JP2004083983A - Ti film forming method - Google Patents

Abstract

An object of the present invention is to provide a method for forming a Ti film which can sufficiently prevent generation of an RF reflected wave during film formation using a plasma CVD method.
First, a Ti film is formed in a process chamber 2 of a plasma CVD apparatus 1 (SP2), and the wafer W is unloaded from the process chamber 2 (SP3). Next, the inside of the process chamber 2 is cleaned with Cl ₂ gas (SP4). Subsequently, an H ₂ gas is supplied into the process chamber 2 to form a plasma (SP5). Thereby, residual substances such as Ni chloride which may be generated by performing the Cl ₂ gas cleaning can be removed from the process chamber 2.
[Selection] Fig. 2

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for forming a Ti film by a plasma CVD method.
[0002]
[Prior art]
In the manufacture of semiconductor devices, aluminum (Al) films and tungsten (W) films are widely used for filling contact holes, via holes, trenches and the like and forming wiring. When a metal film made of an Al film or a W film is formed, a mixed film of a titanium (Ti) film and a titanium nitride (TiN) film for protecting an underlayer is generally formed as a barrier metal film, and then formed thereon. A method of forming a metal film has been adopted.
[0003]
As a method for forming such a barrier metal film, a CVD method is widely used in addition to a PVD method using sputtering such as an IMP method. When the CVD method is used, specifically, for example, a method in which a Ti film is formed by a plasma CVD method and a TiN film is formed by a thermal CVD method is used. In the case where the barrier metal film is formed by a single-wafer process, the formation of the Ti film as the first layer of the mixed film has been conventionally performed, for example, in the following procedure.
[0004]
That is, first, a wafer provided with an underlayer is accommodated in a CVD chamber, and titanium tetrachloride (TiCl ₄ ) Gas and hydrogen (H ₂ ) A Ti film is formed by a plasma CVD method using a gas as a reaction gas. After that, the wafer is unloaded from the chamber and chlorine (Cl) is loaded in the chamber before loading the next wafer into the chamber. ₂ ) Purging with a gas, whereby the Ti-based compound or the like adhering to the inside of the chamber is peeled to some extent and discharged to the outside of the chamber.
[0005]
The latter Cl ₂ The gas purging is a process for preventing the Ti-based compound attached in the chamber from being a main factor of particles, and is a process for preventing the Ti-based compound. This is called processing. Such Cl ₂ By performing gas cleaning, it is possible to prevent particles from increasing with time when performing a Ti film deposition process on a large number of wafers, and particularly high film thickness uniformity and adhesion are required. The quality of the Ti film is maintained.
[0006]
[Problems to be solved by the invention]
However, we have found that Cl ₂ A detailed study of the above-described conventional Ti film forming method using gas cleaning revealed that high frequency (RF) reflected waves could be generated during the processing of a plurality of successive wafers. In this case, the growth thickness of the Ti film varies from wafer to wafer, and there is a possibility that a problem that uniformity of film quality between wafers cannot be ensured satisfactorily. In particular, in the case of single-wafer processing, continuous stability, which is an important factor in production, and tends to adversely affect maintenance of a high yield.
[0007]
Such RF reflected waves do not always tend to occur at the same time or at the same time in a processing campaign under the same conditions, and may not be highly reproducible because they may occur irregularly, discontinuously, or rarely. . Normally, a matching network including an impedance matching device is interposed between a shower head or the like of a chamber to which RF power is applied and the RF power source, thereby matching impedance and suppressing generation of reflected waves. . However, if the system is capable of switching the impedance stepwise, or if the reflected wave fluctuates greatly instantaneously even though continuous variable adjustment is possible, it may not be possible to sufficiently follow the change.
[0008]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a Ti film forming method capable of sufficiently preventing generation of an RF reflected wave at the time of film formation using a plasma CVD method.
