(12) United States Patent
`Rulkens
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`Us 6,762,849 B1
`Jul. 13, 2004
`
`US006762849Bl
`
`(54) METHOD FOR IN-SITU FILM THICKNESS
`MEASUREMENT AND ITS USE FOR IN-SITU
`CONTROL OF DEPOSITED FILM
`
`6,129,807 A
`6,226,086 B1
`6,570,662 B1 *
`
`10/2000 Grimbergen et al.
`5/2001 H01l>f60k Ct a1~
`5/2003 Schietmger et al.
`
`...... .. 356/630
`
`THICKNESS
`
`* cited by examiner
`
`(75)
`
`Inventor: Ron Rulkens, Milpitas, CA (US)
`
`(73) Assignee: Novellus Systems, Inc., San Jose, CA
`(US)
`
`*
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`patent is extended or adjusted under 35
`U.S.C. 154(b) by 121 days.
`
`(21) APPL N05 10/170118
`<22)
`Filed:
`J“-19=2°°2
`(51)
`Int. Cl.7 ............................ .. G01B 9/07; G01B 4/28
`(52) U.s. Cl.
`...................................... .. 356/630; 356/503
`(58) Field of Search ............................... .. 356/503, 630,
`356/632, 492, 485
`
`(56)
`
`References Cited
`
`Us PATENT DOCUMENTS
`5,308,414 A
`5/1994 OaNefl1 et al.
`5,450,205 A
`9/1995 Sawin et 211.
`5,754,297 A
`5/1998 Nulman
`
`Primary Examiner—Frank G. Font
`Assistant Examiner—Patricl< Connolly
`(74) Attorney, Agent, or Firm—DeLio & Peterson, LLC;
`Kelly M. Reynolds, Esq.
`
`(57)
`
`ABSTRACT
`
`A method and system for real-time, in-situ measurement of
`a film being deposited onto a surface of a Wafer in a tool
`during semiconductor, optical component and electro-optic
`component processing and manufacturing. The method and
`§§§§§i?o$“3i§i‘3,?nriEi'“f§§i iilfiilf i“fei§2Iii3“§fia‘La13VZ1§§
`surface and subsequently diffusely reflected off internal
`roughened surfaces of the processing chamber. The emitted
`radlanon may be derlved from the Plasma Wlthm the
`chamber, or alternatively, an external energy source.
`In
`detecting and analyzing the radiation reflected off the inter-
`nal surfaces of the processing tool, the instant method and
`system monitors the deposition process of the film and
`automatically controls the deposition of such film in
`response to the measurements taken.
`
`36 Claims, 5 Drawing Sheets
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`Radiation
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`Source
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`Analysis
`Tool
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`ASML 1238
`ASML 1238
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`U.S. Patent
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`Jul. 13, 2004
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`Sheet 1 of 5
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`US 6,762,849 B1
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`U.S. Patent
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`Jul. 13, 2004
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`Sheet 2 of 5
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`US 6,762,849 B1
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`U.S. Patent
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`Jul. 13, 2004
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`Sheet 3 of 5
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`US 6,762,849 B1
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`34
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`Source
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`Radiation
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`Analysis
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`110
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`U.S. Patent
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`Jul. 13, 2004
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`Sheet 4 of 5
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`US 6,762,849 B1
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`U.S. Patent
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`Jul. 13, 2004
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`Sheet 5 of 5
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`US 6,762,849 B1
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`US 6,762,849 B1
`
`1
`METHOD FOR IN-SITU FILM THICKNESS
`MEASUREMENT AND ITS USE FOR IN-SITU
`CONTROL OF DEPOSITED FILM
`THICKNESS
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`This invention relates to the fields of semiconductor,
`optical component and electro-optic component processing
`and manufacturing, and in particular,
`to a method and
`apparatus for in-situ monitoring and controlling deposited
`film thicknesses in real-time.
`
`2. Description of Related Art
`the fabrication pro-
`In semiconductor manufacturing,
`cesses that are used to date must be very accurately con-
`trolled due to the constant increase in integration density of
`the resultant integrated circuit. One of the important process
`steps in semiconductor processing, as well as in other types
`of device processing, is the deposition of films, such as those
`formed into interconnect
`lines, bus structures, Schottky
`barriers, ohmic contacts or other device structures.
