JP7281372B2 - Evaluation method and vacuum deposition apparatus - Google Patents

Description

The present invention stores a solid organic material in a storage box, and heats the organic material in the storage box with a heating means in a vacuum chamber having a vacuum atmosphere to sublimate or vaporize the organic material. The present invention relates to an evaluation method for evaluating the heat load applied to a vacuum deposition apparatus and a vacuum deposition apparatus capable of implementing this evaluation method.

For example, in the manufacturing process of an organic EL element, there is a process of vapor-depositing an organic film (including an organic multilayer film) on the surface of a substrate such as a glass substrate in a vacuum atmosphere, and a vacuum vapor deposition apparatus is widely used for this vapor deposition process. (See, for example, Patent Document 1). A vacuum deposition apparatus includes a vacuum chamber capable of forming a vacuum atmosphere, and the vacuum chamber is provided with a storage box for storing an organic material and a heating means such as a sheath heater for heating the organic material in the storage box. there is As the organic material, those highly purified (for example, 99.99% or more) by a known method such as sublimation purification are generally used so that an organic film having a desired film quality that determines the performance of the device can be deposited. be.

When forming an organic film on a substrate surface using the above-mentioned vacuum deposition apparatus, a solid (specifically, powdery) organic material is poured into a storage box from above in the vertical direction in a vacuum chamber in an atmospheric atmosphere. Fill at the specified filling rate. At this time, the surface of the upper layer of the organic material (that is, the sublimation surface or vaporization surface of the organic material) is flattened with little unevenness. Next, when the inside of the vacuum chamber is evacuated and reaches a predetermined pressure, the outer wall surface of the storage box is heated by the heating means. As a result, the organic material is heated by heat transfer and radiation from the wall surface of the storage box, and the organic material is sublimated or vaporized from the upper surface of the organic material. An organic film is formed by being ejected from an injection nozzle in accordance with a predetermined cosine law and adhering and depositing on the substrate surface.

Here, the heating means such as the sheath heater is designed and controlled so that the amount of heat applied to the storage box is substantially uniform. External factors may cause local differences in the thermal load applied to the organic material within the containment box. At this time, if an excessive heat load is applied to the portion of the organic material filled in the container, if the organic material is sublimable, the organic material may be locally decomposed or thermally deteriorated. As a result, there arises a problem that an organic film having a desired film quality cannot be deposited. On the other hand, if the organic material is volatile, for example, bumping occurs and the organic material is wasted, or uneven melting occurs and the deposition rate becomes unstable. . In recent years, as the size of the substrate to be deposited has increased, the volume of the storage box has also increased, making the design and control of the heating means more complicated. There is an early demand for the development of a simple method for evaluating the heat load on the organic material when the organic material in the container is heated by a heating means.

JP 2014-77193 A

In view of the above points, it is an object of the present invention to provide an evaluation method and a vacuum deposition apparatus that can easily evaluate the heat load on the organic material when the organic material in the storage box is heated by a heating means. and

In order to solve the above problems, a storage box is filled with a solid organic material, and the organic material in the storage box is heated by a heating means in a vacuum chamber in a vacuum atmosphere, prior to sublimation or vaporization of the organic material. Therefore, in the evaluation method of the present invention for evaluating the heat load on an organic material, impurities that are thermally degraded before the organic material reaches the sublimation temperature or the vaporization temperature are included in the organic material at a predetermined weight ratio. a step of continuously or stepwise heating the organic material in the storage box by a heating means; and identifying the magnitude of the heat load to the organic material from the surface state of the organic material exposed in the storage box. and a step. In the present invention, the step of adding impurities to the organic material includes not only the process of adding impurities to the organic material filled in the storage box, but also the organic material before being highly purified by sublimation purification (that is, (Organic material containing impurities in the above ratio). Impurities contained in the organic material are not particularly limited as long as they are thermally degraded (carbonized) before the organic material reaches the sublimation temperature or vaporization temperature. Moreover, when the storage box is filled with the organic material, it is sufficient that at least the upper layer portion of the storage box contains an organic material layer containing impurities in a predetermined weight ratio.

