Patent Publication Number: US-2006002833-A1

Title: Apparatus to suppress ascending gas flow and method for exhaust control thereof

Description:
PRIORITY STATEMENT  
      This U.S. non-provisional application claims priority under 35 U.S.C. §119 from Korean Patent Application No. 2004-51178, filed on Jul. 1, 2004 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
     BACKGROUND  
      1. Field of the Invention  
      The present invention relates in general to a semiconductor manufacturing apparatus and, more particularly, to a spin process apparatus that may suppress generation of particles while rotating a substrate and an exhaust control method of the spin process apparatus.  
      2. Description of Related Art  
      The manufacture of semiconductor devices may involve a spin process that may be used, for example, to apply a photoresist coating, perform wet cleaning and/or perform wafer drying. Some efforts have been made to control the exhaust of a gas that may be used during a spin process. Such exhaust control techniques may enhance a completion of the spin process, for example.  
      According to one technique, an inverter may be installed at an exhaust fan to alter a rotation speed of the exhaust fan. In this way, an exhaust pressure may be controlled. According to another technique, a motor for rotating a substrate and a damper in an exhaust pipe line may be controlled to control an exhaust.  
      A trend toward smaller design rules may make it desirable to manufacture semiconductor devices with higher precision. Accordingly, semiconductor products may be affected by particles having a size on the order of microns or less, for example. During a spin process, an ascending gas flow may be generated around a substrate. The ascending gas flow may occur, for example, when the substrate is rotated at a relatively high speed. It has been reported that an ascending gas flow may be generated when a descending gas flow is driven between a bowl wall and a substrate lateral surface, and an exhaust differential pressure is insufficient.  
      Contaminants (such as particles, for example) may reside in the bowl. The contaminants may be lifted from the bowl by an ascending gas flow. The contaminants (which may be floating in the ascending gas flow) may land on (and become attached to) a substrate to contaminate the substrate. In case of relatively smaller and lighter particles, e.g., nano-sized particles, an ascending gas flow may have a greater effect on semiconductor devices. For this reason, substrate contamination caused by an ascending gas flow may be more prevalent in the nano-device generation.  
      Conventionally, an exhaust may be controlled during a spin process and thus a suitable environment may be established in a bowl to offer a desired dry environment and/or to suppress a drying of respective wafer areas to form a uniform resist layer. Although the conventional wisdom is generally thought to provide acceptable results, it is not without shortcomings. For example, conventional techniques offer no countermeasure to control particles generated by an ascending gas flow that may be generated when a substrate is rotated at a relatively high speed.  
     SUMMARY  
      According to an example, non-limiting embodiment of the invention, an apparatus may include rotation supporting means for supporting and rotating a substrate. Shielding means may be provided for surrounding a periphery of the rotation supporting means. Sensing means may be mounted on the shielding means for sensing an ascending gas flow of a gas in the shielding means. A conduit may be coupled to the shielding means. The conduit may accommodate a flow of the gas from the shielding means. Flow control means may be provided for controlling a flow rate of the gas through the conduit. Control means may be provided for controlling the flow control means based on the ascending gas flow sensed by the sensing means.  
      According to another example, non-limiting embodiment of the invention, an apparatus may include a chuck to support and rotate a substrate. A bowl may surround a periphery of the chuck. A sensor may be mounted on the bowl to sense an ascending gas flow of a gas in the bowl. A conduit may be coupled to the bowl. The conduit may accommodate a flow of the gas from the bowl. A damper may be connected to the conduit to control a flow rate of the gas through the conduit. A control unit may control the damper to increase a flow rate of the gas through the conduit when the sensor senses an ascending gas flow in the bowl.  
      According to another example, non-limiting embodiment of the invention, a method may involve providing a substrate in a vessel where a descending gas flow of a gas is present. An ascending gas flow in the vessel may be sensed. An exhaust flow rate of the gas from the vessel may be increased when the ascending current is sensed. The exhaust flow rate of the gas from the vessel may be decreased when the ascending gas flow is not sensed.  
