Optics: measuring and testing – Plural test
Reexamination Certificate
2001-05-18
2004-06-29
Nguyen, Tu T. (Department: 2877)
Optics: measuring and testing
Plural test
Reexamination Certificate
active
06757056
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed toward measuring thin films and defects on silicon wafers, magnetic thin film disks and transparent and coated glass substrates and more particularly toward measuring thin film thickness, and wear, surface roughness, scratches, particles, stains, pits, mounds, surface topography, step heights, and inclusions using a laser directed toward a thin film disk at many angles including non-Brewster's angles of an absorbing layer of the thin film.
2. Description of Background Art
Coated thin film disks are used in a variety of industries including the semiconductor and the magnetic hard disk industry. A computer hard disk (magnetic storage device) is a non-volatile memory device that can store large amounts of data. One problem that the manufacturers of hard disks experience is how to maximize the operating life of a hard disk. When a hard disk fails the data stored therein may be difficult, expensive, or impossible to retrieve. Failure of a hard disk may be caused by defects on the surface of the thin film disk. It is crucial to be able to detect and classify these defects in order to prevent disk drive failure and to control the manufacturing process.
A schematic of a thin film disk used in magnetic storage devices is shown in FIG.
1
. It includes a magnetic thin film (layer)
106
which is deposited upon a substrate
108
(typically a NiP plated Al—Mg alloy or glass). The magnetic thin film
106
can be protected by a thin film of carbon
104
(carbon layer), for example, whose thickness is typically 20 to 200 Angstroms (Å) The carbon layer
104
is typically coated with a thin layer (
10
to 30 Angstroms) of a fluorocarbon lubricant
102
(lubricant layer). The lubricant layer
102
serves to increase the durability of the underlying carbon layer
104
particularly when the magnetic read/write head contacts the disk, for example when the disk drive is turned off. The hard disk drive industry has been dramatically improving storage capacity by flying the thin film. head closer to the surface of the thin film disk. As a result even very small defects can cause a hard drive to fail. These defects may be topographic such as scratches, pits, mounds, or particles or they may be non-topographic such as stains or inclusions. It is necessary to measure all these types of defects to control the disk manufacturing process and improve disk drive manufacturing yield.
A schematic of a semiconductor wafer is shown in FIG.
2
. The structure of a semiconductor wafer can be very complex and
FIG. 2
shows only one example of a wafer that is undergoing the copper dual damascene process. With reference to
FIG. 2
, illustrated are a copper layer
201
, a second plasma enhanced chemical vapor deposited (PECVD) oxide layer
202
, a first PECVD oxide layer
203
and is a silicon substrate
204
. The copper layer
201
is polished using a chemical mechanical polishing (CMP) process until only the via holes and copper lines remain. The problem is that the CMP process can leave residual copper, nitride, or CMP slurry on the surface of the wafer. In addition, stains, particles, scratches, and micro-waviness may be present on the polished wafer. It is necessary to detect and measure such defects to control the process of making the wafer. Fewer defects will also mean greater wafer yields at the end of the process.
A problem in the hard disk, semiconductor and photonics industries is to inspect these magnetic disks and wafers for defects such as particles, scratches, pits, mounds, stains, topographic irregularities and inclusions. Conventional techniques to solve these problems are discussed in U.S. Pat. No. 4,674,875, U.S. Pat. No. 5,694,214, U.S. Pat. No. 5,748,305, and U.S. Pat. No. 6,157,444. These patents describe techniques to measure defects using essentially sophisticated scatterometers and reflectometers. None of these systems enables the simultaneous measurement of topographic and non-topographic defects. This invention enables this measurement through the use of a combined reflectometer, scatterometer, ellipsometer, profilometer and Kerr effect microscope.
