Patent Publication Number: US-9900098-B2

Title: Optical device module and optical communication network system using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a divisional of U.S. application Ser. No. 13/934,006, filed on Jul. 2, 2013, which claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2013-0019230, filed on Feb. 22, 2013, the entireties of which are incorporated by reference herein. 
    
    
     BACKGROUND 
     The inventive concept relates to an optical communication device and, more particularly, to an optical device module including an optical waveguide of a silicon-compound and an optical communication network system using the same. 
     As electronic devices become smaller and faster, researches are being conducted for increasing integration degree of elements constituting the electronic devices. Fast signal transmission between the elements is required along with small sizes of the elements for small sizes and high speed of the electronic devices. 
     An optical communication technique may be applied between the electronic devices for increasing a signal transmission speed between the elements. If the optical communication technique is applied into the electronic device, the signal transmission speed may increase, and various problems (e.g., high resistance, occurrence of high heat, and/or parasitic capacitance, etc.) of a conventional signal transmission method may be alleviated. 
     Recently, various researches are being conducted for applying an optical fiber-communication technique in the maturity stage to a computer. For example, a silicon photonics technology uses an optical waveguide of a silicon material for transmission of an optical signal. Additionally, an optical fiber may be inserted in a printed circuit board (PCB) of the computer to directly use the optical fiber-communication technique. 
     SUMMARY 
     Embodiments of the inventive concept may provide an optical device module capable of increasing or maximizing coupling efficiency and an optical communication network system using the same. 
     In one aspect, an optical device module may include: a substrate; an interlayer insulating silicon oxide (SiO 2 ) layer on the substrate; an optical waveguide core layer consisting of silicon nitride or silicon oxynitride (Si 3 N 4 , or Si x O y N z , where x, y, z are arbitrary numbers) on the interlayer insulating layer; an optical device consisting of a vertical cavity surface emitting laser (VCSEL) or a photodiode on the optical waveguide; and a prism disposed between the optical device and the optical waveguide, the prism having a refractive index greater than a refractive index of the optical waveguide core. 
     In an embodiment, the prism may have a wedge-shape having an incline plane tilted with respect to an extending direction of the optical waveguide. 
     In an embodiment, the prism of the wedge-shape may include gallium phosphide or silicon. 
     In an embodiment, the prism of the wedge-shape may include the gallium phosphide; and the incline plane of the prism may have an inclination angle of about 35.2 degrees with respect to the extending direction of the optical waveguide. 
     In an embodiment, the prism of the wedge-shape may include the silicon; and the incline plane of the prism may have an inclination angle of about 29.5 degrees with respect to the extending direction of the optical waveguide. 
     In an embodiment, the optical device may be bonded to the incline plane; and the optical device may further include a laser diode, or an optical fiber. 
     In an embodiment, the optical device module may further include: a buffer layer disposed between the prism and the optical waveguide. The buffer layer may have a refractive index greater than the refractive index of the optical waveguide. 
     In an embodiment, the buffer layer may include index-matching oil or adhesive. 
     In an embodiment, the optical device module may further include: an upper insulating layer adjacent to the prism and covering a portion of the optical waveguide. 
     In an embodiment, the interlayer insulating layer and the upper insulating layer may include silicon oxide. 
     In an embodiment, the prism may have a hexahedral shape including flat surfaces parallel to the optical waveguide. 
     In an embodiment, the optical device module may include an upper buffer layer and an upper optical waveguide. 
     In an embodiment, the optical device module may further include a top upper insulating layer adjacent to the prism and covering a portion of the upper optical waveguide. 
     In an embodiment, the optical device module may further include: a semiconductor device disposed within the interlayer insulating layer. 
     In another aspect, an optical communication network system may include: a substrate including a sub-control region, a connection region, and a sub-unit cell region; sub-control parts disposed on the sub-control region, each of the sub-control parts including first light sources and first detectors; sub-unit cell parts including second detectors and second light sources disposed on the sub-unit cell region, the second detectors and the second light sources communicating with the first light sources and the first detectors; optical waveguides disposed on the sub-control region, the connection region, and the sub-unit cell region, the optical waveguides connecting the first light sources to the second detectors and connecting the first detectors to the second light sources; and a prism disposed between the optical waveguides and at least one of the first light source, the first detector, the second light source, and the second detector, the prism having a refractive index greater than a refractive index of the optical waveguides. 
