Method of using a thermal laser evaporation system and thermal laser evaporation system - Patents.com

Abstract

The present invention relates to a method of using a thermal laser evaporation (TLE) system, the system comprising a reaction chamber capable of being filled with a reaction atmosphere, one or more sources arranged in the reaction chamber, each source comprising a source material, and a laser light source for providing laser radiation to a surface of the source, thereby evaporating the source material.The present invention further relates to a thermal laser evaporation system comprising a reaction chamber capable of being filled with a reaction atmosphere, one or more sources arranged in the reaction chamber, each source comprising a source material, and coupling means provided by the reaction chamber for coupling the laser radiation into the reaction chamber for evaporating the source material by impinging on a surface of the source.

Description

[Technical field]

[0001] The present invention relates to a method of using a thermal laser evaporation system, the system comprising a reaction chamber capable of being filled with a reaction atmosphere, one or more sources arranged in the reaction chamber, each source comprising a source material, and a laser light source for providing laser radiation to a surface of the source, thereby evaporating the source material.The present invention further relates to a thermal laser evaporation system comprising a reaction chamber capable of being filled with a reaction atmosphere, one or more sources arranged in the reaction chamber, each source comprising a source material, and coupling means provided by the reaction chamber for coupling the laser radiation into the reaction chamber for evaporating the source material by impinging on a surface of the source. [Background technology]

[0002] In thermal laser evaporation (TLE), material is evaporated by laser heating in a controlled environment, specifically a reaction chamber filled with a reactive atmosphere, usually with the aim of coating a surface with a thin film. The efficiency of TLE depends on the local heating of the source surface, since the growth rate increases exponentially with the power density in the laser irradiation spot.

[0003] A single such heating spot 70 is shown on the left side of Figure 1, labeled "A", forming a most simplified laser intensity pattern 60. When locally heated by a laser beam 54, typically by laser radiation 52, a solid block of source material 32 of the source 30 to be evaporated forms a spatially confined molten volume 36, either within the source material 32 itself or within a crucible, as shown by the dashed arc in the right diagram of Figure 1, labeled "B".

[0004] As already shown in view "B" of Figure 1, the molten source material 32 forms convection currents 38 within the melt volume 36. The convection currents 38 are typically driven by the lower density of the hotter, thermally expanded liquid, causing the upward movement of the lighter liquid in the gravitational field and the downward movement of the cooler, denser source material 32. Depending on the properties of the source material 32, the flow direction may be reversed, and the details of the process may vary significantly for different source materials and different boundary conditions.

[0005] FIG. 2 shows the state after the evaporation process of FIG. 1, view "B". As shown, convection currents 38 often cause turbulence in the evaporation process. In particular, strong convection currents 38 carry a significant amount of source material 32, which increases the diameter and especially the depth of the melt volume 36. In particular, strong convection currents 38 can generate height differences due to peaks and valleys on the surface 34 of the melt volume 36 in the source 30. These become turbulent and unstable, and in some cases are amplified by the uneven heating of different slope elements of the dynamic slope of the surface 34 by the impinging laser beam 54. This is shown in FIG. 2 by two different dashed arrows representing the reflected laser beam 56. At high power densities, this can cause unstable evaporation and droplet splashing, resulting in defects and non-uniformity in the deposited film.

[0006] In view of the above, it is an object of the present invention to provide an improved method of using a thermal laser evaporation system and an improved thermal laser evaporation system that do not have the above-mentioned drawbacks of the state of the art. In particular, it is an object of the present invention to provide an improved method of using a thermal laser evaporation system and an improved thermal laser evaporation system that allows stable high flux evaporation from large surface areas. Summary of the Invention

[0007] This object is achieved by the respective independent patent claims. In particular, this object is achieved by a method using a thermal laser evaporation system according to independent claim 1 and by a thermal laser evaporation system according to independent claim 20. The dependent claims describe preferred embodiments of the invention. In a technical sense, details and advantages described with respect to the method according to the first aspect of the invention also apply to the thermal laser evaporation system according to the second aspect of the invention and vice versa.

[0008] According to a first aspect of the invention, the object is achieved by a method using a thermal laser evaporation (TLE) system. The system includes a reaction chamber capable of being filled with a reaction atmosphere, one or more sources disposed within the reaction chamber, each source containing a source material, and a laser light source for providing laser radiation to a surface of the source, thereby evaporating the source material. The laser radiation has a spatially modulated intensity pattern, the spatially modulated intensity pattern including two or more spaced apart heating spots having at least a local maximum intensity.

