Patent Publication Number: US-2021175052-A1

Title: Substrate processing apparatus, bevel mask and substrate processing method

Description:
This application claims the benefit of and priority to U.S. Patent Application No. 62/945,061 filed on Dec. 6, 2019, in the United States Patent and Trademark Office, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     Examples are described which relate to a substrate processing apparatus, a bevel mask and a substrate processing method. 
     BACKGROUND 
     For example, formation of a film on the front side of a substrate may cause the substrate to be warped. In order to suppress the warpage of the substrate, a highly stressed film may be formed on the back side of the substrate. At this time, in order to perform processing on the back side of the substrate while suppressing processing on the front side of the substrate, a bevel mask may be made close to a bevel of the substrate. According to one example, the bevel mask has been used to suppress film formation on the front side of a substrate. If the bevel mask conceals or chucks an outer edge of the back side of the substrate, it would be impossible to perform uniform processing on the back side of the substrate. For example, when a film is formed on the back side of a substrate, the film thickness in a region of several mm inside the bevel on the substrate is smaller than the film thickness in the center of the substrate. The inability to perform uniform processing on the back side of the substrate makes it impossible to completely chuck the substrate in subsequent steps, or causes pattern misalignment, defective film formation or the like. 
     SUMMARY 
     Some examples described herein may address the above-described problems. Some examples described herein may provide a substrate processing apparatus, a bevel mask and a substrate processing method that enable substantially uniform processing to be performed on the back side of a substrate while suppressing processing on the front side of the substrate in substrate processing using a bevel mask. 
     In some examples, a substrate processing apparatus includes a chamber, a shielding component that is a susceptor or an upper cover provided in the chamber, and a bevel mask that is provided in the chamber and has an inclined surface on which a vertical distance from the shielding component increases toward a center side of the shielding component. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a substrate processing apparatus; 
         FIG. 2  is a bottom view of the bevel mask; 
         FIG. 3  is a cross-sectional view of the substrate processing apparatus; 
         FIG. 4  is an enlarged view of the bevel mask and its vicinity; 
         FIG. 5  is a cross-sectional view showing a bevel mask according to another example; 
         FIG. 6  is a cross-sectional view showing a bevel mask according to another example; 
         FIG. 7  is a cross-sectional view showing a bevel mask according to another example; 
         FIG. 8  is a cross-sectional view showing a bevel mask according to another example; 
         FIG. 9  is a cross-sectional view of a substrate processing apparatus according to another example; and 
         FIG. 10  is an enlarged view of the bevel mask and its vicinity. 
     
    
    
     DETAILED DESCRIPTION 
     A substrate processing apparatus, a bevel mask, and a substrate processing method will be described with reference to the drawings. The same or corresponding components are represented by the same reference signs, and repeated description thereof may be omitted. 
     Embodiment 
       FIG. 1  is a cross-sectional view showing a configuration example of a substrate processing apparatus  10  according to one example. The substrate processing apparatus  10  includes a susceptor  16  provided in a chamber  12 . The susceptor  16  is fixed to a shaft  18 . The shaft  18  is moved up and down by a lifting mechanism, which also enables up-and-down movement of the susceptor  16 . A susceptor pin  17  fixed to the chamber  12  protrudes above the upper surface of the susceptor  16  when the susceptor  16  is located on a lower side. Furthermore, the susceptor pin  17  is positioned below the susceptor  16  when the susceptor  16  is located on an upper side, and thus it does not protrude above the upper surface of the susceptor  16 . 
     A shower plate  14  is placed above the susceptor  16 . The shower plate  14  is provided with a plurality of slits  14   a . A gas introduction pipe  22  is fixed to the shower plate  14  via an insulating component  20 . Arbitrary gas supplied from a gas source is passed through the gas introduction pipe  22  and the slits  14   a , and provided to a space above the susceptor  16 . A gas supply direction is indicated by an arrow. 
     A parallel plate structure is provided by the susceptor  16  and the shower plate  14  described above. High-frequency power is applied to the shower plate  14  while providing gas to the space between the susceptor  16  and the shower plate  14 , whereby plasma can be generated in this space. 
