Abstract:
A method for bonding patterned imprint by transferring is disclosed, which comprises the following steps: (a) providing a first module having a molding substrate, a molding layer and a patterned molding features, and a second module having a substrate; wherein said molding layer and said patterned molding features are located on said molding substrate; (b) coating a release layer on said molding features; (c) filling a transfer layer into the recess which is located between the patterned molding features; (d) coating an adhesion layer on said substrate of said second module; (e) combining and contacting said second module and said first module together for transferring said transfer layer to said substrate of said second module; and (f) separating said second module from said first module.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a method for bonding and transferring patterned imprint by, and more particularly, to a method and apparatus for fabricating integrated circuits and various nano-devices through bonding and transferring imprints.  
           [0003]    2. Description of Related Art  
           [0004]    It is known that the conventional photolithography used for manufacturing integrated circuit have to achieve several complicate steps subsequently. These complicate steps include coating photoresist, pre-baking, exposure, post-baking, etching and developing. For performing these subsequent steps in the photolithography, a plurality of expensive machines (e.g. a Deep UV Scanner, etc.) is required. In conventional photolithography, the minimum width of lines on the chips are frequently achieved or controlled by a Deep UV Scanner. However, owing to the limit of the wavelength of the light used in the Deep-UV Scanner, it is very difficult to form a line having a width in nanoscale order (i.e. &lt;100 nm).  
           [0005]    Currently, most of the chips having line width in nanoscale order are achieved through “Nanoimprint Lithography” or “Step and Flash Imprint Lithography⇄. Both of them can massively produce chips having nanoscale width imprint. However, they also suffer some serious drawbacks. Taking nanoimprint lithography method for example, high temperature and high pressure are required in this method. The substrate will be distorted owing to thermal expansion when it is heated. Also, the precision of the line width of the imprint is badly affected. On the other hand, the materials that can be applied for step and flash imprint lithography method and their sources are seriously limited. Therefore, the application of the step and flash imprint lithography method is not popular. Moreover, since etching is required in both “Nanoimprint Lithography” and “Step and Flash Imprint Lithography”, the procedure of these two methods for forming final patterns in nanoscale is inevitably complicate.  
           [0006]    The method of imprint lithography was disclosed in U.S. Pat. No. 5,772,905, which teached that a mold having at least one protruding feature was firstly pressed into a film on a substrate, and then the patterns in the mold were replaced in the film after the mold was removed from the film. However, it was a complicated step to pressed the mold into the film because a sufficiently high molding pressure was needed to transfer the mold pattern to the film, which might need some thermal treatment to become softening simultaneously. The pressure and heating temperature must be precisely controlled, which was not easy to achieve. Besides, the thin film in the recess was removed by etching process, which made the method of imprint lithography more complicated.  
           [0007]    The method of step and flash imprint lithography was disclosed in U.S. Pat. No. 6,334,960. The method disclosed in U.S. Pat. No. 6,334,960 is shown in FIG. 7( a ) to  7 ( e ). The procedure is achieved first by making the transfer layer  720  on the substrate  710  contacts with a mold  730  having a relief structure formed therein, as shown in FIG. 7( a ). Then, a solution of photo-curable polymer composition  740  is poured for filling the interspaces of the relief structures in the mold  730 , as shown in FIG. 7( b ). The photo-curable polymer composition  740  is cured through UV exposure and further form a solidified polymeric material  750  on the transfer layer  720 . The transfer layer  720  and the solidified polymeric material  750  are then subjected to an environment such that the transfer layer  720  is selectively etched relative to the solidified polymeric material  750 . As a result, a relief image is formed in the transfer layer  720 . In these processes, the materials suitable for molds, substrates and photo-sensitive polymers are limited. Besides, one of the mold or the substrate must be transparent and thermal-resistant. In addition, etching step requirement also increases the complexity of the process.  
           [0008]    A polymer bonding process for nanolithography was disclosed in Borzenko et al. (2001) Applied Physics Letters, 79 (14): 2246˜2248, wherein a PMMA film was first coated on the mold, and then transferred to a PMMA coated substrate. Nevertheless, it also needed a thermal treatment with a temperature above the glass transition temperature, which led to the thermal expansion of the mold and needed a long period of time to cool down. Also, the final etching step increased the complexity of the process.  
           [0009]    Therefore, it is desirable to provide an improved method and apparatus for bonding lithographic imprint to a substrate to mitigate and obviate the aforementioned problems. A method and apparatus for bonding lithographic imprint by adhering means is disclosed as following.  
