DEPOSITION CELL FOR VACUUM DEPOSITION CHAMBER AND ASSOCIATED DEPOSITION METHOD - Patent application

Abstract

To provide a vapor deposition cell for a vacuum vapor deposition chamber, and a related vapor deposition method.SOLUTION: A vapor deposition cell for a vacuum vapor deposition chamber comprises: a crucible 5 formed to receive a solid or liquid material sublimated or evaporated; heating means 3 for heating the material in the crucible; a nozzle 6 being installed in an open end of the crucible 5 and including a truncated cone portion 61 having an opening 60 passing a flow of the evaporated or sublimated material toward the vacuum vapor deposition chamber; and a cover 7 being installed above the nozzle 6 and having an opening arranged around the truncated cone portion 61 of the nozzle 6. The cover 7 includes at least one of truncated cone portions 71, 72 and 73 arranged around the truncated cone portion 61 of the nozzle 6 and forms a heat shield barrier between the crucible 5 and the vacuum vapor deposition chamber.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates generally to the field of equipment for vacuum deposition of thin film materials.

[0002] More particularly, the present invention relates to a method and apparatus for depositing material onto a substrate.

[0003] More particularly, the invention applies to the deposition of thin films of inorganic or organic materials formed from metal halides, metal oxides, and / or metal chalcogenides. [Background technology]

[0004] The prior art US Pat. Nos. 5,999,103 and 5,999,106 disclose methods and devices for depositing a material on a substrate. Generally, the deposition of the material is carried out in a vacuum chamber comprising a heating means, a vacuum pump and a source cell, also called deposition cell, in which the source material is placed. The source material is heated in the source cell to a temperature higher than 150° C. and evaporated. In practice, the source cell has at least one opening that allows the gas phase material to pass towards the substrate. Thus, on contact with the substrate, the gas phase material condenses and deposits a thin layer of solid material. It is thus possible to deposit a layer of a material or to successively stack thin layers of several materials of several thicknesses.

[0005] The source cell involved in the evaporation method for depositing a material film on a substrate includes several elements such as a crucible and a heating means. The heating means is generally arranged around the crucible. The crucible generally has an upper open end and a lower closed end, in which the source material is deposited. The upper open end of the crucible allows the passage of the evaporation material in the gas phase towards the substrate. An insert with an opening of a given size is often placed in the upper open end of the crucible. The insert has as its main function to control the distribution of the evaporation material flow at the outlet of the source cell. This insert also makes it possible to limit the passage of, for example, radiation of solid and / or liquid material that occurs during the evaporation of the source material on the substrate. Such radiation of material causes non-uniformities or defects in the deposited material film. The insert can also improve the reproducibility of the layer thickness during its formation on the substrate.

[0006] However, the presence of the opening in the insert causes high heat losses at the top of the crucible. Condensation phenomena can be observed on the insert, which may lead to blockage of the insert opening. Blockage of the insert opening leads to an unstable flow of material deposition during the process of material deposition on the substrate. The phenomenon of material condensation on the insert is more accelerated at low temperatures of evaporation or sublimation of the source material, especially at temperatures below 600°C. This phenomenon depends on the nature of the material to be evaporated.

[0007] For the production of organic light emitting diode (OLED) display screens, different materials are used, in particular metal halides, metal oxides and / or metal chalcogenides.

[0008] For example, when depositing lithium fluoride for large OLED display screens, the crucible temperature is moderate, between 800°C and 900°C. The deposition rate of lithium fluoride is very slow, on the order of 1-50 g / h. The lithium fluoride deposition process is very long, and can last for several hours or even tens of hours. Partial condensation of the lithium fluoride material is observed on the insert cover. This condensation around the insert openings can cause the distribution of the gaseous material flow towards the substrate to change over time, leading to blockage of the insert openings. Such condensation of material around the insert openings makes it very difficult to maintain a constant deposition rate during deposition or between deposition on one substrate and the other, which is detrimental to the uniformity of the deposited layer. This phenomenon makes the manufacturing process of organic light emitting diode (OLED) display screens very unpredictable. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] US Patent Application Publication No. 2007 / 074654 [Patent Document 2] U.S. Pat. No. 5,104,695 Summary of the Invention [Problem to be solved by the invention]

[0010] It is therefore necessary to develop an evaporation apparatus and method, in particular for depositing metal halide, metal oxide and / or metal chalcogenide deposits, and in particular for depositing lithium fluoride, that allows to avoid the problem of blockage of the insert opening.

