News Column

Patent Application Titled "In-Sequence Spectrographic Sensor" Published Online

June 12, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- According to news reporting originating from Washington, D.C., by VerticalNews journalists, a patent application by the inventors Zhang, Jimin (San Jose, CA); Wang, Zhihong (Santa Clara, CA); Tu, Wen-Chiang (Mountain View, CA); McClintock, William H. (Los Altos, CA), filed on November 21, 2012, was made available online on May 29, 2014.

The assignee for this patent application is Applied Materials, Inc.

Reporters obtained the following quote from the background information supplied by the inventors: "An integrated circuit is typically formed on a substrate by the sequential deposition of conductive, semiconductive, or insulative layers on a silicon wafer. One fabrication step involves depositing a filler layer over a non-planar surface and planarizing the filler layer. For certain applications, the filler layer is planarized until the top surface of a patterned layer is exposed. A conductive filler layer, for example, can be deposited on a patterned insulative layer to fill the trenches or holes in the insulative layer. After planarization, the portions of the metallic layer remaining between the raised pattern of the insulative layer form vias, plugs, and lines that provide conductive paths between thin film circuits on the substrate. For other applications, such as oxide polishing, the filler layer is planarized until a predetermined thickness is left over the non planar surface. In addition, planarization of the substrate surface is usually required for photolithography.

"Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is typically placed against a rotating polishing pad. The carrier head provides a controllable load on the substrate to push it against the polishing pad. An abrasive polishing slurry is typically supplied to the surface of the polishing pad.

"Variations in the slurry distribution, the polishing pad condition, the relative speed between the polishing pad and the substrate, and the load on the substrate can cause variations in the material removal rate. These variations, as well as variations in the initial thickness of the substrate layer, cause variations in the time needed to reach the polishing endpoint. Therefore, determining the polishing endpoint merely as a function of polishing time can lead to overpolishing or underpolishing of the substrate. Various in-situ monitoring techniques, such as optical or eddy current monitoring, can be used to detect a polishing endpoint."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventors' summary information for this patent application: "In some systems, the substrate is monitored in-situ during polishing, e.g., by optically or eddy current techniques. However, existing monitoring techniques may not reliably halt polishing at the desired point. A spectrum from the substrate can be measured by an in-sequence metrology station. That is, the spectrum can be measured while the substrate is still held by the carrier head, but at a metrology station positioned between the polishing stations. A value can be calculated from the spectrum which can be used in controlling a polishing operation at one or more of the polishing stations.

"In one aspect, a method of controlling a polishing system includes polishing a substrate at a first polishing station, transporting the substrate to an in-line optical metrology system positioned between the first polishing station and a second polishing station, at the in-line optical metrology system measuring a spectrum reflected from the substrate, and generating a characterizing value from the spectrum, determining that the substrate needs rework based on the characterizing value, returning the substrate to the first polishing station and performing rework of the substrate at the first polishing station; and transporting the substrate to the second polishing station and polishing the substrate at the second polishing station.

"Implementations may include one or more of the following features. The substrate may be held by a carrier head and the carrier head is suspended from a track, and transporting the substrate may be performed by moving the carrier head along the track. Generating the characterizing value may include obtaining a plurality of measured spectra with the optical metrology system from a plurality of different measurement spots within an area on the substrate, generating a plurality of values based on the plurality of measured spectra, and combining the values to generate the characterizing value. Generating the plurality of values may include comparing each of the plurality of measured spectra to a reference spectrum to generate a similarity value. The substrate may have a plurality of dies, and the area may be substantially equal to an area of one of the dies. Generating the characterizing value may include at least one of identifying a matching reference spectrum from a library of reference spectra and determining the characterizing value associated with the matching reference spectrum, determining a wavelength or width of a peak or valley in the spectrum, or fitting an optical model to the spectrum. Another spectrum reflected from the substrate may be measured at the in-line optical metrology system positioned between the first polishing station and a second polishing station after performing rework and before transporting the substrate to the second polishing station. Polishing the substrate at the first polishing station may include a filler layer clearing recipe, and polishing the substrate at the second polishing station may include an underlying layer polishing recipe. Polishing the substrate at the first polishing station may be a bulk polishing step of a copper damascene process. Polishing the substrate at the second polishing station may be a dielectric exposure step of a copper damascene process. The substrate may be transported to a cassette before returning the substrate to the first polishing station and performing rework of the substrate at the first polishing station. At least one other substrate may be polished at the first polishing station before returning the substrate to the first polishing station and performing rework of the substrate at the first polishing station.

"In another aspect, a polishing system includes a first polishing station including a first support for a first polishing pad, a second polishing station including a second support for a second polishing pad, a carrier head to hold a substrate, the carrier head supported by a support structure and movable between the first polishing station and the second polishing station, an in-line optical metrology system positioned between the first polishing station and the second polishing station, the optical metrology system configured to measure a spectrum reflected from the substrate and generate a characterizing value from the spectrum, and a controller configured to cause the carrier head to move to the first polishing station, to cause the substrate to be polished at the first polishing station, to cause the carrier head to move to the in-line metrology system, to determining whether the substrate needs rework based on the characterizing value, to cause the carrier head to return to the first polishing station and performing rework of the substrate at the first polishing station, to cause the carrier head to move to the second polishing station, and to cause the substrate to be polished at the second polishing station.

"Implementations may include one or more of the following features. The support structure may be a track and the carrier head may be movable along the track. The carrier head may be suspended from a carriage on the track. The controller may be configured to cause the carrier head to move to the in-line optical metrology system and to receive another spectrum reflected from the substrate at the in-line optical metrology system after performing rework and before transporting the substrate to the second polishing station. The system may include a cassette and a robot to transfer the substrate from the carrier head to the cassette. The controller may be configured to cause the robot to transport the substrate from the carrier head to the cassette before the substrate is returned to the first polishing station and rework of the substrate is performed at the first polishing station. The controller may be configured to cause polishing of at least one other substrate at the first polishing station before the substrate is returned to the first polishing station and rework of the substrate is performed at the first polishing station.

"Implementations can include one or more of the following potential advantages. Polishing endpoints can be determined more reliably, and within-wafer non-uniformity (WIWNU) and wafer-to-wafer non-uniformity (WTWNU) can be reduced.

"The details of one or more implementations are set forth in the accompanying drawings and the description below. Other aspects, features and advantages will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

"FIG. 1 is a schematic plan view of an example of a polishing apparatus.

"FIG. 2 is a schematic cross-sectional view of an example of a polishing apparatus.

"FIG. 3 is a schematic cross-sectional view of an example of an in-sequence optical metrology system.

"FIG. 4 illustrates an example spectrum.

"FIG. 5 is a schematic cross-sectional view of a wet-process optical metrology system.

"FIG. 6 is a schematic cross-sectional view of another implementation of a wet-process optical metrology system.

"FIG. 7 is a schematic top view of a substrate.

"Like reference symbols in the various drawings indicate like elements."

For more information, see this patent application: Zhang, Jimin; Wang, Zhihong; Tu, Wen-Chiang; McClintock, William H. In-Sequence Spectrographic Sensor. Filed November 21, 2012 and posted May 29, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=2230&p=45&f=G&l=50&d=PG01&S1=20140522.PD.&OS=PD/20140522&RS=PD/20140522

Keywords for this news article include: Applied Materials Inc.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


For more stories covering the world of technology, please see HispanicBusiness' Tech Channel



Source: Politics & Government Week