JP4858461B2 - Method for forming tungsten silicide film and method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a formation method for forming tungsten silicide (WSi _X ) on polycrystalline silicon or single crystal silicon in manufacturing a semiconductor device, and a manufacturing method of a semiconductor device to which this is applied.

A semiconductor device has a structure in which tungsten silicide (WSi _X ) is formed (deposited) on polycrystalline silicon (Poly Si; hereinafter referred to as “Poly Si” or “polysilicon” as appropriate) or single crystal silicon (Si) on a silicon wafer. To be applied. Tungsten silicide (WSi _X ) has the potential to achieve low electrical resistance, but the film deposition process is greatly affected by the surface and interface of polysilicon (Poly Si) or Si. It is difficult to stably deposit a film having excellent characteristics that is likely to occur, which has been a problem in mass production applications. Note that in this specification, the term “silicon wafer” is used to include polycrystalline silicon and single crystal silicon.

  The present invention has been made to solve the above-described problems, and has an object to stably obtain a tungsten silicide film having excellent performance.

A tungsten silicide film forming method according to the present invention includes a temperature raising step of placing a silicon wafer in an inert gas atmosphere and raising the temperature,
A first DCS treatment step in which dichlorosilane (DCS) is introduced to cause a surface reaction of the silicon wafer;
A first deposition step of introducing tungsten hexafluoride in addition to dichlorosilane to deposit tungsten silicide on the surface of the silicon wafer;
A second DCS treatment step that stops tungsten hexafluoride and introduces dichlorosilane;
A second deposition step for depositing tungsten silicide by introducing tungsten hexafluoride in addition to dichlorosilane;
A third DCS treatment step to stop tungsten hexafluoride and introduce dichlorosilane;
The treatment step of stopping the dichlorosilane and introducing the inert gas is carried out sequentially,
Introducing dichlorosilane from the first deposition step to the third DCS treatment step, the introduction amounts of dichlorosilane and tungsten hexafluoride in the first deposition step and the second deposition step are as follows. different Ri,
Prior to the first DCS treatment step, a surface treatment step of processing the surface of the silicon wafer into a surface state in which dichlorosilane is easily decomposed is performed.
The surface treatment step includes a step of treating the surface of the silicon wafer with a dilute hydrofluoric acid aqueous solution (DHF), and a step of drying while leaving an F component on the surface of the silicon wafer.

A tungsten silicide film forming method according to the present invention includes a temperature raising step of placing a silicon wafer in an inert gas atmosphere and raising the temperature,
A first DCS treatment step in which dichlorosilane (DCS) is introduced to cause a surface reaction of the silicon wafer;
A first deposition step of introducing tungsten hexafluoride in addition to dichlorosilane to deposit tungsten silicide on the surface of the silicon wafer;
A second DCS treatment step that stops tungsten hexafluoride and introduces dichlorosilane;
Sequentially performing a second deposition step of depositing tungsten silicide by introducing tungsten hexafluoride in addition to dichlorosilane,
Introducing dichlorosilane from the first deposition step to the second deposition step, the introduction amounts of dichlorosilane and tungsten hexafluoride in the first deposition step and the second deposition step are different. ,
Prior to the first DCS treatment step, a surface treatment step of processing the surface of the silicon wafer into a surface state in which dichlorosilane is easily decomposed is performed.
The surface treatment step includes a step of treating the surface of the silicon wafer with a dilute hydrofluoric acid aqueous solution (DHF), and a step of drying while leaving an F component on the surface of the silicon wafer.

According to the present invention, according to the present invention, the stability of the tungsten silicide film can be improved.
In addition, a tungsten silicide film having excellent adhesion to the silicon wafer can be formed.
In addition, a uniform tungsten silicide film can be formed on the entire surface of the silicon wafer.
Furthermore, it is possible to obtain a tungsten silicide film in which film peeling does not occur.

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding steps.
Embodiment 1 FIG.
FIG. 1 is a process flow diagram for explaining a method of forming a tungsten silicide film according to Embodiment 1 of the present invention.
In the first embodiment, in the process of depositing a tungsten silicide (WSi _X ) film on polysilicon (Poly Si) or Si single crystal, the kind and flow rate of gas are defined.

With reference to FIG. 1, a process for forming a tungsten silicide film will be described.
First, a Si wafer is introduced into a processing chamber (not shown). The temperature is maintained at 550 ° C. or higher in an Ar atmosphere under a pressure lower than 133 Pa (1 Torr) (step 1 in FIG. 1, temperature rising step).
Next, dichlorosilane (DCS: dichlorosilane: SiH ₂ Cl ₂ ) (hereinafter referred to as DCS as appropriate) is introduced so that the pressure becomes 199.5 ± 66.5 Pa (1.5 ± 0.5 Torr), and the Si wafer surface is prepared. (Step 2 in FIG. 1. First DCS treatment step, hereinafter referred to as DCS treatment 1 as appropriate). Although this process depends on the volume of the processing chamber, a flow rate of 300 sccm or more is secured in this embodiment. This temperature increase and the DCS treatment 1 have a reducing action on the surface of the silicon wafer.

