Abstract:
A method for making an OLED device includes providing a substrate having one or more test regions and one or more device regions, moving the substrate into a least one deposition chamber for deposition of at least one organic layer, and depositing the at least one organic layer through a shadowmask selectively onto the at least one device region and at least one test region on the substrate. The method also includes measuring a property of the at least one organic layer in the at least one test region, and adjusting the deposition process in accordance with the measured property.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to monitoring and controlling the formation of organic layers deposited in making organic light-emitting devices. 
     BACKGROUND OF THE INVENTION 
     Full color organic electroluminescent (EL), also known as organic light-emitting devices (OLED), have recently been demonstrated as a new type of flat panel display. In simplest form, an organic EL device is comprised of an electrode serving as the anode for hole injection, an electrode serving as the cathode for electron injection, and an organic EL medium sandwiched between these electrodes to support charge recombination that yields emission of light. An example of an organic EL device is described in U.S. Pat. No. 4,356,429. In order to construct a pixilated display device such as is useful, for example, as a television, computer monitor, cell phone display or digital camera display, individual organic EL elements can be arranged as an array of pixels in a matrix pattern. To produce a multicolor display, the pixels are further arranged into subpixels, with each subpixel emitting a different color. This matrix of pixels can be electrically driven using either a simple passive matrix or an active matrix driving scheme. In a passive matrix, the organic EL layers are sandwiched between two sets of orthogonal electrodes arranged in rows and columns. An example of a passive matrix driven organic EL device is disclosed in U.S. Pat. No. 5,276,380. In an active matrix configuration, each pixel is driven by multiple circuit elements such as transistors, capacitors, and signal lines. Examples of such active matrix organic EL devices are provided in U.S. Pat. Nos. 5,550,066, 6,281,634, and 6,456,013. 
     In an OLED device, the deposition of the organic layers must be accurately controlled in order to achieve the desired properties of the OLED device such as operating voltage, efficiency, and color. One control technique commonly used for OLED devices that are deposited by evaporation is the use of crystal mass sensor device (also referred to as a quartz oscillator) over the deposition sources to monitor deposition thickness at a location near the substrate. The crystal mass sensor is calibrated to relate the mass of the material deposited onto the sensor to a layer thickness on the device substrate. This technique, however, has the disadvantage that the crystal mass sensor will have a large film build-up in a high volume mass production environment, which can alter the calibration over time and require frequent changing. Another disadvantage is that the crystal mass sensor is located outside the area of the device and therefore must be calibrated to relate to the deposition on the substrate that is in a physically different location. In some deposition systems, such a those which are constructed with a thermal evaporation source, the uniformity of the deposition in the chamber can vary over time, such as when the amount of organic material in the source is depleted. Therefore, this technique has the inherent disadvantage of not being able to measure the actual films being deposited on the substrate. 
     Another method of monitoring the layer thickness proposed in U.S. Pat. No. 6,513,451 is to use an optical measurement system such as an interferometer or spectrophotometer to measure the thickness on a moving member which is in the path of the deposition. The moving member can be, for example, a disc which is rotated or indexed so that the surface is also refreshed to avoid layer build up or to permit the measurement of an individual layer. The member can also be cleaned to permit for improved uptime. This method, however, still has the problem that the measurement device is outside the area of the substrate and requires cross calibration that can vary over time. Inaccuracy of the calibration can result in the thickness of the film being different in the target that might result in sub-optimal device characteristics or manufacturing yield loss. Device characteristics, which might suffer from the film being deposited off target include, for example, emission color, efficiency, and device lifetime. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a new way of measuring the thin film layers deposited on the OLED device substrate. 
     It is another object of the present invention to improve control of the deposition process for the thin film, thereby reducing the occurrence of devices having sub-optimal device characteristics or improving manufacturing yield loss. 
     These objects are achieved by a method for making an OLED device, comprising: 
     a) providing a substrate having one or more test regions and one or more device regions; 
     b) moving the substrate into a least one deposition chamber for deposition of at least one organic layer; 
     c) depositing the at least one organic layer through a shadowmask selectively onto the at least one device region and at least one test region on the substrate; 
     d) measuring a property of the at least one organic layer in the at least one test region; and 
     e) adjusting the deposition process in accordance with the measured property. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a cross section of a three-color OLED device; 
         FIG. 2  depicts the top-side layout of an OLED substrate having a plurality of OLED devices; 
         FIGS. 3A to 3E  depict shadowmasks for use in depositing the organic layers according to the present invention; 
         FIG. 4  depicts a manufacturing system useful for fabricating the OLED devices according to the present invention; 
         FIG. 5  depicts a simplified cross sectional view of the measurement chamber of the manufacturing system; and 
         FIG. 6  depicts a simplified cross section view of the material deposition chamber having a measurement system useful for fabricating the OLED devices according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An OLED device is constructed by sandwiching two or more organic layers between a first and second electrode. In a passive matrix device, the first electrode is supplied on the device substrate forming laterally spaced rows. Alternately, in an active matrix device, thin film transistors, capacitors, and electrode lines are formed over the substrate and first electrode connections are formed on the substrate and are electrically connected to the active matrix circuitry. 
