Instantaneous Fluid Film Imaging in Chemical Mechanical Planarization

Abstract

Dual Emission Laser Induced Fluorescence (DELIF) is employed to attempt to experimentally determine the nature of the lubrication regime in Chemical Mechanical Planarization. Our DELIF setup provides images of the polishing slurry between the wafer and pad. Static images were taken to provide a baseline, then dynamic runs were conducted. Analyzing these images shows that the wafer only contacts the pad in a small number of places around the wafer, mainly due to the pad's topography.

CMP Method and Practice

“…During polishing, the gap between the wafer and the pad is around 40 μm [2], which is of a similar magnitude as the pad roughness. During polishing, the gap between the wafer and the pad is around 40 μm [2], which is of a similar magnitude as the pad roughness.…”

Determining Pad-Wafer Contact using Dual Emission Laser Induced Fluorescence

“…The DELIF system uses the ratio of two different wavelength bands to estimate contact (for a complete DELIF overview see [8]). As illustrated in figure 3, a Nd/YAG laser firing at its third harmonic frequency, 355nm, is used as the excitation source for the high energy fluorophore, the polyurethane pad.…”

“…Dual Emission Laser Induced Fluorescence (DELIF) has been used to attain highresolution 3D slurry layer and polishing pad profiles 7 and is capable of measuring instantaneous slurry layer thickness during the polishing process (in-situ) 8 . Previous investigations of padwafer interactions using DELIF include in-situ measurements of average fluid layer thickness, asperity layer compressibility, surface roughness measurements and polishing pad rebound into etched wells 9 .…”

Effect of Various CVD-Coated Conditioning Disc Designs and Polisher Kinematics on Fluid Flow Characteristics during CMP

“…Some have been based on computational fluid dynamics and other numerical methods. 5,11,[13][14][15][24][25][26][27][28][29][30][31][32] These studies have highlighted the vast computational resources needed to accomplish the task (with no, or very limited, experimental validation) especially when the effect of pad micro-texture is included in the analyses. Other methods have primarily dealt with qualitative flow visualization using dyed slurries and fluorescent fluids that would get illuminated when excited by a YAG laser 18,[32][33][34] or with an ultraviolet (UV) light source.…”

“…5,11,[13][14][15][24][25][26][27][28][29][30][31][32] These studies have highlighted the vast computational resources needed to accomplish the task (with no, or very limited, experimental validation) especially when the effect of pad micro-texture is included in the analyses. Other methods have primarily dealt with qualitative flow visualization using dyed slurries and fluorescent fluids that would get illuminated when excited by a YAG laser 18,[32][33][34] or with an ultraviolet (UV) light source. 16,32 While the latter studies have certainly shed light on the complex flow patterns, the works have lacked quantifiable data and were somewhat less relevant to today's needs as the polishers that were used in those cases were small in size (i.e.…”