Abstract:
The vacuum processing apparatus of the present invention comprises a process chamber in which predetermined processing is performed on a target object in a predetermined vacuum condition, a mount stage provided in the process chamber, for mounting thereon the target object, a shower head provided so as to oppose to the mount stage, for supplying a process gas in the process chamber, an exhaust path provided in a housing forming the process chamber, and extending so as to surround the mount stage outside the mount stage, an exhaust port formed around the mount stage, for connecting the exhaust path with the process chamber, a porous member provided at the exhaust port so as to partition the exhaust path and the process chamber from each other, and having a plurality of ventilation holes for making the exhaust path communicating with the process chamber, branching means for branching a gas flowing from the process chamber through the ventilation holes of the porous member, into a plurality of directions, such that the gas flows to the exhaust path, a plurality of upper exhaust pipes extending in an upper side of the process chamber and communicating with the exhaust path, and a lower exhaust pipe extending toward a lower side of the process chamber and communicating with all the upper exhaust pipes.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a vacuum processing apparatus for making predetermined processing on a target object such as a LCD (Liquid Crystal Display) substrate, a semiconductor wafer, or the like. 
     In general, a vacuum processing apparatus for performing predetermined processing (such as etching or the like) on a target object such as a LCD substrate, a semiconductor wafer, or the like comprises a load lock chamber provided with a transfer arm, and a process chamber provided adjacent to the load lock chamber. Each of the chambers is set to be a predetermined vacuum condition. A target object set in the load lock chamber is transferred into the process chamber by the transfer arm, and predetermined processing is performed thereon in the process transferred. Upon completion of processing in the process chamber by the transfer arm, the target object is returned to the load lock chamber by the transfer arm. 
     FIG. 11 shows a conventional vacuum processing apparatus. As shown in the figure, the vacuum processing apparatus comprises a process chamber (b). 
     A mount stage (susceptor) (i) as a lower electrode where a semiconductor wafer W as a target object to be processed is mounted on the bottom portion of the process chamber (b). A lamp unit (p) for heating the wafer W through the mount stage (i) is provided under the mount stage (i). The lamp unit (p) comprises a plurality of halogen lamps (j) which are used as a heat source to heat the wafer W. 
     Above the mount stage (i), a shower head (c) as an upper electrode is provided opposing to the mount stage (i). The shower head (c) comprises a head body (e) and a porous disk (d) fixed to the head body (e) by screws (f). The shower head (c) diffuses a process gas supplied to the head body (e) through a gas supply pipe (a) from a process gas supply source to supply the gas uniformly over the wafer W mounted on the mount stage (i). When forming a film on the wafer W on the mount stage (i) by a process gas supplied through the shower head (c), for example, a high-frequency voltage is applied to the shower head (c) from a high-frequency power source so that a plasma is generated at a process space between the shower head (c) and the mount stage (i). 
     An exhaust path (h) is provided around the process chamber (b). An porous plate (g) used for exhaustion and provided so as to surround the mount stage (i) separates the process chamber (b) and the exhaust path (h) from each other. Four exhaust pipes (k) are connected to the exhaust path (h). The four exhaust pipes (k) are arranged at intervals of 90° along the circumferential direction of the exhaust path (h) and are connected together to a forced exhaust pipe (m) provided under the process chamber (b). Therefore, the gas in the process chamber (b) flows to the exhaust path (h) through the porous plate (g) for exhaustion and is forcibly exhausted from the forced exhaust pipe (m) through the four exhaust pipes (k). If four exhaust pipes (k) are thus provided around the mount stage (i), the gas in the processing chamber (b) can be uniformly exhausted. 
     If four exhaust pipes (k) are arranged so as to surround the lamp unit (p) as shown in FIG. 11, there is a drawback that maintenance of the lamp unit (p) (and particularly a periodical service of replacing the halogen lamps (j)) is obstructed by the four exhaust pipes (k) and the entire apparatus is enlarged. 
