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Removal rates of low-k SiCOH dielectric and scratch defect density of Cu barrier CMP on a soft polyurethane pad with conditioning are characterized and compared between conventional diamond tip conditioner and two types of microreplicated diamond-coated conditioners. Data collected from high volume manufacturing environment demonstrate stable and uniform SiCOH removal rates plus lower scratch density with up to 1000 wafer passes on the soft pad with the microreplicated conditioners, relative to the conventional diamond tip conditioner. Scratch defects are categorized based upon their length and severity. The formation mechanism for each type of scratches are hypothesized. Groove depth and asperity height of soft pads are analyzed in order elucidate the observed differences in removal rates and scratch density with various different pad conditioners.

Shallow trench isolation (STI) requires a high quality oxide with superior fill capability provided by High Density Plasma (HDP) oxide. Unfortunately, the HDP deposition process can create large within die topographies that are difficult to polish directly using conventional silica slurries. As a result, etch back integration schemes have traditionally been incorporated for STI polish. A more revolutionary approach is the use of Fixed Abrasive (FA) CMP [1]. FA CMP allows direct STI polish with good planarization/process stability, eliminating the need for prior etch back. The planarization efficiency is strongly dependent on the shape of the pad composites that hold the CeO2 mineral. Fixed abrasive pads with pyramid and pole shapes are available. In this work, three different fixed abrasive pads supplied by 3M corporation were evaluated for STI CMP polish performance using the Obsidian 8200C web format CMP tool. Basic polish characteristics such as planarity (dependence on sub-pad/pattern density), selectivity to topography, oxide dishing and nitride erosion are presented. The FA pads discussed here have been classified as “slow”, “medium” or “fast” depending on blanket oxide removal rate.The slow rate pad had a very high selectivity to topography and very low dishing of the down area oxide. The removal rate of blanket oxide was less than 100 Å/min. The pad was best suited to the polish of isolation trench structures with small, controlled overfill (> 200 Å) across the wafer. A large process window was demonstrated. The removal rate of the “medium” pad also decreased significantly at the onset of planarization with a blanket oxide removal rate of ca. 200 Å/min. Unlike the slow rate pad, the medium rate pad did not provide a suitable overpolish process window required for a manufacturable STI process. It is believed this pad would be a good choice for BPSG polish. In contrast to the slow and medium rate pads, the blanket oxide removal rate of the fast pad was ca. 2000 Å/min with no self-stopping capability at the onset of planarization. The removal rate was extremely center fast, such that it could not be compensated by adjustment of tool parameters. Use of a modified process developed within the DRAM development alliance (DDA) at East Fishkill (IBM/ Infineon) enabled the fast pad to polish deep STI structures that would otherwise be impossible using the slow or medium rate pads.

Polyurethane (PU) pad debris is identified as one of the major polish residue defects in Cu CMP processes when a barrier pad is conditioned. AES analysis of the debris confirms the organic nature of such defects while FT-IR analysis reveals the characteristic peaks of polyurethane from the pad debris. Hybrid cleans (i.e. acidic plus basic cleans) and basic cleans can both remove the pad debris effectively. The efficiency of basic-only cleans can be improved by increasing time and/or chemistry concentration in the brush modules. The PU pad can endure harsh chemical environments at both low and high pH without any detectable decomposition or morphological changes. The advantages and disadvantages of acidic vs. basic cleans are discussed and the cleaning mechanisms of pad debris PR are elucidated.

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