Viewing Asperity Behavior under the Wafer during CMP

Abstract

Recent experimental advances using dual emission laser induced fluorescence and image processing have provided high spatial and temporal resolution maps of the slurry layer during chemical mechanical polishing ͑CMP͒. Intensity differences in the images correspond to fluid layer thickness variations as the slurry passes between different pad and wafer topographies. Asperities expand under 14 µm deep wells and are compressed beyond the trailing edge of the well. Air pockets travel from the leading to the trailing edge of the wafer through 27 µm deep wells. The pads tested were Freudenberg FX9, Rodel IC1000, and experimental pads from Cabot Microelectronics.

A review on chemical and mechanical phenomena at the wafer interface during chemical mechanical planarization

“…Philipossian's group modified this tool with high spatial resolution images, high-intensity UV laser pulses, and enhanced fluorescence [Fig. 2(a)] [24]. They used two different fluorescent dyes that can be excited at different wavelengths and recorded the fluorescence intensities of the dye molecules in the slurry using two high-resolution cameras.…”

“…The intensity ratio of light detected by each camera was converted to slurry film thickness after proper calibration [Fig. 2(a)] [23,24]. They also studied the dependence of the slurry film thickness on the type of conditioner disk (design, kinematics, and pressure) [26] and pad properties (asperities, roughness, and groove) [25].…”

“…Slurry film thickness was in situ monitored by analyzing the fluorescence intensities of the two different dye molecules in the slurry using a dual emission UV-enhanced fluorescence technique with a dual-camera imaging system [Fig. 2(a); Table 2] as described in the Hydrodynamic lubrication section [23,24]. Mueller et al [127] used tracer particles to study fluid flow characteristics over pad asperities and recorded a video at 30 frames/s using high definition camera to obtain in situ slurry fluid flow data during polishing (Table 2) and manually analyzed the qualitative information of the slurry flow characteristics from the video.…”

Simulated Effects of Measurement Noise on Contact Measurements Between Rough and Smooth Surfaces

“…DELIF is used to measure the fluid, i.e. slurry layer thickness, between the wafer and pad surfaces [16][17][18]. High-intensity (brighter) areas on a DE-LIF image represent valleys between asperities in which the fluid layer is the thickest.…”

Quantitative In-Situ Measurement of Asperity Compression Under the Wafer During Polishing

“…Since then, DELIF has been used to attain spatially and temporally averaged values for variables that include pH [6], temperature [6,7] and slurry film thickness [8]. Recently the technique has been refined such that we can now capture high spatial and temporal resolution images during CMP [9]. This paper will explore the feasibility of studying pad characteristics such as mean asperity compression and pad surface roughness based upon slurry film thickness measurements.…”