Abstract:
A method for fabricating a distributed Bragg reflector waveguide is disclosed, which includes forming a first distributed Bragg reflector on a substrate; forming a sacrificial pattern on the first distributed Bragg reflector; forming a second distributed Bragg reflector on the sacrificial pattern and the first distributed Bragg reflector; and removing the sacrificial pattern. A distributed Bragg reflector waveguide is also disclosed.

Description:
RELATED APPLICATIONS 
     This application claims priority to Taiwan Application Serial Number 97141198, filed Oct. 27, 2008, which is herein incorporated by reference. 
     BACKGROUND 
     1. Field of Invention 
     The present invention relates to a waveguide. More particularly, the present invention relates to a distributed Bragg reflector waveguide and fabricating method thereof. 
     2. Description of Related Art 
     With continuous progress in network technology, the demand for communication bandwidth has increased continuously. Meanwhile, various transmission media are also developed subsequently, such as microwave communication, satellite communication, etc. Among those transmission media, fiber optic communication plays an increasingly important role. 
     The waveguide is an important structure for fiber optic communication. The electromagnetic wave can proceed in the waveguide rapidly by the total reflection within the waveguide. However, the electromagnetic wave could not be totally reflected at the corner of the conventional waveguide, especially at corners that are approximately at a right angle. A part of the electromagnetic wave may pass through the sidewall of the waveguide directly at the corner causing wastage of the electromagnetic wave at the corner. 
     Moreover, plenty of processes, such as a grinding process, a polishing process, or a wafer bonding process are required when the waveguide is utilized in a semiconductor component. The complex fabricating processes thereof would generate extraneous cost and time to use the waveguide to the semiconductor component. 
     SUMMARY 
     An embodiment of the invention provides a method for fabricating a distributed Bragg reflector waveguide, which includes forming a first distributed Bragg reflector on a substrate; forming a sacrificial pattern on the first distributed Bragg reflector; forming a second distributed Bragg reflector on the sacrificial pattern and the first distributed Bragg reflector; and removing the sacrificial pattern. 
     Another embodiment of the invention provides a distributed Bragg reflector waveguide, which includes a substrate having a surface, a distributed Bragg reflector film stack formed on the surface of the substrate, and a channel disposed in the distributed Bragg reflector film stack. The interface contact the channel is continuous. 
     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings, 
         FIG. 1  illustrates a schematic diagram of the fabricating method of an embodiment of the invention; 
         FIG. 2  illustrates a side view diagram of an embodiment of the distributed Bragg reflector waveguide of the invention; 
         FIG. 3  illustrates a schematic diagram of the fabricating method of another embodiment of the invention; and 
         FIG. 4  illustrates a side view diagram of another embodiment of the distributed Bragg reflector waveguide of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     Refer to  FIG. 1 .  FIG. 1  illustrates a schematic diagram of the fabricating method of the first embodiment of the invention. The method for fabricating a distributed Bragg reflector waveguide starts at step S 10 . In step S 10 , a substrate  110  is provided, and a first distributed Bragg reflector (DBR)  120  is formed on the substrate  110 . 
     In step S 12  a photoresist layer  130  is formed on the first distributed Bragg reflector  120 . In step S 14 , the photoresist layer  130  is exposed and developed to form a sacrificial pattern  132  on the first distributed Bragg reflector  120 . In step S 16  a second distributed Bragg reflector  140  is formed on the sacrificial pattern  132  and the first distributed Bragg reflector  120 , wherein the sacrificial pattern  132  is wrapped by the first distributed Bragg reflector  120  and the second distributed Bragg reflector  140 . 
     Finally, the sacrificial pattern  132  is removed in step S 18 , and a distributed Bragg reflector waveguide  100  having a channel  150  is formed. The channel  150  is wrapped by the first distributed Bragg reflector  120  and the second distributed Bragg reflector  140 . 
