JP2013209701A - Method of forming metal film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of forming a metal film, by which incubation time can be shortened for film formation when a metal amidinate-based material is used to form a metal film.SOLUTION: A substrate to be processed is placed in a processing container, and a metal amidinate-based compound gas as a film forming material and a reaction gas are supplied into the processing container to be reacted with each other on the heated substrate, thereby forming a metal film on the substrate. At this time, before the supply of the reaction gas, the metal amidinate-based compound gas is supplied first into the processing container to be adsorbed onto the substrate, and then the reaction gas is supplied into the processing container in addition to the metal amidinate-based compound gas to form a metal film on the substrate.

Description

  The present invention relates to a metal film forming method for forming a metal film by chemical vapor deposition (CVD).

  In recent years, semiconductor devices have been demanded to further increase the operation speed and reduce power consumption. For example, in order to reduce the resistance of source and drain contact portions and gate electrodes of MOS type semiconductors, Silicide is formed by the salicide process. As such a silicide, nickel silicide (NiSi), which consumes less silicon and can reduce resistance, has attracted attention.

  For forming a NiSi film, a method of forming a nickel (Ni) film on a Si substrate or a polysilicon film by a physical vapor deposition (PVD) method such as sputtering and then annealing and reacting in an inert gas is often used. (For example, Patent Document 1).

  Attempts have also been made to use the nickel film itself as a capacitor electrode of a DRAM.

However, with the miniaturization of semiconductor devices, PVD has a drawback of poor step coverage, and a method of forming a nickel film by chemical vapor deposition (CVD) with good step coverage has been studied. Discloses that a nickel film is formed by a CVD method using nickel amidinate as a film forming material (precursor) and ammonia (NH ₃ ) as a reducing gas.

JP-A-9-153616 JP 2011-66060 A

However, as in Patent Document 2, when a nickel film is formed by CVD using nickel amidinate as a film forming material (precursor) and ammonia (NH ₃ ) as a reducing gas, depending on conditions, It was found that the initial film formation hardly occurred and the incubation time was prolonged. Thus, when the incubation time becomes long, the thickness of the nickel film varies. Such a problem also exists when another metal film is formed using an amidinate-based material.

  The present invention has been made in view of such circumstances, and in the case of forming a metal film using a metal amidinate-based material, a method for forming a metal film that can be formed with a short incubation time is provided. The issue is to provide.

In the above-mentioned Patent Document 2, the nickel amidinate gas and NH ₃ gas are simultaneously supplied after preheating the substrate during film formation. It turns out that the incubation time is long. Then, it tried to supply nickel amidate gas which is a film-forming raw material (precursor) after supplying and adsorbing NH ₃ gas which is a reactive gas (reducing gas) first. As a result, in a certain temperature range, NH ₃ is quickly adsorbed to the substrate and initial film formation is likely to occur, and the incubation time can be shortened, but depending on the substrate temperature during film formation, it may be difficult to adsorb. found.

On the other hand, by supplying the nickel amidinate gas first, the nickel amidinate gas can be physically adsorbed on the substrate, and the nickel film is rapidly formed on the nickel amidate gas. It was found that the film could be formed with a short incubation time even under conditions where no effect was observed even when NH ₃ gas was supplied.

  The present invention has been made based on such knowledge. A substrate to be processed is arranged in a processing container, and a metal amidinate compound gas as a film forming raw material and a reaction gas are supplied into the processing container. A film forming method for forming a metal film on a substrate to be processed by reacting them on a heated substrate, and supplying a metal amidinate compound gas into the processing container prior to supply of the reaction gas. Supplying a metal film onto the substrate to be processed, and then supplying a reaction gas into the processing vessel in addition to the metal amidinate compound gas to form a metal film on the substrate to be processed. A film forming method is provided.

  In the present invention, the film formation is performed with the substrate to be processed placed on a susceptor, and the substrate to be processed is preheated on the susceptor prior to the film formation, and the preheating is started when the preheating is started. It is preferable to start supplying the metal amidinate compound gas into the processing vessel. In this case, it is preferable to start supplying the metal amidinate-based compound raw material within 30 seconds after the substrate to be processed is placed on the susceptor.

  It is preferable to supply the reaction gas 15 to 60 seconds after supplying the metal amidinate compound gas.

  Nickel amidinate can be used as the metal amidinate compound as the film forming raw material, and a nickel film can be formed as the metal film. In this case, the heating temperature of the substrate to be processed is preferably 160 to 230 ° C.

