Abstract:
A thin film deposition apparatus including a substrate mounting error detector, a chamber and a substrate support positioned in the chamber. The substrate support is configured to support a substrate. The substrate mounting error detector includes: a light source configured to provide a light beam to the substrate, such that the substrate reflects the light beam; a collimator configured to selectively pass at least a portion of the light beam reflected by the substrate; and an optical sensor configured to detect the at least a portion of the reflected light beam passed by the collimator. The detector is positioned and oriented to detect substrate position on a lowered support prior to raising the support into contact with an upper cover of a clamshell reactor arrangement. This configuration allows a thin film deposition process only if the substrate is correctly mounted on the substrate support. Thus, abnormal deposition due to a substrate mounting error is prevented in advance.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2007-0130392 filed in the Korean Intellectual Property Office on Dec. 13, 2007, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a deposition apparatus. More particularly, the present invention relates to a substrate mounting error detector for a deposition apparatus. 
     2. Description of the Related Art 
     In manufacturing semiconductor devices, various apparatuses and processes have been developed to provide a high quality thin film on a substrate. Several methods have been used to form a thin film, employing surface reaction of a semiconductor substrate. The methods include vacuum evaporation deposition, Molecular Beam Epitaxy (MBE), different variants of Chemical Vapor Deposition (CVD) (including low-pressure and organometallic CVD and plasma-enhanced CVD), and Atomic Layer Epitaxy (ALE). ALE was studied extensively for semiconductor deposition and electroluminescent display applications, and has been more recently referred to as Atomic Layer Deposition (ALD) for the deposition of a variety of materials. 
     Certain deposition apparatuses include one or more reactors housed in a chamber. The reactors may be a chemical vapor deposition reactor or an atomic layer deposition reactor. Each of the reactors can include a substrate support on which a substrate is mounted during a deposition process. If the substrate is not correctly mounted on the substrate support, an abnormal deposition may be made on the substrate, adversely affecting the quality of a deposited film on the substrate. However, because the substrate is inside the chamber, it may be difficult to determine from the outside whether the substrate has been correctly mounted on the substrate support. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form prior art already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     In one embodiment, a deposition apparatus includes: a chamber and a substrate support positioned in the chamber. The substrate support is configured to support a substrate. The apparatus also includes a substrate mounting error detector including: a light source configured to provide a light beam to the substrate, such that the substrate reflects the light beam; a collimator configured to selectively pass at least a portion of the light beam reflected by the substrate when the substrate is property mounted; and an optical sensor configured to detect the at least a portion of the reflected light beam passed by the collimator. 
     In another embodiment, a deposition apparatus includes: a substrate support configured to support a substrate; and a substrate mounting error detector. The substrate mounting error detector includes: a light source configured to generate a light beam directed to the substrate support; a collimator including one or more openings that are configured to selectively pass particularly oriented and directed portions of the light beam as reflected from the substrate or the substrate support; and an optical sensor configured to detect the portions of the light beam passed by the collimator. 
     In yet another embodiment, a method of depositing a thin film includes: loading a substrate onto a substrate support within a chamber; providing a light beam onto the substrate such that the light beam is reflected by the substrate; passing at least a portion of the reflected light beam when the substrate is positioned at a correct location of the substrate support while blocking the entire portion of the light beam when the substrate is positioned at an incorrect location of the substrate support; and detecting the at least a portion of the light beam. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a deposition apparatus including a substrate mounting error detector according to one embodiment. 
         FIG. 2  is a side view of a collimator of a substrate mounting error detector in a deposition apparatus according to one embodiment. 
         FIG. 3  illustrates paths of a light beam during the operation of the substrate mounting error detector of  FIG. 1(A)  when no substrate is mounted on a substrate support and (B) when a substrate is correctly mounted on the substrate support, respectively. 
         FIG. 4  illustrates paths of a light beam during the operation of the substrate mounting error detector of  FIG. 1(C)  when a substrate is incorrectly mounted on a substrate support and (B) when a substrate is correctly mounted on the substrate support, respectively. 
         FIG. 5  to  FIG. 9  are cross-sectional views of the apparatus of  FIG. 1  illustrating a method of loading a substrate into a deposition apparatus according to one embodiment. 
       
