Abstract:
An alignment system includes two or more alignment devices arranged in close proximity and sharing a common processing device. The alignment devices are located adjacent to one another, yet while one substrate is being processed, a second substrate can be prepared for processing without affecting or interfering with the first substrate, thereby resulting in greater utilization of the process resource.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to alignment systems for inspecting or processing substrates used for production in the semiconductor industry. In particular, the invention relates to alignment systems for use with vision inspection systems or laser scribing systems and the like. 
     2. Brief Description of the Related Art 
     Robot manipulated substrates used for production in the semiconductor industry, including semiconductor wafers, flat panels, reticles, and the like, usually require accurate orientation and placement relative to a mark or indicator before a processing step can be applied. The steps of identifying initial substrate orientation and placement before aligning the substrate to a known position, called “profiling,” consume a significant portion of the total substrate process time budget and impact the throughput of substrate material in the system. Typically during the substrate handling or aligning steps, the processing station remains inactive which equates to smaller yields and wasted resources. 
     To minimize the processing station idle time, robot-based substrate handlers traditionally utilize multiple end effector transport mechanisms and prealignment stations that mechanically center and profile substrate orientation marks for use in subsequent processing steps. Prealigning is a process of orienting and centering a substrate on the robot end effector so that an orientation mark, such as a flat or notch on the substrate surface, is set at a predefined angle and the substrate center is positioned at a predefined location on the end effector. Prealigning ensures that successively processed substrates are all oriented with the mark in the same direction and centered during the process. Prealigner-equipped systems typically use a robotic substrate handler which prealigns the end effector with respect to the substrate material, picks up the substrate material from a sourcing device, and then delivers the substrates to a process module for processing. 
     Processing a substrate exemplarily involves using a scribing system to mark the substrate surface in a desired location based upon the substrate profiling information. The substrates introduced into a process module are oriented and placed relative to the orientation and placement restrictions imposed by the equipment. The robotic substrate handler then moves to another sourcing device to retrieve a second substrate. 
     If the first substrate is improperly placed or misaligned, the design of these alignment systems requires the robotic substrate handler to traverse the processing station to recover the misplaced or misaligned substrate and attempt to correct the substrate&#39;s orientation or position problem in the process module. The robotic substrate handler will then re-traverse the processing station and return to the second substrate, still waiting in its sourcing device. This realignment process repeats until the first substrate is properly oriented and positioned in the process module. These physical alignment and orientation corrections may require significant time to complete and accordingly decrease the system throughput of substrate material. 
     Accordingly, it would be desirable to provide a multi-chamber, shared resource substrate processing system, whereby while one processing station performs the necessary orientation and placement for substrate profiling, a second processing station can prepare a second substrate for alignment and substrate profiling. 
     SUMMARY OF THE INVENTION 
     The present invention relates to dual alignment mechanisms in close proximity to a shared processing device and the method of use thereof. Substrate alignment devices and related technology improve system throughput for substrate processing equipment, and particularly for substrate scribing equipment. 
     In accordance with one aspect of the present invention, there is provided an alignment system having at least two alignment devices in close proximity to one processing device (e.g., a marking device) such that two substrates can extend into the processing area of the processing device. The processing device is able to process one substrate without affecting or interfering with another substrate being prepared for processing. The alignment devices rotate but do not lift to reorient the substrate, thus eliminating mechanical reorientation of the substrate by the robot. The present invention utilizes information collected by a sensing system of the alignment devices to adjust the laser beam during the marking of the substrate surface. 
     In accordance with an additional aspect of the present invention, the method for processing a substrate using the substrate processing system includes the steps of transporting a substrate to an alignment device for processing and then sensing the orientation and position of the substrate relative to the alignment device. While the processing system prepares the substrate for processing, by adjusting the orientation and position of the substrate with respect to the alignment device, the processing system can transport a second substrate to a second alignment device. 