[0011] One of the objects of the present invention is to provide a method for producing a tertiary amine having a vapor pressure of 10 -3 The method involves depositing a thin layer of a material selected from metal halides, metal oxides and / or metal chalcogenides at temperatures between 700°C and 1000°C at pressures between 1 mbar and 1 mbar. [Means for solving the problem]

[0012] To that end, the invention proposes a deposition cell for a vacuum deposition chamber, comprising a crucible adapted to receive a solid or liquid material to be sublimated or evaporated, heating means for heating the material in the crucible, a nozzle placed at the open end of the crucible, the nozzle including a truncated conical portion with an opening adapted to pass a flow of evaporated or sublimated material towards the vacuum deposition chamber, and a cover placed on the nozzle, the cover having an opening arranged around the periphery of the truncated conical portion of the nozzle.

[0013] In accordance with the invention, the cover has at least one frusto-conical portion disposed about the frusto-conical portion of the nozzle, the cover forming a thermal barrier between the crucible and the vacuum deposition chamber.

[0014] According to a particularly advantageous embodiment, the frusto-conical portion of the cover and the frusto-conical portion of the nozzle, having the same apex angle and the same axis, are arranged at a mutual distance of a few tenths to a few millimeters.

[0015] According to one embodiment, at least one frustoconical portion of the cover comprises several frustocones of the same apex angle and the same axis, said frustocones being interdigitated around the frustoconical portion of the nozzle.

[0016] Advantageously, two adjacent cones of said truncated cone have a contact area less than or equal to 5% of their respective surface areas.

[0017] According to one embodiment, the cover is formed from a metal sheet.

[0018] Advantageously, the cover covers the open end of the crucible.

[0019] According to a particularly advantageous embodiment, the nozzle comprises a cylindrical wall and two bottom plates, the cylindrical wall connecting the two bottom plates to a frusto-conical portion of the nozzle, the cylindrical wall comprising radially oriented openings, each of the two bottom plates comprising at least one opening, said at least one opening of the two bottom plates being arranged in a zigzag manner.

[0020] According to a particularly advantageous embodiment, the heating means comprise a first heating zone arranged around the lower part of the crucible and a second heating zone arranged around the nozzle.

[0021] According to an exemplary embodiment, the material to be sublimed or evaporated is selected from metal halides, metal oxides, and metal chalcogenides.

[0022] The present invention also relates to a method for evaporating lithium fluoride, comprising the steps of heating lithium fluoride in a crucible at a temperature higher than the evaporation temperature of lithium fluoride and at a pressure to form a stream of gaseous lithium fluoride; filtering and directing the stream of gaseous lithium fluoride through a nozzle disposed at the mouth of the crucible, the nozzle having a frusto-conical portion and an opening, and insulating the nozzle from the deposition chamber by a cover disposed around the nozzle opening, the cover having at least one frusto-conical portion disposed around the frusto-conical portion of the nozzle.

[0023] Of course, the different features, variants and embodiments of the invention can also be associated with each other in various combinations, unless they are mutually inconsistent or exclusive.

[0024] Furthermore, various other features of the present invention will become apparent from the accompanying description taken in conjunction with the following drawings, which illustrate non-limiting embodiments of the invention. [Brief description of the drawings]

[0025] [Figure 1] FIG. 2 is an exploded view of a deposition cell according to one embodiment. [Diagram 2] 1 is a cross-sectional view of a filtering nozzle according to certain embodiments. [Diagram 3] FIG. 2 is a cross-sectional view of a cover according to one embodiment. [Figure 4] FIG. 1 is a schematic partial cross-sectional view of a deposition cell according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] It should be noted that in these figures, structural and / or functional elements that are common to different variants may have the same reference numbers.

[0027] An evaporation source cell (or deposition cell, also referred to as evaporation source in this document) is used as a material source for thin film deposition in a vacuum chamber.

[0028] 1 shows a schematic exploded view of an evaporation source 1 according to one embodiment of the present disclosure. The evaporation source 1 includes a furnace 2, which includes at least one heating element 3, a crucible 5, a nozzle 6, a cover 7, and possibly a washer 4.

