Patent Publication Number: US-2023154782-A1

Title: Tape pressure bonding apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a tape pressure bonding apparatus for pressure bonding a tape that is pressure bonded to an annular frame having an opening for accommodating a wafer in a center of the annular frame to a back surface of the wafer. 
     Description of the Related Art 
     A wafer having a device region and a peripheral surplus region formed on a front surface thereof, the device region in which a plurality of devices such as integrated circuits (ICs) and large-scale integration circuits (LSIs) are partitioned by a plurality of intersecting streets, and the peripheral surplus region surrounding the device region. The back surface side of the wafer described above is ground, and the wafer is formed into a desired thickness and is thereafter divided into individual device chips by a dicing apparatus or a laser processing apparatus. Then, the device chips thus divided is utilized for electric equipment such as a mobile phone and a personal computer. 
     The present inventor has proposed a technology in which, for facilitating conveyance of a ground wafer, a ring-like reinforcement section is left on the back surface corresponding to the peripheral surplus region, and, after predetermined processing is conducted, a dicing tape is pressure bonded to the back surface of the wafer and the wafer is supported by an annular frame, and the ring-like reinforcement section is removed from the wafer (see, for example, Japanese Patent Laid-Open No. 2010-62375). 
     However, in the technology disclosed in Japanese Patent Laid-Open No. 2010-62375, there has been a problem in that an operation of pressure bonding the dicing tape to the back surface of the wafer formed with a ring-like reinforcement section at the periphery thereof and uniting the wafer with an annular frame through the dicing tape is difficult to be performed, and it is difficult to cut and remove the ring-like reinforcement section from the wafer, resulting in poor productivity. 
     To address this problem, it may be considered to utilize a wafer table that supports the front surface side of the wafer for an operation to attach the dicing tape to the back surface of the wafer to unit the wafer with the annular frame. To prevent damage to the device region formed on the front surface of the wafer, the wafer table is preferably formed with a circular recess that supports only the peripheral surplus region and that is not in contact with the device region. 
     SUMMARY OF THE INVENTION 
     However, the configuration in which only the peripheral surplus region on the front surface side of the wafer is supported by the wafer table having the circular recess and the tape of an annular frame attached with the tape is pressure bonded to the back surface of the wafer by a pressing roller may cause damage to the wafer. 
     Accordingly, it is an object of the present invention to provide a tape pressure bonding apparatus which would not damage a wafer even if a tape of an annular frame attached with the tape is pressure bonded to the back surface of the wafer by a pressing roller. 
     In accordance with an aspect of the present invention, there is provided a tape pressure bonding apparatus which pressure bonds a tape that is pressure bonded to an annular frame having an opening for accommodating a wafer in a center of the annular frame to a back surface of the wafer, the tape pressure bonding apparatus including an upper chamber, a lower chamber accommodating a wafer table that has a holding surface including a circular recess for supporting only a peripheral surplus region of the wafer and making a device region a non-contact state, a lifting mechanism that switches between a closed state in which the upper chamber is moved downward to be brought into contact with the lower chamber and an open state in which the upper chamber is separated from the lower chamber, a vacuum section that evacuates the upper chamber and the lower chamber in the closed state, an atmosphere opening section that opens the upper chamber and the lower chamber to the atmosphere, and positive pressure generating means that supplies air into the circular recess of the wafer table to establish a positive pressure state in the circular recess, the positive pressure state in which a pressure in the circular recess is made higher than a pressure in the upper chamber and the lower chamber. In a state in which a tape of the annular frame attached with the tape is positioned on the back surface of the wafer supported by the wafer table, the upper chamber and the lower chamber are evacuated while maintaining the closed state by operating the lifting mechanism, and the tape of the annular frame attached with the tape is pressure bonded to the back surface of the wafer by a pressing roller disposed in the upper chamber. 
     Preferably, the positive pressure generating means may operate when the pressing roller presses the wafer through the tape. A ring-like reinforcement section may be formed in a projecting manner on the back surface corresponding to the peripheral surplus region of the wafer. 
     The tape pressure bonding apparatus of the present invention includes the positive pressure generating means that supplies air into the circular recess of the wafer table to establish a positive pressure state in the circular recess, the positive pressure state in which a pressure in the circular recess is made higher than a pressure in the upper chamber and the lower chamber, and therefore, the tape pressure bonding apparatus would not damage the wafer even if the tape of the annular frame attached with the tape is pressure bonded to the back surface of the wafer by the pressing roller. 
