Abstract:
Provided is a wafer lens aligning method including the steps of: preparing a lens mold that has a lens forming portion formed in the central portion thereof and a groove formed around the lens forming portion; preparing a wafer that has two or more position recognition patterns formed at arbitrary positions thereof and a plurality of minute patterns formed in array at lens formation positions; loading the wafer, searching the position recognition patterns, and setting a coordinate system; causing the coordinate system of the wafer to coincide with the coordinate system of the lens mold; causing the center among the minute patterns formed on the wafer to coincide with the center of the lens mold so as to align the wafer with the lens mold; and forming a master lens in the lens formation positions arranged on the wafer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2007-0134231 filed with the Korea Intellectual Property Office on Dec. 20, 2007, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a wafer lens aligning method and a wafer lens manufactured by the same. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, a mastering process, a stamping process, an embossing process, and a dicing process are sequentially performed to manufacture a plurality of wafer lenses in the form of single lens. 
         [0006]    In this case, polymer which is to be cured by ultraviolet (UV) light is injected into a mold for molding a lens in the mastering process. Further, the polymer is attached on one surface of a substrate-type wafer and is cured by UV irradiation such that a lens is attached to the surface of the wafer. Then, the lens is transferred to the next process. 
         [0007]    The wafer lens manufactured through the above-described manufacturing process is managed in accordance with a strict standard tolerance of less than several μm in the respective processes, in order to maintain resolution determined at a design step. Further, the respective lenses are manufactured in an array type in the mastering process. Accordingly, when an error occurs, the error is handed down until a product is finalized through the following process. Therefore, the standard tolerance should be strictly managed. 
         [0008]    In such a mastering process, various methods for aligning a wafer with a mold are used to reduce an error occurring between the wafer and the mold. Now, a conventional wafer aligning method will be described as follows. 
         [0009]    First, patterns are formed on a wafer at a distance corresponding to the diameter of a mold such that the periphery of the mold is positioned inside the patterns. Then, the alignment between the wafer and the mold is achieved. 
         [0010]    In such an aligning method, however, the outer circumferential surface of the mold is not relatively precisely processed, compared with a lens forming portion which is precisely processed. Therefore, alignment accuracy between the wafer and the mold decreases. Then, the wafer lens may be formed in an elliptical shape, or eccentricity may occur. 
         [0011]    Further, the alignment between the wafer and the mold may be achieved by driving a motor coupled to the mold, without a pattern formed on the wafer. However, when the mold is attached to and detached from a jig connected to the motor, an assembling error may occur. Further, the mold is inevitably moved by a release impact of the motor which is generated when the lens is molded. Therefore, there are difficulties in aligning the wafer with precision. 
         [0012]    To solve such a problem, a method has been disclosed, in which alignment between a wafer and a mold is achieved through Moire fringes formed by overlapping patterns formed in the wafer and the mold. 
         [0013]      FIG. 1  is a cross-sectional view of a mold and a wafer when the wafer is aligned by the conventional wafer aligning method.  FIGS. 2A and 2B  are plan views of Moire fringes emerging when the wafer is aligned by the conventional wafer aligning method. 
         [0014]    In the conventional wafer aligning method, a first alignment mark  120  composed of a plurality of grooves is formed around a lens forming portion  110  of a mold  100 , and a second alignment mark  130  having shading patterns  241  and  251  corresponding to the first alignment mark  120  is formed on a substrate  200 . 
         [0015]    At this time, shading patterns are formed on the surface of the substrate  200  through the grooves of the first alignment mark  120  by the light irradiated from above the substrate  200 . 
         [0016]      FIGS. 2A and 2B  are diagrams showing Moire fringes which emerge after the mold  100  and the substrate  200  are aligned by the conventional wafer aligning method. When the mold  100  and the substrate  200  are accurately aligned with each other, concentric Moire fringes emerge as shown in  FIG. 2A . Otherwise, when the mold  100  and the substrate  200  are not aligned with each other, Moire fringes are formed as shown in  FIG. 2B . Then, an operator checks the Moire fringes with naked eyes so as to judge whether the mold  100  and the substrate  200  are aligned with each other or not. 
         [0017]    In such a conventional wafer aligning method, the first alignment mark  120  formed in the mold  100  is accurately processed. However, the operator should judge whether the substrate  200  and the mold  100  are aligned with each other or not. Therefore, there are difficulties in automating the aligning process. 
