Patent Application
20100196591
Embodiments of the present invention relate to a modular PVD system for depositing thin layers on flexible substrates, and which can be used for manufacturing layer stacks of flex PV modules. In particular, embodiments relate to a thin-film deposition system having one or more chambers, which are based on a common platform. Specifically, they relate to a system for thin film deposition on a flexible substrate; and to a method of manufacturing a layer stack of a flexible photo voltaic cell with such a system.
The current trend of an increasing number of electronic and optoelectronic devices such as printed circuit boards, displays and solar cells on flexible substrates has the desire to use cheap substrates to make the devices cheaper. Accordingly, there is an increasing need for and an increasing development of roll-to-roll thin film deposition apparatuses. Thus, there is a desire for deposition platform concepts that permit low cost deposition for different substrate materials and different stacks of thin film layers.
For thin film deposition systems in the field of manufacturing consumer electronic devices, downtimes of systems is a serious and challenging factor. Thereby, stock holding of spare parts or deposition components of e.g. an inline processing line in a factory and maintenance are only a few of the aspects that need to be considered. Additionally, manufacturing costs for manufacturing the deposition equipment needs to be decreased for low cost production of the consumer electronic and optoelectronic devices. Of course, these considerations have to be taken into account on top of optimized deposition characteristics for each of the layers deposited in a layer stack.
According to one embodiment, a system for thin film deposition on a flexible substrate having at least a first deposition region is provided. The system includes a first chamber being based on a platform, wherein the first deposition region is within the first chamber, wherein the first chamber has a first support member configuration configured for supporting at least two different substrate guiding systems and wherein one substrate guiding system is supported by the first support member configuration, and wherein the platform is configured for at least two different deposition units and wherein one deposition unit of the at least two different deposition units is enclosed by the first chamber.
According to a further embodiment, a method of manufacturing a layer stack of a flexible photo voltaic cell is provided. The method includes unwinding a flexible substrate from a roll; guiding the flexible substrate in a first chamber being based on a common platform; depositing a first layer on the flexible substrate; guiding the flexible substrate from the first chamber to a second chamber, wherein the second chamber is based on the second platform; depositing a second layer above the first layer; guiding the flexible substrate from the second chamber; and winding the flexible substrate on a roll.
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 platform concept that permits low cost deposition irrespective of the substrate material and thickness used. Currently, the majority of flexible photovoltaic devices is manufactured on stainless steel, aluminum, PET or PEN substrates, whereas polyimide is used almost exclusively for flexible printed circuit boards and both PET and PEN are used for flexible displays. For example, typically the substrate thickness can be 25 μm to 150 μm and used dependent upon both the heat load delivered to the substrate and the desired final product's mechanical properties.
A flexible substrate or web as used within the embodiments described herein can typically be characterized in that it is bendable. The term “web” may be synonymously used to the term “strip” or the term “flexible substrate”. For instance, the web as described in embodiments herein may be a foil as described above.
According to embodiments described herein, a thin film deposition system 100, as shown in
From the unwinding station 110, the flexible substrate is guided to the first deposition chamber 120 and to a second deposition chamber 120 and further to a winding station where the flexible substrate is wound on a roll 114′ in the winding station 110′. Again, the winding station 110′ can include one or more rollers 112′ in order to guide the flexible substrate and to control tension, winding characteristics, or the like.
Each of the chambers used in the thin film deposition system, i.e. in
As shown in
According to yet further embodiments, which can be combined with other embodiments described herein, the substrate guiding system used in the first (left) chamber in
Examples of a gas cushions, which can be used with embodiments described herein, are described in U.S. patent application Ser. No. 12/255,389, entitled “Hover cushion transport for webs in a web coating process” filed Oct. 21, 2008, which is incorporated herein by reference to the extent the applications are not inconsistent with this disclosure. Therein, for example, a guiding device for contact-free guiding a web is provided with the device having a surface for facing the web and a multitude of gas outlets disposed in the surface and adapted for providing a hover cushion for the web; or a guiding device for contact-free guiding a web is provided with the device having a surface for facing the web and a multitude of gas outlets disposed in the surface wherein the surface is non-rotatable.
According to yet further embodiments, which can be combined with other embodiments described herein, the gas passing through the gas outlets can be used to control the temperature of the web. Thus, means for cooling or heating the gas passing through the gas outlets can be provided such that the temperature of the web being guided by the gas cushion roller can be increased or decreased depending on the desired temperature for the subsequent deposition process.
