WO2020057737A1

WO2020057737A1 - Method of pretreating an oscillation crystal for measuring a deposition rate, deposition rate measurement device, evaporation source and deposition apparatus

Info

Publication number: WO2020057737A1
Application number: PCT/EP2018/075372
Authority: WO
Inventors: Sebastian Franke; Andreas MÜLLER; Julian AULBACH; Stefan Keller
Original assignee: Applied Materials, Inc.
Priority date: 2018-09-19
Filing date: 2018-09-19
Publication date: 2020-03-26
Also published as: CN112703269A; KR102609982B1; KR20210049157A

Abstract

A method of pretreating an oscillation crystal (110) for measuring a deposition rate is described. The method includes polarizing a measurement surface (115) of the oscillation crystal. In particular, the method includes pretreating the measurement surface of the oscillation crystal with an oxygen containing plasma, wherein pretreating is conducted at a temperature of 10°C ≤ T≤ 80°C for a time period t of 1 min ≤ t ≤ 5min. Further, a deposition rate measurement device, an evaporation source and a deposition apparatus are described.

Description

METHOD OF PRETREATING AN OSCILLATION CRYSTAL FOR MEASURING A DEPOSITION RATE, DEPOSITION RATE

MEASUREMENT DEVICE, EVAPORATION SOURCE AND DEPOSITION

APPARATUS

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to methods of pretreating an oscillation crystal for measuring a deposition rate as well as relating to deposition rate measurement devices. Further embodiments of the present disclosure relate to evaporation sources including a deposition rate measurement device as well as relating to deposition apparatuses having an evaporation source with a deposition rate measurement device. In particular, embodiments of the deposition rate measurement device are configured for measuring deposition rates of materials used for display production, e.g. for the production of organic light-emitting diodes (OLED).

BACKGROUND

[0002] Organic and metal evaporators are a tool for the production of organic light-emitting diodes (OLED). OLEDs are a special type of light-emitting diode in which the emissive layer comprises a thin-film of certain organic compounds. Organic light emitting diodes (OLEDs) are used in the manufacture of television screens, computer monitors, mobile phones, other hand-held devices, etc., for displaying information. OLEDs can also be used for general space illumination. The range of colors, brightness and viewing angle possible with OLED displays is greater than that of traditional LCD displays because OLED pixels directly emit light and do not involve a back light. Therefore, the energy consumption of OLED displays is considerably less than that of traditional LCD displays. Further, the fact that OLEDs can be manufactured onto flexible substrates results in further applications.

[0003] The functionality of an OLED depends on the coating thickness of the organic material. This thickness has to be within a predetermined range. In the production of OLEDs, the deposition rate at which the coating with organic and electrode material is controlled to lie within a predetermined tolerance range. In other words, the deposition rate of an organic or metal evaporator has to be controlled thoroughly in the production process.

[0004] Accordingly, for OLED applications but also for other evaporation processes, a high accuracy of the deposition rate over a comparably long time is needed. There is a plurality of measurement systems for measuring the deposition rate of evaporators available. However, these measurement systems suffer from either insufficient accuracy and/or insufficient stability over the operating time period. [0005] Accordingly, there is a continuing demand for providing improved deposition rate measurement systems, evaporators and deposition apparatuses.

SUMMARY

[0006] In light of the above, a method of pretreating an oscillation crystal for measuring a deposition rate, a deposition rate measurement device, an evaporation source and a deposition apparatus according to the independent claims are provided. Further aspects, advantages, and features are apparent from the dependent claims, the description, and the accompanying drawings.

[0007] According to one aspect of the present disclosure, a method of pretreating an oscillation crystal for measuring a deposition rate is provided. The method includes polarizing a measurement surface of the oscillation crystal.

[0008] According to a further aspect of the present disclosure, a method of pretreating an oscillation crystal for measuring a deposition rate is provided. The method includes pretreating a measurement surface of the oscillation crystal with an oxygen containing plasma, wherein pretreating is conducted at a temperature of lO°C < T< l00°C for a time period t of 1 min < t < 15min, particularly at a temperature of lO°C < T< 40°C for a time period t of 1 min < t < 5min. [0009] According to another aspect of the present disclosure, a deposition rate measurement device is provided. The deposition rate measurement device includes an oscillation crystal for measuring a deposition rate. The oscillation crystal has a polarized measurement surface.

[0010] According to a further aspect of the present disclosure, a deposition apparatus for applying material to a substrate in a vacuum chamber at a deposition rate is provided. The deposition apparatus includes at least one evaporation source according to any embodiments described herein.

