Patent Publication Number: US-2005118740-A1

Title: Method of manufacturing a branch optical waveguide

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates generally to methods of manufacturing a branch optical waveguide, and more particularly to a method of manufacturing a branch optical waveguide of a polymer resin material, using lamination, photolithography, and reactive ion etching (RIE).  
      2. Description of the Related Art  
      Y-branch optical waveguide devices with a Y-branch optical waveguide using a polymer resin material have lower light propagation characteristics, but have the advantages of far better productivity and far lower manufacturing costs than quartz branch optical waveguide devices. Accordingly, branch optical waveguide devices are often used as optical module components.  
      A description is given of a process for manufacturing a conventional branch optical waveguide device using a polymer resin material. According to actual manufacturing, multiple branch optical waveguides are formed on a silicon wafer in a matrix manner using lamination and photolithography, and the silicon wafer is scribed into pieces at the end. Here, a description is given in such a way as to form a single branch optical waveguide.  
       FIG. 1  is a perspective view of a Y-branch optical waveguide device  1  manufactured through processes shown in  FIGS. 2A through 2G . In  FIG. 1 , Z 1 -Z 2 , X 1 -X 2 , and Y 1 -Y 2  indicate the directions of length, width, and thickness (height), respectively, of the Y-branch optical waveguide device  1 . The Y-branch optical waveguide device  1  includes a Y-branch optical waveguide  2  made of a polymer resin material and a silicon substrate  3 . The Y-branch optical waveguide  2  is formed on the upper surface of the silicon substrate  3 . The Y-branch optical waveguide  2  includes a core  4  made of a polymer resin material such as a fluorinated polyimide resin and lower and upper clad layers  5  and  6  surrounding the core  4 . The lower and upper clad layers  5  and  6  are also made of a fluorinated polyimide resin. The core  4 , which has a Y-letter shape, includes an entrance-side core  4   a  and two branch cores  4   b  and  4   c  that branch off therefrom. In  FIG. 1 , the core  4  is shown with solid lines for convenience of description.  
      First, as shown in  FIG. 2A , a fluorinated polyimide resin having a refractive index of n 1  is applied on the surface of the silicon substrate  3  so that the lower clad layer  5  is formed. Then, as shown in  FIG. 2B , a fluorinated polyimide resin having a refractive index of n 2  (&gt;n 1 ) is applied on the lower clad layer  5  so that a core layer  10  is formed. Then, as shown in  FIG. 2C , a resist layer  11  containing silicon is applied and formed on the core layer  10 . A mask member  20  includes a quartz plate  21  and a Y-shaped mask pattern  22  of, for instance, a chromium film that blocks ultraviolet rays, formed on the lower surface of the quartz plate  21 . The mask pattern  22  is shown with solid lines for convenience of description. Next, as shown in  FIG. 2D , the mask member  20  for exposure is adhered onto the resist layer  11 , and is exposed to ultraviolet rays  25  of a wavelength of approximately 400 nm so as to develop the resist layer  11 . Then, cleaning is performed so that as shown in  FIG. 2E , a resist mask  12  for RIE is formed. Next, RIE is performed to remove the core layer  10  so that the Y-shaped core  4  is formed as shown in  FIG. 2F . Next, as shown in  FIG. 2G , the resist mask  12  is removed. Finally, a fluorinated polyimide resin having the refractive index of n 1  is applied so that the upper clad layer  6  is formed to cover the core  4 . As a result, the Y-branch optical waveguide device  1  shown in  FIG. 1  is manufactured. Such an optical waveguide manufacturing method is disclosed in Japanese Laid-Open Patent Application No. 7-92338.  
      As shown in  FIG. 3A , light  101 , which is substantially one half of light  100  that enters the entrance-side core  4   a  and is propagated therethrough, is propagated through the branch core  4   b , and remaining light  102  is propagated through the branch core  4   c.    
