Samsung Electronics Co., Ltd. v. Demaray LLC
`Samsung Electronic's Exhibit 1041
`Exhibit 1041, Page 1
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`DISCLAIMER
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`Library of Congress Cataloging in Publication Data
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`Wolf, Stanley and Tauber, Richard N.
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`Silicon Processing for the VLSI Era
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`Volume 1: Process Technology
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`Includes Index
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`1. Integrated circuits-Very large scale
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`integration. 2. Silicon. I. Title
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`ISBN 0-9616721-6-1
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`98765432
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`PRINTEDIN THE UNITED STATES OF AMERICA
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`Ex. 1041, Page 2
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`Ex. 1041, Page 2
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`dominant technique for depositing a variety of metallic films in VLSI and ULSI fabrication,
`including aluminum alloys, titanium,titanium:tungsten,titanium nitride, tantalum, and cobalt.
`Sputtering displaced the original PVD technique for depositing metal films (evaporation) for
`the following reasons:
`1. Sputtering can be accomplished from large-area targets, which simplifies the problem of de-
`positing films with uniform thickness over large wafers.
`2. Film thickness control is relatively easily achieved by selecting a constant set of operating
`conditions, and then adjusting the deposition timeto reachit.
`3. The alloy composition of sputter-deposited films can be more tightly (and easily) controlled
`than that of evaporatedfilms.
`4. Many important film properties, such as step coverage and grain structure can be controlled
`by varying the negative bias and heat applied to the wafers. Other film properties (including
`stress and adhesion), can be controlled by altering such process parameters as power & pressure.
`5. The surface of the substrates can be sputter-cleaned in vacuum prior toinitiating film depos-
`ition (and the surface is not exposed again to ambient after such cleaning).
`6. There is sufficient material in most sputter targets to allow many deposition runs before target
`replacementis necessary.
`7. Device damage from x-rays generated during electron-beam evaporation is eliminated (al-
`though someother radiation damage maystill occur).
`Asis true with other processes, however,sputtering also has its drawbacks. They include:
`1. Sputtering processes involve high capital equipmentcosts;
`2. Since the processis carried out in low-medium vacuum ranges (comparedto the high vacuum
`conditions under which evaporation is conducted), there is greater possibility of incorporating
`impurities into the deposited film.
`3. Better step coverage can generally be achieved using CVD.
`In general, the sputtering process consists of four steps:
`1. Ions are generated anddirected ata target.
`2. The ions sputter target atoms;
`3. The ejected (sputtered) atoms are transported to the substrate.
`4. Upon reaching the substrate they condense and formathinfilm.
`Althoughit is of interest to note that sputtering can be conducted by generating the energetic
`incident ions by other means(e.g., ion beams),
`in virtually all VLSI and ULSI sputtering
`processes their source is a glow-discharge. The discussion of sputtering in this section will be
`limited to glow-discharge sputtering.4>.
`11.2.1 Introduction to Glow Discharge Physics
`The energetic particles used to strike target materials to be sputtered in ULSI sputter deposition
`systemsare generated by glow-discharges.*> A glow-discharge is a self-sustaining type of plas-
`ma(a plasmais defined as a partially ionized gas containing an equal numberofpositive and
`negative charges as well as some numberof neutral gas particles). In Fig. 11-3 a simple de-
`diode type system that can be employed to study properties of glow discharges used in
`
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`Ex. 1041, Page 3
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`

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`ALUMINUMTHIN FILMS AND PHYSICAL VAPOR DEPOSITION IN ULSI
`
`439
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`GLASS ENVELOPE
`ANODE
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`(+)
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`ANODE DARK
`SPACE
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`SPACE
`AK
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`COLUMN
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`CATHODE
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`ZAAA
`ra
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`NEGATIVE
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`| DARK SPACE GLOW
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`alaaee
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`VOLTAGE pe|
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`(c)
`
`Fig. 11-3 (a) Structure of a glow discharge in a de diode system. (b) Charged particle concentration in a
`glow discharge. (c) Voltage variation in a de diode glow discharge.
