Ulllted States Patent [19]
`Cheung et al.
`
`US005968324A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,968,324
`Oct. 19, 1999
`
`[54] METHOD AND APPARATUS FOR
`DEPOSITING ANTIREFLECTIVE COATING
`
`1-187239
`6-240459
`
`7/1989 Japan .
`8/1994 Japan ~
`
`[75] Inventors: David Cheung, Foster City; Joe Feng,
`Santa Clara; Judy H- Huang, LOS
`GatOS; Wai-Fan Yall, Mountain View,
`all Of Calif-
`
`[73] Assignee: Applied Materials, Inc., Santa Clara,
`Calif
`
`[21] Appl. No.: 08/672,888
`_
`_
`Flled'
`
`[22]
`
`Jun‘ 28’ 1996
`.
`.
`Related [18' Apphcatlon Data
`-
`-
`-
`-
`-
`t
`63 C t
`—
`— tf l
`t N.08567338D .5
`lggninséiaférllrégar 0 app lea Ion 0
`[
`]
`/
`’
`’
`e0 ’
`6
`Int. Cl. ................................................... .. C23C 14/54
`[51]
`[52] US. Cl. .................. .. 204/192.28; 427/569; 427/579;
`438/636; 438/786; 438/787; 438/788; 438/792
`[58] Field Of Search ..................... .. 204/192.28; 427/569,
`427/579; 438/636, 786, 787, 788, 792
`_
`References C1ted
`U.S. PATENT DOCUMENTS
`
`[56]
`
`OTHER PUBLICATIONS
`Tsu, et al, “Local atomic structure in thin ?lms of silicon
`nitride and silicon diimide produced by remote plasma—en
`hanced chemical—vapor deposition,” Physical RevieW B:
`Condensed Matter, vol. 33, No. 10, American Physical
`Society, pp 70694076, May 1986_
`Database CAPLUS, Chemical Abstracts, vol. 105, (Colum
`bus, OH), abstract No. 49711, issued 1986, ‘Infrared spec
`troscopic study of silcon oxide (SiOx) ?lms produced by
`plasma enhanced chemical vapor deposition’, Pai, et al,
`Journal of Vacuum Science and Technology, 4(3, Pt. 1),
`689—94, (No month available).
`Database CAPLUS, Chemical Abstracts, vol. 119, (Colum
`bus OH) abstract No. 60911 issued 1993 Smith et al
`’
`’
`’
`’
`‘Chemistry of silicon dioxide plasma deposition’, Journal of
`the Electrochemical Society, 140(5), 1496—503, (No month
`available)
`Database CAPLUS, Chemical Abstracts, VOL 120, (Comm
`bus, OH) abstract No. 121821, issued 1994, Kushner, Mark
`J” ‘Plasma chemistry of helium/oxygen/silane and heliurn/
`nitrous oxide/silane mixtures for remote plasma—activated
`chemical vapor deposition of silicon dioxide’, Journal of
`Applied Physics, 1993, 74(11), 6538—53, (NO month avail
`able)
`
`3,990,100 11/1976 Mamine et al. ........................ .. 357/30
`
`(Ust Continued on next Page)
`
`4,877,641 10/1989 Dory .............. ..
`
`.. 427/38
`
`~
`
`~
`
`-
`
`,
`
`,
`
`,
`
`,
`
`5’288’527
`5 330 883
`573407621
`5,436,463
`5,665,214
`
`FOREIGN PATENT DOCUMENTS
`
`0 291 181 A2 11/1988 European Pat. Off. .
`0 588 087 A2 3/1994 European Pat. Off. .
`
`4,888,190 12/1989 Felts 61 a1.
`4,910,122
`3/1990 Arnold et al.
`4,992,299
`2/1991 Hochberg et al.
`4,992,306
`2/1991 Hockberg et al.
`5,068,124 11/1991 Batey et a1~
`flail“? a:
`2/1994 Jousse et a1‘
`7
`427/571
`8/1994 MatsumOto et aL _
`250/55904
`7/1995 Rostoker ............ ..
`9/1997 Iturralde ........................... .. 204/29803
`
`. 427/10
`430/313
`427/38
`427/2553
`427/39
`
`427/579
`
`asuaea..
`
`/1994 Garza ................. ..
`
`.. 430/513
`
`d & C
`igmary ixamltmjjean \émcent d & T
`Omey’ g6”) Or ‘rm— Ownsen
`Ownsen
`reW
`[57]
`ABSTRACT
`
`-
`
`-
`
`-
`
`~~
`
`-
`
`~
`
`A stable process for depositing an antire?ective layer.
`Helium gas is used to loWer the deposition rate of plasma
`enhanced sllane oxide, sllane oxynltrlde, and sllane nltrlde
`processes. Hellum ls also used to stablllZe the process, so
`that dlfferent ‘?lms can be deposlted. The lnventlon also
`Provldes Condltlons under WhICh Process Parameters can be
`Controlled to produce antire?ective layers With varying
`optimum refractive index, absorptive index, and thickness
`for obtaining the desired optical behavior.
`
`_
`
`_
`
`_
`
`_
`
`37 Claims, 3 Drawing Sheets
`
`EFFECT OF INCREASE ON
`n
`k
`T
`I’
`INCREASE lN:
`T
`T
`T
`T
`TEMPERATURE
`T
`T
`T
`T
`PRESSURE
`T,
`T
`T
`T
`POWER
`T
`T
`T
`T
`SPACING
`T
`T
`T
`T
`siH4
`T
`T
`T
`T
`N20
`T
`T
`T
`T
`NHS
`T
`T
`T
`T
`N2
`T
`T
`T
`T
`He
`TOTAL GAS FLOW T
`T
`T
`T
`
`MICRON Ex.1006 p.1
`
`