      According to another example, non-limiting embodiment of the invention, a method may be implemented for controlling an exhaust of an apparatus connected to suction means for drawing the exhaust from the apparatus. The apparatus may include rotation supporting means for supporting and rotating a substrate. Shielding means may be provided for surrounding a periphery of the rotation supporting means. Sensing means may be mounted on the shielding means for sensing an ascending gas flow of a gas in the shielding means. A conduit may be coupled to the shielding means and the suction means. The conduit may accommodate a flow of the gas from the shielding means. Flow control means may be provided for controlling a flow rate of the gas through the conduit. Control means may be provided for controlling the flow control means. The method may involve providing a substrate in the shielding means where a descending gas flow of a gas is present while rotating the substrate. An ascending gas flow in the shielding means may be sensed using the sensing means. The flow control means may be controlled using the control means when an ascending gas flow is sensed in the shielding means to increase a flow rate of the gas through the conduit. The flow control means may be controlled using the control means when an ascending gas flow is not sensed in the shielding means to decrease a flow rate of the gas through the conduit.  
      According to another example, non-limiting embodiment of the invention, a method may be implemented for controlling an exhaust of an apparatus connected to a pump for drawing the exhaust from the apparatus. The apparatus may include a chuck to support and rotate a substrate. A bowl may surround a periphery of the chuck. A sensor may be mounted on the bowl to sense an ascending gas flow of a gas in the bowl. A conduit may be coupled to the bowl and the pump. The conduit may accommodate a flow of the gas from the bowl. A damper may be connected to the conduit to control a flow rate of the gas through the conduit. A control unit may control the damper. The method may involve providing a substrate in the bowl where a descending gas flow of a gas is present while rotating the substrate. An ascending gas flow in the bowl may be sensed using the sensor. An open ratio of the damper may be increased using the control unit when an ascending gas flow is sensed in the bowl to increase a flow rate of the gas through the conduit. The open ratio of the damper may be decreased using the control unit when an ascending gas flow is not sensed in the bowl to decrease a flow rate of the gas through the conduit.  
      According to another example, non-limiting embodiment of the invention, an apparatus may include a vessel to accommodate a gas flow of a gas. A sensor may be mounted on the vessel to sense a direction of the gas flow in the vessel. A conduit may be coupled to the vessel to exhaust the gas from the vessel. A control unit may be provided to adjust a flow rate of the gas through the conduit based on the direction of the gas flow in vessel sensed by the sensor.  
      According to another example, non-limiting embodiment of the invention, a method may involve providing a gas flow of a gas in a vessel. A direction of the gas flow in the vessel may be sensed. The gas may be exhausted from the vessel at an exhaust flow rate. The exhaust flow rate may be adjusted based on the sensed direction of the gas flow in the vessel.  
      According to another example, non-limiting embodiment of the invention, a control unit may include a controller. The controller may adjust an exhaust flow rate from a vessel based on a detected direction of a gas flow in the vessel. The exhaust flow rate may be decreased when the detected direction of the gas flow in the vessel is in a first direction. The exhaust flow rate may be increased when the detected direction of the gas flow in the vessel is in a second direction that is counter to the first direction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Example, non-limiting embodiments of the present invention will be readily understood with reference to the following detailed description thereof provided in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements.  
       FIG. 1  is a schematic view of an apparatus according to an example, non-limiting embodiment of the present invention.  
       FIG. 2  is a schematic view of the operation of a damper that may be implemented in the apparatus shown in  FIG. 1 .  
       FIG. 3  is a graph illustrating example gas flows that may occur within a bowl that may be implemented in the apparatus shown in  FIG. 1 .  
       FIG. 4  is a graph illustrating a relationship between the rotational speed of a substrate and the number of particles.  
       FIG. 5  is a graph illustrating a relationship between an exhaust differential pressure and the number of particles.  
       FIG. 6  is a graph illustrating the effects of increasing an exhaust differential pressure. 
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS  
      Example, non-limiting embodiments of the present invention will now be described more fully with reference to the accompanying drawings. The invention may, however, be embodied in different forms and should not be construed as limited to the example embodiments set forth herein. Rather, the disclosed embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The principles and features of this invention may be employed in varied and numerous embodiments without departing from the scope of the invention.  
      Well-known structures and processes are not described or illustrated in detail to avoid obscuring the present invention.  
      An element is considered as being mounted (or provided) “on” another element when mounted (or provided) either directly on the referenced element or mounted (or provided) on other elements overlaying the referenced element. Throughout this disclosure, the terms “ascending,” “descending,” “top”, and “bottom” are used for convenience in describing various elements or portions or regions of the elements as shown in the figures. These terms do not, however, require that the structure be maintained in any particular orientation.  
      As illustrated in  FIG. 1 , an apparatus according to an example, non-limiting embodiment of the invention may include a chuck  110 . The chuck  110  may serve as rotation supporting means. The chuck  110  may support a substrate W. A motor  120  may be provided for rotating the chuck  110 . The motor  120  may be a stepping motor, for example.  