     A flow control ring (FCR)  38  is placed on the chamber  12 , for example, via an O-ring. An exhaust duct  30  is placed on the chamber  12 , for example, via an O-ring  34 . The exhaust duct  30  can be formed of an insulator such as ceramic. Furthermore, the shower plate  14  is placed on the exhaust duct  30 , for example, via an O-ring  32 , whereby the chamber  12  and the shower plate  14  are electrically insulated from each other. An exhaust passage  36  having an annular shape in plan view is provided by the exhaust duct  30  and the FCR  38 . This exhaust passage  36  is connected to an exhaust duct  24 . A vacuum pump, a valve, and the like, which make it possible to perform pressure adjustment in the chamber  12  are provided in the middle of the exhaust duct  24  or in the end portion of the exhaust duct  24 . 
     A bevel mask  39  is placed on the FCR  38  in the chamber  12 . The bevel mask  39  is a ring formed in an annular shape in plan view. The material of the bevel mask  39  is, for example, AlN, but may be any insulator. The bevel mask  39  includes a flat surface  39   a  and an inclined surface  39   b  inside the flat surface  39   a . In the example of  FIG. 1 , the bevel mask  39  is placed on the FCR  38  with the flat surface  39   a  being in contact with the upper surface of the FCR  38 . The inclined surface  39   b  is a surface on which the vertical distance from the susceptor  16  increases toward the center side of the susceptor  16 . In other words, the inclined surface  39   b  is a surface which is non-parallel to the horizontal direction and is higher toward the center of a portion surrounded by the bevel mask  39 . 
       FIG. 2  is a bottom view of the bevel mask  39 . According to an example, the bevel mask  39  includes a flat surface  39   a  and an inclined surface  39   b  which is connected to the flat surface  29   a  and located inside the flat surface  39   a . The inclined surface  39   b  may be formed in an annular shape in plan view and in bottom view. 
     Next, a substrate processing method using the substrate processing apparatus  10  will be described. First, as shown in  FIG. 1 , a substrate  40  is introduced into the chamber  12 , and placed on the susceptor pins  17 . For example, a wafer transfer arm holding the substrate  40  is introduced into the chamber  12 , and the arm is moved down above the susceptor pins, thereby placing the substrate  40  on the susceptor pins  17 . 
     Next, the susceptor  16  and the shaft  18  are raised by a lifting mechanism provided outside the chamber  12 .  FIG. 3  is a cross-sectional view showing a configuration example of the substrate processing apparatus in a state where the susceptor  16  is raised. When the susceptor  16  is raised, the susceptor  16  and the substrate  40  come into contact with each other, and the substrate  40  separates from the susceptor pins  17 . During the upward movement of the susceptor  16 , the susceptor  16  and the bevel mask  39  come into contact with each other, and the bevel mask  39  separates from the FCR  38 . Then, as shown in  FIG. 3 , the substrate  40  and the bevel mask  39  are supported by the susceptor  16 . 
       FIG. 4  is an enlarged view of the bevel mask  39  of  FIG. 3  and its vicinity. According to one example, the substrate  40  has a device surface  40   a  that is a surface on which a device is formed, and a back side  40   b  which is a surface opposite to the device surface  40   a . An inclined portion at the outer edge portion of the substrate  40  is a bevel  40 A. The device surface  40   a  is subjected to a well-known semiconductor process to form a device, and as a result, the substrate  40  may be warped to some extent. 
     In the example of  FIG. 4 , the susceptor  16  includes an upward convex portion  16 A, an intermediate portion  16 B, and a central portion  16 C. Of the three portions, the upper surface of the upward convex portion  16 A is the highest. The intermediate portion  16 B is a slope which decreases in height from the upward convex portion  16 A to the central portion  16 C. The upper surface of the central portion  16 C is a flat surface. 
     In the example of  FIG. 4 , the bevel mask  39  includes a main body portion  39 A and a convex portion  39 B at the lower surface on an inner edge side of the main body portion  39 A. In this example, the bevel mask  39  is placed on the susceptor  16  with the flat surface  39   a  being in contact with the upward convex portion  16 A. Further, the inclined surface  39   b  is in contact with the bevel  40 A. In this example, the bevel mask  39  is in contact with only the bevel  40 A, and is in contact with neither the back side  40   b  nor the device surface  40   a . For example, by bringing the inclined surface  39   b  into contact with the bevel  40 A, the warped substrate  40  can be pressed against the susceptor  16 . According to another example, the inclined surface  39   b  is in proximity to the bevel  40 A, but not in contact with the bevel  40 A. In that case, an inclined surface is provided slightly above the inclined surface  39   b  of  FIG. 4 . As a result, there is no contact between the bevel mask  39  and the substrate  40 . 
