Method for coating ophthalmic lenses, physical vapor deposition system and crucible for physical vapor deposition

Abstract

This invention relates to coating spectacle lenses (3) by physical vapor deposition (PVD). A method for physical vapor deposition is presented, comprising: providing a crucible containing a first evaporation material (41) and a second evaporation material (42), wherein the first evaporation material has a first vapor pressure and the second evaporation material has a second vapor pressure different from the first vapor pressure, wherein the ratio of the exposed surface of the first evaporation material to the exposed surface of the second evaporation material in the crucible is adapted to offset the vapor pressure difference between the first evaporation material and the second evaporation material; and simultaneously evaporating the first evaporation material and the second evaporation material from the same crucible. This disclosure further relates to a crucible for physical vapor deposition and a physical vapor deposition system, particularly for coating optical surfaces such as spectacle lenses.

Description

Technical Field

[0001] This disclosure relates to the coating of spectacle lenses. More generally, this disclosure relates to the field of physical vapor deposition (PVD). PVD is widely used for coating optical surfaces such as spectacle lenses. In particular, the present invention relates to methods for physical vapor deposition, crucibles for physical vapor deposition, and vapor deposition systems. Background Technology

[0002] Physical vapor deposition (PVD), sometimes also called physical vapor transport (PVT), is a vacuum deposition method used to create thin films and coatings on surfaces. In PVD, the material changes from a condensed phase to a gaseous phase and then back to the film condensation phase. A favorable application is coating optical surfaces such as eyeglass lenses.

[0003] Coatings can be applied to optical surfaces, for example, to provide anti-reflective coatings or to achieve specific filter characteristics, such as filtering unwanted blue light or infrared (IR) components. High-performance lens coatings can make eyeglasses extremely durable in preventing scratches or sticky dirt. As a benefit, lenses can remain dirt-free for longer periods, making them significantly easier to clean.

[0004] Modern light sources and displays emit disproportionately large amounts of blue light. While the human body needs a certain amount of blue light to regulate the sleep / wake cycle, too much of the 'wrong' kind of blue light can pose a health threat and may cause eye problems. Lenses with custom-coated lenses, such as the applicant's ZEISS Dura-Vision BlueProtect, feature special filters that can help provide comfortable vision, even when there are high blue light components.

[0005] In some applications, it may be desirable to provide coatings containing different material components or compositions. Different material components can be evaporated in parallel from different evaporation sources. Each evaporation source includes a crucible containing one material component, which can be individually heated to the temperature required to obtain the coating composition.

[0006] GB 2 230 792 A discloses apparatus and methods for use in physical vapor deposition processes for producing alloys. It is recommended to provide at least two separate evaporation sources with individual temperature control for different evaporation materials.

[0007] The method described in GB 2 230 792 A includes: evaporating components from at least two evaporators maintained at independent temperatures, allowing the component vapors to flow into a container defining a vapor mixing chamber therein, heating the container walls in the portion defining the vapor mixing chamber to a temperature at least as high as that of the hotter or most heated evaporator, thereby enhancing the mixing of the corresponding component vapors by vapor reflection while suppressing vapor condensation on the chamber walls, and allowing the mixed vapors to pass through an outlet in the container and impact a temperature-controlled collector.

[0008] WO 2011 / 085109 A1 relates to coating of turbine engines. It discloses a method for co-evaporation and deposition of materials with different vapor pressures. A multi-source evaporation process is proposed, wherein two closely adjacent crucibles containing elements of a first material and a second material are co-evaporated by applying an electron beam. The two closely adjacent crucibles are also referred to as a dual crucible. The electron beam is used at a first power to evaporate the first material having a first vapor pressure for deposition onto a substrate. The electron beam is used at a second power to evaporate the second material having a second vapor pressure for deposition onto the substrate. The proposed deposition method will improve direct vapor deposition processes by enabling vapor deposition from multiple evaporation sources to form new deposition layer compositions over larger and wider substrate surface areas.

[0009] JP H01 275747 A describes the fabrication of thin metal films. A controlled electron beam from a secondary electron beam source is deflected to selectively heat primary vapor deposition materials and secondary vapor deposition materials with different concentrations of high vapor pressure components.

[0010] However, the inventors recognize that the disadvantage of the above methods is that they are quite complex and require substantial modifications to existing vacuum deposition equipment. Summary of the Invention

[0011] The object of this invention is to provide improved systems and methods for physical vapor deposition. In particular, it is advantageous to reduce the cost of producing complex coatings and / or to produce high-quality coatings with limited effort. It is also advantageous to enable the retrofitting of existing physical vapor deposition systems, especially without requiring substantial modifications to existing vacuum deposition equipment.

