Method and apparatus for sputter coating

The present invention relates to a method of sputter-coating workpieces in which two opposing Sputtering against each other and between atomized the sputtering creates a gas flow and against at least one workpiece is directed. In further relates the present invention on a Sputterbeschichtungsquelle with two opposing sputtering surfaces, a provided between the sputtering anode assembly and a defined in between the sputtering surfaces Gap acting gas outlet, according to the Preambles of claims 1 and 15. In further relates The present invention is directed to a sputter coating with such a source according to claim 24 and uses of the invention Method, the inventive source or the novel Installation according to claims 26-28.

From US 4,094,764 it is known, for the sputter coating a workpiece flow of gas through the sputtering to realize, to the flowing inert or noble gas with abgestäubtem Target material to push against the workpiece. In order to will, compared with conventional cathodic sputtering, achieves significantly higher deposition rate.

Similarly, the procedure is according to DE-PS 42 10 125, by a gas flow is not about the sputtering of a Planar targets according to the US-A 4,094,764, but along the inner surface a hollow conical targets - a hollow cathode target - Is created and the sputtered from the target material is supplied to a substrate workpiece by means of the flow.

In H. Koch et al. "Hollow cathode discharge sputtering device for uniform large area thin film deposition ", J. Vac. Sci. Technol. A9 (4) on Jul / August 1991 are the benefits of such Hollow cathode sputtering discussed, in particular with respect to utilization the electrons for ionization of the volume in the reaction Gas contained. It is therefore proposed there, in a provide target block a transverse slot and a gas flow directed through this slot against a workpiece through use.

On slit two sputtering of targets are close to compared to what the unwanted restocking other system components minimized as the target itself.

This is particularly important in reactive DC sputtering, in which electrically insulating reaction products as a coating material are produced and recycled is.

However, this procedure has the following disadvantage:

If the assignment of the opposing sputtering surfaces minimized with already reacted target material and maximizes the electron impact ionization efficiency for the , so must the selected gap width and thus the distance be kept small between the two sputtering. The design of the gap with near opposite sputtering surfaces but requires correspondingly short Spaltbreiten- or Graduation surfaces. This is in turn with respect to the electron impact yield extremely disadvantageous in that in which they SchlitzEndbereichen are reflected and finally, without their Energy completely through the shock cascade to the gas particles deliver, partly accessed discharged via the anode will. There is therefore the use of a hollow cathode slot the type generally shown in the above-mentioned items the problem is that the better the target assignment problem is solved along the sputtering, namely with smallest possible slit width, the higher the loss to electron impact yield in the Schlitzendbereichen. In the Usually consists in the longitudinal direction of the slit an electron drift, preferably against a slot end what unequal to Plasma longitudinal distribution and thus Abstäub distribution leads.

The present invention sets itself the goal that aforementioned To solve problems. This is starting from the process obgenannter Kind achieved by the opposing sputtering surfaces are each self-contained and the gas flow by a self-contained gap, essentially is generated transversely to section planes, in which the gap is in closed whereby a closed plasma loop appears, arises.

Characterized in that the gap is closed in itself, realized by two opposing, each self-contained sputtering, For example, an inner cylinder and Targets an outer hollow cylindrical target is achieved that in many Limits dimensioned the slit width and especially short can be adapted to particular return-mentioned assignment problems to take account of that but anyway, thanks the self-contained sputtering, although possibly because corners are provided, as in use of Cuboid target, no split ends at the circumferential gap present and thus the electrons along and within move the plasma loop, as long as it can circulate until they caused by impacts to the gas particles as possible their energy have fully discharged, resulting in a more efficient plasma discharge leads. This is evident from the lower discharge voltages and the stable operation.

If, as preferably proposed any of the self Sputtering formed at its own target, it follows the further a preferred stable arrangement. Each of the intended targets may also with a separate Generator assembly are fed to optimum performance balance to achieve, or to different target materials Mixing materials to produce.

