Abstract:
A deposition apparatus includes a dome rotatable around the central axis; a loop chain surrounding the central axis on the dome; a power transmission shaft transmitting rotational motion of the dome; a first gear section transforming the rotational motion of the dome to rotational motion of the shaft; a second gear section provided with a chain-driving sprocket and configured to transform the rotational motion of the shaft to rotational motion of the sprocket; and a tray holder located beside the loop chain, the tray holder including a first internal power transmission shaft and a rotating portion holding a tray. The sprocket is rotated through the rotation of the dome to drive the loop chain, the first internal power transmission shaft of the tray holder is rotated by motion of the loop chain, and the rotating portion is rotated through rotation of the first internal power transmission shaft.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    The present invention relates to a deposition apparatus and a manufacturing process including a film-forming step by a deposition apparatus. 
         [0003]    2. Description of the Related Art 
         [0004]    A deposition apparatus is used to form anti-reflection films on surfaces of optical elements such as lenses and diffraction gratings, for example. The deposition apparatus includes a deposition source for supplying a material which is used to form a film, and a dome which covers the deposition source and is rotatable around the central axis. Plural trays are attached to the dome and plural works, for example, lenses or diffraction gratings are attached to each of the trays. 
         [0005]    In order to realize uniform deposition amount over each work, deposition apparatuses that is configured such that trays are made to move around the deposition source (movement around the deposition source) and each tray is made to rotate on its own central axis (rotation on its own central axis) have been developed (JPS62-270768A and JPH4-329869A, for example). 
         [0006]    However, the mechanisms of the deposition apparatuses described above are not sufficient for reliable rotation of many trays installed on the dome on their own central axes. Further, the movement around the deposition source and the rotation on its own central axis of each tray are not sufficient for reduction of unevenness in deposition amount on respective faces of each work when each work has a three dimensional shape. On the other hand, from the standpoint of manufacturing and maintenance costs, deposition apparatuses should preferably be as simple as possible in structure. 
         [0007]    Thus, a deposition apparatus and a manufacturing process including a film-forming step by a deposition apparatus that can ensure reliable rotation of many trays installed on the dome on their own central axes and can reduce unevenness in deposition amount on respective faces of each of works having a three dimensional shape and attached to one of the trays have not been developed. 
       PATENT DOCUMENTS 
       [0008]    Patent document 1: JPS62-270768A 
         [0009]    Patent document 2: JPH4-329869A 
         [0010]    Accordingly, there is a need for a deposition apparatus and during rotation of the dome that can ensure reliable rotation of many trays installed on the dome on their own central axes and can reduce unevenness in deposition amount on respective faces of each of works having a three dimensional shape and attached to one of the trays. 
       SUMMARY 
       [0011]    A deposition apparatus according to a first aspect of the present invention includes a dome configured to be rotatable around the central axis; a loop chain arranged on the dome, the loop chain surrounding the central axis; a power transmission shaft configured to transmit rotational motion of the dome; a first gear section configured to transform the rotational motion of the dome to rotational motion of the power transmission shaft; a second gear section provided with a chain-driving sprocket and configured to transform the rotational motion of the power transmission shaft to rotational motion of the chain-driving sprocket; and a tray holder located beside the loop chain on the dome, the tray holder including a first internal power transmission shaft and a rotating portion configured to hold a tray. The deposition apparatus is configured such that the chain-driving sprocket is rotated through the rotation of the dome to drive the loop chain, the first internal power transmission shaft of the tray holder is rotated by motion of the loop chain, and the rotating portion is rotated through rotation of the first internal power transmission shaft. 
         [0012]    In the deposition apparatus according to the present aspect, the loop chain arranged on the dome is driven through rotation of the dome, and the first internal power transmission shaft of each tray holder located beside the loop chain on the dome is rotated through the loop chain. Thus, in each tray holder located beside the loop chain on the dome, rotation of a tray (rotation on its own central axis) is generated so that unevenness in amount of material deposited on each portion of each work having a three-dimensional shape and attached to the tray can be reduced. 
