Abstract:
A peeling tap adhering method for adhering a peeling tape ( 4 ) to a surface protection film ( 11 ) adhered to the front surface of a wafer ( 20 ), comprises the steps of: supporting the wafer on a table ( 31 ) under the condition that the surface protection film is directed upward; adhering the peeling tape onto the surface protection film by pressing the peeling tape onto the surface protection film when a peeling tape adhering means ( 46 ) is lowered; detecting the pressure between the surface protection film of the wafer and the peeling tape adhering means; and stopping the peeling tape adhering means from lowering in the case where a pressure detection value (P) is not less than a predetermined value (P 0 ). Due to the foregoing, it is possible to prevent the wafer from being cracked. Further, it is possible to prevent the peeling tape and the dicing tape from adhering to each other. When the distance (L) between the surface protection film of the wafer and the peeling tape adhering means becomes a value not more than a predetermined value (L 0 ), the peeling tape sticking means may be stopped from lowering.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a peeling tape adhering method for adhering a peeling tape to a surface protective film adhered on a wafer. The present invention also relates to a peeling tape adhering device for carrying out this peeling tape adhering method. 
         [0003]    2. Description of the Related Art 
         [0004]    In the field of manufacturing semiconductors, there is a tendency for large-sized wafers to be used year after year. Further, in order to enhance the packing density, the wafer thickness is reduced. In order to reduce the wafer thickness, back-grinding is conducted on the back surface of a semiconductor wafer. At the time of back-grinding, in order to protect a semiconductor element formed on the front surface of a wafer, a surface protection film is adhered to the front surface of the wafer. 
         [0005]      FIG. 8  is an enlarged sectional view showing a circular wafer onto which a surface protection film is adhered. As can be seen from  FIG. 8 , an edge portion of  25  of the circular wafer  20  is chamfered in the beginning. A surface protection film  11  is adhered to a front surface  21  of the wafer  20 . As shown in the drawing, a back surface of the wafer  20  is ground, that is, back-grinding is conducted on the back surface of the wafer  20 . When the thickness of the wafer  20  is reduced from thickness Z 0  to thickness Z 1 , a chamfered portion  27  on the back surface side of the wafer  20  is eliminated. Therefore, the newly formed back surface  22  (a ground surface) of a wafer  20  reaches a chamfered portion  26  on the front surface side. 
         [0006]    Next, as shown in  FIG. 9 , a dicing tape  3  is adhered to the back surface  22  of the wafer  20 . Due to this dicing tape  3 , the wafer  20  is integrated with a mount frame  36  into one body. Concerning this matter, refer to Japanese Unexamined Patent Publication No. 2003-124146. After that, the wafer  20  is supported on a table  131  in such a manner that the surface protection film  11  is located upward as shown in  FIG. 10 . After a peeling tape  4  has been drawn out on the surface protection film  11 , a peeling roller  146  is pressed onto the surface protection film  11 , so that the peeling tape  4  can be adhered to the surface protection film  11 . Next, by moving the table  131  for supporting the wafer  20  in the horizontal direction, the surface protection film  11  is peeled from the wafer  20  together with the peeling tape  4 . 
         [0007]    As described before, since the wafer  20  has been greatly reduced in thickness in recent years, the rigidity of the wafer itself is also greatly reduced. Accordingly, when the peeling tape  4  is adhered to the surface protection film  11  by the peeling roller  146 , there is a possibility that fractures or cracks are formed on the wafer  20 , which decreases yield. Even when no fractures or cracks are generated, internal strain may be generated on the wafer  20 . Thus, there is a possibility that fractures or cracks will appear on the wafer in the next step due to internal strain. 
         [0008]    Further, since the wafer  20  is greatly reduced in thickness, when the peeling roller  146  is strongly pressed in the case of adhering the peeling tape  4  to the wafer  20 , there is a high possibility that the peeling tape  4  will hang down as shown in  FIG. 10  and adhere to the dicing tape  3 . In this case, the adhesive faces of the tapes  3 ,  4  adhere to each other. Accordingly, when these tapes  3 ,  4  once adhered to each other, they become difficult to separate from each other without causing damage to the wafer  20 . 
