Subclass
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`SSUECLASSIFICATION
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`PATENT DATE
`UTILITY
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`NUMBER
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`‘SERIAL NUMBER.
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`5711849
`ua
`||
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`
`
`AN 27 1998
`
`mam
`
`Ate tm)
`
`
`
`
`et
`
`Foreign priority claimed
`O yes {dno
`35 USC 119 conditions met O
`no
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` Verified and Acknowledged
`
`EMoar J20 Center, BAF,
`“2Cf
`
`2OF4
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`U.S. DEPT. OF COMM.) PAT. & TM—PTO-436L_(Rev.12
`
`
`
`—
`_ eer!
`
`Assistant Examiner
`/
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`
`Syd
`AAi SAY
`LE f Mw vy
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`. .
`Sheets Drwg.
`<7SS) 2a7
` “MARTIVANGEBRANNOT
`
`
`ISSUE
`BATCH
`& Primary Examiner|NUMBER AAS
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`
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`
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`
`
`(Rev. 8/92)
`;
`on .
`—nne
`‘ERSEA reeey
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`Page | of 210
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`PRIMARY EXAMINER
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`WARNING:
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`Theinformation disclosed herein may berestricted. Unauthorized disclosure may be prohibited ff
`by the United States Code Title 35, Sections 122, 181 and 368. Possession outside the U.S.
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`Patent & Trademark Office is restricted to authorized employees and contractors only.
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`Samsung Exhibit 1002
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`PARTS OF APPLICATION
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`Samsung Exhibit 1002
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`ia y
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`i aainani:
`
`a
`ae
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`.
`
`. PATENT APPLICATION
`APPROVEDFORLICENSETy:
`ATA ape8352S ad
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`08433623
`bees
`>.
`ae
`ere
`CONTENTS — a1|
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`4
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`
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`Be
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`1. Appjication _—__________ papers.
`
`2. (Te LE PEE, S/W ATURE
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`oussren[TO
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`INDEX OF CLAIMS
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`nee i
`ORIGINAL CLA’
`IFICATION
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`CROSSREFERENCED)
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`2
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`class
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`ART UNIT
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`Page 4 of 210
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`sie, tf 666.) (RIGHT OUTSIDE)
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`INTERFERENCE SEARCHED
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`Class
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`PATENT APPLICATION SERIAL NO.
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`a
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`B<
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`*
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`U.S. DEPARTMENT OF COMMERCE
`PATENT AND TRADEMARK OFFICE
`FEE RECORD SHEET
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`BAR CODE LABEL
`
`SERIAL NUMBER
`
`08/433,623
`
`FILING DATE
`
`05/03/95
`
`GROUP ART UNIT
`
`1109
`
`DANIEL L. PLAMM, WALNUT CREEK, CA;
`*
`
`JOHN P. VERBONCOEUR, HAYWARD, CA.
`
`X*CONTINUING DATARS ARR ARR AHR RR RHR RRR
`VERIFIED ~
`'
`
`**FOREIGN/PCT APPLICATIONS**####kkHH RH
`VERIFIED
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`FOREIGN FILING LICENSE GRANTED 08/08/95
`INDEPENDENT
`CLAIMS
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`*keee SMALL ENTITY *****
`FILING FEE
`ATTORNEY DOCKET NO.
`RECEIVED
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`$501.00
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`16655-000100
`
`ADDRESS
`
`RICHARD T OGAWA
`TOWNSEND AND TOWNSEND KHOURIE AND CREW
`STEUART STREET TOWER
`ONE MARKET PLAZA 20TH FLOOR
`SAN FRANCISCO CA 94105
`
`PROCESS OPTIMIZATION IN GAS PHASE DRY ETCHING
`
`WL U.S. PATENTAPPLICATION
`
`COMMISSIONER OF PATENTS AND TRADEMARKS Date
`
`This is to certify
`
`that annexed heretois a true copy from the records of the United States
`
`Patent and Trademark Office of the application whichis identified above.
`By authority of the
`
`Certifying Officer.
`
`Page 7 of 210
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`Page 7 of 210
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`.
