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`Case 5:20-cv-09341-EJD Document 145-7 Filed 04/01/22 Page 1 of 12
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`EXHIBIT F
`EXHIBIT F
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`Case 5:20-cv-09341-EJD Document 145-7 Filed 04/01/22 Page 2 of 12
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`ew"TTTAEA
`
`(06350353B2
`
`(12) United States Patent
`US 6,350,353 B2
`(10) Patent No.:
`
`Gopalraja et al. *Feb. 26, 2002 (45) Date of Patent:
`
`
`F/A998 Xuetal. we 438/639
`5,780,357 A
`
`.......... 204/192.12
`9/1998 Givens et al.
`5,807,467 A
`9/1998 Sellers eee 204/298.08
`5,810,982 A
`1/1999 Drummond et al.
`.... 204/192.12
`5,863,392
`5,968,327 A * 10/1999 Kobayashi et al.
`.... 204/298.08
`OTHER PUBLICATIONS
`
`U.S. application No. 08/989,759, Tanaka, filed Dec. 12,
`1997, “Step Coverage And Overhang Improvement By
`Pedestal Bias Voltage Modulation”.
`U.S. application No. 08/768,058, Ramaswami,filed Dec. 16,
`1996, “Sclective Physical Vapor Deposition Conductor Fill
`in IC Structure”.
`U.S. application No. 08/718,656, Mosley, filed Sep. 23,
`1996, “Semi-Selective Chemical Vapor Deposition”.
`US. application No. 09/219,187, Sivaramakrishnan, filed
`Dec. 21, 1998, “Improved Physical Vapor Deposition of
`Semiconducting and Insulating Materials”.
`
`* cited by examiner
`
`Primary Examiner—Mark F. Huff
`Assistant Examiner—Daborah Chacko-Davis
`(74) Attorney, Agent,
`or Firm—Moser, Patterson &
`Sheridan, LLP
`
`(57)
`
`ABSTRACT
`
`The present invention provides a method and apparatus for
`achieving conformal step coverage on a substrate by PVD.
`A target provides a source of material to be sputtered by a
`plasma and then ionized. Ionization is facilitated by main-
`taining a sufficiently dense plasma using, for example, an
`inductive coil. The ionized material is then deposited on the
`substrate which is biased to a negative voltage. A signal
`provided to the target during processing includes a negative
`voltage portion and a zero-voltage portion. During the
`negative voltage portion, ions are attracted to the target to
`cause sputtering. During the zero-voltage portion, sputtering
`from the target is terminated while the bias on the substrate
`cause reverse sputtering therefrom. Accordingly, the nega-
`tive voltage portion and the zero-voltage portion are alter-
`nated to cycle between a sputter step and a reverse sputter
`step. The film quality and uniformity can be controlled by
`adjusting the frequency of the signal, the chamberpressure,
`th
`lied t
`hotib
`t
`6
`doth
`© power supplied
`to each
`of
`the support memberand other
`process parameters.
`
`21 Claims, 4 Drawing Sheets
`
`(54)
`
`(75)
`
`ALTERNATE STEPS OF IMP AND
`SPUTTERING PROCESS TO IMPROVE
`SIDEWALL COVERAGE
`
`Inventors: Praburam Gopalraja, Sunnyvale;
`Sergio Edelstein, Los Gatos; Avi
`Tepman, Cupertino; Peijun Ding, San
`Jose; Debabrata Ghosh, San Jose;
`Nirmalya Maity, San Jose, all of CA
`(US)
`
`(73)
`
`Assignee: Applied Materials, Inc., Santa Clara,
`CA (US)
`
`(*)
`
`Notice:
`
`This patent issued on a continued pros-
`ecution application filed under 37 CFR
`1.53(d), and is subject to the twenty year
`patent
`term provisions of 35 U.S.C.
`154(a)(2).
