United States Patent [19]
`Campbell et al.
`
`[75]
`
`[54] HIGH DENSITY PLASMA DEPOSffiON
`AND ETCHING APPARATUS
`Inventors: Gregor A. Campbell, Glendale;
`Robert W. Conn, Los Angeles; Dan
`Katz, Beverly Hills; N. William
`Parker, Fairfield; Alexis de
`Chambrier, Glendale, all of Calif.
`[73] Assignee: Plasma & Materials Technologies,
`Inc., Chatsworth, Calif.
`[21] Appl. No.: 979,574
`Nov. 20, 1992
`[22] Filed:
`
`Related U.S. Application Data
`[63] Continuation-in-part ofSer. No. 964,149, Oct. 19, 1992,
`which is a continuation-in-part of Ser. No. 887,278,
`May 21, 1992, abandoned, which is a continuation of
`Ser. No. 650,788, Feb. 4, 1991, Pat. No. 5,122,251,
`which is a continuation-in-part of Ser. No. 365,533,
`Jun. 13, 1989, Pat. No. 4,990,229.
`Int. Cl.6 ....................... C23C 16/50; HOIL 21/00
`[51]
`[52] u.s. a ................................. 1181723 R; 1181719;
`118/723 MP; 118/723 AN; 156/345;
`204/298.37; 204/298.38
`[58] Field of Search ............... 118/723 MP, 723 MW,
`118/723 ME, 723 MR, 723 MA, 723 AN, 723
`E, 723 ER, 723 IR, 723 R; 156/345;
`204/298.37, 298.38
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`4,433,228 2/1984 Nishimatsu et al ..
`4,963,242 10/1990 Sato et al ................... 204/298.37 X
`4,990,229 2/1991 Campbell et al ............... 118/723 X
`5,089,441 2/1892 Moslehi ............................... 437/225
`
`llllllllllllllllllllllllllllllll IIIII IIIII IIIII IIIII IIIII 111111111111111111
`US005429070A
`5,429,070
`[I 1] Patent Number:
`[45] Date of Patent:
`Jul. 4, 1995
`
`5,122,251 6/1992 Campbell et al ............... 1181723 X
`
`FOREIGN PATENT DOCUMENTS
`63-77120 4/1988 Japan ................................... 156/345
`63-274148 11/1988 Japan .
`
`Primary Examiner-R. Bruce Breneman
`Assistant Examiner-Jonathan D. Baskin
`Attorney, Agent, or Firm-Skjerven, Morrill,
`MacPherson, Franklin & Friel; Alan H. MacPherson;
`David T. Millers
`[57]
`ABSTRACT
`Plasma deposition or etching apparatus is provided
`which comprises a plasma source located above and in
`axial relationship to a substrate process chamber. The
`plasma source may include a sapphire or alumina source
`tube for use with plasmas containing fluorine. Sur(cid:173)
`rounding the plasma source are an inner magnetic coil
`and an outer magnetic coil arranged in the same plane
`perpendicular to the axis of the plasma source and the
`substrate process chamber. Preferably a first current is
`provided through the inner coil and a second current in
`a direction opposite to the direction of the first current
`is provided through the outer coil. The inner and outer
`coils are wrapped with a thin sheet of conducting mate(cid:173)
`rial to shield the coils from RF signal generated by the
`plasma source. The result is to advantageously shape
`the magnetic field in the process chamber to achieve
`extremely uniform processing, particularly when a
`unique diamond shaped pattern of gas feed lines is used
`wherein the diamond is arranged to be approximately
`tangent at four places to the outer circumference of the
`workpiece being processed in the apparatus.
`
`13 Claims, 21 Drawing Sheets
`
`TSMC-1114
`TSMC v. Zond, Inc.
