CN112359324A

CN112359324A - Evaporation crucible

Info

Publication number: CN112359324A
Application number: CN202011181339.8A
Authority: CN
Inventors: 徐天宇; 黄秦霏; 肖昂; 刘洋; 郭雄飞; 徐豹; 朱伍权; 付佳佳; 孟德芬; 易平安; 赵希瑾; 贾克飞
Original assignee: BOE Technology Group Co Ltd; Chengdu BOE Optoelectronics Technology Co Ltd
Current assignee: BOE Technology Group Co Ltd; Chengdu BOE Optoelectronics Technology Co Ltd
Priority date: 2020-10-29
Filing date: 2020-10-29
Publication date: 2021-02-12
Anticipated expiration: 2040-10-29
Also published as: CN112359324B

Abstract

The invention discloses an evaporation crucible, relates to the technical field of evaporation equipment, and can reduce the speed fluctuation of steam sprayed out of a nozzle and reduce the possibility that a coating material is attached to the inner side of the nozzle and continuously grows. The evaporation crucible comprises: the crucible comprises a crucible body, a crucible body and a crucible cover, wherein the crucible body comprises a bottom wall and a side wall arranged around the bottom wall, and the bottom wall and the side wall enclose an accommodating cavity with an opening; the surface of the side wall close to the accommodating cavity is a first surface, and the first surface comprises a supporting surface parallel to the bottom wall; the screen plate component comprises at least one screen plate with meshes and abuts against the supporting surface; the nozzle is installed at the opening of holding the chamber, and the nozzle has the fumarole. The evaporation crucible is used for an evaporation process.

Description

Evaporation crucible

Technical Field

The invention relates to the technical field of evaporation equipment, in particular to an evaporation crucible.

Background

The vapor deposition is a process of vaporizing a coating material (or called a coating material) and depositing the material on the surface of a substrate by adopting a certain heating mode under a vacuum condition; the method is widely applied to the manufacturing process of the display panel. The evaporation crucible is one of the most important devices in the evaporation process, and the evaporation crucible provided by the prior art generally comprises a crucible body with a containing cavity and a nozzle arranged at the opening of the crucible body.

In the evaporation crucible in the prior art, as the evaporation process is continuously carried out, the coating material in the crucible body is gradually reduced, the steam generation speed of the coating material is gradually reduced, the gas pressure in the crucible body is reduced, and the gas injection rate of a nozzle is caused to fluctuate; but also the deposition material is attached to the inner side of the nozzle and continuously grows (usually, the vapor of the deposition material is formed on the inner side wall of the nozzle by sublimation), which affects the stability of the deposition process and the yield of the deposition product.

Disclosure of Invention

Embodiments of the present invention provide an evaporation crucible capable of increasing a gas pressure in the evaporation crucible during an evaporation process, reducing a rate fluctuation of vapor ejected from a nozzle, and reducing a possibility of a coating material adhering to an inner side of the nozzle and continuously growing.

In order to achieve the above purpose, the embodiment of the invention adopts the following technical scheme:

an evaporation crucible comprising: the crucible comprises a crucible body, a crucible body and a crucible cover, wherein the crucible body comprises a bottom wall and a side wall arranged around the bottom wall, and the bottom wall and the side wall enclose an accommodating cavity with an opening; the surface of the side wall close to the accommodating cavity is a first surface, and the first surface comprises a supporting surface parallel to the bottom wall; the screen plate component comprises at least one screen plate with meshes and abuts against the supporting surface; the nozzle is installed at the opening of holding the chamber, and the nozzle has the fumarole.

In some embodiments, the sidewall includes a flange extending toward an inside of the receiving cavity, the flange is located between the bottom wall and the opening of the receiving cavity, and the flange is annular in a circumferential direction of the receiving cavity; the support surface is the surface of the flange remote from the bottom wall.

In some embodiments, the first surface further comprises a first extension section and a second extension section extending in a direction perpendicular to the bottom wall, the second extension section is located on a side of the first extension section away from the bottom wall, and the diameter of the first extension section is smaller than that of the second extension section; one side of the supporting surface is connected with the first extending section, and the other side of the supporting surface is connected with the second extending section.

