JP2004207560A - Semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device which improves the dielectric breakdown properties or interface-state generation of the gate insulating film, stress-induced leakage current properties, and NBT degradation; and to provide a method for manufacturing the semiconductor. <P>SOLUTION: When forming an MOS transistor on a semiconductor substrate wherein elements are separated by a silicon oxide film or the like, the gate insulating film is permitted to have a stacked structure of a first insulating film 2 comprising fluorine and a second insulating film 5 consisting of a silicon nitride film. The second insulating film 5 is formed by depositing an amorphous silicon film on the first insulating film 2, followed by supplying nitrogen radicals 4 activated by microwave discharge or the like to the amorphous silicon film. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor device and a method for manufacturing the same, and more particularly, to a technique for improving electrical reliability of a gate insulating film.
[0002]
[Prior art]
In order to achieve miniaturization, higher performance, and lower power consumption of LSI devices, the thickness of the gate insulating film is also becoming thinner at an accelerating pace. Problems such as securing long-term reliability, as typified, have become apparent.
In recent years, for example, to use a dual-gate CMOS (NMOS uses an N-type gate electrode and PMOS uses a P-type gate electrode) to align the thresholds with NMOS and PMOS, and to suppress the short channel effect It is becoming common to use a surface channel type transistor. At the same time, new problems have emerged with such changes in device structure.
[0003]
From the viewpoint of the reliability of the gate insulating film, negative bias temperature instability (NBTI) is cited as one of the major problems. NBTI is a phenomenon in which the threshold voltage of a transistor shifts under a stress condition that raises the substrate temperature by applying a negative bias to the gate electrode, especially in a PMOSFET, and the on-current decreases in actual operation of the LSI device. In the worst case, normal operation may not be possible.
[0004]
Furthermore, it is reported that this problem of NBTI is remarkable in the case of an oxynitride film. The oxynitride film is used as a gate insulating film for the purpose of suppressing the diffusion of boron and increasing the dielectric constant to reduce the leak current. Ensuring long-term reliability is a major issue.
[0005]
On the other hand, it has been proposed that the hydrogen bond near the gate insulating film / substrate interface is broken by a hole in the inversion layer as a cause of the NBT deterioration. For this reason, it has been reported that an isotope of hydrogen is introduced into an interface or a halogen element such as fluorine is introduced in order to make it difficult to break a hydrogen bond (for example, Patent Document 1, Patent Document 2, and Non-Patent Document 2). Patent Document 1).
[0006]
Conventionally, as a method of adding fluorine, fluorine ions are introduced into a gate electrode formed on the gate insulating film by using an ion implantation method or the like, and the fluorine is diffused by, for example, a heat treatment. Had been introduced.
[0007]
FIG. 1 shows a method of manufacturing a halogen-added gate insulating film by a conventional method. First, as shown in FIG. 1A, for example, an n-type silicon substrate 1 having a plane orientation (100) and a specific resistance of 1 to 2 Ωcm is prepared, and as shown in FIG. A gate oxide film 13a is formed on the surface of the silicon substrate 1 using, for example, dry oxygen.
[0008]
Subsequently, as shown in FIG. 1C, for example, a nitrogen monoxide (NO) gas 14 is supplied to the heated substrate to form a nitrogen-added gate oxide film 13b. Next, as shown in FIG. 1D, a polycrystalline silicon film 7 deposited by, for example, monosilane (SiH4) gas is formed on the nitrogen-added gate oxide film 13b. Next, as shown in FIG. 1 (e), halogen ions 15 are implanted so that the polycrystalline silicon film 7 has a peak. Here, an example in which fluorine ions are implanted is shown as an example.
[0009]
Subsequently, as shown in FIG. 1 (f), this is heat-treated at, for example, 900 ° C. for 30 minutes in a nitrogen atmosphere, whereby fluorine diffuses from the polycrystalline silicon film 7 into the gate insulating film. The method of introducing was taken.
[0010]
[Patent Document 1]
JP-A-6-13372
[Patent Document 2]
JP-A-8-116059
[Non-patent document 1]
PETER J. WRIGHT and KRISHNA C. SARASWAT, IEEE TRANSACTIONS ON ELECTRON DEVICES, Vol. 36, NO.5, MAY 1989, p. 879-889
[0011]
[Problems to be solved by the invention]
FIG. 2 is a diagram plotting the state of NBT degradation when fluorine is added to the gate oxide film and the gate oxynitride film, using the threshold change (ΔVth) of the transistor as an index. In FIG. 2, the NBT stress application time T_STRESSIs plotted on the horizontal axis, and the threshold change (ΔVth) of the transistor at that time is plotted on the vertical axis. ΔVth is obtained from the threshold value Vth (0) obtained from the initial gate voltage (Vg) -drain current (Id) before NBT stress application and the Vg-Id characteristic measured after applying NBT stress for a certain time τ. Is defined as a difference from the threshold value Vth (τ), that is, ΔVth = Vth (τ) −Vth (0).