[0009]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, obtained the following findings. As described above, the RF reflected wave sometimes occurs irregularly or discontinuously, and it is difficult to imagine that the cause is due to a change over time in the electric system or the chamber structure. On the other hand, the impedance on the chamber side is likely to be affected by the state of the plasma sheath. However, while supplying a source gas for Ti film formation at a constant flow rate and applying a constant output RF power while maintaining a constant pressure in the chamber, the ratio, concentration, It is hard to imagine that the energy distribution fluctuates dramatically.
[0010]
On the other hand, TiCl is used as a source gas for Ti film formation. ₄ And H ₂ When gas is used, TiCl ₄ Ti dissociated from the GaN deposits and grows on the wafer, and part of the Ti adheres to the chamber as a Ti-based compound. On the other hand, most of the dissociated Cl is H ₂ Combine with H originating in gas to form HCl, or Cl ₂ Most of the gas is exhausted out of the chamber. At this time, a part of Cl may be taken into the Ti film and may adhere to the chamber as a chlorine-based compound.
[0011]
These substances adhering to the chamber are formed by Cl, which is continuously performed after the Ti film is formed. ₂ It can be removed by cleaning the chamber by purging the gas. However, at this time Cl supplied in gaseous form ₂ There is a possibility that a product such as a chlorine-based compound generated by reacting with an adhering substance in the chamber or a constituent material of a structure in the chamber may remain in the chamber. When plasma for forming a Ti film is formed in a chamber where such a residual substance exists, active species originating from the residual substance may be generated. In such a case, the impedance on the chamber side may be drastically changed so that the matching circuit cannot follow.
[0012]
The present inventors have presumed that there is a close causal relationship between the generation of the residual chlorine-based material in the chamber and the RF reflected wave, and have completed the present invention based on the above findings. Was.
[0013]
That is, in the Ti film forming method according to the present invention, a Ti film forming step of accommodating a substrate in a chamber and forming a Ti film on the substrate by a plasma CVD method is performed. ₂ A method of treating a plurality of substrates by repeatedly performing a cleaning step of purging with a gas, the method including a plasma processing step of forming plasma in a chamber after performing the cleaning step.
[0014]
When such a Ti film forming method is used, for example, TiCl ₄ Gas and H ₂ A Ti film forming process using a gas as a source gas; ₂ A Ti film is formed by single-wafer processing in which a gas cleaning process is alternately performed. At this time, since the plasma processing step is performed between the cleaning step and the Ti film forming step for the next substrate, the inside of the chamber where residual substances such as chlorine-based compounds generated in the cleaning step may be exposed to the plasma. . As a result, the active species constituting the plasma attack the chlorine-based compounds and react with them to decompose and dissociate the compounds, thereby removing, as it were, “striking” from the chamber.
[0015]
As a result, a chemical species derived from a chlorine-based compound or a nickel (Ni) -based compound Is sufficiently suppressed from being contaminated by the chemical species derived from.
[0016]
Alternatively, separately from the viewpoint of processing a plurality of substrates in a single-wafer manner, if attention is paid to the Ti film forming process on each substrate, the Ti film forming method according to the present invention accommodates the substrate in a chamber and A method of forming a Ti film on a substrate, comprising: a cleaning step of purging the chamber with chlorine gas before accommodating the substrate in the chamber; and a plasma processing step of forming plasma in the chamber subjected to the cleaning step. And a Ti film forming step of forming a Ti film by a plasma CVD method while accommodating a substrate in a chamber subjected to a plasma processing step.
[0017]
Specifically, in the plasma processing step, H ₂ It is desirable to supply gas. In this way, in the plasma processing step, hydrogen ions (H ⁺ ) And hydrogen radicals (H ^* ) Is formed. As a result, chlorine ions (Cl ⁻ ) And chlorine radicals (Cl ^* ) Can be combined with the hydrogen active species, so that the efficiency of discharging residual substances out of the chamber is enhanced.
[0018]
Here, the present inventor conducted a more detailed study on the conventional Ti film forming method, and found that the following problems could occur in addition to the generation of the RF reflected wave.