Thereafter, WF ₆ (tungsten hexafluoride) is mixed to about 1/300 or less of the flow rate of DCS without changing the pressure while securing the flow rate of DCS (step 3 in FIG. 1, first deposition step, Hereinafter, this is referred to as DCS / WF ₆ introduction / deposition 1).
Subsequently, the flow rate of DCS is reduced to about 1/3 of about 100 sccm, and WF ₆ mixing is stopped at the same time. At this time, the pressure is reduced to 1 torr or less (step 4 in FIG. 1. Second DCS treatment step, hereinafter referred to as DCS treatment 2 as appropriate). Subsequent process steps are performed while maintaining this low pressure.

Immediately after the second DCS introduction step, the introduction of WF ₆ is started again while maintaining the introduction of DCS. Second WF ₆ introduction, it is desirable to ensure a more than three times the flow rate of the first time of introduction (in FIG. 1 step 5. second deposition step, following appropriate, referred to as DCS / WF ₆ introducing and depositing 2 ). In this step, tungsten silicide (WSi _X ) can be substantially chemically deposited (CVD: Chemical Vapor Deposition).

Subsequent to this substantial deposition step, the mixing of the WF ₆ is stopped, and the post-deposition surface treatment is performed while increasing the DCS flow rate by a factor of 2.5 (step 6 in FIG. 1, third DCS treatment step, Hereinafter, this is referred to as DCS treatment 3).
Finally, the introduction of DCS is also stopped, and the purge is performed only by introducing Ar (step 7 in FIG. 1).

FIG. 2 is a diagram showing the structure of a device to which the tungsten silicide film forming method according to this embodiment is actually applied. This will be described with reference to FIG.
Polysilicon (Poly Si) 22 was formed on the Si wafer 21, and simple surface treatment by DCS treatment 1 was performed thereon. By this treatment, a very small amount of Si remains at the interface at the molecular level, but this does not have a thickness as shown in FIG. Next, DCS / WF ₆ introduction / deposition step 1 was performed to form 100 タ ン グ ス テ ン tungsten silicide (WSi _X ) 23.

Further, after this, DCS treatment 2 was performed, followed by DCS / WF ₆ introduction / deposition 2 to form 600 タ ン グ ス テ ン tungsten silicide (WSi _X ) 24 having a composition different from the former. After this, DCS treatment 3 was performed and then purged. By adopting such a structure, stable characteristics were obtained, but the best characteristics were obtained when the structure after film formation was completed from the bottom of polysilicon (Poly Si) /WSi2.4/WSi2.5 It was when it was in order.

As described above, in this embodiment, a high tungsten component layer is deposited on the interface with the silicon wafer, and a low tungsten component layer is deposited on the high tungsten component layer to form a tungsten silicide film.
Further, the tungsten silicide film is preferably formed so that the ratio of tungsten atoms to silicon atoms is 2.4 or less in the high tungsten layer and 2.5 or more in the low tungsten layer. Further, it is preferable that the high tungsten layer is formed to be 2.2 or more.
It should be noted that a tungsten silicide film similar to the structure shown in FIG. 2 can also be obtained by the embodiments described later, but the film structure is represented here.

Some characteristics of the film formation process of this embodiment are as follows.
First, DCS treatment 1 and DCS / WF ₆ introduction / deposition 1 are performed at an atmospheric pressure 1.5 to 3.0 times the atmospheric pressure in the temperature raising step, DCS treatment 2 and DCS / WF ₆ introduction / deposition 2. carry out.
Further, the mixing ratio of WF ₆ and DCS in DCS / WF ₆ introduction / deposition 1 is set in the range of 1: 300 to 1: 500, and the mixing ratio of WF ₆ and DCS in DCS / WF ₆ introduction / deposition 2 is 1:30. The range is ˜1: 50.
Also, the DCS introduction amount in the DCS process 2 and the DCS / WF ₆ introduction / deposition 2 is made substantially equal.
Further, the flow rate ratio of DCS in DCS / WF ₆ introduction / deposition 1 and DCS / WF ₆ introduction / deposition 2 is set to a range of 1: 1 to 5: 1. More preferably, the range is 3: 1 to 5: 1.
In the present application, the liquid mixing ratio is represented by weight ratio, and the gas mixing ratio is represented by flow rate ratio or volume ratio, although not specifically mentioned.

  According to this embodiment described above, the stability of the formation of the tungsten silicide film can be improved. In addition, a tungsten silicide film having excellent adhesion to the silicon wafer can be formed. In addition, a uniform tungsten silicide film can be formed on the entire surface of the silicon wafer. Furthermore, it is possible to obtain a tungsten silicide film in which film peeling does not occur.

Embodiment 2. FIG.
FIG. 3 is a process flow diagram for illustrating a method of forming a tungsten silicide film according to the second embodiment of the present invention.
The present embodiment relates to a process for adjusting the surface of polysilicon (Poly Si) in advance so that DCS is easily decomposed when a tungsten silicide (WSi _X ) film is formed on polysilicon (Poly Si). is there.

