Patent Publication Number: US-2007095284-A1

Title: Gas treating device and film forming device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This is a Continuation Application of PCT Application No. PCT/JP2005/010152, filed Jun. 2, 2005, which was published under PCT Article 21(2) in Japanese.  
      This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-167237, filed Jun. 4, 2004, the entire contents of which are incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a gas treating device which separately and independently discharges a plurality of gases from a shower head to treat the gases, and a film forming device which forms a thin film on a substrate to be treated by a CVD method using such a shower head.  
      2. Description of the Related Art  
      In a semiconductor manufacturing process, a thin film made of various materials is formed on a semiconductor wafer (wafer hereinafter), and diversity/complexity has progressed in materials or combinations used for forming a thin film in response to diversity or the like of physical properties required of the thin film.  
      A recent focus of attention has been a Pb (Zr 1-x Tix)O 3  film (PZT film hereinafter) which has ferroelectricity as a capacitor material of a planar stack-type FeRAM and which is a crystal film of a perovskite structure, and development of a technology of generating a high-quality PZT film with good reproducibility has been advanced. For example, Jpn. Pat. Appln. KOKAI Publication No. 2000-260766 proposes chemical vapor deposition (CVD) which supplies a source gas and an oxidizing gas into a treatment container while heating a wafer therein to deposit a multielement metal oxide thin film such as PZT on the wafer.  
      A PZT deposition temperature is normally in a range of 500 to 650° C., and oxygen gas (O 2 ) is generally used for an oxidizing agent. However, depending on a device structure, a permissible PZT deposition temperature may be 500° C. or less. In the case of forming a film in a temperature range lower than normal, such as 500° C. or less, for example as described in Jpn. Pat. Appln. KOKAI Publication No. 2000-58526, nitrogen dioxide gas (NO 2 ) having a high oxidizing force is used as an oxidizing agent. According to this conventional technology, the NO 2  gas is supplied to a wafer in a treatment container by using a post mix type shower head.  
      However, physical properties (especially reactivity) vary among gases of different components. Consequently, when a gas discharge port is only bored in a shower head bottom surface formed to be planar as in the case of the conventional shower head, gas reactivity or uniform reaction may not be always achieved as desired.  
      Furthermore, in the case of forming a film by using a strong oxidizing agent such as NO 2  gas, a reaction product sticks to a peripheral wall of the gas discharge port of the shower head, and the stuck reaction product grows to gradually narrow the gas discharge port, causing gradual deterioration of uniformity and reproducibility of the formed film. The reaction product is peeled off from the peripheral wall of the discharge port to scatter as particles, creating a risk that these will stick to a wafer surface.  
     BRIEF SUMMARY OF THE INVENTION  
      An object of the present invention is to provide a gas treating device capable of adjusting reaction or the like of gases of different kinds, and a film forming device. Another object of the present invention is to provide a film forming device capable of suppressing sticking of a reaction product to a compound forming gas discharge port of a shower head when a metal compound film is formed on a substrate based on gas characteristics, a source gas containing a metal, and a compound forming gas for forming a compound with the metal.  
      A first aspect of the present invention comprises, a gas treating device comprising a mounting base to support a substrate to be treated, a treatment container to surround the substrate to be treated on the mounting base, a shower head to separately and independently discharge a first gas and a second gas to the substrate to be treated on the mounting base, and a gas supply mechanism having a first gas flow path to supply the first gas to the shower head and a second gas supply path to supply the second gas to the shower head, characterized in that the shower head has: a bottom surface which faces the substrate to be treated on the mounting base via a predetermined space; a groove formed in the bottom surface; a plurality of first gas discharge ports communicating with the first gas flow path of the gas supply mechanism, and bored in the bottom surface except the groove to discharge the first gas; and a plurality of second gas discharge ports communicated with the second gas flow path of the gas supply mechanism, and bored in the groove to discharge the second gas.  
      A second aspect of the present invention comprises, a gas treating device comprising a mounting base to support a substrate to be treated, a treatment container to surround the substrate to be treated on the mounting base, a post mix type shower head arranged to face the substrate to be treated on the mounting base, and a gas supply mechanism having a first gas flow path to supply a first gas to the shower head and a second gas supply path to supply a second gas to the shower head, characterized in that the shower head has: a plurality of first gas discharge ports communicating with the first gas flow path of the gas supply mechanism to discharge the first gas; a plurality of second gas discharge ports communicating with the second gas flow path of the gas supply mechanism to discharge the second gas; a first surface arranged to face the substrate to be treated on the mounting base via a predetermined space and having the first gas discharge ports bored therein; and a second surface arranged to face the substrate to be treated on the mounting base via a predetermined space, and having the second gas discharge ports bored therein and a step with respect to the first surface.  
