Abstract:
A vapor-phase deposition source including a vessel equipped with two zones. The first zone is for the production of vapor. It is equipped with a receptacle for the material and element for heating the material placed in the receptacle. The second is a diffusion zone including a vessel communicating with the production zone and equipped with at least one opening so that the vapor-phase material is transmitted towards the exterior of the vessel through the opening. The source is characterized in that it includes elements for closing the orifice and elements for moving the closing elements between an active closed position and an orifice open position without changing the volume of the diffusion zone.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The general field of the present invention concerns the vapor deposition of materials in the micro-electronics industry. More especially, it addresses the creation of vapor sources to enable continuous deposition on large surfaces that can be interrupted without inconvenience. 
       STATE OF THE TECHNIQUE 
       [0002]    The ever-increasing number of electronic and optical components and their integration within a same device has led to the development of sophisticated techniques for depositing various materials, on a substrate to form the thin layers that constitute these devices. 
         [0003]    Vapor-phase deposition covers a very broad range of processes, especially those described as vapor-phase chemical deposition, and generally designated by their English acronym of CVPD, “chemical vapor-phase deposition”. As the name suggests, this type of deposition involves a chemical reaction occurring during the operation by, for instance, prior introduction of a precursory gas into the deposition chamber or by a chemical reaction taking place with a layer of a material that has already been deposited on the substrate, and even with the substrate itself. Other types of chemical vapor-phase depositions do not involve such chemical reactions. These consist of simple physical deposition by evaporation in a controlled neutral atmosphere and/or in more or less vacuum conditions. 
         [0004]    All the vapor-phase deposition techniques require a mechanical device in order to create in the deposition chamber the source of the evaporated material to be deposited. This is always a critical factor to be applied in order to obtain a uniform thickness of the thin layers deposited and good control over their physico-chemical characteristics. It is becoming increasingly difficult to create the source as the mass production, at low cost, of electronic and optical devices requires that the substrates on which they are applied become increasingly large in size in order to produce an increasing number of devices, or increasingly large devices, during the same production cycle. Therefore, it is not surprising that a source that allows continuous vapor-phase deposition of various materials over widths that may be measured in tens of centimeters, even around one meter, is required. Moreover, the industrial production of such devices implies that deposition can be interrupted and restarted at will without damage to the source and the evaporated material. 
         [0005]    This facilitates a certain flexibility in the deposition of different films for different devices, without changing the configuration of the chamber. 
         [0006]    Although the micro-electronics industry has for a long time been faced with the need to deposit materials such as dielectrics or metals, the manufacture of electroluminescent devices such as displays and screens containing organic electroluminescent diodes (OLEDs) requires recourse to the deposition of much more fragile organic materials. 
         [0007]    Evaporation from a linear source of broad widths of organic material raises the critical problem of the temperature variation that has to be observed between the point of vapor creation and the points of its diffusion, i.e. nozzles installed over the full width of the source, in the deposition chamber. Indeed, to avoid the condensation of material on the walls of the tubes transporting the vapor and on those of the diffuser constituting the source, it is an advantage to be able to maintain a temperature gradient that is always positive in order to prevent any cold zones bringing the temperature of the gas to below its dewpoint. This is all the more difficult to carry out in that, as is the case for organic materials, the destruction temperature of the material to be deposited is close to its evaporation temperature. Moreover, very broad linear sources consisting of multiple chambers are more sensitive than the point sources since it is necessary to monitor this slight gradient over all the diffuser surface, from the evaporation crucible up to each nozzle. 