`Appropriate thickness of the deposited metal film is
`imperative to the performance of the resultant device. The
`thickness of the film must be precisely controlled because
`variations in thickness may affect the electrical properties of
`the layers and adjacent device patterns, particularly in the
`interconnections between different layers of microelectronic
`devices. For example, if too thin a metal film is deposited,
`an interconnect line formed from that film may be unac-
`ceptably resistive or may have a greater likelihood of
`becoming an open circuit either during subsequent process-
`ing steps or during the normal operation of the device. A
`thick metal film is also undesirable as the film deposition
`process takes too long and the film thickness may be in
`excess of the tolerances of later processing steps.
`Accordingly, it is desirable to maintain film thicknesses near
`their optimal levels.
`In so stating, tools used for such semiconductor manu-
`facture processing have becoming more and more complex
`over the years. For example, typical processing tools may
`include a plurality of chambers, whereby each chamber runs
`a number of varying processing steps. A wafer is sequen-
`tially introduced within each of the plurality of chambers
`and processed sequentially therein, generally under the
`control of a computer. Typically, the deposition monitoring
`techniques within such chambers are often performed using
`repetitive techniques and generally require test wafers. The
`film thickness is generally measured on one or more of the
`test wafers, after the film has been deposited thereon, to
`determine if the film thickness is near an optimal level and
`if the process is within normal operating parameters. If the
`measured film thickness and parameters are not within the
`desired tolerances, the process parameters are adjusted and
`more test wafers are measured to assure optimal film thick-
`ness and process compliance. These processes have a num-
`ber of disadvantages including, for example, being costly as
`one or more test wafers must be utilized, time consuming as
`the film thickness must be measured after the film is depos-
`ited thereon, unreliable from wafer-to-wafer and inefficient
`compared to current deposition monitoring techniques.
`Accordingly, as variations of certain process variables
`cannot be accurately predicted over the course of many
`process runs using the above systems, new methods for tool
`and process characterization such as gas analysis, in-situ
`monitoring and the like, are now of common use in the
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`film thickness
`semiconductor industry. Further, external
`metrology,
`located outside of the wafer processing tool,
`typically is used as a film thickness monitor. However, as it
`is advantageous to monitor the progress of critical wafer
`processing steps to ensure that
`the steps are properly
`completed, it is desirable to utilize in-situ process monitor-
`ing systems. In-situ monitoring systems improve both pro-
`cess monitoring as well as control of the processing steps
`based on such process monitoring.
`In-situ monitoring systems have been developed to moni-
`tor and control the deposition of a film onto a wafer surface,
`as well as for film removal systems such as those for
`detecting an endpoint of a process. The endpoint determi-
`nation is used to monitor the progress of the process and/or
`to control the process, such as by automatically terminating
`the specific processing operation being monitored. In film
`removal systems and processes, it must be accurately deter-
`mined when enough of the film has been removed; i.e., to
`detect the endpoint of the removal operation. If an etch step
`exceeds the predetermined endpoint, the substrate, insulat-
`ing layer and/or resultant circuit pattern may be damaged. As
`such, these systems typically rely on in-situ measurements
`to determine the progressive depth of the etch process as
`these systems provide greater control of the etch process and
`improve uniformity over a batch of processed wafers.
`There has been some success in the art of developing
`in-situ film thickness deposition and etch depth measuring
`systems that utilize optical emission spectroscopy to monitor
`light emissions from the plasma as the etch process
`progresses. Such a system may monitor the optical emission
`intensity of the plasma in a narrow band as well as a wide
`band and generates signals indicative of the spectral inten-
`sity of the plasma by collecting the optical emissions using
`an optical fiber. When the signals diverge, a termination
`signal is generated thereby terminating the etch process.
