Abstract:
A light emitting device is provided, including a substrate and a light emitting structure on the substrate, comprising a first semiconductor layer, a second semiconductor layer on the first semiconductor layer, and an active layer between the first and second semiconductor layers. The substrate has at least one side surface extending outwardly. The at least one side surface includes a first portion, a transition portion connected to the first portion, and a second portion connected to the transition portion, the first portion provides a first obtuse inclination angle with reference to the bottom surface of the substrate and the transition portion provides a second obtuse inclination angle with reference to the bottom surface of the substrate, the second obtuse inclination angle is larger than the first obtuse inclination angle. The second portion includes a vertical side surface with reference to the bottom surface of the substrate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of co-pending U.S. application Ser. No. 14/166,583 filed on Jan. 28, 2014, which is a continuation of U.S. application Ser. No. 13/934,021 filed on Jul. 2, 2013 (now U.S. Pat. No. 8,698,183, issued Apr. 15, 2014), which is a continuation of U.S. application Ser. No. 13/308,146 filed on Nov. 30, 2011 (now U.S. Pat. No. 8,502,256, issued Aug. 6, 2013), which is a continuation of U.S. application Ser. No. 12/438,808 filed on Feb. 25, 2009 (now U.S. Pat. No. 8,404,566, issued Mar. 26, 2013), which is the national phase of PCT international Application No. PCT/KR2007/004587 filed on Sep. 20, 2007, and which claims priority to Korean Patent Application No. 10-2006-0092732 filed on Sep. 25, 2006. The entire contents of all of the above applications are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     Embodiments relate to a light emitting diode and a method for manufacturing the same. 
     2. Background Art 
     Light emitting diodes (LEDs) are manufactured through a scribing process of separating a plurality of unit chips after forming a compound semiconductor on the substrate. 
     The scribing process is to irradiate laser onto a substrate or a compound semiconductor. The substrate or the compound semiconductor, which is adjacent to a scribing region irradiated with the laser, may be damaged during the laser irradiation. 
     A portion of light generated from an active layer of the LED is emitted to the outside through the scribing region. However, it is difficult for light to pass through a portion of the substrate or the compound semiconductor damaged by the laser, which degrades light efficiency of the LED after all. 
     SUMMARY OF THE INVENTION 
     Embodiments provide a light emitting diode (LED) and a method for manufacturing the same. 
     Embodiments provide an LED with improved light efficiency and a method for manufacturing the same. 
     An embodiment provides a method for manufacturing a light emitting diode (LED), comprising: forming a semiconductor layer; forming a mask layer on the semiconductor layer; irradiating laser onto a scribing region of the mask layer to divide the semiconductor layer into a plurality of light emitting diodes; etching the scribing region; removing the mask layer; and separating the plurality of light emitting diodes. 
     An embodiment provides a method for manufacturing a light emitting diode, comprising: forming a semiconductor layer on a substrate; forming a mask layer on the semiconductor layer; irradiating laser onto a scribing region of the substrate to divide the substrate into a plurality of light emitting diodes; etching the scribing region; removing the mask layer; and separating the plurality of light emitting diodes. 
     An embodiment provides a light emitting diode comprising: a substrate; a semiconductor layer on the substrate; and an electrode on the semiconductor layer, wherein the substrate or the semiconductor layer has at least one etched side surface having a predetermined tilt angle. 
     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
     Embodiments can provide a light emitting diode (LED) and a method for manufacturing the same. 
     Embodiments can provide an LED with improved light efficiency and a method for manufacturing the same. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 to 6  are sectional views illustrating a light emitting diode (LED) and a method for manufacturing the same according to a first embodiment. 
         FIGS. 7 to 11  are sectional views illustrating an LED and a method for manufacturing the same according to a second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to a light emitting diode (LED) and a method for manufacturing the same, examples of which are illustrated in the accompanying drawings. 
       FIGS. 1 to 6  are sectional views illustrating an LED and a method for manufacturing the same according to a first embodiment. 
     Referring to  FIG. 1 , a semiconductor layer  20 , a first electrode  31  and a second electrode  41  are formed on a substrate  10  so as to form an LED. 
