Abstract
The invention relates to a source arrangement for a deposition apparatus with a direct surface heater for applying a heating power onto a source surface of a source element, comprising a holding structure with a support and at least one source element arranged at the support, the source element comprising a source surface and a second surface opposite to the source surface, wherein the source material can be vaporized and/or sublimated from a source area on the source surface when heated by the surface heater of the deposition apparatus. Further, the invention is related to a deposition apparatus comprising such a source arrangement and to a method for depositing source material on a target material in the deposition apparatus, whereby the deposition apparatus comprises a surface heater and such a source arrangement.
Claims
1.-33. (canceled)
34. Source arrangement for a deposition apparatus with a direct surface heater for applying a heating power onto a source surface of a source element, comprising a holding structure with a support and at least one source element arranged at the support, the source element comprising the source surface and a second surface opposite of the source surface, wherein source material can be vaporized and/or sublimated from a source area on the source surface when heated by the surface heater of the deposition apparatus, and wherein the source element consists of a source material and is arranged self-supporting at the support.
35. Source arrangement according to claim 34, wherein the holder and the source element are constructed crucible-free.
36. Source arrangement according to claim 34, wherein the at least one source element is supported by the support at three or more support positions, wherein the contact areas between the support and the source element at the support positions are point like or at least essentially point like contact areas.
37. Source arrangement according to claim 34, wherein the at least one source element comprises at least one reducing opening extending in the source element from the source surface to the second surface for a reduction of thermal conductivity within the at least one source element.
38. Source arrangement according to claim 34, wherein the at least one source element is divided in a first part and at least one second part separate to the first part, wherein the first part comprises the source surface and wherein the first part and the at least one second part are stacked to form the source element, whereby the first part is sup-ported by the at least one second part at three or more support positions, wherein the contact areas between the first part and the at least one second part at the support positions are point like or at least essentially point like contact areas.
39. Source arrangement according to claim 34, wherein the at least one source element comprises at least one emission section for an emission of thermal energy, wherein the at least one emission section is provided by an emission region arranged radially in the source element with respect to the source area and/or is shaped as a protrusion protruding from the second surface.
40. Source arrangement according to claim 34, wherein the source arrangement comprises an actuator for altering the relative position of the source element within the source arrangement for a variation of the location of the source area on the source surface when heated by the surface heater of the deposition apparatus.
41. Source arrangement according to claim 34, wherein the source arrangement comprises a temperature sensor for a temperature measurement at the source element arranged at the second surface of the source element,
42. Source arrangement according to claim 41, wherein the temperature sensor is arranged at a symmetric center of the second surface, or at a symmetric center of the source element, or at a common symmetric center of the second surface and the source element.
43. Source arrangement according to claim 41, wherein the second surface comprises an inlet guide section for guiding the temperature sensor into its position arranged at the source element at a symmetric center of the second surface and/or the source element.
44. Source arrangement according to claim 41, wherein the temperature sensor is arranged in direct contact with the second surface.
45. Source arrangement according to claim 41, wherein the temperature sensor is arranged spaced apart from the second surface.
46. Deposition apparatus, comprising a source arrangement with a source element, a target arrangement with a target element, a reaction chamber comprising a wall and containing a reaction atmosphere, an atmosphere controller configured to control the reaction atmosphere and a surface heater configured to heat a source area on a source surface of the source element, whereby the source arrangement and the target arrangement are positioned within the reaction atmosphere in the reaction chamber such that the source material can be deposited on the target element in a con-trolled way by heating the source area by usage of the surface heater by applying a heating power onto a heating spot on the source surface, wherein the source arrangement is constructed according to claim 34.
47. Deposition apparatus according to claim 46, wherein the surface heater comprises a laser light source for emitting laser light into the reaction chamber and/or an aperture in the wall of the reaction chamber for coupling of laser light into the reaction chamber, whereby the laser light is directed onto the source area on the source surface of the source element.
48. Deposition apparatus according to claim 46, wherein the reaction chamber comprises a cooler for cooling of the reaction chamber and/or the reaction atmosphere
49. Deposition apparatus according to claim 46, wherein the atmosphere controller comprise a vacuum pump for providing a reaction atmosphere with a pressure between 10−11 mbar and 1 mbar.
50. Method for depositing source material on a target material in a deposition apparatus, the deposition apparatus comprising a surface heater and a source arrangement comprising a holding structure with a support and at least one source element arranged at the support, the source element comprising the source surface and a second surface opposite of the source surface, wherein source material can be vaporized and/or sublimated from a source area on the source surface when heated by the surface heater of the deposition apparatus, wherein the source element consists of a source material and is arranged self-supporting at the support, the meth-od comprising the following steps: a) Arranging the source arrangement and thereby providing the source element within the reaction chamber, b) Heating the source area on the source surface of the source element by the surface heater by applying a heating power onto a heating spot on the source surface for vaporizing and/or sublimating the source material, c) Measuring a temperature of the source element by the temperature sensor of the source arrangement, and d) Adjusting the heating of the source area by the surface heater according to the temperature measured in step c).
