Abstract:
The present invention provides a CVD apparatus and a CVD method for use in forming an Al/Cu multilayered film. The Al/Cu multilayered film is formed in the CVD apparatus comprising a chamber for placing a semiconductor wafer W, a susceptor for mounting the semiconductor wafer W thereon, an Al raw material supply system for introducing a gasified Al raw material into the chamber and a Cu raw material supply system for introducing a gasified Cu raw material into the chamber. The Al/Cu multilayered film is formed by repeating a series of steps consisting of introducing the Al raw material gas into the chamber, depositing the Al film on the semiconductor wafer W by a CVD method, followed by generating a plasma in the chamber in which the Cu raw material gas has been introduced and depositing the Cu film on the semiconductor wafer W by a CVD method. The Al/Cu multilayered film thus obtained is subjected to a heating treatment (annealing), thereby forming a desired Al/Cu multilayered film.

Description:
This application is a Division of application Ser. No. 09/092,060 filed on Jun. 5, 1998, now U.S. Pat. No. 6,089,184. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a CVD (chemical Vapor Deposition) apparatus and a CVD method, and more particularly, a CVD apparatus and a CVD method for forming an Al/Cu multilayered film. 
     In a semiconductor device, wiring (e.g., metal) is generally formed on a device formation region on a silicon semiconductor wafer by, for example, etching an Al—Cu film formed by sputtering using an Al-0.5 wt % Cu-target. 
     Recently, with the trend toward high integration of the semiconductor device, it has been desired to reduce the wiring width. However, it is difficult for a hitherto-used sputtering method to form a fine wiring which will be required by a design rule in future. 
     Then, as a technique replaceable for the sputtering method, a CVD method has been studied. Since the CVD method includes a vapor deposition step, a film is easily formed on a complicated substrate surface and minute portions such as portions having a large aspect ratio and contact holes. 
     However, it is difficult to form the Al—Cu film suitable for wiring by the CVD method. 
     To form the Al—Cu film, conventionally employed is a method in which a Cu component is added to an Al film (CVD) formed by the CVD method. In the conventional method, the Cu component is diffused into the Al film (CVD) by depositing an Al—Cu film or a Cu film on the Al film (CVD) by sputtering and annealing the obtained film. 
     The Al—Cu film of this type is reported in “Symposium on VLSI technology Digest of Technical Papers (1996), p42”. 
     In the case where the Cu component is dispersed into the Al film (CVD) by use of a single wafer process system having a multichamber type, two process chambers are required; one is to form the Al film by the CVD method and the other is to form the Al—Cu film or the Cu film by sputtering. However, film-formation has to be performed two times by transporting a single wafer between two process chambers. As a result, the throughput thereof inevitably decreases. 
     To overcome the decrease in throughput, if a plurality of chambers are prepared for each of the Al-film formation and Al—Cu film or the Cu film formation, the entire apparatus becomes quite large, raising a manufacturing cost. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a CVD apparatus and a CVD method capable of obtaining an Al/Cu multilayered film with a high throughput but without increasing the size of the apparatus. 
     The present invention provides a CVD (chemical vapor deposition) apparatus comprising: 
     a chamber capable of maintaining vacuum conditions having an exhausting system; 
     a susceptor disposed in the chamber, for mounting an object to be processed; 
     an Al raw material supply system having a first passage for introducing a gasified Al raw material into the chamber, for forming an Al film; 
     a Cu raw material supply system having a second passage for introducing a gasified Cu raw material into the chamber, for forming a Cu film, the first passage being independent of the second passage; and 
     exhausting means for vacuum-exhausting a gas including the gasified raw material introduced into the chamber; 
     wherein the Al film (formed of the Al raw material gas) and the Cu film (formed of the Cu raw material gas) are alternately stacked one upon the other by chemical vapor deposition (CVD) on a surface of the object to be processed by introducing the Al raw material gas or the Cu raw material gas alternately. 