     Meanwhile, in order to supply the process gas uniformly over the wafer W, the distance between the mount stage (i) and the porous disk (d) must be set to be small as much as possible. However, a transfer arm for transferring a wafer W into and out of the process chamber (b) comes in and out through the space between the mount stage (i) and the porous disk (d). Also, the mount stage (i) is provided with a clamp ring for clamping a peripheral edge portion of the wafer W. Further, there is a limitation to downsizing of the transfer arm and the clamp ring (or reduction of the thickness of them). Therefore, the distance between the mount stage (i) and the porous disk (d) is generally set to 18 mm. 
     However, if the distance between the mount stage (i) and the porous disk (d) is set to 18 mm, a process gas supplied through the porous disk (d) escapes to the outer peripheral side of the process chamber so that the process gas is not applied uniformly onto the wafer W. 
     In relation to the problems described above, for example, U.S. Pat. No. 4,340,462 discloses a plasma processing apparatus capable of adjusting the distance between a shower head as an upper electrode and a mount stage as a lower electrode. However, in the apparatus disclosed in the U.S. Patent, the entire shower head moves up and down (e.g., the head body (e) and the porous disk (d) integrally move up and down). Therefore, the drive mechanism has a large size, and a sealing means provided between the shower head and the process chamber to seal the process chamber from the outside is enlarged (which means a large sealing area). Therefore, the leakage rate is high and a great deal of particles are generated. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention has a first object of providing a compact vacuum processing apparatus in which maintenance services for its lamp unit are not obstructed by exhaust pipes. Also, the present invention has a second object of providing a vacuum processing apparatus capable of improving uniformity of film formation without obstructing transportation of a target object into and from a process chamber. 
     The first objects of the present invention are achieved by a vacuum processing apparatus as follows. The vacuum processing apparatus comprises: a process chamber in which predetermined processing is performed on a target object in a predetermined vacuum condition; a mount stage provided in the process chamber, for mounting thereon the target object; a shower head provided so as to oppose to the mount stage, for supplying a process gas in the process chamber; an exhaust path provided in a housing forming the process chamber, and extending so as to surround the mount stage outside the mount stage; an exhaust port formed around the mount stage, for connecting the exhaust path with the process chamber; a porous member provided at the exhaust port so as to partition the exhaust path and the process chamber from each other, and having a plurality of ventilation holes for making the exhaust path communicating with the process chamber; branching means for branching a gas flowing from the process chamber through the ventilation holes of the porous member, into a plurality of directions, such that the gas flows to the exhaust path; a plurality of upper exhaust pipes extending in an upper side of the process chamber and communicating with the exhaust path; and a lower exhaust pipe extending toward a lower side of the process chamber and communicating with all the upper exhaust pipes. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments give below, serve to explain the principles of the invention. 
     FIG. 1A is a front view showing a vacuum processing apparatus according to an embodiment of the present invention; 
     FIG. 1B is a side view showing the vacuum processing apparatus shown in FIG. 1A; 
     FIG. 2 is a longitudinal cross-sectional view showing the process chamber of the vacuum processing apparatus shown in FIG. 1A; 
     FIG. 3 is a cross-sectional view along the line  3 — 3  shown in FIG. 2; 
     FIG. 4 is a cross-sectional view along the line  4 — 4  shown in FIG. 2; 
     FIG. 5 is a schematic view showing the flow of a gas through exhaust passages of the vacuum processing apparatus shown in FIG. 1A; 
     FIG. 6 is a view showing the structure of the shower head and its elevation mechanism thereof of the vacuum processing apparatus shown in FIG. 1A (where the porous disk is moved up); 
     FIG. 7 is a view showing the structure of the shower head and its elevation mechanism thereof of the vacuum processing apparatus shown in FIG. 1A (where the porous disk is moved down); 
     FIG. 8 is a plan view showing the shower head; 
     FIG. 9 is an enlarged cross-sectional view showing a part of the elevation mechanism of the shower head; 
     FIG. 10 is an enlarged cross-sectional view showing a part of the elevation mechanism of the shower head; and 
     FIG. 11 is a view schematically showing a conventional vacuum processing apparatus. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following, an embodiment of the present invention will be explained with reference to the drawings. 
