Abstract:
A new and improved wafer support for supporting wafers in a process chamber such as an edge bead removal (EBR) chamber. The wafer support comprises multiple wafer support units each including a gripper block that engages an edge portion or bevel of the wafer. The gripper block is attached to an engaging and disengaging mechanism for selectively causing engagement of the gripper blocks with the wafer to support the wafer and disengagement of the gripper blocks from the wafer to release the wafer for removal of the wafer from the chamber. The gripper blocks contact little or none of the surface area on the patterned surface of the wafer to prevent or substantially reduce the formation of contact-induced defects on the wafer.

Description:
FIELD OF THE INVENTION 
   The present invention relates to electrochemical mechanical deposition (ECMD) systems used in the deposition of metal layers on semiconductor wafer substrates in the fabrication of semiconductor integrated circuits. More particularly, the present invention relates to a new and improved wafer support for an edge bead removal (EBR) chamber in an electrochemical plating (ECP) system, which wafer support engages the edges of the wafer to prevent contact-induced defects on the patterned surface of the wafer. 
   BACKGROUND OF THE INVENTION 
   In the fabrication of semiconductor integrated circuits, metal conductor lines are used to interconnect the multiple components in device circuits on a semiconductor wafer. A general process used in the deposition of metal conductor line patterns on semiconductor wafers includes deposition of a conducting layer on the silicon wafer substrate; formation of a photoresist or other mask such as titanium oxide or silicon oxide, in the form of the desired metal conductor line pattern, using standard lithographic techniques; subjecting the wafer substrate to a dry etching process to remove the conducting layer from the areas not covered by the mask, thereby leaving the metal layer in the form of the masked conductor line pattern; and removing the mask layer typically using reactive plasma and chlorine gas, thereby exposing the top surface of the metal conductor lines. Typically, multiple alternating layers of electrically conductive and insulative materials are sequentially deposited on the wafer substrate, and conductive layers at different levels on the wafer may be electrically connected to each other by etching vias, or openings, in the insulative layers and filling the vias using aluminum, tungsten or other metal to establish electrical connection between the conductive layers. 
   Deposition of conductive layers on the wafer substrate can be carried out using any of a variety of techniques. These include oxidation, LPCVD (low-pressure chemical vapor deposition), APCVD (atmospheric-pressure chemical vapor deposition), and PECVD (plasma-enhanced chemical vapor deposition). In general, chemical vapor deposition involves reacting vapor-phase chemicals that contain the required deposition constituents with each other to form a nonvolatile film on the wafer substrate. Chemical vapor deposition is the most widely-used method of depositing films on wafer substrates in the fabrication of integrated circuits on the substrates. 
   Due to the ever-decreasing size of semiconductor components and the ever-increasing density of integrated circuits on a wafer, the complexity of interconnecting the components in the circuits requires that the fabrication processes used to define the metal conductor line interconnect patterns be subjected to precise dimensional control. Advances in lithography and masking techniques and dry etching processes, such as RIE (Reactive Ion Etching) and other plasma etching processes, allow production of conducting patterns with widths and spacings in the submicron range. Electrodeposition or electroplating of metals on wafer substrates has recently been identified as a promising technique for depositing conductive layers on the substrates in the manufacture of integrated circuits and flat panel displays. Such electrodeposition processes have been used to achieve deposition of the copper or other metal layer with a smooth, level or uniform top surface. Consequently, much effort is currently focused on the design of electroplating hardware and chemistry to achieve high-quality films or layers which are uniform across the entire surface of the substrates and which are capable of filling or conforming to very small device features. Copper has been found to be particularly advantageous as an electroplating metal. 
   Electroplated copper provides several advantages over electroplated aluminum when used in integrated circuit (IC) applications. Copper is less electrically resistive than aluminum and is thus capable of higher frequencies of operation. Furthermore, copper is more resistant to electromigration (EM) than is aluminum. This provides an overall enhancement in the reliability of semiconductor devices because circuits which have higher current densities and/or lower resistance to EM have a tendency to develop voids or open circuits in their metallic interconnects. These voids or open circuits may cause device failure or burn-in. 
