United States Patent [19J
`Flamm
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006017221A
`[11] Patent Number:
`[45] Date of Patent:
`
`6,017,221
`Jan.25,2000
`
`[54] PROCESS DEPENDING ON PLASMA
`DISCHARGES SUSTAINED BY INDUCTIVE
`COUPLING
`
`5,431,968
`5,534,231
`5,637,961
`
`7/1995 Miller eta!. .
`7/1996 Savas .
`6/1997 Ishii et a!. .
`
`[76]
`
`Inventor: Daniel L. Flamm, 476 Green View Dr.,
`Walnut Creek, Calif. 94596
`
`[21] Appl. No.: 08/866,040
`
`[22] Filed:
`
`May 30, 1997
`
`Related U.S. Application Data
`
`[ 63] Continuation-in-part of application No. 08/736,315, Oct. 23,
`1996, abandoned, which is a continuation of application No.
`08/567,224, Dec. 4, 1995, abandoned.
`
`Int. Cl? ..................................................... HOlL 21/00
`[51]
`[52] U.S. Cl. .......................... 437/225; 437/228; 437/233;
`156/643; 156/192.25; 204/192.32
`[58] Field of Search ............................ 118/50.1; 156/643,
`156/345, 646, 659.1; 219/121.41, 121.44;
`204/192.1, 192.12, 192.25; 427/12; 216/2;
`437/225, 228, 233
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`3,873,884
`4,368,092
`4,918,031
`4,943,345
`5,234,529
`5,241,245
`5,304,282
`5,361,016
`
`3/1975 Gabriel .
`1!1983 Steinberg et a!. .
`4/1990 Flamm eta!..
`7/1990 Asmussen et a!. ..................... 156/643
`8/1993 Johnson .
`8/1993 Barnes eta!. .
`4/1994 Flamm.
`11/1994 Ohkawa eta!. ................... 315!111.41
`
`OTHER PUBLICATIONS
`
`Asmussen et al., "The Design of a Microwave Plasma
`Cavity," Proc. of IEEE, 62(1):109-117 (Jan. 1974).
`Eckert, "The Hundred Year History of Induction Dis(cid:173)
`charges," 2nd Ann. Int'l Conf Plasma Chern. Tech., (1984).
`Fossheim et al., "Broadband tguning of helical resonant
`cavitites," J. Phys. E. Sci. Instrum., 11:892-893 (1978).
`Niazi et al. "Operation of a helical resonator plasma source,"
`Plasma Sources Sci. Techno!., 3:482-495 (1994).
`Rappel et al., "Low temperature oxidation of silicon using a
`microwave plasma disk source," J. Vac. sci. Techno!.,
`B4(1):295-298 (Jan./Feb. 1986).
`Zverev et al., "Realization of a Filter with Helical Compo(cid:173)
`nents," IRE Trans. on Component Parts, pp. 99-110, (Sep.
`1961).
`
`Primary Examiner-Laurie Scheiner
`Attorney, Agent, or Firm-Townsend and Townsend and
`Crew LLP
`
`[57]
`
`ABSTRACT
`
`A process for fabricating a product 28, 119. The process
`comprises the steps of subjecting a substrate to a composi(cid:173)
`tion of entities, at least one of the entities emanating from a
`species generated by a gaseous discharge excited by a high
`frequency field in which the vector sum of phase and
`anti-phase capacitive coupled voltages from the inductive
`coupling structure substantially balances.
`
`7 Claims, 13 Drawing Sheets
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`Page 1 of 26
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`Samsung Exhibit 1001
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`U.S. Patent
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`Jan.25,2000
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`Jan.25,2000
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`

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`6,017,221
`
`1
`PROCESS DEPENDING ON PLASMA
`DISCHARGES SUSTAINED BY INDUCTIVE
`COUPLING
`
`CROSS REFERENCES TO RELATED
`APPLICATIONS
`
`This application is a continuation-in-part of application
`Ser. No. 08/736,315 filed Oct. 23, 1996, now abandoned,
`which is a continuation of application Ser. No. 08/567,224
`filed Dec. 4, 1995, now abandoned. All of these documents
`are hereby incorporated by reference for all purposes.
`
`BACKGROUND OF THE INVENTION
`
`This invention relates generally to plasma processing.
