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`PROVISIONAL APPLRCATION
`
`7" P137‘/V/A»
`
`
`Atty. Docket No. 16655-000800
`ll
`- u
`Express Mail Label No. EM415713600US
`Date of Deposit Kriiéoz’ // fi7Z
`
`I hereby certify that this is being deposited with the U.S.
`Postal Service "Express Mail Post Office to Addressee"
`service under 37 CFR 1.10 on the date indicated above,
`addressed to the Asst. Commissioner of Patents, Box
`Provisional App1n., Washington, DC 20231.
`
`By: LZaaz
`
`BOX PROVISIONAL PATENT APPLICATION
`ASST. COMMISSIONER OF PATENTS
`AND TRADEMARKS
`
`Washington, D. C. 20231
`
`Sir:
`
`
`
`Transmitted herewith for filing is a provisional patent application under 37 CFR 1.53(b)(2) of:
`
`
`
`Title: MULTI-TEMPERATURE PLASMA ETCHING PROCESS
`
`Enclosed are:
`
`29 pages of the specification.
`[X]
`3
`pages of claims.
`[X]
`1
`pages of abstract.
`[X]
`12
`sheet(s) of informal draWing(s).
`[X]
`1
`Exhibit.
`[X]
`[ ] A Verified statement to establish small entity status under 37 CFR 1.9 and 37 CFR 1.27.
`[ ] The invention was made by or under a contract with the following agency of the United States Government:
`under Government contract number:
`
`1
`
`[ 1
`Please charge Deposit Account No. 20-1430 as follows:
`[X] Filing fee
`[X] Any additional fees associated with this paper or
`during the pendency of this application.
`
`$ 150.00
`
`2
`
`extra copies of this sheet are enclosed.
`
`Respectfully submitted,
`
`Correspondence Address:
`
`TOWNSEND and TOWNSEND and CREW LLP
`
`TOWNSEND and TOWNSEND and CREW LLP
`Two Embarcadero Center, 8th Floor
`
`San Francisco, CA 941 11-3834 ‘chard T. Ogawa
`
`Telephone: (650) 326-2400
`
`nolwarkl1665518-pravapp.tm
`
`Reg. No.: 37,692
`Attorneys for Applicant
`
`LAM Exh 1006-pg 1
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`LAM Exh 1006-pg 1
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`

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`16655-000800
`
`PROVISIONAL PATENT APPLICATION
`
`MULTI—TEMPERATURE PLASMA ETCHING PROCESS
`
`Inventor 2
`
`Daniel L. Flamm, a citizen of the United States, residing at 476 Green
`View Drive, Walnut Creek, California 94596
`
`Entity Status:
`
`Small
`
`
`
`TOWNSEND and TOWNSEND and CREW LLP
`
`Two Embarcadero Center, 8th Floor
`
`San Francisco, CA 9411-3834
`
`(415) 326-2400
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`5
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`METHOD AND DEVICE MADE BY PLASMA ETCHING
`
`CROSS—REFERENCE TO RELATED APPLICATIONS
`
`This present application is a continuation-in-part of U.S. Application
`
`Serial No. 08/567,224 filed December 4, 1995 (Attorney Docket No. 16655-5), which
`
`is hereby incorporated by reference for all purposes.
`
`BACKGROUND OF THE INVENTION
`
`This invention relates generally to plasma processing. More particularly,
`
`one aspect of the invention is for greatly improved plasma processing of devices using
`
`an inductive discharge. Another aspect of the invention is illustrated in an example with
`
`regard to plasma etching or resist stripping used in the manufacture of semiconductor
`
`devices. The invention is also of benefit in plasma assisted chemical vapor deposition
`
`15
`
`(CVD) for the manufacture of semiconductor devices. But it will be recognized that the
`
`invention has a wider range of applicability. Merely by way of example, the invention
`
`also can be applied in other plasma etching applications, and deposition of materials such
`
`as silicon, silicon dioxide, silicon nitride, polysilicon, among others.
`
`Plasma processing techniques can occur in a variety of semiconductor
`
`20
`
`manufacturing processes. Examples of plasma processing techniques occur in chemical
`
`dry etching (CDE), ion-assisted etching (IAE), and plasma enhanced chemical vapor
`
`deposition (PECVD), including remote plasma deposition (RPCVD) and ion-assisted
`
`plasma enhanced chemical vapor deposition (IAPECVD). These plasma processing
`
`techniques often rely upon radio frequency power (rt) supplied to an inductive coil for
`
`25
`
`providing power to gas phase species in forming a plasma.