[0029] The furnace provides the energy necessary for the evaporation of the material introduced into the crucible in the form of heat. The furnace 2 is generally cylindrical in shape. It may be made of a material selected from tantalum, molybdenum, tungsten, graphite, boron nitride, alumina and / or stainless steel. In the example shown, the furnace 2 is open at its lower end for the passage of an electric wire and at its upper end for the insertion and removal of a crucible 5 therefrom.

[0030] Washer 4 is an optional element that serves to keep crucible 5 centered within furnace 2 .

[0031] The crucible 5 is generally cylindrical in shape. It includes an open end and a closed bottom. In operation, the open end of the crucible 5 is turned up and the bottom is placed at the bottom of the evaporation source 1. The evaporation source material, called filler, is placed at the bottom of the crucible 5. The filler is generally introduced into the crucible 5 in solid or liquid form. After heating, depending on the material and the heating temperature, the filler sublimes or evaporates into the gas phase. Generally, the initial height of the filler corresponds to about one third of the total length of the crucible 5.

[0032] The material to be evaporated is placed in a crucible 5. The crucible 5 is then inserted into a furnace. Advantageously, the crucible 5 is removable to allow for refilling and / or filler replacement. The filler is for example selected from materials with evaporation temperatures between 150°C and 1500°C or sublimation temperatures between 150°C and 1500°C. In the case of lithium fluoride, the heating temperature is between 800°C and 900°C.

[0033] In one exemplary embodiment, the heating means 3 heats the crucible 5 over its entire length. In another exemplary embodiment, the heating means 3 is divided into two parts, namely a first heating zone and a second heating zone. The first heating zone is located in the lower part of the evaporation cell, for example extending from the bottom up to two thirds of the evaporation source height. Advantageously, the second heating zone is located in the upper part of the evaporation source cell, for example in the upper third of the evaporation source cell 1 up to the open end of the crucible. Such a heating means allows the heating temperature at the bottom of the crucible and around the nozzle 6 to be adjusted separately.

[0034] The heating means may, for example, comprise one or more heat generating resistive elements, also called filaments or heating elements. Typically, the heating means are arranged around the outer portion of the crucible 5. In FIG. 1, the heating means are arranged within the furnace 2 and around the side walls of the crucible. The heating temperature range of the crucible is 150° C. to 1500° C. depending on the filler material used.

[0035] The nozzle 6, also called insert, is placed at the open end of the crucible 5 so as to direct the flow of the evaporation material. Advantageously, the nozzle 6 comprises a truncated cone section 61, which has, for example, a circular cross section. The truncated cone section 61 thus has a first open end, arranged downwards, with a diameter slightly smaller than the inner diameter of the crucible 5, and a second end, arranged upwards, forming an opening 60 with a diameter smaller than that of the first end. The truncated cone section 61 and the opening 60 allow to control the flow of material to be deposited on the substrate in the deposition chamber. The truncated cone section 61 of the nozzle 6 is defined by geometric parameters such as the opening angle A with respect to the axis 100 of the cone, the total length H1 and the diameter D1 of the opening 60. The inverted truncated cone nozzle is placed at the end of the upper part of the crucible, whereby the vapor of the material emanating from the filler enters at the widest part of the cone and leaves at the narrowest opening. Typically, the opening angle A is between 0 degrees and 60 degrees, the height E1 is between 5 mm and 80 mm, and the opening diameter D1 is between 2 mm and 100 mm. As a non-limiting example, in FIG. 4, the opening angle A is 35 degrees, the height E1 is 21 mm, and the opening diameter D1 is 27 mm. In an exemplary embodiment, the nozzle 6 is fabricated from a sheet. In another exemplary embodiment, the nozzle 6 is machined from a solid material. The nozzle 6 may be manufactured from a material selected from, for example, tantalum, molybdenum, titanium, niobium, tungsten, graphite, alumina, or boron nitride. The conical shape of the nozzle 6 allows for controlling the flow of the gas phase material and thus the uniformity of the material deposition on the substrate. The nozzle 6 is adapted to be placed or fixed on the open end of the crucible 5.