`sputtering is shown.It consists of a glass tube that is evacuated and then re-filled with a gas at
`low pressure. Within the tube there are two electrodes (a positively charged anode and a
`negatively charged cathode) and a dc potential difference is applied between them.
`11.2.2 The Creation of Glow Discharges
`Consider the system shownin Fig. 11-3 to examine the case whena tubeis filled with Ar at an
`initial pressure of 1 torr, the distance between the electrodes is 15 cm, and a 1.5 kV potential
`difference is applied between them. Atthe outset no current flowsin the circuit, as all the Ar gas
`atoms are neutral and there are no charged particles in the gas. The full 1.5 kV is thus dropped
`between the two electrodes. If a free electron enters the tube (most likely created from the
`ionization of an Ar atom by a passing cosmic ray), it will be accelerated by the electric field
`existing between the electrodes (whose magnitude is: E= V/d = 1.5 kV/15 cm = 100 V/cm).
`The average distance that a free electron will travel at P = 1 torr before colliding with an Ar
`atom (i.e., the mean free path 4) is 0.0122 cm (Chap. 3). Most electron-atom collisions are
`elastic, in which virtually no energy is transferred between the electron and gas atom. Such
`elastic collisions occur because the mass of the electron is much smaller than that of the atom.
`Thus, the minumum distance an electron musttravel before it can undergo an inelastic collision
`(in which significant energy is transferred to the atom, either by the excitation of an atomic
`electron to a higher energy level, or to cause its escape from the atom) is about ten times A, or
`0.122 cm.If this is the minimum distance that must be traveled by electrons between inelastic
`collisions, there must be a significant number of electron path lengths in the range of 0.5-1.0
`cm.If a free electron travels 1 cm in the 100 V/cm electric field, it will have picked up 100 eV
`of kinetic energy. With this amount ofenergy, the free electron can transfer enough energy to an
`Ar electron to cause it to be excited or ionized. If this transferred energy Eis less than the
`ionization potential (e.g., 11.5 eV< E < 15.7 eV forAr), the orbital electron will be excited to a
`
`ee _
`Ex. 1041, Page 4
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`J
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`

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`ALUMINUMTHIN FILMS AND PHYSICAL VAPOR DEPOSITION IN ULSI
`
`443
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`SHIELD
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`SHIELD TARGET
`RR
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`
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`Fig. 11-7 (a) Potential distribution in vicinity of cathode shield (b) Reducing rim effect by extending
`cathode shield. (c) Reducing rim effect by wrapping shield around the cathode.8 From L. Maissel and R.
`Glang, Eds., Handbook of Thin Film Technology 1970. Reprinted by permission of McGraw-Hill Book Co.
`dark space however, the ion production rate becomes reduced, and the voltage across the
`electrodes must rise to increase the secondary electron emission. Such a glow is known as an
`obstructed glow. In most practical sputter deposition systems the glow is obstructed. Thatis, in
`order to most effectively collect the sputtered material onto the substrate, the anode (on which
`the wafers are sometimes mounted)is placed as close to the cathode as possible (typically just
`far enough awayto avoid extinguishing the negative glow).
`It is typically necessary to insure that sputtering is allowed to occur only at the front side of
`the target, as the backside contains cooling coils and attachmentfixtures which are definitely not
`to be sputtered. To guarantee that no sputtering takes place except from desired surfaces, a
`shield of metal (at a potential equal to that of the anode) is placed at a distance less than the
`Crookes dark space at all other cathode surfaces (Fig. 11-7). Since no discharge will occur
`between two electrode surfaces separated by less than this distance, such shielding (termed
`dark-space shielding)is effective in preventing sputtering from unwanted cathode surfaces.
`
`11.3 THE PHYSICS OF SPUTTERING
`
`Whena solid surface is bombarded by atoms, ions, or molecules, many phenomena occur. The
`kinetic energy of the impinging particles largely dictates which are the most probable events.