With reference to FIG. 3, the formation process of the tungsten silicide film will be described.
First, polysilicon (Poly Si) is formed on a wafer (not shown).
While rotating the wafer at 300 rpm, 0.05% dilute hydrofluoric acid (DHF: dilute hydrofloride; hereinafter referred to as DHF as appropriate) is dropped from above (step 31 in FIG. 3). According to the experiment, when the substantial contact time between the polysilicon (Poly Si) surface and DHF reaches 30 seconds, the natural oxide film on the polysilicon (Poly Si) is sufficiently removed. Judged by the corner.

Conventionally, after removing the natural oxide film by DHF, it is usually washed with water, and after removing HF from the polysilicon (Poly Si), additional or continued washing with water is sufficient to bond with Si existing on the surface. Substituting and removing the F component.
However, in this embodiment, the washing time is shortened and the F component is intentionally left on the surface (step 32 in FIG. 3). Specifically, conventionally, the washing time is usually 300 seconds, but in this embodiment, for example, it is 15 seconds.
After this shortened water washing, the rotational speed is increased to 3000 rpm and shake-off drying is performed (step 33 in FIG. 3).
According to experiments, in another evaluation after this, it was found that about 17% of Si hands on the surface were terminated with F.

With this surface held, a wafer is loaded into an inert gas, DCS is introduced after heating, and DCS treatment 1 is performed. At this time, since F remained on the wafer surface, DCS was stably decomposed on the outermost surface, and a very small amount of Si-based sites remained, and tungsten silicide (WSi _X ) formed immediately above the polysilicon (Poly Adhesion with Si) improved. Thereafter, the process steps shown in Embodiment 1 were repeated, but the reproducibility of the film formation was good.

FIG. 4 is a diagram showing a process flow according to a modification of this embodiment. In this modified example, after removing the natural oxide film by DHF (step 41 in FIG. 4), the process is further accelerated. In this modification, water washing is not performed (step 42 in FIG. 4), and the DHF is spun off and dried. (Step 43 in FIG. 4). In this method, the desired result was obtained as in the case where the washing with water was shortened.
The DHF treatment in the present embodiment is not limited to the single wafer type.

  As described above, in this embodiment, prior to the DCS process 1, a surface treatment process for processing the surface of the silicon wafer into a surface state in which DCS is easily decomposed is performed. Moreover, the surface state is made to be Si termination by F. This makes it possible to form a tungsten silicide film with a stable film formation process and excellent adhesion.

Embodiment 3 FIG.
FIG. 5 is a sectional view showing an outline of a semiconductor wafer processing apparatus for forming a tungsten silicide film according to the third embodiment of the present invention. FIG. 6 shows a method for forming a tungsten silicide film according to the third embodiment. It is a process flow figure for explaining.
In this embodiment, when a tungsten silicide (WSi _X ) film is formed on polysilicon (Poly Si), an apparatus and process for adjusting the polysilicon (Poly Si) surface in advance so that DCS is easily decomposed It is about.

With reference to FIGS. 5 and 6, the process of forming the tungsten silicide film will be described.
First, polysilicon (Poly Si) is formed on the wafer 51. The wafer 51 is introduced into the processing chamber 52 (step 61 in FIG. 6). The chamber 52 actually consists of two parts, for example, an upper chamber 53 (first chamber) and a lower chamber 54 (second chamber), respectively. The upper chamber 53 and the lower chamber 54 are partitioned by a movable wall 55 (partition wall means).

  The wafer 51 is introduced into the chamber 52 from the loader 56, guided to the lower chamber 54 (step 62 in FIG. 6), and sealed with the movable wall 55. The lower chamber 54 has a wafer fixing table 57 (supporting means) that rotates after fixing the wafer 51, and the wafer 51 is held on the wafer fixing table 57 (step 63 in FIG. 6).

  In the lower chamber 54, a chemical solution discharge pipe 58 (chemical solution introduction means) is installed at the same time, and the discharge port 59 of the chemical solution discharge pipe 58 moves so as to be directly above the wafer 51. When the wafer fixing table 57 starts rotating and the rotational speed becomes constant at 300 rpm, 0.05% DHF (dilute hydrofloride) is dropped from above (step 64 in FIG. 6). Although not shown, a control means for controlling the type of chemical solution or processing gas to be introduced and the introduction time is provided.

  This rotational speed is determined by the ratio between the hydrophilic surface and the hydrophobic surface on the wafer, the flatness including the step, and the wafer diameter. In the case of the device applied in the present embodiment, the wraparound of the chemical solution and the etching A rotation speed of 300 rpm was appropriate from the viewpoint of uniformity.

  Since the natural oxide film on the polysilicon (Poly Si) is sufficiently removed when the substantial contact time between the polysilicon (Poly Si) surface of the wafer 51 and the DHF reaches 30 seconds, the chemical solution discharge pipe 58 Is stopped, the number of rotations of the wafer fixing table 57 is increased to 3000 rpm, and shake-off drying is performed.

