LASER ABLATION METHOD TO FABRICATE COLOR ORGANIC LIGHT EMITTING DIODE DISPLAYS

Abstract: Laser radiation may be used to ablate organic materials (310, 520 and 730) as well as metals (400, 600 and 800). A method of using such laser ablation to selectively remove organic material and metal material from an organic light emitting device (OLED) work piece (1000) is disclosed. The ablation enables fabrication of multi-color pixels in OLED displays. A novel OLED structure having adjacent multi-colored organic stakes (10, 20 and 30) is disclosed. Further, a novel ablation chamber (900) in which an OLED structure (1000) may be subjected to laser ablation is also disclosed. The ablation chamber includes means for moving an OLED structure within the chamber, means for detecting an ablation endpoint, and means for suctioning ablated material from the chamber.

Description: LASER ABLATION METHOD TO FABRICATE COLOR ORGANIC LIGHT EMITTING DIODE DISPLAYS Cross Reference To Related Patent Application This application relates to and claims priority on a provisional application (unassigned) filed July 11, 1997 and entitled "Laser Ablation Method To Fabricate Color Organic Light Emitting Diode Displays". Field of the invention The invention relates to organic light emitting devices having multi-colored pixels and apparatus and methods for making such devices. Background of the Invention Organic light emitting devices (OLED's) may be used to provide displays. The displays may comprise a collection of light emitting diodes that are arranged into picture elements (pixels). In order to provide a full color display, it is desirable to make OLED's with multi-color pixels, or more specifically with red, blue and green subpixels. In order to produce an OLED with red, blue and green subpixels, it may be necessary to employ lithographic processing techniques to build the red, green and blue subpixels. It may be difficult, if not impossible, however, to practice the required lithographic techniques without introducing some small amount of water into the OLED. Unfortunately, OLED's are extremely sensitive to the presence of water and oxygen. Small amounts of moisture, on the order of parts per billion, can cause significant degradation in the performance of the display. This sensitivity to water may pose a serious challenge to OLED manufacturers who wish to make multi-colored OLED displays. One potential alternative to lithographic processing involves the use of shadow masks during evaporation of the organic layers in the OLED. The mechanical strength of the shadow mask limits the fineness of the mask, however, the process of using a shadow mask does have the advantage of being water free. The limitation on the fineness of the pattern, in turn, limits the resolution of the subpixels produced with the shadow mask. Consequently, the subpixels that may be attained using a shadow mask are larger than those that may be attained using other processing methods because of the limitation on the fineness of the mask. The same limitation on subpixel size (i. e. display resolution) may result from the use of dry etch processes, such as plasma and RIE processes. Thus, the display resolution attained using water-free processing techniques may be less than desirable. One solution to the foregoing problems has been to make a single color OLED display and convert it to a multi-color display by using color filters and/or color conversion from a shorter wavelength. These OLED's may be very inefficient, and therefore undesirable, because a large fraction of the emitted light from a filtered or converted subpixel may be lost. The addition of filters and converters may also complicate manufacturing of the OLED by adding the need for extra processing steps. Based upon the limitations that may result from using an OLED with filters or converters, applicant believes that the use of individual color emitters forming red, green, and blue subpixels may be the preferred method of providing multi-colored OLED displays. Accordingly, there is a need for an OLED, and a method of making the OLED, in which the use or production of water is reduced. Further, there is a need for an OLED and method in which the smallness in size of the subpixels is not undesirably limited. The foregoing needs may be met by applicant's laser ablation method to fabricate color organic light emitting diode displays. Techniques for laser ablation are disclosed in U.S. Patent No. 4,925,523 (May 15, 1990) to Braren et al., and U.S. Patent No. 5,232,549 (Aug. 3, 1993) to Cathey et al., each of which are hereby incorporated by reference herein. Objects of the Invention It is therefore an object of the present invention to provide an OLED that is less likely to include water. It is another object of the present invention to provide a method of making an OLED which reduces the likelihood of water being included in the OLED. It is a further object of the present invention to provide an OLED and method of making the same, that includes subpixels of a desirable size for a high resolution display. It is still another object of the present invention to provide an OLED with individual red, blue and green subpixels. It is yet another object of the present invention to make an OLED using laser ablation. It is still yet another object of the present invention to provide a laser ablation system for making an OLED. It is still a further object of the invention to detect the ablated material in an OLED work piece by detecting material fluorescence. Additional objects and