     As described above, the substrate  40  is placed on the susceptor  16  so that the device surface  40   a  and the susceptor  16  face each other. Next, after the susceptor is moved to a process position as necessary, the back side  40   b  is subjected to a plasma treatment. Gas supply to the space between the susceptor  16  and the shower plate  14  and application of high-frequency power to the shower plate  14  are performed alternately or simultaneously. By generating plasma in this space, film formation on the back side  40   b , etching processing on the back side  40   b , modification of the film on the back side  40   b  or the like is performed. According to one example, this plasma treatment is applied to the entire back side  40   b . However, since the bevel mask  39  is in contact with or in proximity to the bevel  40 A, there is no significant plasma treatment on the bevel  40 A. According to an example, it is possible to avoid occurrence of any step on the back side by forming a film on the entire back side  40   b  with the plasma treatment. 
     In the above example, plasma is generated by the parallel plate structure, but plasma can be generated by another method. In the example of  FIG. 1 , the shower plate  14  is adopted as a plasma unit provided in connection with the susceptor. However, a well-known microwave plasma generation apparatus or a well-known inductively coupled plasma apparatus can be adopted as the plasma unit as described above. 
       FIG. 5  is a cross-sectional view showing a bevel mask  39  according to another example. The inclined surface of the lower surface of the convex portion  39 B includes a flat inclined surface  39   b  and a concave curved surface  39   c . The curved surface  39   c  is a surface which is in contact with or in proximity to the bevel  40 A. According to an example, the curved surface  39   c  enables surface contact between the convex portion  39 B and the bevel  40 A, or suppresses gas intrusion through the gap between the convex portion  39 B and the bevel  40 A. 
       FIG. 6  is a cross-sectional view showing a bevel mask  39  according to another example. A concave curved surface  39   d  is provided as the inclined surface of the lower surface of the convex portion  39 B. In this example, the entire lower surface of the convex portion  39 B serves as the curved surface  39   d . Therefore, even when the substrate  40  is misaligned, the curved surface  39   d  and the bevel  40 A can be brought into contact with or proximity to each other. 
     By making the curvatures of the curved surfaces of  FIGS. 5 and 6  be coincident with or close to the curvature of the bevel  40 A, it is possible to further suppress the intrusion of gas through the gap between the convex portion  39 B and the bevel  40 A. 
       FIG. 7  is a cross-sectional view showing a bevel mask  39  according to another example. An inclined surface  39   b  and a convex curved surface  39   e  are provided as the inclined surface of the lower surface of the convex portion  39 B. The convex curved surface  39   e  is a surface that is in contact with or in proximity to the bevel  40 A. 
       FIG. 8  is a cross-sectional view showing a bevel mask  39  according to another example. A convex curved surface  39   f  is provided as the inclined surface of the lower surface of the convex portion  39 B. The entire lower surface of the convex portion  38 B serves as a convex curved surface  39   f.    
     According to the examples of  FIGS. 7 and 8 , by providing the convex curved surface  39   e  or the convex curved surface  39   f , the bevel mask  39  and the bevel  40 A can be surely brought into contact with or made sufficiently close to each other. 
       FIG. 9  is a cross-sectional view of a substrate processing apparatus according to another example. This substrate processing apparatus is a parallel plate type plasma processing apparatus. A door  13  is attached to a chamber  12  so as to be able to provide a substrate to inside of the chamber  12  or take out a substrate from the chamber  12 . The chamber  12  can be provided as part of a Dual Chamber Module (DCM) or part of a Quad Chamber Module (QCM). An upper cover  80  is provided inside the chamber  10 . According to an example, the upper cover  80  is provided as a ground electrode. The ground electrode is an electrode for grounding. 