[0011] Embodiments are also directed at apparatuses for carrying out the disclosed methods and include apparatus parts for performing the described method aspect. These method aspects may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, embodiments according to the disclosure are also directed at methods for operating the described apparatus. The methods for operating the described apparatus include method aspects for carrying out every function of the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following:

FIG. 1A shows a schematic front view of a deposition rate measurement device having an oscillation crystal according to embodiments described herein; FIG. 1B shows a schematic sectional side view of the deposition rate measurement device of FIG. 1A;

FIG. 2A shows a schematic sectional side view of a deposition rate measurement device according to embodiments described herein, wherein the measurement surface of the oscillation crystal is subjected to a polarization treatment;

FIG. 2B shows a schematic sectional side view of a deposition rate measurement device according to embodiments described herein after the measurement surface of the oscillation crystal has been subjected to a polarization treatment;

FIGS. 3 A to 3 C show flowcharts for illustrating a method of pretreating an oscillation crystal according to embodiments described herein;

FIG. 4 shows a schematic view of a deposition rate measurement device according to further embodiments described herein; FIGS. 5 A and 5B show schematic side views of an evaporation source according to embodiments described herein;

FIG. 6 shows a schematic perspective view of an evaporation source according to embodiments described herein; and

FIG. 7 shows a schematic view of a deposition apparatus according to embodiments described herein.

DETAILED DESCRIPTION OF EMBODIMENTS

[0013] Reference will now be made in detail to the various embodiments of the disclosure, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the disclosure and is not meant as a limitation of the disclosure. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations. [0014] With exemplary reference to FIGS. 1A, 1B, 2A and 2B a deposition rate measurement device 100 according to the present disclosure is described. FIG. 1A shows a schematic front view and FIG. 1B shows a schematic sectional side view of a deposition rate measurement device 100 according to embodiments described herein. [0015] According to embodiments which can be combined with other embodiments described herein, the deposition rate measurement device 100 includes an oscillation crystal 110 for measuring a deposition rate.

[0016] In the present disclosure, an“oscillation crystal for measuring a deposition rate” may be understood as an oscillation crystal for measuring a change in mass due to deposited material on the oscillation crystal per unit area by measuring the change in frequency of an oscillation crystal resonator. In particular, in the present disclosure an oscillation crystal may be understood as a quartz crystal resonator. More particularly, an“oscillation crystal for measuring a deposition rate” may be understood as a quartz crystal microbalance (QCM). [0017] In particular, the deposition rate measurement device 100 may include a holder 120 for holding the oscillation crystal 110. For instance, the oscillation crystal 110 may be arranged inside the holder 120. As exemplarily shown in FIG. 1B showing a schematic sectional side view of the deposition rate measurement device 100, a measurement opening 121 may be provided in the holder 120. In particular, the measurement opening 121 may be configured and arranged such that evaporated material may be deposited on a measurement surface 115 of the oscillation crystal for measuring the deposition rate of the evaporated material. As exemplarily indicated in FIG. 2B, according to embodiments of the present disclosure the measurement surface 115 of the oscillation crystal 110 is a polarized measurement surface 115P. Typically, the polarized measurement surface 115P is obtained by polarizing the measurement surface 115 by conducting a method of pretreating an oscillation crystal as described herein. The pretreating of the oscillation crystal 110 is schematically indicated by the arrows in FIG. 2A. Although FIG. 2A shows a pretreating of the oscillation crystal when in a state in which the oscillation crystal is mounted to the holder 120, it is to be understood that alternative pretreating of the oscillation crystal may be conducted in an unmounted state, i.e. prior to mounting the oscillation crystal to the holder. In other words, typically pretreating of the oscillation crystal is carried before the oscillation crystal has been mounted to the holder. Alternatively, a pretreating of the oscillation crystal may be carried out in situ, i.e. in a mounted state of the oscillation crystal to the holder, particularly within a deposition apparatus as described herein. A “polarized measurement surface” can be understood as the measurement surface of the oscillation crystal which provides for an increased electrochemical potential compared to an unpolarized measurement surface, i.e. non-treated measurement surface, of the oscillation crystal.

[0018] Accordingly, embodiments of the deposition rate measurement device of the present disclosure are improved compared to the state of art, particularly with respect to quality of the measurement signal of the deposition rate. In particular, it has been found that pretreating the oscillation crystal as described herein beneficially provides for improving the measurement accuracy of the deposition rate measurement device. More specifically, it has been found that providing a polarized measurement surface of the oscillation crystal has the advantage that the adhesion of evaporated materials, e.g. metals or organic materials, to be measured can be improved resulting in an improved measurement sensitivity and accuracy. In particular, it has been found that the adhesion of metals, e.g. Ag, Mg and other metals, can be improved by providing a polarized measurement surface of the oscillation crystal. In particular, providing a polarized measurement surface of the oscillation crystal can help to improve the adhesion of materials having a low sticking coefficient (e.g. a sticking coefficient of the order of the sticking coefficient of Mg) and/or having a relatively low evaporation temperature (e.g. an evaporation temperature of the order of the evaporation temperature of Mg).

