Abstract:
An optical module, in which one or more grooves on which a plurality of optical fibers or optical parts are mounted, are formed to different depths and a stopper hole is manufactured so as to prevent a convex corner phenomenon so that an optical axis is precisely aligned, and a method of manufacturing the same are provided. The method of manufacturing an optical module includes the steps of first etching to form one or more grooves on a first surface of a wafer, and second etching to form one or more stopper holes so that a second surface of the wafer is etched to penetrate the wafer. The optical module having one or more grooves for mounting one or more optical parts on a substrate, includes stopper holes which are formed by penetrating the bottom surface of the substrate to center a region which corresponds to a predetermined region among the grooves.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical module and a method for manufacturing the same, and more particularly, to an optical module, in which one or more grooves, in which are mounted a plurality of optical fibers or optical parts are formed to different depths and a stopper hole is manufactured so as to prevent a convex corner phenomenon so that an optical axis is precisely aligned, and a method for manufacturing the same. 
     2. Description of the Related Art 
     Recently, transmission methods in an optical communication system have been replaced by wavelength division multiplexing (WDM) transmission methods, with increase in transmission data in an optical communication network. As connection between networks is required in the WDM system, an optical crossing connector (OXC), that is, an optical module, is an essential element. 
     Referring to  FIG. 1A , the optical module includes a micro-mirror  10 , an actuator  15  for driving the micro-mirror  10 , an input optical fiber  20  for transmitting an optical signal to the micro-mirror  10  around the actuator  15 , an output optical fiber  22  for receiving an optical signal reflected from the micro-mirror  10  and transmitting the optical signal, and an optical module  30  in which ball lenses  25  and  27 , aligned for focusing light, are arranged between the input and output optical fibers  20  and  22  and the micro-mirror  10 . The input and output optical fibers  20  and  22  are arranged in the V-grooves  35 , and the ball lenses  25  and  27  are arranged in micro-pits  40  which communicate with the V-groove  35 . The optical fibers  20  and  22 , the ball lens  25 , and the micro-mirror  10  are all aligned with an optical axis. 
     In the optical module having the above structure, an optical signal transmitted from the input optical fiber  20  passes through the ball lens  25 , is reflected by the micro-mirror  10 , passes through the ball lens  27 , and is output through the output optical fiber  22  and transmitted to a predetermined place. The ball lenses  25  and  27  focus the optical signal to reduce optical loss and to minimize the optical path. 
     As shown in  FIG. 1B , a convex corner  45  is formed in a portion where a hole  17  for installing the actuator  15  is connected to the micro-pit  40  and the micro-pit  40  is connected to the V-grooves  35 . Since the sizes of the actuator  15 , the ball lenses  25  and  27 , and the optical fibers  20  and  22  are different, the depths of the hole  17 , the V-groove  35 , and the micro-pit  40  for receiving these elements must be different in order to align their centers on the optical axis. 
     However, when manufacturing the optical module having the above structure by etching, the optimum conditions for etching such as time or temperature, are different according to the width or depth of the groove to be etched. In other words, since the hole  17 , the V-groove  35 , and the micro-pit  40  have different widths and depths, etching must be performed under different conditions for the hole  17 , the V-groove  35 , and the micro-pit  40 . However, in the prior art, etching is performed by patterning once, under the ideal conditions for only one of the hole  17 , the V-groove  35 , and the micro-pit  40 , or under conditions which are the average of the ideal conditions for the hole  17 , the V-groove  35 , and the micro-pit  40 . Thus, in this case, the conditions for etching are not appropriate for the other regions except for the groove when the groove is a standard, and etching cannot be performed as patterned; defects in etching occur even under the average conditions. 
     In particular, a convex corner phenomenon in which the shapes of the micro-pit  40  or the hole  17  are not precisely etched and their pattern shapes are damaged, occurs in the convex corner  45  of the micro-pit  40  or the hole  17 .  FIG. 1B  illustrates that the patterns of the convex corners  45  before etching are greatly damaged after etching. Due to damage of the convex corner  45 , the standard of correct dimensions as designed cannot be obtained, and thus, the arrangement of optical elements such as the optical fibers  20  and  22 , or the ball lenses  25  and  27 , varies. As a result, the optical axes of the elements are not aligned, and thus, the optical signal cannot be precisely transmitted, thereby causing optical loss. 
