Abstract:
A spin chuck using at least three clamping rollers for clamping a substrate during the rotation of the substrate. The clamping rollers are driven by a planetary gear transmission mechanism that is on a rotatable body. The final rotation speed of the substrate is determined by the cooperation of the rotation speeds of the clamping rollers and the body. The spin chuck is capable of providing simultaneous dual-sided processing, and the angular velocity and angular acceleration of the spin chuck have a wide range of adjustment.

Description:
FIELD OF THE INVENTION 
     The invention relates to a spin chuck used in a chamber, in particular, to a spin chuck capable of providing simultaneous dual-sided processing (including cleaning processes), and capable of widely adjusting the angular velocity and angular acceleration thereof. 
     BACKGROUND OF THE INVENTION 
     In a conventional manufacturing process of a semiconductor device or a liquid crystal display (LCD) including wet etching, cleaning, wet spin etching, coating, and developing, various types of acid tanks or chambers are utilized. In a conventional chamber, a wafer or LCD substrate is clamped on a chuck that is driven to rotate by a driving device (e.g. a motor). 
     A conventional driving system utilizes a single motor as a driving source. A wafer clamped on a chuck is driven to rotate as shown in U.S. Pat. No. 5,312,487. 
     Referring to FIG. 1, a conventional driving system of a spin chuck for driving a substrate  101  to rotate includes a motor  102 , a chuck  104 , and a controller  105 . The motor  102  includes a rotating shaft  103 . The rotating shaft  103  drives the chuck  104 , used to clamp a substrate  101 , to rotate. The controller  105  is used for controlling the angular velocity of the motor  102 . The substrate  101  is clamped on the chuck  104  by way of vacuum pressure. Therefore, the driving system further includes a vacuuming conduit  106  penetrating through the motor  102 . 
     In the driving system, the chuck  104  is driven by the motor  102  to rotate substrate  101 . The end product of the complicated processes substrate  101  undergoes is determined by the properties of the processing materials, the patterns on the substrate  101 , the angular velocity control and the angular acceleration control of the substrate  101 , among others. After the processing materials and the patterns on the substrate  101  are determined, control over both angular velocity and angular acceleration of the substrate  101  becomes an important issue. 
     Referring to FIG. 2, the horizontal axis represents time, and the vertical axis represents the rotation speed of the substrate. Time t is the time required for the substrate to increase its rotation speed from 0 to N (where N is an integer) rpm (revolutions per minute). A line  107  represents the speed variation of the substrate. Time t is also the time required for the substrate to decrease its speed from 0 to −N rpm. A line  108  represents the speed variation of the substrate. The maximum rotation speed of the substrate is N or −N rpm. 
     A line  109  represents the rotation speed of the substrate after it reaches N rpm, while a line  110  represents the rotation speed of the substrate after it reaches −N rpm. An area  111  shaded with diagonal lines is the speed variation of the substrate. The maximum angular acceleration of the substrate can be determined from the slopes of lines  107  and  108 . 
     In general, variations in the angular velocity and the angular acceleration of the motor  102 , which drives the substrate  101 , are ideally as large as possible. However, after the motor  102  is manufactured, the performance (e.g., the maximum instant torque, the maximum rotating speed, the minimum rated rotating speed, the maximum angular acceleration, and related characteristics) of the motor  102  and those of the controller  105  are fixed. When the motor  102  is designed for rotating at high speeds, its rotation condition is not stable or easily controlled at low rotation speeds. In addition, when the motor  102  is designed for rotating at low rotation speeds, its rotation condition is not stable or easily controlled at high rotation speeds. 
     Recently, the line widths of semiconductor products have greatly decreased. More time is needed for the processing material to fill into the narrow trenches and cover the surfaces of the trenches. After the processing material has filled into the narrow trenches, the redundant processing material cannot be ejected from the trenches due to the surface tension of the processing material. In order to avoid this phenomenon, the driving system has to provide greater angular velocity or angular acceleration to force out the redundant processing material in the trenches. 
     The design of the motor  102  or controller  105  can be improved to let the angular velocity and the angular acceleration of the motor  102  satisfy the process requirements. However, it is extremely difficult for a single set of one motor  102  and one controller  105  to reach wide controls of angular velocity and angular acceleration, unless the manufacturing costs of the motor  102  and the controller  105  are increased. Even then, a motor  102  and a controller  105  are often unable to satisfy the process requirements. 