[0019] For instance, for conducting the method of pretreating an oscillation crystal as described herein, a revolver type QCM system can be used which can be loaded, for example, with up to ten individual oscillation crystals. Typically, the oscillation crystals are pretreated subsequently.

[0020] According to some embodiments which can be combined with other embodiments described herein, polarizing a measurement surface of the oscillation crystal may include employing a 100W radio frequency (RF) plasma, for instance at 0.3 mbar, particularly for about 5 minutes. Typically, air can be used as plasma gas in embodiments described herein.

[0021] According to some embodiments which can be combined with other embodiments described herein, polarizing a measurement surface of the oscillation crystal may include an UV-ozone exposure of the measurement surface in air, particularly for about 5 min.

[0022] According to some embodiments which can be combined with other embodiments described herein, polarizing a measurement surface of the oscillation crystal may include employing a 130W radio frequency (RF) plasma, for instance at atmospheric pressure, particularly for about 1 minutes. For instance, an argon (Ar) oxygen (0₂) mixture, particularly 95% Ar and 5 % 0₂, can be used as plasma gas can be used.

[0023] Further, it has been found that by using an oscillation crystal having a polarized measurement surface, the time for obtaining a stable measurement signal can significantly be reduced. In particular it has been found that, compared to an oscillation crystal with a non-polarized measurement surface with the oscillation crystal having a polarized measurement surface as described herein, the time for obtaining a stable measurement signal can be reduced by a factor of 3 or more, particularly 4 or more. According, to an example, with an oscillation crystal having an untreated measurement surface the time for obtaining a stable measurement signal was determined to be approximately 210 min. In contrast, with an oscillation crystal having a pretreated measurement surface as described herein, the time for obtaining a stable measurement signal was determined to be approximately 45 min.

[0024] With exemplary reference to the flowcharts shown in FIGS. 3A to 3C, embodiments of a method 400 of pretreating an oscillation crystal 110 for measuring a deposition rate according to the present disclosure are described.

[0025] According to embodiments which can be combined with other embodiments described herein, the method includes polarizing (represented by block 410 in FIG. 3 A) a measurement surface 115 of the oscillation crystal. In particular, polarizing the measurement surface 115 of the oscillation crystal 110 can include conducting an oxygen treatment (represented by block 411 in FIG. 3B) of the measurement surface of the oscillation crystal.

[0026] In the present disclosure, an “oxygen treatment of the measurement surface” can be understood as a treatment of the measurement surface 115 of the oscillation crystal 110 using 02 (dioxygen), 03 or oxygen in the form of one or more oxidations states of oxygen O (e.g. oxidations states of O: -2, -1, 0, +1, +2).

[0027] For instance, conducting the oxygen treatment can include conducting a plasma treatment (represented by block 412 in FIG. 3B). For instance, conducting the plasma treatment may include using a plasma including an oxygen content of more than 0.5%, particularly more than 20%. In particular, a plasma including an oxygen content of more than 20% may be used at a low pressure (e.g. a pressure of less than 100 mbar, particularly less than 10 mbar, more particularly less than 1 mbar). According to an example, the plasma may consist of oxygen. Alternatively, the plasma may include an oxygen content in the range of 0. 5% to 10%, particularly 0.5% to 8%, more particularly 0.5% to 5%, for instance for plasma applications at an atmospheric pressure.

[0028] According to some embodiments which can be combined with other embodiments described herein, the oxygen of the plasma may be in the form of 0₂. Additionally or alternatively, the oxygen of the plasma may be in the form of 0₃. For instance, the plasma may include a mixture of 0₂ and 0_3. Further, the plasma may include oxygen in the form of one or more oxidations states of oxygen O (e.g. oxidations states of O: -2, -1, 0, +1, +2).

[0029] According to another embodiment which can be combined with other embodiments described herein, conducting an oxygen treatment of the measurement surface of the oscillation crystal can include exposing the measurement surface 115 of the oscillation crystal 110 to ozone (O₃).

[0030] According to some embodiments which can be combined with other embodiments described herein, polarizing the measurement surface 115 of the oscillation crystal 110 includes exposing (represented by block 413 in FIG. 3C) the measurement surface of the oscillation crystal to ultraviolet UV light. In particular, exposing the measurement surface of the oscillation crystal to ultraviolet UV light may be conducted in an oxygen containing environment. Accordingly, by exposing the oxygen 0₂ (dioxygen) in the oxygen containing environment to UV light, ozone (03) can be formed. The ozone may react with the measurement surface 115 of the oscillation crystal 110 to provide a polarized measurement surface 115.

[0031] According to some embodiments which can be combined with other embodiments described herein, the oxygen treatment is conducted for a time period t of 0.5 min < t < 10 min, particularly 1 min < t < 5min. [0032] According to some embodiments which can be combined with other embodiments described herein, the oxygen treatment is conducted at a temperature T of l0°C < T < 80°C, particularly l5°C < T < 50°C.