     Thus, in order to prevent damage to patterns caused by the convex corner effect, specific corner compensation patterns  50  and  52  as shown in  FIG. 2  are required. That is, in consideration of the convex corner effect, compensation patterns for supplementing are formed on an etching mask  65  so that the phenomenon during etching is suppressed, allowing the optical module to be manufactured with the desired shape. Here, reference numerals  17 ′ and  40 ′ denote a hole area and a micro-pit area, which are formed in the etching mask  65 , respectively. 
     A method for manufacturing an optical module using the corner compensation patterns  50  and  52  will be described as follows. 
     As shown in  FIGS. 3A and 3B , silicon dioxide (SiO 2 )  63  is coated on a upper silicon wafer  60  of (100) in which both surfaces of the upper silicon wafer  60  are polished, and silicon nitride (Si 3 N 4 )  65  is deposited on both surfaces of the upper silicon wafer  60  using a low pressure chemical vapor deposition (LPCVD) method so that silicon dioxide  63  can be used as a silicon etching mask on the upper silicon wafer  60 . Next, as shown in  FIG. 3C , silicon nitride (Si 3 N 4 ) layers  65  on both surfaces of the upper silicon wafer  60  are patterned by a reactive ion etching (RIE) process. The corner compensation patterns  50  and  52  are added to the silicon nitride (Si 3 N 4 ) layers  65  so that the pattern shapes are not damaged by the convex corner effect during etching. 
     Also, as shown in  FIGS. 4A and 4B , silicon oxide (SiO)  72  and silicon nitride (Si 3 N 4 )  75  are sequentially deposited on a lower silicon wafer  70  and are patterned by the RIE process, as shown in  FIG. 4C . 
     Next, anisotropic wet etching of the upper and lower silicon wafers  60  and  70  is performed using a KOH aqueous solution, thereby forming a V-groove area  67 , a micro-pit area  68 , and hole areas  69  and  69 ′, as shown in  FIGS. 3D and 4D . The upper and lower silicon wafers  60  and  70  are bonded together, as shown in  FIGS. 5A and 5B . 
     The actuator  15  for a micro-mirror is installed in the hole  17  of the optical module, and the optical fibers  20  and  22 , and the ball lenses  25  and  27  are installed respectively in the V-groove  35  and the micro-pit  40 , to be aligned with the optical axis. 
     At present, the optical module is manufactured by the above-mentioned manufacturing process, using the corner compensation patterns  50  and  52 . However, the corner compensation patterns  50  and  52  are appropriate only when there is a minor difference in depth between the V-groove  35  and the micro-pit  40 , and their length should be three times the etching depth. The corner compensation patterns  50  and  52  complicate and enlarge the entire patterns for manufacturing the optical module. 
     Also, if the location of the optical axis is changed, the depth of etching must also be changed, requiring new compensation patterns. In other words, the compensation patterns  50  and  52  must be designed according to the width or depth of the micro-pit  40  or the hole  17 . Thus, whenever the optical axis varies, new compensation patterns must be prepared. 
     In particular, since the compensation patterns  50  and  52  become complicated where input/output terminals of the optical fibers are adjacent, or where the convex corner effect occurs greatly, the optical path cannot be minimized, causing optical loss due to differences in the optical path. Furthermore, as the number of channels of the optical module increases, it is difficult to form the compensation patterns, and part of the convex corner  45 ′ can be damaged, even though the compensation patterns are used, as shown in the photo of  FIG. 6 , and thus the requirements for miniature optical elements cannot be satisfied. 
     SUMMARY OF THE INVENTION 
     To solve the above problem, it is an object of the present invention to provide an optical module, in which one or more grooves of different depths are included so as to prevent a convex corner phenomenon without compensation patterns, and a substrate is passed through the grooves or etched to a predetermined depth to form a stopper hole, and a method for manufacturing the same. 