     In a conventional spin chuck driving system, a motor is in direct contact with a chuck. Thus, the heat energy generated from the motor is easily transferred to the chuck, causing the substrate temperature to rise. Furthermore, since the tangential velocity of the circumferential edge of the rotating substrate relative to the air is high, the heat energy at the circumferential edge of the substrate is easily transferred to the air. In addition, since the tangential velocity at the center of the rotating substrate relative to the air is low, the heat energy at the center of the substrate is not easily transferred to the air. As a result, a temperature difference between the circumferential edge and the center of the substrate is induced, which deteriorates the qualities of product. 
     FIG. 3A is a front cross-sectional view illustrating a flow status of an etchant on a substrate in a conventional etching process. FIG. 3B is a top view illustrating a flow status of an etchant on a substrate in a conventional etching process. FIG. 3C is a front cross-sectional view illustrating the etched substrate as shown in FIG.  3 A. FIG. 3D is a top view illustrating the etched substrate as shown in FIG.  3 B. 
     Referring to FIGS. 3A and 3B, an etchant  121  flows through a trench  123  of a substrate  122 . An arrow indicates the direction of flow of the etchant  121 . In the prior art, the direction of flow of the etchant  121  is fixed because the rotation direction of the substrate  122  is fixed. FIGS. 3C and 3D show the change in the trench patterns and the deteriorating quality of the substrate from the etching process. 
     In order to prevent the lower surfaces of the wafers or LCD substrates from having direct contact with a spin chuck, a spin chuck using a protective layer of gas and a clamp pin, as disclosed in U.S. Pat. No. 5,421,056, is used. A schematic illustration of the above spin chuck is shown in FIG.  4 A. 
     Referring to FIG. 4A, the spin chuck  141  has six clamp pins  142 . The clamp pins  142 , that clamp or release substrate  140 , form a ring that is adjusted by an extension rod (not shown) and a swingable lever. A supply passage  143  is provided within the spin chuck  141  to support the substrate  140  using a flow of gas. It should be noted that the arrow indicates the gas&#39;s direction of flow. 
     The substrate  140  is not in direct contact with the spin chuck  141 , solving substrate  140 &#39;s lower surface pollution problem. However, because there is no relative motion between each of the clamp pins  142  and the substrate  140 , unwanted pin marks  144  are easily formed in the contact regions between each of the clamp pins  140  and the substrate  140 , as shown in FIG.  4 B. Therefore, uniform product quality is not easily obtained. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a spin chuck capable of providing simultaneous dual-sided processing (including cleaning processes), wide ranges of angular velocity and angular acceleration, and uniform substrate quality. The spin chuck in accordance with the invention can rotatably clamp the outer periphery of the substrate so as to provide simultaneous dual-sided processing. 
     In accordance with an aspect of the invention, a spin chuck used for clamping a substrate to rotate in a chamber includes three roller shafts and three clamping rollers. The respective roller shafts are driven to rotate by a planetary gear transmission mechanism. The planetary gear transmission mechanism includes a gear shaft driven to rotate by a driving device, and three output shafts. The rotation speed of each of the three output shafts has a predetermined relationship with the rotation speed of the gear shaft so as to drive each of the three respective roller shafts to rotate. The three clamping rollers are fixed on the three roller shafts, and are driven to rotate by each of the three respective roller shafts so as to rotatably clamp the substrate. 
     In accordance with another aspect of the invention, a spin chuck used for clamping a substrate to rotate in a chamber includes a body, an input/output conduit, a gear shaft, two conoids, a frame, a planetary gear transmission mechanism, three roller shafts, and three clamping rollers. 
     The body is driven to rotate by a driving device, the body has a through hole penetrating through the body, a first space substantially perpendicular and communicating with the through hole, three holes allowing the first space to communicate with the outside, a plurality of upper guiding portions communicating with the first space and located above the first space, and a plurality of lower guiding portions communicating with the first space and located below the first space. 
     The input/output conduit penetrates through the through hole and is for supplying a predetermined processing material to the substrate and for allowing a predetermined processing material drain out. 
     The gear shaft is received in the through hole and rotatably mounted between the body and the input/output conduit. The two conoids are rotatably mounted on the gear shaft and each conoid is separated from the other by a predetermined distance. Each of the conoids has a plurality of slanting guiding portions. 