         [0013]    A deposition apparatus according to a first embodiment of the first aspect of the present invention includes plural loop chains and plural power transmission shafts, each of the plural power transmission shafts corresponding to a separate one of the plural loop chains. 
         [0014]    In the deposition apparatus according to the present embodiment, many trays held by many tray holders located beside the plural loop chains are rotated (rotation on their own central axes) so that unevenness in amount of material deposited on each portion of works having three-dimensional shapes and attached to the many trays can be reduced. 
         [0015]    In a deposition apparatus according to a second embodiment of the first aspect of the present invention, each tray holder is further provided with; a fixing portion fixed on the dome of the deposition apparatus; a swinging portion fixed to a swing pivot held rotatably by the fixing portion so as to be swingable; and a second internal power transmission shaft connected to the first internal power transmission shaft through a universal joint and held rotatably by the swinging portion. The first internal power transmission shaft is held rotatably by the fixing portion, the rotating portion is held by the second internal power transmission shaft and configured to hold a tray, and the rotating portion is configured to rotate with the second internal power transmission shaft and to swing with the swinging portion when the first internal power transmission shaft is rotated by each loop chain. 
         [0016]    A tray in the deposition apparatus according to the present embodiment is made to rotate with the rotating portion, and the rotating portion is made to swing with the swinging portion when the first internal power transmission shaft is rotated. Thus, the tray undergoes rotation (rotation on its own central axis) and swing, and therefore unevenness in amount of material deposited on each portion of each work having a three-dimensional shape and attached to the tray can be further reduced. 
         [0017]    In a deposition apparatus according to a third embodiment of the first aspect of the present invention, each tray holder is further provided with a crank mechanism including a rotating plate and a crank rod, the rotating plate is configured to be rotated through the rotation of the first internal power transmission shaft, and the crank rod connecting the rotating plate and the swinging portion is configured to swing the swinging portion through the rotation of the first internal power transmission shaft. 
         [0018]    In the deposition apparatus according to the present embodiment, the crank mechanism is configured to generate swing of the swinging portion from rotational motion of the first internal power transmission shaft. 
         [0019]    In a deposition apparatus according to a fourth embodiment of the first aspect of the present invention, each tray holder is configured such that a distance between the position where the crank rod is connected to the rotating plate and the center of the rotating plate can be changed to change the maximum value of an angle of inclination of a tray face with respect to a reference position. 
         [0020]    In the deposition apparatus according to the present embodiment, the maximum value of an angle of inclination of a tray face with respect to the reference position can be easily changed by changing the distance between the position where the crank rod is connected to the rotating plate and the center of the rotating plate. 
         [0021]    A manufacturing process according to a second aspect of the present invention includes a film forming step by a deposition apparatus. The deposition apparatus includes: a dome configured to be rotatable around the central axis; a loop chain arranged on the dome, the loop chain surrounding the central axis; and a tray holder located beside the loop chain and configured to transform rotational motion of the dome transmitted though the loop chain to rotational motion around a rotating axis of the tray holder and swinging motion around a swinging axis of the tray holder. In the manufacturing process, a film is formed on a work attached to a tray held by the tray holder through deposition while the rotational motion and the swinging motion in the tray holder are carried out during rotation of the dome. 
