Abstract:
The present invention is a monolithic, multi-colored LED chip and a method for making the same. The LED chip is comprised of a substrate and a plurality of light emitting structures, each light emitting structure capable of emitting a wavelength of light unique compared to others and each structure layered on top of another structure and separated by a dielectric layer. The light emitting structures are then capable of independent or tandem activation, yielding the original colors of each section, blends of colors, and white light. The method starts with the base for such a chip and etches layers of the chip away, leaving exposed sections, to reach electrical contact layers for each light emitting structure. Electrically conductive material is then used to fill the exposed sections and is, in turn, etched away to leave contacts. An insulating material is then used to fill in the resultant areas.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     This invention is a continuing-in-part application of application Ser. No. 11/176,696, filed on Jul. 7, 2005 and published as publication number 20060027820 on Feb. 9, 2006. It, in turn, claims priority on prior filed provisional application 60/585,988, filed Jul. 7, 2004. This Application claims priority on both and incorporates the same herein by reference in their entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to the field of LED chips and more particularly relates to the field of LED chips capable of generating multiple colors.  
       BACKGROUND OF THE INVENTION  
       [0003]     Light emitting diodes (LEDs) will be the source for next generation lighting. White light and other color LEDs will be essential for different applications. Currently, the each LED chip is emitting one individual color. Multiple colors including white are generated through mixing of different color chips or combine second step excitation. For example, white LED can be generated by mixing red, green, and blue, or using blue or UV chips to excite phosphor.  
         [0004]     One chip in the prior art, U.S. Pat No. 6,060,727 (2000) to Shakuda, places multiple colored LED chip fragments on a single substrate to create a multiple colored single LED chip. These fragments are, however, adjacent to each other and the resultant LED chip is not comprised of one set of epitaxial layers.  
         [0005]     In the parent Application, an invention to produce an integrated chip containing red, green, and blue emissions in one chip by one step epitaxial process was disclosed. A trench structure has been disclosed to make electrical contracts for each LED structures.  
         [0006]     In this invention, new LED structures using one step epitaxial process to integrate red, green, and blue emitting structures together in one chip with different contact formats to emit multiple colors, are disclosed.  
       SUMMARY OF THE INVENTION  
       [0007]     In view of the foregoing disadvantages inherent in the known types of LED chips, this invention provides a multi-colored LED chip. As such, the present invention&#39;s general purpose is to provide a new and improved multi-colored LED chip that is easily manufactured with a single step epitaxial process and with easily accomplished etching techniques to install electrical connectors to the same.  
         [0008]     In its basic construction, the LED chip comprises a single substrate with a plurality of light emission structures stacked on top of the substrate. Each light emission structure is isolated from each other with an isolation layer or dielectric layer and each emits a different color. Electrical contacts are positioned by first etching away proper layers in each emitting structure to allow for the contacts to be positioned appropriately for each emitting structure and filling the etched portions with conductive material. The conductive material is then etched to form the required contacts and the resultant space filled with an insulating material. Thus, each light emitting structure can be individually controlled per requirements.  
         [0009]     The more important features of the invention have thus been outlined in order that the more detailed description that follows may be better understood and in order that the present contribution to the art may better be appreciated. Additional features of the invention will be described hereinafter and will form the subject matter of the claims that follow.  
         [0010]     Many objects of this invention will appear from the following description and appended claims, reference being made to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.  
         [0011]     Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.  
         [0012]     As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods, and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a sectional view of the epitaxial structure of an LED chip manufactured by a one-step epitaxial process for the first stage of the process according to the present invention.  
         [0014]      FIG. 2  is a series of sectional views of the manufacturing process according to the present invention.  
         [0015]      FIG. 3  is a sectional view of a multiple color emitting chip after undergoing the process depicted in  FIG. 2 .  
         [0016]      FIGS. 4   a  and  4   b  are top plan views of completed chips according to the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]     With reference now to the drawings, the preferred embodiments of the LED chip and method of manufacture are herein described. It should be noted that the articles “a,” “an,” and “the,” as used in this specification, include plural referents unless the content clearly dictates otherwise.  
