Thermal physical vapor deposition source using pellets of organic material for making OLED displays

A thermal physical vapor deposition source for vaporizing compacted pellets of organic materials onto a surface of a substrate in forming a display, including a housing defining a plurality of spaced passages each for receiving compacted pellets, a cover plate over the housing, with a first plurality of openings corresponding to the spaced passages of the housing and an electrical heater structure disposed over the cover plate. The thermal physical vapor deposition source further including an aperture plate, disposed over the electrical heater structure, an electrically insulating spacer member located between the electrical heater structure and an aperture plate, and circuitry for applying current to the electrical heater structure to produce heat sufficient to vaporize the pellets and permit vapor efflux of materials to pass through the cover plate, the heater structure, the electrically insulating spacer member and the aperture plate, onto the substrate.

FIELD OF THE INVENTION

The present invention relates to physical vapor deposition of organic material to form an organic layer, which will form part of an organic light-emitting display (OLED). More particularly, the present invention relates to using an improved vapor deposition physical vapor deposition source wherein pellets of compacted organic materials are used.

BACKGROUND OF THE INVENTION

An organic light-emitting device, also referred to as an organic electroluminescent device, can be constructed by sandwiching two or more organic layers between first and second electrodes.

In a passive matrix organic light-emitting device (OLED) of conventional construction, a plurality of laterally spaced light-transmissive anodes, for example indium-tin-oxide (ITO) anodes, are formed as first electrodes on a light-transmissive substrate such as, for example, a glass substrate. Two or more organic layers are then formed successively by vapor deposition of respective organic materials from respective sources, within a chamber held at reduced pressure, typically less than 10−3torr (1.33×10−1pascal). In addition to doped or undoped organic light-emitting material, typical organic layers used in making OLED displays are doped or undoped organic hole-injecting material, doped or undoped organic hole-transporting material, and doped or undoped organic electron-transporting material, where doping refers to adding a minor constituent to enhance the electrical performance, optical performance, stability, or life time of a given material or device constructed thereof A plurality of laterally spaced cathodes is deposited as second electrodes over an uppermost one of the organic layers. The cathodes are oriented at an angle, typically at a right angle, with respect to the anodes.

Applying an electrical potential (also referred to as a drive voltage) operates such conventional passive matrix organic light-emitting devices between appropriate columns (anodes) and, sequentially, each row (cathode). When a cathode is biased negatively with respect to an anode, light is emitted from a pixel defined by an overlap area of the cathode and the anode, and emitted light reaches an observer through the anode and the substrate.

In an active matrix organic light-emitting device (OLED), an array of anodes are provided as first electrodes by thin-film transistors (TFTs) which are connected to a respective light-transmissive portion. Two or more organic layers are formed successively by vapor deposition in a manner substantially equivalent to the construction of the aforementioned passive matrix device. A common cathode is deposited as a second electrode over an uppermost one of the organic layers. The construction and function of an active matrix organic light-emitting device is described in commonly-assigned U.S. Pat. No. 5,550,066, the disclosure of which is herein incorporated by reference.

Organic materials, thicknesses of vapor-deposited organic layers, and layer configurations, useful in constructing an organic light-emitting device, are described, for example, in commonly-assigned U.S. Pat. Nos. 4,356,429; 4,539,507; 4,720,432, and 4,769,292, the disclosures of which are herein incorporated by reference.

Other kinds of imaging devices, such as imaging phosphors for computed radiography and x-ray photoconductive devices for digital radiography, depend on the ability to coat the active materials uniformly over large areas. While the following discussion pertains to OLED displays, it should be readily apparent that the same invention can be applied to the deposition of alkalihalide phosphors, amorphous semiconductors, and other luminescent or photoactive layers, as well as a variety of other materials used in devices based on such luminescence or photoactive layers.

For sufficiently small substrates, a point source approach can be implemented wherein the material to be deposited emanates from a localized heated crucible and the substrate is placed sufficiently far from the localized region of vaporization that the coating is sufficiently far from the localized region of vaporization that the coating is sufficiently uniform along the substrate. As substrate size increases or working distance increases, rotary or planetary motion of the substrate relative to the localized source is often required to produce the desired uniformity.