`More particularly, the invention is for plasma processing of
`devices using an inductive discharge. This invention is
`illustrated in an example with regard to plasma etching and
`resist stripping of semiconductor devices. The invention also
`is illustrated with regard to chemical vapor deposition 20
`(CVD) 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 mate(cid:173)
`rials such as silicon, silicon dioxide, silicon nitride, 25
`polysilicon, among others.
`Plasma processing techniques can occur in a variety of
`semiconductor manufacturing processes. Examples of
`plasma processing techniques occur in chemical dry etching
`(CDE), ion-assisted etching (IAE), and plasma enhanced 30
`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 fre(cid:173)
`quency power (rf) supplied to an inductive coil for providing 35
`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.
`In other manufacturing processes, ion bombardment to
`substrate surfaces is often undesirable. This ion 45
`bombardment, however, is known to have harmful effects on
`properties of material layers in devices and excessive ion
`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 pro(cid:173)
`cesses. 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 photoresist stripping, often termed ashing or
`stripping. Conventional resist stripping relies upon a reac(cid:173)
`tion between a neutral gas phase species and a surface
`material layer, typically for removal. This reaction generally 65
`forms volatile products with the surface material layer for its
`removal. The neutral gas phase species is formed by a
`
`2
`plasma discharge. This plasma discharge can be sustained by
`a coil (e.g., helical coil, etc.) operating at a selected fre(cid:173)
`quency in a conventional photoresist stripper. An example of
`the conventional photoresist stripper is a quarter-wave heli-
`5 cal resonator stripper, which is described by U.S. Pat. No.
`4,368,092 in the name of Steinberg et al.
`Referring to the above, an objective in chemical dry
`etching is to reduce or even eliminate ion bombardment (or
`ion flux) to surfaces being processed to maintain the desired
`10 etching selectivity. In practice, however, it is often difficult
`to achieve using conventional techniques. These conven(cid:173)
`tional techniques generally attempt to control ion flux by
`suppressing the amount of charged species in the plasma
`source reaching the process chamber. A variety of tech-
`15 niques 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 to directly suppress charge density downstream of
`the plasma source by interfering with convective and diffu(cid:173)
`sive transport of charged species. They tend to promote
`recombination of charged species by either increasing the
`surface area (e.g., baffles, etc.) relative to volume, or increas(cid:173)
`ing flow time, which relates to increasing the distance
`between the plasma source and the process chamber.
`These baffles, however, cause loss of desirable neutral
`etchant species as well. The baffles, shields, and alike, also
`are often cumbersome. Baffles, shields, or the large separa(cid:173)
`tion distances also cause undesirable recombinative loss of
`active species and sometimes cause radio frequency power
`loss and other problems. These baffles and shields also are
`a potential source of particulate contamination, which is
`often damaging to integrated circuits.
`Baffles, shields, spatial separation, and alike, when used
`alone also are often insufficient to substantially prevent
`unwanted parasitic plasma currents. These plasma currents
`40 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
`accelerated and dissociative collisions with neutral particles
`can multiply the concentration of charge to higher levels. If
`sufficient "seed" levels of charge and rf potentials 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
`50 greater than plasma density within the source plasma region,
`thereby causing even more ion flux to the substrate.
`Charge densities also create a voltage difference between
`the plasma source and processing chamber or substrate
`support, which can have an additional deleterious effect.
`55 This voltage difference enhances electric fields that can
`accelerate extraction of charge from the plasma source.
`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
`60 assisted etching.
`Conventional ion assisted plasma etching, however, often
`requires control and maintenance of ion flux intensity and
`uniformity within selected process limits and within selected
`process energy ranges. Control and maintenance of ion flux
`intensity and uniformity are often difficult to achieve using
`conventional techniques. For instance, capacitive coupling
`between high voltage selections of the coil and the plasma
`
`Page 15 of 26
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`

`

`6,017,221
`
`25
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`30
`
`3
`~ischarge ?ften cause high and uncontrollable plasma poten(cid:173)
`tials relative to ground. It is generally understood that
`voltage difference between the plasma and ground can cause
`damaging high energy ion bombardment of articles being
`processed by the plasma, as illustrated by U.S. Pat. No. 5
`5,234,529 in the name of Johnson. It is further often under(cid:173)
`stood that rf component of the plasma potential varies in
`tim~ si?ce 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 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 ele(cid:173)
`ments into the processing apparatus downstream of the
`source. When the 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 contami(cid:173)
`nation is even greater when there is capacitive discharge (ion
`bombardment from capacitive discharge is a potential source
`of sputtered material). Contamination is damaging to the
`manufacture of integrated circuit devices.
