TWI791534B - Method of depositing OLED - Google Patents

Abstract

The invention relates to a device and a method for depositing layers on a substrate (5), wherein in a preparatory step a first mass of starting material is deposited on the storage face of the storage element (1), and In the coating step the starting material is evaporated from the storage surface and the measured mass of the starting material is fed by means of the carrier gas (C) into the process chamber (2), where on the substrate (5) there will be A layer of starting material or reaction product of starting material is deposited on the substrate (5). A mass greater than at most 10 percent of the measured mass, but preferably just the measured mass, is deposited on the storage surface in the preparatory step and evaporated by heating during the coating step.

Description

Methods of Depositing OLEDs

The invention relates to a method for depositing a layer on a substrate, wherein in a preparatory step a first mass of starting material is deposited on the storage surface of a storage element and in a coating step the starting material is freed from The storage surfaces are evaporated and the measured mass of the starting material is transported by a carrier gas into a process chamber where a layer with the starting material or a reaction product of the starting material is deposited on a substrate on this substrate.

WO 2012/175128, WO 2012/175126 and WO 2012/175124 A1 disclosed a method of the same type. The solid foam forms, with its open-celled walls, storage surfaces on which, in a preparatory step, the previously evaporated organic starting material is deposited. In the coating step, this solid foam is heated to a constant evaporation temperature. The carrier gas flow is passed through a storage element where the evaporated starting material is fed at a constant evaporation rate. The temporally constant vapor flow produced by the above-mentioned measures is fed into the process chamber of the deposition reactor, in which the substrates are placed on cooled substrate holders. A starting material or a reaction product of the starting material is deposited on the surface of the substrate.

US 7,238,389 describes a device having a powder evaporator for evaporating powder which feeds steam into a solid foam used as a source of steam.

DE 10 2011 051 260 A1 describes an aerosol generator for generating aerosols from stored organic starting materials. This aerosol is fed by means of a carrier gas into an evaporator consisting of a solid foam, to which evaporation energy is supplied from the outside, so that the aerosol particles are evaporated on the surface of this solid foam. The vapor thus generated is fed into the process chamber where the substrate to be coated is arranged.

The object of the present invention is to improve a method of the same type for its use, and in particular to provide means for simplifying the adjustment of the precisely determined mass of the starting material fed into the process chamber.

This object is achieved by means of the inventions given in the claims, wherein the dependent item is not only an advantageous improvement of the invention given in the independent item, but also an original solution to the purpose. Each feature of the claimed patent scope can be combined with each feature of other claimed patent scope arbitrarily.

The method of the invention is firstly and substantially improved by depositing, in the preparatory step, a predetermined mass of the starting material on the storage surfaces. The mass may be exactly the mass deposited during the coating step. The total mass of the starting material deposited on the storage surfaces may be slightly greater than the mass reevaporated during the coating step, wherein the mass difference is a maximum of 10 percent, preferably a maximum of 1 percent. The advantage of a certain "overfilling" of the reservoir is that constant energy pulses of approximately constant length or constant energy can be used for evaporation and this coating step can be extremely short. For technical reasons, the steam generation rate decreases approximately exponentially at the end of the energy application, so that the steam generation is stopped when only less than 10 percent of the stored mass remains on the storage surface. The evaporation process is preferably stopped when less than 1 percent of the stored mass is present on the storage surface. Nevertheless, the time of energy application for evaporating the starting material is not critical compared to conventional methods, since the evaporation rate decreases exponentially at the end of the evaporation step and the emitted mass is easily kept within tolerances. If the storage element has undergone the relevant process and carries a small amount of starting material on its storage surface, just the determined mass of the starting material can be deposited on the storage surface. In the coating step, the mass of starting material deposited on the storage surface is completely evaporated up to the above-mentioned remaining amount within the tolerance range and fed into the process chamber.

