Method of using a thermal laser vaporization system and a thermal laser vaporization system

Abstract

The present invention relates to a method of using a thermal laser evaporation (TLE) system (100), comprising a reaction chamber (10) capable of being filled with a reaction atmosphere (14), one or more sources (30) arranged in the reaction chamber (10) each comprising a source material (32), and a laser source (50) for providing laser radiation (52) to a surface (34) of the source (30) for sublimating the source material (32). The present invention further relates to a thermal laser evaporation system (100), comprising a reaction chamber (10) capable of being filled with a reaction atmosphere (14), one or more sources (30) arranged in the reaction chamber (10) each comprising a source material (32), and coupling means (12) provided by the reaction chamber (10) for coupling the laser radiation (52) into the reaction chamber (10) for incident laser radiation (52) on a surface (34) of the source (30) for sublimating the source material (32).

Description

[Technical field]

[0001] The present invention relates to a method of using 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 comprising a source material, and a laser source for providing laser radiation to a surface of the source to sublimate the source material.Furthermore, the present invention 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 comprising a source material, and coupling means provided by the reaction chamber for coupling the laser radiation into the reaction chamber for incident laser radiation on a surface of the source to sublimate the source material. [Background technology]

[0002] In thermal laser evaporation (TLE), materials are evaporated and / or sublimated by laser heating in a controlled environment, typically in a reaction chamber filled with a reactive atmosphere, to coat a surface with a thin film. The efficiency of TLE depends on the localized heating of the source surface, since the growth rate increases exponentially with the power density in the laser radiation spot.

[0003] Such a single heated spot 70 forms the simplest laser intensity pattern 60, as shown in Figure 1A. When locally heated by a laser beam 54, typically laser radiation 52, a solid block of source material 32 of source 30 is sublimated from a spatially confined sublimation region 38. As shown in Figure 1B, this sublimation region 38 can be as large as the spot region 36 formed by the laser beam 54 incident on surface 34, especially if the spot region 36 covers the entire surface 34.

[0004] In most embodiments, however, the spot area 36 is generally smaller than the surface 34 of the source 30. In particular, when the spot area 36 is smaller than the surface 34 of the source 30, as shown in Figure 2A, a sublimation region 38 is constructed by the spot area 34 surrounded by a sufficiently heated region defined by the thermal conductivity of the respective source material 32. In other words, upon localized heating, a spatially restricted sublimation region 38 is produced on the surface 34 of the solid block of source material 32.

[0005] First, this sublimation region 38 forms a concave depression on the surface 34 (see FIG. 2B), which then sinks along the direction of the laser beam 54 according to the incidence angle 58 of the laser beam 54, forming a hole (see FIG. 2C). This occurs because the sublimation rate is usually highest at the center of the laser beam 54, where the radiation power density is highest. Although the initially slightly convex curvature may be beneficial for efficient deposition, this hole is very inefficient, since it blocks the flux of the sublimated source material 32 from propagating towards the substrate 42 (vertically upwards in the figure, see also FIG. 8). Also, the flux of the sublimated source material 32 from the hole peaks in the direction of the incidence of the laser beam 54, thereby increasing the coating of the entrance window or mirror of the laser beam. Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above, it is an object of the present invention to provide an improved method of use of a thermal laser evaporation system and an improved thermal laser evaporation system that do not have the above-mentioned disadvantages of the prior art. In particular, it is an object of the present invention to provide an improved method of use of a thermal laser evaporation system and an improved thermal laser evaporation system that allow for stable high flux sublimation from large surface areas. [Means for solving the problem]

[0007] The above object is achieved by the respective independent claims in the appended claims. In particular, the above object is achieved by a method for using a thermal laser evaporation system according to independent claim 1 and by a thermal laser evaporation system according to independent claim 23. The dependent claims describe preferred embodiments of the invention. Details and advantages described with respect to the method according to the first aspect of the invention also refer, wherever technically meaningful, 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 above object is achieved by a method of using a thermal laser evaporation (TLE) system, comprising a reaction chamber capable of being filled with a reaction atmosphere, one or more sources arranged in the reaction chamber, each containing a source material, and a laser source for providing laser radiation to a surface of the source to sublimate the source material, where the laser radiation has 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. Each of the heating spots is capable of sublimating the source material at a spot area on the surface. The respective spot areas of two adjacent heating spots on the surface seamlessly merge or partially overlap.