     The Al raw material supply system of the CVD apparatus comprises an Al raw material supply line for supplying an Al raw material. The Al raw material supply line includes: 
     Al raw material gas generating means for generating a predetermined amount of an Al raw material gas from a liquid-state Al raw material contained in a vessel by bubbling with a predetermined carrier gas or direct gasification; 
     Al gas bypass means for either supplying the generated Al raw material gas to the Al raw material supply system or exhausting the generated Al raw material gas outside using the exhausting means by switch operation of a valve; 
     first gas purge means for purging a remaining gas in the chamber or in a gas pipe by supplying a predetermined carrier gas either from the Al raw material gas supply line to the chamber or from the Al raw material supply line to the Al raw material gas bypass means; and 
     Al raw material switching means for switching either between the Al raw material gas bypass means and the Al raw material supply line or between the first gas purge means and the Al raw material supply line. 
     The Cu raw material supply system comprises a Cu raw material supply line for supplying a Cu raw material. 
     The Cu raw material supply line includes 
     Cu raw material gas generating means for generating a predetermined amount of a Cu raw material gas gasified by heating a solid-state Cu raw material contained in a vessel with the aid of a predetermined carrier gas; 
     Cu gas bypass means for either supplying the generated Cu raw material gas to the Cu raw material supply system or exhausting the generated Cu raw material gas outside using the exhausting means by switch operation of a valve; 
     second gas purge means for purging a remaining gas in the chamber or in a gas pipe by supplying a predetermined carrier gas either from the Cu raw material gas supply line to the chamber or from the Cu raw material supply line to the Cu raw material gas bypass means; and 
     Cu raw material switching means for switching either between the Cu raw material gas bypass means and the Cu raw material supply line or between the second gas purge means and the Cu raw material supply line. 
     The present invention further provides a CVD method of forming a film from the raw material on a surface of an object to be processed which is placed in an atmosphere mainly consisting of a predetermined raw material gas. The CVD method comprises: 
     a multilayered film formation step for forming an Al/Cu multilayered film by repeating, predetermined times, Al film formation for forming an Al film on a surface of the object to be processed by introducing a gasified Al raw material (Al raw material gas) into the atmosphere and Cu film formation for forming a Cu film on a surface of the object to be processed by introducing a gasified Cu raw material (Cu raw material gas) into the atmosphere, thereby forming an Al/Cu multilayered film in which the Al film and the Cu film are stacked alternately on the object to be processed surface; and 
     a heat treatment step for annealing the Al/Cu multilayered film under predetermined conditions, thereby forming a desired Al/Cu alloy film in which diffusion between the Al film and the Cu film takes place. 
     As mentioned in the foregoing, the present invention provides a CVD apparatus and a CVD method for use in forming an Al/Cu multilayered film. The Al/Cu multilayered film is formed in the CVD apparatus comprising a chamber for placing an object to be processed, a susceptor for mounting the object to be processed thereon, an Al raw material supply system for introducing a gasified Al raw material into the chamber and a Cu raw material supply system for introducing a gasified Cu raw material into the chamber. The Al/Cu multilayered film is formed by repeating a series of steps consisting of introducing the Al raw material gas into the chamber, depositing the Al film on the object to be processed by a CVD method, followed by introducing the Cu raw material gas into the chamber and depositing the Cu film on the object to be processed by a CVD method. The Al/Cu multilayered film thus obtained is subjected to a heating treatment (annealing), thereby forming a desired Al/Cu multilayered film. 
     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 hereinbefore. 
    
    
     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 given below, serve to explain the principles of the invention. 
     FIG. 1 is a view showing a schematic structure of a CVD apparatus according to an embodiment of the present invention; 
     FIG. 2 is a view showing an Al raw material supply system for supplying Al gas into the CVD apparatus shown in FIG. 1; 
     FIG. 3 is a view showing a Cu raw material supply system for supplying Cu gas into the CVD apparatus shown in FIG. 1; and 
     FIG. 4 is a view showing an modified example of the Cu raw material supply system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Now, embodiments of the present invention will be described with reference to the accompanying drawings. 
     FIG. 1 is a schematic cross-sectional view showing a structure of the CVD apparatus according to the present invention. 