What is needed is a system and method for examining thin film disks, silicon wafers and transparent wafers that: (1) measures topographic and non-topographic defects; (2) measures the optical profile on these substrates; (3) enables the measurements to be performed simultaneously; (4) measures the thickness of thin films; (4) enables measurement on patterned or unpatterned silicon or photonic wafers; (5) is performed in situ or in line; and (6) measures only a single side of a transparent substrate.
SUMMARY OF THE INVENTION
A system and method for measuring topographic and non-topographic defects and topography on thin film magnetic disks, silicon wafers and transparent substrates. This invention enables the measurement of the height of a defect on a thin film disk or a silicon wafer having a first electromagnetic signal source for generating a first signal toward a first position on the thin film magnetic disk at a first angle, a second electromagnetic signal source for generating a second signal toward the first position on the thin film magnetic disk at a second angle, a spinning device for rotating the object to change the first position, a first position sensitive detector to receive a portion of said first signal that reflects off of the object, and to determine a radial portion of the first signal (S
1
r
) and a circumferential portion of said first signal (S
1
c
), a second position sensitive detector positioned at a right angle from the first position sensitive detector, to receive a reflected portion of the second signal that reflects off of the object, and to determine a radial portion of the second signal (S
2
r
) and a circumferential portion of the second signal (S
2
c
).
The system also includes a processor for determining the height of the first position based upon a difference between S
2
c
and S
1
c
that does not include slope information. The system also enables the detection of topographic and non-topographic defects through the measurement of the phase shift of the optical wave. A feature of this invention is its ability t o remove a semiconductor pattern from the data and enhance the ability to detect the presence of defects on the patterned silicon or photonics wafer. Several miniaturized embodiments are presented that enable measurement on both sides of disks or wafers.
REFERENCES:
patent: 3885875 (1975-05-01), Rosenfeld et al.
patent: 4332477 (1982-06-01), Sato
patent: 4585348 (1986-04-01), Chastang et al.
patent: 4668860 (1987-05-01), Anthon
patent: 4870631 (1989-09-01), Stoddard
patent: 4873430 (1989-10-01), Juliana et al.
patent: 5017012 (1991-05-01), Merritt, Jr. et al.
patent: 5129724 (1992-07-01), Brophy et al.
patent: 5189481 (1993-02-01), Jann et al.
patent: 5196906 (1993-03-01), Stover et al.
patent: 5270794 (1993-12-01), Tsuji et al.
patent: 5293216 (1994-03-01), Moslehi
patent: 5313542 (1994-05-01), Castonguay
patent: 5406082 (1995-04-01), Pearson et al.
patent: 5416594 (1995-05-01), Gross et al.
patent: 5446549 (1995-08-01), Mazumder et al.
patent: 5463897 (1995-11-01), Prater et al.
patent: 5608527 (1997-03-01), Valliant et al.
patent: 5610897 (1997-03-01), Yamamoto et al.
patent: 5633747 (1997-05-01), Nikoonahad
patent: 5644562 (1997-07-01), de Groot
patent: 5694214 (1997-12-01), Watanabe et al.
patent: 5726455 (1998-03-01), Vurens
patent: 5748305 (1998-05-01), Shimono et al.
patent: 5777740 (1998-07-01), Lacey et al.
patent: 5798829 (1998-08-01), Vaez-Iravani
patent: 5864394 (1999-01-01), Jordan, III et al.
patent: 5875029 (1999-02-01), Jann et al.
patent: 5880838 (1999-03-01), Marx et al.
patent: 5903342 (1999-05-01), Yatsugake et al.
patent: 5951891 (1999-09-01), Barenboim et al.
patent: 5978091 (1999-11-01), Jann et al.
patent: 5985680 (1999-11-01), Singhal et al.
patent: 5986761 (1999-11-01), Crawforth et al.
patent: 5986763 (1999-11-01), Inoue
patent: 5995226 (1999-11-01), Abe et al.
patent: 6081325
Kudinar Rusmin
Meeks Steven W.
Candela Instruments
Nguyen Tu T.
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