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21)
`
`(22)
`
`(51)
`(52)
`
`(58)
`
`(56)
`
`Appl. No.: 09/449,202
`
`Filed:
`
`Nov. 24, 1999
`
`Int. Cle sxscsreceenssersecersss C23C 14/34; C23C 14/35
`USC swcnnevveevenevervensevess 204/192.3; 204/298.08;
`204/298 .06; 204/192.12; 204/192.32; 204/298.13
`Field of Search .........0000000000... 204/298.08, 192.3,
`204/298.06, 192.12, 192.32, 298.13
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`AAAA
`
`AAAAAA
`
`3,410,774
`4,874,493
`4,874,494
`4,963,239
`4,999,096 A *
`§,510,011 A
`B:08078
`5,639,357
`5,651,865
`5,718,813
`5,725,739
`5,770,023
`
`11/1968 Barson et al. ow... 204/192
`10/1989 Pan ...........
`- 204/192.11
`
`« 204/192.12
`* 10/1989 Ohmi
`.
`10/1990 Shimamura et al.
`.... 204/192.12
`3/1991 Nihei et al. w.... 204/192.3
`4/1996 Okamura etal.
`........ 204/192.3
`
`conse 360/46
`
`TE90 Shuinkle? sce
`
`6/1997 Xu .......
`we 204/192.3
`F/1997 Sellers veces. 204/192.13
`2/1998 Drummondet al.
`.... 204/192.12
`BLOOB. Tie wicicnsawnensieawenennvene 204/192.3
`6/1998 Sellers... 204/192.3
`
`Be
`
`
`104—~
`
`|
`I 130
`
`art
`PULSE
`
`
`GENERATOR
`SIGNAL
`
`Art
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`220
`228
`
`
`
`e
`
`e
`+
`226
`0218S A
`M<y
`231
`
`e
`Art
`
`f
`
`
`
`=
`-—_
`
`
`
`134
`
`CS
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`
`
`
`
`— 232
`
`
`
`

`

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`Case 5:20-cv-09341-EJD Document 145-7 Filed 04/01/22 Page 3 of 12
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`U.S. Patent
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`Feb. 26, 2002
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`Sheet 1 of 4
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`US 6,350,353 B2
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`12
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`20 20
`18
`
`1
`Fig.
`(PRIOR ART)
`
`Fig. 2
`(PRIOR ART)
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`20 20
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`

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`U.S. Patent
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`Feb. 26, 2002
`
`Sheet 2 of 4
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`US 6,350,353 B2
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`2
`
`x>
`
`yt
`
`x
`
`MICROPROCESSOR/CONTROLLER
`
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`J PULSE
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`

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`Case 5:20-cv-09341-EJD Document 145-7 Filed 04/01/22 Page 5 of 12
`Case 5:20-cv-09341-EJD Document 145-7 Filed 04/01/22 Page 5 of 12
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`U.S. Patent
`
`Feb. 26, 2002
`
`Sheet 3 of 4
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`US 6,350,353 B2
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`TIME
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`“— 200
`
`204
`
`M F
`
`ig. 4
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`Case 5:20-cv-09341-EJD Document 145-7 Filed 04/01/22 Page 6 of 12
`Case 5:20-cv-09341-EJD Document 145-7 Filed 04/01/22 Page 6 of 12
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`U.S. Patent
`
`Feb. 26, 2002
`
`Sheet 4 of 4
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`US 6,350,353 B2
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`PULSE
`SIGNAL
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`PULSE
`SIGNAL
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`GENERATOR
`GENERATOR
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`Fig. 6
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`

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`Case 5:20-cv-09341-EJD Document 145-7 Filed 04/01/22 Page 7 of 12
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`US 6,350,353 B2
`
`1
`ALTERNATE STEPS OF IMP AND
`SPUTTERING PROCESS TO IMPROVE
`SIDEWALL COVERAGE
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`10
`
`15
`
`The present invention relates to an apparatus and method
`for processing substrates. Specifically, the invention relates
`to a method for depositing a conformal layer of material on
`a substrate using physical vapor deposition process.
`2. Background of the Related Art
`Sub-quarter micron multi-level metallization represents
`one of the key technologies for the next generation of ultra
`large-scale integration (ULSDfor integrated circuits (IC). In
`the fabrication of semiconductor and other electronic
`devices, directionality of particles being deposited on a
`substrate is important
`to improve adequate in filling of
`electric features. As circuit densities increase, the widths of
`vias, contacts and other features, as well as the dielectric .
