TW201640111A - Qcm sensor to be cleaned by heating and use thereof in an ovpd coating system - Google Patents

Abstract

The invention relates to a device for determining the concentration of a vapor in a volume (2) and controlling the mass flow of the vapor conveyed through the volume (2) by a carrier gas, wherein the volume (2) can be heated to a temperature above the condensation temperature of the vapor by means of a heating apparatus (8), said device comprising a sensor (1) which provides a sensor signal dependent on the concentration or the partial pressure of the vapor, wherein the sensor (1) has an oscillatory body (17), which can be made to oscillate and the oscillation frequency of which is influenced by a mass accumulation formed on an active surface (18) of the oscillatory body (17) by the condensed vapor, and comprising an evaluating apparatus, which determines the concentration or the partial pressure from the change in the oscillator frequency over time. In order to be able to clean the sensor, the active surface (18) according to the invention is electrically conductive and has electrical contacts (19, 20) for introducing an electrical heating current (I), by means of which the active surface (18) can be heated.

Description

Heatable and cleanable QCM sensor and its application in OVPD coating system

The present invention relates to a device for determining the concentration or partial pressure of steam within a volume, in particular for determining or controlling the mass flow of steam transported by the carrier gas through the volume, wherein the volume can be heated Heating to a temperature above the condensation temperature of the steam, comprising: a sensor providing a sensor signal associated with the concentration or partial pressure of the vapor, wherein the sensor has an oscillatable vibrating body, The oscillation frequency of the vibrating body is affected by the mass accumulation formed by the condensed vapor on the active surface of the vibrating body; and an analyzing device that obtains the concentration or the partial pressure according to the time-dependent change of the oscillator frequency.

Furthermore, the present invention relates to the use of a sensor and a method of cleaning the active surface of a sensor in an OVPD coating system.

"High Temperature Microbalance Sensor Crystal" is commercially available. The sensor is applied to deposition devices of PVD, CVD, ALD and OLED. A single crystal composed of GaPO ₄ (gallium phosphate) has piezoelectric characteristics and can oscillate by about 5.8 Mhz by applying an alternating voltage. The vibrating body formed by the crystal has an active surface facing the steam on which the vapor can be condensed. The condensate/sediment forms a layer and thus a mass buildup which has an effect on the vibration behavior of the vibrating body. Specifically, the frequency of the vibrating body changes. Based on the frequency change per unit time, the vapor phase vapor concentration before the active surface can be inferred so that the vapor partial pressure can be determined.

A description of the QCM sensor and its application in the OVPD method is found in DE 10 2014 102 484.

DE 1 598 401 describes a piezoelectric crystal on which an electrical heating element is formed. It is customary to use a QCM sensor with a heatable sensor face for desorption and to heat the temperature to 120 °C.

The invention also relates to an OLED coating device as described in DE 10 2011 051 931 A1. A susceptor is provided in the deposition reactor, the surface of which is cooled and carries the substrate to be coated. The carrier gas-steam mixture is fed from the intake mechanism to the process chamber, which is heated to a temperature above the vapor condensation temperature. The vapor condenses on the surface of the substrate, wherein the quality of the layer is related on the one hand to the concentration of the vapor in the process chamber (partial pressure) and on the other hand to the surface temperature of the substrate. When carrying out the method of depositing an OLED layer on a substrate, it is preferred to allow steam to flow into the process chamber at a time constant flow rate. Steam is produced in a steam generator by heating a solid or liquid starting material. The starting material can be fed to the evaporation volume in the form of a gas gel. A carrier gas for feeding steam into the process chamber passes through the evaporation volume. The carrier gas is fed to the piping system of the evaporation unit by the mass flow controller. A sensor signal affected by the concentration (partial pressure) of the vapor is obtained through the second sensor.

A so-called QCM (Quartz crystal microbalance) sensor is disclosed in WO 2010/130775 A1, US 2006/0179918 A1 and US Pat. No. 8,215,171 B1. These sensors are applied to a vacuum evaporation device, a so-called VTE (Vacuum thermal evaporation) system. The QCM sensor consists of a quartz crystal that is excited to vibrate at its resonant frequency. For example, when evaporating a metal-containing (e.g., gold) object or evaporating a non-metallic object, a certain amount of vapor condenses in the surface portion of the vibrating body formed by the quartz. The vibrating body is in the prior art The temperature was maintained at about 50 °C during the operation. During the coating procedure, a condensate layer is grown on the surface of the vibrating body. This additional mass detunes the vibrating body, causing the frequency to change over time. This result is based on the so-called Sauerbrey equation. In a conventional application of the QCM sensor, the coating procedure ends when the oscillator frequency reaches a predetermined final value.