After deposition in the first chamber 120, the substrate 10 is guided to the second (right) chamber 120. Therein, guiding rollers 141 can be provided similarly as the guiding rollers 131 in the last chamber. The substrate guiding system 140 in the right chamber 120 includes, in the example shown in
As shown in
According to embodiments described herein, the substrate guiding system 140 in the right chamber and the substrate guiding system 130 in the left chamber can both be provided in the same chamber housing. In light of the above, according to different embodiments described herein, which can be combined with other embodiments described herein, the chamber 120 provides a common or uniform platform for different substrate guiding systems 130, 140 and different deposition units 150 and 160. Thus, the modularity of the deposition system can be provided. This improves the flexibility of a factory for manufacturing consumer electronic devices, it reduces the number of spare parts that need to be provided for avoiding significant downtimes of the deposition system, it increases the flexibility for combining different deposition processes, or reduces the costs for manufacturing deposition chambers and, thus, deposition systems.
Thereby, a “universal” roll-to-roll platform designed for example for the type of PVD processes found particularly in “Flex PV” includes the high temperature deposition of the aluminum back contact. In order to achieve the desired aluminum back contact properties (e.g. surface roughness) free span deposition can be provided and a cooling roller or cooling drum can be used to reduce the substrate temperature thereafter prior to the next PVD back contact process step (e.g. TCO deposition). As the TCO deposition typically uses a coating drum system, modularity is therefore beneficial for embodiments described herein.
According to yet further embodiments, which can be combined with other embodiments described herein, the modularity for providing different substrate guiding units allows a cooling or heating of the web between different processes. Thereby, the system can be adapted for a transport speed of the flexible substrate is from 0.1 m/min to 10 m/min, typically the processes are conducted at a substrate speed of about 1 m/min to 5 m/min. Accordingly, typical implementations can have a time between the depositing of the first layer and the time between depositing a second layer of about 10 min or less, typically 5 min or less, or even 1 min/less.
According to embodiments describe herein, a high temperature of about 400° C. and above, e.g. about 500° C. can be provided in the first (left) chamber 120 of
Immediately thereafter, a second PVD process is used for the deposition of the ZnO back contact capping/scattering layer within the same PVD system. The second deposition process can thereby typically be a process carried out at a substrate temperature of 100° C. or below. For example, the second process can be a room temperature process wherein the substrate temperature might however be slightly elevated above room temperature due to the energy provided to the substrate during the deposition process. Due to the large difference in substrate temperature between these two processes inline, roll-to-roll processing according to embodiments described herein provide a method of accurately and controllably cooling the flexible substrate.
The modular design described within with respect to embodiments described herein, permits the combination of a processing system with a free-span substrate transport and processing system with a cooling drum/roller transport between a single set of unwinding and winding rollers. Furthermore, this modularity can be provided by similar vacuum chambers forming a common platform for containing different internal substrate transport and processing systems.
As described with respect to
As shown in
According to some embodiments, the cathodes can for example be rotatable cathodes, such as rotatable targets for magnetron sputtering of the material to be deposited on the web.
According to yet further embodiments, a deposition unit or deposition unit assembly 160 can be provided as shown in
According to yet further embodiments, which can be combined with other embodiments described herein, a gas separation unit 164 can be provided between one or more groups of cathodes 162. Thereby, the deposition areas or deposition zones through which the web is guided over a roller or the like can be separated such that a different atmosphere can be provided within the chamber 120. Accordingly, different processing gases or different pressure ranges can be applied to the respective deposition zones, thereby providing a further improved flexibility for manufacturing of consumer electronic and optoelectronic devices such as solar cells. For example, gas separation units may be incorporated to separate metallic from reactive PVD processes within different areas within the same vacuum chamber.
In light of the above described embodiments, a combination of system features can provide the modularity for PVD coating of flexible substrates.
According to embodiments described herein, a thin film deposition system for depositing a thin film on a flexible substrate as shown in
According to yet further embodiments, which can be combined with other embodiments described herein, the same platform of the chamber 120 can be provided for depositing a front contact of a flexible solar cell. Thereby, a chamber with a drum substrate guiding system and planar cathodes is used for depositing indium doped tin oxide (ITO). An example of the corresponding thin film deposition system 700 is shown in
Therein, an unwinding station 110 is provided with a roll 114 providing a flexible substrate 10. Further, the unwinding station 110 includes a guiding roller 112. Generally, one or more guiding rollers can be provided in order to guide the substrate to the subsequent chamber, to tension the web to the desired tension, to control the speed of the web, or the like.