      A third aspect of the present invention comprises, a film forming device comprising a mounting base to support a substrate to be treated, a treatment container to surround the substrate to be treated on the mounting base, a shower head to separately and independently discharge a source gas and a compound forming gas to the substrate to be treated on the mounting base, and a gas supply mechanism having a first gas flow path to supply the source gas to the shower head and a second gas supply path to supply the compound forming gas to the shower head, the source gas containing a metal element and the compound forming gas containing a component element reacted with the metal element to form a compound, characterized in that the shower head has: a bottom surface which faces the substrate to be treated on the mounting base via a predetermined space; a groove formed in the bottom surface; a plurality of source gas discharge ports communicating with the first gas flow path of the gas supply mechanism, and bored in the bottom surface except the groove to discharge the source gas; and a plurality of compound forming gas discharge ports communicating with the second gas flow path of the gas supply mechanism, and bored in the groove to discharge the compound forming gas.  
      A fourth aspect of the present invention comprises, a film forming device comprising a mounting base to support a substrate to be treated, a treatment container to surround the substrate to be treated on the mounting base, a post mix type shower head arranged to face the substrate to be treated on the mounting base, and a gas supply mechanism having a source gas flow path to supply a source gas to the shower head and a compound forming gas supply path to supply a compound forming gas to the shower head, characterized in that the shower head has: a plurality of source gas discharge ports communicating with the source gas flow path of the gas supply mechanism to discharge the source gas; a plurality of compound forming gas discharge ports communicated with the compound forming gas flow path of the gas supply mechanism to discharge the compound forming gas; a first surface arranged to face the substrate to be treated on the mounting base via a predetermined space and having the source gas discharge ports bored therein; and a second surface arranged to face the substrate to be treated on the mounting base via a predetermined space, having the compound forming gas discharge ports bored therein, and positioned more apart from the substrate to be treated than the first surface.  
      In this specification, a “post mix type shower head” is a shower head of a type which has pluralities of different gas supply paths/discharge ports separately, and separately supplies different kinds of gases (e.g., source gas and oxidizing gas) into the treatment container via the gas supply paths/discharge ports, and mixes these gases after they are out of the different discharge ports.  
      The third and fourth aspects exemplify an oxidizing gas such as NO 2  as the compound forming gas. An organic metal gas is exemplified as the source gas. In the case of forming a PZT film, a Pb containing source gas, a Zr containing source gas, and a Ti containing source gas are mixed to be used as the organic metal gas. Specifically, Pb (dpm) 2 , Ti (O-i-Pr) 2  (dpm) 2 , and at least one of Zr (dpm) 4  and Zr (O-i-Pr) 2  (dpm) 2  can be used respectively as the Pb containing source gas, the Ti containing source gas, and the Zr containing source gas. These organic metal gases are thermally decomposed, and reacted with the oxidizing gas to form a PZT film on the substrate.  
      According to the first and second aspects, by adjusting the depth of the groove or the size of the step, reaching timing of the first and second gases to the substrate to be treated can be controlled, and reactivity thereof or the like can be properly adjusted.  
      According to the third aspect of the present invention, as the compound forming gas discharge port is more apart from the substrate than the source gas discharge port, a flow of the compound forming gas prevents flowing of the source gas to the compound forming gas discharge port (inside of the groove), making it difficult for the source gas to reach the compound forming gas discharge port. As a result, reaction is difficult to occur between the source gas and the compound forming gas around the compound forming gas discharge port, whereby sticking of a reaction product around the compound forming gas discharge port is suppressed. Moreover, as a sticking area of the reaction product is increased by an amount equal to the depth of the groove, a time until the compound forming gas discharge port is closed is greatly extended.  
      According to the fourth aspect of the present invention, as the second surface is more apart from the substrate than the first surface, a flow of the compound forming gas prevents flowing of the source gas to the compound forming gas discharge port (second surface), making it difficult for the source gas to reach the compound forming gas discharge port (second surface). Hence, as in the case of the third aspect, reaction occurs with difficulty between the source gas and the compound forming gas around the compound forming gas discharge port, whereby sticking of a reaction product around the compound forming gas discharge port is suppressed. Moreover, as a sticking area of the reaction product is increased by an amount equal to the step between the first and second surfaces, a time until the compound forming gas discharge port is closed is greatly extended. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       FIG. 1  is a sectional block diagram showing a film forming device according to an embodiment of the present invention.  