advantages of the invention are set forth, in part, in the description which follows and, in part, will be apparent to one of ordinary skill in the art from the description and/or from the practice of the invention. Summary of the Invention In response to the foregoing challenge, Applicant has developed an innovative organic light emitting device comprising: a support substrate; a transparent hole injector layer overlying said substrate; and spaced first and second subpixel stacks overlying said hole injector layer, wherein: said first subpixel stack comprises (1) an active lower layer that is capable of producing a first color of light and is overlying the hole injector layer, and (2) a first conductor layer overlying the active lower layer capable of producing the first color of light, and said second subpixel stack comprises ( 1 ) an active lower layer that is capable of producing a second color of light and is overlying the hole injector layer, (2) a second conductor layer overlying the active lower layer capable of producing the second color of light, and (3) an inactive upper layer overlying the second conductor layer, said inactive upper layer being comprised of the same material as that of the active lower layer of the first subpixel stack. Applicant has also developed an innovative method of providing light emitting subpixels in an organic light emitting device comprising the steps of: providing a substrate with an overlying hole injector layer; providing a lower layer of organic material on the hole injector layer; providing an upper layer of electrically conductive material overlying the lower layer; and selectively ablating portions of the lower and upper layers such that a portion of the hole injector layer is exposed and light emitting subpixels are formed from a remaining strip of electrically conductive material overlying a strip of organic material. More specifically, in a method of forming an organic light emitting device having subpixel strips that include organic and hole injector material and that are adapted to emit light of different wavelengths, applicant has developed the improvement comprising the step of selectively ablating organic and hole injector material from said device in order to form said subpixel strips. Applicants have further developed an innovative laser ablation system comprising: a chamber for isolating a work piece in a controlled ambient; means for controlling the amount of moisture in said chamber; means for controlling the location of a work piece in said chamber; means for focusing laser light on a work piece in said chamber; means for detecting the location of ablated material on said work piece in said chamber; and means for removing ablated material from said chamber. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated herein by reference, and which constitute a part of this specification, illustrate certain embodiments of the invention, and together with the detailed description serve to explain the principles of the present invention. Brief Description of the Drawings Figs. 1 -7 are cross-sectional views in elevation that illustrate sequential steps in the formation of an OLED embodiment of the invention. Fig. 8 is a flow chart that illustrates the process steps of a method embodiment of the invention. Fig.9 is a pictorial view of an ablation chamber embodiment of the invention that may be used to make an OLED. Figs. 10-12 are cross-sectional views in elevation that illustrate sequential steps in the formation of an OLED in accordance with an alternative embodiment of the invention. Detailed Description of the Preferred Embodiments Reference will now be made in detail to a preferred embodiment of the present invention, an example of which is illustrated in the accompanying drawings. A preferred method of making an OLED is illustrated by the sequence of process steps shown in Figs 1-7. With reference to Fig.7, the completed OLED may include multiple red 10, green 20, and blue 30 stacks patterned on parallel strips of hole injector material 200 overlying a substrate 100. The red stack 10 may comprise an active lower red subpixel strip 310, a first strip of electron injector material 410 overlying the lower strip 310, an inactive green subpixel strip 510 overlying the first strip of electron injector material 410, a second strip of electron injector material 610 overlying the inactive green subpixel strip 510, an inactive upper blue subpixel strip 710 overlying the second strip of electron injector material 610, and a third strip of electron injector material 810 overlying the inactive blue subpixel strip 710. The green subpixel stack 20 may comprise an active lower green subpixel strip 520, a fourth strip of electron injector material 620 overlying the green strip 520, an inactive upper blue subpixel strip 720 overlying the fourth strip of electron injector material 620, and a fifth strip of electron injector material 820 overlying the inactive blue subpixel strip 720. The blue subpixel stack 30 may comprise an active blue subpixel strip 730 and a sixth strip of electron injector material 830 overlying the active blue subpixel strip 730. It is appreciated that the color of the active lower layer in each stack (10, 20, and 30) can be varied without departing from the scope of the invention. For example, stack 10 may include an active lower layer of green material, or of blue material, in alternative embodiments of the invention. The completed OLED of Fig. 7 may be made according to the process illustrated by Figs. 1-6. Figure 