     Two or more organic layers are formed over the first electrode. For example, the OLED can be formed by first depositing a hole-transporting layer, then an emission layer, and finally an electron-transporting layer. The organic layers are typically deposited by using evaporation sources where the organic materials are heated such that vapor is produced and deposited on the substrate. The layers are typically deposited in vacuum chambers. Shadowmasks are used to control where on the substrates the organic layers are deposited. For example, the organic layers can be deposited over the emission regions and blocked over areas where the electrical connections are made to the device or where the device is sealed to an encapsulating member. In multicolor devices, different organic layers and materials can be used for each differently colored emission region. In this case, shadowmasks can be used to form separate OLED emission regions for each color. In such a device, either all the layers can differ from each color, or only the emission layer might differ such as is described in U.S. Pat. No. 6,281,634. 
     Each layer is deposited preferably in a separate vacuum chamber or in a separate shielded area of a single large vacuum chamber. Vacuum is preferable as many of the OLED materials are known to degrade in the presence of moisture or oxygen. The vacuum pressure is preferably maintained at less than 0.1 Pa and more preferably less than 0.001 Pa. This permits for all deposition sources to be used in parallel, increasing manufacturing throughput. Each layer is also preferably deposited with a separate shadowmask. 
       FIG. 1  shows a cross section of an example three-color red, green, and blue OLED device. The OLED device is constructed with a substrate  100 , a first electrode  110 , a hole-transporting layer (HTL)  120 , a red emitting layer (EML-1)  130   a , a green emitting layer (EML-2)  130   b , a blue emitting layer (EML-3)  130   c , an electron-transporting layer (ETL)  140 , a second electrode  150 , a seal  160 , and an encapsulating member  170 . The OLED device described in  FIG. 1  is an example OLED configuration, however, many other OLED devices which have multiple emitting layers, hole injection layers, electron injection layers, four color pixels, or other modifications are known in the art and can be successfully practiced using the present invention. 
       FIG. 2  shows the top-side layout of a substrate  200  constructed with eight devices regions  210   a ,  210   b ,  210   c ,  210   d ,  210   e ,  210   f ,  210   g , and  210   h . These device regions can be separated by, for example, scribing or dicing, to form separate OLED devices such as shown in  FIG. 1 . Substrate  200  also has test regions  220   a ,  220   b ,  220   c ,  220   d , and  220   e.    
       FIGS. 3   a  through  3   e  show shadowmasks for use in depositing the organic layers according to the present invention for the OLED device shown in  FIG. 1 . These figures show an example embodiment where eight OLED devices are made on the same substrates. However, the number of OLED devices per substrate can vary. 
       FIG. 3   a  shows a first shadowmask  10   a  for use in depositing the first organic layer, which in this embodiment is the hole-transporting layer (HTL). Shadowmask  10   a  has openings such as opening  20   a  for depositing the hole-transporting layer in the device regions. Shadowmask  10   a  also has a test opening  30   a  for use in depositing the hole-transporting layer in a test region. 
       FIG. 3   b  shows second shadowmask  10   b  for use in depositing the second organic layer, which in this embodiment is the red emitting layer (EML-1). Shadowmask  10   b  has openings such as opening  20   b  for depositing the red emitting layer in the device regions. Shadowmask  10   b  also has a test opening  30   b  for use in depositing the red emitting layer in a test region. The test region that is open to shadowmask  10   b  via test opening  30   b  is a different test region than that which is open to shadowmask  10   a  via test opening  30   a . This permits each different organic layer to be deposited in its own test region. 
       FIG. 3   c  shows third shadowmask  10   c  for use in depositing the third organic layer, which in this embodiment is the green emitting layer (EML-2). Shadowmask  10   c  has openings such as opening  20   c  for depositing the green emitting layer in the device regions. Shadowmask  10   c  also has a test opening  30   c  for use in depositing the green emitting layer in a test region. The test region that is open to shadowmask  10   c  via test opening  30   c  is a different test region than that which is open to the other shadowmasks for the other organic layers. 