`However, such systems typically require a separate light
`source, the measurement is done on spots on the wafer, and
`in the case where multiple spots need to be measured at least
`part of the measurement equipment needs to be duplicated
`for such measurement as well as the computation time
`increasing. As such, these methods and technologies for film
`thickness determinations are slow, costly, inefficient, unre-
`liable and negatively impact production yield. Other tech-
`niques include the use of laser interferometry, beamsplitters
`and diffraction gratings to measure the phase shift of a laser
`beam reflected from two closely spaced surfaces. For
`example, the phase shift between a first beam reflected off
`the mask pattern and the beam reflected off an etched portion
`of the wafer is measured and compared to a predetermined
`phase shift
`that corresponds to the desired etch depth.
`Unfortunately, the above discussed optical emission spec-
`troscopy and other monitoring and measuring systems are
`plagued by inadequate signal
`to noise ratios to achieve
`in-situ or real time data processing, as well as the minimum
`etch depth being limited by the wavelength of the light
`source used in the monitor. Also, the film thickness or film
`thickness change is typically measured at a fixed spot, such
`as a fixed spot on a wafer. Disadvantageously, the overall
`film thickness across the wafer is unknown as only the
`thickness at that measured spot is determined, thus leading
`to an increased risk of detecting film thickness from the
`incorrect location where features of the film thickness may
`not be representative for the entire wafer. Furthermore, these
`systems often have the disadvantage of requiring substantial
`modification of the conventional equipment and processes
`thereby making them undesirable, expensive,
`time
`consuming, difficult to integrate, inefficient and impracti-
`cable.
`
`

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`US 6,762,849 B1
`
`3
`Accordingly, a need continues to exist in the art for low
`cost
`improved systems and methods for accurately and
`directly measuring, monitoring and controlling film deposi-
`tion thickness across the entire wafer surface within a
`
`deposition tool whereby the deposited material is uniform
`from wafer to wafer.
`
`Bearing in mind the problems and deficiencies of the prior
`art,
`it
`is therefore an object of the present invention to
`provide an improved low-cost method and system for direct,
`real-time measurement of thickness of deposited film during
`the deposition process.
`Another object of the present invention is to provide a
`method and a system for real-time, in-situ wafer fabrication
`processes that prevents misprocessing errors, corrects for
`process drifts and detection of incorrect tool operation by
`real-time detection of deposited film thickness during wafer
`processing by detecting unusual signal behaviors of the
`system hardware or processing problems that would nega-
`tively affect the film measurement.
`It is another object of the present invention to provide a
`method and a system for real-time, in-situ wafer fabrication
`processes that significantly reduce the wafer reworking.
`Yet another object of the present invention is to provide a
`method and a system for real-time, in-situ wafer fabrication
`processes that drastically reduce processing costs, process-
`ing time and wafer waste.
`Still another object of the present invention is to provide
`a method and a system for a real-time, in-situ wafer fabri-
`cation process whereby the deposition process may be
`stopped at an exact moment when the deposited film has
`reached a desired thickness.
`
`Yet another object of the invention is to provide a method
`and a system for real-time, in-situ wafer fabrication pro-
`cesses that actively, in real-time, recognize the type wafer
`for depositing the desired film and film thickness thereon a
`surface of such wafer.
`
`A further object of the invention is to provide a method
`and a system for real-time, in-situ wafer fabrication pro-
`cesses including processing tools having low costs and
`simplicity of such tools associated therewith.
`Another object of the present invention is to provide a
`method and a system for a real-time, in-situ wafer fabrica-
`tion process that obviates the need for human control for
`better automation.
`
`Still other objects and advantages of the invention will in
`part be obvious and will
`in part be apparent from the
`specification.
`SUMMARY OF THE INVENTION
`
`The above and other objects, which will be apparent to
`those skilled in art, are achieved in the present invention
`which is directed to, in a first aspect, a method for measuring
`film thickness on a substrate in a processing chamber both
`in real-time and in-situ. The method includes providing a
`processing chamber having roughened internal surfaces and
`emitting a radiation within the processing chamber whereby
`the radiation is directed toward and contacts a wafer surface
`
`having a film being processed thereon. The radiation is
`reflected off the wafer surface and directing toward and
`contacts the roughened internal surfaces. The radiation then
`diffusely reflects off the roughened internal surfaces and is
`collected to measure a thickness of the film being processed
`thereon the wafer surface. The roughened internal surfaces
`may have a variety of shapes including dome-shaped,
`hemispherical, cylindrical, oval, square, cylindrical square,
`cylindrical parabolic and combinations thereof.