With this surface held, the movable wall 55 is opened, and the wafer 51 is loaded into the upper chamber 53. The movable wall 55 is closed and Ar is introduced promptly.
Thereafter, the process shown in the first embodiment is performed.
Note that the processing apparatus shown in FIG. 5 can be used in other embodiments, and FIG. 5 will be referred to as appropriate thereafter.

Embodiment 4 FIG.
FIG. 7 is a process flow diagram for illustrating a method of forming a tungsten silicide film according to the fourth embodiment of the present invention.
In this embodiment, when a tungsten silicide (WSi _X ) film is formed on polysilicon (Poly Si), the surface of the polysilicon (Poly Si) is adjusted in advance by AHF (Anhydrous Hydro Floride) so that DCS is easily decomposed. It is about the process to keep.

With reference to FIG. 7, the process of forming the tungsten silicide film will be described. Refer to FIG. 5 for the processing apparatus.
First, polysilicon (Poly Si) is formed on the wafer 51 (not shown). The wafer 51 is introduced into the processing chamber 52 (step 71 in FIG. 7).

The wafer 51 is introduced from the loader 56 into the chamber 52 and sealed.
In the chamber, the natural oxide film existing on the polysilicon (Poly Si) surface of the wafer 51 is sufficiently removed by AHF gas (step 72 in FIG. 7). When the natural oxide film is sufficiently removed, the process shown in the first embodiment is performed while maintaining this surface.

  According to experiments, it was found that 20% or more of the wafer surface immediately after the AHF gas treatment was terminated by F. Since this effect has a higher termination rate than that shown in the second embodiment, it is inferred that a higher effect can be obtained. As a result of the actual film formation, the reliability related to adhesion was high as intended.

Incidentally, description has been given of the case using the AHF gas in the above, as the process gas, further, then in addition to the HF gas to be described, can be used NF ₃ gas or ClF ₃ gas.

Embodiment 5 FIG.
FIG. 8 is a process flow diagram for illustrating a method of forming a tungsten silicide film according to the fifth embodiment of the present invention.
In the fourth embodiment, very high adhesion stability was obtained, but when AHF was used, a delay time until the etching of the oxide film started sometimes occurred. This is because the reaction (a) when AHF etches SiO ₂ is
H ₂ O
4HF + 2SiO ₂ ⇒ SiF ₄ + 2H ₂ O ... (a)
And because it requires H ₂ O as an initiator.

The fifth embodiment is improved in order to solve this delay time problem and obtain a better process.
With reference to FIG. 8, the process of forming the tungsten silicide film will be described.
First, the temperature of the wafer is appropriately raised (step 81 in FIG. 8). Next, AHF is vented into the IPA and ionized in advance before reaching the wafer surface (step 82 in FIG. 8). By introducing the ionized HF gas, the delay time can be substantially eliminated, and a more uniform natural oxide film removability can be obtained.
Subsequently, the method of the first embodiment was applied, and a uniform tungsten silicide (WSi _X ) film could be formed on the entire wafer surface.

Embodiment 6 FIG.
FIG. 9 is a process flow diagram for illustrating a method of forming a tungsten silicide film according to the sixth embodiment of the present invention.
According to the fourth embodiment and the fifth embodiment, it is possible to provide a sufficiently stable process for the current device manufacturing. However, the sixth embodiment is a current product that is a future product. It is intended to provide a marginal process for the products inside.

With reference to FIG. 9, the formation process of the tungsten silicide film will be described.
In general, the reaction rate of a chemical reaction increases exponentially with temperature. In the present embodiment, after the wafer 51 is loaded into the chamber 52 and sealed, the film forming process is started. At this time, the temperature is raised to 120 ° C., for example (step 91 in FIG. 9). The natural oxide film on the surface is removed by passing HF gas under this temperature rise, and at the same time, the bond on the surface is terminated with F (step 92 in FIG. 9).

Subsequently, the film forming process described in the first embodiment is performed. This makes it possible to form a tungsten silicide (WSi _X ) film with higher adhesion in a shorter processing time.
In the above example, the HF gas is passed at an elevated temperature, but this may be conducted at a reduced pressure and / or at an elevated temperature.

Embodiment 7 FIG.
FIG. 10 is a process flow diagram for illustrating a method of forming a tungsten silicide film according to the seventh embodiment of the present invention.
In general, the semiconductor manufacturing process is preferably performed at a temperature as low as possible in order to avoid diffusion of impurities such as metals in the semiconductor and generation of stress. The above embodiment is intended to perform the natural oxide film removal process at the lowest possible temperature.
However, in some cases, heat treatment that does not exceed 850 ° C. is said to have no serious adverse effects.
In this embodiment, the natural oxide film is removed at an elevated temperature to obtain a uniform clean surface.