     In an embodiment, the optical waveguides may include: a first optical waveguide connected between the first light source and the second detector; and a second optical waveguide connected between the first detector and the second light source. The first optical waveguide may not cross the second optical waveguide. 
     In an embodiment, each of the sub-control parts may be connected to N sub-unit cell parts through the optical waveguides to constitute a unit cell part, where ‘N’ denotes a natural number equal to or greater than 2; the number of the sub-control parts may be N such that N unit cell parts may be disposed on the network; and the N unit cell parts may include N 2  sub-unit cell parts. 
     In an embodiment, the optical communication network system may further include: main control parts of which each is connected to the N 2  sub-unit cell parts through the optical waveguides. In this case, the main control parts and the unit cell parts connected thereto may constitute N upper unit cell parts; and the N upper unit cell parts may include N 3  sub-unit cell parts. 
     In an embodiment, the optical waveguides may include silicon nitride or silicon oxynitride. 
     In an embodiment, the prism may include a crystal structure material having a refractive index greater than the refractive index of the optical waveguides; and the crystal structure material may include gallium phosphide or silicon. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The inventive concept will become more apparent in view of the attached drawings and accompanying detailed description. 
         FIG. 1  is a plan view illustrating a general optical communication network system; 
         FIG. 2  is a plan view illustrating an optical communication network system according to example embodiments of the inventive concept; 
         FIG. 3  is a plan view illustrating a sub-control part and sub-unit cell parts of  FIG. 2  in more detail; 
         FIG. 4  is a cross-sectional view illustrating an optical device module according to a first embodiment of the inventive concept; 
         FIG. 5  is a cross-sectional view illustrating an optical device module according to an application example of the inventive concept; 
         FIG. 6  is a cross-sectional view illustrating an optical device module according to a second embodiment of the inventive concept; and 
         FIG. 7  is a cross-sectional view illustrating some elements of each of optical device modules according to embodiments of the inventive concept. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the inventive concept are shown. The advantages and features of the inventive concept and methods of achieving them will be apparent from the following exemplary embodiments that will be described in more detail with reference to the accompanying drawings. It should be noted, however, that the inventive concept is not limited to the following exemplary embodiments, and may be implemented in various forms. Accordingly, the exemplary embodiments are provided only to disclose the inventive concept and let those skilled in the art know the category of the inventive concept. In the drawings, embodiments of the inventive concept are not limited to the specific examples provided herein and are exaggerated for clarity. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular terms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it may be directly connected or coupled to the other element or intervening elements may be present. 
     Similarly, it will be understood that when an element such as a layer, region or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present. In contrast, the term “directly” means that there are no intervening elements. It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Additionally, the embodiment in the detailed description will be described with sectional views as ideal exemplary views of the inventive concept. Accordingly, shapes of the exemplary views may be modified according to manufacturing techniques and/or allowable errors. Therefore, the embodiments of the inventive concept are not limited to the specific shape illustrated in the exemplary views, but may include other shapes that may be created according to manufacturing processes. Areas exemplified in the drawings have general properties, and are used to illustrate specific shapes of elements. Thus, this should not be construed as limited to the scope of the inventive concept. 
     It will be also understood that although the terms first, second, third etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, a first element in some embodiments could be termed a second element in other embodiments without departing from the teachings of the present invention. Exemplary embodiments of aspects of the present inventive concept explained and illustrated herein include their complementary counterparts. The same reference numerals or the same reference designators denote the same elements throughout the specification. 
     Moreover, exemplary embodiments are described herein with reference to cross-sectional illustrations and/or plane illustrations that are idealized exemplary illustrations. Accordingly, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, exemplary embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an etching region illustrated as a rectangle will, typically, have rounded or curved features. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of example embodiments. 
       FIG. 1  is a plan view illustrating a general optical communication network system. 