     The upper cover  80  includes a shaft portion  80   a  and a disk portion  80   b  connected to the shaft portion  80   a . The shaft portion  80   a  is fixed at a first lifting mechanism  51  which can move in a z positive-negative direction. According to an example, the first lifting mechanism  51  is provided by a plate  51   a  fixed at the shaft portion  80   a  being fixed at an upper end of a bellows  51   b , and a plate  51   c  fixed at the chamber  12  being fixed at a lower end of the bellows  51   b . As the first lifting mechanism  51 , various configurations which move the upper cover  80  up and down inside the chamber  10  can be employed. 
     The disk portion  80   b  has a circular shape or a substantially circular shape in planar view. A lower surface of the disk portion  80   b  which is a lower surface of the upper cover  80  has, for example, a first lower surface  80   c , and a second lower surface  80   d  which surrounds the first lower surface  80   c  and which is located below the first lower surface  80   c . Therefore, the lower surface of the disk portion  80   b  has a shape having a dent at the center. 
     The upper cover  80  which is a ground electrode, functions as an upper electrode in a parallel plate structure. To enable plasma coupling and prevent or reduce electric discharge, a difference in height between the first lower surface  80   c  and the second lower surface  80   d  can be made, for example, equal to or less than 1 mm. 
     A bevel mask  90  is provided inside the chamber  12 . The bevel mask  90  includes a flat surface  90   a , and an inclined surface  90   b  surrounded by the flat surface  90   a . The inclined surface  90   b  is a surface on which the vertical distance from an upper cover  80  increases toward the center side of the upper cover  80 . In other words, the inclined surface  90   b  is a surface which is non-parallel to the horizontal direction and decreases in height toward the center of a portion surrounded by the bevel mask  90 . 
     According to an example, the bevel mask  90  is supported or suspended by a support bar  91 . The support bar  91  is fixed to a second lifting mechanism  53  that is driven by a motor  52 . The second lifting mechanism  53  is configured to move the support bar  91  and the bevel mask  90  up and down inside the chamber  10 . In other words, the support bar  91  and the bevel mask  90  can be moved up and down by the motor  52  and the lifting mechanism  53 . According to an example, the second lifting mechanism  53  is provided by a plate  53   a  fixed at the support bar  91  being fixed at the upper end of the bellows  53   b , and a plate  53   c  fixed at the chamber  12  being fixed at the lower end of the bellows  53   b . As the second lifting mechanism  53 , various configurations which moves the bevel mask  90  up and down inside the chamber  12  can be employed. 
     The support bar  91  and the bevel mask  90  can be formed as one body with, for example, a dielectric body. The bevel mask  90  has an annular shape in planar view. The bevel mask  90  includes an annular flat surface  90   a  and a inclined surface  90   b  located immediately below the upper cover  80 . In some examples, as shown in  FIG. 9 , a height of the flat surface  90   a  is equal to or higher than a height of the inclined surface  90   b . A difference in height between the flat surface  90   a  and the inclined surface  90   b  is, for example, greater than a thickness of the substrate  40  to be processed. According to another example, as shown in  FIG. 10 , a height of the flat surface  90   a  may be lower than a height of the inclined surface  90   b.    
       FIG. 10  is an enlarged view of the bevel mask  90  and its vicinity. The bevel mask  90  includes a main body portion  90 A and a convex portion  90 B at the upper surface on an inner edge side of the main body portion  90 A. The main body portion  90 A has the flat surface  90   a , and the convex portion  90 B has the inclined surface  90   b . The inclined surface  90   b  is an inclined surface on which the vertical distance from the main body portion  90 A decreases toward the center side of the bevel mask  90 . In some examples, slanted third lower surface  80   e  contacts the bevel  40 A. According to another examples, the third lower surface  80   e  is omitted so that the upper cover  80  does not contact the substrate  40 . 
     The inclined surface  90   b  is in contact with the bevel  40 A, whereby the substrate  40  is supported by the bevel mask  90 . According to an example, the bevel mask  90  contacts only the bevel  40 A of the substrate  40 , and does not contact any part of the substrate  40  other than the bevel  40 A. Therefore, the back side  40   b  of the substrate  40  is exposed, so that the plasma treatment can be performed on the entire back side  40   b . The inclined surfaces having various shapes described above can be adopted as the inclined surface  90   b.    