[0033] According to an example which can be combined with other embodiments described herein, the method of pretreating an oscillation crystal 110 for measuring a deposition rate, includes pretreating a measurement surface 115 of the oscillation crystal 110 with an oxygen containing plasma and pretreating is conducted at a temperature of l0°C < T< 40°C for a time period t of 1 min < t < 5min. [0034] Accordingly, embodiments of the method of pretreating an oscillation crystal for measuring a deposition rate as described herein beneficially provide for improving the measurement signal quality of a deposition rate measurement device as of the present disclosure. In particular, it has been found that by conducting a method of pretreating an oscillation crystal as described herein beneficially provides for a polarized measurement surface of the oscillation crystal having the advantage that adhesion of evaporated materials to be measured can be improved resulting in an improved measurement sensitivity and accuracy.

[0035] According to some embodiments which can be combined with other embodiments described herein, polarizing a measurement surface of the oscillation crystal may include coating the measurement surface, e.g. by using a dip coating process, with a coating or a layer configured for providing a polarized surface. Alternatively, polarizing a measurement surface of the oscillation crystal may include exposing the measurement surface of the oscillation crystal to hydrogen peroxide.

[0036] With exemplary reference to FIG. 4, some further optional aspects of a deposition rate measurement device 100 of the present disclosure are described.

[0037] FIG. 4 shows a measurement assembly 190 for measuring a deposition rate of an evaporated material. The measurement assembly 190 includes a deposition rate measurement device 100 having an oscillation crystal 110 and a movable shutter 140 configured for blocking evaporated material provided from a measurement outlet 151. FIG. 4 shows a state of the movable shutter 140 blocking evaporated material (indicated by the arrows in FIG. 4) provided from a measurement outlet 151. As schematically shown in FIG. 4, typically the measurement outlet 151 is configured for providing evaporated material to the oscillation crystal 110. The double sided arrow in FIG. 4, schematically indicates that the movable shutter 140 can be moved such that evaporated material provided through the measurement outlet 151 can be deposited on the measurement surface 115 of the oscillation crystal 110. [0038] With exemplary reference to FIG. 4, according to embodiments which can be combined with any other embodiments described herein, the deposition rate measurement device 100 may include a heater 114 configured for applying heat to the oscillation crystal 110, such that material deposited on the oscillation crystal 110 can be evaporated, particularly for cleaning the measurement surface 115 of the oscillation crystal 110 after deposition rate measurement. For instance, the heater 114 may be provided in the holder 120 for the oscillation crystal 110.

[0039] Additionally or alternatively, a further heater 116 may be provided in the movable shutter 140 of the measurement assembly 190, as exemplarily shown in FIG. 4. In particular, the further heater 116 provided in the movable shutter 140 can be configured for applying heat to the movable shutter such that material deposited on the movable shutter can be evaporated. Typically, the heater 114 and/or the further heater 116 are configured for providing a heating temperature which corresponds to at least the evaporation temperature of the material deposited on the oscillation crystal and/or deposited on the shutter. Accordingly, the oscillation crystal may be cleaned by heating as described herein. Further, also the shutter may be cleaned by heating the shutter.

[0040] With exemplary reference to FIG. 4, according to some embodiments which can be combined with other embodiments described herein, the movable shutter 140 may include a thermal protection shield 117. As exemplarily shown in FIG. 3, the thermal protection shield 117 may be arranged on a side of the movable shutter 140 which faces the measurement outlet 151. In particular, the thermal protection shield 117 may be configured for reflecting heat energy provided by evaporated material provided through the measurement outlet. According to embodiments which can be combined with other embodiments described herein, the thermal protection shield 117 may be a plate, for example a sheet metal. Alternatively, the thermal protection shield 117 may include two or more plates, e.g. sheet metals, which may be spaced with respect to each other, for example by a gap of 0.1 mm or more. For example the sheet metal may have a thickness of 0.1 mm to 3.0 mm. In particular, the thermal protection shield includes a ferrous or non-ferrous material, for example at least one material selected from the group consisting of copper (Cu), aluminum (Al), copper alloy, aluminum alloy, brass, iron, titanium (Ti), ceramic and other suitable materials.

[0041] According to embodiments which can be combined with any other embodiment described herein, the further heater 116 of the movable shutter 140 may be provided on a side of the movable shutter 140 which faces the oscillation crystal 110. Accordingly, by providing a heater as described herein, for instance in the holder or a shutter, an oscillation crystal of a deposition rate measurement device as described herein may be cleaned in situ by evaporating deposited material on the oscillation crystal by applying heat by the heater. This can be beneficial for the overall lifetime of the oscillation crystal and the achievable measurement accuracy.

