WO2021230859A1

WO2021230859A1 - Evaporation source, evaporation system, and method of monitoring material deposition on a substrate

Info

Publication number: WO2021230859A1
Application number: PCT/US2020/032464
Authority: WO
Inventors: Avishek GHOSH; Bhaskar PRASAD; Krishnakumar DURAISWAMY; Naga Deepika BEVARA; Srinivas Salugu
Original assignee: Applied Materials, Inc.
Priority date: 2020-05-12
Filing date: 2020-05-12
Publication date: 2021-11-18

Abstract

An evaporation source is described. The evaporation source includes an evaporation crucible evaporating a material; a distribution pipe in fluid communication with the evaporation crucible, the distribution pipe having a plurality of outlets, the outlets providing nozzles directed in a vapor emission direction towards a substrate; an excitation source emitting electromagnetic radiation; a beam guiding element guiding the electromagnetic radiation along an excitation beam path crossing the vapor emission direction; a first detector for detecting a first signal travelling along a first signal beam path, the first signal beam path having a first signal direction crossing the vapor emission direction and crossing the excitation beam path; and a spectrometer or a filter provided upstream of the first detector in the first signal beam path.

Description

EVAPORATION SOURCE, EVAPORATION SYSTEM, AND METHOD OF MONITORING MATERIAL DEPOSITION ON A SUBSTRATE

FIELD

[0001 ] The present disclosure relates to in-situ metrology, particularly of in-situ metrology of a deposition rate or in-situ measurement for control of a deposition rate. The present disclosure relates to metrology for a deposition source and/or in an evaporation system for use in a vacuum installation, a coating installation including the evaporation system, and a method of using the same. The disclosure particularly relates to an organic evaporation system with a measurement system for measuring a deposition rate, a coating installation having such an evaporation system and a method for use thereof. Specifically, embodiments of the present disclosure relate to an evaporation source, an evaporation system for evaporating a material to be deposited on a substrate, and a method of monitoring material deposition on a substrate.

BACKGROUND

[0002] Organic evaporators are a tool for the production of organic light-emitting diodes (OLED). OLEDs are a type of light-emitting diodes in which the emissive layer comprises a thin-film of certain organic compounds. Such systems can be used in television screens, computer displays, portable system screens, and so on. OLEDs can also be used for general space illumination. The range of colours, brightness, and viewing angle possible with OLED displays are greater than viewing angle of traditional LCD displays because OLED pixels directly emit light and do not require a back light. Therefore, the energy consumption of OLED displays is considerably less than the energy consumption of traditional LCD displays. Further, the fact that OLEDs can be printed onto flexible substrates opens the door to new applications such as roll-up displays or even displays embedded in clothing.

[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, it is therefore beneficial that the coating rate at which the coating with organic material is effected lies within a predetermined tolerance range. In other words, the coating rate of an organic evaporator has to be controlled thoroughly in the production process.

[0004] In order to do so, it is known in the art to use so called oscillating crystals for the determination of the coating rate. The measurement of the actual oscillating frequency of these oscillating crystals allows the conclusion on the actual coating rate. However, these crystals are also coated with organic material in the coating process. Therefore, the crystals have to be replaced periodically because they tolerate only a limited amount of material coating. This reduces their usability particularly in large scale production plants with very long service lives. Furthermore, in order to replace the oscillating crystals, interventions into the vacuum chamber are necessary. Regenerating the vacuum is time-consuming and expensive. Revolver type quartz crystal buffers, for example, with an indexing head, have been proposed to utilize one oscillating crystal after the other. Further, choppers have been proposed to elongate the lifetime of the quartz crystal. Yet, deposition rate measurements with a quartz crystal microbalance or a quartz crystal membrane (QCM) have an inherent limitation due to the measurement principle.

[0005] Further, inherent limitations of a QCM include heat load of actuators, for example, motors, for the indexing head and the chopper. The motors can result in electromagnetic interference. A chopper or another shutter results in the deposition rate information being available only at limited times. The utilization is shorter the higher the deposition rate is. Further, an indexing head and/or a chopper results in a plurality of components, and particularly movable parts, that impacts reliability and can, thus, reduce the uptime of the system.

[0006] Alternatively, it is known in the art that the deposited layer is analyzed after the deposition is complete in order to determine the coating rate. In this case, the feedback control of the deposition system is only possible with a certain delay. In particular, this procedure can result in one or more substrates being coated with a layer being out of range before the control can take corrective action. These substrates are rejects.

[0007] In view of the above, apparatuses and methods for improved deposition rate monitoring are beneficial, particularly for monitoring the deposition rate of organic material in a display manufacturing apparatus. SUMMARY

[0008] In light of the above, an evaporation source, an evaporation system for evaporating a material to be deposited on a substrate, and a method of monitoring material deposition on a substrate are provided. Further aspects, advantages, and features are apparent from the dependent claims, the description, and the accompanying drawings.

[0009] According to an embodiment, an evaporation source is provided. The evaporation source includes an evaporation crucible evaporating a material; a distribution pipe in fluid communication with the evaporation crucible, the distribution pipe having a plurality of outlets, the outlets providing nozzles directed in a vapor emission direction towards a substrate; an excitation source emitting electromagnetic radiation; a beam guiding element guiding the electromagnetic radiation along an excitation beam path crossing the vapor emission direction; a first detector for detecting a first signal travelling along a first signal beam path, the first signal beam path having a first signal direction crossing the vapor emission direction and crossing the excitation beam path; and a spectrometer or a filter provided upstream of the first detector in the first signal beam path.