[0019]
(1) Risk of metal contamination
When performing a Ti film forming process on a plurality of wafers using the conventional method, a significant amount of metal may adhere to the wafer, and rarely deviate from the allowable value of metal contamination. This tends to occur particularly when the number of processed sheets increases. In this case, it is necessary to increase the frequency of replacement of the process kit in the chamber, and in some cases, to change the material of the kit base material. In particular, the change of the kit base material is nothing less than a change in the process, and involves very great difficulties.
[0020]
Then, when an attempt was made to qualify and quantify the contaminated metal, it was found that nickel (Ni) was the main component. In general, a process kit such as a gas supply unit (shower head) provided in a plasma CVD chamber for Ti film formation is exposed to a high-temperature corrosive environment of 600 ° C. or more (for example, a temperature near a face plate of a shower head), and thus is deformed. In order to sufficiently prevent corrosion and corrosion, Ni is often used as a constituent material. In some cases, an aluminum material is used after being coated with Ni, but in order to impart sufficient resistance, a material obtained by cutting a solid Ni material is useful. From this, it was confirmed that the possibility that the contaminated metal was derived from the base material of the process kit was extremely high.
[0021]
In addition, even if a chamber having a shower head made of Ni is used, Cl ₂ Without cleaning by gas purging, it is difficult to maintain good film properties. ₂ The degree of contamination was lower than when gas cleaning was performed for each wafer process. As a result, the chlorine-based compound remaining in the chamber is combined with the base material component of the process kit, which is etched in a small amount at the time of forming the Ti film, for example, Ni _x Cl _y It is presumed that a Ni-based compound such as Ni chloride is generated, and this probably adheres to the wafer.
[0022]
(2) Foreign matter (including particles) may be generated
When performing a Ti film formation process on a plurality of wafers using the conventional method, particles may be generated particularly during the initial stage of the processing campaign, that is, for a certain period after the chamber is started. If such particles are present, they may hinder the subsequent process and adversely affect the yield.
[0023]
When the components of such particles were analyzed, those containing Ni in addition to the Ti-based compound were confirmed. This Ni is considered to be derived from the process kit in the chamber as described in (1) above. That is, Cl ₂ Ni separated from the base material of the kit by gas cleaning, and Ni-based compounds generated by reacting with other substances such as Cl, reach the wafer surface, and react with, for example, silicon (Si) on the wafer surface to become abnormal. It is supposed to grow.
[0024]
On the other hand, when a Ti film forming method of the present invention in which a plasma processing step is performed between a Ti film forming step and a cleaning step using a chamber having a shower head made of a Ni base material, metal contamination and foreign matter are generated. When the amount was measured, the Ni amount on the wafer surface was less than the lower limit of detection, and there was almost no foreign matter such as particles throughout the processing campaign. In particular, in the plasma processing step, H ₂ It has been confirmed that the effect can be further enhanced by using a gas.
[0025]
That is, in the present invention, TiCl is used as the chamber. ₄ This is extremely effective when using a gas-introduced reaction gas supply unit having at least a surface made of Ni. In this case, the active species (H ₂ In the case of plasma, the chlorine-based compound and the Ni-based compound described above are wiped off by the hydrogen active species, and the precursor which is a metal component and a foreign substance which can be deposited on the substrate to be subsequently processed is fundamentally removed. Is eliminated.
[0026]
Further, in the plasma processing step, it is more preferable that the plasma forming time is 5 to 20 seconds. By doing so, the chlorine-based compound and the Ni-based compound remaining in the chamber are sufficiently decomposed and removed, and at the same time, Ti which is deposited on a process kit in the chamber, particularly a face plate of a shower head, is useful in terms of film forming properties. Excessive removal of the system material is suppressed.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail. The positional relationship such as up, down, left, and right is based on the positional relationship shown in the drawings unless otherwise specified. The dimensional ratios in the drawings are not limited to the illustrated ratios.
