`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Samsung Electronics Co., Ltd. v. Demaray LLC
`Samsung Electronic's Exhibit 1047
`Exhibit 1047, Page 1
`
`

`

`
`
`
`
`
`
`
`
`
`
`A. Billard, C. Frantz/Surface and Coatings Technology 86-87 (1996) 722-727
`
`
`723
`
`
`2. Experimental
`
`3. Results and discussion
`
`
`
`
`
`
`3.1, Electric instabilities (suppression ofarcing)
`
`To prevent arcing, d.c. pulsed power waspreferred to
`t.f. power which presents several drawbacks: (1) a lower
`
`The deposition of 1-6 pm thick stoichiometric ceramic
`films (Al,03, Si0,, TiO,, ZrO,, AIN, SizN,, TiN) was
`performed using a 401 cylindrical vacuum chamber
`pumped downto 2 x 1074 Pa (1.5 x 107 Torr) by anoil
`diffusion pump before refilling with the appropriate
`reactive sputtering gas mixture (argon + oxygen ornitro-
`gen). The magnetron sputter source is a 50 mm diameter
`target (Al, Si (resistivity lower than 0.5 Q-cm), Ti, Zr).
`Before each deposition,
`the target is pre-sputtered in
`pure argon for a period of approximately 15 min.It is
`powered from a SAIREMpulsed d.c. prototype genera-
`tor in the unipolar mode (10-66 kHz) or in the bipolar
`mode (10-33 kHz). The voltage signal can also be
`modulated at low-frequency (1-100 Hz). The generator
`is equipped with a fast arc detector able to cut microarcs
`within 1-2 ps. For all depositions, the generator ran in
`the power-controlled mode constant (150-250 W) which
`results in discharge voltages between — 300 and —430 V
`and in a deposition rate of 4-6 ym h™! (1.1-1.7 nm
`s') at a target-to-substrate distance of 80mm. The
`flow rates of argon, oxygen or nitrogen were controll-
`ed with MKS mass flowmeters. The total working
`pressure was measured using an MKSBaratron capac-
`itance manometer and the oxygen or nitrogen partial
`pressure was measured using both mass spectrometry
`and the capacitance manometer. Optical emission spec-
`troscopy (OES) was also performed for plasma dia-
`gnostics. During deposition, the argon mass flow was
`kept between 30 and 45 standard cm* min™'
`(sccm)
`
`and the argon partial pressure P,,, between 0.30 and
`0.90 Pa (2.28 and 6.84mTorr) while the oxygen or
`nitrogen mass flow wasvaried from 0 to 10 sccm (partial
`pressure in the 0-0.1 Pa range (0—-0.76 mTorr)).
`Substrate materials were polished steel samples and
`glass slides. Prior to sputter cleaning, the samples were
`ultrasonically rinsed in acetone and alcohol. Their tem-
`perature starts at room temperature and is lower than
`400 K during sputtering. No negative bias was applied
`to the substrate during deposition.
`The chemical and structural study of the deposits was
`performed by means of electron probe microanalysis
`(EPMA) using as reference samples pure Al, Si, Ti, Zr
`and metallized samples of oxides or nitrides of known
`composition, Auger electron spectrometry (AES), X-ray
`diffraction (XRD), optical microscopy (OM), transmis-
`sion and scanning electron microscopy (TEM-SEM)
`and atomic force microscopy (AFM).
`
`
`
`
`
`deposition rate than for d.c.; (2) the necessity of good
`impedance matching for powertransfer to the plasma;
`(3) high cost of r.f. power supplies.
`The conditions of reactive d.c. pulsed magnetron
`sputtering with an argon partial pressure of 0.90 Pa
`(6.84 mTorr) will be first considered because they lead
`for all the systems to a time-stable sputtering regime
`with a target practically non-poisoned by the reactive
`gas [3,4]. At this operating pressure, the stability of the
`sputtering process is due to a pumping speed of the
`reactive gas (about 1301s~') by the vacuum system
`greater
`than the
`critical pumping speed
`(about
`100 1s~! for Al,O, deposition) leading to instability.
