Patent Application
20050247267
The present invention relates to a molecular beam source for use in accumulation of organic thin-films, for heating a material to be formed on a surface of a solid body or matter, such as, a substrate, etc., in the form of a thin-film, thereby melting and evaporating the film-forming material; i.e., generating evaporated molecules for growing up the thin-film upon the surface of the solid body, and it relates to, in particular, a molecular beam source for use in accumulation of the thin-film of an organic material, being suitable for accumulating the thin-film of an organic material upon the film forming surface of the solid body, such as, the substrate, etc.
In recent years, attention is paid upon organic thin-film elements, such as, an organic electro luminescence (i.e., EL) and/or an organic semiconductor, as being typical or representative ones thereof. With such the thin-film elements, an organic material is heated within a vacuum, so as to blast the vapor thereof onto the substrate, and then it is cooled down; thereby, to be solidified or bonded thereon. In general, the following method is applied, wherein an organic material is put into a melting pot or a crucible, which is made of a material having high meting-point, such as, tungsten, etc., and then the material to be formed into a film is heated up through heating the periphery of the crucible by means of a heater; thereby, generating the vapor thereof to be blasted onto the substrate.
However, since almost of the organic materials, i.e., the film forming materials, are inferior, in particular, in the heat conductivity thereof, it is impossible to head the film-forming material in uniform, by means of such the evaporating means as was mentioned above, and therefore there is a drawback that it results into unevenness or un-uniformity in generation of the vapor. It is also apparent that, such the drawback brings about a further large problem, in particular, if trying to put a large amount of the organic material into the crucible.
Then, as is described in the following Patent Document 1, it is proposed to put a material being thermally and chemically stable, as wall as, being greatly superior to the film forming material in the thermal conductivity thereof, together with that film forming material, into the crucible; thereby, obtaining solution of such the drawback mentioned above.
Further, as another drawback relating to the evaporating means of the film forming material, there is also pointed out an ill effect; i.e., since the vapor of the organic film-forming material can be generated under the condition of high vapor pressure and low temperature, the vapor of the film forming material is unintentionally or unexpectedly generated if only putting that material into the crucible and disposing it within a vacuum, and thereby bringing about the contamination onto the substrate. For dealing with such the drawback mentioned above, there is proposed an idea, as is described in the following Patent Document 2, of adjusting an amount of vapor through a needle valve, while bringing the crucible into a closed type in the structure thereof.
Patent Document 1: Japanese Patent Laying-Open No. 2003-2778; and
Patent Document 2: Japanese Patent Laying-Open No. 2003-95787.
From studies made by the inventors of the present invention, it is possible to generate the vapor uniformly, by putting the material into the crucible, being superior in the thermal conductivity, together with the film forming material. However, it is also found out that, if trying to form a thin-film of the organic material, uniformly or evenly, upon the film-forming surface of a large-sized substrate, it is necessary to take a large distance between an evaporation source and the substrate, and therefore it deteriorates or lowers an efficiency of using the material, greatly. Also, though an interruption of an opening for discharging molecules by means of such the needle valve is a superior one for achieving control upon discharge/stoppage of the vapor of material, however, it is too narrow, as being the opening for discharging the molecules therefrom; i.e., near to a point-like, and therefore, there also brings about a drawback that it cannot be applied into the forming of a uniform thin-film upon such the film-forming surface of the large-sized substrate.
Also, the organic film-forming material has the high vapor pressure, and it generates the vapor thereof at low temperature; however, it can be easily re-condensed due to lowering of temperature. For this reason, when the vapor of the film-forming material makes contact with a wall surface in the vicinity of the opening for discharging the molecules and when the temperature goes down, then the organic film-forming material is separated or deposited on the wall surface. As a result of this, the opening for discharging the molecules therefrom is narrowed or it is blocked; thereby, lowering the efficiency of the film-forming on the substrate, or brining about ill effects in the film-forming. In addition thereto, the organic film-forming material re-condensed or solidified in vicinity of the opening for discharging the molecules therefrom is exfoliated from the wall surface, to be dispersed within a vacuum space floating under the dust-like condition thereof; i.e., increasing the chance that it adheres upon the film surface, on which a film should be formed.
According to the present invention, being achieved by taking the drawbacks owned in relation to such the conventional molecular beam source for use in accumulation of organic thin-films as was mentioned above into the consideration thereof, in particular, by making studies upon the structures of portions for discharging molecules, in particular, in the opening for discharging molecules therefrom, and as a result thereof, an object is to provided a molecular beam source for use in accumulation of organic thin-films, enabling to form an uniform thin-film upon the film-forming surface of the large-sized substrate, as well as, preventing the film-forming material from being separated or deposited in the opening for discharging molecules of the film-forming material, thereby hardly causing narrow and/or blockage in the opening for discharging.
