JP2006040977A - Method of manufacturing semiconductor device having insulation film, and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce leakage current by lowering the CET (converted equivalent SiO<SB>2</SB>thickness) of an insulation film in MOSFET. <P>SOLUTION: The surface of an Si substrate is radical-nitrided by nitrogen radicals. Then, an HfO<SB>2</SB>film is formed as a high dielectric constant film on the Si substrate whose surface is now radically nitrided. Thereafter, at least the high dielectric constant film is radically nitrided by nitrogen radicals, and the semiconductor formed with the high dielectric constant film after nitriding is heat-treated (RTO) in an oxygen atmosphere. The insulation film which has been applied with RTO treatment after radical nitriding of the Si substrate and radical nitriding of the HfO<SB>2</SB>film is found to have a lower CET and lower leakage current than an insulation film which has been applied with RTO treatment without conducting any one of radical nitriding of the Si substrate and radical nitriding of the HfO<SB>2</SB>film formed on the Si substrate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor device such as an FET having a dielectric film and an electrode, a floating gate transistor, and a capacitor, and a manufacturing method thereof.

With the miniaturization and high integration of semiconductor devices, the gate insulating films of MOSFETs and MISFETs have been made thinner. At present, the film thickness is about 1 nm in terms of SiO ₂ , and the manifestation of tunnel leakage current due to the thinning is regarded as a problem. From the viewpoint of power consumption and reliability, introduction of a high dielectric constant material that can reduce the leakage current by increasing the physical film thickness of the gate insulating film while ensuring the amount of signal charge necessary for device operation is required. .

Therefore, in Patent Document 1 below, HfO ₂ which is a high dielectric constant material is used for the gate insulating film in the MIS transistor. In this transistor, after a high dielectric film such as HfO ₂ is formed on a silicon substrate, the surface of the high dielectric film is nitrided with radical nitrogen to form a nitride layer on the surface, and p is formed on the nitride layer. A gate electrode is formed of a p-type polycrystalline silicon layer containing type impurities. At this time, in the nitride layer on the surface of the high dielectric film, boron (B) used as a p-type impurity of the gate electrode diffuses through the high dielectric film and diffuses into the silicon substrate by various heat treatments. Is preventing. That is, the nitride layer on the surface of the high dielectric film prevents diffusion of p-type impurities into the p-channel and contributes to preventing fluctuations in the threshold voltage of the p-channel MOS transistor.

Further, high dielectric constant thin films such as HfO ₂ and ZrO ₂ transmit oxygen in the atmosphere in the heat treatment step, so that the oxygen reaches the interface with the silicon substrate, and an SiO ₂ film is formed. When the SiO ₂ film is formed, the SiO ₂ film has a relative dielectric constant smaller than that of HfO ₂ , ZrO _2, etc., so that the SiO ₂ equivalent film thickness of the insulating film becomes large, that is, the equivalent ratio of the insulating film There is a problem that the dielectric constant decreases and the electrostatic capacity using the insulating film as a medium decreases. Therefore, according to the following Patent Document 2, in order to control the film thickness of the SiO ₂ film formed at the interface with the silicon substrate to the atomic layer level in the heat treatment step, the residual oxygen partial pressure in the atmosphere in the heat treatment step is set to 1. It is carried out with × 10 ⁻⁴ Torr and a residual moisture pressure of 5 × 10 ⁻⁵ Torr or less.

According to the following Patent Document 3, in order to suppress the formation of the SiO ₂ film formed at the interface between the high dielectric constant film and the silicon substrate, before forming the high dielectric constant film, nitrogen ions are implanted into the substrate surface. In addition, it is known that the substrate surface is nitrided with nitrogen radicals.

However, Patent Document 1 discloses a technique for nitriding the surface of a high dielectric film in order to prevent p-type impurities from passing through the high dielectric film. The formation of the SiO ₂ film at the interface with the substrate is not prevented, and the SiO ₂ equivalent film thickness of the high dielectric film is not prevented from increasing.

Further, Patent Document 2, when heat treatment of the silicon substrate formed with a high dielectric constant thin film in an atmosphere containing oxygen gas, although the SiO ₂ film is formed on the interface between the high dielectric constant film and the silicon substrate, the SiO ₂ film In order to prevent the formation of, the heat treatment is disclosed in an environment where the partial pressure of oxygen gas is extremely low. That is, it is disclosed that in a desirable state, it is best to heat-treat in an environment without oxygen gas, and there is no suggestion that the leakage current characteristics will be improved by heat-treating in an oxygen atmosphere. .

In Patent Document 3, the surface of the silicon substrate is nitrided with nitrogen radicals to control the SiO ₂ equivalent film thickness of the insulating film for each transistor for each application. However, there is no disclosure of reducing the SiO ₂ equivalent film thickness of the insulating film or further improving the current leakage characteristics.

Non-Patent Document 1 compares the characteristics when HfON is used as the insulating film with the characteristics when HfO ₂ is used. However, there is no disclosure of reducing the SiO ₂ equivalent film thickness of the insulating film or further improving the current leakage characteristics.