`Wewill see later that with decreasing the argon partial
`pressure the critical pumping speed will increase and the
`hysteresis effect will no longer be avoided.
`
`@ For dc. sputtered deposits, OM and SEM [3,4]
`showed a rough surface with a great density of
`growth defects and droplet projection due to arcing,
`as confirmed here by AFM (Figs. 1(a) and (b)). One
`hundred to 1000 arcss~! can be detected and sup-
`pressed by the fast arc detector for the most reactive
`systems (e.g., Al,O3, AIN, SiO;). These arcs are in
`reality microarcs responsible for more than 104
`defects cm ~? in the deposits. The dimensions of these
`defects in the plane of 1-2 ym thick deposits are
`generally submicron while their maximum heightis
`about
`200nm.
`For
`amorphous
`stoichiometric
`ALO,films, the index of refraction measured in the
`800-2000 nm range has an average value of 1.65.
`@ The use of rectangular unipolar pulsed d.c. discharge
`can reduce by several orders of magnitude the growth
`defect and projection density thanks to a quasi-
`suppression of arcing. The “pulse-on” time must be
`short enough (10—40 ps) to prevent the breakdown
`of the insulating layer formed on the target surface
`and which charges positively under Ar* ion bom-
`bardment. The “pulse-off”’ time must be long enough
`(e.g., 10 ps) to discharge that poisoned layer under
`bombardment with electrons which are still present
`in the plasma before its total extinction. Experiment
`shows that 50 or 20 kHz unipolar negative rectangu-
`lar pulses with a “pulse-off time” of 10 ps are really
`suited to prevent arcing, respectively for Al,O3, AIN
`or Si0,, SizN,, TiO,, ZrO,. The film surface is in
`fact very smooth and the maximum height of the
`residual defects is about 10nm (Fig. 1(c)). The
`refractive index of Al,O, is 1.67. However, very fine
`microporosity (about 20nm in diameter) was
`detected by TEM [3,4] in the aluminafilms deposited
`at this argon partial pressure of 0.90 Pa (6.84 mTorr).
`This pressure is therefore not optimised for a good
`compactness of alumina deposits.
`@ The use of bipolar pulsed d.c. discharge has been
`
`Ex. 1047, Page 2
`
`Ex. 1047, Page 2
`
`

`

`724
`
`
`
`
`
`
`
`
`
`
`
`A. Billard, C. Frantz/Surface and Coatings Technology 86-87 (1996) 722-727
`
`6 vfas
`kena7
`We,yyTh
`
`Fig. 1. AFM images of the topography of a 1.5 wm thick amorphous alumina film deposited on glass slide: (a,b) d.c. discharge; (c) pulsed d.c.
`discharge (50 kHz); (d) pulsed d.c. discharge (50 kHz) modulated at low-frequency (about 1 Hz). For a, b, ¢ deposits, argon partial pressure is
`0.90 Pa. It is 0.30 Pa for d deposit.
`
`pte
`
`
`
`to increase sharply, whereas the deposition rate rapidly
`decreases. The reactive sputtering is thus characterized
`by two stable states (with fast transition from one to
`the other) which can be conveniently discriminated by
`reference to the different generic hysteresis curves repre-
`
`senting, as a function of the mass flow ®, ofthe reactive
`the partial pressure P, of the reactive gas;
`the
`gas:
`
`metalloid concentration Cy, or the deposition rate Rp
`of the deposits; the optical emission intensity of sput-
`tered metal atoms;
`the electric characteristics of the
`
`target (voltage and intensity).