`Another limitation is that the shield or electrode elements
`generally require small holes therein as structural elements.
`These small holes are designed to allow gas to flow there(cid:173)
`through. The small holes, however, tend to introduce
`unwanted pressure drops and neutral species recombination.
`If the holes are made larger, the plasma from the source
`tends to survive transport through the holes and unwanted
`downstream charge flux will often result. In addition, unde(cid:173)
`sirable discharges to these holes in shields can at times
`produce an even more undesirable hollow cathode effect. '
`In conventional helical resonator designs, conductive
`external shields are interposed between the inductive power
`(e.g., coil, etc.) and walls of the vacuum vessel containing
`the plasma. A variety limitations with these external capaci(cid:173)
`tive shielded plasma designs (e.g., helical resonator, induc(cid:173)
`tive discharge, etc.) have been observed. In particular, the
`capacitively shielded design often produces plasmas that are
`difficult to tune and even ignite. Alternatively, the use of
`unshielded plasma sources (e.g., conventional quarter-wave
`resonator, conventional half-wave resonator, etc.) attain a
`substantial plasma potential from capacitive coupling to the
`coil, and hence are prone to create uncontrolled parasitic
`plasma currents to grounded surfaces. Accordingly, the use
`of either the shielded or the unshielded sources using
`conventional quarter and half-wave rf frequencies 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 limit. Power
`dissipation in the structure causes heating and thereby
`increases the difficulty and expense of implementing effec(cid:173)
`tive 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 60
`power loss and heating. Conventional capacitive shielding in
`helical resonator discharges utilized a shield which was
`substantially split along the long axis of the resonator to
`lessen eddy current loss. However, such a shield substan(cid:173)
`tially perturbs the resonator characteristics owing to
`unwanted capacitive coupling and current which flows from
`the coil to the shield. Since there are no general design
`
`4
`equations, nor are properties currently known for resonators
`which are "loaded" with a shield along the axis, sources
`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, independent of input power, pressure, gas com(cid:173)
`position and other variables. In many cases, it is desired to
`have the plasma potential be substantially at ground poten-
`10 tial (at least offset from ground potential by an amount
`insignificantly different from the floating potential or intrin(cid:173)
`sic DC plasma potential). For example, when a plasma
`source is utilized to generate neutral species to be trans(cid:173)
`ported downstream of the source for use in ashing resist on
`15 a semiconductor device substrate (a wafer or fiat panel
`electronic display), the concentration and potential of
`charged plasma species in the reaction zone are desirably
`reduced to avoid charging damage from electron or ionic
`current from the plasma to the device. When there is a
`20 substantial potential difference between plasma in the source
`and grounded surfaces beyond the source, there is a ten(cid:173)
`dency for unwanted parasitic plasma discharges to form
`outside of the source region.
`Another undesirable effect of potential difference is the
`acceleration of ions toward grounded surfaces and subse-
`quent impact of the energetic ions with surfaces. High
`energy ion bombardment may cause lattice damage to the
`device substrate 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 particularly for anisotropic ion(cid:173)
`induced plasma etching procedures (for a discussion of
`ion-enhanced plasma etching mechanisms See Flamm (Ch.
`2, pp.94-183 in Plasma Etching, An Introduction, D. M.
`Manos and D. L. Flamm, 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 undesirable.
`Referring to the above limitations, conventional plasma
`sources also have disadvantages when used in conventional
`plasma enhanced CVD techniques. These techniques com(cid:173)
`monly form a reaction of a gas composition in a plasma
`45 discharge. One conventional plasma enhanced technique
`relies upon ions aiding in rearranging and stabilizing the
`film, 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
`50 inductive discharges often produce parasitic plasma currents
`from capacitive coupling, which often detrimentally influ(cid:173)
`ences film quality, e.g., an inferior film, etc. These parasitic
`plasma currents are often uncontrollable, and highly unde(cid:173)
`sirable. These plasma sources also have disadvantages in
`55 other plasma processing techniques such as ion-assisted
`etching, and others. Of course, the particular disadvantage
`will often depend upon the application.