51. Method according to claim 50, wherein step d) comprises an adjustment of the heating power provided by the surface heater onto the source area.
52. Method according to claim 51, wherein the adjustment of the heating power (82) comprises a pulsed operation of the surface heater (62) in at least one alternating on-phase (90) and off-phase (92), whereby the heating power (82) is adjusted by choosing suitable durations (94) of the at least one on-phase (90) and off-phase (92).
53. Method according to claim 50, wherein step d) comprises a spatial variation of a position of the source area on the source surface of the source element.
54. Method according to claim 53, wherein the spatial variation of the position of the source area is brought about by altering a position of the heating spot of the surface heater relative to the surface element and/or by altering the position of the surface element relative to the position of the heating spot
Description
[0060] The present invention is further described hereinafter with reference to illustrated embodiments shown in the accompanying drawings. There is shown:
[0061] FIG. 1 a deposition apparatus,
[0062] FIG. 2 two possible embodiments of source arrangements,
[0063] FIG. 3 two further embodiments of source arrangements,
[0064] FIG. 4 possible arrangements of the temperature sensor,
[0065] FIG. 5 possible embodiments of protrusions as emission sections,
[0066] FIG. 6 a source arrangement with an emission region,
[0067] FIG. 7 a source arrangement with reducing openings,
[0068] FIG. 8 possible embodiments of source arrangements with a source element split in several parts,
[0069] FIG. 9 a temporal distribution of the heating power, and
[0070] FIG. 10 possible embodiments for spatial variations of heating power onto a source surface.
[0071] FIG. 1 shows a possible embodiment of a deposition apparatus 60 according to the invention, In the deposition apparatus 60 a source arrangement 10 according to the invention is arranged. The source arrangement 10 especially comprises a holding structure 12 with a support 14, wherein the support 14 supports the actual source element 20. According to the invention, the source element 20 consists of a source material 42 and is arranged self-supporting at the support 14. As depicted, the holder 14 and the source element 20 are constructed crucible-free. A direct surface heater 62, in this embodiment a laser light source, provides laser light 64 directed onto a heating spot 66 of the source element 20, whereby the heating spot 66 corresponds to a source area 30 on the source surface 28. Source material 42 is vaporized and/or sublimated and the respective vapor 44 is deposited onto a target 80 held by a target arrangement 68 within the reaction chamber 70. The reaction chamber 70 is filled with a reaction atmosphere 76 controlled by an atmosphere controller 78, for instance a vacuum pump. A cooler 74 fitted into or near to the wall 72 of the reaction chamber 70 helps controlling the reaction atmosphere 76 and further absorbs reflected laser light 64.
[0072] According to a method according to the invention in a first step a) the source arrangement 10 is arranged within the reaction chamber 70. The next step b) comprises a heating of the source area 30 by applying a heating power 82 onto a heating spot 66 on the source element 20. In particular, in the next step c) a temperature of the source element 20 is measured by the temperature sensor 18 of the source arrangement 10 according to the invention. In the last step d) of a method according to the invention, this permits an adjustment of the heating of the source area 30 by the surface heater 62 based on the temperature measured by the temperature sensor 18 in step c). In other words, this allows establishing a closed loop control of the heating power 82 based on the measured temperatures of the source element 20.
[0073] Additionally, the deposition apparatus 60 shown in FIG. 1 comprise a temperature controller 87 for controlling the temperature of the target 80. This temperature controller 87 can comprise both temperature sensors 88 to measure the temperature of the material of target 80 and a target heater 89 to adjust the temperature of the material of target 80. Especially a closed loop control for the temperature of the material of target 80 can be established. The temperature sensors 88 can be contact sensors, as for example thermocouples, or contact-free sensors, as for example pyrometers. The target heater 89 can, as depicted in FIG. 1, preferably use a suitable laser beam for heating the material of target 80.
[0074] FIGS. 2 and 3 show possible embodiments of source arrangements 10 according to the invention. In all embodiments, a holding structure 12 comprises a support 14 with cone-shaped protrusions to provide point-like contact areas 52 at the support positions 50 for the respective source element 20 of each source arrangement 10. Each of the source elements 20 is constructed self-supporting and especially without any crucible. Further, each of the source arrangements 10 comprises a temperature sensor 18 directly connected to a second surface 32 of the respective source element 20, especially at a symmetrical center 26 of the second surface 32. This second surface 32 is in all of the embodiments shown in the figures located opposite to the source surface 28 which comprises in its center the source area 30 heated by the heating spot 66 of the laser light 64. Vapor 44 made out of vaporized and/or sublimated source material 42 is indicated by an arrow.
