JP2004289082A - Method of forming high-dielectric-constant gate insulating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a high-quality high-dielectric-constant gate insulating film. <P>SOLUTION: The high-quality High-K gate insulating film which is dense and gives small gate leakage current can be formed by forming an interface layer of a silicon nitride film after cleaning a Si substrate, exposing the surface of the silicon nitride film to a mixed gas of O<SB>2</SB>gas and H<SB>2</SB>gas, H<SB>2</SB>O gas, or O<SB>2</SB>gas, depositing a high-dielectric-constant insulating film containing Hf, and carrying out an annealing process. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a silicon semiconductor device, and more particularly to a method for forming a high dielectric constant gate insulating film.
[0002]
[Prior art]
2. Description of the Related Art MOSFETs have been miniaturized along with recent technological developments for high integration and high speed in semiconductor devices. As the thickness of the gate insulating film is reduced with miniaturization, a problem such as an increase in gate leak current due to a tunnel current becomes apparent. In order to suppress this problem, a gate insulating film using a high dielectric constant material such as HfO ₂ and ZrO ₂ in the gate insulating film (hereinafter, referred to as High-K gate insulating film) by a thin SiO ₂ equivalent thickness ( A method of increasing the physical film thickness while realizing (EOT) has been studied. The following is known as a conventional method for forming a High-K gate insulating film (see Non-Patent Document 1).
[0003]
Hereinafter, a conventional example will be described with reference to FIG. FIG. 6 is a process flow diagram of a conventional example. First, using an Si substrate, after performing standard RCA cleaning and cleaning with hydrofluoric acid, an interface layer of a silicon nitride film is formed by treatment with NH ₃ gas at 700 ° C. for 10 seconds. Next, using the _{N 2} gas as a carrier gas for _C 16 _H 36 HfO _4, CVD of mixed with oxygen gas for 3 minutes at 500 ℃ (Chemical Vapor Deposition) processing, 4 nm a film thickness of about HfO ₂ film Is deposited. As a heat treatment after the deposition, an annealing treatment (post-deposition annealing treatment) is performed in a temperature range of 700 ° C. to 900 ° C. for 30 seconds in N ₂ gas. Next, amorphous silicon is deposited at 540 ° C. and doped at 900 ° C. using POCl ₃ . Thereafter, the activation treatment of the dopant of the gate electrode is performed at 900 ° C. to 1000 ° C. for 30 seconds to 60 seconds. By obtaining such a process, an n-type MOSFET is formed.
[0004]
[Non-patent document 1]
S. J. Lee et al. _{, "High Quality CVD HfO 2 Gate} Stack with Poly-Si Gate Electrode", International Electron Devices Meeting Technical Digest, 2000, p31.
[0005]
[Problems to be solved by the invention]
However, the above configuration has a problem that the gate leakage current is increased due to many defects in the film.
[0006]
The present invention has been made in view of the above problems, and provides a method for forming a High-K gate insulating film with few defects.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, a method of forming a high dielectric constant gate insulating film according to the present invention comprises the steps of: (a) cleaning a silicon substrate; and forming a silicon nitride film, a silicon oxynitride film or a silicon oxide film on the silicon substrate. Forming an interface layer consisting of: (b) exposing a gas containing at least oxygen to the interface layer; and (c) depositing a high dielectric constant insulating film on the interface layer after the step (c). (D), a step (e) of performing an annealing process on the high dielectric constant insulating film, and a step (f) of forming a gate electrode on the high dielectric constant insulating film after the step (e). It is characterized by the following.
[0008]
With this structure, a high-quality high-K gate insulating film which is dense and has low gate leakage current can be formed.
[0009]
In the above method for forming a high dielectric constant gate insulating film, the gas containing oxygen is preferably a mixed gas of oxygen gas and hydrogen gas, water vapor gas, or oxygen gas.
[0010]
In the above method for forming a high dielectric constant gate insulating film, it is preferable that in the step (c), a hydroxyl group is formed on the surface of the interface layer by exposing a gas containing oxygen to the interface layer.
[0011]
In the above method for forming a high dielectric constant gate insulating film, the high dielectric constant film is preferably an oxide film of a metal forming the high dielectric constant film.
[0012]
In the above-described method for forming a high dielectric constant gate insulating film, it is preferable that the high dielectric constant film is a silicate film made of silicon and a metal forming the high dielectric constant film.