  Further, the present invention is a storage medium that operates on a computer and stores a program for controlling the film forming apparatus, and the program performs the metal film forming method when executed. A storage medium is provided that causes a computer to control the film formation apparatus.

  According to the present invention, prior to the supply of the reaction gas, the metal amidinate compound gas, which is the film forming raw material gas, is supplied into the processing vessel and adsorbed on the substrate to be processed. In addition, when the reaction gas is supplied into the processing container, a metal film is quickly formed, and the incubation time can be shortened.

It is a schematic diagram which shows an example of the film-forming apparatus for enforcing the film-forming method of the metal film which concerns on one Embodiment of this invention. It is a figure which shows the sequence of the film-forming method of the metal film which concerns on one Embodiment of this invention. A case of forming a nickel film after the Ni-AMD _soak, obtained by depositing a nickel film after the NH 3 soak, a diagram showing the relationship between film formation time and the nickel film thickness. It is the scanning microscope (SEM) photograph of the surface at the time of forming into a film formation time 30sec, 60sec, and 120sec after performing Ni-AMD soak. It is a figure which shows the relationship between the film-forming time and the nickel film thickness in the case where Ni-AMD soak is performed before and after the wafer temperature is increased, and when NH ₃ soak is performed.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
In the present embodiment, a case where a nickel film is formed as a metal film will be described. FIG. 1 is a schematic view showing an example of a film forming apparatus for carrying out a metal film forming method according to an embodiment of the present invention.

  The film forming apparatus 100 has a substantially cylindrical chamber 1 that is hermetically configured, and a susceptor 2 for horizontally supporting a wafer W that is a substrate to be processed is an exhaust chamber described later. It is arrange | positioned in the state supported by the cylindrical support member 3 which reaches the center lower part from the bottom part. The susceptor 2 is made of a ceramic such as AlN. Further, a heater 5 is embedded in the susceptor 2, and a heater power source 6 is connected to the heater 5. On the other hand, a thermocouple 7 is provided in the vicinity of the upper surface of the susceptor 2, and a signal of the thermocouple 7 is transmitted to the heater controller 8. The heater controller 8 transmits a command to the heater power supply 6 in accordance with a signal from the thermocouple 7, and controls the heating of the heater 5 to control the wafer W to a predetermined temperature. Above the heater 5 inside the susceptor 2, an electrode 27 for applying high-frequency power is embedded. A high-frequency power source 29 is connected to the electrode 27 via a matching unit 28, and it is also possible to generate plasma by applying high-frequency power to the electrode 27 as necessary to perform plasma CVD. . The susceptor 2 is provided with three wafer raising / lowering pins (not shown) so as to be able to project and retract with respect to the surface of the susceptor 2, and is projected from the surface of the susceptor 2 when the wafer W is transferred. To be.

A circular hole 1 b is formed in the top wall 1 a of the chamber 1, and a shower head 10 is fitted so as to protrude into the chamber 1 therefrom. The shower head 10 is for discharging a film-forming gas supplied from a gas supply mechanism 30 to be described later into the chamber 1, and a first introduction path for introducing a film-forming material gas is provided above the shower head 10. 11 and a second introduction path 12 for introducing NH ₃ gas and H ₂ gas as reaction gas (reducing gas).

As a nickel amidinate used as a film forming source gas, for example, Ni (II) N, N′-di-tert-butylamidinate (Ni (II) (tBu-AMD) ₂ ) shown in FIG. 1 is used. Can be mentioned. Other nickel amidinates include Ni (II) N, N′-di-isopropylamidinate (Ni (II) (iPr-AMD) ₂ ), Ni (II) N, N′-di-ethylamino. Examples thereof include dinate (Ni (II) (Et-AMD) ₂ ), Ni (II) N, N′-di-methylamidinate (Ni (II) (Me-AMD) ₂ ) and the like.

Inside the shower head 10, spaces 13 and 14 are provided in two upper and lower stages. A first introduction path 11 is connected to the upper space 13, and a first gas discharge path 15 extends from the space 13 to the bottom surface of the shower head 10. A second introduction path 12 is connected to the lower space 14, and a second gas discharge path 16 extends from the space 14 to the bottom surface of the shower head 10. That is, the shower head 10 discharges nickel amidinate as a film forming raw material gas, NH ₃ gas, and H ₂ gas independently from the discharge passages 15 and 16.