`materials between them, decrease to 0.25 um or
`less,
`whereas the thickness of the dielectric layer remains sub-
`stantially constant. Thus, the aspect ratios for the features,
`Le., the ratio of the depth to the minimum lateral dimension,
`increases, thereby pushing the aspect ratios of the contacts ,
`and vias to 5:1 and above. As the dimensionsofthe features
`
`decrease, it becomes even more important to get direction-
`ality in order to achieve conformal coverage of the feature
`sidewalls and bottoms.
`
`2
`of power, such as RF, to the susceptorto attract the sputtered
`target ions in a highly directionalized mannerto the surface
`of the substrate to fill the features formed on the substrate.
`
`One of the problems with HDP-PVD processes is the
`inability to achieve conformal step coverage in the increas-
`ingly smaller device features. Conformal coverage of the
`bottoms and sidewalls of the features is needed to optimize
`subsequent processes such as electroplating. Electroplating
`requires conformalbarricr and sced layers within the device
`features in order to ensure uniform filling of the feature.
`While conventional HDP-PVD achieves good bottom cov-
`erage due to the directionality of the ions provided by the
`bias on the substrate, the sidewall coverage can be less than
`conformal. This result is caused in part by the induced high
`directionality of ions towards the bottom of the features with
`little directionality toward the sidewalls.
`The effects of a bias on film deposition on and into the
`features in/on a substrate can be described with reference to
`FIGS, 1-2 which illustrate the direction of metal ions 12
`entering a via 16 formed on a substrate 10. FIG. 1 illustrates
`a DC magnetron PVD processing environment wherein no
`bias is supplied to the substrate 10 (the presence or absence
`of an applied bias being substantially irrelevant to traditional
`planartarget DC sputtering). As a result, the directionality of
`the ions 12 is determined primarily by the ejectionprofile of
`material (usually atoms) from the target and by the inelastic
`collisions with other particles in the chamber, such as Ar
`ions which are provided in a plasma. The angular distribu-
`tion 22 of the ions in FIG. 1 typically results in little
`deposition on the bottom 18 of the via 16. In addition to the
`angular distribution of the incoming ions 12, the feature
`dimensionsalso determine the resulting step coverage. Thus,
`where the feature opening is wider than the depth of the
`feature, deposition material can reach all surfaces of the
`feature for relatively uniform deposition. However, where
`the feature is narrow compared to the depth, the particles
`travelling substantially non-parallel
`to the feature depth
`deposit around the feature opening, resulting in less depo-
`sition at the bottom 18 of the via 16.
`
`FIG. 2 illustrates the processing environment in a HDP-
`PVDprocess wherein the angular distribution of the ions 12
`is influenced by the electrical field E due to interaction
`between the charged target material and the applied or
`self-bias at the surface of the substrate. The electric field E
`is oriented perpendicular to the substrate 10 and the posi-
`lively charged ions 12 are influenced into a trajectory
`parallel to the electric field E toward the bottom 18 of the via
`16. The angular distribution 23 of the ions 12 in FIG. 2
`typically results in moderate to lower deposition on the
`sidewalls 20 and higher to moderate deposition on the
`bottom 18 than is possible without ionization of the sput-
`tered material. As comparedto the angular distribution 22 of
`FIG. 1, the distribution 23 exhibits a tighter distribution
`indicating more directionality parallel to the electric field E.
`Therefore,
`there is a need to provide a technique for
`depositing a layer conformal over the surface of features,
`particularly sub-half micron and higheraspectratio features.
`SUMMARY OF THE INVENTION
`
`The present invention generally provides an apparatus and
`method for depositing a conformal layer on device features
`in a plasma chamber by PVD. In oneaspect of the invention,
`a chamber having a target, a power supply coupled to the
`target adapted to provide a signal having a desired
`waveform, a substrate support member, a power supply
`connected to the substrate support member, and a magnetic
`
`Conventionally, physical vapor deposition (PVD) systems
`have been used to deposit materials in device features
`formed on a substrate. PVD systems are well known in the
`field of semiconductor processing for forming metal films.
