Patent Document

CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit of French patent application number 10/54472, filed on Jun. 8, 2010, entitled “METHOD FOR MANUFACTURING SEMICONDUCTOR CHIPS FROM A SEMICONDUCTOR WAFER,” which is hereby incorporated by reference to the maximum extent allowable by law. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for manufacturing semiconductor chips from a semiconductor wafer. 
     2. Discussion of the Related Art 
     The manufacturing of semiconductor chips especially comprises steps during which components and interconnect metallizations are formed inside and on top of a semiconductor wafer, followed by a step during which the wafer is cut into individual chips, for example, by means of a saw. Various individual chip testing steps are generally provided after the cutting. 
       FIGS. 1A ,  1 B and  2 A,  2 B schematically illustrate steps of a method for cutting a semiconductor wafer  10  into individual chips by means of a saw.  FIGS. 1A and 2A  are top views and  FIGS. 1B and 2B  respectively are cross-section views along planes B-B of  FIGS. 1A and 2A . 
       FIGS. 1A and 1B  illustrate an initial step in which wafer  10  is arranged on a surface of an adhesive film  12  stretched on a support frame  14 . Generally, wafer  10  has an approximately round shape and frame  14  has a round inner contour with a diameter greater than the diameter of wafer  10 . In this example, the outer contour of frame  14  has a generally approximately square shape with rounded corners and comprises location notches  16 . 
     The specific shape of frame  14 , and more specifically of its outer contour, enables to accurately position the wafer in a processing machine, for example, a sawing machine. In a given production line, frame  14  generally is an element of standard shape and dimension, used at various steps of the manufacturing during which the wafer should be maintained on a support. Thus, the various machines of a given manufacturing line are provided to receive a type of support frame  14 , of given shape and dimensions. 
       FIGS. 2A and 2B  illustrate the actual operation of cutting of wafer  10  into individual chips  18 . The cutting is conventionally performed by means of a circular saw (not shown) running through the wafer along a grid of lines and columns. The cutting is performed across the entire thickness of the wafer and stops in the upper portion of adhesive film  12 , without however cutting this film. It should be noted that, in practice, a semiconductor wafer comprises a much greater number of elementary chips  18  than what has been shown. It should be noted that generally, the semiconductor wafer is not perfectly circular but has a flat side, not shown, enabling to align all wafers in the same way with respect to frame  14 . 
     After the wafer has been cut, the individual chips remain on frame  14 , and other manufacturing steps may be provided, during which the cut wafer is processed in machines capable of receiving frame  14 . Such steps for example are a visual inspection of the chips, a probe test, a marking of defective chips, etc. Adhesive film  12  especially enables chips  18  to remain in place during these steps and during subsequent transportations of frame  14 . 
     In some cases, the user or the customer desires to receive the cut chips to assemble them in various electronic devices. The chips are then shipped on the support frame  14  on which they have been cut. On reception of the chips, the test and/or inspection steps may be implemented again by using equipment capable of receiving frame  14 . The actual mounting of the chips, for example, their mounting on printed circuit boards, is also carried out by means of machines capable of receiving frame  14 . 
     The different manufacturers and users of semiconductor chips do not necessarily use the same support frame standards. Now, generally, given equipment is equipped to receive frames of a single standard. Accordingly, in such a production system, a manufacturer of semiconductor chips using a given type of frame can only sell his production to users equipped to receive this type of frame. 
       FIGS. 3 and 4  are top views schematically showing, respectively, a frame  34  and a frame  44 , corresponding to two standards much used in the art to support wafers having a 20-cm diameter (approximately 8 inches), that is, standard FF-108 and standard FF-105. Frames  34  and  44  have approximately identical general shapes but different dimensions. The general shapes of frames  34  and  44  are similar. Frame  44  has dimensions slightly smaller than the dimensions of frame  34 , and in particular outer dimensions smaller than the outer dimensions of frame  34  but greater than the inner diameter of frame  34 . In this example, the inner diameter of frame  44  is slightly smaller than the inner diameter of frame  34 . The difference in outer dimensions especially results in that the machines capable of receiving frame  34  are not capable of receiving frame  44 , and conversely. 
     It would be desirable for a manufacturer having equipment capable of receiving frame  34  to be able to sell his production to a user having equipment capable of receiving frame  44  (smaller than frame  34 ) without for one or the other of the manufacturer and of the user to have to modify his machines. 
     SUMMARY OF THE INVENTION 
     Thus, an embodiment provides a method for manufacturing semiconductor chips from a semiconductor wafer, which overcomes at least some of the disadvantages of existing methods. 
     An embodiment provides such a method capable of producing, in a production line capable of processing semiconductor wafers arranged on a frame of a first type, semiconductor chips arranged on a support frame of a second type having smaller outer dimensions than the frame of the first type. 
     An embodiment provides such a method which is easy to implement. 
