Embodiments of the present invention generally relate to thin-film deposition systems and evaporation devices used in systems for forming thin-films. In particular, the present invention relates to an evaporator device having evaporator crucibles for evaporation of deposition material to be deposited onto substrates. In addition to that, the present invention relates to a method for depositing a thin film onto a substrate using an evaporation system.
Devices for an efficient conversion of solar energy into electrical energy are of increasing importance. Such energy conversion devices may be based on thin-film solar cells which can be produced by depositing appropriate thin films onto substrates such as wafers. It is a current trend to provide large area solar cells formed on large substrates. These substrates may be transported through a deposition apparatus being adapted for applying different thin films onto the substrates.
Evaporator devices may be used for evaporating deposition material for forming thin films onto the substrates. Specifically, e.g. for large area solar cells, a good layer uniformity with respect to composition and layer thickness is desired. Additionally, manufacturing costs for manufacturing thin-film devices need to be decreased and deposition material needs to be utilized in an effective manner.
According to one embodiment, a deposition system adapted for depositing a thin film onto a substrate is provided, the deposition system including a substrate carrier adapted for carrying the substrate; and at least one tilted evaporator crucible adapted for directing evaporated deposition material towards the substrate in a main emission direction, wherein the main emission direction of the tilted evaporator crucible is different from a direction normal to the substrate.
According to a further embodiment, a method for depositing a thin film onto a substrate is provided, the method including providing at least one evaporator crucible, providing a substrate carrier in the vicinity of the at least one evaporator crucible, loading the substrate onto the substrate carrier, and evaporating deposition material from the at least one evaporator crucible towards the substrate in a main emission direction different from a direction normal to the substrate.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the invention and are described in the following:
Reference will now be made in detail to the various embodiments of the invention, 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. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the invention and is not meant as a limitation of the invention. For example, 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 present invention includes such modifications and variations.
Embodiments described herein refer inter alia to a deposition system adapted for depositing a thin film onto a substrate, wherein depositing deposition material onto a substrate surface typically is based on evaporating the deposition material. The deposition system includes an evaporator device having a number of evaporator crucibles. The evaporator crucibles may be arranged such that a good layer uniformity of a layer deposited onto the substrate surface may be achieved.
Solar cells may be manufactured using large area substrates. These substrates may be transported through the deposition system in a substrate transport direction. The substrates may be transported by means of a substrate carrier which is adapted to hold the substrate during transportation and during the deposition process. The substrates may be provided as individual wafers which are held by means of appropriate substrate carriers. Moreover, the substrate may be provided as a flexible web that is guided through a deposition region of the deposition system. For example, the web may be a foil which is transported through the deposition system in the substrate transport direction.
According to embodiments described herein, a thin-film deposition system may include a number of evaporator crucibles 201 as shown in
It is thus possible to provide a tilt angle 303 between a surface normal 302 of the substrate to be coated and the main emission direction 301. As can be seen from the schematic setup shown in
As will be shown herein below, a number of evaporator crucibles 201 may be arranged, typically in a line, each evaporator crucible 201 providing an individual main emission direction 301. Thus, layer uniformity may be influenced by an appropriate adjustment of the individual main emission directions 301 of the respective evaporator crucibles 201. Furthermore, the vapor cone 304 (see
According to a typical embodiment, the main emission direction 301 may be tilted by a tilt angle 303 in a range from −60° to +60°, typically in a range from −25° to +25°, more typically in a range from −15° to +15°, and even more typically in a range from −5° to +5°, with respect to the surface normal 302 of the substrate 101. Furthermore, according to yet another typical embodiment, the vapor cone 304 may be adjusted prior to a deposition process.
The evaporator crucible may provide a vapor cone 304 having a cosine exponent in a range from 1 to 5. Typically, the vapor cone 304 is extended approximately symmetrically with respect to the main emission direction 301 of the evaporator crucible 201.
It is noted here that the evaporator crucible 201 may be tilted in both directions with respect to the surface normal 302 of the substrate 101, i.e. in addition to a clockwise tilt shown in
By tilting the tiltable support unit 204 with respect to the surface normal 302, an individual deposition direction, i.e. a main emission direction 301 of an evaporator crucible 201 may be provided. It is noted here that the expression “normal to the substrate” indicates a direction of the surface normal 302 defined at a right angle with respect to the surface of the substrate 101.
The substrate 101 may be transported in a direction which is perpendicular to the plane of drawing of
It is noted here that a plurality of evaporator crucibles 201 may be arranged at a fixed distance with respect to each other, i.e. at a pitch in a range from 20 mm to 100 mm, and typically the evaporator crucibles 201 are arranged at a pitch of approximately 80 mm with respect to one another. Alternatively, the evaporator crucibles 201 may be arranged at variable distances with respect to one another, i.e. the distance between two adjacent evaporator crucibles 201 may be different from another distance between two other adjacent evaporator crucibles 201.
According to the graphs shown in
The deposition system 100 in accordance with a typical embodiment is arranged such that a distance between the substrate carrier 102 and the evaporation device 200 is in a range from 50 mm to 400 mm, and typically amounts to approximately 200 mm. Furthermore, the at least one evaporation crucible 201 is adapted for providing a vapor cone having a cosine exponent in a range from 1 to 5. According to another typical embodiment which can be combined with other embodiments described herein, the vapor cone may range from 3 to 4, and more typically may have a value of approximately 3.5. Moreover, evaporating deposition material from the at least one evaporator crucible 201 may include varying a vapour cone of the at least one evaporator crucible 201.