Thus, in the prior art, SiO ₂ is formed at the interface between the silicon substrate and the high dielectric constant film, and this SiO ₂ increases the equivalent SiO ₂ equivalent film thickness of the high dielectric constant film. A manufacturing method has been provided in which it is difficult to form an SiO ₂ film at the interface of a silicon substrate, but a sufficiently thin insulating film having an equivalent SiO ₂ equivalent film thickness is still formed to further reduce leakage current. The manufacturing method to reduce is not established.

Therefore, the present invention provides a manufacturing method of a semiconductor device having an insulating film and an electrode thereon, and a manufacturing method that has a sufficiently thin insulating film with an equivalent SiO ₂ equivalent film thickness and can significantly reduce a leakage current. The purpose is to provide.
It is another object of the present invention to provide a semiconductor device having a low driving voltage and improved leakage characteristics.

JP 2003-282873 A JP 2002-184773 A JP2003-100956 The Electrical and Material Chracterization of Hafnium Oxynitride Gate Dielectrics With TaN-Gate Electrode IEEE TRANSACTION ON ELECTRON DEVICES, VOL.51, NO.2, FEBRUARY 2004

  According to a first aspect of the present invention for solving the above problem, in a method of manufacturing a semiconductor device having an insulating film on a semiconductor and an electrode formed on the insulating film, the surface of the semiconductor is formed by nitrogen radicals. A first radical nitriding step for radical nitriding, a high dielectric constant film forming step for forming a high dielectric constant film on a semiconductor whose surface is radical nitrided, and a second radical nitriding at least the high dielectric constant film with nitrogen radicals A method of manufacturing a semiconductor device, comprising: a radical nitriding step; and a heat treatment step of heat-treating a semiconductor in which a high dielectric constant film is formed after nitriding in an oxygen atmosphere.

Here, Si, GaAs, GaAsP, GaN, AlGaN, AlGaInN or the like can be used as the substrate material, but generally Si is frequently used. Generally, nitrogen atom radicals, which are neutral particles obtained by converting nitrogen gas into plasma and removing charged particles, are used as nitrogen radicals. In addition, it is desirable to supply a nitrogen radical to the surface of the semiconductor separately from the plasma generation chamber and the semiconductor processing chamber. The temperature range for radical nitriding the semiconductor surface is preferably 0 ° C. to 800 ° C., and the atmospheric pressure is preferably 10 ⁻⁵ Torr to 10 ⁻² Torr. As a method of forming a high dielectric constant film, it is desirable to use an electron beam evaporation method in view of reducing the film thickness, but any method can be used as long as it is a method of forming a film on the order of nm. High dielectric constant materials include Al ₂ O ₃ , Ta ₂ O ₃ , ZrO ₂ , HfO ₂ , Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ , PrO ₂ , Gd ₂ O ₃ , Sc ₂ O ₃ , A metal oxide film such as LaAlO ₃ , ZrTiO ₄ , (Zr, Sn) TiO ₄ , SrZrO ₄ , LaAl ₃ O ₄ , SrTiO ₃ , or BaSrTiO _3, or a mixed crystal such as silicate may be used. In the present invention, HfO ₂ is most desirable. The method and conditions for radical nitriding the high dielectric constant film may be the same as the method and conditions for radical nitriding the substrate. Further, in the subsequent heat treatment in an oxygen atmosphere, the temperature range is 500 ° C. to 1000 ° C., the oxygen partial pressure is 10 ⁻³ Torr to 10 ³ Torr, and the remaining inert gas or nitrogen gas is 10 ¹⁰ Torr to ^{10 2.} Torr is desirable. The high dielectric constant film after radical nitridation and heat treatment in an oxygen atmosphere is different from the crystal structure of the high dielectric constant film in the deposited state before these treatments.

The invention of claim 2 is the semiconductor manufacturing method according to claim 1, wherein the semiconductor is silicon, and the invention of claim 3 is characterized in that the high dielectric constant film is made of HfO _2. A semiconductor manufacturing method according to claim 1 or 2.
The case where the semiconductor is silicon (Si) and the high dielectric constant film is HfO ₂ is the most common in the present invention, and the effects of the present invention can be sufficiently exhibited.

According to a fourth aspect of the present invention, in the semiconductor according to any one of the first to third aspects, the oxygen partial pressure in the atmosphere in the heat treatment step is 10 ⁻³ Torr to 10 ³ Torr. It is a manufacturing method.
Good characteristics as an insulating film can be obtained by heat-treating the high dielectric constant film after radical nitriding and the semiconductor in an oxygen atmosphere within this range.