`As an example, the schematic Pp-®, curve is presented
`in Fig. 2. It is typical of a strongly reactive metal (or
`semiconductor)/gas system such as Al/O, for forming
`
`Al,O;. The straight
`line in Fig.2 shows the linear
`increase in Pp that would result from increasing ®, if
`no sputtering took place. In the metal sputtering mode
`
`(nonpoisoned target) where ®, < ®g,, there is negligible
`change in partial pressure Pg as ®p is varied. In the
`compound sputtering mode (poisoned target) where
`@p>Pzz, the partial pressure varies linearly with @,
`
`in suppressing
`revealed to be still more efficient
`arcing but care must be taken to avoid sputtering of
`the reactor walls and accessories during the positive
`pulses if their magnitudeis not kept to about 10-20%
`of the magnitude of the negative pulses.
`
`4. Instability of the reactive sputtering process: new
`stabilizing-method
`
`
`
`
`
`
`
`4.1, Recall of the general processes ofreactive sputtering
`
`The hysteresis effect that often occurs in reactive d.c.
`or r.f. sputtering of ceramic compoundsis a well known
`phenomenonresulting from the sudden covering of the
`target surface by reaction products (oxides, nitrides,
`carbides) which generally exhibit a lower sputtering rate
`[11~13]. The getter pumping effect due to the reaction
`between the sputtered atoms andthe reactive gas is thus
`reduced, causing the partial pressure of the reactive gas
`and the metalloid concentration (O, N, C) in the deposits
`
`
`
`
`
`
`
`
`Ex. 1047, Page 3
`
`Ex. 1047, Page 3
`
`
`

`

`A. Billard, C. Frantz/Surface and Coatings Technology 86-87 (1996) 722-727
`
`725
`
`
`
`
`
`Reactivegaspartialpressure(Pp)
`
`
`Reactive gas mass flow (@g)
`
`because of the increase of the critical pumping speed of
`the reactive gas as the working pressure decreases. For
`the aluminium—oxygen system and a 50 kHz unipolar
`pulsed discharge which prevents arcing, Fig. 3 shows
`the classical sputtering instability observed at an argon
`partial pressure of 0.30 Pa on the curves which relate
`the oxygen partial pressure and the electric characteris-
`tics of the discharge (target voltage and current) to the
`total oxygen mass flow entering the reactor. A similar
`phenomenonis observed for r.f. reactive sputtering of
`aluminium in Ar/O,plasmaevenif the working pressure
`is kept at 0.90 Pa (6.84 mTorr). Then, it becomes very
`difficult to synthesize a stoichiometric compound on the
`substrate, other than sputtering a totally poisoned target
`which often leads to a drastic drop in the deposition
`rate, especially for Al,O3, TiO, and, to a lesser extent,
`for ZrO,, TIN and AIN. For SiO, and Si;N,, poisoning
`of the target may be tolerable because the sputtering
`yield of the oxide or nitride is only little lower than that
`of puresilicon.
`In the case of the aluminium—oxygen system where
`the rise in the reactive gas partial pressure is very rapid
`when mass flow control is used, the high rate deposition
`of stoichiometric amorphousoptically transparent alu-
`mina is impossible because it requires a critical value
`
`Pc, of the oxygen partial pressure just slightly above
`
`P, in the unstable region, for instance in F on the
`hysteresis curve OABCD(Fig.2).
`In the case of moderately reactive systems, a solution
`to the instability problem can sometimes be found by
`controlling the partial pressure of the reactive gas instead
`of the mass flow with the help of a more orless
`sophisticated closed-loop feedback control system [6-
`9]. With such a control, the curve of the reactive gas
`partial pressure with the mass flow is reversible when
`equilibrium is reached and exhibits an S-shape (Fig. 2).
`To obtain stoichiometric compoundfilms with satisfac-
`
`
`
`
`
`Fig. 2. Schematic curve of the reactive gas partial pressure with the
`mass flow for a strong reactive system (e.g., aluminium—oxygen
`system). Without discharge, linear relation between Pp and ®,; with
`discharge, hysteresis curve OABCD underreactive gas mass flow con-
`trol; reversible S, shape curve OACB underreactive gas partial pres-
`sure control.
