Abstract:
An apparatus for use in orienting an object at a reference angle includes a pin gauge having at least two projections located at an end of the body of the apparatus. The projections are located at certain X Y coordinates of an X, Y Z Cartesian coordinate system. A horizontal support supports the body so as to be movable horizontally in the longitudinal direction of the projections. A mechanical drive member is operable to move the body mechanically in the horizontal direction. The apparatus may also include a vertical support and vertical drive member. The pin gauge is mechanically moved into contact with a surface of an object to provide a reference angle for the object. Then the object is pivoted, if necessary, to bring the surface into point contact with all of the projections of the pin gauge, whereupon the object is oriented at the reference angle. Process errors in aligning the object using the reference angle are reduced because the orienting of the object at the reference angle is accomplished using mechanical elements.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method of and apparatus for use in orienting an object at a predetermined reference angle with respect to a given plane(s). More particularly, the present invention relates to a process of aligning a chuck relative to equipment by which a substrate supported by the chuck will be processed. 
     2. Description of the Related Art 
     Currently, semiconductor memory devices are being developed at a rapid pace due to the widespread use of computers for processing various types of information. To this end, the current art is focused on developing and realizing memory devices having a high degree of integration, response speed, and reliability. Accordingly, highly precise process techniques are required for fabricating today&#39;s semiconductor memory devices. 
     Semiconductor devices are fabricated by such processes as an ion implantation process, a thin film forming process and a patterning process. Needless to say, all of the conditions under which these fabrication processes are performed must be controlled. If the process conditions are not completely controlled, process errors may be generated. Moreover, a semiconductor substrate is supported by a chuck during semiconductor device fabrication processing, such as during the thin film forming process, pattern forming process, and ion implantation process. Therefore, one of the process conditions usually requiring control is the positioning or aligning of the chuck on which the semiconductor substrate is placed. 
     The position of the chuck is controlled as follows, using the ion implantation process as an example. 
     Referring to FIG. 1, a substrate  10  should be tilted relative to an ion beam during the implantation process to prevent a channeling effect from occurring. The channeling effect refers to a situation in which ions injected into the substrate pass through voids in the substrate, i.e., spaces where atoms are not present. Japanese Patent Laid-Open Publication No. 2000-68226 and U.S. Pat. No. 5,406,088 (issued to Brune, et al.) each disclose a method of preventing the channeling effect from occurring during the ion implantation process. More specifically, Japanese Patent Laid-Open Publication No. 2000-68226 discloses a method in which the scanning angle of an ion beam is controlled to prevent the channeling effect. On the other hand, U.S. Pat. No. 5,406,088 discloses a method in which the chuck is manipulated to prevent the channeling effect. 
     In the latter case, the chuck on which the substrate  10  is placed is preferably tilted at the angle of 7 degrees with reference to the vertical before the ion implantation process begins. The process of tilting the chuck to position the substrate  10  relative to the ion beam will hereinafter be referred to as the process of aligning the chuck. 
     The process of aligning the chuck includes the steps of first orienting the chuck vertically and then tilting the chuck 7 degrees with respect to the vertical. The step of orienting the chuck vertically is performed by a reference angle providing apparatus shown in FIG.  2 . 
     Referring to FIG. 2, the reference angle providing apparatus  20  is disposed on the bottom surface  17  of the process chamber. The reference angle providing apparatus  20  includes a surface contact portion  200  that makes surface contact with the chuck  15 , and a supporting portion  210  for supporting the surface contact portion  200 . The supporting portion  210  includes a supporting bar  210   a  for supporting the surface contact portion  200  and a bottom portion  210   b  for supporting the supporting bar  210   a . The bottom portion  210   b  is mounted to the bottom surface  17  of the process chamber. The chuck  15  is also mounted to the bottom surface  17  of the chamber. 
