Abstract:
A method for plating includes positioning a substrate facing a plating solution. The method also includes immersing the substrate into the plating solution while plating a layer of material over a surface of the substrate, wherein an immersion speed of the substrate is about 100 millimeters per second (mm/s) or more while at least one portion of the substrate contacts the plating solution.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to semiconductor methods and fabrication apparatus thereof, and more particularly to methods for plating and fabrication apparatus thereof. 
         [0003]    2. Description of the Related Art 
         [0004]    With advances associated with electronic products, semiconductor technology has been widely applied in manufacturing memories, central processing units (CPUs), liquid crystal displays (LCDs), light emission diodes (LEDs), laser diodes and other devices or chipsets. In order to achieve high-integration and high-speed goals, dimensions of semiconductor integrated circuits continue to shrink. Various materials and techniques have been proposed to achieve these integration and speed goals and to overcome manufacturing obstacles associated therewith. In order to achieve these targets, copper (Cu) technology has been used in highly integrated circuits to reduce resistance of metal structures therein. 
         [0005]      FIG. 1  is a schematic cross-sectional view showing a prior art method for electrical plating a copper layer over a substrate. A substrate  100  is held by a substrate holder  120 . A shaft  130  is configured to move, rotate and tilt the substrate  100  held by the substrate holder  120 . During an electrical plating process, a current is applied to the substrate  100  via the shaft  130 . The substrate holder  120  holding the substrate  100  is moved toward a plating solution  115  confined within a plating cell  110  in the direction indicated by the arrow  140 , while the substrate  100  is rotated and tilted to an angle with respect to the surface of the plating solution  115 . Generally, the immersion speed of the substrate  100  is less than 100 millimeters per second (mm/s). The plating solution  115  is provided for electroplating a layer of copper on the surface of the substrate  100 . Because the substrate  100  is tilted with an angle, the portion  100   a  of the substrate  100  is immersed in the plating solution  115  earlier than the remaining portion of the substrate  100 . The portion  100   a  is generally referred to as the “immersion side” of the substrate  100  and subjected to the electrical plating process first. 
         [0006]    The material begins being plated on the surface of the substrate  100  when the portion  100   a  of the substrate  100  touches the top surface of the plating solution  115 , because a current path is provided from an anode of a power supply (not shown), the plating cell  110 , plating solution  115 , immersed portion  100   a , substrate holder  120 , shaft  130  to a cathode of the power supply (not shown). Once the portion  100   a  of the substrate  100  touches the top surface of the plating solution  115 , charge carriers will crowd at the portion  100   a  due to its small area. A vigorous electrochemical reaction occurs at the portion  100   a  of the substrate  100 , resulting in fast copper plating on the portion  100   a . The fast plated copper on the portion  100   a  is non-uniform and rough. This is generally referred to as “hazy phenomenon.” When the immersion speed of the substrate  100  is reduced, this phenomenon becomes worse, because charge carriers will crowd at the portion  100   a  longer. 
         [0007]    From the foregoing, plating methods and plating apparatus thereof are desired. 
       SUMMARY OF THE INVENTION 
       [0008]    In accordance with some exemplary embodiments, a method for plating comprises the steps of: (a) positioning a substrate facing a plating solution; and (b) immersing the substrate into the plating solution while plating a layer of material over a surface of the substrate, wherein an immersion speed of the substrate is about 100 millimeters per second (mm/s) or more while at least one portion of the substrate contacts the plating solution. 
         [0009]    In accordance with some exemplary embodiments, an apparatus for plating comprises an enclosure, a plating cell, a substrate holder, a shaft and an actuator. The plating cell comprises a plating solution introduced therein. The enclosure is operable toward the plating cell. The substrate holder is disposed within the enclosure and operable facing toward the plating cell. The shaft is configured to perform at least one function comprising moving, rotating and tilting the substrate holder. The actuator is coupled to the shaft, wherein the actuator is configured to actuate the shaft to move the substrate holder toward the plating cell with a relative speed about 100 millimeters per second (mm/s) or more, while at least one portion of the substrate contacts the top surface of the plating solution. 
         [0010]    The above and other features of the present invention will be better understood from the following detailed description of the preferred embodiments of the invention that is provided in connection with the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Following are brief descriptions of exemplary drawings. They are mere exemplary embodiments and the scope of the present invention should not be limited thereto. 