     The frame is received in the body and includes a plurality of section-shaped sub-frames. Each of the sub-frames has a gear-room, and an upper sliding portion and a lower sliding portion. The upper and lower sliding portions are located above and under each sub-frame&#39;s respective gear-room. The upper sliding portion shifts within the upper guiding portion, while the lower sliding portion shifts within the lower guiding portion. 
     Each of the sub-frames further includes an upper shifting portion and a lower shifting portion located at the inner periphery of the sub-frame and spanning from the top to the bottom which allows shifting within the slanting guiding portion while the frame is being enlarged and reduced by the two conoids and the plurality of slanting guiding portions. 
     The planetary gear transmission mechanism is received in the gear-room, it includes a sun gear, three planet gears, and three output shafts. The sun gear is fixed on the gear shaft between the two conoids with the gear shaft serving as a rotating shaft. The three planet gears are arranged around the sun gear. The three output shafts are fixed on the three planet gears and penetrate through the frame. 
     The three roller shafts are received within the gear shafts and driven to rotate by the three output shafts. The three clamping rollers are mounted to the three roller shafts to rotate and rotatably clamp the substrate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration showing a conventional driving device of a spin chuck. 
     FIG. 2 is a chart illustrating the relationship between the rotation speed of a conventional substrate and time. 
     FIG. 3A is a front cross-sectional view illustrating a flow status of an etchant on a substrate in a conventional etching process. 
     FIG. 3B is a top view illustrating a flow status of an etchant on a substrate in a conventional etching process. 
     FIG. 3C is a front cross-sectional view illustrating the etched substrate as shown in FIG.  3 A. 
     FIG. 3D is a top view illustrating the etched substrate as shown in FIG.  3 B. 
     FIG. 4A is a schematic illustration showing a conventional spin chuck as disclosed in U.S. Pat. No. 5,421,056. 
     FIG. 4B is a view illustrating pin marks on the substrate caused by the spin chuck in FIG.  4 A. 
     FIG. 5 is a schematic illustration showing a spin chuck in accordance with a preferred embodiment of the invention. 
     FIG. 6 is a schematic illustration showing the body of the spin chuck as shown in FIG.  5 . 
     FIG. 7 is a schematic illustration showing the input/output conduit as shown in FIG.  5 . 
     FIG. 8A is a top view illustrating an arrangement of a frame, a conoid, and a gear shaft. 
     FIG. 8B is a bottom view illustrating an arrangement of a frame, a conoid, and a gear shaft. 
     FIG. 9A is a pictorial view of the conoid as shown in FIG.  5 . 
     FIG. 9B is a schematic illustration showing the relative motion between the conoid and the sub-frame as shown in FIG.  5 . 
     FIG. 10A is a schematic illustration showing the relative motion between the frame and the body when pushing the gear shaft up. 
     FIG. 10B is a schematic illustration showing the relative motion between the frame and the body when not pushing the gear shaft up. 
     FIG. 11 is a schematic illustration showing the arrangement of an operating spin chuck in accordance with the invention. 
     FIG. 12 is an example illustrating a relationship between the rotation speed of the substrate and time when using the spin chuck of the invention. 
     FIG. 13 is an example illustrating the shaking effect when using the spin chuck of the invention. 
     FIG. 14 is a schematic cross-sectional view illustrating a spin chuck in accordance with another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments will be described with reference to the accompanying drawings. 
     Referring to FIG. 5, a spin chuck is used for clamping a substrate  1  (e.g. a wafer or LCD substrate) during rotation of the substrate  1 . The spin chuck includes a body  2 , an input/output conduit  3 , a gear shaft  4 , two conoids  5 , a frame  6 , a planetary gear transmission mechanism  8 , six roller shafts  9 , and six clamping rollers  10 . 
     The body  2  is driven to rotate by a first driving device (e.g. a motor) that is not shown. 
     The input/output conduit  3  is used for supplying a predetermined processing material (e.g. a cleaner or etchant) to the substrate  1 , or draining out unwanted processing material. 
     The gear shaft  4  is driven to rotate by a second driving device (e.g. a motor) that is not shown. 
     The frame  6 , which includes three section-shaped sub-frames  7 , is capable of enlarging or reducing its diameter. 
     The gear shaft  4  drives the planetary gear transmission mechanism  8 . 
     A corresponding output shaft  84  of the planetary gear transmission mechanism  8  drives each of the roller shafts  9 . 
     Each of the clamping rollers  10  is fixed on a corresponding roller shaft  9  and rotatably clamps the substrate  1 . 