       FIG. 3   d  shows fourth shadowmask  10   d  for use in depositing the fourth organic layer, which in this embodiment is the blue emitting layer (EML-3). Shadowmask  10   d  has openings such as opening  20   d  for depositing the blue emitting layer in the device regions. Shadowmask  10   d  also has an opening  30   d  for use in depositing the green emitting layer in a test region. The test region that is open to shadowmask  10   d  via opening  30   d  is a different test region than that which is open to the other shadowmasks for the other organic layers. 
       FIG. 3   e  shows fifth shadowmask  10   e  for use in depositing the fourth organic layer, which in this embodiment is the electron-transporting layer (ETL) (EML-3). Shadowmask  10   e  has openings such as opening  20   e  for depositing the electron-transporting layer in the device regions. Shadowmask  10   e  also has a test opening  30   e  for use in depositing the green emitting layer in a test region. The test region that is open to shadowmask  10   e  via test opening  30   e  is a different test region than that which is open to the other shadowmasks for the other organic layers. 
     While only a single test region is shown for each layer, multiple test regions spaced about the substrate could be provided to permit for measurements of uniformity across the substrate. Also, while the above embodiment shows that each layer has its own separate test region, sites where multiple layers are deposited in the same test region can also be provided to determine multiple layer stack measurements. While the above embodiment shows a test region for each layer, other embodiments where one or more layers are not measured using test regions are also possible. 
       FIG. 4  shows a manufacturing system  300  useful for fabricating the OLED device described above. The manufacturing system is composed of several controlled environment chambers such as a loading chamber  301 , a HTL deposition chamber  302 , an EML-1 deposition chamber  303 , an EML-2 deposition chamber  304 , an EML-3 deposition chamber  305 , an ETL deposition chamber  306 , a measurement chamber  307 , and an electrode deposition chamber  308 . These chambers are connected to a central chamber  310  and are shuttled from chamber to chamber by use of a transferring robot  320 . These chambers are control to reduce moisture or oxygen, which are known to degrade OLED devices. This can be achieved, for example, by reducing the pressure of the chambers to &lt;0.1 Pa, or more preferably &lt;0.001 Pa through the use of vacuum pumps. Alternately, some chambers can be maintained in controlled environments of non-reactive gasses such as Ar or N. Other chambers can also be attached to this cluster for performing such tasks as substrate cleaning, device encapsulation, or the deposition of additional layers. Alternately, the above chambers and other additional functions can be split into multiple clusters and the substrates could be transferred between these clusters. The substrates are loaded into the cluster via the load chamber  301 . The load chamber  301  can be configured to hold a single substrate or a plurality of substrates. When the substrates are completed through all the processes in the cluster, the substrates can be removed through the load chamber  301 . Alternately an additional chamber, such as an un-load chamber, could be added to the cluster to improve the throughput of this task. The measurement chamber  307  is a chamber to which the substrate can be transferred in the controlled environment, where the organic layers that are deposited in the test region can be measured. 
       FIG. 5  illustrates a simplified cross sectional view of the measurement chamber. The measurement chamber is composed of a substrate holder  410  which holds substrate  400 . The substrate holder  410  is capable of moving in the plane of the substrate. Attached to the measurement chamber is a measurement system  420 . Measurement system  420  can be composed of one or more measurement devices such as an ellipsometer, an interferometer, a reflectometer, a spectrophotometer, an optical spectrometer, or a luminescent type measurement system. An example of a luminescent type measurement system is the fluorescence measurement technique described in U.S. patent application Publication 2003/0193672 A1. While the measurement system is shown as being incorporated into the walls of the chamber, the measurement system could alternately be located entirely outside the chamber, and the measurement could be conducted remotely through windows in the chamber wall or via fiber optic cables that pass through the chamber walls. The measurement system is also shown as being pointed directly at the measurement area on the substrate, however, alternate configurations which utilize mirrors or other optical elements could be used to permit for non-line-of-sight arrangements. Also, the measurement system can include components such as a computer for data analysis that are outside the chamber but connected to the measurement system. 
     The measurement system shown in  FIG. 5  illustrates an embodiment where the substrate is held above the measurement source, however, alternate embodiments where the substrate is below the measurement system and is resting on, for example, an X-Y stage are also possible.  FIG. 5  also shows the substrate as moving, however, the measurement system can also be made to move which would permit the substrate to be in a fixed position. Alternately, another embodiment, where both the substrate and the measurement system move, is also possible. 
     While the thickness is the most common property that can be measured in the test region as described above, properties other than thickness can also be measured using measurement tools and techniques known in the art. Such properties include, for example, chemical composition, dopant concentration, or optical properties such as absorption, transmission, or refractive index. 