1 is a cross-sectional view of an OLED substrate 100 with one or more hole injector strips 200 (preferably transparent indium tin oxide (ITO)) patterned thereon. In the alternative, hole injector strips 200 may be indium zinc oxide (IZO). The substrate 100 may be a transparent and rigid material, such as glass, that is capable of supporting the overall device 1000 when completed. The ITO strips 200 may be formed on the substrate 100 by wet etching using photolithic methods or by laser ablation. The ITO strips 200 may run across the substrate 100 (left to right as shown in Fig. 1) and may have a width that is appropriate for the width of a pixel and a thickness in the range of 0.05 to 0.15 microns. With reference to Fig.2, one or more lower layers 300 of organic material that are capable collectively of producing a first color of light may be provided on the ITO strip 200. For example, if the first color of light is chosen to be in the red wavelengths, lower layers 300 may comprise a stack of CuPc (copper pthalocyanine), NPB (4,4'-bis[N-(l- naphthyl)-N-phenyl-amino]-biphenyl), and Alq (aluminum hydroxy quinolene). A layer of electron injector material 400, which may be an electrical conductor (e.g. MgAg), may be provided overlying or on top of the lower layers 300. The electron injector material 400 may be deposited using an evaporation process and be in the range of 0.2 to 1.0 microns thick when completed. With reference to Fig. 3, a high power laser beam, such as an excimer laser, may be used to ablate the electron injector layer 400 and the red layer 300 in selected regions so as to produce a strip of red subpixels 310 and electron injector material 410 (running into the page as shown in Fig. 3) in the red stack 10. Depending on the wavelength of the laser and the optics design, the laser beam can be focused to submicron size to form the red subpixels in a very thin strip if desired. In order to detect the point of ablation at which the ITO strip 200 is reached, a light detector may be used. Ablation of the organic red layer 300 produces a visible light fluorescence. Ablation of the ITO strip 200, however, does not produce significant fluorescence. Thus, the ablation point at which the ITO strip 200 is reached may be determined by detecting a decrease or ceasing of fluorescence. The point at which the ITO strip 200 is reached may be fairly accurately determined because the ablation is preferably carried out in pulses, which allows the level of fluorescence to be measured after each pulse. With reference to Fig. 4, one or more intermediate layers 500 of organic material that are capable collectively of producing a second color of light (e.g. green) may be provided on the ITO strip 200 and the red stack 10. A second layer of electron injector material 600 may be provided overlying or on top of the intermediate layers 500. Selective laser ablation may be carried out on the intermediate layers 500 and the second layer of electron injector material 600 to produce the structure shown in Fig. 5. The ablation may be used to create a small gap (on the order of 2.0 microns) between the red stack 10 and the green stack 20. With reference to Fig. 5, the red stack 10 comprises an active lower red subpixel strip 310, a first strip of electron injector material 410 overlying the lower red strip 310, an inactive green subpixel strip 510 overlying the first strip of electron injector material 410, and a second strip of electron injector material 610 overlying the inactive green subpixel strip 510. With continued reference to Fig. 5, the green stack 20 may comprise an active lower green subpixel strip 520 and a fourth strip of electron injector material 620 overlying the lower green strip 520. With reference to Fig. 6, one or more upper or top layers 700 of organic material that are capable collectively of producing a third color of light (e.g. blue) may be provided on the ITO strip 200, the red stack 10 and the green stack 20. A sixth layer of electron injector material 800 may be provided overlying or on top of the upper layers 700. Selective laser ablation may be carried out on the upper layers 700 and the sixth layer of electron injector material 800 to produce the structure shown in Fig. 7. With reference to Fig. 7, the completed OLED may include a red stack 10, a green stack 20 and a blue stack 30. The red stack may comprise an active lower red subpixel strip 310, a first strip of electron injector material 410, an inactive green subpixel strip 510, a second strip of electron injector material 610, an inactive upper blue subpixel strip 710, and a third strip of electron injector material 810. The green stack 20 may comprise an active lower green subpixel strip 520, a fourth strip of electron injector material 620, an inactive upper blue subpixel strip 720, and a fifth strip of electron injector material 820. The blue subpixel stack 30 may comprise an active blue subpixel strip 730 and a sixth strip of electron injector material 830. With continued reference to Fig. 7, in operation of the completed OLED 1000, voltage may be applied only to the bottom most electron injector strips (/ ' . e. first strip 410, fourth strip 620, and sixth strip 830) in each of the respective subpixel stacks 10, 20, and 30. The intermediate and upper electron injector strips (i.e. second strip 610, third strip 810, and fifth strip 720) may be shorted with the bottom most electron injector strips in order to avoid complications of unconnected floating electrodes. The lower most subpixel strip in each