         [0018]    Further, the Moire fringes should be checked through a microscope. In this case, the Moire fringes may differ depending on the magnification and resolution of the microscope. Therefore, there are difficulties in setting operation standards during the wafer aligning. 
         [0019]    [Patent Document] Korean Patent No. 10-631989 
       SUMMARY OF THE INVENTION 
       [0020]    An advantage of the present invention is that it provides a wafer lens aligning method, in which the coordinate system of a wafer is set by position recognition patterns formed at arbitrary positions, a mold is moved in accordance with the set coordinate system, and minute patterns formed in each lens formation position of the wafer are aligned with a groove formed on the mold such that the mold can be accurately aligned with the lens formation position. 
         [0021]    Another advantage of the invention is that it provides a wafer lens manufactured by the wafer lens aligning method. 
         [0022]    Additional aspects and advantages of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept. 
         [0023]    According to an aspect of the invention, a wafer lens aligning method comprises the steps of: preparing a lens mold that has a lens forming portion formed in the central portion thereof and a groove formed around the lens forming portion; preparing a wafer that has two or more position recognition patterns formed at arbitrary positions thereof and a plurality of minute patterns formed in array at lens formation positions; loading the wafer, searching the position recognition patterns, and setting a coordinate system; causing the coordinate system of the wafer to coincide with the coordinate system of the lens mold; causing the center among the minute patterns formed on the wafer to coincide with the center of the lens mold so as to align the wafer with the lens mold; and forming a master lens in the lens formation positions arranged on the wafer. 
         [0024]    Preferably, polymer-based resin for molding a lens is injected into the lens forming portion formed in the central portion of the lens mold, and the mold is closely contacted with the lens formation position of the wafer. 
         [0025]    Preferably, the position recognition patterns are formed in a dot shape, a cross shape, or a circular shape. 
         [0026]    Preferably, the minute patterns are formed of metal. 
         [0027]    Preferably, the minute patterns are formed in a linear shape so as to be spaced at a predetermined distance from the groove, the minute patterns being symmetrical with each other. 
         [0028]    Preferably, the minute patterns are formed in a circular arc having an approximate curvature to the circumference of the groove. 
         [0029]    According to another aspect of the invention, there is provided a wafer lens manufactured by the wafer lens aligning method according to the above-described aspect. 
         [0030]    Preferably, the wafer lens has a projection formed on the surface thereof corresponding to the top surface of the lens mold, the projection being formed by transferring resin into the groove. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
           [0032]      FIG. 1  is a cross-sectional view of a mold and a wafer when the wafer is aligned by the conventional wafer aligning method; 
           [0033]      FIGS. 2A and 2B  are plan views of Moire fringes emerging when the wafer is aligned by the conventional wafer aligning method; 
           [0034]      FIG. 3  is a cross-sectional view of a mold which is adopted in a wafer lens aligning method according to the invention; 
           [0035]      FIG. 4  is a plan view of the mold of  FIG. 3 ; 
           [0036]      FIG. 5  is a plan view of a wafer adopted in the wafer lens aligning method according to the invention; 
           [0037]      FIGS. 6A and 6B  are schematic views showing a state where minute patterns formed on a wafer and a groove of the lens mold are aligned with each other; 
           [0038]      FIG. 7  is a flow chart showing a wafer lens aligning method according to the invention; and 
           [0039]      FIG. 8  is a cross-sectional view of a lens manufactured by the wafer lens aligning method according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0040]    Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures. 
         [0041]    Hereinafter, a wafer lens aligning method and a wafer lens manufactured by the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
         [0042]      FIG. 3  is a cross-sectional view of a mold which is adopted in a wafer lens aligning method according to the invention.  FIG. 4  is a plan view of the mold of  FIG. 3 . 
         [0043]    As shown in the drawings, the lens mold  100  adopted in the wafer lens aligning method according to the invention has a lens forming portion  11 , into which polymer-based resin is injected to mold a lens and which is formed in the central portion thereof, and a circular groove  12  formed around the lens forming portion  11 . 
         [0044]    The depth of the lens forming portion  11  is determined depending on the height of a designed lens which is to be formed on one surface of a wafer. Since the resin is transformed from the lens forming portion  11  to form the lens, micro-processing should be achieved. 