     The CVD apparatus has a chamber  1  formed of aluminium so as to maintain a vacuum state. In the chamber  1 , a susceptor  2  is fixed by a supporting member  3  which is immobilized on the bottom portion  1   b  of the chamber  1 . The susceptor  2  is responsible for holding a (object to be processed) such as a semi-conductor wafer W horizontally. 
     A guide ring  4  is arranged in the outer periphery of the susceptor  2 , for guiding the semiconductor wafer W to fit in a holding position while covering the susceptor to prevent an extra film from being deposited. 
     A heater  5  is embedded inside the susceptor  2 . The heater  5  applies heat to the semiconductor wafer W held by the susceptor  2 , upon supplying power from the power source  6 , thereby raising temperature to a desired value. The temperature of the heater  5  is controlled by a controller  7  via the power source  6  in accordance with a signal sent from a temperature sensor (not shown). 
     An exhausting port  8  is formed in the bottom portion  1   b  of the chamber  1 . To the exhausting port  8 , an exhausting system  9  (a vacuum pump etc.) is connected. The atmosphere and a gas contained in the chamber  1  are exhausted outside by the exhausting system  9 . As a result, the pressure is reduced to obtain a predetermined degree of vacuum. 
     A shower head  10  for supplying a process gas (described later) is provided on the upper cover  1   a  of the chamber  1 . The shower head  10  is constituted of three blocks, namely, upper block  10   a,  middle block  10   b,  and the lower block  10   c,  which are integrated into one body in the vertical direction. 
     In the upper surface of the upper block  10   a,  an Al raw material inlet  11  and a Cu raw material inlet  12  are provided. The Al raw material inlet  11  is used for introducing an Al raw material from a Al raw material supply system  20  (described later). The Cu raw material inlet  12  is used for introducing a Cu raw material from a Cu raw material supply system  40  (described later). A pipe extending from the Al raw material inlet  11  is branched into a plurality of Al raw material passages  13  inside the upper block  10   a.  Each of the branched Al raw material passages  13  is communicated with an Al raw material passage  15  formed in the middle block  10   b,  and further connected to an Al raw material gas-ejecting orifice  17  in the lower block  10   c.    
     On the other hand, a pipe is arranged extending from the Cu raw material inlet  12  but it is not communicated with Al raw material inlet  11 , the Al raw material passage  13 , and Al raw material gas-ejecting orifice  17 . More specifically, the pipe extending from the Cu raw material inlet  12  is branched into a plurality of Cu raw material passages  14  inside the upper block  10   a.  Each of the Cu raw material passages  14  is communicated with a Cu raw material passage  16  formed in the middle block  10   b,  and further connected to a Cu raw material gas-ejecting orifice  18  in the lower block  10   c.    
     As described above, the shower head  10  has the Al raw material supply route and the Cu raw material supply route which are completely independent of each other. The Al and Cu raw material gas-ejecting orifices  17  and  18  are arranged alternately at predetermined intervals. Furthermore, a cooling water passage is formed in the shower head  10 . A cooling water is supplied from a water inlet pipe  19  and circulate through the shower head  10 , thereby controlling temperature thereof. 
     The chamber  1  has a transporting system (not shown) for transporting a semiconductor wafer W to the susceptor  2  and has a load-and-unload rock chamber (not shown) for loading and unloading the semiconductor wafer W into and out of the chamber  1 . 
     Now, the Al raw material supply system  20  will be explained with reference to FIG.  2 . 
     The Al raw material supply system  20  has an Al raw material supply line  21  and an Al raw material vessel  22 . The Al raw material supply line  21  is connected to the Al raw material inlet  11  of the shower head  10  and responsible for supplying an Al raw material. The Al raw material vessel  22  is filled with an Al raw material such as dimethylaluminium hydride (DMAH). The vessel  22  may be heated. 
