Solution tempering device for rotational coating systems

Abstract

The invention relates to a device for solution temperature control for spin coating systems. The device comprises at least one heat exchanger, which is formed from at least one Peltier element (2, 2') and at least one heat accumulator (1). The at least one Peltier element (2, 2') is in direct thermal contact with the at least one heat accumulator (1). Heat exchange fins (4, 4', 4'', 4''') are arranged on the side of the at least one Peltier element (2, 2') facing away from the heat accumulator (1), and on these, in turn, at least one driven turbomachine (3, 3', 3'', 3'''). At least one recess for receiving solution reservoirs or for directly receiving solution (5, 6, 7) is provided in the at least one heat accumulator (1).

Description

The invention relates to a solution tempering device for spin coating installations, such as one used in chemical technology for adjusting the temperature of a solution for spin coating.It is generally known that reactions or processes with regard to chemistry and in particular also physiology may be temperature-dependent. In physicochemical chemistry, this relates in particular to the kinetics of reactions, i.e. the rate or the time sequence of the reaction, transport processes such as diffusion, evaporation, solidification, and here in particular crystallization and others. The influencing of reactions or processes with regard to processes which are dependent on the temperature, as listed above by way of example, is thus the subject matter of, for example, chemical and electrochemical process technology. The setting and control of the temperature both in its increase (heating) and in its reduction (cooling) can be effected in a variety of ways. Examples are direct contact with a heating plate or heat sink (conduction), contact with a heating medium or a cooling liquid, as is usually in heat exchangers, or e.g. simply via thermal radiation.An example of temperature-dependent processing is the so-called spin coating for depositing thin layers, as is used, for example, for producing solar cells. In spin coating, solutions are deposited on a workpiece, usually a disk such as a wafer, wherein the solutions can be solution mixtures which react after the coating and evaporate the solvent or solutions in which the dissolved substance precipitates and solidifies or crystallizes as a result of the evaporation (concentration) of the solvent, wherein the precipitation and crystallization or solidification can also be effected by temperature change or both mechanisms--concentration of the solution and temperature change--cooperate. The kinetics of the evaporation of the solvent have an influence on the quality and type of crystallization, and also on a possible temperature profile or constant temperature, in particular for layers to be deposited for which crystallization is intended. The evaporation is in particular temperature-dependent and further dependent, for example, on a flow rate of a gas and the pressure. The workpiece is rotated during the deposition, for which purpose it is fixed on a rotary plate by means of vacuum suction. The turntables used for vacuum suction of workpieces are referred to as "chuck". Rotational speeds of up to 10,000 / min and more are achieved in the spin coating.U.S. Pat. No. 4,886,012 discloses a spin coating plant in which the solution to be spun is initially stored at a reaction temperature, in order to then be heated in the supply of the solution for spinning, so that the solution can then react through on the rotating substrate. The spin coating takes place here in a process chamber. The heating of the solution in the feed for the rotary coating takes place via heating ribs which are arranged on the outside of the feed pipe for the solution. The substrate is mounted on a chuck.Cooling of the process chamber of a spin coating plant is disclosed in U.S. Pat. No. 6,001,418. Here, cooling coils are mounted inside the process chamber to condense excess CO 2.The object is to provide a method for performing a processIt is an object of the invention to provide a solution tempering device for spin coating plants, with which solutions can be both heated and cooled and with which a temperature constancy which is improved compared with the prior art can be achieved and which is of simplified construction and can be produced.The object is achieved by the subject matter of claim 1.The invention is based on the use of a heat exchanger for tempering storage containers for solutions using at least one Peltier element in cooperation with heat exchange ribs and a heat store. A heat exchanger in the sense of the invention is a device with which heat transport is realized, i.e. a transfer of thermal energy from one system to another.The heat store is formed from a material having a high "volumetric" heat capacity, i.e. a "volumetric" heat capacity y in the range of approximately 2500 kJ / (m 3 K) (1000-3500 kJ / (m 3 K) with at the same time not too low a thermal conductivity, i.e. a thermal conductivity λ in the range of 15 W / (m·K) ≤ λ ≤ 5300 W / (m·K) (stainless steel to graphene), and is preferably provided as a block, i.e. solid, in which recesses are provided as receptacles for solution reservoirs or for forming the reservoirs themselves. The block can be designed as a cuboid, cylinder or similar shape, advantageously as a shape with flat boundary surfaces, such as a cuboid or a prism. Possible suitable materials for forming a heat store are, for example, aluminum, silicon and gold, wherein aluminum combines the most advantages (in terms of heat capacity, thermal conductivity, price and moldability).A reservoir in the sense of the invention is to be considered a storage container, wherein the "container" can also be formed by recesses, also referred to as depressions or recesses for receiving