[0028]
FIG. 1 is a schematic configuration diagram showing an example of a plasma CVD apparatus as a substrate processing apparatus for effectively implementing a Ti film forming method according to the present invention. In FIG. 1, the plasma CVD apparatus 1 includes a process chamber 2 (chamber). The process chamber 2 includes a chamber body 3 and a lid 4 provided on an upper portion of the chamber body 3. .
[0029]
A susceptor 5 for supporting a wafer W (substrate) is disposed in the process chamber 2, and a heater (not shown) for heating the wafer W is provided in the susceptor 5. The susceptor 5 constitutes a lower electrode made of a conductive metal such as nickel and is grounded to a predetermined potential.
[0030]
Further, a vacuum pump 7 is connected to a side wall of the process chamber 2 via a throttle valve 6. The vacuum pump 7 depressurizes the inside of the process chamber 2 and exhausts the inside of the process chamber 2. Further, on the side wall of the process chamber 2, a wafer loading port 3 a for loading and unloading the wafer W into and from the process chamber 2 is provided.
[0031]
On the other hand, the lid 4 is provided with a gas flow path 8 including a gas mixing section 8a, and the gas mixing section 8a is connected to each of the gas mixing sections 8a via a pipe provided with a mass flow controller (MFC; not shown). , TiCl ₄ Gas supply system 14, H ₂ Gas supply system 15, Cl ₂ Gas supply system 16, Ar gas supply system 17, and N ₂ A gas supply system 18 is connected. A blocker plate 9 having a plurality of gas introduction holes (not shown) is provided on the lower surface of the lid 4, and a face plate 10 is disposed below the blocker plate 9 so as to face the susceptor 5. Have been. A shower head (reactive gas supply unit) is constituted by the blocker plate 9, the face plate 10, and the space defined by these.
[0032]
The face plate 10 is a circular plate forming an upper electrode, and is formed of a conductive metal such as Ni or Al having a surface coated with Ni by plating or the like. The face plate 10 has a plurality of gas introduction holes 11, and the process gas sent from the gas flow path 8 via the blocker plate 9 is placed on the susceptor 5 through the gas introduction holes 11. The wafer W is supplied toward the wafer W. Further, the surface B of the face plate 10 facing the susceptor 5 is subjected to a rough surface treatment such as a blast treatment as necessary.
[0033]
A high frequency (RF) power supply 13 is connected to the face plate 10 via an impedance matching device 12. When the RF power supply 13 is turned on, a space S between the face plate 10 and the susceptor 5 has a constant frequency. RF power is applied to form a plasma.
[0034]
An example of a wafer processing method using the plasma CVD apparatus 1 configured as described above will be described below. FIG. 2 is a flowchart showing a procedure for forming a Ti film on a wafer W according to a preferred embodiment of the Ti film forming method of the present invention. First, in a state where the wafer W is not housed in the process chamber 2 or a state where a dummy wafer is housed, a source gas is supplied into the process chamber 2 under a predetermined Ti film forming condition, and the plasma CVD apparatus 1 is started. Thereafter, a processing campaign for a plurality of wafers W is started.
[0035]
Next, the wafer W is loaded (loaded) from the wafer loading port 3a by the wafer transfer robot (not shown) into the process chamber 2 in which the pressure is reduced to a desired degree of vacuum by the vacuum pump 7, and is heated to a desired temperature. (Step SP1; Ti film forming step).
[0036]
Next, TiCl using helium as a carrier gas ₄ Gas is TiCl ₄ While being supplied from the gas supply system 14, H ₂ Gas to H ₂ The gas is supplied from the gas supply system 15 into the process chamber 2. Note that TiCl ₄ Gas and H ₂ The gas is introduced into the process chamber 2 while the flow rate is controlled by an MFC (not shown) (hereinafter, the same applies to other gases). These TiCl ₄ Gas and H ₂ The gas is mixed in the gas mixing section 8a and supplied to the face plate 10 via the gas flow path 8 and the blocker plate 9. This mixed gas is uniformly diffused from each gas introduction hole 11 of the face plate 10 toward the wafer W.