`Sir:
`Transmitted herewith for filing is the
`[x] patent application of
`[ ] design patent application of
`[ ] continuation-in-part patent
`
`|Boer:[DANIEL u{euan
`
`appligation of
`
`VERBONCOEUR
`
`I hereby certify that this is being deposited with the
`United States Postal Service "Express Mail Post Office
`to Addressee" service under 37 CFR 1.10 on the date
`indicated above and is addressed to the Commissioner
`
`
`
`Date of Deposit___MAY3,1995.
`
` Cn
`"Express Mail" Label No.
`_7B175028216US
`*
`
`COMMISSIONER OF PATENT AND TRADEMARKS
`Washington, D. C. 20231
`
`For: PROCESS OPTIMIZATION IN GAS PHASE DRY ETCHING
`
`Enclosed are:
`
`[x] informal drawing(s).
`
`sheet(s) of [ ] formal
`13___
`[x]
`{] An assignment ofthe invention to
`(x] A[] signed [x] unsigned Declaration & Power of Attorney.
`{] AE[] signed [] unsigned Declaration.
`[] A Power ofAttorney.
`[] A verified statement to establish small entity status under 37 CFR 1.9 and 37 CFR 1.27.
`[] A certified copy ofa
`:
`application.
`[]
`Information Disclosure Statement under 37 CFR 1.97.
`[]
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`In view of the Unsigned Declaration as filed with this application and pursuant to 37 CFR §1.53(d),
`Applicant requests deferral of the filing fee until submission of the Missing Parts of Application.
`
`DO NOT CHARGETHE FILING FEE AT THIS TIME.
`
`Telephone:
`(415) 543-9600
`APPNOFEE.TRN 12/92
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`.
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`
` T. Ogawa
`
`i
`Reg. No.: 37,692
`Attorneys for Applicant
`
`Page 8 of 210
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`
` PATENT APPLICATION
`
`Attorney Docket No. 016655~-0001
`
`Inventors:
`
`Daniel L. Flamm, a U.S. citizen,
`residing at
`476 Green View Drive
`Walnut Creek, California
`
`94596; and
`
`John Verboncoeur, a U.S.
`citizen, residing at
`3350 Oakes Drive
`Hayward, California
`
`94542.
`
`Assignee:
`
`Jonathan International
`476 Green View Drive
`Walnut Creek, CA
`94596
`
`Entity:
`
`Small
`
`TOWNSEND and TOWNSEND KHOURIE and CREW
`Steuart Street Tower, 20th Floor
`One Market Plaza
`San Francisco, California 94105
`(415) 326-2400
`
`Page 9 of 210
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`
`
`
`1 4,VOTVerve
`PATENT
`Attorney Docket No. 016655-0001
`PROCESS OPTIMIZATION IN GAS PHASE DRY ETCHING
`
`5
`
`:
`
`BACKGROUND OF THE INVENTION
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`
`The present invention relates to integrated circujts
`and their manufacture.
`The present invention is illustrated
`in an example with regard to plasma etching, and more
`particularly to plasma etching in resist strippers in
`semiconductor processing. But it will be recognized that the
`invention has a wider range of applicability in other
`technologies such as flat panel displays,
`large area substrate
`processing, and the like. Merely by way of example,
`the
`invention may be applied in plasma etching of materials such
`as silicon, silicon dioxide, silicon nitride, polysilicon,
`photoresist, polyimide,
`tungsten, among others.
`Industry utilizes or has proposed several techniques
`for plasma etching. One such method is conventional chemical
`gas phase dry etching. Conventional chemical gas phase dry
`etching relies upon a reaction between a neutral gas phase
`species and a surface material layer, typically for removal.
`. The reaction generally forms volatile products with the
`surface material layer for its removal.
`In such method,
`
`the
`
`neutral gas phase species may be formed by way of a plasma
`discharge.
`
`A limitation with the conventional plasma etching
`technique is obtaining and maintaining etching uniformity
`within selected predetermined limits.
`In fact,
`the
`conventional technique for obtaining and maintaining uniform
`etching relies upon a "trial and error" process.
`The trial
`and error process often cannot anticipate the effects of
`parameter changes for actual wafer production. Accordingly,
`the conventional technique for.obtaining and maintaining
`etching uniformity is often costly,
`laborious, and difficult
`to achieve.