[0009] The method according to the first aspect of the invention is intended for use in a thermal laser evaporation system (TLE system for short). In particular, the scope of the invention encompasses TLE systems in which a laser is used to sublimate a source material. Such systems are generally already known. A laser beam provided by a laser source is most often used to sublimate a source material and to deposit the sublimated source material on a substrate provided as a target. Due to the deposition of laser energy on the surface of the source, the source material is sublimated directly from its solid phase into a flux of source material. In the following, the combined flux of source material sublimated by the laser radiation as a whole is designated as "sublimation pattern". However, within the scope of the invention, the expression sublimation process also encompasses a process in which source material is evaporated from a pool of liquid source material melted by the incident laser radiation.

[0010] The source is disposed within a reaction chamber. The reaction chamber can be sealed to the surrounding atmosphere and can be filled with a reaction atmosphere. The reaction atmosphere can be a vacuum, particularly a 10 -12 The pressure can be as low as 100 kPa or less, or can include a reactant gas at a pressure appropriate for the material to be deposited, e.g. a reactant gas providing oxygen for the deposition of an oxide of a sublimated source material. The maximum pressure tested so far is 100 kPa at a working distance of 60 mm. -2 hPa and high. 10 -2 Since deposition was possible without problems at 100 MPa, it is believed that even higher values ​​are possible.

[0011] The laser radiation is most often 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 comprise adaptive optics for shaping the laser radiation incident 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 with at least a local maximum intensity.

[0013] At least a local maximum intensity of the laser radiation at one of the heating spots means, in the sense of the present invention, that the heating spot is surrounded by an area in the intensity pattern, the intensity of which is less than or equal to the intensity of the laser radiation at the heating spot, in other words, the intensity of the laser radiation in the area surrounding each heating spot is not higher than the heating spot itself.

[0014] 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, a local maximum of the intensity of the laser radiation is reached at the location of at least one of the two or more heating spots. In summary, by implementing the method according to the first aspect of the invention, it is prohibited to provide a laser radiation with a single heating spot. The energy deposition from the laser radiation to the source material is distributed over a larger area than the surface of the source material.

[0015] Preferably, the heating spot according to the invention is circular, in particular has a circularly symmetric Gaussian intensity profile, for example provided by focusing the laser radiation on the surface of the source material. The spot size is preferably defined as the maximum half of the full width of the Gaussian profile. Here, the diameter can be less than 10 mm, preferably less than 1 mm, up to several cm, in particular 10 cm or more.

[0016] The individual heat spots can sublimate the source material in a sublimation region formed by the respective heat spot on the surface of the source and further surrounding the respective heat spot and defined by the thermal conductivity of the source material, in other words, the region surrounding the spot region is a region where the temperature of the source material provided by the transport of thermal energy from the respective heat spot spot region is high enough to cause sublimation of the source material.

[0017] However, for each of these heated spots, locally limited sublimation leads to the formation of holes in the bulk of the source material, according to the angle of incidence of the incident laser radiation, as explained with respect to FIG.

[0018] Therefore, according to the present invention, two or more heat spots of a spatially modulated intensity pattern are arranged such that the respective spot areas of two adjacent heat spots on a surface seamlessly merge or partially overlap, whereby the two or more heat spots no longer each form an individual depression or hole in the bulk of the source material, and the wall remaining between each depression formed by two adjacent heat spots is automatically sublimated.

[0019] In other words, the trailing edge of the cavity formed by one of the heating spots is the same as and / or overlaps with the leading edge of the cavity formed by the adjacent heating spot in front of it, so that the sublimation regions of the two adjacent heating spots merge, which results in an increased area of ​​the surface of the source material that is sublimated during the sublimation process, and as this area is involved in the sublimation process as a whole, the flux of the sublimated source material can be increased.

[0020] In summary, by implementing the method according to the first aspect of the invention for use with a TLE system, sublimation of an extended area of ​​the surface of the source can be defined and stabilized, resulting in high flux sublimation from a large surface area with increased uniformity, thus enabling high flux and uniform overall deposition.

[0021] The method according to the invention may also include that the spot areas of all the heating spots of the intensity pattern located on the surface of a single source form a continuous sublimation area on the surface of the respective source. A continuous sublimation area according to the invention is in particular a gapless area on the surface of the source where the incident laser radiation causes the sublimation of the source material. Thus, sublimated source material emerges from each part of the continuous sublimation area. This can further improve the uniformity of the provided flux of sublimated source material.

[0022] Furthermore, the method according to the first aspect of the invention can be characterized in that the intensity of the laser radiation is equal or at least essentially equal in two or more heated spots of the intensity pattern projected on the surface of the single source. Thus, the energy deposition from the laser radiation on the source material of the single source is also equal or at least essentially equal in the heated spots. This results in equal or at least essentially equal sublimation of the source material in each sublimation region. As a result, the uniformity of the flux of sublimated source material across the surface of the single source can be further improved.