[0037]
Next, while the pressure of the mixed gas introduced into the process chamber 2 is controlled by the throttle valve 6, the RF power supply 13 is turned on to apply RF power to the space S between the face plate 10 and the susceptor 5. Then, TiCl ₄ Gas and H ₂ The mixed gas with the gas is turned into plasma in the space S, and TiCl ₄ Gas and H ₂ The gas is dissociated and decomposed, and the binding reaction between the chlorine active species and the hydrogen active species is promoted. If the wafer W has an oxide film such as a Si oxide film formed thereon, a metal Ti film is formed on the wafer W (step SP2). Alternatively, if the wafer W is a pure Si wafer, when plasma is generated in the space S, a bonding reaction occurs at the Si-Ti interface in addition to the bonding reaction between the chlorine active species and the hydrogen active species, and the wafer W Titanium silicide (TiSi _x ) Is formed (step SP2).
[0038]
Step SP2 is performed until the thickness of the Ti film to be formed reaches a desired thickness required as the first layer of the barrier layer. For example, the thickness of the Ti film is generally 100 to 150 ° (1.0 × 10 ^-5 ~ 1.5 × 10 ^-5 mm), and depending on the type of device and the like, in some cases, 200 to 300 ° (2.0 × 10 ^-5 ~ 2.0 × 10 ^-5 mm) in some cases.
[0039]
In step SP2 for forming a Ti film in this manner, TiCl ₄ Cl inside is H ₂ Although it reacts with H derived from gas to become HCl and is mostly discharged to the outside of the process chamber 2, it is considered that a part of Cl is mixed into the Ti film. Therefore, in order to remove Cl in the Ti film and improve the adhesion of the TiN film as the second layer of the barrier film formed on the Ti film in the post-process of forming the Ti film to the Ti film, a predetermined film is formed. In order to form a thick Ti film, after performing step SP2 for a certain period of time, the surface of the Ti film is modified as necessary.
[0040]
In this case, first, TiCl ₄ Gas and H ₂ With the supply of gas stopped and the high-frequency power kept constant at a low output, H was introduced into the process chamber 2 of the plasma CVD apparatus. ₂ Gas supply system 15, Ar gas supply system 17, and N ₂ H from the gas supply system 18 ₂ Gas, Ar gas, and N ₂ The gas is supplied at a predetermined flow rate. These gases are mixed in the gas mixing section 8a to become a mixed gas, and are introduced into the space S through the shower head. At the same time, while the pressure of the mixed gas is controlled by the throttle valve 6, the output of the high-frequency power is increased to a constant value to convert the mixed gas into plasma. As a result, each gas is dissociated and decomposed, and particularly, the very surface of the Ti film is nitrided by the nitrogen active species.
[0041]
Next, H ₂ Gas and N ₂ The supply of gas is stopped, the supply of RF power 13 is stopped, and the application of RF power is stopped to extinguish the plasma. Then, the pressure in the process chamber 2 is adjusted by adjusting the throttle valve 6, and after the supply of the Ar gas is stopped, the wafer W is unloaded (unloaded) from the process chamber 2 (step SP3).
[0042]
Next, Cl 2 is introduced into the process chamber 2. ₂ Cl from gas supply system ₂ A gas is supplied at a constant flow rate, and an appropriate amount of Ar gas is supplied as needed. Thus, the inside of the process chamber 2 is ₂ By purging with a gas, dry cleaning of Ti, Ti-based compounds, and the like adhered to the surface of the process kit in the process chamber 2 in the Ti film forming step (Step SP2) (Step SP4; cleaning step). At this time, Cl ₂ The gas flow rate and the purge time are desirably set so that Ti or a Ti-based compound deposited on the surface B of the face plate 10 of the shower head or the like is not excessively removed.
[0043]
When the apparatus is started prior to the processing, an appropriate amount of Ti or a Ti-based compound is deposited on the face plate 10, so that a Ti film is formed on the wafer W to be processed first in the campaign. Good film thickness uniformity and film characteristics are ensured. Therefore, also in step SP4, by maintaining the state in which a certain amount of useful deposits exist on the face plate 10, the characteristics of the Ti film formed on the wafer W to be subsequently processed are favorably maintained. You.