`
`Plasmas can be used to form neutral species (i.e. , uncharged) for purposes
`
`of removing or forming films in the manufacture of integrated circuit devices. For
`
`instance, chemical dry etching generally depends on gas-surface reactions involving these
`
`neutral species without substantial ion bombardment.
`
`30
`
`In a number of manufacturing processes, ion bombardment to substrate
`
`surfaces is often undesirable. This ion bombardment, however,
`
`is known to have
`
`harmful effects on properties of material
`
`layers in devices and excessive ion
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`5
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`10
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`bombardment flux and energy can lead to intermixing of materials in adjacent device
`
`layers, breaking down oxide and "wear out," injecting of contaminative material formed
`
`in the processing environment into substrate material layers, harmful changes in substrate
`
`morphology (e. g. amophotization), etc.
`
`Ion assisted etching processes, however, rely upon ion bombardment to
`
`the substrate surface in defining selected films. But these ion assisted etching processes
`
`commonly have a lower selectivity relative to conventional CDE processes. Hence,
`
`CDE is often chosen when high selectivity is desired and ion bombardment to substrates
`
`are to be avoided.
`
`One commonly used chemical dry etching technique is conventional
`
`plasma assisted photoresist stripping, often termed ashing or stripping. Conventional
`
`resist stripping relies upon a reaction between a neutral gas phase species and a surface
`
`material layer, typically for removal. This reaction generally forms volatile products
`
`with the surface material layer for its removal. The neutral gas phase species is formed
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`15
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`by a plasma discharge. This plasma discharge can be sustained by an inductive
`
`applicator (e.g., a helical coil) operating at a selected frequency in a conventional
`
`photoresist stripper. An example of the conventional photoresist stripper is a quarter-
`
`wave helical resonator stripper, which is described by U.S. Patent No. 4,368,092 in the
`
`name of Steinberg e_t a_l.
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`20
`
`Among the pervasive applications of patterned photoresist in device
`
`fabrication is their use as an ion implantation mask to shield selected areas from
`
`unwanted ion implantation. Unfortunately when ions bombard the mask an unwanted
`
`result is often modification of the near surface region of the mask by the ion beam.
`
`In
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`particular, ions striking the mask break chemical bonds within the photoresist and cross-
`
`25
`
`link polymer chains in regions they penetrate while eliminating hydrogen that is bonded
`
`to the polymer backbone. Moreover, many of the ions striking the resist mask are
`
`implanted into the resist. These processes result in a hardened, more highly cross—linked
`
`and relatively impermeable near surface zone of resist (a “crust” of more diamond—like
`
`carbon), which overlies the original patterned resist material. This cross—linked layer is
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`30
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`undesirable from a processing point of View because it etches more slowly than the
`
`underlying material and is less permeable to low molecular weight monomer and residual
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`2
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`solvent within the photoresist matrix.
`
`Ideally the etch rate could be increased to compensate for this effect by
`
`heating the resist and substrate. Unfortunately, when a cross—linked crust is present,
`
`the
`
`processing temperature must be limited to avoid undue vapor pressure of solvent and
`
`5
`
`monomeric material within the resist. If an excessive temperature is used to achieve and
`
`increased rate of resist stripping, the pressure of volatile solvent and low molecular
`
`weight residue within the resist matrix often increases and ruptures the hardened crust
`
`when it is thinned by etching. This phenomena has been termed “popping” and it is
`
`impermissible because it generates harmful contaminative particulate matter.
`
`10
`
`Unimplanted resist does not suffer this problem as great an extent for
`
`several reasons. One reason is that it is more easily etched by an oxygen plasma and can
`
`therefore be removed by treatment at a lower temperature. An addition reason is that
`
`the near surface region of unimplanted resist is more permeable and elastic, hence allows
`
`volatile material to escape more easily.
`
`In some processes another limitation on
`
`15
`
`maximum permissible resist stripping temperature stems from the fact that wafer
`
`temperature must be maintained below about 180°C to avoid the degradation of
`
`antireflection layers. Hence there is a need for a fast etching process which is capable
`
`of removing an ion-implanted resist crust at relatively low temperatures.