[0010] According to an embodiment, an evaporation system for evaporating a material to be deposited on a substrate is provided. The evaporation system includes a vacuum chamber having a support for supporting a substrate; and an evaporation source according to any of the embodiments described herein, the evaporation source being provided at least partially inside the vacuum chamber.

[0011] According to an embodiment, a method of monitoring material deposition on a substrate is provided. The method includes guiding evaporated material towards a substrate via outlets providing nozzles in a vapor emission direction; guiding an electromagnetic radiation along an excitation beam path crossing the vapor emission direction; and detecting a first signal travelling along a first signal beam path with a first detector, the first signal beam path having a first signal direction crossing the vapor emission direction and crossing the excitation beam path. 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:

FIGS. 1A to 1C show different views of a measurement principle of an in-line metrology or in-situ metrology of a deposition rate of an evaporation source according to embodiments of the present disclosure;

FIG. 2 shows a schematic view of a deposition system or deposition apparatus having a deposition source, for example, an evaporation source, and a deposition rate measurement according to embodiments of the present disclosure;

FIG. 3 shows a schematic view of a measurement arrangement for deposition rate measurement according to embodiments of the present disclosure;

FIGS. 4A and 4B show results of deposition rate measurement utilizing embodiments of the present disclosure;

FIGS. 5A and 5B show different views of an excitation with a laser beam into a vacuum chamber for deposition rate measurement according to embodiments of the present disclosure;

FIG. 6 shows a schematic view of an optical metrology setup for a deposition rate monitor according to embodiments of the present disclosure;

FIG. 7 shows a schematic view of a free space detection of an optical metrology for deposition rate monitor according to embodiments of the present disclosure;

FIG. 8 shows a schematic view of a fiber-optic detection of an optical metrology for a deposition rate monitor according to embodiments of the present disclosure; and FIG. 9 shows a flowchart illustrating a method of monitoring material deposition on the substrate according to embodiments of the present disclosure.

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] Embodiments of the present disclosure related to a laser induced photoluminescence detection, particularly of a molecule density that is directly deposited on the substrate. As compared to previous QCM measurements and other measurements, the molecule density of material deposited on the processed substrate can be measured. According to some embodiments, which can be combined with other embodiments described herein, a measurement of organic material from an evaporation source, particularly for display manufacturing, and more particularly on large area substrates, is provided.

[0015] According to some embodiments, laser induced photoluminescence is detected and may be provided for a closed loop process for deposition rate control. The density of molecules, for example, organic molecules for an organic light emission device (OLED) is measured in front of a nozzle of an evaporation source directing material on the substrate. The density of molecules is measured between the deposition source and the substrate. The characteristic wavelength emission of a photoluminescence can be considered to be proportional to the molecule density or essentially proportional to the molecule density. Accordingly, the deposition rate can be considered to be proportional or essentially proportional to the molecule density. Additional effects like laser bleaching on the organic material may be considered. Yet, it could be shown that the photobleaching rate or the amount of photobleaching of OLED molecules are only induced when OLEDs are excited by laser powers higher than a certain threshold and only in the presence of 02/water vapor-rich environments. In high vacuum conditions, the photobleaching effects are minimal.

[0016] FIG.1A shows a schematic side view of an evaporation source 100. The side view is provided in the x-z-plane. FIG. IB is a corresponding schematic side view in the y-z-plane and FIG. 1C is a corresponding schematic side view in the y-y -plane. The evaporation source 100 includes the evaporation crucible 102 and a distribution pipe 104. The evaporation crucible 102 evaporates the material, for example, the organic material. The distribution pipe 104 is in fluid communication with the evaporation crucible 102. The distribution pipe 104 receives the vapor from the evaporation crucible. The evaporated material is directed towards the substrate 20 through nozzles 105. A plurality of nozzles 105 or outlets are provided in the distribution pipe 104. For example, the nozzles 105 can be arranged in a line. The evaporation source 100 can be a line source. As described with respect to FIG. 2, two or more, for example, three evaporation sources can be provided next to each other. Co-evaporation can be provided, particularly for organic material. According to embodiments of the present disclosure, the evaporation source includes an evaporation crucible evaporating material, particularly, and organic material. The evaporation source further includes a distribution pipe in fluid communication with the evaporation crucible, the distribution pipe having a plurality of outlets or nozzles.

[0017] As shown in FIG. IB and also in FIG. 2, the distribution pipe 104 can be a non-circular distribution pipe. The distribution pipe can be an essentially triangular shaped distribution pipe and/or the side of the distribution pipe having the outlets or nozzles can be smaller than the opposing side of the distribution pipe. Accordingly, for co-evaporation, the nozzles of neighboring distribution pipes can be closer together. Mixing of co-evaporated materials can be improved.

