DE102009032152A1 - Method for coating a substrate with a transparent metal oxide layer using magnetron sputtering comprises directing the plasma for the sputtering onto the sputtered target material in the coating region - Google Patents

Abstract

Method for coating a substrate (5) with a transparent metal oxide layer using magnetron sputtering comprises directing the plasma for the sputtering onto the sputtered target material in the coating region. A layer for the screens (24) for the substrate is produced so that transport of the substrate is unimpeded and the passage of plasma and sputtered target material does not reach the space outside of the spatial expansion region of the plasma and the sputtered target material. Independent claims are also included for the following: (1) Coating chamber for coating substrates using magnetron sputtering; and (2) Coating installation containing the coating chamber.

Description

The The invention relates to a method for coating a substrate with a transparent metal oxide layer by means of magnetron sputtering, by placing the substrate in one coating chamber at one or more Passing cathodes comprising the sputterable target material. The cathodes each have at least over the Length of the cathode extending magnet system. The metal oxide layer is applied in an aperture-limited coating area on the Substrate deposited.

The The invention also relates to a coating chamber for a coating system for carrying out the method.

At the Magnetron sputtering is in the process gas between the to be coated Substrate and a cathode ignited a plasma whose positive charge carriers by the so-called sputtering effect (dusting, d. H. Ion bombardment induced hammering out of atoms from the solid surface) the upper layers ablate a target surface. It can be metals in the presence of oxygen in the coating atmosphere sputtered and as an oxide on the substrate or alternatively non- or partially reactively deposited by an oxidic target.

As well It is possible to use oxides or other metal compounds as Insert and sputter target material. When the latter comes it often leads to dissociation, d. H. Release of oxygen during the sputtering process. But it is also possible that the metal oxides or metal compounds without dissociating sputtered and deposited on the substrate. In presence of oxygen in the process gas, the eroded sputtering material reacts with the oxygen as reactive gas and turns out to be Oxide on a substrate arranged opposite low. The chemical reaction to stoichiometric compound layers on the substrate is by the associated with the sputtering process Plasma discharge and the resulting energetic excitation the reactants, also referred to as species, amplified.

A Provision of the reactive gas or its supplement at Losses due to vacuum generation or when setting a defined gas fraction takes place either by a targeted supply into the coating chamber by means of a gas inlet system.

to Support for plasma formation as well as acceleration The ions on the target surface are on the plasma opposite side of the target a magnet system with juxtaposed Magnets of locally changing polarity arranged. As is known, exists such, used for magnetron sputtering magnet system from a central magnetic pole the second, opposite Magnetic pole surrounds annular. Because of this training, tunnel-shaped and self-contained Magnetic field will be the target material across the gap between two magnetic poles, where the magnetic field lines parallel to the target surface run, in particular, worn, so that in this area an annular sputter trench is formed.

This is also known as Racetrack. The local course of the magnetically guided, self-contained plasma ring correlates with the erosion of the target material.

To the Magnetron sputtering uses planar or alternatively tubular cathodes. The latter are especially for coating of various large areas Substrates known and are often used as a double cathode used. A cathode comprises a magnet system which extends over the entire length of the cathode extends and in cross section considered from at least three adjacent magnets consists. As a result of this magnet arrangement forms each one annular racetrack on the target, and extends parallel to its longitudinal axis over its entire Length.

In the German utility model DE 20 2005 015 067 U1 describes a cathode arrangement and a coating chamber in which the cathode arrangement is used for coating flat substrates in a continuous process. There are a single enlarged tube cathode or two tube cathodes arranged side by side. In order to keep away the coating material of components and walls of the coating chamber which propagates in the entire space of the coating chamber and in particular between the tube cathodes and the substrate, shutters are arranged next to the tube cathodes and perpendicular to the transport direction of the substrate, which also cover the edge areas of the substrate.

Also in the US 6,488,824 B1 For example, apertures over the substrate are described which are intended to prevent the deposition of large angle sputtered and thus low energy target material on the substrate. Between the substrate and the orifices, the gas supply for the reactive gas is arranged, so that the reactive gas propagates in this intermediate space.