     The input/output conduit  3  penetrates through the body  2 . The hollow gear shaft  4  is placed between the input/output conduit  3  and the body  2 . A plurality of bearings  12  is provided between the gear shaft  4  and the body  2 , and between the gear shaft  4  and the input/output conduit  3 . Therefore, the gear shaft  4  can rotate independently of the body  2  and the input/output conduit  3 . 
     The planetary gear transmission mechanism  8  includes a sun gear  81 , three planet gears  82 , six planet gears  83 , and six output shafts  84 . 
     The sun gear  81  is fixed to the gear shaft  4  and located between the two conoids  5 . The gear shaft  4  serves as the rotating shaft of the sun gear  81 . The planet gears  82  mesh with the sun gear  81 . The six planet gears  83  mesh with the three sun gears  81 . Two adjacent planet gears  83  are one set. Each of the output shafts  84  is fixed to the corresponding outermost planet gear  83  and projects over the sub-frame  7 . 
     Six roller shafts  9  are driven to rotate by their six respective output shafts  84 . 
     Six clamping rollers  10  are fixed on their six respective roller shafts  9  so as to rotatably clamp the substrate  1 . 
     The structure of each of the other elements will be described in detail with reference to FIGS. 6 to  9 . 
     Referring to FIG. 6, the body  2  has a through hole  21 , a first space  22 , six holes  23 , three upper guiding portions  24 , three lower guiding portions  25 , and a second space  26 . 
     The through hole  21  penetrates through the body  2 . The first space  22  vertically communicates with the through hole  21 . The holes  23  communicate with the first space  22  and with the outside. The upper guiding portions  24  communicate with the first space  22  and are located above the first space  22 . The lower guiding portions  25  communicate with the first space  22  and are located under the first space  22 . The second space  26  communicates with the through hole  21  and with the outside. 
     Referring to FIG. 7, the input/output conduit  3  includes an output conduit  31 , an input conduit  32 , and a collecting portion  34 . The output conduit  31  penetrates through the input/output conduit  3 . The input conduit  32  has an inlet  33  and six outlets  35 . The six outlets  35  are allocated around the output conduit  31 . The inlet  33  is used for inputting a predetermined processing material. The outlets  35  are used for spraying the predetermined processing material on the lower surface of the substrate to be treated. The collecting portion  34  communicates with the output conduit  31  and the input conduit  32  collects the processing material to be drained. 
     Referring now to FIGS. 8A and 8B, the frame  6  is composed of three sub-frames  7 . An upper sliding portion  72  and a lower sliding portion  73  are above and under each of the sub-frames  7 , respectively. An upper shifting portion  74  and a lower shifting portion  75  are at the inner periphery of each of the sub-frames  7 . Furthermore, it is understood from FIG. 5 that each of the sub-frames  7  is a hollow structure for receiving the planetary gear transmission mechanism  8 . The receiving space is referred to as a gear-room  71 . 
     Referring to FIGS. 9A and 9B, the conoid  5  has three slanting guiding portions  51 . Pulleys  76  are mounted on each of the upper shifting portions  74  of the sub-frames  7  and each of the lower shifting portions  75  of the sub-frames  7 . Three slanting guiding portions  51  allow the pulleys  76  to slide within the slanting guiding portions  51  (the arrows indicate the directions to which the pulleys  76  can slide). The slanting guiding portions  51  are T-slots of the embodiment. Thus, the pulleys  76  are always in contact with the slanting guiding portion  51 . The conoids  5  are rotatably mounted on the gear shaft  4 . The sun gear  81  is not fixed to the two conoids  5 . The frame  6  can move with respect to the conoids  5 . The pulleys  76  can slide down when pushing up the gear shaft  4  and the pulleys  76  can slide up when pulling down the gear shaft  4 . 
     The diameter of the frame  6  can be enlarged or decreased as described in the following. 
     Referring to FIG. 10A, when the gear shaft  4  is pushed up as indicated by the vertical arrows, the upper shifting portions  74  and the lower shifting portions  75  slide downwards along the slanting guiding portions  51  of the conoids  5  since the upper sliding portions  72  are guided by the upper guiding portions  24 . Furthermore, the upper shifting portions  74  and the lower shifting portions  75  slide downwards and outwards (as indicated by the horizontal arrows) due to the slope of each of the slanting guiding portions  51 . The frame  6  can stably enlarge its diameter by with the guidance and limitations imposed on it by the upper guiding portions  24  and its corresponding upper sliding portion  72  and by each of the lower guiding portions  25  and its corresponding lower sliding portion  73 . Enlarging frame  6  compresses the three springs  11  located at the lower guiding portions  25 . 