   Electrochemical mechanical deposition (ECMD) is a technique which has been developed recently for plating a conductive material on a semiconductor wafer or workpiece surface. One goal of ECMD is to uniformly fill holes and trenches on the wafer/workpiece surface with the conductive material while maintaining the planarity of the surface. During the ECMD process, a conductive material, such as copper from a typically copper anode, is applied in holes, trenches and/or other desired areas on the wafer using an electrolyte solution in the anode assembly. The electrolyte solution flows from the anode and the copper cations from the anode are reduced to form a copper layer on the wafer. 
   After the electrochemical plating process, the wafer is normally subjected to an edge bead removal, or edge bevel removal (EBR), process to remove residual copper precipitate and electrolytes from the wafer. In the EBR process, the wafer is contained in an EBR chamber and subjected to a three-step cleaning process. The first step involves rinsing the wafer with deionized water to remove residual copper electrolytes from the wafer. In a second step, the edges of the wafer are rinsed with a cleaning solution, such as sulfuric acid (H 2 SO 4 ), to remove copper precipitate from the wafer edge. Finally, the wafer is again rinsed with deionized water to remove the cleaning solution from the wafer. During the EBR process, the wafer is typically supported by a wafer support hoop in the EBR chamber. 
   A typical conventional wafer support hoop  10  is shown in FIG.  1  and includes a circular frame  12  fitted with typically at least three triangle-shaped wafer support pins  14 . As shown in  FIG. 1A , the wafer  16  rests on the wafer support pins  14 , with the patterned surface of the wafer  16  in contact with the upper surfaces of the wafer support pins  14 . One of the problems inherent in the conventional wafer support hoop  10  is that, due to the large surface area of the wafer  16  in contact with each of the wafer support pins  14 , a large quantity of residual particles tend to accumulate on the wafer support pins  14 . Consequently, particle-induced defects frequently form in the patterned surface of the wafer  16 . For example, the particles tend to scratch or peel the wafer  16  upon inadvertent movement of the wafer  16  on the wafer support pins  14  during the EBR process, as well as upon positioning or removal of the wafer  16  on or from the wafer support pins  14 . Accordingly, a new and improved wafer support for an EBR chamber is needed which minimizes or eliminates contact between the patterned surface of the wafer and the wafer support elements. 
   An object of the present invention is to provide a new and improved device for supporting a wafer in a process chamber. 
   Another object of the present invention is to provide a new and improved wafer support which prevents contamination or formation of defects on a wafer during support of the wafer in a process chamber. 
   Still another object of the present invention is to provide a new and improved wafer support which may be adapted for use in electroplating systems for semiconductor fabrication. 
   Yet another object of the present invention is to provide a new and improved wafer support which includes multiple gripping elements that engage the edges or bevels of a wafer to prevent or minimize contact of the wafer support with the patterned surface on the wafer. 
   A still further object of the present invention is to provide a new and improved wafer support which includes multiple gripping elements that may be moved into engagement with the edges of a wafer to support the wafer in a process chamber while substantially minimizing contact with the patterned surface on the wafer. 
   Yet another object of the present invention is to provide a new and improved wafer support which may include multiple wafer-gripping elements that engage the bevel or edge of a wafer at different locations on the wafer bevel or edge to support the wafer in a process chamber. 