the solution reservoirs or the solutions themselves, in the heat store. A storage container is otherwise provided, for example, by test tubes or test tubes, depending on the solution, for example made of glass or plastic, which are to be arranged in an advantageous manner in a form-fitting manner in the recesses or receptacles in the heat store. For supplying solution to a spin coating plant, corresponding suction devices are to be arranged on or in the solution reservoirs.The heat exchanger is formed using at least one Peltier element in cooperation with heat exchange ribs for tempering the heat accumulator. In addition, depending on requirements, flow machines driven for the discharge or supply of heat, such as fans, and heat exchange ribs, are provided.Peltier elements are electrothermal transducers in which a temperature difference is generated in the case of a current flow or a current flow (Seebeck effect) is generated in the case of a temperature difference, wherein the Peltier elements are usually configured such that the temperature difference is present between two sides of the Peltier element, which are usually also plate-shaped, as is also the case for the Peltier elements contemplated according to the invention. The temperature difference is dependent on the current flow quantity and controllable via the latter. It forms in the Peltier element in relation to the ambient temperature and can be influenced in particular by a targeted temperature control of one side of the Peltier element. The polarity of the temperature difference is also reversible by changing the direction of the current flow through the Peltier element. Peltier elements can accordingly be used both for cooling and for heating. Peltier elements are usually brought into direct physical contact (conduction) with a workpiece to be cooled or heated for temperature control. The side not brought into contact with the workpiece to be temperature-controlled is overflowed with a fluid for transporting away heat if necessary for the purpose of discharging or supplying heat, in particular in the case of cooling a workpiece for the purpose of discharging. The invention makes use of the properties of the Peltier elements of the possibility of a rapid and simple reversal of the polarization, i.e. switching between cooling and heating and the very good constant temperature. The very good constant temperature means a very good constant temperature control of the heat accumulator, which in turn controls the temperature of the solutions, from which a very good thermostatting of the same takes place. Peltier elements also have the advantage that cooling fluids are not necessarily required for their use, but can also be sufficiently cooled with gas streams, so that a device according to the invention, which is equipped with Peltier elements, can be operated safely even in environments with a special atmosphere, such as evacuated chambers or chambers with an inert atmosphere, in particular, for example, glove boxes as well, since an escape of a liquid is ruled out.According to the invention, the at least one Peltier element is in direct thermal contact with the heat accumulator. The heat store advantageously has at least one contact surface for contacting by the at least one Peltier element. As is provided in one embodiment, the heat store is advantageously shaped as a cuboid and makes contact with Peltier elements on all four side surfaces. This redundancy increases the temperature constancy and the cooling or heating power. On the side of the at least one Peltier element opposite the heat exchanger, the latter is equipped with heat exchange ribs, on which a driven turbomachine for removing or supplying heat from the Peltier element is in turn arranged, preferably a fan. The turbomachine is configured in such a way that a generated flow is directed onto the side of the Peltier element to be temperature-controlled or leads away from the latter. The side of the Peltier element to be temperature-controlled is the side which faces outwards with respect to the heat accumulator. To produce a sufficient contact for heat transfer between a Peltier element and the heat store or a Peltier element and the heat exchange ribs associated therewith, heat-conducting paste can be arranged in each case on the contact surfaces.The heat exchange fins can be designed in any form that promotes increased heat exchange through increased surface area. Examples of forms of heat exchange fins are, for example, lamellae, strips, plates, corrugated or flat or rods, round or angular, corrugated or straight or also, for example, provided by lattice-like arrangements of the mentioned forms. In the case according to the invention, the heat exchange ribs serve in particular for cooling, i.e. dissipation of heat from the side of the Peltier element which faces away from the heat accumulator (directed outwards). The heat exchange fins are made of a material having a thermal conductivity λ in the range of 15 W / (m·K)≤λ≤5300 W / (m·K) (stainless steel to graphene). Aluminum having a specific thermal conductivity of 235 W / (m·K) is also advantageous for forming the heat exchange fins with good formability and low price. In order to produce the greatest possible cooling effect in cooperation with a driven turbomachine, the heat exchange ribs are preferably arranged in such a way that the intermediate spaces between the ribs form flow channels or flow paths which allow unhindered flow from the turbomachine to the Peltier element.Driven turbomachines within the meaning of the invention are, for example, fans, propellers and centrifugal pumps. Fans are advantageous for the functionality of the invention, since these are suitable for simple arrangement in or at the ends of the flow channels for reasons of design. Fans are also advantageously suitable with respect to the fluid to be