     Referring to  FIG. 1 , a general optical communication network system may include a plurality of sub-unit cell parts  110  and a plurality of optical waveguides  30 . The sub-unit cell parts  110  may be arranged in matrix form. The optical waveguides  30  may be divided into pairs and may be connected between the sub-unit cell parts  110 . A pair of the optical waveguides  30  may input and output an optical signal between the sub-unit cell parts  110 . For example, N sub-unit cell parts  110  may be connected to each other through 2 N  optical waveguides  30 , where denotes a natural number equal to or greater than 2. In a two-dimensional plane, the optical waveguides  30  may necessarily have crossing points thereof. An optical switch (not shown) may be disposed at each of the crossing points. The optical switches may complex an optical communication network. Thus, it may be difficult that the general optical communication network system is designed to have a two-dimensional plane structure. 
       FIG. 2  is a plan view illustrating an optical communication network system according to example embodiments of the inventive concept. 
     Referring to  FIG. 2 , an optical communication network system according to inventive concept may include main control parts  120 , sub-control parts  112 , sub-unit cell parts  110 , and optical waveguides  30 . The optical waveguides  30  may be connected to the main control parts  120 , the sub-control parts  112 , and the sub-unit cell parts  110  in the order named. The main control parts  120  may output control signals controlling the sub-control parts  112  and the sub-unit cell parts  110  and may receive response signals. The sub-control parts  112  may communicate with the main control parts  120  and may control the sub-unit cell parts  110 . One sub-control part  112  and  16  sub-unit cell parts  110  connected thereto may constitute a unit cell part  114 . The optical communication network system according to inventive concept may include a plurality of the unit cell parts  114 . If the optical communication network system according to inventive concept includes 16 unit cell parts  114 , the 16 unit cell parts  114  may include 16 2  sub-unit cell parts  110 . Additionally, one main control part  120  and the 16 unit cell parts  114  connected thereto may constitute an upper unit cell part  116 . Even though not shown in the drawings, 16 upper unit cell parts  116  may include 16 3  sub-unit cell parts  110 . The upper unit cell parts  116  and a super main control part (not shown) may constitute a high dimensional unit cell part. Thus, the optical communication network system according to inventive concept may include M-dimensional unit cell parts  114  and 16 M  sub-unit cell parts  110 , where ‘M’ denotes a natural number. 
     The sub-control part  112  may output the optical signal of a selected sub-unit cell part  110  to another sub-unit cell part  110  in the same unit cell part  114 , another unit cell part  114 , or another upper unit cell part  116 . Each of the main control parts  120 , the sub-control parts  112  and the sub-unit cell parts  110  may perform a photoelectric converting operation between the optical signal and an electrical signal. 
       FIG. 3  is a plan view illustrating the sub-control part  112  and the sub-unit cell parts  110  of  FIG. 2  in more detail. 
     Referring to  FIGS. 2 and 3 , the sub-control part  112  may include first light sources  72  and first detectors  74 . Each of the sub-unit cell parts  110  may include a second detector  76  and a second light source  78 . Each of the first and second light sources  72  and  78  may include a vertical cavity surface emitting laser (VCSEL) or a laser diode. Each of the first and second detectors  74  and  76  may include a photo diode. The first light source  72  and the second detector  76  may be connected to each other by a first optical waveguide  32 . The first light source  72 , the first optical waveguide  32 , and the second detector  76  may constitute a first communication line. A second optical waveguide  34  may connect the first detector  74  to the second light source  78 . Likewise, the first detector  74 , the second optical waveguide  34 , and the second light source  78  may constitute a second communication line. The first optical waveguide  32  and the second optical waveguide  34  do not cross each other and may connect the sub-control part  112  to the sub-unit cell part  110 . 
     The first light source  72 , the first detector  74 , the second light source  78 , and a second detector  76  are optical devices. The optical devices may be combined with the optical waveguides to constitute an optical device module  100 . The optical waveguides  30  may connect the optical device modules  100  to each other. The sub-unit cell parts  110  may have a plurality of optical device modules  100  transmitting and receiving optical signals. 
     Hereinafter the optical device module  100  capable of maximizing optical coupling efficiency will be described in detail with reference to embodiments. 
       FIG. 4  is a cross-sectional view illustrating an optical device module  100  according to a first embodiment of the inventive concept. 
     Referring to  FIGS. 2 to 4 , an optical device module  100  according to a first embodiment of the inventive concept may include a substrate  10 , an interlayer insulating layer  20 , an optical waveguide  30 , an upper insulating layer  40 , a buffer layer  50 , a prism  60 , and an optical device  70 . 
     The substrate  10  may include crystalline silicon. The crystalline silicon may have a refractive index of about 3.45. The optical device module  100  is a small part of component by which the optical network Even though not shown in the drawings, the optical communication network is comprised of a plurality of optical device module  100 , where the network may have a sub-control region, a connection region, and a sub-unit cell region. The sub-control region may correspond to the sub-control parts  112 . The sub-unit cell region may correspond to the sub-unit cell parts  110 . The connection region is disposed between the sub-control region and the sub-unit cell region. The interlayer insulating layer  20  may be disposed on the substrate  10 . The interlayer insulating layer  20  may include silicon oxide. The silicon oxide may have a refractive index of about 1.45. 