[0012] To better address one or more of these problems, according to a first aspect of the invention, a method for physical vapor deposition, particularly for coating optical surfaces such as spectacle lenses, is provided. The method includes: providing a crucible containing a first evaporating material and a second evaporating material, wherein the first evaporating material has a first vapor pressure and the second evaporating material has a second vapor pressure different from the first vapor pressure, wherein the ratio of the first evaporating material and the second evaporating material in the crucible is adapted to offset the vapor pressure difference between the first evaporating material and the second evaporating material; and simultaneously evaporating the first evaporating material and the second evaporating material from the same crucible. More specifically, the ratio of the exposed surface area of ​​the first evaporating material to the exposed surface area of ​​the second evaporating material at the surface of the crucible can be adapted to offset the vapor pressure difference between the first evaporating material and the second evaporating material.

[0013] According to another aspect, a crucible is provided for physical vapor deposition, particularly for coating optical surfaces such as spectacle lenses. The crucible contains a first evaporation material and a second evaporation material, wherein the first evaporation material has a first vapor pressure and the second evaporation material has a second vapor pressure different from the first vapor pressure. The ratio of the first evaporation material to the second evaporation material in the crucible is adapted to offset the vapor pressure difference between the two materials. More specifically, the ratio of the exposed surface area of ​​the first evaporation material to the exposed surface area of ​​the second evaporation material at the surface of the crucible can be adapted to offset the vapor pressure difference between the two materials.

[0014] According to another aspect, a physical vapor deposition system is provided, particularly for coating optical surfaces such as spectacle lenses, the system comprising: a vacuum chamber; a crucible as described above; and an evaporation unit adapted to simultaneously evaporate a first evaporation material and a second evaporation material from the same crucible.

[0015] The inventors recognize that existing vacuum deposition systems typically have only a single heating source or evaporation unit and are used to evaporate a single material from a single crucible at a time. Different crucibles with different evaporation materials can then be provided to the evaporation unit, for example, to deposit layer sequences such as dielectric antireflective coatings onto optical surfaces. More complex vacuum deposition systems can include multiple heating sources or evaporation units connected in parallel, each with its own crucible. Because the evaporation materials can have different vapor pressures, the different evaporation units are individually controlled and use different electron beam powers to achieve the desired deposition rate. However, construction and control are complex.

[0016] The basic concept of this invention is to specifically adapt the composition of the contents of a single crucible so that the evaporation of first and second evaporation materials from the crucible provides a desired coating composition on the surface to be coated. Instead of adapting the electron beam power to compensate for the different vapor pressures of the first and second evaporation materials in different crucibles, it is proposed to modify the composition of the contents of a single crucible. The ratio of the first and second evaporation materials in the crucible is adapted to offset the vapor pressure difference between the first and second evaporation materials. Therefore, even if the first and second evaporation materials have different vapor pressures, a desired stoichiometry or stoichiometric ratio can be achieved, allowing the desired coating composition to be obtained. Therefore, it is not necessary to evaporate the first and second evaporation materials with different heating or electron or laser beam powers. This simplifies control. Furthermore, existing vapor deposition equipment can be used without substantially modifying the crucible arrangement or the adaptation control and / or beam control of the evaporation unit.

[0017] Preferred embodiments of the invention are defined in the dependent claims. It should be understood that the claimed crucible and physical vapor deposition system may have similar and / or identical improvements or preferred embodiments to the claimed method for physical deposition, particularly as defined in the dependent claims and disclosed herein.

[0018] It should be understood that, depending on the desired coating composition, three or more evaporating materials may optionally be used. The third evaporating material may have yet another third vapor pressure different from the first and / or second vapor pressures. The ratio of the first, second, and third evaporating materials can be adapted accordingly to offset the vapor pressure differences between the first, second, and third evaporating materials. The same consideration applies if additional evaporating materials are used.

[0019] The following sections will briefly explain and define some of the terms used throughout the application:

[0020] As used herein, vapor pressure (equilibrium or saturated vapor pressure) can refer to the pressure exerted by vapor in a closed system at a given temperature in thermodynamic equilibrium with its condensed phase (solid or liquid). Equilibrium vapor pressure is an indicator of the evaporation rate of a liquid. It relates to the tendency of particles to escape from the liquid or solid. The first and second evaporation materials are typically provided in solid form and evaporated via an evaporation unit. Therefore, the term evaporation material refers to the material to be evaporated. The evaporation unit can be a heat source, particularly using an electron or laser beam to evaporate (sublimate) the first and second evaporation materials.