       FIG. 9  illustrates a rotating arm  92  located in the vicinity of an inner wall of the chamber  12 . The rotating arm  92  is provided to transfer the substrate to inside of four chambers which constitute, for example, the QCM. The substrate processing apparatus includes a plasma unit which is configured to generate plasma in a region below the upper cover  80  and the bevel mask  90 . In the example in  FIG. 9 , the plasma unit includes a shower plate  93 , gas sources  94  and  95  and an RF power supply  96 . The shower plate  93  is provided below the upper cover  80  so as to face the upper cover  80 . The shower plate  93  includes plates  93   a  and  93   c  which have slits for providing gas in a z positive direction from the gas sources  94  and  95 , and a spacer  93   b  provided between the plates  93   a  and  93   b . The whole of the shower plate  93  can be formed with a metal. According to another example, at least the plate  93   c  is formed with a metal. The gas sources  94  and  95  provide gas necessary for plasma processing. The RF power supply  96  provides high-frequency power for putting gas into a plasma state, to the shower plate  93 . In this manner, the substrate processing apparatus can perform plasma processing with a parallel plate structure including the upper cover  80  and the shower plate  93 . 
     In some examples, the upper cover  80  is evacuated upward by, for example, a motor  50  moving the first lifting mechanism  51 . Further, the bevel mask  90  is evacuated upward by, for example, a motor  52  moving the second lifting mechanism  53 . Thereafter, a support pin which is part of the rotating arm  92  is provided to a substrate receiving position inside the chamber  12  by the rotating arm  92  rotating. Support pins for supporting the substrate are provided to one of the four chambers by the rotating arm  92  rotating. The support pins may be disposed at positions surrounded by the bevel mask  90 . Then, after the bevel mask  90  is moved downward below upper ends of the support pins, the substrate is put on the support pins provided immediately below the upper cover  80 . Then, the inclined surface  90   b  is brought into contact with the bevel  40 A by the bevel mask  90  being moved upward. As the result of this contact, the support pins are separated from the substrate  40 , and are evacuated from positions immediately below the upper cover  80  by the rotating arm  92  rotating. 
     Then, the flat surface  90   a  is brought into close contact with the upper cover  80  while contact between the upper cover  80  and the substrate  40  is avoided. In this example, the flat surface  90   a  is brought into close contact with the second lower surface  80   d  by the upper cover  80  being moved downward. According to an example, it is possible to prevent contact between the upper cover  80  and the substrate  40  by providing the first lower surface  80   c  located above the second lower surface  80   d.    
     The flat surface  90   a  is located immediately below the second lower surface  80   d , and, when the second lower surface  80   d  comes into contact with the flat surface  90   a , flow of gas through space between the upper cover  80  and the bevel mask  90  is inhibited. In another example, in a case where a lower surface of the disk portion  80   b  of the upper cover  80  is made flat, as a result of the lower surface of the upper cover contacting the flat surface  90   a , flow of gas through space between the lower surface of the upper cover  80  and the flat surface  90   a  is inhibited. 
     In some examples, space surrounded by the substrate  40 , the bevel mask  90  and the upper cover  80  becomes enclosed space. In this case, gas supplied from the gas sources  94  and  95  and plasma provided between parallel plates are not virtually provided to the enclosed space. 
     Then, plasma processing is performed on the back side  40   b  of the substrate  40 . In some examples, it is possible to protect the device surface  40   a  by avoiding contact between the substrate  40  and the upper cover  80 . It is possible to ensure this avoidance of contact by providing a concave portion on the lower surface of the upper cover  80 . According to an example, the film formed at the back surface  40   b  of the substrate  40  through the plasma processing alleviates warpage of the substrate  40 . 
     In some of the foregoing examples, a shielding component which is the susceptor or the upper cover faces the device surface of the substrate. When the shielding component is the susceptor, the susceptor  16  and the substrate  40  are in contact with each other, and the contact between the bevel  40 A of the substrate  40  and the bevel mask  39  may be not essential. On the other hand, when the shielding component is the upper cover  80 , the bevel mask  90  and the bevel  40 A of the substrate  40  are in contact with each other, and the contact between the substrate  40  and the upper cover  80  may be not essential. 
     At least partially inclined surface of the bevel mask described in each of the foregoing examples may be circular in bottom view, or may have a shape with consideration for a notch or an orientation flat. Specifically, the inclined surface of the bevel mask can be adjusted so that the notch or the orientation flat and the inclined surface of the bevel mask can be brought into contact with or proximity to each other.