     FIG. 1 shows a vacuum processing apparatus according to an embodiment of the present invention. In the figure, the reference  10  denotes a process chamber and a lamp unit  11  is provided below the process chamber  10 . The lamp unit  11  can be rotated downward about a predetermined support axis for the purpose of maintenance services or the like, as indicated by a broken line in the figure. Two upper exhaust pipes  12  communicating with an exhaust path  18  described later are provided above the process chamber  10 . A lower exhaust pipe  13  connected with the upper exhaust pipes  12  is provided under the process chamber  10 . Note that the lower exhaust pipe  13  is located at a position where the pipe  13  it is kept away from the lamp unit, viewed from the front of the vacuum processing apparatus (in FIG.  1 A), i.e., at the corner in the front right side of the process chamber  10 . 
     As shown in FIG. 2, a mount stage (susceptor)  14  where a semiconductor wafer W as a target object to be processed is mounted is provided under the process chamber  10 . A shower head  15  is provided above the process chamber  10  so as to oppose to the mount stage  14 . The periphery of the process chamber  10  is surrounded by a partition wall  16  so that the chamber  10  is constructed as a sealed container. A ring member  17  for supporting the outer periphery of the mount stage  14  is provided at the bottom portion of the partition wall  16 . 
     The process chamber  10  is provided adjacent to a load lock chamber (not shown), and a wafer W held by the transfer arm (not shown) is transferred in one after another from the load lock chamber into the process chamber  10  through a gate valve (not shown) provided on the partition wall  16 . 
     As shown in FIGS. 3 and 4, the partition wall  16  is provided with a circular exhaust path  18  located so as to surround the outside of the ring member  17 . Also, exhaust bores  19  communicating with the exhaust path  18  are provided at two positions of the partition wall  16  which are symmetrical to each other with respect to the mount stage  14 . As shown in FIG. 2, the exhaust bores  19  extend upward in the partition wall  16  and are open at the upper end of the partition wall  16 . The exhaust bores  19  respectively communicate with two exhaust pipe connection ports  21  provided in a base plate  20  supporting the shower head  15 . The exhaust pipe connection ports  21  are respectively connected with ends of upper exhaust pipes  12 . The other ends of the two upper exhaust pipes  12  are connected to be merged with an upper end portion of a lower exhaust pipe  13 . The base plate  20  is fixed to the partition wall  16 . 
     Between the outer circumferential surface of the ring member  17  and the partition wall  16 , a clearance  22  (or exhaust port) is formed so as to surround the outer circumference of the mount stage  14  and connects the process chamber  10  with the exhaust path  18 . The clearance  22  is provided with a ring-like exhaust porous plate  23  which partitions the process chamber  10  and the exhaust path  18  from each other. The exhaust porous plate  23  has a number of exhaust small-holes  23   a,  so that the gas in the process chamber  10  is exhausted to the exhaust path  18  through the exhaust small-holes  23   a  positioned at the outer circumference of the mount stage  14 . 
     Communicating portions  18   a  of the exhaust path  18  communicating with the exhaust bores  19  spread like a sector as shown in FIG. 3, so that the gas in the exhaust path  18  flows smoothly to the exhaust bores  19 . The communicating portions  18   a  of the exhaust path  18  are provided with baffle plates  25  positioned apart from the outer circumferential surface of the ring member  17  by a predetermined distance. These baffle plates  25  are formed like arcs along the curvature of the ring member  17 , thereby forming branch exhaust passages  24  between the plates  25  and the ring member  17 . Exhaust portions  26   a  and  26   b  are formed at both end portions of each branch exhaust passage  24 . Therefore, a gas exhausted through the exhaust small-holes  23   a  of the exhaust porous plate  23  is not directly guided to the exhaust bores  19  but flows to the left and right exhaust portions  26   a  and  26   b  through the branch exhaust passages  24  formed by the baffle plates  25 . The gas is exhausted from the exhaust portions  26   a  and  26   b  to the exhaust path  18 . Specifically, the gas in the process chamber  10  is uniformly exhausted from the outer circumference of the mount stage  14  substantially through total four exhaust portions  26   a  and  26   b  (two of which are provided for each of two branch exhaust passages  24 ). The distance between the exhaust portions  26   a  and  26   b  can be adjusted by adjusting the length of the baffle plates  25 . 