[0042] With exemplary reference to FIG. 4, according to embodiments which can be combined with other embodiments described herein, the deposition rate measurement device 100 may include a heat exchanger 132. In particular, the heat exchanger may be arranged in the holder 120, for example next to or adjacent to the oscillation crystal and/or next to or adjacent to the heater 114. The heat exchanger 132 may be configured to exchange heat with the oscillation crystal and/or with the holder 120 and/or with the heater 114. For example, the heat exchanger may include tubes through which a cooling fluid may be provided. The cooling fluid may be a liquid, e.g. water, or a gas, e.g. air. Additionally or alternatively, the heat exchanger may include one or more Peltier element(s). Typically, the heat exchanger is employed during a measurement of the oscillation crystal and switched off during a cleaning procedure conducted by heating the oscillation crystal using a heater as described herein. Accordingly, by providing the deposition rate measurement device 100 with a heat exchanger 132, negative effects of high temperature on the quality, accuracy and stability of the deposition rate measurement may be reduced or even eliminated. In particular, providing the deposition rate measurement device 100 with a heat exchanger may be beneficial for cooling the measurement device after the measurement device has been cleaned by heating in order to evaporate deposited material from the deposition rate measurement device.

[0043] With exemplary reference to FIG. 4, according to embodiments which can be combined with other embodiments described herein, the deposition rate measurement device 100 may include a temperature sensor 118 for measuring the temperature of the oscillation crystal 110 and/or the holder 120. By providing the deposition rate measurement device 100 with a temperature sensor 118, information about the temperature of the deposition rate measurement device 100 may be obtained such that a critical temperature at which the oscillation crystal tends to measure may be inaccurately detected. Accordingly, in the case that a critical temperature of the oscillation crystal is detected by the temperature sensor, an adequate reaction may be initiated, for example a cooling by employing the heat exchanger.

[0044] According to embodiments which can be combined with other embodiments described herein, the deposition rate measurement device 100, particularly for measuring a deposition rate, may include a temperature control system for controlling the temperature of the oscillation crystal and/or the temperature of the holder. In particular, the temperature control system may include one or more of a temperature sensor 118, a heat exchanger 132, a heater 114 and a sensor controller 133. As exemplarily shown in FIG. 4, the sensor controller 133 may be connected to the temperature sensor 118 for receiving data measured by the temperature sensor 118. Further, the sensor controller 133 may be connected to the heat exchanger 132 for controlling the temperature of the holder 120 and/or the oscillation crystal 110. Further, the sensor controller 133 may be connected to the heater 114 and or the further heater 116 in order to control the heating temperature of the holder 120 of the oscillation crystal and/ or the movable shutter 140, e.g. during cleaning as described herein.

[0045] With exemplary reference to FIGS. 5A, 5B and 6, embodiments of an evaporation source according to the present disclosure are described. [0046] FIGS. 5 A and 5B show schematic side views of an evaporation source 200 according to embodiments as described herein. According to embodiments, the evaporation source 200 for evaporation of material includes an evaporation crucible 210. The evaporation crucible is configured to evaporate a material, for example an organic material. Further, the evaporation source 200 includes a distribution assembly 220, e.g. a distribution pipe, with one or more outlets 222 provided along the length of the distribution assembly for providing evaporated material, as exemplarily shown in FIG. 5B. Typically, the distribution assembly 220, particularly the distribution pipe, is in fluid communication with the evaporation crucible 210, for example via a vapor conduit. The vapor conduit can be provided at the lower end of the distribution pipe. Further, the evaporation source 200 according to embodiments described herein includes a deposition rate measurement device 100 according to embodiments described herein, as for example described with reference to FIGS. 1 A through FIG. 4.

[0047] In the present disclosure, an“evaporation crucible” can be understood as a device having a reservoir for the material to be evaporated by heating the crucible. Accordingly, a“crucible” can be understood as a source material reservoir which can be heated to vaporize the source material into a gas by at least one of evaporation and sublimation of the source material. Typically, the crucible includes a heater to vaporize the source material in the crucible into a gaseous source material. For instance, initially the material to be evaporated can be in the form of a powder. The reservoir can have an inner volume for receiving the source material to be evaporated, e.g. an organic material. For example, the volume of the crucible can be between 100 cm³ and 3000 cm³, particularly between 700 cm³ and 1700 cm³, more particularly 1200 cm³. In particular, the crucible may include a heating unit configured for heating the source material provided in the inner volume of the crucible up to a temperature at which the source material evaporates. For instance, the crucible may be a crucible for evaporating organic or metal materials, e.g. organic materials having an evaporation temperature of about l00°C to about 600°C and metals about 300°C to about l500°C. [0048] As exemplarily shown in FIGS. 5A and 5B, according to embodiments which can be combined with other embodiments described herein, the evaporation source 200 may include a controller 250 connected to the deposition rate measurement device 100 and to the evaporation crucible 210. For instance, the controller 250 may provide a first control signal 251 to the evaporation crucible 210 for adjusting the deposition rate. Typically, the controller 250 is configured to receive and analyze the measurement data acquired by the deposition rate measurement device 100. Further, the controller 250 may provide a second control signal 252 to the deposition rate deposition rate measurement device, e.g. for controlling a position of the movable shutter 140 of the measurement assembly 190 as exemplarily described with reference to FIG. 4.