With reference to FIG. 10, the formation process of the tungsten silicide film will be described.
In this embodiment, after the wafer 51 is loaded into the chamber 52 and sealed, the film forming process is started. At this time, the temperature of the wafer 51 is first raised to, for example, 830 ° C. (step 101 in FIG. 10). The treatment is performed for about 1 minute through H ₂ gas at this temperature rise (step 102 in FIG. 10). This removes the natural oxide film on the surface and terminates the bond on the surface with H. Next, the film forming process described in Embodiment 1 is performed as it is. As a result, formation of a tungsten silicide (WSi _X ) film having higher adhesion can be realized in a shorter processing time.
In the above example, the HF gas is passed at an elevated temperature, but this may be conducted at a reduced pressure and / or at an increased temperature of 830 ° C.

Since this embodiment handles hydrogen at a high temperature, care must be taken in terms of safety.However, since the surface is completely terminated with hydrogen, a homogeneous clean surface can be obtained, and tungsten silicide (WSi _X ) The effect is that the initial deposition on the Si surface can be performed uniformly.

In the above description, the H2 gas treatment is performed by raising the temperature to 830 ° C., but this is effective if the treatment is performed in the range of 300 ° C. to 850 ° C.
In this embodiment, the DCS process 1 is performed after the H2 gas process. However, the DCS process 1 may be omitted and the DCS / WF ₆ introduction / deposition 1 may be continued.

Embodiment 8 FIG.
FIG. 11 is a process flow diagram for illustrating a method of forming a tungsten silicide film according to the eighth embodiment of the present invention.
The present embodiment relates to a process of intentionally uniformly covering a polysilicon (Poly Si) surface with a chemical oxide film in advance when a tungsten silicide (WSi _X ) film is formed on polysilicon (Poly Si). It is.

The problem with conventional tungsten silicide (WSi _X ) film formation is that when WF ₆ or the like is introduced and deposition of tungsten silicide (WSi _X ) is started, it grows after wet cleaning such as RCA cleaning once. The film was not uniformly grown in the plane. For this reason, tungsten silicide (WSi _X ) started to deposit on the Si surface and there was a place where deposition did not start on the same surface, so that the film was not uniformly deposited, causing film peeling and the like.
In this embodiment, this is prevented and the film is deposited uniformly.

With reference to FIG. 11, the process of forming the tungsten silicide film will be described. Refer to FIG. 5 for the processing apparatus.
In the present embodiment, a chemical solution containing 30% H ₂ O ₂ and simultaneously containing 0.005% HF is applied to the wafer 51 on which polysilicon (Poly Si) has been formed (step 111 in FIG. 11). As a result, the natural oxide film on the wafer surface is removed, a chemical oxide film is forcibly formed, and a chemical oxide film of several atomic layers is uniformly formed on the surface.

  A specific process will be described. A wafer 51 on which polysilicon (Poly Si) is formed is introduced into a chamber 52 from a loader 56 and sealed. The movable wall 55 is opened, the wafer 51 is guided to the lower chamber 54, held on the wafer fixing table 57, and the movable wall 55 is sealed.

While rotating the wafer 51, a chemical solution containing 30% H ₂ O ₂ and simultaneously containing 0.005% HF is applied from the chemical solution discharge pipe 58, and is substantially contacted for 3 minutes. To form.
Next, the number of rotations of the wafer fixing table 57 is increased to 3000 rpm, and swing-off drying is performed.
Next, the movable wall 55 is opened, and the wafer 51 is inserted into the upper chamber 53 and sealed with the movable wall 55. After that, film formation is performed by the process described in Embodiment Mode 1.

In this embodiment, tungsten silicide (WSi _X ) was deposited well from the initial stage, but the inventors have found that the wafer surface is uniformly uniform under the concentration conditions of this embodiment. This is thought to be due to the fact that a trace amount of F component remains in the chemical oxide film, which promotes the formation of Si sites on the surface by the first DCS.

Conventionally, after pretreatment, trace amounts of organic substances are adsorbed on the surface from the air and others, and are present at the interface between polysilicon (Poly Si) and tungsten silicide (WSi _X ). Although the film formation failure occurred, it is considered that the film formation stability is further improved because the chemical treatment of the present embodiment simultaneously solves this problem.
From the experimental example, prior to DCS / WF ₆ introduction / deposition 2, the outermost surface of the silicon wafer may be substantially covered with SiO ₂ having a molecular layer of 1.8 nm or less.

In the above example, the chemical solution in this embodiment is a mixed solution of H ₂ O ₂ and HF. However, the same effect can be obtained by using a chemical solution having an HF concentration of 0.005% containing 10 ppm of ozone instead. It was.

Embodiment 9 FIG.
FIG. 12 is a process flow diagram for illustrating a method of forming a tungsten silicide film according to the ninth embodiment of the present invention.
In this embodiment, when a tungsten silicide (WSi _X ) film is formed on polysilicon (Poly Si), a uniform chemical oxide film is previously formed on the polysilicon (Poly Si) surface and then removed. In particular, the present invention relates to a process in which polysilicon (Poly Si) exposed on the surface is etched by several atomic layers to be very clean and uniform.