     As shown in FIG. 6, a hole  115  having a circular cross section is provided in the base plate  20  fixed to the partition wall  16  and has a gap portion  115   a  on its inner circumference. The base plate  20  supports the shower head  15  by the hole  115 . The shower head  15  comprises a head body  116  formed like a disk, and a porous disk  117  which is arranged to be elevated up and down with respect to the head body  116  and has a number of gas injection holes  117   a  in its plate surface. The outer circumferential portion of the head body  116  is provided with a gap portion  116   a  to be engaged with the gap portion  115   a  of the base plate  20 . An O-ring  118  for sealing is provided at the joining surfaces of the gap portions  115   a  and  116   a.  In order to hold air-tightly the head body  116  on the base plate  20 , the head body  116  is fixed to the base plate  20  by a plurality of fixing screws  119  outside the O-ring  118 , as shown in FIG.  9 . 
     As shown in FIG. 6, a diffusion chamber  122  is formed inside the shower head  15  by a concave portion  120  provided at the lower surface of the head body  116  and by a concave portion  121  provided at the upper surface of the porous disk  117  so as to oppose to the concave portion  120 . The diffusion chamber  122  communicates with a process gas supply port  123  provided at the center portion of the head body  116 . The process gas supply port  123  communicates with a process gas supply source (not shown) through a gas supply pipe. 
     A motor support member  124  is fixed to the upper surface of the head body  116  by fixing screws  125 . A stepping motor  126  is vertically attached to an upper portion of a side surface of the motor support member  124 , with the rotation shaft of the motor oriented upward. In addition, the rotation shaft of the stepping motor  126  is engaged with a pulley  127 . Bearings  128  are respectively provided at upper and lower portions of the other side surface of the motor support member  124 , which opposes to the stepping motor  126 . Both end portions of a screw rod  129  are rotatably supported on the bearings  128 . The upper end of a screw rod  129  is engaged with a pulley  130  and a timing belt  131  is tensioned between the pulleys  130  and  127 . Therefore, the torque of the stepping motor  126  is transmitted to the screw rod  129  through the timing belt  131 . 
     A nut  132  is screwed on a screw portion of the screw rod  129 . The nut  132  is fixed to a part of an elevation ring  133  which can be elevated up and down above the head body  116 . The elevation ring  133  has an outer diameter substantially equal to the outer diameter of the head body  116  and is elevated up and down, kept in parallel to the head body  116  by regularly and inversely rotating the screw rod  129 . 
     A plurality of elevation shafts  134  (four shafts in the present embodiment) are fixed to the elevation ring  133 . Each elevation shaft  134  has a tubular shape so that a cooling water passage is formed along the lengthwise direction of the shaft. Each elevation shaft has a screw portion at its upper end portion, and the screw portions are screwed into the elevation ring  133  and nuts  135 . The lower end portion of each elevation shaft  134  penetrates through the head body  116  and projects downward from the lower surface of the head body  116 . 
     A fixing ring  136  is fixed to the lower end portion of each elevation shaft  134 , and the fixing ring  136  is arranged to have an outer diameter substantially equal to the outer diameter of the porous disk  117 . As shown in FIG. 10, the porous disk  117  is fixed to the lower surface of the fixing ring  136  by screws  137 . By loosening the screws  137 , the porous disk  117  can be detached from the fixing ring  136 . 