[0036] According to the variant shown in Fig. 2, the nozzle 6 further comprises a truncated cone section 61, a side grid 68, a first plate 64, also called collimator or throttling mechanism, and a second plate 62, also called impactor. The first plate 64 comprises, for example, a central opening 65 or several openings. The second plate 62 advantageously comprises several openings 63 arranged at the periphery. The openings 63 of the second plate 62 are arranged in a zigzag manner with respect to the central opening 65 or the openings of the first plate 64. The size of the openings of the first plate 64 is such that their total surface area is greater than or equal to the surface area of ​​the openings 63 of the impactor 62.

[0037] The lateral grid 68 is formed, for example, from a sheet and possibly a network of perforated holes 66. As a variant, the grid 68 may be manufactured, for example, from a perforated or expanded sheet or, for example, from a woven or welded wire mesh. The material used to manufacture the grid 68 is preferably selected from tantalum (Ta), pyrolytic boron nitride (pBN), molybdenum (Mo), titanium (Ti), niobium (Nb), tungsten (W), alumina (Al2O3), and graphite.

[0038] On the one hand, the truncated cone part 61 of the nozzle 6 is welded to the side grid 68. On the other hand, the first plate 64 and the second plate 62 are also welded to the side grid 68. The flow of the evaporated material leaving the crucible is thus forced to pass through the impactor 62 and then through the collimator 64 or through the side grid. The assembly of the truncated cone part 61, the side grid 68, the collimator 64 and the impactor 62 thus forms a filtering nozzle. The filtering nozzle is integrated into the open end of the crucible as shown in FIG. 4. The total length H1 of the filtering nozzle is, for example, 80 mm. The height E1 of the truncated cone part 61 of the nozzle is, for example, 21 mm. The filtering nozzle reduces the fluid conductance of the insert. However, the nozzle may be heated to a higher temperature to retain the flow value of the evaporated material.

[0039] If the heating means comprises two heating zones, the second heating zone advantageously extends around the filtering nozzle over a height H1, making it possible to thermally separate, on the one hand, the heating of the filler to form the flow of evaporation material and, on the other hand, the heating of the nozzle to avoid any condensation of material at the opening 60.

[0040] According to the present disclosure, the deposition cell further comprises a cover 7. The cover 7 comprises a support part 75 that rests on the mouth of the furnace 2 of the cell (see FIG. 4). The cover 7 comprises at least a part of a truncated cone shape 71. In a particularly advantageous embodiment, the cover 7 comprises several truncated cone parts 71, 72, 73, as shown in FIG. 3. The cover 7 also comprises an annular part 74 arranged transversely to the axis 100 of the cone, which connects the support part 75 to the truncated cone parts 71, 72, 73. The annular part 74 of the cover contributes to insulating the nozzle 6 with respect to the deposition chamber. However, the annular part 74 receives a heat flow from the furnace 2, which is arranged to keep the annular part 74 at a temperature high enough to re-evaporate the species that have been backscattered from the deposition chamber to the cover 7.

[0041] Advantageously, the truncated cone portions 71, 72, 73 have a circular cross section. Advantageously, the truncated cone portions 71, 72, 73 have the same apex angle B and the same axis 100. The truncated cone portions 71, 72, 73 are arranged along the same axis 100 with an axial offset of 0.1 mm to 5 mm, providing a gap between two adjacent truncated cone portions. In a particularly advantageous embodiment, the apex angle of the truncated cone portion 71 is the same as the apex angle A of the truncated cone portion 61 of the nozzle 6. During operation of the deposition cell, the truncated cone portion 71 of the cover 7 is separated from the truncated cone portion 61 of the nozzle 6 by a distance of 0.1 mm to 10 mm. Thus, the truncated cone portion 71 of the cover surrounds a part of the truncated cone portion 61 of the nozzle 6. The truncated cone portion 71 of the cover forms a heat shield between the vacuum deposition chamber and the nozzle 6. In a further advantageous manner, the truncated conical portions 71, 72, 73 form a much more efficient heat shield between the vacuum deposition chamber and the nozzle 6. Typically, the cover 7 is made of tantalum. In an exemplary embodiment, each of the sheets of the truncated conical portions 71, 72, 73 is provided with a mechanical device that makes it possible to maintain a distance between adjacent truncated conical portions while ensuring that the contact between these adjacent conical portions is minimized. The mechanical device may consist of a protrusion or a recess that is made in the sheets of the truncated conical portions 71, 72, 73. In a variant, the truncated conical portions 71, 72, 73 are held apart from one another by rivets. The truncated conical portions 71, 72, 73 are for example welded to an annular portion 74 around the opening 70. In an advantageous manner, the opening 70 is circular and has a diameter D2. The height H2 of the frusto-conical portions 71, 72, 73 is less than or equal to the height E1 of the frusto-conical portion 61 of the nozzle 6.

