JP2004214335A - Film deposition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film deposition method by which a metal film can be deposited at a practical film deposition speed using metal carbonyl without having a harmful effect on a base. <P>SOLUTION: In order to deposit a prescribed metal film such as a W film on a processed substrate using a metal carbonyl gas such as W(CO)<SB>6</SB>, the processed substrate is carried into a vacuum chamber (process 1), and is heated to a metal carbonyl gas decomposition temperature (process 2), and then a metal carbonyl gas is introduced into the chamber to form a first metal film on the processed substrate by thermal decomposition of the gas (process 4). Then, in addition to the metal carbonyl gas, hydrogen is also introduced into the chamber, and a second metal film is deposited on the first metal film by reaction between the metal carbonyl gas and hydrogen (process 5). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a film forming method for forming a metal film such as tungsten (W) on a semiconductor substrate in a semiconductor device manufacturing process.
[0002]
[Prior art]
In a semiconductor manufacturing process, W () is used as a material for embedding a contact hole or a via hole between wirings formed on a semiconductor wafer (hereinafter, simply referred to as a wafer) to be processed and as a material of an interdiffusion barrier thereof. Tungsten) is used.
[0003]
In the past, physical vapor deposition (PVD) was used as a film forming process for W. However, W is a high melting point metal, and it is difficult for PVD to cope with high coverage due to recent miniaturization of devices. For this reason, chemical vapor deposition (CVD) that can cope with high coverage and sufficiently cope with miniaturization of devices has been performed.
[0004]
Such a CVD-W film is formed by using, for example, tungsten hexafluoride (WF ₆ ) as a processing gas and H ₂ gas as a reducing gas, and reacting with WF ₆ + 3H ₂ → W + 6HF on the wafer. However, in recent years, the design rules have been increasingly miniaturized. When such an F-containing gas is used, the withstand voltage is reduced or the interface state changes due to F existing in the gate oxide film and at the interface. This causes an effect such as an increase in leakage current, and causes device failure.
[0005]
On the other hand, tungsten carbonyl (W (CO) ₆ ), which is an organometallic compound gas, is known as a processing gas during CVD-W film formation without using an F-containing gas (Patent Documents 1, 2, and 3). Non-Patent Document 1 describes that a metal film is formed by CVD using a metal carbonyl such as W (CO) ₆ . Further, Patent Document 4 discloses that a W film is formed on a semiconductor device by a CVD process using W (CO) ₆ . Metal carbonyls, such as W (CO) ₆ , are promising as source gases for CVD, as they do not cause any inconvenience to the device with F, such as WF ₆ .
[0006]
[Patent Document 1]
JP-A-2-225670 [Patent Document 2]
Japanese Patent Application Laid-Open No. 4-173976 [Patent Document 3]
JP-A-4-27136 [Patent Document 4]
Japanese Patent Application Laid-Open No. 2002-124488 [Non-Patent Document 1]
J. Vac. Scl. Technol. 14 (2), Mar / Apr 1996 pp. 415-424.
[Problems to be solved by the invention]
Incidentally, when forming a W film using W (CO) ₆ is to decompose W (CO) ₆ by thermal decomposition, only the thermal decomposition has a problem that it is not practical slow deposition rate. Such a problem can be solved by supplying hydrogen as a reducing substance, but in this case, hydrogen damages the base. Specifically, when a W film is formed using such a reaction to fill a contact hole or a via hole, an organic low dielectric constant film (Low-k film) is used as an interlayer insulating film. The film is eroded by hydrogen, and the dielectric constant increases.