[0013]
In the above method for forming a high dielectric constant gate insulating film, the metal is preferably hafnium or zirconium.
[0014]
In the above method for forming a high dielectric constant gate insulating film, the high dielectric constant film preferably further contains nitrogen.
[0015]
In the above method for forming a high dielectric constant gate insulating film, the high dielectric constant film is preferably formed by a chemical vapor deposition method.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 is a process flow chart of a method for forming a high dielectric constant gate insulating film in the present embodiment. First, using an Si substrate, after performing standard RCA cleaning and cleaning with hydrofluoric acid, an interface layer of a silicon nitride film is formed by treatment with NH ₃ gas at 700 ° C. for 10 seconds. Thereafter, a mixed gas of O ₂ gas and H ₂ gas, H ₂ O gas or O ₂ gas is exposed to the surface of the silicon nitride film. Next, an N ₂ gas is used as a carrier gas of C ₁₆ H ₃₆ HfO ₄ , mixed with an oxygen gas, and subjected to a CVD process at 500 ° C. for 3 minutes to deposit an HfO ₂ film having a thickness of about 4 nm. As a heat treatment after the deposition, an annealing treatment (post-deposition annealing treatment) is performed in a temperature range of 700 ° C. to 900 ° C. for 30 seconds in N ₂ gas.
[0018]
Next, amorphous silicon is deposited at 540 ° C. and doped at 900 ° C. using POCl ₃ . Thereafter, the activation treatment of the dopant of the gate electrode is performed at 900 ° C. to 1000 ° C. for 30 seconds to 60 seconds. By obtaining such a process, an n-type MOSFET is formed.
[0019]
FIG. 2 shows a change in the relative dielectric constant K according to the temperature of the annealing process (post-deposition annealing process) after the deposition of the HfO ₂ film in the conventional example. The relative dielectric constant K indicates an average value of the entire gate insulating film including both the interface layer and the HfO ₂ layer. In the case of the conventional example, the quality of the HfO ₂ film is poor, and when residual oxygen passes through the film during the post-deposition annealing, the Si substrate is oxidized to form a SiO ₂ layer having a low relative dielectric constant. As a result, the relative dielectric constant K of the entire gate insulating film is greatly reduced. In the conventional example, the change (decrease) in the relative dielectric constant K is 5.5.
[0020]
FIG. 3 shows a change in the relative dielectric constant K depending on the temperature of the annealing (post-deposition annealing) after the deposition of the HfO ₂ film in the present invention. In the case of the present invention, the HfO ₂ film has good film quality and can prevent the residual oxygen from permeating the film during the post-deposition annealing process. As a result, the change (decrease) in the relative dielectric constant K of the entire gate insulating film is reduced as compared with the case of the conventional example, and can be improved to 1.0.
[0021]
FIG. 4 shows a comparison of the gate leak current density depending on the thickness of the HfO ₂ film in the present invention and the conventional example. Note that the thickness of the HfO ₂ film was measured by an ellipsometry method, and the gate leak current density was measured by a leak current flowing through the insulating film when a voltage of −1 V was applied to the gate electrode. In the case of the present invention, the gate leak current density was reduced by about 4 to 5 digits as compared with the conventional example, and a very large improvement effect was exhibited.
[0022]
FIG. 5 shows a conceptual diagram of the surface treatment method according to the present invention. In step 1, an ultra-thin silicon nitride film (Si ₃ N ₄ ) is formed on the Si substrate by NH ₃ gas treatment. The outermost surface of the film is covered with Si—N—H bonds. Then, in step 2, a mixed gas of O ₂ gas and H ₂ gas, H ₂ O gas or O ₂ gas is exposed, and the bonding of the outermost surface of the film is changed from the bonding of Si—N—H to the bonding of Si—N—OH. Change to When a mixed gas of O ₂ gas and H ₂ gas is used in this step, OH groups are generated by the reaction in the gas, and the surface of the ultra-thin silicon nitride film (Si ₃ N ₄ ) is effectively replaced. I do. When H ₂ O gas is used, the H ₂ O gas is decomposed on the surface of the ultra-thin silicon nitride film (Si ₃ N ₄ ), and the generated OH groups effectively replace the surface. When O ₂ gas is used, the O ₂ gas reacts with the Si—N—H bond existing on the surface of the ultra-thin silicon nitride film (Si ₃ N ₄ ), and Si—N—O—H To rearrange and effectively cover the surface. Finally, as shown in Step 3, the outermost surface of the film is covered with OH groups.