     The Al raw material supply system  20  further comprises a bubbling line  25 , a purge line  32 , and a bypass line  36 . The bubbling line  25  supplies a carrier gas such as H 2  gas into the Al raw material vessel  22  to bubble DMAH. Since DMAH is a liquid form at normal temperature, it is gasified by the bubbling operation. The purge line  32  is responsible not only for purging the raw material gas remaining in the Al raw material supply line  21  and in the chamber  1  but also for controlling an inner pressure of the chamber  1  by introducing a gas into the chamber before the raw material gas is supplied. The bypass line  36  is branched from the bubbling line  25  and the purge line  32  and plays a role in exhausting the raw material gas to prevent the raw material gas from being supplied to the apparatus. 
     The Al raw material supply line  21  is constituted of a valve  26 , switch valves  28 ,  29  and a pipe connecting the elements mentioned. An end of the Al raw material supply line is inserted into the Al raw material vessel  22  but not in contact with the Al raw material. The other end thereof is connected to the Al raw material inlet  11  of the shower head  10 . The valve  26  plays a role in initiating and terminating the raw material gas supply. The switch valve  28  is responsible for switching a gas flow to a branched bypass line  36 . The switch valve  29  is responsible for switching the gas flow to a branched purge line. 
     To prevent the gasified raw material from returning to a liquid form, the Al raw material vessel  22  is maintained at, e.g., 25° C. and the gas supply pipe of the Al raw material supply line  21  is maintained at e.g., 35° C. 
     The bubbling line  25  is constituted of a gas source  24 , a valve  30 , a mass-flow controller  27 , a switch valve  31 , and a pipe connecting the elements mentioned. As the gas source  24 , use may be made of, for example, a gas cylinder which is filled with a carrier gas (H 2 ) for use in bubbling. The valve  30  is responsible for initiating and terminating the carrier-gas supply. The mass-flow controller  27  is responsible for controlling the flow rate of the Al raw material gas, which is generated by controlling a flow rate of the carrier gas. The switch valve  31  plays a role in switching the gas flow from a main pipe to a branched bypass line  36 . The open end of the gas pipe is inserted into DMAH contained in the Al raw material vessel  22 . 
     It is preferable that the same type of gas should be used as the purge gas (to be supplied to the purge line  32 ) and as the carrier gas for use in bubbling. For example, H 2  gas is preferable. 
     The purge line  32  is constituted of a purge gas source  33 , a valve  34 , a mass-flow controller  35 , and a pipe connecting the elements mentioned. An end of the purge line  32  is connected to the switching valve  29 . As the purge gas source  33 , use may be made of a gas cylinder which is filled with H 2  gas. The valve  34  is responsible for initiating and terminating the carrier-gas supply. The mass-flow controller  35  plays a role in controlling the flow rate of the purge gas. 
     The bypass line  36  is constituted of a pipe line branched from the switching valve  28  of the Al raw material supply line  21  and a pipe line branched from the switching valve  31  of the bubbling line  25 , and the branched lines are merged into an exhausting pipe, which is further connected to the evacuation system. 
     Now, the Cu raw material supply system  40  will be explained with reference to FIG.  3 . 
     The Cu raw material supply system  40  has a Cu raw material supply line  41  and a Cu raw material vessel  42 . The Cu raw material supply line  41  is connected to the Cu raw material inlet  12  of the shower head  10  and responsible for supplying the Cu raw material. The Cu raw material vessel  42  is filled with a Cu raw material such as cyclopentadienylcoppertriethylphosphine (CpCuTEP). Since CpCuTEP is a solid material, CpCuTEP is coated over a plurality of spherical bodies, which are accommodated in the Cu raw material vessel  42  in this embodiment. 
     Furthermore, since CpCuTEP is present in a solid form at normal temperature, a heater is provided in the Cu raw material vessel  42  to heat CpCuTEP. The Cu raw material supply system is constituted of a gasification line  45 , a purge line  52 , and a bypass line  56 . The gasification line  45  plays a role in introducing H 2  gas into the vessel  42  to gasify CpCuTEP, thereby producing the Cu raw material gas. The purge line is responsible not only for purging the raw material gas left in the Cu raw material supply line  41  and in the chamber  1  but also for introducing a gas before the raw material gas is introduced into the chamber  1  to control the inner pressure thereof. The bypass line  56  is branched from the gasification line  45  and the purge line  52 , and plays a role in exhausting the raw material gas to prevent the raw material gas from being supplied to the apparatus. 