[0018] FIGS. 1A to 1C exemplarily show a plume 115 of evaporated material of one of the nozzles 105. The plume 115 of evaporated material has a main evaporation direction or a mainb evaporation path, i.e. a vapor emission direction 116. The vapor emission direction is provided by the nozzle and is directed towards the substrate 20. A measurement area 130 is provided in the plume of the evaporated material directed towards the substrate 20. The material molecules, for example, the organic molecules are excited in the measurement area. As shown in FIGS. 2 A and 2C, an excitation source 120 is provided. The excitation source can be a laser and emits electromagnetic radiation. The electromagnetic radiation, for example, a laser beam 121 can be guided by a beam guiding element. For example, the beam guiding element can be one or more mirrors 122, one mirror being exemplarily shown in FIG. IB, an optical fiber, one or more beam expanders, one or more lenses, one or more beam splitters, one or more polarizers, one or more windows, one or more filters, one or more apertures, one or more periscopes, and combinations thereof. According to some embodiments, which can be combined with other embodiments described herein, a mirror can be a steering mirror configured to adjust the deflection direction of the beam of electromagnetic radiation.

[0019] The electromagnetic radiation, for example the laser beam 121 can be guided along an excitation beam path. The excitation beam path crosses the vapor emission direction or the vapor emission path, for example, at the measurement area 130. According to some embodiments, which can be combined with other embodiments described herein, the vapor emission direction 116 and the excitation beam path can be essentially perpendicular to each other, for example, can have an angle of 70° to 110°. Some radiation of the laser beam 121 may pass the measurement area 130. A transmitted laser beam 121B may exist depending on the absorption of the molecules in the plume 115 of the evaporated material.

[0020] According to some embodiments, which can be combined with other embodiments described herein, the excitation source can be a laser source. For example, the excitation source can have a wavelength shorter than the photoluminescence emission of the excited material, for example, the organic material. Particularly, the laser source can have a wavelength of 350 to 450 nm, such as 375 to 405 nm, for example around 400 nm.

[0021] According to some embodiments, which can be combined with other embodiments described herein, an array of nozzles or outlets can be provided. For example, the array can be a one-dimensional area such as a line. The measurement area 130 can be provided between the array of nozzles or outlets and the substrate 20. [0022] A characteristic wavelength emission is generated from the plume 115 of evaporated material, particularly in the measurement area 130. Photoluminescence emission 132 is exemplarily shown in FIGS. 1 A and IB. A signal of photoluminescence emission is generated along a first signal beam path 135 towards a first detector 138. The first signal beam path 135 has a first signal direction. The first signal direction crosses the vapor emission direction (or the vapor emission path, respectively) and crosses the excitation beam path. According to some embodiments, which can be combined with other embodiments described herein, the first signal direction has an angle relative to the vapor emission direction 116 and the excitation beam that can be essentially perpendicular. For example, the angle between the first signal direction and the vapor emission direction can be 70° to 110°. The angle between the first signal direction and the excitation beam can be 70° to 110°.

[0023] According to embodiments of the present disclosure, a first detector 138 for detecting a signal traveling along the first signal beam path is provided. For example, the first detector can be a photodetector. Further, a spectrometer or a filter can be provided upstream of the first detector in the first signal beam path. The spectrometer or the filter allows for detection of a specific wavelength or a wavelength range of the photoluminescence signal. Photoluminescence signal count can be associated with the molecule density in the plume 115 of the evaporated material.

[0024] According to embodiments of the present disclosure, the molecule density deposited on a substrate, particularly the processed substrate, can be measured. The molecule density to be deposited on the substrate or deposited on the substrate is directly measured. The geometrical arrangement of the excitation beam path, the vapor emission direction and the signal beam path allow for a direct measurement of the molecule density to be deposited on the substrate in a display manufacturing fabrication, i.e. manufacturing process for displays. Details of the manufacturing process for processing substrates, particularly large area substrate, for display manufacturing are described with respect to FIG. 2.

[0025] FIG. 2 is a schematic view of an evaporation system 200 according to embodiments described herein. The evaporation system 200 includes a vacuum chamber 211 and an evaporation source 100 arranged in the vacuum chamber 211. The evaporation source 100 includes a vapor distribution assembly with a plurality of vapor nozzles. The vapor distribution assembly may include an evaporation crucible in fluid communication with a vapor distribution pipe. The plurality of vapor nozzles may be provided in a front wall of the vapor distribution pipe. The evaporation source further includes a shielding device for at least partially blocking the evaporated source material emitted from the plurality of vapor nozzles, the shielding device being magnetically held at the vapor distribution assembly.

[0026] According to embodiments described herein, the vapor distribution pipe may be a linear distribution pipe extending in a first direction, particularly in an essentially vertical direction. “Essentially vertical” as used herein may be understood to include deviations of 10° or less from an exactly vertical direction. In some embodiments, the vapor distribution assembly may include a vapor distribution pipe having the cross-sectional shape of a cylinder or triangle. In some embodiments, the evaporation source may include two or three evaporation crucibles and two or three associated distribution pipes arranged next to each other on a common support which may be movable.

[0027] As is schematically depicted in FIG. 2, the evaporation source 100 can move past the substrate 20 that is arranged in a first deposition area for depositing the evaporated source material on the substrate 20 through a mask 22, particularly along a linear source path. Thereupon, the vapor distribution assembly can rotate, e.g. by an angle of about 180°, until the plurality of vapor nozzles is directed toward a second substrate 20 that is arranged in a second deposition area on an opposite side of the evaporation source 100. The evaporation source 100 can then move past the second substrate 20 for depositing the evaporated source material on the second substrate 20 through a second mask 22, particularly along a linear source path.