[0023] According to an alternative embodiment of the method according to the first aspect of the invention, the intensity of the laser radiation is different in two or more heating spots of the intensity pattern projected on the surface of the single source. Thus, the energy deposition from the laser radiation on the source material of the single source is also different in the heating spots. Thereby, a specific shaping of the sublimation pattern over the surface of the single source can be provided.

[0024] Also, the method according to the first aspect of the invention can be characterized in that the thermal laser evaporation system comprises two or more sources, where the spatially modulated intensity pattern is equal or at least essentially equal for at least two of the two or more sources. Thus, even if two or more sources are used for sublimation, the energy deposition for each source can be equal. In particular, but not exclusively, in the case of sources providing the same source material, a particularly uniform sublimation of the source material from all sources present in the TLE system can be provided.

[0025] Alternatively or additionally, the method according to the first aspect of the invention can be characterized in that the thermal laser evaporation system comprises two or more sources. Here, the spatially modulated intensity pattern is different for at least two of the two or more sources. Thus, when two or more sources are used for sublimation, the energy deposition for each source can be specifically set. In particular, each source can preferably contain its own source material. In other words, the source materials provided by the different sources are different. As a non-limiting example, as source materials, a first source can provide titanium, a second source can provide niobium, and a third source can provide tantalum. Providing different spatially modulated intensity patterns for the different sources allows certain boundary conditions to be taken into account, such as for example the sublimation temperature of the respective source material. Thereby, a uniform and in particular simultaneous sublimation of the different source materials can be provided.

[0026] According to another embodiment of the method according to the first aspect of the invention, two or more of the two or more heating spots are connected in a spatially modulated intensity pattern by a linear heating line with at least a local maximum intensity. Here, 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 extends between the heating spots in an intensity pattern with at least a local maximum intensity of the laser radiation. Thus, the energy deposition in the source material is also increased along the heating line, which results in the formation of a sublimation region also with respect to the heating line. In other words, the respective sublimation regions of the two heating spots are seamlessly connected by a sublimation region formed around the heating region of the respective heating line. In summary, the possibilities of forming and controlling a sublimation pattern on the surface of the source can be increased.

[0027] In particular, each heating line with at least a local maximum intensity of the laser radiation can be described as connecting two heating spots at their respective end points. Also closed heating lines within the intensity pattern are possible. Two heating spots can be defined at any position along such a closed heating line. As a result, they are automatically connected by a closed heating line.

[0028] Also, the method according to the first aspect of the invention can be further enhanced by gradually, in particular monotonically, varying the intensity of the laser radiation 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 gradually, in particular monotonically, varying the intensity along the heating line, irregular or stepwise changes in intensity along the heating line can be prevented. Thereby, a uniform sublimation pattern can be more easily formed. The gradual change according to the invention includes only smooth intensity changes along the heating line. Here, the monotonous change further requires that the intensity of the laser radiation along the heating line only decreases or only increases or remains constant along the complete heating line.

[0029] 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 arc-shaped. This list includes preferred shapes of the heating lines, but other shapes and combinations of these shapes are also possible. In particular, the shape of the respective heating line can be selected depending on the boundary conditions of the sublimation process and / or the intended sublimation pattern, in particular the source material used.

[0030] 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 or axis of symmetry. By providing a rotationally symmetric spatially modulated intensity pattern, the resulting sublimation pattern is also rotationally symmetric. This can increase the uniformity of the flux of the sublimated source material. Furthermore, the source and / or the provided source material often contain such rotational symmetry about a point 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.

[0031] The method according to the first aspect of the invention may be further enhanced by making the spatially modulated intensity pattern rotationally symmetric by 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 angles of rotational symmetry, but other angles are possible.

[0032] According to another embodiment of the method according to the first aspect of the invention, the spatially modulated intensity pattern is periodic. In a periodic intensity pattern, small building blocks, such as heating spots or heating lines, containing a small number of elements that are fixedly positioned relative to each other, are repeated two or more times to form the overall intensity pattern. This keeps the distance and relative orientation between the elements of adjacent building blocks constant. This makes it easier to form a uniform sublimation pattern.

[0033] 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, a small building block containing a small number of elements, such as heating spots or heating lines, is repeated two or more times to form an overall intensity pattern. However, the distance and relative orientation between adjacent building blocks, as well as the internal arrangement of the elements of any building block, is changed, most often increased, depending on the distance to the selected fixing element. Preferably, the fixing element can be a symmetry point or axis to provide an overall rotationally symmetric intensity pattern, or a mirror surface. Thereby, sublimation patterns with spatial dependence, especially radial dependence or mirror symmetry or inversion symmetry, can be more easily provided.