`
`but is typically lower than that measured in the absence
`of sputtering:
`the greater the ratio of the sputtering
`yields of the metal atoms from the metal and the
`compound, the smaller will be the value of the reduction
`in pressure. Due to the kinetics of the sputtering and
`reaction processes, a runaway situation appears between
`these two states that shifts the operating point from A
`to B or from C to D depending on whether the reactive
`gas flow @, is increased or decreased. Thus the AB and
`CD parts of the curves define a hysteresis region,all the
`wider and steeper, as the difference between the respec-
`tive sputtering yields of the target
`in its metal and
`poisoned states increases. Experiment shows that the
`operating point of the sputtering reactor must often be
`kept in that unstable region between a clean target and
`a poisoned target in order to synthesize on the substrate
`the desired ceramic compound. It is noteworthy that
`changes in shape of hysteresis curves can be observed
`as a function of the pumping speed, the location of the
`reactive gas inlet and the effective area of the reactor
`walls. Indeed, the width of the hysteresis curve decreases
`as the reactive gas inlet is moved closer to the pump
`entrance [13] and tends to disappear as the pumping
`speedis increased [13-15] or as the wall areais artificially
`decreased by using adequateshields [16]: however, these
`factors are not always sufficient, especially when the
`reactive gas strongly reacts with the vapour emitted by
`the target (getter effect) or when the working pressure
`is lowered.
`
`
`
`
`
`
`
`4.2, New stabilizing method of the reactive sputtering
`
`process
`
`The improvement of the ceramic films quality (mor-
`phology and compactness of the microstructure) often
`requires a lowering of the working pressure. However,
`for a critical argon partial pressure (e.g., 0.80 Pa for
`Al,O; or 0.30 Pa for TiO, ZrO, and TiN), the sputter-
`ing instability with its associated hysteresis effect occurs
`
`1000
`
`800
`
`2”
`:
`
`0.08
`
`0.06
`
`0.02 -
`mai
`
`O2 flow rate (sccm)
`
`:
`
`Fig. 3. Sputtering instability observed at P,.=0.30 Pa and average
`power =240 W for aluminium—oxygen system:
`target current (I),
`target voltage (V) and oxygen partial pressure (Po,) as a function of
`the total oxygen mass flow for a negative unipolar 50 kHz pulsed
`discharge.
`
`Ex. 1047, Page 4
`
`Ex. 1047, Page 4
`
`
`

`

`726
`
`
`
`
`
`
`
`
`
`
`
`A. Billard, C. Frantz/Surface and Coatings Technology 86-87 (1996) 722-727
`
`tory deposition rates requires to be able to operate on
`the negative slope of the processing curve OACB, for
`instance in F’.
`In the case of very reactive systems where the ceramic
`compoundshave a low sputtering yield, a new method
`which allows the control
`in real-time of the target
`poisoning [10] is proposed. The principle of this method
`consists of a low-frequency (1-10 Hz) modulation of
`the voltage signal applied to the target,
`in order to
`cyclically reduce and increase the instantaneous power
`in such a manner as to alternate controlled chemical
`reaction (e.g., oxidation, nitriding, carburizing) between
`the target surface and the reactive gas and sputtering of
`the reaction products. Within a period of this mod-
`ulation,
`the instantaneous operating point oscillates
`between two steady limits corresponding, respectively,
`to conditions close to the metal and compound sputter-
`ing modes. Several characteristics (period, shape and
`magnitude) of this modulation were tested. It seems that
`a simple voltage ramp, with a period of about 1s and
`a magnitude of about 100 V, works well in keeping the
`average operating point of the reactor in the normally
`unstable region and in avoiding any risk of chemical
`modulation of the film.
`As a nonrestrictive example, an application of this
`method is shown in Fig. 4 for alumina prepared at the
`argon partial pressure of 0.30 Pa (2.28 mTorr) with a
`
`
`
`
`0
`
`
`200
`
`
`400
`
`
`600
`
`
`
`
`goo 1000 1200
`
`Fig. 4. Example of a low-frequency modulation (about 1 Hz) of the
`50 kHz pulsed voltage applied to an aluminium target under Ar/O,
`plasma leading to stoichiometric amorphous alumina at the argon
`partial pressure of 0.30 Pa. Oxygen mass flowis fixed at 4.2 sccm.