[0028] In some embodiments, a shielding wall 250 may be provided in the vacuum chamber 211 for blocking the evaporated source material during a rotation of the evaporation source from the first deposition area to the second deposition area. The shielding wall 250 may optionally be supported on the same movable support as the vapor distribution pipes and may move together with the evaporation source past the substrate.

[0029] According to some embodiments, which can be combined with other embodiments described herein, an evaporation source for organic material includes an evaporation crucible, wherein the evaporation crucible is configured to evaporate the organic material and a distribution pipe with one or more outlets, wherein the distribution pipe is in fluid communication with the evaporation crucible. The distribution pipe is rotatable around an axis during evaporation. A support for the distribution pipe is provided, wherein the support is connectable to a first drive or includes the first drive, wherein the first drive is configured for a translational movement of the support and the distribution pipe.

[0030] Embodiments described herein particularly relate to deposition of organic materials, e.g. for OLED display manufacturing on large area substrates. According to some embodiments, large area substrates or carriers supporting one or more substrates may have a size of at least 0.174 m². For instance, the deposition system may be adapted for processing large area substrates, such as substrates of GEN 5, which corresponds to about 1.4 m² substrates (1.1 m x 1.3 m), GEN 7.5, which corresponds to about 4.29 m² substrates (1.95 m x 2.2 m), GEN 8.5, which corresponds to about 5.7 m² substrates (2.2 m x 2.5 m), or even GEN 10, which corresponds to about 8.7 m² substrates (2.85 m x 3.05 m). Even larger generations such as GEN 11 and GEN 12 and corresponding substrate areas can similarly be implemented. According to yet further implementations, half sizes of the above-mentioned substrate generations can be processed in the evaporation system 200. Alternatively or additionally, semiconductor wafers may be processed and coated in the evaporation system.

[0031] As shown in FIG. 2, excitation source 120 can be provided. The excitation source 120 can be a laser. According to some embodiments, which can be combined with other embodiments described herein, the excitation source can be provided outside the vacuum chamber 211. Beam guiding elements like a mirror 122 and optionally a beam splitter 222 are provided to guide the beam of electromagnetic radiation, for example, the laser beam 121 into the vacuum chamber 211. The laser beam can be guided through view ports 232 into the vacuum chamber 211. A first portion of the laser beam can be guided to a plume 115 of evaporated material in the first deposition area. A second portion of the laser beam can be guided to a plume of evaporated material if the evaporation source processes the substrate in the second deposition area. According to some embodiments, which can be combined with other embodiments described herein, a first detector 138 can be mounted to the deposition source, for example, vertically above the distribution pipe 104 (see, for example, FIG. 1A). Accordingly, the first detector 138 be supported (indirectly) by the same movable support. The first detector can move together with the evaporation source past the substrate.

[0032] According to some embodiments, which can be combined with other embodiments described herein, one or more of the beam guiding elements can adjust the deflection of the beam of electromagnetic radiation. Accordingly, the measurement area 130 in the plume 115 of evaporated material can be provided at a constant distance from the distribution pipe 104 even though some displacement of the distribution pipe may occur during movement of the evaporation source on the movable support.

[0033] According to one embodiment, an evaporation system for evaporating a material to be deposited on a substrate is provided. The evaporation system includes a vacuum chamber having a support for supporting a substrate and an evaporation source according to embodiments of the present disclosure inside the vacuum chamber. The evaporation source includes an evaporation crucible evaporating a material and a distribution pipe in fluid communication with the evaporation crucible, the distribution pipe having a plurality of outlets, the outlets providing nozzles directed in a vapor emission direction towards a substrate. Further, an excitation source emitting electromagnetic radiation and a beam guiding element guiding the electromagnetic radiation along an excitation beam path crossing the vapor emission direction are provided. A first detector detects a first signal travelling along a first signal beam path, the first signal beam path having a first signal direction crossing the vapor emission direction and crossing the excitation beam path. Further, a spectrometer or filter is provided upstream of the detector in the first signal beam path.

[0034] According to some embodiments, the excitation source can be provided outside the vacuum chamber. Further, at least one of a view port or an optical fiber is provided for guiding the electromagnetic radiation into the vacuum chamber.

[0035] FIG. 3 shows a schematic view of an implementation of a measurement arrangement for deposition rate measurement which can be combined with other embodiments of the present disclosure. Compared to FIG. 2, the excitation beam has been guided through view ports 232, i.e. providing a free space excitation, and the measurement arrangement of FIG. 3 utilizes an optical fiber 321. An excitation source 120, for example, a laser is powered by a power supply 320. The laser beam 121 is coupled into the optical fiber 321 with a fiber coupler 332. For example, an FC/APC coupler (fiber coupler/angled physical contact) can be utilized. The angled physical contact of the coupler can be particularly beneficial for a single mode optical fiber. Having a fiber and a phase which is slightly angled, for example, by 8° eliminates disturbance by reflective light. The optical fiber 321 can be fed through a wall of the vacuum chamber. Inside the vacuum chamber, a fiber collimator 334 can be provided to have the laser beam exiting the optical fiber. For example, an FC/APC fiber collimator can be used.