`To clarify certain concepts used in this application, it will
`be convenient to introduce these definitions.
`Ground (or ground potential): These terms are defined as
`a reference potential which is generally taken as the poten(cid:173)
`tial of a highly conductive shield or other highly conductive
`surface which surrounds the plasma source. To be a true
`ground shield in the sense of this definition, the RF con-
`65 ductance at the operating frequency is often substantially
`high so that potential differences generated by current within
`the shield are of negligible magnitude compared to paten-
`
`35
`
`40
`
`Page 16 of 26
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`

`6,017,221
`
`6
`planar spiral above the top surface of the plasma reactor
`tube. U.S. Pat. No. 5,241,245 in the names of Barnes et al.
`teach the use of conventional helical resonators in which the
`spiral cylindrical coil is entirely deformed into a planar
`5 spiral arrangement with no helical coil component along the
`sidewalls of the plasma source (this geometry has often been
`referred to as a "transformer coupled plasma," termed a
`TCP).
`From the above it is seen that an improved technique,
`10 including a method and apparatus, for plasma processing is
`often desired.
`
`5
`tials intentionally applied to the various structures and
`elements of the plasma source or substrate support assembly.
`However, some realizations of plasma sources do not incor(cid:173)
`porate a shield or surface with adequate electrical suscep(cid:173)
`tance 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 trans-
`mission 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.
`Inductively Coupled Power: This term is defined as power
`transferred to the plasma substantially by means of a time(cid:173)
`varying magnetic flux which is induced within the volume
`containing the plasma source. A time-varying magnetic flux 25
`induces an electromotive force in accord with Maxwell's
`equations. This electromotive force induces motion by elec(cid:173)
`trons and other charged particles in the plasma and thereby
`imparts energy to these particles.
`RF inductive power source and bias power supply: In
`most conventional 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.
`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. Pat. No. 4,918,031 in the names of Flamm et
`al., U.S. Pat. No. 4,368,092 in the name of Steinberg et al.,
`U.S. Pat. No. 5,304,282 in the name of Flamm, U.S. Pat. No.
`5,234,529 in the name of Johnson, U.S. Pat. No. 5,431,968
`in the name of Miller, and others. In these configurations,
`one end of the helical resonator applicator coil has been 45
`grounded to its outer shield. In one conventional
`configuration, a quarter wavelength helical resonator section
`is employed 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 50
`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 heli-
`cal resonator section was employed in which both ends of 55
`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 character(cid:173)
`istics" and "reduce the possibility of coupling stray current
`to nearby objects." See U.S. Pat. No. 4,918,031.
`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 et al., IRE Transactions on Component
`Parts, pp. 99-110, Sept. 1961. Johnson (U.S. Pat. No.
`5,234,529) teaches that one end of the cylindrical spiral coil
`in a conventional helical resonator may be deformed into a
`
`20
`
`15
`
`SUMMARY OF THE INVENTION
`The present invention provides a technique, including a
`method and apparatus, for fabricating a product using a
`plasma discharge. The present technique relies upon the
`control of the instantaneous plasma AC potential to selec(cid:173)
`tively control a variety of plasma characteristics. These
`characteristics include the amount of neutral species, the
`amount of charged species, overall plasma potential, the
`spatial extent and distribution of plasma density, the distri-
`bution of electrical current, and others. This technique can
`be used in applications including chemical dry etching (e.g.,
`stripping, etc.), ion-enhanced etching, plasma immersion ion
`implantation, chemical vapor deposition and material
`growth, and others.
`In one aspect of the invention, a process for fabricating a
`product is provided. These products include a varieties of
`devices (e.g., semiconductor, fiat panel displays, micro-
`30 machined structures, etc.) and materials, e.g., diamonds, raw
`materials, plastics, etc. The process includes steps of sub(cid:173)
`jecting a substrate to a composition of entities. At least one
`of the entities emanates from a species generated by a
`gaseous discharge excited by a high frequency field in which
`35 the vector sum of phase and anti-phase capacitive coupled
`voltages (e.g., AC plasma voltage) from the inductive cou(cid:173)
`pling structure substantially balances. This process provides
`for a technique that is substantially free from stray or
`parasitic capacitive coupling from the plasma source to
`40 chamber bodies (e.g., substrate, walls, etc.) at or near ground
`potential.