`
`Another limitation with the conventional plasma
`etching technique is reaction rates between the etching
`species and the etched material are often not available.
`Accordingly, it is often impossible to anticipate actual etch
`
`J
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`rates from reaction rate constants since no accurate reaction
`
`In fact, conventional
`rate constants are available.
`techniques require the actual construction and operation of an
`etching apparatus to obtain accurate etch rates. Full scale
`prototype equipment and the use of actual semiconductor wafers
`are often required,
`thereby being an expensive and time
`consuming process.
`From the above it is seen that a method and
`
`apparatus of etching semiconductor wafers that is easy,
`reliable, faster, predictable, and cost effective is often
`desired.
`
`SUMMARY OF THE INVENTION
`
`According to the present invention, a plasma etching
`method that includes determining a reaction rate coefficient
`based upon etch profile data is provided.
`The present plasma
`etching method provides for an easy and cost effective way to
`select appropriate etching parameters such as reactor
`dimensions,
`temperature, pressure, radio frequency (rf) power,
`flow rate and the like by way of the etch profile data.
`In a specific embodiment, the present invention
`provides an integrated circuit fabrication method.
`The
`present method includes steps of providing a plasma etching
`apparatus having a substrate therein. The substrate includes
`a top surface and a film overlying the top surface.
`The film
`includes a top film surface.
`The present method also includes
`chemically etching the top film surface to define an etching
`profile on the film, and defining etch rate data which
`includes an etch rate and a spatial coordinate from the
`etching profile.
`A step of extracting a reaction rate
`constant from the etch rate data, and using the reaction rate
`constant in adjusting a plasma etching apparatus is also
`included.
`
`the present
`In an alternative specific embodiment,
`invention also provides a method of designing a reactor.
`The
`present method includes providing a first plasma etching
`apparatus having a substrate therein. The substrate has a top
`surface and a film overlying the top surface.
`The film has a
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`3
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`The present method also includes chemically
`top film surface.
`etching.the top film surface to define an etching profile on
`the film, and defining etch rate data which has an etch rate
`and a spatial coordinate from the etching profile.
`A step of
`extracting a reaction rate constant from the etch rate data,
`and using the reaction rate constant in designing a second
`plasma etching apparatus is also included.
`A further alternative embodiment provides another
`method of fabricating an integrated circuit device. The
`present method includes steps of providing a uniformity value
`for an etching reaction. The etching reaction includes a
`substrate and etchant species.
`The present method also
`includes defining etching parameterfg ranges providing the
`uniformity value.
`A step of adjusting at least one of the
`etching parameters to produce a selected etching rate is also
`included.
`The etching rate provides an etching condition for
`fabrication of an integrated circuit device.
`The present invention achieves these benefits in the
`context of known process technology. However, a further
`understanding of the nature and advantages of the present
`invention may be realized by reference to the latter portions
`‘of the specification and attached drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Fig. we a simplified diagram of a plasma etching
`apparatus accordingto the present invention;
`Fig. 1A‘’is a simplified cross-sectional view of a
`wafer profile according,gf the plasma etching apparatus of
`Fig. 1;
`Fig.
`> ks a simplified diagram of an alternative
`
`embodiment of a plasma etching apparatus according to the
`present invention;
`
`Figs. Alco simplified flow diagrams of plasma
`Fig. sx a plot of uniformity,
`temperature,
`
`etching methods acgording to the present invention;
`
`pressure, and gap for an etching process according to the
`present invention;
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`4
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`Fig. 6 is a simplified plot of 1/ash rate vs. LCD
`plate number according to the present invention;
`
`Figs. (2stusteate an example with regard to
`circular substrates according to the present invention; and
`Figs. 104 illustrate an example with regard to
`rectangular substrates according to the present invention.
`
`DESCRIPTION OF THE SPECIFIC EMBODIMENT
`U:
`
`. - Fig. 1 is a simplified diagram of a plasma etching
`apparatus 10 according to the present invention.
`The plasma
`etching apparatus also known as a co-axial reactor includes at
`least three processing zones.