[0012]
The NBT stress referred to here means that the element to be measured is heated to a certain temperature, here, for example, 140 ° C., and the source, drain and substrate (or well) are short-circuited and grounded, and the gate electrode is negatively charged. When a bias, for example, -2.3 V is applied here, for example, in the case of a p-channel MOSFET, it refers to a stress performed in a state where a hole inversion layer is formed.
[0013]
According to this, in the case of the gate oxide film (SiO 2), ΔVth is reduced by introducing fluorine, whereas in the case of the oxynitride film (SiON), the effect of adding fluorine is not seen. In the case of an oxide film, fluorine atoms can diffuse through the film, and fluorine has the property of being unevenly distributed at the oxide film interface, so it replaces hydrogen bonds that cause NBT degradation at the oxide film / substrate interface. Form a fluorine bond. Fluorine bonds have a higher binding energy than hydrogen bonds, and therefore are less likely to break during NBT stress.
[0014]
Therefore, in the case of a gate oxide film, NBT degradation was suppressed by fluorine. On the other hand, in the case of an oxynitride film, nitrogen in the film reduces diffusion of fluorine, and fluorine cannot sufficiently reach the gate insulating film / substrate interface originating from NBTI. For this reason, the hydrogen bond which causes NBT deterioration cannot be replaced, and as a result, the effect of suppressing the deterioration due to fluorine has not been seen. Against this background, a nitrogen-added gate insulating film having a structure that efficiently introduces a halogen element into the gate insulating film / substrate interface and suppresses NBT deterioration has been required.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problems and provide a structure capable of realizing a nitrogen-added gate insulating film with high electrical reliability and a method of manufacturing the same, the present invention employs the following configuration.
[0016]
A semiconductor device according to a first aspect of the present invention is a semiconductor device formed on a semiconductor substrate or a semiconductor layer and a main surface of the semiconductor substrate or a main surface of the semiconductor layer, and contains both or at least one of oxygen atoms and nitrogen atoms and a halogen element. A first insulating film having the same, a gate insulating film formed on the first insulating film and being a stack of a second insulating film having nitrogen atoms, a gate electrode formed on the surface of the gate insulating film, and the semiconductor substrate And a pair of source / drain diffusion layers formed on the main surface of the semiconductor layer or the main surface of the semiconductor layer and sandwiching the gate electrode from both sides.
[0017]
Note that a halogen element is contained in the first insulating film in an amount of 1 × 10¹⁶From 1 × 10^{twenty two}atom / cm^-3It is preferable that this halogen element is bonded to a silicon atom or a nitrogen atom in the first insulating film.
[0018]
Note that the halogen element is preferably fluorine.
[0019]
It is preferable that the second insulating film is a silicon nitride film formed by nitriding a silicon film.
[0020]
The silicon film used for forming the second insulating film is preferably an amorphous silicon film.
[0021]
It is preferable that the second insulating film is a nitride film nitrided by activated nitrogen active species.
[0022]
Further, the method of manufacturing a semiconductor device according to the second aspect of the present invention is a method for manufacturing a semiconductor device, comprising: a semiconductor substrate or a semiconductor layer; and a main surface of the semiconductor substrate or a main surface of the semiconductor layer; Forming a first insulating film having a halogen element by exposing it to an atmosphere containing an element, and forming a second insulating film made of a silicon nitride film obtained by nitriding a silicon film on the surface of the first insulating film. Forming, forming a gate electrode on the second insulating film, and forming a pair of source / drain diffusion layers sandwiching the gate electrode from both sides on the main surface of the semiconductor substrate or the main surface of the semiconductor layer. And a step of performing
[0023]
Note that the step of forming the first insulating film may be performed using a fluorine compound gas.
[0024]
Preferably, the step of forming the second insulating film is a silicon nitride film formed by nitriding an amorphous silicon film.
[0025]
Preferably, the step of forming the second insulating film is a nitride film formed by nitriding an amorphous silicon film with an active species of nitrogen.