         
           
                 
               
                 
                 
                 
               
             
                 
                     
                 
                 
                   &lt;Description of Reference Numerals For Components in the Drawings&gt; 
                 
                 
                     
                 
               
               
                 
                     
                 
               
            
             
                 
                     
                    10: chamber 
                    20: substrate support 
                 
                 
                     
                    30: upper cover 
                    40: substrate transfer device 
                 
                 
                     
                   110: light source 
                   120: reflecting mirror 
                 
                 
                     
                   130: collimator 
                   140: optical sensor 
                 
                 
                     
                     
                 
               
            
           
         
       
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the invention. 
     The drawings are not to scale, but rather have dimensions exaggerated for clarity. Like reference numerals designate like elements throughout the specification. It will be understood that when an element, such as a device or part, is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
       FIG. 1  is a cross-sectional view of a deposition apparatus having a substrate mounting error detector according to one embodiment. The illustrated deposition apparatus includes a chamber  10  housing a plurality of reactors, a substrate transfer device  40 , a substrate loader  50  for each reactor, a substrate support driver  60  for each reactor, a plurality of substrate mounting error detectors, first light transmission windows  150 , and second light transmission windows  160 . 
     The chamber  10  serves to house the plurality of reactors. The chamber  10  may include a top plate  10   a,  sidewalls  10   b,  and a bottom plate  10   c,  which together define an isolated space therein. While the chamber  10  is shown in cross-section to house two reactors in the illustrated embodiment, a skilled artisan will appreciate that the number of reactors in the chamber  10  can vary widely, depending on the design of the deposition apparatus. 
     The reactors may be used for atomic layer deposition (ALD) or chemical vapor deposition (CVD). Each of the reactors may include a substrate support  20  and an upper cover  30  that together define a reaction space for a deposition process. 
     The substrate support  20  serves to support a substrate  1  thereon during a deposition process. In the illustrated embodiment, the substrate support  20  is vertically movable between a lower position and an upper position. The upper cover  30  is positioned over the substrate support  20  while being spaced apart therefrom by a gap during loading or unloading a substrate. After a substrate is loaded on the substrate support  30  for deposition, the substrate support  20  is moved upward toward the upper cover  30 . During a deposition process, the substrate support  20  may be in contact with peripheral portions of the upper cover  30  to form the reaction space. The upper cover  30  and the substrate support  20  together form a so-called clamshell reactor. 
     The substrate transfer device  40  serves to transfer a substrate  1  into and out of the chamber  10 . The substrate transfer device  40  may include a robot arm and an end effector. In the illustrated embodiment, there is only one door for the robot arm, and the positions of the reactors may change such that one of the reactors is positioned close to the robot arm when loading a substrate onto the reactor or unloading the substrate from the reactor. In some embodiments, the substrate supports  20  of the reactors may be mounted on a rotating platform. In other embodiments, the substrate supports  20  may be configured to rotate around the center of the chamber  10 , using any suitable mechanism. A skilled artisan will appreciate that various configurations of transfer devices can be adapted for use in the apparatus. 
     The substrate loader  50  serves to place the substrate  1  onto the substrate support  20  or lift it from the substrate support  20 . When the substrate  1  is loaded into the reactor, it is transferred into the chamber  10  by the substrate transfer device  40 . Then, the substrate loader  50  loads the substrate  1  onto the substrate support  20 . The substrate loader  50  is installed at the substrate support  20 . The substrate loader  50  may include a plurality of substrate supporting pins  51  for holding the substrate  1 , and a substrate supporting pin elevating member  52  connected to the substrate supporting pins  51  to elevate them. The substrate supporting pin elevating member  52  may include an electrical motor or an air cylinder. In the illustrated embodiment, the substrate supporting pin driver  52  includes an air cylinder. In other arrangements, the pins could be stationary while movement of the support relative to the stationary pins accomplishes the loading and unloading. 