         [0009]    The present invention has been accomplished in view of the above circumstances. It is an object of the present invention to provide a peeling tape adhering method capable of preventing the generation of fractures or cracks on a wafer and also capable of preventing the adhesion between a peeling tape and a dicing tape. It is another object of the present invention to provide a peeling tape adhering device for executing this peeling tape adhering method. 
       SUMMARY OF THE INVENTION 
       [0010]    In order to accomplish the above object, according to the first aspect, a peeling tape adhering method for adhering a peeling tape to a surface protection film adhered to a front surface of a wafer comprises the steps of: supporting the wafer on a table under the condition that the surface protection film is directed upward; adhering the peeling tape onto the surface protection film of the wafer by pressing the peeling tape onto the surface protection film when a peeling tape adhering means is lowered; detecting pressure between the surface protection film of the wafer and the peeling tape adhering means; and stopping the peeling tape adhering means from lowering in the case where a detected pressure value is not less than a predetermined value. 
         [0011]    According to the second aspect, a peeling tape adhering device for adhering a peeling tape to a surface protection film adhered to a front surface of a wafer, comprises: a table for supporting the wafer while the surface protection film is being directed upward; a peeling tape adhering means for pressing and adhering the peeling tape onto the surface protection film of the wafer; and a pressure detection means for detecting pressure between the surface protection film on the wafer and the peeling tape adhering means, wherein when the peeling tape is pressed and adhered to the surface protection film by lowering the peeling tape adhering means, in the case where a pressure value detected by the pressure detection means is not less than a predetermined value, the peeling tape adhering means is stopped from lowering. 
         [0012]    In the first and the second aspect, when the pressure generated between the surface protection film and the peeling tape adhering means is raised to a value higher than a predetermined value, the peeling tape adhering means is stopped from lowering. Therefore, it is possible to prevent fractures or cracks from being formed on the entire wafer. In the case where the wafer and the mount frame are integrated with each other into one body, it is not necessary to use excessive force to press the peeling tape adhering means. Therefore, it is possible to prevent the peeling tape and the dicing tape from adhering to each other. Further, since the pressing force applied to the peeling tape can be directly controlled, even in the case where the thickness of the wafer and/or the thickness of the surface protection film is different, the peeling tape can be adhered by the same amount of pressing force. 
         [0013]    According to the third aspect, as in the second aspect, the pressure detection means is incorporated into a portion of the peeling tape adhering means coming into contact with the surface protection film. 
         [0014]    In the third aspect, pressure generated between the surface protection film and the peeling tape adhering means can be directly detected. Therefore, pressing of the peeling tape can be finished at the correct timing. 
         [0015]    According to the fourth aspect, as in the second embodiment, the pressure detection means is incorporated into a portion of the table located corresponding to the peeling tape adhering means. 
         [0016]    In the fourth aspect, it is possible to ensure a sufficiently large space for installing a pressure detection means. Accordingly, a relatively large pressure detection means having high performance can be installed. 
         [0017]    According to the fifth aspect, a peeling tape adhering method for adhering a peeling tape to a surface protection film adhered to a front surface of a wafer, comprises the steps of: supporting the wafer on a table under the condition that the surface protection film is directed upward; adhering the peeling tape to the surface protection film of the wafer by pressing the peeling tape onto the surface protection film when a peeling tape adhering means is lowered; detecting a distance between the surface protection film of the wafer and the peeling tape adhering means; and stopping the peeling tape sticking means from lowering in the case where a detected distance value is not more than a predetermined value. 