[0026]
According to the present invention, for example, taking a fluorine-added oxynitride film as an example of the first insulating film, fluorine is introduced into the gate insulating film / substrate interface where the channel inversion layer is formed. H-Si≡ (Si)_ThreeAnd D-Si≡ (Si)_3-n(O)_n (1 ≦ n ≦ 3), that is, instead of hydrogen bonding as in the state where oxygen is bonded to deuterium-bonded silicon, F-Si≡ (Si)_ThreeAnd F-Si≡ (Si)_3-n(O)_n (1 ≦ n ≦ 3) is formed.
[0027]
Further, by forming the second insulating film by nitriding the silicon film, the dielectric constant can be increased, and the leak current can be reduced. Further, by forming this silicon film as an amorphous silicon film, it is easier to be nitrided than a crystalline silicon film, and a uniform film can be obtained. Further, by using an active species (nitrogen radical) of nitrogen excited for the nitridation, the process can be lowered in temperature, and as shown in FIGS. 3 (a), (b) and (c), Fluorine atoms diffuse into the silicon film during nitridation, break Si-Si bonds in the silicon thin film, and promote nitridation. As a result, the bond is strengthened by fluorine in the vicinity of the gate insulating film interface, and it is possible to suppress the generation of defects that deteriorate the reliability of the gate insulating film, including NBT deterioration, and realize a highly reliable gate insulating film.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(1st Embodiment)
FIG. 4 is a structural sectional view of a p-channel transistor according to the present invention. In this embodiment, a silicon oxide film 6 for element isolation is formed on an n-type silicon substrate 1. On the surface of the silicon substrate, p-type source and drain diffusion layers 10a and 10b are formed by boron ion implantation. On the surface of the silicon substrate, a first insulating film 2 in which fluorine is added to an insulating film mainly containing silicon and oxygen or nitrogen, or all of silicon, oxygen and nitrogen as a gate insulating film is formed. On the first insulating film 2, a second insulating film 5 containing silicon and nitrogen as main components is formed. A silicon nitride film 8b is formed on the side wall of polycrystalline silicon serving as a p-type gate electrode containing boron or the like.
[0029]
Further, a silicide film is formed in the source and drain regions. After the CVD silicon oxide film 11 is deposited on the entire surface, a contact hole is opened, and an Al electrode 12 to be a wiring is formed by sputtering and patterned. The above is a cross-sectional view of the structure of the p-channel transistor according to one embodiment of the present invention.
[0030]
FIG. 5 shows an analysis from the substrate side using a secondary ion mass spectrometer (SIMS) to measure the fluorine concentration in the gate insulating film at the interface between the gate insulating film 2 and the substrate 1. It is a characteristic view showing the result of having performed. When the amount of fluorine contained in the gate insulating film formed by the present invention is set to 100, the result of plotting the relative amount of fluorine contained in the gate insulating film formed by the conventional method (see FIG. 1) is shown. FIG.
[0031]
According to this, the amount of fluorine introduced in the vicinity of the gate insulating film / substrate interface according to the present invention can be increased to about 2.5 times the conventional method. In the conventional method, the amount of fluorine that can be introduced near the interface is 1 × 10¹⁶atom / cm^-3Whereas, according to the present invention, 1 × 10¹⁶atom / cm^-3It has been confirmed that the above fluorine is introduced. At the same time, 1 × 10¹⁶atom / cm^-3The characteristics can be improved by introducing the above fluorine.
[0032]
On the other hand, when excessive fluorine is introduced, not only the strong Si—O bond or Si—N bond is cut by fluorine, but also a large amount of cut free oxygen or nitrogen is diffused. However, the interface between the first insulating film and the substrate is oxidized or nitrided, and the interface characteristics and the film characteristics are significantly deteriorated. The maximum amount of fluorine introduction that does not cause the characteristic deterioration is 1 × 10^{twenty two}atom / cm^-3Met.
[0033]
FIG. 6 is a characteristic diagram of the semiconductor device according to the example of the present invention. This is because the stress application time T between the oxynitride film according to the conventional method and the insulating film according to the present invention._STRESSOf the threshold shift (ΔVth) with respect to. In the oxynitride film according to the conventional method, a dry oxide film as a base oxide film is formed by oxidizing a substrate surface of 2 nm and then performing oxynitriding at 950 ° C. using NO gas.