     The Cu raw material supply line  41 , one end of which is inserted into the Cu raw material contained in the Cu raw material vessel  42 , and the other end of which is connected to the Cu raw material inlet  12  of the shower head  10 . The Cu raw material supply line  41  is constituted of a valve  46 , switching valves  48 ,  49 , and a pipe connecting the elements mentioned. The valve  46  is responsible for initiating and terminating the Cu raw material supply. The switching valves  48  and  49  play a role in switching the flow into a branched bypass line  56  and a branched purge line  52 , respectively. 
     Note that a heater  58  is provided in the periphery of the Cu raw material supply line  41 , extending from the Cu raw material vessel  42  to the chamber  1 . The Cu raw material supply line  41  is heated by the heater  58  to a predetermined temperature, e.g., 75° C. On the other hand, a heater  59  is provided in the periphery of the carrier gas pipe  45 . The gas pipe  45  is heated to a predetermined temperature, e.g., 65° C. Furthermore, the Cu raw material vessel  43  is heated by a heater  60  to a predetermined temperature, e.g., 65° C. 
     The gasification line  45  is constituted of a gas supply source  44 , a valve  50 , a mass flow controller  47 , a switch valve  51 , and a pipe connecting the elements mentioned. As the gas supply source  44 , use may be made of, for example, a gas cylinder which is filled with a carrier gas (H 2 ). The valve  50  is responsible for initiating and terminating the carrier gas supply. The mass-flow controller  47  controls a flow rate of the raw material gas, which is generated by controlling a flow rate of the carrier gas. The switching valve  51  plays a role in switching the flow into the branched bypass line  56 . The open end of the gasification line  45  is inserted into the Cu raw material vessel  42  but not in contact with the Cu raw material. 
     The purge line  52  is constituted of a purge gas source  53 , a valve  54 , a mass-flow controller  55 , and a pipe connecting the elements mentioned. As the purge gas source  53 , use may be made of, for example, a gas cylinder which is filled with gas (H 2 ). The valve  54  is responsible for initiating and terminating purge gas supply. The mass-flow controller plays a role in detecting a flow rate of the purge gas. The purge line  52  is connected to the switching valve  49 . 
     It is preferable that the same type of gas should be used as the purge gas (to be supplied to the purge line  52 ) and as the carrier gas for use in bubbling. For example, H 2  gas is preferable. 
     The bypass line  56  is constituted of a pipe line branched from the switching valve  48  of the Cu raw material supply line  41  and a pipe line branched from the switching valve  51  of the bubbling line  45 , and the branched lines are merged into the exhausting pipe which is further connected to the evacuation system  9 . 
     In the CVD apparatus having the Al raw material supply system  40  and the Cu raw material supply system  40 , an Al raw material gas (DMAH) is supplied into the chamber  1  from the Al raw material supply line  21  when an Al film is formed. At this time, the switching valve  48  is opened and the switching valve  49  is closed. By virtue of these operation, the Cu raw material gas is led into a branched bypass line  56  and exhausted from the exhausting system  9 . The Cu raw material gas is therefore successfully prevented from being introduced into the chamber  1 . 
     When the Cu film is formed, the Cu raw material gas (CpCuTEP) is supplied from the Cu raw material supply line  41  to the chamber  1 . At this time, the switching valve  28  is opened and the switching valve  29  is closed. By virtue of these operations, the Al raw material gas is led into the branched bypass line  36  and exhausted from the exhausting system  9 . The Al raw material gas is therefore successfully prevented from being introduced into the chamber  1 . 
     Next, we will explain the method of forming an Al/Cu multilayered film by using the CVD apparatus according to this embodiment. 
     The chamber  1  (under atmospheric pressure) is drawn by a vacuum pump through the exhausting system  9  to obtain a highly-vacuumed state. While this state is maintained, a semiconductor wafer W having a TiN film formed on the substrate surface is loaded into the chamber  1  from the loadlock chamber (not shown) and set on the susceptor  2 . Then, the semiconductor wafer W is heated to 190° C. by the heater  5  embedded in the susceptor  2 . 