`Generally, a power supply connected to a processing cham-
`ber creates an electrical potential between a target and a 3
`substrate support member within the chamber and generates
`a plasma of a processing gas in the region betweenthe target
`and substrate support member. Ions from the plasma bom-
`bard the negatively biased target and sputter material from
`the target which then deposits onto a substrate positioned on
`the substrate support member. However, while such pro-
`cesses have achieved good results for lower aspect ratios,
`conformal coverage becomes difficult
`to achieve with
`increasing aspectratios. In particular, it has been shownthat
`coverage of the bottoms of the vias decreases with increas-
`ing aspect ratios.
`One process capable of providing greater directionality to
`particles is ionized metal plasma-physical vapor deposition
`(IMP-PVD), also known as high density physical vapor
`deposition (HDP-PVD). Initially, a plasma is generated by
`introducing a gas, such as helium orargon,into the chamber
`and then biasing a target to produce an electric field in the
`chamber, thereby ionizing a portion of the gas. An energized
`coil positioned proximate the processing region of the
`chamber couples electromagnetic energy into the plasma to
`result
`in an inductively-coupled medium/high density
`plasma between the target and a susceptor on which a
`substrate is placed for processing. The ions and electrons in
`the plasma are accelerated toward the target by the bias
`applied to the target causing the sputtering of material from
`the target. Under the influence of the plasma, the sputtered
`metal flux is ionized. An electric field due to an applied or
`self-bias, develops in the boundary layer, or sheath, between
`the plasma and the substrate that acccleratcs the metal ions
`towards the substrate in a direction substantially parallel to
`the electric field and perpendicular to the substrate surface.
`The bias energy is preferably controlled by the application
`
`40
`
`45
`
`60
`
`65
`
`

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`US 6,350,353 B2
`
`3
`field generator is provided. The target comprises a material
`to be sputtered by a plasma formed adjacent to the target
`during processing. The signal supplied by the power supply
`coupledto the target preferably comprises a negative voltage
`portion and a zero-voltage portion. Preferably, the power
`supply connected to the substrate support member supplies
`a substantially constant negative bias to the substrate.
`In another aspect of the invention, a plasmais supplied to
`a chamber to sputtcr a matcrial from a target. A coil is
`energized proximate the chamber to enhance ionization of
`the sputtered material. During processing, a modulated
`signal is provided to the target. In one embodiment, the
`modulated signal
`is varied between a negative voltage
`portion during which the target material is sputtered onto a
`substrate and a zero-voltage portion during which the depos-
`ited material is re-sputtered from the substrate. A bias is
`provided to the substrate to influence the direction of ions in
`the chamber during processing.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`10
`
`15
`
`So that the manner in which the above recited features,
`advantages and objects of the present invention are attained
`and can be understood in detail, a more particular descrip-
`tion of the invention, briefly summarized above, may be had ,
`by reference ta the embodiments thereof which are illus-
`trated in the appended drawings.
`It is to be noted, however, that the appended drawings
`illustrate only typical embodiments of this invention and are
`therefore not to be considered limiting of its scope, for the 3
`invention may admit
`to other equally effective embodi-
`ments.
`
`FIG. 1 is a cross-section of a substrate having a via formed
`therein andillustrates cosine distribution of sputtered mate-
`rial.
`
`FIG. 2 is a cross-section of a substrate having a via formed
`therein and illustrates over-cosine distribution of sputtered
`material.
`
`FIG. 3 is a cross-section of a simplified processing
`chamber of the invention having a coil disposed therein.
`FIG. 4 is a graphical illustration of a signal applied to a
`target.
`FIG. 5 is a graphical illustration of a signal applied to a
`substrate.
`
`45
`
`FIG. 6 is a cross section of a substrate and a target
`illustrating sputtering.