After a certain number of coating procedures have been applied, the sensor must be replaced or cleaned to maintain its ability to vibrate because the layer deposited on the quartz crystal acts as a damping effect that affects frequency and amplitude.

In order to remove deposits or condensate from the active side of the vibrating body, it has been proposed to heat the vibrating body to a temperature above the evaporating temperature of the condensate or deposit. The associated heating device has a heating tube that not only heats the vibrating body but also heats the holding device that holds the vibrating body. Therefore, the cleaning process is extremely time consuming. Under poor conditions, the time required to clean the active side of the vibrating body may exceed the time required for the coating procedure.

It is an object of the present invention to improve the efficiency of a coating apparatus, particularly to reduce the cleaning time of the active surface of the vibrating body.

This object is achieved by the invention given in the scope of the patent application.

The coating apparatus has a QCM sensor having a oscillatable vibrating body whose oscillation frequency is affected by mass accumulation (particularly layer) formed by condensed steam on the surface of the vibrating body. The oscillator frequency is related on the one hand to the thickness of the layer and on the other hand to the quality of the layer, ie the physical and chemical properties. The sensor is mounted in a volume of a gas delivery line, and in particular the vapor of the organic starting material is carried by the carrier gas stream through the gas delivery line. The vapor concentration inside the volume of the transfer line can be derived from the rate of change of the resonant frequency of the oscillator formed by the vibrating body. According to the carrier gas that is controlled to be fed into the volume and through the volume of the transfer line The flow rate, and depending on the vapor concentration obtained or the partial pressure obtained, the flow rate (mass/time) of steam entering the coating device can be obtained. Mass accumulation occurs in a few minutes on the surface of the vibrating body composed of crystals, and the sensor cannot be used unless the mass accumulation is removed in advance. The prior art heated the entire crystal to a temperature of about 350 ° C for about 30 minutes. The crystal must then be cooled again. A large amount of heat (energy) needs to be provided. It is desirable to heat this portion through the crystal and to the active surface overlying the layer to be evaporated.

According to the present invention, the vibrating body has an active surface which is electrically conductive and can conduct a heating current, so that only the layer directly adjacent to the surface of the vibrating body needs to be heated, so that the active surface can be evaporated to the deposit or condensed. The temperature of the object. It is sufficient that the conductive surface occupies at least 90% of the flat surface defined by the edges of a prism or cylinder. The conductive surface may be formed by a conductive coating on the surface of the vibrating body. Preferably, the electrodes/contacts are provided on the edge of the face, i.e., at a maximum extent away from each other. The active surface can have a circular contour. However, it can also have a non-circular profile. In this case, there is a maximum length distance between the two opposite edge points on the surface. The distance separating the contacts is preferably more than half the length of the distance. If the vibrating body is an elongated object, the electrodes/contacts are preferably provided on a narrow surface. But it can also be set on a wide surface. The resistance between the electrodes/contacts is preferably between 0.5 ohms and 5 ohms. The electrodes/contacts are connected to the electrical energy source via a feed line through which current generated by the electrical energy source can heat the active surface. The energy required to clean the sensor is much lower than the aforementioned method of heating the entire vibrating body and the holding device holding the vibrating body. It is only necessary to heat the active surface and the volume section of the vibrating body directly adjacent to the active surface. The coating can be composed of a metal such as gold. The contacts can be fused or pressed or bonded to the coating. The coated surface faces the steam. It is particularly beneficial if the surface is heated only substantially, rather than the entire crystal, such as a quartz body. Both the heating time and the subsequent cooling time are in the range of 1-2 minutes. When cooling, this part The heat separation can enter the vibrating body from the heated surface boundary layer. The apparatus constructed in accordance with the present invention can be used not only in the transfer line of the coating apparatus, but also directly in the coating apparatus to measure the vapor concentration or the vapor partial pressure. In the meantime, the specially coated active surface of the vibrating body faces the deposition process, for example facing the susceptor carrying the substrate.

The invention particularly relates to the use of the aforementioned sensor in a gas supply system of an OVPD coating apparatus, the OVPD coating apparatus having a deposition reactor having a chillable susceptor for accommodating one or several The substrate to be coated. With regard to the technical solution of such a gas supply system, please refer to the entire disclosure of DE 10 2014 102 484, the content of which is an integral part of the disclosure of this application.

Embodiments of the invention are described below in conjunction with the drawings.