Magneron sputtering can be used to deposit a wide variety of materials, both electrically conductive and dielectric. The Target exists z. B. of metals, alloys or oxide materials. In the WO 92/01081 two or more tube cathodes are used side by side with divergent target material to deposit a mixed layer by so-called cross-contamination. In this case, a portion of the sputtered target material of each tube cathode is directed to the other tube cathode, so that sputtered from both tube cathodes, a mixture of both target materials to deposit a layer which is composed evenly of the two target materials. The contamination of the respective other target is effected by a rotation of the magnet arrangement in each tube cathode in the direction of the other tube cathode.

By reactive magnetron sputtering of metallic targets or magnetron sputtering of metal oxide targets are z. B. metal oxide layers, at Using suitable sputtering materials can be transparent, deposited. Such oxide layers are due to their optical Properties for a number of different applications used. Applications are z. B. transparent electrodes in flat screens, in thin film solar cells or optically selective components Layer systems.

Corresponding The application possibilities come from different substrates into consideration, for. As glass, metal, silicon or flexible plastic films. It is known, transparent conductive layers of different In addition, through metal oxide layers produce suitable doping with a material of the third main group of Periodic table of elements, eg. As aluminum or gallium the required Conductivity may have. Such transparent conductive layers are as TCO layer (Transparent Conducting Metal Oxide TCO) known, for. B. layers of indium oxide, tin oxide or indium tin oxide (ITO), with layers of zinc oxide being important gain as they make cheaper, non-toxic, easy to dope and durable under hydrogen-containing atmosphere are. The coating takes place in vacuum coating systems, the depending on the layers or layer systems to be applied or more coating chambers.

A Essential requirement for a transparent metal oxide layer is their transmission, which is directly linked to the sheet resistivity is, and the homogeneity of the optical properties. In The known method has the problem that the transmission the deposited layer at least in sections through a sub-layer is diminished, which is not or substoichiometric Oxidized target material above or below the actual Metal oxide layer is deposited. This parasitic Intermediate layer has a due to the different layer composition higher absorption and thus a much lower degree of transmission on, the optical properties of the metal oxide layer in not negligibly changes.

It Therefore, an object of the present invention is a method for magnetron sputtering and to provide an apparatus for carrying out the method, with which it is possible, the transmission of the continuous process to increase prepared metal oxide layers by the Formation of parasitic, light-absorbing sublayers is avoided.

With The described methods and devices make it possible everywhere there in the coating chamber where atomized, vaporous target material over abutting the substrate, plasma of the desired density and to provide homogeneity, so that throughout, through diaphragms, chamber wall and possibly other components the coating chamber limited coating area, in which sputtered target material deposits on the substrate, the sputtering plasma on the sputtered target material acts.

method and device allow it, the access of plasma and atomized Target material in a space outside the spatial Expansion range of the plasma and the sputtered target material to avoid.

The includes that to avoid the effects of scattered steam on the transmission of the metal oxide layer either all the substrate shading installations, in particular screens from the spatial Extension area are removed, so that more adjacent to the substrate Scattering steam is avoided or that, according to an embodiment of the process and the coating chamber used therefor unavoidable littering steam by means of the special, from the usual deviating arrangement of diaphragms is kept away from the substrate.

In In the latter case, the apertures become as close as possible arranged the substrate. Ie. there will be such a gap between Apertures and substrate set that substrate transport just barely can take place unhindered. Apertures, usually in the Edge region of the substrate and usually mounted on the chamber wall are so close to the substrate that no or only a negligible proportion of littering vapor on the substrate and also no plasma viewed from the cathode behind the panels, d. H. between the screen and the substrate can.

In the former case diaphragms, z. B. to protect the internals in the coating chamber are necessary, in position and shape so designed to create a space opening to the substrate limit. This variant can in particular uneven substrates be applied.