`
`Referring to the above, an objective in chemical dry etching is to reduce
`
`20
`
`or even eliminate ion bombardment (or ion flux) to surfaces being processed to avoid
`
`damaging the substrate and to maintain the desired etching selectivity.
`
`In practice,
`
`however,
`
`ideal chemical dry etching often difficult to achieve using conventional
`
`techniques. These conventional techniques generally attempt to control ion flux by
`
`suppressing the amount of charged species in the plasma source reaching the process
`
`25
`
`chamber. A variety of techniques for suppressing these charged species have been
`
`proposed.
`
`These techniques often rely upon shields, baffles,
`
`large separation
`
`distances between the plasma source and the chamber, or the like, placed between the
`
`plasma source and the process chamber. The conventional techniques generally attempt
`
`30
`
`to directly suppress charge density downstream of the plasma source by interfering with
`
`convective and diffusive transport of charged species.
`
`They tend to promote
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`LAM Exh 1006-pg 5
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`recombination of charged species by either increasing internal surface area (e.g. , baffles,
`
`etc.) relative to volume, or increasing flow time, which relates to increasing the distance
`
`between the plasma source and the process chamber.
`
`The baffles, however, cause loss of desirable neutral etchant species as
`
`5
`
`well. The baffles, shields, and alike, also are often cumbersome. Baffles, internal
`
`shields, or large separation distances also cause undesirable recombinative loss of active
`
`species and sometimes cause radio frequency power loss and other problems. These
`
`baffles and internal shields also are a potential source of particulate contamination, which
`
`is often damaging to integrated circuits.
`
`10
`
`Baffles, shields, spatial separation, and alike, when used alone also are
`
`often insufficient to substantially prevent unwanted parasitic plasma currents. These
`
`plasma currents are generated between the wafer and the plasma source, or between the
`
`plasma source and walls of the chamber.
`
`It is commonly known that when initial
`
`charged species levels are present
`
`in an electrical field,
`
`the charged species are
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`15
`
`accelerated and dissociative collisions with neutral particles can multiply the
`
`concentration of charge to higher levels.
`
`If sufficient "seed" levels of charge and
`
`electrical fields are present, the parasitic plasma in the vicinity of the process wafer can
`
`reach harmful charge density levels.
`
`In some cases, these charge densities may be
`
`similar to or even greater than plasma density within the source plasma region, thereby
`
`20
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`causing even more ion flux to the substrate.
`
`Charge densities can enhance electrical fields between the plasma source
`
`and processing chamber or substrate support, which can have an additional deleterious
`
`effect. Time—average voltage differences corresponding to the electric fields can
`
`accelerate extraction of charge from the plasma source and charged particle
`
`25
`
`bombardment of the substrate and chamber elements. Hence, their presence often
`
`induces increased levels of charge to be irregularly transported from the plasma source
`
`to process substrates, thereby causing non-uniform ion assisted etching.
`
`Conventional ion assisted plasma etching, however, often requires control
`
`and maintenance of ion flux intensity and uniformity within selected process limits and
`
`30
`
`within selected process energy ranges. Control and maintenance of ion flux intensity and
`
`uniformity are often difficult to achieve using conventional techniques. For instance,
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`4
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`capacitive coupling between high voltage selections of an inductive applicator coil and
`
`the plasma discharge often cause high and uncontrollable plasma potentials relative to
`
`ground.
`
`It is generally understood that voltage difference between the plasma and
`
`ground can cause damaging high energy ion bombardment of chamber walls and articles
`
`5
`
`being processed by the plasma, as illustrated by U.S. Patent No. 5,234,529 in the name
`
`of Johnson and U.S. Patent No. 5,534,231 in the name of Savas.
`
`It is further often
`
`understood that the rf component of the plasma potential varies in time since it is derived
`
`from a coupling to time varying rf excitation. Hence, the energy of charged particles
`
`from plasma in conventional inductive sources is spread over a relatively wide range of
`
`10
`
`energies, which undesirably tends to introduce uncontrolled variations in the processing
`
`of articles by the plasma.