1‧‧‧ sensor

2‧‧‧ volume

3‧‧‧Evaporation components

4‧‧‧Injector

5‧‧‧ gas gel generator

6‧‧‧ Controller

7‧‧‧Quality Flow Controller

8‧‧‧ heating device

9‧‧‧Deposition reactor

10‧‧‧Air intake mechanism

11‧‧‧Substrate

12‧‧‧ Pedestal

13‧‧‧Transportation pipeline

14‧‧‧Steam feed line

15‧‧‧Cooling channel

16‧‧‧ venting holes

17‧‧‧ crystal

18‧‧‧Active surface

19‧‧‧Electrical contacts

20‧‧‧Electrical contacts

21‧‧‧current source

22‧‧‧ Coating

23‧‧‧Electrode

24‧‧‧ electrodes

25‧‧‧ edge

I‧‧‧heating current

1 is a schematic structural view of an OLED coating apparatus; FIG. 2 is a plan view of the sensor 1; FIG. 3 is a cross-sectional view taken along line III-III of FIG. 2; and FIG. 4 is a second embodiment corresponding to FIG. The view.

The coating apparatus shown in Fig. 1 has a deposition reactor 9. The deposition reactor is an airtight container having a process chamber capable of setting the total pressure to 0.1 mbar to 100 mbar. Specifically, a total control pressure of 0.1 mbar to 10 mbar can be set in the process chamber. The interior of the deposition reactor 9 is provided with a susceptor 12 having a cooling passage 15 through which a coolant can be passed to maintain the susceptor 12 at a definite deposition temperature. The substrate 11 to be coated is laid flat on the top surface of the base.

A showerhead type air intake mechanism 10 is disposed above the base 12, and the air intake mechanism The vapor-carrier gas mixture can be introduced into a process chamber disposed between the susceptor 12 and the air intake mechanism 10. The intake mechanism 10 maintains a temperature above the vapor condensation temperature such that the gaseous starting material is fed into the process chamber and the vapor can condense on the substrate 11. The condensate of steam forms an OLED layer.

The intake mechanism 10 provides a carrier gas-steam mixture from a steam feed line 14, which is produced in the steam generators 2, 3, 4. The heating device 8 maintains the steam generators 2, 3, 4 and the steam feed line 14 at a temperature above the steam condensation temperature but below the steam decomposition temperature.

A carrier gas (e.g., nitrogen) of a clear flow rate is introduced into the evaporators 2, 3, 4 through the mass flow controller 7 through a transfer line 13 forming an inlet.

In an embodiment, the evaporator has a spray chamber into which the sprayer 4 opens to feed the solid to be evaporated or the liquid to be evaporated into the spray chamber in the form of a gas gel. The gas gel enters the high temperature evaporation element 3 where it evaporates. The liquid or solid is from a storage container and is transported by a conveyor. The ejector 4 can be an integral part of the guttata generator 5 which delivers the solid or liquid as a gas gel into the carrier gas stream. The delivery rate of the solid or liquid starting material to be evaporated or the mass flow rate of the carrier gas is specified by the controller 6.

In the evaporation element 3, heat is supplied to the solid to be evaporated or the liquid to be evaporated, in particular the produced gas gel, to change the state of aggregation of the solid or liquid. The starting material exits the evaporation element 3 via a line 14 forming an outlet in the form of steam carried by the carrier gas. The starting material reaches a volume 2 provided with a sensing element 1, which is capable of determining the mass concentration or partial pressure of the vapor inside the volume 2. Thus, the mass flow rate of the steam passing through the line 14 (i.e., the outlet line) connected to the volume 2 can be determined based on the carrier gas mass flow rate set in the mass flow controller 7.

The controller 6 obtains the sensor signal of the sensor 1 or a measurement signal obtained by the sensor signal 1 and proportional to the steam mass flow as an input variable.

The steam mass flow can be adjusted and adjusted by changing the delivery rate of the solid to be evaporated or the liquid to be evaporated or by changing the evaporation temperature of the material to be evaporated and changing the mass flow value provided in the mass flow controller 7. Keep it constant in time.

However, the sensor 1 can also be applied to the deposition reactor 9 to determine the vapor concentration or vapor partial pressure inside the volume between the vent hole 16 and the substrate 11.

2 and 3 show a first embodiment of the sensor 1. The sensor 1 has a crystal 17 which forms a vibrating body. Electrodes 23, 24 are provided on the bottom surface of the crystal 17, and the electrodes are connected to an oscillating means to cause the crystal 17 to vibrate at about 5.8 Mhz. The crystal is a piezoelectric crystal, in particular gallium phosphate. An alternating voltage is applied to the electrodes 23, 24 to excite the piezoelectric crystal to vibrate.

