EVAPORATION BOAT

Abstract

The invention relates to an evaporation boat comprising an evaporator body, wherein the evaporator body comprises an evaporator surface which extends along a longitudinal direction of the evaporator body. The evaporator surface has a pyramidally structured surface which can be created by mechanically machining the evaporator surface in two mutually perpendicular machining directions. The pyramidally structured surface comprises a plurality of structural elements which are directly adjacent to one another and have a substantially rectangular bottom surface and lateral surfaces which taper conically to a top surface or point.

Claims

1. An evaporation boat comprising an evaporator body, wherein the evaporator body comprises an evaporator surface which extends along a longitudinal direction of the evaporator body, wherein the evaporator surface has a pyramidally structured surface which can be created by mechanically machining the evaporator surface in two mutually perpendicular machining directions, wherein the pyramidally structured surface comprises a plurality of structural elements which are directly adjacent to one another and have a substantially rectangular bottom surface and lateral surfaces which taper conically to a top surface or point.

2. The evaporation boat according to claim 1, wherein the opposite lateral surfaces of two adjacent structural elements span an external angle α of 85-95°.

3. The evaporation boat according to claim 1, wherein the top surface or point of the structural element has a height relative to its substantially rectangular bottom surface of 0.5-4 mm.

4. The evaporation boat according to claim 1, wherein the structural elements have a substantially square bottom surface.

5. The evaporation boat according to claim 1, wherein the length S.sub.K of one side of the substantially rectangular bottom surface corresponds to a distance S.sub.P between two points of two adjacent structural elements, wherein the distance S.sub.P has a length of 1-8 mm.

6. The evaporation boat according to claim 1, wherein the two mutually perpendicular machining directions extend in straight lines without interruptions.

7. The evaporation boat according to claim 1, wherein the pyramidally structured surface has a surface area that is at least 5% larger than the evaporator surface prior to mechanical machining.

8. The evaporation boat according to claim 1, wherein the evaporation boat can be heated by direct passage of current as a resistance.

9. The evaporation boat according to claim 1, wherein the evaporation boat is made of a sintered ceramic material selected from the group consisting of TiB.sub.2—BN, TiB2—BN—AlN and TiB2—BN—AlN—W.

10. The evaporation boat according to claim 2, wherein the external angle α is about 90°.

11. The evaporation boat of according to claim 3, wherein the height relative to the substantially rectangular bottom surface is 0.6-1.5 mm.

12. The evaporation boat of according to claim 3, wherein the height relative to the substantially rectangular bottom surface is 0.8-1.2 mm.

13. The evaporation boat according to claim 5, wherein the distance S.sub.P has a length of 3-6 mm.

14. The evaporation boat according to claim 5, wherein the distance S.sub.P has a length of 4-5 mm.

15. The evaporation boat of claim 7, wherein the surface area is at least 10 percent larger than the evaporator surface area prior to mechanical machining.

16. A method for producing an evaporation boat comprising a pyramidally structured surface according to claim 1, wherein the method comprises the following steps: a) providing an evaporation boat having an evaporator body, wherein the evaporator body comprises an evaporator surface; b) mechanically machining the evaporator surface in two mutually perpendicular machining directions using a groove milling cutter with a V-shaped cutting insert and thus creating the pyramidally structured surface.

17. Use of an evaporation boat having a pyramidally structured surface according to claim 1 for evaporating metal in a PVD metallization system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Further advantages and features will emerge from the following description and from the accompanying drawings. The figures show:

[0037] FIG. 1 in a perspective view, the evaporation boat according to the invention comprising a pyramidally structured surface,

[0038] FIG. 2 in a plan view, the evaporation boat of FIG. 1,

[0039] FIG. 3 in a plan view, a pyramidally structured region of the evaporation boat of FIG. 1,

[0040] FIG. 4 in a plan view, an intersection and four structural elements of the evaporation boat of FIG. 1,

[0041] FIG. 5 in a sectional view along the section line V, the evaporation boat of FIG. 1.

DETAILED DESCRIPTION

[0042] FIGS. 1 and 2 show an evaporation boat 10 which extends along a longitudinal axis D and comprises an evaporator body 12 and a first clamping end 14 and a second clamping end 16 which adjoin the end faces of the evaporator body 12 in one piece in the direction of the longitudinal axis L.

[0043] The evaporation boat 10 has the basic shape of a cylinder having an isosceles trapezium as the base surface 5.

[0044] Such a body can also be described as a regular prism, i.e., a straight prism having a regular polygon as the bottom surface.

[0045] In the illustrated embodiment, the evaporator body 12 can have the basic shape of a regular prism, while the first and the second clamping end 14, 16 can have any shape. The evaporation boat 10 comprises an evaporator surface 18 which extends along the evaporator body 12 and is flush with the clamping ends 14, 16.

