Abstract:
A coordinate measuring machine is disclosed having an orientor automatically orienting a substrate associated therewith. A control and computing unit is further associated with the coordinate measuring machine, so that self-calibration may be performed on the basis of at least two different and automatically set orientations of the substrate.

Description:
[0001]    This claims the benefit of German Application No. DE 10 2007 030 390.6 filed on Jun. 29, 2007 and hereby incorporated by reference herein. 
         [0002]    The present invention relates to a coordinate measuring machine. 
         [0003]    The invention further relates to a method for calibrating the coordinate measuring machine. 
       BACKGROUND 
       [0004]    A coordinate measuring device is sufficiently well-known from prior art. See, for example, the lecture script “Pattern Placement Metrology for Mask Making” by Dr. Carola Bläsing. The lecture was given on the occasion of the Semicon conference, Education Program, in Geneva on Mar. 31, 1998, wherein the coordinate measuring machine was described in detail. The structure of a coordinate measuring machine as known, for example, from prior art will be explained in more detail in the following description associated with  FIG. 1 . A method and a measuring device for determining the position of structures on a substrate is known from German published application DE 10047211 A1. For details regarding the mentioned position determination see that document. 
       SUMMARY OF THE INVENTION 
       [0005]    It is an object of the present invention to provide a coordinate measuring machine with which automatic self-calibration may be performed. 
         [0006]    The present invention provides a coordinate measuring including: a means for automatically orienting a substrate wherein the means is associated with the coordinate measuring machine; a control and computing unit for performing a self-calibration, based on at least two different and automatically set orientations of the substrate; a measurement table movable in a X-coordinate direction and a Y-coordinate direction, on which the automatically oriented substrate is deposited; an illumination means for illuminating the substrate, wherein the illumination means includes an incident light arrangement and/or a transmitted light arrangement; and a camera having at least one measurement window for measuring a at least one edge of a structure on a substrate. 
         [0007]    It is a further alternate or additional object of the invention to provide a method with which self-calibration of the coordinate measuring machine may be performed. 
         [0008]    The present invention also provides a method including the steps of: measuring at least one edge of a structure on the substrate in a first orientation of the substrate, automatically setting a second orientation with a means for orienting, measuring the at least one edge of the structure on the substrate in the second orientation at the same location as in the first measurement, and using the data sets obtained from the differing orientations of the structure for the calibration of the coordinate measuring machine. 
         [0009]    It is particularly advantageous if a means for automatically orienting the substrate is associated with the coordinate measuring machine. A control and computing unit is further associated with the coordinate measuring machine, so that self-calibration may be performed based on at least two different and automatically set orientations of the substrate. 
         [0010]    There is provided a transfer station having a robot associated therewith which delivers the substrate to the means for orienting. After the orientation, the robot removes the substrate from the means for orienting and inserts the newly oriented substrate into the coordinate measuring machine. 
         [0011]    There is provided a measurement table movable in the X-coordinate direction and in the Y-coordinate direction, on which the automatically newly-oriented substrate is deposited. There is further provided a camera having at least one measurement window for measuring the structure. There is also provided an illumination means for illuminating the substrate. The illumination means includes an incident light arrangement and/or a transmitted light arrangement. The circumstances of the measurement are decisive for the choice whether the substrate is illuminated with incident light and/or with transmitted light. 
         [0012]    It may be advantageous if the coordinate measuring machine, the means for orienting, the illumination means, the camera, a magazine and at least one transport means are arranged in a common climatic chamber. In addition, it is also advantageous if the means for orienting is arranged in an air flow of the climatic chamber. The advantage consists in the fact that particles or dust that may adhere to the substrate may be blown away in the air flow. 
         [0013]    The means for orienting may be associated with an illumination means having a camera associated therewith which captures an image of the substrate on which the orientation may be determined. The camera includes an evaluation unit for an identification of the substrate. The identification is applied to a free part of the surface of the substrate. It is also contemplated that an extra capturing unit for the identification of the substrate may be associated with the means for orienting. 
         [0014]    The means for orienting may have a computer associated therewith with the help of which the user may set a predetermined orientation of the substrate. The computer may also be used for image evaluation to evaluate the images of the substrate acquired by the camera and determine the orientation of the substrate based on the evaluation. The computer may also be used to execute a predefined recipe and set given orientations of the substrate. 