Here, the present inventors have made intensive studies and found that the organic material is sublimable, such as an aluminum quinolinol complex (Alq ₃ ) or an aromatic diamine, and is used, for example, to produce an organic EL device. A storage box was filled with a material (for example, 99.5%) before being highly purified to a purity level, and the outer wall surface of the storage box was heated in a vacuum atmosphere. Impurities in the material are first thermally degraded (carbonized), and after reaching the sublimation temperature, they remain as burn marks on the upper layer surface (sublimation surface) of the organic material filled in the storage box without sublimation. I came to know that. Even when the organic material is volatile such as α-NPD, impurities in the organic material are thermally degraded to form burn marks before the upper surface of the organic material is liquefied.

Therefore, in the present invention, based on the above knowledge, when filling the container with the organic material, impurities are contained in a predetermined weight ratio, so that the organic material is contained by a heating means to a temperature equal to or lower than the sublimation temperature or the vaporization temperature. When the organic material in the box is heated continuously or step by step, impurities in the organic material are thermally degraded (carbonized) and charred sequentially from the part where the organic material receives a large heat load in the storage box. It becomes like a trace. Therefore, by identifying (specifying) the portion of the upper layer surface of the organic material filled in the storage box that is thermally degraded (carbonized), a predetermined amount of heat is continuously or stepwisely applied to the storage box by the heating means. It is possible to evaluate the magnitude of the heat load applied to the organic material in the container when the temperature is raised in addition to the target by a very simple method (in other words, for example, the temperature inside the container can be measured using a plurality of thermocouples). The temperature distribution in the storage box can be practically confirmed without As a result, if the heating means is appropriately controlled based on the evaluation of the magnitude of the heat load, the portion of the organic material filled in the storage box will not be subjected to an excessive heat load at a location where the heat load is relatively large. This is advantageous because it is possible to prevent preferential sublimation or vaporization and unbalanced consumption as much as possible. Impurities remaining in the organic material after the above evaluation are also thermally degraded (carbonized) before the organic material is heated to the sublimation temperature or the vaporization temperature. does not adversely affect the deposition of organic films.

In the present invention, the weight ratio is preferably set within the range of 0.2% by weight to 5% by weight. If the impurity content is less than 0.2% by weight, it is difficult to visually identify the portion that is thermally degraded (carbonized). In addition, the remaining impurities such as burn marks inhibit the sublimation of the high-purity organic material in the lower layer, suppress the amount of evaporation of the organic material in the housing box, and eventually cause a decrease in the film formation rate.

Further, the vacuum deposition apparatus of the present invention capable of carrying out the above-described evaluation method includes a storage box that is placed in a vacuum chamber capable of forming a vacuum atmosphere and stores an organic material containing impurities, and an organic material in the storage box. and a first see-through window provided on the wall surface of the vacuum chamber and a second see-through window provided in the container so that the surface state of the organic material exposed in the container can be visually recognized. It is characterized by

According to the present invention, by providing the first transparent window and the second transparent window, prior to forming a predetermined organic film on the surface of a substrate such as a glass substrate in a vacuum atmosphere (that is, mass production), When the organic material in the storage box is heated by the heating means to be sublimated or vaporized, the surface state of the organic material is visually observed from the outside of the vacuum chamber through the first see-through window and the second see-through window, and the inside of the box is If the magnitude of the heat load applied to the organic material is evaluated, and the heating means is appropriately controlled accordingly, the portion of the organic material filled in the container box will be heated more than necessary at the location where the heat load is relatively large. It is possible to prevent, as much as possible, the application of a thermal load of 100% and preferentially sublimating or vaporizing to cause an unbalanced consumption.

BRIEF DESCRIPTION OF THE DRAWINGS The partial perspective view which made the one part cross section explaining the vacuum deposition apparatus of embodiment of this invention. FIG. 2 is a partial cross-sectional view of the vacuum deposition apparatus of the present embodiment as seen from the front side; BRIEF DESCRIPTION OF THE DRAWINGS It is a photograph explaining the experimental result which confirms the effect of this invention, (a) is a photograph which shows the surface state of the organic material before heating, (b) is a photograph which shows the surface state of the organic material during heating.