In the case of the method according to the invention for depositing a layer on a substrate, a precisely measured amount of powder is fed into the process chamber as a vapor amount by means of a carrier gas. There the layers are deposited on the substrate. In the prior art, this amount of steam is determined by the following way: the steam generator first enters into an operating state where it generates a constant steam rate. The carrier gas flow then introduces a temporally constant mass flow of the starting material into the process chamber. This quantity is determined within a defined time period during which this temporally constant mass flow is fed into the process chamber. According to the invention, the storage element is charged with precisely determined amounts of the starting material. This can be done in the same device that is also used to carry out the coating step. The carrier gas-vapor mixture is fed via a delivery tube into a gas-permeable storage element, but its condensation surface is kept at a low temperature, in particular at room temperature. The temperature of the storage element is preferably at least 20°C below the condensation temperature of the starting material. The vaporous starting material can be generated for filling the storage element in various ways, for example the amount of starting material can be weighed out and completely evaporated in a crucible and the vapor condensed on the storage surface of the storage element. As an alternative, however, an aerosol or particle flow can be generated which is evaporated in an evaporator, wherein a steady flow of vapor is generated and the time of storage on the storage surface is determined by the time of vapor deposition. amount of starting material. It is also possible to deposit solid or liquid constituents of the aerosol or particle flow directly on the storage surface of the storage element. The material deposited on the storage surface is determined here over the period of time during which the aerosol is applied. In the case of this method, the evaporation rate or aerosol generation rate of the starting material in the evaporator or aerosol generator can be varied over time if the time average of the evaporation rate or aerosol generation rate does not change. completely changed. Furthermore, the method of the invention allows the temporal separation of the preparation step and the coating step. There are options to simultaneously charge several storage elements each with precisely determined masses of the starting material, or to store storage elements with precisely determined masses and to use them as required. During the coating step, an energy pulse is applied to the storage element. This can be done by energizing, ie by feeding in electrical energy. After energy application, the temperature of the storage element continues to rise until reaching a maximum temperature which is higher than the condensation or evaporation temperature of the starting material but lower than the temperature at which the starting material undergoes a chemical or physical transformation. The starting materials refer to the organic starting materials used in the manufacture of OLEDs. As the cooler storage element is heated from room temperature or a higher temperature below the condensation temperature to a maximum temperature, the temperature of the storage surface continues to rise. A temperature ramp is formed to a certain extent. The steam generation rate therefore varies during the coating step. The steam generation rate rises from zero and reaches a maximum value. After all the starting material stored in the storage element has been evaporated, the evaporation rate drops back to zero after a maximum value. By means of the invention, reproducible quantities of material are evaporated in a hotter evaporator with a higher material efficiency and a short residence time period of the material. In series production, several precipitation steps are carried out in succession, wherein several cycles can also be carried out in succession to deposit layers, in which cycles the storage element is first charged and the starting material is subsequently evaporated, wherein , the total mass of the starting material carried by the stored element may be slightly greater than the mass required for the coating step. It is important that when charging, the same amount of starting material is always delivered to the storage surface, preferably only this amount is evaporated from the storage surface in the subsequent coating step. This ensures that a reproducible quality of organic material is evaporated, wherein the tolerances are easy to follow because the vapor generation rate decreases exponentially with increasing evaporation, especially when at least 90 percent of the stored mass is evaporated. Small. Therefore, it is preferable to deposit a discretely defined amount of material in the coating step, i.e. the amount of material just used for the coating step, on the cooler evaporator. The temperature of the evaporator need only be below the evaporation temperature. After the preparatory step (which to some extent refers to the charging step of the evaporator formed by the storage element) can start the coating step by heating the evaporator with energy pulses so that the deposits on the storage surface The above material is substantially completely evaporated, that is, evaporated to a technically acceptable margin. The coating step can be shorter than the preparation step. The material stored on the storage surface can be substantially completely evaporated within seconds. Subsequently, the evaporator, ie the storage element, is recooled and recharged after reaching a temperature below the evaporating temperature. Substrate changes can be performed within the process chamber during loading, ie during preparation steps. The storage element is preferably charged by condensing the organic starting material transported as vapour, so that the storage element constitutes the condensate carrier.

1‧‧‧storage element

2‧‧‧Process room

3‧‧‧Gas inlet components

4‧‧‧Substrate rack

5‧‧‧substrate

6‧‧‧Transportation channel

7‧‧‧Conveying pipe

C‧‧‧carrier gas

H‧‧‧thermal power

Q‧‧‧quantity

V‧‧‧Steam

t‧‧‧time

Embodiments of the present invention are described below according to the accompanying drawings. Wherein: Fig. 1 is the device that is used for storing element 1 charging, as shown schematically in Fig. 2, this device can be the part of coating equipment, but also can be separated from it in space, Fig. 2 is coating device , FIG. 3 is the time curve of the steam generation rate of the steam source in the prior art (WO 2012/175128), and FIG. 4 is the steam generation rate of the steam source of the present invention.

FIG. 1 shows a device for charging a storage element 1 which performs the function of a condensate carrier as a storage medium for storing precisely measured quantities of organic starting materials. In addition, the storage element 1 has the function of an evaporator. The evaporator is constructed of an electrically conductive solid foam as described in WO 2012/175128 or US 7,238,389.