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`In the invention, the processing chamber may comprise a
`material having a naturally occurring surface roughness to
`provide the roughened internal surfaces. Alternatively, the
`roughened internal surfaces may be provided by a method
`including grinding, polishing, sand blasting, etching, and
`machining the internal surfaces of the processing chamber.
`Still further, the roughened internal surfaces may be pro-
`vided by conformally coating internal surfaces of the pro-
`cessing chamber with a material having a naturally occur-
`ring roughness.
`The at least one optical view port may be provided at any
`location along a perimeter of the processing chamber for
`collecting the radiation diffusely reflected off the roughened
`internal surfaces to measure the thickness of the film. The
`
`optical view port has roughened internal surfaces to ran-
`domize directionality of incident radiation resulting in dif-
`fusely reflected radiation. In accordance with the invention,
`the at least one optical view port may comprise a window
`retracted into a small opening located at any location along
`the perimeter of the processing chamber. Alternatively, the at
`least one optical view port may include a fine metal mesh
`screen over an internal surface of the at least one optical
`view port to prevent deposition of the film thereon the
`internal surface of the at least one optical view port.
`In the first aspect, the film being processed may include
`depositing a film thereon the wafer surface, or alternatively,
`etching a deposited film thereon the wafer surface. The
`radiation may be emitted from a plasma generated within the
`processing chamber, or alternatively, the radiation may be
`emitted into the processing chamber from an external radia-
`tion source.
`
`In a second aspect, the invention discloses a method for
`measuring a deposited film thickness on a substrate in a
`deposition chamber both in real-time and in-situ. The
`method includes providing a processing chamber having
`roughened internal surfaces, at least one optical view port at
`any location along a perimeter of the processing chamber
`and a radiation source. A radiation is emitted within the
`
`processing chamber from the radiation source whereby the
`radiation is directed toward and contacts a wafer surface
`
`having a film being deposited thereon. The radiation is
`reflected off the wafer surface and directing toward and
`contacts the roughened internal surfaces. The radiation then
`diffusely reflects off the roughened internal surfaces and is
`collected using the at least one optical view port. Athickness
`of the film across the wafer surface is then analyzed based
`on the collected diffuse radiation. The processing chamber
`may comprise a deposition tool including a physical vapor
`deposition, a chemical vapor deposition, a plasma enhanced
`chemical vapor deposition and a high density plasma depo-
`sition. The processing chamber may also comprise a plasma
`etching or plasma cleaning tool.
`In the second aspect, the degree of roughness average of
`the roughened internal surfaces at least equals a wavelength
`of the deposited film. The at least one optical view port may
`be located below the wafer surface for collecting the dif-
`fusely reflected radiation. Further, the at least one optical
`view port may comprise a material
`including sapphire,
`alpha-alumina and yttrium aluminum garnet. Optionally, the
`second aspect may further include a plurality of optical view
`ports located at a variety of locations along the perimeter of
`the processing chamber both above and below the wafer
`surface.
`
`the radiation source
`In accordance with the invention,
`may comprise a plasma generated within the processing
`chamber
`including,
`for example, helium, neon, argon,
`
`

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`US 6,762,849 B1
`
`5
`fluorine, nitrogen, nitrogen
`krypton, xenon, oxygen,
`monoxide, carbon monoxide, chlorine, bromine, hydrogen
`and silicon, or ions thereof. Alternatively,
`the radiation
`source may comprise an external radiation source emitting
`radiation into the processing chamber including,
`for
`example, ultra violet, visible, X-Ray and near infrared
`radiation source. The deposited film may include,
`for
`example, silicon oxide, fluorinated silicon oxide, phospho-
`rus doped silicon oxide, boron doped silicon oxide,
`diamond-like carbon, polymers, silicon nitride,
`titanium
`nitride, tantalum nitride and carbon nitride deposited to a
`thickness ranging from about 50 A to about 20,000
`The
`collected diffuse radiation may have a wavelength ranging
`from about 0.1 nm to about 5000 nm. The thickness of the
`
`film across the wafer surface is analyzed by calculating, in
`parallel, a plurality of wavelengths from a plurality of
`emissions reflecting off the wafer surface and diffusely
`reflecting off the roughened internal surfaces.