     The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a tape pressure bonding apparatus of an embodiment of the present invention; 
         FIG.  2    is an exploded perspective view of the tape pressure bonding apparatus depicted in  FIG.  1   ; 
         FIG.  3    is a sectional view of the tape pressure bonding deice depicted in  FIG.  1   ; 
         FIG.  4 A  is a perspective view of a wafer with a reinforcement section; 
         FIG.  4 B  is a perspective view of a wafer without a reinforcement section; 
         FIG.  5    is a perspective view of an annular frame attached with a tape; 
         FIG.  6    is a schematic sectional view depicting a state in which pressing of the tape is started; and 
         FIG.  7    is a schematic sectional view depicting a state in which pressing of the tape is finished. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A tape pressure bonding apparatus of an embodiment of the present invention will be described with reference to the drawings. 
     Tape Pressure Bonding Apparatus  2   
     As illustrated in  FIG.  1   , the tape pressure bonding apparatus  2  includes an upper chamber  4 , a lower chamber  6 , a lifting mechanism  8  that switches between a closed state in which the upper chamber  4  is moved downward to be brought into contact with the lower chamber  6  and an open state in which the upper chamber  4  is separated from the lower chamber  6 , a vacuum section  10  that evacuates the upper chamber  4  and the lower chamber  6  in the closed state, and an atmosphere opening section  12  that opens the upper chamber  4  and the lower chamber  6  to the atmospheric air. 
     Upper Chamber  4   
     The upper chamber  4  includes a circular top plate  14 , and a cylindrical side wall  16  extending downward from a peripheral edge of the top plate  14 , and a lower part of the side wall  16  is opened. Referring to  FIGS.  2  and  3   , in an accommodating space defined by a lower surface of the top plate  14  and an inner peripheral surface of the side wall  16 , there are disposed a pressing roller  18  for pressure bonding a tape of an annular frame attached with the tape to a wafer, a support piece  20  that rotatably supports the pressing roller  18 , and an X-axis feeding mechanism  22  (see  FIG.  2   ) that moves the support piece  20  in an X-axis direction indicated by an arrow X in  FIG.  2   . 
     As depicted in  FIG.  2   , the X-axis feeding mechanism  22  includes a ball screw  24  connected to the support piece  20  and extending in the X-axis direction, and a motor  26  for rotating the ball screw  24 . The X-axis feeding mechanism  22  converts a rotational motion of the motor  26  into a rectilinear motion and transmits the rectilinear motion to the support piece  20  by the ball screw  24 , thereby moving the pressing roller  18  together with the support piece  20  along a pair of guide rails  28  extending in the X-axis direction. 
     Lower Chamber  6   
     As illustrated in  FIGS.  2  and  3   , the lower chamber  6  has a cylindrical side wall  30 . The side wall  30  is opened at an upper part and is closed at a lower part. A wafer table  32  that holds the wafer and the annular frame is accommodated in the side wall  30 . 
     The wafer table  32  has a holding surface  34  formed in a recessed shape so as to hold only a peripheral surplus region of the wafer and to make a device region a non-contact state. The holding surface  34  includes an annular holding section  36  hat holds the peripheral surplus region of the wafer and the annular frame, and a circular recess  38  corresponding to the device region. The annular holding section  36  has a rubber ring  40  disposed along a peripheral edge of the circular recess  38 , and the rubber ring  40  is provided with a plurality of suction holes  40   a  at intervals along a circumferential direction. Each of the suction holes  40   a  is connected to a suction source  44  (see  FIG.  2   ) through a channel  42 . 
     Lifting Mechanism  8 , Vacuum Section  10 , Atmosphere Opening Section  12   
     The lifting mechanism  8  can be configured by an appropriate actuator such as an air cylinder mounted to an upper surface of the top plate  14  of the upper chamber  4 . The vacuum section  10  can be configured by an appropriate vacuum pump. The vacuum section  10  is connected to the lower chamber  6  through a channel  46 . In addition, the channel  46  is provided with the atmosphere opening section  12  including an appropriate valve capable of opening the channel  46  to the atmospheric air. 
     Positive Pressure Generating Means  48   
     Continuing a description with reference to  FIGS.  2  and  3   , the tape pressure bonding apparatus  2  of the present embodiment includes positive pressure generating means  48  that supplies air into the region (circular recess  38 ) of the wafer table  32  formed in a recessed shape to establish a positive pressure state in the circular recess  38 , i.e., to make a pressure in the circular recess  38  higher than a pressure in the upper chamber  4  and the lower chamber  6 . The positive pressure generating means  48  includes a supply hole  50  formed in the circular recess  38  and an air supply source  54  (see  FIG.  2   ) connected to the supply hole  50  through a channel  52 . 