       FIG. 6  shows a cross-sectional view of an organic material deposition chamber of an alternate manufacturing system having a measurement system  520  and at least one deposition source  530  in the same chamber. The deposition source could be any of a large variety of deposition sources known in the art, such as, for example, a point source such as a crucible, a linear deposition source, or a shower-head style source. A substrate  500  and a shadowmask  10  which has a test opening  40  located relative to a test region of the substrate are held in place in the chamber by mechanical means (not shown) and can optionally be aligned by an alignment system (not shown) as known in the art. 
     Using the example of the shadowmasks  10   a ,  10   b ,  10   c ,  10   d , and  10   e  and manufacturing system  300  having a measurement chamber as described above, a first method for manufacturing an OLED device will be described. First, one or more OLED substrates are loaded into manufacturing system by, for example, the loading chamber  301 . The substrate already has deposited on it the first electrode and any optional active matrix circuitry located in device regions of the substrate. The substrate further includes test regions which will correspond to the test openings in the shadowmasks used for the organic depositions. The substrate is then moved into the HTL deposition chamber  302 , where the hole-transporting layer is deposited using shadowmask  10   a  to control the regions on the substrate where the organic material is deposited. The hole-transporting layer is deposited onto the substrate in the device regions and the at least one test region as defined by the openings such as opening  20   a  and test opening  30   a , respectively. A conventional control system, such as a crystal mass sensor device, is used to control the properties, such as film thickness, of the layer. The substrate is then moved into the EML-1 deposition chamber  303 . If the loading chamber  301  is configured to hold a plurality of substrates, after the first substrate is moved out of the HTL deposition chamber, a second substrate can be moved into the HTL deposition chamber so that multiple substrates are fabricated in parallel, thereby improving throughput. In the EML-1 deposition chamber  303 , the red emitting layer is deposited using shadowmask  10   b  to control the regions on the substrate where the organic material is deposited. The red emitting layer is deposited onto the substrate in a portion of the device regions and the at least one test region as defined by the openings such as opening  20   b  and test opening  30   b , respectively. A conventional control system, such as a crystal mass sensor device, is used to control the properties, such as film thickness, of the layer. The substrate is then moved into the EML-2 deposition  304  chamber where the green emitting layer is deposited using shadowmask  10   c  to control the regions on the substrate where the organic material is deposited. The green emitting layer is deposited onto the substrate in a portion of the device regions and the at least one test region as defined by the openings such as opening  20   c  and test opening  30   c , respectively. A conventional control system, such as a crystal mass sensor device, is used to control the properties, such as film thickness, of the layer. The substrate is then moved into the EML-3 deposition  305  chamber where the blue emitting layer is deposited using shadowmask  10   d  to control the regions on the substrate where the organic material is deposited. The blue emitting layer is deposited onto the substrate in a portion of the device regions and the at least one test region as defined by the openings such as opening  20   d  and test opening  30   d , respectively. 
     A conventional control system, such as a crystal mass sensor device, is used to control the properties, such as film thickness, of the layer. The substrate is then moved into the ETL deposition  306  chamber where the electron-transporting layer is deposited using shadowmask  10   e  to control the regions on the substrate where the organic material is deposited. The electron-transporting layer is deposited onto the substrate in the device regions and the at least one test region as defined by the openings such as opening  20   e  and test opening  30   e , respectively. A conventional control system, such as a crystal mass sensor device, is used to control the properties, such as film thickness, of the layer. The substrate is then moved into the measurement chamber  307  where the measurements of the layers are taken on each of the test regions. The information on the measured properties of each of the layers, such as film thickness, are fed back into the control systems of the respective layers to adjust the calibration of the control system. The device is then moved into the electrode deposition chamber  308  where the second electrode is applied to the device. Alternately, the electrode can be applied prior to measurement if the electrode chamber uses a shadowmask that prevents electrode material from depositing on the test regions. The device is then returned to the loading chamber  301  where it can be unloaded or transferred to another system for additional processing such as, for example, encapsulation. 
     Using the example of the shadowmasks  10   a ,  10   b ,  10   c ,  10   d , and  10   e  and manufacturing system  300  having a measurement chamber as described above, a second method for manufacturing an OLED device will be described. First, one or more OLED substrates are loaded into the manufacturing system by, for example, the loading chamber  301 . The substrate already has deposited on it the first electrode and any optional active matrix circuitry. The substrate is then moved into the HTL deposition chamber  302  where the hole-transporting layer is deposited using shadowmask  10   a  to control the regions on the substrate where the organic material is deposited. A conventional control system, such as a crystal mass sensor device, is used to control the properties, such as film thickness, of the layer. The substrate is then moved into the measurement chamber  307 . If the loading chamber  301  is configured to hold a plurality of substrates, after the first substrate is moved out of the HTL deposition chamber, a second substrate can be moved into the HTL deposition chamber so that multiple substrates are fabricated in parallel, thereby improving throughput. In measurement chamber  307 , measurements of the hole-transporting layer are taken in the corresponding test region. The information on the measured properties, such as film thickness, is fed back into the control systems of the HTL deposition chamber  302  to adjust the calibration of the control system. 