`Page 1 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 1 of 21
`
`5,429,070
`
`•
`C!J
`LL
`
`TSMC-1114 / Page 2 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 2 of 21
`
`5,429,070
`
`-
`
`FIG. 2A
`
`12
`
`FIG. 28
`
`FIG. 2C
`
`TSMC-1114 / Page 3 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 3 of 21
`
`5,429,070
`
`11
`
`16
`
`~~------------------
`,,,
`,
`' ' ',,
`--------------------
`
`-,,
`
`,,'
`
`15
`
`21
`
`20
`
`18
`
`FIG. 3
`
`TSMC-1114 / Page 4 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 4 of 21
`
`5,429,070
`
`11
`
`24
`
`19
`
`FIG. 4A
`
`TSMC-1114 / Page 5 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 5 of 21
`
`5,429,070
`
`11
`
`FIG. 48
`
`TSMC-1114 / Page 6 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 6 of 21
`
`5,429,070
`
`11
`
`10'
`\._
`----
`-----::::::=----
`Q ==-----
`
`18
`
`19
`
`38
`
`11'
`
`3A
`
`FIG. 5A
`
`,,
`,
`'
`,
`'
`,
`'
`
`I
`
`\
`
`~-~--~~
`
`• • I
`
`, ___ _
`
`I
`I
`
`FIG. 58
`
`TSMC-1114 / Page 7 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 7 of 21
`
`5,429,070
`
`4A
`
`FIG. 6A
`
`FIG. 68
`
`TSMC-1114 / Page 8 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 8 of 21
`
`5,429,070
`
`----~:.:.:.:::.~:.:.-:~
`
`.,.--:.----
`.. ....
`
`4flli' - -
`
`18
`
`19
`
`12'
`
`38
`
`11'
`
`12 FIG. 7A
`
`N
`
`10'
`
`73
`
`FIG. 78
`
`TSMC-1114 / Page 9 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 9 of 21
`
`5,429,070
`
`11
`
`80
`
`18
`
`19
`
`38
`
`83
`
`FIG. 8
`
`94
`
`TSMC-1114 / Page 10 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 10 of 21
`
`5,429,070
`
`100
`
`50
`
`o~--~~~~~~--------~--~~
`1000
`10
`100
`
`B-FIELD [G]
`
`FIG. 9
`
`TSMC-1114 / Page 11 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 11 of 21
`
`5,429,070
`
`JSAT [rnA I cm2]
`
`1oo~--------------,
`
`80
`
`60
`
`40
`
`20
`
`o~~~~~~~~~~~~~~
`0
`20
`40
`60
`80
`100 120
`140
`160
`
`B-FIELD [G)
`
`FIG. 10
`
`FLUX [A]
`1s~------------~~
`14
`13.
`12 11
`10
`9
`8
`7
`6
`5
`4
`3
`2
`1
`a~--~------~--~--~--~~
`3.0
`2.0
`1.0
`0
`
`POWER[KW]
`FIG. 11
`
`TSMC-1114 / Page 12 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 12 of 21
`
`5,429,070
`
`JSAT [rnA I cm2]
`
`100~--------------------------~
`
`80
`
`60
`
`40
`
`20
`
`0
`
`0
`
`0
`
`3
`2
`PRESSURE [mTORR]
`FIG. 12
`
`4
`
`5
`
`Jsat [rnA I cm2]
`40~--------------------------~
`
`,' ~-
`
`I
`I
`I
`I
`I
`I
`
`,
`,
`,
`
`3()_
`
`20-
`.
`
`10-
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`I)
`
`I
`I
`I
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`I
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`-
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`\
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`\
`\.
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`'
`'
`'
`\
`
`0~--~--~--~--~r---.-.--.-~
`0
`1.0
`2.0
`3.0
`
`POSITION [em]
`FIG. 13
`
`TSMC-1114 / Page 13 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 13 of 21
`
`5,429,070
`
`FIG. 14A
`
`TSMC-1114 / Page 14 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 14 of 21
`
`5,429,070
`
`132 -""""==---~;;...-
`133-+---
`
`I
`
`148
`
`FIG. 148
`
`150
`
`FIG. 14C
`
`TSMC-1114 / Page 15 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 15 of 21
`
`5,429,070
`
`0.25
`
`0.2
`
`131
`
`0.15
`
`0.1
`
`0.05
`
`0.
`
`139a
`
`139
`
`FIG. 15A
`
`TSMC-1114 / Page 16 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 16 of 21
`
`5,429,070
`
`0.25
`
`0.1
`
`0.05
`
`0.
`
`135
`
`FIG. 158
`
`TSMC-1114 / Page 17 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 17 of 21
`
`5,429,070
`
`148
`
`FIG. 168
`
`133
`203
`
`216 ____ ____.
`215 ____ ____.
`214 - - - - - . . . J I
`
`213
`
`FIG. 16A
`
`TSMC-1114 / Page 18 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 18 of 21
`
`5,429,070
`
`/ /\
`
`171
`
`45"
`
`FIG. 17A
`
`'.