`

`5,968,324
`Page 2
`
`OTHER PUBLICATIONS
`
`HishikaWa, et al, ‘Principles for controlling the optical and
`electrical properties of hydrogenated amorphous silicaon
`deposited from a silane plasma’, Journal of Applied Physics,
`73 (9), 4227—42.31, May 1993.
`Database CAPLUS, Chemical Abstracts, vol. 111, (Colum
`bus, OH), abstract No. 145111, issued 1989, ‘The effect of
`helium dilution on PECVD silicon dioxide’, Rahman,
`Saadah Abdul, Jurnal FiZik Malaysia, 10(1), 20—3, (No
`month available).
`
`OgaWa, T., et al., “SiOXNy:H, high performance anti—re
`?ective layer for the current and future optical lithography,”
`SPIE (1994), 2197:722—732. (No month available).
`Tsu, et al., “Deposition of silicon oXynitride thin ?lms by
`remote plasma enhanced chemical vapor deposition,” J.
`Vacuum Science & Technology, Part A 5(4):1998—2002,
`Jul/Aug. 1987.
`Knolle, “Correlation of refractive indeX and silicon content
`of silicon oXynitride ?lms,” Thin Solid Films, 168:123—132
`(Jan. 1989).
`
`MICRON Ex.1006 p.2
`
`

`

`U.S. Patent
`
`Oct. 19, 1999
`
`Sheet 1 of 3
`
`5,968,324
`
`
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`
`MICRON Ex.1006 p.3
`MICRON Ex.1006 p.3
`
`
`
`
`

`

`U.S. Patent
`
`Oct. 19,1999
`
`Sheet 2 0f 3
`
`5,968,324
`
`y/M
`
`CANCELLED{
`
`ABSORBEDJ
`
`LAYER
`
`AIR
`
`PHOTORESIST
`
`UNDERLYING LAYER
`
`SUBSTRATE
`
`LAYER
`AIR
`
`PHOTORESIST
`
`ARL
`
`SUBSTRATE
`
`FIG. 2
`
`FIG. 3
`
`MICRON Ex.1006 p.4
`
`

`

`U.S. Patent
`
`Oct.19,1999
`
`Sheet 3 of3
`
`5,968,324
`
`EFFECT OF INCREASE ON
`n
`k
`t
`r
`INCREASE IN:
`T
`T
`T
`T
`TEMPERATURE
`T
`T
`T
`T
`PREssuRE
`T
`T
`T
`T
`POWER
`T
`T
`T
`T
`SPACING
`T
`T
`T
`T
`STH4
`T
`T
`T
`T
`N20
`T
`T
`T
`T
`NH3
`T
`T
`T
`T
`N2
`T
`T
`T
`T
`He
`TOTAL GAS FLOW T
`T
`T
`T
`
`FIG. 4
`
`MICRON Ex.1006 p.5
`
`