[0021] As used herein, the term "crucible" can refer to a replaceable receiver of evaporating material. It refers to a single, individual crucible, not a double crucible consisting of two closely adjacent crucibles. The crucible can be placed in a crucible holder within the vacuum chamber of a physical vapor deposition system. First and second evaporating materials are evaporated from the same single crucible by applying heat (particularly using an electron or laser beam) to the evaporating material.

[0022] As used herein, the ratio of the first and second evaporating materials in the crucible can refer to the concentration ratio of the first and second evaporating materials in the crucible. It should be understood that there are different ways to express the concentration of a component, and similarly, different ways to express the composition of a mixture. This ratio can be expressed as mole fraction, volume fraction, mass fraction, etc. A potential teaching is to adapt the ratio of the first and second evaporating materials in the crucible to offset the vapor pressure difference between the first and second evaporating materials. For example, the first evaporating material could be Ag and the second evaporating material could be SiO2, and the desired coating would contain similar amounts of Ag and SiO2. If a 1:1 ratio of Ag to SiO2 is provided at a temperature of, for example, 1000°C, this would mean a low vapor pressure of approximately 10 for SiO2. -3 Up to 10 -2 Pa (a pressure unit) and Ag has a high vapor pressure of about 1 Pa. Therefore, if Ag and SiO2 are evaporated from the same single crucible (without matching electron beam power for different evaporation materials), this would mean that approximately 100 to 1000 times more Ag would be deposited compared to SiO2. Thus, in a given example, the vapor pressure difference can be offset or compensated by providing 100 to 1000 times more SiO2 in the crucible. It should be understood that, in addition to being adapted to offset the vapor pressure difference between the first and second evaporation materials, the ratio of the first and second evaporation materials in the crucible can also be adapted to provide a desired mixing ratio of the first and second evaporation materials in the coating to be deposited.

[0023] Unless otherwise specified, the terms used in the context of this application correspond to the definitions in standard ISO 13666:2019(E).

[0024] In an improvement to the method for physical vapor deposition, the ratio of the exposed surface area of ​​the first evaporating material and the exposed surface area of ​​the second evaporating material at the surface of the crucible is adapted to offset the vapor pressure difference between the first and second evaporating materials. In other words, the ratio of the first evaporating material and the second evaporating material in the crucible can refer to the surface ratio of the first and second evaporating materials. It should be noted that the surface ratio can be intentionally varied as the first and second evaporating materials are evaporated during the vapor deposition process. This allows for careful adjustment of the composition of the coating to be deposited. The advantage is that complex control strategies are not required and separate crucibles are not needed for different materials.

[0025] The ratio of the exposed surfaces of the first and second evaporating materials can be inversely proportional to the ratio of their vapor pressures. In other words, as used herein, inverse proportionality means that a smaller exposed surface is provided for the evaporating material that evaporates more easily (e.g., at lower temperatures or with higher vapor pressures), and a larger exposed surface is provided for the evaporating material that evaporates less easily (e.g., at higher temperatures or lower vapor pressures), thus offsetting the vapor pressure difference between the first and second evaporating materials. It should be understood that additional factors can be considered to characterize the desired ratio of the first and second evaporating materials. For example, if the ratio of Ag to SiO2 to be provided is 2:1, the ratio of exposed surfaces can also be proportional to the desired ratio of the first and second materials to be deposited and inversely proportional to the ratio of their vapor pressures. Therefore, the control of the electrons or beams used to evaporate the first and second evaporating materials can be simplified. Instead of adapting the control of the heating source, the configuration of the contents of the first and second evaporating materials is adapted.

[0026] As noted above, an electron beam or laser beam can be used to evaporate the first and second evaporation materials. Advantageously, the electron beam or laser beam can be set to the same power for evaporating the first and second materials. An advantage is that control can be simplified. For example, conventional systems can be used without having to modify the beam power. The beam can simply scan the entire crucible without modification. Existing controls can be used. Advantages may include ease of modification.