         [0008]    Linear sources are the subject of great interest, in particular for their capacity to achieve high speeds deposition. They also ensure efficient use of the material mainly, due to the source-substrate distance which is much smaller than with a point source. The presence of multiple nozzles and their design, that is intended to ensure uniform deposits over a large surface, is a major asset which makes their use essential for the large-scale production of devices such as the electroluminescent devices mentioned above. However this short distance, combined with a high speed of evaporation, makes the conventional closing systems (which stop the process of deposition on the substrate) difficult to carry out for mechanical reasons. In addition, they are not easy to use due to the speed with which they are become clogged. Therefore, sources equipped with a valve making it possible to close the vapor transport tube in order to interrupt its diffusion towards the substrate and not to waste the material to be evaporated. When closed, the valve then greatly reduce the volume of the pipe connected to the point at which the vapor is created. This significant reduction of the volume produces a sharp variation of the vapor generation system load, which increase the pressure in the steam creation zone very significantly. This strong pressure variation then causes a rise in the temperature until saturation of the vapor creation zone. This rise in temperature will in turn create thermal degradation of the material to be deposited. 
         [0009]    Therefore, it is a general aim of the invention to overcome at least in part one of the shortcomings described above found in the linear sources used in vapor-phase deposition systems that are required to operate continuously with deposition stopping and restarting phases. It is also an aim of the invention to describe an advantageously linear source that enables the deposition of organic materials whose destruction temperature is close to the evaporation temperature. 
         [0010]    Other aims, characteristics and advantages of this invention will become clear on examination of the following description and the accompanying drawings. It is understood that other advantages may be incorporated. 
       SUMMARY OF THE INVENTION 
       [0011]    To achieve these aims, the invention describes a source for phase-phase deposition of a material. This consists of a vessel divided into two zones. The first zone is a zone generating the vapor. It is equipped with a receptacle for the material and means for heating the material placed in the receptacle. The second is a diffusion zone communicating with the production zone. It is equipped with at least one orifice so that the material in vapor phase is transmitted towards the exterior of the vessel through this orifice. The source is characterized in that it includes means for closing the orifice and means for moving the means for closing between an active closed position and an orifice open position. 
         [0012]    The invention may also include the following options: 
         [0013]    It comprises orifices in the form of vapor nozzles. 
         [0014]    The diffusion zone comprises a diffuser with cylindrical body on which the diffusion nozzles are positioned side by side. 
         [0015]    The means for closing comprise a cylindrical sleeve in contact with the inner face of the diffuser, the cylindrical sleeve comprising on the one hand several openings capable of being positioned opposite several diffusion nozzles in the open position and moreover, an opening opposite the steam production zone. 
         [0016]    The cylindrical sleeve is configured to move inside the diffuser in order to close the series of diffusion nozzles while keeping opened the vapor production zone. 
         [0017]    Means for moving the cylindrical sleeve comprising an axial rod joined to the cylindrical sleeve and accessible through the diffuser. 
         [0018]    Means for moving the cylindrical sleeve comprises means for rotating the axial rod. 
         [0019]    The means for moving the cylindrical sleeve include lateral translation means operated by the axial rod. 
         [0020]    The diffuser includes at least one nozzle opened separately from the movement of the cylindrical sleeve. 
         [0021]    Here, at least one independent nozzle is placed advantageously in the axis of the diffuser at the end opposite the axial rod. 
         [0022]    The material receptacle is a cylindrical crucible the opening of which connected to the diffuser has a diameter that is identical to the inner diameter of the cylindrical sleeve. 
         [0023]    The diffusion zone and the production zone are tubular cylinders assembled to form a T, the production zone of which is the branch centered on the branch forming the diffuser. 
         [0024]    The means for closing are configured in order to maintain the diffusion zone in connection with the production zone when the orifice is in the open position. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0025]    The aims, purposes, characteristics and advantages of the invention will be better understood from the detailed description of its embodiment which is shown on the following accompanying drawings on which: 
           [0026]      FIGS. 1A and 1B  illustrate the linear vapor-phase deposition source according to the invention in which the valve closing the nozzles consists of a rotary sleeve. 
           [0027]      FIGS. 2A and 2B  show a variant of the linear vapor-phase deposition source according to the invention in which the valve closing the nozzles consists of a sliding sleeve. 