In some embodiments, the number of the mesh plates is multiple, the mesh plates are arranged in a stacked manner, and an avoidance gap is formed between any two adjacent mesh plates.

In some embodiments, the screen plate comprises a lower screen plate and an upper screen plate, the lower screen plate comprises a screen plate body and a supporting frame arranged around the screen plate body, and steps are arranged on the inner side of the supporting frame; the upper-layer net plate is sleeved in the supporting frame and is abutted to the surface of the step far away from the net plate body.

In some embodiments, a plurality of clamping protrusions extending inwards are arranged on the edge of the support frame away from the screen plate, and the clamping protrusions are arranged at intervals along the circumferential direction of the support frame; the circumference edge of upper screen plate is equipped with a plurality of draw-in grooves that correspond with the joint arch, and upper screen plate joint is between joint arch and step, and the carriage rotation can be relatively supported to upper screen plate.

In some embodiments, the radial dimension at the location of the slot of the upper web is greater than the diameter of the inside edge of the step.

In some embodiments, the mesh panel comprises a planar mesh panel comprising a mesh region and a flat panel region surrounding the mesh region, wherein a plurality of meshes are arranged in the mesh region, and the mesh region and the flat panel region have the same thickness; the screen plate assembly further comprises an annular supporting piece, the annular supporting piece is arranged between any two adjacent plane screen plates, and two ends of the annular supporting piece are respectively abutted to the two plane screen plates.

In some embodiments, the avoidance gap is filled with silicon nitride particles.

In some embodiments, the screen assembly is made of a material that is resistant to high temperatures and does not react with the coating material.

According to the evaporation crucible provided by the embodiment of the invention, the screen plate assembly is additionally arranged in the crucible body, and during evaporation, a coating material is placed between the screen plate assembly and the bottom wall. The otter board subassembly can reduce the cross sectional area of vapour (the vapour that coating material evaporation or sublimation formed) diffusion passageway (from the regional passageway of diffusing to nozzle department in otter board subassembly below), and then increases and hold the atmospheric pressure of chamber downside (hold the space that the chamber otter board subassembly is close to diapire one side). On one hand, the air pressure at the lower side of the accommodating cavity is increased, so that the speed of the steam passing through the mesh plate assembly is more stable; the steam quantity on the lower side of the accommodating cavity can be increased, so that the air pressure fluctuation on the lower side of the accommodating cavity caused by the fluctuation of the steam generation quantity is reduced, the speed fluctuation of steam passing through the screen plate assembly is reduced, and the fluctuation of the air injection speed of the nozzle is reduced. On the other hand, according to the ideal gas state equation (PV ═ nRT), it can be known that the gas pressure on the lower side of the accommodating chamber is increased, which is beneficial to raising the temperature on the lower side of the accommodating chamber; i.e. to raise the temperature of the vapour. The increase of the steam temperature can reduce the possibility of the steam attaching to the inner side of the nozzle and continuously growing (the temperature is high and the steam is not easy to desublimate). In summary, compared with the prior art, the evaporation crucible provided by the embodiment of the invention can increase the stability of the evaporation process and the yield of the evaporation product by adding the screen plate assembly between the coating material and the nozzle.

Drawings

FIG. 1 is a schematic structural view of an evaporation crucible according to an embodiment of the present invention;

FIG. 2 is a schematic view showing the structure of a crucible body according to the first embodiment;

FIG. 3 is a schematic structural view of a crucible body in a second embodiment;

FIG. 4 is a top view of a lower screen of an embodiment of the present invention;

FIG. 5 is a cross-sectional view A-A of FIG. 4;

FIG. 6 is a top view of an upper screen according to an embodiment of the present invention;

FIG. 7 is a cross-sectional view taken along line B-B of FIG. 6;

FIG. 8 is a schematic view of an assembly structure of an upper screen and a lower screen according to an embodiment of the present invention;

FIG. 9 is a top view of the embodiment of the present invention with the clamping protrusion facing the clamping groove;

FIG. 10 is a top view of an embodiment of the present invention with the clamping projections and clamping slots misaligned;

FIG. 11 is a top view of a flat mesh panel according to an embodiment of the present invention;

FIG. 12 is a cross-sectional view C-C of FIG. 11;

fig. 13 is a schematic structural diagram of an annular support according to an embodiment of the present invention.