[0034] According to yet another alternative embodiment of the method according to the first aspect of the invention, the spatially modulated intensity pattern is aperiodic, whereby an intensity pattern capable of providing an arbitrary shape of the intensity pattern can be provided.

[0035] As a particular 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 periodic and / or quasi-periodic in their components. In particular, in the case of a TLE system with multiple sources, each source has its own source material, and the components of the intensity pattern dedicated to each source can be periodic and / or quasi-periodic according to the needs of the respective source material. Here, the intensity pattern is non-periodic as a whole.

[0036] 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 intensity of the laser radiation is zero or at least essentially zero. In other words, the intensity pattern has a sharp and abrupt boundary at least between the area of ​​local intensity maximum and all other areas, thereby providing a specifically localized energy deposition on the source material. In most cases, this provides a high degree of control over the sublimation pattern.

[0037] Alternatively, the method according to the first aspect of the invention may include that, outside the heating spots and / or heating lines, within the spatially modulated intensity pattern, the intensity of the laser radiation is gradually reduced, in particular gradually reduced to zero. For example, the intensity may be reduced depending on the distance to the respective heating spot and / or heating line, in particular proportional to the distance, or polynomially, or with any suitable monotonic functional dependency. In other words, the intensity pattern includes a smoothly modulated intensity change. Thus, abrupt changes in the energy deposition on the source material may be prohibited. This may lead to a higher stability of the formed sublimation pattern. Also, a gradual reduction in the intensity of the laser radiation may be more easily provided compared to abrupt drops in intensity to zero.

[0038] The method according to the first aspect of the invention may also include that the spatially modulated intensity pattern is selected as a function of the source material. By selecting the respective intensity pattern as a function of the source material, the properties of the source material and thus the resulting boundary conditions for the sublimation process can be taken into account. Thereby, a uniform sublimation pattern and thus a high flux of sublimated source material can be more easily provided.

[0039] Alternatively or additionally, the spatially modulated intensity pattern is selected depending on the intended flux distribution of the sublimated source material, including, for example, the general direction of the flux of the sublimated source material and / or the spatial variations within the sublimation pattern, in particular the local density of each flux of the sublimated source material, thereby providing a specific sublimation pattern adapted to the respective needs and boundary conditions.

[0040] The method according to the invention can be further enhanced by selecting the spatially modulated intensity pattern according to the intended flux distribution of the sublimated source material. This involves selecting the angle of incidence at which the laser radiation strikes the surface of the source. As mentioned above, each of the heating spots causes the formation of pits and, in the long term, holes in the surface of the source material according to the angle of incidence of the incident laser radiation. By actively selecting the angle of incidence, the formation of pits and / or holes can also be regulated and adapted to the current needs and boundary conditions.

[0041] Furthermore, the method according to the first aspect of the invention can be enhanced by the fact that the selection of the spatially modulated intensity pattern as a function of the source material is based on calculations and / or simulations. Calculations and / or simulations can be provided for a wide variety of source materials and / or sources of different shapes. As the material constants of the ultra-high purity elements used as source materials are well known, the most suitable intensity pattern for the laser radiation can be found and defined easily, in particular quickly and at low cost.

[0042] 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 as a function of the source material is performed on the basis of experimental results. The use of experimental results to select the optimal intensity pattern allows already integrated knowledge to be incorporated into 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 reaction chamber actually used. Thus, sources of error based on inappropriate assumptions during the selection process can be avoided.

[0043] 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 intensity of the laser radiation. Such a time-dependent modulation can be, for example, a simple decrease and / or increase of the overall intensity. This leads, for example, to a pulsed flux of sublimated source material. However, a time-dependence of the spatial shape of the intensity pattern is also possible, such as a global rotation or lateral shift of the intensity pattern. Also a complete modification of the spatial shape is feasible. This can provide a time-dependent flux control, including the spatial shape of the flux of sublimated source material. This can serve 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.

[0044] According to a second aspect of the invention, the above 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 and each containing a source material, and coupling means provided by the reaction chamber for coupling the laser radiation into the reaction chamber for incident on a surface of the source to sublimate the source material, wherein the laser source provides laser radiation with a spatially modulated intensity pattern, wherein the spatially modulated intensity pattern comprises two or more spaced apart heating spots having at least a locally maximum intensity, each of the heating spots being capable of sublimating the source material in a spot area on the surface, wherein the respective spot areas of two adjacent heating spots on the surface seamlessly merge or partially overlap.

[0045] In a thermal laser evaporation system according to the second aspect of the invention, a laser beam provided by a laser source is most often used to sublimate a source material and deposit the sublimated source material on a substrate provided as a target. Due to the deposition of laser energy on the surface of the source, the source material is sublimated directly from the solid phase of the source material into a flux of source material. In the following, the combined flux of source material sublimated by the laser radiation as a whole is also referred to as a "sublimation pattern". However, within the scope of the invention, the expression sublimation process also encompasses the melting and subsequent evaporation of the source material. The laser radiation is coupled into the reaction chamber via coupling means. The coupling means can be, for example, a simple window in the chamber wall of the reaction chamber.

