Chemical mechanical planarization (CMP) slurry quality control process and particle size distribution measuring systems

Abstract

A sensitive particle distribution probe uses special processing including a modified Twomey/Chahine iterative convergence technique and a specially constructed sample cell to obtain particle size distribution measurements from optically dense slurries, such as the slurries used in the semiconductor industry for chemical mechanical planarization. Spectral transmission data is taken over the spectral range of 0.20-2.5 microns, utilizing specially constructed, chemically resistant sample cells of 50-2000 microns thickness, and miniature, fixed grating, linear detector array spectrometers. At wavelengths greater than one micron, the preferred design utilizes InGaAs linear detector arrays. An ultrasonic disrupter can be employed to breakup harmless soft agglomerates. In addition to direct particle size distribution measurement, the invention described here could be used to detect other fundamental causes of slurry degradation, such as foaming and jelling. The probe accomplishes continuous, real time sampling of undiluted slurry. A three-position chopper allows automated operation in an industrial environment without the need for frequent reference spectra, which would require taking the probe off-line. In other embodiments, the invention provides a quality control and/or particle size measuring system for CMP slurries using transmission data through an as-used CMP slurry flow. The process of the invention detects transmission through the flow, at select wavelengths, and determines changes in the logarithmic slope of transmission versus wavelength to detect acceptable or unacceptable CMP slurries. The process can further determine CMP slurry particle size through empirical extinction data stored in memory.

Description

RELATED APPLICATIONS[0001]This application is a continuation-in-part of commonly-owned and U.S. application Ser. No. 09 / 069,682, filed on Apr. 29, 1998, <?insert-start id="INS-S-00001" date="20070821" ?>now U.S. Pat. No. 6,246,474 <?insert-end id="INS-S-00001" ?>which is incorporated herein by reference.FIELD OF THE INVENTION[0002]The invention pertains to the field of measurements performed on slurries to determine the slurry particle size distribution. More specifically, the measurements concern a use of instrumentation to determine particle concentration as a function of particle size in substantially opaque slurries, such as chemical mechanical planarization (“CMP”) slurries currently used in semiconductor manufacturing. The invention further relates to quality control processes used to improve semiconductor manufacturing processes.BACKGROUND OF THE INVENTION[0003]CMP processes are used in the semiconductor and optics industries to provide ultra-smooth surfaces. CMP...

AI Technical Summary

Benefits of technology

[0019]In one aspect, sample cells of the invention are formed of a chemically resistant housing that retains a first window and a second window in spaced relationship to provide a suitable optical depth. These windows are preferably made of a hard, chemically resistant, artificial crystal such as sapphire. The housing includes a tapered ramp that widens at it narrows from an inlet to the separation between the windows, and thins as it thickens from the separation to an outlet. The outlet preferably returns undiluted slurry to the day tank or main process slurry line after particle size distribution measurements have been obtained from the sample. The use of multiple sample cells yields measurements of greater accuracy by tuning the optical path length (i.e., window spacing) of each cell to a different wavelength regime. Specifically, greater accuracy measurements can be obtained by keeping the transmission, measured through the slurry, within the approximate range of 0.05-0.90.

[0020]In still another aspect, a light chopper is positioned between

Problems solved by technology

It is difficult to check the quality the particle size distributions within these slurries due to the sub-micron sizes of the particles and the substantially opaque nature of the slurry.

Particles having dimensions that exceed a delimiting value for a particular application are analogous to sandpaper having grit that is too large, and disadvantageously score or scratch the surface that is being smoothed.

It has been observed that semiconductor wafers can be scratched and thereby damaged if a significant concentration of large particles appear in the slurry through either contamination or agglomeration.

Commercially available sensor devices are presently unable to meet the needs of those who wish to measure the particle size distribution of CMP slurries.

Furthermore, dilution combined with continuous sampling creates large volumes of waste slurry.

These measurement techniques are problema

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