       FIG. 2  is a bottom diagram of a shower head used for the film forming device of  FIG. 1 .  
       FIG. 3  is a partially enlarged diagram showing an enlarged part of a bottom surface of the shower head of  FIG. 2 .  
       FIG. 4  is a partially cutout sectional diagram of a plate of the shower head showing a gas supply path and a discharge port.  
       FIG. 5A  is a partially cutout enlarged sectional diagram of a shower head of a conventional device showing an enlarged gas discharge port.  
       FIG. 5B  is a partially cutout enlarged sectional diagram of the shower head of the device of the present invention showing the enlarged gas discharge port.  
       FIG. 6A  is a photo showing a state of an opening portion of an NO 2  gas discharge port in the shower head of the conventional device.  
       FIG. 6B  is a photo showing a state of an opening portion of an NO 2  gas discharge port in the shower head of the device of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Hereinafter, a best mode for carrying out the present invention will be described with reference to the accompanying drawings.  
      A film forming device of an embodiment includes a case  1  whose two-dimensional projection shape on an XZ plane is roughly rectangular. The case  1  is made of a metal such as aluminum or an aluminum alloy. A cylindrical treatment container  2  having a bottom is disposed in the case  1 . As shown in  FIG. 1 , an opening  2   a  is formed in the bottom of the treatment container  2 , and a transmission window  2   d  is fitted into the opening  2   a  from the outside. The transmission window  2   d  is made of transparent quarts, and a surface that abuts on the treatment container  2  is sealed by an O ring  2   c  to maintain airtightness in the treatment container  2 . A lamp unit  100  is mounted to a bottom of the transmission window  2   d , and a wafer W is heated by a heating lamp such as a halogen lamp (not shown). A lid  3  for supporting a shower head  40  is disposed to be opened/closed in an upper opening of the treatment container  2 . When the lid  3  is closed, the wafer W on a mounting base  5  and the shower head  40  face each other via a predetermined space.  
      In the treatment container  2 , a cylindrical shield base  8  is erected from the bottom of the treatment container  2 . An annular base ring  7  is arranged in an opening above the shield base  8 , an annular attachment  6  is supported on an inner peripheral side of the base ring  7 , and the mounting base  5  supported by a step of an inner peripheral side of the attachment  6  to mount the wafer W is disposed. A baffle plate  9  (described below) is disposed outside the shield base  8 .  
      A plurality of exhaust ports  9   a  are formed in the baffle plate  9 . In an inner peripheral bottom of the treatment container  2 , a bottom exhaust path  71  is disposed in a position around the shield base  8 , and the treatment container  2  is uniformly exhausted by communicating the inside of the treatment container  2  with the bottom exhaust path  71  via the exhaust ports  9   a  of the baffle plate  9 .  
      The bottom exhaust path  71  communicates with exhaust combining units (not shown) symmetrically arranged sandwiching the treatment container  2  in diagonal positions of the bottom of the case  1 . This exhaust combining unit communicates with an upward exhaust path (not shown) disposed in a corner of the case  1 , a downward exhaust path (not shown) arranged through the corner of the case  1  via a horizontal exhaust tube (not shown) disposed in an upper part of the case  1 , and an exhaust device  101  arranged below the case  1 .  
      A wafer entrance  15  communicating with a treatment space S is disposed in a side face of the case  1 , and a load lock room (not shown) is connected through a gate valve  16  to the wafer entrance  15 .  
      In a space surrounded by the mounting base  5 , the attachment  6 , the base ring  7 , and the shield base  8 , a cylindrical reflector  4  is erected from the bottom of the treatment container  2 . This reflector  4  reflects heat rays emitted from the lamp unit  100  and guides them to the bottom surface of the mounting base  5  so that the mounting base  5  can be efficiently heated. A heating source is not limited to the aforementioned lamp. A resistive heater may be buried in the mounting base  5  to heat the same.  