For obtaining the film thickness profiles shown in
According to a typical embodiment which can be combined with other embodiments described herein, the evaporation rate of the outermost evaporator crucibles is larger than the evaporation rate of inner evaporator crucibles by an amount in a range from 5% to 50%, typically in a range from 10% to 30%, and more typically by an amount of approximately 25%.
It is noted here that, in order to explain the principles of typical embodiments, the deposition system 100 adapted for obtaining film thickness profiles 504 shown in
As shown in
As indicated herein above, a positive angle represents a tilt in the clockwise direction in
The second film thickness profile 506 shown in
Table 1: Tilt angles 303 (in degrees; °) of the individual evaporator crucibles 201a-201h for obtaining the film thickness profiles 505-510 shown in the graphs of
The fifth film thickness profile 509 shown in
The sixth film thickness profile 510 has been obtained by an additional tilt of the outermost evaporator crucibles 201a and 201h, respectively, towards the center of the substrate 101. The respective tilt angles or the film thickness profiles 505-510 are summarized in table 1 herein above. It is noted again that a positive tilt angle represents a tilt in the clockwise direction, wherein a negative tilt angle represents a tilt in the counter-clockwise direction, with respect to the arrangement shown in
The arrangements shown in
The respective main emission directions 301 may be different from each other. In particular, the main emission direction 301 of a tilted evaporator crucible 201a-201h may be different from a direction normal to the substrate 101, i.e. the surface normal 302 (see
Thus, deposition material is evaporated from the plurality of evaporator crucibles 201a-201h in different main emission directions 301, i.e. the emission directions 301 of the individual evaporator crucibles 201 may be different from each other. According to a typical embodiment, it is thus possible to optimize the individual tilt angle 303 of the evaporator crucibles 201a-201h such that a layer thickness inhomogenity is decreased.
In particular, if the substrate 101 is transported in the substrate transport direction 511, deposition material may be evaporated from at least two evaporator crucibles 201 which are arranged symmetrically to a plane defined by the transport direction 511 and the surface normal 302. The individual evaporator crucible 201 is continuously variable, e.g. the evaporator crucible 201 is adapted to be tilted continuously.
A substrate 101 is loaded onto the substrate carrier at a block 404. At a block 405, a deposition material is evaporated from the at least one evaporator crucible 201 towards the substrate 101 in a main emission direction 301 different from a direction normal 302 to the substrate 101. The procedure is ended at a block 406.
In light of the above, a plurality of embodiments have been described. For example, according to one embodiment, a deposition system adapted for depositing a thin film onto a substrate is provided, the deposition system including a substrate carrier adapted for carrying the substrate; and at least one tilted evaporator crucible adapted for directing evaporated deposition material towards the substrate in a main emission direction, wherein the main emission direction of the tilted evaporator crucible is different from a direction normal to the substrate. According to a further embodiment at least two evaporator crucibles are provided which are adapted for directing the evaporated deposition material towards the substrate in respective main emission directions, wherein the respective main emission directions are different from each other. According to at least one further embodiment which can be combined with other embodiments described herein, at least two evaporator crucibles are arranged symmetrically to a plane which is perpendicular to the substrate. According to an optional modification thereof, a plurality of evaporator crucibles arranged at a pitch in a range from 50 mm to 400 mm, and typically at a pitch of approximately 80 mm with respect to one another are provided. Furthermore, a plurality of evaporator crucibles are arranged in a line perpendicular to a transport direction of the substrate. According to yet further embodiments, which can be combined with any of the other embodiments and modifications above the evaporator crucible is tilted such that the main emission direction and the normal of the substrate form an angle in a range from −60 degrees to +60 degrees, typically in a range from −45° to +45°, more typically in a range from −25° to +25°, even more typically in a range from −15° to +15°, and even more typically in a range from −5 degrees to +5 degrees. According to yet another optional modification thereof the evaporator crucible is adapted to be tilted continuously. According to yet further additional or alternative modifications at least one evaporation crucible is adapted for providing a vapor cone having a cosine exponent in a range from 1 to 5. Moreover, the deposition system may include a tiltable or tilted support unit for each of the plurality of evaporator crucibles, the tiltable or tilted support unit being adapted for individually adjusting the main emission direction of a respective evaporator crucible. In addition to that, or alternatively, an even number of evaporator crucibles symmetrically arranged with respect to a plane defined by the transport direction and the normal of the substrate are provided. According to another embodiment, a method of depositing a thin film onto a substrate is provided including providing at least one evaporator crucible, providing a substrate carrier in the vicinity of the at least one evaporator crucible, loading the substrate onto the substrate carrier, and evaporating deposition material from the at least one evaporator crucible towards the substrate in a main emission direction different from a direction normal to the substrate. According to an optional modification thereof, at least two evaporator crucibles are provided and wherein the main emission directions of the evaporated deposition material of the at least two evaporator crucibles are different from each other. According to yet further embodiments, which can be combined with any of the other embodiments and modifications above, the main emission direction may be tilted by an angle in a range from −60 degrees to +60 degrees, typically in a range from range from −15 degrees to +15 degrees, and more typically in a range from −5 degrees to +5 degrees, with respect to a normal of the substrate. Furthermore, the substrate is transported in a transport direction, and wherein deposition material is evaporated from at least two evaporator crucibles arranged symmetrically to a plane defined by the transport direction and the normal of the substrate. According to yet another embodiment evaporating deposition material from the at least one evaporator crucible may include spatially varying a vapour cone of the at least one evaporator crucible.
While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Number | Date | Country | Kind |
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10189131.5 | Oct 2010 | EP | regional |