     Therefore, according to the structure as described above, when the elevation ring  133  is elevated down by the stepping motor  126 , four elevation shafts  134  are simultaneously moved down, and, rather than the entire shower head  15 , only the porous disk  117  fixed to the lower end portions of the elevation shafts  134  by the fixing ring  136  is moved down, kept in parallel. Inversely, when the elevation ring  133  is moved up, four elevation shafts  134  are simultaneously moved up, and, rather than the entire shower head  15 , only the porous disk  117  is moved up, kept in parallel. In the present embodiment, the elevation stroke of the porous disk  117  is 15 mm, and the porous disk  117  can be moved to a position close to a position which is distant by 3 mm from the mount stage  14  from a position which is distant by 18 mm from the mount stage  14 . 
     As shown in FIGS. 8 and 10, three rods  144  vertically project from the upper surface of the head body  116 . The rods  144  are located so as to avoid four elevation shafts  134 . The upper end portions of the rods  144  project upward, penetrating thorough engaging holes  145  formed in the elevation ring  133 . A coil spring  146  is engaged with the outer circumference of each rod  144 . The coil springs  146  are compressed and inserted between the upper surface of the head body  116  and the elevation ring  133 , energizing the elevation ring  133  in a direction in which the elevation ring  133  is pushed upward. 
     As shown in FIG. 9, each elevation shaft  134  penetrates through one of four gapped holes formed in the head body  116 . Each gapped hole consists of a large-diameter through hole  137  and a small-diameter through hole  138 . The inner diameter of the small-diameter through hole  138  is set to be slightly larger than the outer diameter of the elevation shaft  134 . As a result, a small clearance  139  is formed between the small-diameter through hole  138  and the elevation shaft  134 . The inner diameter of the large-diameter through hole  137  is sufficiently larger than the outer diameter of the elevation shaft  134 . As a result, a large clearance  140  is formed between the large-diameter through hole  137  and the elevation shaft  134 . A bellows  141  to be engaged with the outer circumference of the elevation shaft  134  is located in the large clearance  140 . The bellows  141  has a lower edge air-tightly sealed and fixed to the bottom portion of the large-diameter through hole  137 , and an upper edge air-tightly sealed and fixed to a flange  134   a  integrally provided in the middle of the elevation shaft  134 . In this structure, the inside of the bellows  141  communicates with the diffusion chamber  122  through the small clearance  139  and is kept in a vacuum condition. Meanwhile, the outside of the bellows  141  communicates with the outside of the head body  116  and is kept at an atmospheric pressure. Thus, the diffusion chamber  122  (process chamber  10 ) is shielded from the outside kept at the atmospheric pressure by the bellows  141  provided at four positions, so that the leakage rate is reduced. 
     As shown in FIG. 9, an inner ring  142  is fixed near the outer circumferential portion of the lower surface of the head body  116 , inside the fixing ring  136 . In addition, an outer ring  143  is provided on the lower surface of the base plate  20 , outside the fixing ring  136 . These rings  142  and  143  form an engaging portion which covers the inner and outer sides of the fixing ring  136 . A clearance is formed between the fixing ring  136  and the inner ring  142  and also between the fixing ring  136  and the outer ring  143 , so that the fixing ring  136  might not move up or down in contact with the inner ring  142  and the outer ring  143  thereby creating particles when the porous disk  117  is elevated up or down. 
     Next, explanation will be made of operation of the vacuum processing apparatus constructed in the structure as described above. 
     When the inside of the process chamber  10  is set in a predetermined vacuum condition, a wafer W is transferred into the process chamber  10  from the load lock chamber by the transfer arm and is mounted on the mount stage  14  provided at the bottom portion of the process chamber  10 . In this time, the porous disk  117  of the shower head  15  is maintained at an upper position distant by 18 mm from the mount stage  14 , as shown in FIG.  6 . Therefore, when transferring the wafer W into the process chamber  10  by the transfer arm, the transfer arm or the wafer W does not interfere with the clamp ring and the like and the wafer can be transferred in without a trouble. The wafer W on the mount stage  14  is thereafter heated from its lower side by the lamp unit  11 . 
