Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/06—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of metallic material
  • C23C16/08—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of metallic material from metal halides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/02—Pretreatment of the material to be coated
  • C23C16/0272—Deposition of sub-layers, e.g. to promote the adhesion of the main coating
  • C23C16/0281—Deposition of sub-layers, e.g. to promote the adhesion of the main coating of metallic sub-layers
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/06—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of metallic material
  • C23C16/08—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of metallic material from metal halides
  • C23C16/14—Deposition of only one other metal element
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/40—Formation of materials, e.g. in the shape of layers or pillars of conductive or resistive materials
  • H10P14/418—Formation of materials, e.g. in the shape of layers or pillars of conductive or resistive materials the conductive layers comprising transition metals
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/40—Formation of materials, e.g. in the shape of layers or pillars of conductive or resistive materials
  • H10P14/42—Formation of materials, e.g. in the shape of layers or pillars of conductive or resistive materials using a gas or vapour
  • H10P14/43—Chemical deposition, e.g. chemical vapour deposition [CVD]

Definitions

• the present invention relates to a method for forming a tungsten layer formed on a surface of an object to be processed such as a semiconductor wafer and a laminated structure of the tungsten layer.
• W tungsten
• WS i tungsten silicide
• a thin film is formed by depositing a metal or a metal compound such as Ti, titanium (Ti), TiN (titanium nitride), or TiSi (titanium silicide).
• the H 2 reduction method is a method of depositing a W film at a temperature of about 400 to 450 ° C. using hydrogen as a reducing gas, for example, to fill holes on a wafer surface such as a concave portion between wirings. .
• WF S (six full Uz of tungsten down) are used.
• a case where a tungsten layer is formed for wiring, embedding, or both of them will be described as an example.
• the WF 6 gas which is the raw material gas, and the reducing gas such as silane or hydrogen gas are flowed little by little at first, and the nucleated crystal film of tungsten stainless steel which becomes the crystal seed on the wafer surface Grow.
• a large amount of the above-mentioned raw material gas or reducing gas is flowed to grow the main tungsten film at a high film forming rate using the above-mentioned nuclear crystal film as a seed. Let it. As a result, a tungsten layer having a desired thickness is obtained as a whole.
• FIG. 6 schematically shows the cross-sectional structure of the tungsten layer at this time.
• a tungsten core crystal film 2 and a main tungsten film 4 are sequentially laminated.
• FIG. 7 is a graph showing the relationship between the time and the film thickness in the film forming step.
• a nucleus crystal film forming step is performed after the pretreatment.
• the thickness of a film to be deposited is generally controlled by controlling the gas flow rate and time.
• the length of each of the incubation times Tl and ⁇ 2 described above is significantly affected by the surface condition of the semiconductor wafer, for example, the quality of a base film such as a TiN film that forms a base when a tungsten film is formed. It is difficult to control artificially.
• the target thickness of the nuclear crystal film 2 is set to 500 angstroms
• one of the incubation times T1 fluctuates, and in fact, as shown by the dashed line in FIG.
• the film thickness changes to 600 angstroms or 400 angstroms.
• the other incubation time T2 also varies, so that the substantial deposition time of the main tungsten film also varies.
• the finally required thickness of the tungsten layer is, for example, about 800 angstroms.
• This amount is the fluctuation amount of the nuclear crystal film 2 described above, for example, 100 It is much larger than Angstrom.
• the variation of the incubation time T2 is small compared to T1
• the influence on the total thickness of the tungsten layer is very small. Therefore, since the difference in the film thickness between the wafers does not become so large, the problem due to the substantial variation in the film forming time did not occur.
• multilayering of semiconductor integrated circuits has been promoted, and accordingly, various laminated films have been reduced in thickness. For example, in the case of the above-described tungsten layer, the target film thickness has been about 800 ⁇ in the past, but the target film thickness of 18 It has been reduced to about 0 Angstrom.
