System comprising an aperture and a dispersing element for applying electromagnetic radiation onto a source material, and method for aligning an aperture

The present invention relates to an aperture (10) for electromagnetic radiation (100), preferably electromagnetic radiation (100) comprising a wavelength between 1 nm and 20 μm, comprising an aperture body (20) made of a body material (22) transparent for the electromagnetic radiation (100). Further, the present invention relates to a method for aligning an aperture (10), and additionally to a system (70) for applying electromagnetic radiation (100) onto a source material and a dispersing element (90) for such a system (70).

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a 371 National Phase Application of Patent Application PCT/EP2019/074253, filed on Sep. 11, 2019, which is incorporated herein by reference, in its entirety.

The present invention relates to an aperture for electromagnetic radiation, preferably electromagnetic radiation comprising a wavelength between 1 nm and 20 μm, comprising an aperture body made of body material transparent for the electromagnetic radiation. Further the present invention relates to a method for aligning an aperture, and additionally to a system for applying electromagnetic radiation onto a source material and a dispersing element for such a system.

A deposition of a source material to a target material in thin deposition layers is a technique widely used in modern technology, for instance in the production of specialized semiconductors for electronic elements. To provide an evaporation and/or sublimation of source material, it is possible to use electromagnetic radiation, for instance provided by a laser beam, directed onto the source material. To control the deposition procedure, it is of advantage to collimate the electromagnetic radiation used in the system. Further on, as for the evaporation and/or sublimation of the source material often a high energy density of the electromagnetic radiation is necessary, the energy deposition into the used collimators and/or apertures has to be minimized to ensure a long lifetime of the used equipment. In addition, also electromagnetic radiation not used for the evaporation and/or sublimation has to be absorbed somewhere in the system. This can lead to problems due to the aforementioned high energy density of the electromagnetic radiation and the resulting energy deposit into structures of the system.

In view of the above, it is an object of the present invention, to provide an improved aperture for electromagnetic radiation, an improved method for aligning an aperture, an improved system for applying electromagnetic radiation onto a source material and an improved dispersing element for such a system, which do not have the aforementioned drawbacks of the state of the art. In particular it is an object of the present invention to provide an aperture, a method for aligning an aperture, a system and a dispersing element which allow controlling an energy deposit into the elements of the system in an especially easy and cost-efficient way.

This object is satisfied by the patent claims. In particular, this object is satisfied by an aperture for electromagnetic radiation according to claim1, by a method for aligning an aperture according to claim26, by a system for applying electromagnetic radiation onto a source material according to claim28and by a dispersing element for such a system according to claim32. The dependent claims describe preferred embodiments of the invention. Details and advantages described with respect to an aperture according to the first object of the invention also refers to a method according to the second aspect of the invention, to a system according to the third aspect of the invention and to a dispersing element according to the fourth aspect of the invention and vice versa, if of technical sense.

According to a first aspect of the invention, the object is satisfied by an aperture for electromagnetic radiation, preferably electromagnetic radiation comprising a wavelength between 1 nm and 20 μm, comprising an aperture body made of a body material transparent for the electromagnetic radiation, the aperture body limited with respect to an impinging direction of the electromagnetic radiation by a facing surface facing the electromagnetic radiation and an averted surface opposite to the facing surface, wherein the aperture body comprises an aperture opening continuously extending between a facing orifice in the facing surface and an averted orifice in the averted surface, and wherein the facing orifice is surrounded by a refraction section, the refraction section being inclined inward with respect to the facing surface into the aperture body by an angle α with respect to the impinging direction, and wherein the averted orifice is surrounded by a reflection section, the reflection section being inclined inward with respect to the averted surface into the aperture body by an angle β with respect to the impinging direction.

An aperture according to the present invention is intended but not limited for a use in a system, in which electromagnetic radiation is applied onto a source material to evaporate and/or sublimate source material. The aperture according to the invention can be used to define the beam of electromagnetic radiation, especially the size of the beam perpendicular to its impinging direction. Preferably, the aperture according to the invention is adapted for an electromagnetic radiation comprising a wavelength between 1 nm and 20 μm, in particular a laser beam.

Especially, an aperture according to the present invention comprises an aperture body, in which an aperture opening is arranged. The aperture body comprises a facing surface, in particular a planar facing surface, facing the electromagnetic radiation and on its opposite side an averted surface, in particular a planar averted surface. In particular, the facing surface and the averted surface can be parallel to each other and are preferably aligned perpendicular to the impinging direction of the electromagnetic radiation. The electromagnetic radiation can traverse the aperture body unhindered through the aperture opening, which extends between a facing orifice in the facing surface and an averted orifice in the averted surface, wherein besides the aperture opening the electromagnetic radiation impinges on the aperture body. In other words, an aperture according to the present invention allows defining a lateral size of the beam of the electromagnetic radiation perpendicular to its impinging direction.

To eliminate or at least minimize an energy deposit of the electromagnetic radiation into the aperture body, the aperture body is made of a body material transparent at least for the respective electromagnetic radiation. In other words, electromagnetic radiation impinging on the aperture body beyond the aperture opening is not absorbed by the body material of the aperture body but can penetrate into the aperture body.

According to the present invention, especially areas surrounding the facing orifice and the averted orifice in the facing surface and the averted surface, respectively, comprise a specific shape. In particular, the facing orifice is surrounded by a refraction section, whereby the refraction section is inclined inward with respect to the facing surface into the aperture body by an angle α with respect to the impinging direction.

In other words, the electromagnetic radiation impinging on the facing surface in the impinging direction impinges onto the facing surface, especially the refraction section, in an angle smaller than 90°. As the aperture body is transparent to the electromagnetic radiation, the electromagnetic radiation is refracted into the body material of the aperture body. In addition, by the inclination of the refraction section with respect to the impinging direction, electromagnetic radiation reflected on the refraction section is pointed away from the original impinging direction. Back-scattering of electromagnetic radiation into its source can therefore be prohibited.

On the other side of the aperture body, the averted orifice is surrounded by a reflection section inclined similarly inward with respect to the averted surface into the aperture body by an angle β with respect to the original impinging direction of the electromagnetic radiation. The electromagnetic radiation refracted on the refraction section travels within the body material of the aperture body and reaches the reflection section of the averted surface of the aperture body. On this reflection section, the refracted electromagnetic radiation is at least partly internally reflected within the body material. Due to the inclination of the reflection section, this internal reflection of the electromagnetic radiation within the body material of the aperture body directs the reflected beam of electromagnetic radiation away from the original impinging direction of the electromagnetic radiation. In other words, electromagnetic radiation impinging on an aperture according to the invention can unhinderedly travel through the aperture via the aperture opening, wherein electromagnetic radiation impinging on the aperture body itself is refracted into the body material of the aperture body and subsequently internally reflected on the reflection section of the averted surface away from the original impinging direction. An especially effective forming of the beam of the electromagnetic radiation of the aperture according to the invention can therefore be provided. In addition, the electromagnetic radiation besides the central beam is guided away from the original impinging direction and can be absorbed somewhere else, preferably in suitable deposition areas.