`
`The voltage difference between the region just outside of a plasma source
`
`and the processing chamber can be modified by introducing internal conductive shields
`
`or electrode elements into the processing apparatus downstream of the source. When the
`
`15
`
`plasma potential is elevated with respect to these shield electrodes, however, there is a
`
`tendency to generate an undesirable capacitive discharge between the shield and plasma
`
`source. These electrode elements are often a source of contamination and the likelihood
`
`for contamination is even greater when there is capacitive discharge (ion bombardment
`
`from capacitive discharge is a potential source of sputtered material). Contamination is
`
`20
`
`damaging to the manufacture of integrated circuit devices.
`
`Another limitation is that internal baffles, shields or electrode elements
`
`generally require small holes therein as structural elements. These small holes are
`
`designed to allow gas to flow therethrough. The small holes, however, tend to introduce
`
`unwanted pressure drops and neutral species recombination.
`
`If the holes are made
`
`25
`
`larger, plasma from the source tends to survive transport through the holes and unwanted
`
`downstream charge flux will often result.
`
`In addition, undesirable discharges to these
`
`holes in shields can, at times, produce an even more undesirable hollow cathode effect.
`
`In conventional helical resonator and inductive applicator designs,
`
`conductive external shields are often interposed between the inductive power (e.g. , coil,
`
`30
`
`etc.) and walls of the vacuum vessel containing the plasma (examples of shields are
`
`described in U.S. Patent 4,918,031 by Flamm et. a1., U.S. Patent 5,234,529 in the
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`LAM Exh 1006-pg 7
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`
`name of Johnson and U.S. Patent 5,534,231 in the name of Savas. A variety of
`
`limitations with these external capacitive shielded plasma designs (e. g. , helical resonator,
`
`inductive discharge, etc.) have been observed.
`
`In particular, the capacitively shielded
`
`design often produces plasmas that are difficult to tune and even ignite. Alternatively,
`
`5
`
`the use of unshielded plasma sources (e. g., conventional quarter-wave resonator,
`
`conventional half—wave resonators etc.) often involve a substantial plasma potential
`
`through capacitive coupling to the inductive applicator (commonly this is a spiral wound
`
`Conductor or coil), and hence are prone to create uncontrolled parasitic plasma currents
`
`to grounded surfaces and energetic ion bombardment upon the walls of the vacuum
`
`10
`
`vessel. Accordingly, the use of either the shielded or the unshielded sources using
`
`conventional quarter and half-wave rf helical
`
`resonator configurations produce
`
`undesirable results.
`
`In many conventional plasma sources a means of cooling is required to
`
`maintain the plasma source and substrates being treated below a maximum temperature
`
`15
`
`limit. Power dissipation in the structure causes heating and thereby increases the
`
`difficulty and expense of implementing effective cooling means.
`
`Inductive currents may
`
`also be coupled from the excitation coil into internal or capacitive shields and these
`
`currents are an additional source of undesirable power loss and heating. Conventional
`
`capacitive shielding in helical resonator discharges utilized a shield which was
`
`20
`
`substantially split along the long axis of the resonator to lessen eddy current loss.
`
`However, such a shield substantially perturbs the resonator or other inductive coupling
`
`characteristics owing to unwanted capacitive coupling and current which flows from the
`
`coil to the shield.
`
`Since there are no general design equations, nor are properties
`
`currently known for resonators which are "loaded" with a shield along the axis, sources
`
`25
`
`using this design must be sized and made to work by trial and error.
`
`In inductive discharges, it is highly desirable to be able to substantially
`
`control the plasma potential relative to ground potential and the potential of substrate
`
`which is being processed, independent of input power, pressure, gas composition and
`
`other Variables. In many cases, it is desired to have the plasma potential be substantially
`
`30
`
`at ground potential (at least offset from ground potential by an amount insignificantly
`
`different from the floating potential or intrinsic DC plasma potential). For example,
`
`
`
`
`
`
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`
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`
`when a plasma source is utilized to generate neutral species to be transported
`
`downstream of the source for use in ashing resist on a semiconductor device substrate
`
`(a wafer or flat panel electronic display), the concentration and potential of charged
`
`plasma species in the reaction zone are desirably reduced to avoid charging damage from
`
`5
`
`electron or ionic current from the plasma to the device. When there is a substantial
`
`potential difference between plasma in the source and grounded surfaces beyond the
`
`source, there is a tendency for unwanted parasitic plasma discharges to form outside of
`
`the source region.