  An exhaust chamber 21 that protrudes downward is provided on the bottom wall of the chamber 1. An exhaust pipe 22 is connected to the side surface of the exhaust chamber 21, and an exhaust device 23 having a vacuum pump, a pressure control valve, and the like is connected to the exhaust pipe 22. By operating the exhaust device 23, the inside of the chamber 1 can be brought into a predetermined reduced pressure state.

  On the side wall of the chamber 1, a loading / unloading port 24 for loading / unloading the wafer W and a gate valve 25 for opening / closing the loading / unloading port 24 are provided. A heater 26 is provided on the wall portion of the chamber 1 so that the temperature of the inner wall of the chamber 1 can be controlled during the film forming process.

The gas supply mechanism 30 is a nickel amidinate (Ni-AMD) that is a film forming raw material, for example, Ni (II) N, N′-di-tert-butylamidinate (Ni (II) (tBu-AMD) _2. ) Is stored in a state dissolved in a solvent. A heater 31a is provided around the film forming material tank 31 so that the film forming material in the tank 31 can be heated to an appropriate temperature. In addition, when using a liquid thing at normal temperature as a nickel amidinate, it can store as it is, without melt | dissolving in a solvent.

  A bubbling pipe 32 for supplying Ar gas as a bubbling gas from above is inserted into the film forming material tank 31 so as to be immersed in the film forming material. An Ar gas supply source 33 is connected to the bubbling pipe 32, and a mass flow controller 34 as a flow rate controller and front and rear valves 35 are interposed. In addition, a raw material gas delivery pipe 36 is inserted into the film forming raw material tank 31 from above, and the other end of the raw material gas delivery pipe 36 is connected to the first introduction path 11 of the shower head 10. A valve 37 is interposed in the source gas delivery pipe 36. The source gas delivery pipe 36 is provided with a heater 38 for preventing condensation of the film forming source gas. Then, by supplying Ar gas, which is a bubbling gas, to the film forming raw material, the film forming raw material is vaporized in the film forming raw material tank 31 by bubbling, and the generated film forming raw material gas is supplied to the raw material gas delivery pipe 36 and the first gas supply pipe 36. 1 is supplied into the shower head 10 through one introduction path 11.

  The bubbling pipe 32 and the raw material gas delivery pipe 36 are connected by a bypass pipe 48, and a valve 49 is interposed in the pipe 48. Valves 35a and 37a are provided on the downstream side of the connecting portion of the piping 48 in the bubbling piping 32 and the raw material gas delivery piping 36, respectively. Then, by closing the valves 35a and 37a and opening the valve 49, the Ar gas from the Ar gas supply source 33 passes through the bubbling pipe 32, the bypass pipe 48, and the source gas delivery pipe 36 into the chamber 1 as purge gas or the like. It is possible to supply.

A pipe 40 is connected to the second introduction path 12 of the shower head 10, and a valve 41 is provided in the pipe 40. The pipe 40 is branched into branch pipes 40a and 40b. An NH ₃ gas supply source 42 is connected to the branch pipe 40a, and an H ₂ gas supply source 43 is connected to the branch pipe 40b. The branch pipe 40a is provided with a mass flow controller 44 as a flow rate controller and a valve 45 before and after the mass flow controller 44, and the branch pipe 40b is provided with a mass flow controller 46 as a flow rate controller and a valve 47 before and after the mass flow controller 46. Has been. Incidentally, it is possible to use in place of NH _3, hydrazine or, NH ₃ derivatives, hydrazine derivatives.

  In addition, when performing plasma CVD by applying high-frequency power to the electrode 7 as necessary, a branch pipe is further added to the pipe 40, and the mass flow controller and its front and rear are connected to the branch pipe. It is preferable to provide an Ar gas supply source for plasma ignition through a valve.

  The film forming apparatus includes a control unit 50 that controls each component, specifically, a valve, a power source, a heater, a pump, and the like. The control unit 50 includes a process controller 51 including a microprocessor (computer), a user interface 52, and a storage unit 53. Each component of the film forming apparatus 100 is electrically connected to the process controller 51 and controlled. The user interface 52 is connected to the process controller 51, and visualizes the operation status of each component of the film forming apparatus and the keyboard on which the operator inputs commands to manage each component of the film forming apparatus. It consists of a display that displays it. The storage unit 53 is also connected to the process controller 51, and the storage unit 53 corresponds to a control program for realizing various processes executed by the film forming apparatus 100 under the control of the process controller 51 and processing conditions. A control program for causing each component of the film forming apparatus 100 to execute a predetermined process, that is, a process recipe, various databases, and the like are stored. The processing recipe is stored in a storage medium (not shown) in the storage unit 53. The storage medium may be a fixed medium such as a hard disk or a portable medium such as a CDROM, DVD, or flash memory. Moreover, you may make it transmit a recipe suitably from another apparatus via a dedicated line, for example.