Further, an aperture according to the invention can be characterized in that the angle α and/or the angle β are larger than 45° and smaller than 90°. For the angle α this range between 45° and 90° is especially suitable to ensure that electromagnetic radiation nevertheless reflected on the refraction surface is not scattered back to the source of the electromagnetic radiation, as already mentioned above. On the other hand for the angle β a range between 45° and 90° is especially suitable to ensure that a reflection, especially an internal reflection, at the reflection section is effectively directed in a large angle away from the original impinging direction of the electromagnetic radiation. An improved separation of the unhindered electromagnetic radiation going through the aperture opening and the remaining electromagnetic radiation impinging somewhere on the aperture body can therefore be provided.

Preferably, according to an embodiment of an aperture according to the present invention, the angle α and the angle β are of the same size. For instance, this allows using the same grinding tool to provide both the refraction section in the facing surface and the reflection section in the averted surface. The production of an aperture according to the invention can therefore be provided more easily.

In particular, an aperture according to the present invention can comprise that the angle α and the angle β are adapted such that an electromagnetic radiation refracted into the aperture body through the refraction section is internally totally reflected on the reflection section. In other words, the angle α and the angle β are chosen such that on the reflection section no electromagnetic radiation is transmitted but all electromagnetic radiation is internally reflected on this reflection section. This can especially be provided for an electromagnetic radiation with a particular wavelength. An even better definition of the beam of electromagnetic radiation collimated by an aperture according to the invention can therefore be provided.

Further, an aperture according to the invention can be improved in that the electromagnetic radiation internally totally reflected on the reflection section comprises a reflection direction at least essentially perpendicular to the impinging direction. In other words, the electromagnetic radiation internally reflected in the aperture body on the reflection section travels perpendicular to the original impinging direction and hence also perpendicular to the direction of the electromagnetic radiation going through the aperture opening. The internally reflected electromagnetic radiation with the reflection direction leaves the aperture body therefore in a maximum angular direction difference from the aperture opening.

According to an embodiment of an aperture according to the invention, the aperture comprises that the reflection section is shaped as a circular area around the facing orifice and/or the reflection section is shaped as a circular area around the averted orifice. Especially, both the circular area of the refraction section and the circular area of the reflection section can be centered on a center of the aperture opening. In other words, such a circular area has the same radial elongation in all directions around the respective opening. Predominant directions in a specific angle around the aperture opening for the refraction section and/or the reflection section can therefore be prohibited.

In a further improvement of an aperture according to the invention, the refraction section and/or the reflection section are shaped as truncated cones. In other words, the angle α and/or the angle β, respectively, are constant throughout the whole refraction section and/or the reflection section, both axially and radially with respect to the center of the aperture opening. Manufacturing of an aperture according to the invention can therefore be provided in an easier way.

Additionally, an aperture according to the invention can be improved by that the opening angle α and a cone height of the refraction section along the impinging direction and the opening angle β and a cone height of the reflection section along the impinging direction are chosen such that all electromagnetic radiation refracted at the refraction section is internally totally reflected at the reflection section. In other words, the refraction section and the reflection section as a whole, especially the parameters for the respective truncated cone of both the refraction section and reflection section, are chosen such, that all electromagnetic radiation impinging on and refracted by the refraction section reaches the reflection section, Further, no part of this electromagnetic radiation leaves the aperture body through the reflection section but all such electromagnetic radiation is internally totally reflected at the reflection section. Also, this preferred embodiment of an aperture according to the invention allows an especially good definition of a beam of electromagnetic radiation confined by an aperture according to the invention.

According to a further embodiment of an aperture according to the invention, the aperture opening comprises a cylindrical middle section connecting the facing orifice in the refraction section and the averted orifice in the reflection section, in particular wherein a central axis of the cylindrical middle section is aligned to the impinging direction. In other words, in this embodiment of an aperture according to the invention the facing orifice and the averted orifice are not identical and not arranged in an overlapping way, but spaced apart from each other and connected by the cylindrical middle section, forming the respective ends of the cylindrical middle section. This allows for instance to choose the aforementioned angles α, β and cone heights more freely, as the truncated cones forming the refraction section and reflections section, respectively, no longer have to meet and to be directly connected to each other. An improved adaptation of an aperture according to the invention, for instance with respect to the used electromagnetic radiation and/or the body material of the aperture body, can therefore be provided. In addition, by providing a cylindrical middle section, the respective angle of the edge of the aperture body at the facing orifice and the averted orifice can be enlarged, especially with respect to an embodiment with no middle section, in which the facing orifice and the averted orifice coincide. Hence, in the present embodiment with a cylindrical middle section, heat conduction within the aperture material away from the respective edges is facilitated.

In an alternative embodiment of an aperture according to the invention, the aperture opening comprises a truncated conical middle section connecting the facing orifice in the refraction section and the averted orifice in the reflection section, wherein the averted orifice is larger than the facing orifice, in particular wherein a central axis of the truncated conical middle section is aligned to the impinging direction. In this embodiment of an aperture according to the invention, the middle section connecting the facing orifice and the averted orifice of the aperture opening has the shape of a truncated cone. Especially the cone opens along the impinging direction, whereby the averted orifice is larger than the facing orifice. In this embodiment, especially the facing orifice defines the size of the beam of the electromagnetic radiation confined by the aperture according to the invention. Especially as the truncated conical middle section opens in direction to the averted orifice, an impingement of electromagnetic radiation on a side surface of the conical middle section is prohibited by geometry. An energy deposit into this conical middle section by impinging electromagnetic radiation can therefore be prohibited.