     The optical waveguide  30  may extend in one direction on the interlayer insulating layer  20 . The interlayer insulating layer  20  may have a refractive index lower than that of the optical waveguide  30 . The optical waveguide  30  may have a refractive index lower than that of the substrate  10 . The optical waveguide  30  may include silicon nitride or silicon oxynitride. The silicon nitride may have a refractive index of about 2.0. The silicon oxynitride may have a refractive index of about 1.7. 
     The upper insulating layer  40  may cover a portion of the optical waveguide  30 . A refractive index of the upper insulating layer  40  may be lower than the refractive index of the optical waveguide  30 . The upper insulating layer  40  may include silicon oxide. 
     The buffer layer  50  may be adjacent to the upper insulating layer  40  and may cover another portion of the optical waveguide  30 . The buffer layer  50  may have a refractive index higher than that of the optical waveguide  30 . The buffer layer  50  may include index-matching oil or adhesive having a refractive index of about 1.7 to about 2.1. 
     The prism  60  may be disposed on the buffer layer  50 . The buffer layer  50  may prevent air from flowing between the prism  60  and the optical waveguide  30 . This is because the air interrupts optical transmission between the prism  60  and the optical waveguide  30 . The prism  60  may have a refractive index higher than that of the buffer layer  50 . The prism  60  may have a wedge-shape having an incline plane  62 . An inclination angle θ of the prism  60  may correspond to a refracting angle. The prism  60  may include crystalline silicon or gallium phosphide (GaP). Crystalline gallium phosphide may have a refractive index of about 3.05. 
     The optical device  70  may be vertically bonded to the incline plane  62  of the prism  60 . The optical device  70  may include the first light source  72 , the first detector  74 , the second detector  76 , or the second light source  78 . 
     The first light source  72  or the second light source  78  may provide a laser beam  200  to the optical waveguide  30 . As described above, each of the first and second light sources  72  and  78  may include a vertical cavity surface emitting laser (VCSEL) or a laser diode. Refracting angles of the laser beam  200  may increase in order when the laser beam  200  travels from the prism  60  into the optical waveguide  30 . The refracting angle of the laser beam  200  may increase whenever the laser beam  200  travels from a medium of a high refractive index into a medium of a low refractive index. If the refractive index of the laser beam  200  is 90 degrees in the optical waveguide  30 , the optical device  70  (e.g., the first light source  72  or the second light source  78 ) and the optical waveguide  30  of the optical device module  100  may have the maximum coupling efficiency. 
     The laser beam  200  may be perpendicularly incident into the incline plane  62  of the prism  60 . In this case, a first incidence angle Φ 1  of the laser beam  200  is 0 (zero). Additionally, a first refracting angle (not shown) of the laser beam  200  is 0 (zero) at the incline plane  62 . If an optical signal is incident from a medium having a low refractive index into a medium having a high refractive index, a refracting angle of the optical signal is smaller than an incidence angle of the optical signal. The laser beam  200  may be incident from air into the prism  60 . 
     Thereafter, the laser beam  200  may be incident on a bottom surface of the prism  60  with a second incidence angle Φ 2 . The second incidence angle Φ 2  is equal to the inclination angle θ of the incline plane  62  of the prism  60 . The laser beam  200  may be refracted in the buffer layer  50  with a second refracting angle Φ 3 . The second refracting angle Φ 3  may be greater than the second incidence angle Φ 2 . If an optical signal is incident from a medium having a high refractive index into a medium having a low refractive index, a refracting angle of the optical signal is greater than an incidence angle of the optical signal. The laser beam  200  may travel in the optical waveguide  30  with a third refracting angle Φ 4 . The third refracting angle Φ 4  may be greater than the second refracting angle Φ 3 . 
     When the laser beam  200  has the third refracting angle Φ 4  of about 90 degrees, the optical device module  100  may have the maximum coupling efficiency. At this time, the laser beam  30  may travel through the optical waveguide  30  in parallel to the optical waveguide  30 . If the third refracting angle Φ 4  is greater or less than 90 degrees, the laser beam  200  may be reflected by a bottom surface of the optical waveguide and then may return toward the optical device  70 . Thus, a coupling efficiency of the optical device module may be reduced. 
     For example, the prism  60  of crystalline silicon may have an inclination angle of about 25 degrees to about 35 degrees. In particular, when the incline plane  62  of the prism  60  of crystalline silicon has the inclination angle of about 29.6 degrees, the optical device module  100  according to the first embodiment may have the maximum coupling efficiency. The prism  60  of gallium phosphide may have an inclination angle of about 30 degrees to about 40 degrees. The following table 1 presents an experimentally measured output power of the laser beam according to the inclination angle of the gallium phosphide prism  60 , 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Inclination angle 
                 Output power (mW) 
               