`In a third aspect, the instant invention is directed to a
`processing chamber for measuring film thickness on a
`substrate in real-time and in-situ. The processing chamber
`includes a chamber body with roughened internal surfaces,
`at least one optical view port located at any location along
`a perimeter of the chamber body and a radiation source. In
`the processing chamber the radiation is emitted from the
`radiation source, reflected off a wafer surface and second-
`arily and diffusely reflected off the roughened internal sur-
`faces of the chamber body whereby the diffusely reflected
`radiation is collected by the at least one optical View port to
`measure a thickness of a film across the wafer surface. The
`
`radiation source may comprise a plasma generated within
`the chamber body, or alternatively, an external radiation
`source emitting radiation into the chamber body.
`In accordance with the third aspect, the roughened inter-
`nal surfaces of the chamber body may be dome-shaped,
`hemispherical, cylindrical, oval, square, cylindrical square,
`cylindrical parabolic and combinations thereof. The cham-
`ber body may comprise a material having a naturally occur-
`ring surface roughness to provide the roughened internal
`surfaces, or alternatively, the roughened internal surfaces
`may comprise a material having a naturally occurring sur-
`face roughness conformally coating on internal surfaces of
`the chamber body.
`The at least one optical view port may have roughened
`internal surfaces to randomize directionality of incident and
`the diffusely reflected radiation, or alternatively, may com-
`prise a window retracted into a small opening located at any
`location along the perimeter of the chamber body. The
`optical view port may further include a fine metal mesh
`screen over an internal surface thereof to prevent deposition
`of the film on an internal surface of the view port.
`Optionally, a plurality of optical view ports may be provided
`whereby they are located at a variety of locations along the
`perimeter of the chamber body, both above and below the
`wafer surface.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The features of the invention believed to be novel and the
`elements characteristic of the invention are set forth with
`
`particularity in the appended claims. The figures are for
`illustration purposes only and are not drawn to scale. The
`invention itself, however, both as to organization and
`method of operation, may best be understood by reference to
`the detailed description which follows taken in conjunction
`with the accompanying drawings in which:
`FIG. 1 illustrates a processing chamber in accordance
`with the invention whereby the processing chamber has
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`roughened internal surfaces for secondarily and diffusely
`reflecting radiation reflected from a surface of a wafer
`having a film being deposited thereon and having a plurality
`of view ports at varying locations for detecting the diffusely
`reflected radiation.
`
`FIG. 2 illustrates a processing chamber in accordance
`with the invention having a differing shape and differing
`locations of the view ports than that of the processing
`chamber of FIG. 1 and showing a plasma emitted within the
`processing chamber as the radiation source.
`FIG. 3A illustrates, in accordance with the invention, the
`view ports may be a window retracted into a small opening
`or tube located at any location along the perimeter of the
`processing chamber.
`FIG. 3B illustrates an alternate embodiment of the view
`
`ports whereby a metal mesh screen or a bundle of small
`diameter tubes may be provided over the internal surface of
`the view port for protecting the internal optical lens of the
`port entry from deposition of a film thereon.
`FIG. 4 illustrates a processing chamber of the invention
`including the processing chamber of FIG. 1 with a plasma
`therein as shown in FIG. 2 whereby the plasma emits
`radiation which is reflected off the wafer surface and then
`
`diffusely reflected off the internal roughened surfaces of the
`processing chamber and detected by the view port for
`analyzing a deposited film thickness in real-time.
`FIG. 5 illustrates an alternate embodiment of FIG. 4
`
`whereby the radiation may be provided by an external
`radiation source into the processing chamber which is
`reflected off the wafer surface, diffusely reflected off the
`internal roughened surfaces of the processing chamber and
`detected by the view port for analyzing a deposited film
`thickness in real-time.
`
`FIG. 6 illustrates a graphical representation of the instant
`invention showing a typical signal of an Argon emission
`whereby the operating conditions within the deposition
`chamber include the view port having roughened internal
`surfaces.