[0008]
The present invention has been made in view of such circumstances, and uses a metal carbonyl such as W (CO) ₆ to form a metal film at a practical film formation rate without adversely affecting the underlayer. It is an object of the present invention to provide a film forming method that can perform the method.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention is a film forming method for forming a predetermined metal film on a substrate to be processed using a metal carbonyl gas, comprising: loading a substrate to be processed into a chamber; A step of introducing a metal carbonyl gas into the chamber while heating the processing substrate to a temperature at which the metal carbonyl gas can be decomposed, and forming a first metal film by thermal decomposition on the substrate to be processed; Forming a second metal film on the first metal layer by introducing hydrogen in addition to the carbonyl gas by a reaction between the metal carbonyl gas and hydrogen. I will provide a.
[0010]
As described above, after the first metal film is formed in a predetermined thickness on the substrate to be processed by the thermal decomposition of the metal carbonyl gas, the second metal film is formed thereon by the reaction between the metal carbonyl gas and hydrogen. Since it is formed, the first metal film due to thermal decomposition serves as a barrier to prevent hydrogen from entering the base. Therefore, the metal film can be formed at a practical film formation rate by the film formation by the reaction between the metal carbonyl gas and hydrogen without adversely affecting the underlayer. At this time, the thickness of the first metal film is preferably 1 nm or more, more preferably 2 nm or more, and preferably 8 nm or less, and more preferably 5 nm or less.
[0011]
In this case, the hydrogen used for the reaction with the metal carbonyl gas is preferably at least one of H ₂ gas, hydrogen ions, and hydrogen radicals. Examples of the metal _{carbonyl, W (CO) 6, Ni} (CO) 4, Mo (CO) 6, Co 2 (CO) 8, Rh 4 (CO) 12, Re 2 (CO) 10, Cr (CO) 6 , Ru ₃ (CO) ₁₂ can be used.
[0012]
The present invention also provides a film forming method for forming a tungsten (W) film on a substrate to be processed using a W (CO) ₆ gas, wherein the step of loading the substrate to be processed into a chamber includes:
A W (CO) ₆ gas is introduced into the chamber while the substrate to be processed is heated to 300 to 600 ° C. to thermally decompose the W (CO) ₆ gas to form a first W film on the substrate to be processed. And then, hydrogen is introduced into the chamber in addition to the W (CO) ₆ gas to form a second W film on the first W film by a reaction between the W (CO) ₆ gas and hydrogen. And a step of forming the film.
[0013]
Also in this case, the hydrogen used for the reaction with the metal carbonyl gas is preferably at least one of H ₂ gas, hydrogen ions, and hydrogen radicals. Further, when the W film is formed on the low dielectric constant material, the W film prevents hydrogen damage to the low dielectric constant material, which is particularly effective.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.
First, a first embodiment will be described. FIG. 1 is a cross-sectional view schematically showing one example of a CVD-W film forming apparatus for performing the film forming method of the present invention.
[0015]
The film forming apparatus 100 has a substantially cylindrical chamber 1 which is airtightly configured. A circular opening 22 is formed at the center of the bottom wall 1b of the chamber 1, and an exhaust chamber 23 that communicates with the opening 22 and protrudes downward is provided in the bottom wall 1b. In the chamber 1, a susceptor 2 for horizontally supporting a wafer W to be processed is provided. The susceptor 2 is supported by a cylindrical support member 3 extending upward from the center of the bottom of the exhaust chamber 23. A guide ring 4 for guiding the wafer W is provided at an outer edge of the susceptor 2. Further, a resistance heating type heater 5 is embedded in the susceptor 2, and the heater 5 is supplied with power from a heater power supply 6 to heat the susceptor 2, and heat the wafer W which is an object to be processed by the heat. I do. This heat causes the W (CO) ₆ gas to be thermally decomposed. At this time, the susceptor 2 is heated to a predetermined temperature between 300 and 600 ° C., which is convenient for film formation. A controller (not shown) is connected to the heater power supply 6, whereby the output of the heater 5 is controlled according to a signal from a temperature sensor (not shown). Also, a heater (not shown) is embedded in the wall of the chamber 1 so that the wall of the chamber 1 is heated to about 40 to 80 ° C.