`

`5,968,324
`
`1
`METHOD AND APPARATUS FOR
`DEPOSITING ANTIREFLECTIVE COATING
`
`CROSS REFERENCE TO RELATED
`APPLICATION
`This is a continuation-in-part patent application of appli
`cation Ser. No. 08/567,338, ?led Dec. 5, 1995, entitled
`“Anti-Re?ective Coating and Method for Depositing Same”
`noW abandoned.
`
`BACKGROUND OF THE INVENTION
`
`The present invention relates to apparatus for, and the
`processing of, semiconductor Wafers. In particular, the
`invention relates to the deposition of antire?ective layers
`during Wafer processing.
`In the manufacture of integrated circuits, photolitho
`graphic techniques are used to de?ne patterns for layers in
`an integrated circuit. Typically, such photolithographic tech
`niques employ photoresist or other light-sensitive material.
`In conventional processing, the photoresist is ?rst deposited
`on a Wafer, and then a mask having transparent and opaque
`regions Which embody the desired pattern, is positioned over
`the photoresist. When the mask is exposed to light, the
`transparent portions alloW light to expose the photoresist in
`those regions, but not in the regions Where the mask is
`opaque. The light causes a chemical reaction to occur in the
`exposed portions of photoresist. A suitable chemical, or a
`chemical vapor or ion bombardment process, then is used to
`selectively attack either the reacted or unreacted portions of
`the photoresist. With the photoresist pattern remaining on
`the Wafer itself noW acting as a mask for further processing,
`the integrated circuit can be subjected to additional process
`steps. For example, material may be deposited on the circuit,
`the circuit may be etched, or other knoWn processes carried
`out.
`In the processing of integrated circuit devices With small
`feature siZes, for example, feature siZes having critical
`dimensions less than one-half micron, sophisticated tech
`niques involving equipment knoWn as steppers, are used to
`mask and expose the photoresist. The steppers for such small
`geometry products generally use monochromatic (single
`Wavelength) light, Which enables them to produce very ?ne
`patterns. As repeated process steps are carried out, hoWever,
`the topology of the upper surface of the substrate becomes
`progressively less planar. This uneven topology can cause
`re?ection and refraction of the monochromatic light, result
`ing in exposure of some of the photoresist beneath the
`opaque portions of the mask. As a result, this differing local
`substrate surface typography can alter the ?ne patterns of
`photoresist, thereby changing the desired dimensions of the
`resulting regions of the semiconductor substrate.
`In the manufacture of semiconductor devices, it is desir
`able that ?uctuations in line Width, or other critical
`dimensions, be minimiZed. Errors in such dimensions can
`result in open or short circuits, thereby ruining the resulting
`semiconductor devices. As a result, some semiconductor
`manufacturers noW require that the dimensional accuracy of
`a photoresist pattern be Within 5 percent. To achieve that
`dimensional accuracy, tWo approaches have been taken.
`Both approaches entail the use of another layer in addition
`to the photoresist layer.
`The ?rst approach uses a relatively thick organic ?lm
`beneath the photoresist that absorbs incident light so that
`minimal re?ection or refraction occurs. A disadvantage of
`such organic ?lms is that they require more process steps,
`and being polymer-based, are dif?cult to etch.
`
`15
`
`25
`
`35
`
`45
`
`55
`
`65
`
`2
`A second approach is the use of an antire?ective ?lm for
`canceling re?ections occurring at the photoresist
`antire?ective layer interface, and at the antire?ective layer
`substrate interface. In the prior art, silicon oxynitride (SiON)
`deposited using NH3 gas has been used as an antire?ective
`?lm. Upon exposure to light, hoWever, an amino group from
`the SiON ?lm reacts With the light sensitive component in
`the photoresist, thereby desensitiZing the photoresist. This
`results in inaccurate photoresist patterns.
`An article entitled “SiOxNyzH, high performance antire
`?ective layer for the current and future optical lithography,”
`SPIE, Vol. 2197 (1994), pp. 722—732, by Tohro OgaWa, et
`al., addresses the thin ?lm interference concerns. The article
`teaches the use of an antire?ective layer (ARL) in conjunc
`tion With the I-line, KrF, and ArF excimer laser lithogra
`phies. The exposure Wavelengths used in these laser lithog
`raphies are 365 nm, 248 nm, and 193 nm, respectively. The
`article describes that as exposure Wavelengths become
`shorter, stronger re?ections from the interface betWeen the
`photoresist and the substrate result. Hence, an ARL is
`needed to reduce the standing Waves and thin ?lm interfer
`ence effects.
`This ARL is described as canceling re?ection from both
`the interface betWeen the photoresist and the ARL, and from
`the interface betWeen the ARL and the substrate. The article
`describes a complicated equi-energy contour-based proce
`dure for determining the parameters to achieve the desired
`cancellation. According to the procedure described in this
`article by Sony, the parameters are obtained by ?nding
`common regions of the equi-energy contour lines for a
`plurality of photoresist ?lm thicknesses. The article
`describes refractive index, absorptive index, and thickness
`values for its ARL, and though the article does not specify
`it, Applied Materials inventors have determined that these
`values correspond to a phase shift of 180° betWeen the
`re?ections. The Applied engineers, hoWever, Were unable to
`achieve the results described in the article, and it is believed
`that the process is unstable.
`Sony has also ?led a European patent application
`(Application No. 931132195, Publication No. EP 0 588 087
`A2) for a process for depositing an ARL With selected
`parameters. The Sony application discusses the SiH4 and
`N20 ratio, and hoW the ratio affects the optical and chemical
`properties of the ARL deposited. The Sony application also
`teaches the use of argon.
`
`SUMMARY OF THE INVENTION
`
`The present invention provides apparatus and a process
`for depositing an antire?ective layer. Because ARL ?lms are
`thin, to have a stable process it is desirable to have a loW
`deposition rate for the process. The invention provides
`apparatus and a process to loWer the deposition rate of
`plasma-enhanced silane oxide, silane oxynitride, and silane
`nitride processes. In a preferred embodiment helium is used.
`Although helium is a knoWn carrier gas in chemical vapor
`deposition, its use in the present invention is for controlling
`the deposition rate of the processes. By adding helium, more
`precise control of the thin ?lm thickness is provided, par
`ticularly over longer periods of equipment operation. The
`helium also helps stabiliZe the process, enabling different
`?lms to be deposited, and the ?lm deposited to be Well
`controlled.
`The present invention also provides equipment and pro
`cess conditions under Which parameters can be controlled to
`produce ARLs With various optimum refractive index,
`absorptive index, and thickness values for obtaining the
`
`MICRON Ex.1006 p.6
`
`