[0034]
In this case, about 5% of nitrogen is introduced near the oxynitride film / substrate interface. The gate insulating film of the present invention has a structure in which a fluorine-added oxynitride film is formed on a substrate and a silicon nitride film is deposited thereon, and both of them are equivalent oxide thickness (EOT) equivalent. The one of 2.3 nm is used. P for stress testing⁺A pMOSFET for the gate is used, and stress is applied in a state where the substrate temperature is overheated to 140 ° C., a voltage of −2.3 V is applied to the gate electrode, and an inversion layer is formed. According to FIG. 6, the threshold shift amount (ΔVth) is suppressed by using the present invention. For example, when the time when ΔVth = −10 mV is defined as the lifetime of the device, the case of an oxynitride film without fluorine addition (□) Is 81 seconds, and in the case of the gate insulating film (膜) according to the present invention, it is 360 seconds, which indicates that the present invention can increase the life by about 4 to 5 times.
(2nd Embodiment)
A method for manufacturing a gate insulating film according to a second embodiment of the semiconductor device and the method for manufacturing the same according to the present invention will be described with reference to FIG.
[0035]
First, as shown in FIG. 7A, for example, an n-type silicon substrate 1 having a plane orientation (100) and a specific resistance of 1 to 2 Ωcm is prepared, and as shown in FIG. A first insulating film 2 is formed on a surface of a silicon substrate 1. This first insulating film 2 is made of nitrogen trifluoride (NF_Three) Is added and supplied to the heated substrate surface to form a thin oxide film to which fluorine is added. Next, as shown in FIG. 7C, a silicon thin film 3 is deposited on the first insulating film 2. This silicon thin film is made of, for example, disilane (Si_TwoH₆) And at a total pressure of 0.5 Torr. At this time, an amorphous silicon thin film is deposited.
[0036]
Subsequently, as shown in FIG. 7D, while the substrate is heated to about 400 ° C., nitrogen radicals excited by microwaves are supplied to the substrate surface. At this time, nitrogen radicals are introduced into the silicon thin film, and the silicon thin film 3 is entirely nitrided to form a silicon nitride film 5 serving as a second insulating film, as shown in FIG.
[0037]
In the above embodiment, as a method of forming the first insulating film, oxygen and nitrogen trifluoride (NF_Three) Is described by way of example, but is not limited thereto. For example, a mixed gas of oxygen and activated nitrogen, NO gas, N 2_TwoO gas and nitrogen trifluoride (NF_Three) May be used. Alternatively, it may be deposited using a CVD method or the like, in which case, for example, SiH_FourAnd Si_TwoH₆, SiH_TwoCl_Two, SiCl_Four, Si_TwoCl₆Gas, oxygen and NF_ThreeUse nitrogen radicals activated by gas or microwave discharge, or use NO gas or N instead of oxygen._TwoThe volume of the fluoridated gate oxide film or the fluorinated oxynitride film is increased using O gas.
[0038]
In addition, deuterium, which is an isotope of hydrogen, is known to improve characteristics when introduced into the interface or film of a gate insulating film. Is directly supplied to the substrate or burned before being supplied to the substrate to produce heavy water (D_Two0) may be generated and supplied to the substrate for oxidation. Further, when the film is formed by deposition, SiD_FourAnd Si_TwoD₆, SiD_TwoCl_TwoIf such a gas is used, a deuterated gate oxide film or a deuterated gate oxynitride film can be formed.
[0039]
In addition, as a nitriding agent used for forming the second insulating film, nitrogen radicals activated by microwave discharge are used, which can be nitrided at a low temperature. It is possible to perform the nitriding treatment at a temperature lower than the temperature at which the nitriding is performed. Further, the present invention is not limited to nitrogen radicals, and similar effects can be obtained by using nitrogen activated by ordinary plasma discharge or using a catalyst.
[0040]
The source gas for generating nitrogen radicals is N 2_Two, NO, N_TwoO, NF_Three, ND_ThreeCan be used. Further, in this embodiment, an amorphous silicon thin film is used as the silicon thin film when forming the second insulating film. This is because an amorphous silicon film is not only uniform in film quality and excellent in flatness, but also has a low density, so that activated nitrogen and fluorine from the first insulating film easily diffuse into the silicon thin film. It also has the advantage. As the silicon thin film for forming the second insulating film, a polycrystalline silicon film other than the amorphous film can be used. In this case, the nitriding treatment can be performed at a higher temperature than in the case of the amorphous film. However, in the case of a polycrystalline silicon film, a crystal grain boundary exists, and supplied nitrogen radicals and the like may diffuse the grain boundary to make the nitridation nonuniform. Therefore, an amorphous silicon thin film is preferable.
[0041]
In this embodiment, as a method of forming this amorphous silicon thin film, Si is used._TwoH₆Although film formation is performed using a gas, the present invention is not limited to this._Four, SiH_TwoCl_Two, SiCl_Four, Si_TwoCl₆The same effect can be obtained by using such a gas. Furthermore, SiD_FourAnd Si_TwoD₆, SiD_TwoCl_TwoIf a gas containing deuterium is used, a large amount of deuterium is introduced into the silicon thin film, and if nitriding is performed in this state, the first insulating film and the second insulating film contain high-concentration deuterium. It is possible to improve the electrical characteristics of the film quality.