[0016]
A shower head 10 is provided on a top wall 1 a of the chamber 1. A large number of gas discharge holes 10 b for discharging gas toward the susceptor 2 are formed in a shower plate 10 a below the shower head 10. An inlet 10c into which W (CO) ₆ gas is introduced from the pipe 12 is formed at an upper end of the shower head 10, and the inside thereof is a diffusion chamber 10d. Further, the shower plate 10a is provided with, for example, a concentric refrigerant flow path 10e in order to prevent the decomposition of W (CO) ₆ gas in the shower head 10, and the refrigerant is supplied from a refrigerant supply source (not shown). Refrigerant such as cooling water is supplied to the flow path 10e, and can be controlled at 20 to 100 ° C.
[0017]
The other end of the pipe 12 is inserted into a film-forming raw material container 13 containing a solid-state W (CO) ₆ raw material S as a film-forming raw material. A heater 13a is provided around the container 13 as heating means. A carrier gas pipe 14 is inserted into the container 13, and, for example, Ar gas is blown into the film forming material container 13 as a carrier gas from the carrier gas supply source 15 via the pipe 14, so that the solid W in the material container 13 is formed. The (CO) ₆ raw material S is heated and sublimated by the heater 13a to become W (CO) ₆ gas, which is carried by the carrier gas, supplied to the shower head 10 via the pipe 12, and further supplied to the chamber 1. . H ₂ gas may be used as the carrier gas. The pipe 14 is provided with a mass flow controller 16 and valves 17 before and after the mass flow controller 16. Further, the pipe 12 is provided with a flow meter 45 for grasping the flow rate thereof based on the amount of the W (CO) ₆ gas, and valves 17 before and after the flow meter. Further, a preflow line 41 is connected to the downstream side of the flow meter 45 of the pipe 12, and the preflow line 41 is connected to an exhaust pipe 24, which will be described later, and stably supplies the raw material gas into the chamber 1. Therefore, exhaust is performed for a predetermined time. Further, the preflow line 41 is provided with a valve 42 immediately downstream of a branch portion from the W (CO) ₆ gas pipe 12. A heater (not shown) is provided around the pipes 12, 14, 41, and is controlled to a temperature at which the W (CO) ₆ gas does not solidify, for example, 20 to 100 ° C, preferably 25 to 60 ° C.
[0018]
On the other hand, _{H 2} gas pipe 18 is connected to the pipe 12, the other end of the _{H 2} gas pipe 18 is connected to the _{H 2} gas supply source 19. H ₂ gas supply source 19 is arranged to supply H ₂ gas as a reducing agent. The H ₂ gas pipe 18 is provided with a mass flow controller 20 and valves 21 before and after the mass flow controller 20.
[0019]
The mass flow controllers 16 and 20 and the valves 17, 21 and 42 are controlled by the controller 40 so that the supply and stop of the carrier gas, the W (CO) ₆ gas and the H ₂ gas, and the flow rates thereof are controlled. A flow meter 45 for grasping the W (CO) ₆ gas flow rate is also connected to the controller 40, and the controller 40 adjusts the value of the flow meter 45 so as to obtain a desired W (CO) ₆ gas flow value. The mass flow controller 16 of the carrier gas is controlled on the basis of the control.
[0020]
An exhaust pipe 24 is connected to a side surface of the exhaust chamber 23, and an exhaust device 25 including a high-speed vacuum pump is connected to the exhaust pipe 24. By operating the exhaust device 25, the gas in the chamber 1 is uniformly discharged into the space 23a of the exhaust chamber 23, and the gas can be rapidly reduced to a predetermined degree of vacuum through the exhaust pipe 24. ing.
[0021]
The susceptor 2 is provided with three (only two of them are shown) wafer support pins 26 for supporting and raising and lowering the wafer W so as to be able to protrude and retract from the surface of the susceptor 2. It is fixed to the plate 27. Then, the wafer support pins 26 are moved up and down via a support plate 27 by a drive mechanism 28 such as an air cylinder.