Reference numerals

1-crucible body; 11-a bottom wall; 12-a side wall; 121-a first surface; 1211-support surface; 1212-a first extension; 1213-second extension; 2-a screen assembly; 20-mesh plate; 21-lower layer screen plate; 211-a mesh plate body; 212-a support frame; 213-step; 214-a snap projection; 22-upper screen plate; 221-card slot; 23-a planar screen; 231-a mesh area; 232-plate area; 24-an annular support; 3-a nozzle; 31-gas injection holes.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.

The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

An embodiment of the present invention provides an evaporation crucible, referring to fig. 1 and 2, including: the crucible comprises a crucible body 1, wherein the crucible body 1 comprises a bottom wall 11 and a side wall 12 arranged around the bottom wall 11, and the bottom wall 11 and the side wall 12 enclose an accommodating cavity with an opening; the surface of the side wall 12 close to the receiving cavity is a first surface 121, and the first surface 121 comprises a support surface 1211 parallel to the bottom wall 11; the screen plate assembly 2, the screen plate assembly 2 includes at least one screen plate 20 with mesh holes, the screen plate assembly 2 is abutted against the supporting surface 1211; and the nozzle 3 is installed at the opening of the accommodating cavity, and the nozzle 3 is provided with an air injection hole 31.

In the evaporation crucible of the embodiment of the invention, the screen plate assembly 2 is additionally arranged between the crucible body 1 and the nozzle 3, and during evaporation, coating materials (such as magnesium and ytterbium) are placed between the screen plate assembly 2 and the bottom wall 11. The mesh plate assembly 2 can reduce the cross-sectional area of the vapor diffusion channel, thereby increasing the gas pressure on the underside of the receiving chamber. On the one hand, increasing the gas pressure at the lower side of the containing cavity can not only make the speed of the vapor passing through the mesh plate assembly 2 more stable; the vapor content on the lower side of the accommodating cavity can be increased, so that the air pressure fluctuation on the lower side of the accommodating cavity caused by the change of the vapor generation amount is reduced, the speed fluctuation of vapor passing through the mesh plate assembly 2 is reduced, and the air injection speed fluctuation of the nozzle 3 is reduced. On the other hand, according to the ideal gas state equation, the gas pressure on the lower side of the accommodating cavity is increased, which is beneficial to increasing the temperature of the lower side of the accommodating cavity, namely, increasing the temperature of the coating material and the vapor of the coating material. The temperature of the vapor is increased, so that the possibility of vapor attaching and growing on the inner side of the nozzle 3 (particularly at the gas injection holes 31) can be effectively reduced. In summary, compared with the prior art, the evaporation crucible provided in the embodiment of the present invention can increase the stability of the evaporation process and the yield of the evaporation product by adding the screen assembly 2 between the coating material and the nozzle 3.

It should be noted that the included angle between the support surface 1211 and the bottom wall 11 is α, and optionally, α is greater than or equal to 0 ° and less than 90 °. The smaller the angle α, i.e. the closer the support surface 1211 is parallel to the bottom wall 11, the better the support surface 1211 supports the screen plate assembly 2; it should therefore be understood that the application of the support surface 1211 parallel to the bottom wall 11 is only one preferred embodiment and not the only possible embodiment. In the application, the supporting surface 121 which is not perpendicular to the bottom wall 11 is arranged on the first surface 121, so that the screen plate assembly 2 can be directly abutted on the first surface 121 of the side wall 12, and additional parts for supporting and connecting the screen plate assembly 2 and the crucible body 1 are not required to be arranged, and the crucible is simple in structure, reliable in installation and simple in operation.

