Abstract:
A method of manufacturing dies formed with a dielectric layer is revealed. A liquid dielectric layer is formed on the dicing tape. The liquid dielectric layer is heated to be sticky. Then, a wafer is attached to the dielectric layer on the dicing tape. The wafer is diced into a plurality of dies on the dicing tape. The dies with attached portions of the dielectric layer are picked up to be peeled and separated from the dicing tape. The implementation of the dicing tape can be expanded to resolve various issues such as wafer contaminations, wafer warpage due to multiple heating and mismatching of thermal expansion coefficients, and wafer singulating problems due to alignment difficulties. The wafer handling steps can further be reduced to increase processing yield and to enhance easy and better processing.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method of manufacturing semiconductor devices by wafer dicing, and more particularly to a method of manufacturing dies formed with a dielectric layer. 
       BACKGROUND OF THE INVENTION 
       [0002]    In semiconductor industries, the manufacture of semiconductor devices primary divides into three stages: wafer fabrication, chip formation, and chip assembly. During wafer fabrication and chip formation processes, a dielectric layer is directly formed on a wafer for die attachment or for wafer-level packaging where the dielectric layer can be B-stage films, solid films or epoxy liquid pastes, however, solid films are more expensive. Therefore, it is more common to dispose liquid pastes on a wafer such as stencil printing on the back surface of a wafer but the wafer is easily contaminated. 
         [0003]      FIG. 1  is the block diagram of a conventional process flow for manufacturing dies with a dielectric layer. Step  1  is to provide a wafer. Step  2  is to attach a protecting tape to the active surface of the wafer to avoid contamination of liquid dielectric materials on the active surface in sequent steps. Step  3  is to turn the wafer upside down with the back surface facing upward. Step  4  is to form a dielectric layer on the back surface of the wafer by stencil printing or any known liquid disposition methods where the cover area of the dielectric layer should be smaller than the one of the back surface of the wafer to avoid liquid bleeding to the sides of the wafer or even to the protecting tape. Step  5  is to thermally cure the dielectric layer on the wafer to reach certain degree of dryness and curing to avoid serious bleeding in Step  6 . In step  5 , since the dielectric layer is thermally cured, dimension shrinkage due to curing is unavoidable. Moreover, the wafer is also under heating at the same time, there is a thermal mismatching issue due to different thermal expansion coefficients and dimensions between the wafer and the dielectric layer. Then, step  6  is to turn the back surface of the wafer downward to attach to a dicing tape so that the dielectric layer is attached to the dicing tape by the adhesion of the dicing tape. Afterward, step  7  is to remove the protecting tape to expose the active surface of the wafer. Then, step  8  is to dice the wafer into a plurality of individual dies. Finally, step  9  is to pick up the dies from the dicing tape. Therefore, the wafer with the dielectric layer will experience multiple heating steps leading to serious wafer warpage issues due to mismatching of thermal expansion coefficients and dimensions, more the worse, the curing shrinkage of dielectric layer causing wafer handling difficulties in the following processes. Furthermore, since the wafer has to go through multiple turning steps, the risk of lower yields and higher cost is relatively increased. Once the back surface of the wafer is not turned upside down in step  6  and the protecting tape is not removed to expose the active surface in step  7 , singulation in step  8  has to be done from the back surface of a wafer where scribe line alignment for wafer dicing processes becomes difficult. 
       SUMMARY OF THE INVENTION 
       [0004]    The main purpose of the present invention is to provide a method of manufacturing dies formed with a dielectric layer to resolve contamination of dielectric layer on the active surface of a wafer as well as the wafer warpage due to multiple heating steps exerted on a wafer during formation of dielectric layer and mismatching of thermal expansion coefficients and dimensions. Moreover, the wafer turning steps are decreased to achieve higher yields with lower cost. 
         [0005]    The second purpose of the present invention is to provide a method of manufacturing dies formed with a dielectric layer is to resolve wafer damages due to turning wafers for wafer dicing processes as well as alignment issues due to wafer dicing from the back surface of a wafer leading to easy and better processing. 