Both Measures cause only there target material on the Substrate can strike, where a sufficient plasma exposure ensures activation of the sputtered target material is. As a result, only homogeneous, stoichiometric and thus depositing highly transparent metal oxide layers on the substrate. The scattered vapor is the atomized target material referred to, either in the edge region of its spatial distribution located inside the coating chamber or in spaces penetrates, which are opposed by apertures or chamber fittings one or more cathodes are shadowed, such as between Apertures and substrate. The spread and effect of littering vapor As expected, the transmission of the metal oxide layer depends on the process parameters, in particular from the process pressure, so that an adaptation of the form and the situation to the respectively applicable Process parameters may be required.

There in the course of substrate transport, each of the perpendicular to the Substrattransportrichtung moving substrate strip is moved under the cathode, are the strips covering the substrate in strips regularly only at the beginning and end of the coating chamber arranged. In this way it is avoided that stray steam under the Input side aperture arrives and there as an absorbing layer precipitates on the substrate before passing through the substrate is deposited over the metal oxide layer and under the exit-side aperture another parasitic forms absorbent layer.

There moving substrates, the cathode with their magnetic systems to achieve a homogeneous over the substrate width layer often extend over the entire substrate width, are at the lateral edge of the substrates no screens for shielding the areas with deposition rates below a predefined size required. In deviating cathode arrangements or in others Use cases, eg. B. to protect special on the side Chamber walls arranged internals, but are also comparable Aperture arrangements on the lateral chamber walls of the coating chamber possible.

Also These panels protect the chamber wall and the internals of the Coating chamber are then to be arranged with such a position to the substrate, that access of plasma and target material in this edge area is not hindered relevant or alternatively prevented as described above. In one embodiment, the panels are used to shield the chamber components combined with the shields to shield the substrate edges, in each case one leg of the panels is so long and so mounted is that he has the chamber wall in the most by target material covered area under the cathode.

Of the Access of target material in gaps depends at the high vacuum conditions required for sputtering mainly from the material properties. So will z. For example, zinc is strongly scattered and diffused in the argon process gas As a result, reinforced as scattering steam throughout Coating chamber off. In addition occurs that z. As zinc a small Sticking coefficient (sticking coefficient) has, so the distribution the scattering vapor by adhesion to components of the coating chamber is reduced only conditionally. So also have more atomic effects Influence on the spread of scattered steam. Consequently, the distance is the covering the substrate on the used Match target materials. Here it proves to be an advantage when the aperture distance to the substrate and thus to the plane, in which the substrate is moved through the coating chamber, is adjustable.

About that In addition, the spread of littering steam in particular for Such problematic materials by the arrangement of a cold trap according to a further embodiment of the method and device used for this purpose be limited. However, only unwanted Scattering vapor and insufficiently activated target material from the Collecting coating area, there is no direct line of sight between such a cold trap and the plasma. That means, a cold trap is outside the spatial Expansion range of the plasma and the sputtered target material, arranged in the so-called steam shadow. The cold trap collects not only scattered vapor but also other easily condensable gas components, In particular, steam, so that a regulation of the partial pressure such gases is possible.

The As described above acting aperture can on different Art be designed and mounted without shading the substrate.

In coating chambers L-shaped panels are often used. In order to achieve the effect described above, these panels are fitted with a, regularly the longer leg on a chamber wall, so that the second leg parallel and with the least possible Distance from the substrate extends. This leg will preferably be designed as short as possible. Such a designed aperture can either extend into the chamber with the angle aligned parallel to the substrate or alternatively in the direction of the chamber wall, z. B. in the transport opening, a passage in the chamber wall through which the substrates are transported through the coating chamber. Thus, the tunnel-like area, which the substrates have to pass through the chamber change, to shorten, so that the action of the plasma is increased. In addition, the deposition of scattered vapor which has passed behind the baffles is avoided since possible gaps are closed.

Instead of an L-shape, the apertures may also have other shapes, which is a shading of the substrate with respect to the plasma avoid. In a further embodiment of the coating chamber, the comma-shaped panels are used, the chamber wall are open, so that the coating area for Substrate is expanded and the substrate in a larger Surface can be coated. Also in this shape For example, the panel may protrude into a passage starting from the L-shape with increasing angle of the angled portion of the aperture the interaction of the plasma can also be improved in the tunnel between two chambers can. Depending on the shape of the chamber wall, installations or possible openings in the wall can the comma-shaped panels mounted directly on the chamber wall or at a distance therefrom be. Also, the influence of other than the transport openings in the chamber wall can be reduced with such panels become.