     Wafer W 
       FIG.  4 A  depicts a disc-like wafer W to be pressure bonded to the tape of the annular frame attached with the tape by the tape pressure bonding apparatus  2 . The wafer W can be formed of an appropriate semiconductor material such as silicon (Si) and silicon carbide (SiC). A front surface Wa of the wafer W has a circular device region Rd and a peripheral surplus region Rs surrounding the device region Rd. The device region Rd is partitioned by streets S in a grid pattern into a plurality of rectangular regions, and a device D such as an IC and an LSI is formed in each of the rectangular regions. Note that a boundary B between the device region Rd and the peripheral surplus region Rs is represented by alternate long and two short dash line as a matter of convenience, but in practice, the boundary B is not present. 
     For the wafer W depicted in  FIG.  4 A , a ring-like reinforcement section R is formed in a projecting manner on a back surface Wb corresponding to the peripheral surplus region Rs. Therefore, a thickness of the peripheral surplus region Rs is greater than a thickness of the device region Rd. 
     In addition, the wafer to be pressure bonded to the tape of the annular frame attached with the tape by the tape pressure bonding apparatus  2  may be a wafer, like a wafer W′ depicted in  FIG.  4 B , not provided with the ring-like reinforcement section on a back surface Wb′ of the wafer W′. Note that, in the following description, a case of pressure bonding the tape to the wafer W provided with the reinforcement section R will be mainly described. 
     Annular Frame Attached With Tape FT 
       FIG.  5    depicts an annular frame attached with a tape FT to which the wafer W is to be pressure bonded. The annular frame attached with the tape FT includes an annular frame F having an opening Fo for accommodating the wafer W, and a circular adhesive tape T pressure bonded to the annular frame F. 
     Next, the operation of the tape pressure bonding apparatus  2  as described above will be described. 
     In the present embodiment, first, the lifting mechanism  8  is operated to establish an open state in which the upper chamber  4  is separated from the lower chamber  6 . Next, as depicted in  FIG.  2   , the wafer W is placed on the holding surface  34  of the wafer table  32  in a state in which the front surface Wa formed with the devices D is directed downward. 
     At a time of placing the wafer W on the holding surface  34 , the peripheral surplus region Rs of the wafer W is positioned at the rubber ring  40  of the annular holding section  36 , and the device region Rd of the wafer W is positioned at the circular recess  38 . As a result, even when the wafer W is placed on the holding surface  34  of the wafer table  32  in a state in which the front surface Wa formed with the devices D is directed downward, the devices D in the device region Rd and the holding surface  34  are not brought into contact with each other, and damaging of the devices D can be prevented. 
     Next, the suction source  44  is operated, to generate a suction force in each suction hole  40   a  of the rubber ring  40 , thereby holding under suction the peripheral surplus region Rs of the wafer W. The pressure in the suction holes  40   a  at this time may be, for example, an absolute pressure of substantially 100 Pa. 
     When the wafer W is held under suction by the wafer table  32 , the annular frame attached with the tape FT is placed on the annular holding section  36  of the wafer table  32  (see  FIG.  2   ). At this time, the tape T of the annular frame attached with the tape FT is positioned on the back surface Wb of the wafer W supported by the wafer table  32 , and an adhesive surface of the tape T is directed downward such that the adhesive surface of the tape T faces the back surface Wb of the wafer W. 
     After the annular frame attached with the tape FT is placed on the wafer table  32 , the upper chamber  4  is lowered by the lifting mechanism  8 , and a lower end of the side wall  16  of the upper chamber  4  is brought into contact with an upper end of the side wall  30  of the lower chamber  6  (see  FIG.  3   ). As a result, the upper chamber  4  and the lower chamber  6  are put into a closed state. Then, as depicted in  FIG.  6   , the pressing roller  18  comes in contact with the annular frame attached with the tape FT, and the adhesive surface of the tape T comes in contact with an upper end of the reinforcement section R of the wafer W. 
     Next, the vacuum section  10  is operated in a state in which the atmosphere opening section  12  is closed, to evacuate the inside of the upper and lower chambers  4  and  6 . It is to be noted that the pressure in the upper and lower chambers  4  and  6  is set higher than the pressure in the suction holes  40   a  (for example, an absolute pressure of substantially 200 Pa). As a result, although a force for sucking the wafer W is slightly weakened, a state in which the wafer W is held under suction by the wafer table  32  can be maintained, even if the upper and lower chambers  4  and  6  are evacuated. 
