Abstract:
An aspect of the present invention is drawn to a device for use with an electrostatic chuck having a top surface and a bottom surface, the top surface being separated from the bottom surface by a width, the electrostatic chuck additionally having a hole therein, the hole having a first width at the top surface and having a second width at the bottom surface, the first width being less than the second width, the top surface being capable of having wafer disposed thereon. The device includes a pin, a shaft, a neck portion and an outer housing portion. The pin has a pin width less than the first width. The shaft has a pin-holding portion, an end portion and a central portion disposed between the pin-holding portion and the end portion. The central portion has a first bearing portion. The outer housing portion has a first end and a second end and includes a second bearing portion. The shaft is disposed within the outer housing portion and is moveable relative to the outer housing portion. The neck portion is disposed at the first end. The second bearing portion is stationary relative to the neck portion. The first bearing portion is movable relative to the second bearing portion.

Description:
BACKGROUND 
     Semiconductor wafers are processed in wafer processing systems. An example conventional wafer processing system will now be described with reference to  FIGS. 1 and 2 . 
       FIGS. 1 and 2  illustrate a conventional wafer processing system. In the figures, wafer processing system  100  includes a confinement chamber portion  102 , an electrode  104 , an electrostatic chuck (ESC)  106 , an electrode driving source  112 , an ESC driving source  114  and a pin lifting system  116 . Confinement chamber portion  102  has an input portion  108  and an output portion  110 . Pin lifting system  116  includes a lifting pin  118 . Confinement chamber portion  102  surrounds a processing space  122  used to process a semiconductor wafer  120 . 
     In operation, as illustrated in  FIG. 1 , semiconductor wafer  120  is disposed onto ESC  106 . ESC driving source  114  applies a voltage to ESC  106 , thereby creating an electric field, which creates a Coulomb force that holds semiconductor wafer  120  onto ESC  106 . While semiconductor wafer  120  is held in place by ESC  106 , a plurality of materials may be supplied to processing space  122  via input portion  108 , while a voltage is applied to electrode  104  via electrode driving source  112  to create plasma within processing space  122 . The created plasma within processing space interacts with semiconductor wafer  120 , either by etching portions of semiconductor wafer  120 , or by depositing material onto semiconductor wafer  120 . When the process is complete, the remaining material within processing space  122  is removed via output portion  110 . Second driving source  114  then stops applying a voltage to ESC  106 , which terminates the Coulomb force, which then releases semiconductor wafer  120 . As illustrated in  FIG. 2 , pin lifting system  116  then pushes up on semiconductor wafer  120  to relieve the surface tension, lifting one edge of semiconductor wafer  120  off of ESC  106 . Semiconductor wafer  120  is then removed from wafer processing system  100 . 
     Great care must be taken in both construction and utilization of wafer processing system  100  in order to maintain the precision required in all aspects of semiconductor wafer processing. ESC  106 , in particular is a very expensive portion of wafer processing system  100 . The operational parameters of ESC  106  must be precisely maintained in order to accurately hold and release semiconductor wafers. Non-limiting examples of operational parameters of ESC  106  include surface resistance, surface capacitance and overall impedance, each of which may be changed as a result to changes, or damage, to the physical integrity of ESC  106 . As such, ESC  106  may not function efficiently, or even at all, if its physical integrity is degraded. 
     ESC  106  is specifically susceptible to damage from lifting pin  118 , as will be described below with respect to  FIGS. 3 and 4 . 
       FIG. 3  is an exploded view of portion A of  FIG. 1 . In  FIG. 3 , lifting pin  118  is separated from the inner wall of ESC  106  by a radial distance  302 . The separation is needed to eliminate contact between lifting pin  118  and ESC  106  thereby preventing damage to ESC  106  from lifting pin  118 . 
       FIG. 4  is an exploded view of an example situation of portion A, when lifting pin  118  is moved closer to semiconductor wafer  120 . In the figure, the longitudinal axis of lifting pin  118  should align perpendicularly with ESC  106 , along line  402 . However, in this example situation, the longitudinal axis of lifting pin  118  is actually aligned along line  404 , which is separated from the axis along line  402  by an angle θ. Because the longitudinal axis of lifting pin  118  is aligned along line  404 , when lifting pin  118  moves close to semiconductor wafer  120 , lifting pin  118  contacts ESC  106  at point  406 . As lifting pin  118  continues to rise toward semiconductor wafer  120 , pin continues to scrape against ESC  106 . Such scraping may damage ESC  106 , which may change the physical integrity of ESC  106 , which may change operational parameters of ESC  106 , and which may result in ESC  106  functioning inefficiently or improperly. In such an event, ESC  106  must be repaired or replaced, either of which is costly. 