According to a fifth aspect of the present invention, there is provided a semiconductor device having an insulating film on a silicon substrate and an electrode formed on the insulating film, a silicon nitride film formed on the surface of the silicon substrate and free of silicon oxide, and silicon nitride And an insulating film made of a high dielectric constant film formed on the film.
This semiconductor device is an MIS type transistor, a capacitor, or the like, but may be any element as long as it has an insulating film formed on a silicon substrate and an electrode thereon. Further, the present invention is characterized in that a silicon nitride film is formed at the interface between the silicon substrate and the high dielectric constant film, and there is no layer made of silicon oxide. With this configuration, the equivalent relative dielectric constant and capacitance of the insulating film can be increased, and the equivalent SiO ₂ equivalent film thickness can be reduced. Conventionally, a silicon oxide film is formed at the interface between the high dielectric constant film and the silicon substrate. However, by using the manufacturing method of the present invention described above, the formation of the silicon oxide film can be eliminated, and the semiconductor As a device, the drive voltage can be reduced and the leakage characteristics can be improved.

A sixth aspect of the present invention is the semiconductor device according to the fifth aspect, wherein the insulating film is formed of a high dielectric constant film obtained by nitriding with nitrogen radicals followed by heat treatment in an oxygen atmosphere.
As will be described later, the high dielectric constant film obtained by nitriding with nitrogen radicals and then heat-treating in an oxygen atmosphere is considered to be different from the crystal before this treatment. This crystal state contributes to reduction of leakage current.

A seventh aspect of the present invention is the semiconductor device according to the fifth or sixth aspect, wherein the high dielectric constant film is made of HfO ₂ .
By making the high dielectric constant film HfO ₂ , the effects of the present invention can be sufficiently exerted. HfO ₂ is HfON next by radical nitriding, but by heat treatment in an oxygen atmosphere is becoming a HfO _2, the process in front of HfO ₂ and HfO ₂ after treatment different crystalline state, thereby greatly the leakage current Reduction is realized.

According to the present manufacturing method, a semiconductor surface is nitrided with nitrogen radicals, a high dielectric constant film is formed on the nitrided surface, and the high dielectric constant film is nitrided with nitrogen radicals, followed by heat treatment in an oxygen atmosphere. Thus, a semiconductor device is manufactured.
According to this method, since the oxide film of the semiconductor is not formed at the interface between the semiconductor and the high dielectric constant film, the equivalent SiO ₂ equivalent film thickness of the high dielectric constant film does not increase and maintains a low value. For this reason, the drive voltage can be reduced and the leakage current can be reduced. In addition, when the semiconductor is silicon and the high dielectric constant film is HfO ₂ , a significant reduction in leakage current is obtained.

The invention of the semiconductor device is characterized in that it has a silicon nitride film formed on the surface of a silicon substrate and free of silicon oxide, and an insulating film made of a high dielectric constant film formed on the silicon nitride film. It is a semiconductor device.
Since no silicon oxide film is formed between the substrate and the high dielectric constant film, the equivalent SiO ₂ equivalent film thickness of the high dielectric constant film is not increased and can be maintained at a low value. For this reason, the drive voltage can be reduced and the leakage current can be reduced.

When the high dielectric constant film is made of HfO ₂ , a significant reduction in leakage current is obtained. HfO ₂ is HfON next by radical nitriding, but by heat treatment in an oxygen atmosphere is becoming a HfO _2, the process in front of HfO ₂ and HfO ₂ after treatment different crystalline state, thereby greatly the leakage current A reduction is expected to be realized.

Hereinafter, specific embodiments of the present invention will be described.
FIG. 1 is a cross-sectional view illustrating a configuration of a semiconductor device 10 according to a specific embodiment. A source region 12 and a drain region 13 made of an n ⁺ region are formed on the surface portion of a silicon substrate 11 made of p-Si, and a p-type channel region 14 is formed between them. An insulating film 15 is formed above the p-type channel region on the surface portion of the silicon substrate 11, and a gate 16 made of polycrystalline silicon is formed on the insulating film 15. A source electrode 17, a drain electrode 18 and a gate electrode 19 made of a metal layer are formed on the source region 12, the drain region 13, and the gate 16, respectively. This embodiment relates to the formation of the insulating film 15 of the MISFET having this structure.

As will be described later, the insulating film 15 is formed by nitriding the surface of the silicon substrate 11 with nitrogen radicals to form an extremely thin SiN layer, and forming a layer made of HfO ₂ on the SiN layer. .

  FIG. 2 is a diagram showing a configuration of a radical nitriding apparatus 50 using nitrogen radicals. A sample stage 60 is provided in the chamber 59, and a semiconductor (sample) 20 to be nitrided is provided on the sample stage 60. In addition, a plasma generation chamber 53 provided with a coil 52 is provided above the chamber 59, and plasma is generated by an induction magnetic field generated from the coil 52. The plasma generation chamber 53 is provided with an exhaust port 56, and the plasma generation chamber 53 is exhausted by an exhaust device (not shown). Along with this exhaust, nitrogen gas which is a raw material of plasma is introduced from the input port 54 into the plasma generation chamber 53.

  A metal plate 30 having a large number of through holes 34 is provided between the plasma generation chamber 53 and the space in which the sample 20 is provided. The metal plate 30 is provided on the ring-shaped insulator 32 and is DC biased to −V volts by the power source 58. On the other hand, the coil 52 is connected to the high frequency power source 51.