`
`1,
`
`- - - -
`
`, ........
`. .. ..
`/ ....
`'
`..
`.. '
`'
`.... ,, ...
`' ...
`..........
`....
`32.59" ........ ~ ...............
`'
`.........
`_L ___ f..,:,
`.. ~ ..
`65.18"
`\ ........ .;.~ ....
`' / ' ,
`..
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`, '
`I
`I
`I
`I
`
`FIG. 178
`
`TSMC-1114 / Page 19 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 19 of 21
`
`5,429,070
`
`\ 45"
`
`FIG. 17C
`
`TSMC-1114 / Page 20 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 20 of 21
`
`5,429,070
`
`FIG. 18
`
`FIG. 20
`
`TSMC-1114 / Page 21 of 36
`
`

`

`U.S. Patent
`
`July 4, 1995
`
`Sheet 21 of 21
`
`5,429,070
`
`...---------------t -tf Selectivity (AVSi02)
`'\] Selectivity (AVPR)
`3m Torr, MORI power 1000W
`0 AI-Si-Cu Etch Rate
`85%CI2·15%BCI3
`0 Si-02 Etch Rate
`~ Resist Etch Rate
`
`LEGEND
`
`10
`
`10
`
`-c:
`-fii cc
`~ 5
`(.) -w
`
`.&:
`
`0
`
`~------------~--------------~----~0
`100
`50
`0
`
`Bias RF Power (W)
`(@13.56 MHz)
`
`FIG. 19
`
`TSMC-1114 / Page 22 of 36
`
`

`

`1
`
`5,429,070
`
`HIGH DENSITY PLASMA DEPOSmON AND
`ETCHING APPARATUS
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`This application is a continuation-in-part of U.S. pa(cid:173)
`tent application Ser. No. 07/964,149 fiJed Oct. 19, 1992
`which is a continuation-in-part of U.S. patent applica(cid:173)
`tion Ser. No. 07/887,278 filed May 21, 1992, now aban(cid:173)
`doned, which is a continuation of U.S. patent applica(cid:173)
`tion No. 07/650,788 filed Feb. 4, 1991 and issued Jun.
`16, 1992 as U.S. Pat. No. 5,122,251, which is a continua(cid:173)
`tion-in-part of U.S. patent application Ser. No.
`07/365,533, filed Jun. 13, 1989 and issued Feb. 5, 1991 as
`U.S. Pat. No. 4,990,229, all of which are hereby incor(cid:173)
`porated by reference.
`
`2
`coatings and the coating of glass. In general, a plasma is
`produced at the sputter target material and the sputter
`target is biased to a negative voltage of around 700 V.
`Plasma ions (generally argon) impact the surface and
`5 sputter the material which then transports as neutral
`atoms to a substrate. Reactive gases can be introduced
`to chemically react with the sputtered atoms at the host
`substrate in a process called reactive sputter deposition.
`Rate is often important and it is therefore important to
`10 make the plasma as dense as possible. Ionization of
`reactive gases is also important and is helped by having
`plasma in the vicinity of the substrate material. Sputter(cid:173)
`ing is also done by ions accelerated in an ion or plasma
`gun and then made to bombard the sputter target. In
`IS this case, a bias voltage on the target is not necessary.
`For sputtering insulating materials, RF voltage bias can
`be applied to the sputter target.
`
`Existing Methods
`There are presently two widely used methods for
`plasma deposition and etching, the parallel plate reactor
`and the ECR plasma deposition system. There are also
`methods based on the use of RF to produce plasma
`including ordinary induction techniques and techniques
`based on whistler waves.
`
`20
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The present invention relates to a plasma deposition
`or etching method and various apparatus for depositing
`a thin film onto a substrate or for removal (etching) of
`a mm from a substrate. The present invention includes
`the use of a new and significantly better high density 25
`plasma deposition and etching apparatus, a significantly
`improved magnetic means for the plasma source region
`and operation with a specified range of processes and
`gases. Applications of the present invention include the
`removal by etching of a layer from a surface, the re- 30
`moval by sputtering of a layer from a surface, or the
`deposition of a layer onto a surface.
