Abstract:
The disclosure is a baking apparatus including a susceptor, lift pins, and guiding blocks positioned at the edge of the susceptor to lead a wafer to be exactly positioned on the susceptor. The guiding blocks are linearly movable within a range of a semidiameter of a plate. A wafer is partially mounted on a wafer guide, being inclined against the susceptor, and thereby may heats uniformly.

Description:
[0001]    This application relies for priority upon Korean Patent Application No. 2003-9164 filed on Feb. 13, 2003, and Korean Patent Application No. 2003-47973 filed on Jul. 14, 2003, the contents of which are herein incorporated by reference in their entirety.  
         FIELD OF THE INVENTION  
         [0002]    The present invention generally relates to semiconductor manufacturing apparatuses and methods and more specifically, to positioning apparatuses and methods for positioning semiconductor substrates.  
         BACKGROUND OF THE INVENTION  
         [0003]    With higher integration densities of semiconductor devices, their chip scales are minimized due to their reduced critical dimensions. These increased integration rates require improved photolithographic technologies for building circuit patterns having finer resolutions. This photolithography technology generally includes the steps of depositing, soft-baking, exposing, hard-baking, and then developing the subject semiconductors devices.  
           [0004]    In baking wafers, an apparatus may be employed including a susceptor on which a wafer is mounted, and a plurality of guiding blocks for positioning the wafer on the susceptor. The susceptor may include a heating plate for warming the wafer, and a spacer for supporting the edges of the wafer on the heating plate. The wafer is moved into a reaction chamber by a transfer arm, and is then mounted on the susceptor by a lift pin.  
           [0005]    During these operations, a wafer may be incorrectly placed on the susceptor in a sloped position. This situation occurs when the edges of the wafer are partially placed on the guiding blocks. This can occur due to malfunctions or positioning errors with respect to the transfer arms. Such an inclinedly positioned wafer may be irregularly heated causing manufacturing defects therein, and, in the extreme resulting in bending or cracking of wafer.  
           [0006]    Furthermore, while a higher temperature during the baking process increases the expansion rate of a wafer, the guiding blocks are disposed at a constant distance from a wafer regardless of the processing temperature. Therefore, a wafer may engage the guiding blocks during a high temperature processing operation such as during baking.  
         SUMMARY OF THE INVENTION  
         [0007]    It is, therefore, an object of the present invention to provide an apparatus and method capable of safely positioning a wafer during a high temperature process.  
           [0008]    According to an aspect of the present invention, there is provided an apparatus for manufacturing semiconductor devices, including: a susceptor on which a substrate is settled; lift pin assembly for loading the substrate on the susceptor; a plurality of guiding blocks disposed around the edge of the susceptor, rendering the substrate to be settled at a normal position on the susceptor; and a guiding block transfer unit for moving the guiding blocks on the susceptor.  
           [0009]    The susceptor includes: a plate; and a spacer disposed at the edge of the plate, on which the edge of the substrate is laid, including a guiding lane leading a motion of the guiding block. Each of the guiding blocks linearly moves along the guiding lane within a range of semidiameter of the susceptor.  
           [0010]    The guiding block transfer unit includes: a shaft rotating by a driver in a predetermined range, being perpendicular to the driver; a plurality of supporting rods horizontally combined with the shaft; and a plurality of transfer rods coupled between the supporting rods and the guiding blocks, the transfer rods being pivotally coupled to the supporting rods. When the shaft rotates, the guiding blocks move along the guiding lanes and the transfer rods pivot. The transfer rod includes: a horizontal portion pivotally coupled to the supporting rods; a vertical portion coupled upward to the horizontal portion; and a connection portion coupled to the vertical portion pivotally and the guiding block.  
           [0011]    In the embodiment, the guiding blocks move with displacement positions variable depending on a processing temperature.  
           [0012]    In the embodiment, the transfer rod is coupled to the guiding block by means of openings formed in the guiding block and transfer rod, a bolt inserted through the openings, and a nut, in a hollow formed a sidewall of the susceptor. The bolt is set to be movable in the opening of the transfer rod to allow variations of the displacement position.  