[0049] As exemplarily shown in FIG. 5A, according to embodiments which can be combined with other embodiments described herein, the distribution assembly 220 may be an elongated cube, e.g. a distribution pipe, including a heating element 215. The evaporation crucible 210 can be a reservoir for material, e.g. organic or metal material, to be evaporated with a crucible heating unit 225. For example, the crucible heating unit 225 may be provided within the enclosure of the evaporation crucible 210. According to embodiments which can be combined with other embodiments described herein, the distribution assembly 220, particularly the distribution pipe may provide a line source. For example, as exemplarily shown in FIG. 5A, a plurality of outlets 222, such as nozzles, can be arranged along at least one line. According to an alternative embodiment (not shown), one elongated opening, e.g. a slit, extending along the at least one line may be provided. According to some embodiments which can be combined with other embodiments described herein, the line source may extend essentially vertically. Alternatively, the distribution assembly may include a plurality of point sources (not explicitly shown).

[0050] According to some embodiments which can be combined with other embodiments described herein, the length of the distribution assembly, particularly the length of the distribution pipe, may correspond to a height of a substrate onto which material is to be deposited in a deposition apparatus. Alternatively, the length of the distribution assembly may be longer than the height of the substrate onto which material is to be deposited, for example at least by 10% or even 20%. Accordingly, a uniform deposition at the upper end of the substrate and/or the lower end of the substrate can be provided. For example, the length of the distribution assembly can be 1.3 m or above, for example 2.5 m or above.

[0051] According to embodiments which can be combined with other embodiments described herein, the evaporation crucible 210 may be provided at the lower end of the distribution assembly, as exemplarily shown in FIGS. 5A and 5B. The material, e.g. organic material, can be evaporated in the evaporation crucible 210. The evaporated material may enter the distribution assembly at the bottom of the distribution assembly and may be guided essentially sideways through the plurality of outlets 222 in the distribution assembly 220, particularly the distribution pipe, e.g. towards an essentially vertical substrate. With exemplary reference to FIG. 5B, the deposition rate measurement device 100 according to embodiments described herein may be provided at an upper portion of the distribution assembly 220, e.g. at the upper end of the distribution pipe.

[0052] With exemplary reference to FIG. 5B, according to embodiments which can be combined with other embodiments described herein, the distribution assembly 220 includes a measurement outlet 151 for providing the evaporated material to the oscillation crystal of the deposition rate measurement device 100. In particular, the measurement outlet 151 may be provided in a wall of the distribution assembly, for example in a wall at the backside 224A of the distribution assembly, particularly at an upper portion of the wall at the backside 224A.

[0053] Although not explicitly shown, it is to be understood that according to embodiments which can be combined with other embodiments described herein, the measurement outlet 151 may be provided in a top wall 224C of the distribution assembly, particularly an upper horizontal top wall of the distribution assembly. As exemplarily indicated by the arrow extending through the measurement outlet 151 in FIG. 5B, the evaporated material may be provided from the inside of the distribution assembly 220 through the measurement outlet 151 to the deposition rate measurement device 100. Accordingly, the measurement outlet 151 is arranged and directed such that evaporated material can be provided to the oscillation crystal, as exemplarily shown in FIG. 4. For example, the deposition rate measurement device 100 can be arranged at the backside 224A of the distribution assembly, particularly at the backside 224A of an upper end portion of the distribution assembly 220, e.g. the distribution pipe. Typically, the backside of the end portion of the distribution assembly faces away from the deposition direction. According to some embodiments, the deposition rate measurement device 100 can be mounted on the backside 224A of the upper end portion of the distribution assembly 220, particularly the distribution pipe. Typically, the deposition rate measurement device 100 is arranged such that the oscillation crystal 110, particularly the measurement surface 115 of the oscillation crystal, faces the measurement outlet 151.

[0054] According to embodiments which can be combined with other embodiments described herein, the measurement outlet 151 may have an opening from 0.5 mm to 4 mm. Further, the measurement outlet 151 may include a nozzle. For example, the nozzle may include an adjustable opening for adjusting the flow of evaporated material provided to the deposition rate measurement device 100. In particular, the nozzle may be configured to provide a measurement flow selected from a range between a lower limit of 1/70 of the total flow provided by the evaporation source, particularly a lower limit of 1/60 of the total flow provided by the evaporation source, more particularly a lower limit of 1/50 of the total flow provided by the evaporation source and an upper limit of 1/40 of the total flow provided by the evaporation source, particularly an upper limit of 1/30 of the total flow provided by the evaporation source, more particularly an upper limit of 1/25 of the total flow provided by the evaporation source. For example, the nozzle may be configured to provide a measurement flow of 1/54 of the total flow provided by the evaporation source.

