Method for using TLE system and TLE system

Abstract

The invention relates to a method of using a thermal laser evaporation (TLE) system (10), the TLE system (10) comprising: a reaction chamber (12) that can be filled with a reaction atmosphere (14); a substrate (16) arranged in the reaction chamber (12); one or more sources (40) arranged in the reaction chamber (12), each source (40) comprising a source component (42) consisting of a source material (44); and a laser source (20) for providing a laser beam (22) that impinges on the source assembly (42) to vaporize or sublimate the source material (44) to provide a flux (70, 72) of vaporized or sublimated source material (44) for deposition on the substrate (16). Further, the invention relates to a corresponding TLE system, the TLE system (10) comprising: a reaction chamber (12), which can be filled with a reaction atmosphere (14); a substrate (16) arranged in the reaction chamber (12); one or more sources (40) arranged in the reaction chamber (12), each source (40) comprising a source component (42) consisting of a source material (44); and a laser source (20) for providing a laser beam (22) that impinges on the source assembly (42) to vaporize or sublimate the source material (44) to provide a flux (70, 72) of vaporized or sublimated source material (44) for deposition on the substrate (16).

Description

Technical Field

[0001] The present invention relates to a method using a thermal laser evaporation (TLE) system, the thermal laser evaporation system comprising: a reaction chamber that can be filled with a reaction atmosphere; a substrate disposed in the reaction chamber; one or more sources disposed in the reaction chamber, each source comprising a source assembly composed of a source material; and a laser source for providing a laser beam that irradiates the source assembly to evaporate or sublime the source material, thereby providing a flux of the evaporated or sublimed source material for deposition on the substrate. Additionally, the present invention relates to a corresponding TLE system, the TLE system comprising: a reaction chamber that can be filled with a reaction atmosphere; a substrate disposed in the reaction chamber; one or more sources disposed in the reaction chamber, each source comprising a source assembly composed of a source material; and a laser source for providing a laser beam that irradiates the source assembly to evaporate or sublime the source material, thereby providing a flux of the evaporated or sublimed source material for deposition on the substrate. Background Art

[0002] In thermal laser evaporation (TLE), source materials are evaporated and / or sublimed in a controlled environment (especially in a reaction chamber filled with a reaction atmosphere) by laser heating, typically intended to coat a substrate that is also disposed in the reaction chamber. In other words, coating the substrate is provided by depositing a flux of the evaporated and / or sublimed source material on the surface of the substrate.

[0003] As shown in FIG. 1, it is known to use a mechanically operated shutter 80 in a prior art thermal laser evaporation system 10 to actively block and release the deposition flux 74 to regulate the coating of the substrate 16. The source material 44 of the source assembly 42 of the source 40 is evaporated and / or sublimed by a laser beam 22 that irradiates the source assembly 42, so that in the illustrated embodiment, the laser beam 22 is further constrained by a small hole 18. The shutter 80 does not block the laser beam 22, and thus a constant deposition flux 74 of the evaporated and / or sublimed source material 44 can be established.

[0004] However, the shutter is always an additional device in the reaction chamber, especially exposed to the reaction atmosphere, which covers different variants including ultra-high vacuum or corrosive gases. Usually extremely high temperatures (sometimes exceeding 3500 °C) act on the shutter because especially in a TLE system, the working distance between the source and the substrate is very short. Also, due to this short distance, there may be an interaction between the material of the shutter and the evaporated and / or sublimed source material, resulting in impurities in the coating and / or malfunction of the shutter. If there is more than one source in the reaction chamber and thus more than one source material, cross-contamination between different sources may occur due to the reflection of the evaporated and / or sublimed source material of one source on the shutter towards another source. Summary of the Invention

[0005] In view of the above, the object of the present invention is to provide an improved method using a thermal laser evaporation system and an improved thermal laser evaporation system, which do not have the above-mentioned disadvantages of the prior art. In particular, the object of the present invention is to provide an improved method using a thermal laser evaporation system and an improved thermal laser evaporation system, so as to be able to provide a flux of source material for evaporation and / or sublimation that can be adjusted (in particular turned on and off) in a controlled and arbitrary manner, and in particular to provide a flux of source material for evaporation and / or sublimation that rises to the desired flux level immediately or at least after a short time and / or drops to the desired flux level immediately or at least after a short time.

[0006] This object is achieved by the respective independent patent claims. In particular, this object is achieved by a method of using a thermal laser evaporation (TLE) system as described in independent claim 1 and by a thermal laser evaporation system as described in independent claim 22. The dependent claims describe preferred embodiments of the present invention. In terms of technical significance, the details and advantages described with respect to the method according to the first aspect of the present invention also relate to the thermal laser evaporation system according to the second aspect of the present invention, and vice versa.

[0007] Hereinafter, the terms "power" and "intensity" of the laser beam are used as synonyms, because intensity represents power per unit area, and in the present application, the area irradiated by the incident laser beam is not relevant, or at least not significantly relevant.

[0008] According to a first aspect of the present invention, this object is achieved by a method of using a thermal laser evaporation (TLE) system, the TLE system comprising: a reaction chamber that can be filled with a reaction atmosphere; a substrate disposed in the reaction chamber; one or more sources disposed in the reaction chamber, each source comprising a source assembly composed of a source material; and a laser source for providing a laser beam that irradiates the source assembly, thereby evaporating or sublimating the source material, so as to provide a flux of evaporated or sublimated source material for deposition on the substrate.

[0009] The method according to the present invention comprises the steps of:

[0010] a) determining a desired flux of the source material evaporated and / or sublimated by the laser beam,

[0011] b) determining a nominal thermal energy stored in the source assembly corresponding to the desired flux,

[0012] c) determining a nominal intensity of the laser beam corresponding to the desired flux when the source assembly stores the nominal thermal energy,

[0013] d) determining the actual thermal energy stored in the source assembly,

[0014] e) determining the operating intensity of the laser beam depending on the deviation between the actual thermal energy and the nominal thermal energy, wherein,

[0015] - If the actual thermal energy is less than the nominal thermal energy, the working intensity is higher than the nominal intensity, and

[0016] - If the actual thermal energy is higher than the nominal thermal energy, the working intensity is less than the nominal intensity, and

[0017] f) Provide a laser beam with this working intensity.

[0018] The method according to the first aspect of the present invention is intended to use a thermal laser evaporation system, or briefly a TLE system. In particular, the scope of the present invention is a TLE system in which a laser is used to evaporate or sublimate a source material. Such systems are generally known. The laser beam provided by the laser source is used to evaporate and / or sublimate the source material, and in most cases, for the deposition of the source material evaporated or sublimated on a substrate set as a target. The source material is provided as a source component in a source arranged in a reaction chamber, where there may be one or more sources, in particular providing the same and / or different source materials. The laser beam is irradiated on the surface (in most cases, the upper surface) of the source component to provide a flux of the source material to be evaporated or sublimated.