           [0013]    In the embodiment, an elastic element is provided being connected between the transfer rod and the plate in a hollow formed in a sidewall of the plate, whereby the elastic element aids the guiding block to return a predetermined position. And, a testing unit is used for inspecting a current positioning state of the substrate on the susceptor, including: a vacuum line led from a vacuum pump, extending to the upper space of the plate; and a sensor for detecting pressure in the vacuum line.  
           [0014]    In the embodiment, the apparatus may be used for baking a semiconductor substrate.  
           [0015]    The present invention also provides a method of positioning a substrate on a susceptor during a semiconductor device fabricating process, including the steps of: transferring and loading the substrate on lift pins protruding above the susceptor through openings formed in the susceptor; descending the lift pins; and moving guiding blocks, which are disposed at the edge of the susceptor, to render the substrate on a normal position of the susceptor.  
           [0016]    The guiding blocks moves in strokes backward and forward with predetermined distance when the lift pins descend under the top level of the susceptor. The lift pins descend when the guiding blocks move on the susceptor outward and the guiding blocks move inward on the susceptor up to a displacement position when the lift pins descend under the top level of the susceptor. The method may further include the step of testing a current positioning state of the substrate.  
           [0017]    The forgoing and other objects, features and advantages of the invention will be apparent from the description of the preferred embodiment of the invention, as illustrated in the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 is a schematic of a baking apparatus according to a preferred embodiment of the invention;  
         [0019]    [0019]FIG. 2 is a plan view of a susceptor employed in the baking apparatus shown in FIG. 1;  
         [0020]    [0020]FIG. 3 is a sectional view illustrating an internal structure of the susceptor shown in FIG. 1 or  2 ;  
         [0021]    [0021]FIG. 4 is a perspective view of a guiding block transfer unit;  
         [0022]    [0022]FIG. 5 is a perspective view illustrating the feature of combination with a guide block, a spacer, and a transfer rod;  
         [0023]    [0023]FIGS. 6A and 6B are sectional views illustrating features of displacement for the guiding block;  
         [0024]    [0024]FIG. 7 is a sectional view illustrating the feature that an elastic element is installed in an insertion hollow formed at the side of a plate;  
         [0025]    [0025]FIGS. 8A and 8B illustrate the sequence of moving the guiding block to position a wafer at a normal position;  
         [0026]    [0026]FIGS. 9A and 9C illustrate another features of sequentially moving the guiding block to position a wafer at a normal position; and  
         [0027]    [0027]FIG. 10 is a flow chart of processing steps for positioning wafers according to the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]    It should be understood that the description of the preferred embodiment is illustrative and that it should not be taken in a limiting sense. Embodiments of this invention will be explained in conjunction with the drawings.  
         [0029]    This preferred embodiment according to the present invention will describe an apparatus and method for carrying out a semiconductor baking process. However, other equipment including a susceptor on which a wafer is mounted may be practiced in accordance with the present invention.  
         [0030]    In this embodiment, “displacement position” of guiding blocks means the position of the guiding blocks during a baking process. “Awaiting position” of the guiding blocks is the position apart from the center of a susceptor, more spaced than the displacement position therefrom, to provide a sufficient margin for loading a wafer on the susceptor. “Normal position” of a wafer means the predetermined position proper to conduct a process (e.g., a baking process). The guiding blocks at the displacement position and the awaiting position are referred by the solid and broken lines in FIG. 2, 300 and  300 ′, respectively.  
         [0031]    [0031]FIG. 1 illustrates a schematic view of an apparatus  10  which can be employed in a semiconductor fabrication process wherein a wafer is subjected to a baking operation. FIGS. 2 and 3 show the plane and sectional features in the area where a wafer is positioned. The apparatus  10  includes a susceptor  100 , a lift pin assembly  200 , guiding blocks  300 , a guide block mover  400 , and a tester  500 .  
         [0032]    The susceptor  100 , which is provided to accommodate a semiconductor substrate, such as a wafer W, comprises a plate  120  and spacers  140 . The plate  120  includes heating elements (not shown) such as heating coils to warm up a wafer to a proper temperature for processing. The top of the plate  120  is round and flattened. The spacers  140  are installed at the top edges of the plate  120  to support the wafer W, contacting with the edges of the wafer W. The spacers  140  may be provided at regular intervals and may be from three to six in number.  