[0046] The source is disposed within a reaction chamber. The reaction chamber can be sealed to the surrounding atmosphere and can be filled with a reaction atmosphere. The reaction atmosphere can be a vacuum, particularly a 10 -12 The pressure may be low, at or below 100 kPa, or may include a reactant gas at a pressure appropriate for the material being deposited, for example a reactant gas that provides oxygen for the deposition of an oxide of a sublimated source material.

[0047] 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 may be connected in the spatially modulated intensity pattern by a heating line. The heating line also has at least a local maximum intensity.

[0048] As mentioned above, the heating spot according to the invention is preferably circular, in particular has a circularly symmetric Gaussian intensity profile, for example provided by focusing the laser radiation on the surface of the source material. The spot size is preferably defined as the maximum half of the full width of the Gaussian profile. Here, the diameter can be less than 10 mm, preferably less than 1 mm, up to several cm, in particular 10 cm or more.

[0049] At least a local maximum intensity of the laser radiation means in the sense of the present invention that the heating spot is surrounded by a region in the intensity pattern, the intensity of which is less than or equal to the intensity of the laser radiation at the heating spot, in other words the intensity of the laser radiation in the region surrounding each heating spot is not higher than the heating spot itself.

[0050] 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, a maximum value of the intensity of the laser radiation is reached at the location of at least one of the two or more heating spots.

[0051] In summary, according to the present invention, TLE systems in which the laser radiation has a single heating spot are not included. The energy deposition from the laser radiation to the source material is distributed to two or more heating spots and thus distributed over a larger area of ​​the surface of the source material. Thus, the area of ​​the surface of the source material sublimated during the sublimation process can be increased. The flux of the sublimated source material can be increased because the area is involved in the sublimation process as a whole.

[0052] Also, each of the heating spots can sublimate the source material in a spot area on the surface, and the respective spot areas of two adjacent heating spots on the surface can seamlessly merge or partially overlap, so that the two or more heating spots no longer form individual depressions and holes respectively in the bulk of the source material, and the wall remaining between the respective depressions formed by the two adjacent heating spots is automatically sublimated. Thereby, the sublimation areas of the two adjacent heating spots merge. As a result, the area of ​​the surface of the sublimated source material during the sublimation process can be increased. Since the area is involved in the sublimation process as a whole, the flux of the sublimated source material can be increased.

[0053] In summary, in the system according to the second aspect of the invention, sublimation from an extended area of ​​the surface of the source can be defined and stabilized, resulting in high flux sublimation from a large surface area with increased uniformity, thus allowing for a high and uniform overall deposition flux.

[0054] Preferably, the thermal laser evaporation system according to the second aspect of the invention may be characterised in that it is adapted to carry out the method according to the first aspect of the invention, thereby providing all the features and advantages mentioned above with respect to the method according to the first aspect of the invention.

[0055] 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. Using adaptive optics is a particularly simple 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 makes it possible to generate different sublimation patterns, even on different sections of the sublimation pattern, such that for example the shape and / or size of the sublimation pattern depends on the distribution of the intensity of the laser radiation incident on the surface of the source. Furthermore, the thermal laser evaporation system according to the second aspect of the invention may comprise a laser source and / or a coupling means 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, a particularly simple optical system can be used to guide the laser radiation into the reaction chamber and finally onto the surface of the source.

[0056] Alternatively, the thermal laser evaporation system according to the second aspect of the invention can 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 for intensity patterns where the intensity is zero or at least essentially zero outside the heating spot and / or heating line, it can be advantageous to use two or more separate laser beams. This makes it easier to provide in particular the zero intensity regions of the spatially modulated intensity pattern.

[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 comprises the same source material or comprises different types of source material. Thereby, a wide variety of sublimation processes can be provided. By having the same source material, the respective sublimated source materials are combined into an overall enhanced flux of sublimated source material. By having different source materials, deposition of a mixture of different source materials can be provided. Preferably, laser radiation comprising a specifically adapted spatially modulated intensity pattern is provided for each of the two or more sources.