In particular, due to the high plasma density in the circumferential Gap it is possible to return assignment problem of sputtering, in particular with electrically insulating reaction products, to minimize the Reaktivzerstäuben further, bringing the proposed approach, in particular for coating with dielectric materials, in particular with oxides, suitable. Therefore, even in a preferred embodiment selected at least one gas component as a reactive gas, preferably with O₂Where a good gas separation ensured , when the inert gas such as Ar, inserted into the gap is, and the reactive gas, removed from the target in the chamber.

Reactive gas is much more preferably not introduced through the gap, but directly into the coating chamber.

In a particularly preferred embodiment, the coating is carried out ferromagnetic with a material having at least one Component or with a dielectric material, both Coating materials known for the preferred here DC sputtering extremely critical. In a further preferred Embodiment, the coating with MgO or made of ITO, this is metal by reactive sputtering Target, or by reactive sputtering, where appropriate, in addition oxidic target, ie, in particular, as with MgO, from materials, because of their extremely low conductivity for DC Sputtering are extremely problematic.

The inventive procedure and due to the fact that the two opposing sputtering ever can be implemented on a target, also results in the Ability different for the two sputtering surfaces use materials and hence more complex coating materials particularly reactive store.

In a particularly preferred embodiment, in the gap generates a magnetic field, preferably in the manner of a Magnetronfeldes, by at least one, preferably along both sputtering surfaces, at least one magnetic tunnel-with Field line profile is generated, wherein the tunnel axes extend along the self-contained sputtering surfaces and preferably also close.

If already using the inventive provision of an in itself closed, circumferential gap opposite slit targets, as mentioned in the aforementioned article, a substantial increase scored the plasma density, this plasma density is with provision the above-mentioned magnetic fields further increased. This, inter alia, due to the increasingly improved electron impact yield (Continuously circulating electron traps).

Although it is possible according to the invention the one or more targets at operate with Procedure AC, is, above all for reasons of cost, in a highly preferred realization form DC used, if necessary, as in the pulse mode, with superimposed AC to perform the operation very stable.

A Sputterbeschichtungsquelle to solve the aforementioned task distinguished by the fact that the sputtering ever form self-contained areas, the gap a self-contained, at least one side is open gap and the Gas outlet of the gap opening provided opposite is.

An inventive sputter coating comprises at least a Sputterbeschichtungsquelle of said type on and for the at least one target, preferably at least two targets, a DC generator, optionally a generator assembly for delivering a DC signal with a superimposed AC signal, preferably a pulsed DC signal.

The inventive method, the inventive source and the inventive system are particularly suitable for Sputter ferromagnetic materials or dielectric Materials, in particular for MgO or ITO coatings or for coating plasma display panels, where large areas have to be coated economically.

In this case, the substrates can, for example, over the linear arrangement of source be carried away. It is also possible to provide several linear sources at appropriate intervals for the distribution so be arranged to increase the total deposition rate or large area, static coating.

Preferred embodiments of the inventive method are specified in claims 2 to 14, according to the invention Source in claims 16 to 23 and according to the invention Investment in claims 24 and 25th

Particularly preferred uses of the invention are defined in claims 26 to 28 specified.

The invention is by example with reference to figures explained. These show:<dl tsize="13"><dt>Fig. 1:</dt><dd>Perspective and a schematic cross section through an inventive sputtering source according to the invention after the A method of cutting;</dd><dt>Fig. 2:</dt><dd>starting from the representation according to FIG. 1, a further Variant for electrical supply of the mentioned Source;</dd><dt>Fig. 3:</dt><dd>a schematic cross-sectional view of another Zerstäubungsflächenanordnung according to the inventive Process or to an inventive Source or system;</dd><dt>Fig. 4 till 8:</dt><dd>further shown in perspective arrangements of Sputtering targets or, in inventive procedure;</dd><dt>Fig. 9:</dt><dd>schematically an inventive sputtering, after the inventive method and working on a inventive system used with principle preferably employed magnetic field; </dd><dt>Fig. 10:</dt><dd>starting from the representation according to FIG. 9, a further Training of the magnetic field are preferably used;</dd><dt>Fig. 11:</dt><dd>a further embodiment of a preferably used magnetic field;</dd><dt>Fig. 12:</dt><dd>over the pro Zerstäubungsflächeneinheit worn Power the DC plasma discharge voltage (a) Procedure according to the prior art,<sl><li>(B), in inventive approach without a magnetic field,</li><li>(C), in inventive approach with magnetic field and</li></sl></dd><dt>Fig. 13:</dt><dd>a slit target known construction with definition its geometrical sizes.</dd></dl>

Referring to FIG. 1 is the basic inventive Procedure will be explained.