During the preparatory steps for charging the storage element 1 with the organic starting material, the temperature of the storage element 1 is below the condensation temperature of the organic starting material. The storage element 1 can be cooled in order to dissipate the heat of condensation. However, the storage element can also have a temperature sufficiently low that it does not reach the evaporation temperature when the starting material fed in vapor form into the device shown in FIG. 1 condenses.

The apparatus shown in FIG. 1 has a delivery duct 7 through which a carrier gas C transports a previously generated vapor V of the organic starting material. In the region of the expanded cross-section of the delivery tube 7 there is a storage element 1 made of an electrically conductive solid foam. The open air chamber wall can be used as a storage surface for steam V to condense.

The steam fed into the duct 7 can be generated by means of a device, which is disclosed in the prior art cited at the opening. In particular, an aerosol generator can be provided for generating an aerosol flow which is evaporated in an upstream further evaporator. However, it is also possible to weigh out a predetermined mass of the organic starting material and heat it in a crucible, and to conduct the resulting vapor V through the delivery pipe 7 towards the storage element 1, whereupon the resulting vapor V is completely condensed in the storage element 1. storage surface of the component. However, it is also possible to charge the storage element 1 by dusting it with powder or by allowing the liquid to solidify. When using the preferred method for steam generation, all the steam V flowing through the delivery pipe 7 condenses on the storage surface of the storage element 1 .

Such storage elements 1 filled with precisely determined quantities of organic starting materials can be stored for later use. In particular, however, the storage element 1 is charged with organic material in the same device which is also used to generate the vapor which is fed into the process chamber 2 for the deposition of the layers.

Figure 2 shows such a device. During the coating step following the preparation step, the carrier gas flow without steam is fed through the delivery channel 6 . The carrier gas flow C passes through the storage element 1, which is heated by feeding thermal energy H. During this process, the temperature of the storage element 1 changes continuously until it is higher than the evaporation temperature of the organic starting material. The heating power H can be supplied by passing an electric current through the electrically conductive storage element 1 .

The evaporation rate in the storage element 1 increases as the temperature increases, until a certain temperature is reached, and the evaporation rate reaches a maximum value (see FIG. 4 ). As the material stored in the storage element 1 is gradually depleted, the mass of organic starting material stored in the storage element 1 is approximately completely evaporated and the coverage of the condensate on the storage surface is less than 50 or 100 percent. In the case of 20/10, the evaporation rate drops to approximately zero. That is, the evaporation rate generally decreases exponentially with time. At an evaporation rate equal to only one percent of the maximum evaporation rate, the energy delivery stops.

Thus, the coating step can generate a flow of vapor flowing through the conveying channel 6 with a continuously changing flow of material.

The delivery channel 6 connects the storage element 1 with the gas inlet member 3, which is arranged in the process chamber 2 and is kept at a temperature above the condensation temperature of the vapor so that 6 The transported steam runs through the gas inlet member 3 completely. The gas inlet member 3 has several nozzles arranged in a mesh shape on the exhaust surface facing the substrate holder 4 . The carrier gas C, which exits from the showerhead-shaped gas inlet element 3 and transports the vapor, transports the vapor V in the direction of the substrate 5 arranged on the cooled substrate holder 4, where a reproducible portion of the vapor condenses as a layer Or a reaction takes place so that the reaction product is deposited as a layer on the substrate 5 .

Fig. 4 shows the steam generation rate generated by the steam source of the present invention, ie the storage element 1, while Fig. 3 shows the steam generation rate of the steam source in the prior art. After the stabilization time of the sharp change in the steam generation rate, the steam generation rate reaches a steady state in which the steam generation rate does not change over time. The quantity Q fed into the process chamber 2 is defined by the feed time during which a steady stream of vapor is fed into the process chamber 2 .

In the method according to the invention ( FIG. 4 ), the stored mass, in particular the condensate mass, of the organic starting material deposited on the storage surface of the storage element 1 forms the quantity Q fed into the process chamber 2 .

The layers to be deposited on the substrate are in particular in the form of several laminated individual layers, wherein each individual layer is deposited in such a way that the storage element 1 is first charged with a starting material in a preparatory step, wherein, Always deposit the same mass on the storage surface of the storage element 1, wherein this mass is approximately the same as the mass evaporated by the storage element 1 again in the coating step after the preparation step, so that after each coating step, An approximately equal residual mass remains on the storage surface, wherein this residual mass preferably only partially covers the storage surface. In the coating step, the storage element 1 is emptied to such an extent that the coverage of the storage surface with the starting material is below 20 percent, and wherein the coverage of the storage surface with the starting material is 100 percent before step.