• the nucleation is caused by the fluctuation of the incubation time T 1 and T 2 as described above. If the thickness of the crystal film fluctuates in the range of, for example, about 400 to 600 angstroms, this fluctuation will be greatly reflected in the main tungsten film forming step as it is.
• the target thickness of the tungsten layer (100 angstroms) is, for example, more than 100% (100 angstroms) of soil. Large fluctuations occur. For this reason, there is a problem that the film thickness greatly differs between wafers, and it is difficult to make the film thickness uniform.
• the respective incubation times T1 and T2 where the film does not adhere it is difficult to further reduce the time required for forming the tungsten layer. In this case, it is conceivable to shorten the time of the entire nuclear crystal film forming process. However, if the time of this step is excessively shortened, the growth of the nuclear crystal film becomes insufficient, and the film growth may not be sufficiently performed in the subsequent step of forming the main tungsten film. Disclosure of the invention
• An object of the present invention is to eliminate the incubation time after the formation of a nucleus crystal film, to increase the overall film formation speed, and to improve the uniformity of the film thickness between the objects to be processed.
• An object of the present invention is to provide a method for forming a tungsten layer and a laminated structure of a tungsten layer, which can be enhanced.
• the present inventors have conducted intensive studies on the formation of a tungsten film. As a result, immediately after the step of forming the nucleus crystal film, the intermediate tungsten having a lower concentration of fluorine (F) gas in the processing gas than in the main tungsten film forming step was used. Intervention of the film formation step eliminates the incubation time that occurred immediately after the nucleation crystal film formation step, and has the knowledge that the overall film formation rate can be significantly improved. This has led to the present invention.
• F fluorine
• the present invention provides a method for forming a tungsten layer on the surface of an object to be processed while supplying a processing gas containing a source gas composed of a tungsten fluoride gas and a reducing gas for reducing the source gas.
• the incubation time that has conventionally occurred immediately after the step of forming a nuclear crystal film is eliminated, and the step of forming an intermediate tungsten film is replaced.
• this intermediate tungsten film forming step the flow rate ratio of the source gas to the reducing gas is made smaller than that in the main tungsten film forming step, so that the amount of fluorine gas, which is a hindrance to the reducing action, is relatively reduced.
• the reduction of the source gas is promoted. This allows the tungsten film to be deposited without the incubation time that occurred immediately after the nucleation film formation process. Therefore, the processing time can be shortened by increasing the average film forming speed as a whole.
• the concentration of fluorine in the processing gas in the step of forming the intermediate tungsten film is lower than the concentration of fluorine in the processing gas in the step of forming the main tungsten film.
• the intermediate tungsten film forming step is performed for about 10 seconds.
• the raw material gas is, for example, WF 6 gas.
• the reducing gas is, for example, hydrogen (H 2 ) gas.
• H 2 hydrogen
• the present invention provides a tungsten layer formed on a surface of an object to be processed while supplying a processing gas containing a source gas composed of a tungsten fluoride gas and a reducing gas for reducing the source gas.
• a processing gas containing a source gas composed of a tungsten fluoride gas and a reducing gas for reducing the source gas A nuclear crystal film of tungsten formed on the surface of the object to be processed; and a main tungsten film formed on the nuclear crystal film, and between the nuclear crystal film and the main tungsten film.
• FIG. 1 is a cross-sectional configuration diagram showing a film forming apparatus for performing a tungsten layer forming method according to the present invention
• FIG. 2 is a partially enlarged cross-sectional view showing a laminated structure of a tungsten layer according to the present invention.
• FIG. 3a is a table showing an example of film forming conditions in a method for forming a tungsten layer according to the present invention.
• FIG. 3B is a table showing film forming conditions in a conventional tungsten layer forming method
• FIG. 4 is a film forming process for explaining a tungsten layer forming method according to the present invention.
• Figure 5 is a graph showing flow ratio of WF 6 gas is compared profilin Ichiru fluorine concentration in the evening tungsten film when different
• FIG. 6 a is a graph showing the relationship between the flow ratio of WF 6 gas to H 2 and the fluorine concentration and C / V value
• FIG. 6 b is a table showing the relationship shown in FIG.