`

`3
`desired cancellations for the different exposure Wavelengths
`and substrates. In one embodiment, the apparatus and pro
`cess described by the present invention use N2 and NH3, in
`addition to a desired ratio of SiH4 to N20, to further control
`the optical and chemical properties of the ARL deposited.
`The effects of N2 and NH3 are particularly dominant in
`process regimes Where SiH4 and N20 have minimal or no
`effect on the ARL properties, e.g., at loW temperature. The
`invention teaches the addition of NH3 and N2 in the process
`to change the composition of the ?lm, alloWing more
`freedom and ?ner tuning of the refractive index and the
`absorptive index. Furthermore, the process is compatible
`With the use of helium, Which is more cost-effective than
`argon. Helium also alloWs for improved stress control of the
`ARL layer deposited. This helps prevent the ?lm from
`becoming too tensile, Which can cause it to ?ake off the
`substrate after deposition.
`As applied to the process above, the addition of helium
`also achieves plasma stability, Which in turn ensures the
`deposition of a uniform ?lm. Furthermore, the helium pro
`vides suf?cient control of the ARL deposition process, so
`that ARLs With optimum values of refractive index, absorp
`tive index, and thickness can be developed Within practical
`process parameters for exposure Wavelengths in the range of
`190—900 nm. This is highly desirable because cancellation
`of the re?ected light for different exposure Wavelengths
`depends on several factors: the incident light Wavelength,
`the phase shift (Which is determined by the thickness of the
`ARL), and the intensity of the re?ection (determined by the
`chemical composition of the ARL). Hence, control of the
`optical and chemical properties of the ARL is necessary to
`achieve the desired cancellations.
`The present invention determines the optimum refractive
`index, absorptive index, and thickness values for phase
`shifts greater than 180° (e.g., 540°, 900°, etc.) using destruc
`tive interference equations. (A sample calculation of hoW the
`refractive index n, absorptive index k, and thickness t values
`are determined by the current invention is shoWn beloW.) For
`an ARL to produce phase shifts of 540° or larger betWeen the
`re?ections, the thickness Will be higher, Which means higher
`absorptive index values, because the ARL must absorb more
`refracted light. In one embodiment, the invention provides
`an ARL With optimum refractive index n, optimum absorp
`tive index k, and optimum thickness t values to produce a
`phase shift of 540° betWeen the re?ections.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a vertical, cross-sectional vieW of one embodi
`ment of a simpli?ed chemical vapor deposition (CVD)
`apparatus used for processing the antire?ective coating
`according to the present invention;
`FIG. 2 is a vertical, cross-sectional vieW of paths of
`re?ected and refracted light of an incident light beam Which
`strikes the surface of a multilayer semiconductor device, for
`example, during a photolithographic process;
`FIG. 3 shoWs the effect of using an antire?ective layer
`according to the present invention; and
`FIG. 4 is a trend chart for the process of depositing the
`antire?ective layer of the present invention.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`DESCRIPTION OF THE SPECIFIC
`EMBODIMENTS
`
`Apreferred embodiment of the process for depositing an
`ARL according to the present invention comprises apparatus
`for and the use of plasma-enhanced chemical vapor depo
`
`65
`
`5,968,324
`
`4
`sition (PECVD) technique to bring about a chemical reac
`tion betWeen SiH4 and N20, in the presence of He, With the
`SiH4 to N2O ratio being betWeen about 0.5 to 3.0 and