[0009] The method according to the first aspect of the invention is intended for use with a thermal laser evaporation system or other than a TLE system. Such systems are generally already known. A laser beam provided by a laser source is used to evaporate a source material, which is most often deposited on a substrate provided as a target. In most cases, the deposition of laser energy on the source surface melts the source material, forming a molten volume of liquid source material. However, within the scope of the invention, the expression evaporation process also encompasses a sublimation process of the source material.

[0010] The source is disposed in a reaction chamber that is sealable from the surrounding atmosphere and can be filled with a reaction atmosphere. -12The vacuum can be as low as 1000 psi or less, or it can contain a reactive gas at a pressure suitable for depositing the material. For example, the reactive gas provides oxygen for the deposition of an oxide of the evaporated source material. To date, the maximum value tested at a working distance of 60 mm is 10 -2 The height in hPa. 10 -2 hPa was successfully deposited, so higher values ​​are probably possible.

[0011] In most cases the laser radiation is coupled into the reaction chamber via a coupling means, which can for example be a simple window in the chamber wall of the reaction chamber, however the coupling means according to the invention can also include adaptive optics for shaping the laser radiation impinging on the surface of the source material.

[0012] In the method according to the first aspect of the invention, the laser radiation has a spatially modulated intensity pattern, in particular the spatially modulated intensity pattern comprises two or more spaced apart heating spots having at least a local intensity maximum.

[0013] Preferably, the heating spot according to the invention is circular, in particular has a circularly symmetric Gaussian intensity profile, provided for example by focusing laser radiation onto the surface of the source material, giving a spot size, preferably defined as the full width at half maximum of the Gaussian profile, of less than 10 mm in diameter, preferably less than 1 mm.

[0014] At least a locally maximum intensity of the laser radiation at one of the heated spots means in the sense of the present invention that the heated spot is surrounded by an area in the intensity pattern where the intensity of the laser radiation is lower or at most equal to the intensity of the laser radiation at the heated spot, in other words, nowhere in the area surrounding each heated spot is the intensity of the laser radiation higher than the heated spot itself.

[0015] In particular, the intensity of the laser radiation at at least one of the two or more heating spots is the maximum intensity reached within the spatially modulated intensity pattern as a whole, in other words, according to the invention, at the location of at least one of the two or more heating spots a local maximum of the laser radiation intensity is reached.

[0016] In summary, by implementing the method according to the first aspect of the invention, it is avoided to provide a laser radiation having a single heating spot. The energy deposition from the laser radiation into the source material is distributed over a large area of ​​the source material surface. Furthermore, the various energy densities, and therefore temperature maxima, defined by this pattern generate temperature maxima and minima, and therefore centres of buoyancy, whose magnitude and position follow the modulation of the laser light pattern.

[0017] The formation of such temperature patterns induces smaller cells formed by convection within the molten volume formed in the source material, which reduces the depth of the convection zone and therefore the depth of the molten volume, allowing for a flatter source that does not melt easily.

[0018] Furthermore, spatial localization of the convective cells can be achieved. For the same surface tension, a smaller convective cell results in less surface turbulence, and therefore improved resistance to source turbulence and splashing. In other words, the uniformity of the evaporated source material flux can be increased.

[0019] At the same time, the surface area of ​​the molten source material during the evaporation process can be increased, which area is more fully involved in the evaporation process, thereby increasing the flux of evaporated source material.

[0020] In summary, by implementing the method according to the first aspect of the invention used in a TLE system, convection patterns can be defined and stabilized within the liquid melt volume of the source or source material, resulting in increased uniformity of high flux evaporation from a large surface area, thus enabling a uniform high total deposition flux.

[0021] Furthermore, the method according to the first aspect of the invention may be characterized in that the laser radiation intensity is at least substantially equal or equal at two or more heating spots. Thus, the energy deposition from the laser radiation into the source material is at least substantially equal or equal at those heating spots. The uniformity of the convection pattern and thus the resistance to turbulence and splashing of the source may be further increased.

[0022] According to an alternative embodiment of the method according to the first aspect of the invention, the laser radiation intensity is different at two or more heating spots for each of one or more sources, and thus the energy deposition from the laser radiation into the source material is also different at these heating spots, which allows a specific shaping of the convection pattern.

[0023] Furthermore, the method according to the first aspect of the invention can be characterized in that the thermal laser evaporation system includes two or more sources. In at least two of the two or more sources, the spatially modulated intensity patterns are at least substantially equal or equal. Thus, even when two or more sources are used for evaporation, the energy deposition for each of the sources can be equal. In particular, but not limited to, for sources providing the same source material, uniform evaporation of source material from all sources present in the TLE system can be achieved.