[0019] The source is arranged in the reaction chamber, which can be sealed relative to the ambient atmosphere and filled with a reaction atmosphere. The reaction atmosphere can be a vacuum, in particular as low as 10 -12 hPa or even lower, or include a reaction gas at a pressure suitable for material deposition, such as a reaction gas providing oxygen for the deposition of oxides of elemental or compound source materials to be evaporated and / or sublimated. The maximum value tested at a working distance of 60 mm is up to 10 -12 hPa. Higher values may be feasible because deposition can be carried out without problems at 10 -12 hPa.

[0020] In most cases, at least the main part of the laser source is arranged outside the reaction chamber, and the laser beam is coupled into the reaction chamber via a coupling device. The coupling device can be, for example, a simple window located in the chamber wall of the reaction chamber. However, the coupling device according to the present invention can also include an adaptive optical component to form a laser beam irradiated on the surface of the source component.

[0021] By the method according to the present invention, it is possible to provide the possibility of turning on and off the flux of the provided evaporated and / or sublimated source material in a controlled and arbitrary manner. In a TLE system according to the prior art, even when using a laser source providing a laser beam with a power of 1 to 10 kW or more, the laser beam provided by the laser source can be turned on and off with a rise time of microseconds and thus turned on and off substantially immediately relative to the flight time of the evaporated and / or sublimated particles. In addition, the power change of the provided laser beam during operation can be achieved so quickly.

[0022] In addition, it has been shown that the actually provided flux strongly depends on the laser power. The experimental data give an approximate Arrhenius-type dependence of the flux on the laser power. In other words, the flux decreases exponentially with the inverse of the laser power. For example, for Al, changing the laser power by a factor of ten, e.g., from 200 W to 2000 W, results in a flux change of approximately three orders of magnitude (1000 times), varying within a range of growth rates from a few to thousands . The method according to the invention makes use of and is based on these findings.

[0023] In a first step a) of the method according to the invention, the main objective of using the TLE system is defined, i.e., the desired flux of the source material to be evaporated and / or sublimated that should be provided. For example, the desired flux may be the flux of the source material to be evaporated and / or sublimated required for a specific coating of a substrate also arranged in the reaction chamber. In other words, the desired flux should be provided within the respective TLE system.

[0024] Due to the given vapor pressure of the source material, the flux of the source material to be evaporated and / or sublimated depends approximately exponentially on the temperature of the source assembly, more precisely on the surface temperature of the source assembly. Thus, the surface temperature is associated with the flux of the source material to be evaporated and / or sublimated emitted from the surface. An irradiated laser beam is used to change the temperature and thus effectively change the provided flux of the source material to be evaporated and / or sublimated.

[0025] However, a non-negligible part of the energy of the irradiated laser beam is stored as heat energy in the source assembly. This occurs as long as the entire source assembly reaches a thermal equilibrium in which the incident energy provided by the laser beam is equal to all the outgoing energy losses including the source material to be evaporated and / or sublimated, but also including, for example, radiation losses. In other words, as long as this equilibrium is not reached, the temperature of the bulk of the source assembly rises, also causing the temperature of the surface of the source assembly to rise. Due to the above-mentioned correlation between the surface temperature and the provided flux of the source material to be evaporated and / or sublimated, the provided flux also rises until the thermal equilibrium is reached.

[0026] It has been pointed out that even in the steady state of this thermal equilibrium, in most cases, there is no uniform temperature in the bulk or at the surface of the source assembly. Due to the effective heat loss via radiation, there are always very strong temperature gradients along the surface and throughout the bulk. However, in the steady state, these gradients are time-invariant. This means that they have a strong spatial variation but no time variation.

[0027] In the next step b) of the method according to the invention, the nominal thermal energy stored in the source component is determined, where the nominal thermal energy corresponds to the desired flux. In the sense of the present invention, the thermal energy "corresponding to the desired flux" is the thermal energy stored in the source component when the above-mentioned thermal equilibrium is reached.

[0028] Thus, in the case where the source component stores the nominal thermal energy, the temperature of the surface is substantially constant, and a stable supply of the desired flux can be ensured by simply providing a laser beam with an appropriate intensity.

[0029] The intensity of the laser beam required after reaching the thermal equilibrium is determined in the next step c) of the method according to the invention by determining the nominal intensity of the laser beam. In other words, if the source component stores the nominal thermal energy, the laser beam irradiating the source component at the nominal intensity results in the desired flux of the evaporated and / or sublimated material.

[0030] However, during the evaporation and / or sublimation of the source material in the TLE system, the above-mentioned thermal equilibrium is not always established. Especially after the desired flux changes, particularly at the beginning of the evaporation and / or sublimation process, the equilibrium is far from being reached, and the actual thermal energy stored in the source component is different from the nominal thermal energy. The actually stored thermal energy of the source component is determined as the actual thermal energy in step d) of the method according to the invention. In other words, after step d) of the method according to the invention, information on the actual value of the thermal energy stored in the source component during this evaporation and / or sublimation process is available.

[0031] In the next step e), all this information determined in steps a) to d) of the method according to the invention is used to determine the working intensity of the laser beam. The working intensity is determined depending on the deviation of the actual thermal energy from the nominal thermal energy. In other words, it is determined whether the actual thermal energy is different from the nominal thermal energy, and if applicable, by how much the actual thermal energy differs from the nominal thermal energy.

[0032] If the actual thermal energy is less than the nominal thermal energy, the above-mentioned thermal equilibrium has not been reached. In other words, the intermediate temperature of the bulk of the source component is less than the surface temperature of the source component required to evaporate and / or sublimate the source material at the desired flux. In particular, due to the dependence of the working intensity on this deviation of the actual thermal energy from the nominal thermal energy, it is considered how much irradiation laser energy is used to heat the bulk of the source component instead of actually evaporating and / or sublimating the source material. Therefore, the working intensity is determined to be higher than the nominal intensity to at least partially compensate for the energy of the laser used to heat the bulk of the source component. In summary, this results in the temperature of the surface of the source component being higher than the temperature of the bulk of the source component, thereby causing the actual flux of the evaporated and / or sublimated source material to be at least closer to the desired flux, preferably substantially equal to the desired flux.

[0033] Conversely, if the actual thermal energy is higher than the nominal thermal energy, the bulk temperature of the source assembly (and thus, in most cases, the temperature of the surface of the source assembly) is higher than the temperature required for the desired flux of the evaporation and / or sublimation source material, resulting in an actual flux that is higher than the desired flux. Therefore, consider how low the operating intensity can be set relative to the nominal intensity to once again achieve thermal equilibrium and at the same time ensure the evaporation and / or sublimation of the source material at the desired intensity, both as quickly as possible. The reduction of the thermal energy of the source assembly is provided, for example, by radiative cooling. This is an effective cooling method especially for the high temperatures of the source assemblies that are often present in TLE systems because this radiative cooling is proportional to the fourth power of the actual temperature.