• FIG. 6 c is a schematic diagram for explaining the definition of the C / V value in FIG. 6 a
• FIG. 7 a is a graph showing the relationship between the flow rate ratio of WF 6 gas to H 2 and the deposition rate
• FIG. 7 b is a table showing the relationship shown in FIG.
• FIG. 8 is a graph showing the relationship between the processing temperature and the film formation rate in a case where the reaction rate is controlled and a case where the supply rate is controlled.
• FIG. 9a is a graph showing the relationship between the processing pressure and the film formation rate in a case where the reaction is controlled and a case where the supply is controlled,
• FIG. 9 b is a table showing the relationship shown in FIG. 9 a by specific numerical values
• FIG. 10 is a partially enlarged cross-sectional view showing a laminated structure of a tungsten layer formed on a conventional semiconductor wafer
• FIG. 11 is a graph showing the relationship between time and film thickness in the film forming process
• FIG. 12 is a view similar to FIG. 11 for explaining the influence of the incubation time when the target film thickness is small.
• FIG. 1 is a cross-sectional configuration diagram showing a film forming apparatus for performing a method for forming a tungsten layer according to the present invention.
• the film forming apparatus 14 has a processing container 16 formed of, for example, aluminum or the like into a cylindrical or box shape. Inside the processing container 16, a cylindrical reflector 18 standing from the bottom of the processing container is provided. On this reflector 18, the semiconductor A mounting table 22 for mounting the body wafer 1 is provided, for example, via a holding member 20 having an L-shaped cross section.
• the reflector 18 and the holding member 20 are made of a heat-transmissive material, for example, quartz.
• the mounting table 22 is made of, for example, a carbon material or an aluminum compound such as A1N having a thickness of about l mm.
• a plurality of, for example, three lift bins 24 are provided so as to rise upward with respect to the support member 26.
• the support member 26 is moved up and down by a push-up rod 28 penetrating the bottom of the processing container, so that the wafer 1 is moved by the lift pin 24 (through the lift pin hole 30 provided on the mounting table 22). It can be moved up and down.
• the lower end of the push-up rod 28 is connected to the actuator 34 via an extendable bellows 32 in order to keep the inside of the processing vessel 16 airtight.
• an approximately ring-shaped ceramic clamp ring along the contour shape of the wafer is provided on the peripheral portion of the mounting table 22.
• the clamp ring 38 is connected to the support member 26 via a support rod 40 that penetrates the holding member 20 in a loosely fitted state, and is moved up and down integrally with the lift pin 24. Has become.
• a coil panel 42 is provided on the support rod 40 between the holding member 20 and the support member 26. This assists the lowering of the clamp ring 38, etc., and ensures the clamping of the wafer.
• the lift pins 24, the support member 26, and the holding member 2 ° are also made of a heat ray transmitting member made of quartz.
• a transmission window 44 made of a heat ray transmission material such as quartz is provided airtightly at the bottom of the processing container directly below the mounting table 22.
• a box-shaped heating chamber 46 is provided so as to surround the transmission window 44.
• a plurality of heating lamps 48 as a heating unit are mounted on a turntable 5 ° also serving as a reflecting mirror.
• the turntable 50 is rotated by a rotary motor 54 provided at the bottom of the heating chamber 46 via a rotary shaft. Therefore, the heat rays emitted from the heating lamp 48 can be transmitted through the transmission window 44 to irradiate the lower surface of the mounting table 22 to heat it.
• a resistance heating heater may be provided instead of the heating lamp 48 as a heating means.
• a ring-shaped rectifying plate having a large number of rectifying holes 60 is provided on the outer peripheral side of the mounting table 22. 62 are supported by a cylindrical support column 64.
• a ring-shaped quartz attachment 66 is provided on the inner peripheral side of the current plate 62 so as to contact the outer peripheral portion of the clamp ring 38 and prevent gas from flowing thereunder.