[0024] Alternatively or additionally, the method according to the first aspect of the invention may include that the thermal laser evaporation system includes two or more sources. In at least two of the two or more sources, the spatially modulated intensity patterns are different. Thus, even if more than one source is used for evaporation, the energy deposition for each of the sources can be specifically set. In particular, each source can preferably include its own source material. In other words, the source materials provided by the different sources are different. As a non-limiting example, a first source can provide titanium as source material, a second source can provide niobium, and a third source can provide tantalum. By providing different spatially modulated intensity patterns to the different sources, specific boundary conditions can be considered, such as the melting temperature of each source material. This allows for uniform evaporation, in particular simultaneous evaporation, of the different source materials.

[0025] According to another embodiment of the method according to the first aspect of the invention, two or more heating spots are connected by a linear heating line of at least a locally maximum intensity in the spatially modulated intensity pattern. A first end of the heating line is connected to one of the two heating spots, and a second end of the heating line is connected to the other of the two heating spots. In other words, according to this embodiment, a heating line of at least a locally maximum intensity of the laser radiation in the intensity pattern extends between the heating spots. Thus, the energy deposition along the heating line into the source material is also increased. In summary, the shaping and control of the convection pattern in the liquid melt volume can be increased.

[0026] Specifically, each heating line with at least a local maximum intensity of the laser radiation can be described as connecting two heating spots at each end point. Also closed heating lines are possible within the intensity pattern. Along such a closed heating line, two heating spots can be defined at any position, which are automatically connected as a result by the closed heating line.

[0027] Furthermore, the method according to the first aspect of the invention can be further improved by gradually, in particular monotonically, varying the laser radiation intensity along the heating line from the intensity of the heating spot at the first end of the heating line to the intensity of the heating spot at the second end of the heating line. By providing a gradually, in particular monotonically varying intensity along the heating line, irregular or step-like variations in intensity along the heating line can be prevented. This makes it easier to ensure a uniform convection pattern. A gradual variation according to the invention includes only smooth intensity variations along the heating line, whereas a monotonically varying further requires that the intensity of the laser radiation along the heating line only decreases, only increases or is constant along the complete heating line.

[0028] Furthermore, the method according to the first aspect of the invention can be characterized in that the heating lines are at least partially straight and / or curved and / or in the form of an arc. This list includes preferred shapes of the heating lines, but other shapes and combinations of shapes are also possible. In particular, the shape of each heating line can be selected with respect to the boundary conditions and / or the intended convection pattern of the evaporation process, in particular with respect to the source material used.

[0029] According to another embodiment of the method according to the first aspect of the invention, the spatially modulated intensity pattern is rotationally symmetric about a point of symmetry. By providing a rotationally symmetric spatially modulated intensity pattern, the resulting convection pattern is also rotationally symmetric. Thus, the uniformity of the flux of evaporated source material can be improved. Furthermore, the source and / or the provided source material often also include such rotational symmetry about a point or axis of symmetry. This can simplify the adaptation of the intensity pattern of the laser radiation to the shape of the source and / or the provided source material.

[0030] The method according to the first aspect of the invention may be further enhanced by the spatially modulated intensity pattern being rotationally symmetric about angles of 30° and / or 45° and / or 60° and / or 72° and / or 90° and / or 135° and / or 180°. This list includes preferred rotationally symmetric angles, although other angles are possible.

[0031] According to another embodiment of the method according to the first aspect of the present invention, the spatially modulated intensity pattern is periodic. In a periodic intensity pattern, small building blocks containing a small number of elements, such as heating spots or heating lines, with a fixed arrangement relative to each other, are repeated once, twice or more times to form the overall intensity pattern, so that the distance and relative orientation between the elements of adjacent building blocks remains constant. This makes it easier to ensure a uniform convection pattern.

[0032] According to an alternative embodiment of the method according to the first aspect of the invention, the spatially modulated intensity pattern is quasi-periodic. In a quasi-periodic intensity pattern, small building blocks containing a small number of elements, such as heating spots or heating lines, are also repeated once, twice or more times to form an overall intensity pattern. However, the distance and relative orientation between adjacent building blocks, and optionally also the internal arrangement of the building block elements, are varied, most often increasing with the distance to the selected fixing element. The fixing element may preferably be a symmetry point or a mirror surface or an axis of symmetry to give an overall rotationally or inversion-symmetric intensity pattern. This makes it easier to provide convective patterns with spatial dependence, especially radial dependence.

[0033] According to another alternative embodiment of the method according to the first aspect of the invention, the spatially modulated intensity pattern is aperiodic, which makes it possible to provide an intensity pattern of any shape.