[0027] The first evaporating material can have a higher vapor pressure than the second evaporating material. Specifically, the first vapor pressure of the first evaporating material can be at least 5 times, at least 10 times, at least 50 times, or at least 100 times that of the second vapor pressure of the second evaporating material. Therefore, the proposed solution can also be advantageously used for materials with significantly different vapor pressures. This is quite surprising, as conventional systems use different crucibles for materials with different vapor pressures, especially for materials with large differences in vapor pressure.

[0028] In this embodiment, a first evaporation material with a higher vapor pressure can be provided as a solid body, and a second evaporation material with a lower vapor pressure than the first evaporation material can be provided as particles surrounding the solid of the first evaporation material. The inventors recognize that this particular arrangement can provide further improved coating quality, particularly high uniformity of the coating to be deposited. If the solid begins to evaporate below the surface level of the crucible contents, the particles slow down the (direct) evaporation of the solid due to their large particle surface area. Thus, a degree of self-balancing of the evaporation of the solid at the higher evaporation pressure and the particles at the lower evaporation pressure is achieved.

[0029] The higher evaporation pressure material, as a solid surrounded by particles of the lower evaporation pressure material, provides favorable heat transfer between the first and second evaporation materials. A possible explanation is that the solidity of the first evaporation material facilitates heat transfer to a lower layer away from the surface of the material heated by electrons or laser beams, thus slowing down the evaporation of the first evaporation material with its higher vacuum pressure; while the particles of the second evaporation material reduce heat transfer, allowing for sufficient evaporation of the second evaporation material. The term "surrounded" as used herein can be understood as at least partially surrounding, i.e., not necessarily surrounding on all sides. The particles as used herein include or consist of a plurality of fine grains having a maximum particle size (maximum fine grain diameter) of no more than 8 mm, particularly no more than 5 mm, particularly no more than 3 mm, particularly no more than 1 mm. The term "particle" can also refer to powder as fine particles. At least one extended portion of the solid of the first evaporation material is at least two times, particularly at least three times, particularly at least four times, particularly at least six times, particularly at least ten times the maximum particle size (maximum fine grain diameter) of the particles of the second evaporation material.

[0030] The solid of the first evaporating material can have the mass or volume of any single portion of the particles of the second evaporating material that is at least 10 times, particularly at least 100 times, particularly 1000 times. The top portion of the solid of the first evaporating material can be evaporated using an electron or laser beam; and the top portion of the particles of the second evaporating material can be evaporated using an electron or laser beam. Thus, the respective (effective) surfaces of the first and second evaporating materials, which are evaporable or exposed for evaporation, can provide a ratio in which the first and second evaporating materials are adapted to counteract the vapor pressure difference between the first and second evaporating materials.

[0031] In the improvement, the first evaporation material can be provided as at least one of a rod, wire, or sheet. Specifically, the solid of the first evaporation material can stand upright within the particles of the second evaporation material. The solid can be provided, for example, as a rod, wire, or sheet that can extend in the height direction of the crucible. The height direction can refer to the direction parallel to gravity when the crucible is placed in the evaporation position within the vacuum chamber.

[0032] Optionally, multiple rods, wires, or sheets of the first evaporation material are provided. It has been found that several smaller rods or wires can provide better performance and coating uniformity compared to a single thick rod, wire, or sheet. This promotes direct sublimation and reduces the risk of forming large material droplets that may laterally penetrate the lower layers of the particles. For example, multiple finer wires, such as those with a diameter not exceeding 0.2 mm, can be used instead of a single thicker wire, such as those with a diameter of at least 0.5 mm. The combination of finer wires has the same cross-sectional area as the thicker wire. Similarly, fine sheets or foils as solids can provide better performance compared to thicker wires or rods. Typically, the geometry of the solid can be adapted to suppress droplet formation, such as allowing direct sublimation or producing only very small droplets rather than large droplets that might prevent heat conduction to deeper layers.

[0033] The solid can be arranged in the crucible without contacting the bottom of the crucible. For example, the solid can stand upright among the particles of the second evaporation material. Below the solid of the first evaporation material can be a bottom layer of particles of the second evaporation material. The advantage of the solid not contacting the bottom of the crucible is that unwanted current paths to the bottom of the crucible can be avoided when using electron beam heating. This can reduce inappropriate localization of the first evaporation material and thus allow for improved quality of the evaporation process and therefore the coating.