       FIG. 3B  is an enlarged view of a branch point part  4   d  of the core  4  shown in  FIG. 3A , which is the base part of the two branch cores  4   b  and  4   c . As shown in  FIG. 3B , the branch point part  4   d  includes a substantially elliptic part  4   e , which is open as if scooped out. Accordingly, the light  100  propagated through the entrance-side core  4   a  is subject to leaking, so that an unignorable portion of the light  100  leaks out from the branch point part  4   d  as indicated by reference numeral  110 , thus resulting in radiation loss. Reference numeral  110  refers to radiation loss light. Therefore, the conventional Y-branch optical waveguide device  1  has a problem in that radiation loss at the branch point part  4   d  is great and the intensity of the light  101  and  102  propagated through the branch cores  4   b  and  4   c , respectively, is reduced due to the radiation loss.  
      Here, the formation of the shape of the base of the branch cores  4   b  and  4   c  is discussed.  
      The core  4  is formed by RIE as shown in  FIG. 2F . The shape of the base of the branch cores  4   b  and  4   c  is substantially determined by the shape of the resist mask  12 , and, traced back further, by the shape of the Y-shaped exposure mask pattern  22  of the mask member  20 , the mask pattern  22  being formed of a chromium film.  
       FIG. 4A  is a diagram showing the conventional exposure mask pattern  22 , and  FIG. 4B  is an enlarged view of a branch point part  22   d  of the exposure mask pattern  22 .  
      Referring to  FIG. 4A , the exposure mask pattern  22  includes a main body mask part  22   a  and first and second branch mask parts  22   b  and  22   c  branching off from the main body mask part  22   a . Referring further to  FIG. 4B , the branch point part  22   d  of the first and second branch mask parts  22   b  and  22   c  has a shape where an edge part  22   b   1  of the first branch mask part  22   b  and an edge part  22   c   1  of the second branch mask part  22   c  are connected by a line VL perpendicular to the center line CL of the exposure mask pattern  22 . The branch point part  22   d  of the first and second branch mask parts  22   b  and  22   c  has a shape determined by the edge part  22   b   1 , the edge part  22   c   1 , and a linear edge part  22   e . The length L of the edge part  22   e  is a few microns. The branch point part  22   d  includes a corner part  22   f  formed by the edge part  22   b   1  and the edge part  22   e  and a corner part  22   g  formed by the edge part  22   c   1  and the edge part  22   e . When the resist layer  11  is subjected to exposure using the exposure mask pattern  22  having the corner parts  22   f  and  22   g  in a small area, the light of the ultraviolet rays  25  radiated on the edge part  22   b   1  side and the light of the ultraviolet rays  25  radiated on the edge part  22   e  side interfere with each other or diffuse in the corner part  22   f . The same phenomenon also occurs in the corner part  22   g . As a result, the ultraviolet rays  25  go around the corner parts  22   f  and  22   g  to their outside (the outside of a predetermined exposure area) so as to expose the resist layer  11  to light. Consequently, the core  4  has the substantially elliptic part  4   e  shown in  FIG. 3B .  
      An exposure mask pattern more conventional than the exposure mask pattern  22  includes a triangle having an extremely small vertical angle formed by the edge part  22   b   1  and the edge part  22   c   1  being extended to meet each other as indicated by two-dot chain lines a and b, respectively, as shown in  FIG. 4B . In the case of employing this exposure mask pattern, the light intensity of ultraviolet rays is reduced in the area of the triangle compared with the other area, thus resulting in a resist mask whose branch point part has an ill-defined outline. As a result, the core also has a branch point part with an ill-defined outline, thus further increasing radiation loss.  
     SUMMARY OF THE INVENTION  
      Accordingly, it is a general object of the present invention to provide a method of manufacturing a branch optical waveguide in which the above-described disadvantage is eliminated.  
      A more specific object of the present invention is to provide a method of manufacturing a branch optical waveguide in which radiation loss at a branch point part is reduced, and an exposure mask employed in the method.  
      The above objects of the present invention are achieved by a method of manufacturing a branch optical waveguide, the method forming a resist pattern by performing exposure using an exposure mask, the method forming a core by performing etching on a layer of a polymer resin material using the resist pattern as a mask, thereby manufacturing the branch optical waveguide, wherein: the exposure mask includes a main body mask part and first and second branch mask parts branching off therefrom at a branch point part; and the branch point part has a shape where first, second, and third linear edge parts connect an edge part of the first branch mask part and an edge part of the second branch mask part in a trapezoidal manner.  