In addition, although the description has been made by taking the fluorine-containing oxide film as an example of the first insulating film, the present invention is not limited to this, and the first insulation film may be a fluorine-containing oxynitride film or a fluorine-containing silicon nitride film.
(Third embodiment)
A method for manufacturing a gate insulating film according to a third embodiment of the semiconductor device and the method for manufacturing the same according to the present invention will be described with reference to FIG.
[0042]
First, as shown in FIG. 8A, for example, an n-type silicon substrate 1 having a plane orientation of (100) and a specific resistance of 1 to 2 Ωcm is prepared, and as shown in FIG. A first insulating film is formed on the surface of the silicon substrate 1. This first insulating film is made of about 1 to 10% nitrogen trifluoride (NF) in oxygen._Three) Is supplied to the heated substrate surface, thereby forming a thin oxide film 2a to which fluorine is added.
[0043]
Next, as shown in FIG. 8C, oxygen radicals 4b activated by microwave discharge or the like are supplied to the first insulating film. At this time, oxygen radicals are present in the film of the gate insulating film and at the interface, repair the weak structure incorporated in the oxide film at the time of oxidation in FIG. 8B, and form the highly reliable gate insulating film 2c. It is formed. Further, the oxygen radicals reach the vicinity of the interface, oxidize the interface, and form an extremely flat interface layer 2b.
[0044]
Next, as shown in FIG. 8D, a silicon thin film 3 is deposited on the first insulating films 2b and 2c. This silicon thin film is made of, for example, disilane (Si_TwoH₆) And at a total pressure of 0.5 Torr. At this time, an amorphous silicon thin film is deposited. Subsequently, as shown in FIG. 8E, the nitrogen radicals 4 excited by the microwave are supplied to the surface of the substrate while the substrate is heated to about 400 ° C. At this time, nitrogen radicals are introduced into the silicon thin film, and the silicon thin film 3 is entirely nitrided to form a silicon nitride film 5 serving as a second insulating film, as shown in FIG.
(Fourth embodiment)
A method for manufacturing a gate insulating film according to a fourth embodiment of the semiconductor device and the method for manufacturing the same according to the present invention will be described with reference to FIG.
[0045]
FIG. 9 shows another method of manufacturing the gate insulating film according to the embodiment of the present invention.
First, as shown in FIG. 9A, for example, an n-type silicon substrate 1 having a plane orientation (100) and a specific resistance of 1 to 2 Ωcm is prepared, and as shown in FIG. A first insulating film is formed on the surface of the substrate 1. This first insulating film forms a thin film nitride film 2e doped with fluorine by simultaneously supplying nitrogen radicals and fluorine radicals activated by, for example, microwave discharge to the heated substrate surface.
[0046]
Next, as shown in FIG. 9C, a silicon thin film 3 is deposited on the first insulating film 2e. This silicon thin film is made of, for example, disilane (Si_TwoH₆) And at a total pressure of 0.5 Torr. At this time, an amorphous silicon thin film is deposited.
[0047]
Subsequently, as shown in FIG. 9D, nitrogen radicals 4 excited by microwave discharge or the like are supplied to the substrate surface while the substrate is heated to about 400 ° C. At this time, nitrogen radicals are introduced into the silicon thin film, and the silicon thin film 3 is entirely nitrided to form a silicon nitride film 5 serving as a second insulating film, as shown in FIG. Here, the first insulating film 2e, which is a silicon nitride film to which fluorine is added, is formed using nitrogen radicals and fluorine radicals activated by microwave discharge or the like. Are separately or microwave-discharged mixed gas.
[0048]
Further, the present invention is not limited to this._ThreeSimilar effects can be obtained by treating the gas by microwave discharge or the like. Further, NH_ThreeGas and F_TwoGas, NH_ThreeGas and NF_ThreeGas may be used, and NH_ThreeND instead of gas_ThreeIf a gas is used, deuterium can be taken into the nitride film, so that the film quality can be further improved. At this time, since the nitride film is a film that is difficult to transmit hydrogen and deuterium, for example, an attempt is made to introduce deuterium into the silicon nitride film which is the first insulating film after forming the second gate insulating film or after forming it. Is also difficult because diffusion is hindered. Therefore, it is desirable to use the technique as described above.