     Accordingly, to achieve the above object, according to one aspect of the present invention, there is provided a method for manufacturing an optical module. The method includes the steps of first etching to form one or more grooves on a first surface of a wafer, and second etching to form one or more stopper holes so that a second surface of the wafer is etched to penetrate the wafer. 
     The method further includes the steps of depositing first etching mask layers on the first and second surfaces of the wafer, patterning one or more groove areas on the first etching mask layer on the first surface of the wafer, to form a first pattern, first etching the first pattern from the first surface of the wafer according to the first pattern, depositing a second etching mask layer on the second surface of the wafer and patterning at least one stopper hole area to form a second pattern, and second etching the second pattern so that the second surface of the wafer is etched to penetrate the wafer according to the second pattern. 
     A V-groove area for mounting an optical fiber, a micro-pit area for mounting optical parts, and a hole area for assembling an actuator are exposed by patterning, in the step of patterning to form a first pattern. 
     The V-groove area, the micro-pit area, and the hole area are etched to different depths, in the step of first etching. 
     The first etching mask layers are formed of silicon dioxide (SiO 2 ) or silicon nitride (Si 3 N 4 ). 
     The second etching mask layer is formed of silicon dioxide (SiO 2 ), aluminum (Al), or a photoresist. 
     The first etching is wet etching selectively using KOH, NH 4 OH, or (CH 3 ) 4 NOH. 
     The second etching is performed by one or more selected from dry etching, sand blasting, and laser drilling. 
     A wet etching mask layer is further deposited on the second etching mask layer. 
     The method further includes, before second etching, the step of depositing Al or oxide or a photoresist on the first surface of the wafer. 
     To achieve the above object, according to another aspect of the present invention, there is provided a method for manufacturing an optical module. The method includes the steps of first etching to form one or more grooves on a first surface of a wafer, and second etching to form one or more stopper holes so that the first surface of the wafer is etched to penetrate the wafer or is etched to a predetermined depth. 
     To achieve the above object, according to another aspect of the present invention, there is provided an optical module having a substrate, a V-groove for mounting an optical fiber on the substrate, a micro-pit for mounting optical parts, and a hole for assembling an actuator. The optical module includes a first stopper hole formed to communicate with the V-groove and the micro-pit, in which the substrate is penetrated in a vertical direction, and a second stopper hole formed to communicate with the micro-pit and the hole, in which the substrate is penetrated in a vertical direction. 
     To achieve the above object, according to another aspect of the present invention, there is provided an optical module having one or more grooves for mounting one or more optical parts on a substrate. The optical module includes stopper holes which are formed by penetrating the bottom surface of the substrate which corresponds to a predetermined region among the grooves. 
     To achieve the above object, according to another aspect of the present invention, there is provided a method of manufacturing an optical module. The method includes the steps of first etching to form one or more stopper holes so that the bottom surface of a wafer is etched to penetrate the wafer, and second etching to form one or more grooves for mounting optical elements on the top surface of the wafer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above objects and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings, in which: 
         FIG. 1A  is a schematic diagram of a conventional optical module; 
         FIG. 1B  compares the state of the conventional optical module before and after etching; 
         FIG. 2  illustrates a case where a convex corner compensation pattern is formed during the manufacture of the conventional optical module; 
         FIGS. 3A through 3D  illustrate the process of manufacturing the conventional optical module; 
         FIGS. 4A through 4D  illustrate the process of manufacturing the conventional optical module; 
       FIGS  5 A and  5 B illustrate the process of manufacturing the conventional optical module; 
         FIG. 6  is a scanning electronic microscope (SEM) photo illustrating a damaged convex corner of the conventional optical module; 
         FIG. 7  is partial cutaway perspective view of an optical module according to the present invention; 