[0044]
Next, Cl ₂ The supply of the gas is stopped, and only the Ar gas is continuously supplied to the process chamber 2 for a certain period of time, so that the Cl ₂ Purge gas. After that, while adjusting the Ar gas flow rate again, ₂ H from gas supply system 15 ₂ Supply gas. At this time, N ₂ Gas may be supplied simultaneously. These Ar gas and H ₂ The gas is mixed in the gas mixing section 8a, supplied to the face plate 10 side through the gas flow path 8 and the blocker plate 9, and uniformly diffused from each gas introduction hole 11 toward the wafer W.
[0045]
Subsequently, while the pressure of the mixed gas introduced into the process chamber 2 is controlled by the throttle valve 6, the RF power supply 13 is turned on to apply RF power to the space S between the face plate 10 and the susceptor 5. Thereby, Ar gas and H ₂ The mixed gas with the gas is turned into plasma in the space S, and each gas is dissociated and decomposed. In the process chamber 2, the purge gas Cl supplied in step SP4 is placed. ₂ In addition, a product generated by a reaction with a substance adhered to the process chamber 2 in the process up to that time and a base material constituting a process kit such as a shower head remains in the chamber. Such a residue includes Ni chloride (which is a chlorine-based compound and also a Ni-based compound) containing Ni and Cl, which are base materials of the face plate 10.
[0046]
In the process chamber 2, mainly hydrogen active species generated in the plasma attack such Ni chloride and the like, dissociate and decompose it, and desorb from the process kit such as the face plate 10. The substance thus desorbed is exhausted to the outside by exhausting the inside of the process chamber 2 (step SP5; plasma processing step). Further, it is conceivable that the chemical species including Cl and Ni generated at this time is further hydrogenated or reduced and shifts to a gaseous phase, thereby further improving the efficiency of removing adhering substances. As described above, by performing step SP5, the inside of the process chamber 2 becomes H ₂ It is cleaned with plasma.
[0047]
In step SP5, H ₂ From the viewpoint of sufficiently reducing metal contamination of the Ti film, the time during which plasma is formed by supplying gas (process time) is preferably 5 seconds or more, more preferably 10 seconds or more. . That is, if this time is less than 5 seconds, the removal of the remaining adhered substances in the process chamber 2 tends to be insufficient so that the metal contamination of the Ti film cannot be sufficiently suppressed.
[0048]
On the other hand, from the viewpoint of sufficiently suppressing the generation of an RF reflected wave in the Ti film forming step (step SP2), the process time of step SP5 is preferably set to 5 seconds or more, more preferably 10 seconds or more. That is, if this time is less than 5 seconds, the change in the impedance on the process chamber 2 side excessively increases and the generation of the RF reflected wave cannot be sufficiently prevented, so that the remaining adhering substance in the process chamber 2 is removed. It tends to be insufficient.
[0049]
On the other hand, from the viewpoint of sufficiently suppressing the generation of foreign matters such as particles, the process time of step SP5 is preferably set to 5 seconds or more, more preferably 10 seconds or more. That is, if the time is less than 5 seconds, the removal of the remaining adhered substances in the process chamber 2 tends to be insufficient such that generation of particles and abnormal growth of foreign substances on the wafer W cannot be sufficiently suppressed. is there.
[0050]
Further, it is desirable that the upper limit of the process time is preferably set to 20 seconds. If the time exceeds 20 seconds, useful deposits on the surface B of the face plate 10 may be excessively peeled off and removed, and the uniformity of the thickness of the Ti film and the barrier properties are impaired. There is a tendency. Note that the preferable range of the process time does not tend to largely depend on the frequency and output of the high frequency, the pressure and the temperature in the process chamber 2, and the like.
[0051]
Other process conditions in step SP5 include, for example:
・ RF output: 300W, 600W, etc.