`The three processing zones are
`defined as a plasma generating zone (PG) 13, a transport zone
`(TZ) 15, a plate stack zone (PS) 17, and others. Also shown
`are a chemical feed F and exhaust E.
`The plasma generating
`zone provides for reactant species in plasma form and others.
`Excitation is often derived from a 13.56 MHz rf discharge 8
`and may use either capacitor plates or a wrapped coil, but can
`also be derived from othersou ces. The co-axial reactor 10
`eontre ier
`-also includes a chemical,ftowsource 14 and a temperature and
`pressure control 12, among other features.
`Chemical effects are often enhanced over ion induced
`
`effects and other effects by way of perforated metal shields
`18 to confine the discharge to a region between an outer wall
`16 and shields 18.
`The co-axial reactor relies substantially
`upon diffusion to obtain the desired etching uniformity.
`The
`co-axial reactor,also relies upon a chemical etch rate which
`is diffusion ,t7
`.
`In particular,
`the chemical etch rate
`is generally defined as a chemical reaction rate of etchant
`species plus at least a diffusion rate of etchant species.
`When the diffusion rate of etchant species is much greater
`than the chemical reaction rate,
`the chemical etch rate is
`often determined by the diffusion rate.
`A more detailed
`analysis of such chemical etch rate will be described by way
`of the subsequent embodiments.
`Etchant species from the plasma generating zone
`diffuse through the transport zone 15 of the reaction chamber,
`
`|
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`5
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`5
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`and enter the plate stack zone space over surfaces of
`substrates 21.
`A concentration of etchant in the transport
`zone, which is often annular, between the plasma generating
`zone and the plate stack zone is defined as njy. As etchant
`diffuses radially from the transport zone into the plate stack
`zone and over surfaces of the substrates, it is consumed by ‘an
`etching reaction.
`A reactant concentration above the
`substrate can be defined as n,(r,z), where r is the distance
`from the center of the substrate and z is the distance above
`
`10
`
`ria!
`
`|
`
`A diffusive velocity v, of etchant species in
`the substrate.
`_the plate stack zone is characterized by Fick's law.
`
`Vn
`v,=-D—
`ny
`
`In a specific embodiment, a gap dgap above the
`substrate is much less than the lateral extent d,,,<<r and gas
`phase mass transfer resistance across the small axial distance
`is negligible so that the axial (z-direction) term of the
`concentration gradient can be ignored.
`The embodiment can be
`applied without this restriction; however, numerical mesh
`. computer solutions are then required to evaluate the reaction
`rate constant and uniformity.
`In the embodiment,
`the surface
`etching reaction bears a first order form:
`
`15
`
`20
`
`O+S ~ SO
`
`where
`
`S is a substrate atom (e.g., resist unit "mer"); and
`O is the gas-phase etchant (for example oxygen
`atoms) with certain etching kinetics.
`The first order etching
`25____reaction can be defined as follows:
`Aioi¥
`Ryg=nAyTe BacBF
`
`where
`
`Ro, defines a reaction rate;
`n, defines a concentration;
`A defines a reaction rate constant;
`
`30
`
`T defines a temperature;
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`6
`
`E,cr defines an activation energy; and
`R defines a gas constant.
`An example of the first reaction is described in D.L. Flamm
`and D.M. Manos "Plasma Etching," (1989), which is hereby
`incorporated by reference for all purposes. Of course, other
`order reactions, reaction relations, and models may be applied
`depending upon the particular application.
`An example of an etched substrate 21 from the plate
`stack zone is illustrated by Fig. 1A. The substrate 21 is
`defined in spatial coordinates such as z and r.
`The substrate
`includes a bottom surface 23, sides 25, and a top surface film
`27. As can be seen, the top surface film includes a convex
`region, or etching profile.
`The etching profile occurs by way
`of different etch rates along the r-direction of the substrate
`corresponding to different etchant species concentrations.
`A
`concentration profile n,(r,z) is also shown where the greatest
`concentration of reactant species exists at the outer
`periphery of the top surface film.
`In the present invention,
`an etch rate constant may be obtained by correlation to the
`etching profile.
`By way of the etch rate constant, other
`etching parameters such as certain reactor dimensions
`including a distance between substrates, pressure,
`“temperature, and the like are easily calculated.