[0034] In the last step f) of the method according to the invention, a laser beam with the operating intensity determined in step e) is provided. In accordance with the above description, the operating intensity of the laser beam is determined so that the corresponding changes (increases and decreases) in the desired flux can be taken into account in a fast and effective manner. In particular, compared to simply turning on a laser source with a fixed power, an increase (even starting from zero) between the desired fluxes can be provided faster by the method according to the invention. In addition, changes (especially increases and decreases) between non-zero desired fluxes can be provided in a fast and reliable manner by the method according to the invention, especially faster than simply ramping the laser source to the next desired intensity. Thus, the flux of the evaporation and / or sublimation source material can be adjusted in a controlled and arbitrary manner. In particular, the flux of the evaporation and / or sublimation source material provided immediately or at least after a short time rises to the desired flux level, and / or immediately or at least after a short time drops to the desired flux level.

[0035] In addition, the method according to the invention may include: in step a), determining the desired flux temperature of the surface of the source assembly corresponding to the desired flux, and wherein, in step e), if the actual thermal energy is less than the nominal thermal energy, setting the operating intensity to a value higher than the nominal intensity such that the desired flux temperature is reached at the surface of the source assembly. As described above, the actual flux of the source material evaporated and / or sublimated from the surface of the source assembly by irradiating the laser depends on the actual temperature of the surface of the source assembly. In other words, if the nominal thermal energy is stored in the source assembly, the desired flux temperature corresponds to the bulk temperature and, in particular, also to the temperature of the surface of the source assembly. In the case where the actual thermal energy is less than the nominal thermal energy, the desired flux temperature is higher than the temperature corresponding to the actual thermal energy. By determining the operating intensity so that the surface of the source assembly includes the desired flux temperature determined in step a), it can be ensured that the actual flux of the evaporation and / or sublimation source material matches the desired flux. Therefore, this results in a strong non-uniformity in the heating of the source assembly, and thus the local temperature at the surface of the source assembly can be much higher than the temperature of the rest of the source assembly (especially the bulk) both in time and space.

[0036] According to an improvement of the method according to the invention, the actual temperature of the surface of the source assembly is measured, and in step e), preferably in closed-loop control, the actual temperature is compared with the desired flux temperature. Due to the correlation between the surface temperature and the flux of the evaporating and / or sublimating source material that has been described, measuring the actual temperature of the surface of the source assembly provides an effective way to monitor the actual flux of the evaporating and / or sublimating source material. The measurement can be provided by a suitable temperature sensor, such as a pyrometer. By comparing the measured actual temperature with the desired flux temperature, the deviation of the actual flux from the desired flux can be identified. If the measured temperature is lower than the desired flux temperature, the working intensity determined in step e) will be increased, and vice versa. Implementing the comparison in closed-loop control can provide a stable flux of the evaporating and / or sublimating source material at the desired flux, especially over a long period of time.

[0037] Furthermore, the method according to the invention may be characterized in that: in step d), the actual thermal energy is determined by performing a calculation considering one or more, preferably all, of the following properties:

[0038] – The initial thermal energy stored in the source assembly

[0039] - The mass of the source assembly

[0040] - The heat capacity of the source material

[0041] - The thermal conductivity of the source material

[0042] - The total laser energy radiated onto the source assembly.

[0043] This list is not complete and can be extended by other properties that may affect the actual thermal energy stored in the source assembly. The initial thermal energy provides the starting point for the calculation. The total laser energy irradiated onto the source assembly allows an inference of the amount of thermal energy absorbed by the source assembly. By considering the mass, heat capacity, and / or thermal conductivity of the source assembly, the response of the source assembly to the absorbed energy provided by the laser beam can be inferred.

[0044] Alternatively or additionally, the method may include: in step d), determining the actual thermal energy by comparing with experimental and / or simulation data. The experimental and / or simulation data can be prepared in advance and provided, for example, as a look-up table (preferably, electronically accessible). Thus, the actual implementation of the method according to the invention can be carried out in a less computationally intensive and complex manner, since the computationally intensive calculations have been performed in advance.

[0045] Furthermore, the method according to the invention may be characterized in that, preferably in closed-loop control, steps d) to f), preferably steps a) to f) are repeatedly executed. In the sense of the present invention, the repetition includes a repetition rate of 100 mHz or lower, up to 10 MHz or higher. In other words, during the evaporation or sublimation process, in particular, a repeated or even continuous determination of the actual thermal energy (step d)) is provided, and based on this, a determination of the working intensity (step e)) is provided. Thus, changes in the actual thermal energy stored in the source assembly can be taken into account in a timely manner. This also allows for the provision of a laser beam with the updated and, if necessary, adjusted working intensity (step f)). Therefore, this provides that the desired flux of the source material for evaporation or sublimation can be repeatedly adjusted. Implementing this repetition in closed-loop control (especially based on the repeatedly determined actual thermal energy stored in the source assembly) can provide a stable flux of the source material for evaporation and / or sublimation with the desired flux, especially over a long period of time.

[0046] In addition, the method according to the invention may include: in step e), determining the working intensity such that the difference between the working intensity and the nominal intensity depends on the difference between the actual thermal energy and the nominal thermal energy, or the ratio of the working intensity to the nominal intensity depends on the ratio of the actual thermal energy to the nominal thermal energy. If the nominal thermal energy is higher than the actual thermal energy, the higher the deviation of the actual thermal energy stored in the source assembly from the nominal thermal energy, the more energy of the irradiation laser beam will be used to heat the bulk of the source assembly, and if the actual thermal energy is higher than the nominal thermal energy, the energy of the laser beam irradiated on the source assembly will prevent the decrease of the actual thermal energy. Both the difference and the ratio of this deviation are variables representing the amount of this deviation, whereby this correlation can be taken into account. Thus, a higher or lower deviation of the actual thermal energy from the nominal thermal energy results in a correspondingly more or less significant deviation of the working intensity from the nominal intensity. Therefore, the above-mentioned thermal equilibrium can be achieved more quickly.

[0047] For example, when the evaporation and / or sublimation process starts immediately after the laser beam is turned on, the deviation between the actual thermal energy and the nominal thermal energy will be at a maximum, and thus the deviation between the determined working intensity and the nominal intensity will also be at a maximum. After some time, the bulk of the source assembly will absorb some laser energy and thus heat up, the actual thermal energy will increase, and thus the deviation from the nominal thermal energy will decrease. Therefore, the deviation between the working intensity and the nominal intensity can also be reduced. Eventually, for a constant desired flux, the working intensity ideally converges to the nominal intensity.

[0048] Furthermore, the method according to the present invention can be improved in the following manner: If the actual thermal energy is less than the nominal thermal energy and the deviation exceeds a first threshold value, the working intensity is set to the maximum intensity of the laser beam, and / or wherein, if the actual thermal energy is higher than the nominal thermal energy and the deviation exceeds a second threshold value, the working intensity is set to the minimum intensity of the laser beam, preferably zero. The laser source cannot provide a laser beam with an intensity higher than its maximum intensity, nor can it provide a laser beam with an intensity lower than its minimum intensity or even zero.