[0034] The cross-sectional area of ​​the solid can vary in a direction perpendicular to the height of the crucible. Therefore, the ratio of the exposed surface area of ​​the first evaporating material to the exposed surface area of ​​the second evaporating material at the surface of the crucible varies as the first and second evaporating materials are evaporated. Thus, a varying concentration distribution across the thickness of the coating to be deposited on the target can be easily produced. Depth-dependent adaptation of the evaporation process to electron or laser beam power is not required, nor is careful adjustment of the beam power for different crucibles necessary. Therefore, the deposition of complex coating profiles can be simplified. The height direction can again refer to the direction of gravity.

[0035] A first evaporating material and a second evaporating material having a lower vapor pressure than the first evaporating material can optionally be provided as a particulate mixture in the crucible. The ratio of the first and second evaporating materials in the particulate mixture in the crucible can be adapted to offset the vapor pressure difference between the first and second evaporating materials. Therefore, the particulate mixture can be provided as an alternative solution. For example, different volume percentages of the first and second evaporating materials can be used. For example, a particulate mixture of SiO2 containing 0.1…1 at% Ag can offset or compensate for the vapor pressure difference.

[0036] A first evaporating material and a second evaporating material having a lower vapor pressure than the first evaporating material can optionally be provided as tablets in a crucible. The ratio of the first and second evaporating materials in the tablet can be adapted to offset the vapor pressure difference between the first and second evaporating materials. As used herein, a tablet can refer to a compressed or molded block of solid material. The tablet can be placed in a crucible. An advantage is ease of handling when loading the crucible.

[0037] It should be understood that, without departing from the scope of the invention, the features mentioned above and those to be explained below can be used not only in the correspondingly indicated combinations, but also in other combinations or individually. Attached Figure Description

[0038] These and other aspects of the invention will become clear and illustrated with reference to the embodiments described below. In the following figures:

[0039] Figure 1 A schematic diagram of an embodiment of a conventional system for physical vapor deposition using different crucibles filled with different evaporation materials is shown;

[0040] Figure 2 A schematic diagram of an embodiment of an exemplary physical vapor deposition system according to aspects of this disclosure is shown;

[0041] Figures 3a to 3f Several exemplary configurations of crucibles containing a first evaporation material and a second evaporation material with different vapor pressures are shown;

[0042] Figure 4 A flowchart is shown for a method of physical vapor deposition, particularly for coating optical surfaces such as spectacle lenses. Detailed Implementation

[0043] Figure 1 A conventional physical vapor deposition system 1 is shown, which is particularly used for coating optical surfaces such as spectacle lenses. The physical vapor deposition system 1 includes a vacuum chamber 2. Inside the vacuum chamber, a crucible 10 and an evaporation unit 20 are provided for evaporating and depositing an evaporation material 41 onto a substrate 3 in a holder 4. The substrate can be an optical element such as a spectacle lens. It should be understood that multiple lens holders can be provided and multiple lenses can be coated in parallel. Figure 1 In the embodiment shown, the crucible 10 is inserted into the evaporation position in the crucible holder 11.

[0044] For physical vapor deposition of materials, electron beam evaporation can be used. An electron beam 22 from source 21 can be used to evaporate the material in crucible 10, i.e., the material to be evaporated. In electron beam physical vapor deposition, the material to be deposited is heated in a high vacuum by electron bombardment and transported by diffusion to be deposited onto the (cooler) workpiece or substrate 3 by condensation. However, other heating methods can also be used. For example, in pulsed laser deposition, a high-power laser can ablate the material from the crucible into vapor.

[0045] Key parameters in physical vapor deposition (PVD) include the vacuum pressure in the vacuum chamber during the deposition process, the scanning mode used for the electron beam (i.e., repeatedly guiding the electron beam through the evaporating material in the crucible), and the electron beam power. The mode and power affect the uniformity of the material surface. In existing vacuum deposition systems, the possibilities for changing the mode and power are often very limited. A fixed mode can be set to perform a statistical scan of the crucible region in a predetermined manner. Despite these limitations, a wider variety of coatings is desired. The evaporation rate Φ from the crucible... e Vacuum chamber pressure P depends on process parameters h The temperature T and the saturated vapor pressure P of the material used are also relevant. e And molar mass M:

[0046]

[0047] Where α e The coefficients are 0…1, N A Let represent Avogadro's constant, and R represent the universal or molar gas constant. The evaporation rate from crucible 10 determines the deposition rate on substrate 3.