`Fig. 2 illustrates an alternative example of an
`The
`etching apparatus 50 according to the present invention.
`etching apparatus 50 is a single wafer etching apparatus with
`elements such as a chamber 53, a top electrode 55, a bottom
`
`The
`
`electrode 57, a power source 59, a platen 64, and others.
`bottom electrode 57 is at a ground potential, and the top
`electrode is operably coupled to the power source 59 at a high
`voltage potential.
`A plasma exists in a region 54 between the
`top electrode 55 and the bottom electrode 57, which is often a
`grid configuration or the like. Reactant species are directed
`via power source from a plasma source to a wafer substrate 61
`by diffusion.
`A temperature and pressure controller 67 and a
`flow controller 69 are also shown.
`The etching apparatus also
`includes a chemical source feed F and a exhaust E. Of course,
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`7
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`other elements may also be available based upon the particular
`application.
`By way of a plate 63 interposed between the wafer
`substrate 61 and the bottom electrode 57,
`the reactant species
`do not directly bombard the wafer substrate.
`The plate is |
`preferably made of an inert material appropriate for the
`particular etching such as pyrex or glass for resist ashing,
`alumina for fluorine atom etching of silicon, silicon nitride,
`or silicon dioxide, and the like.
`In an ashing reaction,
`the
`plate is placed at a distance ranging from about 5 mm to 50 mm
`and less from the wafer substrate 61. Of course, other
`dimensions may be used depending upon the particular
`application.
`The reactant species are transported via
`diffusion from the plasma source to the wafer substrate around
`the periphery of the plate ‘63. Accordingly,
`the reaction rate
`at the wafer substrate is controlled by a balance between
`chemical reaction and diffusion effects, rather than
`directional bombardment.
`
`By way of the diffusion effects, an etching rate
`constant may be obtained for the etching apparatus 50 of Fig.
`_2.
`In particular,
`the etching rate constant derives from a
`etching profile 65, which can be measured by conventional
`techniques.
`The present invention uses the etching rate
`constant to select other etching rate parameters such as
`reactor dimensions) such<ae spacing between the substrate and
`its adjacent surface,
`temperatures, pressures, and the like.
`But the present invention can be used with other reactor types
`where etching may not be controlled by diffusion.
`For
`example,
`the present invention provides a reaction rate which
`can be used in the design of reactors where diffusion does not
`control such as a directional etcher and the like.
`The
`
`reaction rate constant may also be used in the directional
`etcher to predict an extent of, for example, undercutting of
`unprotected sidewalls while ion bombardment drives reaction in
`a vertical direction. Of course,
`the invention may be applied
`to other reactors such as large batch, high pressure,
`chemical, single wafer, and others. The invention can also be
`applied to different substrate materials, and the like.
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`PlasmaEtchingMethod
`
`' Figs. 3-5 illustrate simplified flow diagrams of
`plasma etching methods according to the present invention.
`The
`present methods provide for improved etching conditions by
`way, a reaction rate constant derived from, for example, an .
`etching profile.
`It should be noted that the present methods
`as illustrated should not be construed as limiting the
`ill in
`invention as defined in the claims. One of ordinary
`the art would easily recognize other applications to, he
`inventions described here.
`In a specific embodiment, a method of extracting a
`rate constant 100 for a plasma etching step according to the
`present invention is illustrated by the flow diagram of Fig.
`3.
`A substrate with an overlying film is placed into a plasma
`etching apparatus or the like.
`The overlying film is defined
`as an etching film.
`In the present embodiment,
`the overlying
`film is a photoresist film, but can also be other films such
`as a silicon film, a polysilicon film, silicon nitride,
`silicon oxide, polyimide, and the like.
`A step of plasma etching the film is performed by
`The plasma etching step occurs at constant pressure
`" step 101.
`and preferably constant plasma source characteristics.~@ More
`preferably,
`the plasma etching step occurs isothermally at
`temperature T,, but can also be performed with changing
`temperatures where temperature and time histories can be
`monitored.
`Plasma etching of the film stops before the
`endpoint (or etch stop). Alternatively, plasma etching stops
`at a first sign of the endpoint (or etch stop).