[0042] As shown in FIG. 4, the support part 75 of the cover 7 rests on the mouth of the furnace 2. The truncated conical parts 71, 72, 73 of the cover 7 are oriented in the same direction and along the same axis 100 as the truncated conical part 61 of the nozzle 6. The opening 70 of the cover is therefore arranged around the periphery of the truncated conical part 61 of the nozzle 6. Advantageously, the opening 70 of the cover is arranged at most at the same height as the opening 60. For optimal results, the opening 70 is located just below the opening 60, for example 1 mm to 8 mm below. The cover 7 and the filtering insert 6 are dimensioned such that after assembly, the cover 7 does not come into physical contact with the filtering insert 6. More precisely, the support part 75 and the annular part 74 of the cover 7 are dimensioned such that a minimum or mutual distance of a few tenths of a millimeter to a few millimeters is provided between the cover 7 and the filtering insert 6. In other words, the cover 7 and the filtering insert 6 are mechanically separated or insulated from each other.

[0043] The cover 7, consisting of a support part 75, an annular part 74 and parts of truncated cone shape 71, 72, 73, forms a heat shield between the truncated cone part 61 of the nozzle 6 and the vacuum deposition chamber. Such a cover 7 avoids heat loss from the evaporation source to the vacuum deposition chamber and makes it possible to keep the truncated cone part 61 at a high temperature. At the same time, the cover 7 is designed in favor of controlling the heat loss from the furnace 2 to the annular part 74. In fact, the annular part 74 faces the vacuum deposition chamber. This annular part receives a heat flow that keeps this annular part 74 at a temperature high enough to re-evaporate materials that may accumulate by condensation on the deposition chamber side.

[0044] The assembly of nozzle 6 and cover 7 makes it possible to avoid condensation of material on cover 7 and / or on nozzle 6 during the use of the evaporation source. This cover 7 makes it possible in particular to avoid condensation of material due to backscattering from the vacuum deposition chamber onto cover 7. Furthermore, annular portion 74 of cover 7 is kept at a temperature high enough to re-evaporate species that may be backscattered at the outlet of the mouth of nozzle 6. Finally, cover 7 makes it possible to keep the inner surface of frusto-conical portion 61 of nozzle 6 at a temperature sufficient to avoid condensation of material on the nozzle.

[0045] The evaporation source allows for better control of the intensity of the molecular jet that is generated during heating of the material in the crucible. A quartz scale can be used to measure the deposition rate in the deposition chamber. The quartz scale is positioned so as not to be interposed between the evaporation source and the substrate that will receive the thin film deposition of the material. The quartz scale is positioned to detect a portion of the molecular jet and measure its intensity. The quartz scale provides a signal that can be used to adjust the heating intensity of the cell through the power applied to the filament to keep the molecular jet as close as possible to a predetermined set point. During production, such a feedback system allows for a constant film thickness to be maintained between substrates within predetermined process limits.

[0046] In the first example, an average deposition rate of the order of 8.05 g / h is thus obtained for a duration of 13 hours. In the second example, an average deposition rate of the order of 6.8 g / h is obtained for a duration of 50 hours. In these two examples, no condensation of material is found on the cover 7, on the impactor 62, or on the inner walls of the nozzle 6. Measurements through a quartz scale show a very high stability of the molecular jet (variations less than ±5%) during the 50 hours of deposition.