For accomplishing the object mentioned above, according to the present invention, firstly there is provided a molecular beam source for use in accumulation of organic thin-films, in particular, for use of evaporation of an organic material, comprising: a vapor generating source; an exterior guide having a taper-like guide wall on a side of a molecule discharge opening for discharging molecules of a film-forming material, which are generated in said vapor generating source, towards a film-forming surface; an interior guide being provided within an inside of said exterior guide, and having a taper-like guide wall; a molecule discharge passage being formed between said exterior guide and said interior guide, and having a taper having a diameter thereof, being gradually enlarged along with a direction of discharging molecules. Heaters are provided within the exterior guide and the interior guide, respectively, and thereby forming the heaters within an outside and an inside of the molecule discharge passage.
With such the molecular beam source of disposing the heater at the molecule discharge opening where the vapor can be easily re-condensed, so that the evaporation material is prevented from being separated or deposited in the vicinity of the molecule discharge opening, narrow and/or blockage will hardly occur in the opening for discharging molecules, which will be caused due to the re-condensation or separation of the vapor. This enables discharging of the vapor, with stability.
Also, according to the present invention, with the molecular beam source disposing such the heaters as was mentioned above, it further comprises a heater, being provided penetrating through said molecule discharge passage, neighboring to members for supporting said exterior guide and said interior guide; therefore, it is possible to prevent the vapor from being produced to be re-condensation or solidification thereof on the support members, which penetrate through the molecule discharge passage. With this, it is also possible to protect the molecule discharge passage from being narrowed and/or blocked, in particularly, in a portion just before reaching to the molecule discharge opening.
And also, according to the present invention, with the molecular beam source disposing such the heaters as was mentioned above, it further comprises a valve provided on a way starting from said vapor generating source and reaching to said molecule discharge opening for discharging the molecules of the film-forming material, which is generated in said vapor generating source, towards the film-forming surface; therefore, it is possible to heat the material, but without leaking out the vapor, by closing the valve when starting the evaporation thereof. For this reason, it is possible to maintain a balanced pressure, easily, at the pressure depending upon the material temperature at a side of the vapor-generating source. Under this condition, it is possible to maintain a completely uniform or even pressure at the side of the vapor-generating source.
However, according to the present invention, within the molecular beam source, disposing such the heaters as was mentioned above, the heater provided at the side of the molecule discharge opening has winding density thereof, being dense or crowded, comparing to that of the heater provided at the side of the vapor generating source. With doing this, it is possible to prevent the vapor from being re-condensed or solidified in the molecule discharge opening, with certainty.
Further, according to the present invention, within the molecular beam source, disposing such the heaters as was mentioned above, the interior guide and the exterior guide are made movable with each other, directing to the film-forming surface. With this, it is possible to adjust an opening portion of the molecule discharge opening to be wide or narrow. Also, since it is possible to shift the central position of the opening portion of the molecule discharge opening, therefore the discharge condition of molecules can be determined, arbitrarily, depending upon, for example, sizes of an area, etc., on the film-forming surface to be formed with a thin-film thereon.
Those and other objects, features and advantages of the present invention will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings wherein:
In accordance with the present invention, a valve is disposed on a route of a vapor, thereby enabling to shut down the vapor to be discharged from. Also, a heater is provided at a side a molecule discharge opening, where the vapor can be easily condensed or solidified; thereby, preventing the evaporation material from being separated or deposited in the vicinity of the molecule discharge opening.
Hereinafter, embodiments according to the present invention will be fully explained by referring to the attached drawings.
A heating material receiving portion 3 of the molecular-beam source cell 1 has a cylinder-like vapor-generating source 31 made of a metal, such as, SUS or the like, i.e., a material having a high thermal conductivity, and within this crucible 31 is received the heating material “a” to be heated. This heating material “a” has, as shown in
Also, in the place of coating of the film-forming material “b” on the surface of the heat-transfer medium “c”, but the film-forming material “b” and the heat-transfer medium “c” may be received within the crucible 31 of the heating material receiving portion 3, under the condition of being uniformly mixed at an appropriate ratio or combination thereof. For example, the volume ratio between the film-forming material “b” and the heat-transfer medium “c”, to be received within is, preferably, 70%:30% or more or less.