In In another embodiment, a diaphragm is a flat plate, in front of a chamber wall in parallel or with a to the substrate towards the opening slope is mounted. This way will in comparison to the L-shaped projecting into the coating chamber Aperture of the coating area extended with simultaneous veneering of protruding into the coating chamber components, so that this Do not shade the substrate and no unwanted gaps form.

In Dependence on the figure, especially in all the Coating area opening aperture, can by means of a Projection in the contour of the aperture Disturbances of the deposited layer avoided by falling on the layer or the substrate particles become. It goes without saying that this lead as well as the screen itself is designed so that no shading of the substrate.

The Invention will be described below with reference to an embodiment be explained in more detail. In the associated Drawing shows

1 a coating chamber having a pair of tubular cathodes;

2 an embodiment of the edge region of a substrate letting aperture and

3A to 3D the cross section of various embodiments of apertures.

In 1 a coating chamber of a sputter coating system is shown. Inside the coating chamber are two cathodes 1 arranged as in the illustrated embodiment as tube cathodes with cylindrical, about its longitudinal axis 3 rotatable carrier tubes 2 are formed. On the lateral surface of the carrier tubes 2 is the target material 4 layered applied, z. B. a material mainly containing zinc. In the exemplary embodiment, both tube cathodes comprise 1 the same target material 4 , Alternatively, there are also different target materials 4 usable, for. B. to form a layer stack, each consisting of a sub-layer of a target material 4 with an intermediate layer of a mixture of both materials.

The tube cathodes 1 extend transversely to the substrate transport direction 6 in which a substrate 5 by means of a suitable transport device 7 through the coating chamber and continuing through the entire coating system. In their longitudinal extent perpendicular to the plane of the drawing correspond to the tube cathodes 1 approximately the width of the substrate or extend beyond.

Inside the tube cathodes 1 are magnetic systems 9 are each arranged a two-pole permanent magnet, both of which have a shape with three poles in cross-section due to the outer, annularly around the inner magnetic pole. The polarity is in the embodiment for both magnet systems 9 displayed as north-south-north, but may also be south-north-south. Both magnet systems 9 should have the same polarity. The magnet systems 9 are relative to the tube cathodes 1 Rotatable about the longitudinal axis, so that they are in the rotation of the tube cathodes 1 remain stationary relative to the surrounding coating chamber.

By using two tube cathodes 1 On the one hand, the operating time of the system can be increased. On the other hand, by a rotated arrangement z. B. with oppositely directed angle of rotation φ, based on the normal of the middle magnetic pole 12 and the normal of the substrate 14 of the two magnet systems 9 improves the plasma density distribution and the distribution of the sputtered target material. If in one embodiment of the invention more than two tube cathodes 1 to be placed in a coating chamber, become pairs of tube cathodes 1 used so that in each pair the magnet systems 9 equally rotated against each other can be arranged.

The substrate 5 becomes in the substrate plane 16 lying through the coating chamber and thereby to the tube cathodes 1 transported by. On the input side and output side, the chamber wall 20 the coating chamber one passage each 22 for extending and retracting the substrate 5 on. Above both passages 22 is on the chamber wall 20 each an L-shaped aperture 24 assembled. The longer of the two legs of the panel 24 is on the chamber wall 20 attached and has such a length that it is the chamber wall 20 below both tube cathodes 1 covered. The shorter leg of the panel 24 protrudes parallel to the surface of the substrate 5 in the coating chamber and in the embodiment has a distance A to the substrate 5 of 20 mm.

As an optional embodiment shows 1 the arrangement of cold traps 28 in the coating chamber. The cold traps 28 are above the cathodes 1 inlet and outlet of the coating chamber arranged. This arrangement ensures that the cold traps 28 Only slightly condensable vapor and gas components such as scattered steam and water vapor condense as a gas component, since they are far outside the spatial expansion range of the pipe target 2 to the substrate 5 propagating target material and plasma.