      This reflector  4  includes, e.g., slits in three places, and lift pins  12  for lifting the wafer W from the mounting base  5  are arranged in positions corresponding to the slits to be elevated. Each lift pin  12  is integrally constituted of a pin portion and a support portion, supported by an annular holding member  13  disposed outside the reflector  4 , and moved up and down by elevating the holding member  13  by an actuator (not shown). This lift pin  12  is made of a material to transmit the heat ray applied from the lamp unit  100 , e.g., quartz or ceramics (e.g., Al 2 O 3 , AlN, SiC).  
      The lift pin  12  is raised from the mounting base  5  to a predetermined height to project when the wafer W is transferred. The lift pin  12  is pulled into the mounting base  5  when the wafer W supported by the lift pin  12  is mounted on the mounting base  5 .  
      The reflector  4  is disposed in the bottom of the treatment container  2  below the mounting base  5 . A gas shield  17  is mounted on an inner periphery of the reflector  4  so that its entire periphery can be supported. The gas shield  17  is made of a heat ray transmission material such as quartz or the like. A plurality of apertures  17   a  are bored in the gas shield  17 .  
      A purge gas (e.g., inactive gas such as N 2  gas or Ar gas) is supplied from a purge gas supply mechanism through a purge gas flow path  19  to a space with the transmission window  2   d  below the gas shield  17 . The purge gas flow path  19  is formed in the bottom of the treatment container  2  to be bored therein from gas supply openings  18  equally arranged in eight places in a lower part inside the reflector  4 .  
      The purge gas thus supplied flows through the plurality of apertures  17   a  of the gas shield  17  into the backside of the mounting base  5 , whereby a treatment gas from the shower head  40  is prevented from entering a space of the backside of the mounting base  5  to give damage such as deposition of a thin film on the transmission window  2   d.    
      The shower head  40  is disposed above the mounting base  5  to face the same. The shower head  40  is made of a metal such as aluminum or an aluminum alloy. The shower head  40  includes a disk shower base  41 , a disk gas diffusion plate  42 , and a disk shower plate  43 . The shower base  41  is formed so that its outer edge can be engaged with an upper part of the lid  3 . The gas diffusion plate  42  is mounted in tight contact with a bottom surface of the shower base  41 . The shower plate  43  is mounted to a bottom surface of the gas diffusion plate  42 .  
      The shower base  41  is fixed to the lid  3  by screws (not shown). A bonded portion between the shower base  41  and the lid  3  is airtightly sealed by an O ring. The shower base  41  and the gas diffusion plate  42  are airghtightly sealed from each other by an O ring, and the shower base  41 , the gas diffusion plate  42 , and the shower plate  43  are fixed by screws.  
      The shower base  41  includes a source gas introduction path  41   a  and a plurality of oxidizing gas introduction paths  41   b . The source gas introduction path  41   a  is disposed in a center of the shower base  41 , and a source gas introduction pipe  51  is connected thereto. The oxidizing gas introduction paths  41   b  are arranged in symmetric positions sandwiching the source gas introduction path  41   a , and oxidizing gas branch pipes  52   a  and  52   b  of an oxidizing gas introduction pipe  52  are connected thereto.  FIG. 1  showing the shower head is a sectional diagram cut along the line I-I of  FIG. 2 , in which left and right sides are asymmetric at a boundary of a center.  
      The source gas introduction pipe  51  and the oxidizing gas introduction pipe  52  are connected to a gas supply mechanism  60 . The gas supply mechanism  60  includes a raw material tank (not shown) of each raw material and a carburetor (not shown). Liquid raw materials supplied from the raw material tanks, e.g., Pb (thd) 2 , Zr (O-i-C 3 H 7 ) (thd) 3 , Ti (O-i-C 3 H 7 ) 2  (thd) 2  dissolved by a solvent of butyl acetate or the like are mixed at a predetermined ratio (e.g., ratio to set Pb, Zr and Ti elements of PZT to a predetermined stoichiometric ratio). Then, the mixed liquid is vaporized by the carburetor to become a source gas, and supplied to the source gas introduction pipe  51 . The gas supply mechanism  60  has an oxidizing gas source (not shown), and NO 2  gas is supplied from this oxidizing gas source to the pipe  52 .  
      On an upper surface side of the gas diffusion plate  42 , a source gas header  42   a  is formed as a concave space to diffuse a source gas. This source gas header  42   a  communicates with the source gas introduction path  41   a  to which the source gas introduction pipe  51  is connected. The source gas header  42   a  also communicates with the source gas path  42   d  penetrated the gas diffusion plate  42 . A plurality of cylindrical projections  42   c  are concentrically disposed in the source gas header  42   a . As a height of the cylindrical projection  42   c  is almost equal to a depth of the source gas header  42   a , an upper end of the cylindrical projection  42   c  adheres to the lower surface of the shower base  41 .  
