FIELD

[1] The present application relates to a method for coating a substrate and a coater, and specifically to a method for sputtering a layer on a substrate with high uniformity and a coater for carrying out the method.

BACKGROUND

[2] Forming a layer on a substrate with a high uniformity (i.e., uniform thickness and electrical properties over an extended surface) is an issue in many technological fields. For example, in the field of thin film transistors (TFTs) thickness uniformity and uniformity of electrical properties may be an issue for reliably manufacturing display channel areas. Furthermore, a uniform layer typically facilitates manufacturing reproducibility.

[3] One method for forming a layer on a substrate is sputtering, which has developed as a valuable method in diverse manufacturing fields, for example in the fabrication of TFTs. During sputtering, atoms are ejected from the target material by bombardment thereof with energetic particles (e.g., energized ions of an inert or reactive gas). The ejected atoms may deposit on the substrate, so that a layer of sputtered material can be formed.

[4] However, forming a layer by sputtering may have high uniformity specifications due to, for example, the geometry of the target and/or the substrate. In particular, uniform layers of sputtered material and ion bombardment over extensive substrates may be difficult to achieve due to an irregular spatial distribution of sputtered material and ion bombardment. The provision of multiple targets over the substrate may improve layer uniformity.

[5] In view of the above, new methods for coating a substrate and coaters, that overcome at least some of the problems in the art, are beneficial. SUMMARY

[6] In light of the above, a method for coating a substrate and a coater are provided. Further aspects, benefits, and features of the present disclosure are apparent from the claims, the description, and the accompanying drawings. [7] According to an aspect, a method for coating a substrate with at least one cathode assembly having three or more rotatable targets, the three or more rotatable targets each including a magnet assembly positioned there within, is provided. The method includes: rotating the magnet assemblies to a plurality of different angular positions with respect to a plane perpendicularly extending from the substrate to the axis of the respective one of the three or more rotatable targets; and varying at least one of: a power provided to the three or more rotatable targets, a staying time of the magnet assemblies, and an angular velocity of the magnet assemblies, which is varied continuously, according to a function stored in a database or a memory.

[8] According to a further aspect, a coater for carrying out the method for coating a substrate is provided.

[9] Further aspects, details, advantages and features are apparent from the dependent claims, the description and the accompanying drawings.

[10] Embodiments are also directed at apparatuses for carrying out the disclosed methods and include apparatus parts for performing each described method aspect. These method aspects may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, embodiments according to the disclosure are also directed at methods for operating the described apparatus. The methods for operating the described apparatus include method aspects for carrying out functions of the apparatus. BRIEF DESCRIPTION OF THE DRAWINGS

[11] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following:

FIG. 1 shows a schematic cross sectional view of a coater illustrating the method for coating a substrate according to embodiments described herein; FIG. 2 shows a schematic cross sectional view of a coater illustrating the method for coating a substrate according to embodiments described herein;

FIGs. 3a and 3b show a schematic cross sectional view of a coater illustrating the method for coating a substrate according to embodiments described herein;

FIG. 4 shows a schematic cross sectional view of a coater illustrating the method for coating a substrate according to embodiments described herein;

FIG. 5 illustrates a variation of a power according to a function according to embodiments described herein;

FIG. 6 illustrates a continuous variation of an angular velocity according to a function according to embodiments described herein; FIG. 7 illustrates a further variation of a power according to a function according to embodiments described herein;

FIG. 8 illustrates a further variation of a power according to a function according to embodiments described herein and a variation of a staying time according to a function according to embodiments described herein; FIG. 9 shows a schematic cross sectional view of the three or more rotatable targets positioned for coating a substrate according to embodiments described herein;

FIGS. 10 and 10b show a comparison of the thickness of a film deposited by a conventional process and by the processes described herein; and

FIGs. 11a and l ib show a comparison of an electric property of a film deposited by a conventional process and by the processes described herein. DETAILED DESCRIPTION OF EMBODIMENTS

[12] Reference will now be made in detail to the various embodiments of the disclosure, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Typically, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the disclosure and is not meant as a limitation of the disclosure. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations.

[13] Sputtering can be undertaken as diode sputtering or magnetron sputtering. The magnetron sputtering is particularly advantageous in that deposition rates are high. Typically, a magnet is positioned within the rotatable target. The rotatable target as used herein is typically a rotatable curved target. By arranging the magnet or the magnets behind the target, i.e. inside of the target in the event of a rotatable target, in order to trap the free electrons within the generated magnetic field, which is generated directly below the target surface, these electrons are forced to move within the magnetic field and cannot escape. This enhances the probability of ionizing the gas molecules typically by several orders of magnitude. This, in turn, increases the deposition rate significantly. [14] The term "magnet assembly" as used herein is a unit capable of generating a magnetic field. Typically, the magnet assembly includes a permanent magnet. Specifically, the magnet assembly can consist of a permanent magnet. This permanent magnet is typically arranged within the rotatable target such that the free electrons are trapped within the magnetic field generated below the rotatable target surface. In many embodiments, the magnet assembly includes a magnet yoke. According to an aspect, the magnet assembly may be movable within a rotatable tube. By moving the magnet assembly, more particularly by rotating the magnet assembly along the axis of the rotatable tube as rotation center, the sputtered material can be directed in different directions.