[0022]
On the side wall of the chamber 1, a loading / unloading port 29 for loading / unloading the wafer W with / from a transfer chamber (not shown) adjacent to the film forming apparatus 100, and a gate valve 30 for opening / closing the loading / unloading port 29. Is provided.
[0023]
Next, a method for forming a W film according to an embodiment of the present invention using such a film forming apparatus will be described.
FIG. 2 is a flowchart showing the process at this time. First, the gate valve 30 is opened, and the wafer W is loaded into the chamber 1 from the loading / unloading port 29, and is placed on the susceptor 2 (Step 1). Next, the susceptor is heated by the heater 5, and the wafer W is heated to 300 to 600 ° C. by the heat (step 2), and the inside of the chamber 1 is evacuated by the vacuum pump of the exhaust device 25, and the pressure in the chamber 1 is reduced to 6 Vacuum exhaust to 0.7 Pa or less (step 3).
[0024]
Thereafter, the solid W (CO) ₆ raw material S contained in the film-forming raw material container 13 is sublimated by the heater 13a, and a carrier gas, for example, an Ar gas is blown into the film-forming raw material container 13 to generate the generated W (CO). _{The six} gases are carried by the carrier gas and introduced into the chamber 1 via the pipe 12 and the shower head 10, and the W (CO) ₆ gas is supplied to the surface of the wafer W for a predetermined time. As a result, thermal decomposition of the W (CO) ₆ gas occurs on the heated wafer W, and a first W film is formed on the wafer W by thermal decomposition (step 4).
[0025]
In the step 4 of forming the first W film by thermal decomposition without using H ₂ , the pressure in the chamber 1 is desirably 0.10 to 666.7 Pa. If the pressure exceeds 666.7 Pa, carbon as an impurity may be taken into the W film, and the specific resistance may be increased. On the other hand, if the pressure is less than 0.10 Pa, the deposition rate may be significantly reduced. The residence time of W (CO) ₆ gas is preferably 100 seconds or less. The W (CO) ₆ gas flow rate is preferably about 0.001 to 5 L / min.
[0026]
After step 4, the valve 21 is opened to introduce the H ₂ gas into the pipe 18 while the supply of the W (CO) ₆ gas is maintained. The H ₂ gas reaches the pipe 12 via the pipe 18, is mixed with the W (CO) ₆ gas therein, and is introduced into the chamber 1 via the shower head 10. Then, W is generated by a reaction between the W (CO) ₆ gas and the H ₂ gas, and a second W film is formed on the first W film by thermal decomposition (Step 5). By-products containing C, H, O generated by this reaction are exhausted.
[0027]
Also in forming the second W film by the reaction between the W (CO) ₆ gas and the H ₂ gas in the step 5, the pressure in the chamber 1 is desirably 0.10 to 666.7 Pa. Also, W _{(CO) 6} gas residence time and W _{(CO) 6} gas flow rate, the same range as in step 4 is preferred. Further, the flow rate of the _{H 2} gas is about 0.005~5L / min is preferred. Hydrogen is not limited to such a form of H ₂ gas, and for example, a plasma generating means such as an inductively coupled plasma (ICP) source or a remote plasma source is arranged in the pipe 18 so that hydrogen ions (H ⁺ ) and hydrogen radicals ( H ^* ) may be used, and these can further increase the reactivity. Hydrogen ions (H ⁺ ) and hydrogen radicals (H ^* ) may be directly introduced into the chamber 1 through another pipe.
[0028]
After deposition of the second W film is finished, W _{(CO) 6} to stop the supply of gas (step 6), W in the chamber 1 to maintain the _{H 2} gas supply from the _{H 2} gas supply source 19 ( (CO) ₆ gas is expelled (step 7). Then, the gate valve 30 is opened to unload the wafer W from the loading / unloading port 29 (Step 8). Thus, the W film forming process is completed.