         FIGS. 8A ,  8 B, and  8 D illustrate the process of manufacturing an optical module according to a first embodiment of the present invention with reference to views taken along lines I—I, III—III, and V—V of  FIG. 7 ; 
         FIGS. 8C and 8E  illustrate the process of manufacturing an optical module according to the first embodiment of the present invention with reference to views taken along lines II—II, IV—IV, and V—V of  FIG. 7 ; 
         FIGS. 9A ,  9 B, and  9 D illustrate the process of manufacturing an optical module according to a second embodiment of the present invention with reference to views taken along lines I—I, III—III, and V—V of  FIG. 7 ; 
         FIGS. 9C and 9E  illustrate the process of manufacturing an optical module according to the second embodiment of the present invention with reference to views taken along lines II—II, IV—IV, and V—V of  FIG. 7 ; 
         FIGS. 10A and 10B  illustrate the process of manufacturing an optical module according to a third embodiment of the present invention with reference to views taken along lines II—II, IV—IV, and V—V of  FIG. 7 ; and 
         FIG. 11  is a SEM photo of an optical bench of the optical module according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 7  is a partial cutaway perspective view of an optical module according to the present invention. Referring to  FIG. 7 , the optical module includes one or more grooves of different depths in a substrate  101 . The grooves include, for example, a V-groove  105  for mounting an optical fiber  100  on the substrate  101 , a micro-pit  115  for mounting optical parts  110  such as a green lens or ball lens, on the substrate  101 , and a hole  125  in which an actuator (not shown) is installed. 
     A first stopper hole  107  having a width smaller than that of the V-groove  105  is formed between the V-groove  105  and the micro-pit  115 . A second stopper hole  117  having a width smaller than that of the micro-pit  115  is formed between the micro-pit  115  and the hole  125 . The first and second stopper holes  107  and  117  should be stably mounted without the optical fiber  105  and the optical parts such as a green lens or a ball lens, being moved. Also, the V-groove  105 , the micro-pit  115 , and the hole  125  communicate with one another through the first and second stopper holes  107  and  117 . Thus, an optical signal transmitted through the optical fiber  100  received in the V-groove  105  passes through an upper portion of the first stopper hole  107 , through the optical parts  110  in the micro-pit  115  and is transmitted into an actuator (not shown) without any obstacle through an upper portion of the second stopper hole  117 . 
     Hereinafter, a method of manufacturing the optical module according to a preferred embodiment of the present invention will be described. 
       FIGS. 8A ,  8 B, and  8 D illustrate the process of manufacturing an optical module according to a first embodiment of the present invention with reference to views taken along lines I—I, III—III, and V—V of  FIG. 7 .  FIGS. 8C and 8E  illustrate the process of manufacturing an optical module according to the first embodiment of the present invention with reference to views taken along lines II—II, IV—IV, and V—V of  FIG. 7 . 
     The method of manufacturing the optical module according to a first embodiment of the present invention includes the step of coating first etching mask layers  130  and  140  on first and second surfaces of a wafer  128 , as shown in  FIG. 8A . The first and second surfaces of the wafer  128  denote the top surface of the wafer  128  and the bottom surface of the wafer  128 , respectively. A silicon wet etching mask layer  130  using silicon nitride (Si 3 N 4 ) or silicon dioxide (SiO 2 ) can be deposited on the top surface of the wafer  128 , and a dry etching mask layer  140  using SiO 2  aluminum (Al), or a photoresist layer can be deposited on the bottom surface of the wafer  128 . Otherwise, a wet etching mask layer can be deposited on both the top and bottom surfaces of the wafer  128 . 
     Next, the first etching mask layer  130  on the top surface of the wafer  128  is first patterned by an exposure process and a reactive ion etching (RIE) process, as shown in  FIG. 8B . A V-groove area  132  for mounting an optical fiber, a micro-pit area  134  for mounting optical parts such as a green lens or ball lens, and a hole area  136  for assembling an actuator are formed as a first pattern. As shown in FIG.  8 C, the first etching mask layer  140  on the bottom surface of the wafer  128  is second patterned, thereby forming a first stopper hole area  152 , a second stopper hole area  154 , and a hole area  156  and depositing a wet etching mask layer  150  as a second etching mask layer, on the first stopper hole area  152 , the second stopper hole area  154 , and the hole area  156 . 