   SUMMARY OF THE INVENTION 
   In accordance with these and other objects and advantages, the present invention is generally directed to a new and improved wafer support for supporting wafers in a process chamber such as an edge bead removal (EBR) chamber. The wafer support comprises multiple wafer support units each including a gripper block that engages an edge portion or bevel of the wafer. The gripper block is attached to an engaging and disengaging mechanism for selectively causing engagement of the gripper blocks with the wafer to support the wafer and disengagement of the gripper blocks from the wafer to release the wafer for removal of the wafer from the chamber. The gripper blocks contact little or none of the surface area on the patterned surface of the wafer to prevent or substantially reduce the formation of contact-induced defects on the wafer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  is a top view of a conventional wafer support hoop for supporting a wafer in a process chamber; 
       FIG. 1A  is a perspective view of a wafer support pin of the conventional wafer support hoop shown in  FIG. 1 , with a wafer (partially in section) shown supported by the wafer support pin; 
       FIG. 2  is a perspective view of a wafer support unit of the wafer support of the present invention, with the wafer support unit shown in the wafer-disengaging configuration; 
       FIG. 2A  is a perspective view of a wafer support unit of the wafer support of the present invention, with the wafer support unit shown in the wafer-engaging configuration; 
       FIG. 3  is a top view of a wafer support unit, with the wafer support unit shown in the wafer-disengaging configuration; 
       FIG. 4  is a side view, partially in section, of a gripper arm element of the wafer support unit; 
       FIG. 5  is a top view of a wafer support unit, with the wafer support unit shown in the wafer-engaging configuration; 
       FIG. 6  is a cross-sectional view, taken along section lines  6 — 6  in  FIG. 2 ; 
       FIG. 7  is a cross-sectional view, taken along section lines  7 — 7  in  FIG. 2A ; and 
       FIG. 8  is a top view of a typical embodiment of the wafer support of the present invention, incorporating three of the wafer support units. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention has particularly beneficial utility in supporting a semiconductor wafer in an EBR (edge bead removal) chamber of an electroplating system for the fabrication of semiconductor wafers. However, the invention is not so limited in application, and while references may be made to such EBR chamber, the present invention may be more generally applicable to supporting semiconductor wafers in other types of process chambers, as well as other substrates in a variety of industrial and mechanical applications. 
   Referring initially to  FIG. 8 , an illustrative embodiment of the wafer support  20  of the present invention typically includes at least three wafer support units  22  which are collectively adapted for supporting a wafer  58  in an EBR chamber  55 . However, it is understood that the invention may include four or more of the wafer support units  22 . The wafer support units  22  are spaced around the EBR chamber  55  in such a manner as to engage or grip respective edge portions of the wafer  58  and securely support the wafer  58  in the chamber  55  during processing, as hereinafter described. As shown in  FIGS. 2 and 2A , each of the wafer support units  22  may be similar in construction and includes a base  24  which is rotatably mounted on a shaft  26 . A piston  38  is selectively extendible from an actuating cylinder  36 , which may be air-actuated or fluid-actuated, and the extending end of the piston  38  is terminated by a piston attachment flange  40  that engages the base  24 . A stabilizing shaft  32  and an arm mount shaft  34  extend upwardly from the base  24 , typically in substantially diametrically-opposed relationship to each other. A fixed plate  28  is mounted on the shaft  26  above the base  24 . A generally arcuate stabilizing shaft slot  33  and a generally arcuate arm mount shaft slot  35  extend through the fixed plate  28  and receive the upwardly-extending stabilizing shaft  32  and arm mount shaft  34 , respectively. A spring mount rod  30  extends downwardly from the bottom surface of the fixed plate  28 , in spaced-apart relationship to the arm mount shaft  34 . A coiled tensioning spring  42  connects the spring mount rod  30  to the arm mount shaft  34  for purposes which will be hereinafter described. 
   As shown in  FIGS. 3-5 , a gripper arm  44  is mounted on the arm mount shaft  34 . The gripper arm  44  is typically disposed beneath the bottom  56  of the chamber  55 , as shown in  FIG. 4 , and may be characterized by a toggle-linkage that includes a proximal arm segment  46 , having an arm collar  46   a  which is attached to the arm mount shaft  34  in non-rotatable relationship thereto. As shown in  FIG. 4 , a distal arm segment  48  includes an arm collar  48   a  which receives a pivot pin  50  that extends through a registering arm collar  46   b  on the distal end of the proxmial arm segment  46 . A gripper block flange  51  extends upwardly from the distal end portion of the distal arm segment  48  and slidably traverses a slot  57  that extends through the bottom  56  of the EBR chamber  55 . A water-tight seal (not shown) is provided between the gripper block flange  51  and the chamber bottom  56  at the edges of the slot  57 , according to the knowledge of those skilled in the art, to prevent leakage of water or cleaning solution from the chamber  55 . 
   A gripper block  52 , which may have an elongated, generally rectangular shape, is mounted on the gripper block flange  51 , above the chamber bottom  56 . The gripper block  52  is constructed of a soft, pliable plastic or rubber material and includes a longitudinal wafer groove  53 . In a preferred embodiment, the gripper block  52  has a height “A”, shown in  FIG. 4 , of typically about 1 cm and a thickness “B” of typically about 1-1.5 cm. The length or longitudinal dimension of the gripper block  52  is typically about 3 cm, and the depth of the wafer groove  53  is typically from about 0.5 cm to about 1 cm. However, it is understood that the gripper block  52  may have other dimensions without departing from the spirit and scope of the invention. 