[0034] As a specific example, a non-periodic intensity pattern in the sense of the present invention also encompasses in particular intensity patterns that are non-periodic as a whole but whose components are periodic and / or quasi-periodic, in particular in TLE systems with several sources, each source containing its own source material, the components of the intensity pattern dedicated to each source can be periodic, symmetrical and / or quasi-periodic depending on the needs of each source material, but the overall intensity pattern is non-periodic.

[0035] Furthermore, the method according to the first aspect of the invention can be characterized in that within the spatially modulated intensity pattern, outside the heating spots and / or heating lines, the laser radiation intensity is at least substantially zero or is zero. In other words, the intensity pattern has a sharp abrupt boundary between at least the area with the locally highest intensity and all other areas. In particular, this can provide a localized energy deposition in the source material. In most cases, this provides a large control over the convection pattern.

[0036] Alternatively, the method according to the first aspect of the invention may comprise gradually reducing the laser radiation intensity outside the heating spots and / or heating lines within the spatially modulated intensity pattern, in particular gradually reducing it to zero. For example, the intensity may be reduced as a function of the distance to each heating spot and / or heating line, in particular proportionally, polynomially or any suitable monotonic functionally dependent on this distance. In other words, the intensity pattern comprises a smoothly modulated intensity change. This can thus prevent abrupt changes in the energy deposition in the source material. This can improve the uniformity of the formed convection pattern. Furthermore, gradually reducing the laser radiation intensity is often easier to perform than abruptly reducing the intensity to zero.

[0037] Furthermore, the method according to the first aspect of the invention may include that a spatially modulated intensity pattern is selected for the source material. By selecting the respective intensity pattern for the source material, the properties of the source material and thus the boundary conditions for the resulting evaporation process can be taken into account. Thus, a uniform convection pattern and thus a high flux of evaporated source material can be more easily provided.

[0038] Furthermore, the method according to the first aspect of the invention can be improved in that the selection of the spatially modulated intensity pattern for the source material is based on calculations and / or simulations, which can be performed for a wide variety of source materials and / or sources of different shapes, making it possible to find and define the most suitable intensity pattern for the laser radiation in an easy and, in particular, fast and low-cost way.

[0039] Alternatively or additionally, the method according to the first aspect of the invention can be characterized in that the selection of the spatially modulated intensity pattern for the source material is based on experimental results. By using experimental results to select the most suitable intensity pattern, already integrated knowledge can be used in the selection process. In particular, the experimental results can be obtained in the same environment, for example with respect to the reaction atmosphere used and / or in the actual reaction chamber used. Thus, possible error sources based on assumptions that are not applicable during the selection process can be avoided.

[0040] In another possible embodiment of the method according to the first aspect of the invention, the spatially modulated intensity pattern further comprises a time-dependent modulation of the laser radiation intensity. Such a time-dependent modulation can be, for example, a simple lowering and / or increasing of the overall intensity, causing, for example, a pulsing of the flux of evaporated source material. However, a time-dependent of the spatial shape of the intensity pattern is also possible, for example a global rotation or a lateral shift of the intensity pattern. It is also possible to perform a complete change of the spatial shape. This allows a time-dependent flux control, including the spatial shape of the flux of evaporated source material. This can act to counteract instabilities or drifts that may occur during the initial heating or final cooling of the source, during flux modulation required by the process, and due to source depletion.

[0041] According to a second aspect of the invention, the object is achieved by a thermal laser evaporation system comprising a reaction chamber capable of being filled with a reaction atmosphere, one or more sources arranged in the reaction chamber, each source containing a source material, and coupling means provided by the reaction chamber for coupling laser radiation into the reaction chamber for evaporating the source material by impinging on a surface of the source. The laser source provides laser radiation having a spatially modulated intensity pattern. The spatially modulated intensity pattern comprises two or more spaced apart heating spots having at least a local maximum intensity.

[0042] In a thermal laser evaporation system according to the second aspect of the invention, a laser beam provided by a laser source is used to evaporate a source material, and in most cases the evaporated source material is deposited on a substrate provided as a target. In the scope of the invention, the evaporation process also encompasses sublimation of the source material. The laser radiation is coupled into the reaction chamber via a coupling means. The coupling means can be, for example, a simple window in the chamber wall of the reaction chamber.

[0043] The source is disposed in a reaction chamber that is sealable from the surrounding atmosphere and can be filled with a reaction atmosphere. -12 The chamber may be vacuumed down to as low as 1000 MPa or contain a reactive gas at a pressure suitable for depositing the material, for example providing oxygen for the deposition of an oxide of the evaporated source material.