      The above objects of the present invention are also achieved by a method of manufacturing a branch optical waveguide, the method forming a resist pattern by performing exposure using an exposure mask, the method forming a core by performing etching on a layer of a polymer resin material using the resist pattern as a mask, thereby manufacturing the branch optical waveguide, wherein: the exposure mask includes a main body mask part and first and second branch mask parts branching off therefrom at a branch point part; and the branch point part has a shape where an edge part curved like an arc connects an edge part of the first branch mask part and an edge part of the second branch mask part.  
      The above objects of the present invention are also achieved by a method of manufacturing a branch optical waveguide, the method forming a resist pattern by performing exposure using an exposure mask, the method forming a core by performing etching on a layer of a polymer resin material using the resist pattern as a mask, thereby manufacturing the branch optical waveguide, wherein: the exposure mask includes a main body mask part and first and second branch mask parts branching off therefrom at a branch point part; and the branch point part has a shape where first and second linear edge parts connect an edge part of the first branch mask part and an edge part of the second branch mask part in a triangular manner.  
      The above objects of the present invention are also achieved by an exposure mask used in a process for forming a resist pattern on an upper surface of a layer of a polymer resin material by exposure, the resist pattern being used for performing etching on the layer of the polymer resin material so as to form a core including an entrance-side core and a plurality of branch cores branching off therefrom, the exposure mask including: a main body mask part; and first and second branch mask parts branching off from the main body mask part at a branch point part, wherein the branch point part has a shape where first, second, and third linear edge parts connect an edge part of the first branch mask part and an edge part of the second branch mask part in a trapezoidal manner.  
      The above objects of the present invention are also achieved by an exposure mask used in a process for forming a resist pattern on an upper surface of a layer of a polymer resin material by exposure, the resist pattern being used for performing etching on the layer of the polymer resin material so as to form a core including an entrance-side core and a plurality of branch cores branching off therefrom, the exposure mask including: a main body mask part; and first and second branch mask parts branching off from the main body mask part at a branch point part, wherein the branch point part has a shape where an edge part curved like an arc connects an edge part of the first branch mask part and an edge part of the second branch mask part.  
      The above objects of the present invention are also achieved by an exposure mask used in a process for forming a resist pattern on an upper surface of a layer of a polymer resin material by exposure, the resist pattern being used for performing etching on the layer of the polymer resin material so as to form a core including an entrance-side core and a plurality of branch cores branching off therefrom, the exposure mask including: a main body mask part; and first and second branch mask parts branching off from the main body mask part at a branch point part, wherein the branch point part has a shape where first and second linear edge parts connect an edge part of the first branch mask part and an edge part of the second branch mask part in a triangular manner.  
      According to the present invention, an exposure mask is employed that includes a main body mask part and first and second branch mask parts branching off therefrom at a branch point part having a shape where three linear edge parts connect the edge part of the first branch mask part and the edge part of the second branch mask part in a trapezoidal manner. The branch point part may alternatively have a shape where an edge part curved like an arc connects the edge part of the first branch mask part and the edge part of the second branch mask part. The branch point part may alternatively have a shape where two linear edge parts connect the edge part of the first branch mask part and the edge part of the second branch mask part in a triangular manner. As a result, it is possible to form a core whose branch point part does not include a substantially elliptic part that is open as if scooped out, and has a shape close to an ideal shape. Accordingly, it is possible to manufacture a branch optical waveguide having the characteristic of reduced radiation loss compared with a conventional one.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:  
       FIG. 1  is a perspective view of a Y-branch optical waveguide device manufactured by a conventional Y-branch optical waveguide device manufacturing method;  
       FIGS. 2A through 2G  are diagrams showing a process for manufacturing the Y-branch optical waveguide device of  FIG. 1 ;  
       FIGS. 3A and 3B  are diagrams showing a core of the Y-branch optical waveguide device of  FIG. 1 ;  
       FIGS. 4A and 4B  are diagrams showing a conventional exposure mask pattern used in the manufacturing of the Y-branch optical waveguide device of  FIG. 1 ;  
       FIG. 5  is perspective view of a Y-branch optical waveguide device manufactured by a Y-branch optical waveguide device manufacturing method according to an embodiment of the present invention;  
       FIGS. 6A and 6B  are diagrams showing a core of the Y-branch optical waveguide device according to the embodiment of the present invention;  
       FIGS. 7A through 7G  are diagrams showing a process for manufacturing the Y-branch optical waveguide device according to the embodiment of the present invention;  
       FIGS. 8A and 8B  are diagrams showing an exposure mask pattern used in the manufacturing of the Y-branch optical waveguide device according to the embodiment of the present invention;  
       FIGS. 9A and 9B  are diagrams showing a resist mask formed using the exposure mask pattern according to the embodiment of the present invention;  
       FIGS. 10A and 10B  are diagrams showing a first variation of the exposure mask pattern used in the manufacturing the Y-branch optical waveguide device according to the embodiment of the present invention; and  
       FIGS. 11A and 11B  are diagrams showing a second variation of the exposure mask pattern used in the manufacturing of the Y-branch optical waveguide device according to the embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      A description is given below, with reference to the accompanying drawings, of an embodiment of the present invention.  