         [0033]    The wafer W is separated from the plate  120 , so that it is not in contact with the plate  120  that is heated up to a high temperature during a process. At the top of the susceptor  100 , a cover  160  is provided to facilitate an airtight condition during processing of the semiconductor substrate. The cover  160  is cylinder-shaped and includes an upper plate  162 , and a sidewall  164  which extends downwardly from the edge of the upper plate  162 .  
         [0034]    The lift pin assembly  200  (FIG. 3), driven by a robot arm (not shown), moves the wafer W above and onto the susceptor  100 . Assembly  200  comprises lift pins  220 , a support plate  240  for the pins  220 , and an elevator device  260 . The lift pins  220 , which are joined to the upholding plate  240  in a square arrangement, receiving the wafers W from the robot arm. The support plate  240  is connected to the elevator device  260 , such as a hydraulic/pneumatic cylinder, and is movable to a plurality of positions in an upward and downward direction. The lift pins  220  are inserted into openings  122  in the support plate  120  for vertically movement within the openings  122 .  
         [0035]    The wafer W is transferred to the lift pins  220  by means of the robot arm when the lift pins  220  ascend to protrude above the top of the plate  120  and then mounted on the susceptor  100  when the lift pins  200  descend under the top of the plate  120  by way of the openings  122 .  
         [0036]    The guiding blocks  300  lead the wafer W to be positioned on an accurate position within the susceptor  100 . The guiding blocks  300  are disposed on the spacers  140 , each including slopes  320  formed inside from the top surface thereof. The wafer W slips down along the slope  320  to be positioned on the accurate position when it strays from the accurate position to result its edges to be partially laid on the tops of the guiding blocks.  
         [0037]    The baking apparatus  10  also includes a guiding block transfer unit  400  for moving the guiding blocks  300  in a predetermined distance to the displacement position or the awaiting position. It is desirable to render the guiding blocks  300  to be moved linearly along guiding lanes  142  within the range of the radius of the plate  120 . The guiding lanes  142  are formed in the spacers  140  to facilitate the linear movement of the guiding blocks  300 . The guiding lanes  142  are shaped in the form of apertures (or openings) or trenches. The guiding blocks  300  may include underlying projections (not shown) which are movably inserted into the guiding lanes  142 .  
         [0038]    Referring to FIG. 4, the guiding block transfer unit  400  is constructed of a driver  420 , a shaft  440 , supporting rods  460 , and transfer rods  480 . The shaft  440  is vertically connected to the driver  420  such as a stepping motor, hydraulic or pneumatic cylinder, or an actuator, and is rotated on its axis by the driver  420 . The topside of the shaft  440  is horizontally combined with the supporting rods  460  at constant intervals, and in the same number as that of the guiding blocks  300 . The other ends of the supporting rods  460  are joined with the transfer rods  480  which are each connected to the guiding blocks  300 . The supporting rods  460  and the transfer rods  480  are pivotally joined one to the other. The transfer rods  480  move in a range of angles when the supporting rods  460  are rotated. This enables the guiding blocks  300  to be linearly movable along the guiding lanes  142 .  
         [0039]    Each of the transfer rods  480  is composed of a horizontal portion  482 , a vertical portion  484 , and a connection portion  486 , respectively. The horizontal portion  462  is linearly connected to the supporting rod  460  by means of a pivotable section on the same plane. The vertical portion  484  perpendicularly extends upwardly from the end of the horizontal portion  482 . The connection portion  486  is disposed parallel to the horizontal portion  482 , and is pivotally attached to the end of the vertical portion  484 . While the horizontal and vertical portions,  482  and  484 , may comprise a single body portion, they may also be combined by attachment devices such as screws.  
         [0040]    [0040]FIG. 5 depicts a feature of combining a guiding block and a transfer rod, utilizing, for example, guiding block  300 , spacer  140 , and transfer rod  480 , respectively. Referring to FIGS. 5, 6A and  6 B, the connection portions  386  of the transfer rods  480  are inserted into hollows  124  formed in the sidewalls of the plate  120  under the spacers  140 . In each illustrative structure, the guiding block  300  and the transfer rod  480  are combined by means of, for example, a bolt  722  and a nut  724 , through openings  302  and  487 , to penetrate the center of the guiding block  300  and the end of the connection portion  486 . The bolt  722  is coupled to the nut  724  through the opening in the guiding block  300 , the holed guiding lane  142  in the spacer  140 , and the opening in the connection portion  486  of the transfer rod  480 .  