(Fifth embodiment)
A method for manufacturing a p-channel MOS transistor according to a fifth embodiment of the semiconductor device and the method for manufacturing the same according to the present invention will be described with reference to FIG.
[0049]
First, as shown in FIG. 10A, for example, an n-type silicon substrate 1 having a plane orientation (100) and a specific resistance of 1 to 2 Ωcm is prepared, and a normal etching and silicon oxide film are formed on the surface of the n-type silicon substrate 1. An element isolation insulating layer 6 called STI (Shallow Trench Isolation) is formed by using the deposition. Next, as shown in FIG. 10B, a first insulating film 2 is formed on the surface of the n-type silicon substrate. This first insulating film 2 is made of nitrogen trifluoride (NF_Three) Is added and supplied to the heated substrate surface to form a thin oxide film to which fluorine is added.
[0050]
Next, as shown in FIG. 10C, a silicon thin film 3 is deposited on the first insulating film 2. This silicon thin film is made of, for example, disilane (Si_TwoH₆) And at a total pressure of 0.5 Torr. At this time, an amorphous silicon thin film is deposited. Subsequently, as shown in FIG. 10D, nitrogen radicals 4 excited by microwaves are supplied to the substrate surface while the substrate is heated to about 400 ° C. At this time, nitrogen radicals are introduced into the silicon thin film, and the silicon thin film 3 is entirely nitrided to form a silicon nitride film 5 serving as a second insulating film, as shown in FIG.
[0051]
Subsequently, as shown in FIG. 10F, a 200-nm-thick polycrystalline silicon film 7 is deposited as a gate electrode on the second insulating film. Next, as shown in FIG. 10G, after patterning with a resist mask, the polycrystalline silicon film is etched by a reactive ion etching method to form a gate portion. Further, the insulating film 8a is formed on the processed polycrystalline silicon film by post-oxidizing the same.
[0052]
Subsequently, as shown in FIG._Two ⁺Ion or B⁺1 × 10 ion 9^Fifteencm^-2Ion implantation is performed to form source / drain regions 10a. The implanted boron is distributed around the peak depth depending on the acceleration energy inside the silicon substrate. Next, as shown in FIG. 10I, a sidewall insulating film 8b made of a silicon nitride film having a thickness of about 50 nm is formed on the sidewall of the gate portion. Although not shown here, the sidewall insulating film is formed by, for example, depositing a silicon nitride film having a thickness of 50 nm on the entire surface by a CVD method, and then etching by a reactive ion etching method.
[0053]
Next, as shown in FIG. 10 (j), for example, BF_Two ⁺Ions 9 are implanted. The implanted boron is distributed around the peak depth depending on the acceleration energy inside the silicon substrate. Thereafter, a heat treatment is performed, for example, at 1050 ° C. for 10 seconds to activate boron in the silicon substrate and the gate electrode, thereby forming a diffusion layer 10b serving as a gate electrode and source / drain regions.
[0054]
Next, as shown in FIG. 10 (k), the entire surface is etched by, for example, reactive ion etching (RIE) to remove the source / drain regions and the insulating film on the upper surface of the gate electrode.
Next, a titanium thin film having a thickness of 25 nm and a titanium nitride thin film having a thickness of 50 nm are sequentially deposited on the entire surface by a sputtering method. Further, the titanium thin film was completely reacted with the silicon substrate by a heat treatment at 700 ° C. for 1 minute in a nitrogen atmosphere, and a titanium silicide film was formed only on the gate electrode and the source / drain regions as shown in FIG. 10 (l). Form. Thereafter, for example, an unreacted titanium thin film on the titanium nitride film and the insulating film is selectively peeled off using an aqueous solution of hydrofluoric acid or a mixed solution of sulfuric acid and hydrogen peroxide.
[0055]
Next, a 300 nm-thick silicon oxide film 11 is deposited on the entire surface by a CVD method. Subsequently, patterning is performed using lithography, and contact holes are opened in the silicon oxide film by anisotropic dry etching as shown in FIG. 10 (m).
[0056]
Thereafter, an 800 nm-thick aluminum film containing, for example, 0.5% each of silicon and copper is formed, and then, as shown in FIG. 10 (n), this is patterned to form a gate electrode and source / drain electrodes 12. I do. Thereafter, heat treatment was performed at 450 ° C. for 15 minutes in a nitrogen atmosphere containing 10% of hydrogen.