[0075] The left embodiment shown in FIG. 2 is an initial point of design of the source elements 20 used in the source arrangement 10 according to the invention. The source element 20 is self-supporting and in particular rotationally symmetric. All surfaces, besides the point-like contact areas 52, are accessible and can be used for thermal regulation of the source element 20 by radiation cooling. At the source area 30, the source material 42 is melted and evaporated and/or sublimated into the vapor 44.
[0076] The embodiment shown on the right side of FIG. 2 is now optimized with respect to material utilization. During the use of the source arrangement 10, the source material 42 is vaporized and/or sublimated and therefore the source element 20 slowly gets less and less. In this embodiment the source element 20 is essentially shaped as a half sphere and therefore the fraction of the source element 20 actually usable for vaporization and/or sublimation is maximized.
[0077] The embodiment shown on the left side of FIG. 3 is suitable especially for locations, where essentially the whole surface area 28 should be usable as source area 30. Therefore, the source element 20 is elongated well above the support 14 and therefore a vaporization and/or sublimation of the source surface 28 as a whole can be provided. In this embodiment, preferably the support is also movable in vertical direction to provide a constant distance from the source area 30 to the target 80.
[0078] The embodiment shown on the right side of FIG. 3 is suitable for source element 20 comprising a source material 42 with high thermal conductivity. The second surface 32 and especially the elongated part of the source element 20 along its vertical direction can radiate thermal energy and therefore the source area 30 can be better contained on the source surface 28. Without the radiation of thermal energy, a melting of the source element 20 as a whole is at risk.
[0079] FIG. 4 shows two possible arrangements of a temperature sensor 18 at the second surface 32, whereby both embodiments comprise an inlet guide section 34 to guide the temperature sensor 18 into its desired position at a symmetrical center 26 of the source element 20.
[0080] As shown on the left side in FIG. 4, a direct contact, for instance for a thermocouple element used as temperature sensor 18, can be provided easily by a conical inlet guide section 34.
[0081] As shown on the right side of FIG. 4, also a cylindrical inlet guide section 34 can be used. This can be preferably established for source materials 42 with very high melting points and very low vapor pressures, when the temperature of the source element 20 is expected to be higher than bearable for the temperature sensor 18. In this case, no direct contact between the temperature sensor 18 and the source element 20 should be established. The tip of the temperature sensor 18 drawn is surrounded in 5 out of 6 orthogonal spatial directions by surfaces of the source element 20, effecting a strong radiative coupling to the temperature of the source element 20. In particular, a pyrometer element can be used as a temperature sensor 18 in these embodiments.
[0082] The next two FIGS. 5 and 6 show other possible embodiments of a source arrangement 10 similar to the embodiment shown on the right side of FIG. 3, with respect to the requirement that thermal radiation has to be emitted from the source element 20. For all other elements of the depicted source arrangements 10 shown in FIGS. 5 and 6 please refer to the FIGS. 2 and 3.
[0083] In the embodiment shown on the left side of FIG. 5, emission sections 38 are provided, essentially as protrusions protruding from the second surface 32. In this embodiment, the protrusions are conical and extend far away from the source surface. Hence, an especially large second surface 32 and an especially effective radiation cooling can be provided.
[0084] On the right side of FIG. 5 other protrusions are used as emission sections 38 at the second surface 32, whereby in this embodiment the protrusions are prism-shaped. For instance, such protrusions can be provided by etching and/or milling and effectively enlarge the second surface 32 in an especially easy way.
[0085] FIG. 6 shows a different embodiment of an emission section 38, whereby this emission section 38 is provided by an emission region 40 arranged radially around the source area 30. This embodiment is especially advantageous for source materials 42 with high thermal conductivity, because a chemical reaction or the formation of an alloy, in particular a eutectic, between the source element 20 and the support 14 at the contact areas 52, which is essentially temperature dependent, can be effectively avoided by radiating away thermal energy by the emission region 40.
[0086] Opposite to that, in other cases, thermal energy should be contained at the source area 30. FIG. 7 shows a source element 20 which comprises reducing openings 36 extending between the source surface 28 and the second surface 32. These reducing openings 36 effectively reduce the thermal conductivity in radial direction within the source element 20. Therefore the heating power 82 projected onto the source area 30 stays contained in the middle of the source element 20 and is not or at least less distributed over the source element 20 as a whole.