     The substrate is then moved into the EML-1 deposition chamber  303  where the red emitting layer is deposited using shadowmask  10   b  to control the regions on the substrate where the organic material is deposited. A conventional control system, such as a crystal mass sensor device, is used to control the properties, such as film thickness, of the layer. The substrate is then moved into the measurement chamber  307  where measurements of the red emitting layer are taken in the corresponding test region. The information on the measured properties, such as film thickness, is fed back into the control systems of the EML-1 deposition chamber  303  to adjust the calibration of the control system. 
     The substrate is then moved into the EML-2 deposition chamber  304  where the green emitting layer is deposited using shadowmask  10   c  to control the regions on the substrate where the organic material is deposited. A conventional control system, such as a crystal mass sensor device, is used to control the properties, such as film thickness, of the layer. The substrate is then moved into the measurement chamber  307  where measurements of the green emitting layer are taken in the corresponding test region. The information on the measured properties, such as film thickness, is fed back into the control systems of the EML-2 deposition chamber  304  to adjust the calibration of the control system. 
     The substrate is then moved into the EML-3 deposition  305  chamber where the blue emitting layer is deposited using shadowmask  10   d  to control the regions on the substrate where the organic material is deposited. A conventional control system, such as a crystal mass sensor device, is used to control the properties, such as film thickness, of the layer. The substrate is then moved into the measurement chamber  307  where measurements of the blue emitting layer are taken in the corresponding test region. The information on the measured properties, such as film thickness, is fed back into the control systems of the EML-3 deposition chamber  305  to adjust the calibration of the control system. 
     The substrate is then moved into the ETL deposition chamber  306  where the electron-transporting layer is deposited using shadowmask  10   e  to control the regions on the substrate where the organic material is deposited. A conventional control system, such as a crystal mass sensor device, is used to control the properties, such as film thickness, of the layer. The substrate is then moved into the measurement chamber  307  where measurements of the electron-transporting layer are taken in the corresponding test region. The information on the measured properties, such as film thickness, is fed back into the control systems of the ETL deposition chamber  306  to adjust the calibration of the control system. 
     The device is then moved into the electrode deposition chamber  308  where the second electrode is applied to the device. The device is then returned to the loading chamber  301  where it can be unloaded or transferred to another system for additional processing such as, for example, encapsulation. The second method has the advantage over the first method that measurement information is produced more quickly and the feed back to the control system is achieved in a shorter amount of time. However, because the second method requires more movements of the substrate, throughput can be reduced. Alternate embodiments of the above methods where two or more sequential layers are deposited between movements to the measurement chamber can also be practiced. 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
     PARTS LIST 
     
         
           10  shadowmask 
           10   a  shadowmask 
           10   b  shadowmask 
           10   c  shadowmask 
           10   d  shadowmask 
           10   e  shadowmask 
           20   a  opening 
           20   b  opening 
           20   c  opening 
           20   d  opening 
           20   e  opening 
           30   a  test opening 
           30   b  test opening 
           30   c  test opening 
           30   d  test opening 
           30   e  test opening 
           40  test opening 
           100  substrate 
           110  first electrode 
           120  hole-transporting layer 
           130   a  red emitting layer 
           130   b  green emitting layer 
           130   c  blue emitting layer 
           140  electron-transporting layer 
           150  second electrode 
           160  seal 
           170  encapsulating member 
           200  substrate 
           210   a  device region 
           210   b  device region 
           210   c  device region 
           210   d  device region 
           210   e  device region 
           210   f  device region 
           210   g  device region 
           210   h  device region 
           220   a  test region 
           220   b  test region 
           220   c  test region 
           220   d  test region 
           220   e  test region 
           300  manufacturing system 
           301  loading chamber 
           302  HTL deposition chamber 
           303  EML-1 deposition chamber 
           304  EML-2 deposition chamber 
           305  EML-3 deposition chamber 
           306  ETL deposition chamber 
           307  measurement chamber 
           308  electrode deposition chamber 
           310  central chamber 
           320  transferring robot 
           400  substrate 
           410  substrate holder 
           420  measurement system 
           500  substrate 
           520  measurement system 
           530  deposition source