     The surface contact portion  200  of the reference angle providing apparatus  20  is brought into contact with the chuck  15  before the ion implantation process begins. An alignment error is judged to occur at that time if the entire surface of the contact portion  200  does not contact the chuck  15 . In that case, X and Y coordinates of the chuck are adjusted such that the chuck  15  contacts the entire surface of the contact portion  200 . Preferably, the chuck  15  is oriented at an angle of 0 degrees relative to the X-Y plane (the vertical) and at an angle of 90 degrees relative to the Y-Z plane (the horizontal). Once the chuck  15  and the surface contact portion  200  are in complete surface contact with each other, the chuck  15  is tilted at an angle of 7 relative to the X axis. 
     However, the reference angle supplying apparatus  20  is subject to the following problems. First, the apparatus  20  itself is moved manually to place the surface contact portion  200  in contact with the chuck  15 . Therefore, the apparatus is shaken during this operation, which shaking can cause an alignment error to occur. Also, alignment errors are produced because the bottom portion  210   b  of the reference angle supplying apparatus  20  is often does not lie precisely flat on the bottom surface  17  of the chamber. Still further, the state of contact between the chuck  15  and the surface contact portion  200  is judged by an operator, whereby the alignment process is prone to human error. Furthermore, the precision or calibration of the reference angle supplying apparatus  20  degrades over time. However, the apparatus  20  has no means by which its own misalignment can be detected. Therefore, the apparatus  20  may be operated continuously while being out of self-alignment. As a result, the chuck  15  is oriented improperly by the apparatus  20 . 
     For the reasons described above, process errors frequently occur when the chuck is aligned using the conventional reference angle providing apparatus. Accordingly, these errors translate so much into the process of fabricating the semiconductor device that the productivity of the fabricating process suffers. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to obviate the above-described problems of the prior art. Accordingly, an object of the present invention is to provide a method and apparatus by which an object to be aligned may first be oriented precisely at a desired reference angle. 
     To achieve this object, the present invention provides an apparatus for providing an object with a reference angle, which apparatus comprises a main body and a pin gauge for making point contact with the surface of the object. 
     The pin gauge has at least two projections which project in the direction of a Z axis away from an end surface of the body. Two or more of the projections are located on X and Y axes, respectively, orthogonal to one another and to the Z axis and spaced from the origin of the coordinate system defined by the X, Y and Z axes. 
     In addition, a mechanical drive member(s) is/are used to bring the pin gauge into initial contact with the object to be aligned. In particular, a horizontal support having a horizontal guide engaged with the main body, and a horizontal drive member are used to move the body horizontally in the direction of the Z axis (longitudinal direction of the projections of the pin gauge) to bring the pin gauge into initial point contact with the object. A vertical support having a vertical guide, and a vertical drive may also be provided to bring the pin gauge up or down to the level of the object to be aligned. 
     The vertical support may include a bottom member on which the horizontal support is disposed, and a vertical member on which the vertical guide is disposed. The vertical guide is engaged with at least the horizontal support. 
     Each mechanical drive member preferably comprises a fixed nut and a drive screw connected to the main body and threaded with the fixed nut. Thus, the drive screw and the body of the apparatus connected thereto will be moved linearly when the drive screw is rotated relative to the fixed nut. An actuating member, such as a knob, allows the drive screw to be rotated. 
     Preferably, the projections comprise proximity sensors for sensing the distances between the ends of the projections and the object. Also, a display is used for displaying the measurements made by the proximity sensors. Therefore, the position of the object relative to the pin gauge providing the reference angle is not judged by the operator but by the sensors. And, the results are displayed to the operator. That is, the relative position of the object is determined objectively. As a result, errors in the process of aligning the object can be minimized. 
     Furthermore, a reference angle calibration unit can be used to check the accuracy of the reference angle providing apparatus. The calibration unit has a reference surface against which the pin gauge can be pressed to check the state of point contact. In this way, if the pin gauge is determined to have become inaccurate due to its continuous use over a long period of time, the pin gauge can be repaired. Accordingly, the reliability of the apparatus is ensured. 