By elongating the vaporization source and providing for translation of source and substrate relative to one another, the desired uniformity can be attained at considerably smaller working distances and thus considerably higher rates and better materials utilization, if desired. Scaling of such a process to large areas (i.e. substrates greater than 15 cm in at least one dimension) is considerably easier than for point sources.

An elongated source for thermal physical vapor deposition of organic layers onto a structure for making an organic light-emitting device has been disclosed by Spahn in commonly assigned U.S. Pat. No. 6,237,529. The source disclosed by Spahn includes a housing, which defines an enclosure for receiving solid organic material, which can be vaporized. The housing is further defined by a top plate which defines a vapor efflux slit-aperture for permitting organic vapors to pass through the slit onto a surface of a structure spaced apart from the elongated source. The housing defining the enclosure is connected to the top plate. The source disclosed by Spahn further includes a conductive baffle member attached to the top plate. This baffle member provides line-of-sight covering of the slit in the top plate so that organic vapors can pass around the baffle member and through the slit onto the substrate or structure while particles of organic materials are prevented from passing through the slit by the baffle member when an electrical potential is applied to the housing to cause heat to be applied to the solid organic material in the enclosure causing the solid organic material to vaporize.

In using the thermal physical vapor deposition source disclosed by Spahn to form an organic layer of a selected organic material on a substrate or structure, it has been found that the vapor efflux slit-aperture causes non-uniform vapor flux of organic material to emanate along a length dimension of the slit. There is a problem when the width dimension of the slit is reduced, for example, to a width dimension less than 0.5 mm. Such spatially non-uniform orientation of opposing slit edges can be thought of as a deviation of planarity of opposing edges which, in turn, can promote a greater fraction of organic vapors to exit the vapor deposition source through a central portion of the slit, with a correspondingly lower fraction of organic vapors exiting the source through remaining portions of the slit along its length dimension. Such non-uniform vapor flux, directed at a substrate or structure, will cause the formation of an organic layer thereon which will have a non-uniform layer thickness in correspondence with the non-uniform vapor flux.

In addition, any nonuniformities in heat generation from the heater or heat absorption by the material to be deposited or distribution of the material within the source can give rise to nonuniformity in deposition along the length of the source. Yet another source of nonuniformity is unintended leaks in the source enclosure other than the apertures used to deliver the organic vapor. If such leak exists at the ends of the source, the flow of vapor from center to end of the source can cause pressure gradients within the source, thereby causing nonuniformity in the resultant deposition.

Forrest et al (U.S. Pat. No. 6,337,102B1) disclosed a method of vaporizing organic materials and organic precursors and delivering them to a reactor vessel wherein the substrate is situated and delivery of the vapors generated from solids or liquids is accomplished by use of carrier gases. In one embodiment of their invention, Forrest et al located the substrates within a suitably large reactor vessel, and the vapors carried thereto mix and react or condense on the substrate. Another embodiment of their invention is directed towards applications involving coating of large area substrates and putting several such deposition processes in serial fashion with one another. For this embodiment, Forrest et al disclosed the use of a gas curtain fed by a gas manifold (defined as “hollow tubes having a line of holes”) in order to form a continuous line of depositing material perpendicular to the direction of substrate travel.

The approach to vapor delivery as disclosed by Forrest et al can be characterized as “remote vaporization” wherein a material is converted to vapor in an thermal physical deposition source external to the deposition zone and more likely external to the deposition chamber. Organic vapors alone or in combination with carrier gases are conveyed into the deposition chamber and ultimately to the substrate surface. Great care must be taken using this approach to avoid unwanted condensation in the delivery lines by use of appropriate heating methods. This problem becomes even more critical when contemplating the use of inorganic materials that vaporize to the desired extent at substantially higher temperatures. Furthermore, the delivery of the organic vapor for coating large areas uniformly requires the use of gas manifolds.

Each one, or a combination, of the aforementioned aspects of organic powders, flakes, or granules can lead to nonuniform heating of such organic materials in physical vapor deposition sources with attendant spatially non-uniform sublimation or vaporization of organic material and can, therefore, result in potentially non-uniform vapor-deposited organic layers formed on a structure.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a thermal physical vapor deposition source which is capable of coating thin uniform layer of organic material.

It is another object of the present invention to provide a thermal physical vapor source that is particularly suited for coating large areas.