・ H ₂ Gas flow rate: 3000 sccm, etc.
Ar gas flow rate: 5000 sccm, etc.
Can be exemplified. Note that Ar gas may be supplied to the rear surface side of the wafer W at a flow rate of, for example, 500 sccm.
[0052]
Then, after step SP5 is completed, it is determined whether or not all the processing target wafers W have been processed, that is, whether or not the processing campaign has been completed. If the campaign has been completed, the Ti film formation processing is completed. I do. On the other hand, if the campaign has not been completed, the process returns to step SP1 to process the next wafer W, and the processing is repeatedly performed according to the above-described procedure.
[0053]
Note that the wafer W after the formation of the Ti film, which is unloaded from the process chamber 2 in step SP3, is transferred to another apparatus such as a thermal CVD apparatus (not shown). ₄ And NH ₃ A TiN is formed on the Ti film by a thermochemical reaction using a raw material gas containing, and a barrier metal film is completed. Further, the wafer W on which the barrier metal film has been formed is transferred to still another thermal CVD apparatus (not shown), for example, tungsten hexafluoride (WF). ₆ ) And monosilane (SiH ₄ ) Or H ₂ A W film is formed on the TiN film by a thermochemical reaction using as a source gas.
[0054]
According to such a Ti film forming method, the inside of the process chamber 2 is H in step SP5. ₂ It is cleaned by plasma, and Cl in step SP4 ₂ At the time of gas cleaning, residual substances mainly attached to the process kit in the chamber and considered to be Ni chloride are discharged out of the chamber. Therefore, even if the plasma of the source gas for the Ti film is formed in the step SP2 of forming the Ti film on the subsequent wafer W, active species are generated from the Ni chloride and mixed into the plasma sheath.
[0055]
Therefore, a rapid change in the ratio, concentration, and energy distribution of the active species in the plasma can be suppressed. As a result, an impedance change that cannot be followed by the impedance matching device 12, that is, an impedance mismatch between the process chamber 2 and the RF power supply 13 is prevented, and generation of an RF reflected wave can be sufficiently suppressed. As a result, the uniformity of the growth thickness of the Ti film between the wafers W can be ensured well, and particularly important continuous stability can be achieved in the single-wafer processing, and a high yield can be maintained. Further, since the source of the RF reflected wave can be fundamentally eliminated, the frequency of replacing a process kit such as a shower head can be reduced, and it is not necessary to take measures such as strengthening a matching circuit including the impedance matching unit 12.
[0056]
In addition, since Ni chloride can be removed from the process chamber 2 and the generation of chemical species originating therefrom can be prevented during Ti film formation, contamination by elements due to such chemical species during Ti film formation, particularly Ni Metal contamination due to chloride-derived Ni can be reliably prevented. Therefore, it is possible to prevent a problem that the amount of metal contamination on the wafer exceeds an allowable value and a decrease in the number of continuously processed wafers W. Also in this regard, the frequency of replacing the process kit in the process chamber 2 can be reduced, and an excessive burden such as a process change due to a change in the material of the kit base material can be avoided.
[0057]
Further, since Ni chloride can be removed from the inside of the process chamber 2, it is possible to sufficiently suppress the generation of foreign substances such as particles during the formation of Ti. Therefore, it is possible to avoid obstacles in later steps and prevent a decrease in yield.
[0058]
Further, H in step SP5 ₂ When the process time for forming the plasma is equal to or longer than the above-described preferable lower limit, generation of an RF reflected wave, generation of metal contamination, and generation of foreign matter can be reliably prevented. Furthermore, if the process time is set to be equal to or less than the above-mentioned preferable upper limit value, the useful Ti-based compound attached and deposited on the surface B of the face plate 10 and the like is not excessively removed, so that the film characteristics of the Ti film can be improved. It has the advantage of being easy to maintain.
