Abstract:
A semiconductor structure fabrication method for removing a tape physically attached to a device side of the semiconductor substrate by an adhesive layer of the tape, wherein the adhesive layer comprises an adhesive material. The method includes the step of submerging the tape in a liquid chemical comprising monoethanolamine or an alkanolamine for a pre-specified period of time sufficient to allow for a separation of the tape from the semiconductor substrate without damaging devices on the semiconductor substrate.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Technical Field  
         [0002]     The present invention relates to tape removal, and more particularly, to tape removal in semiconductor structure fabrication.  
         [0003]     2. Related Art  
         [0004]     In a typical semiconductor structure fabrication process, a wafer can be coated with a UV (Ultraviolet) tape on the wafer&#39;s device side (i.e., the top side) so as to protect the devices on the wafer while the wafer&#39;s other side (i.e., the bottom side) can be grinded so as to make the wafer thinner. After that, the UV tape can be exposed to UV light so as to make the UV tape come off the wafer without causing any damage to the devices on the wafer. However, during the grinding process, the UV tape may be subjected to high temperatures which can cause the UV tape to lose such a characteristic (i.e., the characteristic of detaching itself from the wafer after being exposed to UV light). If so, trying to remove the UV tape from the wafer may cause damage to the devices on the wafer. As a result, there is a need for a novel method for removing the UV tape from the device side of the wafer essentially without causing any damage to the devices on the wafer.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention provides a semiconductor structure fabrication method, comprising (a) providing (i) a semiconductor substrate and (ii) a tape physically attached to a device side of the semiconductor substrate by an adhesive layer of the tape, wherein the adhesive layer comprises an adhesive material; and (b) submerging the tape in a liquid chemical comprising monoethanolamine for a pre-specified period of time sufficient to allow for a separation of the tape from the semiconductor substrate without damaging devices on the semiconductor substrate.  
         [0006]     The present invention also provides a semiconductor structure fabrication method, comprising (a) providing (i) a semiconductor substrate and (ii) a tape physically attached to a device side of the semiconductor substrate by an adhesive layer of the tape, wherein the adhesive layer comprises an adhesive material; and (b) submerging the tape in a liquid chemical comprising an alkanolamine for a pre-specified period of time sufficient to allow for a separation of the tape from the semiconductor substrate without damaging devices on the semiconductor substrate.  
         [0007]     The present invention also provides an apparatus, comprising (a) a semiconductor substrate and a tape physically attached to a device side of the semiconductor substrate by an adhesive layer of the tape, wherein the adhesive layer comprises an adhesive material; and (b) a body of a liquid chemical comprising essentially only monoethanolamine, wherein the tape is submerged in the body of the liquid chemical.  
         [0008]     The present invention provides a novel method for removing the UV tape from the device side of the wafer essentially without causing any damage to the devices on the wafer. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  illustrates a semiconductor structure, in accordance with embodiments of the present invention.  
         [0010]      FIG. 2  is an enlarged view of a region of the semiconductor structure of  FIG. 1 , in accordance with embodiments of the present invention.  
         [0011]      FIG. 3  illustrates an apparatus for removing a UV (Ultraviolet) tape from the semiconductor structure of  FIG. 1 , in accordance with embodiments of the present invention.  
         [0012]      FIG. 4  illustrates a chemical reaction associated with the operation of the apparatus of  FIG. 3 , in accordance with embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]      FIG. 1  illustrates a cross section view of a semiconductor structure  100 , in accordance with embodiments of the present invention. The semiconductor structure  100  can comprise a semiconductor substrate  110  coated on top with a UV (Ultraviolet) tape  122 , 124 . In other words, the UV tape  122 , 124  is physically attached to the device side of the semiconductor substrate  110 . The device side is the side of the semiconductor substrate  110  on which semiconductor devices (e.g., transistors, resistors, capacitors, etc.) are fabricated. Coating the device side of the semiconductor substrate  110  with the UV tape  122 , 124  can protect the devices on the device side of the semiconductor substrate  110  (i) while the semiconductor substrate  110  is back grinded on the bottom side (opposite to the device side) to make the semiconductor substrate  110  thinner or (ii) while the semiconductor substrate  110  is cut into chips on the bottom side (called chip dicing).  
         [0014]     In one embodiment, the UV tape  122 , 124  can comprise a frame layer  122  and an adhesive layer  124  physically attaching the frame layer  122  to the semiconductor substrate  110 . The adhesive layer  124  can comprise an adhesive material that is capable of attaching itself to a rugged surface of an object (not shown). The adhesive material can have a gel state and is capable of attaching itself to the rugged surface of the object by filling tiny holes and trenches at the rugged surface.  
         [0015]      FIG. 2  illustrates an enlarged view of a region  126  of  FIG. 1 . It can be seen from  FIG. 2  that the adhesive layer  124  physically attaches the frame layer  122  to the semiconductor substrate  110  by filling tiny holes  210  at the surface  212  of the frame layer  122  and by filling tiny holes  220  at the surface  222  of the semiconductor substrate  110 .  
         [0016]     In one embodiment, the adhesive material of the UV tape  122 , 124  can have a characteristic of contracting (reduction in size) and losing elasticity when being exposed to UV light. As a result, in one embodiment, the UV tape  122 , 124  can be removed from the semiconductor substrate  110  by first exposing the UV tape  122 , 124  to UV light (the frame layer  122  can comprise a material transparent to UV light so that UV light can reach the adhesive layer  124 ). Then, the UV tape  122 , 124  can be peeled off the semiconductor substrate  110  essentially without damaging the devices on the semiconductor substrate  110 .  