           [0012]      FIG. 1  is a schematic cross-sectional view showing a prior art method for electrically plating a copper layer over a substrate. 
           [0013]      FIG. 2A  is a schematic cross-sectional view of an exemplary plating apparatus. 
           [0014]      FIG. 2B  is a schematic cross-sectional view of another exemplary plating apparatus. 
           [0015]      FIG. 3  is a flowchart showing an exemplary plating process. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]    This description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. 
         [0017]      FIG. 2A  is a schematic cross-sectional view of an exemplary plating apparatus. A plating apparatus  200  is provided for electrochemical plating or electroless plating, for example. In some embodiments, the plating apparatus  200  comprises an enclosure  210 , a plating cell  220 , a substrate holder  230 , a shaft  235  and an actuator  240 . The enclosure  210  comprises an opening (not shown) corresponding to the plating cell  220 . The opening provides a path through which a substrate, such as substrate  215 , can be loaded to or unloaded from the substrate holder  230 . The substrate  215  can be a silicon substrate, III-V compound substrate, display substrate such as a liquid crystal display (LCD), plasma display, electro luminescence (EL) lamp display, or light emitting diode (LED) substrate (collectively referred to as, substrate  215 ), for example. In some embodiments, the substrate  215  comprises a structure (not shown), such as a via/contact hole or a dual-damascene opening, upon which a layer of material, such as copper or other plating material, is to be formed. 
         [0018]    The enclosure  210  is operable toward the plating cell  220 . In some embodiments, the enclosure  210  is connected with the plating cell  220  as shown in  FIG. 2A . For example, the enclosure  210  is fixed and the plating cell  220  is configured to seal the opening of the enclosure  210 ; the plating cell  220  is fixed and the enclosure  210  is configured to connect with the plating cell  220  to seal the opening of the enclosure  210 ; or both of the enclosure  210  and plating cell  220  are operable toward each other so that the plating cell  220  can be connected with the enclosure  210  to seal the opening of the enclosure  210 . In other embodiments, the enclosure  210  is not connected with the plating cell  220 . For example, the enclosure  210  and the plating cell  220  do not seal the opening of the enclosure  210 . The plating cell  220  may have a sidewall  221  whose top surface  221   a  is higher than a surface  225   a  of a plating solution  225  as shown in  FIG. 2B . 
         [0019]    The plating cell  220  comprises a space (not shown) for accommodating the plating solution  225  so that a plating process can be performed therein. In some embodiments, the plating cell  220  comprises at least one valve (not shown) coupled to a delivery system (not shown) for introducing and/or draining the plating solution  225  into and/or from the plating cell  220 . The plating solution  225  comprises chemical of a material that is to be plated over the surface  215   c  of the substrate  215 . In some embodiments, the plating solution may comprise a catholyte solution including a desired amount of acid, halides, supporting electrolyte, additives and/or other components. 
         [0020]    The substrate holder  230  is disposed within the enclosure  210  and operable facing toward the plating cell  220 . The substrate holder  230  comprises, for example, a clamp, knob clamp, clip, electrostatic chuck, or other device that is adapted to fasten the substrate  215  to the substrate holder  230 . The shaft  235  is configured to move (translate), rotate and/or tilt the substrate holder  230 . 
         [0021]    The actuator  240  is coupled to the shaft  235 . The actuator  240  can be, for example, a motor driving device to move (i.e., translate), rotate and/or tilt the substrate holder  215 . In some embodiments, the actuator  240  comprises, for example, a motor (not shown) to actuate the shaft  235 . The actuator  240  is adapted to actuate the shaft  235  to move the substrate holder  215  toward the plating cell  220  with a relative speed of about 100 millimeters per second (mm/s) or more in the directions indicated by double-sided arrow  245 , for example. 