     Thus, an embodiment provides a method for manufacturing semiconductor chips from a semiconductor wafer, comprising the steps of: fastening, on a first support frame, a second support frame having outer dimensions smaller than the outer dimensions of the first frame and greater than the inner dimensions of the first frame; arranging the wafer on a surface of a film stretched on the second frame; carrying out wafer processing operations by using equipment capable of receiving the first frame; separating the second frame from the first frame and removing the first frame; and carrying out wafer processing operations by using equipment capable of receiving the second frame. 
     According to an embodiment, the processing operations in equipment compatible with the first frame comprise a step during which the wafer is cut into semiconductor chips and at least one semiconductor chip test step. 
     According to an embodiment, the processing operations in equipment compatible with the second frame comprise a step of assembly of the semiconductor chips in electronic devices. 
     According to an embodiment, the first frame comprises, on the side of a surface, guiding and fastening means capable of receiving the second frame, these means being contained, in top view, within the outer contour of the first frame. 
     According to an embodiment, the outer and inner contours of the first frame respectively have a square general shape with rounded corners and a circular shape. 
     According to an embodiment, the guiding and fastening means comprise: three guide rails fastened in the vicinity of three sides of the square forming the outer contour of the first frame, these guide rails delimiting a space inside of which the second frame is capable of being inserted; and a removable lug capable of being fastened in the vicinity of the fourth side of the square forming the outer contour of the first frame. 
     According to an embodiment, the step during which the second frame is fastened to the first frame comprises the operations of: removing the removable lug from the first frame; inserting the second frame between the guide rails of the first frame; and fastening the removable lug to the first frame. 
     According to an embodiment, the separation step comprises the operations of: removing the removable lug from the first frame; and removing the second frame from the guide rails of the first frame. 
     Another embodiment provides a support frame for a semiconductor wafer, comprising, on the side of a surface, fastening means capable of receiving a second frame of outer dimensions respectively smaller than and greater than the outer and inner dimensions of the support frame, these means being contained, in top view, within the outer contour of the support frame. 
     According to an embodiment, this support frame has an outer contour of generally square shape with rounded corners and a circular inner contour, said means comprising: three guide rails fastened in the vicinity of three sides of the square forming the outer contour of the support frame, these guide rails delimiting a space inside of which the second frame is capable of being inserted; and a removable lug capable of being fastened in the vicinity of the fourth side of the support frame. 
     The foregoing and other objects, features, and advantages will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A ,  1 B and  2 A,  2 B, previously described, schematically illustrate steps of a conventional method for cutting a semiconductor wafer into individual chips by means of a saw; 
         FIG. 3 , previously described, is a top view schematically showing an example of a first type of semiconductor wafer support frame; 
         FIG. 4 , previously described, is a top view schematically showing an example of a second type of a semiconductor wafer support frame, of dimensions smaller than the dimensions of the support frame of  FIG. 3 ; and 
         FIGS. 5A ,  5 B,  5 C,  6 A,  6 B,  7 A,  7 B, and  8 A,  8 B schematically illustrate steps of a method for manufacturing semiconductor chips, capable of producing, in a production line specifically adapted to process semiconductor wafers arranged on a first frame, chips arranged on another frame of smaller outer dimensions. 
     
    
    
     DETAILED DESCRIPTION 
     For clarity, the same elements have been designated with the same reference numerals in the different drawings and, further, the various drawings are not to scale. 
       FIGS. 5A ,  5 B,  5 C,  6 A,  6 B,  7 A,  7 B, and  8 A,  8 B schematically illustrate steps of a method for manufacturing semiconductor chips, capable of producing, in a production line specifically adapted to process semiconductor wafers arranged on a frame  34  of the type described in relation with  FIG. 3 , chips arranged on a frame  44  of the type described in relation with  FIG. 4 , of outer dimensions smaller than those of frame  34 . 
       FIGS. 5A ,  6 A,  7 A, and  8 A are top views,  FIG. 5B ,  6 B,  7 B, and  8 B respectively are cross-section views along planes B-B of  FIGS. 5A ,  6 A,  7 A, and  8 A, and  FIG. 5C  is a bottom view corresponding to  FIG. 5A . 
       FIGS. 5A ,  5 B, and  5 C illustrate a step during which frames  34  and  44  are superposed, and then fastened to each other. 
     In this example, frame  34  comprises three guide rails  51   a  to  51   c  previously fastened to its lower surface, for example, by welding or by gluing, in the vicinity of three side of the square forming the outer contour of the frame. Guide rails  51   a ,  51   b , and  51   c  delimit a space inside of which frame  44  is capable of being inserted so that frames  34  and  44  are superposed, that is, their inner contours have approximately the same center in top view. The interval between two guide rails  51   a  and  51   c  fastened to opposite sides of frame  34  substantially corresponds to the outer width of frame  44 , and the distance between the center of frame  34  and third guide rail  51   b  substantially corresponds to half the outer width of frame  44 . 