     Subsequently, H 2  gas is introduced into the chamber  1  from both or either of the purge gas sources  33 ,  53  at a flow rate of, e.g, 1000 SCCM, by operating the switch valves  29  and  49 . As a result, the degree of vacuum of the chamber  1  is adjusted at, e.g, 5 Torr. 
     At the same time, H 2  gas is supplied into the bypass lines  36 ,  56  at a flow rate of 1000 SCCM from the gas supply sources  24 ,  44  by operating the switching valves  31 ,  51 ,  28  and  48 . 
     At this time, pressures inside the pipe lines upstream of pressure controllers (not shown), which are respectively fitted on the Al raw material supply line  21  and the Cu raw material supply line  41 , are controlled equal to those of the raw material vessels  22  and  42  by means of the pressure controllers. 
     In this case, the pressure of the Al raw material vessel  22  is set at, e.g., 100 Torr. The pressure of the Cu raw material vessel  42  is set at, e.g., 160 Torr. 
     After the pressure is stabilized, the carrier gas is supplied into the Al raw material vessel  22  and the Cu raw material vessel  42  from the bypass lines  36 ,  56  respectively by operating the switch valves  31 ,  51 . 
     DMAH (Al raw material) is bubbled and gasified by the aforementioned operation. The gasified DMAH is sent to the Al raw material supply line  21  together with a carrier gas (H 2 ). The DMAH flow is switched into the branched bypass line  36  by the operation of the switch valve  28 . In this manner, DMAH is exhausted from the bypass line  36 . In the same manner, CpCuTEP (Cu raw material) is gasified and sent to the Cu raw material supply line  41  together with the carrier gas (H 2 ). The CpCuTEP flow is switched into the branched bypass line  56  by the operation of the switch valve  48 , and then exhausted. 
     When a chamber pressure is stabilized and temperature of the semiconductor wafer reaches a predetermined value, the raw material gas is supplied into the chamber  1  by operating either switch valves  28  and  29  or switch valves  48  and  49 . In this way, film formation is started. The Al film may be formed first or the Cu film may be formed first. 
     Now, we will explain the case where the Cu film is formed after the Al film is formed in accordance with the aforementioned process. When the film is formed, temperature of the wall portion of the chamber  1  is set at, e.g., 50° C. to prevent an extra film from being deposited. 
     By virtue of the aforementioned operation, the carrier gas is supplied into the chamber  1  via the switch valve  29  and the Al raw material gas is supplied into the branched bypass line  36 . Similarly, the Cu raw material gas is supplied into the bypass line  56  via the switch valve  48 . 
     While the supply of the H 2  gas into the chamber  1  is terminated by operating switch valves  28  and  29 , the Al raw material gas (DMAH+H 2 ) flowing into the bypass line  36  is then changed to flow into the chamber  1 . The Cu raw material gas (CpCuTEP+H 2 ) is supplied into the bypass line  56 . 
     At that time, a flow rate of the H 2  gas (carrier gas) is set at, e.g., 1000 SCCM. An inner pressure and temperature of the Al raw material vessel  22  are set at about 100 Torr and about 65° C., respectively. Temperature of the Al raw material supply line  21  is set at, e.g., 35° C. 
     In this way, a first Al film is formed on the semiconductor wafer W  45 . 
     A predetermined time after the first Al film is formed in a predetermined thickness, the switch valve  28  is operated. The Al raw material gas flowing into the chamber  1  through the Al raw material supply line  21  is switched to flow into the bypass line  36 . In this manner, the Al raw material gas is exhausted. 
     Thereafter, the switch valve  48  is operated to supply the Cu raw material gas, which has been supplied to the bypass line  56 , into the chamber  1 . 