      The chuck  110  may be provided in a bowl  130 . The bowl  130  may serve as shielding means to the extent that it may prevent dispersion of a solution supplied to a surface of the wafer W. The bowl  130  may have an open top. The bowl  130  may have a closed bottom. An exhaust port  140  may be provided in the bottom of the bowl  130 . As shown, the bowl  130  may have a “C” shape. In alternative embodiments, the bowl  130  may have any other geometric shape. For example, the bowl  130  may have side walls that taper. Also, the exhaust port  140  may be located in a side wall of the bowl  130  (as opposed to the bottom of the bowl  130 ).  
      A gas (e.g., an ambient gas) may flow into the bowl  130 . The gas may provide a descending gas flow  10 . The gas may be removed from the bowl  130 , as schematically shown by an exhaust gas flow  10   a.    
      A sensor  210  may be mounted on a sidewall of the bowl  130 . The sensor  210  may sense an ascending gas flow  10   b  that may be present in the bowl  130 . By way of example only, the sensor  210  may be mounted on the bowl  130  at the height of the substrate W, and/or in the vicinity of the substrate W. The sensor  210  may be, for example, a 3-dimensional flow meter. The chuck  110 , the motor  120 , the bowl  130 , and the sensor  210  may constitute a rotation treating unit for rotating a substrate W to perform a process.  
      A conduit  150  may be connected to the exhaust port  140  of the bowl  130 . A downstream end (relative to the exhaust gas flow  10   a ) of the conduit  150  may be connected to a pump  170 . The pump  170  may operate to draw the gas from the bowl  130  and into the conduit  150 . A damper  160  may be disposed in the conduit  150 . An open ratio of the damper  160  may be controlled by a control unit  200 .  
      The control unit  200  may include a velocity meter  220 . The velocity meter may display a velocity of the ascending gas flow  10   b.  The control unit  200  may include an actuator  240 . The actuator may control an open ratio of the damper  160 . The control unit  200  may include a controller  230 . The controller  230  may receive information on the velocity of the ascending gas flow  10   b  from the velocity meter  220  to control the operation of the actuator  240 .  
      The control unit  200  may receive a signal from the sensor  210  to determine whether there is an ascending current  10   b  in the bowl  130 . Based on the signal from the sensor  210 , the control unit  200  may regulate the open ratio of the damper  160  to control a flow rate of the exhaust gas flow  10   a  through the conduit  150 . The control unit  200  may control the operation of the damper  160  as well as the operation of the pump  170 .  
      The operation of the apparatus will be described in detail below.  
       FIG. 3  is a graph illustrating the example gas flows that may occur in the bowl  130 . Here, the transverse axis may denote a distance “x” from an inner surface of the sidewall of the bowl  130  to a central portion of the bowl  130 . The longitudinal axis may denote a velocity “u” of a gas flow. The portion of the graph above a reference line (labeled “ 0 ”) may denote an ascending current, and the portion of the graph below the reference line (labeled “ 0 ”) may denote a descending current. When an exhaust differential pressure of the conduit  150  is not sufficiently high and a substrate W rotates at a high speed (e.g., 5,000 rpm), an ascending current region “α” may occur near the inner surface of the sidewall of the bowl  130 , which may be adjacent to a lateral surface of the substrate W.  
       FIG. 4  is a graph illustrating a relationship between the rotational speed of the substrate and the number of particles that may contaminate the substrate. If a rotation speed of the substrate W increases from 4,000 rpm (line II) to 5,000 rpm (line I), particles (which may contaminate the substrate) may increase in number.  
      If the rotational speed of the substrate increases, an associated ascending gas flow may occur, which may result in an increased number of particles (e.g., micro-sized particles) being lifted from the bowl  130  and possibly contaminating the substrate. The rotational speed of the substrate may be decreased in an effort to reduce the number of potentially contaminating particles. However, some process specifications may allow for only slight variations in the rotational speed of the substrate. Accordingly, rather than lowering the rotational speed of the substrate, an exhaust differential pressure may be increased to suppress an ascending gas flow, which may reduce the number of potentially contaminating particles.  