[0055] FIG. 6 shows a perspective view of an evaporation source 200 according to embodiments described herein. As exemplarily shown in FIG. 6, the distribution assembly 220, particularly the distribution pipe, may be designed in a triangular shape. A triangular shape of the distribution pipe may be beneficial in the case where two or more distribution pipes are arranged next to each other. In particular, a triangular shape of distribution pipes makes it possible to bring the outlets of neighboring distribution pipes as close as possible to each other. This allows for achieving an improved mixture of different materials from different distribution pipes, e.g. for the case of the co-evaporation of two, three or even more different materials. Further, the embodiment shown in FIG. 6 illustrates that typically a measurement outlet 151 for providing evaporated material to an oscillation crystal of the deposition rate measurement device 100 are provided, for instance at an upper end of the distribution assembly as exemplarily described with reference to FIGS. 5A and 5B.

[0056] With exemplary reference to FIG. 6, the distribution assembly 220 may include walls, e.g. side walls 224B and a wall at the backside 224A of the distribution assembly. As exemplarily shown in FIG. 6, the measurement outlet 151 may be provided in the wall at the backside 224A of the distribution assembly 220. Further, the side walls 224B and the wall at the backside 224A can be heated by a heating element 215. For instance, the heating element 215 may be mounted or attached to the walls of the distribution assembly 220, particularly the distribution pipe, as exemplarily shown in FIG. 6. According to some embodiments, which can be combined with other embodiments described herein, the evaporation source 200 may include a shield 204. The shield 204 may reduce the heat radiation towards the deposition area. Further, the shield 204 may be cooled by a cooling element 216. For example, the cooling element 216 may be mounted to the shield 204 and may include a conduit for cooling fluid.

[0057] With exemplary reference to FIG. 7 embodiments of a deposition apparatus according to the present disclosure are described.

[0058] FIG. 7 shows a schematic top view of a deposition apparatus 300 for applying material to a substrate 333 in a vacuum chamber 310 according to embodiments described herein. According to embodiments which can be combined with other embodiments described herein, the deposition apparatus 300 includes an evaporation source 200 as described herein. In particular, the evaporation source 200 may be provided in the vacuum chamber 310 of the deposition apparatus 300, for example on a track, e.g. a linear guide 320 or a looped track. The track or the linear guide 320 may be configured for a translational movement of the evaporation source 200. Accordingly, a drive for the translational movement can be provided for the evaporation source 200 at the linear guide 320 within the vacuum chamber 310. According to embodiments which can be combined with other embodiments described herein, a first valve 305, for example a gate valve, may be provided which allows for a vacuum seal to an adjacent vacuum chamber (not shown in FIG. 7). The first valve can be opened for transport of a substrate 333 or a mask 332 into the vacuum chamber 310 or out of the vacuum chamber 310.

[0059] According to some embodiments which can be combined with other embodiments described herein, a further vacuum chamber, such as maintenance vacuum chamber 311 may be provided adjacent to the vacuum chamber 310, as exemplarily shown in FIG. 7. Accordingly, the vacuum chamber 310 and the maintenance vacuum chamber 311 may be connected with a second valve 307. The second valve 307 may be configured for opening and closing a vacuum seal between the vacuum chamber 310 and the maintenance vacuum chamber 311. The evaporation source 200 can be transferred to the maintenance vacuum chamber 311 while the second valve 307 is in an open state. Thereafter, the second valve 307 can be closed to provide a vacuum seal between the vacuum chamber 310 and the maintenance vacuum chamber 311. If the second valve 307 is closed, the maintenance vacuum chamber 311 can be vented and opened for maintenance of the evaporation source 200 without breaking the vacuum in the vacuum chamber 310.

[0060] As exemplarily shown in FIG. 7, two substrates may be supported on respective transportation tracks within the vacuum chamber 310. Further, two tracks for providing masks thereon can be provided. Accordingly, during coating, the substrate can be masked by respective masks. For example, the mask may be provided in a mask frame 331 to hold the mask 332 in a predetermined position.

[0061] According to some embodiments which can be combined with other embodiments described herein, the substrate 333 may be supported by a substrate support 326, which can be connected to an alignment unit 312. The alignment unit 312 may adjust the position of the substrate 333 with respect to the mask 332. As exemplarily shown in FIG. 7, the substrate support 326 may be connected to the alignment unit 312. Accordingly, the substrate may be moved relative to the mask 332 in order to provide for a proper alignment between the substrate and the mask during deposition of the material, which may be beneficial for high quality display manufacturing. Alternatively or additionally, the mask 332 and/or the mask frame 331 holding the mask 332 can be connected to the alignment unit 312. Accordingly, either the mask 332 can be positioned relative to the substrate 333 or the mask 332 and the substrate 333 can both be positioned relative to each other.