According to yet further embodiments, which can be combined with other embodiments described herein, an interleaf layer can be wound between the layers of the flexible substrate on provided from and onto the roll 114. Thus, according to some embodiments, an interleaf layer, which can for example be made of a plastic material and which has been provided between the layers of the flexible substrate in a previous step, can be wound on the roll 113 in the unwinding chamber 110. Further, another interleaf layer such as a fresh interleaf layer can be wound from the roll 113 in the winding station 110′, and can be fed between the layers of the flexible substrate. Thereby, a direct contact between the backside of the flexible substrate of one layer and the front side of the substrate of the subsequent layer can be avoided. In light of the above, an interleaf layer roll 113 can be provided. An interleaf layer can be provided when the substrate is on the roll 114, the substrate is transported through the deposition system without the interleaf layer, and another interleaf layer is again provided when the substrate is wound on another roll 114. According to yet further embodiments, the above described principle of providing an interleaf layer can be provided for any of the embodiments described herein. Thereby, it can be understood, that for the very first time a roll of substrate is used in a system, no interleaf layer is provided, and after the first deposition step an interleaf layer is inserted. Further, some steps might be less critical to a contact between the front and back surface of the web. Thus, after those steps an interleaf layer may also be omitted. Accordingly, different further embodiments may include an interleaf layer roll 113 on the winding side only or on the unwinding side only.
In the figures shown herein, the rollers 112 and 112′ are schematically drawn such that the front surface of the substrate would be touched by the roller. It is to be understood, that due to other arrangements of rollers 112, 113, and 114, respectively, or due to additional rollers 112, a contact of the front surface of the web can be avoided. Such arrangements, which can be combined with any of the other embodiments described herein, yield yet further embodiments. Alternatively, rollers 112, 112′ and/or other rollers may be provided as contact-less gas cushion roller, e.g. as described above.
From the unwinding station 110, the flexible substrate is guided to the deposition chamber 120 and further to the winding station where the flexible substrate is wound on a roll 114′ in the winding station 110′. Again, the winding station 110′ can include one or more rollers 112′ in order to guide the flexible substrate and to control tension, winding characteristics, or the like.
According to yet further embodiments, the modularity of a thin film deposition system can be further increased as shown in
As shown in
According to yet further embodiments, which can be combined with other embodiments described herein, the substrate guiding system used in the first (left) chamber of
After deposition in the first chamber, the substrate 10 is guided to the second (right) chamber. Therein, guiding rollers 141 can be provided similarly as the guiding rollers 131 in the last chamber. The substrate guiding system 140 in the right chamber 120 includes, in the example shown in
According to embodiments described herein, the substrate guiding system 140 in the right chamber and the substrate guiding system 130 in the left chamber can both be provided in the same chamber housing. In light of the above, according to different embodiments described herein, which can be combined with other embodiments described herein, the chamber 120 provides a common or uniform platform for different substrate guiding systems 130, 140 and different deposition units 150 and 160. Thus, the modularity of the deposition system can be provided. This improves the flexibility of a factory for manufacturing consumer electronic devices, it reduces the number of spare parts that need to be provided for avoiding significant downtimes of the deposition system, it increases the flexibility for combining different deposition processes, or reduces the costs for manufacturing deposition chambers and, thus, deposition systems.
As shown in
According to some embodiments, the deposition unit assembly illustrated by the cathodes 162 is supported by plate 622. As indicated by the arrow in
Thereby, the deposition unit assembly and the substrate guiding unit can be separated while the substrate is in a guiding position through the deposition system. Accordingly the substrate can stay within the chamber 120 during maintenance for which the chamber is open. In other words, the substrate remains in the deposition area while the cathodes 162 can be removed (towards the left as shown in
A further thin film deposition system 1000 is shown in
As shown for example in
For example, the system shows regions 1110 in the winding and unwinding station, regions 1011 in the load lock chambers 1010, regions 1024 in the laser scribing chambers 1020, gas cushion regions 1123 in the processing chambers 120, web guiding regions 1122 in the processing chambers 120, and processing regions 1121 and 1120 in the processing chambers. One or more of these regions each can have different atmospheres, e.g., pressures. For example, the gas insertion due to the gas cushion regions can be separated to reduce the influence on other regions by gas separation means.