[0049] In particular, for determining the working intensity depending on this deviation, the deviation may be so large that this dependence may result in a correspondingly high or low working intensity determined in step e) of the method according to the present invention, which cannot be provided by the laser source. Preferably, the first and second threshold values are selected such that this particularly large deviation can be recognized and at least partially satisfied by providing a laser beam with its maximum or minimum intensity respectively. Therefore, also for a particularly large deviation between the actual thermal energy and the nominal thermal energy, the execution of the method according to the present invention can be ensured by setting the working intensity to a value that cannot be provided, without endangering the structural integrity of the laser source.

[0050] In another improved embodiment of the method according to the present invention, the difference between the working intensity and the nominal intensity is proportional to the difference between the actual thermal energy and the nominal thermal energy, or wherein, the ratio of the working intensity to the nominal intensity is proportional to the ratio of the actual thermal energy to the nominal thermal energy. A ratio is a very simple mathematical relationship between two values, respectively representing the difference or ratio of the actual thermal energy and the nominal thermal energy, and the working intensity and the nominal intensity. In addition, the proportional relationship can be easily implemented in a control algorithm. Therefore, by using a ratio for this relationship, the method according to the present invention can be simplified.

[0051] In addition, the method according to the present invention may include: In step e), if the difference between the actual thermal energy and the nominal thermal energy exceeds 10%, particularly exceeds 1%, preferably exceeds 0.1%, the deviation between the actual thermal energy and the nominal thermal energy is determined. In other words, according to this embodiment, the existence of the deviation is determined only when the actual thermal energy includes values outside the range around the nominal thermal energy.

[0052] In the absence of this range, every determined deviation, even very small, will cause a change in the determined working intensity. In particular, in the later stage of the evaporation and / or sublimation process (in this stage, at least approximately the thermal equilibrium of the source assembly is reached, and thus the working intensity is at least close to the nominal intensity), this may cause an unexpected oscillation of the determined working intensity around the nominal intensity, and thus cause an unexpected oscillation of the actually provided flux of the evaporated and / or sublimated source material around the desired flux. By implementing the above range (within which no deviation is determined), this unexpected oscillation can be avoided.

[0053] In addition, the method may be characterized in that the desired flux is determined over a period of time and / or includes a time dependence. In other words, the desired flux may include a start time and an end time. Thereby, for example, an integrated value of the flux of the provided evaporation and / or sublimation source material may be set. In addition, the time period may also be fragmented, in other words, an active time period (with interruptions therebetween) may be used to determine the desired flux. Additionally or alternatively, the time dependence of the desired flux determined in the sense of the present invention also includes possible variations in the value of the flux itself during the active time period, such as an increase and / or decrease in the flux. Thus, a variety of possible determined desired fluxes may be provided.

[0054] According to an improved embodiment of the method, the desired flux determined in step a) includes one or more constant segments. The coating process generally requires a constant flux of the evaporation and / or sublimation source material, especially due to purity reasons and because this can support the uniform growth of the coating. By providing a determined flux having one or more constant segments, the constant flux can also be provided by implementing the method according to the present invention.

[0055] The method according to the present invention may be further improved in such a way that the desired flux includes at least two segments having a constant desired flux, wherein the respective desired fluxes differ by a factor of 2 or more, particularly by a factor of 10 or more, preferably by a factor of 100 or more. Thus, preferably, the two segments are parallel and / or consecutive. As described above, the flux of the actually provided evaporation and / or sublimation source material strongly depends on the laser power and thus correspondingly on the desired intensity and the working intensity. In particular, by changing the intensity of the provided laser beam, a large flux change can be provided on an extremely short time scale. Since the abundance of the evaporation and / or sublimation source material reaching the substrate affects the surface mobility on the substrate, this can be used, for example, to control the growth kinetics. Parallel and / or consecutive segments in the sense of the present invention generally include segments that are immediately adjacent to each other. However, segments that are joined to each other by short transition segments are also considered parallel and / or consecutive (if the duration of such segments is negligible with respect to the duration of the two corresponding segments having a constant desired flux).

[0056] According to another improvement, the method according to the invention may include: the desired flux determined in step a) includes one or more increasing and / or decreasing segments, in particular, linear increasing and / or linear decreasing segments. For some applications, it may also be appropriate to increase and / or decrease the flux of the source material to be evaporated and / or sublimated. According to the invention, the change in flux is provided by a change in the working intensity, and the change in the working intensity can be implemented on a very short time scale of microseconds or even faster. Since steps a) to f) are preferably repeatedly executed, this applies not only to the transition between segments of a constant desired flux with different values, but also similarly to segments with an increasing and / or decreasing desired flux, in particular, segments with a linearly increasing and / or linearly decreasing desired flux.

[0057] In another improved embodiment of the method according to the invention, the desired flux determined in step a) includes a repeating pattern of segments having a constant desired flux during a first time period and segments having no desired flux during a subsequent second time period, wherein the first time period and the second time period are selected such that the nominal thermal energy is not reached during the evaporation and / or sublimation of the source material. Providing a source material for evaporation and / or sublimation with a continuous desired flux will ultimately cause the source assembly to store the nominal thermal energy. Therefore, the source assembly (in particular, its surface) continuously includes a desired flux temperature corresponding to the said nominal heat. However, this inevitably leads to generally non-negligible parasitic heating around the source assembly, for example due to the radiative cooling of the source assembly. However, this may be harmful to other components of the TLE system (especially for the substrate). By determining the desired flux as a repeating pattern as described above, these negative parasitic heatings of the source assembly to the environment can be significantly reduced.

[0058] As an advantage of the method according to the invention, the constant desired flux during the first time period can be provided almost immediately at the beginning of each time period. However, the source assembly only provides a desired flux temperature corresponding to the desired flux at the surface, and the bulk of the source assembly remains at a lower temperature. During the second time period, without any further heating by the laser beam, the temperature of the source assembly equalizes, still at a temperature value far lower than the desired flux temperature. Then, this process is repeated. In short, the average temperature of the source assembly continuously remains far lower than the desired flux temperature. Thus, the overall impact of parasitic heating can be reduced at the cost of the time required to provide an appropriate total amount of flux of the source material to be evaporated and / or sublimated.

[0059] Furthermore, the method according to the invention can also be improved in the following way: during a first time period, the average value of the actual thermal energy is less than 0.5 times the nominal thermal energy, particularly less than 0.25 times the nominal thermal energy. This average thermal energy directly defines the average temperature of the source assembly, particularly the average temperature of the surface of the source assembly. Since radiative cooling is proportional to the fourth power of the temperature, reducing the average value of the actual thermal energy to half or even a quarter of the nominal thermal energy can more significantly reduce the influence of parasitic heating.

[0060] In addition, the method according to the invention can be characterized in that: the source includes a cooling device, and wherein the method includes actively cooling the source assembly by means of the cooling device during the evaporation and / or sublimation of the source material. The cooling device can for example include cooling pipes thermally attached to a cooling body of the source assembly, so that a cooling fluid (such as water or liquid nitrogen) flows through the cooling pipes. As described above, if the actual thermal energy is higher than the nominal thermal energy, the bulk of the source assembly generally includes a temperature higher than the temperature corresponding to the desired flux. Therefore, the source assembly must be cooled to remove at least a part of the stored thermal energy. By providing a cooling device, the cooling can be enhanced and accelerated, especially compared to radiative cooling alone.