         [0018]    According to the sixth aspect, a peeling tape adhering device for adhering a peeling tape to a surface protection film adhered to a front surface of a wafer, comprises: a table for supporting the wafer while the surface protection film is being directed upward; a peeling tape adhering means for pressing and adhering the peeling tape to the surface protection film on the wafer; and a distance detection means for detecting a distance between the surface protection film of the wafer and the peeling tape adhering means, wherein when the peeling tape is pressed and adhered to the surface protection film by lowering the peeling tape adhering means, in the case where a distance value detected by the distance detection means is not more than a predetermined value, the peeling tape sticking means is stopped from lowering. 
         [0019]    In the fifth and the sixth aspect, when the distance between the surface protection film and the peeling tape adhering means is reduced to a value not more than a predetermined value, the peeling tape adhering means is stopped from lowering. Therefore, it is easy to prevent fractures or cracks from being form on the entire wafer. Further, even in the case where the wafer is integrated with a mount frame into one body, the peeling tape adhering means is not pressed excessively. Therefore, it is possible to prevent the peeling tape and the dicing tape from adhering to each other. In this connection, the predetermined value of the distance is a value a little higher than zero. Alternatively, the predetermined value of the distance may be zero. Further, since the pressing force given by the peeling tape can be directly controlled, even in the case where the thickness of the wafer and/or the thickness of the surface protection film is different, the peeling tape can be adhered by the same amount of pressing force. 
         [0020]    These and other objects, features and advantages of the present invention will be more apparent in light of the detailed description of exemplary embodiments thereof as illustrated by the drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    In the drawings: 
           [0022]      FIG. 1  is a side view showing an outline of a surface protection film peeling device having a peeling tape adhering unit of the present invention; 
           [0023]      FIG. 2  is a top view briefly showing a peeling tape adhering unit of the present invention; 
           [0024]      FIG. 3  is a flow chart showing an operation program of a surface protection film peeling device having a peeling tape adhering unit of the first embodiment of the present invention; 
           [0025]      FIG. 4   a  is a first view for explaining operation of a surface protection film peeling device having a peeling tape adhering unit of the present invention; 
           [0026]      FIG. 4   b  is a second view for explaining operation of a surface protection film peeling device having a peeling tape adhering unit of the present invention; 
           [0027]      FIG. 5   a  is a third view for explaining operation of a surface protection film peeling device having a peeling tape adhering unit of the present invention; 
           [0028]      FIG. 5   b  is a fourth view for explaining operation of a surface protection film peeling device having a peeling tape adhering unit of the present invention; 
           [0029]      FIG. 6  is a partial enlarged view showing a peeling tape adhering unit of another embodiment of the present invention; 
           [0030]      FIG. 7  is a flow chart showing an operation program of a surface protection film peeling device having a peeling tape adhering unit of the second embodiment of the present invention; 
           [0031]      FIG. 8  is an enlarged sectional view of a wafer onto which a surface protection film is adhered; 
           [0032]      FIG. 9  is a top face view showing a wafer integrated with a mount frame; and 
           [0033]      FIG. 10  is a sectional view showing a state in which a peeling tape is adhered to a surface protection film on a wafer of the prior art. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    Referring to the accompanying drawings, an embodiment of the present invention will be explained below. Like reference numerals are used to indicate like parts in the following drawings. In order to facilitate understanding, the reduced scale of these drawings has been appropriately changed. 
         [0035]      FIG. 1  is a schematic illustration showing a surface protection film peeling device according to the present invention. A back surface of a wafer  20 , which is supplied to the surface protection film peeling device  10 , is ground to a chamfered portion  26  on a front surface side by the method of back-grinding. For example, the wafer  20  is not more than  100  micrometers thick. As well known, a surface protection film  11  for protecting a circuit pattern has already been adhered to the front surface of a wafer  20 . Further, as explained before referring to  FIG. 9 , a dicing tape  3  is adhered to a grinding surface  22  of the wafer  20 . Therefore, the wafer  20  is integrated with a mount frame  36  into one body by the dicing tape  3 . 