• An exhaust port 68 is provided at the bottom below the current plate 62.
• An exhaust path 70 connected to a vacuum pump (not shown) is connected to the exhaust port 68 so that the inside of the processing container 16 can be maintained at a predetermined degree of vacuum.
• a gate valve 72 that is opened and closed when a wafer is loaded and unloaded is provided on a side wall of the processing container 16.
• a shower head 74 for introducing a processing gas or the like into the processing container 16 is provided on the processing container ceiling facing the mounting table 22.
• the shower head 74 has a head main body 76 formed into a circular box shape from, for example, aluminum or the like.
• a gas inlet 78 is provided at the ceiling of the head body 76.
• the gas inlets 78 are provided with gas required for processing via a gas passage, for example, WF 6 , A]? , S i H 4 , H 2 , N 2, etc., are connected in a flow controllable manner.
• the lower part 79 of the head body 76 is provided with a number of gas injection holes 80 for discharging the gas supplied into the head body 76 to the processing space S.
• These gas injection holes 80 are arranged on substantially the entire surface of the lower portion 79 of the head main body 76 to discharge gas over the surface of the wafer.
• a diffusion plate 84 having a large number of gas dispersion holes 82 is provided in the head main body 76 so as to supply gas more evenly to the wafer surface.
• FIG. 2 is a partially enlarged sectional view showing a laminated structure of a tungsten layer according to the present invention
• FIG. 3 is a graph showing a relationship between a time chart and a film thickness for explaining the method of the present invention.
• the case of the conventional method is also shown by a dashed line.
• the surface of a semiconductor wafer 1 of, for example, silicon (S i) single crystal as an object to be processed is provided with a tungsten nucleation crystal film 2 by the method of the present invention described later.
• the intermediate tungsten film 6 and the main tungsten film 4 are sequentially laminated. These three layers 2, 4, and 6 are used as a whole on the wafer 1 Layer is formed.
• a base film (not shown) such as, for example, TiN is formed as a NORMAL layer.
• the formation of such a tungsten layer is generally performed to form a wiring film, to bury a contact hole or a via hole, or to perform them simultaneously.
• the film forming process for the three films 2, 6, and 4 is performed substantially continuously in the same film forming apparatus. Next, a method for forming a tungsten layer will be specifically described.
• the gate valve 72 provided on the side wall of the processing container 16 is opened, and the wafer 1 is loaded into the processing container 16 by the transfer arm.
• the wafer 1 is transferred to the lift pins 24 by raising the lift pins 24.
• the lift pins 24 are lowered to place the wafer 1 on the mounting table 22.
• the peripheral portion of the wafer 1 is removed. Press and fix with clamp ring 3 8.
• a processing gas containing WF 6 (raw material gas), SiH 4 , H 2 (reducing gas), Ar, N 2 (diluting gas), etc. is supplied from a processing gas source (not shown) to the shower head section 7. 4. Supply a predetermined amount to 4 and mix. Then, the processing gas is supplied from the gas injection holes 80 on the lower surface of the head body 76 into the processing container 16 substantially uniformly. At the same time, the inside of the processing container 16 is set to a predetermined vacuum by sucking and exhausting the internal atmosphere from the exhaust port 68. In addition, heat is radiated while rotating a heating lamp 48 located below the mounting table 22.
• the emitted heat rays are transmitted through the transmission window 44 and then irradiate the back surface of the mounting table 22 to heat it. Since the mounting table 22 is very thin, about 1 mm as described above, it is quickly heated, and therefore, the wafer 1 mounted thereon can be quickly heated to a predetermined temperature. .
• the supplied processing gas causes a predetermined chemical reaction, and depending on the film forming conditions, for example, a tungsten nucleation crystal film 2, an intermediate tungsten film 6, and a main tungsten film 4 shown in FIG. 2 are deposited and formed on the surface of the wafer 1. Will be done.
• the step of forming a nucleus crystal film, the step of forming an intermediate tungsten film, and the step of forming a main tungsten film are sequentially and substantially continuously performed.