         SUMMARY OF THE INVENTION  
         [0010]    The object of the present invention is to provide a method and apparatus for bonding and transferring lithographic imprint to a substrate by adhering means, for achieving nanoscale (&lt;100 nm) feature imprint transferring, , avoiding adverse effect on the precision of the line width caused by thermal expansion of the mold or substrate, and increasing the precision of the transferred imprints on the chips.  
           [0011]    The other object of the present invention is to provide a method and apparatus for bonding and transferring lithographic imprint by adhering means, to increase the variety of source of imprint and bonding material, simplifying the formation of the patterned imprint in nanoscale without complicate etching process, and also reducing the cost of mass production.  
           [0012]    To achieve the objects described above, the method for bonding patterned imprint by transferring, comprises the following steps: (a) providing a first module having a molding substrate, a molding layer and a patterned molding features, and a second module having a substrate; wherein said molding layer and said patterned molding features are located on said molding substrate; (b) coating a release layer on said molding features; (c) filling a transfer layer into the recess which is located between the patterned molding features; (d) coating an adhesion layer on said substrate of said second module; (e) contacting and bonding said second module and said first module together for transferring said transfer layer to said substrate of said second module without any rotation; and (f) separating said second module from said first module. These movements ensure the perfect parallelism between said first module and said second module.  
           [0013]    To achieve the objects described above, the apparatus for bonding lithographic imprint by adhering means comprises a first holder for holding and carrying a first module having a mold substrate, a molding layer and a patterned transfer layer; a second holder for holding and carrying a second module having a substrate and an adhesion layer; an aligning unit positioned at one side of said second holder for moving and aligning said first holder or said second holder; at least one sensor for sensing and parallelizing the relative positions between said first module and said second module; and a controller for receiving electrical signals from said sensor, and for transmitting signals to said first holder or said second holder for aligning said two modules; wherein said sensor transmits electrical signals of the positions of said two holders to said controller, and then said controller controls the align unit electrically to align said first holder and said second holder horizontally and to move said first holder and said second holder vertically for combining said first module and said second module. These movements ensure the perfect parallelism between said first module and said second module.  
           [0014]    In the present invention, the mold substrate can be any conventional substrates. Preferably, the mold substrate is silicon, glass, metal, ceramic or polymer substrates. The method for forming a transfer layer of the invention can be any conventional method. Preferably, the method for forming a transfer layer of the invention is spin coating, PVD—(Physical Vapor Deposition), CVD—(Chemical Vapor Deposition), plating, electroless plating, sol-gel process or FHD—(Flash Hydration Deposition).  
           [0015]    The distance (D 1 ), the width (W 1 ), the length (L 1 ) and the ratio (L 1 /W 1 ) of recesses formed on transfer layer can be any size. Preferably, D 1  ranges from 1 nm to 10 mm, W 1  ranges from 1 nm to 11 mm, and L 1 /W 1  ratio ranges from 0.1 to 10.  
           [0016]    The selection of the material of transfer layer of the present invention is in coordination with the material of adhesion layer for achieving strong bonding between the transfer layer and the adhesion layer and facilitating releasing of the relief structure. Generally speaking, the bonding between the release layer and the transfer layer is weaker than that induced between the transfer layer and the adhesion layer. The material of transfer layer may be any one of conventional transfer layer material. Preferably, the transfer layer is semi-conductors, dielectric materials, high polymer materials, metal or combinations thereof. More preferably, when the transfer layer is made of polycarbonate (PC), polymethyl methacrylate (PMMA), polyimide (PI), Epoxy resin, UV curing gel or poly t-butylarcylate (PBA), then the material of adhesion layer is polycarbonate (PC), polymethyl methacrylate (PMMA), polyimide (PI), Epoxy resin, UV curing gel or poly t-butylarcylate (PBA) and the combinations thereof. Moreover, when the material of transfer layer is silver, lead-tin alloy, or other metal or ceramics, the material of adhesion layer is preferred to be gold, silver, lead-tin alloy, Epoxy resin, or UV curing gel, etc. Furthermore, tinsels (made with silver or aluminum, etc.) may be added into the polymer material to increase the electric and heat conductivities.  