[15] The substrate may be continuously moved during coating ("dynamic coating") or the substrate to be coated may be at rest during coating ("static coating"). According to embodiments described herein, the methods provide a static deposition process. Typically, particularly for large area substrate processing, such as processing of vertically oriented large area substrates, it can be distinguished between static deposition and dynamic deposition. A dynamic sputtering, i.e. an inline process where the substrate moves continuously or quasi- continuously adjacent to the deposition source, would be easier due to the fact that the process can be stabilized prior to the substrates moving into a deposition area, and then held constant as substrates pass by the deposition source. Yet, a dynamic deposition can have other disadvantages, e.g. particle generation. This might particularly apply for TFT backplane deposition. According to embodiments described herein, a static sputtering can be provided, e.g. for TFT processing, wherein the plasma can be stabilized prior to deposition on the pristine substrate. It should be noted that the term static deposition process, which is different as compared to dynamic deposition processes, does not exclude any movement of the substrate as would be appreciated by a skilled person. A static deposition process can include, for example, a static substrate position during deposition, an oscillating substrate position during deposition, an average substrate position that is substantially constant during deposition, a dithering substrate position during deposition, a wobbling substrate position during deposition, a deposition process for which the cathodes are provided in one chamber, i.e. a predetermined set of cathodes provided in the chamber, a substrate position wherein the deposition chamber has a sealed atmosphere with respect to neighboring chambers, e.g. by closing valve units separating the chamber from an adjacent chamber, during deposition of the layer, or a combination thereof. Accordingly, a static deposition process can be understood as a deposition process with a static position, a deposition process with a substantially static position, or a deposition process with a partially static position of the substrate. Accordingly, a static deposition process, as described herein, can be clearly distinguished from a dynamic deposition process without that the substrate position for the static deposition process being fully without any movement during deposition.

[16] The term "vertical direction" or "vertical orientation" can be understood to distinguish over "horizontal direction" or "horizontal orientation". That is, the "vertical direction" or "vertical orientation" can relate to a substantially vertical orientation e.g. of the carrier and the substrate, wherein a deviation of a few degrees, e.g. up to +/-10 ⁰ or even up to +/-15°, from an exact vertical direction or vertical orientation can be still considered as a "substantially vertical direction" or a "substantially vertical orientation". The vertical direction can be substantially parallel to the force of gravity.

[17] According to embodiments described herein, which can be combined with other embodiments described herein, substantially vertically can be understood particularly when referring to the substrate orientation, to allow for a deviation from the vertical direction of +/- 20° or below, e.g. of +/-10° or below. This deviation can be provided for example because a substrate support with some deviation from the vertical orientation might result in a more stable substrate position. Yet, the substrate orientation during deposition of the organic material can be considered to be substantially vertical, which can be considered to be different from the horizontal substrate orientation.

[18] The term "substantially perpendicular" can relate to a substantially perpendicular orientation e.g. of the rotation axis and the support surface or substrate surface, wherein a deviation of a few degrees, e.g. up to +/-10° or even up to +/-15°, from an exact perpendicular orientation can be still considered to be " substantially perpendicular". [19] The examples described herein can be utilized for deposition on large area substrates, e.g. for lithium battery manufacturing or electrochromic windows. As an example, a plurality of thin film batteries can be formed on a large area substrate using the cooling device for processing a layer including a material having a low melting temperature. According to some examples, a large area substrate can be GEN 4.5, which corresponds to about 0.67 m ² substrates (0.73x0.92m), GEN 5, which corresponds to about 1.4 m ² substrates (1.1 m x 1.3 m), GEN 7.5, which corresponds to about 4.29 m ² substrates (1.95 m x 2.2 m), GEN 8, which corresponds to about 5.3m ² substrates (2.16 m x 2.46 m), or even GEN 10, which corresponds to about 9.0 m ² substrates (2.88 m x 3.13 m). Even larger generations such as GEN 11, GEN 12 etc. and corresponding substrate areas can similarly be implemented. [20] The term "substrate" as used herein shall particularly embrace inflexible substrates, e.g., glass plates. The present disclosure is not limited thereto and the term "substrate" may also embrace flexible substrates such as a web or a foil.

[21] Sputtering can be used in the production of displays. In more detail, sputtering may be used for the metallization such as the generation of electrodes or buses. Sputtering is also used for the generation of thin film transistors (TFTs). Sputtering may also be used for the generation of the ITO (indium tin oxide) layer.

[22] Sputtering can also be used in the production of thin-film solar cells. A thin-film solar cell includes a back contact, an absorbing layer, and a transparent and conductive oxide layer (TCO). Typically, the back contact and the TCO layer is produced by sputtering whereas the absorbing layer is typically made in a chemical vapour deposition process.

[23] In the context of the present application, the terms "coating", "depositing", and "sputtering" are used synonymously.

[24] According to embodiments described herein, a method for coating a substrate is provided. The method can be carried out by a coater. The coater includes at least one cathode assembly having three or more rotatable targets. The three or more rotatable targets, specifically each of the three or more rotatable targets include a magnet assembly positioned there within. Typically, the magnet assemblies are rotated to a plurality of different angular positions with respect to a plane perpendicularly extending from the substrate to the axis of the respective one of the three or more rotatable targets, particularly during deposition of a material on the substrate. Specifically, for each of the plurality of different angular positions, the magnet assemblies have an angle with respect to the plane perpendicularly extending from the substrate to the axis of the respective one of the three or more rotatable targets. Typically, the three or more rotatable targets can each be a cylindrical sputter cathode rotatable around a rotational axis.