     A more detailed description of a conventional pin lifting system will now be described with reference to  FIGS. 5 and 6 . 
       FIG. 5  illustrates conventional pin lifting system  116  in a first state. As seen in the figure, pin lifting system  116  includes lifting pin  118 , a pin holding shaft  504 , a housing neck  506 , a housing outer portion  508 , a first bearing  510 , a bearing separating portion  512 , a second bearing  514  and a bellows portion  516 . Bearing separating portion  512  separates first bearing  510  from second bearing  514  and additionally has a window  518  cut therein. Window  518  enables a lifting arm (not shown) to lift pin holding shaft  504  via notch  520 . Pin holding shaft  504  includes a pin holding portion  522 , an intermediate portion  524 , a seat portion  526  and an end portion  528 , which includes notch  520 . Housing neck  506  includes a shaft guiding portion  532 , a cap portion  534  and an inner portion  536 . Housing outer portion  508  includes a lip portion  530 . 
     Pin lifting system  116  is mountable into ESC  106  in a mounting hole  540 . Mounting hole  540  includes a neck portion  542 , a pin portion  544  and pin opening  546  at the top surface of ESC  106 . Neck portion  542  is designed to pass lifting pin  118  and to retain shaft guiding portion  532 . Pin portion  544  is operable to pass lifting pin  118 , whereas pin opening  546  is designed to pass the tip of lifting pin  118 . A fastening plate  548  retains pin lifting system  116  within mounting hole  540 . 
     Cap portion  534  is connected to housing outer portion  508 . One end of bellows portion  516  is connected to inner portion  536  of housing neck  506 , whereas the other end of bellows portion  516  is connected to seat portion  526 . First bearing  510  is connected to lip portion  530  of housing outer portion  508 , and is additionally connected to bearing separating portion  512 . Bearing separating portion  512  is additionally connected to second bearing  514 . As such, first bearing  510  remains a constant distance d from second bearing  514 . 
     In this state, lifting pin  118  is disposed below the top surface of ESC  106 . As such, there is a space  538  between the top of pin holding portion  522  and shaft guiding portion  532 . 
     A second state, a wafer-lifting state, of pin lifting system  116  will now be described with reference to  FIG. 6 . 
     To lift lifting pin  118  out through pin opening  546  of ESC  106 , a lifting arm (not shown) engages and pin holding shaft  504  through window  518  at notch  520 . Pin holding shaft  504  is continually lifted until seat portion  526  is separated from first bearing  510  and the top of pin holding portion  522  reaches the top of shaft guiding portion  532 . 
     The problem of a lifting pin damaging an ESC, for example as discussed above with respect to  FIG. 4 , will now be described as applied to pin lifting system  116 , with reference to  FIGS. 7-10 . 
       FIG. 7  is an exploded view of portion B of  FIG. 5 . In the figure, end portion  528  of pin holding shaft  504  does not actually touch first bearing  510 . End portion  528  is spaced a distance  702  from first bearing  510 . Pin lifting system  116  is designed in this manner to provide friction free movement along the axis parallel with the length of pin holding shaft  504 . 
       FIG. 8  is an exploded view of portion C of  FIG. 5 . In the figure, end portion  528  of pin holding shaft  504  does not actually touch bearing separating portion  512 . End portion  528  is spaced a distance  802  from bearing separating portion  512 . Pin lifting system  116  is designed in this manner to provide friction-free movement along the axis parallel with the length of pin holding shaft  504 . 
     The outer diameter of pin holding shaft  504  is conventionally designed to be as close to the inner diameter of each of first bearing  510  and bearing separating portion  512  to limit lateral movement of pin holding shaft  504 . However, as discussed above, in order to provide friction-free movement of pin holding shaft  504 , gaps still remain. These gaps may lead to a tilting of lifting pin  118 , as will be described with reference to  FIGS. 9 and 10  below. 
     Presume that arrow  902  of  FIG. 9  represents the ideal longitudinal axis of pin holding shaft  504 , wherein the longitudinal axis of lifting pin  118  is normal to the upper surface of ESC  106 . In this example, further presume that pin holding shaft  504  is actually tilted such that end portion  528  touches bearing separating portion  512  at point  550 , as illustrated in  FIG. 5 , whereas end portion  528  additionally touches first bearing  510  at point  552 . In such a case, the longitudinal axis of pin holding shaft  504  actually is parallel with arrow  904  of  FIG. 9 . In this example, therefore, pin holding shaft  504  is tilted by an angle φ. 
     As discussed above, the distance d is the distance between first bearing  510  second bearing  514 . The spacing Δ 1    906  is the spacing between end portion  528  and first bearing  510 , which is additionally illustrated as distance  702  in  FIG. 7 . As such, in  FIG. 9 , distance d and spacing Δ 1    906  are related to angle φ as:
 
