Abstract:
Disclosed is a lighted wafer cassette for use in semiconductor wafer processing. Also disclosed are systems and methods employing a wafer cassette lighted with one or more affixed light sources for facilitating cassette alignment with standard semiconductor processing apparatus.

Description:
PRIORITY DATE  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/344,201, filed Dec. 28, 2001. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The invention relates to devices, systems, and methods for providing an illuminated wafer cassette and facilitating alignment of a semiconductor process transfer blade apparatus with the wafer cassette. More particularly, the invention relates to providing precise wafer cassette illumination useful in performing alignment procedures.  
         BACKGROUND OF THE INVENTION  
         [0003]    It is standard in the semiconductor industry to use a wafer cassette to hold a lot of (usually 25) wafers. Many of the tools for the various semiconductor processor activities, such as implantation, photo resist, and testing, use the same apparatus having a transfer blade designed to insert and retrieve wafers from a standard cassette. The transfer blade of such apparatus requires mechanical alignment with the wafer shelves of the cassette. It is known in the arts to align the top wafer shelf in the cassette, the bottom wafer shelf in the cassette, e.g., the 25 th  wafer, and a wafer selected from somewhere near the middle. These three alignment points are generally sufficient to ensure that the remainder of the wafer shelves are suitably aligned with the transfer blade. Adjustments are made through an operator interface generally requiring the use of the operator&#39;s hands. Typically, the operator peers into the wafer cassette and performs the alignment by observing the position of the transfer blade mechanism relative to the wafer shelves of a cassette, making mechanical adjustments as required.  
           [0004]    Problems arise in the art due to conditions hampering the visual observation. For example, it is generally dark within the wafer cassette. It is known for the operator to attempt to shine a flashlight into the cassette. This solution is successful to some degree, but does not provide ideal illumination due to obstructions. Additionally, this requires one of the operator&#39;s hands, which would otherwise be available for making mechanical adjustments. Additionally, because the wafers have a highly reflective surface, glare and reflected light make observation of crucial areas difficult. These and other complications in making visual observations in order to perform transfer blade alignment lead to additional problems such as increased time required to perform the alignment process, decreased yield due to improper alignment, and possibly damaged wafers.  
           [0005]    It would be desirable in the arts to develop devices, systems and methods providing improved illumination for transfer blade alignment relative to a wafer cassette. Such improvements would provide many advantages, including reduced cycle time, increased yield, convenience, and more accurate alignment.  
         SUMMARY OF THE INVENTION  
         [0006]    In general, the invention provides devices, systems, and methods for illuminating critical areas of wafer cassettes and semiconductor processing apparatus transfer blades for purposes of alignment.  
           [0007]    According to one aspect of the invention, a lighted wafer cassette for use in semiconductor wafer processing is provided. A cassette framework has a number of wafer shelves with at least one light source affixed to one or more of the wafer shelves. The light sources are positioned for illuminating one or more of the wafer shelves within the cassette.  
           [0008]    According to another aspect of the invention, a system for aligning wafer-processing apparatus relative to a wafer cassette is provided. Wafer-processing apparatus designed to receive a wafer cassette and having a moveable transfer blade is equipped with a wafer cassette. The wafer cassette has multiple wafer shelves designed to hold semiconductor wafers. One or more light sources are affixed to the wafer cassette and positioned for illuminating one or more of the wafer shelves. The system also includes a power source used to provide power to the light sources. Means are provided for aligning the transfer blade with the wafer shelves.  
           [0009]    An additional aspect of the invention provides a method of aligning a moveable blade of a wafer-processing apparatus and the wafer shelves of a wafer cassette. The method includes steps of coupling the wafer cassette to the wafer-processing apparatus and illuminating one or more wafer shelves using one or more light sources affixed to the wafer cassette. A step of mechanically aligning the moveable blade relative to the one or more illuminated wafer shelves is also provided.  
           [0010]    According to still another aspect of the invention, a method of illuminating the transfer blade of a wafer-processing apparatus and a wafer shelf of a wafer cassette for alignment purposes is disclosed. One or more light sources are attached to a selected wafer shelf of the wafer cassette. The wafer cassette is coupled to the wafer-processing apparatus such that moving the transfer blade into alignment with the selected wafer shelf is facilitated by illuminating the transfer blade and the selected wafer shelf using the one or more light sources.  
           [0011]    Technical advantages are provided by the invention, including but not limited to precise placement of illumination in locations crucial to properly aligning wafer cassette shelves with semiconductor processing apparatus. Further advantages realized include reduced alignment time, more accurate alignment, improved yields, reduced costs, and convenience to the operator. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    For a better understanding of the invention including its features, advantages and specific embodiments, reference is made to the following detailed description along with accompanying drawings in which:  
         [0013]    [0013]FIG. 1 is a rear view of an example of a preferred embodiment of a lighted cassette of the invention;  
         [0014]    [0014]FIG. 2 is a front view of an example of a preferred embodiment of a lighted cassette of the invention;  
         [0015]    [0015]FIG. 3 is a side view of an example of a preferred embodiment of a lighted cassette of the invention;  
         [0016]    [0016]FIG. 4 is a schematic diagram of an example of the circuitry of the embodiment of the invention shown in FIG. 1; and  
         [0017]    [0017]FIG. 5 is a perspective view of an example of a preferred embodiment of a lighted cassette in use in a semiconductor processing apparatus according to the invention. 