`FIG. 7 shows the substrate and target of FIG. 6 and
`illustrates re-sputtering of a material from the substrate.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`The embodiments described belowpreferably use a modi-
`fied ionized metal plasma (IMP) processthat can be carried 5
`oul using process equipment, such as an Endura® platform,
`available from Applied Materials, Inc.,
`located in Santa
`Clara, Calif. with modifications as described below. The
`equipmentpreferably includesan integrated platform having
`a preclean chamber, an IMP-PVDbarrier layer chamber, a
`PVD chamber, an IMP-PVDseed layer chamber, and a CVD
`chamber. One ion metal plasma (IMP) processing chamber,
`known as an IMP VECTRA™/ELECTRA™ Chamber is
`available from Applied Materials,Inc., of Santa Clara, Calif.
`FIG. 3 is a schematic cross-sectional view of an IMP
`chamber 100 according to the present invention. The cham-
`ber 100 includes walls 101, lid 102, and bottom 103. A target
`
`60
`
`65
`
`4
`104 comprising the material to be sputtered is mounted to
`the lid 102 and disposed in the chamber 100 to define an
`upper boundaryto a processing region 107. Magnets 106 are
`disposed behind the lid 102 and are part of a rotatable
`magnetron which traps electrons during operation and
`increases the density of a plasma adjacentto the target 104.
`A substrate support member 112 supports the substrate
`110 and defines the lower boundary to the processing region
`107. The substrate support membcr 112 is movably disposed
`in the chamber 100 and provides an upper support surface
`105 for supporting a substrate 110. The support member 112
`is mounted on a stem 109 connected to a motor assembly
`114 that raises and lowers the substrate support 112 between
`a lowered loading/unloading position and a raised process-
`ing position. An opening 108 in the chamber 100 provides
`access for a robot (not shown) to deliver and retrieve
`substrates 110 to and from the chamber 100 while the
`substrate support member 112 is in the lowered loading/
`unloading position.
`A coil 122 is mounted in the chamber 100 between the
`
`substrate support member 112 and the target 105 and, when
`an AC current is passed therethrough, provides electromag-
`netic fields in the chamber 100 during processing to assist in
`gencrating and maintaining a plasma betwecnthe target 104
`and substrate 110. The electromagnetic fields produced by
`the coil 122 induces currents in the plasma to densify the
`plasma,ire., to increase the ionization of the gas and the
`sputtered target material. The ionized material is attracted
`toward the substrate 110 by virtue of the electrical attraction
`between the positively charged ions and the negatively
`biased substrate support member 112 (whichis biased either
`with a power supply or is self biased). By virtue of this
`“attraction” the sputtered material ions reaching the sub-
`strate are aligned more parallel to the depth access of the
`features. In addition, the coil 122 itself attains a negative
`self-bias causing the coil 122 to be sputtered.
`The chamber 100 optionally includes a process kit com-
`prising a process shield 128 and a shadow ring 129. The
`process shield 128 is an annular member suspended from the
`lid 102 between the coil 122 and the body 101. An upwardly
`turned wall 131 of the process shield 128 is adapted to
`support the shadow ring 129 while the support member 112
`is in a lowered position. To provide a return path for RF
`currents in the chamber 100 the process shield is preferably
`coupled to ground.
`One or more plasma gases are supplied to the chamber
`100 through a gas inlet 136 from gas sources 138, 140 as
`metered by respective mass flow controllers 142, 144. One
`or More vacuum pumps 146 arc connected to the chamber
`100 at an exhaust port 148 to exhaust the chamber 100 and
`maintain the desired pressure in the chamber 100. Preferably
`the vacuum pumps146 include a cryopumpand a roughing
`pumpandare capable of sustaining a base pressure of about
`10-* mTorr.
`
`Three powersupplies are preferably used to bias elements
`of the chamber 100. A first power supply 130 delivers a
`modulated or oscillating power signal to the target 104. The
`first power supply 130 maybe a direct current (DC)or radio
`frequency (RF) power supply capable of providing a signal
`to the target 104 having a desired waveform. However, the
`particular arrangement used to provide the signal
`to the
`target 104 is not limiting of the present invention and may
`include any conventional componcnts known in theart, such
`as switches, pulse generators, microprocessors andthelike.