[0036] According to some embodiments, which can be combined with other embodiments described herein, an intensity attenuator 336, such as variable intensity attenuator can be provided. The intensity attenuator can adjust the excitation entity of the excitation radiation. Additionally or alternatively, a beam splitter 322 and a second detector 342 can be provided. According to some embodiments, the beam splitter can split a small portion of the excitation intensity to the second detector 342. Typically, the small portion can be between 0.5 % to 2% of the intensity incident on the beam splitter. A reference signal can be generated by the second detector. For example, the reference signal can be used to normalize the photoluminescence signal. Variations in the photoluminescence signal resulting from a variation in the intensity of the excitation source can be eliminated by normalization. According to some embodiments, the second detector can be a power meter or a silicon photodiode. The laser intensity can be monitored in the reference path, e.g. to keep monitoring the laser.

[0037] According to some embodiments of the present disclosure, an evaporation source further includes a beam splitter that splits the electromagnetic radiation into a first signal and a second signal traveling along a second signal beam path having a second signal direction. For example, the evaporation source further includes a second detector for detecting the second signal, particularly wherein the second signal is a reference signal.

[0038] The laser beam impinges on the evaporated molecules, for example, organic molecules in the measurement area 130. Photoluminescence signal is generated by excitation of the organic material by the laser beam. A carrier distribution in the molecules can relax within a certain time. A recombination, particularly after relaxation or partial relaxation, of the electrons and holes in the molecule results in comparably narrow emission (photoluminescence) at wavelengths larger than the excitation wavelength, i.e. at a lower energy after the carrier relaxation.

[0039] Photoluminescence occurs inter alia along the first signal beam path 135. A filter 352 is provided between the measurement area 130 and the first detector 138. As described above, the first signal beam path crosses the mission and direction of the evaporated material and the excitation beam path. FIG. 3 shows a schematic drawing only and the first signal beam path 135 is not in the paper plane of FIG. 3. For example, the filter 352 can be a long wavelength path filter.

[0040] According to some implementations, further optical elements like a collector lens 354 can be provided. Additionally or alternatively, a condenser can be provided. For example, the further optical elements can be threaded to the first detector. According to some embodiments, which can be combined with other embodiments described herein, the first detector can be a photodiode, particularly a silicon photodiode. According to yet further implementations, which can be combined with other embodiments described herein, a switchable gain detector may be provided. According to embodiments of the present disclosure, a switchable gain detector allows to switch between different amplifications. Accordingly, measurements can be conducted for various luminescence intensities.

[0041] According to some embodiments, the detector may include a CCD camera, a CMOS detector or another detector having at least one line of pixels, e.g. an array of pixels. A spectrum may be detected by the pixels in combination with the spectrometer.

[0042] The first detector 138, the filter and optional further optical elements provide a first detection arrangement 360. According to some embodiments, a second detection arrangement 362 and optionally a third detection arrangement 364 can be provided. The count of photons from the photoluminescence can be increased due to the further detection arrangements.

[0043] For example, FIG. 4A is a graph 450 illustrating a first photoluminescence (PL) intensity spectrum 452, a second PL intensity spectrum 454, and a third PL intensity spectrum 456. The PL intensity is shown as a function of the wavelength. The intensity spectra are generated via photoluminescence measurement, e.g. with the first detection arrangement 360. A PL peak intensity variation with respect to the film thickness can be observed. The molecule density in the plume 115 results in a different thickness of Tris(8- hydroxyquinoline)aluminum(III), known as A1Q3. Specifically, PL intensity spectrum 452 is generated for a first A1Q3 layer that is 10 nm thick, PL intensity spectrum 454 is generated for a second A1Q3 layer that is 30 nm thick, and PL intensity spectrum 456 is generated for a third A1Q3 layer that is 50 nm thick. The magnitude of the peak intensities of PL intensity spectra, which is shown in FIG. 4B, varies significantly as a function of the molecule density. This is shown in graph 460.

[0044] The examples shown above are measured with a laser power of smaller than 0.5 pW and an excitation of 405 nm. An acquisition time of 100 ps has been provided. According to some embodiments, which can be combined with other embodiments described herein, the power of the excitation source 120 or the power of the excitation radiation in the measurement area can be limited to avoid laser bleaching of the organic material. Accordingly, the power of excitation light can be limited to 1 pW or below. In other embodiments, the power of excitation light can be varied depending on the organic material evaporated by the evaporation source and the duration of exposure of the organic material to excitation light. Thus, in some embodiments, the power of excitation light can be as much as about 10 pW or below.

[0045] FIGS. 5A and 5B show schematic views of an implementation of a measurement arrangement for deposition rate measurement that can be combined with other embodiments of the present disclosure. As compared to FIG. 3, wherein the excitation beam is guided via an optical fiber, FIGS. 5A and 5B show a laser beam coupling through a view port 232. According to some embodiments, which can be combined with other embodiments described herein, a view port 232 can be provided in a wall 213 of the vacuum chamber 211 (see FIG. 2). FIG. 5 A is an exemplary top view of a laser emission coupling into a vacuum chamber. FIG. 5B is an exemplary top view of a laser emission coupling into a vacuum chamber.

[0046] An excitation source 120, for example, a laser is powered by, for example a power supply and generates a laser beam 121. The laser beam can be guided by a first mirror 122 and optionally by a second mirror 522. According to yet further implementations, further mirrors or other beam guiding elements can be provided. The first mirror 122 can be a steering mirror. The steering mirror can be tilted to guide the laser beam through the opening of the optical aperture 532. Further apertures can be provided in the beam path of the laser beam. For example, the first mirror 122 and the second mirror 522 can be silver mirrors.