[0029]
As described above, in the present invention, when forming a W film, the first W film is first formed by thermal decomposition, and then the second W film is formed by a reaction using hydrogen. A practical film formation rate can be obtained while preventing diffusion to the substrate.
[0030]
That is, by using hydrogen as the reducing substance, the film formation rate is significantly increased as compared with the case of only thermal decomposition, and a practical film formation rate can be obtained, but hydrogen may adversely affect the underlying film. Specifically, when the underlying film is a Low-k film, hydrogen pulls out C and O constituting the Low-k film, and the dielectric constant ε of the Low-k film increases. That is, the RC delay time becomes longer, and the response speed of the device becomes slower. On the other hand, by forming the first W film by thermal decomposition first, the film exhibits a barrier function, so that a practical deposition rate can be obtained without adversely affecting the underlying film. In order to exhibit such a function, it is preferable that the first W film has a thickness of 1 nm or more, more preferably 2 nm or more. However, if the thickness is too large, the first W film formed by thermal decomposition without using H ₂ has a high specific resistance. Therefore, the thickness is preferably 8 nm or less, more preferably 5 nm or less.
[0031]
Next, application examples of the W film of the present embodiment will be described with reference to FIGS. FIG. 3 shows an example of application to a contact portion, and FIG. 4 shows an example of application to a gate electrode portion.
FIG. 3 shows a case where a Low-k film 52 as an interlayer insulating film is formed on a Cu film 51 as a lower wiring, and a W film as a barrier layer is formed in a via hole 53 formed in the Low-k film 52. First, a first W film 54 is formed by thermal decomposition, and a second W film 55 is continuously formed thereon by a reaction using hydrogen. Next, a wiring layer 56 made of, for example, Cu is formed. In this case, if the second W film is formed by a reaction directly using hydrogen without using the first W film 54, hydrogen from the W film damages the Low-k film 52 and the film quality is reduced. However, by forming the first W film 54 by thermal decomposition, this functions as a hydrogen barrier layer, and the deterioration of the Low-k film 52 is prevented. Although the barrier property can be maintained only by the first W film 54, since the film formation rate is low and the resistance is high as described above, a sufficient barrier property of metal such as Cu is secured. In order to obtain a good film at a practical film formation rate, a second W film 55 having a high film formation rate and a low resistance is formed on the first W film 54.
[0032]
In FIG. 4A, an oxide film 72 and a High-k film 73 are formed on a Si substrate 71, a first W film 75 by thermal decomposition is formed thereon as a barrier layer, and a gate is formed thereon. A second W film 76 is formed by a reaction using hydrogen as an electrode. In this case, the hydrogen does not significantly affect the High-k film 73, but the barrier function of the first W film 75 suppresses the diffusion of hydrogen into the High-k film 73, so that a better result is obtained. Properties can be obtained. Further, the first W film 75 functions as a barrier for the second W film 76 which is a gate electrode. Reference numeral 74 indicates an interlayer insulating film made of TEOS or the like.
[0033]
In FIG. 4B, an oxide film 82 and a High-k film 83 are formed on a Si substrate 81, a first W film 85 is formed thereon by thermal decomposition, and hydrogen is used thereon. A second W film 86 is formed by the reaction, and the first and second W films 85 and 86 are used as barrier films. Next, a gate electrode 87 made of Cu or the like is formed thereon. Also in this case, the diffusion of hydrogen from the second W film 86 to the High-k film 83 is prevented by the first W film 85 due to thermal decomposition. Further, the first and second W films 85 and 86 exhibit a good barrier function for the gate electrode 87. When the gate electrode 87 is made of Cu, the barrier function of the first and second W films 85 and 86 against the gate electrode 87 is important. Reference numeral 84 denotes an interlayer insulating film made of TEOS or the like. When the gate electrode 87 is made of Cu, a Low-k film is used as the interlayer insulating film 84.