[25] According to an aspect of the present disclosure, at least one of: varying at least one of: a power provided to the three or more rotatable targets, a staying time of the magnet assemblies, and an angular velocity of the magnet assemblies, which is varied continuously, according to a function. That is, a non-constant power is provided to the three or more rotatable targets and/or different staying times are used and/or a constantly varied angular of the magnet assemblies is used. Typically, the sputter power, the staying time and/or the angular velocity is changed depending on the magnet assembly position. Notably, the sputter power normally corresponds directly to the power applied to the rotatable target. Apart from values of close to 0V, the relation between applied voltage and sputter power is linear in a first approximation. Accordingly, a description of a variation of the provided power to the three or more rotatable targets 20 can be understood as a variation of a voltage provided to the three or more rotatable targets 20, and vice versa. Specifically, in practice, the sputter power may be varied which can lead to a variation of the power applied to the three or more rotatable targets. Typically, the voltage can be varied in a range from -200 V to -800 V, specifically in a range from -300 V to -550 V. Furthermore, it is also possible to vary the current provided to the three or more rotatable targets. Accordingly, a description of a variation of the provided power to the three or more rotatable targets 20 can be understood as a variation of a voltage provided to the three or more rotatable targets 20 and/or as a variation of a current provided to the three or more rotatable targets 20, and vice versa. [26] According to embodiments described herein, varying staying time of the magnet assemblies at respective angular positions is performed according to a discrete function and/or varying the angular velocity of the magnet assemblies at respective angular positions is performed according to a continuous function.

[27] According to embodiments described herein, the function for at least one of: the variation of the power provided to the three or more rotatable targets, the variation of the staying time of the magnet assemblies, and the continuous variation of the angular velocity of the magnet assemblies is read from a database or a memory. The variation of at least one of: the power provided to the three or more rotatable targets, the staying time of the magnet assemblies, and the angular velocity of the magnet assemblies, which varies or is varied continuously, is then carried out according to the function. Specifically, the function can be determined in advance, e.g. for a specific process, and read from the database or the memory before that specific process is performed. For instance, different functions for different thicknesses of the layer to be sputtered can be stored.

[28] That is, a function is stored in a memory and a variation is carried out according to the function. Typically, the function can be a function dependent on the angular position, i.e. the function can include different values for different angular positions. According to embodiments, an amount of material that is sputtered on the substrate at the angular positions can be determined by the function. That is, by including values that are dependent on the angular position, it can be possible to sputter a layer on the substrate having a high uniformity when practicing embodiments. Typically, the function can be determined in advance based on a number of trails. [29] Typically, the power provided to the three or more rotatable targets and one of: the staying time of the magnet assemblies, and the angular velocity of the magnet assemblies, which is varied continuously, are varied according to the function. Specifically the staying time of the magnet assemblies can be varied according to a discrete function and/or the angular velocity of the magnet assemblies can be varied according to a continuous function. That is, the power provided to the three or more rotatable targets and the staying time of the magnet assemblies are varied according to the function, or the power provided to the three or more rotatable targets and continuously the angular velocity of the magnet assemblies are varied according to the function. [30] In the context of the present application, a continuous variation of the angular velocity can be differentiated from a non-continuous variation of the angular velocity, such as a stepwise variation of the angular velocity, i.e. from zero to a certain value and vice versa.

[31] When practicing embodiments, formation of layers having a high quality can be facilitated on a substrate. In particular, the thickness of the deposited layer on the substrate may be highly uniform throughout the whole substrate. Furthermore, a high homogeneity of the layer can be facilitated (e.g., in terms of characteristics such as structure of a grown crystal, specific resistance, and/or layer stress). For instance, embodiments may be advantageous in practice for forming metalized layers in the production of TFTs (e.g., for the manufacturing of TFT-LCD displays) since, therein, the signal delay is dependent on the thickness of the layer, so that thickness non-uniformity might result in pixels that are energized at slightly different times. Moreover, embodiments may be advantageous in practice for forming layers that are subsequently etched, since uniformity of layer thickness facilitates achieving the same results at different positions of the formed layer.

[32] In the context of the present application, the three or more rotatable targets can each be a cylindrical sputter cathode rotatable around a rotational axis.

[33] According to embodiments, a coating system includes a vacuum chamber, in which the sputtering process is performed. The term "vacuum" within the present application refers to a pressure below 10 ^~2 mbar (such as, but not limited to, approximately 10 ^~2 mbar, as the case may be when a processing gas flows within vacuum chamber) or, more specifically, a pressure below 10 ^~3 mbar (such as, but not limited to, approximately 10 ^~5 mbar, as the case may be when no processing gas flows within the vacuum chamber). The coating system may form a process module forming part of a manufacturing system. For example, the coating system may be implemented in a system for TFT manufacturing or, more specifically, a system for TFT-LCD manufacturing such as, but not limited to, an AKT-PiVot PVD system (Applied Materials, Santa Clara, CA).

[34] Fig. 1 schematically illustrates a substrate 100 being positioned on a substrate holder 110. A rotatable target 20 of a cathode assembly 10 can be positioned over the substrate 100. A negative potential can be applied to the rotatable target 20. A magnet assembly 25 is schematically shown located within the rotatable target 20. In many embodiments, an anode (not shown in Fig. 1), to which a positive potential can be applied, can be positioned close to the rotatable target 20. Such an anode may have the shape of a bar, with the axis of the bar being typically arranged in parallel to the axis of the angular tube. In other embodiments, a separate bias voltage may be applied to the substrate. "Positioning the magnet assembly" as used herein can be understood as operating the coater with the magnet assembly located at a certain constant position. In Fig. 1, only one rotatable target 20 of the three or more rotatable targets 20 is shown. However, the same principles can apply for two or more of the three or more rotatable targets 20.