  Then, if necessary, a predetermined processing recipe is called from the storage unit 53 by an instruction from the user interface 52 and executed by the process controller 51, so that the film forming apparatus 100 can control the process controller 51. Desired processing is performed.

  Next, a method for forming a metal film according to an embodiment of the present invention performed by the film forming apparatus 100 will be described. FIG. 2 is a diagram showing a film forming sequence at this time.

First, the gate valve 25 is opened, and the wafer W is loaded into the chamber 1 through the loading / unloading port 24 by a transfer device (not shown), and placed on the susceptor 2 that has been heated to the film formation temperature in advance by the heater 5. (Step 1). Next, prior to film formation, preheating of the first stage of the wafer W is performed (step 2). Preheating is a process for heating the wafer W on the susceptor 2 until the film formation temperature is reached before film formation. At this time, the inside of the chamber 1 is evacuated by the exhaust device 23 to bring the inside of the chamber 1 to a predetermined pressure, and nickel amidate (Ni-AMD) as a film forming material stored in the film forming material tank 31, for example, Ni (II) N, N'-di-tert-butylamidinate (Ni (II) (tBu-AMD) ₂ ) is vaporized by bubbling with Ar gas, and the raw material gas delivery pipe 36 and the first introduction path 11. A predetermined amount smaller than the amount at the time of film formation is supplied into the chamber 1 through the shower head 10. After a predetermined time has elapsed, the supply amount of Ni-AMD gas is increased to the amount during film formation, and second-stage preheating is performed (step 3). Thus, during the preheats 1 and 2 in steps 2 and 3, Ni-AMD gas, which is a film forming raw material gas, is supplied without supplying the reaction gas (reducing gas), and Ni-AMD is applied to the surface of the wafer W. Gas is adsorbed (Ni-AMD soak).

After elapse of a predetermined time, in addition to Ni-AMD gas, NH ₃ gas and H ₂ gas, which are reactive gases (reducing gas), are branched piping 40a, 40b, reactive gas supply piping 40, second introduction channel 12, and shower head. The nickel film is supplied into the chamber 1 through 10 and the nickel-AMD gas and the reactive gas (reducing gas) are reacted on the surface of the wafer W on the susceptor 2 to form a nickel film by thermal CVD (step 4). ). The temperature during the film forming process is preferably 160 to 230 ° C. Further, when forming the film, a nickel film may be formed by plasma CVD by applying high frequency power from the high frequency power source 29 to the electrode 27 in the susceptor 2 as necessary. At this time, hydrazine, an NH ₃ derivative, or a hydrazine derivative can be used instead of NH ₃ supplied as a reaction gas (reducing gas). Further, H ₂ gas is not essential, by supplying H ₂ gas as a reaction gas (reducing gas), it is possible to remove impurities in the film.

After a predetermined time has elapsed, the supply of Ni-AMD gas is stopped and post-processing is performed (step 5). Thereafter, the supply of NH ₃ gas and H ₂ gas is stopped, and the chamber 1 is evacuated to evacuate the chamber 1 1 is purged (step 6). Ar gas from the Ar gas supply source 33 may be supplied to the chamber 1 as needed during the purge. After the purge is completed, the gate valve is opened and the film-formed wafer is unloaded through the loading / unloading port 24.

In the main film formation in step 4 above, conventionally, after preheating, Ni-AMD gas, which is a film forming raw material gas, and a reactive gas (reducing gas) are simultaneously supplied into the chamber to form a film. When supplied simultaneously, the adsorptivity of the raw material is poor and the incubation time is long. On the other hand, when NH ₃ gas, which is a reactive gas (reducing gas), is first supplied and adsorbed (NH ₃ soak), and then Ni-AMD gas, which is a film forming raw material gas, is supplied, NH ₃ is formed in a certain temperature range. Although the film is readily adsorbed on the substrate and initial film formation is likely to occur, and the incubation time can be shortened, depending on the wafer temperature, it is difficult to adsorb and the effect of shortening the incubation time is reduced.

  On the other hand, when the Ni-AMD gas, which is the film forming raw material gas, is first supplied and the Ni-AMD gas is adsorbed (Ni-AMD soak) as in this embodiment, the Ni-AMD gas is used. Since it can be physically adsorbed on the wafer W, which is a substrate, and a nickel film is rapidly formed thereon, the incubation time can be shortened regardless of the conditions. For this reason, variation in the thickness of the nickel film can be suppressed, and film formation in a region where the film formation temperature is lower is possible.