It is another object of the present invention to make effective use of pellets of organic material that can be vaporized by the thermal physical vapor deposition source.

The above objects are achieved by a thermal physical vapor deposition source for vaporizing pellets containing organic materials onto a surface of a substrate in forming a display, comprising:(a) a housing defining a plurality of spaced passages each for receiving compacted pellets of organic materials;(b) a cover plate over the housing, with a first plurality of openings corresponding to the spaced passages of the housing;(c) an electrical heater structure disposed over the cover plate;(d) an aperture plate, disposed over the electrical heater structure and having at least one aperture;(e) an electrically insulating spacer member located between the electrical heater structure and engaging the aperture plate, such electrically insulating spacer member having at least one opening, corresponding to the first plurality of openings of the cover plate and the spaced passages of the housing; and(f) means for applying current to the electrical heater structure to produce heat sufficient to vaporize the pellets and permit vapor efflux of materials to pass through the first plurality of openings of the cover plate, the heater structure, the electrically insulating spacer member and the apertures of the aperture plate, onto the substrate.

A feature of the present invention is the provision of the thermal physical vapor deposition source, which is designed to make use of compacted pellets of organic material that is capable of depositing thin layers to form a part of an OLED display.

Another feature of the present invention is that the thermal physical vapor deposition source is capable of depositing uniform organic layers which include at least one host component and at least one dopant component on a relatively large structure.

Yet, another beneficial feature of the present invention is that the compacted pellet of mixed organic materials can be evaporated for a longer time from a single thermal physical vapor deposition source rather than co-evaporation from a multiple deposition sources as in single component powders.

DETAILED DESCRIPTION OF THE INVENTION

The term “substrate” denotes at least a portion of an OLED display, which includes one or more layers onto which another organic layer is to be formed.

Turning toFIG. 1, a thermal physical deposition source100is illustrated, wherein a housing110, defining a plurality of spaced passages120, each spaced passage120having a closed first end112and an open second end114is shown. The spaced passages120can be of any shape and size and are fabricated such that compacted pellets215(seeFIG. 2) of organic materials can be inserted through the open second end114.

The housing110can be formed from thermally insulating materials such as high temperature glasses like quartz, alumino-boro-silicate glass and ceramics like alumina, zirconia, boron nitride, or magnesia. The purpose of using thermally insulating materials is to manage the thermal characteristics of the housing110when compacted pellets215used have more than one organic component, the details of which will be described hereinafter. Alternatively, if the thermal physical vapor deposition source100is used primarily for depositing organic layers from the compacted pellet215including a single component, the housing110can be made using thermally conductive materials such as stainless steel, tantalum, tungsten, or molybdenum. Further, the temperature of the housing110can be controlled using a variety of different methods, including controlling the temperature source (not shown), using integrated cooling or heating lines (not shown) to pass liquid or gaseous fluids through the housing110or integrating one or more heating elements (not shown) in the housing110.

The thermal physical vapor deposition source100further includes a cover plate130disposed over the housing110. The cover plate130defines a first plurality of openings134, each opening134corresponding to one of the spaced passages120of the housing110. The cover plate130can be made of electrically insulating materials such as alumina, high temperature glass like Pyrex®, silicon carbide or silicon nitride.

The thermal physical vapor deposition source100further includes an electrical heater structure140. In this embodiment, the electrical heater structure140includes an electrically conductive heater plate141disposed over the cover plate130. The electrical heater structure140can be either a single unit as shown inFIG. 1or it can be a heating array442(seeFIG. 4) of heating elements443(see FIG.4). The heating elements443are driven by a DC power supply148. The heater plate141includes a second plurality of openings144, each one of the second plurality of openings144corresponds to each one of the first plurality of openings134of the cover plate130.

The DC power supply148provides drive current through the heater plate141. As current passes through the heater plate141, thermal radiation is produced which is absorbed by the upper portions of the compacted pellets215causing vaporization of portions of the compacted pellets215in a vaporization zone235(see FIG.2). Vaporization occurs in the vaporization zone235, which is disposed between the heater plate141and the housing110. The heater plate141can be made from electrically conductive materials, such as a metal or a conductive alloy. The conductive materials included in the heater plate141are selected to prevent condensation of the vaporized materials during operation of the thermal physical deposition source100.