     The substrate support driver  60  is connected to the bottom of the substrate support  20  to vertically drive it. The substrate support driver  60  may include a shaft  61  connected to the substrate support  20 , and a shaft elevating member  62  for elevating the shaft  61 . The shaft elevating member  62  may include an electrical motor or an air cylinder. In the illustrated embodiment, the shaft elevating member  62  includes an air cylinder. 
     Each of the substrate mounting error detectors may include a light source  110 , a reflecting mirror  120 , a collimator  130 , and an optical sensor  140 . In one embodiment, each of the reactors may be provided with a substrate mounting error detector. In other embodiments, two or more of the reactors may share the same substrate mounting error detector. 
     The light source  110  may be positioned over the top plate  10   a  of the chamber  10  outside the chamber  10 . The light source  110  serves to provide a light beam for detection of a substrate mounting error. The light beam may be a visible light beam or laser, The light source  110  may include a head that includes a lens. The lens serves to provide a focused light beam. The light beam travels into the chamber  10  through the first light transmission window  150  in the top plate  10   a  of the chamber  10 . A skilled artisan will appreciate that the position of the light source can vary widely, depending on the design of the deposition apparatus. 
     In the illustrated embodiment, the light source  110  is oriented to provide a light beam such that the light beam travels substantially perpendicular to the first light transmission window  150 . This configuration allows the light beam to pass through the first light transmission window  150  with minimal or no loss. Therefore, the light beam from the light source  110  placed outside the chamber  10  can pass through the chamber  10  with minimal or no loss, and reach the reflecting mirror  120 . 
     The reflecting mirror  120  is positioned within the chamber  10 . The reflecting mirror  120  is oriented such that it can reflect the light beam from the light source  110  toward the substrate support  20 . If the mirror is partially transparent, preferably the angle of incidence is such that the reflecting mirror  120  may substantially totally reflect the light beam from the light source  110  toward the substrate  1 . The reflecting mirror  120  may be installed such that it does not interfere with vertical movements of either or both of the substrate support  20  and the upper cover  30 . In the illustrated embodiment, the reflecting mirror  120  is fixed to a lower surface of the top plate  10   a  of the chamber  10 . The reflecting mirror  120  may include a plate coated with a specular material. In other embodiments, the reflecting mirror  120  can include a conventional mirror. 
     The collimator  130  is positioned at or outside the sidewall  10   b  of the chamber  10  such that it is interposed between the optical sensor  140  and the second light transmission window  160 . The collimator  130  is positioned at a point on a path of the light beam that originates from the light source  110  and is reflected by the substrate  1  in the reactor. The collimator  130  blocks at least a portion of the light beam reflected by the substrate  1  such that it passes the light beam to the optical sensor  140  only when the substrate  1  is correctly or properly mounted on the substrate support  20 . In the illustrated embodiment, a substrate is “correctly” or “properly” mounted if it sits in a pocket of the substrate support  20 , and is flush with the support surface of the substrate support  20 . In other embodiments, a substrate is “correctly” or “properly” mounted if it is flush with the support surface of a substrate support at a selected location of the substrate support. The details of the collimator  130  will be described later in detail. 
     The optical sensor  140  serves to sense the light beam that has passed the collimator  130 . The optical sensor  140  may include any suitable light sensor for detecting a light beam reflected by the substrate  1 . A sensor amplifier (not shown) may be connected to the optical sensor  140  to amplify an output signal from the optical sensor  140  to enhance the accuracy of detecting a substrate mounting error. The optical sensor  140  may include a light-receiving head that receives a light beam. In the illustrated embodiment, the term “light-receiving head” refers to an area that forms a light-sensitive surface. In one embodiment, the head may have a selected diameter of about 2 mm to about 3 mm. When the optical sensor  140  receives no light beam at the light-receiving head, it outputs no signal, indicating that a substrate mounting error has occurred. 
     Each of the first light transmission windows  150  may be installed at the top plate  10   a  of the chamber  10 . The first light transmission window  150  is positioned to provide a passage through the top plate  10   a  such that the light beam from the light source  110  can reach the mirror  120  in the inner space of the chamber  10 . The first light transmission window  150  may be formed of a substantially transparent material, such as quartz. 