[0047] According to some embodiments, which can be combined with other embodiments described herein, an optical assembly 534 including one or more of polarization optics, neutral density (ND) filters, a beam expander, beam focusing optics, one or more quarter waveplates, one or more half waveplates, and apertures can be provided. The optical assembly adjusts the excitation electromagnetic radiation for interaction with the organic molecules to generate the photoluminescence signal. A quarter waveplate and a half waveplate may change the polarization of the laser beam to adapt excitation of the organic molecules.

[0048] According to some embodiments, a beam splitter 322 and a second detector 342 can be provided. According to some embodiments, the beam splitter can split a small portion of the excitation intensity to the second detector 342. Typically, the small portion can be between 0.5 % and 2 %. A reference signal can be generated by the second detector. For example, the reference signal can be used to normalize the photoluminescence signal. Variations in the photoluminescence signal resulting from a variation in the intensity of the excitation source can be eliminated by normalization. According to some embodiments, the second detector can be a power meter or a silicon photodiode.

[0049] According to yet further implementations, that can be combined with other embodiments described herein, a periscope 540 can be provided. The periscope can be provided by a first periscope mirror 542 and a second periscope mirror 546 to adjust the position of the optical axis of the laser beam. For example, according to some embodiments, which can be combined with other embodiments described herein, the periscope may allow for a movement of the second periscope mirror 546 by 20 mm or more, such as about 100 mm. The axis of the laser beam can be moved by 20 mm or more, such as about 100 mm. The laser beam axis can be adjusted to the view port 232, such as a center of the view port, and/or the plume of evaporated material in the vacuum chamber.

[0050] FIG. 6 schematically illustrates a measurement arrangement similar to the measurement arrangement shown in FIG. 3, wherein an optical fiber 321 is utilized. FIG. 6 illustrates the plume 115 of evaporated material. In the schematic illustration, the plume comes out of the paper plane. The detected photoluminescence signal is in the paper plane, i.e. essentially perpendicular to the evaporation direction.

[0051] The laser beam is generated by the excitation source 120, e.g. a laser, and the laser beam is coupled in the optical fiber 321. On the excitation side, the laser beam is guided out of the fiber with a fiber collimator 334, an optical assembly 534 is shown, and/or a beam splitter 322 guides a portion of the excitation beam to the second detector configured to generate a reference signal. Further details, aspects, features, and implementations may be utilized from other embodiments of the present disclosure. On the detection side, a collector lens 354 and the spectrometer 638 are shown in FIG. 6. The spectrometer provides a spectral resolution that can be detected by the first detector 138, e.g. a CCD camera, a CMOS camera or another pixel camera. Further details, aspects, features, and implementation may be utilized from other embodiments of the present disclosure.

[0052] FIG. 6 shows a first atmospheric box 620 and a second atmospheric box 630. The first atmospheric box can be provided adjacent to the evaporation source 100. The second atmospheric box can be provided adjacent to the evaporation source. For example, with reference to FIG. 2, the first atmospheric box and the second atmospheric box can move together with the evaporation source or an assembly of evaporation sources during deposition of organic material on the substrate, for example, a large area substrate.

[0053] According to embodiments of the present disclosure, and atmospheric box is provided inside a vacuum chamber, i.e. a processing chamber, of the processing system or deposition system. The atmospheric box is provided within a vacuum environment, i.e. at the technical vacuum of 1*10³ mbar or a lower pressure. Inside the atmospheric box, there is essentially atmospheric pressure, i.e. around 1013 mbar, for example 800 mbar to 1200 mbar. A plurality of the optical components, optoelectronic components, and electronic components can be provided in the atmospheric box.

[0054] According to some embodiments, which can be combined with other embodiments described herein, components of a first detection arrangement can be provided in the first atmospheric box 620. For example, one or more of the first detector 138, the filter 352 and the collector lens 354 can be provided in the first atmospheric box 620. The first atmospheric box can be coupled to the evaporation source 100. According to some embodiments, which can be combined with other embodiments described herein, components of an excitation arrangement can be provided in the second atmospheric box the 630. For example, one or more of the fiber collimator 334, the optical assembly 534, the beam splitter 322 and the second detector 342 can be provided in the second atmospheric box 630. The second atmospheric box 630 can be coupled to the evaporation source 100. Coupling of the atmospheric boxes to the evaporation source allows for movement of components of the measurement arrangement together with the evaporation source. The components of the measurement arrangement are carried with the evaporation source if the evaporation source moves, for example, past the substrate for material deposition on the substrate.

[0055] According to some embodiments, which can be combined with other embodiments described herein, an evaporation source or an evaporation apparatus may beneficially include a first atmospheric box, wherein at least the first detector is provided in the first atmospheric box. Further, optionally a second atmospheric box can be provided, wherein at least the second detector is provided in the second atmospheric box.