`
`FIG. 7 illustrates another graphical representation of the
`instant
`invention showing a typical signal of an Argon
`emission whereby the operating conditions within the depo-
`sition chamber include the view port not having roughened
`internal surfaces.
`
`DESCRIPTION OF THE PREFERRED
`
`EMBODIMENT(S)
`
`In describing the preferred embodiment of the present
`invention, reference will be made herein to FIGS. 1-7 of the
`drawings in which like numerals refer to like features of the
`invention.
`
`The instant invention solves the above problems in the
`prior art by providing a reliable and efficient method and
`apparatus for depositing a film on a wafer whereby such
`deposited film thickness is uniform from wafer to wafer. The
`wafers made in accordance with the invention, i.e., having
`uniform film thickness deposited on surfaces thereof, pro-
`vide for reliable and easy subsequent processing steps in the
`production of the resultant semiconductor chip. The inven-
`tion provides in-situ monitoring of deposited film thickness
`having a close loop control of deposited film thickness
`whereby a desired thickness of the film, with an acceptable
`but non-specified error, is deposited for every wafer pro-
`vided within the deposition chamber. The invention advan-
`tageously measures, monitors and controls, in real-time, the
`film deposition across the entire wafer surface by detecting
`
`

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`US 6,762,849 B1
`
`7
`and analyzing radiation secondarily and diffusely reflected
`off roughened internal surfaces of a deposition tool to obtain
`the average film thickness across the wafer, all without
`requiring any direct line-of-sight.
`In so doing, the invention uses a radiation source, pref-
`erably emitted from a plasma formed within the deposition
`chamber, in combination with roughened internal surfaces of
`a deposition chamber as a reflecting surface to perform
`simultaneously both real-time in-situ measuring of a depos-
`ited film thickness and in-situ control of such deposited film.
`Optimally, the radiation emitted from the plasma is reflected
`off the deposited film as the film thickness increases and
`goes through phases. Optionally,
`the deposited film may
`absorb the radiation emitted from the plasma. In accordance
`with the invention,
`the radiation intensity increases and
`decreases in a sinusoidal pattern with a decaying amplitude
`versus time. The film thickness may be calculated from the
`shape of the radiation intensity-versus time curve whereby
`such calculations may be done for one wavelength, or
`alternatively,
`in parallel for a plurality of emissions for
`increased measurement accuracy across the wafer.
`Thus, the various aspects of the present invention provide
`real-time, in-situ measurement of a film being deposited
`onto a surface of a wafer, or other substrate, within a
`processing chamber by detecting and analyzing plasma
`emitted radiation reflected off a wafer surface, or substrate
`surface, and diffusely reflected off internal roughened sur-
`faces of the processing chamber for both monitoring the
`deposition process of the film and automatically controlling
`the deposition of such film in response to the measurements
`taken. The roughness of the internal surfaces of the chamber
`eliminates any signal arising from the etching or depositing
`of the film onto or off the chamber surface.
`The instant invention will be easier understood in accor-
`
`dance with the description below referring to FIGS. 1-7.
`Referring to FIG. 1, a wafer 20 is provided on a support
`pedestal 10 for vertical movement of the wafer after delivery
`by a robot within a plasma deposition chamber 30. The
`reaction chamber 30 may comprise a deposition chamber
`including those used to deposit and/or etch an active plasma
`such as a physical vapor deposition (PVD), Chemical Vapor
`Deposition (CVD), Plasma Enhanced Chemical Vapor depo-
`sition (PECVD), High Density Plasma deposition (HDP)
`and the like. Alternatively,
`the reaction chamber 30 may
`comprise a plasma etching or plasma cleaning tool. The
`reaction chamber 30 has a top portion 32 attached to
`chamber sidewalls 34 which are directly attached to a
`bottom surface of the chamber body. The top portion 32 of
`the chamber body is directly over a wafer 20 provided within
`the chamber body. In the invention, the top portion 32 may
`comprise internal and external surfaces having a variety of
`shapes suitable to build such reactors including, but not
`limited to, dome-shaped, hemispherical, cylindrical, oval,
`square, cylindrical square or parabolic and the like.