Hereinafter, with reference to the drawings, a sublimable aluminum quinolinol complex (Alq ₃ ) is used as the solid organic material Om, the organic material Om is filled in a container, and the container is heated by heating means in a vacuum chamber in a vacuum atmosphere. An evaluation method according to an embodiment of the present invention for evaluating the heat load on the organic material Om prior to heating the organic material Om in the interior to sublimate the organic material Om, and a vacuum capable of implementing this evaluation method The vapor deposition device DM will be described. Hereinafter, terms such as "up" and "down" are based on the posture of the vacuum deposition apparatus DM shown in FIGS.

Referring to FIGS. 1 and 2, the vacuum deposition apparatus DM includes a vacuum chamber 1, which is connected to a vacuum pump Vp through an exhaust pipe, and is evacuated to a predetermined pressure (degree of vacuum). It is designed to hold. A substrate transfer device 2 is also provided above the vacuum chamber 1 . The substrate transfer device 2 has a carrier 21 that holds the substrate Sw with its lower surface as a vapor deposition surface open. to move. Since a known device can be used as the substrate transfer device 2, further explanation is omitted. Also, hereinafter, the direction of relative movement of the substrate Sw with respect to the vapor deposition source Ds, which will be described later, is defined as the X-axis direction, and the width direction of the substrate Sw perpendicular to the X-axis direction is defined as the Y-axis direction.

A plate-like mask plate 3 is provided between the substrate Sw transported by the substrate transport device 2 and the vapor deposition source Ds. In this embodiment, the mask plate 3 is attached integrally with the substrate Sw and transported together with the substrate Sw by the substrate transport device 2 . The mask plate 3 can also be fixedly arranged in the vacuum chamber 1 in advance. A plurality of openings 31 are formed through the mask plate 3 in the plate thickness direction, and the adhesion range of the organic material Om to the substrate Sw is limited at positions where there are no openings 31, so that the organic material Om adheres to the substrate Sw in a predetermined pattern. vapor-deposited. The mask plate 3 may be made of metal such as Invar or made of resin such as polyimide. A storage box Ds as a vapor deposition source is provided on the bottom surface of the vacuum chamber 1 so as to face the substrate Sw that is moved in the X-axis direction.

The storage box Ds includes an outer container 41 and an inner container 42 having an open top, which is installed in the outer container 41. The inner container 42 is filled with a powdery (solid) organic material Om at a predetermined filling rate. be done. In the outer container 41, sheath heaters 43a to 43d are provided as heating means so as to surround the wall surface of the inner container 42 (side surface extending in the Y-axis direction). In this case, the inner container 42 is divided into a plurality (four in this embodiment) of blocks 42a to 42d in the longitudinal direction (Y-axis direction), and sheath heaters 43a to 43d are provided independently for each of the blocks 42a to 42d. , are energized from power sources (not shown) to control heating. In the upper wall 41a of the outer container 41, a plurality of discharge openings (injection nozzles) 44, which are cylindrical bodies having a predetermined height, are arranged at predetermined intervals in the Y-axis direction (six in this embodiment). there is When the sheath heaters 43a to 43d are energized to heat the inner container 42, the organic material Om is heated by heat transfer from the wall surface of the inner container 42 and radiation from the upper wall (facing the substrate Sw) 41a of the outer container 41. , the organic material Om is sublimated from the upper surface Om1 of the organic material Om (that is, the sublimation surface of the organic material Om) filled in the inner container 42, and the sublimated organic material Om is discharged from the emission opening 44 in accordance with the predetermined cosine law. It is released into the space inside the chamber 1 .