When nitrogen gas is introduced into the plasma chamber 53 from the input port 54 and a high frequency is applied to the coil 52, plasma composed of electrons, N ⁺ ions, N radicals, etc. is generated from N ₂ . Among these, when passing through the through-hole 34, the cation collides with the side wall 35 and emits electrons. This gives N radicals. These neutral particles fly toward the sample 20 at a predetermined velocity corresponding to energy obtained by subtracting the energy released from collision from the acceleration energy of ions. Since the particles accelerated in the vertical direction by the electric field are neutralized and passed through the through-hole 34, the flight direction of the neutral particles is a vertical direction, and the beam has excellent directivity. The through holes 34 of the metal plate 30 are formed in a grid pattern.

  Next, in order to understand the properties of the insulating film 15, an insulating film was formed by a different manufacturing method, various characteristics were measured, and each insulating film was evaluated.

1. Experimental Method Using a radical nitriding device 50 on a p-type silicon substrate (p-Si (100)) that has been subjected to a rare HF treatment, radical nitriding at a substrate temperature of 600 ° C. and a nitrogen partial pressure of 5 × 10 ⁻⁵ Torr. Then, an ultrathin Si nitride film having a thickness of about 1 nm was formed. Radical nitrogen is generated by exciting energy of molecular nitrogen with a high frequency of 13.56 MHz, and further passing the excited nitrogen through an ion trapper device (metal plate 30), so that only electrically neutral ones are generated. The sample was irradiated.

Thereafter, HfO ₂ was deposited by an electron beam evaporation method with an EB (electron beam) gun at a substrate temperature of 500 ° C., and then the surface of the HfO ₂ / SiN was radically nitrided again. The total film thickness was about 5 nm.

Using this experimental method, as shown in FIG. 3B, a sample in which the HfO ₂ layer 15 is formed on the silicon substrate 11 (hereinafter, this sample is simply referred to as “HfO ₂ ”), FIG. 3 (c), a sample in which the surface of the silicon substrate 11 is radical-nitrided to form the SiN film 25 and the HfO ₂ layer 15 is formed (hereinafter, this sample is simply referred to as “HfO ₂ / SiN”. 3) As shown in FIG. 3 (d), three samples were prepared: a sample obtained by radical nitriding the sample (hereinafter, this sample is simply referred to as “HfON / SiN”). The effects of radical nitriding were compared. Heat treatment is performed at 700 ° C. by a rapid heat treatment method in a nitrogen atmosphere (hereinafter referred to as “RTA” (Rapid Thermal Annealing)) or a rapid heat treatment method in an oxygen atmosphere (hereinafter referred to as “RTO” (Rapid Thermal Oxidation)). I went for 30 seconds. The conditions for each of these processing steps are shown in FIG.

  For the film thickness evaluation of these samples, a transmission electron microscope (TEM) was used, and the bonding state in the film was measured by X-ray photoelectron spectroscopy (XPS). The electrical characteristics were evaluated using capacitance-voltage (C-V) characteristics and current-voltage (J-V) characteristics by making MIS capacitors with a Pt / insulator / Si / Al structure.

2. 4. Heat treatment characteristics of HfO ₂ film FIGS. 4, 5, and 6 show the RTA treatment immediately after the HfO ₂ single-layer film having a thickness of about 5 nm which is not subjected to radical nitriding treatment on both the silicon substrate and the HfO ₂ film. CV characteristics (Fig. 4), JV characteristics (Fig. 5), and equivalent SiO ₂ equivalent film thickness obtained from these characteristics (hereinafter referred to as "CET" (Capacitance Equivalent) (Oxidide Thickness)) and the leakage current density (FIG. 6). It can be seen from FIG. 6 that CET increases as RTA processing and RTO processing are performed. In particular, when the RTO treatment is performed, the CET immediately after the film formation is 1.5 nm, whereas after the RTO treatment, it increases greatly to 2.1 nm. This is because HfO ₂ is generally said to be an oxygen-permeable oxide, and high-temperature heat treatment in an oxygen atmosphere diffuses external oxygen in the film, and the oxidation reaction is promoted at the Si substrate interface. Is interpreted as having been formed.

On the other hand, an increase in CET was confirmed even after RTA treatment. There are two types of oxygen permeation: one in which oxygen in the film diffuses into the Si substrate interface and the other in which external oxygen permeates through the film and diffuses into the Si substrate interface during heat treatment. The HfO ₂ film immediately after is confirmed to be almost stoichiometric, and since there is no excess oxygen in the film, the increase in CET accompanying the RTA treatment is a trace amount contained in the inert gas (nitrogen). This is probably because oxygen permeated the HfO ₂ film and reached the Si substrate, causing an interface oxidation reaction on the Si substrate surface. Such an interfacial oxidation reaction results in a decrease in the effective dielectric constant of the entire film, and thus a solution is inevitable.