       FIG. 5  is a perspective view of a Y-branch optical waveguide device  41  manufactured by a Y-branch optical waveguide device manufacturing method according to the embodiment of the present invention. In  FIG. 5 , Z 1 -Z 2 , X 1 -X 2 , and Y 1 -Y 2  indicate the directions of length, width, and thickness (height), respectively, of the Y-branch optical waveguide device  41 . The Y-branch optical waveguide device  41  includes a Y-branch optical waveguide  42  made of a polymer resin material and a silicon substrate  43 . The Y-branch optical waveguide  42  is formed on the upper surface of the silicon substrate  43 . The Y-branch optical waveguide  42  includes a core  44  made of, for instance, a fluorinated polyimide resin having a refractive index of n 2  and lower and upper clad layers  45  and  46  surrounding the core  44 . The lower and upper clad layers  45  and  46  are made of a fluorinated polyimide resin having a refractive index of n 1  (&lt;n 2 ). The core  44 , which has a Y-letter shape, includes an entrance-side core  44   a  and two branch cores  44   b  and  44   c  that branch off therefrom. In  FIG. 5 , the core  44  is shown with solid lines for convenience of description. The entrance-side core  44   a  and the branch cores  44   b  and  44   c  are fine, each having a width W 1  of approximately 5 μm and a height H 1  of approximately 5 μm, and are for a single mode. The distance A between the branch cores  44   b  and  44   c  at the Z 1  end is narrow, being approximately 125-250 μm. A branch angle θ 1  is set to 0.5-3°, thus being extremely small.  
      As shown in  FIG. 6A , light  101 A, which is substantially one half of the light  100  that enters the entrance-side core  44   a  and is propagated therethrough, is propagated through the branch core  44   b , and remaining light  102 A is propagated through the branch core  44   c.    
       FIG. 6B  is an enlarged view of a branch point part  44   d  of the core  44  shown in  FIG. 6A , which is the base part of the two branch cores  44   b  and  44   c . As shown in  FIG. 6B , the branch point part  44   d  has a shape where the branch cores  44   b  and  44   c  have respective inner edge parts  44   b   1  and  44   c   1  thereof connected by an arcuate part  44   e . Accordingly, the light  100  propagated through the entrance-side core  44   a  is less likely to leak than conventionally, so that radiation loss light  110 A leaking out from the branch point part  44   d  is less than the conventional radiation loss light  110  ( FIG. 3A ). Accordingly, the Y-branch optical waveguide device  41  has the characteristic of reduced radiation loss at the branch point part  44   d  compared with the conventional Y-branch optical waveguide device  1  ( FIG. 1 ), and propagates the lights  101 A and  102 A of higher intensity than conventionally through the branch cores  44   b  and  44   c , respectively.  
      Next, a description is given of a process for manufacturing the Y-branch optical waveguide device  41 . According to actual manufacturing, multiple branch optical waveguides are formed on a silicon wafer in a matrix manner using lamination and photolithography, and the silicon wafer is scribed into pieces at the end. Here, a description is given in such a way as to form a single branch optical waveguide.  