[35] A typical permanent magnet as used in embodiments described herein has a first magnet having a first magnetic pole and a pair of second magnets having a second magnetic pole. These poles refer each to a surface of the magnet assembly. The surfaces typically face the rotatable target from the inside.

[36] According to embodiments described herein, the magnet assembly has a first magnetic pole in the direction of a first plasma racetrack and a second magnetic pole in the direction of a second plasma racetrack. The first magnetic pole can be a magnetic south pole and the second magnetic pole can be a magnetic north pole. In other embodiments, the first magnetic pole can be a magnetic north pole and the second magnetic pole can be a magnetic south pole. The pair of second magnets can have the second magnetic poles (e.g., south poles or north poles) in the direction of the first plasma racetrack and the first magnetic poles (e.g., north poles or south poles) in the direction of the second plasma racetrack. [37] Accordingly, three magnets, each of which may consist of one or more sub-magnets, can form two magnetrons, one magnetron forming the first plasma racetrack and one magnetron forming the second plasma racetrack. The first plasma racetrack and the second plasma racetrack each can have a main direction of material emission from the target upon bombardment of the ions of the plasma. Accordingly, the magnet assembly 25 can include a main direction of material emission, which can be a superposition of the main directions of the first plasma racetrack and the second plasma racetrack.

[38] In Fig. 1, an enlargement of the magnet assembly 25 is shown that illustrates an exemplary situation as described herein. As shown, the south poles are positioned in the middle, whereas the north poles enframe the south poles.

[39] The surface of the substrate can define a plane that is horizontally arranged in the figures shown. In the context of the present application, an angle of the magnet assemblies is defined with respect to a plane perpendicularly extending from the substrate 100 to the axis of the rotatable target 20. In embodiments described herein, this plane can also be perpendicular to the substrate holder. In the context of the present application, this plane can be referred to as the "substrate-target interconnection plane". In Figs. 1, 3a and 3b, this plane is exemplarily shown as the vertically arranged dotted line having reference number 22.

[40] Although the embodiments shown in the figures illustrate the rotatable target 20 to be arranged above a horizontally arranged substrate 100 and the definition of the substrate-target interconnection plane was illustratively explained with respect to those embodiments, other orientations are possible as well. Specifically, the orientation of the substrate can also be vertical as described herein. In particular, in view of large-area coating, it might simplify and ease transportation and handling of a substrate if the substrate is oriented vertically. In other embodiments, it is even possible to arrange the substrate somewhere between a horizontal and a vertical orientation.

[41] According to embodiments described herein, the magnet assemblies 25 can be rotated to a plurality of different angular positions in which the magnet assemblies 25 have an angle with respect to the plane 22 perpendicularly extending from the substrate 100 to the axis 21 of the respective one of the three or more rotatable targets. The angle of the angular positions can be equal to or greater than -60°, specifically equal to or greater than -40°, typically equal to or greater than -15° and/or equal to or smaller than 60°, specifically equal to or smaller than 40°, typically equal to or smaller than 15°.

[42] Further, the magnet assemblies 25 can have a starting angle or reference angle from which the magnet assemblies 25 are rotated to the first one of the plurality of different angular 5 positions. The starting angle can be non-zero, such as +/- 5° to +/- 15 with respect to the plane 22 perpendicularly extending from the substrate 100 to the axis 21 of the respective one of the three or more rotatable targets 20. Further, the herein specified range for the angular positions can be with respect to the starting angle. That is, an angular position can be measured with respect to the starting angle, which may zero or non-zero with respect to the plane 22 10 perpendicularly extending from the substrate 100 to the axis 21 of the respective one of the three or more rotatable targets 20.

[43] Typically, the rotatable targets 20 have the shape of a cylinder. In order to specify the angular position of elements such as the magnet assembly within the cylinder, cylindrical coordinates can be used. Given the particular interest in the angular position, within the 15 present disclosure, the angle is used for the indication of the position. Within the present disclosure, the zero angle position shall be defined as the position within the rotatable target that is closest to the substrate. The zero angle position therefore typically lies within the direct substrate target connection plane 22.

[44] As shown in Fig. 2, the magnet assemblies 25 can be positioned at an angular position 20 having an angle a within the rotatable targets 20. More specifically, the magnet assemblies 25 can be positioned at a plurality of angular positions having an angle a within the rotatable targets 20. That is, the magnet assemblies 25 can be rotated to a plurality of different angular positions in which the magnet assemblies have an angle a with respect to a plane 22 perpendicularly extending from the substrate 100 to the axis 21 of the respective one of the 25 three or more rotatable targets 20.

[45] Figs. 3a and 3b exemplary illustrate a situation in which the magnet assembly 25 is rotated to a first angular position having a negative angle -a (see Fig. 3a) and a second angular position having a positive angle a (see Fig. 3b.) of the plurality of different angular positions. Reference number 23 illustrates the direction of material emission from the magnet assembly 30 25. [46] For instance, the magnet assemblies 25 can be rotated with an angular velocity having an absolute value greater than zero to the plurality of angular positions. Specifically, the magnet assemblies can be rotated from one limit, e.g. the upper limit, of the range for the angle a to the other limit, e.g. lower limit, of the range for the angle a, and vice versa. At the limits of the range, a turning of the angular velocity can occur, i.e. the angular velocity can change the sign.