     Similarly, referring to FIG. 10B, when the gear shaft  4  is pulled down as indicated by the vertical arrows, the upper shifting portions  74  and the lower shifting portions  75  slide upwards and inwards (as indicated by the horizontal arrows), along the slanting guiding portions  51  of the conoids  5 . Thus, the diameter of the frame  6  is decreased. It should be noted that the springs  11  exerts an assistant force that assists in clamping the substrate  1 . 
     Referring again to FIG. 5, when frame  6  enlarges its diameter, both the output shafts  84  and the clamping rollers  10  shift outwards enlarging the region enclosed by them and unloading the substrate  1 . When frame  6  decreases its diameter, both the output shafts  84  and the clamping rollers  10  shift inwards decreasing the region enclosed by them and clamping the substrate  1 . 
     Six guiding blocks  13  are set at the intersections of each of the output shafts  84  and the frame  6  to prevent the processing material (e.g. a cleaner or etchant) from flowing into the planetary gear transmission mechanism  8  along the roller shafts  9  and the output shafts  84 . 
     Referring to FIG. 11, in addition to the spin chuck, there is a nozzle  14  above the spin chuck to supply a predetermined processing material onto the substrate  1 . Furthermore, a material supplying device  15  is selectively communicated with the inlet  33  of the input/output conduit  3  to supply cleaner, etchant, or nitrogen to the lower surface via the input conduit  32  and the outlets  35 . Moreover, to drain away the unwanted processing material the output conduit  31  is connected to a waste-liquid tank  16 . The body  2  is driven to rotate by a first motor  17 . The gear shaft  4  is driven to rotate by a second motor  18  and is biased up and down by a push rod (not shown). 
     The operation of the spin chuck in accordance with the above embodiment of the invention is described in the following. 
     First, when no substrate  1  is clamped on the spin chuck, unwanted processing material is sprayed out by nozzle  14 . The unwanted processing material can be drained into the waste-liquid tank  16  via the collecting portion  34  and the output conduit  31 . 
     Next, the gear shaft  4  is biased up by the push rod, and the region enclosed by the six clamping rollers  10  is enlarged. The substrate  1  is then transferred to a predetermined position. Thereafter, the gear shaft  4  is biased down by the push rod. At this time, the frame  6  shrinks, and the region enclosed by the six clamping rollers  10  decreases to clamp the substrate  1 . 
     When the first motor  17  drives the body  2  to rotate and the second motor  18  halts, the substrate  1  will rotate. In this case, a processing material can be supplied to the upper surface of the substrate  1  via the nozzle  14 , and another processing material (e.g. a cleaner or etchant) can also be supplied to the lower surface of the substrate  1  from the material supplying device  15 . 
     When the second motor  18  drives the gear shaft  4  to rotate and the first motor  17  halts, the sun gear  81  is driven to rotate by the gear shaft  4 , while the two conoids  5  are not driven to rotate. In this case, the planet gears  82  are driven to rotate by the sun gear  81 ; the planet gears  83  and the output shafts  84  are driven by the planet gears  82 ; and the roller shafts  9  and the clamping rollers  10  are driven to rotate by the output shaft  84 . Thereafter, the six clamping rollers  10  drive the substrate  1  to rotate so as to rotatably clamp the substrate  1 . 
     Therefore, when the substrate  1  requires a specific rotation speed, the first motor  17  and second motor  18  are simultaneously driven to rotate clockwise or counterclockwise and the rotation speed of the substrate  1  is controlled by the first motor  17  and the second motor  18 . 
     The effect of cooperation of the first motor  17  and the second motor  18  will be described with reference to FIG.  12 . Referring to FIG. 12, the horizontal axis represents time, and the vertical axis represents the rotation speed of the substrate. Assuming that the performance of the first motor  17  and that of the second motor  18  are the same, both the maximum angular velocity and the maximum angular acceleration of the substrate  1  can be doubled in comparison with the those of the gears  1923 ,  1922 , and  1921  in FIG.  2 . 