      In a lower surface side of the gas diffusion plate  42 , an oxidizing gas header  42   b  is formed as a concave space to diffuse an oxidizing gas. This oxidizing gas header  42   b  communicates through an oxidizing gas path  42 e put through the gas diffusion plate  42  with the oxidizing gas introduction path  41   b  of the shower base  41 . In the oxidizing gas header  42   b , a plurality of cylindrical projections  42 f are concentrically disposed. The source gas path  42   d  penetrates at least a part of the cylindrical projections  42   f . As a height of the cylindrical projection  42   f  is almost equal to a depth of the oxidizing gas header  42   b , a lower end of the cylindrical projection  42   f  adheres to the upper surface of the shower plate  43 .  
      As described above, the shower base  41  and the gas diffusion plate  42  are brought into direct contact with each other by the plurality of cylindrical projections  42   c , and the gas diffusion plate  42  and the shower plate  43  are brought into direct contact with each other by the plurality of cylindrical projections  42   f . Thus, a heat conduction area is increased for the entire shower head  40  to improve heat responsiveness. As a result, the shower plate  43  can be quickly cooled or heated by cooling means  94  or heating means  95 .  
      One of the cylindrical projections  42   f  in which the gas path  42   d  is formed is arranged to communicates with the source gas path  42   d  in a position of the source gas discharge port  43   a  of the shower plate  43 . Gas paths  42   d  may be formed in all the cylindrical projections  42   f.    
      As shown in FIGS.  2  to  4 , the source gas discharge ports  43   a  and the oxidizing gas discharge ports  43   b  are alternately arranged adjacently to penetrate the shower plate  43 . That is, the plurality of source gas discharge ports  43   a  are arranged in positions to overlap the source gas path  42   d  of the gas diffusion plate  42 . Each of discharge ports  43   a  is communicated with the source gas path  42   d . The plurality of oxidizing gas discharge ports  43   b  are arranged to be bored in apertures of the plurality of cylindrical projections  42   f  in the oxidizing gas header  42   b  of the gas diffusion plate  42 .  
      In the shower plate  43  of the embodiment, the plurality of source gas discharge ports  43   a  connected to the source gas introduction pipe  51  are arranged in an outermost periphery. As shown in  FIG. 3 , inside thereof, the oxidizing gas discharge ports  43   b  and the source gas discharge ports  43   a  are alternately arranged equally.  
      As shown in FIGS.  2  to  4 , grooves  44  are formed in the bottom surface (lower surface of the shower plate  43 ) of the shower head  40 . A plurality of oxidizing gas discharge ports  44   b  are bored in bottom surfaces of the grooves  44 . On the other hand, a plurality of source gas discharge ports  44   a  are bored in portions other than the grooves  44 .  
      The grooves  44  have a lattice 2-dimensional projection shape, and includes longitudinal and horizontal grooves. The oxidizing gas discharge port  44   b  is positioned at an intersection between the longitudinal and horizontal grooves. The source gas discharge port  44   a  is disposed in a center of an island  45  partitioned by the grooves  44 . That is, as shown in  FIG. 4 , the oxidizing gas discharge port  44   b  and the source gas discharge port  44   a  are formed on different surfaces (first and second surfaces) which have a step L 3 , and the oxidizing gas discharge port  44   b  is bored more apart from the wafer W than the source gas discharge port  44   a . The step L 3  (i.e., depth of the groove) is preferably set within a range of 0.5 to 10 mm. A width d 3  of the groove  44  is preferably set within a range of 0.5 to 10 mm. According to the embodiment, the depth L 3  (step) of the groove is set to about 2 mm, and the groove width d 3  is set to about 3 mm.  
      As shown in  FIGS. 4 and 5 B, the island  45  to define the groove  44  has a corner  48  subjected to R processing (chamfering). In this case, a curvature radius of the roundish portion of the corner  48  is preferably set within a range of 0.1 to 1 mm. The source gas discharge port  44   a  and the oxidizing gas discharge port  44   b  can both be formed wider toward the ends as shown. A diameter d 1  of the source gas discharge port  43   a  is preferably set within a range of 0.5 to 3 mm, and a diameter d 2  of the oxidizing gas discharge port  43   b  is preferably set within a range of 0.5 to 3 mm. Diameters of the lower ends of the source gas discharge port  44   a  and the oxidizing gas discharge port  44   b  can be set within a range of 0.5 to 3 mm.  