According to different embodiments, which can be combined with other embodiments described herein, the regions 1123 for enclosing the gas cushion rollers 135 can have a pressure of 1 mbar to about 1˜10-2 mbar, whereas during operation the other regions my be evacuated during operation to a pressure of 1·10-2 mbar to 1·10-4 mbar.
According to yet further embodiments, which can be combined with other embodiments described herein, after each of the processing chambers 120 a further substrate treating chamber 1020 is provided. The substrate treating chambers 1020 each include equipment for laser processing the front surface of the substrate. According to different embodiments, a laser 1022, one or more mirrors 1024, and/or at least one lens 1026 are provided in the laser scribing chambers 1020. A laser beam 1028 is guided onto the front surface of the substrate, i.e. the surface onto which the thin film has been deposited in the previous processing chamber 120. Thereby, the contacts for a solar cell can be defined by the laser scribing of the contact material.
According to some embodiments, which can be combined with other embodiments described herein, the processing chamber 120 is designed such as to allow a deposition of a transparent conductive oxide layer onto the substrate which is preferably a flexible substrate. The transparent conducive oxide TCO may be deposited by a sputtering process, especially a reactive sputtering process or Low Pressure Chemical Vapour Deposition LPCVD, so that the processing chamber 120 can be further equipped with a cathode evaporation device.
According to yet further embodiments, which can be an optional modification of other embodiments described herein, the TCO layer deposited in the treating chamber 6 may be an aluminium doped zinc oxide layer, a fluorine doped tin oxide (F—SnO), indium doped tin oxide (ITO) or a similar layer used in the photovoltaic industry for making the front contact.
The system 100 is designed to handle flexible substrates. In order to achieve a high electrical output from a solar cell module, the modules are made of an array of single photovoltaic cells being arranged in rows and columns adjacent to each other on the module. In order to produce such a plurality of separated photovoltaic cells, the layers deposited to form a photovoltaic structure are patterned or structured in order to form trenches in the respective layers so as to separate specific areas forming single photovoltaic cells. Accordingly, this process is also designated as trenching.
In light of the above, the system 1000 can include a further processing chamber 120 following successively the first chamber along the transport path of the web.
The patterning step in the treating chamber 1020 can be carried out by a laser process. Thereby, a laser having a laser beam focused by lens 1026 scans over the surface of the substrate or the layer deposited in the processing chambers, respectively, in order to cut a trench into said layer. Accordingly, this process is also designated as scribing a pattern or structure into a surface of the substrate. Instead of moving the laser beam over the surface to be treated, the substrate may be moved with respect to the fixed laser beam or combined movement may be carried out. Such a relative movement can also be applied to other patterning methods like mechanical patterning or maser patterning.
During the patterning step in treating chamber 1020, the particles removed by laser cutting may be blown away by a blowing gas stream of inert gas directed onto the surface of the substrate to be treated and/or sucked off from the surface of the substrate by suction means. For this purpose, nozzles for blowing inert gas onto the substrate as well as to suck off a surface area of the substrate may also be moved over the surface of the substrate similar to the laser beam. In addition, other cleaning processes may be simultaneously carried out during the patterning step. For example, electrostatic cleaning may be used. For this process, the substrate is set to a specific electrical potential in order to charge the particles removed by the laser beam. Spaced apart from the substrate, counter electrodes may be provided to electrically attract the charged particles and thereby remove the loose particles from the substrate.
Alternatively or in addition to the cleaning during the patterning step, a further treating chamber (not shown) for carrying out a cleaning step may be provided.
After depositing a semiconductor layer in the processing chamber 120, the substrate 10 is moved to the chamber 1020 wherein a patterning or structuring of the deposited layer is performed. For this purpose, a laser device 1022 is disposed inside or outside the vacuum chamber 1020. The laser device produces a focused laser beam 1028 which is directed onto the surface of the substrate 10 or the layer deposited thereon, respectively. If, according to some embodiments, the laser is provided outside the chamber, a window being transparent for the laser light produced by the laser is disposed in the respective sidewall of the chamber.
The laser light beam can be moved over the surface of the substrate in order to produce trenches. By the trenches, the deposited layer is divided into separate areas to form separate photovoltaic cells on a common substrate.