     The substrate  10  may include, for example, a sapphire substrate. The semiconductor layer  20  has a multi-stacked structure of a compound semiconductor, which will be more fully described in  FIG. 6  later. 
     A portion of the semiconductor layer  20  may be selectively etched, and the first electrode  31  is formed on an etched portion of the semiconductor layer  20 . Accordingly, heights of the first and second electrodes  31  and  41  differ from each other even though they are formed on the same semiconductor layer  20 . 
     The embodiment of  FIGS. 1 to 6  illustrates sectional views for convenience in description, which illustrate processes of forming first, second and third LEDs  51 ,  52  and  53 . 
     Referring to  FIG. 2 , a mask layer  60  is formed on the semiconductor layer  20 , the first electrode  31  and the second electrode  41 . 
     The mask layer  60  protects the semiconductor layer  20  during a scribing process, and is formed of a material which can be wet-etched or dry-etched. A material for used in the mask layer  60  will be described in detail later. 
     In  FIG. 2 , reference numeral  61  denotes a scribing region. In this embodiment, laser is irradiated onto the scribing region  61  using a laser irradiation apparatus, thus dividing the semiconductor layer  20  into the first, second and third LEDs  51 ,  52  and  53 . 
     Referring to  FIG. 3 , when the laser is irradiated onto the scribing region  61 , the mask layer  60 , the semiconductor layer  20  and the substrate  10  in the scribing region  61  are removed. 
     During laser irradiation, the layers in the scribing region  61  onto which the laser is irradiated are damaged, causing a damaged region  12  with a rugged surface to be formed, as illustrated in  FIG. 3 . 
     The light emitted from the active layer of the LED does not pass through but is absorbed at the damaged region  12 , and thus the damaged region  12  is removed so as to improve light efficiency of the LED in this embodiment. 
     The removal of the damaged region  12  may be performed using wet etching or dry etching process. 
     The wet etching process is performed using a first etchant including at least one of hydrochloric acid (HCl), nitric acid (HNO 3 ), potassium hydroxide (KOH), sodium hydroxide (NaOH), sulfuric acid (H 2 SO 4 ), phosphoric acid (H 3 PO 4 ) and aluetch (4H 3 PO 4 +4CH 3 COOH+HNO 3 ). A temperature of the first etchant is between 200° C. and 400° C. 
     The mask layer  60  prevents the semiconductor layer  20  from being etched during the etching of the damaged region  12 . The mask layer  60  may be formed of, for example, silicon nitride (Si 3 N 4 ) or an oxide-based material such as silicon oxide (SiO 2 ), which is hardly etched by the first etchant. 
     That is, the first etchant has a higher etch selectivity to the damaged region  12  than to the mask layer  60 . 
     Since the mask layer  60  is hardly etched by the first etchant, the damaged region  12  can be selectively etched while minimizing the etch amount of the semiconductor layer  20 . 
     The dry etching may be performed through an inductively coupled plasma/reactive ions etcher (ICP/RIE) or an RIE. In addition, the dry etching may be performed using a first etching gas including at least one of BCl 3 , Cl 2 , HBr and Ar. 
     The mask layer  60  configured to prevent the semiconductor layer  20  from being etched during the etching of the damaged region  12  may be formed of an oxide-based material such as SiO 2 , TiO 2  and ITO or a metallic material such as Cr, Ti, Al, Au, Ni and Pt, which is hardly etched by the first etching gas. 
     That is, the first etching gas has a higher etch selectivity to the damaged region  12  than to the mask layer  60 . 
     The wet etching and the dry etching may be performed for several minutes to several tens of minutes depending on etching environments.  FIG. 4  illustrates that the damaged region  12  of the scribing region  61  is removed. 
     Referring to  FIG. 5 , the mask layer  60  formed on the semiconductor layer  20  is removed after the removal of the damaged region  12 . 
     The removal of the mask layer  60  may be performed using at least one of the wet etching and the dry etching. 
     For example, the mask layer  60  is removed through the wet etching using a second etchant including at least one of buffer oxide etchant (BOE) or hydrofluoric acid (HF). 