The thermal physical vapor deposition source100further includes an electrically insulating spacer member150disposed between the heater plate141and an aperture plate160. The electrically insulating spacer member150has at least one opening154, corresponding to the second plurality of openings144of the heater plate141. The electrically insulating spacer member150is located between the aperture plate160and the heater plate141to electrically insulate the aperture plate160from the current passing through the heater plate141. The electrically insulating spacer member150can be made from electrically insulating materials such as ceramic, glass and mica.

A mixing zone255(seeFIG. 2) is disposed between the heater plate141and the aperture plate160. The electrically insulating spacer member150can also include materials selected to remove any potential for internal vaporized material condensing on the spacer member150.

The aperture plate160having at least one aperture164to permit vapors of organic materials to pass through the aperture plate160and deposit on a substrate270(see FIG.2). The shape and number of the apertures164is selected to control the rate and pattern of vapor efflux and to promote sufficient deposition thickness uniformity on the substrate270. The aperture plate160can include refractory metals like W, Ta or Mo or ceramics like alumina, zirconia, magnesia, or high temperature glass like quartz or Pyrex®.

When the power supply148drives current through the heater plate141sufficient heat is generated in the vaporization zone235to cause a portion of the compacted pellet215to vaporize. The vapor of organic material produced in the vaporization zone235sequentially passes through the first plurality of openings134in the cover plate130, the second plurality of openings144in the heater plate141, the electrically insulating spacer member150and the apertures164of the aperture plate160. Further, additional heating elements may be placed on or near the cover plate130, spacer member150, and aperture plate160to prevent vaporous material from condensing on the cover plate130, the spacer member150, or the aperture plate160.

Turning toFIG. 2, a cross-sectional view of another embodiment of a thermal physical deposition source200is shown. The compacted pellets215are placed in a plurality of spaced passages220of a housing210the details of which have been described hereinbefore (see FIG.1). The spaced passages220can include multiple shapes, having an open first end212and an open second end214and each spaced passage220is adapted to receive the compacted pellet215.

The spaced passages220are formed so that compacted pellets215can be inserted through the open second end214of the spaced passages220. In this embodiment, a way of advancing the compacted pellets215so that the top portion of the compacted pellets215are in the vaporization zone235includes a plurality of push rods225. The push rods225are insertable into the open first ends212of the spaced passages220and engage the compacted pellets215in the spaced passages220in order to adjust the position of the compacted pellets215to compensate for material loss during vaporization in the vaporization zone235. The vaporization zone235is defined as the region between the housing210and the electrical heater structure240.

The compacted pellets215are inserted into the spaced passages220and the push rods225are inserted into the open first ends212of the spaced passages220until the push rods225engage the compacted pellets215. During vaporization of the compacted pellets215the top portion of the compacted pellet215is vaporized in the vaporization zone235. The push rods225move the compacted pellets215through the spaced passages220and expose the compacted pellets215to the vaporization zone235until the pellets215are completely vaporized. To this end, the push rods225are engaged by a thumb screw assembly227which can be manually adjusted to change the position of the push rods.

Alternative embodiments can be used to position the push rods225including barreled screws, a common base connected to each of the push rods225being driven by a single screw, a hydraulic or pneumatic jack pushing all the push rods225at the same time, or an automatic or computer controlled system for operating the movement of the push rods225.

The thermal physical vapor deposition source200further includes a cover plate230over the housing210. The cover plate230defines a first plurality of openings234, each opening234corresponding to each one of the spaced passages220of the housing210. The cover plate230can be made of thermally conducting and electrically insulating materials such as alumina, high temperature glass like Pyrex®, silicon carbide or silicon nitride.

The thermal physical vapor deposition source200further includes an electrical heater structure240. In this embodiment, the electrical heater structure240includes an electrically conductive heater plate241disposed over the cover plate230. The heater plate241includes a second plurality of openings244, wherein each one of the second plurality of openings244corresponding to each one of the first plurality of openings234of the cover plate230.

A DC power supply148(seeFIG. 1) provides a drive current through the heater plate241. As current passes through the heater plate241, thermal radiation is produced from the heater plate241. The thermal radiation is absorbed by the upper portion of the compacted pellets215causing vaporization of the compacted pellets215. The heater plate241can include electrically conductive materials, such as quartz bulbs, strip tantalum, cartridge heaters, and other metals. The materials of the heater plate241can be selected to prevent condensation of the vaporized materials during operation of the thermal physical deposition source200.