There are two self-contained sputtering 3a and 3b is provided so that it has a peripheral to a therebetween Opening 10 at least one open side, self-contained circumferential gap 5 define. The sputtering 3a and 3b, the possibility, as shown in dashed lines at 1, by incorporating the gap 5 in a uniform be designed target block, but preferably are the Sputtering surfaces 3a and 3b each sputtering of a target, namely an outer target 6a and an all-round and in substantially rod targets 6b.

At one end of the gap 5 an anode arrangement 8 provided, which, as shown, from a common anode can be designed for both targets 6a and 6b, where appropriate but also comprise two separately feedable anode rings can. but the anode may also advantageously on the exit side be placed (10) and simultaneously the cathode from the outside enclose with dark space distance, or even isolated be mounted. You can also simultaneously as a slit diaphragm be formed. Anodes are preferably operated at ground. Bias supply to control the particle is also possible. Such an anode assembly is shown in phantom in Fig. 2 at 8a shown.

There is a gas flow G along the gap 5 generated, and Although substantially transversely to the cutting surface, such as E, wherein the gap appears 5 circumferentially as closed. With the gas flow G are coating particles from the gap 5 by the gap opening 10 to one or more workpieces 12 carried and stored there gently. In reactive sputtering, a Reactive gas admitted also only there.

The one or, as shown, the two, the sputtering surfaces 3a and 3b defining targets 6a, 6b are preferably each individually DC or optionally with DC and superimposed AC fed, each by an associated generator 14a or 14b. Alternatively, they are, if appropriate, as shown in Fig. 2, fed by a common generator 14c.

The workpiece 12 or a novel on the system provided for this workpiece carrier (not shown), in a vacuum chamber of the sputtering device according to the invention with the above described source 16, potential-floating or on Reference potential, such as ground, or on a bias potential, preferably DC potential or a DC potential with superimposed held AC potential, as shown schematically in Fig. 1 with is the possibility of switch 20 shown.

In Fig. 3 is schematically illustrated in cross-sectional view of another Arrangement of the sputtering surfaces 3a or 3b according to FIG. 1 shown. This narrows the gap 5 'to the gas outlet opening 10 out which pressure stages similarly accelerated Gas flow G is achieved against the workpiece 12th As phantom 3 further illustrated in Fig., Can the illustrated with reference to FIG. 1, the present invention is based Expand principle inasmuch as also the interior 22 optionally with an additional sputtering 3c coating effectively - be exploited - as a hollow cathode can and / or providing additional sputtering 3d and corresponding additional circumferential columns 10a an increasingly implemented complex inventive source space saving can be.

Without in FIGS. 4 to 8 show further details, except for the arrangement the sputtering surfaces and, accordingly, the formation of the one or two measures provided for in minimal configuration targets represent, these figures show different Ausformungsvarianten the peripheral gap 10 and thus of this defining, also revolving sputtering 3a or 3b.

In Fig. 4, the circumferential gap 10 is rectangular in plan frame-shaped, as shown in FIG. 5 of a circular ring or elliptical, said the gap defining sputtering in the FIGS. 4 and 5 parallel to a central axis A and equidistantly are. It tighten the sputtering as shown in FIGS. 4 and 5 namely cuboid surfaces or cylindrical surfaces or cylinder-like Surfaces 3a 3b on.

In the arrangement according to FIG. 6 clamp the sputtering surfaces 3a, 3b truncated pyramid surfaces, as shown in FIG. 7 essentially kreiskegel- or ellipsoidkegelförmige surfaces.