`For low energy particles (<10 eV), most interactions occur only at the surface of the target
`material. At very low energies (<5 eV) such events are limited to reflection or physisorption of
`the bombarding species. For low energies which exceed the binding energy of the target
`material (S—10 eV), surface migration and surface damage effects can take place. At much
`higher energies (>10 keV), the impinging particles travel well into the bulk of the sample before
`slowing downand depositing their energy. Thus, such particles are most likely to be embedded
`in the target, and this mechanismis the basis of ion-implantation. At energies between the two
`extremes, two other effects also arise: 1) some fraction of the energy of the impinging ionsis
`transferred to the solid in the form of heat, and lattice damage; and 2) another fraction of such
`energy causes atoms from the surface to be dislodged and ejected into the gas phase
`(sputtering).
`
`Ex. 1041, Page 5
`
`

`

`444 SILICON PROCESSING FOR THE VLSI ERA
`
`3
`
`aay.
`oOo
`1
`/ NEUTRALIZED
`~~ —*
`GAS MOLECULE,
`REBOUNDED FROM
`THE TARGET SURFACE
`
`~
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`BOMBARDING IONIZED
`
`GAS MOLECULE TARGET ANDIAS
`
`se INDICATE DINECIION OF
`MOMEN LUM TRANSFER.
`
`x
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`\
`“
`}Nf
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`‘
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`SPUTTERED ATOM
`
`Fig. 11-8 (a) Binary collision between atom A and B, followed by a binary collision between atom B and
`C.(b) Collision process responsible for sputtering and fast neutral generation.
`11.3.1 The Billiard Ball Model of Sputtering
`The exact mechanisms which lead to the ejection of atoms under ion bombardmentare not
`known, and a comprehensive theory of sputtering is not likely to be developed in the near future
`since many parameters are involved. These include the kinetic energy of the ions, lattice
`structure, and binding energy oflattice atoms. Someofthe details, however, are reasonably well
`understood and can be aptly described with a relatively simple momentum-transfer model. G.K.
`Wehner, whose theoretical work first established a solid scientific basis for sputtering, often
`described sputtering as a game of three-dimensional billiards, played with atoms.? Using this
`analogy,it is possible to visualize how atoms maybe ejected from a surface as the result of two
`binary collisions (Figs, 11-8b and 11-8c) when a surface is struck by a particle with a velocity
`normal to the surface (e.g., atom A in Fig. 11-8b). Note that a binary collision is one in which
`the primary incoming particle (e.g., atom A)strikes a single object (e.g., atom B in Fig. 11-8b),
`and gives up a significant fraction of its energy to the struck atom, while retaining the remaining
`fraction. As a consequenceofthe collision, atom B may leave the point of impact at an angle
`greater than 45°.
`If atom B then undergoes a secondary collision with atom C, the angle at
`which atom C leaves the secondary impact point may again be greater than 45°. Thus, it is
`possible that atom C can have a velocity component greater than 90° (and thus be directed
`toward the surface). As a result, there is a finite probability that atom C will be ejected from the
`surface as a result of the surface being struck by atom A.
`Whenthe directions of sputtered atoms from the surface of polycrystalline materials (and
`most cathode materials in sputter applications are polycrystalline) are measured for the case of
`normalincidence, it is found that the ejected atoms leave the surface in essentially a cosine
`distribution. A cosine distribution, however, does not describe the sort of small-angle ejections
`that would be expected from the simple collision processes described above. Evidently in actual
`sputtering events, more than twocollisions are involved, and the energy delivered by impinging
`ions during normal incidence is so randomly distributed that
`the effect of the incident
`momentum vector is lost. Note that the energy range of sputtered atoms leaving the targetis
`
`i1
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`Ex. 1041, Page 6
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`

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`ALUMINUM THIN FILMS AND PHYSICAL VAPOR DEPOSITION IN ULSI
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`445
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`typically 3-10 eV, and the bombarding species also recoil from the cathode face with some en-
`ergy. Thus, the target surface is a source of sputtered atoms and energetic backscattered species.