     The first distributed Bragg reflector  120  can be coated on the substrate  110  in step S 10 . The coating process to form the first distributed Bragg reflector  120  can be a low-pressure chemical vapor deposition (LPCVD), a plasma-enhanced chemical vapor deposition (PECVD), an atomic layer deposition (ALD), a spin on coating, a molecular beam epitaxy (MBE), a sputtering, a metal-organic chemical vapor deposition, a thermal coating, or a E-gun coating. 
     The material of the substrate  110  can be silicon, germanium, semiconductor III-V, semiconductor II-VI, silicon dioxide (SiO 2 ), alumina (Al 2 O 3 ), calcium carbonate (CaCO 3 ), or plastic. 
     Plural pairs of dielectric material layers  122  and  124  are coated and stacked on the substrate  110  to form the first distributed Bragg reflector  120 . The first distributed Bragg reflector  120  is a film stack of plural pairs of dielectric material layers  122  and  124 , and the first distributed Bragg reflector  120  has a high reflectivity. The refractive index of two dielectric material layers  122  and  124  in pair is different form each other. The higher difference between the refractive index of the dielectric material layers  122  and  124  is, the less pairs of the dielectric material layers  122  and  124  is required. 
     The material of the dielectric material layer  122  and  124  can be silicon, silicon dioxide (SiO 2 ), silicon nitride (Si 3 N 4 ), titanium dioxide (TiO 2 ), gallium arsenide (GaAs), AlGaAs, AlGaInP, or AlInP. 
     The photoresist layer  130  is exposed and developed in step S 14  to define the sacrificial pattern  132 . The shape of the sacrificial pattern  132  is defined according to the shape of the distributed Bragg reflector waveguide  100 . The shape of the sacrificial pattern  132  in this embodiment is a rectangle. 
     The second distributed Bragg reflector  140  can be coated on the sacrificial pattern  132  and the first distributed Bragg reflector  120 . The second distributed Bragg reflector  140  is a film stack of plural pairs of dielectric material layers  142  and  144 , and the second distributed Bragg reflector  140  has a high reflectivity. The second distributed Bragg reflector  140  includes plural pairs of dielectric material layers  142  and  144 . The refractive index of two dielectric material layers  142  and  144  in pair is different from each other. The sacrificial pattern  132  is wrapped by the first distributed Bragg reflector  120  and the second distributed Bragg reflector  140 . 
     The sacrificial pattern  132  (not shown) is removed in step S 18 . The substrate  110  and the structure thereon can be soaked in a photoresist stripper to remove the sacrificial pattern  132 , and the channel  150  is formed between the first distributed Bragg reflector  120  and the second distributed Bragg reflector  140 . 
     The photoresist stripper can be an organic solution or an inorganic solution. The structure of the sacrificial pattern  132  would be destroyed in the organic solution, and the sacrificial pattern  132  would be solved in the organic solution, such as acetone, dimethyl sulfuroxide (DMSO), methylethyl amide (MEA), phenol base solution, or other organiv solution. In step S 18  the sacrificial pattern  132  can also be soaked in the inorganic solution mixed by sulfuric acid and hydrogen peroxide to remove the sacrificial pattern  132 . 
     Refer to  FIG. 2 .  FIG. 2  illustrates a side view diagram of the first embodiment of the distributed Bragg reflector waveguide of the invention. The distributed Bragg reflector  200  includes a substrate  210 , a distributed Bragg reflector film stack  220 , and a channel  230 . The substrate  210  has a surface  212 . The surface  212  is a plane surface in this embodiment. The distributed Bragg reflector film stack  220  is formed on the surface  212  of the substrate  210 . The distributed Bragg reflector film stack  220  includes plural pairs of dielectric material layers  222  and  224 . The channel  230  is disposed in the distributed Bragg reflector film stack  210 . 