subpixel stack will define the color emitted by the stack. The emission spectrum of the strips of organic layer in contact with the ITO layer may not be impacted by the other organic layers on top of it, because there are no hole injectors available to the upper organic layers. For example, with reference to Fig. 7, the red stack 10 may only emit red light because the red subpixel layer is the only layer which contacts both an electron injector strip (first strip 410) and a hole injector strip (ITO strip 200). The green strip 510 and the blue strip 710 in the red stack 10 may not emit light because there is no hole injector (ITO) in contact with these strips. In like manner, the green stack 20 may only emit green light, and the blue stack 30 may only emit blue light. Each of the strips of electron injector material (410, 610, 810, 620, 820, and 830) may be provided by a strip of Mg/Ag metal. One advantage of using this particular type of metal is that it provides a reflective surface adjacent to the lower most red, green, and blue strips (310, 520, and 730). The strips of electron injector material 410, 620, and 830 may prohibit light from entering the upper layers of the organic stacks 10, 20, and 30, thereby reducing light loss and unwanted color noise. In addition, the reflective metal surfaces may reflect most or all of the light generated in the lower most active strips back to the viewing side of a display, thereby enhancing display brightness. In an alternative embodiment of the invention, the completed OLED of Fig. 7 may be made according to the process illustrated by Figs. 10-12. Figure 10 is a cross- sectional view of an OLED substrate 100 with one or more hole injector strips 200 (preferably transparent indium tin oxide (ITO)) patterned thereon, one or more lower layers 300 of organic material capable collectively of producing a first color of light overlying the ITO strip 200, and a layer of electron injector material 400 overlying the lower layers 300. With reference to Fig. 11 , a high power laser beam, such as an excimer laser, may be used to ablate the electron injector layer 400 in selected regions so as to produce a strip of electron injector material 410 (running into the page as shown in Fig. 11). Depending on the wavelength of the laser and the optics design, the laser beam can be focused to submicron size to form the electron injector material into a very thin strip. With reference to Fig. 12, a thin strip of organic material 310 may be formed under the strip of electron injector material 410 using an etching process (preferably - oxygen plasma etching). The electron injector material 410 may be used as an etch mask so that the strip of organic material 310 is coextensive with the electron injector material 410. The foregoing process, explained with reference to Figs. 10-12, may be used to produce additional organic stacks (not shown) next to the stack 10, just as the process explained with reference to Figs. 1 -7 may be repeated to form stacks 10, 20, and 30. A laser ablation system embodiment of the invention, which is useful for making the OLED of the invention, is shown in Fig. 9. The system may comprise a gas tight chamber 900, a translation stage 910 within the chamber, a laser ablation detector 920, an optics subsystem 930, an ambient fill port 940, a suction port 950, and a laser beam input port 960. The chamber 900 may be used to isolate an OLED work piece 1000 in a controlled ambient environment for the laser ablation process. For example, an inert gas, such as Argon or Nitrogen, may be introduced into the chamber 900 through the ambient fill port 940 to provide an ambient of inert gas around the work piece 1000. The introduction of inert gas through the fill port 940 may provide a means for reducing the amount of moisture and oxygen in the chamber 900 during processing as well as helping the suction process to remove the ablated debris. The work piece 1000 may be supported on and secured to the translation stage 910 within the chamber 900 during laser ablation processing. The stage 910 may provide a means for controlling the location of the work piece 1000 relative to the laser beam 962 and may include one or more servo motors 912 for translating the stage in one, two, or three dimensions. The stage 910 may be translated in the x-y plane in order to scan a stationary laser beam 962 across the work piece 1000. The stage 910 may be translated in the z direction in order to focus the laser beam 962 on the work piece 1000. A laser (not shown) may be located outside the chamber 900 and may provide a laser beam 962 that is coupled into the chamber through a first set of optics located at the laser beam input port 960. Once inside the chamber 900, the laser beam 962 may be directed and focused on the work piece 1000 held on the translation stage 910 using the optics subsystem 930. The optics subsystem 930 may include numerous optical elements, such as mirror(s) 932 and lens(es) 934 and thus may provide means for focusing laser light on the work piece 1000. The optics subsystem 930 may also include a mask and projection optics with appropriate reduction factors. The chamber 900 may include a detector 920 that is capable of detecting the composition of ablated material on the work piece 1000. Preferably, the detector 920 may be fixed to the chamber 900. If laser ablation is carried out by translating the stage 910 or by means of a projection mask, then the detector may be directed to a fixed location, because the intersection of the laser beam 