`preferably 1.0. The process further includes the addition of
`NH3, N2, and He gases. FIG. 1 illustrates one embodiment
`of a simpli?ed, parallel plate PECVD system 10 having a
`vacuum chamber 15 in Which the antire?ective layer can be
`deposited according to the present invention.
`System 10 contains a gas distribution manifold 11 for
`dispersing the deposition gases to a substrate, not shoWn, but
`Which is placed ?at on the supporter 12. The supporter 12 is
`highly heat-responsive and is mounted on supports 13 so
`that supporter 12 (and the substrate supported on the upper
`surface of supporter 12) can be controllably moved betWeen
`a loWer loading/of?oading position, and an upper processing
`position 14 represented by a dashed line, Which is closely
`adjacent to manifold 11.
`Depending on the desired refractive index, absorptive
`index, and thickness to be achieved, the spacing betWeen
`supporter 12 and manifold 11 is in the range of 200—600
`mils, the substrate temperature is in the range of 200—400°
`C., and the chamber pressure is maintained at 1—6 torr. ARLs
`With varying refractive index, absorptive index, and thick
`ness can be deposited Within these process parameters for
`any exposure Wavelengths betWeen 190—900 nm; and the
`different optimum refractive index, absorptive index, and
`thickness for the different Wavelengths can be consistently
`achieved by varying the parameters and the rate at Which the
`SiH4, N2O, NH3, N2, and He gases are introduced into the
`chamber. Within these ranges, the preferred range for the
`spacing is 400—600 mils. For the substrate temperature, the
`preferred range is 300—400° C., and the preferred range for
`the chamber pressure is 4.5—5.5 torr.
`When supporter 12 and the Wafer are in processing
`position 14, they are surrounded by a baf?e plate 17 having
`a plurality of spaced holes 23 Which alloW gas to exhaust
`into an annular vacuum manifold 24. Deposition gases are
`supplied through lines 18, having control valves (not
`shoWn), into a gas mixing chamber 19 Where they are
`combined and supplied to manifold 11. Although He is a
`knoWn carrier gas, its use in the present process is for
`controlling the parameters of the process. As Will be
`described later, the amount of He used affects the optical and
`chemical properties of the ARL deposited. Furthermore, He
`helps achieve the desired chamber pressure Without altering
`the chemical composition of the ?lm, thereby ensuring
`process stability, Which in turn ensures the deposition of a
`uniform ?lm. Because the ARL is a thin ?lm, thickness
`control is important, and a loW deposition rate is necessary
`to achieve control over the desired thickness. The addition of
`He loWers the deposition rate, thus alloWing for thickness
`control, in addition to the control of the ?lm properties.
`During processing of a Wafer, gas inlet to manifold 11 is
`vented toWard, and uniformly distributed radially across, the
`surface of the substrate as indicated by arroWs 22 and 21
`representing gas ?oW. SiH4 and N20 are both introduced
`into chamber 19 at a rate of 5—300 sccm, With the SiH4 to
`N2O ratio betWeen about 0.5 and 3.0, but preferably about
`1.0. NH3, N2, and He may be added as explained beloW,
`depending on the values of refractive index, absorptive
`index, and thickness desired, and the process regimes. If a
`Wider range of refractive index, absorptive index, and thick
`ness values is desired, NH3, N2, and additional He Will be
`added to the process, and are introduced into the chamber at
`a rate of 0—300 sccm, 0—4000 sccm, and 5—5000 sccm,
`respectively. Within these ranges, the preferred range for
`introducing SiH4 into the chamber is 15—160 sccm; for N20,
`
`MICRON Ex.1006 p.7
`
`