The thermal physical vapor deposition source200further includes an electrically insulating spacer member250located over the heater plate241and an aperture plate260located over the electrically insulating spacer member250. The electrically insulating spacer member250has at least one opening254, corresponding to the second plurality of openings244of the heater plate241first plurality of openings234of the cover plate230and the spaced passages220of the housing210. The electrically insulating spacer member250is located between the aperture plate260and the heater plate241to electrically insulate the aperture plate260from the current passing through the heater plate241. The electrically insulating spacer member250can be made of electrically insulating materials such as ceramic, glass and mica.

The mixing zone255is disposed between the heater plate241and the aperture plate260. The electrically insulating spacer member250can include materials selected to remove any potential for internal vaporized material condensing on the spacer member250.

The aperture plate260having at least one aperture264to permit vapors of organic materials to pass through the aperture plate260and deposit on the substrate270. The shape and number of the apertures264is selected to control the rate and pattern of vapor efflux and promote sufficient deposition thickness uniformity on the substrate270.

In this embodiment, the compacted pellets215made of organic material are vaporized in the vaporization zone235. The vapor of organic material passes sequentially through the first plurality of openings234in the cover plate230, the second plurality of openings244in the heater plate241, the electrically insulating spacer member250and the apertures264of the aperture plate260. The aperture plate260can include refractory metals like W, Ta or Mo or ceramics like alumina, zirconia, magnesia, or high temperature glass like quartz or Pyrex®. The materials of the aperture plate260can be selected to prevent condensation of vaporized material during vaporization of the compacted pellets215. Further, additional heating elements may be placed on or near the cover plate230, electrically insulating spacer member250, and aperture plate260to prevent vaporous material from condensing on the cover plate230, the spacer member250, or the aperture plate260.

Turning toFIG. 3, another embodiment of a thermal physical deposition source300is illustrated, wherein compacted pellets315are placed in a plurality of spaced passages320of a housing310. The spaced passages320can include multiple shapes and have an open first end312and an open second end314and are adapted to receive the compacted pellets315.

In this embodiment, the spaced passages320include both large cross-sectional area spaced passages321and small cross-sectional area spaced passages322to receive the compacted pellets315of different sizes and different compositions. For example, pellets including a host organic material can be contained in the large cross-sectional area spaced passages321and pellets including a dopant organic material can be contained in the small cross-sectional area spaced passages322to support the deposition of multi-component thin films. Such host and dopant organic materials will mix upon vaporization and be deposited on a substrate in the proportions controlled by the cross-sectional area of the spaced passages320and the rate of vaporization.

The housing310can be made of thermally and electrically insulating or conductive materials such as graphite, quartz, tantalum, ceramics, and metals. Further, the temperature of the housing310can be controlled using a variety of different methods, including controlling the temperature source (not shown), using integrated cooling or heating lines (not shown) to pass liquid or gaseous fluids through the housing310or integrating one or more heating elements (not shown) in the housing310.

The spaced passages320are formed so that compacted pellets315can be inserted into the open second ends314of the spaced passages320. In this embodiment, a way of advancing the pellets so that the top portion of the compacted pellets315are in the vaporization zone335includes a plurality of push rods325. The push rods325are insertable into the open first ends312of the spaced passages320and engage the pellets315in the spaced passages320in order to adjust the position of the pellets315to compensate for material loss during vaporization in the vaporization zone335. The vaporization zone335is defined as the region between the housing310and the electrical heater structure340.

The compacted pellets315are inserted into the spaced passages320and the push rods325are inserted into the open first ends312of the spaced passages320until the push rods325engage the compacted pellets315. During vaporization of the compacted pellets315the top portion of the pellets315are vaporized in the vaporization zone335. The push rods325move the compacted pellets315through the spaced passages320and expose the compacted pellets315to the vaporization zone335until the pellets315are completely vaporized. To this end, the push rods325are engaged by a thumb screw assembly327, which can be manually adjusted to change the position of the push rods325.