The problem with the conventional tungsten silicide (WSi _X ) film formation is that, as described in the eighth embodiment, when WF ₆ or the like is introduced and deposition of tungsten silicide (WSi _X ) is started, RCA cleaning is performed once. The natural oxide film that grows after wet cleaning such as the above does not grow uniformly in the plane. For this reason, tungsten silicide (WSi _X ) started to deposit on the Si surface and there was a place where deposition did not start on the same surface, so that the film was not uniformly deposited, causing film peeling and the like.
In this embodiment, this is prevented and the film is deposited uniformly.

With reference to FIG. 12, the process of forming the tungsten silicide film will be described. Refer to FIG. 5 for the processing apparatus.
In the present embodiment, a chemical solution containing 3% H ₂ O ₂ and simultaneously containing 0.1% HF is applied to the wafer 51 on which polysilicon (Poly Si) has been formed (step 121 in FIG. 12). As a result, a chemical oxide film is forcibly formed on the wafer surface, and a chemical oxide film of several atomic layers is uniformly formed on the surface, while removing an etchant having a higher etching rate at the same time, Finally, the polysilicon (Poly Si) where F remains on the surface is exposed.

  Specifically, the process will be described. A wafer 51 on which polysilicon (Poly Si) is formed is introduced into a chamber 52 from a loader 56 and sealed. The movable wall 55 is opened, the wafer 51 is guided to the lower chamber 54, held on the wafer fixing table 57, and the movable wall 55 is sealed.

While rotating the wafer 51, a chemical solution containing 3% of H ₂ O ₂ and simultaneously containing 0.1% HF is applied from the chemical solution discharge pipe 58, preferably substantially in contact for 3 minutes to form a uniform chemical oxide film on the entire surface. Let it form.

Next, the number of rotations of the wafer fixing table 57 is increased to 3000 rpm, and swing-off drying is performed.
Next, the movable wall 55 is opened, and the wafer 51 is inserted into the upper chamber 53 and sealed with the movable wall 55. After that, film formation is performed by the process described in Embodiment Mode 1.

In this embodiment, tungsten silicide (WSi _X ) was deposited well from the initial stage, but the inventors have found that the wafer surface is uniformly uniform under the concentration conditions of this embodiment. This is considered to be due to the fact that a larger amount of the collected F component than that of the eighth embodiment remains on the surface, and the formation of Si sites by the first DCS on the surface was promoted.

Conventionally, after pretreatment, trace amounts of organic substances are adsorbed on the surface from the air and others, and are present at the interface between polysilicon (Poly Si) and tungsten silicide (WSi _X ). Although the film formation failure occurred, this problem was solved at the same time by the chemical treatment of the present embodiment, and it is considered that the film formation stability was further improved.
The chemical solution of the present embodiment was able to obtain the same effect even when a chemical solution containing 1 ppm of ozone was applied instead of 3% of H ₂ O ₂ as described above.
It can also be treated with a chemical solution in which a small amount of HF is contained in a solution in which hydrogen peroxide solution and ozone are dissolved.

Embodiment 10 FIG.
FIG. 13 is a process flow diagram for illustrating a method of forming a tungsten silicide film according to the tenth embodiment of the present invention.
In this embodiment, when a tungsten silicide (WSi _X ) film is formed on polysilicon (Poly Si), a uniform chemical oxide film is previously formed on the polysilicon (Poly Si) surface and then removed. Thus, the present invention relates to a process for making polysilicon exposed on the surface (Poly Si) to be very clean and uniform by etching several atomic layers.

The problem with the conventional tungsten silicide (WSi _X ) film formation is that once WF ₆ or the like is introduced and deposition of tungsten silicide (WSi _X ) is started, as described in the eighth and ninth embodiments. The natural oxide film that grows after wet cleaning such as RCA cleaning does not grow uniformly in the surface. For this reason, tungsten silicide (WSi _X ) started to deposit on the Si surface and there was a place where deposition did not start on the same surface, so that the film was not uniformly deposited, causing film peeling and the like.
In this embodiment, this is prevented and the film is deposited uniformly.

With reference to FIG. 13, the formation process of the tungsten silicide film will be described. Refer to FIG. 5 for the processing apparatus.
In this embodiment, a chemical solution containing only 30% of H ₂ O ₂ is applied to the wafer 51 on which polysilicon (Poly Si) has been formed (step 131 in FIG. 13). Thereby, a chemical oxide film is forcibly formed on the wafer surface, and a chemical oxide film of several atomic layers is uniformly formed on the surface.

  Specifically, the process will be described. A wafer 51 on which polysilicon (Poly Si) is formed is introduced into a chamber 52 from a loader 56 and sealed. The movable wall 55 is opened, the wafer 51 is guided to the lower chamber 54, held on the wafer fixing table 57, and the movable wall 55 is sealed.

While rotating the wafer 51, a chemical solution containing 30% of H ₂ O ₂ is applied from the chemical solution discharge tube 58 and is substantially brought into contact for 3 minutes to form a uniform chemical oxide film on the entire surface.
Next, the number of rotations of the wafer fixing table 57 is increased to 3000 rpm, and swing-off drying is performed.
Next, the movable wall 55 is opened, and the wafer 51 is inserted into the upper chamber 53 and sealed with the movable wall 55. After that, the film forming process shown in Embodiment Mode 1 is performed.