`

`5,968,324
`
`5
`the preferred range is 15—160 seem; for NH3, the preferred
`range is 0—300 seem; for N2, the preferred range is 0—500
`seem; and for He, the preferred range is 500—4000 seem.
`After the reactions are complete, the remaining gases are
`exhausted via ports 23 into the circular vacuum manifold 24
`and out through an exhaust line (not shown). The optimal
`values for the gases are SiH4 40—120 seem, N20 30—120
`seem, He 1500—2500 seem, N2 0—300 seem, and NH3 0—150
`seem. The ratio of the selected ?oW rate of He to the
`combined ?oW rate of SiH4 and N20 is at least 6.25:1. These
`are representative values for an eight-ineh chamber as made
`by Applied Materials. Other siZes of ehambers or ehambers
`made by other manufacturers Will have different values.
`A controlled plasma of SiH4 and N20 is formed adjacent
`to the substrate by RF energy applied to manifold 11 from
`RF poWer supply 25. Gas distribution manifold 11 is also an
`RF eleetrode, While supporter 12 is grounded. The RF poWer
`supply 25 supplies poWer ranging from 50—500 Watts, to
`manifold 11 to sloW doWn or enhance the decomposition of
`the SiH4 and N20 introduced into chamber 15.
`Aeireular external lamp module 26 provides a eollimated
`annular pattern of light 27 through quartZ WindoW 28 onto
`supporter 12. Such heat distribution compensates for the
`natural heat loss pattern of the supporter and provides rapid
`and uniform supporter and substrate heating for effecting
`deposition. A motor, not shoWn, raises and loWers supporter
`12 betWeen a processing position 14 and a loWer, substrate
`loading position.
`The motor, control valves connected to lines 18, and RF
`poWer supply 25 are controlled by a processor 34 over
`control lines 36, of Which only some are shoWn. Using these
`control lines, the processor controls the entire process of
`depositing the ARL. Processor 34 operates under the control
`of a computer program stored in a memory 38. The computer
`program dictates the timing, mixture of gases, chamber
`pressure, chamber temperature, RF poWer levels, supporter
`position, and other parameters of the process. Typically, the
`memory eontains computer readable information for causing
`the processor to introduce a ?rst process gas eomprising
`SiH4 and N20 into the chamber, and a second process gas
`eomprising He into the chamber.
`The above description is mainly for illustrative purposes
`and should not be considered as limiting the scope of the
`present invention. Variations of the above described system
`such as variations in supporter design, heater design, loca
`tion of RF poWer eonneetions, ete., are possible.
`Additionally, other plasma CVD equipment such as electron
`cyclotron resonance (ECR) plasma CVD equipment,
`induetion-eoupled RF high density plasma CVD equipment,
`or the like may be employed. The ARL and method for
`forming such a layer of the present invention is not limited
`to any speei?e apparatus or to any speei?e plasma exeitation
`method.
`Similarly, the use of helium for controlling the deposition
`rate of the process and for stabiliZing the process, is appli
`cable to thin ?lm depositions in general, and is not limited
`to ARL ?lm depositions. Speei?eally, it could be used to
`loWer the deposition rate of existing plasma-enhaneed silane
`oxide, silane oxynitride, and silane nitride proeesses.
`Although helium is used in the preferred embodiment, other
`inert gases may also be used instead of helium.
`FIG. 2 is a vertical, cross-sectional view of typical paths
`of re?eeted and refraeted light of an incident light beam that
`strikes the surface of a multi-layer semiconductor device
`during a photolithographie process. As shoWn in FIG. 2, for
`an incident light beam 1 that strikes the semiconductor
`
`15
`
`35
`
`45
`
`55
`
`65
`
`6