`2. Related Art
`
`Etching
`Plasma etching involves using chemically active
`atoms or energetic ions to remove material from a sub(cid:173)
`strate. It is a key technology in the fabrication of semi(cid:173)
`conductor integrated circuits. However, before the
`advent of microwave plasmas utilizing electron cyclo- 40
`tron resonance (ECR), it was becoming difficult for
`conventional plasma etching techniques to satisfy the
`requirements dictated by the increase in device packing
`density. Specifically, the requirement for fine pattern
`etching without undercutting (anisotropic etching) and 45
`the requirements for low damage and high selectivity
`could hardly be satisfied at the same time.
`
`Parallel Plate Reactor (Diode)
`The RF diode has been widely used for both deposi(cid:173)
`tion and etching. It is described in detail in the book by
`Chapman ("Glow Discharge Processes" John Wiley &
`Sons 1980). It uses RF at 13.56 MHz capacitively cou(cid:173)
`pled to one electrode while the other electrode is
`grounded. The pressure in the system is typically 1
`35 mtorr to 1 torr and the plasma density is typically lQIO
`electrons per cm3. The rate at which both deposition or
`etching occurs is dependent on the density of the plasma
`and the density (pressure) of the reactive gas used to
`etch, or, in CVD processes, to deposit.
`In etching, the high pressure needed to sustain the
`discharge causes collisions between the ions and the
`background gas. This causes the paths of the etching
`ions or atoms to be randomized or non-directional,
`leading to undercutting of the mask. This is referred to
`as an isotropic etch. It is desirable to have the etch
`atoms or ions be directional so that straight anisotropic
`etches can be achieved. At the high pressure used in RF
`diode discharges, it is necessary for the ions to have
`high energy (up to 1 KeV) to achieve an anisotropic
`etch. However, the high energy of the ions can cause
`damage to the substrate, fllm materials or photoresist.
`The plasma is sustained by secondary electrons that
`are emitted by ions impacting the cathode. These elec(cid:173)
`trons are accelerated by the voltage drop across the
`sheath which is typically 400-1000 V. These fast elec(cid:173)
`trons can bombard the substrate causing it to have a
`high voltage sheath drop. This high voltage can accel(cid:173)
`erate the ions leading to damage of the substrate or film
`material. The presence of high energy electrons leading
`to high voltage sheath drops is undesirable.
`
`Deposition
`Plasma Enhanced Chemical Vapor Deposition SO
`(PECVD) is a widely used technique to deposit materi-
`als on substrates in a host of applications. In normal
`Chemical Vapor Deposition (CVD) the chemical reac(cid:173)
`tion is driven by the temperature of the substrate and for
`most reactions this temperature is high (>800• C.). The 55
`high substrate temperature needed precludes use of this
`method in a number of applications particularly in mi(cid:173)
`croelectronics, displays and optical coatings. The role
`of the plasma is to dissociate and activate the chemical
`gas so that the substrate temperature can be reduced. 60
`The rate of dissociation, activation and ionization is
`proportional to the density of the plasma. It is therefore
`of importance to make the plasma as dense as possible.
`
`Sputtering
`Sputtering is also a widely used method for deposit(cid:173)
`ing materials onto substrates for a wide variety of appli(cid:173)
`cations such as the production of hard or decorative
`
`Electron Cyclotron Resonance Plasmas
`The advent of using microwaves at 2.45 GHz and a
`magnetic field of 875 Gauss to utilize electron cyclotron
`65 resonance allowed the generation of high density plas(cid:173)
`mas at low pressure. The advantages of this technique
`for plasma etching are described by Suzuki in U.S. Pat.
`No. 4,101,411 and in an article entitled "Microwave
`
`TSMC-1114 / Page 23 of 36
`
`

`

`5,429,070
`
`4
`the maximum of the ionization potential of the gas we
`wish to ionize. From the dispersion relation for the
`m=O mode, the higher the value of kz, the higher the
`density. However, the phase velocity of the wave is
`C.rl/kz and so increasing kz decreases the energy of the
`electrons that are accelerated by the wave. If the kz is
`too high then the energy of the electrons may fall below
`the ionization potential.
`Also, Campbell, Conn and Shoji in the above-men-
`lO tioned patents use a magnetic bucket means in conjunc(cid:173)
`tion with the plasma generator to provide a uniform
`plasma density over large circular or rectangular areas.