     Each of the second light transmission windows  160  may be installed at the sidewall  10   b  of the chamber  10  on a path of the light beam from the substrate  1  to the optical sensor  140 . The second light transmission window  160  may be formed of a transparent material, such as quartz. The light beam reflected from the substrate  1  may be refracted before reaching the optical sensor  140 , depending upon the refractive index of the second light transmission window  160 . Thus, the position of the optical sensor  140  may be selected to account for any refraction. 
     Referring to  FIGS. 2 and 3 , the configuration of the collimator  130  according to one embodiment will be described below in detail. As shown in  FIG. 3 , the light-receiving head of the optical sensor  140  may have a relatively large diameter D of, for example, about 2 mm to about 3 mm. Absent the collimator  130 , even when the substrate  1  is not correctly mounted on the substrate support  20 , the light-receiving head of the optical sensor  140  may receive the light beam reflected by the substrate  1 . Thus, the optical sensor  140  may erroneously indicate that the substrate is mounted without an error. 
     The collimator  130  serves to prevent such an error by narrowing the light beam. The collimator  130  passes at least a portion of the reflected light beam only when the substrate is correctly mounted on the substrate support  20 . 
       FIG. 2  is an enlarged side view of the collimator  130  installed at the sidewall  10   b  of the chamber  10 . The illustrated collimator  130  includes a vertically moving member  131 , and a horizontally moving member  132 . The vertically moving member  131  includes a horizontal slit  131   a  for light passage. The vertically moving member  131  is vertically movable. The horizontally moving member  132  includes a vertical slit  132   a  for light passage. The horizontally moving member  132  is horizontally movable. In one embodiment, the horizontal slit  131  a may have a length of about 10 mm to about 20 mm, and a width of about 0.9 mm to about 1.1 mm. The vertical slit  132   a  have a length of about 10 mm to about 20 mm, and a width of about 0.9 mm to about 1.1 mm. 
     The vertically moving member  131  and the horizontally moving member  132  partially overlap with each other such that the vertical slit  131   a  and the horizontal slit  132   a  cross each other. The vertical slit  131   a  and the horizontal slit  132   a  together form a square-shaped opening  135  where they overlap with each other. In one embodiment, the opening  135  may have horizontal and vertical widths, each of which may be about 0.9 mm to about 1.1 mm. The opening  135  of the collimator  130  has a dimension that is smaller than the diameter D of the light-receiving head of the optical sensor  140  and accordingly covers a smaller area than the head of the optical sensor  140 . In addition, the opening  135  of the collimator  130  may allow the reflected light beam to pass therethrough only when the light beam is oriented to have a selected angle relative to the collimator  130  such that it travels in a specific direction defined by the opening of the collimator  130 . In the illustrated embodiment, the position of the opening  135  may be calibrated by moving the vertically and horizontally moving members  131 ,  132 . 
     When no substrate is mounted on the substrate support  20  or a substrate  1  is incorrectly mounted on the substrate support  20 , the light beam reflected by the substrate support  20  or the incorrectly mounted substrate may not reach the opening  135  of the collimator. In such instances, even if the light beam reaches the opening  135 , it may not be oriented to have the selected angle that would allow the light beam through the collimator  130 . Thus, in such instances, the collimator  130  does not allow the light beam to reach the optical sensor  140 . The light-receiving head of the optical sensor  140  does not receive the light beam, and the optical sensor  140  indicates that the substrate is not correctly mounted on the substrate support  20 . 
     Referring to  FIG. 3 , the operation of the substrate mounting error detector will now be described below in detail.  FIG. 3  illustrates possible paths A, B of a light beam provided by the light source  110 . As shown in  FIG. 3 , the light path A when the substrate  1  is not mounted on the substrate support  20  is different from the light path B when the substrate  1  is correctly mounted on the substrate support  20 . In the illustrated embodiment, a distance between the light paths A, B may be about 1.6 mm. 
     When no substrate is mounted on the substrate support  20 , a light beam reflected from the substrate support  20  may not reach the optical sensor  140  because it is blocked by the collimator  130 . Because the optical sensor  140  has a relatively big light-receiving head, absent the collimator  130  the reflected light beam may reach the head of the optical sensor  140 , resulting in an erroneous reading of a present substrate. However, the collimator  130  blocks the entire portion of the light beam from reaching the optical sensor  140  when the substrate is absent, and the optical sensor  140  does not detect a light. Thus, the substrate mounting error detector can provide a correct result. 