     The switch valves  28  and  48  may be operated either simultaneously or separately. To be more specific, after the Al raw material gas flow is switched to the bypass line  36 , the Cu raw material gas may be supplied into the chamber  1 . Note that if the Al raw material gas is co-present with the Cu raw material gas in the chamber  1 , the gases may react with each other and generate a reaction product. To prevent the reaction, it is preferred to employ either a method in which the chamber  1  is purged with H 2  gas supplied from the purge gas source  33  after the Al raw material gas flow is switched to the bypass line  36 , or a method in which after the Al raw material gas is exhausted by a vacuum pump, the Cu raw material gas is supplied into the chamber  1 . In the opposite case where the Cu raw material gas is supplied before the Al raw material gas, the switching operation of the supplied gas may be carried out in the similar manner. 
     When the Cu raw material gas is supplied in place of the Al raw material gas, H 2  gas (carrier gas) is supplied at a flow rate of e.g., 1000 SCCM. Inner pressure and temperature of the Cu raw material vessel  42  are set at about 100 Torr and about 65° C. , respectively. Temperature of the gasification line  45  is set at about 65° C. Temperature of the Cu raw material supply line  41  is set at about 75° C. 
     After a first Cu film is formed on the first Al film in a desired thickness under these conditions, the Cu raw material gas is supplied into the bypass line  56  by the operation of the switch valve  48 . In this way, the Cu film formation step is terminated. 
     Then, to form a second Al film, the Al raw material gas is supplied into the chamber  1  switching from the bypass line  36  by the operation of the switch valve  28 . In this way, the second Al film is formed on the first Cu film. 
     If the aforementioned operations are repeatedly performed, it is possible to form Al/Cu multilayered film in which the Al film and Cu film are alternately stacked in a desired layer-number. 
     When a series of film-formation processes is terminated, the valves  30 ,  50  are first operated to stop the carrier gas. Then, switch valves  31 ,  51  are operated to exhaust the carrier gas left in the pipe. 
     Thereafter, the chamber  1  is drawn by a vacuum pump to a high degree of vacuum, thereby exhausting the remaining gas. Alternatively, the chamber  1  may be drawn by a vacuum pump after post flow is performed for a predetermined time period by introducing H 2  gas into the chamber  1  from the purge gas sources  33 ,  53  and terminating the H 2  gas supply by the operation of the switch valves  29 ,  49 . 
     The Al/Cu multilayered film thus formed on the semiconductor wafer W is subjected to an annealing step under predetermined conditions. The annealing treatment induces diffusion between the Al film and the Cu film. As a result, a desired Al/Cu alloy film is formed. 
     The multilayered film is formed under the typical film formation conditions below. 
     First, the substrate is heated to 190° C. and inner pressure of the chamber  1  is set at 5 Torr. Then, the Al raw material (DMAH) is supplied together with H 2  gas (carrier gas) at a flow rate of 1000 SCCM for 234 seconds by use of a bubbler (Step (1)). The pressure at an outlet of the bubbler is 100 Torr and a vapor pressure of DMAH at room temperature is about 2 Torr. Thereafter, H 2  gas serving as a purge gas is supplied at a flow rate of 1000 SCCM for 20 seconds (Step (2)), and then, CpCuTEP gas (Cu raw material gas) set at 80° C., 100 Torr, is supplied for 60 seconds together with H 2  carrier gas (Step (3)). Subsequently, H 2  purge gas is supplied for 20 seconds at 1000 SCCM (Step (4)). A series of steps (1) to (4) is repeated 7 times. In this manner, an Al/Cu multilayered film having an overall thickness of 25,000 Å is formed. The obtained multilayered film is then subjected to an annealing step performed at 400° C. for 30 minutes under an hydrogen atmosphere. As a result, an Al/Cu alloy film is obtained. 
     In the case where the alloy film is formed from the multilayered film in which the Al film and the Cu film are stacked one upon the other a plurality of times, it is generally preferable that a single film should be formed in a thickness of about 2000 Å or less. In view of smoothness of each film, it is preferred to set the thickness of the single film at about 500 Å; however, the film formation step is inevitably repeated more. This means that the throughput decreases. Hence, most preferably, the thickness of the single film is within the range of 1000 to 2000 Å. 