962 and the work piece are fixed relative to the detector. In an alternative embodiment, ablation may be carried out by scanning the laser beam 962 across a fixed position work piece 1000 by adjusting the optics subsystem 930. If laser ablation is carried out by scanning the laser beam 962 across a stationary work piece, then the detector 920 may be adapted to scan in coordination with the laser beam. The detector 920 may provide signals that indicate the presence of ablated material to a controller (not shown). Responsive to the receipt of such signals from the detector 920, the controller may adjust the location of ablation by moving the translation stage 910 or the laser beam 962. The detector may operate by detecting the fluorescence of ablated organic material. Ablation is a photochemical effect which may produce fluorescence in the UV to visible light range in organic material. The ablation of organic material (such as the material comprising red strip 310, green strip 520, and blue strip 730 of Fig. 7) accordingly may produce light. Conversely, the ablation of ITO material produces very little, if any, fluorescent light. The detector 920 may be used to monitor the characteristic fluorescence emission from various layers of polymers or metals in the work piece 1000 during ablation. An abrupt change in characteristic fluorescence intensity may indicate the ablation endpoint. The detector 920 may include a filter in front of the detector that prevents ablating laser light from being detected. By detecting the emission of light, or the lack thereof, in the ablation region, the detector 920 may be used to determine the point in the ablation process at which the layer of ITO material is reached. By applying the laser beam to the work piece 1000 in discrete pulses, the precise transition point between organic material and ITO material may be detected. Because it is desirable to ablate down to, but not into, the ITO material, the foregoing process is very useful in controlling the depth of ablation. The type of detector 920 that is used may be very sensitive; e.g. capable of detecting the emission of a few photons at a time. Such detectors have been used in a limited fashion to detect ablation end points when ablating plaque on the interior wall of an artery. The chamber 900 may also include one or more suction devices 952 for removing ablated material from the chamber. The suction device 952 may be introduced into the chamber through a suction port 950. The suction may be provided by means of a suction pump such as a Turbo pump, which would not contaminate the chamber by back- streaming of oil, etc. The ablation of selective portions of the OLED to leave the red, green and blue subpixel stacks (10, 20, and 30, Fig. 1) may be carried out in the above described chamber 900 using pulsed laser beam(s) of one or more wavelengths. One embodiment of the ablation method of the invention is described with reference to the flow chart shown in Fig. 8 and the ablation system of Fig. 9. First, in accordance with step 1100 of Fig. 8, the work piece, which includes a substrate to be coated with organic material, may be loaded into a deposition chamber. In step 1110, the work piece may be coated with ITO, organic, and electron injector material in the appropriate patterns consistent with the steps illustrated by Figs. 1-2. In step 1120 the work piece may be unloaded from the deposition chamber. In step 1130 the work piece may be secured to the translation stage within the laser ablation chamber. The laser ablation chamber then may be sealed and filled to a nominal pressure of 1.0 to 1.1 atmospheres with an inert gas, such as Argon or Nitrogen. Laser ablation and the suctioning of ablated material may then be carried out consistent with the step illustrated by Fig. 3. In step 1140 the same deposition chamber referenced above, or a different chamber, may be loaded. In step 1150 the work piece may be coated with second layers of organic and electron injector material in the appropriate patterns consistent with the step illustrated by Fig. 4. In step 1160 the work piece may be unloaded from the deposition chamber. Returning to step 1130, the work piece may be secured again to the translation stage within the laser ablation chamber; the laser ablation chamber may be sealed and filled with an inert gas; and the required laser ablation may be carried out consistent with the step illustrated by Fig. 5. In step 1170 the deposition chamber may be loaded for a third time. In step 1180 the work piece may be coated with third layers of organic and electron injector material in the appropriate patterns consistent with the step illustrated by Fig. 6. In step 1190 the work piece may be unloaded from the deposition chamber. It will be apparent to those skilled in the art that various modifications and variations can be made in the construction, configuration, and/or operation of the present invention without departing from the scope or spirit of the invention. For example, in the embodiments mentioned above, various changes may be made in the order and selection of light emitting organic materials without departing from the scope and spirit of the invention. Further, it may be appropriate to make additional modifications or changes to the system used to ablate the work piece and the system used to detect the ablation end point without departing from the scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of the invention provided they come within the scope of the appended claims and their equivalents.