`The plasma
`etching step preferably stops before etching intoan etch stop
`layer underlying the film to define a "clean": etching profile.
`The substrate including etched film is removed from
`the chamber of the plasma etching apparatus.
`The etched film
`includes an etching profile (step 103) made by way of plasma
`etching (step 101).
`The etching profile converts into a
`relative etch rate, relative concentration ratio, a relative
`etch depth, and the like at selected spatial coordinates.
`The
`relative etch rate is defined as an etch rate at a selected
`
`25
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`35
`
`spatial coordinate over an etch rate at the substrate edge.
`
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`

`9
`
`The relative concentration ratio is defined as a concentration
`
`of etchant species at a selected spatial coordinate over a
`concentration of etchant at the substrate edge.
`In x-y-z coordinates,
`the relative etch rate in the
`z-direction, and the spatial coordinates are defined in the x-
`y coordinates.
`The etching profile is thereby characterized
`as a relative etch rate u, a x-location, and a y-location“tn.
`(x, y).
`In cylindrical coordinates,
`the relative etch rate i$
`also in the z-direction, and the spatial coordinates are
`defined in the r and 6 coordinates.
`The etching profile is
`characterized as a relative etch rate u, a r-location, and a
`@-location (u, r, 8). An array of data points in either the
`x-y coordinates or r-8 coordinates define the etching
`profile.
`The array of data points can be defined as ann x 3
`array, where n represents the number of points sampled and 3
`represents the etch rate and two spatial dimensions. Of
`course,
`the choice of coordinates depends upon the particular
`application.
`in a non-isothermal condition, an
`Optionally,
`average etch rate is measured.
`By approximate integration of
`a time dependent etch rate, suitable starting point
`‘ approximations for an etching rate constant pre-exponential
`and activation energy can be selected. The etch rate is
`integrated over time (and temperature) using measured
`temperature-time data (or history). An etched depth profile
`and the etching rate from the integration can then be compared
`with actual data.
`A rate constant is appropriately readjusted
`and the aforementioned method is repeated as necessary.
`An etch constant (or a reaction rate constant) over
`diffusivity (k,./D) and an etch rate at an edge is calculated
`at step 105. The etch constant over diffusivity correlates
`with data points representing the etch rate profile.
`In x-y
`coordinates,
`the eationship between k,,/D and the relative
`etch rate u(x,y) fs{detinea as follows:
`where
`
`a and b define substrate lengths in, respectively,
`an x-direction and a y-direction.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`Page 18 of 210
`
`Page 18 of 210
`
`

`

`
`
`10
`
`*
`
`-T}} mK
`
`r\o%
`
`coshl/kyo/D+ (inat/b) “a costy
`mm coshl/K,o/D* (mn/b) =
`+
`u(x,y)=>> sin
`coshl/k,,/D+ (mn 2 cosMEX
`A
`2
`2
`cosh/K,_/D* (mn/a) 72
`
`k
`
`+
`
`
`
`—
`
`ee
`
`.
`In cylindrical coordinates, the relationship between
`the etch constant over diffusivity k,,/D and the relative etch
`rate u(r) is defined as follows:
`
`Oa f~
`Vaya
`
`*
`
`u(r) =
`
`k
`I, >"
`—wZ{ D |
`k
`
`I
`
`|
`
`
`
`where
`:
`a
`a is an outer radius (or edge) of the substrate 3
`In step 106, a diffusivity is calculated for the
`particular etchants.
`The binary diffusivity D,, may be
`calculated based upon the well known Chapman-Enskog kinetic
`———.___theory equation:
`“ThA ih
`
`-
`
`5
`
`.
`
`Sur
`vy
`
`:
`
`Dag = 2.2646 X 105
`
`T
`
`1+_—
`1
`Ms
`My
`Gxp2QDasc
`
`10.
`
`where
`
`_
`
`T is a temperature;
`c is a total molar concentration;
`M, and Mp are molecular weights;
`Dap is a binary diffusivity;
`Ogg is a collision diameter; and
`Collision
`.
`Qpap is ay
`integral.
`The Chapman-Enskog kinetic theory equation is described in
`detail in part III of R.B. Bird, W.E. Stewart, and E.N.