[0061] In an improved embodiment of the method according to the invention, the source assembly is continuously and actively cooled by means of the cooling device. In other words, the cooling device operates continuously, particularly without being repeatedly turned on and off. Thereby, the implementation of the method according to the invention can be simplified, particularly a TLE system configured to implement the method according to the invention.

[0062] Furthermore, the method according to the invention can be improved in the following way: when determining the nominal intensity in step c), the active cooling of the source assembly by means of the cooling device is taken into account. The active cooling of the source assembly by means of the cooling device (particularly if this cooling is provided continuously) removes the thermal energy finally provided by the irradiated laser beam. In the sense of the present invention, "taking this active cooling into account" particularly means determining the operating intensity such that an additional intensity is added to compensate for this active cooling. Thereby, while providing the overall advantages of the method according to the invention (a rapid, particularly almost immediate response to an increase in the desired flux, especially in the starting phase of the evaporation and / or sublimation process), the positive effects of this cooling can be provided, particularly a faster response of the actual flux to a reduction in the desired flux.

[0063] Additionally, the method according to the present invention may include: the TLE system includes two or more sources, wherein each source includes a source component composed of a source material, and wherein, for the evaporation and / or sublimation of the corresponding source material, steps a) to f) are respectively performed for each source material. In other words, in this TLE system, more than one source material can be evaporated and / or sublimated, and the evaporation and / or sublimation process can be performed using the method according to the present invention. The evaporation and / or sublimation processes of the different source materials can be performed at the same or different times. Therefore, for each source material, the flux of the evaporated and / or sublimated source material can be adjusted in a controlled and arbitrary manner. In particular, the flux of the correspondingly provided evaporated and / or sublimated source material immediately or at least after a short time rises to the desired flux level, and / or immediately or at least after a short time drops to the desired flux level.

[0064] Furthermore, the method according to the present invention can be further improved in the following way: the desired flux determined in step a) performed for the first source material is higher than the desired flux determined in step a) performed for the second source material, so that the corresponding step e) is performed simultaneously for the two source materials. By implementing this embodiment of the method according to the present invention, it can be provided that: compared with the second source material, the first source material exists on the surface of the substrate to be coated in a larger abundance. This can be used, for example, to ensure a specific stoichiometric ratio of the two source materials on the substrate surface.

[0065] It should be noted that the improvement described in the previous paragraph is not limited to two source materials, but can be similarly implemented for three or more source materials. In particular, the method according to the present invention may further include: performing step a) for three or more source materials to determine the corresponding desired flux of each of the three or more source materials, so that the corresponding step e) is performed simultaneously for all three or more source materials. Therefore, a desired specific stoichiometric ratio of the three or more source materials on the substrate surface can also be provided.

[0066] The embodiment described in the previous paragraph is not limited to two source materials and can therefore be implemented for three or more source materials that are evaporated and / or sublimated simultaneously and / or subsequently in the same TLE system.

[0067] According to a second aspect of the present invention, this object is achieved by a thermal laser evaporation (TLE) system, which includes: a reaction chamber that can be filled with a reaction atmosphere; a substrate arranged in the reaction chamber; one or more sources arranged in the reaction chamber, each source including a source component composed of a source material; and a laser source for providing a laser beam that irradiates the source component to evaporate or sublimate the source material to provide a flux of the evaporated or sublimated source material for deposition on the substrate. The TLE system according to the second aspect of the present invention is configured to perform the method according to the first aspect of the present invention. Thus, the thermal laser evaporation system according to the second aspect of the present invention provides all the features and advantages described above with respect to the method according to the first aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The present invention will be explained in detail below by way of examples and with reference to the accompanying drawings. In particular, in the drawings:

[0069] FIG. 1 shows a schematic view of a TLE system with a baffle according to the prior art;

[0070] Figure 2 Graphs showing the relationship between power, flux, and source temperature and time during the preparation stage and in a first embodiment of the method according to the present invention;

[0071] Figure 3 Graphs showing the cooling device and the relationship between power, flux, and source temperature and time in a second embodiment of the method according to the present invention;

[0072] Figure 4 Graphs showing the relationship between power, flux, and source temperature and time in a third embodiment of the method according to the present invention;

[0073] Figure 5 Graphs showing the relationship between power, flux, and source temperature and time in a fourth embodiment of the method according to the present invention;

[0074] Figure 6 Graphs showing the relationship between flux and substrate temperature and time in two different embodiments of the method according to the present invention; and

[0075] Figure 7 Schematic view showing a thermal laser evaporation system according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0076] In the Figures 2 to 5 several schematic diagrams are shown, which schematically illustrate the relationship between the attribute laser power (denoted as "P"), and the resulting laser intensities 30, 32, the desired and actual fluxes 70, 72 (denoted as "F") of the evaporated and / or sublimated source material 44, and the source temperature 60, 62 (denoted as "T") (especially the surface temperature 62) and time (denoted as "t").

[0077] It should be noted that in Figures 2 to 5 , the fluxes 70, 72 and the temperatures 60, 62 are represented by the same line to simplify the curve. In fact, the line shown is the graph of the fluxes 70, 72. Due to the approximate Arrhenius-type dependence of the fluxes 70, 72 on the temperatures 60, 62 (especially on the surface temperature 62), the corresponding graphs of the temperatures 60, 62 will show slightly different curves, in particular, with less pronounced variations. In particular, due to the above-mentioned Arrhenius-type dependence, there is no general proportional dependence between the fluxes 70, 72 and the temperatures 60, 62.

[0078] In addition, Figures 2 to 5 and Figure 6 all the graphs of Figure 7 are illustrated for a single source component 42 (see

[0079] for images of the corresponding TLE system 10 and its components). However, the described embodiments of the method according to the invention are also applicable to a TLE system 10 comprising two or more sources 40, so that the evaporation and / or sublimation processes for the two or more sources 40 can be carried out simultaneously and / or subsequently, and thus, for each process, the method according to the invention is carried out adapted to that particular evaporation and / or sublimation process. Figures 2 to 6 For all the mentioned components of the TLE system 10 not shown in Figure 7 .

[0080] Figure 2 The graph of the preparation stage is shown in subfigure A, and the graph of the actual embodiment of the method according to the invention is shown in subfigure B. Both figures show the evaporation and / or sublimation process with the desired flux 70, and the desired flux 70 should be provided starting from the first time point t1 and ending at the second time point t2. Note that the desired flux 70 corresponds to the desired flux temperature 60, and the correspondence follows the conventional Arrhenius-type dependence of the vapor pressure.