[0057]
In the above embodiment, as a method of forming the first insulating film, oxygen and nitrogen trifluoride (NF_Three) Is described by way of example, but is not limited thereto. For example, a mixed gas of oxygen and activated nitrogen, NO gas, N 2_TwoO gas and nitrogen trifluoride (NF_Three) May be used. Alternatively, it may be deposited using a CVD method or the like, in which case, for example, SiH_FourAnd Si_TwoH₆, SiH_TwoCl_Two, SiCl_Four, Si_TwoCl₆Gas, oxygen and NF_ThreeUse nitrogen radicals activated by gas, microwave discharge, or NO gas or N instead of oxygen._TwoThe volume of the fluoridated gate oxide film or the fluorinated oxynitride film is increased using O gas.
[0058]
In addition, deuterium, which is an isotope of hydrogen, is known to improve characteristics when introduced into the interface or film of a gate insulating film. Is directly supplied to the substrate or burned before being supplied to the substrate to produce heavy water (D_Two0) may be generated and supplied to the substrate for oxidation. Further, when the film is formed by deposition, SiD_FourAnd Si_TwoD₆, SiD_TwoCl_TwoBy using such a gas, a deuterated gate oxide film or a deuterated gate oxynitride film can be formed. In addition, as a nitriding agent used for forming the second insulating film, nitrogen radicals activated by microwave discharge are used, which can be nitrided at a low temperature. It is possible to perform the nitriding treatment at a temperature lower than the temperature at which the nitriding is performed.
[0059]
Furthermore, the present invention is not limited to nitrogen radicals, and similar effects can be obtained by using nitrogen activated by ordinary plasma discharge or using a catalyst. The source gas for generating nitrogen radicals is N 2_Two, NO, N_TwoO, NF_Three, ND_ThreeCan be used.
[0060]
Further, in this embodiment, an amorphous silicon thin film is used as the silicon thin film when forming the second insulating film. This is because an amorphous silicon film is not only uniform in film quality and excellent in flatness, but also has a low density, so that activated nitrogen and fluorine from the first insulating film easily diffuse into the silicon thin film. It also has the advantage. As the silicon thin film for forming the second insulating film, a polycrystalline silicon film other than the amorphous film can be used. In this case, the nitriding treatment can be performed at a higher temperature than in the case of the amorphous film.
[0061]
However, in the case of a polycrystalline silicon film, a crystal grain boundary exists, and supplied nitrogen radicals and the like may diffuse the grain boundary to make the nitridation nonuniform. Therefore, an amorphous silicon thin film is preferable. In this embodiment, as a method of forming this amorphous silicon thin film, Si is used._TwoH₆The film is formed by gas, but the film is not limited to this._Four, SiH_TwoCl_Two, SiCl_Four, Si_TwoCl₆The same effect can be obtained by using such a gas. Furthermore, SiD_FourAnd Si_TwoD₆, SiD_TwoCl_TwoIf a gas containing deuterium is used, a large amount of deuterium is introduced into the silicon thin film, and if nitriding is performed in this state, the first insulating film and the second insulating film contain high-concentration deuterium. It is possible to improve the electrical characteristics of the film quality.
[0062]
In addition, although the description has been made by taking the fluorine-containing oxide film as an example of the first insulating film, the present invention is not limited to this, and the first insulation film may be a fluorine-containing oxynitride film or a fluorine-containing silicon nitride film.
[0063]
In the embodiments of the present invention, a silicon thermal oxide film, a silicon nitride film, or an oxynitride film is described as an example of a gate insulating film. However, the present invention is not limited to this. The present invention is also applicable to a body film and an oxide film or a silicate film of the interface layer. In this case, for example, the silicate film may be an HfSiO film, a ZrSiO film, an AlSiO film, or an HfSiON film, a ZrSiON film, or an AlSiON film each containing nitrogen. These films are deposited by a sputtering method or a CVD method. Nitrogen may be added, for example, by using a target of HfN, ZrN, or SiN at the time of sputtering, or, in the case of CVD, a source gas in which nitrogen is bonded to a source gas. .
[0064]
After the HfSiO film, the ZrSiO film, and the AlSiO film are formed, the film may be treated with nitrogen radicals activated by microwave discharge or the like to introduce nitrogen into the silicate film. Further, as the high dielectric film, ZrO_TwoMembrane, HfO_TwoFilm, Al_TwoO_ThreeMembrane, La_TwoO_ThreeMembrane, Pr_TwoO_ThreeMembrane, CeO_TwoMembrane, Dy_TwoO_ThreeFilm, TiO_TwoMembrane, Ta_TwoO_FiveA membrane is feasible, but is preferably ZrO_TwoMembrane, HfO_TwoFilm, Al_TwoO_ThreeA film is desirable from the viewpoint of film quality stability.