         [0036]    The surface protection film peeling device  10  shown in  FIG. 1  includes: a supply portion  42  for supplying a peeling tape  4  to be adhered onto the surface protection film  11  on the wafer  20 ; and a winding portion  43  for winding the peeling tape  4  sent from the supply portion  42 . The peeling tape  4 , which will be explained below, is a so-called pressure sensitive tape, which exhibits an adhesion action when the tape is given pressure. Alternatively, the peeling tape may be a so-called heat sensitive tape, which exhibits an adhesion action when heated. 
         [0037]    As shown in  FIG. 1 , in the downstream of the supply portion  42 , guide rollers  47 ,  65  are arranged for guiding the peeling tape  4  and for giving a predetermined tension to the peeling tape  4 . The peeling tape  4  passes through an adhering member  46  of the surface protection film peeling device  10  and is guided to the winding portion  43 . As shown in the drawing, a cross section of the tip portion of the adhering member  46  is a rectangle or a triangle. This adhering member  46  is arranged in a direction so that the tip portion of the sticking member  46  can be contacted with the wafer  20  in a small area. There are provided a guide roller  56 , a dancer roller  55 , a pair of guide rollers  51  and other dancer rollers  59  between the adhering member  46  and the winding portion  43 . These dancer rollers  55 ,  59  are operated according to an amount of the peeling tape  4  which has been drawn out. 
         [0038]    A peeling tape adhering unit  60  of the surface protection film peeling device  10  has a shaft  62  inserted into a cover guide portion  63 . A motor  61  is attached to an upper portion of the cover guide portion  63 . As shown in the drawing, the adhering member  46  is arranged at a bottom end portion of the shaft  62 . The guide rollers  56 ,  65  related to the adhering member  46  are arranged at predetermined positions of the shaft  62 . Accordingly, when the shaft  62  is elevated and lowered along the cover guide portion  63  by the motor  61 , the adhering member  46  and the guide rollers  56 ,  65  are integrally elevated and lowered. In this connection, it is possible to employ an air cylinder for elevating and lowering the shaft  62  instead of the motor. 
         [0039]    Below the adhering member  46 , a support table  31  is provided which supports the wafer  20  and the mount frame  36 . This support table  31  can be moved in the horizontal direction, that is, this support table  31  can be moved in the lateral direction in  FIG. 1 . A distance sensor  91  arranged behind the guide roller  65  detects the distance between the surface protection film  11  on the wafer  20  supported by the support table  31  and the tip portion  46   a  of the adhering member  46 . 
         [0040]    As shown in  FIG. 1 , a pressure sensor  92 , for example, a sheet-type pressure sensor is arranged at a tip portion  46   a  of the adhering member  46 .  FIG. 2  is a top view briefly showing the peeling tape adhering unit of the present invention. As can be seen from  FIGS. 1 and 2 , the pressure sensor  92  is embedded in a portion of the adhering member  46  coming into contact with the wafer  20 . To be specific, the pressure sensor  92  is embedded in the adhering member  46  in such a manner that a pressure detection face of the pressure sensor  92  can be on the same plane as that of the portion of the adhering member  46  coming into contact with the wafer  20 . 
         [0041]    Accordingly, the pressure sensor  92  can detect pressure generated between the adhering member  46  and the surface protection film  11  at the time of pressing the adhering member  46  to the surface protection film  11 . The embedded pressure sensor  92  is advantageous for directly detecting the pressure generated between the adhering member  46  and the surface protection film  11 . 
         [0042]      FIG. 3  is a flow chart showing an operation program of the surface protection film peeling device having the peeling tape adhering unit of the first embodiment of the present invention. This operation program is incorporated into a memory of a control portion  95  (not shown) and executed by the control portion  95 . In this connection, each element of the surface protection film peeling device  10  is connected to and controlled by the control portion  95 . 
         [0043]      FIGS. 4   a ,  4   b ,  5   a  and  5   b  are views explaining the operation of the surface protection film peeling device with the peeling tape adhering unit  60  of the present invention. So as to simplify the explanation, the distance sensor  91  is omitted from these drawings. 