Example one

In some embodiments, with reference to fig. 2, the side wall 12 comprises a flange 122 extending towards the inside of the housing cavity, the flange 122 being located between the bottom wall 11 and the opening of the housing cavity, and the flange 122 being annular along the circumference of the housing cavity; the support surface 1211 is the surface of the flange 122 remote from the bottom wall 11. Illustratively, there may be a space of not less than five millimeters between the mesh plate assembly 2 and the coating material to allow the vapor to be collected in a certain amount at the lower side of the receiving chamber; when the coating material is placed, the height of the coating material is lower than that of the annular flange 122, so that the coating material is prevented from directly contacting the screen assembly 2. In the evaporation process, according to the difference of evaporation materials, the temperature in the accommodating cavity can reach 800 ℃ or even more than 1000 ℃, and under the temperature, the reliability of a conventional detachable connecting structure (such as a screw connection structure, a clamping structure or an adhesive and the like) is poor, and other impurities can be introduced, so that the steam purity can be reduced. In this embodiment, referring to fig. 1 and 2, an annular flange 122 is provided on the side wall 12, and the screen plate assembly 2 is directly placed and abutted on the upper surface (support surface 1211) of the flange 122, so that the screen plate assembly 2 is reliably mounted in the crucible body 1 by means of gravity and the structure of the crucible body 1 itself. The structure reliability is high, and the problems of connection failure or up-and-down sliding of the screen plate assembly 2 can be avoided; meanwhile, the screen plate assembly 2 is convenient and quick to mount and dismount and convenient to use.

It should be noted that, in other embodiments, a plurality of support blocks may be disposed on the side wall 12 and spaced circumferentially along the receiving cavity; the annular flange 122 of the above embodiment is replaced by a plurality of support blocks disposed at intervals.

Example two

In some embodiments, referring to fig. 3, the first surface 121 further includes a first extension segment 1212 and a second extension segment 1213 extending in a direction perpendicular to the bottom wall 11, the second extension segment 1213 is located on a side of the first extension segment 1212 away from the bottom wall 11, and a diameter of the first extension segment 1212 is smaller than a diameter of the second extension segment 1213; the support surface 1211 is connected to the first extension 1212 at one side and to the second extension 1213 at the other side. Compared to the manner of providing the annular flange 122 on the sidewall 12, in the present embodiment, the first surface 121 is in a step shape, and one side of the sidewall 12 away from the bottom wall 11 is recessed in a direction away from the accommodating cavity (toward the outside), and the supporting surface 1211 is a surface parallel to the bottom wall 11 at the step. Wherein the diameter of the screen assembly 2 is larger than the diameter of the first extension 1212, so that the screen assembly 2 can be placed and abutted on the first surface 1211; the diameter of the mesh plate assembly 2 may be slightly smaller than that of the second extension 1213, for example, the diameter of the mesh plate assembly 2 may be 0.5-2 mm smaller than that of the second extension 1213, so that the mesh plate assembly 2 can be smoothly installed in and taken out of the accommodating cavity.

In some embodiments, referring to fig. 1, the number of the mesh plates 20 is multiple, a plurality of mesh plates 20 are stacked, and an escape gap is formed between any two adjacent mesh plates 20, so that the diffusion channel of the vapor is not completely blocked during the stacking process of the plurality of mesh plates 20. Illustratively, the projections of the meshes of any two adjacent mesh plates 20 on the bottom wall 11 are arranged in a staggered manner, i.e. the meshes of two adjacent mesh plates 20 are not arranged right opposite to each other. Compared with the single-layer mesh plate 20, the multi-layer mesh plate 20 has more remarkable blocking effect on vapor diffusion, and the air pressure at the lower side of the accommodating cavity is obviously increased. It should be noted that the number of the mesh plates 20 is not as large as possible, and it is necessary to satisfy the requirement that the vapor can pass through the mesh plate assembly 2 at a certain speed, so as to avoid affecting the efficiency of the evaporation.