Further an aperture according to the invention can be improved by that the truncated conical middle section comprises an opening angle γ, whereby the opening angle γ is smaller than 90° minus a sum of the opening angle α and an angle ε of electromagnetic radiation refracted at the refraction section. The angle ε is thereby measured between the direction of the refracted electromagnetic radiation and a normal to the surface of the refraction section. Electromagnetic radiation impinging on the refraction section is refracted into the body material of the aperture body. By choosing the opening angle γ of the conical middle section such, that the opening angle γ is smaller than 90° minus a sum of the opening angle α of the refraction section and an angle ε in which the electromagnetic radiation is refracted into the body material of the aperture body at the refraction section, it can be ensured that an internal impingement of the electromagnetic radiation refracted at the refraction section onto a side surface of the truncated conical middle section can be excluded. In other words, the angle ε is chosen such that it is smaller than the angle between the impinging direction and a direction of the refracted electromagnetic radiation within the aperture body. The advantage of facilitated heat conduction away from the respective edges of the aperture body at the facing orifice and the averted orifice, respectively, as described above with respect to a cylindrical middle section can also be provided with a middle section in shape of a truncated cone due to a similar enlargement of the angles at the respective edges.

Additionally, an aperture according to the present invention can be characterized in that at least the refraction section is coated with an anti-reflection coating. In other words, a reflection of impinging electromagnetic radiation onto the refraction section can be diminished, preferably minimized, by this anti-reflection coating. The amount of back scattered electromagnetic radiation from the refraction section can therefore be scaled down.

In another embodiment, the aperture according to the present invention comprises that at least the reflection section, in particular the entire averted surface, preferably also the facing surface except the refraction section, is coated with a total-reflection coating, whereby a refractive index of the totally reflection coating is smaller than the refractive index of the body material. In other words, with this total reflection coating the total reflection, especially at the reflection section but preferably also on the rest of the surfaces of the aperture body except the refraction section, is not based on the refractive index difference between the body material and the surrounding atmosphere but on the difference of the refracting indices of the body material and the total reflection coating. This provides the advantage that an aperture according to the invention can be used independently of the atmosphere present in the system in which the aperture according to the invention is used. In addition, also material deposition on the aperture body during usage, especially deposition of source material evaporated and/or sublimated by the electromagnetic radiation, takes place on the total reflection coating and thereby has no influence on the total reflection within the aperture according to the invention.

Similar advantages can be achieved with a coating with a high index of refraction as for instance a metallic coating, so that reflection occurs at the interface between the aperture body and the preferably metallic coating. This coating with a high index of refraction can also be arranged at the reflection section, in particular at the entire averted surface, preferably also at the facing surface except the refraction section. Although this metallic coating absorbs the electromagnetic radiation, it is possible to choose a coating material with low absorption at the wavelength if the incident electromagnetic radiation such as silver (Ag). Especially the advantages of a prevention of a higher absorption and/or change in absorption over time, respectively, due to a subsequent deposition of evaporated and/or sublimated source material can also be provided with such a coating with a high index of refraction.

Alternatively or additionally an aperture according to the invention can be characterized in that a shielding aperture, in particular an opaque shielding aperture, with a central opening is arranged at the averted surface, the central opening comprises at least the size of the facing orifice and is aligned to the aperture opening of the aperture body. In other words, in this embodiment of an aperture according to the invention with respect to the impinging direction after the aperture an additional shielding aperture is arranged. Source material evaporated and/or sublimated by the electromagnetic radiation is therefore deposited on the shielding aperture and cannot reach the aperture body of the aperture according to the invention. An influence of deposited source material, especially on the ability of the aperture according to the invention to internally totally reflect electromagnetic radiation, can therefore be prohibited.

Further, an aperture according to the present invention can be characterized in that the aperture body comprises an exit surface connecting the facing surface and the averted surface spaced to the aperture opening, wherein the exit surface comprises a concave and/or convex shape for a dispersive outcoupling of the electromagnetic radiation out of the aperture body. As described above, electromagnetic radiation entering the aperture body, preferably through the reflection section, is essentially totally reflected within the aperture body and guided away from the aperture opening. Preferably at an outer rim of the aperture body this electromagnetic radiation reaches the exit surface of the aperture body and is coupled out of the aperture body. Especially, this exit surface comprises a concave and/or convex shape and therefore the respective outcoupling of the electromagnetic radiation out of the aperture body is a dispersive one. This allows spreading the electromagnetic radiation coupled out of the aperture body onto a larger area and therefore the spatial energy density of the electromagnetic radiation is diminished. Damage caused by this electromagnetic radiation can therefore be prohibited and/or the energy deposited by the electromagnetic radiation can be removed more easily.

In particular, an aperture according to the invention can be characterized in that the aperture body is made of sapphire. Sapphire as body material is durable and transparent for a wide range of possible electromagnetic radiations. Further, sapphire has a high melting point and therefore can absorb heat deposited by the electromagnetic radiation, for instance at its exit surface without losing its geometrical form.

In addition, an aperture according to the present invention can comprise that the aperture body is adapted for a laser as electromagnetic radiation, especially an infrared or visible laser, in particular a laser with a wavelength of 1030 nm, 515 nm or 450 nm. Lasers as electromagnetic radiations comprise especially the advantage that the impinging direction of the electromagnetic radiation can be defined very precisely. Further in most of the cases lasers are monochromatic and therefore the geometrical constraints for the total internal reflection of the electromagnetic radiation refracted into the aperture body can be fulfilled more easily.

In particular, an aperture according to the invention can be characterized in that the aperture comprises a holding structure for an arrangement of the aperture body in a path of the electromagnetic radiation within a vacuum vessel, especially within an aperture feedthrough in a cooling shroud of the vacuum vessel. In other words, this holding structure allows a placement and/or arrangement of the aperture with respect to the impinging electromagnetic radiation. In particular, the holding structure can provide a reversible arrangement of the aperture according to the present invention in the respective aperture feedthrough. When used in a system, especially for directing electromagnetic radiation onto a source material, this can preferably be provided within an aperture feedthrough in a cooling shroud of a vacuum vessel. Electromagnetic radiation impinging on the refraction section and therefore guided away from the impinging direction can be directed in direction of the cooling shroud and therefore the energy deposited by this unused electromagnetic radiation can be absorbed in the cooling shroud.