`In another aspect of the invention, another process for
`fabricating a product is provided. The process includes steps
`of subjecting a substrate to a composition of entities. At least
`one of the entities emanates from a species generated by a
`gaseous discharge excited by a high frequency field in which
`the vector sum of phase and anti-phase capacitive coupled
`voltages from the inductive coupling structure is selectively
`maintained. This process provides for a technique that can
`selectively control the amount of capacitive coupling to
`chamber bodies at or near ground potential.
`A further aspect of the invention provides yet another
`process for fabricating a product. This process includes steps
`of subjecting a substrate to a composition of entities. At least
`one of the entities emanates from a species generated by a
`gaseous discharge excited by a high frequency field in which
`the vector sum of phase and anti-phase capacitive coupled
`voltages from the inductive coupling structure is selectively
`maintained. A further step of selectively applying a voltage
`60 between the at least one of the entities in the plasma source
`and a substrate is provided. This process provides for a
`technique that can selectively control the amount of capaci(cid:173)
`tive coupling to chamber bodies at or near ground potential,
`and provide for a driving voltage between the entities and a
`65 substrate.
`Another aspect of the invention provides another process
`for fabricating a product. The process comprises steps of
`
`Page 17 of 26
`
`

`

`7
`subjecting a substrate to a composition of entities and using
`the resulting substrate for completion of the product. At least
`one of the entities emanates from a species generated by a
`gaseous discharge provided by a plasma applicator, e.g., a
`helical resonator, inductive coil, transmission line, etc. This
`plasma applicator has an integral current driven by capaci(cid:173)
`tive coupling of a plasma column to elements with a selected
`potential greater than a surrounding shield potential sub(cid:173)
`stantially equal to capacitive coupling of the plasma column
`to substantially equal elements with a potential below shield 10
`potential.
`In a further aspect, the invention provides an apparatus for
`fabricating a product. The apparatus has an enclosure com(cid:173)
`prising an outer surface and an inner surface. The enclosure
`houses a gaseous discharge. The apparatus also includes a 15
`plasma applicator (e.g., helical coil, inductive coil, trans(cid:173)
`mission line, etc.) disposed adjacent to the outer surface. A
`high frequency power source operably coupled to the plasma
`applicator is included. The high frequency power source
`provides high frequency to excite the gaseous discharge to 20
`provide at least one entity from a high frequency field in
`which the vector sum of phase and anti-phase capacitive
`current coupled from the inductive coupling structure is
`selectively maintained.
`In another aspect, the present invention provides an 25
`improved plasma discharge apparatus. This plasma dis(cid:173)
`charge apparatus includes a plasma source, a plasma appli(cid:173)
`cator (e.g., inductive coil, transmission line, etc.), and other
`elements. This plasma applicator provides a de-coupled
`plasma source. A wave adjustment circuit (e.g., RLC circuit, 30
`coil, transmission line, etc.) is operably coupled to the
`plasma applicator. The wave adjustment circuit can selec(cid:173)
`tively adjust phase and anti-phase potentials of the plasma
`from an rf power supply. This rf power supply is operably
`coupled to the wave adjustment circuit.
`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.
`
`35
`
`40
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a simplified diagram of a plasma etching
`apparatus according to the present invention;
`FIGS. 2A-2E are simplified configurations using wave
`adjustment circuits according to the present invention;
`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 according to the present invention;
`FIG. 6 is a conventional quarter-wave helical resonator
`plasma etching apparatus with stray plasma which results
`from the coupling in the conventional design;
`FIG. 7 is a simplified diagram of the rf voltage distribu(cid:173)
`tion along the coil of the FIG. 6 apparatus;
`FIG. 8 is a simplified top-view diagram of a stripping
`apparatus according to the present experiments; and
`FIG. 9 is a simplified side-view diagram of a stripping
`apparatus according to the present experiments.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`FIG. 1 is a simplified diagram of a plasma etch apparatus
`10 according to the present invention. This etch apparatus is
`
`6,017,221
`
`s
`
`8
`provided with an inductive applicator, e.g., inductive coil.
`This etch apparatus depicted, however, is merely an
`illustration, and should not limit the scope of the claims as
`defined herein. One of ordin