cos φ=Δ 1   /d.   (1)
 
Therefore, with a known distance d and spacing Δ 1    906 , the maximum tilt angle φ of pin holding shaft  504  may be calculated.
 
     Once the maximum tilt angle φ of pin holding shaft  504  is calculated, the maximum, unwanted, lateral displacement of lifting pin  118  may be determined. Returning to  FIG. 5 , distance D is the distance from the upper surface of ESC  106  to point  550 , where end portion  528  touches bearing separating portion  512 . Using maximum tilt angle φ of pin holding shaft  504  and the distance D, the maximum lateral displacement of lifting pin  118  may be determined. 
     As illustrated in  FIG. 10 , presume that arrow  1002  represents the ideal longitudinal axis of pin holding shaft  504 , wherein the longitudinal axis of lifting pin  118  is normal to the upper surface of ESC  106 . In this example, further presume that pin holding shaft  504  is tilted the maximum tilt angle φ. In such a case, the longitudinal axis of pin holding shaft  504  actually is parallel with arrow  1004  of  FIG. 10 . Further, the maximum lateral displacement of lifting pin  118  is Δ 2    1006 . As such, distance D and maximum tilt angle φ are related to Δ 2    1006  as:
 
Δ 2   =D  cos φ.  (2)
 
Therefore, with a known distance D and known maximum tilt angle φ, spacing Δ 2    1006  may be calculated.
 
     Plugging equation (1) into equation (2), yields:
 
Δ 2 =( D/d )Δ 1 .  (3)
 
Therefore, it is clear that the maximum lateral displacement Δ 2  of lifting pin  118  is directly related to the proportion of the distance D from the upper surface of ESC  106  to point  550  to the distance d between first bearing  510  second bearing  514 .
 