[0047] The present disclosure also relates to a method for vapor deposition of a metal halide, metal oxide, or metal chalcogenide. x , M.I. x , MCl x , M.F. xThe metal oxides have the formula MO, where M is the metal and Br, I, Cl, and F are bromine, chlorine, iodine, and fluorine atoms, respectively. x The metal chalcogenides have the formula MSe, where M is the metal and O is the oxygen atom. x , M.S. x , M.T.e. x These materials have a chemical formula of the type, where M is a metal and Se, S, and Te are selenium, sulfur, and tellurium atoms, respectively. These materials generally have poor thermal conductivity and are therefore thermal insulators.

[0048] The material is used in various technical fields in the semiconductor industry. In particular, lithium fluoride (LiF) is used in the manufacture of flat display screens of the OLED type. In the form of a thin film, lithium fluoride is transparent. It is generally used to passivate electronic devices and / or for optical functions, such as light extraction.

[0049] However, the deposition of lithium fluoride by evaporation is accompanied by technical difficulties. Lithium fluoride is a material with a moderate vapor pressure and a typical evaporation temperature of 800-900°C. Lithium fluoride is an electrically insulating and thermal insulating material. Lithium fluoride vaporizes in molecular form by congruent evaporation. The evaporation rate is generally 1-50 g / h. The deposition rate on the substrate is of the order of 0.1 nm / s-0.5 nm / s. Here, the duration of the lithium fluoride deposition method can reach several hours or even tens of hours. Under these conditions, it is generally observed in the prior art methods that lithium fluoride condenses on the nozzle of the prior art evaporation cell, forming snow, which prevents the maintenance of a constant deposition rate and causes the nozzle opening to become blocked over time. The condensation of lithium fluoride is even faster when the intensity of the molecular jet is high.

[0050] As a non-limiting example, a lithium fluoride deposition method is described, which comprises the following steps: heating lithium fluoride in solid form at a temperature above the evaporation temperature of lithium fluoride, typically between 900° C. and 1200° C., and at a given pressure, typically between 0.06 mbar and 6 mbar, to form a gaseous lithium fluoride stream, and filtering and directing the gaseous lithium fluoride stream through a nozzle 6 having a truncated cone section 61 and an opening 60 into a vacuum deposition chamber, the nozzle 7 having at least one truncated cone section 71 arranged around the truncated cone section 61 of the nozzle 6 and insulating the nozzle 6 from the deposition chamber. In a particularly advantageous embodiment, the method comprises heating the nozzle 6 and the cover 7 to a temperature (typically between 900° C. and 1200° C.) sufficient to avoid condensation of material on the nozzle 6 and on the cover 7.

[0051] By this deposition method, lithium fluoride is deposited on a substrate placed in a vacuum deposition chamber at a deposition rate of 0.1 nm / s to 0.5 nm / s for a duration of 1 minute to 50 hours, resulting in a deposited film thickness of 0.1 nm to 100 nm.

[0052] Of course, various other modifications may be made to the invention within the scope of the appended claims. [Explanation of symbols]

[0053] 1 Evaporation cell 2 furnace 3 Heating means 4 Washers 5. Crucible 6 Nozzles 7 Cover 60 Nozzle opening 61 Nozzle truncated cone part 62, 64 Nozzle bottom plate 63, 65 Bottom plate opening 66 Drilling holes 68 Nozzle Side Grid 70 Cover opening 71, 72, 73 Cone-headed part of cover 74 Circular Section 75 Support part 100 Axis A: Apex angle of the truncated cone part of the nozzle B Apex angle of the truncated cone part of the cover D1, D2 diameter E1, H2 height H1 full length