         [0017]     Alternatively, the UV tape  122 , 124  can be removed from the semiconductor substrate  110  by submerging the semiconductor substrate  110  coated with the UV tape  122 , 124  in 100% monoethanolamine (NH2-CH2-CH2-OH) in room conditions (23° C. temperature, 1 atm pressure) for 4 to 6 hours. As a result, the UV tape  122 , 124  comes off the semiconductor substrate  110  by itself or can be peeled off the semiconductor substrate  110  without damaging the devices on the semiconductor substrate  110 .  
         [0018]      FIG. 3  illustrates an apparatus  300  for removing the UV tape  122 , 124  from the semiconductor structure  110  of  FIG. 1 , in accordance with embodiments of the present invention. Illustratively, the apparatus  300  can comprise a vessel  310  and an exhaust hood  320  positioned directly above the vessel  310 . The vessel  310  can contain 100% monoethanolamine  312 . The semiconductor substrate  110  coated with the UV tape  122 , 124  can be submerged in the monoethanolamine  312  in room conditions (23° C. temperature, 1 atm pressure) for 4 to 6 hours. As a result, the UV tape  122 , 124  comes off semiconductor substrate  110  by itself as seen in  FIG. 3  or can be peeled off the semiconductor substrate  110  without damaging the devices on the semiconductor substrate  110 . The exhaust hood  320  can be used to collect any released gases that may be created in the process (i.e., submerging in the vessel).  
         [0019]     The inventors of the present invention have found that if the semiconductor substrate  110  coated with the UV tape  122 , 124  is submerged in the monoethanolamine  312  for more than 6 hours, the devices at top of the semiconductor substrate  110  can be damaged by the monoethanolamine. However, if the semiconductor substrate  110  coated with the UV tape  122 , 124  is submerged in the monoethanolamine  312  for less than 4 hours, it is likely that the UV tape  122 , 124  does not come off the semiconductor substrate  110  by itself, and trying to peel the UV tape  122 , 124  off the semiconductor substrate  110  may damage the devices at top of the semiconductor substrate  110 .  
         [0020]     The inventors of the present invention have also found that if the semiconductor substrate  110  coated with the UV tape  122 , 124  is submerged in the monoethanolamine  312  in room conditions for 4 to 6 hours, the UV tape  122 , 124  comes off the semiconductor substrate  110  by itself or can be peeled off the semiconductor substrate  110  without damaging the devices on the semiconductor substrate  110 , even if the UV tape  122 , 124  has earlier been (i) exposed to UV light or (ii) subjected to high temperatures (i.e., above 100° C.), or both (i) and (ii).  
         [0021]     The effect of monoethanolamine can be explained as follows. When the semiconductor substrate  110  coated with the UV tape  122 , 124  is submerged in the monoethanolamine  312 , monoethanolamine chemically reacts with and breaks Ester bonds (—COOH—) in the adhesive material of the adhesive layer ( FIGS. 1 and 2 ) causing the adhesive material to disintegrate. As a result, the UV tape  122 , 124  comes off the semiconductor substrate  110  by itself or can be peeled off the semiconductor substrate  110  without damaging the devices on the semiconductor substrate  110 .  
         [0022]      FIG. 4  illustrates the chemical reaction between a monoethanolamine atom and an Ester bond. The letters C, H, O, and N represent carbon, hydrogen, oxygen, and nitrogen atoms, respectively. R and R′ each represents a group of atoms. R and R′ may or may not have chemical bond(s) with each other besides via the —COO— Ester bond. The chemical reaction between the monoethanolamine atom and the Ester bond can be described as follows. The N atom  410  releases an H atom  420  so that the N atom can attach to the C atom  430  of the Ester bond thereby breaking the single bond between the C atom  430  and the O atom  440  and forming the product A in the process. The released H atom  420  combines with the O—R′ group to form product B. With the Ester bonds in the adhesive material of the adhesive layer  124  being broken, with reference to  FIG. 2 , the adhesive layer  124  disintegrates and the UV tape  122 , 124  comes off the semiconductor substrate  110  by itself or can be peeled off the semiconductor substrate  110  without damaging the devices on the semiconductor substrate  110 .  
         [0023]     Monoethanolamine diluted in water can have the same effect (i.e., the removal of the UV tape  122 , 124 ) as 100% monoethanolamine, although it may take longer (i.e., longer than 6 hours) to get the same result as in the case in which 100% monoethanolamine is used. Ambient temperature and pressure conditions other than room conditions may accelerate or delay the final result (i.e., the removal of the UV tape  122 , 124 ) compared with from 4 to 6 hours if the removal process is performed in room conditions (23° C. temperature, 1 atm pressure).  
         [0024]     In the embodiments above, monoethanolamine is used to remove the UV tape  122 , 124  ( FIG. 1 ). In general, monoethanolamine can be used to remove any tape from the semiconductor substrate  110  if the tape is physically attached to the semiconductor substrate  110  by an adhesive material that disintegrates when chemically reacting with monoethanolamine.  
         [0025]     In the embodiments above, monoethanolamine is used to remove the UV tape  122 , 124  ( FIG. 1 ). In general, another alkanolamine can be used. An alkanolamine can be defined as having the formular: H 3-n N[(CH 2 ) m (HCOH)(R)] n , wherein m can be 1 or 2, R can be H or C 1 -C 3  alkyl, and n can be 1, 2, or 3. For example, when m=n=1, the alkanolamine is monoethanolamine.  
         [0026]     While particular embodiments of the present invention have been described herein for purposes of illustration, many modifications and changes will become apparent to those skilled in the art. Accordingly, the appended claims are intended to encompass all such modifications and changes as fall within the true spirit and scope of this invention.