     Because the semiconductor layer  20  is hardly etched by the second etchant, the mask layer  60  can be selectively etched while minimizing the etch amount of the semiconductor layer  20 . 
     That is, the second etchant has a higher etch selectivity to the mask layer  60  than to the semiconductor layer  20 . 
     For example, the mask layer  60  is removed through the dry etching using a second etching gas including at least one of O 2  and CF 4 . 
     The mask layer  60  can be selectively etched while minimizing the etch amount of the semiconductor layer  20  because the semiconductor layer  20  is hardly etched by the second etching gas. 
     That is, the second etching gas has a higher etch selectivity to the mask layer  60  than to the semiconductor layer  20 . 
     Thereafter, a physical impact is applied to the substrate  10  and the semiconductor layer  20 , so that the first LED  51 , the second LED  52  and the third LED  53  are separated from each other by the scribing region  61 . 
     A lapping process may be performed to reduce the thickness of the substrate  10  before applying the physical impact to the substrate  10  and the semiconductor layer  20 . The lapping process may be performed through at least one process of chemical mechanical polishing (CMP), dry etching, wet etching and mechanical polishing using slurry. 
       FIG. 6  illustrates the first LED  51  separated by the scribing region. 
     The first LED  51  includes the semiconductor layer  20 , the first electrode  31  and the second electrode  41  which are formed over the substrate  10 . 
     The semiconductor layer  20  includes a buffer layer  21 , an n-type semiconductor layer  22 , an active layer  23 , a p-type semiconductor layer  24  and a transparent electrode layer  25 . 
     The buffer layer  21  relieves stress between the substrate  10  and the n-type semiconductor layer  22  and enables the semiconductor layer to easily grow. The buffer layer  21  may have at least one structure of AlInN/GaN, In x Ga 1-x N/GaN and Al x In y Ga 1-x-y N/In x Ga 1-x N/GaN. 
     The n-type semiconductor layer  22  may include a GaN layer doped with silicon, and may be formed by supplying silane gas containing n-type dopant such as NH 3 , trimethylgallium (TMGa) and Si. 
     The active layer  23  may have a single-quantum well or a multi-quantum well (MQW) structure formed of InGaN/GaN. The p-type semiconductor layer  24  may be formed of trimethylaluminum (TMAl), bis(ethylcyclopentadienyl)magnesium (EtCp2Mg), or ammonia (NH 3 ). 
     The transparent electrode layer  25  is formed of a material such as ITO, ZnO, RuOx, TiOx and IrOx. The first electrode  31  may be formed of titanium (Ti) and the second electrode  41  may be formed of a metallic material such as nickel (Ni). 
     The first LED  51  emits light from the active layer  23  when a power is supplied to the first and second electrodes  31  and  41 . 
     In  FIG. 6 , a point light source  70  is exemplarily illustrated. A portion of the light emitted from the point light source  70  is reflected by the substrate  10  and emitted to the outside through sides of the first LED  51 . 
     Since the damaged region  12  on the sides of the first LED  51  has been removed through the wet etching or the dry etching, the light is scarcely absorbed at the sides of the first LED  51 , and thus it is possible to effectively emit the light to the outside. 
       FIGS. 7 to 11  are sectional views illustrating an LED and a method for manufacturing the same according to a second embodiment. 
     Referring to  FIG. 7 , a semiconductor layer  20 , a first electrode  31  and a second electrode  41  are formed on a substrate  10  so as to form an LED. In addition, a mask layer  60  and a support member  80  are formed on the semiconductor layer and the first and second electrodes  31  and  41 . 
     The substrate  10  may include, for example, a sapphire substrate. The semiconductor layer  20  has a multi-stacked structure of a compound semiconductor. 
     A portion of the semiconductor layer  20  may be selectively etched, and the first electrode  31  is formed on the etched portion of semiconductor layer  20 . Accordingly, heights of the first and second electrodes  31  and  41  differ from each other even though they are formed on the same semiconductor layer  20 . 