[0044] In the system according to the second aspect of the invention, the laser radiation has a spatially modulated intensity pattern. In particular, the spatially modulated intensity pattern comprises two or more spaced apart heating spots having at least a local maximum intensity. The two or more heating spots can also be connected by heating lines in the spatially modulated intensity pattern, the heating lines also comprising at least a local maximum intensity.

[0045] Again, the heating spot according to the invention is circular, in particular has a circularly symmetric Gaussian intensity profile, provided for example by focusing laser radiation onto the surface of the source material, giving a spot size, preferably defined as the full width at half maximum of the Gaussian profile, of less than 10 mm in diameter, preferably less than 1 mm.

[0046] At least locally maximum intensity of the laser radiation means in the sense of the present invention that the heated spots are surrounded by areas in the intensity pattern where the intensity of the laser radiation is lower or at most equal to the intensity of the laser radiation at the heated spot, in other words, nowhere in the area surrounding each heated spot is the intensity of the laser radiation higher than the heated spot itself.

[0047] In particular, the intensity of the laser radiation at at least one of the two or more heating spots is the maximum intensity reached within the spatially modulated intensity pattern as a whole, in other words, according to the invention, the highest laser radiation intensity is reached at the location of at least one of the two or more heating spots.

[0048] In summary, according to the present invention, a TLE system is not claimed in which the laser radiation has a single heated spot. The energy deposition from the laser radiation into the source material is distributed over a large area of ​​the source material surface. Moreover, the various energy densities, and therefore temperature maxima, defined by this pattern create temperature maxima and minima, and therefore centers of buoyancy, whose magnitude and position follow the modulation of the laser light pattern.

[0049] The formation of such temperature patterns induces smaller cells formed by convection within the molten volume formed in the source material, which reduces the depth of the convection zone and therefore the depth of the molten volume, allowing for a flatter source that does not melt easily.

[0050] Furthermore, spatial localization of the convective cells can be achieved. For the same surface tension, a smaller convective cell results in less surface turbulence, and therefore improved resistance to source turbulence and splashing. In other words, the uniformity of the evaporated source material flux can be increased.

[0051] At the same time, the surface area of ​​the molten source material during the evaporation process can be increased, which area is more fully involved in the evaporation process, thereby increasing the flux of evaporated source material.

[0052] In summary, the system according to the second aspect of the invention allows for defined and stabilized convection patterns within the liquid melt volume of the source or source material, resulting in high flux evaporation with increased uniformity and temporal stability from a large surface area, thus enabling a large uniform and stable total deposition flux.

[0053] Preferably, the thermal laser evaporation system according to the second aspect of the invention may be characterised in that the thermal laser evaporation system is constructed to carry out the method according to the first aspect of the invention, thereby providing all the features and advantages described above with respect to the method according to the first aspect of the invention.

[0054] In another embodiment of the thermal laser evaporation system according to the second aspect of the invention, the laser source and / or the coupling means comprises adaptive optics for providing the laser radiation with a spatially modulated intensity pattern. The use of adaptive optics is a particularly easy and effective way to provide a spatially modulated intensity pattern of the laser radiation. In particular, adaptive optics can be used to dynamically change the provided intensity pattern during operation of the TLE system. This allows for example to generate different convection patterns with cell shapes or sizes depending on the overall intensity of the laser radiation impinging on the source surface.

[0055] Furthermore, the thermal laser evaporation system according to the second aspect of the invention may comprise a laser source and / or a coupling means for providing the laser radiation with a spatially modulated intensity pattern as a single laser beam. In other words, the complete intensity pattern including the spatial modulation is provided as a single laser beam. Thus, particularly simple optics can be used to direct the laser radiation into and / or within the reaction chamber and ultimately onto the source surface.

[0056] Alternatively, the thermal laser evaporation system according to the second aspect of the invention may be characterized in that the laser source and / or the coupling means provide the laser radiation with a spatially modulated intensity pattern as two or more separate laser beams. In particular, the use of two or more separate laser beams may be advantageous for intensity patterns where the intensity is at least substantially zero or zero outside the heating spot and / or heating line. In particular, this allows the zero intensity areas of the spatially modulated intensity pattern to be provided more easily.

[0057] According to another embodiment of the thermal laser evaporation system according to the second aspect of the invention, the system comprises two or more sources, each source having the same source material or being a different type of source material. This allows providing a wide variety of evaporation processes. By having the same source material, the evaporated respective source materials can be combined to provide an overall increased evaporation source material flux. By having different source materials, deposition of a mixture of different source materials can be performed. Preferably, for each of the two or more sources, laser radiation is provided that includes a spatially modulated intensity pattern.