      First, as shown in  FIG. 7A , a fluorinated polyimide resin having a refractive index of n 1  is applied on the surface of the silicon substrate  43  so that the lower clad layer  45  is formed. Then, as shown in  FIG. 7B , a fluorinated polyimide resin having a refractive index of n 2  (&gt;n 1 ) is applied on the lower clad layer  45  so that the core layer  10  is formed. Then, as shown in  FIG. 7C , the resist layer  11  containing silicon is formed on the core layer  10 . A mask member  20 A includes the quartz plate  21  and a Y-shaped exposure mask pattern  22 A (an exposure mask) of a chromium film formed on the lower surface of the quartz plate  21 . The mask pattern  22 A is shown with solid lines for convenience of description. Next, as shown in  FIG. 7D , the mask member  20 A is adhered onto the resist layer  11 , and is exposed to the ultraviolet rays  25  of a wavelength of approximately 400 nm so as to develop the resist layer  11 . Then, cleaning is performed so that as shown in  FIG. 7E , a resist mask  12 A for RIE is formed. Next, RIE is performed to remove the core layer  10  so that the core  44  is formed as shown in  FIG. 7F . Next, as shown in  FIG. 7G , the resist mask  12 A is removed. Finally, a fluorinated polyimide resin having the refractive index of n 1  is applied so that the upper clad layer  46  is formed to cover the core  44 . As a result, the Y-branch optical waveguide device  41  shown in  FIG. 5  is manufactured.  
       FIG. 8A  shows the exposure mask pattern  22 A, and  FIG. 8B  is an enlarged view of a branch point part  22 Ad of the exposure mask pattern  22 A.  
      The exposure mask pattern  22 A includes a main body mask part  22 Aa and first and second branch mask parts  22 Ab and  22 Ac branching off from the main body mask part  22 Aa. The branch point part  22 Ad of the first and second branch mask parts  22 Ab and  22 Ac has a shape where linear edge parts  51 ,  52 , and  53  connect an edge part  22 Ab 1  of the first branch mask part  22 Ab and an edge part  22 Ac 1  of the second branch mask part  22 Ac in a trapezoidal manner, or in such a manner as to form a trapezoidal shape therebetween.  
      That is, in the branch point part  22 Ad, the edge connecting the edge parts  22 Ab 1  and  22 Ac 1  is defined by the edge parts  51 ,  52 , and  53 , which are connected so as to form a trapezoidal shape that is open in a direction away from the main body mask part  22 Aa. In other words, the closed end of the space between the edge parts  22 Ab 1  and  22 Ac 1  is defined by the edge parts  51 ,  52 , and  53 , which are connected so as to form a trapezoidal shape with a line connecting the connection of the edge parts  22 Ab 1  and  51  and the connection of the edge parts  22 Ac 1  and  52 , the trapezoidal shape being formed on the main body mask part  22 Aa side of the line.  
      The edge part  51  is inclined clockwise at an angle α to the edge part  22 Ab 1 . The edge part  52  is inclined counterclockwise at the angle α to the edge part  22 Ac 1 . The edge part  53  is an edge part along a line VL perpendicular to the center line CL of the exposure mask pattern  22 A, and corresponds to part of the edge part  22   e  shown in  FIG. 4B . In  FIG. 8B , the shape of the branch point part  22   d  shown in  FIG. 4B  is indicated by two-dot chain lines.  
      Compared with the branch point part  22   d  shown in  FIG. 4B , the branch point part  22 Ad has a shape where its part corresponding to the corner parts  22   f  and  22   g  of  FIG. 4B  and their vicinity in which no chromium film is formed is filled with a chromium film.  
      Using the mask member  20 A including the above-described exposure mask pattern  22 A, the resist mask  12 A shown in  FIG. 9A  is formed. The resist mask  12 A includes a main body mask part  12 Aa and first and second branch mask parts  12 Ab and  12 Ac branching off from the main body mask part  12 Aa. A branch point part  12 Ad of the first and second branch mask parts  12 Ab and  12 Ac has a shape where an edge part  12 Ab 1  of the first branch mask part  12 Ab and an edge part  12 Ac 1  of the second branch mask part  12 Ac are connected by an arcuate part  12   e  as shown in  FIG. 9B .  
      As a result of performing RIE on the structure of  FIG. 7E  where the resist mask  12 A is formed, the branch point part  44   d  of the core  44  has a shape where the inner edges  44   b   1  and  44   c   1  of the branch cores  44   b  and  44   c , respectively, are connected by the arcuate part  44   e  as shown in  FIG. 6B .  