     As an example, presume that in a conventional pin lifting system, the distance d between first bearing  510  second bearing  514  is 1.2 cm, the distance D from the upper surface of ESC  106  to point  550  is 4.4 cm and the spacing Δ 1  between end portion  528  and first bearing  510  is 1.4 mm. In such an example, the proportion of the distance D from the upper surface of ESC  106  to point  550  to the distance d between first bearing  510  second bearing  514  is 3.6. Using equation (3), the maximum lateral displacement Δ 2  of lifting pin  118  is calculated to be 5.1 mm. In other words, lifting pin  118  has 5.1 mm of unwanted lateral play, with which lifting pin  118  may contact and damage ESC  106 . 
     What is needed is a pin lifting system that decreases the lateral displacement of the pin. 
     BRIEF SUMMARY 
     It is an object of the present invention to provide a pin lifting system that decreases the lateral displacement of the pin. 
     An aspect of the present invention is drawn to a device for use with an electrostatic chuck having a top surface and a bottom surface, the top surface being separated from the bottom surface by a width, the electrostatic chuck additionally having a hole therein, the hole having a first width at the top surface and having a second width at the bottom surface, the first width being less than the second width, the top surface being capable of having wafer disposed thereon. The device includes a pin, a shaft, a neck portion and an outer housing portion. The pin has a pin width less than the first width. The shaft has a pin-holding portion, an end portion and a central portion disposed between the pin-holding portion and the end portion. The central portion has a first bearing portion. The outer housing portion has a first end and a second end and includes a second bearing portion. The shaft is disposed within the outer housing portion and is moveable relative to the outer housing portion. The neck portion is disposed at the first end. The second bearing portion is stationary relative to the neck portion. The first bearing portion is movable relative to the second bearing portion. 
     Additional objects, advantages and novel features of the invention are set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
    
    
     
       BRIEF SUMMARY OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form a part of the specification, illustrate an exemplary embodiment of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
         FIG. 1  illustrates a conventional wafer processing system in a first state when a wafer-lifting pin is below the surface of an ESC; 
         FIG. 2  illustrates the conventional wafer processing system in a second state when the wafer-lifting pin is above the surface of the ESC; 
         FIG. 3  is an exploded view of portion A of  FIG. 1 ; 
         FIG. 4  is an exploded view of an example situation of portion A, when the pin is moved closer to semiconductor wafer; 
         FIG. 5  illustrates a conventional pin lifting system in a first state; 
         FIG. 6  illustrates a conventional pin lifting system in a second state; 
         FIG. 7  is an exploded view of portion B of  FIG. 5 ; 
         FIG. 8  is an exploded view of portion C of  FIG. 5 ; 
         FIG. 9  illustrates a relationship between an ideal orientation of a pin holding shaft of the conventional pin lifting system of  FIG. 5  when in the first state and an actual orientation of the pin holding shaft when tilted in the first state; 
         FIG. 10  illustrates a relationship between an ideal orientation of a pin holding shaft of the conventional pin lifting system of  FIG. 6  when in the second state and an actual orientation of the pin holding shaft when tilted in the second state; 
         FIG. 11  illustrates an example pin lifting system, in a first state, in accordance with an aspect of the present invention; 
         FIG. 12  illustrates the example pin lifting system of  FIG. 11 , in a second state, in accordance with an aspect of the present invention; 
         FIG. 13  is an exploded view of portion D of  FIG. 11 ; 
         FIG. 14  is an exploded view of portion E of  FIG. 11 ; 
         FIG. 15  illustrates a relationship between an ideal longitudinal axis of a pin holding shaft of pin lifting system of  FIG. 11  when in the first state and an actual longitudinal axis of the pin holding shaft when tilted in the first state; 
         FIG. 16  illustrates a relationship between an ideal longitudinal axis of a pin holding shaft of pin lifting system of  FIG. 12  when in the second state and an actual longitudinal axis of the pin holding shaft when tilted in the second state; and 
         FIG. 17  illustrates a relationship between an ideal longitudinal axis of a pin holding shaft of pin lifting system of  FIG. 12  when in the second state and an actual longitudinal axis of the pin holding shaft when tilted in the second state. 
     