         [0006]    According to the present invention, a method of manufacturing dies formed with a dielectric layer is revealed, primarily comprising the following steps: Firstly, a dicing tape is provided. A liquid dielectric layer is formed on the dicing tape. The liquid dielectric layer is heated to be sticky, i.e., in B-staged or partially cured state. A wafer is attached to the dielectric layer on the dicing tape. The wafer and the dielectric layer are diced to form a plurality of dies each having a certain portion of the dielectric layer attached. The dies are picked up with the corresponding attached portions of the dielectric layer are peeled and separated from the dicing tape. 
         [0007]    The method of manufacturing dies formed with a dielectric layer according to the present invention has the following advantages and functions:
   1. Through the sequence of processing steps by preforming the dielectric layer on the dicing tape then the wafer is attached as a technical means, dicing tape can commonly implement in formation of dielectric layer as well as in wafer dicing step to resolve the contamination of dielectric layer on the active surface of the wafer as well as the wafer warpage due to multiple heating steps exerted on the wafer during formation of dielectric layer and mismatching of thermal expansion coefficients and dimensions. Moreover, the wafer turnover time is also decreased to achieve higher yields with lower cost.   2. Through the sequence of processing steps by performing the dielectric layer on the dicing tape then the wafer is attached as a technical means, dicing tape can commonly implement in formation step of dielectric layer as well as in wafer dicing step to expose the active surface of the wafer to resolve wafer damages due to turning wafers for wafer dicing processes as well as alignment issues due to wafer diced from the back surface of a wafer leading to easy and better processing.   3. Through the assembly of a spin-coating stage and positioning ring and the sequence of processing steps as a technical means, the excess bleeding of dielectric layer can be accommodated by the annular groove on the spin-coating stage to avoid bleeding contamination of dielectric layer to the attaching area of positioning ring.   4. Through the dielectric layer having the characteristic of multiple-curing stages and transferred from the dicing tape to the wafer as a technical means, the preformed dielectric layer can replace the conventional adhesive film as die-attaching paste or encapsulant for wafer level packaging to reduce the cost.   
 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a process flow block diagram for a conventional method of manufacturing dies formed with a dielectric layer. 
           [0013]      FIG. 2  is a process flow block diagram for a method of manufacturing dies formed with a dielectric layer according to the first embodiment of the present invention. 
           [0014]      FIGS. 3A to 3G  are the cross-sectional views of components in processing steps during the method according to the first embodiment of the present invention. 
           [0015]      FIGS. 4A to 4G  are the three-dimensional views and cross-sectional views of components in the processing steps during the method according to the second embodiment of the present invention. 
           [0016]      FIGS. 5A to 5C  are enlarged cross-sectional views of components from the formation step of the dielectric layer to the wafer attaching step during the method according to the second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    With reference to the attached drawings, the present invention is described by means of the embodiment(s) below where the attached drawings are simplified for illustration purposes only to illustrate the structures or methods of the present invention by describing the relationships between the components and assembly in the present invention. Therefore, the components shown in the figures are not expressed with the actual numbers, actual shapes, actual dimensions, nor with the actual ratio. Some of the dimensions or dimension ratios have been enlarged or simplified to provide a better illustration. The actual numbers, actual shapes, or actual dimension ratios can be selectively designed and disposed and the detail component layouts may be more complicated. 
         [0018]    According to the first embodiment of the present invention, a method of manufacturing dies formed with a dielectric layer is illustrated in  FIG. 2  for process flow block diagram and  FIGS. 3A to 3G  for the cross-sectional views of components in processing steps during the method. The method of manufacturing dies formed with a dielectric layer primarily comprises the steps as shown in  FIG. 2  where the detail description of each step is described as follows. 
         [0019]    Firstly, step  11  is performed to provide a dicing tape  110 , as shown in  FIG. 3A . The dicing tape  110  can be a UV blue tape or other photosensitive adhesive tapes to firmly hold the dies during wafer singulation processes without separation where the adhesion of the dicing tape  100  can be reduced or eliminated by radiating UV light in the following processes. The dicing tape  110  is attached to a stage  140  in order to keep the dielectric layer  120  horizontal (as shown in  FIG. 3C ). The stage  140  can be a hot plate to heat the dielectric layer  120  during wafer attaching step which will be explained in detail in step  14 . Preferably, a positioning ring  170  is attached to the peripheries of the dicing tape  110  to support the dicing tape  110  in step  11  so that the wafer  130  is not damaged nor deformed during processing. Normally, the positioning ring  170  can be made of metal such as stainless steel, aluminum, iron, etc. having an opening larger than the attached wafer  130  (as shown in  FIG. 3E ). 