Especially, the aperture according to the present invention can be improved by that that the holding structure arranges the aperture body within the vacuum vessel between a coupling window for coupling the electromagnetic radiation into the vacuum vessel and a radiation target within the vacuum vessel on which the electromagnetic radiation is directed, whereby the aperture, in particular the aperture body, comprises a size perpendicular to the impinging direction of the electromagnetic radiation such that the aperture, in particular the aperture body, covers at least a solid angle of the coupling window as seen from the radiation target. In other words, the aperture is arranged within the vacuum vessel in the path of the electromagnetic radiation along the impinging direction somewhere between the coupling window, at which the electromagnetic radiation is coupled into and enters the vacuum vessel, and the radiation target, on which the electromagnetic radiation is directed. Preferably, a radiation target can be a source material provided in a source holder which is to be evaporated and/or sublimated by an energy deposit of the electromagnetic radiation. In particular, a size of the aperture, especially of the aperture body, is chosen such that a solid angle of the radiation window as seen from the radiation target is completely covered by the aperture when the aperture is arranged within the vacuum vessel. In other words, neither electromagnetic radiation scattered back at the radiation target against the impinging direction, nor source material evaporated and/or sublimated by the impinging electromagnetic radiation can reach the coupling window as both the electromagnetic radiation and the evaporated and/or sublimated material, respectively, are stopped by the aperture. Hereby the tiny fraction of radiation and/or material passing through the aperture opening can be neglected. In summary, an extensive protection of the coupling window, especially against coating by evaporated and/or sublimated material within the vacuum vessel can be provided.

In a preferred embodiment of an aperture according to the invention, the holding structure comprises two or more reception sections, in particular metal reception sections, in direct contact to an outer rim of the aperture body for fixing the aperture body within the holding structure. These reception sections are located at the outer rim of the aperture body and hence at the exit surface of the aperture body.

Electromagnetic radiation totally reflected within the aperture body is therefore directed to these reception sections and, especially if the reception sections are metal reception sections, absorbed by the reception sections. By surveying these reception sections, for instance by measuring the temperature of these reception sections, the amount of absorbed electromagnetic radiation by the respective reception section can be determined. Differences between the at least two reception sections with respect to the determined absorbed electromagnetic radiation can be used to determine an alignment of the aperture according to the invention with respect to the impinging electromagnetic radiation.

An aperture according to the invention can be further improved by that the two or more reception sections are equally distributed along the outer rim of the aperture body and/or are arranged equally distanced to the aperture opening. In other words, the two or more reception sections are arranged such at the aperture body that a comparison of the determined amount of absorbed electromagnetic radiation in the respective reception sections directly allow a determination of a correct alignment of the aperture opening with respect to the impinging electromagnetic radiation. If the two or more reception sections are equally distributed along the outer rim of the aperture body and are arranged equally distant to the aperture opening this comparison can be provided especially easily, as with a perfectly aligned impinging beam of electromagnetic radiation, the amount of energy deposited in the respective reception sections should be identical.

In addition, an aperture according to the invention can be improved by that the outer rim of the aperture body comprises three or more corners equally distant to the aperture opening and to each other, whereby each of the two or more corners is fixed by a reception section. In other words, the reception sections fix the corners of the aperture body, whereby these corners are equally distanced both to each other and to the aperture opening, respectively. This can be provided for instance by a shape of the aperture body of an equilateral triangle, a square, or any other equilateral polygon. Hence a symmetrical arrangement of the corners with respect to the aperture opening and also of the respective reception sections can be provided especially easily.

Further, an aperture according to the invention can be improved by that the holding structure comprises at least one sensor element to monitor the two or more reception sections. By monitoring the reception sections by a sensor element, the amount of electromagnetic radiation absorbed in the respective reception section can be determined. Out of this determination based on data provided by the sensor element, an alignment of the aperture with respect to the impinging direction of the electromagnetic radiation can be provided.

Especially, an aperture according to the invention can be improved by that the at least one sensor element is a camera and/or temperature detecting device. By measuring the temperature, an amount of absorbed electromagnetic radiation in the respective reception section, which causes a rise of temperature of the respective reception section, can be determined especially easily. Further, if the amount of absorbed electromagnetic radiation is high enough, there will be a visible change of the appearance of the reception section. This can be easily detected by a camera as sensor element. A combination of these two possibilities is an infrared camera, which can already detect shifts in the temperature of the respective reception section by detecting the heat radiation of the respective reception section starting in the infrared part of the electromagnetic spectrum.

In particular, an aperture according to the invention can be characterized in that the holding structure comprises an actuator for a relative placement of the aperture body within the holding structure, in particular based on the monitoring of the two or more reception sections by the at least one sensor element. As described above, by monitoring the two or more reception sections, an alignment of the aperture, especially the aperture body, with respect to the impinging direction of the electromagnetic radiation can be provided. Based on this measurement, the actuator of the holding structure can provide a relative placement of the aperture body, and therefore of the aperture opening, with respect to the impinging direction of the electromagnetic radiation. An alignment of the aperture opening to the impinging electromagnetic radiation, especially for instance to a laser beam, can therefore be provided, preferably constantly be provided, for instance by implementing an open loop control.

According to a second aspect of the invention, the object is satisfied by a method for aligning a suitable aperture according to the first aspect of the invention, wherein a beam of electromagnetic radiation is impinging on the aperture, the method comprising the following steps:a) Monitoring the two or more reception sections by the at least one sensor element,b) Comparing the monitoring result for the two or more reception sections determined in step a), andc) Determining an alignment of the aperture, especially of the aperture opening, with respect to the beam of the electromagnetic radiation based on the result of the comparison in step b).

The method according to the second aspect of the invention is carried out with a suitable aperture according to the first aspect of the invention. Therefore, all advantages described above with respect to the suitable aperture according to the first aspect of the invention can also be achieved by a method for aligning this aperture according to the second aspect of the invention.

In the first step a) of the method according to the second aspect of the invention, the two or more reception sections, which hold the aperture body within the holding structure, are monitored by the at least one sensor element. This allows in the next step b) to compare the data of this monitoring, whereby in particular differences of the monitored data for the two or more reception sections are determined. Based on these differences, an alignment of the aperture is determined in the last step c) of a method according to the second aspect of the invention. Especially an alignment of the aperture opening with respect to the impinging electromagnetic radiation can be determined. In other words, after a completion of the step a), b) and c) of a method according to the invention there is information present about the alignment, in particular of a present misalignment, of the aperture and especially the aperture opening with respect to the impinging electromagnetic radiation.

Further, a method according to the invention can be improved by that the holding structure of the aperture comprises an actuator, wherein the actuator moves the aperture body within the holding structure based on the alignment determined in step c) to center the beam of electromagnetic radiation with respect to the aperture opening. In this additional step an actuator of the holding structure is used to move and actively align the aperture body and thereby especially the aperture opening in the aperture body, with respect to the beam of electromagnetic radiation impinging onto the aperture. An especially good and centered alignment of the aperture body and especially the aperture opening with respect to the beam of electromagnetic radiation can therefore be provided.