[0081] For the preparation stage shown in subfigure A, the laser source 20 provides a constant operating intensity 32 corresponding to the nominal intensity 30, and simply turns on at t1 and turns off again at t2. This is correspondingly depicted by the rectangular shape of the nominal intensity and the operating intensity 30, 32. However, at t1, the bulk of the source component 42 includes a temperature far lower than the desired flux temperature 60. Therefore, a non-negligible part of the energy of the irradiated laser beam 22 is used to heat the source component 42. Effectively, this results in a slow rising curve of the actual temperature 62 and thus a slow rising curve of the actual flux 72 actually provided, as shown in Figure 2 subfigure A of

[0082] In contrast,Figure 2 Sub - figure B shows a similar graph, but it is a graph of the evaporation and / or sublimation process provided by the first embodiment of the method according to the present invention. Similar to sub - figure A, the desired flux 70 represented by the desired flux temperature 60 is set in the first step a) of the method according to the present invention, and the actual flux 72 should satisfy the desired flux 70. Note that after t2, the desired flux temperature 60 drops to zero. As shown, the desired flux 70 may include or consist of a section of constant value.

[0083] Furthermore, in the next step b), if the average temperature of the source component 42 is the desired flux temperature 60, the nominal thermal energy corresponding to the desired flux 70 is determined so that the source component 42 stores this nominal thermal energy.

[0084] In addition, in the next step c), the nominal intensity 30 is determined, which also corresponds to the desired flux 70 and the nominal thermal energy. In particular, if the source component 42 stores this nominal thermal energy, the nominal intensity 30 is the intensity of the specific laser beam 22 required to provide the desired flux 70.

[0085] The next two steps d) and e) are the main differences from simply turning on the laser beam 22 as shown in sub - figure A. First, in step d), the actual thermal energy stored in the source component 42 is determined. In other words, after step d), there is information about the degree to which the source component 42 has been heated during the ongoing evaporation and / or sublimation process.

[0086] This information is used in the next step e), where the actual thermal energy is compared with the nominal thermal energy. Thus, the deviation between these values can be determined.

[0087] If the nominal thermal energy is greater than the actual thermal energy, the energy of the laser beam 22 will be at least partially used to heat the bulk of the source component 42 rather than for evaporating and / or sublimating the source material 42, and vice versa. This finding is used to determine the working intensity 32, which will be higher than the nominal intensity 30 in the first case and lower than the nominal intensity 30 in the latter case. To avoid unexpected oscillations of the determined working intensity 32, it is foreseeable that the deviation between the actual thermal energy and the nominal thermal energy is determined only when the values of the thermal energy differ by more than 10%, particularly more than 1%, preferably more than 0.1%.

[0088] In the last step f) of the method according to the present invention, a laser beam 22 with the working intensity 32 determined in the previous step e) is provided.

[0089] Thus, as long as the actual thermal energy stored in the source component 42 does not reach the nominal thermal energy, the working intensity 32 is determined to have a higher value to compensate for the energy loss caused by heating the source component 42. Thus, the actual temperature 62 at the emission surface 46 of the source component 42 can be decoupled from the actual thermal energy. Since the actual flux 72 originating from the source component 42 is strongly correlated with the actual temperature 62 of the emission surface 46, this allows, as shown in subfigure B, the actual flux 72 corresponding to the desired flux 70 to be provided almost immediately after t1, without the need for a baffle 80.

[0090] After t2, the desired flux 70 is set to zero. Thus, the actual thermal energy stored in the source component 42 suddenly becomes greater than the nominal thermal energy determined in step b) of the method according to the invention. Thus, the working intensity 32 is also determined to be as low as possible, i.e., also zero. Thus, the actual thermal energy stored in the source component 42 also decreases, mainly due to radiative cooling in the Figure 2 embodiment. In particular, for the high temperatures of the source component 42 that are often present in the TLE system 10, this is an effective cooling method, since this radiative cooling is proportional to the fourth power of the actual temperature 62 at the surface 46 of the source component 42. Thus, the actual temperature 62 of the surface 46 also very quickly becomes lower and lower, and the actual flux 72 rapidly reaches the desired flux 70 and stops.

[0091] Preferably, the desired flux temperature 60 is determined together with the desired flux 70. As already described, the actual flux 72 originating from the source component 42 is strongly correlated with the actual temperature 62 of the emission surface 46 of the source component 42. Thus, in step e), the working intensity 32 is preferably determined such that the desired flux temperature 60 is reached at this surface 46. For actual control, in particular closed-loop control, the actual temperature 62 can be measured by a suitable temperature sensor 66, and when determining the working intensity 32 in step e) of the method according to the invention, the comparison of the measured actual temperature 62 with the desired flux temperature 60 can be taken into account.

[0092] Overall, it is advantageous if the steps a) to f) or at least steps d) to f) of the method according to the invention are repeatedly executed. Additionally, or alternatively, for the above-described closed-loop control based on the temperatures 60, 62, closed-loop control based on the thermal energy stored in the source component 42 is also feasible. In particular, the actual thermal energy stored by the bulk of the source component 42 can be determined by a calculation taking into account the properties of the correspondingly arranged source component 42 and / or the properties of the ongoing evaporation and / or sublimation processes, and / or by comparison with experimental and / or simulation data.

[0093] To reach the nominal thermal energy as quickly as possible, preferably, the deviation between the nominal thermal energy and the actual thermal energy is considered during the determination of the working intensity 32. Generally, a larger deviation in the thermal energy results in a larger deviation between the working intensity 32 and the nominal intensity 30. To consider this deviation, for example, the corresponding difference or ratio between the actual thermal energy and the nominal thermal energy can be used as the basis for determining the corresponding difference or ratio between the working intensity 32 and the nominal intensity 30. For example, the difference value or ratio value can be proportionally related to each other.

[0094] This process is clearly visible in Sub - figure B, for example. At t1, the actual thermal energy stored in the source component 42 is the minimum, and thus, the deviation between the actual thermal energy and the nominal thermal energy is large. Therefore, at the beginning of the evaporation and / or sublimation process, the deviation between the determined working intensity 32 and the nominal intensity 30 also includes its maximum value. If this deviation exceeds the threshold, the maximum intensity that the laser source 20 can provide can also be set as the working intensity 32 to avoid damaging the laser source 20. Towards t2, the source component 42 is heated, and thus, the actual thermal energy stored in the source component 42 gets closer and closer to the nominal thermal energy. This behavior is also transferred to the determined working intensity 32, which converges towards the nominal intensity 30.

[0095] As described with respect to Figure 2 Sub - figure B, when the desired flux 70 suddenly drops to zero, the actual thermal energy stored in the source component 42 must be removed. Figure 3 Shows a preferred improvement, where the source component 42 is cooled not only by radiative cooling but also by a dedicated cooling device 50.

[0096] Sub - figure A shows a schematic image of the source 40 including the source component 42 and the cooling device 50. The block of the source component 42 composed of the source material 44 is thermally coupled to the body 52 of the cooling device 50. Inside the body 52, cooling pipes 54 are arranged for the flow of a coolant fluid 56 (such as water or liquid nitrogen). Preferably, the cooling device 50 works continuously, in other words, the source component 42 is always cooled.