     The distributed Bragg reflector film stack  220  includes plural pairs of dielectric material layers  222  and  224 , and the refractive index of two dielectric material layers  222  and  224  in pair is different from each other. The material of the dielectric material layer  222  and  224  can be silicon, silicon dioxide (SiO 2 ), silicon nitride (Si 3 N 4 ), titanium dioxide (TiO 2 ), gallium arsenide (GaAs), AlGaAs, AlGaInP, or AlInP. 
     The higher difference between the refractive index of the dielectric material layers  222  and  224  is, the less pairs of the dielectric material layers  222  and  224  is required. The reflectivity surround the channel  230  can be highly improved by the pairs of dielectric material layers  222  and  224 , and the wastage of the electromagnetic wave at the corner of the distributed Bragg reflector waveguide  200  can be reduced. 
     The channel  230  is wrapped by two adjacent dielectric material layers  222   a  and  222   b , and an interface between the dielectric material layers  222   a,    222   b , which contact the channel  230  is continuous. Namely, the interface between the dielectric material layers  222   a  and  222   b  would not be cut when the channel  230  is formed. The adjacent dielectric material layers  222   a  and  222   b  have the same refractive index. The cross sectional shape of the channel  220  can be a rectangle. The distributed Bragg reflector waveguide  200  could further include a fluid filled in the channel  230 . 
     Refer to  FIG. 3 .  FIG. 3  illustrates a schematic diagram of another embodiment of the fabricating method of the invention. A groove  312  is formed on the substrate  310  in step S 30 . The first distributed Bragg reflector  320  is formed on the groove  312  and the substrate  310 . 
     Step S 34  forms the photoresist layer  330  on the first distributed Bragg reflector  320 . Then, step S 36  removes the unwanted part of the photoresist layer to define the sacrificial pattern  332  on the first distributed Bragg reflector  320 , wherein the sacrificial pattern  332  is formed in the groove  312 . 
     Step S 38  forms the second distributed Bragg reflector  340  on the sacrificial pattern  332  and the first distributed Bragg reflector  320 . The sacrificial pattern  332  is wrapped by the first distributed Bragg reflector  320  and the second distributed Bragg reflector  340 . 
     Finally, the sacrificial pattern  332  is removed in step S 40  to form the channel  350  in the distributed Bragg reflector waveguide  300 . The channel  350  is formed in the groove  312 , and the channel  350  is wrapped by the first distributed Bragg reflector  320  and the second distributed Bragg reflector  340 . 
     Refer to  FIG. 4 .  FIG. 4  illustrates a side view diagram of another embodiment of the distributed Bragg reflector waveguide of the invention. The distributed Bragg reflector waveguide  400  includes a substrate  410 , a distributed Bragg reflector film stack  420 , and a channel  430 . The distributed Bragg reflector waveguide  400  has the groove  414  formed on the surface  412  of the substrate  410 . The distributed Bragg reflector film stack  420  is formed on the groove  414  and the surface  412  of the substrate  410 . 
     The distributed Bragg reflector film stack  420  includes plural pairs of dielectric material layers  422 ,  424 , and the refractive index of two dielectric material layers  422 ,  424  in pair is different from each other. The higher difference between the refractive index of the dielectric material layers  422 ,  424  is, the less pairs of the dielectric material layers  422 ,  424  is required. 
     The channel  430  is disposed in the distributed Bragg reflector film stack  420 , and is disposed in the groove  414 . The channel  430  is wrapped by two adjacent dielectric material layers  422   a ,  422   b , and the interface between the dielectric material layers  422   a ,  424   b , which contact the channel  430  is continuous. Namely, the interface between the dielectric material layers  422   a,    422   b  would not be cut when the channel  430  is formed. The adjacent dielectric material layers  422   a ,  422   b  have the same refractive index. The cross sectional shape of the channel  420  can be a rectangle. The distributed Bragg reflector waveguide  400  could further include a fluid filled in the channel  430 . 
     The distributed Bragg reflector waveguide in the invention can be fabricated by the coating the distributed Bragg reflector film stack on the substrate. The fabrication of the distributed Bragg reflector waveguide can be integrated with other semiconductor components on the substrate. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.