Claims

1. A deposition cell (1) for a vacuum deposition chamber, comprising: a crucible (5) adapted to receive a solid or liquid material to be sublimated or evaporated; heating means (3) for heating said material in said crucible; a nozzle (6) placed at an open end of said crucible (5), said nozzle (6) including a truncated conical portion (61) having an opening (60) adapted to pass a flow of evaporated or sublimated material towards said vacuum deposition chamber; and a cover (7) placed on said nozzle (6), said cover (7) having an opening (70) arranged around the periphery of said truncated conical portion (61) of said nozzle (6), said cover (7) also comprises at least one support portion, at least one frusto-conical portion (71, 72, 73) and at least one annular portion connecting said at least one support portion to said at least one frusto-conical portion, said at least one frusto-conical portion (71, 72, 73) extends in said at least one annular portion from said opening (70) of said cover (7) in the same direction and along the same axis as said frusto-conical portion (61) of said nozzle (6); said at least one frusto-conical portion (71, 72, 73) being arranged around said frusto-conical portion (61) of said nozzle (6); The cover (7) forms a thermal barrier between the crucible (5) and the vacuum deposition chamber. In the deposition cell (1), The nozzle (6) comprises a cylindrical wall (68) and two base plates (62, 64), the cylindrical wall (68) connecting the two base plates (62, 64) to the frusto-conical portion (61) of the nozzle (6); A gap is formed between the cylindrical wall and the crucible (5), the cylindrical wall (68) includes a radially oriented opening (66) connected to the gap between the cylindrical wall and the crucible; Each of the two bottom plates (62, 64) includes at least one opening (63, 65), and the at least one opening (63, 65) of the two bottom plates (62, 64) is arranged in a zigzag pattern; the nozzle is configured such that a flow of evaporated or sublimated material passes through the radially oriented openings (66) in the two bottom plates (62, 64) or in the cylindrical wall (68); The heating means (3) comprises a first heating zone arranged around the lower part of the crucible (5) and a second heating zone arranged around the nozzle (6).

2. 2. The deposition cell of claim 1, wherein the truncated conical portion (71) of the cover and the truncated conical portion (61) of the nozzle, having the same apex angle (A) and the same axis (100), are positioned at a mutual distance of a few tenths of a millimeter to a few millimeters.

3. 3. The deposition cell according to claim 1 or 2, wherein at least one frusto-conical portion (71, 72, 73) of the cover comprises several frusto-cones (71, 72, 73) of the same apex angle (B) and the same axis (100), the frusto-cones (71, 72, 73) being inter-fitted around the frusto-conical portion (61) of the nozzle (6).

4. 4. The deposition cell of claim 3, wherein two adjacent ones of the truncated cones (71, 72, 73) have a contact area of ​​5% or less of their respective surface areas.

5. The deposition cell according to any one of the preceding claims, wherein the cover (7) is made from a metal sheet.

6. The deposition cell according to any one of claims 1 to 5, wherein the cover (7) covers the open end of the crucible (5).

7. A deposition cell according to any preceding claim, wherein the material to be sublimated or evaporated is selected from metal halides, metal oxides and metal chalcogenides.

8. In the method for evaporating lithium fluoride, the evaporation method includes the steps of: heating the lithium fluoride in the crucible (5) by heating a first heating zone arranged around a lower part of the crucible (5) at a temperature higher than the evaporation temperature of lithium fluoride and at a pressure to form a gaseous lithium fluoride stream; filtering said flow of gaseous lithium fluoride through a nozzle (6) and directing it towards a vacuum deposition chamber, said nozzle (6) being positioned at the mouth of said crucible (5); heating a second heating zone disposed around the nozzle (6), the nozzle (6) having a frusto-conical portion (61) and an opening (60); wherein said nozzle (6) comprises a cylindrical wall (68) and two bottom plates (62, 64), said cylindrical wall (68) connecting said two bottom plates (62, 64) to said frusto-conical portion (61) of said nozzle (6); A gap is formed between the cylindrical wall and the crucible (5), the cylindrical wall (68) includes a radially oriented opening (66) connected to the gap between the cylindrical wall and the crucible; Each of the two bottom plates (62, 64) includes at least one opening (63, 65), and the at least one opening (63, 65) of the two bottom plates (62, 64) is arranged in a zigzag pattern; the nozzle is configured such that a flow of evaporated or sublimated material passes through the radially oriented openings (66) in the two bottom plates (62, 64) or in the cylindrical wall (68); The evaporation method further comprises: Insulating the nozzle (6) from the deposition chamber by a cover (7) arranged around the opening (60) of the nozzle (6), the cover (7) having at least one frusto-conical portion (71, 72, 73) arranged around the frusto-conical portion (61) of the nozzle (6); said cover (7) also comprises at least one support portion, at least one frusto-conical portion (71, 72, 73) and at least one annular portion connecting said at least one support portion to said at least one frusto-conical portion (71, 72, 73); said at least one frusto-conical portion (71, 72, 73) extends in said at least one annular portion from said opening (70) of said cover (7) in the same direction and along the same axis as said frusto-conical portion (61) of said nozzle (6); Evaporation method.

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