[0097] In Sub - figure B, a graph of the evaporation and / or sublimation process similar to Figure 2 Sub - figure B is shown. The difference is that the source 40 for the shown evaporation and / or sublimation process is equipped with a cooling device 50. Since the cooling device 50 preferably cools the source component 42 in a continuous manner, therefore, when determining the working intensity 32, this cooling is preferably considered because the additional energy loss caused by this cooling must be compensated. This is done in Figure 3 because the actual flux 72 also reaches the desired flux 70 almost immediately after t1. Similarly, the desired flux 70 corresponds to the desired flux temperature 60. For the remaining general features of the method according to the invention shown in Figure 3 Sub - figure B, please refer to the corresponding description of Sub - figure B with respect to Figure 2 above.

[0098] The main advantage of the implementation of the cooling device 50 becomes visible after t2, such that, at this point in time, the desired flux 70 is again expected to drop to zero. Since the cooling device 50 cools the source assembly 42 in a more efficient manner (in particular starting from a lower actual temperature 62) compared to cooling only by radiation, the actual thermal energy reaches the nominal thermal energy more quickly, and thus the actual temperature 62 of the surface 46 also drops more rapidly to the desired flux temperature 60. Therefore, it is also possible to provide the shutdown of the actual flux 72 provided in an almost immediate manner, especially in the absence of the baffle 80.

[0099] As Figure 2 , Figure 3 shown, the desired flux 70 may include a section having a constant value for the desired flux 70. However, since the response time of the commonly used laser source 20 is in the microsecond range, the method according to the invention is not limited to this constant desired flux 70.

[0100] As Figure 4 shown, it is also feasible to define a section with (in particular, linear) increasing and / or decreasing values as the desired flux 70, i.e., increasing linearly between t1 and t2 and decreasing linearly between t2 and t3. Accordingly, the nominal intensity 30 is determined during the execution of the method according to the invention, and in particular the working intensity 32 is also determined, and thus the actual temperature 62 and thus also the actual flux 72 respectively follow almost immediately the desired flux temperature 60 and the desired flux 70. Similarly, the desired flux 70 corresponds to the desired flux temperature 60.

[0101] In Figure 5 shown is a diagram showing a more complex evaporation and / or sublimation process. After an initial constant section of the desired flux 70 between t1 and t2, there follows a second constant section of the desired flux 70 between t2 and t3, which has a lower value of the desired flux 70. Similarly, the desired flux 70 corresponds to the desired flux temperature 60.

[0102] Similarly, the determined working intensity 32 compensates for the deviation between the actual thermal energy stored in the source assembly 42 and the nominal thermal energy determined during the execution of the method according to the invention. At the start of t1, the source assembly 42 is colder and has to be heated. Therefore, the determined working intensity 32 is highest at the start and converges towards a first value of the nominal intensity 30 towards t2.

[0103] After t2, the desired flux 70 drops to its lower new value. Consequently, the actual thermal energy stored in the source assembly 42 is higher than the nominal thermal energy. Therefore, the value of the working intensity 32 is determined to be zero, allowing the source assembly 42 to cool. When the desired flux temperature 62 is reached on the surface 46 of the source assembly 42 shortly thereafter, the determined value of the working intensity 32 begins to rise again, converging towards the new value of the nominal intensity 30. After t3, the desired flux 70 drops to zero, which also causes the working intensity 32 to be determined to be zero. Due to the imperfect cooling of the source assembly 42, the actual drop in the actual temperature 62 and thus the actual flux 72 is somewhat delayed.

[0104] Note that the difference between the two values of the constant desired flux 70 shown is for illustrative purposes only. By implementing the method according to the invention, the values of the desired flux 70 can differ by a factor of two or more, particularly by a factor of ten or more, preferably by a factor of one hundred or more.

[0105] Figure 6 Another advantageous use of the method according to the invention is shown, namely the avoidance of parasitic heating, in particular the parasitic heating of the substrate 16. The two subfigures A, B show graphs of the fluxes 70, 72 and the substrate temperature 64 as a function of time. By using the method according to the invention as described above to provide the actual flux 72, in particular, its rapid convergence towards the desired flux 70.

[0106] In subfigure A, the desired flux 70 and thus the actual flux 72 are provided as a continuous flux 70, 72 with a constant value. Therefore, the source assembly is heated until it stores the nominal thermal energy and the actual temperature 62 is equal to the desired flux temperature 60 (the temperatures 60, 62 of the source assembly 42 are not shown). However, at all times, the radiative cooling of the source assembly 42 is active, resulting in a slow heating of the substrate 16, which is visible in the rising substrate temperature 64. Unfortunately, the high substrate temperature 64 is not only harmful to the coating process but also, in the worst case, to the structural integrity of the substrate 16.

[0107] Sub - figure B shows a possible solution to the parasitic heating problem provided by the method according to the present invention. As described above, by implementing the method according to the present invention, an actual flux 72 of the source material 44 for evaporation and / or sublimation can be provided that can be turned on and off almost immediately, especially in the absence of a baffle 80. Thus, in this case, the desired flux 70 (and thus at least substantially also the actual flux 72) includes a repeating pattern of a section with a constant flux 70, 72 and a section with no flux 70, 72. The time periods of the sections are selected such that the actual thermal energy never reaches the nominal thermal energy. In fact, preferably, the average value of the actual thermal energy is less than 0.5 times the nominal thermal energy, especially less than 0.25 times the nominal thermal energy. However, the desired flux 70 can be provided because the corresponding working intensity 32 (not shown) is determined. As can be seen in sub - figure B, there is still some parasitic heating of the substrate 16, but the substrate temperature 64 oscillates around a significantly lower value. Thus, the harmful effects of this parasitic heating can be avoided.

[0108] Figure 8 shows a schematic and simplified cut - away side view of a thermal laser evaporation (TLE) system 10 according to the present invention. The TLE system 10 is configured to perform the method according to the present invention. Inside the reaction chamber 12, a source 40 (providing a source assembly 42 including a source material 44) and a substrate 16 are arranged. Additionally, there is a cooling device 50 to actively cool the source assembly 42. A temperature sensor 66 is used to measure the actual temperature 62 of the source assembly 42 (see Figures 2 to 5 ). The reaction chamber 12 is filled with a reaction atmosphere 14 (such as a vacuum or a suitable reaction gas).