     For instance, the reliability in of the apparatus in facilitating the aligning of a chuck of semiconductor fabricating equipment is ensured. In this case, the reference angle providing apparatus is placed on the bottom surface of a process chamber in which the chuck is disposed. The pin gauge is moved mechanically towards the chuck until the pin gauge contacts the surface of the chuck. Accordingly, the gauge is not shaken as it contacts the chuck, whereby the maintains a high degree of accuracy. 
     Once the pin gauge contacts the surface of the chuck, the state of point contact between the end of each of the projections of the pin gauge and the surface of said chuck is checked, i.e., the distances between the projections of the pin gauge and the surface of the chuck is sensed by the proximity sensors. The chuck is then pivoted, if necessary, to place the surface of the chuck in point contact with the ends of all of the projections of the pin gauge. Hence, the chuck is oriented at the reference angle. Finally, the chuck is tilted a predetermined amount from the reference angle. In the case of an ion implanter, the chuck is tilted 7 degrees to prevent the channeling effect from occurring during the implantation process. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become more apparent by referring to the following detailed description of the preferred embodiments thereof made in conjunction with the accompanying drawings, of which: 
     FIG. 1 is a schematic diagram of a substrate tilted to prevent a channeling effect from occurring during an ion implantation process; 
     FIG. 2 is a schematic diagram of a conventional reference angle providing apparatus for use aligning the chuck on which the substrate is supported during the ion implantation process; 
     FIG. 3 is a schematic diagram of a first embodiment of an apparatus for providing an object with a reference angle according to the present invention; 
     FIG. 4 is a front view of the apparatus showing a pin gauge thereof; 
     FIG. 5 is a schematic diagram of the front of the apparatus, showing the manner in which a chuck is provided with the reference angle using the pin gauge of the apparatus; 
     FIG. 6 is a schematic diagram of the chuck oriented at the reference angle by use of the apparatus of FIG. 3; 
     FIG. 7 is a perspective view of part of the apparatus of FIG. 3 that is disposed on the bottom surface of a process chamber, 
     FIG. 8 is a schematic diagram of a pin gauge in the form of proximity sensors in the apparatus of FIG. 3; 
     FIG. 9 is a schematic diagram of a unit for checking the calibration of the pin gauge of the apparatus of FIG. 3; and 
     FIG. 10 is a schematic diagram of a second embodiment of an apparatus for providing an object with a reference angle according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of apparatus for use in providing a reference an object to be aligned with a reference angle according to the present invention will be described in detail hereinafter with reference to the accompanying drawings. Note, the reference angle refers to an angle relative to the vertical. The apparatus according to the present invention can be adapted for use in orienting an object (the plane of the object) at various reference angles. 
     Referring now to FIG. 3, a first embodiment of an apparatus  30  for providing an object to be aligned with a reference angle includes a generally cylindrical body  300 , and a pin gauge  310  disposed at one end of the cylindrical body  300 . The pin gauge  310  comprises at least two pins or projections  310   a ,  310   b  extending from the end surface of the body  300 . Each of the pins projects in the direction of a Z axis, and is located on a respective one of X and Y axes orthogonal to one another and to the Z axis as spaced from the origin of a coordinate system comprising the X, Y and Z axes. 
     FIG. 4 shows the relative position of the pins  310   a ,  310   b  of the pin gauge  310  in detail. Referring to FIG  4 , the pins are laid out along the corners of a diamond on the end surface of the body  300 , respectively. Two of the pins  310   a  are disposed opposite each other along the X axis, and two other pins  310   b  are disposed opposite each other along the Y axis. That is, the first pins  310   a  disposed along the X axis project from an upper portion and from a lower portion of the end surface of the body  300 , respectively. On the other hand, the second pins  310   b  disposed along the Y axis project from a right hand side and a left hand side of the end surface of the body  300 , respectively. Also, as shown in FIG. 4, the first and second pins  310   a ,  310   b  are therefore located alongside the outer peripheral edge of the end surface of the body  300 . 