`For the case when the surface is bombarded by ionsat an oblique angle (i.e., 45°-90°), there
`is a higher probability that the primary collision between incident ions and surface atoms will
`lead to sputtering events. Furthermore, oblique incidence confines the action closer to the sur-
`face, and thus sputtering is enhanced.In cases of oblique bombardment, the incident momentum
`vector becomes important, and sputtered atomsare ejected strongly in the forward direction. In
`addition, the sputter yield (defined as the number of atoms ejected per incident ion), may be as
`muchas an order of magnitude larger than that resulting from normal incidence by bombarding
`ions (Fig. 11-9). This effect also leads to faceting, whichis covered in Sect. 11.7.4.
`11.3 2 Sputter Yield
`The sputter yield is important because it largely (but not completely) determines the rate of
`sputter deposition. Sputter yield depends on a number of factors besides the direction of
`incidence of the ions, and these include: a) the target material; b) the mass of bombardingions;
`and c) the energy of the bombarding ions. There is a minimum energy threshold for sputtering
`that is approximately equal to the heat of sublimation (e.g., 13.5 eV for Si). In the energy range
`of sputtering (10-5000 eV), the yield increases with ion energy and mass. Figure 11-10 shows
`the sputter yield of copper as a function of energy for various noble gas ions. The sputter yields
`of various materials in argon atdifferent energies is given in Table 11-2.9
`Several matters related to sputter yield should be noted. First, although the sputtering yields
`of various materials are different, as a group they are muchcloserin value to one anotherthan,
`for example,
`the vapor pressure of comparable materials. This makes the deposition of
`multilayer or multi-component films much more controllable by sputtering. The details of sput-
`tering from multi-componenttargets are discussed in the section on Process Considerations in
`Sputter Deposition. Second, since the bombarding ions are by no means monoenergetic in glow-
`discharge sputtering, it is not necessarily valid to use the sputter yield values for pure metals if
`alloys, compounds, or mixtures are being sputtered. Tabulations of sputtering yields, however,
`are useful for obtaining rough indications of deposition or etch rates of various materials.
`
` INCIDENT 10N
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`SPUTTERING
`
`YIELD,Ste)
`
`max
`ANGLE OF INCIDENCE 141
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`m2
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`Fig. 11-9 Schematic diagram showing variation of sputtering yield with ion angle of incidence.
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`Ex. 1041, Page 7
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`

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`446 SILICON PROCESSING FOR THE VLSI ERA
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`Table 11-2 SPUTTER YIELDS FOR METALSIN ARGON (ATOMS/ION)
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`Target
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`At.Wt/Dens.
`
`100 eV
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`300 eV
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`600eV
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`1000 eV
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`2000 eV
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`Al
`Au
`Cu
`Ni
`Pt
`Si
`Ta
`Ti
`Ww
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`10.0
`10.2
`7.09
`6.6
`9.12
`12.05
`10.9
`10.62
`14.06
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`0.11
`0.32
`0.5
`0.28
`0.2
`0,07
`0.1
`0.08
`0.12
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`0.65
`1.65
`1.6
`0.95
`0.75
`0.31
`0.4
`0.33
`0.41
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`1.2
`2.8
`2.3
`1.5
`1.6
`0.5
`0.6
`0.41
`0.75
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`1.9
`3.6
`3.2
`24
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`0.6
`0.9
`0.7
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`2.0
`5.6
`4.3
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`0.9
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`11.3.3 Selection Criteria for Process Conditions and Sputter Gas
`The information gleaned from sputter yields and the physics of sputtering can also be applied
`toward an understanding of how process conditions and materials are selected for sputtering
`including: a) type of sputtering gas; b) pressure range of operation; and c) electrical conditions
`for the glow discharge.4® That is,
`in purely physical sputtering (as opposed to reactive
`sputtering) it is important that the ions or atomsof the sputtering gas not react with the growing
`film. This limits the selection of sputtering species to the noble gases. Furthermore, argon is
`generally the gas of choice, since it is easily available (hence low in cost), and its mass is a good
`match to those of the elements most frequently sputtered (Al, Cu, Si, and Ti), giving adequate
`sputtering yields for these elements. The pressure range of operationis set by the requirements
`of the glow discharge (lower limit ~2-3 mtorr for magnetron sputtering) and the scattering of
`sputtered atoms by the sputter gas (upper limit 100 mtorr). In addition, a desired goal of sputter
`deposition is to obtain maximum deposition rates. As a result, electrical conditions are selected
`
`Almen & Bruce
`(1961)
`
`xe
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`Copper
`
` 20+
`
`=°
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`3E°g <~
`
`0
`
`10
`
`20
`
`30
`
`40
`
`—_*
`50
`60
`70
`kev
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`Fig. 11-10 Sputtering yields of the noble gases on copper, as a function of energy.!9
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`lon Energy
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`Ex. 1041, Page 8
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`

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`increment gives a progressively smaller increase in sputter yield. This occurs because higher
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`energy ions implant themselves, and thus end up dissipating a greater proportion of their energy
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`via non-sputtering processes. The most efficient ion energies for sputtering are typically
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`obtained for electrode voltages of several hundred volts.