[0109] A laser beam 22 provided by a laser source 20 is coupled into the reaction chamber 10 to irradiate the surface 46 of the source assembly 42. By implementing the method according to the present invention, for example, in one of the embodiments described above regarding Figures 2 to 6 , the actual flux 72 of the source material 44 for evaporation and / or sublimation can be adjusted in a controlled and arbitrary manner. In particular, the actual flux 72 of the source material 44 for evaporation and / or sublimation provided rises immediately or at least after a short time to the value of the desired flux 70, and / or falls immediately or at least after a short time to the value of the desired flux 70. List of reference numerals 10 TLE system 12 Reaction chamber 14 Reaction atmosphere 16 Substrate 18 Orifice 20 Laser source 22 Laser beam 30 Nominal intensity 32 Working intensity 40 Source 42 Source assembly 44 Source material 46 Surface 50 Cooling device 52 Body 54 Cooling pipe 56 Coolant fluid 60 Desired flux temperature 62 Actual temperature 64 Substrate temperature 66 Temperature sensor 70 Desired flux 72 Actual flux 74 Deposition flux 80 Baffle

Claims

1. A method of using a thermal laser evaporation (TLE) system (10), the TLE system (10) comprising: A reaction chamber (12) capable of being filled with a reaction atmosphere (14); A substrate (16) disposed in the reaction chamber (12); One or more sources (40) disposed in the reaction chamber (12), each source (40) including a source assembly (42) composed of a source material (44); and a laser source (20) for providing a laser beam (22) that irradiates the source assembly (42) to evaporate or sublime the source material (44) to provide a flux (70, 72) of the evaporated or sublimed source material (44) for deposition on the substrate (16), The method includes the steps of: a) Determining a desired flux (70) of the source material (44) evaporated and / or sublimed by the laser beam (22), b) Determining a nominal thermal energy stored in the source assembly (42) corresponding to the desired flux (70), c) When the source assembly (42) stores the nominal thermal energy, determining a nominal intensity (30) of the laser beam (22) corresponding to the desired flux (70), d) Determining the actual thermal energy stored in the source assembly (42), e) Depending on the deviation of the actual thermal energy from the nominal thermal energy, determining an operating intensity (32) of the laser beam (22), where - If the actual thermal energy is less than the nominal thermal energy, the operating intensity (32) is higher than the nominal intensity (30), and - If the actual thermal energy is higher than the nominal thermal energy, the operating intensity (32) is less than the nominal intensity (30), and f) Providing the laser beam (22) having the operating intensity (32).

2. The method according to claim 1, Among them, In step a), determining a desired flux temperature (60) of the surface (46) of the source assembly (42) corresponding to the desired flux (70), and wherein, in step e), if the actual thermal energy is less than the nominal thermal energy, setting the operating intensity (32) to a value higher than the nominal intensity (32) so that the desired flux temperature (60) is reached at the surface (46) of the source assembly (42).

3. The method according to claim 2, Among them, Measuring an actual temperature (62) of the surface (46) of the source assembly (42), and wherein, in step e), preferably in a closed-loop control, comparing the actual temperature (62) with the desired flux temperature (60).

4. The method according to any one of the preceding claims, Among them, In step d), calculating to determine the actual thermal energy by considering one or more of the following properties, preferably considering all of the following properties: - An initial thermal energy stored in the source assembly (42); - The mass of the source assembly (42); - The heat capacity of the source material (44); - The thermal conductivity of the source material (44); - The total laser energy radiated onto the source assembly (42).

5. The method according to any one of the preceding claims, Among them, In step d), determining the actual thermal energy by comparing with experimental and / or simulation data.

6. The method according to any one of the preceding claims, Among them, Preferably in closed-loop control, steps d) to f) are repeated at least, and preferably steps a) to f) are repeated.

7. The method according to any one of the preceding claims, Among them, In step e), the working intensity (32) is determined such that the difference between the working intensity (32) and the nominal intensity (30) depends on the difference between the actual thermal energy and the nominal thermal energy, or The ratio of the working intensity (32) to the nominal intensity (30) depends on the ratio of the actual thermal energy to the nominal thermal energy.

8. The method according to claim 7, Among them, If the actual thermal energy is less than the nominal thermal energy and the deviation exceeds a first threshold, the working intensity (32) is set to the maximum intensity of the laser beam (22), and / or Wherein, if the actual thermal energy is higher than the nominal thermal energy and the deviation exceeds a second threshold, the working intensity (32) is set to the minimum intensity of the laser beam (22), preferably zero.

9. The method according to claim 7, Among them, The difference between the working intensity (32) and the nominal intensity (30) is proportional to the difference between the actual thermal energy and the nominal thermal energy, or Wherein, the ratio of the working intensity (32) to the nominal intensity (30) is proportional to the ratio of the actual thermal energy to the nominal thermal energy.

10. The method according to any one of the preceding claims, Among them, In step e), if the difference between the actual thermal energy and the nominal thermal energy exceeds 10%, specifically exceeds 1%, preferably exceeds 0.1%, the deviation between the actual thermal energy and the nominal thermal energy is determined.

11. The method according to any one of the preceding claims, Among them, The desired flux (70) is determined for a period of time, and / or the desired flux (70) includes time dependence.

12. The method according to claim 11, Among them, The desired flux (70) determined in step a) includes one or more constant sections.

13. The method according to claim 12, Among them, The desired flux (70) includes at least two sections with a constant desired flux (70), wherein the corresponding desired fluxes (70) differ by a factor of 2 or more, specifically differ by a factor of 10 or more, preferably differ by a factor of 100 or more, so that, preferably, the two sections are parallel and / or subsequent.

14. The method according to any one of claims 11 to 13, Among them, The desired flux (70) determined in step a) includes one or more increasing and / or decreasing sections, specifically, linearly increasing and / or linearly decreasing sections.

15. The method according to any one of claims 11 to 14, Among them, The desired flux (70) determined in step a) includes a repeating pattern of a section with a constant desired flux (70) during a first time period and a section without a desired flux (70) in a subsequent second time period, wherein the first time period and the second time period are selected such that the nominal thermal energy is not reached during the evaporation and / or sublimation of the source material (44).

16. The method according to claim 15, Among them, During the first time period, the average value of the actual thermal energy is less than 0.5 times the nominal thermal energy, specifically less than 0.25 times the nominal thermal energy.

17. The method according to any one of the preceding claims, Among them, wherein the source (40) comprises a cooling device (50), and wherein the method comprises actively cooling the source assembly (42) by means of the cooling device (50) during evaporation and / or sublimation of the source material (44).

18. The method according to claim 17, Among them, actively cooling the source assembly (42) continuously by means of the cooling device (50).

19. The method according to claim 17 or 18, Among them, wherein when determining the nominal intensity (30) in step c), the active cooling of the source assembly (42) by means of the cooling device (50) is taken into account.

20. The method according to any one of the preceding claims, Among them, wherein the TLE system (10) comprises two or more sources (40), wherein each source (40) comprises a source assembly (42) consisting of a source material (44), and wherein steps a) to f) are carried out separately for each of the source materials (44) for evaporation and / or sublimation of the respective source material (44).

21. The method according to claim 20, Among them, wherein the desired flux (70) determined in step a) carried out for the first source material (44) is higher than the desired flux (70) determined in step a) carried out for the second source material (44), such that the respective step f) is carried out simultaneously for the two source materials (44).

22. A thermal laser evaporation (TLE) system (10), the TLE system comprising: A reaction chamber (12) capable of being filled with a reaction atmosphere (14); A substrate (16) arranged in the reaction chamber (12); One or more sources (40) arranged in the reaction chamber (12), each source (40) comprising a source assembly (42) consisting of a source material (44); and a laser source (20) for providing a laser beam (22) which irradiates the source assembly (42) so as to evaporate or sublime the source material (44) to provide a flux (70, 72) of the evaporated or sublimed source material (44) for deposition on the substrate (16), wherein the TLE system (10) is configured to carry out the method according to any one of the preceding claims.

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