According to a third aspect of the invention the object is satisfied by a system for applying electromagnetic radiation onto a source material. The system according to the third aspect of the invention comprisesa system volume,a source holder with a source material arranged in the system volume,a source of electromagnetic radiation to be coupled into the system volume for an application onto the source material,a cooling shroud surrounding at least parts of the system volume,an aperture feedthrough extending through the cooling shroud for coupling of the electromagnetic radiation into the system volume,a dispersion feedthrough extending through the cooling shroud for coupling electromagnetic radiation reflected by the source material out of the system volume,
wherein the system further comprises an aperture according to the first aspect of the invention arranged in the aperture feedthrough, and further wherein the system comprises a dispersing element arranged in the dispersion feedthrough with a dispersing body for at least partly diverting electromagnetic radiation scattered at the source material in a scattering direction to the cooling shroud.

A system according to the third aspect of the invention comprises an aperture according to the first aspect of the invention. Therefore, all advantages described above with respect to an aperture according to the first aspect of the invention can also be achieved by a system according to the third aspect of the invention. Especially, as the aperture according to the first aspect of the invention is arranged within an aperture feedthrough in a cooling shroud of a system according to the third aspect of the invention, electromagnetic radiation collimated by the aperture is refracted and reflected into the aperture body and led to the cooling shroud, which at least partly surrounds the aperture feedthrough. An energy deposit of this collimated electromagnetic radiation into the coolant of the cooling shroud can therefore be provided especially easily. Additionally, located opposite to the aperture feedthrough in the cooling shroud, also a dispersion feedthrough is arranged and extends through the cooling shroud, whereby the dispersion feedthrough is arranged such that electromagnetic radiation scattered at the source material in a scattering direction reaches this dispersion feedthrough. In the dispersion feedthrough a dispersing element is arranged to disperse this scattered electromagnetic radiation in direction to the cooling shroud. An energy deposit of the scattered electromagnetic radiation into the coolant of the cooling shroud can therefore also be provided especially easily.

In particular, a system according to the invention can comprise that the cooling shroud is adapted to be used with a liquid coolant, in particular water, preferably liquid nitrogen. Liquid coolants, in particular water, preferably liquid nitrogen, are especially suitable because of their high heat capacity and/or low temperature.

Further, the liquid coolant can be pumped through the cooling shroud and therefore an energy deposit from electromagnetic radiation into the cooling shroud can easily be transported out of the system. Constant temperatures of the cooling shroud and therefore also of the system volume can therefore be provided.

According to the fourth aspect of the invention the object is solved by a dispersing element for a system according to the third aspect of the invention, with a dispersing body for at least partly diverting electromagnetic radiation scattered in a scattering direction on the source material by deflection and/or distribution and/or combined absorption and reemission of the electromagnetic radiation. A dispersing element according to the invention is characterized in that the dispersing element comprises an arranging structure for reversible arrangement within the dispersion feedthrough of the cooling shroud. A dispersing element according to the fourth aspect of the invention can be used and is intended for a usage within a system according to the third aspect of the invention. Therefore, all advantages described above with respect to a system according to the third aspect of the invention can also be achieved by a dispersing element according to the fourth aspect of the invention.

Additionally, the dispersing element comprises an arranging structure. Hence, a dispersing element according to the fourth aspect of the invention is reversibly arrangeable within the dispersion feedthrough of the cooling shroud. This allows choosing the most adapted and suitable dispersing element, which comprises the best features for the respective electromagnetic radiation present within the system.

The dispersing element is intended to be arranged within the dispersion feedthrough of the cooling shroud and hence within the system volume. In other words, during operation the dispersing element will be coated with the source material evaporated and/or sublimated by the electromagnetic radiation. This enhances absorption of the electromagnetic radiation scattered at the source material by the dispersion element. The absorbed energy subsequently will be reemitted by the dispersing element, preferably perpendicular to its surface. Consequently, a small angle, in particular smaller 45°, preferably smaller 15°, between the impinging scattered electromagnetic radiation and the surface of the dispersion element is of advantage. On the one hand, scaling down the aforementioned angle allows enlarging the surface area of the dispersing element and hence diminishing the temperature rise of the dispersing element caused by the absorbed electromagnetic radiation. On the other hand, as the absorbed electromagnetic radiation is reemitted mainly perpendicular to the surface of the dispersing element, a reemission of this absorbed electromagnetic radiation back into the system volume in direction of the source holder can be suppressed.

According to an embodiment of a dispersing element according to the invention, the dispersing element comprises that the dispersing body at least essentially fills a cross-section of the dispersing feedthrough perpendicular to the scattering direction of the electromagnetic radiation scattered at the source material. In other words, the cross section of the dispersion feedthrough perpendicular to the scattering direction of the electromagnetic radiation is completely filled by the dispersing body of the dispersing element. Hence no electromagnetic radiation scattered at the source material in the scattering direction can traverse the dispersion feedthrough, as this cross-section is completely filled with the dispersing body, which redirects the electromagnetic radiation in direction of the cooling shroud.

Further, a dispersing element according to the invention can be characterized in that the dispersing body comprises a passage opening, preferably a central passage opening. In other words, through this passage opening electromagnetic radiation can transverse the dispersing body of the dispersing element for further use.

In addition, a dispersing element according to the invention may comprise that the dispersing body is of a conical shape aligned to the scattering direction of the electromagnetic radiation scattered at the source material and points in direction of the source material. In other words, the electromagnetic radiation scattered at the source material in the scattering direction impinges on the dispersion body on its inclined surface area. An especially easy redirection of the electromagnetic radiation scattered at the source material in the scattering direction in direction to the cooling shroud can therefore be provided. To achieve this, the conical shape preferably comprises a small opening angle, in particular smaller 45°, preferably smaller 15°.

According to an alternative embodiment of a dispersing element according to the invention, the dispersion body comprises a flat dispersion surface, especially an elliptical dispersion surface, wherein the dispersion surface is tilted with respect to the scattering direction of the electromagnetic radiation scattered at the source material. In contrast to the aforementioned embodiment, in which the dispersing body is of a conical shape, the dispersing body of the present embodiment comprises a flat dispersion surface. Again, this flat dispersion surface can preferably fill the cross-section of the dispersion feedthrough. As the dispersion surface is flat, the electromagnetic radiation coming from the source material is redirected especially and preferably in the half space defined by the surface of the flat dispersion surface. This allows for instance, redirecting the scattered electromagnetic radiation into a specific part of the cooling shroud if necessary. To achieve this, the angle of the tilt between the scattering direction and the flat dispersion surface is preferably small, in particular smaller 45°, preferably smaller 15°.