moved with the turbomachine, namely gas, in particular air. This also applies to the volumes and velocities of the gas streams to be expected according to the invention. All forms of fans, such as axial, diagonal or radial fans, can be used functionally. The turbomachines can also be those in which the direction of the gas stream generated can be reversed by reversing the direction of rotation. The turbomachines used according to the invention are driven machines, i.e. machines driven by motors.In a further embodiment, the device is equipped with a thermal insulation which additionally increases the temperature stability by preventing the heat exchange with the environment. The thermal insulation is to be produced in particular from materials which are suitable for 3D printing and are thus to be produced per se with 3D printing. The thermal insulation is also to be configured such that it comprises guides for the electrical contactings, e.g. of the Peltier elements.The dimensioning of the apparatus depends on the size of the spin coating plant and the amounts of solution processed there. The dimensioning can be flexibly adapted by appropriate configuration of the individual components. In the case of customary volumes of solution reservoirs for spin coating installations, the edge length is in a range from 10 cm to 30 cm.The temperature T p which can be set with the device proposed here for tempering solutions, is in a range of 4° C.≤T p ≤80° C.The inventive solution tempering can be advantageously economically assembled from already manufactured components, wherein certain parts, such as e.g. the thermal insulation, are also to be manufactured by 3D printing. Due to the provision of the Peltier elements, it has a constant temperature of ±0.1° C. over the entire temperature range. A further advantage is that solutions can be both heated and cooled.Example:The invention is described in more detail with reference to an exemplary embodiment and with reference to 1 figure.The figure shows: FIG. 1 : Schematic illustration in oblique plan view of an apparatus according to the invention for solution tempering for spin coating plantsFIG. 1 schematically shows an exemplary embodiment of an apparatus according to the invention for solution tempering for spin coating plants. In the example, the heat store 1 is made of aluminum as a cuboid and has the dimensions 55 m high 70 mm wide 70 mm deep. On one side of the cuboid, a total of six recesses in the form of blind holes with three different diameters 5, 6, 7 are formed. The smallest diameter recess 5 is provided for receiving thermometers for temperature control. The remaining recesses 6, 7 serve, in the example, for the form-fitting reception of test tubes as solvent reservoirs with different volumes. The side with the recesses in the cuboid defines the top side of the device. On the surrounding four sides of the heat accumulator 1, a Peltier element 2, 2' (the remaining two are not shown for the sake of perspective illustration) is arranged in each case in direct thermal contact with the heat accumulator 1. On the four Peltier elements 2, 2' heat exchange ribs 4, 4', 4", 4"' of aluminum in the form of rods are arranged, respectively, for improved heat transport from the Peltier element. On the heat exchange ribs, driven fluid-flow machines in the form of fans 3, 3', 3", 3"' are in turn arranged, which additionally ensure heat transport by gas flow. For reasons of clarity, the electrical connections of the individual components are not shown, as are devices for suctioning or transporting the solutions to a spin coating plant.The Peltier elements 2, 2' are commercially available and have a maximum input power of 142 W each and can achieve a temperature difference of up to 68 K between their two sides.In a further exemplary embodiment (not shown), a positive thermal insulation made of 3D pressure-compatible plastic is produced for the device with the aid of 3D pressure. This arrangement additionally improves the constant temperature.Temperatures of 4°C to 80°C can be established. The constant temperature is at ±0.1° C. over the entire temperature range using the apparatus according to the invention described above. The advantages of the invention of a temperature constancy which is improved compared with the prior art and which is simple and flexible production are thus demonstrated. With the aid of the Peltier elements, both cooling and heating can be carried out.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedU.S. Pat. No. 4,886,012

[0004] U.S. Pat. No. 6,001,418

[0005]

Claims

Device for solution tempering for spin coating installations comprising at least one heat exchanger, formed from at least one Peltier element (2, 2') and at least one heat accumulator (1), and wherein the at least one Peltier element (2, 2') is in direct thermal contact with the at least one heat accumulator (1) and heat exchange ribs (4, 4', 4", 4"') are arranged on the at least one Peltier element (2, 2') on its side facing away from the heat accumulator (1), on which ribs at least one driven turbomachine (3, 3', 3", 3"') is arranged in turn, and wherein at least one cutout for receiving solution reservoirs or for directly receiving solution (5, 6, 7) is provided in the at least one heat accumulator (1).Device according to Claim 1, characterized in that the heat store (1) is designed in the form of a cuboid having four side walls and a Peltier element (2, 2') is arranged in each case on all four side walls, and heat exchange ribs (4, 4', 4", 4"') being arranged on each Peltier element (2, 2') on a side facing away from the heat store (1), on which ribs at least one driven turbomachine (3, 3', 3", 3"') is arranged in turn.Device according to claim 1 or 2, characterised in that the device is provided with a thermal insulation.

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