[0023]
Thereafter, an HfO ₂ film having a thickness of about 4 nm is deposited by CVD. At this time, since the surface of the underlying ultra-thin silicon nitride film (Si ₃ N ₄ ) is covered with an OH group, the silicon nitride film (Si ₃ N ₄ ) and the upper HfO ₂ film are chemically formed. The HfO ₂ film is firmly bonded and the HfO ₂ film grows densely and with good film quality. As a result, the penetration of oxygen can be suppressed as shown in FIG. 3, and a high-quality gate insulating film having a low gate leak current as an electrical characteristic can be formed as shown in FIG.
[0024]
According to the present embodiment, after cleaning the Si substrate, an interface layer of the silicon nitride film is formed, and thereafter, a mixed gas of O ₂ gas and H ₂ gas, H ₂ O gas or O ₂ gas is applied to the surface of the silicon nitride film. To form a high-quality high-K gate insulating film that is dense and has a low gate leakage current by providing a structure for depositing a high dielectric constant insulating film containing Hf and performing an annealing process. it can.
[0025]
Note that the ultra-thin silicon nitride film (Si ₃ N ₄ ) on the Si substrate in the present embodiment is a high dielectric constant film having a diffusion barrier property to prevent a reaction in which silicon (Si) of the substrate is oxidized. ing. If an interface layer having a relative dielectric constant close to that of SiO ₂ is formed in the oxide layer of the Si substrate, the relative dielectric constant K of the film as a whole is extremely lowered, thereby preventing the oxidation of the Si substrate. The diffusion preventing layer between the Si substrate and the HfO ₂ film may be formed by a method such as thermal nitriding or plasma nitriding in a gas containing N. Further, a process may be provided in which a gas containing N is introduced into an initial portion of HfO ₂ vapor deposition and the Si substrate side is directly used as a nitrogen-containing high dielectric insulating film. In addition, when a diffusion prevention film such as Si ₃ N ₄ is formed on the Si substrate side before depositing the High-K material, it is effective to include H or the like in the diffusion prevention film.
[0026]
In the present embodiment, instead of exposing a mixed gas of O ₂ gas and H ₂ gas or H ₂ O gas to the surface of an ultra-thin silicon nitride film (Si ₃ N ₄ ) on the Si substrate, An ultra-thin silicon chemical oxide film (SiOx) or an ultra-thin silicon oxide film (SiO ₂ ) or a silicon oxynitride film (SiOxNy) is formed, and a mixed gas of O ₂ gas and H ₂ gas, H ₂ O The OH group may be terminated by exposing the gas, O ₂ gas, or H ₂ gas.
[0027]
In this embodiment, a high-dielectric-constant film having a second diffusion barrier property is provided on the High-K film, which is an HfO ₂ film, so that the gate electrode material, polysilicon and hafnium react more than necessary. Can be prevented, and a decrease in the relative dielectric constant K can be suppressed. The high dielectric constant film having the second diffusion barrier property contains nitrogen to enhance the barrier effect. Further, the diffusion prevention film on the HfO ₂ film can be formed by thermal nitridation or plasma nitridation in a gas containing nitrogen, or deposition of a silicon nitride layer. Further, a method in which nitrogen gas is introduced at the initial stage of gate electrode formation and the surface of HfO ₂ is nitrided is also effective. Alternatively, a nitrogen-containing gas may be introduced into the final portion of the HfO ₂ vapor deposition to form a nitrogen-containing high dielectric insulating film on the surface side. Further, nitrogen may be contained in the entire gate insulating film or in any part of the film.
[0028]
In the present embodiment, the description has been made using the HfO ₂ film. However, the effect of the present invention can be obtained by using a ZrO ₂ film instead. Further, the case where an element forming an oxide such as Si, Al, Ta, Ti, or La is mixed into the HfO ₂ film can be similarly performed. That is, since the High-K film can be generalized as a chemical reaction regardless of the composition or material at the time of deposition, the effect of the present invention is not limited to HfO ₂ and ZrO ₂ , and TiO ₂ , Ta ₂ O ₅ , La _{The present invention} is also applicable to ₂ O ₃ , CeO ₂ , Al ₂ O _3, BST, or the like, or a ternary oxide film (for example, HfxAlyO ₂ ), or a silicate film containing Si in these oxide films.