7 and 8 show the Si2p spectrum (FIG. 7) and O1s spectrum (FIG. 8) by XPS immediately after the formation of the HfO ₂ single film, after the RTA treatment and after the RTO treatment. In each spectrum, the binding energy was corrected by the Si-Si signal of the substrate. As can be seen from the Si2p (Fig. 7) and O1s (Fig. 8) spectra, the signal intensity of the Si-O bond component (Si2p: 103.5 eV, O1s: 533.0 eV) increases as RTA processing and RTO processing are performed. You can confirm that These results mean that the oxidation reaction at the interface is promoted with the heat treatment, which is in good agreement with the above interpretation. From the Si2p spectrum, it can be concluded that the oxide produced by the interfacial reaction is Hf-Silicate because the sub-oxide peak is slightly shifted to the lower energy side than the SiO ₂ bond peak.

3. Si substrate surface nitriding effect (HfO ₂ / SiN film)
Nitriding of the Si substrate surface corresponds to the first radical nitriding step, and the step of depositing HfO ₂ after nitriding corresponds to the high dielectric constant film forming step.
9, 10, and 11 show three cases in which the Si substrate surface is subjected to nitridation and HfO ₂ is deposited on the surface of the HfO ₂ / SiN film having a thickness of about 5 nm, immediately after the RTA treatment, and after the RTO treatment. FIG. 9 shows CV characteristics (FIG. 9), JV characteristics (FIG. 10), and the relationship between CET obtained from these characteristics and the leakage current density (FIG. 11).

Here, in order to compare and examine the effect of radical nitriding on the surface of the Si substrate, the characteristics (FIG. 6) in the case of a single HfO ₂ film are shown. As can be seen from FIG. 11, the increase in CET accompanying the heat treatment is small compared to the HfO ₂ single film. In particular, the CET after the RTA treatment is almost constant compared to the case immediately after the deposition. So far, we have stated that the increase in CET is due to the oxidation reaction at the Si substrate interface. These results suggest that the interfacial oxidation reaction is suppressed by introducing a SiN film at the HfO ₂ / Si substrate interface.

On the other hand, the bulk Si ₃ N ₄ generally has an electron barrier height of 2.1 eV, which is larger than 1.5 eV of HfO ₂ , so the introduction of a Si nitride film is expected to reduce the leakage current. It was. However, as shown in FIG. 11, the sample manufactured this time showed no significant change in the leakage current density as compared with the case of the HfO ₂ single film. This is thought to be because the band gap inherent to bulk Si ₃ N ₄ is not formed because the nitride film at the interface is as thin as about 1 nm.

FIGS. 12 and 13 show the Si2p spectrum (FIG. 12) and O1s spectrum (FIG. 13) by XPS immediately after the formation of the HfO ₂ / SiN film, after the RTA treatment and after the RTO treatment, respectively. As is clear from the Si2p (FIG. 12) and O1s (FIG. 13) spectra, it can be seen that both spectra after the RTA treatment and both spectra immediately after film formation have substantially the same shape. In particular, the Si2p spectrum shows a peak showing Si-N bonds (101.8 eV) immediately after film formation and after RTA treatment, and no peak showing Si-O bonds is observed. It can be seen that there is a Si nitride film at the interface. From these facts, it can be considered that the Si nitride film at the interface functions as a barrier against oxygen diffusion to the substrate caused by the RTA treatment during the film formation, and as a result, the interface oxidation reaction is suppressed. The above results are consistent with the above-described electrical characteristics.

On the other hand, as shown in FIG. 12, in the Si2p spectrum after the RTO treatment, the peak indicating Si—N bond is shifted to the Si—O bond side. This can be interpreted as that the oxidation reaction at the silicon substrate interface was promoted by the RTO treatment. Compared to the RTA process, the RTO process has a larger amount of oxygen permeating through the film, so it is considered that the Si nitride film did not completely function as a barrier. However, in the case of the HfO ₂ single film (Figure 7) In comparison, since the peak position is on the lower energy side than the peak position of the Si-O bond, it is considered that the diffused oxygen is taken into the Si nitride film at the interface. Therefore, the reaction layer at the interface seems to be a Si oxynitride film.

4). Effect of HfO ₂ surface nitriding (HfON / SiN film)
The process of nitriding HfO ₂ corresponds to the second radical nitriding process.
14, 15, and 16 show three cases immediately after the formation of an about 5 nm-thickness HfON / SiN film when the Si substrate surface and the HfO ₂ surface are nitrided, after the RTA treatment, and after the RTO treatment. FIG. 14 shows CV characteristics (FIG. 14), JV characteristics (FIG. 15), and the relationship between CET and leakage current density obtained from these characteristics (FIG. 16). In FIG. 16, in order to compare and examine the effect of radical nitriding on the HfO ₂ surface, the case of an HfO ₂ / SiN film without radical nitriding (FIG. 11) is shown. By applying radical nitridation treatment to the HfO ₂ surface, the leakage current immediately after film formation was reduced by about three orders of magnitude compared to the case where it was not added (HfO ₂ / SiN film).