According to FIG. 6, 7 and 8 is reduced, despite equidistant Sputtering, the gas flow cross-section of the gap according to the opening 10 toward, more pronounced in training Fig. 3. This results in one hand, an increasingly intense Contact gas flow with the sputtering and a Gas flow acceleration toward against the workpiece. This effect can - as mentioned with respect to FIG. 3 - in all Increased embodiments according to Figures 4 to 8 characterized are that the sputtering surfaces not equidistant be, but down against the outlet opening 10, preferably steadily approaching. In the embodiment shown in FIG. 8, emanating from that of Fig. 7, is shown as an example, as with all embodiments a pronounced Pressure stage between gap 5 and workpiece coating chamber B can be realized, with a corresponding increase in speed Gasausströmungs toward the in Fig. 3 shown Workpiece 12th

With reference to FIGS. 1 to 8 to the expert is unequivocally clear how In principle and according to the invention, the sputtering surfaces form and are to be arranged, and it opens up to him so that further Opportunities for gas savings or even better separation of inert gas and reactive gas.

In Fig. 9 is a cross-sectional view of an inventive Conditioning with erfindungemässer sputtering, after the inventive method works, illustrated with more, described most preferably used measures it to be, the course described at all so far Embodiments of the invention preferably also realized will.

According to FIG. 9 is a novel in a treatment chamber 30 Plant an inventive source 16 is provided. It is a workpiece carrier shown schematically 32 against. It may be formed by any of the various with reference to FIGS. 1 to 8 illustrated variants. The gas outlet 10 of the gap 5 of the opposite Gap region is closed and carries a rotating anode ring 34. In the final gap 36 is a Gasverteilraum 38 provided that circulating for example by means of a Ring line 40 is fed from a gas tank arrangement 42, which is preferably an inert gas such as a noble gas, for example, Ar contains.

In addition, and as in all variants according to Figures 1 to 8 embodiments preferred variant illustrated, is in Gap 5 creates a magnetic field H. There are permanent and / or Solenoid arrangements 44 are provided, on at least one, as shown on both, sputtering 3a or 3b far preferably tunnel-shaped on and exiting H-field lines produce, wherein the tunnel axes, as shown at A_T in Fig. represented 9, along the circumferential, self-contained also circulate sputtering surfaces, and preferably also in are closed.

In Fig. 10 is another arrangement of the magnetic tunnel- and therefore represented the magnet systems 44, from which the Skilled person will appreciate that depending on the gap stretch and desired Effect on the tunnel fields preferably employed the two sputtering different, such as are shown in Fig. 10, realized locally staggered can. are suitable especially for ferromagnetic targets also homogeneous fields from target to target, which, for example by Yoke assemblies according to FIG. 11 can be achieved, or mixed forms homogeneous and inhomogeneous fields.

The inventive method or the source or system these are in particular suitable for sputter coating Workpieces with materials which at least one ferromagnetic have share or dielectric materials. Thus, at least one, preferably both sputtering surfaces and consequently the associated targets preferably made of a ferromagnetic material or of a dielectric formed material, if the latter is not formed reactively and is stored. In particular, for depositing dielectric Dielectric layers is in addition to or instead of providing Targets the gas G_r or at least one component this gas formed by a reactive gas from the tank assembly 43 be, in addition to the inert gas G from tank assembly 42. Thus, For example, and in the particularly preferred application an MgO layer are deposited, this is by sputtering MgO target, optionally with subsequent post oxidation in an O₂ containing gas G_rmetallic, or by sputtering from Mg target and reaction with the O₂ containing gas G_r, allows particular, the formation of the source as a circular source it, circular substrate wafers sputterzubeschichten, such as storage discs of all known genera, wherein the invention with linear education in particular suitable for the production of PDP, a so-called plasma display Panels.

For operation of an inventive source following<u>parameter</u> advised: <u>Total pressure</u> in the coating room B: 0.1 to 10 mbar

For <u>reactive sputtering</u> of oxides: <u>partial pressure</u> O₂: Up to 10% of the total pressure in the coating chamber B with inlet from 0₂ (G_r) In room B.