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

[0059] Hereinafter, the present invention will be described in detail with reference to the embodiments of the present invention and the accompanying drawings. [Figure 1] FIG. 1 is a schematic diagram of intensity patterns and sublimation processes in the art. [Diagram 2] FIG. 2 is a more detailed diagram of the prior art sublimation process shown in FIG. 1. [Diagram 3] FIG. 2 is a schematic diagram of a spatially modulated intensity pattern and sublimation process in accordance with the present invention. [Figure 4] FIG. 2 illustrates two different flux distributions of sublimated source material provided by the sublimation process according to the present invention. [Diagram 5]1A-1C show two examples of spatially modulated intensity patterns according to the present invention. [Figure 6] 5A-5C show two further examples of spatially modulated intensity patterns in accordance with the present invention; [Figure 7] 5A-5C show two further examples of spatially modulated intensity patterns in accordance with the present invention; [Figure 8] FIG. 1 is a schematic diagram of a thermal laser evaporation system in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0060] Figure 3A shows a spatially modulated intensity pattern 60 achieved by a method according to the invention and provided to a system 100 according to the invention (see Figure 8). Figures 3B and 3C show a sublimation process using intensity pattern 60.

[0061] The intensity pattern 60 includes seven heating spots 70 arranged in a rotationally symmetric pattern with a rotation angle of 60°. The central heating spot 70 forms a point of symmetry 90 of the intensity pattern 60 and the intersection of the axis of symmetry perpendicular to the plane of the drawing with the plane of the drawing.

[0062] Outside the heating spot 60, the intensity of the laser radiation 52 (see Figs. 3B and C) is zero, or at least close to zero. In an alternative embodiment (not shown), the intensity can be gradually reduced outside the heating spot 70.

[0063] FIGURE 3B is a cross-sectional view through a source 30 containing a source material 32. Laser radiation 52, provided as multiple laser beams 54 having angles of incidence 58, is incident on a surface 34 of the source 32 according to an intensity pattern 60 shown in FIGURE 3A. Individual heating spots 70 can sublimate the source material 32 in respective sublimation regions 38 surrounding respective spot areas 36. In each sublimation region 38, sublimation of the source material forms a depression in the surface 34.

[0064] However, the sublimation regions 38 seamlessly merge or partially overlap. Thus, the trailing edge of the depression formed by one of the heat spots 70 is identical to and / or overlaps with the leading edge of the depression formed by the adjacent heat spot 70 in front of it. The sublimation regions 38 of the two adjacent heat spots 70 thereby merge. As a result, the area of ​​the surface 34 of the source material 32 that is sublimated during the sublimation process is increased and further smoothed.

[0065] Sublimation of source material 32 from surface 34 of source 30 causes the surface to recede. In most cases, substrate 42 (see FIG. 8) to be coated remains stationary, so depletion can be corrected by moving source 30 perpendicular to its surface 34. This procedure can be performed by actuator 110 (see FIG. 8) and is shown by the upward arrow next to source 30 in FIG. 3C. This allows the distance between surface 34 of source 30 and substrate 42 to be kept constant, thereby extending the period of uniform deposition.

[0066] Two different flux distributions of sublimated source material 32 are shown diagrammatically in Figure 4. Figure 4A shows sublimation from a perfectly flat surface. This produces a cosine-shaped flux distribution, as shown by the circular plot in polar coordinates. However, the ideal case of a perfectly flat surface 34 is rarely met.

[0067] FIG. 4B shows a flux distribution for surface 34 that deviates from a perfectly flat shape. In particular, previous sublimation of source material 32 by the incident laser beam 54 can form visible depressions in surface 34. However, the resulting flux distribution can be inferred from that from flat surface 34 by assuming that the infinitesimal surface elements of the curved surface individually follow the same cosine-shaped distribution as shown in FIG. 4A. The individual contributions are then summed or integrated to obtain the flux distribution for curved surface 34. Since surface elements close to the edge of the concave depression in the sublimated surface 34 are tilted towards the center of the depression, their individual flux distributions are also tilted towards the normal symmetry axis of the depression. This results in a forward-peaked flux distribution as shown in FIG. 4B.

[0068] It should be noted that the flux distribution shown in Fig. 4B is merely exemplary. Also, other types of distributions are possible, such as a dispersed distribution and / or a distribution with peaks in any direction. In summary, by appropriately selecting the spatially modulated intensity pattern 60 of the laser radiation 52, a flux distribution of the sublimated source material 32 that meets the needs and boundary conditions of the present sublimation process can be provided.

[0069] 5 to 7 show some possible embodiments of the spatially modulated intensity pattern 70. In the following, general characteristics of the intensity pattern 70 provided by the present invention are described. The examples shown in the figures are included in the description.

[0070] Generally, all the intensity patterns 60 shown in the figures include multiple heating spots 70 and / or multiple 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. 8 ) having multiple different sources 30 containing different source materials 32, a suitable intensity pattern 60 can be used for each source material 32. This includes, but is not limited to, parameters such as the maximum intensity of the laser radiation 52, the intensity of each heating spot 70, the intensity along each heating line 80, and their respective spatial arrangements within the intensity pattern 60. Also, the incidence angle 58 of the incident laser beam 54 can be appropriately selected.