     FIG. 5 illustrates the manner in which a chuck  55  is oriented at the reference angle using the pin gauge  310  of the apparatus  30 . First, the pin gauge  310  is brought into point contact with the chuck  55 . Then, if necessary, the chuck  55  is rotated about the X and Y axes by respective rotary members until the chuck  55  completely contacts all of the pins  310   a ,  310   b  of the pin gauge  310 . In the case of ion implantation equipment, after the chuck  55  is oriented at the reference angle using the pin gauge  310 , the (plane of the) chuck  55  is tilted at an angle of 7 degrees with respect to the reference angle. 
     FIG. 6 shows the chuck  55  oriented at the reference angle. Referring to FIG. 6, the reference angle is 0 degrees with respect to the X axis direction (the vertical) and 90 degrees with respect to the Y axis direction (in this case, representing the horizontal). 
     Referring back to FIG. 3, the apparatus  30  also includes a body support  320 . The body support  320  has the overall form of a plate, and is disposed on a bottom surface ( 77 , FIG. 7) of a chamber to support the body  300 . The chuck  55  is mounted on the same surface  77  of the chamber. The body support  320  includes a horizontal guide  320   a  that is in a sliding engagement with the body  300  such that the body  300  may be moved horizontally along the body support. That is, movement of the body  300  is directed by the horizontal guide  320   a  to bring the pin gauge  310  into point contact with the surface of the chuck  55 . 
     Referring specifically now to FIG. 7, the mounting surface of the body support  320  is planar to within a tolerance of less than 1 μm. Therefore, the body support  320  has a very high degree of uniformity such that the pins of the pin gauge  310  will extend substantially parallel to the bottom surface  77  of the chamber when the apparatus  30  is disposed thereon. The bottom surface of the body support  320  is machined by means of a planer, a planomiller and the like, which are high precision devices, to impart the high degree of flatness to the bottom surface thereof. The thickness of the body support  320  is such that the pin gauge  310  will be located at the same level as the chuck  55  when the body support  320  is disposed on the bottom surface  77  of the chamber. Accordingly, a precise reference angle can be provided. 
     The apparatus  30  also includes a drive member  330  for moving the body  300  towards the chuck  55 , and an actuating member  340  for actuating the drive member  330 . The drive member  330  is integral with the body  300 . More specifically, the drive member  330  comprises a fixed nut  330   a , and a horizontal drive screw  330   b  threaded to the fixed nut  330   a  and connected to the body  300 . The body  300  is driven along the horizontal guide  320   a  by the horizontal drive screw  330   b  as the screw  330   b  is rotated relative to the fixed nut  330   a . The horizontal drive screw  330   b  can be rotated by means of the actuating member  340  (a knob, as shown in the figure). When the horizontal drive screw  330   b  of is moved linearly by turning the actuating member  340 , the pin gauge  310  of the apparatus  30  is brought into point contact with the chuck  55 . Thus, the chuck  55  can be oriented at the reference angle. 
     In one form of the apparatus  30 , the pins or projections of the pin gauge  310  comprise distance measuring sensors, known in the art per se and often referred to as proximity sensors. FIG. 8 shows the manner in which such an apparatus  30  is used to orient the chuck  55  at the reference angle. For example, if only one of the pins  310   b  disposed along the Y axis makes point contact with the chuck  55  once the pin gauge  310  has been moved into contact with the chuck  55 , the sensor constituting the other pin  310   b  disposed along the Y axis measures the distance between the end thereof and the surface of the chuck  55 . 
     The angle θ by which the chuck  55  deviates from the reference position can be easily determined because tan θ is equal to the sensed distance (between the end of the pin  310   b  and the chuck  55 ) divided by the known distance between the pins  310   b  disposed along the Y axis. Accordingly, the chuck  55  is pivoted an angular amount θ about the point where the one pin  310   b  makes contact with the chuck  55 , whereby the chuck is brought into contact with the other pin  310   b . Thus, the chuck is oriented at the reference angle. 