In some embodiments, the plurality of mesh panels 20 includes a lower mesh panel 21 and an upper mesh panel 22, referring to fig. 4 and 5, the lower mesh panel 21 includes a mesh panel body 211 and a support frame 212 disposed around the mesh panel body 211, and the inner side of the support frame 212 is provided with a step 213; referring to fig. 6, 7 and 8, the upper-layer mesh plate 22 is sleeved in the supporting frame 212, and the upper-layer mesh plate 22 abuts against the surface of the step 213 away from the mesh plate body 211. In this embodiment, a support frame 212 is provided at the edge of the lower screen plate 21, the upper screen plate 22 abuts against the inner wall (step 213) of the support frame 212, and an escape gap is formed between two adjacent screen plates 20 (the lower screen plate 21 and the upper screen plate 22) by the support frame 212. The screen plate assembly 2 has a small number of parts and is convenient and simple to assemble and install.

When the mesh plate assembly comprises a plurality of lower mesh plates 21 and a plurality of upper mesh plates 22, the lower mesh plates 21 and the upper mesh plates 22 are alternately arranged, and the lowermost mesh plate is the lower mesh plate 21 directly abutted on the supporting surface 1211, for example, referring to fig. 8, the mesh plate assembly 2 comprises one lower mesh plate 21 and one upper mesh plate 22, and the lower mesh plate 21 is positioned on one side of the upper mesh plate 22 close to the bottom wall 11.

In some embodiments, referring to fig. 6 and 7, the edge of the support frame 212 away from the screen body 211 is provided with a plurality of clamping protrusions 214 extending inwards, and the plurality of clamping protrusions 214 are arranged at intervals along the circumference of the support frame 212; the peripheral edge of upper screen 22 is equipped with a plurality of draw-in grooves 221 that correspond with joint arch 214, and upper screen 22 joint is between joint arch 214 and step 213, and upper screen 22 can rotate relative to carriage 212. Illustratively, the number of the clamping protrusions 214 and the clamping grooves 221 may be three, four or six, and the plurality of clamping protrusions 214 and the plurality of clamping grooves 221 are evenly distributed. Referring to fig. 9, when the clamping groove 221 of the upper screen 22 is disposed opposite to the clamping protrusion 214, the upper screen 22 may be installed in the supporting frame 212 or taken out from the supporting frame 212; referring to fig. 10, after the upper screen 22 is mounted in the supporting frame 212 and abuts against the step 213, the upper screen 22 is rotated to make the slot 221 dislocated with the clamping protrusion 214, and the upper screen 22 is clamped between the step 213 and the clamping protrusion 214; the air pressure under the containing cavity is prevented from being too large, and the upper net plate 22 is jacked up to generate jumping.

In some embodiments, the radial dimension of the upper mesh plate 22 at the position of the slot 221 (the diameter corresponding to the slot 221) is larger than the diameter of the inner edge of the step 213, so that the step 213 can block the slot 221 to prevent vapor from passing through the slot 221 after the upper mesh plate 22 is mounted on the support frame 212.

In other embodiments, referring to fig. 11 and 12, the mesh panel 20 includes a planar mesh panel 23, the planar mesh panel 23 includes a central mesh region 231, and a flat plate region 232 surrounding the mesh region 231, a plurality of meshes are disposed in the mesh region 231, and the thickness of the mesh region 231 is the same as that of the flat plate region 232. Referring to fig. 13, the mesh panel assembly 2 further includes an annular support 24, the annular support 24 is installed between any two adjacent planar mesh panels 23, and two ends of the annular support 24 are respectively abutted to the two planar mesh panels 23. In this embodiment, an avoidance gap is formed between two adjacent planar mesh plates 23 by the annular support member 24, and the structure of the planar mesh plates 23 is simpler.

In some embodiments, referring to fig. 8, the avoiding gap between two adjacent mesh plates 20 is filled with silicon nitride particles, the silicon nitride particles can absorb ash (the main component is oxide, impurities and other components of the coating material) in vapor in the evaporation process, and the vapor can penetrate through the mesh plate assembly and diffuse to the upper side of the accommodating cavity (the side of the mesh plate assembly 2 away from the bottom wall 11), without being affected by the silicon nitride particles. It should be noted that silicon nitride may be replaced by silicon carbide particles or other particles that are resistant to high temperature, do not react with the coating material, and do not deform.