This will be described with reference to FIG. FIG. 3 shows a case where a Si wafer whose surface is cleaned with dilute hydrofluoric acid is used as a substrate, and a nickel film is formed after performing a Ni-AMD soak according to the recipe shown in FIG. 2, and NH ₃ gas is supplied during preheating. It was obtained by depositing a nickel film after the NH ₃ soak in a diagram showing the relationship between film formation time and the nickel film thickness. In addition, the conditions at the time of performing these are as follows.
Ni-AMD soak
Preheat 1
Pressure: 665 Pa (5 Torr)
Ni-AMD supply amount: 100 mg / min
Ar gas flow rate: 400 mL / min (sccm)
Time: 90sec
Preheat 2
Pressure: 665 Pa (5 Torr)
Ni-AMD supply amount: 200 mg / min
Ar gas flow rate: 100 mL / min (sccm)
Time: 30sec
NH ₃ soak
Preheat 1
Pressure: 1333 Pa (10 Torr)
NH ₃ gas flow rate: 300 mL / min (sccm)
Time: 90sec
Preheat 2
Pressure: 665 Pa (5 Torr)
Ni-AMD supply amount: 200 mg / min
Ar gas flow rate: 100 mL / min (sccm)
NH ₃ gas flow rate: 300 mL / min (sccm)
Time: 30sec

The conditions for film formation were unified under the following conditions.
Pressure: 665 Pa (5 Torr)
Ni-AMD supply amount: 200 mg / min
Ar gas flow rate: 100 mL / min (sccm)
NH ₃ gas flow rate: 200 mL / min (sccm)
H ₂ gas flow rate: 75 mL / min (sccm)
Temperature: 220 ° C

As a result, as shown in FIG. 3, in the case of NH ₃ soak, almost no film is formed even after 120 seconds from the start of film formation, whereas in the case of Ni-AMM soak, the film is formed 30 seconds after the start of film formation. It was confirmed that the film started and the nickel film thickness increased in a short time. From this, it can be seen that by performing Ni-AMD soak, the initial film formation is started early and the incubation time can be shortened.

  FIG. 4 shows a scanning microscope (SEM) photograph of the surface in the case where the film formation time is 30 sec, 60 sec, and 120 sec after Ni-AMD soak. In the film formation time of 30 sec, nuclei are present sparsely, but during Ni-AMD soak, the initial film formation can be performed in a shorter time by increasing the supply amount of Ni-AMD or increasing the pressure. Incubation time can be further reduced.

  The Ni-AMD soak time is preferably 15 to 60 sec. If this time is less than 15 seconds, it is difficult to obtain the adsorption effect of Ni-AMD gas, and if it exceeds 60 seconds, the effect is saturated, and only the throughput is reduced. Note that the Ni-AMD soak is practically terminated when the preheating of the wafer W is terminated.

Next, adsorption of nickel amidinate will be described.
The nickel amidinate used as a film forming raw material is Ni (II) N, N′-di-tert-butylamidinate (Ni (II) (tBu-AMD) ₂ ) as an example (1 ).
That is, an amidinate ligand is bonded to Ni as a nucleus, and Ni substantially exists as Ni ²⁺ . The Ni-AMD soak is physically adsorbed on the wafer W in the state of molecules having such a structure or in a state where the molecules are decomposed in half.

Thus, in order to physically adsorb the nickel amidinate while maintaining the molecular state substantially, the temperature of the wafer W should be low. Nickel amidinate represented by Ni (II) N, N′-di-tert-butylamidinate (Ni (II) (tBu-AMD) ₂ ) starts to decompose at about 110 ° C., and 140 ° C. The above becomes difficult to adsorb.

  For this reason, as described above, it is preferable to start supplying the nickel amidinate gas before the wafer temperature is increased by preheating. For this reason, it is preferable to start supplying the nickel amidinate gas when the preheating of the wafer W is started. Specifically, it is preferable to start supplying the nickel amidinate gas within 30 seconds after the wafer W is placed on the susceptor 2 in the chamber 1. More preferably, it is within 5 sec. Once the nickel amidinate is adsorbed, there is no problem even if the wafer temperature is increased by preheating.