       FIGS. 10A through 11B  show other exposure mask patterns  22 B and  22 C according to this embodiment.  
      The exposure mask pattern  22 B of  FIG. 10A  (a first variation) includes a main body mask part  22 Ba and first and second branch mask parts  22 Bb and  22 Bc branching off from the main body mask part  22 Ba. A branch point part  22 Bd of the first and second branch mask parts  22 Bb and  22 Bc has a shape where an arcuate edge part  61  connects an edge part  22 Bb 1  of the first branch mask part  22 Bb and an edge part  22 Bc 1  of the second branch mask part  22 Bc as shown enlarged in  FIG. 10B . In  FIG. 10B , the shape of the branch point part  22   d  of  FIG. 4B  is indicated by two-dot chain lines.  
      That is, the closed end of the space between the edge parts  22 Bb 1  and  22 Bc 1  is defined by the arcuate edge part  61 , which is an edge part curved like an arc protruding in a direction toward the main body mask part  22 Ba.  
      The exposure mask pattern  22 C of  FIG. 11A  (a second variation) includes a main body mask part  22 Ca and first and second branch mask parts  22 Cb and 22 Cc branching off from the main body mask part  22 Ca. A branch point part  22 Cd of the first and second branch mask parts  22 Cb and  22 Cc has a shape where linear edge parts  71  and  72  connect an edge part  22 Cb 1  of the first branch mask part  22 Cb and an edge part  22 Cc 1  of the second branch mask part  22 Cc in a triangular manner, or in such a manner as to form a triangular shape therebetween, as shown enlarged in  FIG. 11B .  
      That is, in the branch point part  22 Cd, the edge connecting the edge parts  22 Cb 1  and  22 Cc 1  is defined by the edge parts  71  and  72 , which are connected so as to form a triangular shape that is open in a direction away from the main body mask part  22 Ca. In other words, the closed end of the space between the edge parts  22 Cb 1  and  22 Cc 1  is defined by the edge parts  71  and  72 , which are connected so as to form a triangular shape with a line connecting the connection of the edge parts  22 Cb 1  and  71  and the connection of the edge parts  22 Cc 1  and  72 , the triangular shape being formed on the main body mask part  22 Ca side of the line.  
      The edge part  71  is inclined clockwise at an angle β to the edge part  22 Cb 1 . The edge part  72  is inclined counterclockwise at the angle β to the edge part  22 Cc 1 . A point  73  at which the edge parts  71  and  72  meet each other corresponds to a point on the edge part  22   e  of the branch point part  22   d  of  FIG. 4B . In  FIG. 11B , the shape of the branch point part  22   d  shown in  FIG. 4B  is indicated by two-dot chain lines.  
      In the case of employing a mask member including any of the above-described exposure mask patterns  22 B and  22 C, the resist mask  12 A of the shape shown in  FIGS. 9A and 9B  is also formed so that the core  44  of the shape shown in  FIGS. 6A and 6B  is also formed as in the case of employing the above-described mask member  20 A.  
      The present invention is also applicable to the manufacturing of a device with a branch optical waveguide having a shape other than a Y-letter shape.  
      Thus, according to the present invention, an exposure mask is employed that includes a main body mask part and first and second branch mask parts branching off therefrom at a branch point part having a shape where three linear edge parts connect the edge part of the first branch mask part and the edge part of the second branch mask part in a trapezoidal manner. The branch point part may alternatively have a shape where an edge part curved like an arc connects the edge part of the first branch mask part and the edge part of the second branch mask part. The branch point part may alternatively have a shape where two linear edge parts connect the edge part of the first branch mask part and the edge part of the second branch mask part in a triangular manner. As a result, it is possible to form a core whose branch point part does not include a substantially elliptic part that is open as if scooped out, and has a shape close to an ideal shape. Accordingly, it is possible to manufacture a branch optical waveguide having the characteristic of reduced radiation loss compared with a conventional one.  
      The present invention is not limited to the specifically disclosed embodiment, and variations and modifications may be made without departing from the scope of the present invention.  
      The present application is based on Japanese Priority Patent Application No. 2003-397472, filed on Nov. 27, 2003, the entire contents of which are hereby incorporated by reference.