     Once the wafer W is mounted on the mount stage  14  and fixed by the clamp ring, the stepping motor  126  is rotated in its regular direction. The torque of the motor  126  is transmitted to the screw rod  129  through the pulley  127 , the timing belt  131 , and the pulley  130  in this order, thereby rotating the screw rod  129 . The rotation movement of the screw rod  129  is converted into linear movement by the nut  132  engaged with the screw rod  129 , thereby move down the elevation ring  133 . In this time, the elevation ring  133  is supported by four elevation shafts  134 , and therefore moves down kept in parallel to the head body  116 . Simultaneously, the coil springs  146  are compressed as the elevation ring  133  moves down. 
     As the elevation ring  133  moves down, four elevation shafts  134  fixed to the ring are simultaneously moved down so that the porous disk  117  is moved close to the wafer W by the fixing ring  136 . In this time, the bellows  141  are compressed by the flanges  134   a  of the elevation shafts  134 . Also, in this time, the fixing ring  136  moves down without making contact with the inner ring  142  or the outer ring  143 , so that particles are not created. This is because clearances are respectively formed between the fixing ring  136  and the inner ring  142  and between the fixing ring  136  and the outer ring  143 . 
     When the downward movement of the porous disk  117  reaches a predetermined value, e.g., 10 mm, the stepping motor  126  is stopped and the elevation ring  133  stops moving down. Therefore, downward movement of the porous disk  117  is stopped, and as shown in FIG. 7, the porous disk  117  is kept close to the wafer W. In this state, a process gas from the process gas supply source is supplied into the diffusion chamber  122  through the process gas supply port  123 , and then, the process gas diffused by the diffusion chamber  122  is injected to the wafer W through a number of gas injection nozzles  117   a.  In this case, since the porous disk  117  is positioned close to the wafer W, the process gas is uniformly supplied to the entire surface of the wafer W. Accordingly, the film formation speed and the film formation uniformity are improved in comparison with a conventional apparatus, so that the processing efficiency is improved. 
     Upon completion of the processing on the wafer W, the process gas in the processing chamber  10  is forcibly exhausted. In the following, explanation will be made of exhaustion of the gas in the process chamber  10 . 
     Since the one lower exhaust pipe  13  provided under the process chamber  10  is connected to a forcible exhaustion source, the inside of the process chamber  10  is rendered negative and the gas in the process chamber  10  is exhausted to the exhaust path  18  through the exhaust small holes  23   a  of the exhaust porous plate  23  provided around the outer circumference of the wafer W. In this case, the gas exhausted through the exhaust small holes  23   a  is not directly discharged to the exhaust path  18  but once flows into the branch exhaust passages  24  constructed by the baffle plates  25  and is thereby branched to the left and right sides of each of the passages  24 . Thereafter, the gas is exhausted to the exhaust path  18  from the exhaust portions  26   a  and  26   b.  That is, the gas is substantially exhausted through four portions. It is therefore possible to exhaust uniformly the gas through the outer circumference of the mount stage  14 . 
     The gas exhausted to the exhaust path  18  flows to the upper exhaust pipes  12  through the exhaust bores  19  provided at two positions. The flows of the gas from the upper exhaust pipes  12  are merged into the one lower exhaust pipe  13  and then exhausted to the outside. Thus, the gas flows around the upper portion of the process chamber  10  and is exhausted below the process chamber  10  (see FIG.  5 ). 
     Apart from the exhaustion of the gas described above, the stepping motor  126  is driven again to rotate inversely upon completion of processing on the wafer W. The torque of the motor  126  is transmitted to the screw rod  129  through the pulley  127 , the timing belt  131 , and the pulley  130  in this order, thereby rotating the screw rod  129 . The rotation movement of the screw rod  129  is converted into linear movement by the nut  132  engaged with the screw rod  129 , thereby moving up the elevation ring  133 . 