The aforementioned embodiments are used to illustrate the inventions included in the application as a whole, and these inventions are independently improved solutions relative to the prior art through at least the following combination of features, wherein two, several or more of these feature combinations can also be combined All combined with each other, that is:

A method, characterized in that in the preparation step a mass greater than at most 10 percent of the measured mass, but preferably just the measured mass, is deposited on the storage surfaces during the coating step This mass was evaporated.

A method, characterized in that the starting material is evaporated from the storage surfaces by heating the storage element 1 with the evaporation rate of the starting material varying over time.

A method, characterized in that the storage element 1 has in the preparation step a temperature below the condensation temperature of the starting material, in particular at least 20° C. below the condensation temperature, and in the coating step from this temperature Heating to a temperature above the condensation temperature of the starting material, wherein the temperature of the storage element 1 continues to rise.

A method, which is characterized in that a solid foam is used as the storage element 1 , which is electrically conductive and which heats the storage element 1 by energizing it.

A method, characterized in that an energy pulse is applied to the storage element 1 in order to evaporate the starting material stored on the storage surfaces.

A method, characterized in that in the preparatory step a carrier gas C transports the starting material towards the storage element 1 as a stream of particles, an aerosol or in a vapor-like state.

A method, characterized in that, in several successive steps, a pre-determined mass of the starting material is deposited on the storage surfaces in a preparatory step and is subsequently applied by means of energy in the coating step The same mass is evaporated, wherein, in particular after the coating step, a maximum of 10 percent of the mass deposited on the storage surfaces before the coating step started is still present on the storage surfaces.

A method, characterized in that a preset energy is used for vaporization.

All disclosed features, either individually or in combination, are essential to the invention. Therefore, the disclosed content of this application also includes all the content disclosed in the relevant/attached priority files (copy of the earlier application), and the features described in these files are also included in the scope of the patent application of this application. The dependent items describe the features of the improvement solution of the present invention to the prior art with its features, and the main purpose is to make a divisional application on the basis of these claims. Furthermore, the invention given in each claim may have one or more of the features disclosed in the preceding description, in particular indicated by elements and/or given in the list of elements. The invention also covers embodiments in which individual ones of the aforementioned features are not achieved, especially if these features are not indispensable for a particular application or can be replaced by other equivalent means.

1‧‧‧storage element

2‧‧‧Process room

3‧‧‧Gas inlet components

4‧‧‧Substrate rack

5‧‧‧substrate

6‧‧‧Transportation channel

7‧‧‧Conveying pipe

C‧‧‧carrier gas

H‧‧‧thermal power

V‧‧‧Steam

Claims (10)

A method for depositing a layer on a substrate (5), wherein in a preparatory step a first mass of starting material is deposited by condensation on storage surfaces of a storage element (1), wherein the temperature of the storage surfaces is being below the condensation temperature of the starting material, and evaporating the starting material from the storage surfaces during the coating step, wherein the storage surfaces are heated to a temperature above the condensation temperature of the starting material, and by The measured mass of the starting material is fed by a carrier gas (C) into a process chamber (2), wherein a layer system with the starting material or a reaction product of the starting material is deposited on the substrate (5), which It is characterized in that a mass greater than at most 10 percent of the measured mass is precipitated in the preparation step and evaporated in the coating step. The method of claim 1, wherein the measured mass is just deposited on the storage surfaces in the preparation step and the mass is evaporated in the coating step. The method of claim 1 or 2, wherein the starting material is evaporated from the storage surfaces by heating the storage element (1) with the evaporation rate of the starting material varying over time . The method according to claim 1 or 2, wherein the storage element (1) has a condensation temperature at least 20°C lower than that of the starting material in the preparation step. °C, and heating from this temperature to a temperature above the condensation temperature of the starting material during the coating step, wherein the temperature of the storage element (1) continues to rise. The method according to claim 1 or 2, wherein a solid foam is used as the storage element (1), the solid foam has electrical conductivity and heats the storage element (1) by passing electricity. A method according to claim 1 or 2, wherein an energy pulse is applied to the storage element (1) in order to evaporate the starting material stored on the storage surfaces. The method as claimed in item 1 or 2, wherein, in the preparation step, the carrier gas (C) will be The starting material is transported towards the storage element (1) as a stream of particles, as an aerosol or in a vapor-like state. The method of claim 1 or 2, wherein, in several successive steps, a predetermined mass of the starting material is deposited on the storage surfaces respectively in the preparation step, and then applied to the storage surfaces by energy The same mass is evaporated during the coating step. The method of claim 8, wherein, after the coating step, at most 10 percent of the mass deposited on the storage surfaces before the coating step begins is still present on the storage surfaces. The method according to claim 1 or 2, wherein a preset energy is used for evaporation.

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