[0065]
In addition, various modifications can be made without departing from the spirit of the present invention.
[0066]
【The invention's effect】
According to the present invention, in a thin insulating film such as a gate insulating film used for a semiconductor processor or a semiconductor memory, it is possible to greatly improve dielectric breakdown, generation of interface states, stress-induced leak current, NBT deterioration, and the like. Therefore, the reliability of the device characteristics can be improved. The present invention can provide a semiconductor device having such an effect and a method for manufacturing the same.
[Brief description of the drawings]
FIG. 1 is a process sectional view showing a method for manufacturing a fluorine-added gate insulating film by a conventional method.
FIG. 2 is a characteristic diagram showing an effect of fluorine on a threshold shift (ΔVth) due to NBT deterioration of a fluorine-added gate oxide film and a fluorine-containing oxynitride film formed by a conventional method.
FIG. 3 is a diagram illustrating the function of fluorine and radical nitrogen for explaining the effect of the present invention.
FIG. 4 is a cross-sectional view illustrating an example of a p-channel transistor formed according to the present invention.
FIG. 5 is a characteristic diagram showing the amount of fluorine introduced at the gate insulating film / substrate interface for explaining the effect of the present invention.
FIG. 6 is a characteristic diagram illustrating an effect of fluorine on a threshold shift (ΔVth) due to NBT deterioration of a fluorine-added oxynitride film for explaining an effect of the present invention.
FIG. 7 is a process sectional view illustrating a method of forming a fluorine-added gate insulating film according to the present invention.
FIG. 8 is a process sectional view showing a method of forming a fluorine-added gate insulating film according to the present invention.
FIG. 9 is a process sectional view showing the method of forming the fluorine-added gate insulating film according to the present invention.
FIG. 10 is a process sectional view illustrating an example of a method for manufacturing a p-channel transistor having a fluorine-added gate insulating film according to the present invention.
[Explanation of symbols]
1 n-type silicon substrate
2, 2a, 2b, 2c, 2e First insulating film
3 Silicon thin film
4 Nitrogen radical
4b Oxygen radical
5 Second insulating film
6. Element isolation insulating film
7 Polycrystalline silicon film
8a, 8b Gate sidewall insulating film
9 BF_Two ⁺Ion or B⁺ion
10a, 10b source / drain diffusion layers
11 CVD silicon oxide film
12 Aluminum electrode

Claims (10)

A semiconductor substrate or a semiconductor layer; a first insulating film formed on the main surface of the semiconductor substrate or the main surface of the semiconductor layer and containing both or at least one of oxygen atoms and nitrogen atoms and a halogen element; A gate insulating film which is a stack of a second insulating film having nitrogen atoms formed thereon, a gate electrode formed on a surface of the gate insulating film, and a main surface of the semiconductor substrate or a main surface of the semiconductor layer. And a pair of source / drain diffusion layers sandwiching the gate electrode from both sides. The first insulating film contains a halogen element in an amount of 1 × 10 ¹⁶ to 1 × 10 ²² atoms / cm ^-3, and the halogen element is bonded to a silicon atom or a nitrogen atom in the first insulating film. 2. The semiconductor device according to claim 1, wherein: 2. The semiconductor device according to claim 1, wherein the halogen element is fluorine. 2. The semiconductor device according to claim 1, wherein the second insulating film is a silicon nitride film formed by nitriding a silicon film. The semiconductor device according to claim 4, wherein the silicon film used for forming the second insulating film is an amorphous silicon film. 5. The semiconductor device according to claim 4, wherein the second insulating film is a nitride film nitrided by activated nitrogen active species. A semiconductor substrate or a semiconductor layer, and a first insulating layer having a halogen element exposed to an atmosphere containing both or at least one of oxygen atoms and nitrogen atoms and a halogen element on the main surface of the semiconductor substrate or the main surface of the semiconductor layer A step of forming a film, a step of forming a second insulating film made of a silicon nitride film obtained by nitriding a silicon film on the surface of the first insulating film, and forming a gate electrode on the second insulating film And a step of forming a pair of source / drain diffusion layers sandwiching the gate electrode from both sides on the main surface of the semiconductor substrate or the main surface of the semiconductor layer. . 8. The method according to claim 7, wherein the step of forming the first insulating film uses a fluorine compound gas. 8. The method according to claim 7, wherein the step of forming the second insulating film is a silicon nitride film formed by nitriding an amorphous silicon film. 8. The method according to claim 7, wherein the step of forming the second insulating film is a nitride film formed by nitriding an amorphous silicon film with an active species of nitrogen.

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