     Surfaces  132 ,  134 , and  136  which are exposed by the first pattern as shown in  FIG. 8B , are first etched. For example, wet etching is performed by a KOH, NH 4 OH or (CH 3 ) 4 NOH aqueous solution, thereby forming the V-groove  105 , the micro-pit  115 , and a hole  125   a  (see  FIG. 8D ). The etching depth is determined in consideration of the diameter of the optical parts  110  such as a green lens or a ball lens, and the location of an optical axis C. Then, the etching depth of the V-groove  105  is determined by its width, and thus, the V-groove  105  is etched to a predetermined depth, and the micro-pit  115  for mounting the optical parts wider than the V-groove  105  is continuously etched deeper than the V-groove  105 . 
     Next, second etching is performed by one or more selected from dry etching, sand blasting, and laser drilling, using second patterns  152 ,  154 , and  156  as shown in  FIG. 8C . The dry etching may be for example, the RIE process. As shown in  FIG. 8E , the bottom surface of the wafer  128  is first etched to penetrate the top surface of the wafer  128 , thereby forming a first stopper hole  107 , a second stopper hole  117 , and a hole  125  for assembling an actuator. 
     Here, the order of the step of first etching and second etching may be changed. That is, after the bottom surface of the wafer  128  is first etched to penetrate the top surface of the wafer  128  and the first stopper hole  107  and the second stopper hole  117  are formed, one or more grooves for mounting optical parts on the top surface of the wafer  128  can be formed. 
     Hereinafter, a method of manufacturing the optical module according to a second embodiment of the present invention will be described. 
       FIGS. 9A ,  9 B, and  9 D illustrate the process of manufacturing an optical module according to a second embodiment of the present invention with reference to views taken along lines I—I, III—III, and V—V of  FIG. 7 .  FIGS. 9C and 9E  illustrate the process of manufacturing an optical module according to the second embodiment of the present invention with reference to views taken along lines II—II, IV—IV, and V—V of  FIG. 7 . 
     As shown in  FIGS. 9A and 9B , first etching mask layers  160  and  170  are deposited respectively on the top and bottom surfaces of a wafer  155 , and a second etching mask layer  180  is coated on the first etching mask layer  170  on the bottom surface of the wafer  155 . The first etching mask layers  160  and  170  are wet etching mask layers, and the second etching mask layer  180  may be a mask layer for deep-reactive ion etching (DRIE). 
     Next, the first etching mask layer  160  on the top surface of the wafer  155  is patterned to form a first pattern by an exposure process and a RIE process, thereby forming a V-groove area  162 , a micro-pit area  164 , and a hole area  166 . Next, the second etching mask layer  180  on the bottom surface of the wafer  155  is patterned to form a second pattern, thereby forming first and second stopper hole areas  182  and  184 , and a hole area  186 . 
     As shown in  FIG. 9C , a third etching mask layer  185  is deposited on a second pattern on the bottom surface of the wafer  155 . The third etching mask layer  185  is a wet etching mask layer. As shown in  FIG. 9D , wet etching is performed on the top surface of the wafer  155  according to the first pattern, thereby forming a V-groove  105  and a micro-pit  115 . Next, as shown in  FIG. 9C , the third etching mask layer  185  is removed, and the second pattern is etched by deep reactive ion etching (DRIE) process, penetrating from the bottom surface to the top surface of the wafer  128 . As a result, a first stopper hole  107 , a second stopper hole  117 , and a hole  125  for assembling an actuator are formed (see  FIG. 9E ). 
     Here, the first etching mask layer  160  on the top surface of the wafer  155  may be formed of SiO 2  or Si x N y , for example, Si 3 N 4 , and the second etching mask layer  180  as an etching mask for a silicon dry etching process, may be formed of SiO 2 , Al, or a photoresist. 
     Meanwhile, in the first and second embodiments, when first etching, that is, when silicon wet etching, a protective jig or passivation can be coated on the bottom surface of the wafers  128  and  155  instead of the wet etching mask layers  150  and  185 . 