         [0022]    In the manufacturing process according to the present aspect, the tray undergoes rotation and swing during rotation of the dome, and therefore unevenness in amount of material deposited on each portion of each work having a three-dimensional shape and attached to the tray can be reduced. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  shows a construction of a deposition apparatus according to the present invention; 
           [0024]      FIG. 2  shows a plan view of the dome of the deposition apparatus  300  according to the present invention; 
           [0025]      FIG. 3  shows a cross section of the dome of the deposition apparatus according to the present invention; 
           [0026]      FIG. 4A  is a plan view of the first gear section and the gear fixed to the bearing section for the rotating shaft of the dome; 
           [0027]      FIG. 4B  is a side view of the first gear section; 
           [0028]      FIG. 4C  is a side view of the first gear section and the gear fixed to the bearing section for the rotating shaft of the dome; 
           [0029]      FIG. 5A  is a plan view of the second gear section and the rotating shaft for power transmission; 
           [0030]      FIG. 5B  is a side view of the second gear section; 
           [0031]      FIG. 5C  is a side view of the second gear section and the rotating shaft for power transmission; 
           [0032]      FIG. 6A  is a plan view of the second gear section and the rotating shaft for power transmission; 
           [0033]      FIG. 6B  is a side view of the second gear section; 
           [0034]      FIG. 6C  is a side view of the second gear section and the rotating shaft for power transmission; 
           [0035]      FIG. 7A  is a side view of a tray holder installed on the dome; 
           [0036]      FIG. 7B  is another side view of the tray holder; 
           [0037]      FIGS. 8A and 8B  illustrate the internal mechanism of the fixing portion and the swinging portion of each of the tray holders; and 
           [0038]      FIG. 9  illustrates how the position of a work on a tray affects an amount of the material deposited on the work by the deposition apparatus. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]      FIG. 1  shows a construction of a deposition apparatus  300  according to the present invention. The deposition apparatus  300  includes a deposition source  320 , a dome  310  and a chamber  330  which encloses them. The chamber  330  is evacuated using an exhaust hole  335  and a predetermined degree of vacuum is maintained inside it. The dome  310  is configured such that works  400  can be attached to the inner wall of it and is installed such that it covers the deposition source  320 . Works  400  are optical element such as diffraction gratings, for example, and are attached to one of trays that are attached to the inner wall of the dome  310  by one of tray holders not shown in the drawing. The trays are not shown in the drawing, either. A material which has been emitted by the deposition source  320  reaches the works  400  attached to the inner wall of the dome  310  and is disposed onto surfaces of the works. During the deposition process the dome  310  is rotated around the central axis by a driving section not shown in the drawing so as to realize uniform deposition amount among the plural works  400  attached to the inner wall of the dome  310 . The descriptions given above are commonly applied to the deposition apparatus  300  according to the present invention and conventional deposition apparatuses. The characteristic construction of the deposition apparatus  300  according to the present invention will be described below. 
         [0040]      FIG. 2  shows a plan view of the dome  310  of the deposition apparatus  300  according to the present invention. The deposition apparatus  300  according to the present invention is configured such that trays attached to one of tray holders  1000  are made to rotate by rotation of a portion of the one of the tray holders  1000  installed on the dome  310  and the rotation of the portion of the one of the tray holders  1000  is realized by rotation of the dome  310 . 
         [0041]    In order to transmit rotational motion of the dome  310  to the tray holders  1000 , the deposition apparatus is provided with a first gear section  150 , second gear sections  160 A and  160 B, and rotating shafts for power transmission (power transmission shaft)  155 A and  155 B. The first gear section  150  is engaged with a fixed gear  3101  attached to a bearing section for a rotating shaft of the dome  310  and generates rotational motion of the rotating shaft for power transmission  155 A when the dome  310  rotates. The second gear section  160 A transforms the rotational motion of the rotating shaft for power transmission  155 A to rotational motion of a sprocket, and the rotational motion of the sprocket drives a loop chain  205 . As a result, rotating portions of the plural tray holders  1000  connected to the loop chain  205  are made to rotate. Further, the rotational motion of the rotating shaft for power transmission  155 A is transmitted to the rotating shaft for power transmission  155 B. The second gear section  160 B transforms the rotational motion of the rotating shaft for power transmission  155 B to rotational motion of a sprocket, and the rotational motion of the sprocket drives a loop chain  210 . As a result, rotating portions of the plural tray holders  1000  connected to the loop chain  210  are made to rotate. 