`Lightfoot, "Transport Phenomena," Wiley (1960) which is hereby
`incorporated by reference for all purposes. Of course, other
`techniques for calculating a diffusivity may also be used.
`
`&
`
`15
`
`20
`
`Page 19 of 210
`
`Page 19 of 210
`
`

`

`bros (a
`
`11
`
`The equivalent volumetric reaction rate constant k,, is
`——_-_——___derived from the diffusivity as follows.
`—y\).0F
`,
`T\t
`‘
`
`k
`
`the surface
`Once the reaction rate constant k,, is extracted,
`reaction rate constant k, may be isolated from the previous
`equation as follows.
`
`k= (Kye) Ayap
`
`Repeat steps 101-106 at different temperatures Ty,
`ee
`T3..-.T, to calculate additional reaction rate constants k(T>),
`k(T3)...k(T,).
`The steps are repeated at least two times and
`more, and preferably at least three times and more. Each
`temperature is at least 5 °C greater than the previous
`temperature. Of course, the selection of temperatures and
`trial numbers depend upon the particular application.
`Extract an activation energy E,,, for a first order
`reaction from the data k(T,), k(T3)..,.kK(T,) at Tz, T3..-Ty
`collected via step 109 by way of eneei equation:
`
`5
`
`10
`
`15
`
`k, (1) =ayT e ™
`
`20
`
`————"—— The activation energy is preferably calculated by a least
`square fit of data collected at step 109 or any other suitable
`statistical technique.
`By way of the same equation,
`the
`present method calculates surface reaction rate constant k, at
`any temperature.
`In step 111, a concentration n, at the substrate
`edge is calculated.
`The concentration n, deduces from the
`following relationship:
`éés
`N=R,/Kyes
`
`&
`
`where
`
`sa 25
`
`R,,is an etch rate.
`
`From the concentration and the surface reaction rate,
`the
`particular etching step can be improved by way of adjusting
`selected etching parameters.
`
`Page 20 of 210
`
`Page 20 of 210
`
`

`

`
`
`12
`
`In an alternative specific embodiment, a method to
`"tune" a plasma source using a loading effect relationship (or
`equation).
`is illustrated by the simplified flow diagram 200 of
`Fig. 4.
`The method includes a step 201 of measuring an etch
`rate against an effective etchable area A,.
`The effective
`etchable area changes by varying the number m of wafers in the
`reactor, varying the size of the wafer, or the like.
`The
`effective area can be changed 209 by altering a gap between a
`wafer and its above surface 211, changing wafer quantity in
`the reactor 213, and varying substrate support member
`dimensions 215.
`The method preferably occurs at constant
`temperature and pressure. However,
`the effective etchable
`area may also be varied by way of changing a temperature
`and/or a pressure.
`The method calculates a uniformity value (step 217)
`from the measured values of etch rate vs. effective area in
`
`10
`
`15
`
`The uniformity is calculated by, for
`
`steps 211, 213, and 215.
`~~example:
`ant
`o
`
`-R
`La-,
`uniformity=100|ee
`ay31
`
`mm
`
`20
`
`25
`
`30
`
`where
`
`Ryax is a maximum etch rate;
`Ryry is a minimum etch rate;
`m is a sample number;
`R; is a general etch rate for an ith sample;
`uniformity is a planarity measurement in
`
`/
`percentage.
`In a specific embodiment, a uniformity of about 90% and
`greater or preferably 95% and greater indicates that the
`effective area of the substrate is substantially equal to the
`actual substrate area (step 221) via branch 216. Of course,
`other methods of calculating a uniformity from etch rates and
`effective areas may also be used depending upon the particular
`application. Alternatively, an etching profile is measured
`and the effective area A,-- is calculated (step 219) by way
`of, e.g.,
`the-loading effect relationship.
`
`Page 21 of 210
`
`Page 21 of 210
`
`

`

`13
`
`At least two and more different effective etchable
`
`areas (step 223) are measured, or preferably at least three
`and more different etchable areas are measured.
`
`the flow diagram returns via branch 224 to step
`Alternatively,
`209, and takes another etch rate measurement at a different
`°
`effective area.
`The flow diagram then turns to step 203.