FIG.1shows an aperture10according to the present invention. The aperture10can be used in a system70according to the present invention (seeFIG.9). It is placed in the path of an impinging electromagnetic radiation100, preferably essentially perpendicular to the impinging direction110of the electromagnetic radiation100. Preferably, the electromagnetic radiation100comprises a wavelength between 1 nm and 20 μm, whereby the electromagnetic radiation100can be provided as a laser, especially an infrared laser, in particular a laser with a wavelength of 1030 nm. Essentially, the aperture10comprises an aperture opening40and hence can be used defining the size of the beam of the electromagnetic radiation100, in particular perpendicular to its impinging direction110.

As exemplarily depicted inFIG.1, the aperture10comprises an aperture body20made of a body material22transparent for the electromagnetic radiation100. For instance, the body material22may comprise sapphire, in particular, the aperture body20as a whole is made of sapphire. The aperture body20preferably is shaped with a larger extent perpendicular to the impinging direction110than along the impinging direction110, resulting in an essentially disc-like and/or platelike form of the aperture body20and the aperture10, respectively. With respect to the impinging direction110of the electromagnetic radiation100, the aperture body is limited by a facing surface24facing the electromagnetic radiation100and an averted surface28opposite to the facing surface24, whereby in particular the facing surface24and the averted surface28can be flat and preferably oriented parallel to each other. The above-mentioned aperture opening40continuously extends between a facing orifice42in the facing surface24and an averted orifice44in the averted surface28. Hence, electromagnetic radiation100can travel through the aperture opening40without interaction with the body material22of the aperture body20of the aperture10according to the present invention.

According to the present invention, the facing orifice42is surrounded by a refraction section26of the facing surface24. Similar, the averted orifice44is surrounded by a reflection section30of the averted surface28. Both, the refraction section26and the reflection section30, respectively, are inclined inward into the aperture body20, whereby the refraction section26is inclined by an angle α120with respect to the impinging direction110, and the reflection section30is inclined by an angle β122with respect to the impinging direction110. Preferably, both the angle α120and the angle β122, respectively, are larger than 45° and smaller than 90°. Further, the refraction section26and/or the reflection section30can be shaped as circular areas around the facing orifice42and/or the averted orifice44, respectively. Preferably and as shown inFIG.1, the refraction section26and the reflection section30are shaped as truncated cones.

By comprising the inclined refraction section26and the inclined reflection section30, an aperture10according to the present invention can provide the following feature. Due to the body material22of the aperture body20being transparent to the respective electromagnetic radiation100, which in most of the cases additionally comprises a refractive index larger than the atmosphere surrounding the aperture10, impinging electromagnetic radiation100is refracted at the refraction section26surrounding the facing orifice42of the aperture opening40by an angle ε126with respect to the normal to the refraction section26. The small part of the impinging electromagnetic radiation100reflected at the refraction section26as surface reflection102comprises a direction different to the impinging direction110due to the angle α120of the refraction section26. The amount of electromagnetic radiation100reflected at the refraction section26as surface reflection102can be minimized by providing an anti-refection coating32on the refraction section26.

Further, the electromagnetic radiation100refracted at the refraction section26into the aperture body20is subsequently reflected at the reflection section30in a reflection direction112, preferably in a reflection direction112perpendicular to the impinging direction110. In particular, the angle α120and the angle β122, in the embodiment depicted inFIG.1additionally also a cone height128of the truncated cones of the refraction section26and the reflection section30, respectively, can be chosen such that the reflection of the electromagnetic radiation100at the reflection section30is total. To provide the respective sizes of the angle α120, the angle β122and the cone heights128, respectively, the aperture opening40can comprise a middle section46, connecting the facing orifice42and the averted orifice44of the aperture opening40. As for instance realized in the embodiment depicted inFIG.1, this middle section46can be shaped as a cylindrical middle section46, whereby in particular a central axis48of the cylindrical middle section46is aligned to the impinging direction110. The aforementioned requirements for an internal total reflection of the electromagnetic radiation100on the reflection surface with respect to the angle α120, the angle β122and the cone heights128, can therefore be fulfilled independent of a distance between the facing surface24and the averted surface28of the aperture body20. In addition, the averted surface28, especially including the reflection section30, and the facing surface24, except the refraction section26, can be coated with a total-reflection coating34. This allows defining the difference and ratio, respectively, of the refractive indices responsible and needed for the internal total reflection of the electromagnetic radiation100within the aperture body20(see alsoFIG.6).

Distanced to the aperture opening40, the aperture body20comprises an exit surface36connecting the facing surface24and the averted surface28. Especially, the exit surface36can be arranged at a rim38of the aperture body20. The electromagnetic radiation100, reflected, preferably totally reflected, within the aperture body20in a reflection direction112, leaves the aperture10through the exit surface36and can, for instance in a system70according to the present invention (seeFIG.9), be directed in direction of a cooling shroud78of the system70to dissipate the energy of the electromagnetic radiation100.

In summary, electromagnetic radiation100impinging on the aperture10according to the invention travels unhindered through the aperture opening40, wherein electromagnetic radiation100impinging on the aperture body20at the refraction section26is refracted into the body material22of the aperture body20and subsequently internally reflected on the reflection section30of the averted surface28away from the original impinging direction110in a reflection direction112. An especially effective forming of the beam of the electromagnetic radiation100by the aperture10according to the invention can therefore be provided. In addition, the electromagnetic radiation100besides the central beam is guided away from the original impinging direction110and can be absorbed somewhere else, preferably in suitable deposition areas such as a cooling shroud78(seeFIG.9).

FIG.2shows another possible embodiment of an aperture10according to the present invention in a partial sectional view. This embodiment shown inFIG.2differs from the embodiment depicted inFIG.1especially by the middle section46of the aperture opening40. All other parts of this embodiment of an aperture10according to the present invention shown inFIG.2are similar to the respective ones depicted inFIG.1and it is hereby referenced to the respective description above.

In the embodiment of the aperture10according to the present invention depicted inFIG.2, the middle section46is formed as a truncated cone connecting the facing orifice42in the refraction section26and the averted orifice44in the reflection section30. The middle section46comprises an opening angle γ124with respect to the impinging direction110, whereby the middle section46opens up in direction of the averted orifice44, which is therefore larger than the facing orifice42. Further, a central axis48of the truncated conical middle section46is aligned to the impinging direction110. In the special embodiment of the middle section46shown inFIG.2, the opening angle γ124is smaller than 90° minus a sum of the opening angle α120and the angle ε126of electromagnetic radiation100refracted at the refraction section26. In other words, the angle γ124is chosen such that electromagnetic radiation100with the impinging direction110refracted at the refraction section26into the aperture body20cannot reach a side surface of the truncated conical middle section46. Also an impingement of the electromagnetic radiation100traveling along the impinging direction100through the aperture opening40, especially the facing orifice42of the aperture opening40, onto the side surface of the truncated conical middle section46can be excluded by geometry.