• the nuclear crystal film forming step is a step of forming a tungsten nuclear crystal film 2 on the surface of the wafer 1 as the object to be processed.
• the main tungsten film forming process includes This is a step of forming the main tungsten film 4 on the film 2.
• the flow ratio of WF 6 (source gas) to H 2 (reducing gas) is smaller between the nucleus crystal film forming step and the main tungsten film forming step than in the main tungsten film forming step.
• FIG. 3A shows an example of film forming conditions in each of the above steps when an 8-inch (20 cm) wafer is used.
• the core crystal film 2 and the intermediate tungsten film 6 are combined to form a 500 angstrom film
• the main tungsten film 4 is further formed to a 500 angstrom film
• a 1000 angstrom thick tungsten layer as a whole is formed.
• the gas flow rate and the film formation time are set with the aim of forming.
• Fig. 3b shows the film forming conditions in the case of the conventional film forming method.
• the semiconductor wafer 1 is subjected to a pretreatment for a predetermined time, for example, several tens of seconds. This pretreatment is performed with a small amount of H 2 , Ar, ⁇ 2 etc.
• the flow of 5 i ⁇ 4 forms a silicon core crystal. This pretreatment assists in the growth of the subsequently formed tungsten core crystal.
• the process proceeds to a nuclear crystal film forming step.
• SiH 4 and WF 6 gas are supplied together with Ar, Hz, and N 2 to reduce the WF 6 gas and form a tungsten core crystal film 2 (see FIG. 2).
• setting the flow rate of the WF 6 gas is very little 15 sc cm, temperature, pressures nucleus crystals are set to easily conditions to grow.
• the nuclear crystal film 2 starts to adhere and deposit after an incubation time T1, which is an indefinite period during which no film is formed. This is the same in the conventional method.
• the process After performing the nucleus crystal film forming process for a certain period of time, here, 25 seconds (45 seconds in the case of the conventional method), the process proceeds to the intermediate tungsten film forming process after performing a certain purging operation and the like. In this process, the temperature is reduced slightly to 420 ° C and the pressure is reduced to 10 ° C.
• the intermediate tungsten film 6 (see FIG. 2) is immediately formed without causing the incubation time T 2 which has conventionally occurred.
• the deposition rate at this time is higher than the deposition rate of the nuclear crystal film 2.
• This step of forming the intermediate tungsten film may be performed for a very short time, for example, about 8 seconds. The reason is that a low fluorine concentration on the outermost surface of the wafer before the main tungsten film 4 is formed is enough to make it difficult to generate an incubation time when the main tungsten film 4 is formed.
• the process proceeds to the main tungsten film forming step.
• the flow rate of the source gas WF 6 gas was significantly increased (to about three times less than that of the nuclear crystal film formation step), and the flow rate of the reducing gas H 2 gas was increased (the flow rate of the nuclear crystal film formation step). About half).
• the pressure and temperature conditions are the same as in the intermediate tungsten film forming step.
• the main tungsten film 4 is continuously formed in time from the formation of the intermediate tungsten film 6.
• the deposition time of the main tungsten film 4 is about 19 seconds, which is the same as the conventional method.
• the total film thickness of the tungsten layer obtained in a total processing time of 52 seconds is 1
• the film thickness was very close to the target film thickness (1,000 ⁇ ), which was about 020 ⁇ .
• a total of 64 seconds was only about 530 ⁇ .
• the intermediate tungsten film forming step in which the flow rate ratio of WF 6 in the processing gas is relatively reduced and the fluorine concentration is relatively low is carried out, thereby producing the conventional tungsten film.
• Incubation after the step of forming a nuclear crystal film, which has been performed, can be eliminated. Therefore, the average film forming speed as a whole can be increased, so that a tungsten film having a desired film thickness can be formed in a short time.
• the average film forming rate refers to an average film forming rate (two film thicknesses / film forming time) from the start of the core crystal film forming step to the end of the main tungsten film forming step.