In some embodiments, the screen assembly 2 is made of a material that is resistant to high temperatures and does not react with the coating material. Wherein, "high temperature resistant" means: can resist the temperature during the evaporation process; particularly, the structure can still keep stable in the evaporation process, and no chemical reaction is generated. Illustratively, the mesh plate assembly 2 may be made of stainless steel (e.g., SUS316 stainless steel), titanium alloy (e.g., technical grade TA1), molybdenum, tungsten, platinum, etc.; on one hand, the material has good heat resistance and stable physical property under a vacuum environment, can not react with a coating material, and is not easy to deform; on the other hand, the material can resist acid washing and can be reused, so that the production cost is saved.

It should be noted that, in the present application, the air pressure at the lower side of the accommodating chamber can be adjusted by adjusting the mesh density and the mesh size (area) of the mesh plate 20; wherein the air pressure at the lower side of the accommodating chamber is inversely related to the density of the meshes on the net plate 20 and inversely related to the sizes of the meshes.

In the description herein, particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. An evaporation crucible, comprising:

the crucible comprises a crucible body, a crucible body and a crucible cover, wherein the crucible body comprises a bottom wall and a side wall arranged around the bottom wall, and an accommodating cavity with an opening is formed by the surrounding of the bottom wall and the side wall; the surface of the side wall close to the accommodating cavity is a first surface, and the first surface comprises a supporting surface parallel to the bottom wall;

the screen plate assembly comprises at least one screen plate with meshes, and the screen plate assembly abuts against the supporting surface;

the nozzle is arranged at the opening of the accommodating cavity and provided with an air injection hole.

2. An evaporation crucible according to claim 1, wherein the side wall comprises a flange extending toward the inside of the accommodating chamber, the flange is located between the bottom wall and the opening of the accommodating chamber, and the flange is annular in the circumferential direction of the accommodating chamber; the support surface is a surface of the flange remote from the bottom wall.

3. An evaporation crucible according to claim 1, wherein the first surface further comprises a first extension section and a second extension section extending in a direction perpendicular to the bottom wall, the second extension section is located on a side of the first extension section away from the bottom wall, and the diameter of the first extension section is smaller than that of the second extension section; one side of the supporting surface is connected with the first extending section, and the other side of the supporting surface is connected with the second extending section.

4. A deposition crucible according to any one of claims 1 to 3, wherein the number of the screen plates is plural, the plural screen plates are stacked, and an escape gap is provided between any two adjacent screen plates.

5. A vaporization crucible according to claim 4, wherein the screen comprises:

the lower-layer screen plate comprises a screen plate body and a supporting frame arranged around the screen plate body, and steps are arranged on the inner side of the supporting frame;

the upper-layer net plate is sleeved in the supporting frame and abuts against the surface, far away from the net plate body, of the step.

6. The evaporation crucible according to claim 5, wherein a plurality of clamping protrusions extending inwards are arranged on the edge of the support frame away from the screen body, and the plurality of clamping protrusions are arranged at intervals along the circumferential direction of the support frame;

the circumference edge of upper screen board be equipped with a plurality ofly with the protruding draw-in groove that corresponds of joint, just upper screen board connect in the joint protruding with between the step, just upper screen board can be relative the carriage rotates.

7. An evaporation crucible according to claim 6, wherein the radial dimension of the upper screen plate at the position of the slot is larger than the diameter of the inner edge of the step.

8. An evaporation crucible according to claim 4, wherein said screen comprises a flat screen, said flat screen comprises a mesh area and a flat area surrounding said mesh area, a plurality of meshes are arranged in said mesh area, and the thickness of said mesh area is equal to the thickness of said flat area;

the screen plate assembly further comprises an annular supporting piece, the annular supporting piece is arranged between any two adjacent plane screen plates, and two ends of the annular supporting piece are respectively abutted to the two plane screen plates.

9. A deposition crucible according to claim 4, wherein the avoiding gap is filled with silicon nitride particles.

10. An evaporation crucible according to claim 1, wherein the screen assembly is made of a material that is resistant to high temperatures and does not react with the coating material.