     The embodiment of  FIGS. 7 to 11  illustrates sectional views for convenience in description, which illustrate processes of forming first, second and third LEDs  51 ,  52  and  53 . 
     The mask layer  60  protects the semiconductor layer  20  during a scribing process, and is formed of a material which can be wet-etched or dry-etched. 
     The support member  80  prevents damages of the first, second and third LEDs  51 ,  52  and  53  which may be caused by a physical force applied to the first, second and third LEDs  51 ,  52  and  53  while laser is irradiated onto the substrate  10  using a laser irradiation apparatus and then the damaged region of the substrate  10  due to the laser irradiation is removed by wet or dry etching. 
     Further, the support member  80  prevents the separation of the first, second and third LEDs  51 ,  52  and  53  caused by external impact before a process of separating the first, second and third LEDs  51 ,  52  and  53  is completed. 
     The support member  80  may be formed of at least one of an adhesive tape, a material which can be wet-etched or dry-etched, a metallic material and a wafer substrate. 
     The support member  80  may be selectively formed depending on thicknesses of the substrate  10  and the semiconductor layer  20 . Thus, the support member  80  may be omitted. 
     In  FIG. 7 , reference numeral  11  denotes a scribing region. In second embodiment, laser is irradiated onto the scribing region  11  using a laser irradiation apparatus, thus dividing the substrate  10  into the first, second and third LEDs  51 ,  52  and  53 . 
     A lapping process may be performed to reduce the thickness of the substrate  10  before irradiating the laser onto the scribing region  11 . The lapping process may be performed through at least one process of chemical mechanical polishing (CMP), dry etching, wet etching and mechanical polishing using slurry. 
     Referring to  FIG. 8 , when the laser is irradiated onto the scribing region  11 , the substrate  10  of the scribing region  11  is selectively removed. 
     During laser irradiation, the layers in the scribing region  11  onto which the laser is irradiated are damaged, causing a damaged region  12  with a rugged surface to be formed, as illustrated in  FIG. 8 . 
     The light emitted from the active layer of the LED does not pass through but is absorbed at the damaged region  12 , and thus the damaged region  12  is removed so as to improve light efficiency of the LED in this embodiment. 
     The removal of the damaged region  12  may be performed using a wet etching or dry etching process. 
     The wet etching process may be performed using a first etchant including at least one of hydrochloric acid (HCl), nitric acid (HNO 3 ), potassium hydroxide (KOH), sodium hydroxide (NaOH), sulfuric acid (H 2 SO 4 ), phosphoric acid (H 3 PO 4 ) and aluetch (4H 3 PO 4 +4CH 3 COOH+HNO 3 ). A temperature of the first etchant is between 200° C. and 400° C. 
     The mask layer  60  prevents the semiconductor layer  20  from being etched during the etching of the damaged region  12 . The mask layer  60  may be formed of, for example, silicon nitride (Si 3 N 4 ) or an oxide-based material such as silicon oxide (SiO 2 ), which is hardly etched by the first etchant. 
     Since the mask layer  60  is hardly etched by the first etchant, the damaged region  12  can be selectively etched while minimizing the etch amount of the semiconductor layer  20 . 
     The dry etching may be performed using an ICP/RIE or an RIE. In addition, the dry etching may be performed using a first etching gas including at least one of BCl 3 , Cl 2 , HBr and Ar. 
     The mask layer  60  configured to prevent the semiconductor layer  20  from being etched during the etching of the damaged region  12  may be formed of an oxide-based material such as SiO 2 , TiO 2  and ITO or a metallic material such as Cr, Ti, Al, Au, Ni and Pt, which is hardly etched by the first etching gas. 
     The wet etching and the dry etching may be performed for several minutes to several tens of minutes depending on etching environments.  FIG. 9  illustrates that the damaged region  12  of the scribing region  11  is removed. 
     Referring to  FIG. 9 , the mask layer  60  and the support member  80  formed on the semiconductor layer  20  are removed after the removal of the damaged region  12 . 
     The support member  80  may be differently removed depending on kinds of the support member  80 . For example, the support member  80  formed of adhesive tape is removed by detaching it, whereas the support member  80  formed of an etchable material is removed by etching process. 