      In the post mix type shower head  40 , as the oxidizing gas discharge port  44   b  is bored separately from the source gas discharge port  44   a , the source gas and the oxidizing gas are discharged separately and independently, and mixed in a space directly above the wafer W.  
      The embodiment has been described by way of example in which the source gas is introduced to the upper source gas diffusion space  42   a  and the oxidizing gas is introduced to the lower oxidizing gas diffusion space  42   d . However, gas introducing positions can be changed in accordance with process conditions. That is, the oxidizing gas may be introduced to the upper source gas diffusion space  42   a , and the source gas may be introduced to the lower oxidizing gas diffusion space  42   b . A shape of the grooves  44  may be defined to be nonlattice by forming a 2-dimensional projection shape of the island  45  into a circle.  
      Thermocouple insertion ports  41   i ,  42   g  and  43   c  are overlapped in a thickness direction to penetrate the shower base  41 , the gas diffusion plate  42 , and the shower plate  43  which have been stacked together. Thermocouples  10  are inserted into these through-ports communicated with one another, a temperature of the lower surface of the shower plate  43  is detected, and its detection signal is input to a controller  80 . As described below, the controller  80  and a temperature control mechanism  90  control a temperature of the shower head  40 .  
      In the upper surface of the shower head  40 , a plurality of annular heaters  91  are disposed, and the temperature control mechanism  90  constituted of a refrigerant flow path  92  through which a refrigerant such as cooling water is distributed is arranged between the heaters  91 . A detection signal of the thermocouple  10  is input to the controller  80 , the controller  80  outputs a control signal to a heater power source  95  and a refrigerant source  94  based on this detection signal, and feedback-controls energization of the temperature control mechanism  90  to the heater  91 , or a temperature or a flow rate of a refrigerant distributed through the refrigerant flow path  92 , whereby a temperature of the shower head  40 , especially a surface temperature of the shower plate  43 , can be controlled.  
      Next, an operation of the film forming device thus configured will be described.  
      First, the inside of the treatment container  2  is exhausted by a vacuum pump (not shown) via an exhaust path such as the bottom exhaust flow path  71  to a vacuum degree of, range of e.g., 66.65 to 1333 Pa, preferably 100 to 500 Pa.  
      In this case, a constant purge gas flow is formed in which a purge gas such as Ar is supplied from a carrier/purge gas supply source (not shown) through the purge gas flow path  19  and through the plurality of gas discharge openings  18  to the backside (bottom surface) of the gas shield  17 , and this purge gas flows through the port  17   a  of the gas shield  17  into the backside of the mounting base  5 , and flows through the apertures of the shield base  8  into the bottom exhaust flow path  71 , thereby preventing damage such as deposition of a thin film or the like on the transmission window  2   d  positioned below the gas shield  17 .  
      In the treatment container  2  of this state, the wafer W is conveyed through the gate valve  16  and the wafer entrance  15  by a robot hand mechanism or the like (not shown), the lift pin  12  held by the holding member  13  is raised by an actuator (not shown) so that its pin portion can project from the mounting base  5 , the wafer W is mounted on the lift pin  12 , and then the robot hand mechanism or the like (not shown) is retreated from the treatment container  2  to close the gate valve  16 .  
      Next, the lift pin  12  is lowered to mount the wafer W on the mounting base  5 , the lamp of the lamp unit  100  is lit to apply a heat ray through the transmission window  2   d  to the lower surface (backside) of the mounting base  5 , thereby heating the wafer W mounted on the mounting base  5  to a temperature of 450° C. to 700° C., e.g., 500° C. The aforementioned lamp of the lamp unit  100  may be always lit for the purpose of shortening a temperature stable time, extending a lamp life, or the like.  
      At this time, the lower surface temperature of the shower plate  43  is detected by the thermocouple  10  based on its detection temperature, and the temperature control mechanism  90  is controlled by the controller  80  to execute temperature control of the shower head  40 .  