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`In general, the higher the current at the cathode, the higher is the film deposition rate, since
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`more ions are striking the cathode (and thus cause more sputtering). The product of the cathode
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`current and the electrode voltage gives the input power of the sputtering process. In magnetron
`sputtering, cathode current densities of 10-100 mA/em?at a few hundred volts are typical.
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`From the foregoing discussion on the mechanism of sputtering one can see that sputtering is
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`a highly inefficient process. In fact, ~70% of the energy consumed during the sputtering process
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`is dissipated as heat in the target, and ~25% by emission of secondary electrons and photons
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`from the target. This heating can raise target temperatures to levels capable of damaging the
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`target, associated vacuum components, or the material that bonds the target to the backing
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`electrode. The target must therefore be cooled to avoid these problems. As we will discusslater,
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`11.3.4 Secondary Electron Production for Sustaining the Discharge
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`be continuously provided with free electrons to keep them sustained. In most dc-sputtering
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`occurs according to the sequence of events shown in Fig. 11-11. Target electrons require a
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`minimum amount of energy g® to escape into free space (where Mis the work function of the
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`close to the target surface it appears as a potential well of 15.67 eV to target electrons occupying
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`space escape energy is released in the form of a photon. If this photon (e.g., of energy 10.67 eV
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`= [15.67 eV - 5 eV]) is absorbed by another electron near the target surface, this electron(i.e.,
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`the Auger electron) may posses enough energy to be emitted from the target into free space.
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`Since this sequence of events is rather improbable, several ions must strike the cathode in order
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`has been measured to be 0.05-0.1 for metal targets. Thus, each secondary electron needs to
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`generate as much as 20 ion-electron pairs before it reaches the anode to sustain the discharge.
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`Besides providing a source of electrons to sustain the discharge, electron emission is also
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`important to the sputtering process in other ways. First, ions bombarding the cathode are
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`neutralized. Thus, it is highly probable that each ion that closely approaches the target will
`extract an electron from the target, and return to the discharge as a neutral atom. Second, the
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`total target current, IJ, is the sum of the ion flux striking the target, I,, and the secondary electron
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`current leaving the electrode, I. Since y,
`is larger for dielectric materials, their I, is also larger.
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`This implies that for the same cathode current, I, dielectrics will sputter more slowly than
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`metals. That is, in dielectric sputtering a larger fraction of I is due to electron emission, and thus
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`for equal valuesof I, a smaller ion flux is striking the dielectric target.
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`Ex. 1041, Page 9
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`Ex. 1041, Page 9
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`

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`448 SILICON PROCESSING FOR THE VLSI ERA
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`4
`SMOLIN,
`C/A SEA OF CONDUCTION ©
`“ ELECTRONS ~~" .-
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`LL Le ONS
`LLL KE 2
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`eV;
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`yy = IONIZATION POTENTIAL
`15.76 VOLTS FOR ARGON
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`[elOFCAPTUREDELECTION
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`TRANSITION OF EXCITED ELECTRON (AUGER PROCESS)
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`Fig. 11-11 Potential energy diagram for ion approaching a metal target.