     As the elevation ring  133  moves up, four elevation shafts  134  fixed to the ring  133  are simultaneously moved up and the porous disk  117  is moved up and apart from the wafer W by the fixing ring  136 . In this time, the fixing ring  136  moves up without making contact with the inner ring  142  or the outer ring  143 , so that particles are not created. 
     When the upward movement of the porous disk  117  reaches a predetermined value, e.g., 18 mm, the stepping motor  126  is stopped so that the elevation ring  133  stops moving up. Therefore, the porous disk  117  stops moving up, and as shown in FIG. 6, the porous disk  117  is kept apart from the wafer W. In this state, a space which is sufficiently large and does not obstruct transportation of the wafer W by the transfer arm is securely maintained between the mount stage  14  and the porous disk  117 . Therefore, the transfer arm or the wafer W does not interfere with the clamp ring or the like. 
     As has been explained above, in the vacuum processing apparatus according to the present embodiment, only one lower exhaust pipe  13  is provided under the process chamber  10 , at a position kept away from the lamp unit  11 . Therefore, the lower exhaust pipe  13  does not obstruct maintenance services for the lamp unit  11 , but services of replacing halogen lamps and the like can be carried out easily. In addition, the apparatus itself is more compact in comparison with a conventional structure in which four exhaust pipes are located surrounding a lamp unit. In the vacuum processing apparatus according to the present embodiment, only two upper exhaust pipes  12  are provided above the process chamber  10 . Therefore, the upper exhaust pipes  12  do not obstruct maintenance services for the elevation mechanism of the porous disk  117  of the shower head  15 , but maintenance services for the elevation mechanism can be carried out easily. Further, in the vacuum processing apparatus according to the present embodiment, the exhaust system is constructed such that the gas in the process chamber is exhausted from symmetrical four positions around the mount stage  14 . Therefore, the gas in the process chamber  10  can be exhausted uniformly from the periphery of the mount stage  14 . 
     Also, in the vacuum processing apparatus according to the present embodiment, the distance between the porous disk  117  of the shower head  15  and the mount stage  14  can be adjusted. Therefore, when a wafer W is transferred into and out of the process chamber  10  by the transfer arm, the porous disk  117  is situated apart from the mount stage  14 , so that the space between the mount stage  14  and the porous disk  117  is maintained to be large enough to transfer in and out the wafer W without problems. In addition, when the wafer W is processed, the porous disk  117  is situated close to the mount stage  14  so that the process gas is uniformly supplied over the entire surface of the wafer W. 
     Also, in the vacuum processing apparatus according to the present embodiment, the entire shower head  15  does not move up and down (or the head body  16  and the porous disk  17  integrally move up and down) unlike in a conventional apparatus, but only the porous disk  117  moves up and down. In addition, the porous disk  117  is moved up and down only by four elevation shafts  134 . Therefore, only the driving parts of the elevation shafts  134  need to be provided with sealing means to be provided between the shower head  15  and the process chamber  10  for the purpose of sealing the process chamber  10  from the outside. As a result of this, the sealing area is reduced and the leakage rate is thereby reduced. Accordingly, generation of particles can be reduced. 
     Although the screw rod  129  is rotated by the stepping motor  126  in the present embodiment, the structure of the drive source and the power transmission system for rotating the rod  129  are not limited to the structure described in the present embodiment. Also, in the present embodiment, the baffle plates  25  are separately provided at the outer circumference of the ring member  17 . However, the ring member  17  and the baffle plates  25  may be formed integrally as one body. Although four elevation rods  134  are provided in the present embodiment, the number of elevation rods is not limited to four. Essentially, the number of elevation rods needs to be equal to or more than the number of elevation rods that are enough to move up and down the elevation ring  133  in parallel with the head body  116 , e.g., three. 
     Additional advantages and modifications will readily occurs to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.