         [0042]      FIG. 3  shows a cross section of the dome  310  of the deposition apparatus  300  according to the present invention. The cross section contains the central axis of the dome  310 . The dome  310  is hung from the ceiling of the chamber  330  and configured to be rotated around the central axis by a driving mechanism not shown in the drawing. The system may be configured such that the rotational speed of the dome  310  can be adjusted between 10 rpm and 20 rpm, for example. When the dome  310  rotates around the central axis, the rotational motion of the dome  310  makes the first gear section  150  generate rotational motion of the rotating shaft for power transmission  155 A as described above. The second gear section  160 A generates rotational motion of a sprocket as well as rotational motion of the rotating shaft for power transmission  155 B through the rotational motion of the rotating shaft for power transmission  155 A. The second gear section  160 B transforms the rotational motion of the rotating shaft for power transmission  155 B to rotational motion of a sprocket. 
         [0043]    Each of the tray holders  1000  includes a fixing portion  1100  and a swinging portion  1200 . A rotating portion of the fixing portion  1100  is rotated by the loop chain  205  or  210 . The tray holders  1000  will be described later. 
         [0044]      FIGS. 4A to 4C  illustrate the first gear section  150 .  FIG. 4A  is a plan view of the first gear section  150  and the gear  3101  fixed to the bearing section for the rotating shaft of the dome  310 .  FIG. 4B  is a side view of the first gear section  150 .  FIG. 4C  is a side view of the first gear section  150  and the fixed gear  3101  attached to the bearing section for the rotating shaft of the dome  310 . As shown in  FIGS. 4A to 4C , an idler gear  1501  of the first gear section  150  is engaged with the fixed gear  3101  attached to the bearing section for the rotating shaft of the dome  310  on the one hand and with a driving gear  1503  of the first gear section  150  on the other. The first gear section  150  is fixed on the dome  310 , and therefore the idler gear  1501  engaged with the fixed gear  3101  is rotated when the dome  310  rotates around the central axis. Further, when the idler gear  1501  rotates, the driving gear  1503  engaged with the idler gear  1501  is rotated. The rotational motion of the driving gear  1503  is transformed to rotational motion of the rotating shaft for power transmission  155 A through a spiral gear  1505 . Thus, the first gear section  150  generates the rotational motion of the rotating shaft for power transmission  155 A by the use of the rotational motion of the dome  310 . 
         [0045]      FIGS. 5A to 5C  illustrate the second gear section  160 A  FIG. 5A  is a plan view of the second gear section  160 A and the rotating shaft for power transmission  155 A.  FIG. 5B  is a side view of the second gear section  160 A.  FIG. 5C  is a side view of the second gear section  160 A and the rotating shaft for power transmission  155 B. 
         [0046]    As shown in  FIG. 5A , rotational motion of the rotating shaft for power transmission  155 A is transmitted to the second gear section  160 A through a universal joint  157 A 2 . 
         [0047]    As shown in  FIGS. 5B and 5C , the rotational motion of the rotating shaft for power transmission  155 A transmitted to the second gear section  160 A is transformed to rotational motion of a sprocket  1603 A through a helical gear  1601 A Sprockets  1603 A and  1605 A are engaged with the loop chain  205  such that the rotational motion of the sprocket  1603 A drives the loop chain  205 . The reason that the sprocket  1605 A is provided in addition to the sprocket  1603 A is to enhance engagement between the sprocket  1603 A and the loop chain  205 . Thus, the second gear section  160 A drives the loop chain  205  by the use of the rotational motion of the rotating shaft for power transmission  155 A. 
         [0048]    As shown in  FIG. 5C , the rotational motion of the rotating shaft for power transmission  155 A is further transmitted to the rotating shaft for power transmission  155 B through the universal joint  157 A 2  and a universal joint  157 B 1 . 
         [0049]      FIGS. 6A to 6C  illustrate the second gear section  160 B.  FIG. 6A  is a plan view of the second gear section  160 B and the rotating shaft for power transmission  155 B.  FIG. 6B  is a side view of the second gear section  160 B.  FIG. 6C  is a side view of the second gear section  160 B and the rotating shaft for power transmission  155 B. 
         [0050]    As shown in  FIG. 6A , rotational motion of the rotating shaft for power transmission  155 B is transmitted to the second gear section  160 B through the universal joint  157 B 1 . 