The crystal 17 has a cylindrical shape with a diameter of 10 mm to 15 mm and a thickness of 0.1 mm to 0.5 mm. A conductive layer 22 is coated on the opposite side of the crystal 17 and the contacts 23, 24. The conductive layer can be a metal layer. The conductive coating 22 covers at least 90% of the surface, preferably covering the entire surface. The coating 22 preferably extends to the edge 25 of the end face of the crystal 17.

The coating 22 has a free surface 18. This surface is the active surface of the sensor 1 exposed to steam. Steam can condense on the active surface 18 to exert an influence on the oscillation frequency of the sensor 1.

A measure is provided to selectively heat the active surface 18 of the sensor 1 to a cleaning temperature (e.g., 350 ° C). However, the active surface 18 can also be heated to 450 ° C or even the most Up to 850 ° C temperature. This can result in evaporation of deposits on the active surface 18.

The energy required to heat the active surface 18 is provided electrically. To this end, electrical contacts 19, 20 as shown in Fig. 2 are provided at locations remote from each other on the coating 22. The electrical contacts 19, 20 are disposed at a maximum distance from one another. Therefore, the electrical contacts are preferably located on the edge 25. Figure 2 shows two contact strips 19, 20 which are distributed parallel to one another. However, the contact strips 19, 20 are preferably also distributed directly along the edge 25, i.e., in an arc shape.

The electrical contacts 19, 20 are connected to the electrical energy source 21 via a feed line, which generates a heating current I.

The heating current I is fed into the conductive layer 22 through the electrical contacts 19, 20. Conductive layer 22 has a resistance between 0.5 ohms and 5 ohms such that a voltage drop occurs across contacts 19, 20. Thereby, electrical energy is converted into heat inside the layer 22, so that the active surface 18 is heated, so that the deposit can be evaporated.

It is particularly advantageous if only the volume area of the sensor 1 (especially the crystal 17) directly adjoins the active surface 18 is heated. When the heating time is short, a relatively steep temperature gradient is formed inside the crystal 17, which allows the heated active surface 18 to cool rapidly after the completion of the thermal energy supply.

If the crystal 17 has an appropriate conductivity, it is not necessary to additionally coat the conductive layer 22. The electrothermal energy can be directly supplied to the vibrating body 17 through the appropriate contacts 19, 20.

Fig. 4 shows a second embodiment of the invention, which differs from the first embodiment only in the arrangement of the electrical contacts 19, 20. Here, the electrical contacts 19, 20 extend along the edge 25 of the end face of the vibrating body 17, which is completely coated with a conductive coating 22. The joints 19, 20 are curved along the circular edge 25, for example at an angle of 90[deg.]. The contacts also partially extend along the cylindrical surface of the vibrating body 17 adjacent to the end face.

In the method of the present invention and the apparatus of the present invention, part of the heat transfer is also employed. The active surface of the QCM (Quartz crystal monitor) of HQCM reaches a temperature by locally heating the active surface, at which temperature the deposit deposited on the active surface is removed. This is achieved by selectively introducing a current into the volume region of the vibrating body 17 directly adjacent to the active surface or into the conductive layer 22 coated on the vibrating body 17.

If the vibrating body 17 has a corresponding electrical conductivity, the heated volume is limited to the layer directly adjacent to the active surface 18.

The foregoing embodiments are intended to illustrate the invention as embodied in the present application, and the inventions are each independently constructed at least separately from the prior art by a combination of the following features: a device characterized in that the active surface 18 is electrically conductive and has electrical connections. Points 19, 20 are used to introduce a heating current I, which can be heated by the heating current.

A device characterized in that the conductive surface 18 occupies at least 90% of the flat surface defined by the edge 25 of a prism or cylinder.

A device characterized in that the conductive surface 18 is formed by a conductive coating on the surface of the vibrating body 17.

A device characterized in that the two contacts 19, 20 are spaced apart from each other on the active surface 18 by more than half the maximum distance from one edge to the other.

A device characterized in that the resistance between the contacts 19, 20 is between 0.5 ohms and 5 ohms.

A device characterized in that the contacts 19, 20 are provided in the region of two opposite sections of the rim 25 of the active surface 18.

An application characterized in that by introducing a current I into the electrically conductive surface 18 and thereby heating the active surface 18, evaporation evaporates on the active surface 18 when measuring the concentration or the partial pressure and The oscillating frequency of the vibrating body 17 has an effect on the coating.

