Characterization of chemical structure, morphology, and mechanical response of polyurethane surface domains as a result of exposure to common chemical mechanical planarization (CMP) environments

A systematic study of the surface domains of segmented polyurethane materials used in such applications as chemical mechanical planarization (CMP) was performed. The study investigates the chemical structure, morphology, and mechanical response of these domains.; X-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SSIMS) are used to map the changes in the surface chemistry of segmented polyurethanes due to exposure to chemical environments commonly found in the CMP process. Shifts in elemental binding energies due to changes in the ratio of rigid to flexible backbone segments at the surface are discernable using these techniques.; Results of XPS analysis on both CMP polishing pads and solid SPU material used to model the pads show a shift in the carbon binding energy as a result of the degradation of the surface due to hydrolysis, leaving the surface enriched with hard segment domains. Static secondary ion mass spectrometry (SSIMS) has reinforced these chemical structure results.; Atomic force microscopy (AFM) and other scanning probe microscopy (SPM) techniques are used to further characterize the surface of the solid SPU material. These techniques allow for a correlation of morphological and mechanical response changes with the surface chemistry changes found using XPS and SSIMS. Nanoindentation and microscratching are included to quantify surface hardness and tribological properties.; The experimental data clearly show that the surface of the segmented polyurethane material degrades from chemical attack when subjected to the hydrogen peroxide environments commonly found in metal CMP processes. Similar chemical induced degradations are now known in CMP applications of these materials. The enrichment of domains on the surface after chemical exposure is due to rigid segments that are free from the polymer chain but loosely bound to each other and tenaciously adsorbed to the surface.; This degradation has significant impacts on the efficiency and stability of the CMP process. This research has contributed to the conclusion that decreasing pad performance over time is due to the accumulation of insoluble byproducts from the decomposition of the pad surface. This conclusion will lead to the development of better performing pad materials and hence an improved efficiency of the CMP process.