In this embodiment, tungsten silicide (WSi _X ) was deposited well from the initial stage, but the inventors have found that the wafer surface is uniformly uniform under the concentration conditions of this embodiment. I think that it was because it became.
Conventionally, after pretreatment, trace amounts of organic substances are adsorbed on the surface from the air and others, and are present at the interface between polysilicon (Poly Si) and tungsten silicide (WSi _X ). Although the film formation failure occurred, the inventor of the present application considers that this problem is also solved by the chemical treatment of the present embodiment, and thus the film formation stability is further improved.

Even when a chemical solution containing 10 ppm of ozone instead of 30% H ₂ O ₂ was applied as the chemical solution of the present embodiment, the same effect was obtained.
Moreover, it can also process with the process liquid which dissolved hydrogen peroxide water and ozone.

Embodiment 11 FIG.
FIG. 14 is a process flow diagram for illustrating a method of forming a tungsten silicide film according to the eleventh embodiment of the present invention.
In Embodiments 8 to 10, higher film formation stability can be obtained and the method is excellent. However, there are places where facilities and environments for sufficient wet cleaning are not prepared depending on the equipment installation location of the semiconductor manufacturing factory.
In the present embodiment, the process realized in the eighth to tenth embodiments is realized by a dry process.

With reference to FIG. 14, the process of forming the tungsten silicide film will be described.
A wafer 51 on which polysilicon (Poly Si) is formed is introduced into a chamber 52 from a loader 56 and sealed. Once the sealed atmosphere is replaced with an inert gas, the temperature is raised to 450 ° C. or lower, for example, 400 ° C. (step 141 in FIG. 14). Next, a mixed gas of HF gas and ozone gas is introduced (step 142 in FIG. 14). The higher the temperature, the faster the reaction and the shorter the time. However, too high a temperature is not preferable because the reaction proceeds rapidly and the surface roughness increases. After that, DCS introduction and subsequent film formation process shown in Embodiment 1 are performed.
In the present embodiment, tungsten silicide (WSi _X ) was deposited well from the initial stage, and the film formation stability was improved.

According to the present embodiment, it is possible to deposit tungsten silicide (WSi _X ) that is more stable than conventional ones while suppressing a large additional cost related to power and environment by a dry process. Further, since the movement between the chambers can be omitted, the total process time can be shortened, the throughput can be improved, and the productivity can be improved.
In the above, the description has been given of the case using the mixed gas of ozone and HF gas, which can also be a mixed gas of a mixed gas or H ₂ O vapor and HF gas, the oxygen gas and HF gas . Further, 0.001 to 0.5% of HF gas may be contained in ozone gas, oxygen gas or H ₂ O vapor.

Embodiment 12 FIG.
FIG. 15 is a process flow diagram for illustrating a method of forming a tungsten silicide film according to the twelfth embodiment of the present invention.
In the eleventh embodiment, the cleaning of the surface and the termination of F are realized by an equilibrium reaction between oxidation and etching by mixing ozone gas and HF gas. However, when polysilicon is contained in polysilicon (Poly Si), etc. On the other hand, due to the increased surface roughness due to accelerated etching, a phenomenon of poor adhesion was observed.
In this case, this embodiment is intended to provide a process in which the process realized in the eighth to tenth embodiments is realized by a dry process and the film formation stability is improved.

With reference to FIG. 15, the process of forming the tungsten silicide film will be described.
A wafer 51 on which polysilicon (Poly Si) is formed is introduced into a chamber 52 from a loader 56 and sealed. Once the sealed atmosphere is replaced with an inert gas, the temperature is raised to 450 ° C. or lower, for example, 450 ° C. (step 151 in FIG. 15). Next, only ozone gas is introduced without supplying HF gas (step 152 in FIG. 15). After that, DCS introduction and subsequent film formation process shown in Embodiment 1 are performed.

  As described above, in this embodiment, only the removal of organic substances by ozone gas and the formation of an ultrathin oxide film are performed prior to the introduction of DCS shown in Embodiment 1 without supplying HF gas. As a result, it was confirmed that adhesion was obtained even when P was contained in polysilicon (Poly Si).

A similar effect was also obtained by changing the introduced gas of the present embodiment from ozone to oxygen. Although the effect was higher with ozone, oxygen can be easily obtained in the semiconductor line, so from the viewpoint of versatility, it is considered that the use of oxygen greatly contributes to production.
Furthermore, although introduction of water vapor was attempted and subtle flow rate control was required, a similar effect was obtained, so water vapor may be used instead of ozone.

Embodiment 13 FIG.
The method for forming a tungsten silicide film described in the above embodiments can be used in various semiconductor device manufacturing processes.
In a semiconductor device such as a memory device, it can be effectively used as a low-resistance conductive film for forming wiring such as a gate electrode, a bit line, and a word line.
The present invention includes the formation of any of the tungsten silicide films described above in the manufacturing process of the semiconductor device. The present invention also includes a tungsten silicide film formed by any one of the forming methods described above in a semiconductor device.