`structure, the photoresist pattern exposure could be distorted
`by a re?eetion 3 betWeen the photoresist layer and an
`underlying layer, and another re?eetion 6 betWeen the
`underlying layer and the substrate which results in light 5
`entering the photoresist.
`In FIG. 3, the dashed light paths illustrate the function of
`an ARL according to the present invention. As shoWn, light
`rays 3 and 5 (Which are almost equal in intensity and have
`a phase difference of 540° or larger) Will substantially cancel
`each other, While light rays 4 and 6 Will be absorbed by the
`ARL. Hence, the only light that exposes the photoresist is
`the incident light from ray 2. As previously mentioned, an
`ARL according to the present invention is compatible With
`the photoresist, thus eliminating the concern that the pho
`toresist may be neutraliZed. Furthermore, as discussed
`beloW, ARLs With different optimum refractive index,
`absorptive index, and thickness values can be achieved for
`cancellation of re?eetions of different exposure Wavelengths
`betWeen 190—900 nm.
`FIG. 4 is a chart shoWing the effects of the different
`process parameters on the process for depositing the anti
`re?eetive layer of the present invention. As described, the
`properties of the ARL can be changed by changing the
`different parameters. As shoWn by the chart, increasing the
`substrate temperature will increase the refractive index n,
`absorptive index k, thiekness t, and re?eetanee r values of
`the ARL deposited. Similarly, increasing the total gas ?oW
`into the chamber, or increasing the rate at which SiH4 is
`introduced into the chamber, Will also increase the refractive
`index n, absorptive index k, thiekness t, and re?eetanee r
`values of the ARL deposited.
`On the other hand, increasing the pressure of chamber 19,
`or the spacing betWeen supporter 12 and manifold 11, has
`the effect of decreasing the refractive index n, absorptive
`index k, thiekness t, and re?eetanee r values of the ARL
`deposited. Alternatively, increasing the poWer supplied to
`RF poWer supply 25 to generate more plasma has the effect
`of decreasing the refractive index n, absorptive index k, and
`re?eetanee r values while increasing the thickness of the
`ARL deposited. A similar effect can also be achieved by
`increasing the rate at which N20 or N2 is being introduced
`into chamber 19. The opposite effect of increasing the
`refractive index n, absorptive index k, and re?eetanee r
`values, while decreasing the thickness of the ARL deposited,
`can be achieved by increasing the rate at which He is
`introduced into chamber 19. Finally, the amount of NH3
`introduced into chamber 19 can be increased to increase the
`refractive index n and thickness t values, while decreasing
`the absorptive index k and re?eetanee r values.
`The following discussion of the ARL explains the calcu
`lations beloW. These calculations pertain to the deposition of
`SiON ?lms by plasma-enhaneed CVD teehniques, an
`example of Which is as described above. The values obtained
`from the calculations are for an exposure Wavelength of
`approximately 248 nm. At this Wavelength, an ARL depos
`ited in this process can have refractive index n ranging from
`1.7 to 2.4, and absorptive index k ranging from 0 to 1.3.
`An effective ARL minimiZes the variation of light avail
`able for PR absorption as the thickness of the PR varies. This
`requires the substantial cancellation of light re?eeted from
`the interface betWeen the PR and the ARL, i.e., the substan
`tial cancellation of light rays 3 and 5 as shoWn in FIG. 3.
`Substantial eaneellation can be achieved if the folloWing tWo
`requirements are met simultaneously for light ray 3 and light
`ray 5. The phase difference betWeen ray 3 and ray 5 is close
`to an odd multiples of 180°.
`
`MICRON Ex.1006 p.8
`
`