[0046] It is also possible to provide the evaporation boat with a plurality of evaporator surfaces. This can be achieved in that the evaporator body 12 has a rotational symmetry, wherein the evaporator body can comprise a number of evaporator surfaces which corresponds to the order of rotational symmetry. Such an evaporation boat is known from DE 10 2020 102 483.5 (not published), for example.

[0047] In the shown embodiment, the evaporator surface 18 is delimited only by the edge 22 of the clamping ends 14, 16. However, it is also conceivable for the evaporator surface 18 to be delimited by further elements, in particular by a raised edge or rim. It is also conceivable for the evaporator surface 18 to be delimited by a depression. The delimitation can be in the direction of the longitudinal axis L or perpendicular to it, in the transverse direction of the evaporator surface. However, it is also in line with the invention if the evaporator surface 18 is not delimited and merges flat into the clamping ends 14, 16.

[0048] The first clamping end 14 and the second clamping end 16 are preferably configured identically. The configuration of the two clamping ends 14, 16 is explained in the following using the first clamping end 14 as an example.

[0049] In an alternative embodiment, the first clamping end 14 and the second clamping end 16 can of, course, be configured differently from one another.

[0050] In the shown embodiment, the clamping end 14 has the same basic shape as the adjacent evaporator body 12, namely a cylinder having an isosceles trapezium as the base surface 5.

[0051] The sides, which represent the lateral surface of the cylinder, respectively form two opposite outer surfaces 8, 9, an underside 7 and an upper side 6 of the clamping end 14, which merges flat into the adjacent evaporator surface 18 of the evaporator body 12.

[0052] The evaporator surface 18 has a pyramidally structured surface 20. In the shown embodiment, the pyramidally structured surface 20 extends over the entire evaporator surface 18. The pyramidally structured surface 20 can in principle occupy any size portion of the evaporator surface 18. In another embodiment, the pyramidally structured surface 20 can occupy at least 50% of the evaporator surface 18, preferably at least 70%, particularly preferably at least 90%. Here, it is conceivable that the pyramidally structured surface 20 can occupy any regions on the evaporator surface 18. These can form contiguous, i.e., connected, regions or be separated from one another by unstructured regions. The thus created pattern of the evaporator surface 18 can have circular, elliptical, rhombohedral, rectangular, radial or lattice-like shapes, for example.

[0053] FIG. 3 shows a plan view of a subsection of the pyramidally structured surface 20. The pyramidally structured surface 20 comprises a periodic arrangement of a plurality of structural elements 24 which are directly adjacent to one another. The position and shape of the structural elements 24 is predetermined by the two mutually perpendicular machining directions, which form a first set of parallel depressions 26 and a second set 28 of parallel depressions, wherein the first set 26 and the second set 28 are perpendicular to one another. According to the invention, any number of depressions can form a first or a second set.

[0054] The depressions 26, 28 within the first and second set in particular always have the same distance from one another. The distance between the depressions 26 within the first set is preferably approximately equal to the distance between the depressions 28 within the second set.

[0055] The first set and second set of parallel depressions 26, 28 form the structural elements 24 of the pyramidally structured surface 20. Due to the symmetry-related predetermination of the machining directions, the structural elements 24 have a substantially rectangular, preferably square bottom surface 30. The substantially square bottom surface 30 is formed by four sides 31 having identical dimensions, each of which is at right angles to the other, wherein each two sides 31 meet at a substantially right-angled corner 21. Each bottom surface 30 of a structural element 24 therefore has four sides 31 having identical dimensions and four substantially right-angled corners 21. One of four lateral surfaces 36 respectively extends over each one of the four sides 31, wherein the lateral surfaces 36 are all congruent with one another. The lateral surfaces 36 can be conical and converge with the other lateral surfaces 36 to a point 32. In this embodiment, the structural element 24 forms the shape of a pyramid having burrs 27 which are rounded as a result of machining. According to another embodiment, the point 32 can be rounded, or flattened and configured as a top surface 34 so that the structural elements 24 then have the shape of truncated pyramids with rounded burrs 27. For the invention, it is irrelevant whether the structural element 24 has a top surface 34 or a point 32.

[0056] It is also conceivable for the configuration of the bottom surface to be exactly square. The lateral surfaces can likewise converge linearly to a top surface 34 or a point 32.

[0057] The structural elements 24 are directly adjacent to one another with the sides 31 of the substantially square bottom surfaces 30, i.e., two opposite sides 31 of two respective opposite bottom surfaces 30 each are connected to one another via one of the depressions 26, 28 such that the sides 31 are flush with one another with their respective ends. The two mutually perpendicular machining directions thus extend in straight lines without interruptions.

[0058] The structural elements 24 form a highly symmetrical cubic arrangement with the first set of depressions 26 and second set of depressions 28. This arrangement is shown in FIG. 4 and will be described in the following.