[47] Alternatively, the magnet assemblies 25 can be rotated in a stepwise manner from one angular position to another angular position. That is, the magnet assemblies 25 can be rotated to one angular position where the magnet assemblies 25 can be kept stationary for a predetermined staying time, and subsequently rotated to another angular position where the magnet assemblies 25 can be kept stationary for the same or another predetermined staying time. Such a stepwise movement can be repeated to rotate the magnet assemblies 25 to the plurality of different angular positions, such as four or more different angular positions.

[48] Further, the angle a can also indicate to the main direction of material emission. That is, material will be specifically sputtered on the substrate in the direction of the angle a. When varying the angular position of the magnet assembly, the main direction of emission can be varied over the substrate 100.

[49] When practicing embodiments, the uniformity of the layer formed can be improved depending on the power applied for the individual angular positions, how long the magnet assemblies stay at the individual positions and/or with which angular velocity the magnet assemblies are rotated. Specifically, sputtering can be performed while the magnet assemblies are stayed at an angular position for the staying time.

[50] In particular, by varying the power provided to the three or more rotatable targets, by varying the staying time of the magnet assemblies, and/or by continuously varying the angular velocity of the magnet assemblies according to the function, the homogeneity of the layer to be sputtered and, in particular, the uniformity can be improved. Therefore, homogeneity may be improved by sputtering with varied time and/or power. In the case of a varied staying time, it is further possible to switch off the sputtering electric field at the time of movement (i.e., where the angular position is being varied), which may further increase the uniformity. [51] Fig. 4 exemplarily illustrates a cathode assembly as used in embodiments described herein in more detail. It is to be understood that the elements shown in Fig. 4 may also be applied in other embodiments described herein, in particular in those embodiments described with respect to Figs. 1, 2, 3a, and 3b. As shown in Fig. 4, the rotatable target 20 can be placed on a backing tube, to which the target material to be sputtered might be applied. In order to reduce the high temperature of the target that results from the sputtering process, a cooling material tube 40 can be provided on the inside of the rotatable target 20. Typically, water can be used as cooling material. When practicing embodiments, a major part of the energy put into the sputtering process - typically in the order of magnitude of some kilo Watts - is transferred into heat of the target which can be cooled as described herein. As shown in the schematic view of Fig. 4, the magnet assembly can be positioned within the backing tube and the cooling material tube so that the magnet assembly can move therein to different angle positions. According to other embodiments, the complete inner part of the target tube is filled with cooling material such as water. [52] The magnet assembly may be mounted on the axis of the target tube. A pivoting movement as described herein may be caused by an actuator, e.g. an electromotor providing a rotational force. In typical embodiments, the cathode assembly is equipped with two shafts: a first shaft on which the rotatable target tube is mounted and a second shaft. The first shaft is rotated in operation of the cathode assembly. The movable magnet assembly is typically mounted to the second shaft. The second shaft can move independently from the first shaft, typically in a manner so as to allow the movement of the magnet assembly as described herein.

[53] Within the present disclosure, the figures illustrate cross sectional schematic views of coaters along with exemplarily shown substrates. Typically, the cathode assemblies 10 include the rotatable target 20 which can have the shape of a cylinder. In other words, the rotatable target 20 extends into the paper and out of the paper when looking at the drawings. The same is true with respect to the magnet assemblies 25 that are also only schematically shown as cross sectional elements. The magnet assemblies may extend along the complete length of the cylinder. For technical reasons, it is typical that the magnet assemblies extend at least 100 % of the cylinder length, more typically at least 105 % of the cylinder length. [54] Fig. 5 illustrates a variation of a power provided to the three or more rotatable targets 20 according to a function. Specifically, the function can provide different values for the power for different angular positions. In the graph illustrated in Fig. 5, the vertical axis is the power U provided to the three or more rotatable targets 20, and the horizontal axis is the angle 5 a.

[55] With increasing distance from the magnet assembly 25 to the substrate 100, the ion bombardment of material emitted on the substrate 100 decreases. Although the distance between the magnet assembly 25 or the rotatable target 20 to the substrate 100 along the plane perpendicularly extending from the substrate 100 to the axis 21 of the rotatable target 20 may 10 be constant, the distance the material emitted from the rotatable target 20 travels to reach the substrate 100 increases with increasing values, or absolute values, of the angle a. Accordingly, less material is deposited for comparably high angles a than for comparably low angles a.

[56] Further, with increasing values, or absolute values, of the angle a, an incident angle 15 under which the material to be deposited reaches the substrate 100 increases, which reduces the energy of the ion bombardment. This effect effects locally the structural, morphological and electrical or optical properties of the growing film by controlling the local ion bombardment energy and intensity..

[57] According to embodiments, the power provided to the three or more rotatable targets 20 20 is varied to compensate for the reduced material deposition at angular positions having high angles a. Specifically, the power provided to the three or more rotatable targets 20 is higher the higher the angle a of an angular positions is, and vice versa. When practicing embodiments, the uniformity of a layer to be deposited can be increased, specifically if sputtering power is varied over time when the magnet is moved.

25 [58] As shown in Fig. 5, the function for varying the power provided to the three or more rotatable targets 20 can be a symmetric function. Further, the function for varying the power provided to the three or more rotatable targets 20 can be an asymmetric function. For instance, the function for varying the power provided to the three or more rotatable targets 20 can be a polynomial function, a trigonometric function, and/or combinations thereof. For instance, the power can be varied in a range from -2 kW to 20 kW, specifically in a range from 5 kW to 10 kW.