   In typical operation of the wafer support  20 , the multiple wafer support units  22  are typically operated in concert with each other to simultaneously engage and support a wafer  58  in the EBR chamber  55  for EBR processing and disengage the wafer  58  during subsequent removal of the wafer  58  from the chamber  55  after processing, as follows. Accordingly, although the multiple wafer support units  22  operate in conjunction with each other, each of the wafer support units  22  is operated in the following manner. As shown in  FIG. 3 , when the piston  38  is retracted into the actuating cylinder  36 , the gripper arm  44  is positioned in such a manner that the distal arm segment  48  is disposed at an acute angle “θ” with respect to the proxmial arm segment  46  and the gripper block  52  is disengaged from the wafer  58 . At that time, the wafer  58  is held in place in the chamber  55  typically by a wafer transfer robot (not shown), in conventional fashion. As the piston  38  is extended from the actuating cylinder  36 , as shown in  FIG. 5 , the blase  24  is rotated typically in the counterclockwise direction, as indicated by the arrow  60 , such that the arm mount shaft  34  traverses the arcuate arm mount shaft slot  35 . Simultaneously, and in like manner, the stabilizing shaft  32  traverses the stabilizing shaft slot  33  and facilitates smooth movement of the arm mount shaft  34  in the arm mount shaft slot  35 . Furthermore, the tensioning spring  42 , normally in the flaccid configuration of  FIGS. 2 and 6  and biasing the gripper arm  44  and gripper block  52  in the wafer-disengaging position, is tensioned or stretched between the moving arm mount shaft  34  and the stationary spring mount rod  30 , as shown in  FIGS. 2A and 7 . Consequently, the gripper block  52  approaches the wafer  58  until the wafer groove  53  of the gripper block  52  receives the edge of the wafer  58 . Continued movement of the arm mount shaft  34  in the arm mount shaft slot  35  in the direction of the arrow  60  in  FIG. 5  causes the gripper block  52  to securely engage the edge of the wafer  58  in the wafer groove  53 . Therefore, the resistance imparted against the gripper block  52  by the stationary wafer  58 , in combination with continued movement of the arm mount shaft  34  in the arm mount shaft slot  35 , causes the distal arm segment  48  to pivot on the pivot pin  50  until the distal arm segment  48  is disposed at an obtuse angle “θ” with respect to the proximal arm segment  46  and the wafer groove  53  rides along the edge of the wafer  58  until the edge portion of the wafer groove  53  in the gripper block  52  receives the edge of the wafer  58 , as shown in FIG.  5 . It will be appreciated from a consideration of  FIG. 4  that the gripper block  52  contacts the wafer  58  at both the upper and lower edges thereof, and little or no contact is made between the gripper block  52  and the upper and lower surfaces of the wafer  58 . At that point, the wafer transfer robot (not shown) releases the wafer  58 , which is securely supported by the gripper blocks  52  of the respective wafer support units  22 , as shown in FIG.  8 . During an EBR process, the wafer  58  is typically subjected to a three-step process in which the wafer  58  is rinsed with water, solvent and water, respectively. After completion of the EBR or other process, the wafer transfer robot again engages the wafer  58 , after which the piston  38  of the wafer support uflit  22  is retracted into the actuating cylinder  36 . This action, imparted by the retracting piston  38  under assistance by the contracting tensioning spring  42 , facilitates typically clockwise rotation of the base  24 , as indicated by the arrow  61  in  FIG. 3 , in such a manner that the stabilizing shaft  32  and the arm mount shaft  34  traverse the respective stabilizing shaft slot  33  and arm mount shaft slot  35 , the distal arm segment  48  pivots with respect to the proximal arm segment  46  to define the acute angle “θ” shown in  FIG. 3 , and the gripper block  52  disengages the edge or bevel of the wafer  58 . Finally, the wafer transfer robot removes the wafer  58  from the chamber  55 , typically in conventional fashion. 
   While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications can be made in the invention and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.