`They use one or multiple plasma generators in conjunc-
`tion with cylindrical or rectangular magnetic buckets to
`provide a uniform density over a large area for the
`coating or etching of substrates such as are needed for
`IC or flat panel display processing. They use expansion
`of the magnetic field to allow deposition or etching
`over a large area.
`Other RF Induction Sources
`Other existing methods use RF circuit resonances to
`generate plasma. These methods are less efficient than
`those using low frequency whistler waves, and do not
`generate high density plasmas. Ogle, in U.S. Pat. No.
`4,948,458 describes an RF means to produce planar
`plasma in a low pressure process gas using an external
`planar spiral coil (or series of concentric rings) and
`connected to a second loop which is positioned to allow
`for effective coupling of the circuit and for loading of
`the circuit at the frequency of operation. Steinberg et
`al., in U.S. Pat. No. 4,368,092, describes a plasma gener-
`ating system employing a helical inductive resonator for
`producing the plasma external to an etching chamber.
`The plasma is non-uniform and passes through a tube
`before utilization. U.S. Pat. No. 4,421,898, describes
`an inductively-coupled plasma generating apparatus,
`where a transformer having a magnetic core induces
`electron circulation in an insulating tube carrying a
`process gas. Gas ionization is non-uniform, and expo(cid:173)
`sure to the wafer occurs downstream. U.S. Pat. No.
`4,626,312, describes a conventional parallel plate plasma
`etcher where the wafer is situated on a lower electrode
`and a plasma is generated by applying radiofrequency
`energy across the lower electrode and a parallel upper
`electrode. U.S. Pat. Nos. 4,668,338 and 4,668,365, de(cid:173)
`scribe magnetically-enhanced plasma processes for re-
`active ion etching and chemical vapor deposition, re(cid:173)
`spectively. Flamm et al. in U.S. Pat. No. 4,918,031 de(cid:173)
`scribes an L-C circuit referred to as a helical resonator
`which consists of an inner helically shaped copper coil
`surrounding a quartz tube and attached at one end to a
`cylindrical copper shield. The opposite end of the inner
`coil is unterminated. No external magnetic field is em(cid:173)
`ployed in these approaches and all generate plasmas at
`low pressure in the 1-10 mtorr range but at moderate
`density in the quartz source tube or just below a planar
`spiral coil and without a high degree of spatial unifor(cid:173)
`mity. No externally generated magnetic field is em(cid:173)
`ployed in these RF plasma generators.
`
`3
`Plasma Etching" published in Vacuum, Vol. 34, No.
`10/11, 1984. Due to a low gas pressure (0.04-0.4 Pa) and
`high plasma density (1.7-7X 1011 electrons/cm3) aniso(cid:173)
`tropic etch with high etch rates is achievable.
`Suzuki, in U.S. Pat. No. 4,101,411, describes a plasma 5
`etching apparatus using ECR. Matsuo, in U.S. Pat. No.
`4,401,054 describes a plasma deposition apparatus utiliz(cid:173)
`ing ECR. In U.S. Pat. No. 4,876,983 there is described
`a plasma etching apparatus to improve uniformity and
`have the specimen close to the source chamber.
`While this technique is desirable over the parallel
`plate reactor in many respects, it has several limitations.
`The magnetic field needed is very high (1-2 kGauss)
`which means that heavy, power consuming electromag(cid:173)
`nets must be used. The maximum density is limited by 15
`either cut-off in certain configurations or by refraction
`in other configurations to the value of 1 X 1012 elec(cid:173)
`trons/cm3 in the source. The expense of the power
`supply and necessary hardware to generate and transmit
`the microwaves is high. The uniformity (or width of the 20
`plasma profile) is not very good.
`RF Helicon Whistler Wave Plasmas
`The first use of helicon type whistler waves to gener(cid:173)
`ate dense plasmas was described in 1970 by Boswell in
`the journal, Physics Letters, Vol. 33A, pp 457-458 25
`(1970) which showed an antenna configuration used by
`Ovchinnikov. This type of antenna excites an m= 1
`mode. The frequency of excitation was 8 MHz. The
`density profile of the 10 em plasma was found to be
`quite peaked, particularly at the higher magnetic field 30
`strengths needed for high densities. In Boswell, U.S.
`Pat. No. 4,810,935, two mathematical relationships are
`required to be satisfied. These equations are in fact
`overly restrictive and not applicable to the approach
`outlined by Campbell, Conn and Shoji in U.S. Pat. Nos. 35
`4,990,229 and 5,122,251.