Claims: I CLAIM: 1. An organic light emitting device comprising: a support substrate; a transparent hole injector layer overlying said substrate; and spaced first and second subpixel stacks overlying said hole injector layer, wherein: said first subpixel stack comprises (1) an active lower layer that is capable of producing a first color of light and is overlying the hole injector layer, and (2) a first conductor layer overlying the active lower layer capable of producing the first color of light, and said second subpixel stack comprises (1) an active lower layer that is capable of producing a second color of light and is overlying the hole injector layer, (2) a second conductor layer overlying the active lower layer capable of producing the second color of light, and (3) an inactive upper layer overlying the second conductor layer, said inactive upper layer being comprised of the same material as that of the active lower layer of the first subpixel stack. 2. The device of Claim 1 wherein the transparent hole injector layer comprises a material selected from the group consisting of indium tin oxide and indium zinc oxide. 3. The device of Claim 1 wherein the first and second colors of light are selected from the group consisting of: red, blue, and green. 4. The device of Claim 1 wherein the first conductor layer includes a reflective surface in contact with the active lower layer capable of producing the first color of light. 5. The device of Claim 1 wherein the first conductor layer comprises a thin strip of conductive material. 6. The device of Claim 1 wherein the hole injector layer comprises a thin strip of conductive material. 7. The device of Claim 1 wherein the second subpixel stack further comprises a third conductor layer overlying the inactive upper layer capable of producing the first color of light; and the device further comprises a third subpixel stack having ( 1 ) an active lower layer that is capable of producing a third color of light overlying the hole injector layer, (2) a fourth conductor layer overlying the active lower layer capable of producing the third color of light, (3) an inactive intermediate layer overlying the fourth conductor layer, said inactive intermediate layer being comprised of the same material as that of the active lower layer of the second subpixel stack, (4) a fifth conductor layer overlying the inactive intermediate layer, (5) an inactive top layer overlying the fifth conductor layer, said inactive top layer being comprised of the same material as that of the active lower layer of the first subpixel stack, and (6) a sixth conductor layer overlying the inactive top layer. 8. An organic light emitting device comprising: a transparent support substrate; a transparent strip of indium tin oxide overlying said substrate; and spaced first, second, and third subpixel stacks overlying said hole injector layer, wherein: said first subpixel stack comprises (1) an active lower layer that is capable of producing a first color of light and is overlying the hole injector layer, and (2) a first conductor layer overlying the active lower layer capable of producing the first color of light, said second subpixel stack comprises (1) an active lower layer that is capable of producing a second color of light and is overlying the hole injector layer, (2) a second conductor layer overlying the active lower layer capable of producing the second color of light, (3) an inactive upper layer overlying the second conductor layer, said inactive upper layer being comprised of the same material as that of the active lower layer of the first subpixel stack, and (4) a third conductor layer overlying the inactive upper layer capable of producing the first color of light, and said third subpixel stack comprises (1) an active lower layer that is capable of producing a third color of light overlying the hole injector layer, (2) a fourth conductor layer overlying the active lower layer capable of producing the third color of light, (3) an inactive intermediate layer overlying the fourth conductor layer, said inactive intermediate layer being comprised of the same material as that of the active lower layer of the second subpixel stack, (4) a fifth conductor layer overlying the inactive intermediate layer, (5) an inactive top layer overlying the fifth conductor layer, said inactive top layer being comprised of the same material as that of the active lower layer of the first subpixel stack, and (6) a sixth conductor layer overlying the inactive top layer, wherein said first, second and fourth conductor layers each include a light reflective surface. 9. An organic light emitting device comprising: a support substrate; a transparent hole injector layer overlying said substrate; and spaced first and second subpixel stacks overlying said hole injector layer, wherein said first subpixel stack comprises (1) a lower layer of a first type of organic material overlying and contacting said hole injector layer, and (2) an upper layer of a second type of organic material overlying said lower layer, and wherein said second subpixel stack comprises a lower layer of the second type of organic material overlying and contacting said hole injector layer. 