`A second powersource 132, preferably a RF powersource,
`supplies electrical power in the megahertz range to the coil
`
`

`

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`US 6,350,353 B2
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`6
`bias to the target 104, i.e., a greater bias resulting in greater
`ion energy. Preferably, the negative voltage portion 202 is
`between about —50 V and -600 V. The metal flux produced
`during the negative voltage portion 202 of the signal 200 is
`then ionized by the plasma maintained by the coil bias and
`the target bias and subsequently forms a layer on the
`substrate 110.
`
`5
`122 to increase the density of the plasma. A third power
`source 134 supplies an RF powersignal to bias the substrate
`support member112 with respect to the plasma and provides
`an electric field adjacent a substrate to attract the ionized
`sputtered material toward the substrate 110.
`In operation, a robot delivers a substrate 110 to the
`chamber 100 through the opening 108. After placing the
`substrate 110 upon the upper surface 105 of the support
`member 112 the robotretracts from the chamber 100 and the
`
`opening 108 is sealed. The substrate support member 112
`then raises the substrate 110 into a processing position.
`During the upward movementof the support member 112
`the shadow ring 129 is lifted from the process shield 128.
`During processing, the shadow ring 129 covers a perimeter
`portion (usually less than 3 millimeters) of the substrate 110.
`Preferably, the space between the target 104 and the sub-
`strate support member 112 in a raised processing position is
`between about 90 mm and 199 mm.
`
`During the subsequent zero-voltage portion 204 of the
`signal 200, the direction of the positively charged Ar ions is
`determined primarily by the negative bias on the substrate
`110 supplied by the third power supply 134. Preferably, the
`bias to the substrate 110 remains constant throughout the
`deposition cycle so that a constant voltage drop is estab-
`lished across a region between the plasma andthe substrate
`110 known asthe sheath or dark space. Due to the resulting
`voltage drop in the sheath, an electric field is generated
`substantially perpendicular to the substrate 110,
`thereby
`causing the ions to accelerate toward the substrate. As in the
`sputtering step described above,the ionsstrike the substrate
`with sufficient energy to cause reverse sputtering, or
`One or more plasma gases are then introduced into the
`re-sputtering, of the material previously deposited onto the
`chamber 100 from the gas sources 138, 140 to stabilize the
`substrate from the target 104. Thus, during the zero-voltage
`chamber 100 at a processing pressure. The target receives a
`portion 202 of the signal 200, sputtering from the target 104
`negative DC bias which, in conjunction with magnets 106,
`is substantially terminated and the previously deposited
`facilitates the formation of a plasma adjacent the target 104.
`material on the substrate 110 is re-sputtered therefrom. The
`The power supply 130 provides a periodic bias which
`result of the reverse sputtering step is to redistribute and
`attracts the charged particles of the plasma toward the target
`planarize the deposited material on the substrate, thereby
`104 to cause sputtering therefrom.
`achieving greater uniformity and superior step coverage. It
`The coil 122 is energized by the third signal generator 132
`should be noted that impinging ions will sputter the substrate
`and operates to increase the density of the plasma, thereby
`110 during the negative voltage portion 202 as well as the
`facilitating ionization of sputtered target material. A portion
`zero-voltage portion 204 due to the constant bias applied to
`the substrate 110. [lowever, the flux of sputtered material
`of the ions formed from the sputtered target material con-
`will be substantially less during zero-voltage portion 204
`tinue to traverse the space between the target 104 and the
`since only the coil 122 will be sputtered. As a result,
`support member 112 and deposit on the substrate 110 which
`negative voltage portion 202 provides for net deposition on
`is biased by the third power supply 134. The biases to the
`the substrate 110, while zero-voltage portion 204 provides
`target 104 and support member 112 are controlled according
`for net re-sputtering of material with onlyalittle deposition
`to the processes described in detail below.
`onto the substrate 110. The effects of the oscillating signal
`Following the deposition cycle,
`the substrate support
`200 on deposition will be described below with reference to
`member 112 is lowered to a loading/unloading position. The
`TIGS. 8-9.