         [0045]    The groove  12  formed around the lens forming portion  11  is formed in a concentric shape with the lens forming portion  11  such that the center of the groove  12  coincides with that of the lens forming portion  11 . 
         [0046]    Typically, the groove  12  is formed by a method of processing a rotating body using a diamond turning machine (DTM). Therefore, the groove  12  can be formed in a circle having the same center as that of the lens forming portion  11 . 
         [0047]    Although it will be described below, the center of the lens forming portion  11  and the center of a lens formation position can be caused to coincide with each other by adjusting a distance between a minute pattern of a wafer and the groove  12 . 
         [0048]      FIG. 5  is a plan view of a wafer adopted in the wafer lens aligning method according to the invention.  FIGS. 6A and 6B  are schematic views showing a state where minute patterns formed on a wafer and the groove of the lens mold are aligned with each other. 
         [0049]    As shown in  FIG. 5 , a wafer  20  adopted in the wafer aligning method according to the invention has two types of patterns  21  ( 21   a  and  21   b ) and  22  formed on one surface thereof. 
         [0050]    One type includes position recognition patterns  21   a  and  21   b  for setting an initial position after the wafer  20  is loaded by an automated equipment, and the other type includes a plurality of minute patterns  22  for alignment between a lens formation position of the wafer and the lens mold  10  after the initial position of the wafer  20  is set. 
         [0051]    The position recognition patterns  21   a  and  21   b  can be formed at two or more arbitrary positions including the center of the wafer  20 . The automated equipment first scans one position recognition pattern  21   a  between the two position recognition patterns  21   a  and  21   b  and stores the position thereof. Then, the automated equipment scans the other position recognition pattern  21   b  and stores the position thereof. 
         [0052]    After the wafer  20  is loaded, a semiconductor equipment having the wafer  20  mounted thereon calculates the rotation angles of the searched position recognition patterns  21   a  and  21   b  and then sets a coordinate system in accordance with the loaded position of the wafer  20 . 
         [0053]    The position recognition patterns  21   a  and  21   b  formed on the wafer  20  may be constructed in a dot shape, a cross shape, a circular shape or the like. Further, the position recognition patterns  21   a  and  21   b  may be constructed in a specific shape of mark for position recognition. 
         [0054]    In this case, if a fixed coordinate system is used in the semiconductor equipment because of a program or a different reason, the wafer  20  can be moved onto the fixed coordinate system such that the coordinate system can be set on the wafer  20 , after the rotation angles of the searched position recognition patterns  21   a  and  21   b  are calculated. 
         [0055]    In the wafer  20  of which the initial position is set by the position recognition patterns  21   a  and  21   b , the lens mold  10  is caused to coincide with the coordinates of the lens formation position of the wafer by the plurality of minutes patterns  22  arranged in array on one surface of the wafer. 
         [0056]    That is, the center among the minute patterns  22  formed on the wafer  20  is caused to coincide with the center of the lens mold  10  which is attached to form a lens in the position where the minute patterns  22  are formed. Then, the coordinate system of the wafer is caused to coincide with the coordinate system of the lens mold  10 . 
         [0057]    As the minute patterns  22  of the wafer  20  and the coordinate system of the lens mold  10  are caused to coincide with each other, the minute patterns  22  of the wafer  20  are aligned with the groove  12  formed on the top surface of the lens mold  10 , as shown in  FIGS. 6A and 6B , such that the lens can be molded in an accurate position. 
         [0058]    As shown in  FIGS. 6A and 6B , the minute patterns  22  arranged on the wafer  20  are positioned outside the groove  12  formed around the lens forming portion  11  of the lens mold  10 . Therefore, as the minute patterns  22  are closely attached to the outside of the groove  12  or spaced at a predetermined distance from the groove  12 , the lens mold  10  is aligned with the lens formation position of the wafer  20 . 
         [0059]    Preferably, the minute patterns  22  are formed of metal. Further, the minute patterns  22  may be formed in a linear shape so as to be symmetrical with each other or may be formed in a circular arc shape having an approximate curvature to the groove  12 . 