10. A method of providing light emitting subpixels in an organic light emitting device comprising the steps of: providing a substrate with an overlying hole injector layer; providing a lower layer of organic material on the hole injector layer; providing an upper layer of electrically conductive material overlying the lower layer; and selectively ablating portions of the lower and upper layers such that a portion of the hole injector layer is exposed and light emitting subpixels are formed from a remaining strip of electrically conductive material overlying a strip of organic material. 1 1. The method of Claim 10 wherein the step of selectively ablating comprises laser ablation. 12. The method of Claim 10 wherein the step of selectively ablating comprises pulsed laser ablation. 13. The method of Claim 10 wherein the step of selectively ablating comprises laser ablation at more than one wavelength. 14. The method of Claim 10 further comprising the step of providing the substrate with overlying hole injector, lower, and upper layers in an ablation chamber having a controlled atmosphere. 15. The method of Claim 14 further comprising the step of providing the ablation chamber with a vacuum atmosphere. 16. The method of Claim 14 further comprising the step of providing the ablation chamber with an inert gas atmosphere. 17. The method of Claim 10 further comprising the step of suctioning ablated material during the step of selectively ablating. 18. The method of Claim 10 further comprising the steps of: monitoring fluorescence emission in the vicinity of ablation during the step of selectively ablating; and controlling ablation responsive to changes in the monitored fluorescence emission. 19. The method of Claim 18 wherein the step of controlling ablation comprises the step of controlling the application of a laser beam to the substrate with overlying hole injector, lower, and upper layers. 20. The method of Claim 18 wherein the step of controlling ablation comprises the step of moving the substrate with overlying hole injector, lower, and upper layers. 21. The method of Claim 18 further comprising the step of filtering monitored fluorescence emission to reduce detection of laser light by a means for monitoring fluorescence emission. 22. The method of Claim 10 wherein the step of selectively ablating includes the step of selectively moving the substrate with overlying hole injector, lower, and upper layers. 23. A method of providing light emitting subpixels in an organic light emitting device comprising the steps of: providing a substrate with an overlying hole injector layer; providing a lower layer of organic material on the hole injector layer; providing an upper layer of electrically conductive material overlying the lower layer; providing the substrate with overlying hole injector, lower, and upper layers in an ablation chamber having a controlled atmosphere; selectively ablating portions of the lower and upper layers with laser pulses such that a portion of the hole injector layer is exposed and light emitting subpixels are formed from a remaining strip of electrically conductive material overlying a strip of organic material; suctioning ablated material during the step of selectively ablating; monitoring fluorescence emission in the vicinity of ablation during the step of selectively ablating; and controlling ablation responsive to changes in the monitored fluorescence emission. 24. A method of forming an organic light emitting device comprising the steps of: providing a substrate with an overlying hole injector layer; providing a first organic layer on the hole injector layer; providing a first electron injector layer on the first organic layer; selectively removing portions of the first organic and first electron injector layers to expose a portion of the hole injector layer and to form a first subpixel strip from a strip of first electron injector material overlying a strip of first organic material; providing a second organic layer on the exposed portion of the hole injector layer and the first subpixel; providing a second electron injector layer on the second organic layer; and selectively removing portions of the second organic and second electron injector layers to re-expose a portion of the hole injector layer and to form a second subpixel strip spaced from and substantially parallel to the first subpixel strip. 25. The method of Claim 24 wherein the first and second organic layers are adapted to provide different wavelengths of visible light during operation of the organic light emitting device. 