    
    
     DETAILED DESCRIPTION 
     An example embodiment of a pin lifting system in accordance with an aspect of the present invention will now be described with reference to  FIGS. 11 and 12 . 
       FIG. 11  illustrates an example pin lifting system  1100 , in a first state, in accordance with an aspect of the present invention. As seen in the figure, pin lifting system  1100  includes a pin  1102 , a pin retaining spring  1136 , a pin holding shaft  1104 , a housing neck  1106 , a housing outer portion  1108  that includes a second bearing portion  1112 , a first bearing  1110  and a bellows portion  1116 . Housing outer portion  1108  has a window  1114  cut therein. Window  1114  enables a lifting arm (not shown) to lift pin holding shaft  1104  via a notch  1118 . Pin holding shaft  1104  includes a pin holding portion  1120 ; an intermediate portion  1122  that includes a tapered portion  1147 , and an end portion  1124 , which includes an indentation  1126  and notch  1118 . Housing neck  1106  includes a shaft guiding portion  1128 , a cap portion  1130  and an inner portion  1132  that is shaped to have a cavity  1148 . Housing outer portion  1108  includes a lip portion  1134 . 
     Pin lifting system  1100  is mountable into ESC  106  in mounting hole  540 . Neck portion  542  is designed to pass pin  1102  and to retain shaft guiding portion  1128 . Pin portion  544  is operable to pass pin  1102 , whereas pin opening  546  is designed to pass the tip of pin  1102 . 
     Pin holding portion  1120  has a channel therein, for holding pin  1102 . A radial force providing device, such as a pin retaining spring  1136 , is annularly disposed around pin  1102  and within pin holding portion  1120 . Pin retaining spring  1136  provides a radial force between the circumference of pin  1102  and the inner circumference of pin holding portion  1120 . This radial force centers pin  1102  within pin holding portion  1120 . 
     The bottom  1138  of pin  1102  may be designed to have a male geometry, whereas the bottom of pin holding portion  1120 , or pin seat  1140 , may be designed to have a corresponding female geometry. A non-limiting example of a male geometry of pin bottom  1138  includes a semi-spherical convex male geometry, whereas a non-limiting example of a female geometry of pin seat  1140  includes a semi-spherical concave female geometry. This geometric relationship between pin bottom  1138  and pin seat  1140  provides additional centering of pin  1102 . 
     Cap portion  1130  is connected to housing outer portion  1108 . One end of bellows portion  1116  is connected to inner portion  1132  of housing neck  1106 , whereas the other end of bellows portion  1116  is connected to first bearing  1110 . First bearing  1110  is additionally connected to intermediate portion  1122  of pin holding shaft  1104 . As will be discussed further below, and in contrast to conventional pin lifting systems as discussed above, first bearing  1110  does not remain at a constant distance d from second bearing portion  1112 . In accordance with an aspect of the present invention, first bearing  1110  is movable relative to second bearing portion  1112 . 
     In this state, pin  1102  is disposed below the top surface of ESC  106 . 
     A second state, a wafer-lifting state, of pin lifting system  1100  will now be described with reference to  FIG. 12 . 
     To lift pin  1102  out through pin opening  546  of ESC  106 , a lifting arm (not shown) engages and pin holding shaft  1104  through window  1114  at notch  1118 . Pin holding shaft  1104  is continually lifted until first bearing  1110  is separated from lip portion  1134  and tapered portion  1147  of intermediate portion  1122  of pin holding shaft  1104  fits into neck cavity  1148 . 
       FIG. 13  is an exploded view of portion D of  FIG. 11 . In the figure, first bearing  1110  does not actually touch housing outer portion  1108 . First bearing  1110  is spaced a distance  1302  from housing outer portion  1108 . Pin lifting system  1100  is designed in this manner to provide friction free movement along the axis parallel with the length of pin holding shaft  1104 . First bearing  1110  may additionally be designed to include an annular space  1142 , which may be filled with lubricant to reduce friction in the event first bearing  1110  contacts housing outer portion  1108 . 
       FIG. 14  is an exploded view of portion E of  FIG. 11 . In the figure, end portion  1124  of pin holding shaft  1104  does not actually touch second bearing portion  1112 . End portion  1124  is spaced a distance  1402  from second bearing portion  1112 . Pin lifting system  1100  is designed in this manner to provide friction-free movement along the axis parallel with the length of pin holding shaft  1104 . Second bearing portion  1112  may additionally be designed to include an annular space  1144 , which may be filled with lubricant to reduce friction in the event end portion  1124  contacts second bearing portion  1112 . 
     The outer diameter of pin holding shaft  1104  is designed to be as close to the inner diameter of second bearing portion  1112  and the outer diameter of first bearing  1110  is designed to be as close to the inner diameter of outer housing portion  1108  to limit lateral movement of pin holding shaft  1104 . However, as discussed above, in order to provide friction-free movement of pin holding shaft  1104 , gaps still remain. These gaps lead to a tilting of pin  1102 , as discussed below with reference to  FIGS. 15 and 16 . 
     In a first state, the pin in a pin lifting system is disposed below the surface of the ESC. Using the example embodiment pin lifting system  1100 , presume that arrow  1502  of  FIG. 15  represents the ideal longitudinal axis of pin holding shaft  1104 , wherein the longitudinal axis of pin  1102  is normal to the upper surface of ESC  106 . In this example, further presume that pin holding shaft  1104  is tilted such that end portion  1124  touches second bearing portion  1112  at point  1146 , as illustrated in  FIG. 11 , whereas first bearing  1110  touches outer housing portion  1108  at point  1149 . In such a case, the longitudinal axis of pin holding shaft  1104  actually is parallel with arrow  1504  of  FIG. 15 . In this example, therefore, pin holding shaft  1104  is tilted by an angle φ′. 
     In this example, let d′ be the distance between first bearing  1110  and second bearing portion  1112 , when pin lifting system  1100  is in the first state. The spacing Δ 1 ′  1506  is the spacing between first bearing  1110  and outer housing portion  1108 , which is additionally illustrated as distance  1302  in  FIG. 13 . As such, in  FIG. 15 , distance d′ and spacing Δ 1 ′  1506  are related to angle φ′ as:
 