Previously, regarding the HfO ₂ / SiN film that is not radically nitrided, it was described that the Si nitride film having an interface thickness of about 1 nm has no effect of reducing the leakage current (FIG. 11). From this, it is considered that radical nitriding on the HfO ₂ surface itself has an effect of reducing leakage current. From the cross-sectional TEM images of the HfON / SiN film and the HfO ₂ / SiN film immediately after film formation, it was confirmed that both samples were crystallized. From this, the reduction in leakage current was caused not by the leakage current caused by the grain boundaries, but by the local nitridation sites caused by defects in the HfO ₂ film being repaired by radical nitriding. Seem. Of particular note in the leakage current characteristics is that the Cf after the RTO treatment of the HfON / SiN film radical-nitrided on the surface of HfO ₂ is almost the same as the CET immediately after the film formation. This is a further reduction of about two orders of magnitude compared to the leakage current immediately after film formation. This RTO treatment of the HfON / SiN film corresponds to the heat treatment process.

FIG. 17 shows a summary of CET before and after RTO treatment for each sample. Increase of CET accompanying RTO process HfO ₂ film is about 0.6 nm, while the HfO ₂ / SiN film is about 0.3 nm, HfON / SiN film is about 0.1 nm, obviously compared to other samples This shows that the increase in CET is suppressed. 18A, 18B and 18C show cross-sectional TEM images of the respective samples subjected to the RTO treatment. The interface layer thickness of the HfO ₂ simplex film sample after RTO treatment is about 2.0 nm. This is because the interface layer thickness of the HfO ₂ / SiN film sample after RTO treatment is about 0.9 nm and the HfON / SiN film. It is clear that the thickness of the interface layer after the RTO treatment of this sample is about 1.1 nm. If the increase in CET accompanying the heat treatment is considered to be due to the interfacial oxidation reaction, it can be said that the HfO ₂ film clearly suppresses the interfacial oxidation reaction by nitriding the silicon substrate. However, after the RTO process, when comparing HfON / SiN film obtained by nitriding the HfO ₂ / SiN film and surface not in nitriding the surface of the HfO ₂ film, is more of HfON / SiN film obtained by nitriding the surface, the interfacial layer Since the film thickness is about 0.2 nm, the effect of reducing the interface layer film thickness is hardly the effect of radical nitriding of the HfO ₂ layer. Therefore, the effect of suppressing the increase in CET by the nitriding treatment on the surface of the HfO ₂ film cannot be explained only by the interface layer thickness.

The improvement of these electrical characteristics will be discussed together with the bonding state of the film. 19, 20, 21, and 22 show XPS Si2p spectra (FIG. 19) and O1s spectra immediately after the formation of the HfON / SiN film obtained by radical nitriding the surface of the HfO ₂ layer, after the RTA treatment and after the RTO treatment (FIG. 20). ). It can be seen that the Si2p (FIG. 19) and O1s (FIG. 20) spectra have substantially the same shape after the RTA and RTO treatments as they were immediately after film formation. In the Si2p spectrum, the sub-oxide peak is shifted to a higher energy side than the Si-N bond even immediately after film formation. This peak position almost coincides with the peak position of the spectrum after the RTO treatment of the HfO ₂ / SiN film shown in FIG. 12, suggesting that the interface is no longer a Si nitride film. In the N1s spectrum shown in FIG. 21, a peak showing an Hf—N bond (396.0 eV) can be confirmed in the spectrum immediately after film formation. Therefore, the energy shift of the sub-oxide peak in the Si2p spectrum is thought to be due to the radical nitridation of HfO ₂ and the unbonded oxygen substituted for nitrogen diffuses to the interface with the silicon substrate, forming a Si oxynitride film. It is done. However, since the sub-oxide peak position and signal intensity are not significantly changed even in the heat treatment after film formation, it is considered that the subsequent interface oxidation reaction has not progressed. In fact, it was confirmed from the cross-sectional TEM image that there was no change in the film thickness of the interface layer immediately after film formation and after RTO treatment.

Next, the change in the bonding state of the film caused by the heat treatment will be considered. In the Hf4f (FIG. 22) spectrum, the peak immediately after film formation is shifted to a lower energy side than the HfO ₂ peak. Since the Hf-N bond energy is reported to be 15.3 eV, this shift is thought to be due to the presence of Hf-N bonds in the HfO ₂ film. Furthermore, it can be seen that the Hf4f spectrum approaches the spectrum of HfO _{2 in} this order when RTA processing and RTO processing are performed. In the N1s spectrum shown in FIG. 21, a peak indicating an Hf—N bond exists immediately after film formation and after RTA treatment, but the peak disappears after RTO treatment. These results mean that the Hf-N bond is replaced with the Hf-O bond by the heat treatment of RTO. From the above, the reason why the interface layer thickness is kept almost constant in the RTO process is as follows. During the RTO process, oxygen permeating through the membrane is replaced by Hf-N bonds in the membrane with Hf-O bonds, which reduces oxygen diffusion to the interface with the silicon substrate. Yes. This is thought to be because the oxidation reaction at the interface was suppressed. Furthermore, since the relative permittivity of HfON is reported to be 21 and is almost the same as the reported value of HfO ₂ , there is no change in the relative permittivity due to this substitution, and CET remains almost constant after heat treatment. It is thought that he was drunk.

