Investigation of the influence of different copper slurry systems on post CMP topography performance
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Investigation of the influence of different copper slurry systems on post CMP topography performance Goetz Springer, Peter Thieme, Pierre Klose IFD3 MDC UPD F Planarization, Infineon Technologies SC300 GmbH & Co. KG ABSTRACT Since the early days of copper CMP much research and development effort was put into formulation of new copper and barrier CMP slurries. Two major motivations for this effort are the improvement of process performance for currently used integration schemes and the preparation for new integration schemes using low-k and ultra low-k dielectric materials. In this paper a systematic procedure for topography investigation after copper and barrier CMP is presented. The procedure is applied to four different copper slurries in order to compare after copper and after barrier CMP topography performance. As a result of the post copper CMP topography investigations, a discussion of advantages and disadvantages of non-selective and selective barrier polish processes will be presented. To complete the discussion of potential topography correction during barrier CMP, an investigation of an observed pronounced dielectric erosion close to large metal features or within high metal density arrays with medium or high selective barrier CMP processes will be presented. INTRODUCTION Four different copper slurries were investigated. Both, blanket wafers for removal rate and selectivity measurements as well as patterned metal CMP test wafers for topography evaluation were applied. After detailed evaluation of the patterned wafer post copper CMP topography the same barrier CMP process was applied in all cases. This allowed a direct comparison of the copper CMP process on post copper and final post barrier CMP topography performance. Table 1 summarizes the major slurry properties and process parameters of all different slurries. As it can be seen very different slurry systems with respect to abrasive and oxidizer material properties were investigated.
Abrasive particle Oxidant Pad type CMP tool type Polishing pressure
Slurry A alumina H2O2 IC1000/SUBA IV (80 mil IC) orbital 2.5 psi 1 psi soft landing
Slurry B silica H2O2 IC1000/SUBA IV (80 mil IC) orbital 4.5 psi 1 psi soft landing
Slurry C no abrasive H2O2 Single IC1000 (80 mil IC) orbital 2.0 psi no soft landing
Slurry D silica APS IC1000/SUBA400 (50 mil IC) rotary 4.3 psi no soft landing
Table 1. Summary of key slurry properties and test conditions for all tested copper CMP slurries. Different tool platforms, polishing pads and machine parameters were applied due to tool availability and process requirements driven by the different slurry characteristics themselves. In order to have a direct comparison between the different processes blanket wafer polishing rates and selectivity’s in addition to topography results for a wide range of polishing times were collected.
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For robust and high yielding copper CMP processes the possibility of high over polish margins is of interest in order to compensate a mismatch in copper deposition and CMP removal pr
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