`
`Another undesirable effect of potential difference is associated with the
`
`10
`
`acceleration of ions toward grounded surfaces and subsequent impact of the energetic
`
`ions with surfaces. High energy ion bombardment may cause lattice damage to device
`
`substrates being processed and may cause the chamber wall or other chamber materials
`
`to sputter and contaminate device wafers.
`
`In other plasma processing procedures,
`
`however, some ion bombardment may be necessary or desirable, as is the case
`
`15
`
`particularly for anisotropic ion-induced plasma etching procedures (for a discussion of
`
`ion—enhanced plasma etching mechanisms §e_e Flamrn (Ch. 2, pp.94—183 in Plasma
`
`Etching, An Introduction, D. M. Manos and D.L. Flarnrn, eds., Academic Press,
`
`1989)). Consequently, uncontrolled potential differences, such as that caused by "stray"
`
`capacitive coupling from the coil of an inductive plasma source to the plasma, are often
`
`20
`
`undesirable.
`
`Those with skill in the art have believed, erroneously, that shielding is
`
`necessary to control or eliminate unwanted plasma potentials which would otherwise be
`
`produced by coupling between inductive plasmas and the high voltages generated across
`
`matched inductive applicators used to generate said inductive plasmas. Hence an axially
`
`25
`
`split shield has often been inserted between the inductive applicator and helical
`
`resonator, as described, for example, in USP 5,304,282, USP 5,234,529 and USP
`
`5,234,231.
`
`An additional limitation of conventional helical resonators and other
`
`inductive plasma source is related to discharge initiation (initiation is often termed
`
`30
`
`“breakdown”).
`
`In particular,
`
`ignition (known as plasma breakdown) of inductive
`
`breakdown generally begins with a capacitive electric field discharge, which is stable at
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`7
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`LAM Exh 1006-pg 9
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`lower currents and powers (gee, for example, I. Amorim, H.S. Maciel and J.P. Sudana,
`
`J. Vac. Sci. Technol. B9, pp. 362-365, 1991). This process requires a potential
`
`difference to be capacitively coupled to a region where plasma is to be formed.
`
`Accordingly, shields tend to block capacitive electric fields, which induce plasma
`
`5
`
`ignition and inductive breakdown.
`
`It is well known to those skilled in the art that the capacitively electrical
`
`field and the potential corresponding to such field required to initiate an electrical
`
`discharge is generally much higher than the field needed to sustain the capacitive plasma
`
`discharge form after it is started. Hence discharge initiation often requires a higher
`
`10
`
`voltage than discharge maintenance. The generation of a sufficiently high voltage often
`
`requires a high power rf generator owing to the fact that the Q of many unshielded coils
`
`and matching networks is limited in practice for values below about several hundred.
`
`However, as noted in an article by Flarnm et al. (Ind. Eng. Chem. Xxxxxxx, ) and in
`
`USP 4,918,031 helical resonators are an exception in that very high Q values are easily
`
`15
`
`attainable.
`
`As noted above, it is often difficult to initiate a plasma in shielded helical
`
`resonators and other inductive discharges despite high Q values. This difficulty comes
`
`from the shielding action itself which are designed to prevent electrical fields from the
`
`applicator coil from penetrating into the plasma discharge zone after the plasma has
`
`20
`
`ignited and been stabilized in an inductive form.
`
`Referring to the above lin1itations, conventional plasma sources also have
`
`disadvantages when used in conventional plasma enhanced CVD techniques. These
`
`techniques commonly form a reaction of a gas composition in a plasma discharge. One
`
`conventional plasma enhanced technique relies upon ions aiding in rearranging and
`
`25
`
`stabilizing the fihn, provided the bombardment from the plasma is not sufficiently
`
`energetic to damage the underlying substrate or the growing film. Conventional
`
`resonators and other types of inductive discharges often produce parasitic plasma
`
`currents from capacitive coupling, which often detrimentally influence film quality, e.g.,
`
`an inferior film, etc. These parasitic plasma currents are often uncontrollable, and
`
`30
`
`highly undesirable. These plasma sources also have disadvantages in other plasma
`
`processing techniques such as ion—assisted etching, and others. Of course, the particular
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`disadvantage will often depend upon the application.
`
`From the above it is seen that an improved technique, including a method
`
`and apparatus, for plasma processing is often desired.