`(curve a) target voltage within a period of the low-frequency modula-
`tion; (curve b) target current. The dotted lines b’ and b” correspond
`to an oxygen flow of 3 and 6 sccm for which the target is respectively
`metallic and oxidized; (curve c) optical emission intensity of aluminium
`atomsat 396.1 nm; (curve d) optical emission intensity of argon atoms
`at 811.5nm. All these quantities are averaged values with respect to
`the 50 kHz negative unipolar pulses.
`
`
`
`
`50 kHz pulsed discharge. All the microporosities have
`disappeared as confirmed by TEM [3,4] and by the
`increase of the refractive index (n=1.69). The alumina
`film is perfectly transparent and chemically homogen-
`eous as confirmed by AES analysis as a function of
`depth. AFM shows (Fig. 1(d)) that the alumina film
`surface is very smooth with a maximum relief of 3 nm.
`With an average power of 240 W,the deposition rate is
`about 1.3nms~?! and is only 20% lower than for pure
`aluminium sputtered under non-reactive conditions.
`With such a method where the reactive gas mass flow
`is fixed at its critical value in the absence of the low-
`frequency modulation of the voltage signal, long time-
`stable sputtering conditions can be achieved with a
`correct positioning of the low-frequency voltage ramp.
`For this purpose, because of the difference in the second-
`ary
`electron
`emission
`yield
`between
`a metallic
`(Fig. 4(b)’) and a poisoned (Fig. 4(b)”) target surface,
`it is often possible as shown by the characteristic shape
`of the target current intensity curve in Fig. 4(b) to know
`if the necessary condition of alternate controlled poison-
`ing and sputter-cleaning of the target surface is satisfied
`within a period of the low-frequency modulation of the
`voltage signal. If the sensitivity of the target current to
`the target surface poisoning is not high enough, OES
`can generally be used. It is based on the intensity of a
`suitable emission line, preferably, belonging to sputtered
`metal atomsandinitially calibrated at two stable sputter-
`ing conditions corresponding to metallic mode and
`compound mode. The prerequisite for this control is the
`steady and monotonouscorrelation between target poi-
`soning and intensity of the plasma emission line chosen.
`For most combinations of target material and reactive
`gas, this requirementis satisfied (e.g., the emission line
`of aluminium atoms at 396.1 nm is suitable for an Al
`target sputtered by Ar/O, (Fig. 4(c))). If both target
`current and OESare not available, it is then necessary
`to perform several tests to find the correct positioning
`of the voltage ramp or, for a given voltage ramp, the
`right mass flow of the reactive gas that leads to the
`desired stoichiometric compound deposited on the sub-
`strate at a high rate. When the right operating conditions
`are found, OESwithits short response time can be very
`useful for a possible automatic working of the reactor
`for a long time in enabling to move, if necessary, the
`voltage ramp up or down according to the intensity
`level of a characteristic optical emission line belonging
`to sputtered target metal atoms.
`It is noteworthy that, as for d.c. pulsed discharge,
`this method could also be successfully applied to r-f.
`discharge when an instability of the reactive sputtering
`process exists.
`
`5. Conclusion
`
`Asrecently reported [1-5], it has been shown thatit
`is possible to deposit by reactive magnetron sputtering
`
`Ex. 1047, Page 5
`
`Ex. 1047, Page 5
`
`
`

`

`A.Billard, C. Frantz/Surface and Coatings Technology 86-87 (1996) 722-727
`
`727
`
`G. Gavoille (LMCPIR URA CNRS809), respectively,
`for their work in atomic force microscopy andrefractive
`index measurements.
`
`References
`
`highly insulating ceramic compoundfilms(e.g., oxides,
`nitrides, carbides) with a low defect density, when a fast
`arc detector is used in conjunction with a medium-
`frequency pulsed d.c. discharge in the 20-50 kHz range.