The heat-transfer medium “c” is stable, thermally and chemically, and further it is made of a material having the heat conductivity higher than that of the film-forming material “b”. For example, the heat-transfer medium “c” is made of a high heat-transfer material, such as, Pyrolithic Boron Nitride (PBN), silicon carbide, or aluminum nitride, etc.
As is shown in
When heating, the film-forming material “b” is heated up through the heat-transfer medium “c”. Since the heat-transfer medium “c” is higher in the heat conductivity than the film-forming material “b”, therefore, the heat is transferred or propagated up to a center of the crucible 31 with an aid of this heat-transfer medium “c”, even in a case where the heat cannot reach up to the center of the crucible 31 only with the film-forming material “b”, and then also the film-forming material “b” locating at the center of the crucible 31 is heated, to be melted and/or evaporated. With doing so, the film-forming material “b” received within the crucible 31 can be heated, melted, and evaporated, thoroughly or uniformly.
Also, since the heat-transfer medium “c” is made of the material, which is stable, thermally and chemically, such as, Pyrolithic Boron Nitride (PBN), silicon carbide, or aluminum nitride, etc., it will not melted nor evaporated, if being heated by the heater 32, up to such a degree that the film-forming material “b” is evaporated. Accordingly, no molecule of the heat-transfer medium “c” is contained within the vapor molecules emitted from a vapor discharge opening 2 of the crucible 31, and therefore it gives no ill influence upon the composition of a film of growing up crystals thereon.
However, in case where the film-forming material “b” is of organic low-molecular material or of organic polymeric material, having an EL luminescence function or capacity, the temperature of vaporization is far low, comparing to that of a metal, such as, copper, etc.; i.e., that of almost of them be equal to or less than 200° C. On the other hand, the heat-durable temperature thereof is also relatively low, and therefore, it is necessary to heat at temperature, being equal or higher than the vaporization temperature and also equal or lower than the heat-durable temperature, for obtaining the evaporation of such the organic low-molecular or organic polymeric material mentioned above.
A valve 33 is provided on a side where molecules of the film-forming material are discharged from the crucible 31. This valve 33, so-called a needle valve, has a sharp needle 34 and a valve seat 35 including a molecule pass opening, which can be closed, or choked or narrowed in the cross-section area of a flow passage thereof, through insertion of a tip of the needle 34. The needle 34 mentioned above is moved into a direction of the center axis thereof, through a linear movement, which is introduced through a bellows 37 with an aid of a servomotor 36.
As is shown in
Between the periphery portion at the tip of the molecule heater chamber 12 and the molecule discharge opening 14, there is provided an exterior guide 13. An inner surface of this exterior guide 13 defines a taper-like guide surface, gradually enlarging the diameter thereof, along a direction from the tip periphery side of the molecule heater chamber 12 to the molecule discharge opening 14.
Further, within an inside of this exterior guide 13, there is provided an interior guide 16. As is shown in
Into the molecule discharge passage 17 defined between the interior guide 16 and the interior guide 13 are inserted supports 23, in radial directions at a distance of 45°. Each of the supports 23 of the embodiment shown in the figure is made up with two (2) pieces of plate-like members, which are disposed on the interior guide 16 and the exterior guide 13 separated at a distance in the circumferential direction thereof. Into those supports 23 are inserted screws 24, and those supports 23 are fixed on to the interior guide 16 and the exterior guide 13 by means of the screws 24. With an aid of such supporting structures of the support members, mainly including those supports 23 and the screws 24, etc., the interior guide 16 and the exterior guide 13 are disposed in a concentric manner with fitting the central axes thereof to each other, and are fixed to each other.
The interior guide 16 is able to move towards the exterior guide 13, into a direction directed to the film-forming surface of a substrate, on which a thin-film should be formed, and to be fixed at an arbitrary position thereon. The movable direction of that interior guide 16 is the vertical direction (or up-down direction) in
On an outside of the exterior guide 13 is disposed a cooling/heating unit 21, which comprises a heater 18 and a cooler 22, and this exterior guide 13 is surrounded by the cooling/heating unit 21. The cooler 22 of the cooling/heating unit 21 cools down or refrigerates the exterior guide 13 from the surrounding thereof, by using of a cooling liquid, for example, a water or a liquid nitrogen, etc. Also, the heater 18 of the cooling/heating unit 21, applying a micro-heater therein, for example, heats up the exterior guide 13 from the surrounding thereof, thereby heating the molecule discharge passage 17 provided within the inside thereof. The density of calorific value of the heater 18 of the cooling/heating unit 21, i.e., an amount of heat generated per a unit area thereof, it is determined to be larger than that of the heater 15, which is provided within the periphery of the molecule heater chamber 12. For this reason, the winding density of the heater 18 is more crowded or denser than that of the heater 15 in the molecule heater chamber 12.