           [0017]    Transfer layer can be stick onto adhesion layer by contacting each other directly with suitable selection of both materials (i.e. transfer layer and adhesion layer). Besides, external force may be applied for bonding the modules by any conventional methods. Preferably, the external force is heat, pressure, exposure of laser pulses or ultraviolet, vacuum or ultrasonication. The external force can be determined based on the material chosen of transfer layer and adhesion layer. If both of transfer layer and adhesion layer are formed with PMMA, the method for bonding the transfer layer on the adhesion layer may be heating (at a temperature higher than Tg), pressurization (under a pressure about 5 MPa). In addition, exposure to laser pulses (e.g. KrF with wavelength of 248 mm or XeCl with wavelength of 308 mm for 20 ns duration,) for a very short period of time (about 200 ns) is another suitable option for the external force. In addition, if the adhesion layer is photo-sensitive polymer and the transfer layer is PMMA, the photo-sensitive polymer could be exposed to an ultraviolet light and then become adhesive with PMMA, i.e. the transfer layer. Moreover, if the transfer layer is made of lead-tin alloy and the adhesion layer is made of lead-tin alloy or gold, then ultra-sonication may be used for cold welding these two layers (i.e. the transfer layer and the adhesion layer). Some of the examples mentioned above are listed in table 1 below.  
                       TABLE 1                       Materials of the   Matched materials of           transfer layer   the adhesion layer   Adequate external force                   Polymers   Non-photo-sensitive   Heat, pressure, vacuum, laser           polymer   pulses       Polymers   Photo-sensitive   Ultraviolet           polymer       Metals   Lead-tin alloy,   Heat (thermal soldering),           soldered tin,   ultrasonication, laser pulses           photo-sensitive   (cold welding)           polymer                  
 
           [0018]    Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    FIGS.  1 ( a )˜ 1 ( d ) are cross-sectional views illustrating the process flow of Example 1 of the present invention;  
         [0020]    FIGS.  2 ( a )˜ 2 ( d ) are cross-sectional views illustrating the process flow Example 2 of the present invention;  
         [0021]    FIGS.  3 ( a )˜ 3 ( d ) are cross-sectional views illustrating the process flow of Example 3 of the present invention;  
         [0022]    FIGS.  4 ( a )˜ 4 ( b ) are cross-sectional views illustrating the process flow of Example 4 of the present invention;  
         [0023]    [0023]FIG. 5 illustrates the apparatus for bonding lithographic imprints by adhering means of the present invention;  
         [0024]    [0024]FIG. 6 is a flow chart illustrating the method for bonding patterned imprint by transferring of the present invention; and  
         [0025]    FIGS.  7 ( a )˜ 7 ( e ) are cross-sectional views illustrating the process flow of the prior art. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     EXAMPLE 1  
       [0026]    With referring to FIGS.  1 ( a )˜ 1 ( d ), there are cross-sectional views for illustrating the process flow (of Example 1) of the present invention. As shown in FIGS.  1 ( a )˜ 1 ( d ), a first module  10  having a molding substrate  12 , a molding layer  13  and a patterned molding features  14  was first provided. The molding substrate  12  and the molding layer  13  of the present invention may be two independent layers or integrated into a unity. In the present example, the molding substrate  12  and the molding layer  13  were integrated into a unity. Then, the patterned molding features  14  were coated with a release layer  15 . Besides, a second module  20  having a substrate  21  on which an adhesion layer  22  forms was also provided. Preferably, the material of the adhesion layer  22  was a photo-sensitive polymer.  
         [0027]    With referring to FIG. 1( b ), the material of transfer layer  16  was filled into the recess located between the patterned molding features  14 . In the present example, the transfer layer  16  was preferred to be a PMMA layer, which had a pattern complementary to that of the molding features  14 . After the molding features  14  and the substrate  21  had been aligned, the contact surface  16   a  of the PMMA transfer layer  16  of the first module  10  was combined and contacted with the photo-sensitive polymer adhesion layer  22  of the second module  20 , as shown in FIG. 1( c ). At this time, an external force F, which was preferred to be the ultraviolet irradiation was exerted to form a strong bonding between the PMMA transfer layer  16  and the photo-sensitive polymer adhesion layer  22 . After the UV irradiation was stopped, the transfer layer  16  and the release layer  15  could be separated easily because the external force F induces a strong bonding force between the transfer layer  16  and the adhesion layer  22 , which is larger than that between the transfer layer  16  and the release layer  15 . In other words, the bonding between the release layer  15  and the transfer layer  16  is weaker than that induced between the transfer layer  16  and the adhesion layer  22 . Thus, the second module  20  having the transfer layer  16  formed thereon is obtained, as shown in FIG. 1( d ).  