[0056] FIGS. 7 and 8 show different embodiments of detection arrangements. Some components like the first detector 138, the filter 352 and a view port 622 may be provided in both embodiments to yield yet further embodiments. Generally, FIG. 7 shows a free space detection arrangement and FIG. 8 shows a fiber-optic detection arrangement. According to some embodiments, which can be combined with other embodiments described herein, the first atmospheric box 620 can include a view port 622. The photoluminescence signal can pass into the first atmospheric box 620 through the view port. The view port can be a window. Particularly, the view port can be configured to provide a vacuum pressure on one side of the view port and atmospheric pressure on the other side of the view port. According to some embodiments, which can be combined with other embodiments described herein, an axis of the signal direction can be moved, for example, away and towards the nozzle. For example, the distance to the nozzle can be varied by 10 mm to 40 mm. Accordingly, the position or measurement area in the plume can be varied. This may vary the molecule density to improve the measurement precision. [0057] The photoluminescence signal is filtered by the filter 352. For example, the filter 352 can be a long wavelength pass filter. Embodiments of the present disclosure that are shown in the figures illustrate a filter for spectrally resolved PL measurement. According to further implementations, embodiments may also include a spectrometer to spectrally resolve the PL signal. According to some embodiments, which can be combined with other embodiments described herein, a spectrometer, such as a micro-spectrometer can be provided. The spectrometer can be configured to generate one or more spectral peaks of the first signal. The spectrometer can be photonic crystal based. For example, the spectrometer can include a photonic crystal. The spectrometer may include a Bragg grating.

[0058] As shown in FIG. 7, a free space detection arrangement can include a lens arrangement 854. The lens arrangement 854 can include a collimating lens and a focusing lens. For example, the focusing lens can focus the photoluminescence signal on the first detector 138. According to some embodiments, the first detector includes an avalanche Si photodiode and/or a switchable gain detector. For example, a Si amplified photodetector can be used. The first detector, e.g. an avalanche Si photodiode and/or a switchable gain detector, and a spectrometer are configured to measure photoluminescence light of the material in a plume of evaporated material. A spectrometer can be advantageous to measure individual peaks or individual wavelengths of the luminescence. For example, an improved correlation between molecule density and emission intensity may be provided for specific wavelengths.

[0059] According to some embodiments, which may be combined with other embodiments described herein, the measurement of the photoluminescence in the plume of evaporated material between the nozzle and the substrate may be utilized to measure a host-to-dopant ratio. Particularly, when a spectrometer is used, some wavelengths may show an intensity correlation with the host-to-dopant ratio. Further, additional measurements may be provided to measure the deposition rate and the host-to-dopant ration. Additional measurements may be provided at different wavelengths and/or further measurements, e.g. reflective measurements may be provided.

[0060] As shown in FIG. 8, a fiber optic detection arrangement can include a fiber collector 832 and an optical fiber 821. According to some embodiments, the optical fiber can be a multimode fiber. The multimode fiber can be coupled with a fiber connector 834 to the first detector 138. According to some embodiments, a fiber optic detection may include a fiber collector within the vacuum chamber of the evaporation system and the optical fiber 821 may guide the signal outside the vacuum chamber of the evacuation system. Yet, signal intensity may be increased for a detection within an atmospheric box close to the measurement area 130, and particularly with a free space detection. Accordingly, a free-space detection in an atmospheric box may be beneficial for signal to noise ratio and for adjustment of the signal beam path. Signal losses can be avoided.

[0061] A flow chart illustrating a method of monitoring material evaporation and/or material deposition on a substrate is shown in FIG. 9. In operation 902, a laser is directed to a vapor plume coming out of a nozzle of a distribution pipe. The laser beam crosses the plume, i.e. the vapor emission direction. Laser absorption results in excitation of the molecules in the vapor, e.g. organic molecules. Recombination of the excited molecules results in photoluminescence (see operations 904 and 906). The wavelength emission of the PL can be characteristic for the organic materials illustrated by operation 908. Detection of the PL signal and count, e.g. intensity count of the signal can be provided according to operation 910. According to some embodiments, which can be combined with other embodiments described herein, the PL signal can be monitored with an amplified detector. The signal is measured along the first signal path crossing the excitation direction and the laser beam. The signal count can be translated to a deposition rate by a tooling factor in operation 912.

[0062] According to one embodiment, a method of monitoring material deposition on a substrate is provided. The method includes guiding evaporated material towards a substrate via outlets providing nozzles in a vapor emission direction and guiding an electromagnetic radiation along an excitation beam path crossing the vapor emission direction. A first signal travelling along a first signal beam path is detected with a first detector. The first signal beam path has a first signal direction crossing the vapor emission direction and crossing the excitation beam path. According to some embodiments, the method further includes at least one of: correlating the first signal to a determined amount of the evaporated material, correlating the first signal to a deviation from the amount of the evaporated material, evaluating the first signal with respect to a deviation of a predetermined value for the first signal, and monitoring the first signal as a function of time. Determining the signal as a function of time may result in a floating average of an intensity per time unit, e.g. intensity per second. For example, correlating the first signal to a determined amount of the evaporated material can include determining a deposition rate of the material.

[0063] According to some embodiments, a degradation of the organic material may be determined based on the detected first signal. For example, organic material may degrade upon excessive heat exposure, particularly for times exceeding a predetermined time. The photoluminescence may strongly vary upon degradation. Accordingly, an error signal indicative of material degradation can be provided by a threshold value of the photoluminescence intensity or by a comparable fast changing photoluminescence intensity, i.e. a threshold value of the first derivative of the photoluminescence intensity.