[0087] FIG. 8 shows another two possible embodiments of source elements 20, whereby these source elements 20 comprise a first part 22 and several second parts 24. The embodiment shown on the left side comprises sphere-shell-like parts 22, 24 the embodiment shown on the right side comprises plane-like parts 22, 24. The parts 22, 24 are stacked together, similar to the connection between the support 14 and the source element 20 by providing support positions 50 and point-like contact areas 52. The support positions 50 and the contact areas 52 are provided by the conical protrusions of the several second parts 24. The respective first parts 22 provide the source area 30. These arrangements have two major advantages, first of all if the first part 22 is completely melted, the succeeding second part 24 catches the liquefied first part 22 and a spoiling of the source material 42 can be avoided. Additionally, due to the thermal isolation described already above, the last second part 24, which is in contact with the support 14, is at a relative low temperature and therefore contact contaminations, chemical reactions and/or alloy and eutectic formations at the support positions 50 between the last second part 24 and the support 14 can be avoided.
[0088] In FIG. 9, a temporal variation of the heating power 82 with respect to the duration (t) is shown. This can be used to adjust the heating power 82 in step d) of a method according to the invention. The upper part of the graph in FIG. 9 shows the actual heating power 82 provided by the surface heater 62. Especially, the heating power 82 is provided in on-phases 90 and off-phases 92 with different durations 94. The lower part of the graph in FIG. 9 shows the surface temperature 86 present at the source area 30 of the source element 20. By an adapted ratio of the durations 94 of the on-phases 90 and off-phases 92, a median heating power 82 can be provided, whereby for instance a vaporization and/or sublimation of source material 42 is provided during the on-phases 90, but due to the cooling during the off-phase 92 a complete melting of the source element 20 can be avoided. While the surface temperature 86 at the end of the on-phases 90 is maximal, leading to strong evaporation or sublimation, the average surface temperature 86, leveling out away from the source area 30 due to non-instantaneous thermal conduction to the temperature sensor 18 and support 14, is reduced according to the duration ratio between the on-phases 90 and the off-phases 92.
[0089] FIG. 10 shows a different possibility of achieving high peak surface temperatures 86 at the source area 30 with low average surface temperatures 86 at the temperature sensor 18 and support 14 (see FIGS. 2, 3, 5, 6), especially to spatially spread the heating power 82 onto a larger part of the source surface 28 for more efficient radiative cooling. This can be provided either by moving the source element 20 relative to the heating spot 66 or vice versa. Also a combined movement of the source element 20 and the heating spot 66 can be used. In summary, the heating power 82 is distributed over the source surface 28, providing a more distributed irradiation to prevent a complete melting of the source element 20. Also a more evenly vaporization and/or sublimation of source material 42 can be provided. The three embodiments shown in FIG. 10 depict different possibilities of this approach.
[0090] The upper left embodiment shown in FIG. 10 is a simple circular movement of the heating spot 66 on the source surface 28 of the source element 20. This can for instance be provided by simply rotating the source element 20 around its symmetrical center 26, especially by using an actuator 16 of the source arrangement 10. It is a preferred embodiment that the temperature sensor 18 on the second surface 28 may be located on the symmetrical center 26 and hence on the rotation axis, thereby having a constant distance to the heating spot 66. Despite the heating spot 66 circling around the symmetrical center 26, the measured or controlled surface temperature 86, especially the surface temperature 86 at the source area 30, remains constant during the rotation, as the thermal distribution remains constant in the rotating reference frame or coordinate system of the heating spot 66.
[0091] The upper right embodiment is similar, but in this case the movement of the heating spot 66 is a spiral one.
[0092] For rectangular source elements 20, a meander-like path of the heating spot 66 on the source surface 28 of the source element can be advantageous, as shown in the lower part of FIG. 10.
[0093] In all of the embodiments the heating power 82 is sequentially distributed over a larger area on the source surface 28 of the source element 20. Therefore a more distributed vaporization and sublimation of the source material 42 can easily be provided.
REFERENCE SIGNS
[0094] 10 source arrangement
[0095] 12 holding structure
[0096] 14 support
[0097] 16 actuator
[0098] 18 temperature sensor
[0099] 20 source element
[0100] 22 first part
[0101] 24 second part
[0102] 26 symmetrical center
[0103] 28 source surface
[0104] 30 source area
[0105] 32 second surface
[0106] 34 inlet guide section
[0107] 36 reducing opening
[0108] 38 emission section
[0109] 40 emission region
[0110] 42 source material
[0111] 44 vapour
[0112] 50 support position
[0113] 52 contact area
[0114] 60 deposition apparatus
[0115] 62 surface heater
[0116] 64 laser light
[0117] 66 heating spot
[0118] 68 target arrangement
[0119] 70 reaction chamber
[0120] 72 wall
[0121] 74 cooler
[0122] 76 reaction atmosphere
[0123] 78 atmosphere controller
[0124] 80 target
[0125] 82 heating power
[0126] 84 spatial variation
[0127] 86 surface temperature
[0128] 87 temperature controller
[0129] 88 temperature sensor
[0130] 89 target heater
[0131] 90 on-phase
[0132] 92 off-phase
[0133] 94 duration