`robot is then extended into the chamber 100 through the
`opening 108 and the substrate 110 is placed on the robot for
`removal from the chamber 100 and delivery to a subsequent
`location. Subsequent locations include various processing
`chambers, such as electroplating chambers, where the sub-
`strate 110 undergoes additional processing.
`The present invention utilizes alternating steps of sput-
`tering and reverse sputtering to achieve conformal coverage
`of the feature formed on the substrate. Good step coverage
`on the device features of the substrate 110 is achieved by
`ensuring proper proportions of bottom coverage and side-
`wall coverage of the features. According to one aspect of the 5
`present invention, the proportions of coverage are controlled
`by adjusting the sputtering and reverse sputtering steps and
`other process parameters. Throughout
`the following
`discussion, periodic reference is made to FIG. 3 where
`necessary.
`the power supply 130
`During the deposition process,
`delivers a signal 200 to the target 104 having a desired
`waveform. The signal 200, shown in FIG. 4,
`is a square
`wave or step function and includes a negative voltage
`portion 202 and a zero-voltage portion 204. Although shown
`here as a square wave, any waveform oscillated between a
`negative voltage portion and a less negative or zero voltage
`portion may be used to advantage. During the negative
`voltage portion 202, the positively charged ions supplicd by
`the plasma gas, such as Ar, bombard the target 104 causing
`ejection of material therefrom. The energy with which the Ar
`ions strike the target 104, can be controlled by adjusting the
`
`10
`
`15
`
`20
`
`2
`
`40
`
`45
`
`60
`
`65
`
`the negative voltage portion 202 and the
`Preferably,
`zero-voltage portion 204 are sequentially alternated to result
`in a series of sputtering steps (or high deposition rate steps)
`and reverse spultering steps (or low deposition rate steps).
`‘The frequency and duty cycle of the signal 200 can be
`adjusted to increase the sputtering step or the reverse sput-
`tering step to achieve the desired results. Preferably, the
`frequency of the signal 200 is between about 0.01 Hz and 1
`Hz. As defined herein,the duty cycle is the ratio of the width,
`tl, of the negative voltage portion 202 to the signal period
`T1, shownin FIG.4. Preferably, the duty cycle is between
`about 10% and about 80%, wherein the negative voltage
`portion width t1 is between about 0.55 seconds and about 60
`seconds.
`
`Although the voltage applied to the substrate 110 may be
`modulated in a mannersimilar to the signal 200 provided to
`the target 104, preferably the voltage is maintained at a
`substantially constant value throughout a deposition cycle.
`FIG. 5 shows an RF signal 201 providedto the substrate 110
`by the third power supply 134. In the presence of a plasma,
`the signal 201 is shifted downwardinto the negative voltage
`region resulting in an induced DC bias (Vdc) on the sub-
`strate 110. The Vdc, shown in FIG. 5 as a signal 206, is
`maintained at a substantially constant value.
`In one
`embodiment, the power from the third power supply 134 is
`sufficient to produce an applicd bias on the substrate 110
`between about 0 V and -300 V. The particular values for
`power and voltage may be adjusted to achieve the desired
`result.
`
`

`

`Case 5:20-cv-09341-EJD Document 145-7 Filed 04/01/22 Page 10 of 12
`Case 5:20-cv-09341-EJD Document 145-7 Filed 04/01/22 Page 10 of 12
`
`US 6,350,353 B2
`
`8
`
`TABLE I
`
`Materials:
`Bias Power to Support Member:
`Bias Voltage induced on Support
`Member:
`Coil Power:
`Coil Frequency:
`Target Power:
`Pressure
`
`Ti, Cu, Ta, W, Al
`0 W to 1000 W
`0 V to -300 V
`100 W to 6000 W
`400 KHz to 60 MHz
`0 V to -600 V
`0.1 mTorr to 100 mTorr
`
`While the foregoing is directed to the preferred embodi-
`ment of the present invention, other and further embodi-
`ments of the invention may be devised without departing
`from the basic scope thereof, and the scope thereof is
`determined by the claims that follow.