         [0044]    Referring to the drawings, the operation of the surface protection film peeling device  10  of the present invention will be explained below. In this connection, before the surface protection film peeling device  10  is driven, the peeling tape  4  has already been drawn out from the supply portion  42  to the winding portion  43  through the adhering member  46 . 
         [0045]    In step  101  of the operation program  100  shown in  FIG. 3 , the wafer  20  and the mount frame  36 , which have been integrated with each other by the dicing tape  3 , are supported on the support table  31 . 
         [0046]    Next, in step  101   a , a position of the wafer  20  on the support table  31  is detected by a sensor (not shown). In particular, the position of one end  28  of the wafer  20  is detected by the sensor (not shown). After that, in step  101   b , the support table  31  is moved in the horizontal direction so that the adhering member  46  is located on one end  28  of the wafer  20 . Concerning this matter, refer to  FIG. 4   a . Alternatively, the support table  31  may be previously positioned at such a position before the wafer  20  is supported. 
         [0047]    Next, in step  102 , the motor  61  is driven and the shaft  62  and the adhering member  46  are slid in the cover guide portion  63  so that the shaft  62  and the adhering member  46  can be integrally lowered. Concerning this matter, refer to arrow Al in  FIG. 4   b . Due to the foregoing, the adhering member  46  presses the peeling tape  4  onto the surface protection film  11  on the wafer  20 . 
         [0048]    Simultaneously, in step  103 , when the adhering member  46  presses the peeling tape  4  onto the surface protection film  11  on the wafer  20 , pressure P generated between the surface protection film  11  on the wafer  20  and the adhering member  46  is detected by the pressure sensor  92 . Next, in step  104 , the thus detected pressure P is compared with a predetermined value P 0 . The predetermined value P 0  is a value at which fractures or cracks or internal strain is not generated on the wafer  20 . This predetermined value P 0  is previously found through experiments etc. and stored in the memory of the control portion  95 . 
         [0049]    In the case where it is determined that the detected pressure P is not less than the predetermined value P 0 , the program proceeds to step  105  and the adhering member  46  is stopped from lowering and maintained at the same height. On the other hand, in the case where it is determined that the detected pressure P is not more than the predetermined value P 0 , the program returns to step  103  and the processing is repeated until the pressure P becomes a value not less than the predetermined value P 0 . 
         [0050]    As described above, in the first embodiment of the present invention, the predetermined value P 0 , at which no fractures or cracks are generated, is previously determined. In the case where pressure P is raised to a value not less than the predetermined value P 0 , the adhering member  46  is stopped from lowering, so that the pressing force given by the adhering member  46  cannot be increased anymore. Therefore, it is possible to prevent the wafer  20  from generating fractures or cracks. Especially, it is possible to prevent the end portion  28  of the wafer  20  from generating fractures or cracks. Further, it is possible to prevent the generation of internal strain on the wafer  20 . 
         [0051]    As shown in the drawing, even in the case where the wafer  20  and the mount frame  36  are integrated with each other into one body, it is not necessary to use excessive force to press the adhering member  46  in the first embodiment of the present invention. Therefore, the peeling tape  4  does not hang down. Accordingly, it is possible to prevent the peeling tape  4  and the dicing tape  3  from adhering to each other. Further, in the first embodiment of the present invention, since the pressing force given to the peeling tape  4  can be directly controlled. In the case where the thickness of the wafer  20  after the completion of back-grinding and/or the thickness of the surface protection film  11  is different, the peeling tape  4  can be adhered by the same pressing force. 
         [0052]    Referring to  FIG. 3  again, in step  106  shown in the operation program  100 , peeling operation of the surface protection film  11  is started. To be specific, as shown by arrow A 2  in  FIG. 5   a , the support table  31  is horizontally moved from the other end  29  of the wafer toward the one end  28 . At the same time, the peeling tape  4  is drawn out from the supply portion  42  and wound up by the winding portion  43 . Due to the foregoing, a portion, at which the peeling tape  4  is adhered, functions as a peeling starting portion. Therefore, the surface protection film  11  is gradually peeled off from the peeling starting portion at one end  28  of the wafer  20 . 