     A removable lug  53  is capable of being fastened, for example by means of screws  55  (three screws in the present example), to the lower surface of frame  34 , in the vicinity of the side of frame  34  which is not provided with a guide rail  51  (on the side of frame  34  opposite to guide rail  51   b ). For this purpose, tapped holes may have been drilled in frame  34 . As an example, when lug  53  is screwed to frame  34 , the interval between lug  53  and guide rail  51   b  is substantially equal to the outer width of frame  44 . 
     To superpose frame  44  to frame  34 , mounting lug  53  is removed and frame  44  is inserted between guide rails  51   a ,  51   b , and  51   c  to have the centers of the frames coincide (in top view). To lock frame  44  in this position, mounting lug  53  is put back in place and screwed to frame  34 . At the end of this assembly step, frames  34  and  44  are superposed and firmly fastened to each other. In this example, the lower surface of frame  34  is placed against the upper surface of frame  44 . 
     Guide rails  51   a  to  51   c  and mounting lug  53  are provided to remain within the outer contour of frame  34 . Thus, in top view, the outer contour of the assembly formed by frames  34  and  44  corresponds to the outer contour of frame  34 . Such an assembly is compatible with processing machines capable of receiving frame  34 . It should be noted that the thickness difference between this assembly and frame  34  alone poses no problem of compatibility with existing equipment. It will however preferably be provided to use a specifically thinned down frame  34  so that the thickness of the assembly is as close as possible to the thickness of a standard frame  34 . 
       FIGS. 6A and 6B  illustrate a step during which a semiconductor wafer  57  is arranged on a surface of an adhesive film  59  stretched on frame  44 . The adhesiveness of film  59  allows an easy bonding of the film to the frame and of the wafer to the film. However, if film  59  is not adhesive, it may be provided to bond the film to the frame and/or the wafer to the film by means of glue or of any other adapted bonding means. In this example, film  59  is bonded on the lower surface side of frame  44 . 
       FIGS. 7A and 7B  illustrate the step during which the semiconductor wafer is cut into individual chips  58 . The cutting is conventionally performed by means of a circular saw (not shown) running through the wafer along a grid of lines and columns. Any other adapted cutting means may however be used. In this example, the cutting is performed across the entire thickness of the wafer and stops in the upper portion of adhesive film  59 , without however cutting this film. 
       FIGS. 8A and 8B  illustrate a final step where frames  34  and  44  are separated and frame  34  is removed. To achieve this, removable mounting lug  53  ( FIG. 7A ) is unscrewed and frame  44  supporting film  59  and individual chips  58  is removed from the space delimited by guide rails  51   a  to  51   c  ( FIG. 7A ). 
     The wafer cut into individual chips  58  can then be shipped to a user on frame  44 , for example, for a mounting of chips  58  in electronic devices by means of equipment which is not compatible with frame  34  but which is capable of receiving frame  44 . 
     It should be noted that other steps, not shown, for example, inspection, testing and/or marking steps, may be provided between the wafer cutting ( FIGS. 7A ,  7 B) and the separation of the frames ( FIGS. 8A ,  8 B). 
     An advantage of such a method is that it enables, by a simple operation, to produce, in a manufacturing line specifically adapted to receiving frames of a first type, semiconductor chips arranged on a frame of a second type having dimensions smaller than those of the frames of the first type. 
     Specific embodiments have been described. Various alterations, modifications and improvements will readily occur to those skilled in the art. 
     In particular, a method comprising a step during which a second smaller frame is fastened to a first frame, a step during which a wafer arranged on the second frame is cut by means of equipment compatible with the first frame, and a step of frame separation to use equipment compatible with the second frame have been described herein. The present invention is not limited to this specific case. It will be within the abilities of those skilled in the art to implement the provided method in the case where the steps of processing, by means of equipment compatible with the first frame, of a wafer arranged on the second frame, are steps other than the cutting and/or test steps. Further, the present invention is not limited to the above-mentioned case in which the processing steps implemented by means of equipment compatible with the second frame, after separation of the frames, are steps of assembly of the cut chips. 
     Further, the frames may have any other shape than those shown and described hereabove, provided however for the outer dimensions of the second frame to be smaller than the outer dimensions of the first frame and greater than the inner dimensions of the first frame. 
     Moreover, it will be within the abilities of those skilled in the art to implement the desired operation by using systems for fastening the second frame to the first frame other than the above-described system. It will however be ascertained for the used fastening system to remain contained within the outer contour of the first frame. 
     Such alterations, modifications and improvements are intended to be part of this disclosure, and are intended to be within the spirit and the scope of the present invention. Accordingly, the foregoing description is by way of example only and is not intended to be limiting. The present invention is limited only as defined in the following claims and the equivalents thereto.

Technology Category: 4