2 shows a comma-shaped embodiment of the aperture 24 consisting of two approximately equal length and with an obtuse angle to each other inclined legs. The upper of the two legs is in turn on the chamber wall 20 the coating chamber mounted so that it partially passes the passage 22 covered. Due to the opening of the comma form to the chamber wall 20 towards covers the aperture 24 the substrate 5 although when viewed perpendicularly to the substrate 5 , However, based on the vapor and plasma spread from the tube cathodes 1 from there is no shading of the substrate 5 , In the exemplary embodiment, the aperture 24 a distance A of 15 mm to the substrate 5 on.

Due to the planar substrates shown in the embodiment 5 Such a distance is sufficient to transport the substrates 5 through the chamber without contact between substrate 5 and aperture 24 to ensure. Become curved substrates 5 coated or their requirements for the flatness less, the distance A of the aperture is adjusted accordingly, so that just an unimpeded substrate transport is possible. Are the passages 22 Already minimized in height, then they can have greater clearance height to allow the extension of the coating area into the passage through a correspondingly designed and arranged aperture.

In the 3A to 3D For example, some examples of possible diaphragm designs are illustrated without any limitation to these embodiments. 3A represents an L-shaped aperture 24 which, with its long, vertical leg on a chamber wall 20 or can be mounted on internals in the coating chamber. The short, horizontal leg protrudes into the coating chamber or alternatively to the chamber wall 20 out.

The aperture 24 according to 3B has a protruding into the coating chamber projection which tapers towards the substrate (not shown) down here. To the shading of the substrate 5 To avoid this projection, the angle of the taper is on the spatial spread of the sputtered target material 5 adapted according to the respective cathode arrangement.

A flat, plate-shaped aperture 24 according to 3C is variable applicable. You can z. B. approximately parallel to the chamber wall 20 or be mounted with an angle (not shown) to the substrate.

A comma-shaped aperture 24 is in 3D shown. Their angled part is towards the chamber wall 20 aligned, z. B. as to 3 described.

During the coating, a plasma is ignited where the magnetic field lines are parallel to the target surface, thus centered between two magnetic poles 10 every magnet system 9 , In this area, the racetracks form 26 ( 1 ), in which the target material 4 from the outer surface of the two rotating tube cathodes 1 is sputtered. As a result of the rotation, however, no trenches are formed. Rather, the target material 4 evenly from the entire surface of the tube cathodes 1 ablated. The sputtered target material spreads towards the substrate 5 reacts with the oxygen introduced into the coating chamber or released by dissociation from the oxidic target material and is expressed as zinc oxide on the substrate 5 deposited.

The embodiments were based on represented by tube cathodes. The described design and use of apertures 24 is also possible in a comparable manner in coating chambers, the one or more planar cathodes 1 use.

1

cathode

2

support tube

3

longitudinal axis

4

target material

5

substratum

6

Substrate transport direction

7

transport device

9

magnet system

10

magnetic pole

12

normal of the middle magnetic pole

14

normal of the substrate, normal of the substrate plane

16

substrate plane

20

chamber wall

22

passage

24

cover

26

Racetrack

28

cold trap

φ

angle

A

distance Lens substrate

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 202005015067 U1 [0009]
• - US 6488824 B1 [0010]
• WO 92/01081 [0011]

Claims (18)