[0029]
Further, in the present embodiment, a liquid Hf source (C ₁₆ H ₃₆ HfO ₄ ) is used as a raw material for the HfO ₂ film, but the following raw materials can be used. When depositing by CVD method, TDEAH (Tetrakis diethylamido hafnium, tetrakis diethylamide _{hafnium, C 16 H 40 N 4 Hf} ), TDMAH (Tetrakis dimethylamino hafnium, tetrakis (dimethylamino) _{hafnium, C 8 H 24 N 4 Hf} ), Hf (MMP ) ₄ (Tetrakis 1-Methoxy-2-methyl-2-propoxy hafnium, tetrakis 1-methoxy-2-methyl-2-propoxyhafnium, Hf [OC (CH ₃ ) ₂ CH ₂ OCH ₃ ] ₄ ) or a solid source (eg, Hf (NO _{3) 4} ). Further, Hf metal, HfCl ₄ , Hft-butoxide, Hf nitrato or TDEA-Hf, etc. are used as Hf raw materials, and O ₂ , H ₂ O, NO, N ₂ O, NH _3, etc. are used as replacement gas raw materials, and each of them is alternated. The present invention can be similarly implemented by using the ALD method of exposing to water. Further, instead of the deposition by the CVD method, a plasma CVD method or a JVD (Jet Vapor Deposition) method can be similarly performed. Further, although O ₂ was used as the oxygen-containing gas, NO, N ₂ O, H ₂ O, O ₃ , or the like can be used in the same manner.
[0030]
In this embodiment, a metal may be used as the gate electrode material instead of polysilicon. For example, after nitriding the surface of the high dielectric constant film, Al / TiN (laminated), Ta, or metal nitride (TiN or TaN) may be formed. Note that Si or Ge may be mixed in the metal nitride gate electrode. _{Furthermore, Ti, SiGe, Ta, TaN} , TaSixNy, Ru, RuO 2, RuO, WN, Mo, MoO, MoN is equally capable of the like.
[0031]
【The invention's effect】
As described above, according to the present invention, an interface layer of a silicon nitride film is formed after cleaning a Si substrate, and then a mixed gas of O ₂ gas and H ₂ gas, H ₂ O gas or O ₂ gas is applied to the silicon nitride film. Forming a high-quality dense high-K gate insulating film having a low gate leakage current by exposing the surface and then depositing a high dielectric constant insulating film containing Hf and performing an annealing process. Can be.
[Brief description of the drawings]
FIG. 1 is a process flow diagram according to a first embodiment of the present invention. FIG. 2 is a diagram showing a relative dielectric constant and a post-deposition annealing temperature dependency in a conventional example. FIG. FIG. 4 is a diagram showing the dependency of the relative dielectric constant and the post-deposition annealing temperature. FIG. 4 is a diagram showing the dependency of the physical film thickness and the gate leak current density in the first embodiment of the present invention. FIG. 6 is a conceptual diagram of a surface treatment in the embodiment of the present invention.

Claims (8)

Cleaning the silicon substrate (a);
(B) forming an interface layer made of a silicon nitride film, a silicon oxynitride film or a silicon oxide film on the silicon substrate;
(C) exposing a gas containing at least oxygen to the interface layer;
(D) depositing a high dielectric constant insulating film on the interface layer after the step (c);
(E) performing an annealing process on the high dielectric constant insulating film;
Forming a gate electrode on the high dielectric constant insulating film after the step (e); and (f) forming a gate electrode on the high dielectric constant insulating film. The method of claim 1, wherein the gas containing oxygen is a mixed gas of oxygen gas and hydrogen gas, water vapor gas, or oxygen gas. 3. The high dielectric constant gate insulation according to claim 1, wherein in the step (c), a hydroxyl group is formed on a surface of the interface layer by exposing the gas containing oxygen to the interface layer. Method of forming a film. The method according to any one of claims 1 to 3, wherein the high dielectric constant film is a metal oxide film forming the high dielectric constant film. The method according to any one of claims 1 to 3, wherein the high dielectric constant film is a silicate film including silicon and a metal forming the high dielectric constant film. . The method according to claim 4, wherein the metal is hafnium or zirconium. 7. The method according to claim 4, wherein the high dielectric constant film further contains nitrogen. The method of claim 4, wherein the high dielectric constant film is formed by a chemical vapor deposition method.

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