[0058] The thermal laser evaporation system may further be characterized in that the system includes one or more actuators for moving each of the one or more sources at least substantially perpendicular or perpendicular to the surface of each of the one or more sources. Preferably, there is an actuator assigned to each of the one or more sources. By moving each source, it is possible to compensate for the depletion of source material that occurs in the sublimation process and thus to compensate for the reduction of the source height that increases the distance between the source surface and the substrate to be coated. Thus, it is possible to obtain a uniformity of the provided sublimation source material flux over a long period of time.

[0059] The invention will be explained in detail below using embodiments and with reference to the drawings. [Brief description of the drawings]

[0060] [Figure 1] FIG. 1 is a schematic diagram of the intensity pattern and evaporation process according to the current state of the art. [Diagram 2] FIG. 2 is a detailed diagram of the evaporation process according to the state of the art shown in FIG. 1. [Diagram 3] FIG. 2 is a schematic diagram of a spatially modulated intensity pattern and evaporation process according to the present invention. [Figure 4] 4A-4D are two examples of spatially modulated intensity patterns in accordance with the present invention. [Diagram 5] 4A-4C are two further examples of spatially modulated intensity patterns in accordance with the present invention. [Figure 6] 4A-4C are two further examples of spatially modulated intensity patterns in accordance with the present invention. [Figure 7] 1 is a schematic diagram of a thermal laser evaporation system according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] FIG. 3 shows, on the left (labeled "A"), a spatially modulated intensity pattern 60 implemented in a method according to the present invention and provided in a system 100 according to the present invention (see FIG. 7), and, on the right (labeled "B"), an evaporation process using intensity pattern 60.

[0062] The intensity pattern 60 includes seven heating spots 70 arranged in a rotationally symmetric pattern with a rotation angle of 60°, with the central heating spot 70 forming a symmetric point 90 of the intensity pattern 60.

[0063] Outside the heating spot 60, the intensity of the laser radiation 52 (see "B" in FIG. 3) is zero, or at least close to zero. In an alternative, but not shown, embodiment, it is also possible to gradually reduce the intensity outside the heating spot 70.

[0064] Figure "B" shows a cross-sectional side view of a source 30 consisting of source material 32. Laser radiation 52 provided as several laser beams 54 impinges on the surface 34 of the source 32 and follows the intensity pattern 60 shown in Figure 3 "A". This spreads out the absorbed energy and creates several counter-rotating cells of convection currents 38. Compared to the situation of a single heated spot 70 shown in Figure 2, the convection currents 38 loops are significantly smaller.

[0065] First, this reduces the depth of the melt volume 36, allowing for a flatter source 32 that does not melt as easily.

[0066] The second effect is the spatial localization of the convective cells formed by the convective currents 38. For the same surface tension, smaller convective cells result in less turbulence on the surface 34, and therefore better resistance to turbulence and splashing of the source material 32. Multiple adjacent convective currents 38 flowing in opposite directions generate spatially fixed and stable undulations of the surface 34. Thus, a stable high-flux evaporation from a large portion of the surface 34 can be achieved, allowing a large total deposition flux of evaporated source material 32 with high uniformity.

[0067] Preferably, the spatially modulated intensity pattern 60 that is implemented is selected relative to the source material 32 to be evaporated. This selection can be based, for example, on calculations, simulations, and / or experimental results.

[0068] At the same time, a strong temperature gradient can be maintained away from the outer edge of the intensity pattern 70 of the laser radiation 52, thereby enabling a preferred mode of operation with a liquid molten volume 36 contained within a solid piece of the same source material 32.

[0069] 4 to 6 show some possible embodiments of spatially modulated intensity patterns 70. In the following, general characteristics of the intensity patterns 70 provided by the present invention are described. Illustrated examples are included in the description.

[0070] Generally, all the illustrated intensity patterns 60 include several heating spots 70 and / or several heating lines 80. The intensities of the heating spots 70 and / or heating lines 80 may be equal or different depending on the actual application. For example, in a thermal laser evaporation system 100 (see FIG. 7 ) in which several different sources 30 include different source materials 32, an intensity pattern 60 suitable for each source material 32 can be used. This includes, but is not limited to, the maximum implemented intensity of the laser radiation 52, the intensity of each heating spot 70, the intensity along each heating line 80, and each spatial location within the intensity pattern 60.

[0071] Furthermore, for the previously described heated spots 70 (see, for example, intensity pattern 70 labeled "A" in FIGS. 4 and 5), the heated lines 80 can be part of the spatially modulated intensity pattern 60. See both intensity patterns shown in FIGS. 4, "B" in FIG. 5, and FIG. 6.