FIG. 5 shows the relationship between the film formation time and the nickel film thickness when Ni-AMD soak is performed before and after the wafer temperature rise. FIG. 5 also shows the results for NH ₃ soak. “Before temperature rise” in FIG. 5 is a case where the nickel amidate gas is supplied when the temperature of the wafer W has not substantially increased 5 seconds after the start of preheating 1, "Is the case where the nickel amidinate gas is supplied when the temperature of the wafer W after the preheating 1 has sufficiently increased. As shown in FIG. 5, when nickel amidinate is supplied after the wafer temperature rises, the initial film formation rate is about the same as NH ₃ soak, and the incubation time is long, but before the wafer temperature rises. It can be seen that when nickel amidinate is supplied, the initial film formation rate is large and the incubation time is short.

Next, preferable conditions for each step will be described.
Preheat 1 (Step 2)
Pressure: 665 to 1333 Pa (5 to 10 Torr)
Ni-AMD flow rate: 200 to 1000 mg / min
Ar gas flow rate: 100 to 500 mL / min (sccm)
Time: 5-60sec
Preheat 2 (Step 3)
Pressure: 665 to 1333 Pa (5 to 10 Torr)
Ni-AMD flow rate: 200 to 1000 mg / min
Ar gas flow rate: 100 to 500 mL / min (sccm)
Time: 0-15sec
Film formation process (step 4)
Pressure: 665 to 1333 Pa (5 to 10 Torr)
Ni-AMD supply amount: 200 to 1000 mg / min
Ar gas flow rate: 100 to 500 mL / min (sccm)
NH ₃ gas flow rate: 50 to 500 mL / min (sccm)
H ₂ gas flow rate: 10 to 500 mL / min (sccm)

The present invention can be variously modified without being limited to the above embodiment. For example, in the above embodiment, Ni (II) (tBu-AMD) ₂ is exemplified as the nickel amidinate constituting the film forming raw material. Good.

  The present invention is also applicable to the case where a metal film is formed using a metal amidinate compound such as Ti (titanium), Co (cobalt), Cu (copper), Ru (ruthenium), or Ta (tantalum). Applicable. In particular, cobalt amidinate has the same structure as nickel amidinate. When a cobalt film is formed using cobalt amidinate, a nickel film is formed using the nickel amidinate. It is considered that the same effect as in the case of filming can be obtained.

  Further, the structure of the film forming apparatus is not limited to that in the above embodiment, and the method for supplying the film forming raw material is not necessarily limited to bubbling as in the above embodiment, and various methods can be applied.

  Furthermore, although the case where the semiconductor wafer was used as a to-be-processed substrate was demonstrated, not only this but another board | substrates, such as a flat panel display (FPD) board | substrate, may be sufficient.

1; chamber 2; susceptor 5; heater 10, showerhead to 30; the gas supply mechanism 31; film forming material tank 42; NH ₃ gas supply source 43; _{H 2} gas supply source 50; the control unit 51; the process controller 53; storage unit W: Semiconductor wafer

Claims (7)

A substrate to be processed is disposed in a processing container, a metal amidinate-based compound gas as a film forming raw material and a reaction gas are supplied into the processing container, and these are reacted on a heated substrate to be processed substrate. A film forming method for forming a metal film on the substrate,
Prior to supplying the reaction gas, a metal amidinate compound gas is supplied into the processing vessel and adsorbed on the substrate to be processed, and then a reaction gas is supplied into the processing vessel in addition to the metal amidinate compound gas. A metal film forming method, comprising forming a metal film on a substrate to be processed.   The film formation is performed in a state where the substrate to be processed is placed on a susceptor, and the substrate to be processed is preheated on the susceptor prior to the film formation, and the preheating is started when the pretreatment is started. 2. The method for forming a metal film according to claim 1, wherein the supply of the metal amidinate compound gas is started.   3. The method of forming a metal film according to claim 2, wherein the supply of the metal amidinate compound gas is started within 30 seconds after the substrate to be processed is placed on the susceptor.   The method for forming a metal film according to any one of claims 1 to 3, wherein the reaction gas is supplied 15 to 60 seconds after the metal amidinate compound gas is supplied.   5. The metal film according to claim 1, wherein the metal amidinate compound used as the film forming raw material is nickel amidinate, and the metal film is a nickel film. Film forming method.   The method for forming a metal film according to claim 5, wherein the heating temperature of the substrate to be processed is 160 to 230 ° C.   A storage medium that operates on a computer and stores a program for controlling a film forming apparatus, wherein the program is executed when the metal film forming method according to claim 1 is executed. A storage medium characterized by causing a computer to control the film forming apparatus.