       
    
    
       [0028]    The attached drawings are given as examples and are not restrictive. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0029]      FIGS. 1A and 1B  illustrate a linear source of vapor-phase deposition according to the invention in which the nozzle closure valve consists of a rotary sleeve. 
         [0030]    The term linear means a source with several nozzles (the preferred embodiment of the invention), the nozzles being placed next to one another according to one dimension of the source. Preferably, this juxtaposition consists of one straight alignment of the nozzles, but this is not restrictive. 
         [0031]    The invention describes how, in a preferred embodiment, a linear vapor-phase deposition source  10  makes it possible to obtain a very flat temperature gradient between material furnace  20  (situated in a vapor production zone) and evaporation nozzles  30  situated in a diffusion zone. Furnace crucible  21  contains material  23  that is to be evaporated, for instance an organic material of the type used to manufacture electroluminescent diodes. 
         [0032]    To avoid any break in the load when the vapor is transmitted to the nozzles, the vertical vapor injection pipe  40  from the crucible and the internal part of horizontal diffuser  50  form a T assembly with identical diameters  51 . This diameter is typically around 40 to 50 mm. The width of diffuser  50  has to be compatible with the size of substrate  1  on which the deposit is to be made. Typically, several tens of centimeters, and even more, may be deposited on the substrate. Maintaining a constant diameter between the crucible, the vertical vapor injection pipe and the diffuser guides it so that it is injected through nozzles into the evaporation chamber, at the same time minimizing the required temperature gradient. This constant diameter concept minimizes the overpressures and therefore the heating of the vapor it encounters. The temperature gradient guarantees the progression and the acceleration of the vapor up to the outlet nozzles. 
         [0033]    Crucible  21 , vertical pipe  40  and diffuser  50  bathe in a heat-transporting liquid  25  found between crucible  21  and its envelope  29 , and in all the annular space between on the one hand vertical pipe  40  and inner wall  52  of diffuser  50 , and on the other, an outer tubular envelope  60  with T-shape whose branches are respectively coaxial with the vertical pipe and the horizontal diffuser. In this arrangement of the invention, heating filaments  27  and  41  surround the outer tubular envelopes in order to indirectly heat crucible  21 , vertical pipe  40  and diffuser  50  by the use of a heat-transporting fluid. This ensures that there is excellent distribution of the heat over all the surfaces in contact with on the one hand the material to be evaporated in the heating furnace, and on the other with the vapor in pipe  40  and diffuser  50 . 
         [0034]    The terms “vertical” and “horizontal” mean substantially the orientation of the invention components in a preferred position of use with the vapor diffusing substantially in a vertical direction. 
         [0035]    For the linear source of the invention to be used for continuous industrial production, means have to be provided for stopping and restarting the process of evaporation without damaging the materials to be evaporated. The purpose of the invention is achieved in this first implementation of the invention by placing a vapor check valve in the diffuser in the form of a sleeve  70  with a diameter that corresponds to the inner diameter of the diffuser and which can be turned using an axial mechanical control using rod  72 . In a preferred embodiment, sleeve  70  is a hollow cylindrical body with circular section that coacts with a diffuser  50  of the same shape and constitutes a space inside diffuser  50  capable of varying the configuration of the diffusion zone between an open position of the orifices and closed position. Orifices  73  are drilled at the position of the nozzles so that the steam can pass through during deposition. Simple rotation of the sleeve is sufficient to mask the nozzles and interrupt the deposition process. It will be observed that this takes place without changing the inner volumes of the source. Lower orifice  71 , which is positioned opposite vapor injection pipe  40 , is such that when rotated to mask the nozzles, the latter do not obstruct the vapor injection pipe. 