               
                   
                 of GaP prism (degree) 
                 with input power 9.69 mW 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 35.06 
                 0.801 
               
               
                   
                 35.2 
                 0.81 
               
               
                   
                 35.35 
                 0.804 
               
               
                   
                 35.5 
                 0.706 
               
               
                   
                   
               
            
           
         
       
     
     Referring to table 1, when the incline plane of the gallium phosphide prism  60  has the inclination angle of about 35.2 degrees, the laser beam was measured to have the maximum output power of about 0.81 mW. Thus, the optical device module  100  according to the first embodiment may have the maximum coupling efficiency. 
     Additionally, the first detector  74  or the second detector  76  may detect the laser beam  200  transmitted from the optical waveguide  30 . Refracting angles of the laser beam  200  may be reduced in order when the laser beam  200  travels from the optical waveguide  30  to the prism  60 . The refracting angle of the laser beam  200  may be reduced whenever the laser beam  200  travels from a medium of a low refractive index into a medium of a high refractive index. If the refractive angle of the laser beam  200  is 0 degree from the prism  60  to the optical device  70  (e.g., the first detector  74  or the second detector  76 ), then the optical waveguide  30  may have the maximum coupling efficiency. Detail descriptions to the traveling of the laser beam  200  may be omitted. 
       FIG. 5  is a cross-sectional view illustrating an optical device module according to an application example of the inventive concept. 
     Referring to  FIGS. 4 and 5 , an optical device module  100  according to an application example of the inventive concept may include an optical fiber  80  bonded to the incline plane  62  of the prism  60 . The optical fiber  80  may include a core  82  and a cladding 84. The cladding 84 may have a refractive index less than that of the core  82 . A laser beam  200  may travel along the core  82 . The core  82  and the cladding 84 may be perpendicularly coupled to the incline surface  62 . The optical device module  100  according to the application example includes the optical fiber  80  instead of the optical device  70  of the first embodiment. 
       FIG. 6  is a cross-sectional view illustrating an optical device module according to a second embodiment of the inventive concept. 
     Referring to  FIG. 6 , an optical device module  100  according to a second embodiment of the inventive concept may include a substrate  10 , an interlayer insulating layer  20 , an optical waveguide  30 , a cap layer  40 , a buffer layer  50 , a prism  60 , an upper buffer layer  52 , an upper cap layer  42 , an upper optical waveguide  32 , an upper interlayer insulating layer  22 , and an upper substrate  12 . 
     The upper substrate  12  and the substrate  10  may be symmetrical with respect to the prism  60 . Likewise, the upper interlayer insulating layer  22  and the interlayer insulating layer  20  may be symmetrical with respect to the prism  60 , and the upper optical waveguide  32  and the optical waveguide  30  may be symmetrical with respect to the prism  60 . The upper cap layer  42  and the cap layer  40  may be symmetrical with respect to the prism  60 , and the upper buffer layer  52  and the buffer layer  50  may be symmetrical with respect to the prism  60 . 
     The upper substrate  12  may include the same crystalline silicon as the substrate  10 . The upper interlayer insulating layer  22  and the upper cap layer  42  may include silicon oxide. The upper optical waveguide  32  may include silicon nitride or silicon oxynitride. The upper buffer layer  52  may include index-matching oil or adhesive. 
     The prism  60  may have a hexahedral shape having a bottom surface and a top surface which are parallel to the optical waveguide  30  and the upper optical waveguide  32 . In  FIG. 6 , the prism  60  of the hexahedral shape is illustrated to have a quadrilateral cross section. The quadrilateral cross section of the prism  60  may have a hypothetical diagonal line  64 . In other words, the prism  60  of the hexahedral shape may have a hypothetical diagonal plane corresponding to the diagonal line  64 . The diagonal line  64  (or the diagonal plane) may correspond to the incline plane  62  described in the first embodiment. In the real fabrication, the prism  60  is one piece of hexahedral without attaching two wedge-shape prisms. 