         [0053]    Next, when the rear end  39  of the support table  31  is moved to the predetermined position P 1  shown in  FIGS. 5   a  and  5   b , it is determined that the surface protection film  11  has been completely peeled off from the entire face of the wafer  20 . Accordingly, when a sensor (not shown) detects that the rear end  39  of the support table  31  has moved to position P 1 , the peeling tape  4  and the support table  31  stop. In this way, the peeling operation made by the surface protection film peeling device  10  is finished. 
         [0054]      FIG. 6  is a partial enlarged view showing a peeling tape adhering unit of another embodiment of the present invention. In  FIG. 6 , the pressure sensor  92  embedded in the adhering member  46  is excluded. Instead of the pressure sensor  92 , another pressure sensor  93  is arranged on the support table  31 . As shown in the drawing, the pressure sensor  93  is embedded in the support table  31  at a position corresponding to the tip portion  46   a  of the adhering member  46  which presses the peeling tape  4  onto the surface protection film  11 . In a case, in which the pressure sensor  93  is embedded in the support table  31 , is compared with a case, in which the pressure sensor  93  is embedded in the adhering member  46 , it is possible to ensure a large space. Therefore, in the embodiment shown in  FIG. 6 , it is possible to arrange a relatively large pressure sensor having high performance. 
         [0055]    The peeling tape  4 , the surface protection film  11 , the wafer  20  and the dicing tape  3  are interposed between the adhering member  46  and the pressure sensor  93 . Therefore, strictly speaking, pressure P′ detected in another embodiment shown in  FIG. 6  is different from pressure P described before. However, even in the case where pressure P′ is employed, the substantially same advantages as those described before can be provided through the operation program  100  shown in  FIG. 3 . 
         [0056]      FIG. 7  is a flow chart showing an operation program of a surface protection film peeling device having a peeling tape adhering unit of the second embodiment of the present invention. Steps  201 ,  202 ,  205  and  206  of the operation program  200  shown in  FIG. 7  are the same as steps  101 ,  102 ,  105  and  106  of the operation program  100  shown in  FIG. 3 . Therefore, explanations are omitted here. 
         [0057]    In step  203  shown in the operation program  200 , distance L between the surface protection film  11  on the wafer  20  and the adhering member  46  is detected by the distance sensor  91  shown in  FIG. 1 . In step  204 , the thus detected distance L is compared with the predetermined value L 0 . The predetermined value L 0  is the distance between the surface protection film  11  and the adhering member  46  at which fractures or cracks or internal strain is not generated on the wafer  20 . This predetermined value L 0  was found through experiments, etc., and stored in the memory of the control portion  95 . Specifically, this predetermined value L 0  is a value a little higher than zero. Alternatively, this predetermined value L 0  may be zero. 
         [0058]    In the case where it is determined that the detected distance L is not more than the predetermined value L 0 , the program proceeds to step  205  and the adhering member  46  is stopped from lowering and maintained at the same height. On the other hand, in the case where it is determined that the detected distance L is not less than the predetermined value L 0 , the program returns to step  203  and the processing is repeated until distance L becomes a value not more than the predetermined value L 0 . 
         [0059]    In the second embodiment of the present invention, the predetermined value L 0 , at which no fractures or cracks are generated, is previously determined. In the case where distance L is lowered to a value not more than the predetermined value L 0 , the adhering member  46  is stopped from lowering, so that the pressing force given by the adhering member  46  cannot be increased anymore. Accordingly, it is clear that the same advantages as those described before can be provided in the second embodiment. 
         [0060]    Of course, a combination of some of the embodiments described before is included in the scope of the present invention. The present invention includes a case in which an adhering member  46 , the cross-section of which is circular, is used, that is, the present invention includes a case in which a so-called peeling roller is used. 
         [0061]    Although the invention has been shown and described with exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be therein and thereto without departing from the scope of the invention.