         [0015]    The inventive method for calibrating the coordinate measuring machine is characterized by the following steps. Initially at least one structure on the substrate is measured in a first orientation of the substrate. Then a second orientation is automatically set by the means for orienting. The substrate is measured in a second orientation, wherein the at least one structure is measured at the same location as in the first measurement. Data sets are obtained from the differing orientations of the substrate, the data sets being used for the calibration of the coordinate measuring machine. It is advantageous if the data sets for the calibration of the coordinate measuring machine are automatically used for calculation. The data sets may also be stored in a computer. An output may indicate that the result of the calibration is within a predetermined tolerance range. 
         [0016]    The calibration may be performed automatically by the coordinate measuring machine in defined time intervals. It is also contemplated that the calibration is performed upon user request. A variety of operating instructions may be made available to the user, which may be combined in any desired way for execution in order to achieve the calibration of the coordinate measuring machine. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    In the following, embodiments will explain the invention and its advantages in more detail with reference to the accompanying figures. 
           [0018]      FIG. 1  schematically shows a prior art coordinate measuring device; 
           [0019]      FIG. 2  shows a schematic representation of the device for measuring coordinates of structures on a substrate, wherein all required elements and means are arranged within a climatic chamber; 
           [0020]      FIG. 3  schematically shows another embodiment of the invention, wherein the means for orienting the substrates is arranged outside the climatic chamber; 
           [0021]      FIG. 4  shows a schematic front view of the coordinate measuring machine and the means associated with the coordinate measuring machine, wherein at least one means is arranged in an air flow within the climatic chamber; 
           [0022]      FIG. 5  shows a substrate provided with at least one marking for the substrate; 
           [0023]      FIG. 6  shows a schematic arrangement of a camera in operating connection with a means for orienting the substrate. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    A coordinate measuring device of the type shown in  FIG. 1  has already been described in detail in prior art and is thus known in detail from prior art. The coordinate measuring device  1  includes a measurement table  20  movable in the X-coordinate direction and in the Y-coordinate direction. The measurement table  20  carries a substrate or a mask for semiconductor production. Several structures  3  are applied to a surface of the substrate  2 . The measurement table itself is supported by air bearings  21  which are, in turn, supported by a granite block  25 . At least one incident light illumination means  14  and/or one transmitted light illumination means  6  are provided for the illumination of the substrate  2 . In the embodiment shown, the light of the transmitted light illumination means  6  is launched into the illumination axis  4  for the transmitted light by means of a deflecting mirror  7 . The light of the illumination means  6  reaches the substrate  2  via a condenser  8 . The light of the incident light illumination means  14  reaches the substrate  2  through the measurement objective  9 . The light coming from the substrate  2  is collected by the measurement objective  9  and is coupled out of the optical axis  5  by a semi-transparent mirror  12 . This measurement light reaches a camera  10  provided with a detector  11 . A computing unit  16  is associated with the detector  11 , with which digital images may be generated from the acquired data. 
         [0025]    The position of the measurement table  20  is measured and determined by means of a laser interferometer  24 . For this purpose, the laser interferometer  24  emits a measurement light beam  23 . The measurement microscope  9  is also connected to a displacing means in the Z-coordinate direction, so that the measurement objective  9  may be focused on the surface of the substrate  2 . The position of the measurement objective  9  may be measured, for example, with the help of a glass scale (not shown). The granite block  25  is further positioned on slabs  26  with an anti-vibration arrangement. All potential building vibrations and natural vibrations of the coordinate measuring device are to be maximally reduced or eliminated by this vibration damping. 