`In these publications the mechanism for efficient cou(cid:173)
`pling of the RF energy to the plasma could not be ex(cid:173)
`plained. Chen, in an Australian National University
`report, explained the mechanism as Landau damping. 40
`Chen, in a paper presented in August 1988 and pub(cid:173)
`lished in the journal, Plasma Physics and Controlled
`Fusion, Vol. 33, 1991, describes a system using whistler
`waves to generate dense plasmas for use in advanced
`accelerators. The type of antenna used in this arrange- 45
`ment was similar to that used by Boswell in that it ex(cid:173)
`cited them= 1 mode and was a type known as the Na(cid:173)
`goya Type III antenna. This type of antenna is ex(cid:173)
`plained in a paper by Watari (1978). The frequency of
`excitation was 30 MHz.
`Campbell, Conn and Shoji, in U.S. Pat. No. 4,990,229
`and Pat. No. 5,122,251 describe new and highly efficient
`antenna means designed to excite the m=O and the
`m= 1 modes, and to control the wave number of the
`excited wave. This is important in obtaining the maxi- 55
`mum plasma density, in generating the broadest spatial
`plasma density profile in the source and process cham(cid:173)
`ber regions, and in providing control over the electron
`temperature in the plasma.
`Efficiency of plasma production by low frequency 60
`whistler waves depends on the coupling of RF energy
`into the plasma. As discussed by Campbell et al. in U.S.
`Pat. No. 4,990,229, an important mechanism for damp(cid:173)
`ing of the RF energy is Landau damping. The phase
`velocity of the whistler wave is given by C.rl/kz, where 65
`kz is given by the dispersion relation and depends on the
`plasma density and vacuum magnetic field strength.
`Ideally, the phase velocity of the wave should be near
`
`50
`
`SUMMARY OF THE INVENTION
`The present invention utilizes low frequency RF
`whistler waves to generate plasmas of high density for
`use in plasma etching, deposition, and sputtering equip(cid:173)
`ment. Plasma is generated in a source tube which is
`typically made of quartz or a fluorine-resistant material
`such as alumina or sapphire. In conjunction with the
`source tube into which a gas is injected and along the
`
`TSMC-1114 / Page 24 of 36
`
`

`

`5,429,070
`
`5
`central axis of which a magnetic field is established, a
`single loop antenna is disposed in a plane transverse to
`the central axis. The angle of the antenna plane is 90" if
`it is desired to excite only M=O mode, or at less than
`90" if it is desired to excite components in both M=O 5
`and M = 1 mode. The gas is a noble or reactive gas at a
`pressure of 0.1 mtorr to 200 mtorr. The magnetic field
`strength is in the range of 10 to 1000 gauss and the
`antenna is driven with RF energy of 100 W to 5 KW at
`a frequency range of 2 MHz to 50 MHz. With the an- 10
`tenna placed along the tube source at a sufficient dis(cid:173)
`tance along the axis from the gas injection end, the
`other end defming an open egress zone leading to a
`process chamber, the single loop antenna surprisingly
`provides highly efficient wave coupling to establish a 15
`high density and high current plasma.
`In accordance with other features of the invention,
`the plasma generated by this plasma source is supplied
`to a process chamber including a magnetic bucket sys(cid:173)
`tem for holding the plasma away from the process 20
`chamber walls. The arrangement provides, in combina(cid:173)
`tion, a uniform plasma density over a large circular
`area, so that a large substrate may be etched or other(cid:173)
`wise processed. Another feature is that a magnetic cusp
`zone may be established, at the material surface being 25
`processed, to homogenize and make more uniform the
`plasma at that location. An aspect of this is that the
`magnetic cusp position relative to the substrate may be
`time modulated to enhance uniformity and reduce sensi(cid:173)
`tivity to substrate location.
`Further, the magnetic field may be expanded to allow
`deposition or etching over a large area and current
`flows may be equalized by serial driving of antennas in
`systems having more than one antenna. Other features
`reside in configurations which employ one or more 35
`multiple geometrical areas for coating or etching of
`square or rectangular substrates, or a linear juxtaposi(cid:173)
`tion for coating or etching large substrates.