     Furthermore, the apparatus  30  includes a display  350  by which an operator can monitor the process of aligning the chuck  55 . In particular, the distances between the ends of the pins  310   a ,  310   b  and the chuck  55  are displayed. The display  350  is connected by a cable  350   b  to a terminal  350   a  attached to a side of the body  300 . However, the display  350  may be directly integrated with the side of the body  300 . In any case, the operator can identify the present state of the chuck  55  through the display  350  and then control the rotary members to which the chuck  55  is connected to orient the chuck  55  at the reference angle. 
     Now, when the apparatus  30  is continuously used for a long period of time, the pin gauge  310  may lose its calibration. Obviously if the pin gauge  310  is not repaired, the apparatus  30  will lose its ability to properly orient the chuck  55  at the correct reference angle. FIG. 9 shows a unit  90  for checking and correcting the calibration of the pin gauge  310 . 
     Referring to FIG. 9, the reference angle calibration unit  90  has a surface  90   b  against which the pin gauge  310  is pressed to check the point contact therewith. This surface  90   b  of the reference angle calibration unit  90  is substantially normal to the horizontal surface  90   a . If point contact is not established between all of the pins  310   a ,  310   b  of the pin gauge  310  of the apparatus  30 , the pin gauge  310  is repaired with reference to its state of contact with the surface  90   b . Also, when the apparatus  30  is not used, the apparatus  30  is received in and stored by the reference angle calibration unit  90  as resting on surface  90   a . That is, the reference angle calibration unit  90  has a structure by which the apparatus can be calibrated as well as being stored. However, the apparatus  30  can be stored in a separate unit (not shown) such as a cabinet. 
     FIG. 10 shows a second embodiment of an apparatus  40  for providing a reference angle for an object according to the present invention. 
     Referring to FIG. 10, the apparatus  40  includes a body  400 , a pin gauge  410 , and a display  450 . The body  400 , pin gauge  410  and display  450  have the same structure and function as those of the first embodiment of the present invention. 
     Also, similar to the first embodiment, the apparatus  40  includes a horizontal support  420  for supporting the body  400 . The horizontal support  420  has the overall shape of a plate, and includes a horizontal guide  420   a  that cooperates with the body  400  to guide the body  400  horizontally. That is, the body  400  is guided for movement along the horizontal guide  420   a  to bring the pin gauge  410  into point contact with the chuck. 
     The apparatus  40  also includes an L-shaped vertical support  480  that supports the horizontal support  420 . The vertical support  480  has a bottom surface  480   b  that makes contact with the bottom surface of the chamber. A base  460  is disposed between the body  400  and the bottom surface  480   b  of the vertical support  480 . The base  460  is connected to the vertical support  480  by means of screws. A surface of the base  460  is machined to have uniformity with respect to the opposite surface of the base support, i.e., a less than 1 μm variation in its planarity. The base  460  is thus formed in the same manner described in connection with the body support  320  of the first embodiment so that the pins  410   a ,  410   b  of the pin gauge  410  will extend substantially parallel to the horizontal bottom surface. 
     The vertical support  480  has a vertical guide  480   a  that guides the vertical movement of the body  400 . Both the body  400  and the horizontal support  420  are engaged with the vertical guide  480   a . The body  400  is moved vertically, as guided by the vertical guide  480   a , so that the pin gauge  410  can be brought face-to-face with the chuck. 
     The apparatus  40  also includes a first drive member  430  for moving the body  400  horizontally along the horizontal guide  420   a  and a first actuating member  440  for actuating the first drive member  430 . The first drive member  430  is integral with the body  400 . More specifically, the first drive member  430  comprises a fixed nut  430   a , and a horizontal drive screw  430   b  threaded to the fixed nut  430   a  and connected to the body  400 . The body  400  is driven along the horizontal guide  420   a  by the horizontal drive screw  430   b  as the screw  430   b  is rotated relative to the fixed nut  430   a . The horizontal drive screw  430   b  can be rotated by means of the actuating member  440  (a knob, as shown in the figure). When the horizontal drive screw  430   b  of is moved linearly by turning the actuating member  440 , the pin gauge  410  of the apparatus  40  is brought into point contact with the chuck. Thus, the chuck can be oriented at the reference angle. 