         [0051]    As shown in  FIGS. 6B and 6C , the rotational motion of the rotating shaft for power transmission  155 B transmitted to the second gear section  160 B is transformed to rotational motion of a sprocket  1603 B through a helical gear  1601 B. Sprockets  1603 B and  1605 B are engaged with the loop chain  210  such that the rotational motion of the sprocket  1603 B drives the loop chain  210 . The reason that the sprocket  1605 B is provided in addition to the sprocket  1603 B is to enhance engagement between the sprocket  1603 B and the loop chain  210 . Thus, the second gear section  160 B generates the rotational motion of the sprocket  1603 B by the use of the rotational motion of the rotating shaft for power transmission  155 B to drive the loop chain  210 . 
         [0052]      FIGS. 7A and 7B  illustrate each of the tray holders  1000 .  FIG. 7A  is a side view of each tray holder  1000  installed on the dome  310 . The side is in the radial direction.  FIG. 7B  is another side view of the tray holder  1000 . The side of  FIG. 7B  is orthogonal to the side of  FIG. 7A . Each of the tray holders  1000  includes the fixing portion  1100 , the swinging portion  1200  and the rotating portion  1300 . The fixing portion  1100  is fixed on the surface of the dome  310  in such a way that the central axis of the fixing portion  1100  is parallel to the central axis of the dome  310 . A swing pivot  1109  of the swinging portion  1200  is attached rotatably to the fixing portion  1100 . The swing pivot  1109  may be set orthogonal to the central axis of the fixing portion  1100 . Further, the swing pivot  1109  may be set orthogonal to a plane containing the central axis of the dome  310  and the central axis of the tray holder  1000 . 
         [0053]    The rotating portion  1300  is configured to hold a tray  1400 A or a tray  1400 B by means of a chuck. The chuck is configured to be adjusted according to size of trays such as the tray  1400 A and the tray  1400 B which are different in size. 
         [0054]      FIGS. 8A and 8B  illustrates the internal mechanism of the fixing portion  1100  and the swinging portion  1200  of each of the tray holders  1000 .  FIG. 8A  corresponds to  FIG. 7A  and  FIG. 8B  corresponds to  FIG. 7B . 
         [0055]    Inside the fixing portion  1100 , a first rotating shaft (a first internal power transmission shaft)  1121  is provided. A sprocket  1101  is connected to an end of the first rotating shaft  1121  such that the first rotating shaft  1121  is rotated when the sprocket  1101  is rotated by the loop chain  205  or  210 . Inside the swinging portion  1200 , a second rotating shaft (a second internal power transmission shaft)  1125  is provided. The second rotating shaft  1125  is connected to the other end of the first rotating shaft  1121  through a universal joint  1123  such that the second rotating shaft  1125  is rotated when the first rotating shaft  1121  rotates. The second rotating shaft  1125  is connected to the rotating portion  1300 . Accordingly, when the sprocket  1101  is rotated by the loop chain  205  or  210 , the first rotating shaft  1121  and the second rotating shaft  1125  are rotated and then the rotating portion  1300  that holds a tray is rotated. 
         [0056]    Thus, when the dome  310  rotates and the sprocket  1101  is rotated by one of the loop chains, the rotating portion  1300  that holds a tray is rotated. The gear ratios are determined such that the rpm of the rotating portion  1300  is ten times as high as that of the dome  310 , for example. 
         [0057]    As shown in  FIG. 7A , the fixing portion  1100  is provided with a rotating plate  1103 . A first end of a first rod  1105  is connected to the rotating plate  1103  at a position spaced d from the center of the rotating plate  1103 . A second end of the first rod  1105  is connected to a first end of a second rod  1107 . A second end of the second rod  1107  is connected to the swinging portion  1200 . As shown in  FIG. 8A , a worm  1127  is attached to the first rotating shaft  1121 . The worm  1127  is engaged with a worm wheel  1129 , and the rotating plate  1103  is attached to the rotating shaft of the worm wheel  1129 . Accordingly, when the first rotating shaft  1121  rotates, the worm  1127  and the worm wheel  1129  are rotated, and then the rotating plate  1103  is rotated. When the rotating plate  1103  rotates, the swinging portion  1200  swings around the swing pivot  1109  by means of the first rod  1105  and the second rod  1107 . In a cross section in the radial direction of the dome  310 , the maximum value of an angle of inclination of a tray face with respect to the tangential plane of the dome  310  at the position of the central axis of the fixing portion  1100  is referred to as a swing angle. In other words, the swing angle is the maximum value of an angle of inclination of a tray face with respect to the reference position and is the angle represented as θ in  FIG. 7A . The swing angle can be changed by changing the distance d between the position at which the first end of the first rod  1105  is connected to the rotating plate  1103  and the center of the rotating plate  1103 . The swing angle increases with the distance d. The distance d is determined such that the swing angle is ±10 degrees, for example. 
