Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2000-01-28
2002-05-07
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S006000, C451S288000
Reexamination Certificate
active
06383058
ABSTRACT:
BACKGROUND
The present invention relates generally to chemical mechanical polishing of substrates, and more particularly to methods and apparatus for detecting a polishing endpoint during a chemical mechanical polishing operation.
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 patterned stop layer, and planarizing the filler layer until the stop layer is exposed. For example, a conductive filler layer may be deposited on a patterned insulative stop layer to fill the trenches or holes in the stop layer. After planarization, the portions of the conductive 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.
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 placed against a rotating polishing disk pad or belt pad. The polishing pad may be either a “standard” pad or a fixed-abrasive pad. A standard pad has a durable roughened surface, whereas a fixed-abrasive pad has abrasive particles held in a containment media. The carrier head provides a controllable load, i.e., pressure, on the substrate to push it against the polishing pad. A polishing slurry, including at least one chemically-reactive agent, and abrasive particles if a standard pad is used, is supplied to the surface of the polishing pad.
One problem in CMP is determining whether the polishing process is complete, i.e., whether a substrate layer has been planarized to a desired flatness or thickness. Variations in the initial thickness of the substrate layer, the slurry composition, 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 cause variations in the time needed to reach the polishing endpoint. Therefore, the polishing endpoint cannot be determined merely as a function of polishing time.
One way to determine the polishing endpoint is to remove the substrate from the polishing surface and examine it. For example, the substrate may be transferred to a metrology station where the thickness of a substrate layer is measured, e.g., with a profilometer or a resistivity measurement. If the desired specifications are not met, the substrate is reloaded into the CMP apparatus for further processing. This is a time-consuming procedure that reduces the throughput of the CMP apparatus. Alternatively, the examination might reveal that an excessive amount of material has been removed, rendering the substrate unusable.
More recently, in-situ optical monitoring of the substrate has been performed, e.g., with an interferometer or reflectometer, in order to detect the polishing endpoint. Unfortunately, noise in the signal generated by the optical monitoring system may make it difficult to determine the proper endpoint.
SUMMARY
In one aspect, the invention is directed to a computer-implemented endpoint detection method for a chemical mechanical polishing operation. In the method a first endpoint criterion, a first time window for the first endpoint criterion, and a second endpoint criterion are stored. A signal is received from a polishing endpoint detection system, and the signal is monitored for the first endpoint criterion. If the first endpoint criterion is not detected within the first time window, polishing is stopped at a default polishing time. On the other hand, if the first endpoint criterion is detected within the first time window, the signal is monitored for the second endpoint criterion and polishing is stopped if the second endpoint criterion is detected.
Implementations of the invention may include one or more of the following features. A second time window for the second endpoint criterion may be stored, and polishing may stop at a default polishing time if the second endpoint criterion is detected before the second time window. If the second endpoint criterion not detected, polishing may stop at the end of the second time window. A third endpoint criterion and a third time window for the third endpoint criterion may be stored. The third time window may be located before the first time window. If the third endpoint criterion is not detected within the third time window, polishing may be stopped at a default polishing time. A detection time at which the first or second endpoint criterion is detected may be stored. The default polishing time may be modified if the second endpoint criterion is detected within the second time window. The first time window may be modified if the first endpoint criterion is detected within the first time window. The endpoint detection system may optically monitors the substrate. The polishing operation may polish a metal or dielectric layer on the substrate. The endpoint detection method may be performed after the first endpoint criteria is detected in the first time window and the second endpoint criteria is detected in the second time window for a plurality of consecutive substrates.
In another aspect, the invention is directed to a computer-implemented endpoint detection method for a chemical mechanical polishing operation. In this method a series of N endpoint criteria are stored, each endpoint criteria associated with a time window. N is equal to or greater than 2. A signal is received from a polishing endpoint detection system, and the signal is monitored for the series of endpoint criteria. Whether an endpoint criterion is detected within the associated time window is determined, and if the endpoint criterion is detected within the associated time window, the signal is monitored for the next endpoint criterion in the series. The determining and monitoring steps are iterated until one of the endpoint criterion is not detected within the associated time window or a last endpoint criterion is detected within the associated time window. If the former, polishing is stopped at a default polishing time. If the later, polishing is stopped based on detection of the last endpoint criterion.
In another aspect, the invention is directed to a method of chemical mechanical polishing. In the method, a substrate is brought into contact with a polishing surface, and relative motion is created between the substrate and the polishing surface. A first endpoint criterion, a first time window for the first endpoint criterion, and a second endpoint criterion are stored. A signal is received from a polishing endpoint detection system, and the signal is monitored for the first endpoint criterion. If the first endpoint criterion is not detected within the first time window, polishing is stopped at a default polishing time. On the other hand, if the first endpoint criterion is detected within the first time window, the signal is monitored for the second endpoint criterion and polishing is stopped if the second endpoint criterion is detected.
In another aspect, the invention is directed to a method of chemical mechanical polishing. In the method, a substrate is brought into contact with a polishing surface, and relative motion is created between the substrate and the polishing surface. A plurality of endpoint criteria, a plurality of time windows and a default polishing time are stored. Each endpoint criterion is associated with one of the time windows. A signal from an endpoint detection system is monitored for the endpoint criteria. The times at which the endpoint criteria are detected are stored. Polishing stops after one of the default polishing times or detection of a last of the endpoint criteria. At least one of the default polishing time and the time windows is adjusted based on at least one of the times at which an endpoint criterion was detected.
Implementations of the invention may include one or more of the fol
Birang Manoocher
Swedek Boguslaw
Applied Materials Inc.
Fish & Richadrson
Ojini Anthony
LandOfFree
Adaptive endpoint detection for chemical mechanical polishing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Adaptive endpoint detection for chemical mechanical polishing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Adaptive endpoint detection for chemical mechanical polishing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2841266