`The invention provides a module with a highly effi(cid:173)
`cient magnetic means of transporting plasma from a 40
`plasma generator means to a substrate located on a
`cooled substrate holder located in a substrate process
`chamber and in which the processing of the substrate is
`highly uniform and the substrate process module is
`compact. The invention shields the magnet means from 45
`- RF signals generated by the antenna and thereby pre(cid:173)
`vents false signals from being received by a control
`system which drives the magnet means. The shielding
`may be a thin sheet of conducting material wrapped
`around the magnet means.
`The invention provides a gas distribution means in
`the top of the process chamber as an integral part of the
`process chamber structure in order to attain highly
`efficient plasma operation and highly uniform process(cid:173)
`ing of the substrate while permitting the process module 55
`to be reduced in height.
`The invention attains highly efficient plasma opera(cid:173)
`tion in a compact substrate process module which can
`attain excellent characteristics for the etching of IC
`wafers as represented by high etch rate, high unifor- 60
`mity, high selectivity, high anisotropy, and low dam(cid:173)
`age.
`The invention achieves high density and highly uni(cid:173)
`form plasma operation at low pressure from 0.3 mtorr to
`5 mtorr for etching an IC substrate and from 1 mtorr to 65
`30 mtorr for deposition of films on to substrates.
`The invention provides a substrate processing system
`capable of operating with a wide variety of gases and
`
`6
`combinations of gases, including highly reactive and
`corrosive gases.
`The invention provides such a substrate processing
`system capable of etching or depositing films listed in
`Table 1 and Table 2 using gases fed into the plasma
`generator region, into the process chamber region, or
`into both regions.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a schematic diagram depicting the principle
`of operation and RF current flow in an antenna con(cid:173)
`structed according to the invention as shown in U.S.
`Pat. No. 4,990,229.
`FIGS. 2A, 2B and 2C are schematic views of anten(cid:173)
`nas constructed according to the principles of the inven(cid:173)
`tion.
`FIG. 3 is a schematic diagram depicting the principle
`of operation and RF current flow in a plasma source
`constructed according to the invention as shown in U.S.
`Pat. No. 5,122,251.
`FIGS. 4A and 4B illustrate in schematic form two
`basic configurations of a plasma deposition or etching
`apparatus accordance with this invention.
`FIG. SA is a schematic diagram of a second example
`of a system in accordance with the present invention in
`which the plasma source region is connected to a mag(cid:173)
`netic bucket region where uniformity requirements are
`important.
`FIG. SB is a plan view of the arrangement of FIG.
`30 SA, taken along the line 3A-3A in FIG. SA.
`FIG. 6A is a perspective view of a third example of a
`system in the present invention for deposition or etch(cid:173)
`ing over a large rectangular area where uniformity is
`important.
`FIG. 6B is a plan view of the arrangement of FIG.
`6A, taken along the line 4A-4A in FIG. 6A.
`FIG. 7 A is a schematic diagram of yet another exam-
`ple of a system in accordance with the present invention
`in which a bottom magnet is added behind the plane of
`the substrate holder to provide a magnetic cusp field,
`the plane of the cusp being approximately the same as
`the plane of the substrate holder.
`FIG. 7B is a plan view of the arrangement of FIG.
`7A, taken along the line SA-SA in FIG. 7A.
`FIG. 8 is a schematic diagram of an example of a
`system in accordance with the invention for sputter
`deposition.
`FIG. 9 is a graph depicting the plasma current density
`at the substrate location according to the example of
`50 FIG. SA using the plasma source depicted in FIG. 3 as
`a function of magnetic field in the source region.
`FIG. 10 is a graph of the same data as in FIG. 9 but
`graphed on a linear scale for magnetic field to show the
`plasma current density at the substrate location where
`the magnetic field is low, varying from zero to 160
`gauss.
`FIG. 11 is a graph depicting the total plasma current
`(or total flux) at the substrate location according to the
`invention as depicted in FIG. SA using the plasma
`source as depicted in FIG. 3 as a function of RF power
`to the source at a gas pressure of 2 mtorr.
`FIG. 12 is a graph depicting the plasma current den(cid:173)
`sity at the substrate location according to the invention
`as depicted in FIG. SA using the antenna as depicted in
`FIG. 3 as a function of the gas pressure.