       FIG. 4  illustrates other possible paths of a light beam provided by the light source  110 . As shown in  FIG. 4 , a light path B is formed when the substrate  1  is mounted at the correct position on the substrate support  20 . A light path C is formed when the substrate  1  is incorrectly mounted on the substrate support  20 . In the illustrated example, the incorrectly mounted substrate  1  is tilted at an angle of, for example, 0.15 degrees. For that example, a distance between the light paths B, C may be about 2.8 mm. 
     When a substrate is incorrectly mounted on the substrate support  20 , a light beam reflected from the substrate  20  may not reach the optical sensor  140  because it is blocked by the collimator  130 . However, because the optical sensor  140  has a relatively big light-receiving head, absent the collimator  130  the reflected light beam may reach the head of the optical sensor  140 , resulting in an erroneous reading of proper substrate mounting. However, the collimator  130  blocks the entire portion of the light beam from reaching the optical sensor  140  when the substrate is so tilted, and the optical sensor  140  does not detect a light. Thus, the substrate mounting error detector can provide a correct result. 
     Referring to  FIGS. 5 to 9 , a method of loading a substrate into the deposition apparatus of  FIG. 1  according to one embodiment will be described below. First, as shown in  FIG. 5 , a substrate  1  is transferred into the chamber  10  using the substrate transfer device  40 . The substrate  1  is positioned at a first vertical level above the substrate support  20 . 
     Next, as shown in  FIG. 6 , the substrate supporting pins  51  are moved up to hold the substrate  1  at a second vertical level above the first vertical level. The transfer device  40  is moved outside of the chamber  10  after unloading the substrate  1  from its end effector. As shown in  FIG. 7 , the substrate supporting pins  51  are moved down to load the substrate  1  onto the substrate support  20 . 
     Subsequently, as shown in  FIG. 8 , a substrate mounting error detector ( 110 ,  120 ,  130 , and  140 ) detects whether or not the substrate  1  has been correctly mounted on the support  20 . The light source  110  provides a light beam to the mirror  120 . The light beam is reflected by the mirror  120  and reaches the top surface of the substrate  1 . The light beam is reflected by the top surface of the substrate  1 , and travels toward the collimator  130 . A portion of the light beam may pass the collimator  130  and reach the optical sensor  140  if the substrate is present and has been correctly mounted on the substrate support  20 . In contrast, if the substrate is absent or has not been correctly mounted on the substrate support  20 , the collimator  130  blocks the entire portion of the light beam, and thus the light beam does not reach the optical sensor  140 . In this manner, depending on whether the optical sensor  140  detects light, the substrate mounting error detector can determine whether the substrate  1  has been correctly mounted on the substrate support  20 . 
     Next, as shown in  FIG. 9 , when it is found that the substrate  1  has been correctly mounted on the substrate support  20 , the substrate support  20  is elevated such that it tightly contacts the upper cover  30  to form a reaction space for deposition. Then, a deposition process is conducted in the reaction space. If the substrate  1  has been incorrectly mounted on the substrate support  20 , the substrate  1  may be returned to the outside by the substrate transfer device  40 . A new substrate  1  may be transferred into the chamber  10 . Alternatively, the returned substrate may be reloaded onto the substrate support  1  after adjustment of the position of the substrate  1 . 
     In the illustrated embodiment, because the substrate support  20  and the upper cover  30  are formed of an opaque material, such as a metal, a light beam cannot pass therethrough. The detection of a substrate mounting error is performed only when the substrate support  20  is at a lower position at which the substrate support  20  is spaced apart from the upper cover  30 . The substrate mounting error detector provides a light beam through a space between the substrate support  20  and the upper cover while the substrate support  20  is at the lower position, but not when the substrate support  20  is in contact with the upper cover  30 . 
     In the embodiments described above, a deposition process is performed after it is determined whether a substrate has been correctly mounted on the support. Thus, abnormal film deposition due to a substrate mounting error can be prevented. Moreover, the proper detection of mounting errors can prevent wasted time and gases (if there was no substrate), and prevent wafer breakage (if the substrate was improperly mounted during reactor closure). Thus, it is possible to prevent the substrate and the film from being damaged due to the substrate mounting error, thereby enhancing the device reliability. 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.