     Subsequently, as depicted in  FIGS.  6  and  7   , the pressing roller  18  disposed in the upper chamber  4  is rolled in the X-axis direction by the X-axis feeding mechanism  22 , and the tape T of the annular frame attached with the tape FT is pressure bonded to the back surface Wb of the wafer W by the pressing roller  18 . At this time, the wafer W is pressed downward through the tape T by the pressing roller  18 . Then, since the wafer W has only the peripheral surplus region Rs supported by the rubber ring  40  of the annular holding section  36  and the device region Rd is positioned at the circular recess  38 , the wafer w is warped downward at a result of the pressing by the pressing roller  18 , and the wafer W may be broken. 
     However, since the tape pressure bonding apparatus  2  of the present embodiment is provided with the positive pressure generating means  48  that supplies air into the circular recess  38  to establish a positive pressure state in the circular recess  38 , the positive pressure state in which the pressure in the circular recess  38  is made higher than the pressure in the upper and lower chambers  4  and  6 , the wafer W can be prevented from being warped due to the pressing by the pressing roller  18  and can be prevented from being broken. 
     Specifically, when the wafer W is pressed by the pressing roller  18  through the tape T, the air supply source  54  of the positive pressure generating means  48  is operated, to supply air into the circular recess  38  through the supply hole  50 , thereby putting the circular recess  38  into a positive pressure state, the positive pressure state in which the pressure in the the circular recess  38  is made higher than the pressure in the upper and lower chambers  4  and  6 . At this time, the pressure in the circular recess  38  is set slightly greater than the pressure in the upper and lower chambers  4  and  6 . For example, in a case where the air pressure in the upper and lower chambers  4  and  6  is an absolute pressure of substantially 200 Pa, the air pressure in the circular recess  38  may be an absolute pressure of substantially 300 Pa. 
     In this way, in the tape pressure bonding apparatus  2  of the present embodiment, since the pressure in the circular recess  38  is made more positive (higher) than the pressure in the upper and lower chambers  4  and  6  by the positive pressure generating means  48 , when the wafer W is pressed by the pressing roller  18  through the tape T, the wafer W can be prevented from being warped, and the wafer W can be prevented from being broken. 
     When the tape T is pressure bonded to the wafer W by the pressing roller  18 , if the upper and lower chambers  4  and  6  are evacuated, the suction force for the wafer W by the wafer table  32  would be weakened, as mentioned above. However, in the present embodiment, the peripheral surplus region Rs of the wafer W is positioned at the rubber ring  40  of the annular holding section  36 . Hence, when the tape T is pressure bonded to the wafer W by the pressing roller  18 , positional deviation of the wafer W is prevented by a frictional force between the rubber ring  40  and the wafer W. 
     In the present embodiment, the back surface Wb of the wafer W is formed with the ring-like reinforcement section R. Accordingly, even when the tape T is pressure bonded to the back surface Wb of the wafer W by the pressing roller  18 , a part with which the tape T is not in close contact may be generated at a root of the ring-like reinforcement section R. 
     In this regard, in the present embodiment, the tape T is pressure bonded to the wafer W by the pressing roller  18  in a state in which the upper and lower chambers  4  and  6  are evacuated. Hence, when the atmosphere opening section  12  is opened after the pressing roller  18  is moved, the tape T can be pressed to the wafer W by the atmospheric pressure, and the tape T can be put into close contact with the wafer W along the root of the reinforcement section R. 
     Note that, in the present embodiment, a case in which the tape T is an adhesive tape has been described, but the tape T may be a thermocompression bonding tape in which an adhesive layer is not formed on a sheet included in the tape. The thermocompression bonding tape is a tape of a thermoplastic synthetic resin (for example, a polyolefin resin), which exhibits an adhesive force by being soften or melted when heated to a temperature in the vicinity of the melting point thereof. 
     In a case in which the tape T is a thermocompression bonding tape, the tape T can be thermocompression bonded to the back surface Wb of the wafer W by the pressing roller  18 , by heating at least one of the pressing roller  18  or the wafer table  32  to a temperature at which the tape T is softened or melted. 
     The present invention is not limited to the details of the above described preferred embodiment. The scope of the invention is defined by the appended claims and all changes and modifications as fall within the equivalence of the scope of the claims are therefore to be embraced by the invention.