`FIG. 13 is a graph depicting the plasma current den(cid:173)
`sity at the substrate location according to the invention
`as depicted in FIG. SA and the plasma source of FIG. 3
`
`TSMC-1114 / Page 25 of 36
`
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`

`5,429,070
`
`8
`antenna 12 that encompasses an intermediate region of
`the source tube 10. The antenna loop 12 comprises in
`this example a not fully circular element lying in a plane
`that is at 90• or less in either sense relative to the central
`axis. The direction of propagation of the plasma is here
`downward toward an exit aperture 13. The antenna
`loop 12 has its opposite ends coupled to the outer con(cid:173)
`ductor 14 and center conductor 15 of a coaxial driver
`line 16 which is energized through a matching box 18 by
`an RF energy source 19. A pair of variable vacuum
`capacitors 20, 21 in the matching box 18 are adjustable
`to tune the circuit so that the antenna loading plus the
`reactive load of the matching box 18 is approximately
`50 ohms to minimize the reflected power.
`The antenna tuning and wave spectrum are adjusted
`to match the conditions in the plasma field, and also in
`relation to an interior axial magnetic field 8 generated
`by at least one magnetic field coil (not shown) about the
`source tube 10. The matching condition is predicted by
`20 theory to be dictated by the dispersion relation:
`
`7
`as a function of position to show the excellent unifor(cid:173)
`mity over a substantial width.
`FIGS. 14A to 14C are diagrams showing the arrange(cid:173)
`ment of the electromagnetic system in the plasma gener(cid:173)
`ator region according to the present invention to make 5
`efficient the transport of plasma from the plasma gener(cid:173)
`ator tube to the substrate process chamber which in(cid:173)
`cludes a magnetic bucket and where uniformity and
`high plasma flux to the substrate are required.
`FIG. 15A is a plot of the magnetic field lines obtained 10
`using one electromagnet surrounding the plasma source
`tube.
`FIG. 15B is a plot of the magnetic field lines obtained
`using two electromagnets surrounding the source tube
`and where the outer magnet coil carries a current in the 15
`opposite direction from the inner magnet coil and has a
`coil current that is 40% as large in magnitude as that of
`the inner coil.
`FIG. 16A is a schematic diagram of the configuration
`of a plasma etching or deposition apparatus.
`FIG. 16B is a plan view of the substrate process
`chamber section of the arrangement of FIG. 16A taken
`along the line 7A-7A in FIG. 16A.
`FIG. 17A is a plan view of the substrate process
`chamber showing the gas feed lines, the nozzle holes for 25
`gas injection into the chamber, the water cooling lines
`and the grooves for the ceramic permanent magnets.
`FIG. 17B is a detail showing the entrance to the gas
`feed line at the top of the substrate process chamber
`shown in FIG. 17A.
`FIG. 17C shows in larger size the gas feed structure
`ofFIG. 17A.
`FIG. 18 is a cross sectional SEM image obtained for
`the etching of poly-Si in pure Ch using the MORI
`plasma source etching system. In this case, the SEM 35
`shows structure with 100% overetch. One sees highly
`anisotropic proftles, no notching, and less than 50 A
`oxide loss.
`FIG. 19 shows the aluminum etch rate, the oxide etch
`rate, and the PR etch rate (left ordinate) and selectivity 40
`to photoresist etching and to oxide etching (right ordi(cid:173)
`nate) as a function of RF wafer bias power applied at
`13.56 MHz. The gas mixture is 85% Ch-15% BCh, the
`MORI source power is 1 KW, and the substrate is lo(cid:173)
`cated in the process chamber 20 em below the end of 45
`the source tube.
`FIG. 20 is a cross sectional SEM image obtained for
`sub micron etching of W on a TiW adhesion layer on
`thermal oxide in pure SF6 using the MORI plasma
`source etching system. The anisotropy is excellent, 50
`there is no CD loss, and there are no residues.
`
`To effect wave coupling and establish a high plasma
`current density, measured in mA/cm2, the antenna loop
`12 is driven at 13.56 MHz and with RF energy of the
`order of2.0 KW (in the range of 100 W to 5 KW) by the
`RF energy source 19. The magnetic field established by
`the magnetic field coil is in the range of 10 to 1000
`30 gauss, for different useful applications. The gas is argon
`and maintained at a pressure of about 1 mtorr in this
`example. However, in addition to a noble gas such as
`argon, reactive gases such as SF6. chlorine, oxygen, and
`mixtures with oxygen have been used with comparably
`useful results. A pressure range of 0.1 mtorr to 200
`mtorr can b