[0048] In some applications, it may be desirable to provide coatings containing different material components or compositions. Different material components can be evaporated in parallel from different evaporation sources. Each evaporation source includes a crucible with one material component, which can be heated individually to obtain the desired coating composition. (See again...) Figure 1 In a conventional physical vapor deposition system, a second crucible 10' and a second evaporation unit 20' are provided for evaporating and depositing a second evaporation material 42. The second crucible 10' is positioned in a second evaporation location within a second holder 11'. The second evaporation unit 20' may include a second electron source 21' providing a second electron beam 22' to the second evaporation material 42 in the second crucible 10'. Thus, the first evaporation material 41 evaporated from the (first) crucible 20 and the second evaporation material 42 evaporated from the second crucible 20' can form a desired coating composition on the substrate 3. The (first) evaporation unit 20 and the second evaporation unit 20' must be carefully controlled.

[0049] However, there may be existing vapor deposition systems in which the second evaporation unit 20' and the second crucible 10' cannot be installed. Therefore, existing vacuum deposition equipment may require substantial modifications. Furthermore, the control of the first and second evaporation units 20, 20' must be carefully calibrated, thereby increasing system complexity.

[0050] Figure 2 A schematic diagram of an embodiment of an exemplary physical vapor deposition system according to aspects of this disclosure is shown. Similar components are provided by... Figure 1 The same reference numerals are used to denote the contents. However, instead of providing different crucibles for the first and second evaporation materials 41, 42, it is proposed to specifically adapt the composition of the contents of a single, independent crucible 10 such that the evaporation of the first and second evaporation materials 41, 42 from the crucible provides the desired coating composition on the substrate 3 to be coated. Thus, the crucible contains a first evaporation material 41 and a second evaporation material 42. The first evaporation material 41 has a first vapor pressure and the second evaporation material 42 has a second vapor pressure different from the first vapor pressure. The ratio of the first evaporation material 41 and the second evaporation material 42 in the crucible 10 is specifically adapted to offset the vapor pressure difference between the first and second evaporation materials. Therefore, even if the first and second evaporation materials have different vapor pressures, the desired stoichiometry or stoichiometric ratio can be achieved, making it possible to obtain the desired coating composition. Therefore, it is not necessary to evaporate the first and second evaporation materials with different heating or electron or laser beam powers. This simplifies control. Furthermore, existing vapor deposition equipment can be used without substantially modifying the crucible arrangement or the adaptation control and / or beam control of the evaporation unit. In particular, the proposed solution enables the deposition of mixed coatings using an evaporation unit with a single heating source. Furthermore, compared to solutions using separate crucibles (where different material components can be received from significantly different angular directions), the uniformity of the coating can be improved. Therefore, non-uniformity can be reduced in a simple and effective manner.

[0051] The inventors recognized that even if there is a difference in the molar mass of the first and second evaporating materials, such differences can generally be ignored because they are usually at least an order of magnitude lower than the vapor pressure difference between the first and second evaporating materials and can therefore be ignored to simplify the procedure.

[0052] Figures 3a to 3f Several exemplary cross-sectional views are shown of the construction of the crucible 10, which includes a first evaporation material 41 and a second evaporation material 42.

[0053] exist Figure 3aIn the example shown, a first evaporation material 41 with a higher vapor pressure is provided as a solid in rod form. A second evaporation material 42 is provided as particles surrounding the solid of the first evaporation material. For example, the first evaporation material 41 may be an Ag rod standing upright in SiO2 particles. The ratio of the exposed surface area of ​​the first evaporation material to the exposed surface area of ​​the second evaporation material at the surface of the crucible 10 is adapted to offset the vapor pressure difference between the first evaporation material 41 and the second evaporation material 42. The solid 41 may be arranged in the crucible 10 without contacting the bottom of the crucible. As explained above, this avoids high current flowing through the solid to the (grounded) bottom of the crucible, which could cause additional heating of the solid in a potentially unstable manner. Therefore, process stability can be further improved.

[0054] exist Figure 3b In this example, multiple filaments of first evaporation material 41 are provided. Second evaporation material 42 is provided as particles surrounding the filaments of the multiple first evaporation materials. The arrangement of the multiple filaments in the crucible 10 can be adapted to meet the following conditions:

[0055]

[0056] Therefore, the ratio of exposed surfaces can be an effective approximation.

[0057] Figure 3c An example is shown, in which a first evaporating material 41, a second evaporating material 42, and a third evaporating material 43 are provided. The third evaporating material 43 has a third vapor pressure that is lower than the first vapor pressure of the first evaporating material 41 but lower than the second evaporating pressure of the second evaporating material 42. The ratio of the first, second, and third evaporating materials is adapted accordingly to offset the vapor pressure difference between the first, second, and third evaporating materials.