     The optical device module  100  according to the second embodiment includes the prism  60  having the hexahedral shape instead of the prism  60  having the wedge-shape of the first embodiment. Additionally, the optical device module  100  according to the second embodiment includes the upper buffer layer  52  and the upper optical waveguide  32  instead of the optical device  70  of the first embodiment. 
     A laser beam  200  may be refracted and travel from the optical waveguide  30  to the upper optical waveguide  32 . Refractive indexes of the elements from the optical waveguide  30  to the prism  60  may increase in order and then refractive indexes of the elements from the prism  60  to the upper optical waveguide  30  may be reduced in order along the traveling direction of the laser beam  200 . The hexahedral prism  60  may have a predetermined width and a predetermined height for improving the coupling efficiency. If the width and height of the prism  60  are not suitable, the laser beam  200  may be reflected between the optical waveguide  30  and the upper optical waveguide  32  to be lost. 
       FIG. 7  is a cross-sectional view illustrating some elements of each of optical device modules according to embodiments of the inventive concept. 
     Referring to  FIG. 7 , the optical device module may include semiconductor devices  28  disposed within the interlayer insulating layer  20 . The semiconductor device  28  may include a memory device such as a dynamic random access memory (DRAM) device or a NAND flash memory device. The semiconductor device  28  may include a word line  22 , a bit line  24 , and a metal line  26 . The word line  22  may be a gate of a thin film transistor (not shown) disposed on the substrate  10 . A source (not shown) and a drain (not shown) of the thin film transistor may be disposed in the substrate  10 . The bit line  24  may be disposed on the word line  22 . The word line  22  and the bit line  24  may be insulated from each other. The bit line  24  may be electrically connected to the source or the drain through a contact plug (not shown) and/or a contact pad (not shown). The metal line  26  may be disposed on the bit line  24 . The bit line  24  and the metal line  26  may be insulated from each other. The metal line  26  may be a circuit line. The metal line  26  may be formed by, for example, a back-end process. 
     As described above, the optical device module according to the above embodiments may include the substrate, the interlayer insulating layer, the optical waveguide, the buffer layer, the prism, and the optical device. The optical waveguide may extend in one direction on the interlayer insulating layer and may include silicon nitride or silicon oxynitride. The buffer layer may cover the optical waveguide. The buffer layer may have the greater refractive index than the optical waveguide. The prism may be disposed on the buffer layer. The prism may have the greater refractive index than the buffer layer. The prism may have the wedge-shape having the incline plane. The incline plane may correspond to the inclination angle. The optical device may include the light source providing the laser beam. The optical device may be bonded to the incline plane of the prism, such that the laser beam may be perpendicularly incident on the incline plane. The refracting angles of the laser beam may progressively increase from the prism to the optical waveguide. If the refracting angle of the laser beam in the optical waveguide is 90 degrees, the optical waveguide and the optical device may have the maximum coupling efficiency. The maximum coupling efficiency may be determined depending on the refractive index of the optical waveguide, the refractive index of the buffer layer, the refractive index of the prism, and the inclination angle of the prism. 
     As a result, the optical device module and the optical communication network system using the same according to the inventive concept may increase or maximize the coupling efficiency. 
     While the inventive concept has been described with reference to example embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the inventive concept. Therefore, it should be understood that the above embodiments are not limiting, but illustrative. Thus, the scope of the inventive concept is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing description.