         [0036]    Therefore rotary sleeve  70  makes it possible to rapidly cut off the evaporation while ensuring that the source remains ready to restart. Closing the source at the level of the nozzles, which is the last point for containing the vapor without this varying the volume of the vapor creation system load, has only a very slight impact on the vapor source and no increase in its temperature is observed during steam saturation. This closure system therefore enables the evaporation to be cut off without consuming the material. 
         [0037]    In order to help maintain the thermodynamic balance of the source, the system for measuring the rate of deposition, which is placed preferably in the axis of the diffuser in order not to disturb the evaporation flux from the source towards the substrate, remains active. This nozzle is used to measure the rate of deposition and therefore to guarantee a rate that is close to the required rate during the source closure phase in order to minimize the stabilization time after reopening the closure system. During closure of the deposition nozzles, nozzle  53 , which is dedicated to the measurement function (the measurement part is not shown on the drawing), is placed in the diffuser axis and remains open in order to minimize the pressure. This also maintains a stable flux throughout the closure period and therefore achieves greater reactivity by reducing the time required to stabilize the flux once the steam closure valve (that is to say the rotary sleeve used to close the nozzles) is once again open in order to continue one deposition or to make another. 
         [0038]      FIGS. 2A and 2B  show a variant to the vapor-phase linear deposition source according to the invention in which the nozzle closure valve consists of a sliding sleeve. 
         [0039]    In this second application of the invention, rotary sleeve  70  is replaced by a sliding sleeve  70 . As this is a little shorter than diffuser  50 , closure of the nozzles is this time achieved by lateral movement of the sliding sleeve using axial control  82 , identical to the previous one. As previously, openings  83  are drilled at the position of the nozzles in order to allow the vapor to pass through during the deposition phase. Here again, deposition is stopped without changing the source inner volumes. Lower orifice  81 , which is positioned opposite vapor vertical injection pipe  40 , has a shape and dimensions such that the lateral displacement in order to mask the nozzles does not obstruct vapor pipe  40  in any way. 
         [0040]      FIGS. 2A and 2B  also show that heating filaments can be placed in the annular space containing heat transporting fluid  25 . Immersed in the heat transporting fluid, filaments  27  and  41  apply heat directly, thereby ensuring that the temperatures are uniform. This concerns both filaments  27  that are used to heat crucible  21  and filaments  41  that are used to maintain the temperature gradient around vertical pipe  40  of diffuser  50 . 
         [0041]    Of course, the embodiment options illustrated on  FIGS. 1A ,  1 B and  2 A,  2 B can be combined without any inconvenience. Filaments  27  and  41  may be placed in the coolant fluid and this may be combined with the use of rotary sleeve  70 . The opposite is also possible (sliding sleeve and heating elements around the envelopes). Moreover, the use of a rotary sleeve  70  or a laterally moving sleeve  70  can also be envisaged with any other heating device while retaining the advantage provided by this type of nozzle closure device that takes place without changing the volume of diffuser  50 . As previously explained, this helps to avoiding deterioration and loss of costly material in crucible  21  during the phases when deposition has to be stopped, and therefore extends the period during which the latter can be used. 
         [0042]    The valve, whether rotary or moving laterally, can therefore be used to instantly cut off and restart the emission of this vapor in the diffusion zone while retaining the source during the evaporation phase. Closure of the diffusion nozzles alone by the valve makes it possible not to alter the volume of the load in crucible  21  and therefore minimizes the overpressure and the temperature increase which would otherwise result from closing the source at the level of the steam production zone. 
         [0043]    Maintaining the steam flux towards the measurement system, even when the valve is closed, maintains the source flow conditions and continues to control the heating devices in order to maintain the quantity of vapor generated. This solution ensures an instantaneously stabilized source once the valve is opened. 
         [0044]    The valve can also be interlocked and used to ensure emitted flux regulation so as to guarantee a rapid change of flux or stability of flux without temperature variations. In particular, this solution quickly smoothes out any flux variations that depend on the level of the material filling crucible  21 .