polished with a ring-type polishing machine at a rotational speed of 30 rpm and 300 g/cm 2 employing a Suba-600 pad. The diamond dresser was used for the dressing. Commercially available fumed silica ͑par-ticle size 0.1 m, pH 10.6͒ and newly developed MnO 2 slurries ͑particle size 0.4 m, pH 8.6͒ were used for these polishings. The polishing mechanism was studied by compositional analyses of the thin surface layer formed by the reaction with slurry employing X-ray photoemission spectroscopy ͑XPS͒.

Polishing of low dielectric constant (low k) organic layers of polyarylether (poly‐AE) has been studied. Removal rate of poly‐AE is 52 nm/min in polishing by MnO2 slurry at pressure of 163 normalg/cm2 . This rate is 4.2 times greater than that achieved by fumed silica slurry. This rate increase is due to the enhancement of chemical polishing through employing a chemically active slurry of MnO2 . Removal rate for tantalum nitride (TaN) barrier is 97 nm/min in MnO2 slurry. This rate is much greater than the 44 nm/min achieved by fumed silica slurry. Although many deep scratches are formed at the surface of the poly‐AE layer by the polishing of fumed silica slurry, no deep scratches are found at the surface polished by MnO2 slurry. © 1999 The Electrochemical Society. All rights reserved.