A first see-through window 11 is provided at a predetermined position on the wall surface (side wall) of the vacuum chamber 1 , and through this first see-through window 11 it is possible to check whether or not the discharge opening 44 is clogged. A second see-through window 45 is also provided at a predetermined position of the upper wall 41a of the outer container 41, and through these first and second see-through windows 11 and 45, the upper surface Om1 of the organic material Om is substantially entirely covered. are visible. As the first see-through window 11 and the second see-through window 45, for example, one made of quartz is used. Although the organic material Om sublimated in the inner container 42 adheres to the second see-through window 45, the second see-through window 45 is also exposed to heat transfer from the wall surface of the inner container 42 when the inner container 42 is heated. Since it is heated, the attached organic material Om is re-sublimated, and its visibility is not impaired. In this case, an anti-adhesion film may be formed on the surface of the second transparent window 45 to prevent the organic material Om from adhering. In this embodiment, the upper wall 41a of the outer container 41 is provided with a second see-through window 45 so that the entire side wall of the inner container 42 can be heated to the same temperature when heated by the sheath heaters 43a to 43d. However, if the upper surface Om1 of the organic material Om filled in the inner container 42 can be visually recognized over substantially the entire surface and the side wall of the inner container 42 can be heated to the same temperature, the second The position and number of the see-through windows 45 are not limited to the above.

The vacuum deposition apparatus DM includes a known control unit (not shown) equipped with a microcomputer, a memory element, a sequencer, etc., and this control unit supervises the control of each component such as the vacuum pump Vp and the substrate transfer device 2. At the same time, the power supplied from the power source to the sheath heaters 43a to 43d is controlled so that heat is applied substantially evenly to the inner container 42 and the organic material Om. A case where a predetermined organic film is formed by the vacuum deposition apparatus DM by applying the evaluation method of the present embodiment will be specifically described below.

First, in the vacuum chamber 1 in the atmosphere, the inner container 42 of the storage box Ds is filled from above with a solid (powder) organic material Om at a predetermined filling rate. At this time, the organic material Om is made to contain impurities at a rate in the range of 0.2% by weight to 5% by weight. The impurities are not particularly limited as long as they are thermally degraded (carbonized) before the organic material Om reaches the sublimation temperature. All that is needed is a layer of contained organic material Om. In the present embodiment, the organic material Om having a predetermined purity (99.5%) before being highly purified to a purity (e.g., 99.99% or more) used for manufacturing an organic EL element is contained in the inner container 42. be filled. If the impurity contained in the organic material Om is less than 2% by weight, it is difficult to visually identify the portion that is thermally degraded (carbonized) as described later. , when the organic material Om is sublimable, the remaining impurities such as burn marks inhibit the sublimation of the high-purity organic material Om in the lower layer, and the amount of evaporation of the organic material Om in the storage box Ds is suppressed, which in turn causes a decrease in the film formation rate.

Next, the vacuum pump Vp evacuates the vacuum chamber 1, and when the inside of the vacuum chamber 1 reaches a predetermined pressure (for example, 1×10 ⁻⁵ Pa), the sheath heaters 43 a to 43 d are operated to heat the inner container 42 . Start. At this time, the inner container 42 is heated while the sheath heaters 43a to 43d are increased at a predetermined temperature rise rate (constant temperature gradient) (that is, the amount of heat continuously applied is increased at a constant temperature gradient). As a result, in the storage box Ds, the organic material Om is continuously heated by heat transfer from the side wall of the inner container 42 and radiant heat from the upper wall 41 a of the outer container 41 . It is also possible to stepwise heat the organic material Om by applying a predetermined amount of heat to the inner container 42 stepwise by controlling the sheath heaters 43a to 43d.

When the organic material Om is continuously heated as described above, impurities in the organic material Om are sequentially thermally degraded (carbonized) from a portion where a large heat load is applied to the organic material Om within the inner container 42 . It becomes like a burn mark. In this way, the thermally degraded (carbonized) portion of the upper surface Om1 of the organic material Om is detected through the second see-through window 45 provided in the outer container 41 and the first see-through window 11 provided in the wall surface of the vacuum chamber 1 . Visually identify (identify) through Then, in the portion where a large heat load is applied to the organic material Om, the sheath heaters 43a to 43d facing this are controlled (for example, the amount of heat applied is reduced or temporarily stopped), and the respective sheath heaters 43a to 43d maintain an equivalent temperature. The gradient heats the organic material Om in the inner container 42 . After that, when the organic material Om reaches the sublimation temperature, the organic material Om is sublimated from the entire upper surface Om1 of the organic material Om with the same amount of sublimation. This sublimated organic material Om is discharged from the discharge opening 44 into the space in the vacuum chamber 1 according to the predetermined cosine law, and an organic film is formed (evaporation) on the surface of the substrate Sw transported by the substrate transport device 2 through the mask plate 3. ) is done. Note that the heat-degraded (carbonized) material does not sublimate, so it does not adversely affect the film formation.