         [0018]      FIG. 1  depicts the epitaxial structure  100  of a multiple color emitting LED chip manufactured using a one step metal organic chemical vapor deposition (MOCVD) process. The resultant LED has three emitting structures, layered one on top of the other with an isolation or dielectric layer between emitting structures. The three emitting structures may emit any color of light, though the preferred embodiment would have structures that emit red, green, and blue light, respectively. The ordering on the structures is not critical to the invention and the light color may be in any order, however, for the purposes of this Application, the example given shall be deemed to have a top structure emitting blue, the middle emitting green and the bottom structure emitting red.  
         [0019]     The epitaxial structure  100  includes three substructures to emit red, green, and blue color, respectively, which are built on top of one substrate  101 . Each structure is isolated by an insulating layer. Substrate  101 , which can be Si, GaAs, GaN, AlN, SiC, Sapphire, or some other suitable material, is used as the base for the LED structure. Buffer layer  102  is positioned on substrate  101  to eliminate lattice mismatch defects. This buffer layer  102  can be GaN or AlN and can also use the technologies disclosed in U.S. Pat. No. 6,815,241, this patent being incorporated herein by reference. Buffer layer  102  is covered by an isolation layer or dielectric layer  103 , which can also be GaN or AlN.  
         [0020]     The three sub-structures are now layered on top of the substrate structure. Each substructure comprises an initial contact layer, a first cladding layer, at least one emission layer(s), a second cladding layer, and a second contact layer. For the initial substructure,  105  is the contact layer for electrical contact, which can be GaN, AlGaN, or GalnN. This layer is heavily doped, either N+ or P+, for contacting purpose. This layer can be coated with reflection layer  104  to reflect all light away from the substrate. The first cladding layer for red color emission is  106  and this layer can be GaN, AlGaN, GalnN, or GaNP. The emitting or active layer for red color  107  may be GaInP, AlGaInP, GaInN, or GaNP. The active layer can consist of multiple quantum wells with materials of GaInP, AlGaInP, GaInN, or GaNP. The second cladding layer  108  may be GaN, AlGaN, GaInN, or GaNP. The second contact layer  109  for electrical contact may be GaN, AlGaN, or GaInN. This layer is also heavily doped, either N+ or P+, for contacting purpose. The structure from layer  106  to  109  emits a red color. On top the red color structure, a structure to emit a green color is constructed, using a similar layering technique. Between the structures is a semi-insulating layer or dielectric layer  110 , which can be GaN, AlN, or other proper materials. First contact layer  111 , which can be GaN, AlGaN, GaInN, or GaNP, is positioned over the insulating layer and the first cladding layer for green color emission  112  positioned on top of first contact layer  111 . The first cladding layer for green emission may be GaN, AlGaN, AlGaInN, GaInN, or GaNP. The emitting or active layer for green color  113  is positioned on top of the fist cladding layer  112  and can be AlGaInN, AlGaN, or GaInN. The emitting layer can consist of multiple quantum wells with materials of AlGaInN, AlGaN, or GaInN. The emission layer  113  is covered with the second cladding layer for green color emission  114  and second contact layer  115  respectfully. The second cladding layer for green color emission  114  may be GaN, AlGaInN, AlGaN, GaInN, GaNP and the second contact layer may be GaN, AlGaN, or GaInN. This second contact layer  115  is heavily doped, either N+ or P+, for contacting purposes. The structure from layer  111  to  115  emits the green color. On top of the green emitting structure, a structure emitting blue color is constructed. The structure, comprising layers  117  through  121 , follows the same pattern as the green and red structures. First is a semi-insulating layer or dielectric layer  116 , which can be GaN or AlN or other proper materials, is formed over the second green contact layer  115 , then the blue structure is built. First contact layer  117  may be formed from GaN, AlGaN, GaInN, or GaNP. First cladding layer  118  can be GaN, AlGaN, AlGaInN, GaInN, or GaNP. The emitting or active layer for blue color  119 , which can be AlGaInN, or GaInN, is formed on top of the first blue cladding layer  118  and covered by second blue cladding layer  120 , which may, like the first blue cladding layer be formed from GaN, AlGaN, AlGaInN, GaInN, or GaNP. The active layer consists of multiple quantum wells with materials of AlGaInN or GaInN. The second contact layer for electrical contact  121  may be GaN, AlGaN, GaNP, or GaInN. Like previous contact layers, layers  117  and  121  should be heavily doped, either N+ or P+, for contacting purposes. The final structure is covered with another insulation layer or dielectric layer  122 . This final dielectric layer  122  may be entirely removed, as shown in following the sections depicted in  FIGS. 2 and 3 .  
