Caprice Gray

Determining Pad-Wafer Contact using Dual Emission Laser Induced Fluorescence

It is becoming increasingly clear that understanding the small scale polishing mechanisms operating during CMP requires knowledge of the nature of the pad-wafer contact. Dual Emission Laser Induced Fluorescence (DELIF) can be used to study the fluid layer profile between the polishing pad and the wafer during CMP. Interactions between the polishing pad surface and the wafer can then be deduced from the fluid layer profile. We present a technique and some preliminary data for instantaneous measurement of in-situ pad-wafer contact, defined as the point at which the fluid film thickness goes to zero, using DELIF. The imaging area is 1.30mmx1.74 mm with a resolution of 2.5 µm/pixel. At this magnification, some regions imaged contain contact, whereas others do not. For the contact regions discussed in this paper, contact percentage varies from 0.07% to 0.27% using a Cabot Microelectronics D100 polishing pad. The asperity contact area increases with applied load, which was varied from 0.28 to 3.1 psi.

Rapid nano impact printing of silk biopolymer thin films

In this paper, nano impact printing of silk biopolymer films is described. An indenter is rapidly accelerated and transfers the nanopattern from a silicon master into the silk film during an impact event that occurs in less than 1 ms. Contact stresses of greater than 100 MPa can be achieved during the short impact period with low power and inexpensive hardware. Ring shaped features with a diameter of 2 µm and a ring width of 100–200 nm were successfully transferred into untreated silk films using this method at room temperature. Mechanical modeling was carried out to determine the contact stress distribution, and demonstrates that imprinting can occur for contact stresses of less than 2 MPa. Thermal characterization at the impact location shows that raising the temperature to 70 °C has only a limited effect on pattern transfer. Contact stresses of greater than approximately 100 MPa result in excessive deformation of the film and poor pattern transfer.

Viewing asperity behavior under the wafer during CMP

RO O F CO PY 0205ESL Viewing Asperity Behavior Under the Wafer during CMP Caprice Gray, Daniel Apone, Chris Rogers, Vincent P. Manno, Chris Barns, Mansour Moinpour, Sriram Anjur, and Ara Philipossian* Department of Mechanical Engineering, Tufts University, Medford, Massachusetts 02155, USA Intel Corporation, Hillsboro, Oregon 97124, USA Cabot Microelectronics, Aurora, Illinois 60504, USA Deptartment of Chemical and Environmental Engineering, The University of Arizona, Tucson, Arizona 85721, USA

QUANTITATIVE IN-SITU MEASUREMENT OF ASPERITY COMPRESSION DURING CHEMICAL MECHANICAL PLANARIZATION

Modifications to the Dual Emission Laser Induced Fluorescence (DELIF) procedure used to collect images of the slurry layer between the polishing pad and wafer during Chemical Mechanical Planarization (CMP) have provided a means to attain instantaneous, high spatial resolution images of slurry film thickness. Presented here is a technique to determine the calibration factor that correlates image intensity to slurry film thickness. This presentation will discuss how to determine slurry layer shape near wafer features, pad roughness, and pad compressibility.Copyright

In-Situ Friction and Pad Topography Measurements During CMP

Duel Emission Laser Induced Fluorescence (DELIF) and friction measurements are taken in-situ during CMP to observe slurry flow beneath a model of an integrated circuit (IC) wafer. Friction measurements average around 7.5 lb and multiple frequencies are observed. Slurry film thicknesses on the order of a 10±3μm were observed during CMP of a flat wafer. The film thickness seems uncorrelated to friction measurements except when the pad and wafer rotation speeds are significantly slowed. DELIF has also accurately measured a 9μm etched step, with noise in the image equal to ±3 μm.