[59] Further, the magnet assemblies 25 can be constantly rotated between the left and right maximum angles ("wobbling"). However, as shown in Fig. 6, the angular velocity of the magnet assemblies 25 can be varied continuously in addition to the variation of the power to increase the uniformity of the layer to be deposited. Further, similar results with regard to uniformity can be obtained in praxis when continuously varying the angular velocity of the magnet assemblies 25 instead of the variation of the power.

[60] Taking the herein described relation between the value of the angle a and the material deposited at the angular position with angle a into account, it can be beneficial to continuously vary the angular velocity of the magnet assembly in such a manner that the angular velocity is higher for comparably smaller absolute values of the angle a than for comparably larger absolute values of the angle a. That is, the magnet assembly 25 is rotated faster for comparably smaller absolute values of the angle a than for comparably larger absolute values of the angle a. Accordingly, the higher deposition rate at angular positions having a comparably smaller absolute value of the angle a can be compensated for by reducing a time, or effective staying time, during which material is deposited at these angular positions, as compared to angular positions having a comparably higher absolute value of the angle a. [61] The function for continuously varying the angular velocity of the magnet assemblies 25 can be a symmetric function. Further, the function for continuously varying the angular velocity of the magnet assemblies 25 can be an asymmetric function. For instance, the function for continuously varying the angular velocity of the magnet assemblies 25 can be a polynomial function, a trigonometric function, and/or combinations thereof. [62] While the function for varying the power provided to the three or more rotatable targets 20 can be an upwardly opened function, i.e. having larger values on the vertical axis for larger absolute values on the horizontal axis, the function for continuously varying the angular velocity of the magnet assemblies 25 can be a downwardly open function, having smaller values on the vertical axis for larger absolute values on the horizontal axis. For instance, the angular velocity can be continuously varied in a range from 0,5 °/s to 500 °/s, specifically in a range from 2 °/s to 200 °/s.

[63] Fig. 7 shows a further example of a function for varying the power provided to the three or more rotatable targets 20. Specifically, Fig. 7 shows an asymmetric function for varying the power provided to the three or more rotatable targets 20.

[64] Further, Fig. 7 shows two different ways of varying the power provided to the three or more rotatable targets 20. The solid line represents a continuous function for varying the power provided to the three or more rotatable targets 20, whereas the individual points in the graph represent a discrete function for varying the power provided to the three or more rotatable targets 20. A continuous function can be used for the case of wobbling magnet assemblies, i.e. continuously rotating magnet assemblies 25 with a constant angular velocity or with a continuously varied angular velocity. A discrete function can be used for the case of stepwise rotated magnet assemblies 25, i.e. where the magnet assemblies 25 are rotated stepwise from one angular position to another angular position. [65] The term "continuous variation" of the angular velocity or a "continuously varied" angular velocity as used herein shall particularly differentiate from a stepwise varied angular velocity as is the case for stepwise rotated magnet assemblies 25. Specifically, for the stepwise rotation, the angular velocity is usually zero while the magnet assemblies 25 stay at an angular position and jumps to a predetermined value when the magnet assemblies are moved from one angular position to the next angular position. Such a movement can be particular understood as a non-continuous movement. Accordingly, the staying time of the magnet assemblies can be varied according to a discrete function, and/or the angular velocity of the magnet assemblies can be varied according to a continuous function.

[66] According to embodiments, the discrete function includes more than four steps. Particularly, the more steps the discrete function has, the closer the discrete function approximates the continuous function. Hence, it can be beneficial for implementing the function into a coater for carrying out the method described herein to use a discrete function while increasing the number of steps to approximate the continuous function. [67] Fig. 8 shows a further example of a function for varying the power provided to the three or more rotatable targets 20 and an example for a function for varying the staying time of the magnet assemblies.

[68] As outlined herein, the magnet assemblies 25 stay for a specific staying time at each step of the stepwise rotation of the magnet assemblies 25. By varying the staying time for a stepwise rotation of the magnet assemblies 25, a similar effect can be achieved as by continuously varying the angular velocity for continuously rotated magnet assemblies 25. Specifically, the staying time can be lower for comparably smaller absolute values of the angle a than for comparably larger absolute values of the angle a. That is, the magnet assembly 25 stays for a shorter amount of time for comparably smaller absolute values of the angle a than for comparably larger absolute values of the angle a. Accordingly, the higher deposition rate at angular positions having a comparably smaller absolute value of the angle a can be compensated for by reducing the staying time during which material is deposited at these angular positions, as compared to angular positions having a comparably higher absolute value of the angle a. Accordingly, the function for varying the staying time of the magnet assemblies 25 can be an upwardly open function. For instance, the staying time can be varied in a range from 0.5 s to 30 s, specifically in a range from 2 s to 10 s.

[69] According to embodiments described herein, the power provided to the three or more rotatable targets 20 and one of: the staying time of the magnet assemblies 25, and the angular velocity of the magnet assemblies 25, which is varied continuously, can be varied according to the function. That is, the power provided to the three or more rotatable targets 20 can be varied together with the staying time of the magnet assemblies 25 in case of a stepwise rotation, together with a continuous variation of the angular velocity of the magnet assemblies 25 in case of wobbled magnet assemblies 25. Fig. 8 illustrates a combination of a variation of the power provided to the three or more rotatable targets 20 and a variation of the staying time. Accordingly, the function can be dependent on multiple variables, be multi-dimensional and/or include one or more sub functions.