         [0060]    The minute patterns  22  are disposed outside the groove  12  formed on the lens mold  10 , and the alignment between the wafer  20  and the lens mold  10  is achieved by adjusting a distance between the minute patterns  22  and the groove  12 . In some cases, however, the minute patterns  22  may be formed so as to be positioned inside the groove  12 . 
         [0061]      FIG. 7  is a flow chart showing a wafer lens aligning method according to the invention. The wafer lens aligning method is performed as follows. First, a lens mold  10  having a lens forming portion  11  and a groove  12  formed around the lens forming portion  11  is mounted on an automated equipment (step S 101 ). Then, a wafer  20  is mounted, in which position recognition patterns  21   a  and  21   b  are formed at arbitrary positions thereof and a plurality of minute patterns  22  are formed in array at lens formation positions (step ST 102 ). 
         [0062]    Next, the wafer  20  is loaded into a semiconductor equipment to scan the position recognition patterns  21   a  and  21   b  formed on the wafer  20 , and a coordinate system of the wafer  20  is then set (step ST 103 ). 
         [0063]    At this time, the coordinate system of the wafer  20  is set so as to set the initial position of the wafer  20  in the automated equipment. The setting of the coordinate system for setting the initial position is performed as follows. One position recognition pattern  21   a  between the two position recognition patters  21   a  and  21   b  formed on the wafer  20  is first scanned, and the position thereof is stored. Then, the other position recognition pattern  21   b  of the wafer  20  is scanned, and the position thereof is stored. On the basis of the position recognition patterns  21   a  and  21   b  of which the positions are stored, the coordinate system of the semiconductor equipment is moved to set the initial position of the wafer  20 . 
         [0064]    Then, when the initial position of the wafer  20  is set, the coordinate system of the wafer  20  is caused to coincide with the coordinate system of the lens mold  10  (step ST 104 ). 
         [0065]    Subsequently, the center among the minute patterns  22  formed on the wafer is caused to coincide with the center of the groove  12  of the lens mold  10  such that the lens mold  10  is aligned with a lens formation position of the wafer  20 . 
         [0066]    At this time, the minute patterns  22  are positioned outside or inside the groove  12  formed in the lens mold  10 , and the distance between the minute patterns  22  and the groove  12  is recognized by a control program. Then, the distance between the minute patterns  22  and the groove  12  is uniformly maintained, so that the center among the minute patterns  22  is caused to coincide with the center of the lens mold  10 . 
         [0067]    Finally, after the lens mold  10  is aligned with the lens formation position of the wafer  20 , resin injected into the lens forming portion  11  of the lens mold  10  is cured by ultraviolet (UV) light such that a master lens for manufacturing a wafer lens is molded on one surface of the wafer  20  (step S 106 ). 
         [0068]      FIG. 8  is a cross-sectional view of a lens manufactured by the wafer lens aligning method according to the invention. As shown in  FIG. 8 , a lens  30  separated from the lens mold  10  has a projection  32  formed with a predetermined height around an optical portion  31  projecting in a semi-circular shape on a bonding surface of the lens mold  10 . 
         [0069]    The projection  32  is formed in a height corresponding to the depth of the groove by transferring resin through the groove  12  formed in the lens mold  10 . 
         [0070]    When a single wafer lens is finalized, decenter can be measured on the basis of the projection  32  formed around the optical portion  31  of the lens  30 . 
         [0071]    According to the present invention, the coordinate system of wafer is set by the position recognition patterns formed on the wafer, the mold is moved in accordance with the set coordinate system, and the minute patterns formed on the wafer are caused to coincide with the groove formed on the mold such that the lens mold can be accurately aligned with a lens formation position. Therefore, an alignment error of the mold is minimized during the manufacturing of the wafer lens, which makes it possible to significantly reduce defective products. Further, as the alignment between the lens mold and the wafer is achieved by the automated equipment, mass production can be achieved, and alignment speed can be enhanced, which makes it possible to increase productivity. 
         [0072]    Further, although foreign matters are attached to the groove formed on the lens mold or the groove is scratched, it does not have an effect because the center of the minute patterns on the wafer is aligned with the center of the groove. Therefore, it is possible to expand the lifespan of the mold. 
         [0073]    Furthermore, as the projection is formed on one surface of the wafer lens after the wafer and the lens mold are aligned, it is possible to measure decenter through the projection. 
         [0074]    Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.