Abstract:
In some embodiments, an adhesive system for supporting thin silicon wafer is presented. In this regard, a method is introduced to bond a silicon wafer to a translucent carrier through the use of an adhesive. Other embodiments are also disclosed and claimed.

Description:
FIELD OF THE INVENTION  
       [0001]     Embodiments of the present invention generally relate to the field of processing silicon wafers, and, more particularly to an adhesive system for supporting thin silicon wafer.  
       BACKGROUND OF THE INVENTION  
       [0002]     In the process of fabricating a microelectronic wafer (hereinafter “wafer”), backside processing is performed generally after a wiring pattern is provided on the front surface of the wafer. Backside processing may include mechanical or chemical methods for thinning the wafer, such as, for example, grinding, chemical-mechanical polishing, and etching. Backside processing may further include processes other than thinning, such as, for example, thin film deposition and/or electroplating. However, backside processing tends to negatively affect the strength and rigidity of the wafer, thus increasing the likelihood that the wafer may be damaged through breakage or warping, especially where the wafer has a thickness below about 300 microns. In order to move and process a silicon wafer, it is typically attached to a more rigid carrier which provides mechanical support. The process of subsequently separating the silicon wafer from the carrier can be quite time consuming and inefficient. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]     The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements, and in which:  
         [0004]      FIGS. 1A-1C  are cross-sectional views of an example adhesive system, in accordance with one example embodiment of the invention; and  
         [0005]      FIGS. 2A-2C  are cross-sectional views of another example adhesive system, in accordance with one example embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0006]     In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that embodiments of the invention can be practiced without these specific details. In other instances, structures and devices are shown in block diagram form in order to avoid obscuring the invention.  
         [0007]     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.  
         [0008]      FIGS. 1A-1C  are cross-sectional views of an example adhesive system, in accordance with one example embodiment of the invention. In accordance with the illustrated example embodiment, adhesive system  100  may include carrier  102 , silicon wafer  104 , adhesive  106 , and bumps  108  as shown in  FIG. 1A .  
         [0009]     Carrier  102  provides mechanical support for silicon wafer  104  during handling and processing and is translucent so as to allow radiation, for example laser or ultraviolet radiation, to pass through it. Carrier  102  may be made of glass, plastic, an acrylic-based material, or any other translucent material.  
         [0010]     Silicon wafer  104  may be a raw silicon wafer or may have been processed to some extent. In one embodiment, silicon wafer  104  is to be processed into a plurality of integrated circuit chips. The backside of silicon wafer  104  may be processed through backgrinding, photolithography, wet etching, dry etching or electroplating.  
         [0011]     Adhesive  106  bonds silicon wafer  104  to carrier  102 . Adhesive  106  may have been applied first to carrier  102  or to silicon wafer  104 . In one embodiment, adhesive  106  softens or weakens when exposed to ultraviolet or laser radiation, for example radiation with a wavelength of about 355 nm, thereby allowing silicon wafer  104  to be separated from carrier  102 . In one embodiment adhesive  106  is spun on, while in another embodiment adhesive  106  is laminated on to either silicon wafer  104  and/or carrier  102 . Adhesive  106  may setup quickly or may need to be cured to harden.  
         [0012]     Bumps  108  may represent a conductive material, for example solder, that has been affixed to the top of silicon wafer  104 . In another embodiment bumps  108  are not present, and in yet another embodiment there are springs or bond pads instead of bumps.  
         [0013]      FIG. 1B  depicts an example method of separating carrier  102  from silicon wafer  104  after processing of silicon wafer  104 . In one embodiment, radiation source  110  is directed at carrier  102  and radiation  112 , which is emitted from radiation source  110 , passes through carrier  102  striking adhesive  106 . In one embodiment radiation source  110  is a laser. In another embodiment radiation source  110  is a radiation lamp. In one embodiment, radiation  112  has a wavelength of about 355 nm. Adhesive  106  may soften or decompose after absorbing the radiation, and carrier  202  may be easily removed.  
         [0014]      FIG. 1C  depicts silicon wafer  104  after being separated from carrier  102 . Remaining adhesive  106  can subsequently be removed by thermal decomposition, peeling, plasma cleaning, pellet cleaning, or chemical stripping.  
         [0015]      FIGS. 2A-2C  are cross-sectional views of another example adhesive system, in accordance with one example embodiment of the invention. In accordance with the illustrated example embodiment, adhesive system  200  may include carrier  202 , silicon wafer  204 , first adhesive  206 , and second adhesive  208  as shown in  FIG. 2A   
         [0016]     Carrier  202  provides mechanical support for silicon wafer  204  during handling and processing and is translucent so as to allow radiation, for example laser or ultraviolet radiation, to pass through it. Carrier  202  may be made of glass, plastic, an acrylic-based material, or any other translucent material.  
         [0017]     Silicon wafer  204  may be a raw silicon wafer or may have been processed to some extent. In one embodiment, silicon wafer  204  is to be processed into a plurality of integrated circuit chips. The backside of silicon wafer  204  may be processed through backgrinding, photolithography, wet etching, dry etching or electroplating.  
         [0018]     First adhesive  206  bonds carrier  202  with second adhesive  208 . First adhesive  206  may absorb radiation with a wavelength of about 355 nm causing first adhesive  206  to lose adhesion strength. First adhesive  206  may be spun on or laminated to carrier  202  and/or second adhesive  208 . In one embodiment, first adhesive  206  is less than about 10 micrometers thick. In one embodiment, first adhesive  206  is a polynorbornene polymer such as Promerus Unity 4698.  
         [0019]     Second adhesive  208  bonds silicon wafer  204  with first adhesive  206 . In one embodiment second adhesive  208  has a higher modulus than first adhesive  206 , providing stronger support for silicon wafer  204 . Second adhesive  208  may be spun on or laminated to silicon wafer  204  and/or first adhesive  206 . In one embodiment, second adhesive  208  may be easily stripped mechanically or chemically. In one embodiment, second adhesive  208  is greater than about 10 micrometers thick.  
         [0020]      FIG. 2B  depicts an example method of separating carrier  202  from silicon wafer  204  after processing of silicon wafer  204 . In one embodiment, radiation source  210  is directed at carrier  202  and radiation  212 , which is emitted from radiation source  210 , passes through carrier  202  striking first adhesive  206 . In one embodiment radiation source  210  is a laser. In another embodiment radiation source  210  is a radiation lamp. In one embodiment, radiation  212  has a wavelength of about 355 nm. First adhesive  206  may soften or decompose after absorbing the radiation, and carrier  202  may be easily removed.  
         [0021]      FIG. 2C  depicts silicon wafer  204  after being separated from carrier  202 . Second adhesive  208  can subsequently be removed by thermal decomposition, peeling, plasma cleaning, pellet cleaning, or chemical stripping.  
         [0022]     Many of the methods are described in their most basic form but operations can be added to or deleted from any of the methods and information can be added or subtracted from any of the described messages without departing from the basic scope of the present invention. Any number of variations of the inventive concept is anticipated within the scope and spirit of the present invention. In this regard, the particular illustrated example embodiments are not provided to limit the invention but merely to illustrate it. Thus, the scope of the present invention is not to be determined by the specific examples provided above but only by the plain language of the following claims.