`In accordance with the invention, the internal surfaces of
`the chamber body 30 have sufficiently roughened internal
`surfaces to randomize an angle of reflection, or angles
`orientation at a variety of differing positions, relative to an
`incoming radiation 64 reflected off the wafer surface.
`Roughness is particularly important on the internal chamber
`surface above the area where the plasma radiation is present.
`The degree of roughness average (“Ra”) depends in part on
`the radiation utilized for the measurement of the deposited
`film and must be equal to, or alternatively larger than, the
`wavelength used for such film measurement. For example,
`wherein an optical emission of 0.2 pm is used for measuring
`
`8
`the film thickness, the degree of roughness average of the
`internal chamber surfaces must be equal to or larger than 0.2
`pm Ra. The instant invention may be used in viewing any
`wavelength of radiation, however, radiation with a wave-
`length varying from about 0.1 nm to about 5000 nm,
`optimally 190 nm to about 2000 nm, is preferred whereby
`the films are deposited onto the wafer surface to a thickness
`ranging from about 50 A to about 20,000
`As shown in FIG. 1, within the chamber body 30, an
`internal surface 33 of top portion 32, i.e., above the wafer 20,
`and internal surfaces 35 of the chamber sidewalls 34 have
`
`roughened surfaces. In providing the internal roughened
`surfaces 33 and 35, the chamber body 30 may be made of a
`material having a naturally occurring roughness, i.e., having
`a sufficiently rough surface as-is, such as, for example, a
`ceramic, including alpha-alumina, aluminum-nitride, or a
`metal including steel, aluminum, and the like. Alternatively,
`the internal surfaces of the chamber body may be artificially
`roughened by grinding, polishing, sand blasting, etching,
`machining or other techniques that result
`in sufficiently
`rough internal surfaces of the chamber body 30. Still further,
`the internal surfaces of the chamber body may be confor-
`mally coated with a material such as, for example, sprayed
`or painted ceramic or metal
`to provide the roughened
`surfaces thereon such internal surfaces.
`In a preferred
`embodiment, the reaction chamber 30 comprises a rough-
`ened alpha-alumina or aluminum-nitride ceramic in combi-
`nation with an aluminum metal chamber body 30.
`The chamber body also has at least one optical view port
`or port entry or window 40 provided at any location along
`a perimeter of either the sidewalls 34 or the top portion 32
`of the ceramic chamber body. Alternatively, a plurality of
`optical port entries 40 may be provided at a variety of
`locations along the perimeter of the sidewalls 34 and/or top
`portion 32 of the ceramic chamber body as shown in FIG. 2.
`As discussed further below, the optical port entry or window
`is used to receive and view radiation 66 reflected off the top
`portion 32 and sidewalls 34 within the chamber body for
`in-situ monitoring and controlling of the deposited film
`thickness. Accordingly, a plurality of potential locations may
`exist on the chamber body whereby the optical fibers may be
`pointed a variety of differing directions for collecting the
`reflected plasma emitted radiation for analysis to determine
`the film thickness. As shown in FIG. 1, the view port 40‘
`depicted at the top portion 32 of the chamber is directly over
`the wafer so as to collect the reflected radiation in the
`
`shortest distance possible thereby improving signal to noise
`and result in a more accurate film measurement.
`
`Preferably, the internal surface of the optical port entry or
`window 40 within the chamber body has a roughened
`surface. The inside surface of the optical view port
`is
`roughened so as to randomize directionality of incident and
`reflected radiation which eliminates intensity fluctuations
`due to film deposition onto the inside surface of the view
`port, as well as allowing for the continuous detection of the
`reflected radiation. The optical port entry may comprise a
`material that is both optically transparent and relatively inert
`to the types of plasma that are used in the deposition
`chamber. A relatively inert material is desired so that any
`aggressive gases or chemical plasmas within the reaction
`chamber do not react with the internal material of the optical
`port entry. The optically transparent port entry 40 may
`comprise a material
`including sapphire, alpha-alumina,
`yttrium aluminum garnet, and the like.
`Alternatively, as shown in FIG. 3A, to prevent deposition
`of the film onto the internal surface of