[0072] A first end 82 of each heating line 80 is connected to one heating spot 70 and a second end 84 is connected to another heating spot 70. As shown in FIG. 6, in a closed heating line 80, each end 82, 84 of the heating line 80 can be arbitrarily selected along each heating line 80.

[0073] The intensity of the laser radiation 52 preferably varies gradually, in particular monotonically, along the heating line 80 from the intensity value of the heating spot 70 at the first end 82 to the intensity value of the heating spot 70 at the second end 84. However, if the intensity values ​​of the heating spots 70 are the same, the intensity along the heating line 80 may also be constant.

[0074] The heating lines 80 can be linear, as shown in Figures 4 and 5 "B," or they can be curved and in the form of an arc, as shown in Figure 6.

[0075] It has been found that a rotationally symmetric shape of the intensity pattern 60 about a point of symmetry (2D) or an axis of symmetry (3D) 90 is advantageous in order to provide a uniform evaporation pattern. In Fig. 4 the intensity pattern is rotationally symmetric with a rotation angle of 180°, in Fig. 5 the rotation angle is 90°. However, a perfectly rotationally symmetric intensity pattern 60 is also possible, as shown in Fig. 6.

[0076] The intensity patterns shown in Figures 4 and 5 are periodic, and the intensity pattern 60 shown in Figure 6 "A" is periodic in that the radial distance between closed circular heating lines 80 is constant.

[0077] However, quasi-periodic shapes of the intensity pattern 60 are also possible, as shown in "B" of Figure 6, where, for example, the radial distance between closed circular heating lines 80 increases in the radial direction.

[0078] As another example, not explicitly shown, non-periodic embodiments of the implemented spatially modulated intensity pattern 60 are also possible. In particular, in a thermal laser evaporation system 100 (see FIG. 7 ) with several different sources, each source containing its own source material 32, it is possible to select a different intensity pattern 60 for each source, and thus an overall non-periodic intensity pattern 60.

[0079] Furthermore, time-dependent modulation of the spatially modulated intensity pattern 60, specifically the intensity patterns shown in Figures 4 to 6, is also possible.

[0080] 7 shows a schematic and simplified cross-sectional side view of a thermal laser evaporation system 100 according to the present invention. A source 30 and a target 40, specifically a substrate 42, are disposed within a reaction chamber 10. The reaction chamber 10 is filled with a reaction atmosphere 14, such as a vacuum or a suitable reaction gas.

[0081] Via the coupling means 12, laser radiation 52 provided as one or more laser beams 54 is coupled into the reaction chamber 10 for impinging on the surface 34 of the source 30. The laser radiation 52 is provided by a laser source 50. Adaptive optics 20, which may be part of the laser source 50 and / or the coupling means 12, is preferably used to provide the laser radiation 52 with an appropriately selected spatially modulated intensity pattern 60 for each source material 32.

[0082] Laser radiation 52 impinges on the surface 34 of the source 30. Because the laser radiation 52 includes the spatially modulated intensity pattern 60 described above, it can provide a high flux evaporation of the source material 32 from a large surface area. In summary, a large total deposition flux (indicated by the arrows in FIG. 7 ) of the source material 32 at the substrate 42 can be achieved. Using the actuator 110, the source 30 can be moved at least substantially perpendicular to the surface 34. This can compensate for depletion of the source material 32 due to the sublimation process. [Explanation of symbols]

[0083] 10 Reaction chamber 12 Coupling means 14 Reaction atmosphere 20 Adaptive Optics 30 Source 32 Sauce Ingredients 34 Surface 36 Melt Volume 38 Convection 40 Target 42 Substrate 50 Laser light source 52 Laser Radiation 54 Laser Beam 56 Reflected Laser Beam 60 Intensity Patterns 70 Heat Spot 80 Heating Line 82 First end 84 Second End 90 Symmetry point 100 Thermal Laser Evaporation System

Claims

1. A method of using a thermal laser evaporation (TLE) system (100), comprising: The system (100) comprises a reaction chamber (10) capable of being filled with a reaction atmosphere (14); one or more sources (30) disposed within the reaction chamber (10), each source (30) comprising a source material (32); a laser source (50) for providing laser radiation (52) to a surface (34) of the source (30) thereby vaporizing the source material (32); the laser radiation (52) having a spatially modulated intensity pattern (60); The method of claim 1, wherein the spatially modulated intensity pattern (60) comprises two or more spaced apart heating spots (70) having at least a local maximum intensity.

2. The method of claim 1 , wherein the intensity of the laser radiation (52) is at least substantially equal or equal in the two or more heating spots (70).

3. The method of claim 1 , wherein an intensity of the laser radiation (52) is different at the two or more heating spots (70) for each of the one or more sources (30).