     The apparatus  40  further comprises a second drive member  490  for moving the body  400  vertically along the vertical guide  480   b , and a second actuating member  470  for handling the second moving member  470 . The second drive member  490  is mounted between the horizontal support  420  and the bottom  480   b  of the vertical support  480 . The second drive member  490  includes a fixed nut  490   a  and a vertical drive screw  490   b  threaded to the fixed nut  490   a . Accordingly, the body  400  is moved along the vertical guide  480   a  as the vertical drive screw  490   b  is rotated by the second actuating member  470 . 
     Note, the reference angle calibration unit  90  of FIG. 9 can be used to also check the accuracy of and calibrate the pin gauge  410  of this embodiment, in the same manner described in connection with the first embodiment. That is, if point contact is not established between all of the pins  410   a ,  410   b  of the pin gauge  410  of the apparatus  40 , the pin gauge  410  is repaired with reference to its state of contact with the surface  90   b.    
     The process of orienting the chuck of the ion implanter at the reference angle using the apparatus according to the present invention will be described below. 
     First, the apparatus is placed in the process chamber of the ion implanter. At that time, the apparatus is situated on the bottom surface of the chamber adjacent to the chuck. The actuating member(s) is/are operated to rotate the drive screw(s). As a result, the main body of the apparatus is moved towards the chuck. In the case of the first embodiment, the height of the apparatus is such that the pin gauge  310  faces the chuck when the apparatus  30  is disposed on the bottom surface of the process chamber. Thus, the actuating member  340  is manipulated (turned) to move the horizontal drive screw  330   b  and the body  300  integral therewith toward the chuck until the pin gauge  310  contacts the chuck. On the other hand, in the case of the second embodiment, the actuating members  440 ,  470  are manipulated to move the body  400  along the horizontal guide  420   a  and the vertical guide  480   a . The manipulation of the actuating members  440 ,  470  is carried out such that the pin gauge  410  is brought up or down to the same level as the chuck, and then the pin gauge  410  is brought into contact with the chuck. At this time, the state of point contact between the end of each of the projections of the pin gauge and the chuck is sensed. This information is used to determine whether the orientation of the chuck is within a certain range. The measurements and the result of this determination are indicated on the display. Subsequently, the rotary members on which the chuck is mounted are rotated by amounts necessary to orient the chuck at the reference angle. Once this orienting of the chuck is completed, the chuck is tilted by an angle of 7 degrees relative to the reference position, i.e., the plane of the chuck is inclined at an angle of 7 degrees relative to the vertical. The aligning of the chuck in this way relative to the ion beam of the implanter prevents the channeling effect from occurring during the implantation process. 
     Also, if the apparatus has been used for a long time, for example, the reference angle calibration unit  90  of FIG. 9 is used to check the accuracy of the pin gauge and, if necessary, calibrate the pin gauge. 
     As described above, the apparatus according to the present invention can provide a precise reference angle for an object because the gauge of the apparatus does not shake as it is positioned against the chuck. That is, the gauge of the apparatus is moved by a mechanism and not manually. Furthermore, the bottom surface of the apparatus that is placed on the bottom of the chamber has a high degree of planarity, which contributes to the precision of the apparatus. In addition, the operator can monitor the operation of the apparatus in real time using the display. 
     Accordingly, the present invention can be used to minimize processing errors otherwise caused by the misalignment of a chuck in semiconductor fabrication equipment, e.g., an ion implanter. 
     Although the present invention has been described above in connection with the preferred embodiments thereof, the present invention is not so limited. For instance, although the present invention has been mainly described for use in orienting a chuck of an ion implanter, the present invention can be used for providing a reference angle for other objects as well. Therefore, various changes to and other uses of the preferred embodiments are seen to be within the true spirit and scope of the invention as defined by the appended claims.