     Because the centrifugal force of an object is directly proportional to the square of the object&#39;s velocity, the rotation speed of the body  2  can be maintained at, for example, 1000 rpm, and the rotation speed of the gear shaft  4  can be shifted within a range of ±10 rpm which allows the rotation speed of the substrate  1  be shifted from 990 to 1010 rpm. In the aforementioned, the processing material on the substrate  1  sustains a greater centrifugal force than from shifting the rotation speed of the substrate  1  from 10 to −10 rpm. 
     Since the maximum angular acceleration and the angular velocity are increased, the substrate  1  can be accelerated or decelerated suddenly. 
     With the sudden acceleration and deceleration, a “shaking effect” on the substrate  1  can be obtained, as shown in FIG.  13 . The “shaking effect” is advantageous in filling the trenches on the substrate  1  with the processing material. 
     Moreover, pin marks can be avoided and simultaneous dual-sided processing is performed since the clamping rollers  10  rotatably clamp the substrate  1 . Since the body  2  is not in direct contact with the substrate  1 , the heat energy generated by the motor that drives the body  2  or the gear shaft  4  can be prevented from directly transferring to the substrate and deteriorating the product. 
     Another embodiment of the invention will be described in the following. 
     Referring to FIG. 14, the body  2  of the spin chuck in FIG. 11 is driven to rotate by a driving device  19 . The driving device  19  includes a base  191 , a first planetary gear transmission mechanism  192 , a second planetary gear transmission mechanism  193 , and a driving shaft  194 . 
     The base  191  has a central hole  1911  penetrating through the base  191 , and first to third rooms  1912  to  1914 , stacked from top to bottom, located within the base  191  and communicating with the central hole  1911 . The first room  1912  is in communication with the outside and receives the body  2 . The second and third rooms  1913  and  1914  communicate with the outside via the central hole  1911 . 
     The first planetary gear transmission mechanism  192  is located in the second room  1913  and includes a sun gear  1921 , three planet gears  1922 , and three planet gears  1923 . The sun gear  1921  is mounted to the body  2  and serves as body  2 &#39;s rotating shaft. The planet gears  1922  mesh with the periphery of the sun gear  1921 . The planet gears  1923  mesh with the periphery of the planet gears  1922 . 
     The second planetary gear transmission mechanism  193  is located in the third room  1914  and includes a sun gear  1931  and three planet gears  1932  arranged around the sun gear  1931 . It should be noted that each of the planet gears  1923  and a corresponding one of the planet gears  1932  are connected with a corresponding one of three rotating shafts  1933 . 
     The driving shaft  194  is for driving the sun gear  1931  of the second planetary gear transmission mechanism  193  to rotate. 
     The operation of the embodiment will be described in the following. The operations of the elements within the body  2  are the same as those in FIG. 11, and detailed descriptions thereof are omitted. Thus, only the operation of the driving device  19 , which drives the body  2 , is described. 
     The base  191  and the driving shaft  194  are driven to rotate separately. When the base  191  rotates and the driving shaft  194  stops, each of the rotating shafts  1933  revolves around the input/output conduit  3  and is driven to rotate by the sun gear  1931  and the planet gears  1932 . Thus, the gears  1923 ,  1922 , and  1921  are driven to rotate. Then, the sun gear  1921  drives the body  2  to rotate. 
     When the base  191  halts and the driving shaft  194  rotates, the planet gears  1923 , the planet gears  1922 , and the sun gear  1921  are sequentially driven to rotate by the sun gear  1931 , the planet gears  1932 , and the rotating shaft  1933 . Then, the sun gear  1921  drives the body  2  to rotate. 
     In the first planetary gear transmission mechanism  192  and the second planetary gear transmission mechanism  193 , the rotation speed of the body  2  is controlled by the superimposition of the rotation speeds of the driving shaft  194  and the base  191 . As a result, the angular velocity (acceleration) of the body  2  is controlled by adjusting the angular velocity (acceleration) of both the driving shaft  194  and the base  191 . Therefore, in this case, with the accumulated angular velocities of the base  191  and the body  2 , the angular velocity (acceleration) of the substrate  1  can be tripled in comparison with the gears  1923 ,  1922 , and  1921  in FIG.  2 . 
     While the invention has been described by way of example and in terms of preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications. 
     For instance, although six clamping rollers  10  are used to clamp the substrate  1  in the above embodiments, four or five clamping rollers can also be used to clamp the substrate. Moreover, although the input conduit  32  surrounds the output conduit  31 , two or three input conduits can be provided around the output conduit  31  to perform the same function as described in the above embodiments.