[70] By combining power variation and time variation (either staying time or angular velocity), the uniformity of the layer to be deposited can be further increased. Further, the power provided to the rotatable targets 20 can be technically limited in the upper and/or lower range of the power that can be provided to the rotatable targets 20. For instance, it might be contemplated to use a value for the power provided to the rotatable targets 20 for which the cathode assembly 10 is not technically specified. Accordingly, a value for the power provided to the rotatable targets 20 can be used that lies within the specified range and the deviation from the contemplated valued can be compensated for by altering the value of the staying time or angular velocity. Specifically, if a power provided to the rotatable targets 20 were to be used for a specific angular position that is larger than the specified range, this deviation can be compensated for by a larger staying time for that specific angular position or a smaller angular velocity for that specific angular position, and vice versa. When practicing embodiments, a high throughput reducing the overall processing time and costs can be achieved.

[71] According to embodiments, a processing chamber is provided. Specifically, the processing chamber can be a vacuum processing chamber. The processing chamber can include the at least one cathode assembly as described herein. Further, the processing chamber can be configured to carry out the method for coating a substrate as described herein. Typically, the processing chamber can be configured for coating one substrate at one point in time. A multitude of substrates can be coated one after the other.

[72] According to embodiments, the at least three rotatable targets can be arranged in a one-dimensional array of rotatable targets that are regularly arranged. Typically, the number of rotatable targets is between 3 and 20, more typically between 8 and 16. [73] According to embodiments, the rotatable targets 20 can be spaced apart from each other equidistantly. Typically, the length of the rotatable targets 20 can be slightly longer than the length of the substrate to be coated. Additionally or alternatively, the area spanned by the rotatable targets 20 can be slightly broader in width than a width of the substrate. "Slightly" typically includes a range of between 100% and 110%. The provision of a slightly larger coating length/width helps avoiding boundary effects. Normally, the cathode assemblies are located equidistantly away from the substrate.

[74] According to embodiments, the three or more rotatable targets 20 can be arranged along an arc's shape. The shape of the arc may be such that the rotatable targets 20 are located closer to the substrate 100 than the outer rotatable targets 20. Such a situation is schematically shown in Fig. 9. Alternatively, it is also possible that the shape of the arc defining the positions of the rotatable targets 20 is such that the outer rotatable targets 20 are located closer to the substrate 100 than the inner rotatable targets 20. The scattering behaviour depends on the material to be sputtered. Hence, depending on the application, i.e. on the material to be sputtered, providing the rotatable targets 20 on an arc shape can further increase the homogeneity in practice. The orientation of the arc can depend on the application.

[75] In addition or alternatively, the three or more rotatable targets 20 can be arranged in such a manner that a distance between two adjacent rotatable targets 20 is varied from inner rotatable targets 20 to outer rotatable targets 20. For instance, the distance between the adjacent outer rotatable targets 20 can be larger than the distance between the adjacent inner rotatable targets 20. Alternatively, the distance between the adjacent outer rotatable targets 20 can be smaller than the distance between the adjacent inner rotatable targets 20. By providing the outer rotatable targets 20 with a smaller distance as between the adjacent inner rotatable targets 20, the outermost rotatable targets 20 are moved closer to the inner part of the substrate. According to embodiments, less material may be wasted. [76] In addition, Fig. 9 shows exemplary anode bars positioned between the cathode assemblies that may be used in some of the embodiments described herein.

[77] According to embodiments, the function for at least one of: a variation of a power provided to the three or more rotatable targets, a variation of a staying time of the magnet assemblies, and a continuous variation of an angular velocity of the magnet assemblies can be identical for all rotatable targets. Alternatively, different functions can be used for different rotatable targets.

[78] For instance, a different function can be used for the outer or outermost targets 20 than for other rotatable targets 20. As the outermost rotatable targets 20 usually sputter material on an area of the substrate 100 in which the deposited layer is a superposition of material from less rotatable targets 20 than in an inner area of the substrate 100, asymmetric functions can be used for the outer or outermost targets 20 to compensate for this deviation in asymmetric deposition. Accordingly, the function can have higher values for the power, higher values for the staying time and/or lower values for the angular velocity for an area in which the deposited layer is a superposition of material from less rotatable targets 20 than in an inner area of the substrate 100. [79] In the context of the present application, an "outer" rotatable target can be understood as a rotatable target that is arranged close to an edge of the substrate, whereas an "inner" rotatable target can be understood as a rotatable target that is arranged close to an inner areas of the substrate. Specifically, when referring to an "outer" rotatable target and an "inner" rotatable target, the "outer" rotatable target can be closer to an edge of the substrate than the "inner" rotatable target. Furthermore, an "outermost" rotatable target can be understood as a rotatable target that is arranged closer to an edge of the substrate than neighbouring rotatable targets.

[80] Figs. 10a and 10b show a comparison of the thickness of a film deposited by a conventional process and by the processes described herein. The deposition takes place using rotatable targets arranged at the location of the solid lines spaced from the substrate.

[81] Fig. 10a schematically shows two film profiles measured after deposition with a conventional process and with the processes described herein. The y-axis represents a metrical unit for the film's thickness, whereas the x-axis represents a metrical unit for the substrate's length. As can be seen from Fig. 10a, the thickness of the film deposited by the processes described herein in an area between the rotatable targets 20 deviates less from the thickness in an area directly under the rotatable targets than it is the case for the conventional process.

[82] Fig. 10b shows a statistical analysis for the deviation of the thickness of a film deposited by a conventional process and by the processes described herein. As can be seen from Fig. 10b, the deviation of the thickness is higher for the conventional process shown on the left side than for the process described herein shown on the right side. When practicing embodiments, a uniformity of layer thickness can be increased.