[0058] Figure 3d An example is shown in which a first evaporating material 41 and a second evaporating material 42 having a lower vapor pressure than the first evaporating material are provided as a particulate mixture in a crucible 10. The ratio of the first evaporating material to the second evaporating material in the particulate mixture in the crucible is adjusted to offset the vapor pressure difference between the first and second evaporating materials. Nevertheless, Figure 3a Examples of -3c are generally preferred. They can provide an even more uniform coating because there is a risk that the higher vapor pressure in the particulate mixture evaporates at such a high rate that the first evaporated material in the particulate mixture may be depleted. Therefore, it is preferable to provide the first evaporated material as a solid, such as a rod or wire. Furthermore, considering that the material in the crucible is usually not completely evaporated, providing the first evaporated material as a solid facilitates the recycling of any remaining material. This also reduces manufacturing costs.

[0059] Figure 3eAn example is shown where a first evaporating material 41 and a second evaporating material 42 having a lower vapor pressure than the first evaporating material are provided as tablets in a crucible. The ratio of the first and second evaporating materials in the tablet is adjusted to offset the vapor pressure difference between the first and second evaporating materials. Such tablets allow for easy handling. Nevertheless, compared to this solution, Figure 3a - 3c examples can offer additional advantages. Different vapor pressures in the tablet can cause stress, which may lead to the bursting of one of the evaporated materials, thus compromising the uniformity of the coating. Furthermore, recovering residual evaporated material from the tablet can be difficult. Optionally, the granular layer 49 can be provided below the tablet, such that the tablet does not contact the bottom of the crucible 10.

[0060] Figure 3f An example is shown in which the cross-sectional area of ​​the solid of the first evaporation material 41 may vary in a direction perpendicular to the height direction of the crucible. Figure 3f In the diagram, the height direction is indicated by arrow z. Therefore, the ratio of the exposed surface area of ​​the first evaporating material 41 to the exposed surface area of ​​the second evaporating material at the surface of the crucible varies as the first and second evaporating materials are evaporated. Thus, a varying concentration distribution across the thickness of the coating to be deposited on the target can be easily produced. Depth-dependent adaptation of the evaporation process to the electron or laser beam power is not required, nor is careful adjustment of the beam power for different crucibles necessary.

[0061] Figure 4 A flowchart is shown for a method of physical vapor deposition, particularly for coating optical surfaces such as spectacle lenses. In a first step S401, a crucible containing a first evaporation material and a second evaporation material is provided. The first evaporation material has a first vapor pressure and the second evaporation material has a second vapor pressure different from the first vapor pressure. The contents of the crucible are specifically adapted such that the ratio of the first evaporation material and the second evaporation material in the crucible is adapted to offset the vapor pressure difference between the first and second evaporation materials.

[0062] In step S402, a vacuum can be provided by evacuating a vacuum chamber in which the crucible is placed in the evaporation position. Optionally, step S403 represents a homogenization stage. The material in the crucible can be preheated during this homogenization stage with a closed shield. The shield blocks the path from the crucible to the element to be coated. In step S404, the shield can be opened. Figure 2 An exemplary optional mask 50 is shown. The mask can be retracted as indicated by arrow 51 and does not obstruct the path from the crucible 10 to the substrate 3 to be coated.

[0063] In step S405, the first and second evaporation materials are simultaneously evaporated from the same crucible. This step can be referred to as the coating stage.

[0064] Advantageously, short homogenization and / or short coating phases are used. This reduces the formation of droplets of the first evaporated material that might escape, for example, from the solid of the first evaporated material into the particles of the second evaporated material. The homogenization and / or coating phases can have a duration of at least one of less than 15 seconds, less than 10 seconds, or less than 5 seconds. Such parameters have proven advantageous because they prevent or at least reduce the melting of the solid and the flow of droplets from the solid into the particles. Therefore, this method can work particularly well for thin coatings, for example, less than 15 nm thick.

[0065] While the invention has been shown and described in detail in the accompanying drawings and the foregoing description, such showing and description are intended to be illustrative or exemplary, and not restrictive; the invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments will be understood and implemented by those skilled in the art in practicing the claimed invention upon studying the drawings, the disclosure, and the appended claims.

[0066] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a / an" does not exclude a plurality / type. A single element or other unit can perform the functions of several items as stated in the claims. The simple fact that certain measures are stated in different dependent claims does not mean that a combination of these measures cannot be used advantageously.