`
`5
`
`SUMMARY OF THE INVENTION
`
`The present invention provides a technique,
`
`including a method and
`
`apparatus, for fabricating a product using a plasma discharge. One aspect of the present
`
`technique relies upon multi—step etching processes for selectively removing a film on a
`
`workpiece using differing temperatures.
`
`It overcomes serious disadvantages of prior art
`
`10
`
`methods in which throughput and etching rate were lowered in order to avoid excessive
`
`device damage to a workpiece. In particular, this technique is extremely beneficial for
`
`removing resist masks which have been used to effect selective ion implantation of a
`
`substrate. In general, implantation of ions into a resist masking surface causes the upper
`
`surface of said resist to become extremely cross—linked and contaminated by materials
`
`15
`
`from the ion bombardment.
`
`In another aspect of the invention, the present invention involves a process
`
`in which utilizes temperature changes to achieve high etch rates while simultaneously
`
`maintaining high etch selectivity between a layer which is being pattered or removed
`
`other material layers. An embodiment of this process advantageously employs a
`
`20
`
`sequence of temperature changes as an unexpected means to avoid various types of
`
`processing damage to the a device and material layers. A novel inventive means for
`
`effecting a suitable controlled change in temperature as part of a process involves the use
`
`of a workpiece support which has low thermal mass in comparison to the heat transfer
`
`means.
`
`In an aspect of this invention, a fluid is utilized to change the temperature of a
`
`25
`
`workpiece.
`
`In another aspect, the thermal capacity of a circulating fluid is sufficiently
`
`greater than the thermal capacity of the workpiece support that it permits maintaining the
`
`workpiece at a substantially uniform temperature.
`
`In another aspect of the invention provides an apparatus for etching a
`
`substrate in the manufacture of a device using different temperatures during etching.
`
`30
`
`The apparatus includes a chamber and a substrate holder disposed in the chamber. The
`
`substrate holder has a selected thermal mass to facilitate changing the temperature of the
`
`LAM Exh 1006-pg ll
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`LAM Exh 1006-pg 11
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`
`substrate to be etched. That is, the selected thermal mass of the substrate holder allows
`
`for a change from a first temperature to a second temperature within a characteristic time
`
`period to process a film. The present apparatus can, for example, provide different
`
`processing temperatures during an etching process or the like.
`
`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. 1 is a simplified diagram of a plasma etching apparatus according to
`
`5
`
`10
`
`,5
`
`
`
`
`the present invention;
`
`Figs. 2A-2E are simplified configurations using wave adjustment circuits
`
`according to the present invention;
`
`15
`
`Fig. 3 is a simplified diagram of a chemical vapor deposition apparatus
`
`according to the present invention;
`
`Fig. 4 is a simplified diagram of a stripper according to the present
`
`invention;
`
`Figs. 5A-5C are more detailed simplified diagrams of a helical resonator
`
`20
`
`according to the present invention;
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`Fig. 6 is a simplified block diagram of a substrate holder according to the
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`present invention; and
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`Fig. 7 is a simplified flow diagram of a heating process according to the
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`present invention.
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`DETAILED DESCRIPTION OF THE INVENTION
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`DEFINITIONS:
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`To clarify certain concepts used in this application, it will be convenient
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`to introduce these definitions.
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`Ground (or ground potential): These terms are defined as a reference
`potential which is generally taken as the potential of a highly conductive
`shield or other highly conductive surface which surrounds the plasma
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`source. To be a true ground shield in the sense of this definition, the RF
`conductance at the operating frequency is often substantially high so that
`potential differences generated by current within the shield are of
`negligible magnitude compared to potentials intentionally applied to the
`various structures and elements of the plasma source or substrate support
`assembly. However, some realizations of plasma sources do not
`incorporate a shield or surface with adequate electrical susceptance to
`meet this definition.
`In implementations where there is a surrounding
`conductive surface that is somewhat similar to a ground shield or ground
`plane, the ground potential is taken to be the fictitious potential which the
`imperfect grounded surface would have equilibrated to if it had zero high
`frequency impedance.
`In designs where there is no physical surface
`which is adequately configured or which does not have insufficient
`susceptance to act as a "ground" according to the above definition,
`ground potential is the potential of a fictitious surface which is equi-
`potential with the shield or "ground" conductor of an unbalanced
`transmission line connection to the plasma source at its RF feed point.