26. The method of Claim 24 further comprising the steps of: providing a third organic layer on the re-exposed portion of the hole injector layer, the second subpixel strip and the first subpixel strip; providing a third electron injector layer on the third organic layer; and selectively removing portions of the third organic and third electron injector layers to form a third subpixel strip spaced from and substantially parallel to the second subpixel strip. 27. The method of Claim 24 wherein at least one of the first, second, and third electron injector layers comprises metal. 28. The method of Claim 24 wherein the hole injector layer comprises indium tin oxide. 29. The method of Claim 24 wherein said steps of selectively removing comprise steps of laser ablation. 30. The method of Claim 29 wherein the laser ablation steps comprise the steps of: providing the device substrate on a moveable stage within an ablation chamber; providing laser light to a focusing system in the ablation chamber; selectively ablating material on the device with laser light received from the focusing system; and suctioning ablated material away from the device. 31. The method of Claim 30 further comprising the steps of: detecting ablated material on the device; and selectively moving the stage to form a desired pattern of ablated material on the device responsive to the detection of ablated material. 32. The method of Claim 24 wherein the steps of providing the first and second organic layers, and the steps of selectively removing are carried out in a moisture controlled environment. 33. In a method of forming an organic light emitting device having subpixel strips that include organic and hole injector material and that are adapted to emit light of different wavelengths, the improvement comprising the step of selectively ablating organic and hole injector material from said device in order to form said subpixel strips. 34. A laser ablation system comprising: a chamber for isolating a work piece in a controlled ambient; means for controlling the amount of moisture in said chamber; means for controlling the location of the work piece in said chamber; means for focusing laser light on the work piece in said chamber; means for detecting the location of ablated material on said work piece in said chamber; and means for removing ablated material from said chamber. 35. The system of Claim 34 wherein said means for controlling the location of the work piece is adapted to control work piece location responsive to signals received from said means for detecting the location of ablated material. 36. The system of Claim 34 wherein the means for controlling the location of the work piece comprises a stage adapted to move along any of three perpendicular axis. 37. The system of Claim 34 wherein the means for removing ablated material comprises a suction source outside of the chamber connected to a suction nozzle inside of the chamber. 38. A method of providing light emitting subpixels in an organic light emitting device comprising the steps of: providing a substrate with an overlying hole injector layer; providing a lower layer of organic material on the hole injector layer; providing an upper layer of electrically conductive material overlying the lower layer; selectively ablating portions of the upper layer such that a portion of the lower layer is exposed; selectively removing portions of the lower layer such that a portion of the hole injector layer is exposed and light emitting subpixels are formed from a remaining strip of electrically conductive material overlying a strip of organic material. 39. The method of Claim 38 wherein the step of selectively removing portions of the lower layer comprises the step of selectively ablating portions of the lower layer. 40. The method of Claim 39 wherein the step of selectively ablating comprises pulsed laser ablation. 41. The method of Claim 39 further comprising the step of suctioning ablated material during the step of selectively ablating. 42. The method of Claim 39 further comprising the steps of: monitoring fluorescence emission in the vicinity of ablation during the step of selectively ablating; and controlling ablation responsive to changes in the monitored fluorescence emission. 43. The method of Claim 42 wherein the step of controlling ablation comprises the step of selectively moving the substrate with overlying hole injector, lower, and upper layers. 44. The method of Claim 42 further comprising the step of filtering monitored fluorescence emission to reduce detection of laser light by a means for monitoring fluorescence emission. 45. The method of Claim 39 wherein the step of selectively ablating includes the step of selectively moving the substrate with overlying hole injector, lower, and upper layers.

Inventors: GHOSH AMALKUMAR P, GHOSH, AMALKUMAR, P.
Applicants: FED CORP, GHOSH AMALKUMAR P, FED CORPORATION, GHOSH, AMALKUMAR, P.
Application year: 1998
Main classification: H01L33
IPC codes: H01L27, H01L51