     The removal of the mask layer  60  may be performed using at least one method of the wet etching and the dry etching. 
     For example, the mask layer  60  is removed through the wet etching process using a second etchant including at least one of buffer oxide etchant (BOE) or hydrofluoric acid (HF). 
     Because the semiconductor layer  20  is hardly etched by the second etchant, the mask layer  60  can be selectively etched while minimizing the etch amount of the semiconductor layer  20 . 
     For example, the mask layer  60  is removed by the dry etching using a second etching gas including at least one of O 2  and CF 4 . 
     The mask layer  60  can be selectively etched while minimizing the etch amount of the semiconductor layer  20  because the semiconductor layer  20  is hardly etched by the second etching gas. 
     Thereafter, a physical impact is applied to the substrate  10  and the semiconductor layer  20 , and thus the first LED  51 , the second LED  52  and the third LED  53  are separated from each other by the scribing region  11 . 
       FIG. 11  illustrates the first LED  51  separated by the scribing region  11 . 
     The first LED  51  includes the semiconductor layer  20 , the first electrode  31  and the second electrode  41  which are formed over the substrate  10 . 
     The semiconductor layer  20  includes a buffer layer  21 , an n-type semiconductor layer  22 , an active layer  23 , a p-type semiconductor layer  24  and a transparent electrode layer  25 . 
     The buffer layer  21  relieves stress between the substrate  10  and the n-type semiconductor layer  22  and enables the semiconductor layer to easily grow. The buffer layer  21  may have at least one structure of AlInN/GaN, In x Ga 1-x N/GaN and Al x In y Ga 1-x-y N/In x Ga 1-x N/GaN. 
     The n-type semiconductor layer  22  may include a GaN layer doped with silicon, and may be formed by supplying silane gas containing n-type dopant such as NH 3 , TMGa and Si. 
     The active layer  23  may have a single-quantum well or a multi-quantum well (MQW) structure formed of InGaN/GaN. The p-type semiconductor layer  24  may be formed of trimethylaluminum (TMAL), bis(ethylcyclopentadienyl)magnesium (EtCp2Mg), or ammonia (NH 3 ). 
     The transparent electrode layer is formed of a material such as ITO, ZnO, RuOx, TiOx and IrOx. The first electrode  31  may be formed of titanium (Ti) and the second electrode  41  may be formed of a metallic material such as nickel (Ni). 
     The first LED  51  emits light from the active layer  23  when a power is supplied to the first and second electrodes  31  and  41 . 
     In  FIG. 11 , a point light source  70  is exemplarily illustrated. A portion of the light emitted from the point light source  70  is reflected by the substrate  10  and emitted to the outside through sides of the first LED  51 . 
     In the LED and the method for manufacturing the same according to the embodiments, the LED having a PN junction is described, which includes the n-type semiconductor layer, the active layer and the p-type semiconductor layer. However, a chip separation process according to the embodiments is also available for an LED having a NPN junction where an n-type semiconductor layer, an active layer, a p-type semiconductor layer and an n-type semiconductor layer are stacked in sequence. 
     Further, in the LED and the method for manufacturing the same according to the embodiments, the chip separation process of an LED having a horizontal configuration is described, in which the first electrode is formed on the n-type semiconductor layer and the second electrode is formed on the p-type semiconductor layer after the p-type semiconductor layer, the active layer and the n-type semiconductor layer are partially removed. 
     However, the chip separation process is also available for an LED having a vertical configuration in which the substrate including a conductive substrate, the first electrode, the n-type semiconductor layer, the active layer, the p-type semiconductor layer and the second electrode are sequentially formed. That is, the first electrode is formed between the semiconductor layer and the substrate and the second electrode is formed on the semiconductor layer, respectively. 
     Any reference in this specification to “a first embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
     Also, it will be understood that when an element is referred to as being ‘on’ or ‘under’ another element, it can be directly on/under the element, and one or more intervening elements may also be present. 
     A light emitting diode (LED) and a method for manufacturing the same according to the embodiments can be applied to a separation process of LEDs having a variety of structures.