[83] Figs. 11a and 1 lb show a comparison of an electric property of a film deposited by a conventional process and using the processes described herein. The deposition takes place using rotatable targets arranged at the location of the solid lines spaced from the substrate.

[84] Fig. 11a schematically shows three film profiles measured after deposition with two different conventional processes and with the processes described herein. The y-axis represents a metrical unit for the film's electric property, whereas the x-axis represents a metrical unit for the substrate's length. As can be seen from Fig. 10a, the illustrated electric property of the film deposited by the processes described herein is more constant, specifically overall more constant than it is the case for the conventional processes.

[85] Fig. 1 lb shows a statistical analysis for the deviation of the electric property of a film deposited by the two conventional processes and by the processes described herein. As can be seen from Fig. 10b, the deviation of the illustrated electric property is higher for the conventional processes shown on the left and middle side than for the process described herein shown on the right side. When practicing embodiments, a uniformity of electric properties of the deposited layer may be increased.

[86] In the following, embodiments resulting in a particularly high uniformity are described.

[87] According to an aspect, a method for coating a substrate with at least one cathode assembly having three or more rotatable targets, the three or more rotatable targets each including a magnet assembly positioned there within, is provided. The method includes: rotating the magnet assemblies to a plurality of different angular positions with respect to a plane perpendicularly extending from the substrate to the axis of the respective one of the three or more rotatable targets; and varying at least one of: a power provided to the three or more rotatable targets, a staying time of the magnet assemblies, and an angular velocity of the magnet assemblies, which is varied continuously, according to a function stored in a database or a memory. [88] According to embodiments, a method for coating a substrate with at least one cathode assembly having three or more rotatable targets, the three or more rotatable targets each including a magnet assembly positioned there within, is provided. The method includes: rotating the magnet assemblies to a plurality of different angular positions in which the magnet assemblies have an angle with respect to a plane perpendicularly extending from the substrate to the axis of the respective one of the three or more rotatable targets; reading a function for at least one of: a variation of a power provided to the three or more rotatable targets, a variation of a staying time of the magnet assemblies, and a continuous variation of an angular velocity of the magnet assemblies from a memory; and varying at least one of: the power provided to the three or more rotatable targets, the staying time of the magnet assemblies, and the angular velocity of the magnet assemblies, which is varied continuously, according to the function.

[89] According to embodiments, a method for coating a substrate with at least one cathode assembly having three or more rotatable targets, the three or more rotatable targets each including a magnet assembly positioned there within, is provided. The method includes: rotating the magnet assemblies to more than four different angular positions in which the magnet assemblies have an angle with respect to a plane perpendicularly extending from the substrate to the axis of the respective one of the three or more rotatable targets; reading a function for a variation of a staying time of the magnet assemblies for the more than four different angular positions; and varying the staying time of the magnet assemblies for the more than four different angular positions according to the function.

[90] According to embodiments, a method for coating a substrate with at least one cathode assembly having three or more rotatable targets, the three or more rotatable targets each including a magnet assembly positioned there within, is provided. The method includes: rotating the magnet assemblies to more than four different angular positions with respect to a plane perpendicularly extending from the substrate to the axis of the respective one of the three or more rotatable targets; and varying a staying time of the magnet assemblies for the more than four different angular positions according to a function stored in a database.

[91] Typically, the staying time is different for each different angular position. [92] According to embodiments, a coater for carrying out the methods described herein is provided. The coater can include a memory from which the function can be read. Specifically, the memory can include a look-up table in which the function is stored.

[93] The method and coater as disclosed herein can be used for depositing material on substrates. More particularly, the method and coater allow for a high uniformity of the deposited layer and can therefore be used in the production of displays such as flat panel displays, e.g., TFTs. Given the improved uniformity, as a further effect thereof, the overall material consumption can be reduced which is particularly desirable when using expensive materials. For instance, the proposed method and coater could be used for the deposition of an indium tin oxide (ITO) layer in the production of a flat panel display. [94] According to certain embodiments, a conductive layer manufacturing process and/or system is provided, which manufacturing process and/or system may be for fabrication of an electrode or a bus (in particular in a TFT), the manufacturing process and/or system respectively including a method of and/or a system for coating a substrate according to embodiments herein. For example, but not limited to, such a conductive layer may be a metal layer or a transparent conductive layer such as, but not limited to an ITO (indium tin oxide) layer. For instance, the method described herein can be used for forming an active layer in a TFT, such as an active layer made of or including IGZO (indium gallium zinc oxide).

[95] For example, at least some embodiments of the present disclosure may yield a high uniformity on resistivity of an aluminum layer or an IGZO layer formed on a glass substrate. For instance, a deviation of a thickness between 0 % and 2 % or even between 0.5 % and ±1.5 % over a substrate area of 406 mm x 355 mm may be achieved. Further, a deviation of an electric property between 2 % and 8 % or even between 5 % and 7 % over a substrate area of 406 mm x 355 mm may be achieved. [96] Within the present disclosure, at least some figures illustrate cross sectional schematic views of coating systems and substrates. At least some of the illustrated targets are shaped as a cylinder. In these drawings, it should be noted that the target extends into the paper and out of the paper when looking at the drawings. The same is true with respect to magnet assemblies that are also only schematically shown as cross sectional elements. The magnet assemblies may extend along the complete length of the cylinder defined by a cylindrical target. For technical reasons, it is typical that the magnet assemblies extend at least 100 % of the cylinder length, more typically at least 105 % of the cylinder length.

[97] While the foregoing is directed to embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.