Method for coating a substrate ( 5 ) with a transparent metal oxide layer by means of magnetron sputtering by the substrate ( 5 ) in a coating chamber on at least one cathode ( 1 ) passing the sputterable target material ( 4 ) and at least over the length of the cathode ( 1 ) extending magnet system ( 9 ) and the metal oxide layer in an aperture-limited coating area on the substrate ( 5 ) is deposited, characterized in that in the coating area, the sputtering plasma acts on the sputtered target material by such a position of the aperture ( 24 ) to the substrate ( 5 ), so that unimpeded substrate transport is still ensured and access of plasma and sputtered target material to a space outside the spatial extent of the plasma and the sputtered target material does not occur. Method according to claim 1, characterized in that such a distance between the diaphragms ( 24 ) and the substrate ( 5 ) that access of plasma and sputtered target material behind the baffles ( 24 ), from the cathode ( 1 ) is prevented. Method according to claim 1 or 2, characterized in that the diaphragms ( 24 ) in the substrate transport direction ( 6 ) views the front and rear chamber walls ( 20 ) of the coating chamber in the region below the cathodes ( 1 ) cover. Method according to one of the preceding claims, characterized in that, outside its spatial propagation zone, scattered vapor of the atomized target material ( 4 ) is collected by means of a cold trap which has no direct line of sight to the plasma. Method according to one of the preceding claims, characterized in that a conductive transparent Layer is deposited. Coating chamber for coating moving substrates ( 5 ) by means of magnetron sputtering with a transport device ( 7 ) for transporting the substrates ( 5 ), with at least one cathode ( 1 ) containing the sputterable target material ( 4 ) and at least over the length of the cathode ( 1 ) extending magnet system ( 9 ) and with diaphragms delimiting a coating area in which the desired layer on the substrate (FIG. 5 ) is deposited, characterized in that the aperture ( 24 ) in such a position to the substrate plane ( 16 ), in which the substrate ( 5 ) is moved through the coating chamber, are arranged so that an unobstructed substrate transport just barely guaranteed and access of plasma and sputtered target material in a space outside the spatial extent of the plasma and the sputtered target material can be prevented. Coating chamber according to claim 6, characterized in that the diaphragms ( 24 ) at such a distance above the substrate plane ( 16 ), in which the substrate ( 5 ) is moved through the coating chamber, it is arranged that access of plasma and atomized target material ( 4 ) behind the panels ( 24 ), from the cathode ( 1 ), preventable. Coating chamber according to Claim 6 or 7, characterized in that the panels cover the coating area in the substrate transport direction ( 6 ) considered front and rear edge region of the coating chamber limit. Coating chamber according to one of claims 6 to 8, characterized in that a diaphragm ( 24 ) has an L-shape, one leg of which on the chamber wall ( 20 ) and whose second leg is parallel to the substrate plane ( 16 ). Coating chamber according to one of claims 6 to 8, characterized in that a diaphragm ( 24 ) has a comma shape and directly with an upper portion on the chamber wall ( 20 ) or at a distance therefrom, while the lower, angled portion to the chamber wall ( 20 ). Coating chamber according to one of claims 9 or 10, characterized in that the lower, angled portion of a diaphragm ( 24 ) at least in sections into a passage in the chamber wall ( 20 protruding, which serves the substrate transport, and that the passage has a size such that the substrate ( 5 ) just unhindered by the through the aperture ( 24 ) narrowed passage is transportable. Coating chamber according to one of claims 6 to 8, characterized in that a diaphragm ( 24 ) formed as a flat wall part and the chamber wall ( 20 ) is pre-faded. Coating chamber according to one of claims 6 to 12, characterized in that a diaphragm ( 24 ) has a projection for catching particles extending from the diaphragm ( 24 ) to solve. Coating chamber according to one of claims 6 to 13, characterized in that the distance of the diaphragm ( 24 ) above the substrate level ( 16 ) is adjustable. Coating chamber according to one of claims 6 to 14, characterized in that further arranged in the coating chamber internals are arranged such that an unimpeded plasma spread from the cathode ( 1 ) to the cathode located in the coating chamber ( 1 ) facing substrate surface is ensured. Coating chamber according to claim 15, characterized in that a cold trap for the condensation of condensable vapor and gas fractions ( 4 ) is installed outside the target area of the sputtered target material. Coating chamber according to one of claims 6 to 16, characterized in that the target material ( 4 ) Tin, zinc, cadmium, gallium, indium, compounds thereof or mixtures containing these materials. Coating plant for coating substrates ( 5 ) in a continuous process by means of reactive magnetron sputtering, characterized in that the coating system comprises at least one coating chamber according to one of claims 6 to 17.