     A method of manufacturing an optical module according to a third embodiment of the present invention includes the steps of patterning a V-groove area for mounting optical fiber on a top surface of a wafer and a micro-pit area for mounting optical parts to form a first pattern and perform first etching, and patterning first and second stopper hole areas and a hole are for assembling an actuator on the top surface of the wafer to form a second pattern and perform second etching. The step of first patterning and first etching is performed like in the first and second embodiments, and thus, a detailed description of first patterning and first etching will be omitted. 
       FIGS. 10A and 10B  illustrate the process of manufacturing an optical module according to a third embodiment of the present invention with reference to views taken along lines II—II, IV—IV, and V—V of  FIG. 7 . First etching mask layers  130 ′ and  140 ′ are deposited respectively on the top and bottom surfaces of a wafer  128 ′. After the first etching mask layers  130 ′ and  140 ′ are first etched, a second etching mask layer  150 ′ is deposited on the first etching mask layer  130 ′ on the top surface of the wafer  128 ′. Next, as shown in  FIG. 10A , the second etching mask layer  150 ′ is second etched, thereby forming first and second stopper hole areas  152 ′ and  154 ′, and a hole area  156 ′. The second etching mask layer  150 ′ is etched according to the second pattern by a dry etching process from the top surface of the wafer  128 ′, thereby forming first and second stopper holes  107  and  117 . 
     The first and second stopper holes  107  and  117  penetrate the wafer  128 ′ (see  FIG. 10B ). Also, in case of second etching from the top surface of the wafer  128 ′, the wafer  128 ′ may be etched only to a predetermined depth instead of penetrated. Thus, as shown in  FIG. 7 , when an optical signal is transmitted into the optical parts  110  such as a green lens or a ball lens, through the optical fiber  100 , or is transmitted from the optical parts  110  into an actuator (not shown), the optical signal can be transmitted without being stopped or disturbed by the first and second stopper holes  107  and  117 . 
     Also, in the first, second, and third embodiments, before second etching, the method of manufacturing the optical module further includes the step of depositing aluminum (Al), oxide, or a photoresist on the top surface of the wafers  128  and  155 , thereby preventing damage to a groove  105  or a micro-pit  115  on the top surface of the wafer which can be etched by a deep-reactive ion gas, in which part of the top surface of the wafer is penetrated when second etching from the bottom surface of the wafer, that is, when performing a deep-reactive ion etching (DRIE) process. 
     Also, in the first, second, and third embodiments, the order of the step of first etching as wet etching and the step of second etching as dry etching may be changed. That is, in order to achieve optical transmission in the present invention, after stopper holes are preformed by dry etching from the top surface or the bottom surface of the wafer, a V-groove area, a micro-pit area, and a hole area can be formed by wet etching. 
     Also, the stopper holes include at least a first stopper hole formed between the V-groove and the micro-pit, and a second stopper hole formed between the micro-pit and the hole. Each stopper hole is used to fix optical parts and allows smooth optical transmission. 
     As described above, in the optical module and manufacturing method thereof according to the present invention, first patterning, second patterning, and first and second etching are performed independently, and thus, a convex corner phenomenon does not occur. Likewise, no mask compensation pattern is needed to compensate for the convex corner effect, thereby minimizing the optical path of optical input/output terminals. As a result, optical loss can be minimized, a plurality of input/output channels can be formed, and the input/output channels can be integrated. Also, the V-groove and the micro-pit for mounting optical parts can be formed so that the convex corner phenomenon does not occur even in complex convex corners where a compensation pattern cannot be applied, and thus, there is no limitation to the scope of application. 
     Further, the number of wet etching processes is reduced to one, removing optical property errors caused by mask layer registration, and improving the reliability of transmission of the optical signal. 
       FIG. 11  is an SEM photo of an optical bench of the optical module according to the present invention. The patterns of the convex corner centering the stopper hole are precisely formed as designed. Reference numerals  105 ,  107 , and  115  denote a V-groove, a first stopper, and a micro-pit, respectively. 
     While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope thereof as defined by the appended claims.