[0067] Any reference numerals in the claims should not be construed as limiting the scope.

Claims

1. A method for physical vapor deposition, the method comprising: - Provide a crucible (10) containing a first evaporation material (41) and a second evaporation material (42). The first evaporating material (41) has a first vapor pressure and the second evaporating material (42) has a second vapor pressure different from the first vapor pressure; and - The first evaporation material (41) and the second evaporation material (42) are simultaneously evaporated from the same crucible (10); The feature is that the ratio of the exposed surface of the first evaporating material (41) to the exposed surface of the second evaporating material (42) at the surface of the crucible (10) is adapted to offset the vapor pressure difference between the first evaporating material and the second evaporating material.

2. The method according to claim 1, wherein, The method is used to coat optical surfaces.

3. The method according to claim 2, wherein, The optical surface is a spectacle lens.

4. The method according to claim 1, wherein, The ratio of the exposed surfaces of the first evaporating material (41) and the second evaporating material (42) is inversely proportional to the ratio of the vapor pressures of the first evaporating material and the second evaporating material.

5. The method according to claim 1, wherein, The first evaporation material (41) and the second evaporation material (42) are evaporated using an electron beam or a laser beam, wherein the electron beam or laser beam is set to the same power for evaporating the first evaporation material and the second evaporation material.

6. The method according to claim 1, wherein, The first evaporating material (41) having a higher vapor pressure is provided as a solid, and wherein the second evaporating material (42) having a lower vapor pressure than the first evaporating material is provided as particles surrounding the solid of the first evaporating material.

7. The method according to claim 6, wherein, The first evaporation material (41) is provided as at least one of a rod, wire or sheet.

8. The method according to claim 6 or 7, wherein, The solid of the first evaporation material (41) stands upright in the particles of the second evaporation material (42).

9. The method according to claim 7, wherein, Multiple rods, multiple wires or multiple sheets of the first evaporation material (41) are provided.

10. The method according to claim 6, wherein, The solid is placed in the crucible (10) without contacting the bottom of the crucible.

11. The method according to claim 6, wherein, The cross-sectional area of ​​the solid varies in a direction perpendicular to the height of the crucible (10).

12. The method according to claim 1, wherein, The first evaporating material (41) and the second evaporating material (42) having a lower vapor pressure than the first evaporating material are provided as a particulate mixture in the crucible (10), wherein the ratio of the first evaporating material and the second evaporating material in the particulate mixture in the crucible (10) is adapted to offset the vapor pressure difference between the first evaporating material and the second evaporating material.

13. The method according to claim 1, wherein, The first evaporating material (41) and the second evaporating material (42) having a lower vapor pressure than the first evaporating material are provided as tablets in the crucible (10), wherein the ratio of the first evaporating material to the second evaporating material in the tablet is adapted to offset the vapor pressure difference between the first evaporating material and the second evaporating material.

14. A physical vapor deposition system, comprising: - Crucibles for physical vapor deposition (10) - First evaporation material (41) and second evaporation material (42). The first evaporating material (41) has a first vapor pressure and the second evaporating material (42) has a second vapor pressure different from the first vapor pressure. The feature is that the ratio of the exposed surface of the first evaporating material (41) and the exposed surface of the second evaporating material (42) in the crucible (10) is adapted to offset the vapor pressure difference between the first evaporating material and the second evaporating material.

15. The system of claim 14, wherein the physical vapor deposition is used to coat an optical surface.

16. The system of claim 15, wherein the optical surface is a spectacle lens.

17. A physical vapor deposition system (1), the system comprising: - Vacuum chamber (2); - Crucible (10); as well as A first evaporating material (41) and a second evaporating material (42) are contained in a crucible (10), wherein the first evaporating material (41) has a first vapor pressure and the second evaporating material (42) has a second vapor pressure different from the first vapor pressure, and the ratio of the exposed surface of the first evaporating material (41) and the exposed surface of the second evaporating material (42) in the crucible (10) is adapted to offset the vapor pressure difference between the first evaporating material and the second evaporating material. - An evaporation unit (20) adapted to simultaneously evaporate the first evaporation material (41) and the second evaporation material (42) from the same crucible (10).

18. The physical vapor deposition system (1) according to claim 17, wherein the physical vapor deposition system (1) is used to coat an optical surface.

19. The physical vapor deposition system (1) according to claim 18, wherein the optical surface is an eyeglass lens.

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