[0059]
As described above, the present invention has been described in detail based on the embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention. For example, the modification process of the Ti film that is performed after step SP2 may not be performed. Further, the apparatus for forming the Ti film may be a chamber system of a type other than the plasma CVD apparatus 1. Further, in step SP5, N ₂ It does not matter if gas is not supplied. ₂ The gas is a suitable plasma forming gas and is not essential, and another reducing gas may be used.
[0060]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
[0061]
<Example 1>
Under the procedure including step SP5 shown in FIG. 2 and the above-described process conditions, a Ti film having a thickness of about 200 ° was formed on the wafer W having the Si base layer.
[0062]
<Comparative Example 1>
A Ti film was formed on the wafer W in the same manner as in Example 1 except that Step SP5 was not performed.
[0063]
<Qualitative elemental analysis on wafer>
Each wafer W on which a Ti film was formed in Example 1 and Comparative Example 1 was subjected to total reflection X-ray fluorescence analysis (TRXRF). As a result, the Ni concentration on the wafer W of Example 1 was 10 ^Thirteen atoms / cm ² On the other hand, the Ni concentration on the wafer W of Comparative Example 1 was 10 ¹⁰ atoms / cm ² It was less than the order (lower detection limit). In addition, in the wafer W of Comparative Example 1, Cu, Co, and Fe were observed in trace amounts as other metal elements, whereas in the wafer W of Example 1, all of these elements were less than the lower detection limit. Was.
[0064]
【The invention's effect】
As described above, according to the Ti film forming method of the present invention, Cl ₂ Since cleaning by plasma processing in the chamber is performed after the cleaning with the gas and before the Ti film is formed on the substrate to be processed next, ₂ It is possible to remove from the inside of the chamber any chlorine-based compounds generated by cleaning with gas and remaining in the chamber and substances contained from compounds containing elements constituting the base material of the process kit. As a result, it is possible to prevent the generation of an RF reflected wave at the time of forming the Ti film, and also to prevent the occurrence of metal contamination and foreign matter.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an example of a plasma CVD apparatus as a substrate processing apparatus for effectively implementing a Ti film forming method according to the present invention.
FIG. 2 is a flowchart showing a procedure for forming a Ti film on a wafer W according to a preferred embodiment of the Ti film forming method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Plasma CVD apparatus, 2 ... Process chamber (chamber), 3 ... Chamber main body, 4 ... Lid, 5 ... Susceptor, 6 ... Throttle valve, 7 ... Vacuum pump, 8 ... Gas flow path, 9 ... Blocker plate, 10 ... Face plate, 11 ... Gas introduction hole, 12 ... Impedance matching device, 13 ... RF power supply, 14 ... TiCl ₄ Gas supply system, 15 ... H ₂ Gas supply system, 16 ... Cl ₂ Gas supply system, 17 ... Ar gas supply system, 18 ... N ₂ Gas supply system, W: wafer (substrate).

Claims (5)

A Ti film forming step of accommodating a substrate in a chamber and forming a Ti film on the substrate by a plasma CVD method, a cleaning step of purging the chamber with Cl ₂ gas with the substrate taken out of the chamber, A method of treating a plurality of substrates by repeatedly performing
A method of forming a Ti film, comprising: a plasma processing step of forming plasma in the chamber after performing the cleaning step. A method for housing a substrate in a chamber and forming a Ti film on the substrate,
Before accommodating the substrate in the chamber, a cleaning step of purging the chamber with chlorine gas;
A plasma processing step of forming plasma in the chamber subjected to the cleaning step,
A Ti film forming step of accommodating the substrate in a chamber subjected to the plasma processing step and forming the Ti film by a plasma CVD method;
A method for forming a Ti film, comprising: 3. The Ti film forming method according to claim 1, wherein a hydrogen gas is supplied into the chamber in the plasma processing step. As the chamber, a chamber having a reaction gas supply unit into which TiCl ₄ gas is introduced and at least a surface of which is made of Ni is used.
The method of forming a Ti film according to claim 1. In the plasma processing step, the plasma forming time is 5 to 20 seconds,
The method of forming a Ti film according to claim 1.

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