         [0022]    In some embodiments, the plating apparatus  200  further comprises a rotational speed controller  250 . The rotational speed controller  250  is coupled to the actuator  240  and can transmit a signal to the actuator  240  to rotate the substrate holder  230  (about a normal to a surface of the substrate) with a rotational speed between about 5 revolutions per minute (rpm) and about 90 rpm in the direction indicated by arrow  265 , for example. In some embodiments, the plating apparatus  200  further comprises an angle controller  260 . The angle controller  260  is coupled to the actuator  240  and can transmit a signal to the actuator  240  to tilt the substrate holder  230  to an angle between about 1° and about 5° with respect to the surface of the plating solution in the directions indicated by double-sided arrow  255 , for example. In some embodiments, the plating apparatus  200  further comprises a power supply  270 . The power supply  270  may be coupled to the substrate holder  230  via the shaft  235 , for example. The power supply  270  may provide a current density between about 2.8 milliamperes per square centimeter (mA/cm 2 ) and about 14 mA/cm 2  to the substrate holder  230  for electrical plating. 
         [0023]      FIG. 3  is a flowchart showing an exemplary plating process. In step  300 , a substrate, e.g., the substrate  215  shown in  FIG. 2A , is loaded to the substrate holder  230  (shown in  FIG. 2A ). As described above, the substrate  215  can be fastened to the substrate holder  230  by a clamp, for example. 
         [0024]    In step  310 , the actuator  240  (shown in  FIG. 2A ) actuates the shaft  235  to move the substrate  215  held by the substrate holder  230  toward the top surface of the plating solution  225  filled within the plating cell  220 . During this step, the substrate  215  has not yet touched or been immersed into the plating solution  225 . In some embodiments, the surface  215   c  of the substrate  215  is substantially parallel to the top surface of the plating solution  225  during the period of step  310 . In some embodiments, the speed of the substrate  215  held by the substrate holder  230  moved by the shaft  235  toward the top surface of the plating solution  225  is about 50 mm/s during this period. 
         [0025]    In step  320 , the angle controller  260  transmits a signal to the actuator  240  to actuate the shaft  235  to tilt the substrate holder  230  so that the surface  215   c  of the substrate  215  facing the plating solution  225  has an angle between about 1° and about 5° with respect to the top surface of the plating solution  225 . 
         [0026]    In step  330 , the rotational speed controller  250  transmits a signal to the actuator  240  to actuate the shaft  235  to rotate the substrate holder  230  so that the substrate  215  is rotated about a normal to a surface of the substrate with a speed between about 5 revolutions per minute (rpm) and about 90 rpm. 
         [0027]    In some embodiments, the sequence of steps  310 - 330  is adjustable. For example, step  330  may be performed before step  320 . In other embodiments, at least two of the three steps can be performed at approximately the same time. In some embodiments, steps  320  and  330  are not performed until the substrate  215  contacts or is immersed into the plating solution  225 . 
         [0028]    In step  340 , the substrate  215  is immersed into the plating solution  225  for plating. In some embodiments, the immersion speed of the substrate  215  held by the substrate holder  230  is about 100 mm/s or more, as soon as at least one portion, e.g., portion  215   a , of the substrate  215  contacts the plating solution  225 . The portion  215   a  of the substrate  215  may be, for example, a point or small area at which the substrate  215  contacts the top surface of the plating solution  225 . The immersion speed of the substrate  215  can be, for example, gradually increased from the speed, e.g., of about 50 mm/s, described in step  310  to the speed of about 100 mm/s or more. The substrate  230  is then completely immersed into the plating solution  225  with the speed of about 100 mm/s or more until the last portion, e.g. portion  215   b , of the substrate  215  is immersed under the top surface of the plating solution  225 . 
         [0029]    In some embodiments, the immersion speed of the substrate  215  is between about 100 mm/s and about 120 mm/s during the period between the time the portion  215   a  of the substrate  215  begins contacting the top surface of the plating solution  225  and the time when the whole surface  215   c  of the substrate  215  is immersed under the top surface of the plating solution  225 . In some embodiments of electrical plating, the power supply  270  provides a current density between about 4.2 mA/cm 2  and about 8.4 mA/cm 2  during this period. Because the immersion speed of the substrate  215  is higher than about 100 mm/s, the period during which current crowds on the portion  215   a  of the substrate  215  is sufficiently short so that the hazy phenomenon described above can be effectively reduced or prevented. In some embodiments, the hazy phenomenon can be further reduced or prevented by rotating the substrate  215  with a speed between about 5 revolutions per minute (rpm) and about 90 rpm. By rotating the substrate  215 , the portion of the substrate  215  contacting the plating solution  225  is rotated so that the charge carriers will not crowd at the same region, i.e., the hazy phenomenon will not occur at the same area. 