FIG.3shows another possible embodiment of an aperture10according to the present invention in a partial sectional view. This embodiment shown inFIG.3also comprises a cylindrical middle section46as part of the aperture opening40, but differs from the embodiment depicted inFIG.1especially by that the angle α120and the angle β122are of the same size. All remaining parts of this embodiment ofFIG.3are similar to the respective ones depicted inFIG.1and it is hereby referenced to the respective description above. The construction of the angle α120and the angle β122comprising the same size allows for instance using the same grinding tool to provide both the refraction section26in the facing surface24and the reflection section30in the averted surface28. The production of an aperture according to the invention can therefore be provided more easily.

The partial sectional views of two embodiments of apertures10according to the present invention depicted inFIG.4are focused on the exit surfaces36of the respective aperture bodies20. In both embodiments, the respective exit surface36is located at a rim38of the aperture body20and connects the facing surface24with the averted surface28. Electromagnetic radiation100travelling within the body material22of the aperture body20in a reflection direction112is coupled out of the aperture body20at the respective exit surface36.

According to the embodiment of the aperture10according to the present invention depicted in the upper part ofFIG.4, the exit surface36is a plane surface tilted with respect to both the impinging direction110and the reflection direction112, respectively. Two possible paths of electromagnetic radiation100are shown, one with total internal reflection at the exit surface36, the other with refraction and outcoupling at the exit surface36. During operation, the wavelength of the electromagnetic radiation and the refraction indices of the body material and its surrounding determine, which of these possibilities is present. In both cases, a reflection of the electromagnetic radiation back on its exact path, and as a result back into the laser source, can be avoided. Stability problems of the laser source caused by back scattered electromagnetic radiation can therefore be prohibited. Further, the above described outcoupling of the electromagnetic radiation at the exit surface with refraction and/or internal reflection leads to a dispersion of the electromagnetic radiation100and spreads the energy of the electromagnetic radiation100onto a larger area. A dissipation of this energy can therefore be provided.

The lower part ofFIG.4shows another possible embodiment of the aperture10according to the present invention, in which the exit surface36comprises a concave shape for a dispersive outcoupling of the electromagnetic radiation100out of the aperture body20. Especially by providing a concave exit surface36this outcoupling of the electromagnetic radiation100out of the aperture body20is a dispersive one. As described above, this allows spreading the energy of the electromagnetic radiation100onto a larger area and therefore the spatial energy density of the electromagnetic radiation100is diminished. Damage caused by this electromagnetic radiation100can therefore be prohibited and/or the energy deposited by the electromagnetic radiation100can be removed more easily.

An aperture10according to the present invention can be used to define electromagnetic radiation100with an impinging direction110, which itself is used to evaporate and/or sublimate a source material. To prevent a deposition of this evaporated and/or sublimated source material onto the aperture10, especially onto the averted surface28of the aperture body20made of body material22, an aperture10according to the present invention can comprise a preferably opaque shielding aperture50, seeFIG.5. The shielding aperture50comprises a central opening52with at least the size of the facing orifice42and is arranged at the averted surface28such that the central opening52is aligned to the aperture opening40of the aperture body20. Hence, with with respect to the impinging direction110the shielding aperture50is arranged after the aperture10. Source material evaporated and/or sublimated by the electromagnetic radiation100is deposited on the shielding aperture50in a deposit layer54and cannot reach the averted surface28with the refraction section30, not to mention the facing surface24with the refraction section26, of the aperture body20of the aperture10. An influence of deposited source material, especially on the ability of the aperture10according to the invention to internally totally reflect electromagnetic radiation100, can therefore be prohibited.

Alternatively or additionally and as depicted inFIG.6, the aperture body20of an aperture10according to the present invention can comprise a total-reflection coating34, for instance provided as layer on the reflection section30and the averted surface28. As the constraints for an internal total reflection of the electromagnetic radiation100into its reflection direction112depend on the ratio of the refraction indices n1 of the body material22and n2 of the total-reflection coating34, an additional deposit layer34cannot influence this internal total reflection, independent of the refraction index n3 of this deposit layer34. Hence, the total-reflection coating34can provide similar advantages as the shielding aperture50described with respect toFIG.5.

FIGS.7and8show a preferred embodiment of an aperture10according to the present invention. For the general features of an aperture10according to the present invention please refer to theFIGS.1to6. In this embodiment, especially shown on the left side ofFIG.7, the aperture10comprises a holding structure60. As depicted, the holding structure60can comprise four preferably metal reception sections62, each of them receipting a corner of the aperture body20. The corners themselves are located at the outer rim38of the aperture body20and are spaced equally, both with respect to the aperture opening40and to each other, respectively. Further, the holding structure60comprises a sensor element64, for instance a heat seeking camera, and an actuator66for a relative movement of the aperture body20with respect to the impinging electromagnetic radiation100(see for instanceFIGS.1to3).

Especially and as described in the following, the sensor element64can be used to detect a misalignment of the aperture10with respect to the impinging electromagnetic radiation100, and based on these measurements, the actuator66can be used to correct the detected alignment error.

For this, in a first step a) of a method according to the present invention, the reception sections62are monitored by the sensor element64. The electromagnetic radiation100impinging on the aperture body20outside of the aperture opening is refracted and reflected within the aperture body20and finally reaches the outer rim38and hence the reception sections62. The reception sections62absorb the electromagnetic energy and are heated up according to the amount of absorbed energy. As the reception sections62are located equally distanced to the aperture opening40and to each other, a comparison of the measurements and especially a determination of a temperature difference of the reception sections62finally allows to determine an alignment and/or misalignment of the aperture10with respect to the impinging electromagnetic radiation100(steps b) and c), respectively, of a method according to the present invention). Based on the determined misalignment, the actuator66can be used to realign the aperture10according to the present invention.

In the right side ofFIG.7, a well aligned aperture10is shown. Each reception section62shows as measurement of the sensor element64essentially the same measurement result.

Possible misalignments of the aperture10according to the present invention are shown inFIG.8. The brighter the reception section62is depicted in the measurement results of the sensor element64shown in the4subfigures ofFIG.8, the more the beam of the impinging electromagnetic radiation100is misaligned in direction to this particular reception section62. In the upper left picture ofFIG.8, the beam is misaligned in direction to the upper right reception section62, in the lower left picture in direction to the lower left reception section62. The upper right picture ofFIG.8shows a misalignment in direction to both lower reception sections62, whereby the lower right picture ofFIG.8shows a slight misalignment of the beam of impinging electromagnetic radiation100to the upper left reception section62.