         [0021]     It should be noted that the chemical composition of each layer is given for the preferred embodiment, that is for an LED chip that will emit red, blue, green or white (when all three regions are activated) light. The chemical composition of any layer may be altered by using equivalent compounds for the colors disclosed or by using any compound for any desired color (i.e. orange, yellow, violet, etc). Likewise, any number of emitting structures may be utilized. The method according to the present invention could be used to make a five, seven, or more colored LED chip just by adding emitting structures of appropriate chemical composition for the colors desired. It should also be noted that the active layer in each emitting structure may actually be a plurality of layers acting in concert, rather than just a single layer. In any event, the addition of layers and structures merely repeats the method described herein for the addition of any additional layer or structure.  
         [0022]      FIG. 2  depicts the process to produce the LED chip structure. The first step  201  is to use a one step epitaxial process to produce an overall LED structure like the one depicted in  FIG. 1 . Then, steps  202  is a first litho and etch process to create one electrical contact area for blue LEDs. Step  203  is a second litho and etch to create another electrical contract are for blue LED and one electrical contact area for green LED. Step  204  is to create anther electrical contact area for green LED. Step  205  is to create one electrical contact area for red LED. Step  206  is to create another electrical contact area for the red LED. Step  207  is to deposit metals for contact areas, which is then etched in Step  208  to form electrodes for different LED structures. Step  209  is to deposit dielectric materials to fill the gap between electrodes and form the final structure.  
         [0023]      FIG. 3  depicts the cross section of final structure of the integrated LED, where  301  is the base substrate,  302  is a buffer layer, and  303  is semi-insulating layer. In a first emitting structure,  304  is the first contact layer for the red LED,  305  is first cladding layer for the red LED,  306  is the emitting layer of the red LED,  307  is a second cladding layer for red LED, and  308  is a second contact layer for the red LED. Electrodes  309 ,  310  are also provided for the red LED layer. A semi-insulating layer  311  is provided between the first, red, emitting structure and the second, green one. The layering continues in the disclosed pattern for the emitting structures, where  312  is the first contact layer for the green LED,  313  is first cladding layer for the green LED,  314  is the emitting layer of the green LED,  315  is the second cladding layer for the green LED, and  316  is second contact layer for the green LED. Like the first layer, electrodes  317 ,  318  are provided for the second, green LED emitting structure and  319  is semi-insulating layer between the second, green, emitting structure and the third, blue one. Again, the layering repeats for the blue LED, where  320  is the first contact layer for the blue LED,  321  is the first cladding layer for the blue LED,  322  is the emitting layer of the blue LED,  323  is the second cladding layer for the blue LED, and  324  is the second contact layer for the blue LED. Electrodes  325 ,  326  are provided for the blue LED. Dielectric materials  327  isolate all of the electrodes.  
         [0024]      FIGS. 4   a  and  4   b  each depict the top view of different LED configurations. In  FIG. 4   a,    401  is an LED with a vertical electrode structure. Electrodes  402  and  404  are the electrodes for the blue LED structure, with isolation pads  403 ,  405  surrounding the electrodes  402 ,  404  respectively. The configuration for the green and red structures are similar, with  406  and  408  being the electrodes for the green LED structure, surrounded by isolation pads  405  and  407 . The red structure&#39;s electrodes  410  and  412  are likewise surrounded by isolation pads  411  and  413 . The emitting area  414  lies encompassed by the electrodes.  
         [0025]      FIG. 4   b  depicts the LED configuration shown in  FIG. 3  as a final product where  415  is the structure. Electrode  416  and  418  are connected to the blue LED and are surrounded by isolation pads  417  and  419 . The green LED is connected to electrodes  420  and  422 , each being surrounded by isolation pads  421  and  423 . Red LED is connected to electrodes  424  and  426 . These electrodes are isolated by pads  425  and  427  respectively. The resultant emitting area  428  is, as a result of this configuration, very broad.  
         [0026]     Although the present invention has been described with reference to preferred embodiments, numerous modifications and variations can be made and still the result will come within the scope of the invention. No limitation with respect to the specific embodiments disclosed herein is intended or should be inferred.