• the temporally unstable incubation time T 2 can be eliminated, the overall thickness of the tungsten layer can be accurately determined even though the thickness is as thin as about 1000 ⁇ . Control becomes possible.
• FIG. 5 is a graph showing the fluorine concentration in the tungsten film when the flow rate of the WF 6 gas was changed.
• Curve A shows the profile of the fluorine concentration (atoms / cm 2 ) when the flow rates of WF 6 and H 2 are 80 sccm and 750 sccm, respectively.
• Curve B shows the profiles of WF 6 and H 2 3 shows the profile of the fluorine concentration when the film formation conditions were 20 sccm and 1900 sccm, respectively.
• the curve A having a larger flow ratio of WF 6 to H 2 has a higher fluorine (F) concentration in the tungsten (W) layer.
• the method essentially (removed as HF) H 2 gas at reducing WF 6 gas from a film-forming method, the flow ratio of WF 6 to H 2 is increased, the fluorine in the process gas It can be assumed that the relatively high concentration inhibits the formation of the tungsten film.
• FIG. 6 a in the intermediate tungsten film forming step, the flow ratio of WF 6 gas to H 2 and (WF e H 2), and the experimental result of examining the relationship between the fluorine concentration and C / V values are shown (Specific figures are shown in Figure 6b).
• the ratio (B / A) of the film thickness B at the bottom of the recess to the film thickness A at the surface is C / V value (%).
• the processing conditions other than the flow rates of WF 6 and H 2 and the flow rate ratio (WF 6 / H 2 ) are the same as those shown in FIG. 3a.
• FIG. 7a shows an experimental result of examining the relationship between the flow ratio (WF 6 / H 2 ) and the deposition rate in the intermediate tungsten film formation step under the same processing conditions (specifically, FIG. The values are as shown in Figure 7b).
• the film forming rate is in the range of 2300 to 2450 (angstrom / min). .
• a “supply-controlled state” is formed in which the film forming reaction does not progress in accordance with the supply of the processing gas.
• the deposition rate is in the range of 3600 to 3850 (angstrom / min).
• the flow rate ratio WF 6 / H is in the range of 0.053 or more
• the deposition rate is in the range of 3600 to 3850 (angstrom / min).
• a “reaction-controlled state” is formed in which the film forming reaction proceeds in accordance with the supply of the processing gas. It is considered that the boundary between these “supply-controlled state” and “reaction-controlled state” is around 0.04 in the flow ratio (WF 6 / H 2 ).
• FIG. 8 shows an experimental result of examining the relationship between the processing temperature and the film forming rate in a case where the reaction rate is limited and a case where the supply rate is limited.
• the reaction-controlled state flow rate ratio of 0.107 to 0.053
• the deposition rate increases as the processing temperature increases, but in the supply-controlled state (flow rate ratio of 0.0 105 to 0.027).
• the supply-controlled state flow rate ratio of 0.0 105 to 0.027
• Fig. 9a shows the experimental results of examining the relationship between the processing pressure and the film formation rate in the case of the reaction rate control and the case of the supply rate control. 9b).
• the reaction-controlled state flow rate ratio 0.107
• the supply-controlled state flow rate ratio In the case of 0.0 105
• the increase in deposition rate due to the processing pressure is extremely small.
• the flow ratio of the WF 6 gas to the H 2 gas in the intermediate tungsten film forming step is 0.04 or less.
• the intermediate stainless steel film forming step it is possible to form the intermediate stainless steel film having a small thickness variation due to processing conditions such as temperature and pressure while maintaining the above “supply-limiting state”.
• the present invention is not limited to the embodiment described above.
• the raw material gas is not limited to WF 6 gas as described above, it is also possible to have use other tungsten fluoride gas.
• the reducing gas is not limited to the above-described H 2 gas, and any other reducing gas can be used as long as it can reduce tungsten fluoride gas as a source gas.
• the object to be processed is not limited to a semiconductor wafer, and an LCD substrate, a glass substrate, or the like may be used as the object to be processed.

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