`In designs where the plasma source is connected to an RF generator with
`a balanced transmission line RF feed, "ground" potential is the average
`of the driven feed line potentials at the point where the feed lines are
`coupled to the plasma source.
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`Inductively Coupled Power: This term is defined as power transferred to
`the plasma substantially by means of a time—varying magnetic flux which
`is
`induced within the volume containing the plasma source.
`A
`tirne—varying magnetic flux induces an electromotive force in accord with
`Maxwell's equations.
`This electromotive force induces motion by
`electrons and other charged particles in the plasma and thereby imparts
`energy to these particles.
`.
`In most conventional
`RF inductive power source and bias power supply:
`inductive plasma source reactors, power is supplied to an inductive
`coupling element (the inductive coupling element is often a multi—turn coil
`which abuts a dielectric wall containing a gas where the plasma is ignited
`at low pressure) by an rf power generator.
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`Conventional Helical Resonator: Conventional helical resonator can be
`defined as plasma applicators. These plasma applicators have been
`designed and operated in multiple configurations, which were described
`in, for example, U.S. Patent No. 4,918,031 in the names of Flamrn et al.,
`U.S. Patent No. 4,368,092 in the name of Steinberg gt a_1., U.S Patent
`No. 5,304,282 in the name of Flamm, U.S. Patent No. 5,234,529 in the
`name of Johnson, U.S. Patent No. 5,431,968 in the name of Miller, and
`others. In these configurations, one end of the helical resonator applicator
`coil has been grounded to its outer shield.
`In one conventional
`configuration, a quarter wavelength helical resonator section is employed
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`with one end of the applicator coil grounded and the other end floating
`(i.e., open circuited). A trimming capacitance is sometimes connected
`between the grounded outer shield and the coil to "fine tune" the quarter
`wave structure to a desired resonant frequency that is below the native
`resonant frequency without added capacitance.
`In another conventional
`configuration, a half-wavelength helical resonator section was employed
`in which both ends of the coil were grounded. The function of grounding
`the one or both ends of the coil was believed to be not essential, but
`advantageous to "stabilize the plasma operating characteristics" and
`"reduce the possibility of coupling stray current to nearby objects." SQ
`U.S. Patent No. 4,918,031.
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`Conventional resonators have also been constructed in other geometrical
`configurations. For instance, the design of helical resonators with a
`shield of square cross section is described in Zverev e_t a_l., IRE
`Transactions on Component Parts, pp. 99-110, Sept. 1961.
`Johnson
`(U.S. Patent No. 5,234,529) teaches that one end of the cylindrical spiral
`coil in a conventional helical resonator may be deformed into a planar
`spiral above the top surface of the plasma reactor tube. U.S. Patent No.
`5,241,245 in the names of Barnes e_t a_l. teach the use of conventional
`helical resonators in which the spiral cylindrical coil is entirely deformed
`into a planar spiral arrangement with no helical coil componentalong the
`sidewalls of the plasma source (this geometry has often been referred to
`as a "transformer coupled plasma," termed a TCP).
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`Radiation: Flux of entities which delivers substantial momentum to a
`surface and transitions materials into an excited state(s). Radiation often
`induces non-thermal processes,
`including sputtering,
`ion enhanced
`etching, or synergistic bond breaking, and may increase reaction rates
`above substantially isothermal chemistry. Energetic ions are a form of
`radiation that can meet both criteria. Energetic ions are often neutralized
`by electrons from a surface prior to actual impact. Hence the behavior
`of energetic neutrals, as typified by high velocity super thermal neutral
`beam may induce similar effects. Electromagnetic radiation may also
`induce non-thermal surface processes such as chemical reaction or
`ablation.
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`Fig. 1 is a simplified diagram of a plasma etch apparatus 10 according to 1
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`the present invention. This etch apparatus is provided with an inductive applicator, e. g. ,
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`inductive coil. This etch apparatus depicted, however, is merely an illustration, and
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`should not limit the scope of the claims as defined herein. One of ordinary skilled in the
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`art may implement the present invention with other treatment chambers and the like.
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`The etch apparatus includes a chamber 12, a feed source 14, an exhaust
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`16, a pedestal 18, an inductive applicator 20, a radio frequency ("rf") power source 22
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`to the inductive applicator 20, wave adjustment circuits 24, 29 (WACS), a radio
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`frequency power source 35 to the