     The device, while novel in and of itself, is utilized in conjunction with the method of using two or more alignment devices in adjacent modules to share process resources, where the process resources are a substrate scribing system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described in greater detail with reference to the embodiments illustrated in the accompanying drawing, in which like elements bear like reference numerals, and wherein: 
     FIG. 1 is a top view of an aligning system in accordance with the present invention; 
     FIG. 2 is a top view of the aligning system with two substrates positioned by a robot at respective alignment stations; 
     FIG. 3 is a side view of the aligning system with three bar code reading systems located above the cassette stations and a scribing system; 
     FIG. 4 top view of a substrate misaligned with respect to the chuck by a distance A and an angle α; and 
     FIG. 5 perspective view of a process resource. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in the drawings, a substrate alignment system  10  for aligning and processing substrates includes one or more substrate sourcing devices  12 ,  32 ,  40 , a robotic substrate handler  16  with an end effector  42 , a process module  14 , and a process resource  24  (FIG.  3 ). Each substrate sourcing device  12 ,  32 ,  40  (e.g., cassette station) contains at least one substrate  18 ,  38 . An example of a substrate  18  having a reference flat  52  or notch on the substrate surface  54  is shown in FIG.  4 . After profiling a substrate  18 ,  38  in the process module  14 , the substrate is oriented such that a laser beam  26  can mark a scribing area  74  of the substrate surface  54 . 
     FIGS.  1 - 4  illustrate one embodiment of a substrate alignment system  10  in accordance with the invention. In the system  10 , a robotic substrate handler  16  includes at least two linkages and a distal-most link  60  supports an end effector  42  which contacts the substrates  18 ,  38 . The robotic substrate handler  16  may be driven by a series of belts and pulleys or by any other known drive mechanism. End effector  42  of the robotic substrate handler  16  allows the handler to transport substrates  18 ,  38  between various regions in the system, such as substrate sourcing devices  12 ,  32 ,  40 , process module  14 , etc. 
     In operation of this embodiment of the substrate alignment system, the end effector  42  removes a substrate  18  from a sourcing device  12  and moves the substrate to an alignment station  28  in the process module  14 . As most clearly shown in FIG. 2, the substrate  18  is placed on a chuck  22  in the alignment station  28  wherein at least a portion of the substrate  18  lies within a processing zone  44 . The chuck  22  supports and rotates the substrate  18  about a Z axis, with the substrate maintaining its position on the chuck preferably by suction between the substrate and chuck. 
     A sensing system  20 , such as a lighthouse, mounted by a post  58  above the rotating chuck  22  includes a light source (not shown) which illuminates the substrate edge  56 . Light sensors (not shown), such as CCD sensors, positioned on an opposite side of the substrate  18  can detect the light not occluded by the substrate and thereby sense the substrate edge  56  and locate the reference flat or notch  52  as the substrate is rotated. The light sensors produce a signal proportional to the size of the shadow cast by the substrate  18  as the edge  56  crosses the lightbeam produced by the light source. 
     This profiling step identifies the initial substrate orientation and placement which are subsequently used, during the scribing process, to compensate for any encountered misalignment, as described below. The physical geometry of the substrate  18 , including center point, radius, and any abnormalities in the substrate&#39;s circumference can then be determined. Specifically, data collection sensors (not shown) transmit the alignment information representing the sensed edge of the substrate  18  to a process resource  24  which, based upon the data, determines the location of the substrate center  46  and whether the substrate center is misaligned relative to a reference point  48  located at the center of the chuck  22 . Knowing the location of the reference flat  52 , the chuck  22  then rotates the substrate  18  such that a desired scribing area  74  on the substrate lies within the processing zone  44 . 
     The process resource  24  is located above the processing zone  44  and directs a laser beam  26  during a marking or scribing process. The marking process involves directing the laser beam  26  in horizontal and vertical directions across at least a portion of a substrate surface such that the laser beam creates the desired mark(s) on said surface. Generally, the system creates a mark on the substrate surface for the purpose of substrate identification. 
     As shown in FIG. 5, a laser beam  26  enters the process resource  24  and is expanded by a beam expander  62 . An optical system contained in the process resource  24 , for example, a system with two mirrors  64 ,  66  can deflect the laser beam  26  in both the X and Y directions, thereby allowing the system to control the focal plane of the beam without causing the laser head to incur a positional shift. The mirrors  64 ,  66  may be steered by galvanometers  68 ,  70  or any other known adjusting mechanism, including but not limited to lead screws and servo motor combinations. The galvanometers  68 ,  70  can steer the mirrors  64 ,  66  about 1° to about 30° to deflect the laser beam  26 . It will be understood that the optical system may comprise any other suitable means, including but not limited to prisms. 