`Such discharges pulsed in the unipolar modeor in the
`bipolar mode can suppress quasi totally micro-arcing
`and are thus a technically and economically interesting
`alternative to r.f. discharges.
`A new method based on the modulation in the
`1-10 Hz range of pulsed d.c. discharges enables the
`deposition of all compounds compositions, in particular
`at low working pressure, without the use ofa relatively
`complex automatic feedback control system of the
`reactive gas partial pressure. Indeed, this simple, eco-
`nomical and efficient method acts in synergy with the
`other known process-stabilizing parameters (pumping
`speed, reactor walls aera, site of reactive gas inlet). It
`keeps stable the average operating point of the reactor
`in the normally unstable region thanks to the dynamic
`control of the target poisoning by the reactive gas and
`its cleaning by sputtering. High rate deposition of
`ceramic compounds having an excellent physical quality
`and chemical homogeneity can be achieved including
`compounds which belong to the most reactive systems
`such as the aluminium—oxygen system. It is believed
`that this method can also be successfully applied to rf.
`discharges.
`
`
`
`{1] S. Schiller, K. Goedicke, J. Reschke, V. Kirchhoff, §. Schneider
`and F. Milde, Surf. Coat. Technol., 61 (1993) 331-337.
`[2] B. Stauder, Thése INPL-Nancy, Juillet, 1994.
`[3] B; Stauder, F. Perry and C. Frantz, Surf: Coat. Technol., 74/75
`(1995) 320-325.
`[4] B. Stauder, F. Perry, F. Sanchette, Tran Huu Loi, A.Billard, Ph.
`Pigeat and C. Frantz, Le Vide Sci. Appl., 275 (1995) 406-409.
`[5] W.D. Sproul, M.E. Graham, M.S. Wong, S. Lopez, D. Li and
`R.A. Scholl, J. Vac. Sci. Technol, A 13(3) May/June (1995)
`1188-1191.
`
`(6] A.F. Amiel, J. Vac. Sci. Technol, A 3(3) May/June (1985)
`592-595,
`
`[7] S. Schiller, U. Heisig, K. Steinfelder, J. Striimpfel, A. Friedrich
`and R. Fricke, Proc. 6th Int. Conf. IPAT, Brighton, UK, 1987,
`p. 23.
`[8] W.D. Sproul, P.J. Rudnik, C.A. Gogol and R.A. Mueller, Surf.
`Coat. Technol., 39/40 (1989) 499.
`[9] A.G. Spencer and R.P. Howson, Thin Solid Films, 186 (1990) 189.
`({10] B. Stauder, F. Perry, A. Billard, P. Pigeat, G. Henrion and C.
`Frantz, French Patent No. 92-15924, 30 Dec. (1992), European
`Patent No. 93 403153.5, 23 Dec.
`(1993), US Patent No. 08/
`172,549, 23 Dec (1993).
`[11] 8. Maniv and W.D. Westwood, J. Vac. Sci. Technol., 17 (1980)
`743.
`
`[12] S. Berg, H.O. Blom, T. Larsson and C. Nender, J. Vac. Sci. Tech-
`nol., A 5(2) (1987) 202.
`[13] W.D. Westwood, Physics of Thin Films, Ch. 14, Academic Press,
`NewYork, 1989.
`[14] R. McMahon,J. Affinito and R.R. Parsons, J. Vac. Sci. Technol.,
`20 (1982) 376.
`[15] R.P. Howson, Proc. 7th IPAT, CEP Consultants, Edinburgh,
`1989, p. 28.
`{16] J. Fletcher, J. Vac. Sci. Technol., A 6 (1988) 3088.
`
`Acknowledgement
`
`The authors acknowledge the Agence Nationale pour
`la Valorisation de la Recherche (ANVAR)forits finan-
`cial support, J.C. Martin (LGEP URA CNRS127) and
`
`Ex. 1047, Page 6
`
`Ex. 1047, Page 6
`
`