         [0026]      FIG. 2  shows a schematic view of the arrangement of the coordinate measuring device  1  and further means associated with the coordinate measuring device  1  to guarantee an efficient inspection or measurement of the substrates  2 . In the embodiment shown in  FIG. 2 , the coordinate measuring device  1  is shown in simplified form. In  FIG. 2 , the coordinate measuring device  1  is shown only with the measurement table  20  and the substrate  2  located on the measurement table  20 . Together with other means, the coordinate measuring means  1  is located in a climatic chamber  30 . In the embodiment shown, a magazine  32  for storing substrates  2  or masks within the climatic chamber  30  is associated with the coordinate measuring means  1 . Means for orienting  34  the substrates is also arranged within the climatic chamber. A transfer station  35  is provided in a wall  30   a  of the climatic chamber  30 . A transport robot  36  and further transport means  38  may further be provided within the climatic chamber  30 . Although a magazine  32  for storing substrates  2  and/or for temperature adaptation of substrates  2  is provided, someone skilled in the art will understand that the magazine within the climatic chamber  30  may be omitted. The robot  36  may move within the climatic chamber along the direction indicated by the double arrow  40 . The substrates  2  may be transferred into the climatic chamber via the transfer aperture  35 . The transport means  38  represents a transfer station. The robot  36  removes the substrate  2  from the transfer station  38  and, depending on the recipe, deposits it on the means  35  for orienting, on the measurement table  20  or in the magazine  32 . 
         [0027]      FIG. 3  shows another embodiment of the arrangement connected to a coordinate measuring machine  1 . Equal elements are referred to by equal reference numerals. In the embodiment shown in  FIG. 3 , the means  34  for orienting is arranged outside the climatic chamber  30 . The means  34  for orienting is connected to the climatic chamber by means of an interface  42 , so that the oriented substrates may be delivered to the coordinate measuring machine  1  via the interface  42 . 
         [0028]      FIG. 4  shows a side view of the arrangement of the various means in the climatic chamber  30  of a coordinate measuring means. The climatic chamber  30  is connected to a ventilator means  50  blowing air of a predetermined clean room degree into the climatic chamber  30 . An air guiding plate  52  may be provided in the climatic chamber  30 , with which an air flow  54  may be generated which is correspondingly directed to the means  34  for orienting the substrates. The air flow may have the advantage that any particles adhering to the substrate  2  may be blown away. 
         [0029]      FIG. 5  shows a schematic representation of a substrate  2 . The substrate  2  is provided with several markings  54  and  56 . The first marking  54  may be a bar code. The second marking  56  may be an alphanumeric marking of the substrate  2 . Based on the markings  54  and  56 , it is possible to determine the orientation of the substrate  2 . 
         [0030]      FIG. 6  shows a schematic arrangement of a detection means  60  for the orientation of the substrate  2 . The substrate  2  is deposited on the means  34  for orienting the substrate  2 . The means  34  for orienting the substrate  2  includes a rotary plate  34   a  carrying the substrate  2 . The means  34  for orienting the substrate  2  is connected to a computing unit  61  with which the orientation of the substrate may be set automatically. Opposite the substrate  2 , a camera  60  is provided with which images of the part of the substrate bearing the markings  54  and  56  may be acquired. It is also contemplated that the whole surface of the substrate  2  may be captured by the camera  60 . The orientation of the substrate may then be determined from the image of the surface of the substrate  2  by means of image processing in the computer  61 . On a display  62 , the current and/or newly set orientation of the substrate  2  may be displayed to the user. It is also contemplated that the user may input data with respect to the orientation of the substrate via the display  62 . A creation of recipes with which predetermined calibration steps may be performed may also be input by means of the display and thus be conveyed to the computer  61 . 
         [0031]    For calibrating the coordinate measuring machine  1 , it is necessary to measure at least one structure  3  on the substrate  2  in a first orientation of the substrate  2 . A second orientation is set by the means  34  for orienting the substrate. Then the substrate is measured in the second orientation of the at least one structure at the same location as in the first measurement. Data regarding the position and/or dimension of the structure  3  on the substrate are then obtained from the differing orientations. These data sets are used for calibrating the coordinate measuring machine. The data sets obtained from the measurement of the various orientations of the substrate may be automatically used for calculation for the calibration of the coordinate measuring machine  1 . It is also contemplated that the data sets are stored in the computer  61  and used for later calibration or correction of the real measurement values. It is also contemplated that there is an output for the user on the display  62  if the result of the calibration is within a predetermined tolerance range. The calibration of the coordinate measuring machine may be performed automatically in defined time intervals. The calibration may also be performed upon user request. A variety of operating instructions may be made available to the user on the display  62 , which may be combined in any desired way on the display  62  for execution. Based on these freely combinable operating instructions, a calibration of the coordinate measuring machine  1  may be achieved. 
         [0032]    The invention has been described with reference to particular embodiments. However, it is contemplated that modifications and changes may be made without departing from the scope of the following claims.