         [0020]    Then, step  12  is performed to form a liquid dielectric layer  120  on the dicing tape  110 , as shown in  FIG. 3C , where the dielectric layer  120  has the characteristic of multiple-curing stages. In the present embodiment, the dielectric layer  120  can be formed on the dicing tape  110  by stencil printing. For example, a stencil  150  is placed on top of the dicing tape  110  as shown in  FIG. 3A , and then a scraper  160  scraps a liquid dielectric material  121  into the stencil  150  as shown in  FIG. 3B . After removing the stencil  150  and the scraper  160 , the dielectric layer  120  transformed from the liquid dielectric material  121  is formed on the dicing tape  110  as shown in  FIG. 3C . The liquid dielectric layer  120  is formed in a printed pattern not smaller than the attaching area of the wafer  130  (as shown in  FIG. 3E ) to allow larger alignment tolerance for easy wafer attachment to enhance the processing steps. 
         [0021]    Next, step  13  is performed to heat the liquid dielectric layer  120  to be sticky as shown in  FIG. 3C  again. In the present embodiment, the liquid dielectric layer  120  is heated by the hot plate  140  where the dielectric layer  120  becomes B-staged or in partially cured state. Therefore, a conventional wafer heating step is eliminated, moreover, the shrinkage of the dielectric layer  120  due to curing will have no effect on the wafer  130 . 
         [0022]    Next, step  14  is performed to attach a wafer  130  to the dielectric layer  120  on the dicing tape  110  as shown in  FIGS. 3D and 3E . Therein, the wafer  130  is attached to the dielectric layer  120  by heating the dielectric layer  120  and pressing the wafer  130 . In the present embodiment, the attaching surface of the wafer  130  adhered by the dielectric layer  120  can be the back surface  132  to make the dielectric layer  120  as a die-attaching adhesive. Even the dielectric layer  120  is bleeding, the active surface  133  of the wafer  130  will not be contaminated to resolve the conventional formation of dielectric layer by multiple heating steps leading to wafer warpage issues and to simplify wafer turnover time to meet the requirements of higher yields with lower cost. In another embodiment, the attaching surface of the wafer  130  for attaching the dielectric layer  120  can be the active surface  133  to make the dielectric layer  120  as a wafer-level packaging layer. 
         [0023]    Next, step  15  is performed to dice the wafer  130  and the dielectric layer  120  as shown in  FIG. 3F . A blade  180  cuts through the wafer  130  and the dielectric layer  120  to form a plurality of individual dies  131  (as shown in  FIG. 3G ). Each die  131  has a certain portion  122  of dielectric layer  120  attached, i.e., the cutting depth of the blade  180  exceeds the thickness of the wafer  130  and the dielectric layer  120  without cutting through the dicing tape  110 . Preferably, after step  15 , the adhesion of the dicing tape  110  to the diced dielectric layer  120  can be reduced or eliminated by radiating UV light. 
         [0024]    Next, step  16  is performed to pick up the dies  131  as shown in  FIG. 3G  Since the dielectric layer  120  is also diced in step  15 , each die  131  is attached with a certain portion  122  of the dielectric layer  120 . In step  16 , the attached portions  122  of the dielectric layer  120  are peeled and separated from the dicing tape  110  when the dies  131  are picked up by a sucker  190 . Furthermore, preferably, the dielectric layer  120  has the characteristic of multiple-curing stages so that the dielectric layer  120  is still adhesive after picking up the dies  131  to be a die-attaching adhesive for die attachment where the dielectric layer  120  can replace the conventional die-attaching film without extra dispensing, printing, or placing die-attaching materials to be low-cost die-attaching materials. 
         [0025]    According to the second embodiment of the present invention, another method of manufacturing dies formed with a dielectric layer is illustrated from  FIG. 4A  to  FIG. 4G  for the three-dimensional views and cross-sectional views of components in the processing steps and from  FIGS. 5A to 5C  for enlarged cross-sectional views of components from the formation step of the dielectric layer to the wafer attaching step. The components used in the method of manufacturing dies with dielectric layer according to the present embodiment are almost the same as the ones in the first embodiment, therefore, the same component numbers are used. 