     
    
       [0018]    References in the detailed description correspond to like references in the figures unless otherwise noted. Like numerals refer to like parts throughout the various figures. The descriptive and directional terms used in the written description such as top, bottom, left, right, etc., refer to the drawings themselves as laid out on the paper and not to physical limitations of the invention unless specifically noted. The drawings are not necessarily to scale and some features of embodiments shown and discussed are simplified or exaggerated for illustrating the principles of the invention.  
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0019]    While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts which can be embodied in a wide variety of specific contexts. It should be understood that the invention may be practiced with wafer cassettes and transfer mechanisms of various types and materials without altering the principles of the invention.  
         [0020]    [0020]FIG. 1 shows a rear view of a wafer cassette  10  in a preferred embodiment of the invention. A framework  12  made of a rigid material such as, for example, plastic or other similar substance, provides a structure for supporting a number of wafer shelves  14 , which, according to one embodiment, consists of 25 wafer shelves, for retaining a lot of 25 semiconductor wafers. Referring to FIGS. 1 and 2, the wafer shelves  14  are parallel to one another and are generally narrower at the front end  16  and wider at the rear  18 . In the presently most preferred embodiment of the invention, light sources  20 , in this case LEDs, are installed at the front end of the top, bottom and middle wafer shelves  22 ,  24  and  26 , respectively.  
         [0021]    As can be seen with further reference to FIG. 1, it is preferred to mount light sources  20  at each side of the selected wafer shelves ( 22 ,  24 ,  26 ). Although it is generally preferred to select the top, middle and bottom wafer shelves for alignment purposes, thereby reasonably assuring that all shelves in the cassette are aligned, those skilled in the arts will appreciate that alternatives are possible. For example, the second, next to last, and other arbitrarily selected wafer shelves may be selected for alignment, or all wafer shelves may be aligned. Preferably, a power source  28  is provided and electrically coupled to the light sources  20 . In this case, a standard battery is shown as the power source  28 . Of course, alternative power sources may be used, such as a vacuum sealed battery, photovoltaic cells, or simply a coupling to an external power source.  
         [0022]    A front view of the lighted wafer cassette  10  of FIG. 1 is shown in FIG. 2. The narrow front  16  is shown obstructing the light sources  20 . It will be clear to those familiar with the arts that the light sources  20  of the invention provide illumination located in areas difficult or impossible to illuminate using the prior art. Also shown in FIG. 2 are top and bottom coupling points  30  and  32 , respectively, for operably coupling the wafer cassette  10  to semiconductor processing apparatus.  
         [0023]    Depicted in FIG. 3 is a side view of the wafer cassette  10  of the invention. A light source cover  34  is shown encasing the light sources  20  (shown as dotted lines) and associated wiring  36 . Control circuitry  38  is preferably included to complete the operable coupling of the power source  28  and light sources  20 . Typically the control circuitry  38  will include a voltage regulator  42  (shown in FIG. 4) and a manually or remotely activated switch  40  for controlling the light sources  20 .  
         [0024]    [0024]FIG. 4 is a schematic diagram illustrating the electrical parts and operation of the lighted wafer cassette  10  according to the invention. In the presently preferred embodiment, the control circuitry  38  has a mechanical switch  40  electrically connected to the power source  28 , in this case a 9-Volt battery which, in turn, is also coupled with a voltage regulator  42  and parallel banks of light sources  20 . In this example clear white light LEDs labeled L 1 -L 6 , are used and coupled to voltage regulator  42 . Thus, in operation, two banks of LEDs, including a first bank  44 , which includes L 1 , L 2  and L 3 , and a second bank  46  made up of L 4 , L 5  and L 6 , are connected in parallel to the output of the voltage regulator  42  which is used to adjust the output from the power source  28  for compatibility with to the LEDs. It is contemplated that the various alternative circuit arrangements are possible, particularly with respect to light sources, intensity, or color. For example, small fluorescent or incandescent lighting may be used and different portions of the visible or non-visible light spectrum may be used without departing from the concept of the invention. Also, alternative switching devices, such as a remotely activated switch, may be used.  
         [0025]    [0025]FIG. 5 shows an example of a lighted cassette  10  configured according to FIGS.  1 - 4 , in use in a load-lock device  50 . A transfer blade  52  is also shown. A bottom wafer  54  is visible at a bottom wafer shelf, and a top wafer  56  is shown at a top wafer shelf. In use, an operator may visually observe the transfer blade  52  as it moves within the lighted cassette  10  and may make adjustments as necessary to achieve proper alignment.  
         [0026]    The embodiments shown and described above are only exemplary. Even though numerous characteristics of the present invention have been set forth in the foregoing description together with details of the method and device of the invention, the disclosure is illustrative only and changes may be made within the principles of the invention to the full extent indicated by the broad general meaning of the terms used in the attached claims.