     As shown most clearly in FIG. 4, when the substrate center  46  is offset from the center of the chuck  22 , a vector V between the substrate center  46  and a reference point  48  having a magnitude of length A and an angle α will represent any misalignment of the substrate  18  with respect to the alignment station  28 . In order to properly mark the scribing area  74  of the substrate surface  54  while the substrate is off-center relative to the alignment station  28 , the substrate  18  and the laser beam  26  must be adjusted relative to the substrate edge  56  to compensate for the placement error. 
     In order to address the problem of misalignment of the substrate with respect to the alignment station, the present invention compensates for this placement error by orienting the substrate  18  relative to the processing zone  44 , then mathematically translating a coordinate system of the process resource  24 . In particular, the alignment station  28  can rotate the substrate  18  to a desired orientation, and the process resource  24  can incorporate the alignment information received from the data collection sensors to mathematically translate its coordinate system by the vector V. Accordingly, the galvanometers  68 ,  70  will translate the laser beam  26  by the vector V such that the laser beam can mark the desired scribing area  74  on the substrate surface  54  despite the off-centering of the substrate relative to the alignment station  28 . Thus, the substrate alignment system  10  can easily and quickly orient and position a misaligned substrate for marking the substrate surface without using the robotic substrate handler  16  to correct the placement error. 
     After transporting the substrate  18  to the alignment device  28  and while the processing resource  24  processes that first substrate  18 , the robotic substrate handler  16  is then free to retrieve a second substrate  38  from a substrate sourcing device  12  and deliver the substrate  38  to the second alignment device  30  within the process module  14  for subsequent processing. As most clearly shown in FIG. 2, the substrate  38  is placed on a chuck  36  in the alignment station  14  wherein at least a portion of the substrate  38  lies within the processing zone  44 . The alignment stations  28 ,  30  are proximally located such that the substrates  18 ,  38  can extend into the processing zone  44  and share the process resource  24 . 
     While the process resource  24  completes the processing or marking of the first substrate  18  in the processing zone, the alignment station  30  will profile the second substrate  38  delivered to the chuck  36  by the end effector  42  of the robotic substrate handler  16 . The alignment station  30  profiles the second substrate  38  as described with respect to the alignment station  28 . Before completing the profiling and marking of the first substrate  18  in the processing zone  44 , the profiling data collected from the lighthouse  34  concerning the second substrate  38  is passed to the shared process resource  24 . After completing the processing of the first substrate  18 , the process resource  24  can signal for adjustment of the galvanometers  68 ,  70  to steer the mirrors  64 ,  66  and direct the laser beam  26  toward the scribing area  74  on the second substrate  38 . 
     The first substrate  18  in the alignment station  28  is free to be removed after it has been completely processed. The chuck  22  will rotate the substrate  18  to the original position and orientation when first delivered from the substrate sourcing device  12 , and the robotic substrate handler  16  can return the substrate to the sourcing device. By following the same path it used to deliver the substrate  18  to the alignment station  28 , the robotic substrate handler  16  can avoid bumping or damaging the substrate edge  56  while returning the substrate to the sourcing device  12 . The robot  16  will then retrieve a subsequent substrate from the substrate sourcing device  12 . Typically, the robotic substrate handler  16  will process the entire substrate set contained with the same substrate sourcing device  12  before taking substrates from a different sourcing device  32 ,  40  to avoid the possibility of mixing substrate sets. 
     A user interface (not shown) allows a user to directly access the substrate alignment system  10  and perform maintenance or other functions. The user interface may be positioned remotely or adjacent to the system  10 . 
     The present invention provides advantages of more efficiently using the process resource. Since the alignment stations are located adjacent to each other to receive wafers for processing, the alignment stations can share a processing device. Further, the system is designed such that the second substrate can be prepared for processing without affecting or interfering with a first substrate being processed. With only one process resource required to serve two or more processing modules in close proximity, cost is reduced relative to those system solutions that utilize multiple process stations in order to increase throughput. 
     While the invention has been described in detail with reference to the embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made and equivalents employed, without departing from the present invention.