<u>effluent</u> of the gas G from the opening 10 into the treatment chamber B:

The Ar gas flow G in the gap in the Knudsen or viscous realized area. Where<sl><li>Knudsen shear area:    10^-2 mbar cm ≤ p · Φ ≤ 0.6 mbar · cm</li><li>Viscous area:    0.6 mbar cm &lt;p · Φ,</li></sl>where P is total pressure in the gap and Φ (see Fig. 9) than the gap width.

Preferably, the gas flow is selected in the Knudsen range. More preferably, the following applies:    10 sccm / cm² ≤ F ≤ 200 sccm / cm². per with F as working and optionally reactive gas flow Stomatal unit area, preferably 20 sccm / cm² ≤ F ≤ 50 sccm / cm²,

<u>gap width</u> or target distance Φ (see Fig. 9):    5 mm ≤ Φ ≤ 40 mm,<sl><li>preferably Φ ≤ 25mm</li><li>preferably 8 mm ≤ Φ ≤ 20 mm.</li></sl>

<u>gap height</u> H_S (See Fig. 9):    1 cm ≤ H_S ≤ 20 cm.

<u>magnetic field:</u> Measured parallel to the sputtering in the Middle of the slit 5:    150 Gauss ≤ H ≤ 1200 gauss, preferably H ≥ 300 Gauss, preferably 300 Gauss ≤ H ≤ 800 Gauss.

An inventive system with circular source constructed substantially according to FIG. 9, has the following dimensions on and was operated as follows:<ul><li>Distance opening plane to the substrate (D, Fig. 9): 40 mm</li><li>entire target area: 301.4 cm²</li><li>Gap height H_S: 40 mm</li><li>Gap width : 30 mm</li><li>Exit surface 10: 113 cm²</li><li>average gap diameter: 120 mm </li><li>Gap length: 377 mm</li><li>Argon flow: 2825 sccm</li><li>Pressure in the coating chamber B: 0.6 mbar</li><li>Power: 9 kW</li><li>Performance target unit area: 29.9 W / cm²</li><li>Argon flow per outlet unit area: 25 sccm / cm²</li><li>Field strength H, parallel to the sputtering surface, on target: 300 Gauss</li></ul>

Result:<sl><li>Al-deposition rate: 22 Å kWs</li><li>Fe-deposition rate: 16 Å kWs</li><li>MgO-coating rate (Mg target with O₂Stake in B about 2%): 18 Å kWs</li></sl>

By increasing the gas flow, the coating rate can order a factor of 2 to 3 can be further increased.

In Fig. 12, the dependence of the discharge power P is of the DC operating voltage U shown.<sl><li>(A) represents the course of an Al-target slot according to the above what is mentioned article H. Koch et al. represents the following slot dimension (S Fig. 12.):<sl><li>Slot length L: 10 cm</li><li>Slit width Φ_S: 30 mm </li><li>Slot height H_Sa: 40 mm</li></sl><u>Ar flow:</u> Gas flow in the coating chamber per Slot unit area: 33 sccm / cm² Total pressure in the coating chamber B: 0.6 mbar</li><li>(B) operation and dimensioning of the inventive system, as specified above, but without a magnetic field H, and with an argon flow G per unit opening area of 35 sccm / cm²,</li><li>- (C) was to run as described in (b) plant subsequently in the gap 10 at each target each one tunnel-shaped created magnetic field in the target center where the field running parallel to the target and measured at the target surface a magnetic field strength of 300 Gauss returned.</li></sl>

How 12 seen in FIG., Takes the required performance for a required operating voltage, starting from the previously known Target slot (a), an inventive arrangement according (B) without a magnetic field and finally (c) with magnetic drastically. This shows the surprising effect of the closure-insich the respective sputtering. In other it can be seen how in accordance with the magnetic field sputtering (C) the curve asymptotically approaches a limit, what a Magnetronkennlinie is typical while and according to (a) (B) increase exponentially, which for cathode sputtering without magnetron field is typical. Low firing voltages for high quality dielectric layers, such as for MgO, as mentioned, considerably.

For the generation of the gas jet G, it is necessary to For cathodic sputtering high pressures to work unusual.