Alternative embodiments can be used to position the push rods325including barreled screws, a common base connected to each of the push rods325being driven by a single screw, a hydraulic or pneumatic jack pushing all the push rods325at the same time, or an automatic or computer controlled system for operating the movement of the push rods325.

The thermal physical vapor deposition source300further includes a cover plate330over the housing320. The cover plate330includes a first plurality of openings334, each one of the first plurality of openings334, corresponding to each one of the spaced passages320of the housing310. The cover plate330can include thermally conducting and electrically insulating materials such as alumina, high temperature glass like Pyrex®, silicon carbide or silicon nitride.

The thermal physical vapor deposition source300further includes an electrical heater structure340. In this embodiment, the electrical heater structure340includes an electrically conductive heater plate341disposed over the cover plate330. The heater plate341includes a second plurality of openings344, each one of the second plurality of openings344corresponding to the first plurality of openings334of the cover plate330.

A DC power supply148(seeFIG. 1) provides drive current through the heater plate341. As current passes through the heater plate341, thermal radiation is produced from the heater plate341. The thermal radiation is absorbed by the upper portion of the compacted pellets315causing vaporization of the compacted pellets315. The heater plate341can include electrically conductive materials, such as quartz bulbs, strip tantalum, cartridge heaters, and other metals. The materials of the heater plate341can be selected to prevent condensation of the vaporized materials during operation of the thermal physical deposition source300.

The thermal physical vapor deposition source300further includes an electrically insulating spacer member350located over the heater plate341and an aperture plate360located over the electrically insulating spacer member350. The electrically insulating spacer member350has at least one opening354, corresponding to the second plurality of openings344of the heater plate341, first plurality of openings334of the cover plate330and the spaced passages320of the housing310. The electrically insulating spacer member350is located between the aperture plate360and the electrical heater structure340to electrically insulate the aperture plate360from the current passing through the heater plate341. The electrically insulating spacer member350can be made from electrically insulating materials such as ceramic, glass and mica.

The mixing zone355is disposed between the heater plate341and the aperture plate360. The electrically insulating spacer member350can also include materials selected to remove any potential for internal vaporized material condensing on the spacer member350.

The aperture plate360includes at least one aperture364to permit vapors of organic materials to pass through the aperture plate360and deposit on the substrate270(see FIG.2). The shape and number of the apertures364is selected to control the rate and pattern of vapor efflux and promote sufficient deposition thickness uniformity on the substrate270.

In this embodiment, compacted pellets315made of organic material are vaporized in the vaporization zone335. The vapor of organic material passes sequentially through the first plurality of openings334in the cover plate330, the second plurality of openings344in the heater plate341, the electrically insulating spacer member350and the apertures364of the aperture plate360. The aperture plate360can include refractory metals like W, Ta or Mo or ceramics like alumina, zirconia, magnesia, or high temperature glass like quartz or Pyrex®. The materials of the aperture plate360can be selected to prevent condensation of vaporized materials during the vaporization of the compacted pellets315. Further, additional heating elements may be placed on or near the cover plate330, spacer member350, and aperture plate360to prevent vaporous material from condensing on the cover plate330, the electrically insulating spacer member350, or the aperture plate360.

Turning toFIG. 4, another embodiment of a thermal physical vapor deposition source400is illustrated, wherein the compacted pellets215(FIG. 2) are placed in a plurality of spaced passages420of a housing410. The spaced passages420can include multiple shapes and sizes and have an open first end412and an open second end414and are adapted to receive the compacted pellet215. The housing410can include thermally and electrically insulating materials such as quartz, tantalum, ceramics, and glass-ceramics.

The spaced passages420are formed so that compacted pellets215can be inserted into the open second ends414of the spaced passages420. In this embodiment, a way of advancing the compacted pellets215so that the top portion of the compacted pellets215are in the vaporization zone235includes the push rods225as described hereinbefore. The push rods225are insertable into the open first ends412of the spaced passages420and engage the compacted pellets215in the spaced passages420in order to adjust the position of the compacted pellets215to compensate for material loss during vaporization in the vaporization zone235. The vaporization zone235is defined as the region between the housing410and the electrical heater structure440.