cos φ′=Δ 1   ′/d′.   (4)
 
Therefore, with a known distance d′ and spacing Δ 1 ′  1506 , an initial maximum tilt angle φ′ of pin holding shaft  1104  may be calculated.
 
     Unlike the conventional pin lifting system discussed above with respect to  FIGS. 5 and 6 , in a pin lifting system in accordance with an aspect of the present invention, the tilt angle of the pin holding shaft does not remain constant. In particular, and as will be described in more detail below, in a pin lifting system in accordance with an aspect of the present invention, the distance between the first bearing and the second bearing portion does not remain constant. As such, the initial maximum tilt angle φ′ of pin holding shaft  1104 , which corresponds to the pin lifting system being in a first state, will be greater than the final maximum tilt angle of pin holding shaft  1104 , which corresponds to the pin lifting system being in a second state. 
     In a second state, the pin in a pin lifting system is disposed above the surface of the ESC. Using the example embodiment pin lifting system  1100 , presume that arrow  1602  of  FIG. 16  represents the ideal longitudinal axis of pin holding shaft  1104 , wherein the longitudinal axis of pin  1102  is normal to the upper surface of ESC  106 . In this example, further presume that pin holding shaft  1104  is tilted such that end portion  1124  touches second bearing portion  1112  at point  1146 , as illustrated in  FIG. 12 , whereas first bearing  1110  touches outer housing portion  1108  at point  1248 . In such a case, the longitudinal axis of pin holding shaft  1104  actually is parallel with arrow  1604  of  FIG. 16 . In this example, therefore, pin holding shaft  1104  is tilted by an angle α. 
     In this example, let d″ be the distance between first bearing  1110  and second bearing portion  1112 , when pin lifting system  1100  is in the second state. The spacing Δ 1 ″  1606  is the spacing between first bearing  1110  and outer housing portion  1108 . As such, in  FIG. 16 , distance d″ and spacing Δ 1 ″  1606  are related to angle α as:
 
cos α=Δ 1   ″/d″.   (5)
 
Therefore, with a known distance d″ and spacing Δ 1 ″  1606 , a final maximum tilt angle α of pin holding shaft  1104  may be calculated.
 