         [0041]    The wafer W expands with heat during a baking process. This narrows the distance between the wafer W and the guiding blocks  300  at the displacement positions. At high processing temperature, the wafer W abuts against the guiding blocks  300 .  
         [0042]    Such abutting action can be overcome by adjusting the displacement position of the guiding blocks  300  in accordance with the processing temperature in the baking apparatus  10 . In the present baking apparatus  10 , the opening  487  in the connection portion  486  of the transfer rod  480  is elongated along the span of the connection portion  486 , as in the case of the guiding lane  142 . Preferably, the length of the elongate opening is larger than the diameter of the bolt  722 . Thus, the elongate opening  487  enables a combinable position between the guiding block  300  and the transfer rod  480  to be varied, which adjusts the displacement position of the guiding block  300 . FIGS. 6A and 6B exemplarily show available features of the displacement positions for the guiding block  300  combined with the transfer rod  480 . The location of the guiding block is dependent on whether relatively lower or high processing temperatures is employed.  
         [0043]    In a lower temperature scenario, as shown in FIG. 6A, the bolt  722  is fixed by the nut  724  at a position adjacent to one end  487   a  of the opening  487 , establishing the displacement position of the guiding block  300  in a location inward on the spacer  140 . In a higher temperature scenario, as shown in FIG. 6B, the bolt  722  is fixed by the nut  724  at a location adjacent to the other end  487   b  of the opening  487 , establishing the displacement position of the guiding block  300  in a location outward on the spacer  140 . For instance, the relative location may set about 0.5 mm for a distance between the wafer (e.g., in diameter of 300 mm) and the guiding block  300  at the locating position of them, about 2.0 mm for the length of the opening  487  in the transfer rod  480  (i.e., a distance between both ends  487   a  and  487   b ).  
         [0044]    As shown in FIG. 7, a resilient element  740 , such as a spring or coil, may be inserted into the hollow  124  formed in the sidewall of the plate  120 , for preventing a heating process from continuing to operate even when the guiding block  300  is positioned at the displacement position in the condition of an abnormal operation of the guiding block transfer unit  400 . The resilient element  740  surrounds the connection portion  486  of the transfer rod  480 , both ends of which attach onto a link  488  embedded at the connection portion  486  and a link  125  embedded in the hollow  124 , respectively. The resilient element  740  maintains its equilibrium, neither compressed nor stretched, when the guiding block  300  is set on the displacement position. The resilient element  740  also has a modulus of elasticity designed to minimize vibration when it is relieved from a compressed state.  
         [0045]    [0045]FIGS. 8A and 8B illustrate a procedure of positioning the wafer W in a normal position by means of the guiding blocks  300 . In FIG. 8A, the solid circle referred to as W denotes a wafer which is out of the normal position. The broken line referred to as W′ denotes the normal position on which the wafer should be placed for processing. When the wafer is loaded onto the susceptor, the guiding blocks  300  are moved to their aligning positions before the lift pins  220  descend. This pre-alignment operation permits sufficient spacing of the wafers and prevents the wafer edges from being partially laid onto the guiding blocks  300 . Thereafter, if the top ends of the lift pins  220  are inserted into the openings  122 , the guiding blocks  300  will move to their displacement positions to correct the positional error of the wafer. As a result, the wafer W will be positioned in their normal position as shown in FIG. 8B.  
         [0046]    [0046]FIGS. 9A, 9B, and  9 C illustrate sequential changes of positioning the guiding blocks  300  to fit the wafer W on the normal position. First, as shown in FIG. 9A, the lift pins  220  on which the wafer W is mounted go down after the guiding blocks  300  have moved into the displacement positions. When the top ends of the lift pins  220  are inserted into the openings  122  by elevating the lift pins  220 , the guiding blocks  300  move to the awaiting positions, and are then returned to the displacement positions, as shown by the arrows in FIGS. 9A and 9B. Even when the edges of the wafer W are initially laid on the guiding blocks  300 , the realignment of the guiding blocks  300  enables the wafer W to be set in the normal position as shown in FIG. 9C.  