     As explained in the foregoing, according to the CVD apparatus of this embodiment, it is possible to form the Al/Cu multilayered film in a single chamber. This is because the Al film (made of the Al raw material gas) and the Cu film (made of the Cu raw material gas) can be formed independently and alternately in the same chamber. Hence, the Al/Cu multilayered film is formed with a high throughput and without increasing the size of the manufacturing apparatus. 
     The Al raw material supply line and Cu raw material supply line are independently connected to the shower head, passed through the shower head without merging, and connected to the chamber. Hence, there is little possibility for the Al raw material to react with the Cu raw material. 
     Furthermore, there are provided a first bypass line (for exhausting the Al raw material gas) and a second bypass line (for exhausting the Cu raw material gas) bypassing the chamber. Hence, when the Al raw material gas is introduced into the chamber through the Al raw material supply line, the Cu raw material gas is introduced into the second bypass line. Whereas, when the Cu raw material gas is introduced into the chamber through the Cu raw material supply line, the Al raw material gas is introduced into the first bypass line. In this way, it is possible to prevent the reaction between the Al raw material and the Cu raw material. 
     In this embodiment, since the aforementioned materials are chosen as raw materials, both Al film and Cu film may be formed on the semiconductor wafer W set at the same temperature. Therefore, while the susceptor is kept at the same temperature by the heater, the films can be formed continuously. It is therefore possible to increase the throughput. 
     Note that the present invention is not limited to the aforementioned embodiments and may be modified in various ways. In the embodiments, the raw materials gases are supplied from raw material supply orifices arranged in a matrix shower form in the head shower which is positioned in the upper portion of the chamber. However, the supply means for the raw materials is not limited to this. Any supply means may be used as long as the Al raw material and Cu raw material can be supplied independently. For example, use may be made of two ring-form supply means having numerous gas spurting-out holes. 
     Furthermore, it is not necessary to use a bubbling scheme to gasify the raw material. A predetermined amount of a liquid material may be directly gasified by using a liquid mass-flow controller. The carrier gas and the purge gas are not limited to H 2  gas. An inert gas such as Ar may be used. 
     Now, we will explain an modified embodiment of the Cu raw material supply system  40  with reference to FIG.  4 . In the aforementioned Cu raw material supply system  40 , cyclopentadienylcopperethylphosphine (CpCuTEP) is employed, whereas, a liquid Cu material is used in the Cu raw material supply system of the modified embodiment. 
     A Cu raw material vessel of the modified embodiment differs in structure from that shown in FIG.  3 . Like reference numerals are used to designate like structural elements corresponding to those in FIG.  3  and any further explanation is omitted for brevity&#39;s sake. 
     As the liquid Cu raw material, hexafluoroacetylacetonatetrymethylvinylsilylcopper (hfacCuVTMS)  62  is used. 
     Liquid-form hfacCuVTMS  62  contained in a Cu raw material vessel  61  is gasified by bubbling and supplied to a Cu raw material supply line  41  in the same manner as in the Al raw material supply system  20 . H 2  gas serving as the carrier gas for use in bubbling is supplied from a gas supply source  44  through a carrier gas pipe  45  to the Al raw material vessel  61 . Upon supplying H 2  gas, hfacCuVTMS  62  is bubbled and pressure-supplied through the pipe  41  into the chamber  1 . 
     As the Al raw material and the Cu raw material, the aforementioned combination is preferable. However, they are not limited to the aforementioned combination. Various combinations may be employed. 
     For example, as the Al raw material, there are triisobutylaluminium (TIBA), dimethylethylaminoalane (DMEAA), trimethylaminealane (TMAA), trimethylaluminium (TMA) and the like. 
     As the Cu raw material, there are cyclopentadienylcoppertrimethylphosphine (CpCuTMP), cyclopentadienylcoppertriisopropylphosphine (CpCuTIPP), ethylcyclopentadienylcoppertriethylphosphine (EtCpCuTEP) and the like. 
     Furthermore, conditions including temperature, pressure at the time of the film-formation may be appropriately set depending upon a film to be obtained. 
     In this embodiment, the Al film is first formed on the semiconductor substrate and then the Cu film is formed. However, the Cu film may be formed first before the Al film. 
     Additional advantages and modifications will readily occur 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.