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`11.3.5 Sputter Deposited Film Growth
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`Upon being ejected from the target surface, sputtered atoms have velocities of 3-6x10° cm/sec
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`and energies of 10-40 eV.It is desirable that as many of these sputtered atoms as possible be
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`deposited upon the substrates to form the specified thin film. To accomplish this, the target and
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`wafers are closely spaced, with spacings of 5-10 cm being typical. The mean free path, A, of
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`sputtered atoms at typical sputter pressures is less than 5-10 cm (e.g., at 5 mtorr, A =1 cm).
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`Thus, it is likely that sputtered atoms will suffer one or more collisions with the sputter-gas
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`atoms before reaching the substrate (Fig. 11-12). The sputtered atoms may therefore: a) arrive at
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`the substrate with reduced energy (~1—2 eV); b) be backscattered to the target or the chamber
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`walls; or c) lose enough energy so that thereafter, they move by diffusion in the same manner as
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`neutral sputter gas atoms. These events imply that the sputtering gas pressure can impact various
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`film deposition parameters, such as the deposition rate and compositionof the film.
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`The formation and growth of the thin film on the substrate proceeds according to the general
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`discussion on thin film formation given in Chap. 4. Therefore, this discussion is restricted to the
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`events that uniquely impact the formation and growth of glow-discharge sputteredfilms.
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`The substrate surface (onto which the desired film of the sputtered target material is
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`deposited) is also subjected to impingement by many species. The sputtered atoms arrive and
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`condense onto the substrate. For a typical deposition rate of 20 nm/min, a monolayer of
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`deposited film will form approximately every second (assuming the size of a typical atom is
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`~0.3 nm). For this case, and even for much higher deposition rates of Al
`(e.g., 620 nm/min), the
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`heat of condensation is not necessarily the most important source of substrate heating.
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`11.3.6 Species that Strike the Wafer During Film Deposition
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`In addition to the sputtered atoms, the substrate is also struck by many other species (Fig. 11-
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`13), the most important being: 1) fast neutral sputter gas atoms, which retain significant energy
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`after striking and recoiling from the cathode. As they impinge upon the substrate, some may
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`embed themselvesin the growing film; 2) negative ions,
`formed near the cathode surface by
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`Ex. 1041, Page 10
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`Ex. 1041, Page 10
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`

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`ALUMINUM THIN FILMS AND PHYSICAL VAPOR DEPOSITION IN ULSI
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`461
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`Fig. 11-23 An spent aluminum circular-planar-magnetrontarget(right) is being changed.
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`reported that deposition rates of 1200-nm/min can be achieved when depositing Al:(0.5%)Cu
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`films on 200-mm wafers.>9 In fact, the maximum sputter deposition rates with such sources are
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`usually not limited by any aspect of the plasma (as in dc and rf diode cases), but rather by the
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`ability to cool the cathode target to keep it from melting.
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`The fact that the annular shape of the plasmain a circular planar magnetron results in a non-
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`uniform erosion of the target also causes the deposition onto nearby wafers to be non-uniform.
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`In fact the deposition profile mirrors the race track when the waferis close to the target, but this
`deposition profile becomes more smeared as the sample is moved further from the target (see
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`Fig. 11-24a). Thus, a tradeoff is often made between deposition rate and thickness uniformity
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`(i.e., uniformity improves as the target-to-wafer spacing is increased, but the deposition rate
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`decreases). Note also from Fig. 11-24 that the target diameter is made larger than the wafer
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`diameter to improve thickness uniformity. As an example, for 200-mm (8 in) wafers, the target
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`diameter is typically 330 mm (14 in). Figure 11-24b shows such a target sputtering onto a
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`smaller wafer. In practice, thickness uniformities of 5% (30) within a wafer can be achieved.