`Whatis claimedis:
`
`1. An apparatus, comprising:
`(a) a processing chamber;
`(b) a substrate support memberdisposedin the processing
`chamber having a first power source coupled to the
`substrate support member and configured to provide a
`constant voltage;
`(c) a target disposed in the processing chamber;
`(d) a second power source coupled to the target adapted
`to vary a voltage applied to the target between rela-
`tively higher and lower voltage values while the con-
`stant voltage is provided to the substrate support mem-
`ber; and
`(c) an electromagnetic field source.
`2. The apparatus of claim 1, wherein the first power
`source is a radio frequency (RF) power source.
`3. The apparatus of claim 1, whercin the second power
`source is selected from the group of a pulsed direct current
`(DC) powersource, a pulsed RF power source, a DC power
`source in combination with a switch and any combination
`thereof.
`
`5
`
`10
`
`20
`
`tonn
`
`7
`As described above, the invention provides a method of
`controlling the deposition of a material deposited on a
`substrate and maybeillustrated with reference to FIGS. 8-9.
`FIG. 6 is a schematic side view of a substrate 110 and a
`target 104 during application of the negative voltage portion
`202 of the signal 200 thereto. The substrate 110 has a feature
`218 such as a via, formed therein. A plasma 220 is main-
`tained between the substrate 110 and the target 104.
`Preferably,
`the plasma is generated using argon due to
`argon’s low sticking coefficient which reduces the potential
`for poisoning the target 104 or the resulting film formed on
`the substrate 110 with substantial argon. However, other
`non-reactive gases such as Hc, N, Xe, Kr and Ne may be
`used to advantage. Subsequent
`to the formation of the
`plasma 220, Ar ionsare attracted to the target 104 under the
`influence of the negative bias provided by the power supply
`130. The Ar ions then strike the target 104 with sufficient
`energy to dislodge, or sputter, material from the target 1 04.
`The target 104 may comprise one or more of Cu, Al, W, Ti,
`and Ta, among other materials. The metal flux ejected from
`the target 104 traverses the processing region 107,where at
`least a portion of it is ionized by the plasma 220. The
`directionality of the ionized target material is then affected
`by the voltage drop across the sheath 226. The voltage drop
`can be modified by application of a bias to the substrate 110 2
`using the third power supply 134. The result of the deposi-
`tion step during the negative voltage portion 202 of the
`signal 200 is to form a layer 228 on the substrate 110. Due
`to the bias applied to the substrate 110, the angular distri-
`bution of the ionized target material results in proportion-
`ately more deposition at the bottom 232 of the feature 218.
`The negative bias on the substrate 110 also attracts the Ar
`ions to cause some re-sputtering of deposited material.
`However, the rate of deposition is higher than the rate of
`re-sputtering, thereby achieving net deposition.
`Once the applied bias to the target 104 is terminated
`during the zero-voltage portion 202 of the signal 200,
`sputtering from the target 104 ceases. Without a target bias,
`the substrate 110 experiences deposition resulting only from
`sputtering of the coil 122. However, as a result of applied
`negative bias provided bythe third power supply 134, the
`substrate 110 continues to experience re-sputtering due to Ar
`ion bombardment. FIG. 7 shows a schematic representation
`of the re-sputtering of layer 228 caused by the Ar ions. In
`particular, the bias to the substrate 110 causes the Ar ions to
`strike the bottom 232 of the feature 218 (as wellas the field
`of the substrate) causing re-sputtering of the deposited layer
`228 onto the sidewalls 231. Accordingly, material can be
`redistributed from the bottom 232 onto the sidewalls 231 to
`
`45
`
`4. The apparatus of claim 1, wherein the second power
`source is a pulsed DC power source adapted to provide a
`signal having a negative voltage portion and a zero-voltage
`portion.
`5. The apparatus of claim 1, wherein the target comprises
`a material selected from the group consisting of Ti, Cu, Ta,
`W, Al and any combination thereof.
`6. The apparatus of claim 1, further comprising a gas
`source coupled to the processing chamberto supply a gas for
`creating a plasma during processing.
`7. The app