      Next, a source gas prepared by mixing, e.g., Pb (thd) 2 , Zr (O-i-C 3 H 7 ) (thd) 3 , and Ti (O-i-C 3 H 7 ) 2  (thd) 2  at a predetermined ratio (e.g., ratio to set elements of Pb, Zr, Ti and the like of PZT to a predetermined stoichiometric ratio) and vaporized by a carburetor (not shown) is discharged and supplied from the plurality of source gas discharge ports  44   a  of the shower pate  43  of the bottom surface of the shower head  40  to the heated wafer W. An oxidizing gas such as NO 2  is discharged and supplied from the oxidizing gas discharge ports  44   b . By thermal decomposition reaction or chemical reaction of the source and oxidizing gases, a thin film made of PZT is formed on the surface of the wafer W.  
      That is, the vaporized source gas that has come from the gas supply mechanism  60  is discharged and supplied together with a carrier gas from the source gas pipe  51  through the header  42   a  of the gas diffusion plate  42 , the source gas path  42   d , and the source gas discharge port  43   a  of the shower plate  43  and from the source gas discharge port  44   a  to the upper space of the wafer W. Similarly, the oxidizing gas supplied from the gas supply mechanism  60  is passed through the oxidizing gas pipe  52 , the oxidizing gas branch pipes  52   a  and  52   b , the oxidizing gas introduction path  41   b  of the shower base  41 , and the oxidizing gas path  42   e  of the gas diffusion plate  42  to reach the header  42   b , and passed through the oxidizing gas discharge port  43   b  of the shower plate  43  to be discharged and supplied from the oxidizing gas discharge port  44   b  to the upper space of the wafer W. Accordingly, the source gas and the oxidizing gas are separately supplied into the treatment container  2  not to be mixed in the shower head  40 .  
      In this case, according to the conventional device, as shown in  FIG. 5A , since the source gas discharge port  144   a  and the oxidizing gas discharge port  144   b  of the shower head  140  having almost equal gas discharge areas are bored on one and the same plane, the source gas easily reaches the oxidizing gas discharge port  144   b  to cause sticking of a reaction product  146  to the peripheral wall of the oxidizing gas discharge port  144   b . The sticking of the reaction product  146  narrows or closes the oxidizing gas discharge port  144   b , causing a problem of deterioration of thickness uniformity of a film or generation of particles.  
      On the other hand, according to the device of the embodiment, as shown in  FIG. 5B , the groove  44  is formed in the lower surface of the shower plate  43 , and the oxidizing gas discharge port  44   b  is bored in the groove  44 , while the source gas discharge port  44   a  is bored in the portion other than the grooves  44 . Thus, the openings of the source and oxidizing gas ports  44   a  and  44   b  are different in coordinate positions of a Z-axis direction. As a result, flowing of the source gas to the oxidizing gas discharge port  44   b  is prevented by the oxidizing gas flow, making it difficult for the source gas to reach the same.  
      Therefore, according to the present invention, reaction is difficult to occur between the source gas and the compound forming gas around the oxidizing gas discharge port  44   b , whereby sticking of a reaction product around the oxidizing gas discharge port  44   b  is suppressed. Moreover, according to the present invention, as a sticking area of the reaction product is increased by an amount equal to the depth L 3  (step) of the grooves  44 , a time until the compound forming gas discharge port is closed can be greatly extended. According to the present invention, the groove only needs to be formed, and it is not necessary to change the positions of the ports of the shower head of the existing facilities.  
      A layout of grooves  44  is a lattice. Thus, all the grooves are continuous, diffusion of the oxidizing gas is high, and a nonuniform density of the oxidizing gas is prevented. As the oxidizing gas discharge ports  44   b  are disposed at the lattice intersections of the latticed grooves  44 , it is possible to further improve diffusion of the gas discharged therefrom.  
      By setting the step (differential of height level) between the two kinds of gas discharge port opening surfaces, reaching timing of these gases can be controlled. As a result, it is possible to properly adjust reactivity thereof or the like.  
      The step L 3  (depth of the groove) shown in  FIG. 4  is preferably set within the range of 0.5 to 10 mm. Accordingly, reaching of the source gas to the oxidizing gas discharge port  44   b  can be effectively suppressed without any excessive costs. The island  45  to define the grooves  44  has the corner  48  subjected to the R processing (chamfering). Accordingly, sticking of a reaction product becomes difficult. From the standpoint of making more difficult the sticking of the reaction product, the curvature radius of the roundish portion is preferably set within 0.1 to 1 mm. Further, the source gas discharge port  44   a  and the oxidizing gas discharge port  44   b  can both be formed wider toward the ends as shown. Hence, the flowing of the source gas to the oxidizing gas discharge port  44   b  is suppressed, whereby the sticking of the reaction product to the oxidizing gas discharge port  44   b  can be made difficult.  