`

`5,968,324
`
`n3-2t=1/2 (mk)
`
`(1)
`
`The intensity of ray 3 and the intensity of ray 5 are almost
`identical.
`
`13=15
`
`(2)
`
`8
`absorptive index k for W—Si are assumed to be 1.96 and
`2.69, respectively. With tWo equations and three unknoWns,
`one can choose the value of refractive index n, absorptive
`index k, or thickness t and then calculate the remaining tWo
`unknoWns. Because the refractive index n value of SiON
`ARL ?lms optimiZed With the above deposition process is
`about 2.2 to 2.3 at 248 nm, the refractive index n value is
`chosen to stay Within this range throughout the calculation
`of Appendix A. Because absorptive index k values are
`tunable over a Wide range With the above process, values of
`absorptive index k are not restricted.
`The solutions provided in Appendix A are not exact
`optimiZed values for the ARL because of the simplicity of
`the model. For example, native oxides of Al, or W—Si, are
`simply neglected and their thicknesses are usually in the
`range of 10 to 20 angstroms. Also, the refractive index n and
`absorptive index k values of the ARL ?lm are assumed to be
`constant throughout the thickness of the ?lm. Thus, the
`solutions to Equations 1 and 2 only provide a guideline to
`the refractive index n, absorptive index k, and thickness of
`the desirable ARL ?lm. Exact values of refractive index n,
`absorptive index k, and thickness for a speci?c application
`are determined experimentally by optimiZing near the solu
`tion values from Equations 1 and 2.
`For an Al substrate With deep UV (248 nm)
`photolithography, at m=3 an appropriate refractive index n
`value is about 2.3, an appropriate absorptive index k value
`is about 0.3 and an appropriate thickness value is about 800
`angstroms. These solutions satisfy Equation 1 to Within 8° of
`a 540° phase difference. For Equation 2, the difference in
`intensity betWeen ray 3 and ray 5 is about 5 percent of
`incident intensity. For a W—Si substrate With deep UV
`photolithography, at m=3, an appropriate refractive index n
`is about 2.3, an absorptive index k is about 0.3 and a
`thickness about 800 angstroms. These solutions satisfy
`Equation 1 to Within 8° of a 540° phase difference. For
`Equation 2, the difference in intensity betWeen ray 3 and ray
`5 is less than 5 percent of incident intensity.
`For an Al substrate With deep UV photolithography, at
`m=5 an appropriate refractive index n value is about 2.3, an
`appropriate absorptive index k value is about 0.17 and an
`appropriate thickness value is about 1350 angstroms. These
`solutions satisfy Equation 1 to Within 8° of a 900° phase
`difference. For Equation 2, the difference in intensity
`betWeen ray 3 and ray 5 is about 5 percent of incident
`intensity. For a W—Si substrate With deep UV
`photolithography, at m=5, an appropriate refractive index n
`is about 2.3, an absorptive index k is about 0.18 and a
`thickness about 1350 angstroms. These solutions satisfy
`Equation 1 to Within 8° of a 900° phase difference. For
`Equation 2, the difference in intensity betWeen ray 3 and ray
`5 is less than 5 percent of incident intensity.
`For an Al substrate With deep UV photolithography, at
`m=7 an appropriate refractive index n value is about 2.3, an
`appropriate absorptive index k value is about 0. 13 and an
`appropriate thickness value is about 1900 angstroms. These
`solutions satisfy Equation 1 to Within 8° of a 1260° phase
`difference. For Equation 2, the difference in intensity
`betWeen ray 3 and ray 5 is about 5 percent of incident
`intensity. For a W—Si substrate With deep UV
`photolithography, at m=7 an appropriate refractive index n is
`about 2.3, an absorptive index k is about 0.13 and a thickness
`about 1900 angstroms. These solutions satisfy Equation 1 to
`Within 8° of a 1260° phase difference. For Equation 2, the
`difference in intensity betWeen ray 3 and ray 5 is about 5
`percent of incident intensity.
`For an Al substrate With deep UV photolithography, at
`m=9 an appropriate refractive index n value is about 2.3, an
`
`MICRON Ex.1006 p.9
`
`10
`
`15
`
`The ?rst of the above requirements is described by the
`destructive interference equation, Which is represented by
`Equation 1. The second equation describes the condition for
`matching the intensities of ray 3 and ray 5.
`For a given substrate and photoresist, conditions 1 and 2,
`as represented by Equations 1 and 2, can be satis?ed
`simultaneously With appropriate choices of refractive index
`n, absorptive index k, and thickness t of the ARL ?lm.
`Solutions for m=3 (540° phase differenc