From the XPS analysis, the structures of the HfO ₂ / SiN film and the HfON / SiN film after the RTO treatment can be considered to be HfO ₂ / SiN films. Assuming that a similar Si oxynitride film is formed on the interface layer after RTO treatment, and assuming that the dielectric constant of the Si oxynitride film is 5, the ratio of HfO ₂ / SiN film without radical nitridation after RTO treatment The dielectric constant was 14.8, whereas the relative dielectric constant of the radical nitrided HfON / SiN film after RTO treatment was 24.7. Furthermore, in consideration of the fact that the leakage current is reduced without changing the EOT in both the case where the HfON / SiN film is formed and the case where the RTO treatment is performed, the Hf-N bond is returned to the Hf-O bond. It can be considered that the HfO ₂ film formed by disposing the film has a higher relative dielectric constant than that of the HfO ₂ film whose substitution is not solved, and has been improved in quality into a low-leakage film. After RTO process, despite the thick HfON / SiN film interface layer than HfO ₂ / SiN film, because the the CET is low relative dielectric constant due to the high quality of the upper HfO ₂ film is increased It is thought that.

This can be schematically explained using the crystal structure as follows. First, as an effect of the surface radical nitriding treatment of the HfO ₂ / SiN film, as shown in FIG. 23, some of the O atoms of HfO ₂ are replaced with N atoms. Also, some of the O atoms released from HfO ₂ move to the silicon substrate interface. Then, SiN formed at the interface is oxidized to form SiNO. Next, when the radically nitrided HfON / SiN film is subjected to RTO treatment, as shown in FIG. 24, O atoms in the atmosphere replace N atoms of HfON, and HfON becomes HfO ₂ . At this time, some of the N atoms dissociated from HfON move to the interface of the silicon substrate, SiNO nitridation formed at the interface becomes SiN, and O atoms dissociated from SiNO are taken into the HfON film, and HfO ₂ It contributes to change.

In this manner, the HfO ₂ / SiN film not subjected to radical nitridation treatment is subjected to radical nitridation treatment to form an HfON / SiN film, and then subjected to RTO treatment to return to the original HfO ₂ / SiN film not subjected to radical nitridation. However, a HfO ₂ / SiN film before undergoing the two steps, HfO ₂ / SiN film after undergoing the two steps is to improve electrical characteristics, realizing suppression of increasingly lower and CET of leakage current We were able to.

5. Conclusion HfO ₂ film was formed after radical nitriding of the silicon substrate to form an HfO ₂ / SiN film. Thereafter, HfO was radical-nitrided to form an HfON / SiN film. Next, this film was heat-treated in an oxygen atmosphere (RTO treatment). The CET of the insulating film thus formed is 1.5 nm, which is only increased by 0.1 nm from 1.4 nm of the CET of the insulating film immediately after film formation. On the other hand, when the silicon substrate was not radically nitrided, CET increased from 1.5 nm to 2.1 nm by 0.6 nm after RTO treatment. Further, HfO ₂ / SiN film formed a HfO ₂ film silicon substrate by radical nitriding, when RTO process, CET was 0.3nm increased to 1.7nm from 1.4 nm. As described above, according to the present invention, CET can be reduced by 0.6 nm from 2.1 nm to 1.5 nm as compared with the case where the conventional silicon substrate is not radical-nitrided and an HfO ₂ film is formed and subjected to RTO treatment. did it. In other words, CET was reduced by 30%. In addition, the CET was reduced by 0.2 nm from 1.7 nm to 1.5 nm compared to the case where the silicon substrate was radical-nitrided to form an HfO ₂ film and RTO treatment. In other words, CET was reduced by 12%. The insulating film according to the method of the present invention has a leakage current of 2 × 10 ⁻⁵ A / cm ² (V _FB −1V), and forms an HfO ₂ film without radical nitridation of a conventional silicon substrate to perform RTO treatment. The leakage current for CET is smaller by the amount that CET can be reduced.

Since the matter discussed above is due to substitution of O atoms and N atoms, the above consideration is considered to be valid if the insulating film is not only an HfO ₂ film but also a metal oxide. Further, it is considered that the substrate may be any semiconductor that can be radically nitrided. Therefore, in the present invention, the insulating film is not limited to the HfO ₂ film, the semiconductor is not limited to silicon, and a number of metal oxides having a high dielectric constant exemplified in the section for solving the problem. Any semiconductor can be used as the substrate.

  The present invention can be used for a MOS, MIS type FET using a gate insulating film, and a method for manufacturing the same, and is particularly effective for realizing a low voltage and a low leakage current. For example, the standby time for a mobile phone can be dramatically improved.