      When the temperature of the shower head  40  is controlled as described above, the lower surface temperature of the shower head  40  is preferably controlled within a range of 165° C. to 17 0 ° C. By controlling the temperature within this range, the sticking of the reaction product to the oxidizing gas discharge port  44   b  is made more difficult.  
      Next, an experiment that has checked effects of the present invention will be described.  
      According to this experiment, PZT films were formed on silicon wafers by using the conventional post mix type shower head and the post mix type shower head of the present invention, and a sticking state of a reaction product to an NO 2  gas discharge port peripheral wall of each shower head was visually checked. In the case of the conventional post mix type shower head, there was no step in a bottom surface. In the case of the post mix type shower head of the present invention, a latticed groove having a depth  2  mm was disposed in a bottom surface, an NO 2  gas discharge port was arranged in the groove portion, and a source gas discharge port was arranged in a portion other than the groove. Diameters of the NO 2  gas discharge ports were 0.7 mm for the conventional shower head, and 1.2 mm for the shower head of the present invention.  
      Deposition conditions were a mounting base temperature: 500° C., pressure: 133.3 Pa, an NO 2  gas flow rate: 400 mL/min, Pb (thd) 2  (liquid) flow rate: 0.13 mL/min, Zr (O-i-C 3 H 7 ) (thd) 3  (liquid) flow rate: 0.27 mL/min, Ti (O-i-C 3 H 7 ) 2  (thd) 2  (liquid) flow rate: 0.42 mL/min, deposition time:  850  sec.  
      After 100 films were formed under the above conditions, shower head bottom surfaces were photographed, and they are shown in  FIGS. 6A and 6B . In the case of the conventional shower head shown in  FIG. 6A , a reaction product greatly stuck to the NO 2  gas discharge ports to close almost all the ports. On the other hand, in the case of the shower head of the present invention shown in  FIG. 6B , almost no sticking of a reaction product to the NO 2  gas discharge ports was observed.  
      The present invention is not limited to the foregoing embodiment. Various changes can be made within its teachings. For example, the embodiment has been described by way of example in which the NO 2  gas is used as the oxidizing gas. However, an oxidizing gas such as  02  gas, N 2 O gas, or  03  gas may be used. The invention can be applied when a gas other than the oxidizing gas is used as a compound forming gas to form another metal compound such as a nitride. The example of forming the PZT thin film has been described. However, the deposition is not limited to this. Deposition using another organic metal raw material such as a BST film (crystal film having a perovskite structure of Ba (Sr 1-x Tix)O 3 ), or deposition using a source gas containing a metal other than an organic raw material may be employed. The invention can be widely applied when gases of two kinds or more are used. Furthermore, the embodiment has been described by way of example of the film forming device of the thermal CVD. However, a film forming device using plasma, and other gas treating devices such as a plasma etching device may be employed. In the case of using the plasma, various waves such a high-frequency wave, and a microwave can be used as plasma sources. In the case of using a high-frequency plasma source, it can be applied to various methods such as capacitance coupled type plasma, inductive coupled type plasma (IPC), ECR plasma, and magnetron plasma.  
      According to the embodiment, the latticed grooves are formed so that all the grooves in the bottom surface of the shower head can be continuous. However, the groove shape is not limited to the lattice. Especially, the continuous formation of all the grooves improves uniformity of a gas density or the like. However, not all the grooves need to be formed continuously. A plurality of grooves having a plurality of compound forming gas discharge ports formed to be continuous may be formed. An example of this is a concentric circular groove. Needless to say, a groove may be disposed for each compound forming gas discharge port.  
      Additionally, the embodiment has been described by taking the example of the semiconductor wafer as the substrate to be treated. However, not limited to this, other substrates such as a glass substrate for a liquid crystal display may be used.  
      According to the present invention, as the sticking of the reaction product to the compound forming gas discharge port of the shower head is suppressed, its closing can be effectively prevented, whereby uniformity and reproducibility of the formed film can be improved, an operation rate of the device can be improved, and maintenance costs can be reduced. The present invention can be widely applied to a film forming device for performing desired deposition processing by supplying a treatment gas from a shower head disposed to face a substrate mounted on a mounting base and heated in a treatment container.