[0071] In addition to the heating spots 70 described above (see, for example, the intensity pattern 70 shown in Figures 5 and 6A), heating lines 80 can also be part of the spatially modulated intensity pattern 60 (see both the intensity patterns shown in Figures 5 and 6B, and Figure 7).

[0072] Of each heating line 80, a first end 82 is connected to one heating spot 70, and a second end 84 is connected to another heating spot 70. As shown in FIG. 7, in the case of a closed heating line 80, each end 82 and 84 of the heating line 80 may be arbitrarily selected depending on each heating line 80.

[0073] Preferably, the intensity of the laser radiation 52 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 be constant.

[0074] As shown in Figures 5 and 6B, the heating lines 80 can be straight. Alternatively, the heating lines 80 can be curved, or even arcuate, as shown in Figure 7.

[0075] It has been found that in order to provide a uniform sublimation pattern, a shape of the intensity pattern 60 that is rotationally symmetric about a point of symmetry 90, i.e. an axis of symmetry, is advantageous. In Fig. 5 the intensity pattern is rotationally symmetric about a rotation angle of 180° and in Fig. 6 it is rotationally symmetric about a rotation angle of 90°. However, intensity patterns 60 with perfect rotational symmetry are also possible, as shown in Fig. 7.

[0076] The intensity patterns shown in Figures 5 and 6 are periodic, and the intensity pattern 60 shown in Figure 7A is periodic in the sense that the radial distance between closed circular heating lines 80 is constant.

[0077] In contrast, quasi-periodic shapes of the intensity pattern 60 are also possible, for example where the radial distance between closed circular heating lines 80 increases radially, as shown in FIG. 7B.

[0078] As another example (not explicitly shown), non-periodic implementations of the realized spatially modulated intensity pattern 60 are also possible. In particular, in a thermal laser evaporation system 100 (see FIG. 8 ) having multiple different sources, each containing its own source material 32, it is possible to select a different intensity pattern 60 for each source, and thus a non-periodic intensity pattern 60 as a whole.

[0079] Also a time-dependent modulation of the spatially modulated intensity pattern 60 is possible, in particular the intensity patterns shown in Figures 5 to 7.

[0080] 8 shows a schematic and simplified cross-sectional view of a thermal laser evaporation system 100 according to the invention. A source 30 and a target 40, in particular a substrate 42, are arranged in a reaction chamber 10. The reaction chamber 10 is filled with a reaction atmosphere 14, for example a vacuum or a suitable reaction gas.

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

[0082] Laser radiation 52 is incident on the surface 34 of the source 30. As the laser radiation 52 comprises the spatially modulated intensity pattern 60 described above, it is possible to provide a high flux sublimation of the source material 32 from a large surface area. In summary, a high and uniform overall deposition of the flux of the source material 32 on the substrate 42 (indicated by the arrows in FIG. 7) can be achieved. Using the actuator 110, the source 30 can be moved at least essentially perpendicularly to its surface 34, thereby providing compensation for the depletion of the source material 32 by 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: Spot area 38: Sublimation area 40: Target 42: Circuit board 50: Laser source 52: Laser radiation 54: Laser beam 58: Angle of incidence 60: Strength pattern 70: Heating spot 80: Heating line 82: First end 84: Second end 90: Symmetry point 100: Thermal laser vaporization system 110: Actuator

Claims

1. A method of using a thermal laser evaporation (TLE) system (100), comprising: 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) including a source material (32); and a laser source (50) for providing laser radiation (52) to a surface (34) of the source (30) to sublimate the source material (32); the laser radiation (52) having a spatially modulated intensity pattern (60); the spatially modulated intensity pattern (60) includes two or more spaced apart heating spots (70) having at least a local maximum intensity, each of the heating spots (70) capable of sublimating the source material (32) at a spot region (36) on the surface (34); the spot areas (36) of each of two adjacent heating spots (70) on the surface (34) seamlessly merge or partially overlap; method.

2. 2. The method of claim 1, wherein the spot areas (36) of all the heating spots (70) of the spatially modulated intensity pattern (60) located on the surface (34) of a single source (30) form a continuous sublimation area (38) on the surface (34) of each of the sources (30).

3. 3. The method of claim 1 or 2, wherein the intensity of the laser radiation (52) is equal or at least essentially equal in two or more of the heating spots (70) of the spatially modulated intensity pattern (60) projected onto the surface (34) of a single source (30).