It is a process flow for demonstrating the formation method of the tungsten silicide film | membrane by Embodiment 1 of this invention. It is a figure which shows the structure of the device which formed the tungsten silicide film | membrane by Embodiment 1 of this invention. It is a process flow figure for demonstrating the formation method of the tungsten silicide film | membrane by Embodiment 2 of this invention. It is a figure which shows the process flow by the modification of Embodiment 2 of this invention. It is sectional drawing which shows the outline | summary of the semiconductor wafer processing apparatus for forming tungsten silicide film | membrane by Embodiment 3 of this invention. It is a process flowchart for demonstrating the formation method of the tungsten silicide film | membrane by this Embodiment 3. It is a process flowchart for demonstrating the formation method of the tungsten silicide film | membrane by Embodiment 4 of this invention. It is a process flowchart for demonstrating the formation method of the tungsten silicide film | membrane by Embodiment 5 of this invention. It is a process flowchart for demonstrating the formation method of the tungsten silicide film | membrane by Embodiment 6 of this invention. It is a process flowchart for demonstrating the formation method of the tungsten silicide film | membrane by Embodiment 7 of this invention. It is a process flowchart for demonstrating the formation method of the tungsten silicide film | membrane by Embodiment 8 of this invention. It is a process flowchart for demonstrating the formation method of the tungsten silicide film | membrane by Embodiment 9 of this invention. It is a process flowchart for demonstrating the formation method of the tungsten silicide film | membrane by Embodiment 10 of this invention. It is a process flowchart for demonstrating the formation method of the tungsten silicide film | membrane by Embodiment 11 of this invention. It is a process flowchart for demonstrating the formation method of the tungsten silicide film | membrane by Embodiment 12 of this invention.

Explanation of symbols

  51 Wafer, 52 Chamber, 53 Upper chamber (first chamber), 54 Lower chamber (second chamber), 55 Movable wall (partition wall means), 56 Loader, 57 Wafer fixing base (support means), 58 Chemical solution discharge pipe (Chemical solution introduction means) 59 Discharge port.

Claims (6)

A temperature raising step of placing and heating the silicon wafer in an inert gas atmosphere;
A first DCS treatment step in which dichlorosilane (DCS) is introduced to cause a surface reaction of the silicon wafer;
A first deposition step of introducing tungsten hexafluoride in addition to dichlorosilane to deposit tungsten silicide on the surface of the silicon wafer;
A second DCS treatment step that stops tungsten hexafluoride and introduces dichlorosilane;
A second deposition step for depositing tungsten silicide by introducing tungsten hexafluoride in addition to dichlorosilane;
A third DCS treatment step to stop tungsten hexafluoride and introduce dichlorosilane;
The treatment step of stopping the dichlorosilane and introducing the inert gas is carried out sequentially,
Introducing dichlorosilane from the first deposition step to the third DCS treatment step, the introduction amounts of dichlorosilane and tungsten hexafluoride in the first deposition step and the second deposition step are as follows. different Ri,
Prior to the first DCS treatment step, a surface treatment step of processing the surface of the silicon wafer into a surface state in which dichlorosilane is easily decomposed is performed.
The tungsten silicide film characterized in that the surface treatment step includes a step of treating the surface of the silicon wafer with a dilute hydrofluoric acid aqueous solution (DHF) and a step of drying leaving an F component on the surface of the silicon wafer. Forming method.   2. The method for forming a tungsten silicide film according to claim 1, wherein the surface state is termination of Si by F (fluorine).   3. A method of manufacturing a semiconductor device, comprising a step of forming a tungsten silicide film by the forming method according to claim 1.   A temperature raising step of placing and heating the silicon wafer in an inert gas atmosphere;
  A first DCS treatment step in which dichlorosilane (DCS) is introduced to cause a surface reaction of the silicon wafer;
  A first deposition step of introducing tungsten hexafluoride in addition to dichlorosilane to deposit tungsten silicide on the surface of the silicon wafer;
  A second DCS treatment step that stops tungsten hexafluoride and introduces dichlorosilane;
  Sequentially performing a second deposition step of depositing tungsten silicide by introducing tungsten hexafluoride in addition to dichlorosilane,
  Introducing dichlorosilane from the first deposition step to the second deposition step, the introduction amounts of dichlorosilane and tungsten hexafluoride in the first deposition step and the second deposition step are different. ,
  Prior to the first DCS treatment step, a surface treatment step of processing the surface of the silicon wafer into a surface state in which dichlorosilane is easily decomposed is performed.
  The tungsten silicide film characterized in that the surface treatment step includes a step of treating the surface of the silicon wafer with a dilute hydrofluoric acid aqueous solution (DHF) and a step of drying leaving an F component on the surface of the silicon wafer. Forming method.   5. The method for forming a tungsten silicide film according to claim 4, wherein the surface state is Si termination by F (fluorine).   6. A method for manufacturing a semiconductor device, comprising a step of forming a tungsten silicide film according to the forming method according to claim 4.

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