     Once the final maximum tilt angle α of pin holding shaft  1104  is calculated, the maximum, unwanted, lateral displacement of pin  1102 , when pin lifting system  1100  is in the second state, may be determined. Returning to  FIG. 12 , distance D″ is the distance from the upper surface of ESC  106  to point  1146 , where end portion  1124  touches second bearing portion  1112 . Using maximum tilt angle α of pin holding shaft  1104  and the distance D″, the maximum lateral displacement of pin  1102  may be determined. 
     As illustrated in  FIG. 17 , when pin lifting system  1100  is in the second state, presume that arrow  1702  represents the ideal longitudinal axis of pin holding shaft  1104 , wherein the longitudinal axis of pin  1102  is normal to the upper surface of ESC  106 . In this example, further presume that pin holding shaft  1104  is tilted the maximum tilt angle α. In such a case, the longitudinal axis of pin holding shaft  1104  actually is parallel with arrow  1704  of  FIG. 17 . Further, the maximum lateral displacement of pin  1102  is Δ 2 ″  1706 . As such, distance D″ and maximum tilt angle α are related to Δ 2 ″  1706  as:
 
Δ 2   ″=D ″ cos α.  (6)
 
Therefore, with a known distance D″ and known maximum tilt angle α, spacing Δ 2 ″  1706  may be calculated.
 
     Plugging equation (5) into equation (6), yields:
 
Δ 2 ″=( D″/d ″)Δ 1 ″.  (7)
 
Therefore, when pin lifting system  1100  is in the second state, it is clear that the maximum lateral displacement Δ 2 ″ of pin  1102  is directly related to the proportion of the distance D″ from the upper surface of ESC  106  to point  1146  to the distance d″ between first bearing  1110  and second bearing portion  1112 .
 
     As an example, presume that in a first state of an example pin lifting system in accordance with the present invention, the distance d′ between first bearing  1110  second bearing portion  1112  is 1.2 cm and the spacing Δ 1 ′ between first bearing  1110  and outer housing portion  1108  is 1.4 mm. In such an example, using equation (4) the initial maximum tilt angle φ′ would be 1.8°. 
     However, when in the second state, the final maximum tilt angle α is smaller than the initial maximum tilt angle φ′. 
     Presume that in a second state of an example pin lifting system in accordance with the present invention, the distance d″ between first bearing  1110  second bearing portion  1112  is now 2.0 cm because first bearing  1110  has moved relative to second bearing portion  1112 . Further, presume that the distance D″ from the upper surface of ESC  106  to point  1146  is 4.4 cm and the spacing Δ 1 ′ between first bearing  1110  and outer housing portion  1108  remains 1.4 mm. In such a case, the proportion of the distance D″ from the upper surface of ESC  106  to point  1112  to the distance d″ between first bearing  1110  second bearing portion  1112  is 2.2. Using equation (7), the maximum lateral displacement Δ 2 ″ of pin  1102 , when pin lifting system  1100  is in the second state, is calculated to be 3.08 mm. In other words, pin  1102  has 3.08 mm of unwanted lateral play, with which pin  1102  may contact and damage ESC  106 . This is a 40% decrease in lateral play over the conventional pin lifting system discussed above. 
     A pin lifting system in accordance with aspect of the present invention decreases the maximum lateral movement of the lifting pin, when the pin lifting system in is a state where the pin is close to the surface of the ESC. A radial force providing device within the pin holding portion of the pin holding shaft provides additional centering of the pin. Further, a collaboration of geometries of the bottom of the pin and the pin seat within the pin holding portion of the pin holding shaft provides addition centering of the pin. Finally, by varying the distance between a first bearing and a second bearing portion of the pin lifting system, the final maximum lateral movement of the lifting pin is decreased. 
     The foregoing description of various preferred embodiments of the invention have been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments, as described above, were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.