         [0026]    As shown in  FIG. 4A , firstly in step  11 , a dicing tape  110  is provided where the dicing tape  110  can be a UV blue tape. The dicing tape  110  is placed on a spin-coating stage  240  for keeping the dielectric layer  120  horizontal (as shown in  FIG. 5B ) in step  12 . The spin-coating stage  240  can be a hot plate to heat the dielectric layer  120  to remove solvent inside in step  13  and to become more adhesive during attaching the wafer  130  (as shown in  FIG. 5C ) in step  14 . Preferably, as shown in  FIGS. 5A to 5C , the spin-coating stage  240  has an annular groove  241  so that the portions of the dicing tape  110  located on the annular groove  241  concavely deform when the dicing tape  110  is fixed by a suction force from the spin-coating stage  240 . 
         [0027]    As shown in  FIG. 4D , a liquid dielectric layer  120  is formed on the dicing tape  110  where the liquid dielectric layer  120  has the characteristic of multiple-curing stages. In the present embodiment, the dielectric layer  120  can be disposed on the dicing tape  110  by spin coating where the actual operations are shown in  FIGS. 4B and 4C . Drops of liquid dielectric material  121  are disposed at the center of the dicing tape  110  on the spin-coating stage  240 . Simultaneously, the spin-coating stage  240  spins to spread the liquid dielectric material  121  as shown in  FIG. 4C  and further to form the liquid dielectric layer  120  as shown in  FIG. 4D . As shown in  FIG. 5A , when the excess liquid dielectric material  121  is dispensed which will bleed out during spin coating, the excess liquid dielectric material  121  may be accommodated in deformed portions of the dicing tape  110  on the annular groove  241  to avoid contaminations of the excess liquid dielectric material  121  bleeding to the peripheral area during spin coating. Then, the dielectric layer  120  is heated to be sticky, such as in B-staged or in partially cured state, as shown in  FIG. 5B  and  FIG. 4D . 
         [0028]    In the present embodiment, as shown in  FIG. 4D  and  FIG. 5B , a positioning ring  170  is attached to the peripheries of the dicing tape  110  after the dropping sub-step mentioned above. Preferably, the positioning ring  170  is not in direct contact with the dielectric layer  120  by accommodation of the annular groove  241 . Then, as shown in  FIG. 4D  and  FIG. 5C , a wafer  130  is attached to the dielectric layer  120  on the dicing tape  110  by pressing to make the wafer  130  closely and smoothly attach to the dielectric layer  120  and the bleeding of the dielectric layer  120  can be accommodated by the annular groove  241 , as shown in  FIG. 5C . During attaching the wafer  130 , the dielectric layer  120  is heated to be adhesive. As shown in  FIG. 4E , the positioning ring  170  carrying with the dicing tape  110 , the dielectric layer  120  and the wafer  130  can easily be released from the stage  240 . 
         [0029]    As shown in  FIG. 4F , a blade  180  dices the wafer  130  and the dielectric layer  120  alone the scribe lines to form a plurality of individual dies  131  (as shown in  FIG. 4G ). Each die  131  has certain portions  122  of the dielectric layer  120  attached (as shown in  FIG. 4G ). Therein, the attached surface of the wafer  130  by the dielectric layer  120  is a back surface  132  with an exposed active surface  133  facing upward. Then, the dicing tape  110  is radiated with UV light to reduce or eliminate the adhesion for easily picking up dies in the following processes. As shown in  FIG. 4G , the dies  131  are picked up by a sucker  190  where the corresponding attached portions  122  diced from the dielectric layer  120  are peeled and separated from the dicing tape  110 . 
         [0030]    Therefore, according to the present invention of manufacturing dies formed with a dielectric layer, the dicing tape  110  can commonly be implemented in formation of dielectric layer  120  and in wafer dicing processes. One of the most specific functions is that when the dielectric layer  120  is formed and attached to the wafer  130 , the active surface  133  of the wafer  130  is exposed facing upward to resolve wafer damages due to turning wafers for conventional wafer dicing processes as well as alignment issues due to wafer dicing from the back surface of a wafer to enhance easy processing. 
         [0031]    The above description of embodiments of this invention is intended to be illustrative but not limited. Other embodiments of this invention will be obvious to those skilled in the art in view of the above disclosure which still will be covered by and within the scope of the present invention even with any modifications, equivalent variations, and adaptations.