Furthermore, also into the interior guide 16 is installed a heater 19. This heater 19, also applying the micro-heater therein, for example, heats up the interior guide 16 from an inside thereof, thereby heating the molecule discharge passage 17 provided in the outside thereof. The density of calorific value of the heater 19 of the interior guide 16, i.e., an amount of heat generated per a unit area thereof, it is determined to be larger than that of the heater 15, which is provided within the periphery of the molecule heater chamber 12. For this reason, the winding density of the heater 19 is more crowded or denser than that of the heater 15 in the molecule heater chamber 12.
Within the molecule discharge passage 17 provided between the exterior guide 13 and the interior guide 16, there is disposed or wired a heater 20, penetrating therethrough. This heater 20 penetrates through the molecule discharge passage 17, under the condition of being inserted into the supports 23 together with the screws inserted into the supports 23 mentioned above; i.e., being close to the supports 23 and the screws 24 therein. As the heater 20 penetrating through the molecule discharge passage 17, it is appropriate to utilize an intermediate line of the heater connecting between the exterior heater 18 and the interior heater 19, however the heater 20 may be made separate from, independently, from those heaters 18 and 19.
In this manner, in addition that the heaters 18 and 19 are disposed in the vicinity of the molecule discharge opening where the vapor can easily re-condensed or solidified, again; i.e., in more details, at the outside and the inside of the molecule discharge passage 17, and further with provision of the heater 20 penetrating through the in the molecule discharge passage 17, then, the evaporation material is prevented from being deposited on or separated from in the vicinity of the molecule discharge opening 14, with certainty. With this, narrow and/or blockage hardly occur in the molecule charge opening, which will be generated due to re-condensation or solidification of the vapor. In particular, since the sensor 20 penetrates through the molecule discharge passage 17 under the condition of being inserted into the supports 23 together with the screws 24 inserted within the supports 23, it enables to prevent the vapor from being re-condensed or solidified on the support members, such as, the support 23, the screw 24, etc., which are provided penetrating through the molecule discharge passage 17, with certainty.
Since the support members, for fixing the exterior guide 13 and also the interior guide 16, are facing or fronting on an outside where the molecules are discharged, they can be easily lowered in the temperature thereof, due to radiation. For this reason, the molecules of the film-forming material to be discharged from the molecule discharge opening 14 can be easily condensed or solidified, again, when they are in touch on or contact with the exterior guide 13 and/or the interior guide 16, due to the heat absorption thereon.
Then, with provision of the heater 18 at the side of the exterior guide 13, having the winding density as four (4) or more times large as the heater 15 at the side of the molecule heater chamber 12; it is possible to bring the wall-surface temperature of the interior guide 16 to be near that of the molecule heater chamber 12. Further, also with provision of the heater 19 at the side of the exterior guide 16, and bringing the winding densities of the both to be as twelve (12) times large as the heater 15 at the side of the molecule heater chamber 12; it is possible to keep the wall-surface temperature of the interior guide 16 to be equal or higher than that of the molecule heater chamber 12. Moreover, with insertion of the heater 20 into the supports 23 together with the screws 24, penetrating through the molecule discharge passage 17; therefore, also the support members, such as, the supports 23 and the screws 24, etc., which are provided penetrating through the molecule discharge passage 17, can be maintained to be similar to, in particular, with the temperature thereof.
As was fully mentioned in the above, according to the molecular beam source for use in accumulation of the organic thin-films, it is possible to prevent the vapor-generating source from unexpectedly discharging the vapor therefrom, thereby, enabling the discharge of vapor under a stable standing condition, and therefore, it is possible to form the thin-film, with stability, on the film-forming surface of the substrate. With this, it is also possible to form a uniform thin-film, even on a large-sized substrate. Further, with the heater(s) provided at the side of vapor discharge opening, it is possible to prevent the vapor of film-forming material from being re-condensed or solidified, to be deposition or separation of the film-forming material in the vapor discharge opening. With this, narrow and/or blockage will hardly occur in the molecule discharge opening; therefore, it is possible to discharge the molecules, with stability for a long time-period. And, it enables a stable film forming.
The present invention may be embodied in other specific forms without departing from the spirit or essential feature or characteristics thereof. The present embodiment(s) is/are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the forgoing description and range of equivalency of the claims are therefore to be embraces therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-57049 | Mar 2004 | JP | national |
| 2004-65318 | Mar 2004 | JP | national |