       FIG. 2  schematically illustrates a relationship between a velocity “u” of a gas flow and an open ratio of the damper  160 . Here, the schematic showings at (a) through (d) may denote various open states of the damper  160 . Assume that a process is performed while rotating the substrate W in the bowl  130 , and further assume that a gas may be directed into the bowl  130 . When the pump  170  operates, the gas may be drawn from the bowl  130  and flow through the conduit  150  as the exhaust gas flow  10   a.  A flow rate of the exhaust gas flow  10   a  may depend on operations of the pump  170  and the damper  160 . By way of example only, the flow rate of the exhaust gas flow  10   a  may be influence more by the operational state of the damper  160  than that of the pump  170 .  
      Referring to  FIG. 2 , an ascending gas flow  10   b  may not be present in the bowl  130 , and therefore it may not be detected by the sensor  210 . Here, a velocity “u” of the gas flow may be below the reference line (labeled “ 0 ”). An open ratio of the damper  160  may be set by the actuator  240  to be relatively low (schematically shown at (a)).  
      An ascending gas flow  10   b  may be present in the bowl  130 , and therefore it may be detected by the sensor  210 . Here, the velocity “u” of the gas flow may be above the reference line (labeled “ 0 ”), as shown by region “A” of the curve. The sensor  210  may transmit a sensing signal to the controller  230 . In response, the controller  230  may activate the actuator  240 , which in turn may operate to increase an open ratio of the damper  160  (as schematically shown at (b)). In this way, the flow rate of the exhaust gas flow  10   a  may increase and an exhaust differential pressure may rise to reduce the velocity “u” of the ascending gas flow  10   b.    
      The ascending gas flow  10   b  in the bowl  130  may diminish and disappear with an increase in the flow rate of the exhaust gas flow  10   a.  Accordingly, the sensor  210  may not detect an ascending current. Thus, the actuator  240  may operate by means of the controller  230  to decrease the open ratio of the damper  160  (as schematically shown at (c)).  
      The ascending gas flow  10   b  may reappear in the bowl  130 , as shown by region “B” of the curve. Here, the sensor  210  may detect the ascending gas flow  10   b  and transmit a sensing signal to the controller  230 , which in turn may activate the actuator  240 , which in turn may operate to increase the open ratio of the damper  160  (as schematically shown at (d)). In this way, the exhaust differential pressure may rise to reduce the velocity “u” of the ascending gas flow  10   b.    
      In some situations, an ascending gas flow in the bowl  130  may not disappear when the open ratio of the damper  160  is increased. In this case, the control unit  200  may further increase the flow rate of the exhaust gas flow  10   a  by increasing an output of the pump  170 .  
       FIG. 5  is a graph illustrating a relationship between an exhaust differential pressure and the number of particles that may contaminate the wafer. In  FIG. 5 , ( 1 ), ( 2 ), and ( 3 ) indicated along the transverse axis may be serial numbers associated with respective spin process, which may be set at random, for example. A left-side longitudinal axis may denote the number of potentially contaminating particles and a right-side longitudinal axis may denote an exhaust differential pressure (mmH 2 O). As illustrated in  FIG. 5 , if an exhaust differential pressure rises by virtue of increasing a flow rate of the exhaust gas flow  10   a,  the number of particles (0.16 micrometer) that become attached to a wafer may decrease.  
       FIG. 6  is a graph illustrating the effects of increasing an exhaust differential pressure. In  FIG. 6 , the point “ 0 ” on the transverse axis may denote an outside boundary portion of the bowl, to the right of the point “ 0 ” may denote the inner side of the bowl and to the left of the point “ 0 ” may denote the outer side of the bowl. A region “β” of the curve may represent an ascending current at the outside boundary portion (i.e., located at point “ 0 ”). If an exhaust differential pressure rises, the portion of the curve to the left of the point “ 0 ” falls (indicating a higher descending gas flow velocity on the outside of the bowl), thereby influencing contaminated air to flow along the outside of the bowl and not into the bowl.  
      In the example embodiments, the apparatus may include only a single exhaust port  140 . In alternative embodiments, the apparatus may include multiple exhaust ports  140 . In the example embodiments, the control unit  200  may include a velocity meter  220 , a controller  230  and an actuator  240 . In alternative embodiments, the control unit  200  may implement numerous alternative components to achieve the desired functionality. Further, the velocity meter  220  need not display the velocity of the ascending gas flow.  
      Numerous modifications and variations to the basic inventive concepts will be apparent to a person skilled in the art from the foregoing disclosure. Thus, while only certain example, non-limiting embodiments of the invention have been specifically described, it will be apparent that numerous modifications may be made thereto without departing from the spirit and scope of the invention, as defined in the appended claims.