[0034]
The present invention can be variously modified without being limited to the above embodiment. For example, in the above embodiment, the case where the W film is formed using W (CO) ₆ as the metal carbonyl has been described. However, the present invention is not limited to this, and W (CO) ₆ , Ni (CO) ₄ , Mo ( At least one selected from CO) ₆ , Co ₂ (CO) ₈ , Rh ₄ (CO) ₁₂ , Re ₂ (CO) ₁₀ , Cr (CO) ₆ , and Ru ₃ (CO) ₁₂ can be employed. Accordingly, a metal such as W, Ni, Mo, Co, Rh, Re, Cr, and Ru can be formed.
[0035]
Further, the case where a semiconductor wafer is used as a substrate to be processed and a film is formed on a Low-k film or a High-k film formed thereon has been described. However, it is effective in all cases where a metal film is formed on a film in which hydrogen diffusion is a problem. Further, the substrate is not limited to a semiconductor wafer, but can be applied to other substrates such as an LCD substrate.
[0036]
【The invention's effect】
As described above, according to the present invention, after a first metal film is formed to a predetermined thickness on a substrate to be processed by thermal decomposition of a metal carbonyl gas, a metal carbonyl gas and hydrogen are formed thereon. Since the second metal film is formed by the reaction, the first metal film serves as a barrier to prevent hydrogen from entering the base. Therefore, the metal film can be formed at a practical film forming rate by the film formation by the reaction between the metal carbonyl gas and hydrogen without adversely affecting the underlayer.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing one example of a CVD-W film forming apparatus used in a film forming method of the present invention.
FIG. 2 is a flowchart showing steps of one embodiment of the present invention.
FIG. 3 is a sectional view showing a structure of a contact portion to which the present invention is applied.
FIG. 4 is a cross-sectional view showing a structure of a gate electrode portion to which the present invention is applied.
[Explanation of symbols]
1; chamber 2; susceptor 5; heater 10, showerhead to 12; line 13; film-forming raw material container 19; _{H 2} gas supply source 25; an exhaust device 54,75,85; first W film 55,76,86; Second W film W: semiconductor wafer

Claims (6)

A film forming method for forming a predetermined metal film on a substrate to be processed using a metal carbonyl gas,
Loading a substrate to be processed into the chamber;
A step of introducing a metal carbonyl gas into the chamber while heating the substrate to be decomposed by the metal carbonyl gas to form a first metal film on the substrate by thermal decomposition;
Forming a second metal film on the first metal layer by the reaction of the metal carbonyl gas and hydrogen on the first metal layer by introducing hydrogen into the chamber in addition to the metal carbonyl gas. Characteristic film forming method. The hydrogen film forming method according to claim 1, wherein the H ₂ gas, a hydrogen ion is at least one hydrogen radical. The metal carbonyl is W (CO) ₆ , Ni (CO) ₄ , Mo (CO) ₆ , Co ₂ (CO) ₈ , Rh ₄ (CO) ₁₂ , Re ₂ (CO) ₁₀ , Cr (CO) ₆ , _3. The film forming method according to claim 1, wherein the film is at least one selected from Ru ₃ (CO) _{12. 4} . A method for forming a tungsten (W) film on a substrate to be processed using a W (CO) ₆ gas,
Loading a substrate to be processed into the chamber;
A W (CO) ₆ gas is introduced into the chamber while the substrate to be processed is heated to 300 to 600 ° C. to thermally decompose the W (CO) ₆ gas to form a first W film on the substrate to be processed. Process and
Thereafter, the step of forming a second W film by reaction with on the first W film by introducing hydrogen into other W (CO) ₆ gas into the chamber, W (CO) ₆ gas and hydrogen A film forming method comprising: The hydrogen film forming method according to claim 1, wherein the H ₂ gas, a hydrogen ion is at least one hydrogen radical. 6. The film forming method according to claim 4, wherein the W film is formed on a low dielectric constant material or a high dielectric constant material.

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