         [0058]    Thus, when the dome  310  rotates and the sprocket  1101  is rotated by the loop chain, the swinging portion  1200  swings. The gear ratios are determined such that a cycle of swing is carried out for a period of revolution of the dome  310 , for example. 
         [0059]    As described above, the rotating portion  1300  is rotated by means of the second rotating shaft  1125  while the dome  310  rotates. Further, since the second rotating shaft  1125  is held inside the swinging portion  1200 , the rotating portion  1300  connected to the second rotating shaft  1125  is made to swing in a similar way when the swinging portion  1200  is made to swing around the swing pivot  1109 . Thus, a tray held by the rotating portion  1300  undergoes rotation and swing. 
         [0060]      FIG. 9  illustrates how the position of a work on a tray affects an amount of the material deposited on the work by the deposition apparatus. It is assumed that the tray is fixed to the dome. It is further assumed that the dome  310  is spherical and the deposition source is located at the center of the sphere. In  FIG. 9 , a work  400   a  is located on the left side of the tray  1400 , a work  400   b  is located in the center of the tray  1400 , and a work  400   c  is located on the right side of the tray  1400 . In this case, the material to be deposited travels along a normal to the inner surface of the dome  310  at the position of each of the works.  FIG. 9  shows a cross section that contains the center of the sphere and the normals at the positions of the works. An angle that a normal along which the material to be deposited travels forms with the central axis of each of the works is referred to as a film-forming angle. The central axis of each of the works is perpendicular to the tray  1400  and passes through the center of each of the works. The film-forming angle is measured clockwise with respect to the central axis of each of the works. The central axes are represented as dot-dash lines. In  FIG. 9 , when the film-forming angle of the work  400   a  is represented as ω, the film-forming angle of the work  400   c  is represented as −ω. Further, the film-forming angle of the work  400   b  is 0. The film-forming angles remain unchanged irrespective of rotational position of the dome  310 . As a result, an amount of the material deposited (thickness of a film generated) on the right side of the work  400   a  is greater than that on the left side of the work  400   a.  Further, an amount of the material deposited on the left side of the work  400   c  is greater than that on the right side of the work  400   c.    
         [0061]    When the tray  1400  is rotated around the central axis of the tray  1400 , that is, the central axis of the work  400   b,  the film-forming angles of the work  400   a  and the work  400   c  vary according to the rotation of the tray  1400 , and therefore unevenness in amount of the material deposited on each portion of each work is reduced. 
         [0062]    Further, by carrying out of swing operation of the tray  1400 , unevenness in amount of the material deposited on each portion of each work can be reduced even if works set on the tray  1400  have three-dimensional shapes. 
         [0063]    The first ratio of the number of revolutions (rotation on its own central axis) of each tray per unit time to the number of revolutions of the dome per unit time and the second ratio of the number of revolutions of rotating plate  1103  per unit time to the number of revolutions of the dome per unit time can be set to desired values by changing gear ratios. The second ratio determines a period of the swing. Further, as described above, by changing the distance d between the position at which the first end of the first rod  1105  is connected to the rotating plate  1103  and the center of the rotating plate  1103 , the swing angle θ can be changed. Thus, the period of rotation of each tray on its own central axis, the period of the swing and the swing angle can be appropriately adjusted according to specifications of works.