[0064] According to some embodiments, which can be combined with other embodiments described herein, material characteristics of the evaporated organic material can be utilized for evaluation of the PL count. For example, the type of organic material can be provided and information of the material characteristics can be obtained. According to some embodiments, information can be obtained from a database. For example, a function providing as a result the deposition rate depending from the PL intensity count can be obtained, e.g. from a database. Yet further additionally or alternatively, different organic molecules will have different photon signatures that can be utilized e.g. for the choice of a filter or detected wavelength.

[0065] According to embodiments, a deposition rate can be evaluated and/or monitored by detecting the PL intensity in a limited wavelength range or at specific emission peaks, i.e. specific wavelength. Additionally or alternatively, a deviation from the deposition rate or a deviation of the molecule density can be monitored. Accordingly, a deviation from a predefined intensity count is monitored. For the above evaluations and monitoring operations, a closed loop control can be provided. For example, the temperature of the evaporation crucible can be adapted based on the measurement results to adapt the deposition rate online. According to some embodiments of the present disclosure which can be combined with other embodiments described herein, a closed loop control and one or more in-situ measurements can be combined. [0066] Yet further, the photon count (of the PL intensity) can be measured and a stable photon count can be evaluated to ensure a constant molecule density. A variation in photon count can be translated in a change in deposition rate. Accordingly, a predetermined deposition rate can be measured offline and a deviation from the predetermined deposition rate can be measure in- si tu and online.

[0067] FIG. 1C shows a controller 190. The controller is connected to the evaporation crucible 102 and the controller is connected to the first detector 138. The controller can be configured to control a temperature of the evaporation crucible based on a count of the first detector. A closed loop control can be provided.

[0068] In light of the above, one or more of the following advantages can be provided. Embodiments of the present disclosure allow for direct measurement of the molecule density of the material to be deposited on the substrate. A measurement in a vacuum evaporation system can be implemented. Signal intensity and ease of optical adjustment can be improved by measurement within an atmospheric box. Material degradation and/or host-to-dopant ration may further be measured.

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

Claims

1. An evaporation source, comprising: an evaporation crucible evaporating a material; a distribution pipe in fluid communication with the evaporation crucible, the distribution pipe having a plurality of outlets, the outlets providing nozzles directed in a vapor emission direction towards a substrate; an excitation source emitting electromagnetic radiation; a beam guiding element guiding the electromagnetic radiation along an excitation beam path crossing the vapor emission direction; a first detector for detecting a first signal travelling along a first signal beam path, the first signal beam path having a first signal direction crossing the vapor emission direction and crossing the excitation beam path; and a spectrometer or a filter provided upstream of the first detector in the first signal beam path.

2. The evaporation source according to claim 1, wherein the first detector comprises an avalanche Si photodiode and/or a switchable gain detector.

3. The evaporation source according to any of claims 1 to 2, wherein the spectrometer or the filter includes a photonic crystal or a long wavelength pass filter.

4. The evaporation source according to claim 3, wherein the spectrometer is configured to generate one or more spectral peaks of the first signal.

5. The evaporation source according to any of claims 1 to 2, wherein the first detector comprises at least one of a pixel camera, an avalanche Si photodiode and a switchable gain detector, particularly wherein the first detector and a spectrometer are configured to measure photoluminescence light of the material in a plume of evaporated material.

6. The evaporation source according to any of claims 1 to 5, further comprising: a first atmospheric box, at least the first detector is provided in the first atmospheric box.

7. The evaporation source according to any of claims 1 to 6, wherein the evaporation source further comprises a beam splitter splitting the electromagnetic radiation into the first signal and a second signal traveling along a second signal beam path having a second signal direction.

8. The evaporation source according to claim 7, wherein the evaporation source further comprises a second detector for detecting the second signal.

9. The evaporation source according to claim 8, further comprising: a second atmospheric box, at least the second detector is provided in the second atmospheric box.

10. The evaporation source according to any of claims 7 to 9, wherein the second signal is a reference signal.

11. The evaporation source according to any of claims 1 to 10, further comprising: a controller connected to the first detector and connected to the evaporation crucible.

12. The evaporation source according to claim 11, wherein the controller is configured to control a temperature of the evaporation crucible based on a count of the first detector.

13. An evaporation system for evaporating a material to be deposited on a substrate, comprising: a vacuum chamber having a support for supporting a substrate; and an evaporation source according to any of claims 1 to 12 provided at least partially inside the vacuum chamber.

14. The evaporation system according to claim 13, wherein the excitation source is provided outside the vacuum chamber.

15. The evaporation system according to claim 14, further comprising: at least one of a view port or an optical fiber for guiding the electromagnetic radiation into the vacuum chamber.

16. A method of monitoring material deposition on a substrate, comprising: guiding evaporated material towards a substrate via outlets providing nozzles in a vapor emission direction; guiding an electromagnetic radiation along an excitation beam path crossing the vapor emission direction; and detecting a first signal travelling along a first signal beam path with a first detector, the first signal beam path having a first signal direction crossing the vapor emission direction and crossing the excitation beam path.

17. The method of claim 16, further comprising at least one of: correlating the first signal to a determined amount of the evaporated material; correlating the first signal to a deviation of an amount of the evaporated material; evaluating the first signal with respect to a deviation of a predetermined value for the first signal; and monitoring the first signal as a function of time.

18. The method of claim 17, wherein correlating the first signal to the determined amount of the evaporated material comprises: determining a deposition rate of the material.

19. The method according to any of claims 17 to 18; further comprising: obtaining information of material characteristics of the material to correlate or evaluate the first signal.