       EXAMPLE 2  
       [0028]    With reference to FIGS.  2 ( a )˜ 2 ( d ), there are cross-sectional views for illustrating the process flow of Example 2 of the present invention. With Referring to FIGS.  2 ( a )˜( d ), all the steps were very similar to that of Example 1, except that the depth L 1  of the pattern formed on the transfer layer  16  could be larger than or equal to the depth L 2  of the patterned molding features  14 . When L 1  was larger than L 2 , a continuous thin film  16   b  would form on the surface of the patterned molding features  14 , as shown in FIG. 2( b ). However, such a continuous thin film would not cause damages while being a bond between the transfer layer  16  and the adhesion layer  22 . On the contrary, the continuous thin film  16   b  increased the bonding surface between the transfer layer  16  and the adhesion layer  22 , which led to strong bonding there between.  
       EXAMPLE 3  
       [0029]    FIGS.  3 ( a )˜ 3 ( d ) are cross-sectional views for illustrating the process flow of Example 3 of the present invention. With referring to FIG. 3( a )˜ 3 ( d ), all the steps of Example 3 were very similar to that of Example 1, except that a transfer layer  16 ′ having an irregular cross-section was formed, which was formed through using a patterned molding feature  14  having an irregular cross-section. The irregular shape of the patterned molding features  14  would produce a complementary pattern in the recesses, which thus formed a transfer layer  16 ′ having an irregular cross-section. After the steps of the method of the present invention had been carried out, the irregular shape of the patterned molding feature  14  would be transferred to the transfer layer  16 ′ on the second module.  
       EXAMPLE 4  
       [0030]    FIGS.  4 ( a )˜ 4 ( b ) were cross-sectional views for illustrating the process flow of Example 4 of the present invention. FIG. 4( a ) shows the cross-section of the second module  20  on which the transfer layer  16  is formed. The transfer layer  16  could act as a lithographic mask for carrying out dry or wet etching, through which the substrate was patterned, as shown in FIG. 4( b ).  
         [0031]    Furthermore, the transfer layer could be formed repeatedly at the same location on the substrate of the second module to produce a transfer layer composed of multi-laminates. Also, the transfer layer could be bonded onto the substrate step by step.  
       EXAMPLE 5  
       [0032]    [0032]FIG. 5 illustrates the apparatus of the present invention, which comprised a first holder  50  for carrying the first module  10  having the molding substrate  12 , the molding layer  13 , the patterned molding features  14 , and the transfer layer  16 ; a second holder  51  for carrying the second module  20  having the substrate  21  and the adhesion layer  22 ; an align unit  53  positioned at one side of the second holder  51  for removing the first holder  50  or the second holder  51  for aligning the first module  10  with the second module  20 ; an external force output unit (not shown) for enhancing the bonding force; at least one sensor  54  for sensing the relative position of the first module  10  and the second module  20 ; and a controller  55  for receiving the signals from the sensor  54  and then further outputting a removing signals to the first holder  50  or the second holder  51  in order to adjust or align the relative position of the two modules  10 , 20 . After the horizontal position had been aligned, the first holder  50  are also arranged parallel to the second holder  51  in vertical position for subsequent process. The first holder  50  and the second holder  51  are then moved vertically for bonding the first module  10  and the second module  20  without rotation (neither horizontally nor vertically). These movements ensure the perfect parallelism between said first module and said second module.  
       EXAMPLE 6  
       [0033]    [0033]FIG. 6 is a flow chart illustrating the method for bonding patterned imprints by transferring of the present invention. First, the parameters were inputted into the controller  55 , and then a preliminary alignment was carried out between the first holder  50  carrying the first module  10  and the second holder  51  carrying the second module  20  after the controller  55  had received the inputted signals. Afterwards, a sensor detected the relative position of the first holder  50  and the second holder  51 , which was then feed-backed to the controller  55 . After that, the controller  55  outputted a signal again to the align unit  53  for performing precise alignment. After the horizontal position had been aligned by the align unit  53 , the first holder  50  and the second holder  51  were removed vertically for bonding the first module  10  and the second module  20 . At the same time, another signal was transmitted to the external force output unit, which subsequently made the two modules bond with each other. Finally, the external force was released and removed vertically for separating the two modules, and the patterned imprint was formed on the second module  20 .  
         [0034]    The apparatus for bonding lithographic imprints by adhering means of the present invention can optionally further comprises a light source, a heater, an ultra-sonicator or a pressurization unit for exerting the external force and bonding the two modules. As a result, the pattern of the transfer layer of the first module is transferred to the adhesion layer of the second module.  
         [0035]    Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.