In light of the above, a plurality of embodiments have been described. For example, according to one embodiment, a system for thin film deposition on a flexible substrate having at least a first deposition region is provided. The system includes a first chamber being based on a platform, wherein the first deposition region is within the first chamber, wherein the first chamber has a first support member configuration configured for supporting at least two different substrate guiding systems and wherein one substrate guiding system is supported by the first support member configuration, and wherein the platform is configured for at least two different deposition units and wherein one deposition unit of the at least two different deposition units is enclosed by the first chamber. According to an optional modification thereof, the system may further include at least a second deposition region; and a second chamber being based on the platform, wherein the second deposition region is within the second chamber, wherein also the second chamber has one of the first support member configurations configure for supporting at least two different substrate guiding systems and wherein one substrate guiding system is supported by the first support member configuration, wherein the first chamber and the second chamber are both provided between unwinding and winding of the flexible substrate. According to yet further additional or alternative modifications, the at least two different substrate guiding systems can be selected from the group consisting of a free-span substrate guiding system and a cooling drum substrate guiding system; the at least two different substrate guiding systems may each include a gas cushion roller for guiding the flexible substrate with the surface of thin film deposition towards the gas cushion roller without mechanical contact to the roller, for example, such that the gas cushion roller is provided in a gas cushion region, which is separated from the first deposition regions such that different pressures can be provided in the gas cushion region and the first deposition region; the system can be a roll-to-roll thin film deposition system; and/or the system can be a PVD thin film deposition system. According to yet further embodiments, which can be combined with any of the other embodiments and modifications above, the first chamber can be adapted for depositing a first layer on the substrate and the second chamber is adapted for depositing a second layer above the first layer, and wherein a free-span substrate guiding system is disposed in the first chamber for allowing a deposition process at a first temperature above 200° C., e.g., above 300° C., and wherein a cooling roller substrate guiding system is disposed in the second chamber for allowing a deposition process at a temperature below 100° C.; the free-span substrate guiding system can be disposed in the first chamber for allowing a deposition process at a first temperature above 300° C.; a first deposition unit of the at least two deposition units can include two or more cathodes; and/or a first cathode of the two or more cathodes and a second cathode of the two or more cathodes can be disposed in different areas separated by a main gas separation unit. For example, the two or more cathodes are planar sputtering cathodes. According to yet further additional or alternative modifications at least four cathode support members can be provided such that at least two of the cathode support members are adapted to electively support a cathode or an optional gas separation unit, respectively; and/or at least one interleaf layer roll can be provided for winding an interleaf layer coming from between layers of the flexible substrate or unwinding an interleaf layer provided between layers of the flexible substrate.
According to another embodiment, a method of manufacturing a layer stack of a flexible photo voltaic cell is provided. The method includes unwinding a flexible substrate from a roll; guiding the flexible substrate in a first chamber being based on a common platform; depositing a first layer on the flexible substrate; guiding the flexible substrate from the first chamber to a second chamber, wherein the second chamber is based on the second platform; depositing a second layer above the first layer; guiding the flexible substrate from the second chamber; and winding the flexible substrate on a roll. According to an optional modification thereof the method can further include heating the substrate to a temperature of 300° C. or above for the depositing of the first layer; and cooling the substrate to a temperature of 100° C. or below for the depositing of the second layer. According to yet further embodiments, which can be combined with the above modification or the above embodiment, the transport speed of the flexible substrate can be from 0.1 m/min to 10 m/min, typically from 1 m/min to 5 m/min; the time between the depositing of the first layer and the time between depositing the second layer can be 60 min or less, typically 5 min or less; the depositing of the first layer can be conducted on a free-span substrate guiding system, and wherein the depositing of the second layer is conducted on a cooling drum substrate guiding system; the substrate can be guided over a gas cushion roller at least for the guiding of the flexible substrate from the first chamber to a second chamber; the substrate can be exposed to at least two different deposition atmospheres in the first and/or the second chamber; and/or a thin film deposition system according to any of the embodiments described herein can be used for the manufacturing of the layer stack of the flexible photo voltaic cell.
According to embodiments described herein, the chambers can be provided in a modular manner such that between unwinding and winding, free-span and cooling rollers can be combined. A combination or switching between free-span and cooling rollers can be provided based on a common platform.
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.