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`11.6 VLSI AND ULSI SPUTTER DEPOSITION EQUIPMENT
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`A number of different sputtering systems have been designed for commercial use in IC
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`fabrication. Only the dominant sputtering systems designs that were used in VLSI and ULSI
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`generations will be described (i.e., those used for IC fabrication on 125-mm, 150-mm, and 200-
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`mm wafers). Sputtering systems used for earlier IC technologies are described in thefirst edition
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`of Vol. 1. In this section the generic components of a sputtering system are discussed first. Then
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`the sputtering systems used in 125-mm and 150-mm wafer processing are briefly examined. The
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`focusof this discussion is on the sputtering systems used for 200-mm wafers (and larger).
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`11.6.1 The Components of a Generic Sputtering System
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`The schematic of a basic sputtering system is shown in Fig. 11-25. It consists of the following
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`subsystems: a) the sputter chamber, in which the substrate holder and sputtering source reside
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`(the source also includes the target); b) vacuum pumps; c) power supplies (dc and/or rf); d)
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`sputtering gas supply and flow controllers; e) monitoring equipment (pressure gauges, volt-
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`Ex. 1041, Page 11
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`Ex. 1041, Page 11
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`

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`462 SILICON PROCESSING FOR THE VLSI ERA
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`Scm THROW
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`Cathode
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`SI
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`Xu
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`|
`Sem
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`ETCH TRACK DIAMETER
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`Spring
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`Wafer
`=< ¢—_
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`Heater
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`block
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`5
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`insulation
`Heater
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`Thermocouple
`Argon
`Fig. 11-24 a) The deposition profile and deposition rate on a sample in front of a magnetron cathode as a
`function of sample distance.” Reprinted with permission of Academic Press. b) Sputter deposition from a
`planar magnetrontarget whose diameteris larger than thatof the wafer.
`(pressure gauges, voltmeters, and residual-gas analyzers); f) wafer holders and handling
`mechanisms; and g) microcomputer controller.
`In modern sputter tools the sputter chambers are isolated from the ambient by a load lock.
`That is, a cassette of wafers to be sputter deposited is placed into the loadiock. Then the valve
`connecting the loadlock to the outside ambient is closed. The loadlock is pumped down, and
`upon reaching the base pressure of the transfer chamber the vacuum valve to the transfer
`chamber is opened. A robotic arm in the transfer chamber removes a wafer from the cassette
`and bringsit into the transfer chamber. The loadlock/transfer chambervalve is then closed. The
`sputter chamber awaiting the wafer has also been pumped to the appropriate low base pressure
`(e.g., 10°°-10°torr), The vacuum valveto the sputter chamberis opened,
`andthe waferis then
`DC/RF
`RF VOLTAGE
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`prose (V)
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`DC VOLTAGE
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`OSCILLOSCO
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`GAS SUPPLY
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`DC/RF/GROUND
`Fig. 11-25 Schematic drawing showing someof the components of a sputtering system.
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`2
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`Ex. 1041, Page 12
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`

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`ALUMINUM THIN FILMS AND PHYSICAL VAPOR DEPOSITION IN ULSI
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`463
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`Fig. 11-26 Examples of sputtering targets for planar circular magnetron sources.
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`inserted into the sputter chamber by the robot arm. After the arm withdraws, the vacuum valve
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`between the sputter chamber and the transfer chamber is closed, and sputter gas is flowed into
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`the chamber to the appropriate pressure (e.g., 5 mtorr) and flow rate. The sputter process can
`then bestarted.
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`11.6.1.1 Sputtering Targets: Sputtering targets consist of the material that is to be sputter-
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`deposited onto the wafer. Targets in circular magnetronsare circular discs 3 to 10 mmthick,as
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`shown in Fig. 11-26. These are bonded to a water-cooled Cu backing plate for good thermal
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`contact, usually by soldering with a low-melting-temperature metal (or with a conductive
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`epoxy). Since over 70% of the energy incident onto the ta