         [0030]    In some embodiments, the substrate  215  is titled by the shaft  235  so that the surface  215   c  of the substrate  215  has an angle between about 1° and about 5° with respect to the surface of the plating solution  225 , while the portion  215   a  contacts the top surface of the plating solution  225 . The substrate  215  is tilted to reduce or prevent bubbles within the plating solution  225  from being blocked under the surface  215   c  of the substrate  215 . The bubbles may be created by, for example, a plating solution delivery system (not shown) which introduces the plating solution  225  into the plating cell  220 . The bubbles may be blocked under the surface  215   c  of the substrate  215 , while the substrate  215  is being immersed into the plating solution  225 . The bubbles may adversely affect physical uniformity and/or electrical characteristics of the material plated on the surface  215   c  of the substrate  215 , specifically at a region where devices or circuits with feature sizes are formed. In still other embodiments, the substrate  215  is immersed into the plating solution  225  in such a way that the surface  215   c  of the substrate  215  is substantially parallel to the top surface of the plating solution  225  as long as the bubbles within the plating solution  225  are not a concern. 
         [0031]    In some embodiments, the immersion speed of the substrate  215  is between about 120 mm/s and about 400 mm/s during the period between the time when the portion  215   a  of the substrate  215  begins contacting the top surface of the plating solution  225  and the time when the whole surface  215   c  of the substrate  215  is immersed under the top surface of the plating solution  225 . For electrical plating, the power supply  270  may provide a current density between about 4.2 mA/cm 2  and about 8.4 mA/cm 2  to the substrate  215 , for example. In some embodiments, the surface  215   c  of the substrate  215  may be substantially parallel to the top surface of the plating solution  225  because the immersion speed of the substrate  215  is sufficiently high so that bubbles within the plating solution  225  may not be blocked under the surface  215   c  of the substrate  215 . Accordingly, the substrate  215  is not tilted. 
         [0032]    Further, due to the high immersion speed, e.g., between about 120 mm/s and about 400 mm/s, rotation of the substrate  215  may be omitted, because the substrate  215  can be immersed into the plating solution  225  in a short period of time, so that current crowding described above can be reduced or prevented. Accordingly, the hazy phenomenon described above can be effectively reduced or prevented. In these embodiments, steps  320  and  330  described above are omitted. 
         [0033]    In other embodiments, the substrate  215  fastened by the substrate holder  230  is rotated between about 5 rpm and about 90 rpm in order to reduce or prevent current crowing effect as described above. In still other embodiments, the substrate  215  may be tilted so that the surface  215   c  of the substrate  215  has an angle between about 1° and about 5° with respect to the surface of the plating solution  225 . The inventor has determined that in some embodiments, for a given motor, the tilt angle of the substrate  215  is correlated with the immersion speed of the substrate  215 . For example, assume the tilt angle is 2° and the immersion speed is 300 mm/s. If the substrate  215  is tilted to an angle of about 4°, the immersion speed is reduced to 150 mm/s, i.e., the larger the tilt angle, the slower the immersion speed. Accordingly, a large tilt angle, e.g., more than 5°, may affect the immersion speed of the substrate  215 . 
         [0034]    In step  350 , the actuator  240  stops moving the substrate  215  so that the substrate  215  is immersed in the plating solution  225  for plating. During the period that the whole surface  215   c  of the substrate  215  is immersed under the top surface of the plating solution  225 , and the moving of the substrate  215  stops, the immersion speed of the substrate  215  can be gradually reduced to zero, for example. In other embodiments, after being immersed in the plating solution  225 , the actuator  240  maintains substantially the same immersion speed applied to the substrate  215  as set forth in connection with step  340  for a period of time, and then the immersion speed of the substrate  215  is gradually reduced to zero. 
         [0035]    In step  360 , after a desired layer of material is plated over the substrate  215 , the actuator  240  removes the substrate  215  from the plating solution  225 . 
         [0036]    Although the present invention has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly to include other variants and embodiments of the invention which may be made by those skilled in the field of this art without departing from the scope and range of equivalents of the invention.