`In step 203, a supply of etchant sT in the reactor
`is calculated. Based upon the different etchable areas a
`slope MAz,¢¢ deduces from the loading effect relationship as
`follows.
`
`1. _ KA,+F, MAgee
`1
`Rm) kn, k,st
`st
`
`noretim is the etching rate at the boundary between the
`
`plate stack zone and transport zone when m substrates are
`present in the reactor.
`The first term includes a
`recombination term proportional to the total effective area A,
`which acts to catalyze loss of etchant on reactor surfaces in
`the reactor plus a convection term F.
`The second term is the
`loading effect relation, where the reciprocal etch rate is
`proportional to the amount of effective etchable substrate
`“area Ajre- times the number of substrates m. When the etching
`across a substrate is uniform, A,rr is the geometrical
`substrate area Aye When etching is nonuniform, on the other
`hand, Ag¢e is a function of k,,/D and geometrical reactor
`dimensions.
`The supply of etchant st may be calculated for a
`different plasma source or plasma source parameters such as
`temperature, pressure, or the like by repetition 207 of steps
`201 and 203.
`By way of the supply of etchant to the reactor,
`other plasma source parameters may be varied to obtain desired
`etching rates and uniformity for the particular reactor.
`Step 205 provides for the modification of chamber
`materials and the like to reduce slope numerator
`(k,, A, + F)
`in selecting the desired etching conditions.
`The chamber
`materials can be modified to reduce, for example,
`the
`recombination rate in the reactor. The recombination rate is
`
`directly related to the effective reactor recombination area
`A,.
`In step 205,
`the recombination rate can be adjusted by
`
`15
`
`20
`
`25
`
`30
`
`35
`
`——
`
`Page 22 of 210
`
`Page 22 of 210
`
`

`

`14
`
`"
`
`5
`
`10
`
`15
`
`20
`
`25
`
`
`30
`
`changing A, via changing chamber material, coating chamber
`surfaces with, for example, a product sold under the trademark
`TEFLON™ or KALREZ™ and the like, among others. Alternatively,
`the slope numerator flow term F is reduced when F contributes
`as a substantial loss term. Of course, the particular
`materials used depend upon the application.
`In step 207,
`the method changes plasma source
`parameters such as rf power,
`flow rate, and the like to select
`desired etching conditions. Once one of the aforementioned
`parameters is adjusted,
`the method returns to step 201 via
`branch 208. At step 201, an etch rate vs. effective etchable
`area is measured and the method continues through the steps
`until: desired etching condition are achieved. Of course,
`other sequences of the aforementioned steps for tuning the
`plasma source may also exist depending upon the particular
`application.
`Fig. 5 is a simplified flow diagram for a method of
`selecting a desired uniformity and desired etching parameters
`within selected ranges to provide a desired etch rate for a
`particular etching process. The etching parameters include
`process variables such as reactor dimensions, a pressure, a
`' temperature, and the like for a particular substrate and
`reactants. Other.etching parameters may also be used
`depending upon theparticular application.
`In step 301, select a uniformity for the selected
`substrate and the reactants.
`The selected uniformity becomes
`an upper operating limit for the reaction according to the
`present method.
`The upper operating limit ensures a "worst
`case" uniformity value for an etched substrate according this
`method. Uniformity can be defined by, for example:
`[t-
`
`& uniformi ty=100,—2"="JRi A
`
`4
`20m3 ~*M
`
`be
`
`Ryax-R
`
`yet
`
`er”
`
`where
`
`—
`
`Ryax is a maximum etch rate;
`Ryry is a minimum etch rate;
`m is a sample number;
`
`Page 23 of 210
`
`Page 23 of 210
`
`

`

`15
`
`R; is a general etch rate for an ith sample;
`uniformity is a planarity measurement in
`
`percentage.
`In certain embodiments,
`the selected uniformity ranges from
`
`about 90 % and greater or more preferably 95 % and greater.”
`Of course, other uniformity values may be selected based upon
`the particular application.
`Based upon the selected uniformity, use the selected
`uniformity as a stating point to extract a plurality of
`teaction rate constants k,.
`The reaction rate constants may
`be also be obtained by an input