4. The thermal laser evaporation system (100) includes two or more sources (30); The method of claim 1 or 2, wherein the spatially modulated intensity patterns (60) are at least substantially equal or equal in at least two of the two or more sources (30).

5. The thermal laser evaporation system (100) includes two or more sources (30); The method of claim 1 , wherein the spatially modulated intensity patterns (60) are different for at least two of the two or more sources (30).

6. the two or more heating spots (70) being connected by a linear heating line (80) of at least a local maximum intensity within the spatially modulated intensity pattern (60); a first end (82) of the heating line (80) is connected to one of the two heating spots (70); The method according to any one of claims 1 to 5, wherein a second end (84) of the heating line (80) is connected to the other of the two heating spots (70).

7. 7. The method of claim 6, wherein an intensity of the laser radiation (52) along the heating line (80) varies gradually, in particular monotonically, from the intensity of the heating spot (70) at the first end (82) of the heating line (80) to the intensity of the heating spot (70) at the second end (84) of the heating line (80).

8. 8. The method according to claim 6 or 7, wherein the heating line (80) is at least partially straight and / or curved and / or in the form of an arc.

9. The method according to claim 1 , wherein the spatially modulated intensity pattern (60) is rotationally symmetric about a point of symmetry.

10. 10. The method of claim 9, wherein the spatially modulated intensity pattern (60) is rotationally symmetric around an angle of 30° and / or 45° and / or 60° and / or 72° and / or 90° and / or 135° and / or 180°.

11. The method according to claim 1 , wherein the spatially modulated intensity pattern (60) is periodic.

12. The method according to claim 1 , wherein the spatially modulated intensity pattern (60) is quasi-periodic.

13. The method according to claim 1 , wherein the spatially modulated intensity pattern (60) is non-periodic.

14. 14. The method according to claim 1, wherein within the spatially modulated intensity pattern (60), the intensity of the laser radiation (52) is at least substantially zero or zero outside the heating spot (70) and / or the heating line (80).

15. 14. The method according to claim 1, wherein within the spatially modulated intensity pattern (60), the intensity of the laser radiation (52) gradually decreases outside the heating spot (70) and / or the heating line (80), in particular gradually decreases to zero.

16. The method of claim 1 , wherein the spatially modulated intensity pattern (60) is selected relative to the source material (32).

17. The method of claim 16, wherein selecting the spatially modulated intensity pattern (60) for the source material (32) is based on calculation and / or simulation.

18. The method of claim 16 or 17, wherein selecting the spatially modulated intensity pattern (60) for the source material (32) is based on experimental results.

19. The method of claim 1 , wherein the spatially modulated intensity pattern (60) further comprises a time-dependent modulation of the intensity of the laser radiation (52).

20. a reaction chamber (10) capable of being filled with a reaction atmosphere (14); one or more sources (30) disposed within the reaction chamber (10), each source comprising a source material (32); coupling means (12) provided by the reaction chamber (10) for coupling laser radiation (52) into the reaction chamber (10) for vaporizing the source material (32) by impinging on a surface (34) of the source (30); A thermal laser evaporation system (100) comprising: the laser source (50) providing the laser radiation (52) having a spatially modulated intensity pattern (60); A thermal laser evaporation system (100), wherein said spatially modulated intensity pattern (60) includes two or more spaced apart heating spots (70) having at least a local maximum intensity.

21. 21. The thermal laser evaporation system (100) of claim 20, wherein the thermal laser evaporation system (100) is configured to perform a method according to one of claims 1 to 19.

22. 22. The thermal laser evaporation system (100) of claim 20 or 21, wherein the laser source (50) and / or the coupling means (12) comprises adaptive optics (20) for providing the laser radiation (52) having the spatially modulated intensity pattern (60).

23. 23. The thermal laser evaporation system (100) of claim 20, wherein the laser source (50) and / or the coupling means (12) provide the laser radiation (52) having the spatially modulated intensity pattern (60) as a single laser beam (54).

24. 23. The thermal laser evaporation system (100) of claim 20, wherein the laser source (50) and / or the combining means (12) provide the laser radiation (52) having the spatially modulated intensity pattern (60) as two or more laser beams (54).

25. The system (100) includes two or more sources (30); The thermal laser evaporation system (100) of any one of claims 20 to 24, wherein each source (30) has the same source material (32) or is a different type of source material (32).

26. 26. The thermal laser evaporation system (100) of claim 20, wherein the system (100) includes one or more actuators (110) for moving each of the one or more sources (30) at least substantially perpendicular or perpendicular to the surface (34) of each of the one or more sources (30).

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