[0059] The first set of depressions 26 and the second set of depressions 28 intersect at a right angle at a plurality of intersections 38. Each corner 21 of a structural element 24 abuts a respective intersection 38. Consequently, four respective corners 21 of four structural elements 24 meet at one intersection 38. This results in a cubic periodicity of structural elements 24 and intersections 38, i.e., each intersection 38 has a four-fold axis of rotation perpendicular to the evaporator surface 18. Therefore, four structural elements 24 are symmetrically connected at an intersection 38 via a four-fold axis of rotation D.sub.4, wherein a 90° rotation (angle ε) about said axis transforms the structural elements 24 into one another.

[0060] Due to the cubic symmetry, the length S.sub.K of a side 31 of the substantially square bottom surface 30 corresponds to a distance S.sub.P between two points or centers of two adjacent structural elements 24.

[0061] According to a preferred embodiment, the opposite lateral surfaces 36 of two adjacent structural elements 24 span an external angle α of 85-95°, in particular about 90° (see FIG. 5). Due to the pyramidal symmetry, the internal angle β associated with the point 32 or the top surface 34 between two opposite lateral surfaces 36 within a structural element 24 likewise has a range of 85-95°. The opening angle γ, which corresponds to half of the angle α or β, is accordingly about 45°.

[0062] In another embodiment, the top surface 34 or point 32 of a structural element 24 has a height relative to its square bottom surface 30. The height preferably has a length of 0.5-4 mm, preferably 0.6-1.5 mm, particularly preferably 0.8-1.2 mm.

[0063] The evaporation boat 10 can act as an electrical heating resistance and be made of a corresponding material and can then be heated by direct passage of current by applying an electrical voltage.

[0064] A method for producing the pyramidal structured surface according to the invention will be described in the following. The evaporation boat can be formed from a green body mass and then hot-pressed and sintered. The thus obtained evaporation boat has an evaporator body comprising an evaporator surface. By mechanically machining the evaporator surface in two mutually perpendicular machining directions, the evaporator surface can be partially or completely converted into the pyramidal structured surface according to the invention. The mechanical machining can be carried out using a V-shaped cutting insert. The use of a grinder is conceivable as well. The mechanical machining of the evaporator surface can therefore include milling or grinding. It is consequently possible to produce such a structured surface retroactively and to modify existing evaporation boats.

[0065] In another embodiment, the pyramidally structured surface can be created directly in the green body mass, for example by embossing the shape using a stamp. The structuring of the surface can thus be carried out prior to the sintering of the evaporation boats.

[0066] Evaporation boats produced in this manner have a larger surface area than evaporation boats that have not been machined.

[0067] A surface area comparison between an evaporation boat prior to mechanical machining comprising a correspondingly “smooth” evaporator surface and an evaporation boat according to the invention after mechanical machining comprising a pyramidally structured surface will be shown in the following.

[0068] The evaporator surface of both evaporation boats includes a rectangular area having the dimensions 35×100 mm. The “smooth evaporator surface” of the evaporation boat of the prior art therefore has a surface area of about 3500 mm.sup.2. A structuring of the same 35×100 mm area with a pyramidal structured surface results in a surface area of 4143 mm.sup.2. This corresponds to an increase in the surface area of 643 mm.sup.2 or 18.4%. In this embodiment, the side length of the structural elements is about 2 mm and the height is about 1 mm, with an opening angle γ of about 45°. In an alternative embodiment, any dimensions can be used, as a result of which increases in the surface area can be adjusted as needed.

[0069] Such an increased surface area enables either a higher evaporation rate with unchanging service life or an unchanging evaporation rate with longer service lives. The evaporation rate can be measured with little effort by gravimetrically determining the quantity of metal deposited using piezo sensors. A change in the service life of the evaporation boats can be determined via the penetration depth of the corrosion in the evaporator body. For this purpose, the service lives of evaporation boats comprising pyramidally structured and “smooth” surfaces can be compared with one another.

[0070] The invention is not limited to the shown embodiment. Individual features of one embodiment can in particular be combined as desired with features of other embodiments, in particular independently of the other features of the respective embodiments.

LIST OF REFERENCE SIGNS

[0071] Base surface 5

[0072] Upper side 6

[0073] Underside 7

[0074] Outer surfaces 8, 9

[0075] Evaporation boat 10

[0076] Evaporator body 12

[0077] First clamping end 14

[0078] Second clamping end 16

[0079] Evaporator surface 18

[0080] Pyramidally structured surface 20

[0081] Corner 21

[0082] Edge 22

[0083] Structural element 24

[0084] First set of parallel depressions 26

[0085] Burr 27

[0086] Second set of parallel depressions 28

[0087] Bottom surface 30

[0088] Sides 31

[0089] Point 32

[0090] Top surface 34

[0091] Lateral surface 36

[0092] Intersection 38

[0093] Axis of rotation D.sub.4

[0094] Longitudinal axis L

[0095] External angle α

[0096] Internal angle β

[0097] Opening angle γ

[0098] Right angle ε

[0099] Length S.sub.K

[0100] Distance S.sub.P