         [0047]    Returning to FIG. 1, the apparatus  10  is associated with a testing unit  500  for monitoring whether or not the wafer W is positioned in the normal position on the susceptor  100  to avoid adversely affecting the baking process due to the misaligned placement of the wafer edges on the guiding blocks  300  which makes the wafer slant. The testing unit  500  is constructed of a vacuum pump  510 , a vacuum line  520  extending from the vacuum pump  510 , a sensor  540  for gauging pressure in the vacuum line  520 , and a display panel  560  showing a value of pressure calibrated by the sensor  540 . The vacuum line  520  extends into the space between the rear of the wafer W and the plate  120 . The pressure in the vacuum line  520  is detected by the sensor  540  when the vacuum pump  510  is started before the baking process begins. The sensor  540  can be a digital vacuum sensor, and the amount of pressure in the vacuum line may be more accurately established without damaging the wafer W. If, however, a pressure value measured by the sensor  540  becomes out of a predetermined range due to the positional error of the wafer W (i.e., the wafer W is laid on the guiding blocks  300 ), an alarm can be generated to inform an operator of the misalignment of the wafer W. Alternatively, vacuum holes may be provided in the spacer  140  around which the edges of the wafer W can be mounted in the normal position, connected to the vacuum line  520 .  
         [0048]    [0048]FIG. 10 summarizes a sequential flow of positioning the wafer W onto the susceptor  100 . First, the displacement positions of the guiding blocks  300  are adjusted wherein the bolt  722  is inserted into the openings  302  and  487  respectively formed at the guiding block  300  and the connection portion  486  of the transfer rod  480 . The transfer rod  480  moves within a predetermined range to set the combining position of the guiding block  300  and the transfer rod  480 . Then, the bolt  722  is joined with the nut  724  to fix the guiding block  300  on the transfer rod  480  (step S 10 ).  
         [0049]    Next, the cover  160  is elevated from the plate  120  so that the lift pins  220  protrude above the top surface of the plate  120 . The wafer W is transferred to the upper work space of the plate  120  by a robot arm to which it is adhered. The wafer W is then laid onto the lift pins  220  by the robot arm (step S 20 ). The lift pins  220  are lowered, and the cover  160  is closed (step S 30 ). If the lift pins  220  descend under the upper surface of the plate  120  through the openings  122 , the driver  420  makes the guiding blocks  300  move from the displacement position to the awaiting position and then back to the displacement position (step S 40 ). The realigning of the guiding blocks  300  causes the wafer W to be positioned on the normal position of the susceptor  100  even when the wafer W is misaligned with respect to the normal position or is mounted on the guiding blocks  300 . Thereafter, the testing unit  500  checks whether the wafer W is positioned at the normal position on the susceptor  100  (step S 50 ). The vacuum pump is actuated and the sensor  540  detects the pressure in the vacuum line  520 . If the measured value of the pressure in the line  520  is under the predetermined range, the baking process is carried out. On the other hand, if the pressure in line  520  is outside of the predetermined range of pressure, an audible signal is generated to inform an operator of misaligned status of the wafer W.  
         [0050]    In the embodiments described so far, while the guiding blocks  300  are linearly movable by the single driver, it may also be possible for the guiding blocks  300  to be continuously moved in a generally circular path. It is also possible to transfer each guiding block by each driver.  
         [0051]    According to the baking apparatus and method of the present invention, it is possible to prevent a misaligned placement of a wafer in which the wafer is positioned away from the normal position or the wafer edges are locally mounted on the guiding blocks.  
         [0052]    Moreover, a wafer can be transferred to the normal position anyway even when the guiding block driver operates abnormally, because the guiding blocks can be returned to a predetermined displacement position for carrying out the process using a resilient element.  
         [0053]    Further, there is provided of an inspecting function by the testing unit to check out whether a wafer is safely laid on the upper surface of the susceptor before continuing the baking process. This prevents carrying out the process with misaligned placement of the wafer on the susceptor.  
         [0054]    Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as described in the accompanying claims