FIG.9shows a system70for applying electromagnetic radiation100onto a source material supported by a source holder76. The electromagnetic radiation100is provided by a source of electromagnetic radiation100outside of a vacuum vessel72of the system70. Source material can be evaporated and/or sublimated by applying the electromagnetic radiation100and subsequently deposited, for instance onto a target86. An especially precise deposition of source material, both in composition and thickness, can thereby be provided.

The system70comprises the aforementioned vacuum vessel72, which essentially confines a system volume74wherein the source holder76is arranged. In the system volume74, an atmosphere suitable and/or necessary for the material to be deposited on the target can be contained. Further, the vacuum vessel72comprises a cooling shroud78at least partly surrounding the system volume74.

In the exemplary system70shown inFIG.9, the wall of the vacuum vessel72is identical to the respective wall of the cooling shroud78. In other embodiments of a system70, there can be a vacuum vessel72and a cooling shroud78, each comprising a distinct wall, whereby these walls can even be spaced from each other for a further reduction of thermal conductivity. The cooling shroud78allows cooling the system volume74, for instance to reach lower internal pressures in the system volume74. The cooling shroud78preferably is adapted to be used with a liquid coolant like water or liquid nitrogen. Liquid coolants are especially suitable because of their high heat capacity. Further, the liquid coolant can be pumped through the cooling shroud78and therefore an energy deposit from electromagnetic radiation100into the cooling shroud78can be easily transported out of the system70according to the present invention.

In addition, the cooling shroud78can be used to absorb energy of the electromagnetic radiation100not used for the evaporation and/or sublimation of the source material. For this purpose, the system70comprises an aperture feedthrough80for coupling of the electromagnetic radiation100into the system volume74and a dispersion feedthrough82for coupling electromagnetic radiation100scattered on the source material in the source holder76out of the system volume74, both of them extending through the cooling shroud78.

In the aperture feedthrough80, an aperture10(seeFIGS.1to8) according to the present invention is arranged using a holding structure60for defining a cross section of the beam of electromagnetic radiation100perpendicular of its impinging direction110. Electromagnetic radiation100filtered out by the aperture10is guided within the aperture10preferably perpendicular to the impinging direction110into the cooling shroud78. In addition, the aperture10, in particular the aperture body comprises a size perpendicular to the impinging direction110of the electromagnetic radiation100such that the aperture10, in particular the aperture body20, covers at least a solid angle of the coupling window104as seen from the radiation target106. Electromagnetic radiation100scattered back along the impinging direction110as well as source material evaporated and/or sublimated as radiation target106at the source holder76is thereby stopped by the aperture10and cannot reach and subsequently damage the coupling window104.

Further, a dispersing element90is arranged using an arranging structure98in the dispersing feedthrough82to disperse electromagnetic radiation100scattered at the source material in a scattering direction114at least partly in direction of the cooling shroud78.

FIG.10shows the basic principle of the functionality of the dispersing element90according to the present invention. The dispersing element90comprises a dispersing body92arranged within the dispersion feedthrough82in the cooling shroud78of a system70according to the present invention. On the left side ofFIG.10, a dispersion element90with a solid dispersion body92is shown. The embodiment shown on the right side ofFIG.10comprises a dispersion body92with a central passage opening94, allowing a small part of the scattered electromagnetic radiation100to transverse the dispersing element90for further use. In both embodiments, electromagnetic radiation100, scattered at a source material in the system70in a scattering direction114, impinges on the dispersion surface96of the dispersion body92and is deflected and/or distributed and/or absorbed and subsequently re-emitted. As the dispersion element90is arranged well within the dispersion feedthrough82of the cooling shroud78, this dispersed electromagnetic radiation100is directed into the cooling shroud78. Absorption of the energy of the electromagnetic radiation100by the cooling shroud78, preferably the cooling liquid within the cooling shroud78, can therefore be provided.

InFIGS.11and12, a possible embodiment of a dispersing element90according to the present invention is shown.FIG.11is focused on the dispersing element90itself,FIG.12on its arrangement within a system70according to the present invention.FIG.12also shows the vacuum vessel72surrounding the system volume74and the impinging electromagnetic radiation100in its impinging direction110. In this embodiment, the dispersing body92is of a conical shape. Further, the dispersing body92is aligned to the scattering direction114of the electromagnetic radiation100and points in direction to the source material on which the electromagnetic radiation110is scattered. In addition, the dispersion body92essentially fills a cross section84of the dispersion feedthrough82in the cooling shroud78of the system70according to the present invention. Hence all of the electromagnetic radiation100scattered in the scattering direction114at the source material in the source holder76is dispersed by the dispersion surface96of the dispersing element90into the cooling shroud78. As the dispersing body92is axially symmetric, the electromagnetic radiation100is essentially also dispersed by the dispersing element90in an axial symmetric way. An especially even distribution of the electromagnetic radiation100dispersed by the dispersing element90can therefore be provided. An arranging structure allows an especially reversible arrangement of the dispersing element90in the dispersion feedthrough82.

FIGS.13and14show an alternative embodiment of a dispersing element90according to the present invention is shown. Again,FIG.13is focused on the dispersing element90itself,FIG.14on its arrangement within a system70according to the present invention, wherebyFIG.14also shows the vacuum vessel72surrounding the system volume74. The dispersing body92of this special embodiment of a dispersing element90according to the present invention comprises a flat elliptical dispersion surface96. In addition, this dispersion surface96is tilted with respect to the scattering direction114of the electromagnetic radiation100scattered at the source material. Further, the dispersion body92and the dispersion surface96, respectively, essentially fills a cross section84of the dispersion feedthrough82in the cooling shroud78. Hence and similar to the embodiment described with respect toFIGS.11and12, all of the electromagnetic radiation100scattered in the scattering direction114at the source material is dispersed on the dispersion surface96of the dispersing element90into the cooling shroud78. In contrast to the embodiment described with respect toFIGS.11and12, as the dispersion surface96is flat, the electromagnetic radiation100coming from the source material is redirected in the half space defined by the surface of the flat dispersion surface96. This allows redirecting the scattered electromagnetic radiation100into a specific part of the cooling shroud78if necessary, for instance and as depicted inFIG.14, if the volume of the cooling shroud78is limited in a specific direction by another feedthrough.

REFERENCE LIST