[0062] As shown in FIG. 7, the linear guide 320 may provide a direction of the translational movement of the evaporation source 200. On both sides of the evaporation source 200, a mask 332 may be provided. The masks may extend essentially parallel to the direction of the translational movement. Further, the substrates at the opposing sides of the evaporation source 200 can also extend essentially parallel to the direction of the translational movement. As exemplarily shown in FIG. 7, the evaporation source 200 provided in the vacuum chamber 310 of the deposition apparatus 300 may include a support 202 which may be configured for the translational movement along the linear guide 320. For example, the support 202 may support two evaporation crucibles and two distribution assemblies, particularly two distribution pipes, provided over the respective evaporation crucible. According to some embodiments, the support 202 may support three evaporation crucibles and three distribution pipes provided over the respective evaporation crucible. Accordingly, the vapor generated in the evaporation crucible can move upwardly and out of the one or more outlets of the distribution pipe. The distribution pipes of the evaporation source may have a substantially triangular cross-section. As described with reference to FIG. 6, a triangular shape of the distribution pipe makes it possible to bring the outlets for depositing the evaporated material on a substrate, e.g. nozzles, of neighboring distribution pipes as close as possible to each other. This allows for achieving an improved mixture of different materials from different distribution pipes, e.g. for the case of the co-evaporation of two, three or even more different materials.

[0063] In view of the above, it is to be understood that by employing a method of pretreating an oscillation crystal for measuring a deposition rate beneficially provides for an improved deposition rate measurement device, an improved evaporation source as well as for an improved deposition apparatus, particularly for OLED manufacturing.

[0064] While foregoing is directed to embodiments, other and further embodiments may be devised without departing from the basic scope, and the scope is determined by the claims that follow.

Claims

1. A method of pretreating an oscillation crystal (110) for measuring a deposition rate, the method comprising polarizing a measurement surface (115) of the oscillation crystal.

2. The method of claim 1, wherein polarizing the measurement surface (115) of the oscillation crystal (110) comprises conducting an oxygen treatment of the measurement surface of the oscillation crystal.

3. The method of claim 2, wherein conducting the oxygen treatment comprises conducting a plasma treatment.

4. The method of claim 3, wherein conducting the plasma treatment comprises using a plasma comprising an oxygen content of more than 0.5%, particularly more than 20%.

5. The method of any of claims 1 to 4, wherein polarizing the measurement surface (115) of the oscillation crystal (110) comprises exposing the measurement surface of the oscillation crystal to ultraviolet (UV) light, particularly in an oxygen containing environment.

6. The method of claim 4 or 5, wherein the oxygen of the plasma is in the form of 0₂ and/or in the form of 0_3.

7. The method of any of claims 2 to 6, wherein the oxygen treatment is conducted for a time period t of 0.5 min < t < 10 min, particularly 1 min < t < 5min.

8. The method of any of claims 2 to 7, wherein the oxygen treatment is conducted at a temperature T of l0°C < T < 80°C, particularly l5°C < T < 50°C.

9. A method of pretreating an oscillation crystal (110) for measuring a deposition rate, the method comprising pretreating a measurement surface (115) of the oscillation crystal with an oxygen containing plasma, wherein pretreating is conducted at a temperature of l0°C < T< l00°C for a time period t of 1 min < t < l5min.

10. A deposition rate measurement device (100) comprising an oscillation crystal (110) for measuring a deposition rate, wherein the oscillation crystal (110) has a polarized measurement surface (115P).

11. The deposition rate measurement device (100) of claim 10, wherein the polarized measurement surface (115P) has been polarized by conducting a method of pretreating an oscillation crystal according to any of claims 1 to 9.

12. An evaporation source (200) for evaporation of material, comprising:

- an evaporation crucible (210), wherein the evaporation crucible is configured to evaporate a material;

- a distribution assembly (220) with one or more outlets (222) provided along a length of the distribution assembly for providing evaporated material, wherein the distribution assembly is in fluid communication with the evaporation crucible; and

- a deposition rate measurement device (100) according to claim 10 or 11.

13. The evaporation source (200) according to claim 12, the distribution assembly (220) comprising a measurement outlet (151) for providing the evaporated material to the oscillation crystal (110) of the deposition rate measurement device (100).

14. The evaporation source (200) according to claim 13, wherein the

distribution assembly (220) is a distribution pipe, wherein the

measurement outlet (150) is provided at an end portion of the distribution pipe, particularly at a backside (224A) of the end portion of the distribution pipe, and wherein the deposition rate measurement

device (100) is arranged such that the oscillation crystal (110) faces the measurement outlet (115).

15. A deposition apparatus (300) for applying material to a substrate (333) in a vacuum chamber (310) at a deposition rate, comprising at least one evaporation source (200) according to any of claims 12 to 14.