According to the above-described embodiment, a predetermined amount of heat is applied to the inner container 42 by an extremely simple method of identifying locations where impurities in the organic material Om are sequentially thermally degraded (carbonized) and become like burn marks. It is possible to evaluate the magnitude of the heat load applied to the organic material Om in the inner container 42 when it is continuously (or stepwisely) added and the temperature is raised. In other words, for example, the temperature distribution inside the inner container 42 can be substantially confirmed without measuring the temperature inside the inner container 42 using a plurality of thermocouples. Then, by controlling the energization of each sheath heater 43a to 43d based on the evaluation of the magnitude of the heat load, it is possible to prevent excessive heat load from being applied to the portion of the organic material Om filled in the inner container 42 and preferentially This is advantageous because it is possible to prevent sublimation and unbalanced consumption as much as possible.

Next, in order to confirm the above effect, the following experiment was conducted using the vacuum deposition apparatus DM. That is, a powdery aluminum quinolinol complex (Alq ₃ ) containing 0.5% by weight of impurities was used as the organic material Om, and the inner container 42 was filled with this organic material Om (see FIG. 3A). After that, the vacuum chamber 1 was evacuated to a predetermined pressure (1×10 ⁻⁵ Pa), and the sheath heaters 43a to 43d started heating the inner vessel 42 to continuously heat the organic material Om. After one hour from the start of heating, as shown in FIG. It was found that the magnitude of the heat load applied to the organic material Om can be evaluated. Then, based on this evaluation result, in the portions where many scorch traces were observed in the organic material Om (that is, the blocks 42b and 42c of the inner container 42 to which a large heat load is applied), the sheath heaters 43b and 43c facing the portions were heated. The input power was controlled (the amount of heat applied was reduced). As a result, it was confirmed that uneven consumption of the organic material Om can be suppressed as compared with the case where the electric power supplied to the sheath heaters 43b and 43c is not controlled (adjusted).

Although the embodiments of the present invention have been described above, various modifications are possible without departing from the scope of the technical idea of the present invention. In the above embodiment, the case where the sheath heaters 43a to 43d are used as the heating means has been described as an example, but the heating means is not limited to this, and any one capable of heating the side wall of the inner container 42 to the same temperature can be used.

In the above embodiment, the sublimable organic material Om is used as an example, but even if the organic material Om is a vaporizable material such as α-NPD, the upper surface of the organic material Om is liquefied. The present invention can be applied because the impurities in the organic material Om are thermally degraded in the previous stage and become like burn marks.

DM... vacuum vapor deposition apparatus, Ds... storage box, Om... organic material, 1... vacuum chamber, 11... first see-through window, 42... inner container (accommodation box), 43a to 43d... sheath heater (heating means), 45... second 2 see-through window.

Claims (3)

Prior to filling a container with a solid organic material and heating the organic material in the container with a heating means in a vacuum chamber having a vacuum atmosphere to sublimate or vaporize the organic material, heat load is applied to the organic material. An evaluation method for evaluating the
A step of making an organic material thermally degraded before it reaches a sublimation temperature or a vaporization temperature as an impurity, and adding the impurity to the organic material in a predetermined weight ratio;
continuously or stepwise heating the organic material in the container with a heating means;
and a step of discriminating the magnitude of the heat load to the organic material from the surface state of the organic material exposed in the storage box. 2. The evaluation method according to claim 1, wherein said weight ratio is set within a range of 0.2% by weight to 5% by weight. A vacuum deposition apparatus capable of performing the evaluation method according to claim 1 or claim 2, wherein the storage box is placed in a vacuum chamber capable of forming a vacuum atmosphere and is filled with an organic material containing impurities; and a heating means for heating the organic material in the storage box,
A vacuum deposition characterized by having a first see-through window provided on the wall surface of the vacuum chamber and a second see-through window provided in the container so that the surface state of the organic material exposed in the container can be visually recognized. Device.

Images