The compacted pellets215are inserted into the spaced passages420and the push rods225are inserted into the open first end412of the spaced passages420until the push rods225engage the compacted pellets215. During vaporization of the compacted pellets215the top portion of the pellet215is vaporized in the vaporization zone235. The push rods225move the compacted pellets215through the spaced passages420and expose the compacted pellets215to the vaporization zone235until the pellets215are completely vaporized. To this end, the push rods225are engaged by a thumb screw assembly227, which can be manually adjusted to change the position of the push rod.

Alternative embodiments can be used to position the push rods225including barreled screws, a common base connected to all the push rods225being driven by a single screw, a hydraulic or pneumatic jack pushing all the push rods225at the same time, or an automatic or computer controlled system for operating the movement of the push rods225.

The thermal physical vapor deposition source400further includes a cover plate430over the housing410. The cover plate430includes a first plurality of openings434, each one of the first plurality of openings434corresponding to the each one of the spaced passages420of the housing410. The cover plate430can include thermally conducting and electrically insulating materials such as alumina, high temperature glass like Pyrex®, silicon carbide or silicon nitride. The materials of the cover plate430can be selected to prevent condensation of vaporized materials onto the surface of the cover plate430during vaporization of the compacted pellets215.

The thermal physical vapor deposition source400further includes an electrical heater structure440. In this embodiment, the electrical heater structure440includes a heater plate441disposed over the cover plate, having a second plurality of openings444corresponding to the first plurality of openings434of the cover plate430and the spaced passages420of the housing410. The electrical heater structure440further includes a heating array442, which includes a plurality of heating elements443over the heater plate441, each such heating element443corresponding to each opening in the heater plate441.

A DC power supply148(seeFIG. 1) provides a drive current through the heating elements443. As current passes through the heating elements443, thermal radiation is produced from the heating elements443proportional to the current applied to the individual heating element443. The thermal radiation is absorbed by the portion of the compacted pellets215in the vaporization zone causing vaporization of the compacted pellets215. The heating elements443in the heating array442and the heater plate441include quartz bulbs, strip tantalum, cartridge heaters, and other metals. The materials of the electrical heater structure440can be selected to prevent condensation of the vaporized materials during operation of the thermal physical deposition source400.

The advantages of using the individually-controlled heating elements443, include producing varying radiation profiles thereby controlling temperature gradients in the heater structure and resulting in better control in the rate of vaporization of individual compacted pellets215. Combining the embodiment ofFIG. 4with the embodiment ofFIG. 3can produce improved controlled deposition by improved control of internal mixing behavior and improved control of the vapor composition deposited on the substrate270.

The thermal physical vapor deposition source400further includes an electrically insulating spacer member450located over the electrical heater structure440and an aperture plate460located over the electrically insulating spacer member450. The electrically insulating spacer member450has at least one opening454, corresponding to the second plurality of openings444of the electrical heater structure440, first plurality of openings434of the cover plate430and the spaced passages420of the housing410. The electrically insulating spacer member450is located between the aperture plate460and the electrical heater structure440to electrically insulate the aperture plate460from the electrical potential and resulting current passed through the electrical heater structure440. The electrically insulating spacer member450can be made from electrically insulating materials such as ceramic, glass and mica.

The mixing zone255is disposed between the heater plate441and the aperture plate460. The electrically insulating spacer member450can also include materials selected to remove any potential for internal vaporized material condensing on the spacer member450.

The aperture plate460includes at least one aperture464to permit vapors of organic materials to pass through the aperture plate460and deposit on a substrate270. The shape and number of the apertures464is selected to control the rate and pattern of vapor efflux and promote deposition thickness uniformity on the substrate270.

In this embodiment, the compacted pellets215made of organic material are vaporized in the vaporization zone235. The vapor of organic material passes sequentially through the first plurality of openings434in the cover plate430, the second plurality of openings444in the heater plate441, the electrically insulating spacer member450and the apertures464of the aperture plate460. The aperture plate460can include refractory metals like W, Ta or Mo or ceramics like alumina, zirconia, magnesia, or high temperature glass like quartz or Pyrex®. The materials of the aperture plate460can be selected to prevent condensation of vaporized materials during the vaporization of the compacted pellets215. Further, additional heating elements may be placed on or near the cover plate430, spacer member450, and aperture plate460to prevent vaporous material from condensing on the cover plate430, the spacer member450, or the aperture plate460.

PARTS LIST