Sectional drawing which showed the structure of the transistor which concerns on the specific Example of this invention. The block diagram which showed the radical nitriding apparatus. Explanatory drawing which showed each formation process of the insulating film which concerns on the specific Example of this invention, and its conditions. Without the Si substrate to the radical nitriding, cross sectional view of a sample HfO ₂ film formed thereon. The Si substrate by radical nitriding, cross sectional view of a sample HfO ₂ film formed on a Si substrate that is radical nitriding. The Si substrate by radical nitriding, HfO ₂ film is formed on a Si substrate that is radical nitriding, then cross sectional view of a sample radical nitriding the HfO ₂ film. Characteristic diagram showing the CV characteristic of a sample to form a HfO ₂ film on the Si substrate. Characteristic diagram showing a JV characteristics of the sample to form a HfO ₂ film on the Si substrate. And CET and leakage current of the sample to form a HfO ₂ film on the Si substrate, the film formation state, after RTA, characteristic diagram showing the relationship between treatment method after RTO. Measurements view showing the XPS spectrum of the sample to form a HfO ₂ film on the Si substrate. Measurements view showing the XPS spectrum of the sample to form a HfO ₂ film on the Si substrate. By surface radical nitridation of the Si substrate, characteristic diagram showing the CV characteristic of a sample to form a HfO ₂ film on its surface. By surface radical nitridation of the Si substrate, characteristic diagram showing a JV characteristics of the sample to form a HfO ₂ film on its surface. The surface of the Si substrate by radical nitriding, the CET and leakage current of the sample to form a HfO ₂ film on the sample and the Si substrate to form a HfO ₂ film on its surface, deposition conditions, after RTA, after RTO The characteristic view which showed the relationship with a processing method. A measurement diagram showing the XPS spectrum of a sample in which the surface of a Si substrate is radically nitrided and an HfO ₂ film is formed on the surface. A measurement diagram showing the XPS spectrum of a sample in which the surface of a Si substrate is radically nitrided and an HfO ₂ film is formed on the surface. And the surface of the Si substrate by radical nitriding, the HfO ₂ film is formed on its surface, characteristic view the HfO ₂ film showed CV characteristic of the sample radical nitridation. And the surface of the Si substrate by radical nitriding, the HfO ₂ film is formed on its surface, characteristic view the HfO ₂ film showed JV characteristics of samples radical nitridation. Radical nitriding the surface of the Si substrate, forming an HfO ₂ film on the surface, radical nitriding the HfO ₂ film and radical nitriding the surface of the Si substrate, forming an HfO ₂ film on the surface The characteristic figure which showed the relationship between the CET and leakage current of the sample which was processed, the film-forming state, the processing method after RTA, and after RTO. A characteristic diagram showing the JV characteristics. HfO _2, HfO ₂ / SiN, measurement view showing the CET before and after RTO processes in each sample HfON / SiN. TEM photograph showing the cross-sectional structure of each of the HfO ₂ , HfO ₂ / SiN, and HfON / SiN samples after RTO treatment. A measurement diagram showing the XPS spectrum of a sample obtained by radical nitriding the surface of a Si substrate, forming an HfO ₂ film on the surface, and radical nitriding the HfO ₂ film. A measurement diagram showing the XPS spectrum of a sample obtained by radical nitriding the surface of a Si substrate, forming an HfO ₂ film on the surface, and radical nitriding the HfO ₂ film. A measurement diagram showing the XPS spectrum of a sample obtained by radical nitriding the surface of a Si substrate, forming an HfO ₂ film on the surface, and radical nitriding the HfO ₂ film. A measurement diagram showing the XPS spectrum of a sample obtained by radical nitriding the surface of a Si substrate, forming an HfO ₂ film on the surface, and radical nitriding the HfO ₂ film. Explanatory view showing the effect of the radical nitridation of the HfO ₂ film according to the present invention method. Explanatory drawing which showed the effect at the time of carrying out RTO processing after radical nitriding of the HfO ₂ film by the method of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Si substrate 15 ... Insulating film 16 ... Gate 19 ... Electrode 50 ... Radical nitriding apparatus

Claims (7)

In a manufacturing method of a semiconductor device having an insulating film on a semiconductor and an electrode formed on the insulating film,
A first radical nitriding step of radical nitriding the surface of the semiconductor with nitrogen radicals;
A high dielectric constant film forming step of forming a high dielectric constant film on the semiconductor whose surface is radically nitrided;
A second radical nitriding step of radical nitriding at least the high dielectric constant film with nitrogen radicals;
And a heat treatment step of heat-treating the semiconductor on which the high dielectric constant film is formed in an oxygen atmosphere after nitriding.   The method of manufacturing a semiconductor according to claim 1, wherein the semiconductor is silicon. The method for manufacturing a semiconductor according to claim 1, wherein the high dielectric constant film is made of HfO ₂ . 4. The method of manufacturing a semiconductor according to claim 1, wherein an oxygen partial pressure in the atmosphere in the heat treatment step is 10 ⁻³ Torr to 10 ³ Torr. 5. In a semiconductor device having an insulating film on a silicon substrate and an electrode formed on the insulating film,
A silicon nitride film formed on the surface of the silicon substrate and free of silicon oxide;
And an insulating film made of a high dielectric constant film formed on the silicon nitride film.   6. The semiconductor device according to claim 5, wherein the insulating film comprises a high dielectric constant film obtained by nitriding with nitrogen radicals and then heat-treating in an oxygen atmosphere. The semiconductor device according to claim 5, wherein the high dielectric constant film is made of HfO ₂ .

Images