A method, characterized in that a heating current I is introduced into a conductive layer directly adjacent to the active surface 18, and the heating surface 18 is heated by the heating current to a temperature higher than an evaporation temperature of the condensate/sediment to thereby evaporate The condensate/sediment is removed from the active face 18.

A method characterized by using a vibrating body 17 composed of GaPO ₄ , in particular, a vibrating body 17 which can be heated to a temperature of at least 450 ° C, preferably to a temperature of 850 ° C.

A device, application or method, characterized in that the means for determining the concentration or partial pressure of steam is part of an OLED coating apparatus and is used to ensure that steam flows into the process chamber at a temporally constant flow rate.

All of the disclosed features (as a single feature or combination of features) are the essence of the invention. Therefore, the disclosure of the present application also contains all the contents disclosed in the related/attached priority file (copy of the prior application), and the features described in the files are also included in the scope of the patent application of the present application. The subsidiary item is characterized by its characteristics for the features of the prior art improvement of the prior art, and its purpose is mainly to carry out a divisional application on the basis of the claims.

1‧‧‧ sensor

17‧‧‧ crystal

18‧‧‧Active surface

19‧‧‧Electrical contacts

20‧‧‧Electrical contacts

21‧‧‧current source

22‧‧‧ Coating

25‧‧‧ edge

I‧‧‧heating current

Claims (14)

A device for determining the concentration or partial pressure of steam in a volume (2), in particular for determining or controlling the mass flow of the steam carried by the carrier gas through the volume (2), wherein the volume (2) a temperature that can be heated by the heating device (8) to a temperature above the condensation temperature of the steam, comprising: a sensor (1) that provides a sensor signal associated with the concentration or partial pressure of the vapor, wherein the sensor The detector (1) has an oscillatable vibrating body (17) whose oscillation frequency is affected by the mass accumulation formed by the condensed steam on the active surface (18) of the vibrating body (17); and an analyzing device, the analysis The device obtains the concentration or the partial pressure according to the time-dependent change of the oscillator frequency, characterized in that the active surface (18) is electrically conductive and has electrical contacts (19, 20) for introducing a heating current (I), the activity The face (18) can be heated by the heating current. The apparatus of claim 1, wherein the mass flow rate of the steam carried by the carrier gas through the volume (2) is measured or controlled by the analysis device. The device of claim 1, wherein the conductive surface (18) occupies at least 90% of a flat surface defined by the edge (25) of a prism or cylinder. The device of claim 3, wherein the conductive surface (18) is formed by a conductive coating on a surface of the vibrating body (17). The device of claim 1, wherein the two contacts (19, 20) are spaced apart from each other on the active surface (18) by more than half the maximum distance from one edge to the other edge. The device of claim 1, wherein the resistance between the contacts (19, 20) is between 0.5 ohms and 5 ohms. The device of claim 1, wherein the contacts (19, 20) are disposed in regions of two opposing segments of the rim (25) of the active surface (18). An application of a sensor that provides correlation with the concentration or partial pressure of steam a sensor signal, wherein the sensor (1) has an oscillatable vibrating body (17) whose oscillation frequency is accumulated by the mass formed by the condensed vapor on the active surface (18) of the vibrating body (17) Influencing, and the active surface (18) of the vibrating body is electrically conductive and has electrical contacts (19, 20) for introducing a heating current (I), and the active surface (18) can be heated by the heating current, the sensor It is used on a device to determine the concentration or partial pressure of steam in a volume (2) which can be heated by a heating device (8) to a temperature above the condensation temperature of the steam. The application of the sensor of claim 8, wherein the mass flow of the steam carried by the carrier gas through the volume (2) is measured or controlled. A method of cleaning an active surface (18) of a sensor (1) of the apparatus of claim 1, characterized in that the active surface (18) is heated to a temperature above the evaporation temperature of the condensate/sediment, The condensate/sediment is thus removed from the active surface (18) by evaporation. The method of claim 10, wherein the vibrating body (17) composed of GaPO _{4 is} used, in particular, a vibrating body (17) which is at least heated to 450 ° C, preferably heated to a temperature of 850 ° C, is used. The apparatus of claim 1, wherein the means for determining the concentration or partial pressure of the vapor is part of an OLED coating apparatus and is for ensuring that steam flows into the process chamber at a temporally constant flow rate. The application of claim 8, wherein the means for determining the concentration or partial pressure of the vapor is part of an OLED coating apparatus and is for ensuring that steam flows into the process chamber at a temporally constant flow rate. The method of claim 10, wherein the means for determining the concentration or partial pressure of the vapor is part of an OLED coating apparatus and is for ensuring that steam flows into the process chamber at a temporally constant flow rate.