4. 3. The method of claim 1 or 2, wherein the intensity of the laser radiation (52) is different in two or more of the heating spots (70) of the spatially modulated intensity pattern (60) projected onto the surface (34) of a single source (30).

5. The method of any one of claims 1 to 4, wherein the thermal laser evaporation system (100) comprises two or more of the sources (30), and the spatially modulated intensity patterns (60) are equal or at least essentially equal for at least two of the two or more of the sources (30).

6. The method of any one of claims 1 to 5, wherein the thermal laser evaporation system (100) comprises two or more of the sources (30), and the spatially modulated intensity pattern (60) is different for at least two of the two or more of the sources (30).

7. 7. The method according to claim 1, wherein two or more of the two or more heating spots (70) are connected in the spatially modulated intensity pattern (60) by a linear heating line (80) having at least a local maximum intensity, a first end (82) of the heating line (80) being connected to one of the two heating spots (70) and a second end (84) of the heating line (80) being connected to the other of the two heating spots (70).

8. 8. The method of claim 7, wherein the intensity of the laser radiation (52) along the heating line (80) changes 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).

9. 9. The method according to claim 7 or 8, wherein the heating line (80) is at least partially straight and / or curved and / or arcuate.

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

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

12. The method of any one of claims 1 to 10, wherein the spatially modulated intensity pattern (60) is periodic.

13. The method of any one of claims 1 to 10, wherein the spatially modulated intensity pattern (60) is quasi-periodic.

14. The method of any one of claims 1 to 10, wherein the spatially modulated intensity pattern (60) is non-periodic.

15. The method according to any one of the preceding claims, wherein within the spatially modulated intensity pattern (60), outside the heating spots (70) and / or the heating lines (80), the intensity of the laser radiation (52) is zero or at least essentially zero.

16. The method according to any one of claims 1 to 14, wherein within the spatially modulated intensity pattern (60), outside the heating spots (70) and / or the heating lines (80), the intensity of the laser radiation (52) is gradually reduced, in particular gradually reduced to zero.

17. The method of any one of claims 1 to 16, wherein the spatially modulated intensity pattern (60) is selected in response to the source material (32).

18. The method of any one of claims 1 to 17, wherein the spatially modulated intensity pattern (60) is selected according to an intended flux distribution of the sublimated source material (32).

19. 20. The method of claim 18, wherein selecting the spatially modulated intensity pattern (60) according to an intended flux distribution of the sublimated source material (32) comprises selecting an angle of incidence (58) at which the laser radiation (52) strikes the surface (34) of the source (30).

20. The method according to any one of claims 17 to 19, wherein the selection of the spatially modulated intensity pattern (60) is based on calculations and / or simulations.

21. The method according to any one of claims 17 to 20, wherein the selection of the spatially modulated intensity pattern (60) is based on experimental results.

22. The method of any one of claims 1 to 21, wherein the spatially modulated intensity pattern (60) further comprises a time-dependent modulation of the intensity of the laser radiation (52).

23. A thermal laser evaporation system (100) comprising a reaction chamber (10) capable of being filled with a reaction atmosphere (14), one or more sources (30) arranged in said reaction chamber (10) each containing a source material (32), and coupling means (12) provided by said reaction chamber (10) for coupling laser radiation (52) into said reaction chamber (10) for incident laser radiation (52) on a surface (34) of said source (30) to sublimate said source material (32), a laser source (50) provides the laser radiation (52) having a spatially modulated intensity pattern (60), the spatially modulated intensity pattern (60) including two or more spaced apart heating spots (70) having at least a local maximum intensity, each of the heating spots (70) capable of sublimating the source material (32) at a spot area (36) on the surface (34), the spot areas (36) of each of two adjacent heating spots (70) on the surface (34) seamlessly merging or partially overlapping; A thermal laser vaporization system (100).

24. A thermal laser evaporation system (100) according to claim 23, configured to carry out the method according to any one of claims 1 to 22.

25. 25. A thermal laser evaporation system (100) according to claim 23 or 24, 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).

26. The thermal laser evaporation system (100) of any one of claims 23 to 25, 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).

27. The thermal laser evaporation system (100) of any one of claims 23 to 25, wherein the laser source (50) and / or the coupling means (12) provide the laser radiation (52) having the spatially modulated intensity pattern (60) as two or more separate laser beams (54).

28. The thermal laser evaporation system (100) of any one of claims 23 to 27, wherein the thermal laser evaporation system (100) includes two or more sources (30) each including the same source material (32) or includes two or more sources (30) each including a different type of source material (32).

29. The thermal laser evaporation system (100) of any one of claims 23 to 28, comprising one or more actuators (110) for moving one or more of the sources (30) perpendicular or at least essentially perpendicular to the surface (34) of each of the sources (30).

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