JP2002110975A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device which has a gate-insulating film that can suppress lowering of dielectric constant and has less defects, can suppress the occurrence of leakage currents to a low level, and can be improved in performance, such as operation speed, power consumption, etc. SOLUTION: The semiconductor device is provided with a silicon oxide-nitride film and a silicon oxide film, formed between the silicon oxide/nitride film and a substrate as the gate insulating film of a MISFIT. Principal bonding, constituting the silicon oxide/nitride film, is composed of an N≡Si3 bonding and an O=Si2 bonding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a MIS type semiconductor device having a MISFET.

[0002]

2. Description of the Related Art In recent years, Metal Oxide Semiconductor Fiel
d With the miniaturization of Effect Transistor (MOSFET), MOSFE, whose gate insulating film is a silicon oxide film
In the case of T, the silicon oxide film must be formed as very thin as 2 nm or less, making it difficult to obtain sufficient reliability.

That is, in a conventional silicon oxide film, a phenomenon that a standby leak current increases due to an increase in direct tunneling occurs, and a p-type MOSFET
, Which is an impurity in the p-type poly-Si gate electrode used in the above, penetrates through the thin silicon oxide film and diffuses into the silicon substrate, causing a change in the threshold voltage of the p-type MOSFET. (T. Kuroi et
al., Jpn. J. Appl. Phys. Vol. 34 (1995) pp. 771).

In order to solve these problems, it is essential to increase the dielectric constant of the gate insulating film and prevent impurity diffusion.

A metal insulator semiconducer using a silicon nitride film (SiN film) or a silicon oxynitride film (SiON film) that satisfies both impurity diffusion prevention and high dielectric constant.
The torField Effect Transistor (MISFET) has been attracting attention. In particular, JVD (Jet Vapor Deposition), LP-CVD (
Low Pressure Chemical Vapor Deposition), RPE-
CVD (Remote Plasma Enhanced Chemical Vapor Depos
)).
(TP MA, Appl. Surf. Sci., 117/118, 259 (1997).
BY Kim, HFLuan and DL Kwong, IEDM, 463 (19
97). H. Yang and G. Lucovsky, IEDM, 245 (1999). However, in the silicon nitride film formed by such a method, many defects exist in the microstructure in the film, and When the SiN film is used as the gate insulating film, there is a problem in that the device characteristics are adversely affected, such as an increase in leakage current and an increase in the speed and power consumption of the semiconductor device.

In order to remove such defects, even in a silicon oxynitride film in which oxygen is introduced into a silicon nitride film, the concentration of introduced oxygen is not uniform, so that not only defects cannot be completely removed, but also the addition of oxygen atoms. There is a problem that the dielectric constant decreases.

A conventional method for manufacturing a semiconductor device will be described with reference to the schematic diagram of the MISFET shown in FIG.

In order to manufacture the MISFET 11, first, S
JVD, LP-CVD, RPE-CVD on i-substrate 12
The oxygen-added SiN film 13 is deposited by such a method. Further, after depositing the polycrystalline Si film 14, gate electrode processing is performed to form source / drain regions 15 in the Si substrate 12 on both sides of the polycrystalline Si film 14.

[0009]

As described above, a conventional gate insulating film using a silicon nitride film has many defects, and a gate insulating film using a silicon oxynitride film into which oxygen is introduced is also used. The problem of a decrease in the dielectric constant due to the addition of oxygen concentration oxygen atoms is inevitable,
There is a need for further reduction of defects in the film.

The present invention solves the above problems and has a gate insulating film with few defects while suppressing a decrease in dielectric constant.
It is an object of the present invention to provide a semiconductor device in which leakage current is suppressed to a low level and high performance such as high speed and low power consumption can be achieved.

[0011]

According to the present invention, there is provided a MISF having a gate electrode on a silicon substrate via a gate insulating film.
In a semiconductor device comprising ET, the gate insulating film comprises a silicon oxynitride film, and a silicon oxide film provided between the silicon oxynitride film and the substrate, and The semiconductor device is characterized in that the main bonds forming the oxynitride film are N≡Si ₃ bonds and O ＝ Si ₂ bonds.

The N】 S in the silicon oxynitride film
The abundance ratio of i ₃ bond and O = Si ₂ bond (N≡Si ₃ bond:
O = Si ₂ bond) 2x: 1−x (0.2 ≦ x ≦ 0.6)
Preferably, the thickness of the silicon oxide film is
It is desirable that the thickness be 0.6 nm or more and 1.2 nm or less.

That is, the present inventor has proposed a method of reducing a defect in a fine structure in a gate insulating film using a silicon nitride film or a silicon oxynitride film used for increasing a dielectric constant, in order to reduce defects in the gate insulating film on the silicon substrate side. Thus, a structure in which a silicon oxide film and a silicon oxynitride film are stacked is adopted. Furthermore, it has been found that it is effective that the main bonds constituting the silicon oxynitride film, that is, the film made of a compound of silicon, oxygen and nitrogen are N≡Si ₃ bonds and OＯSi ₂ bonds.

FIG. 7 is a model diagram showing the bonding state of atoms in the gate insulating film according to the present invention. In FIG. 7, the silicon substrate 12 on which the source / drain regions 15 are formed
A silicon oxide film 16 and a silicon oxynitride film 17 are formed thereon.

The silicon substrate 12 and the silicon oxynitride film 17
A silicon oxide film 16 corresponding to an interface region between the silicon substrate 12 and the silicon substrate 12 has a defect that becomes a fixed positive charge in the vicinity of the silicon substrate. In order to reduce the crystal strain on the silicon nitride film 17 and to form a smooth junction, the interface state between the silicon substrate 12 and the silicon oxynitride film 17 is reduced, and is indispensable for suppressing deterioration of mobility and increase in leak current.

The N≡Si ₃ unit constituting the bulk region made of the silicon oxynitride film 17 has a stable bonding state, and changes in the bonding between atoms which cause a leak current (such as cutting). Is unlikely to occur. However, if the bulk region is composed of only N≡Si ₃ units, the structure is stable and rigid, so that the entire film is distorted, which causes defects. Therefore, Si that can flexibly change the bonding angle
It is considered that the presence of the —O—Si unit between the N≡Si ₃ units makes it possible to alleviate the strain and suppress the defects.

The bond between nitrogen, oxygen and silicon is Si
-O-Si bond is not only N≡Si ₃ bond, but also Si-O-
N, N-O-N, N≡O 3, Si-N = O 2, Si 2 = N
-O and the like are considered, but the bond between the atoms is N≡S
The effect of the present invention cannot be achieved with a silicon oxynitride film having these bonds as main bonds, because it is more unstable than i ₃ and changes (such as disconnection) of bonds that cause a leak current are likely to occur.

According to the present invention, defects at the interface with the substrate in the gate insulating film and defects in the bulk in the gate insulating film are reduced, the leakage current is suppressed, and high speed and low power consumption are achieved. Performance can be improved.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing a manufacturing process of a MIS type semiconductor device having a MIS transistor according to an embodiment of the present invention.

First, as shown in FIG.
On the surface of the hydrogen-terminated n-type silicon substrate 12 whose main surface is
The surface of the silicon substrate 12 is oxidized by performing one of the oxidations (including no oxidation) under the five oxidation conditions shown in Table 1 below, thereby forming five types of silicon oxide films 16 having different oxide thicknesses. did.

[0022]

[Table 1]

Next, as shown in FIG. 1B, active nitrogen atoms are generated by down-flow plasma, and SiH ₄ gas and oxygen gas are independently introduced from different systems, respectively, on the silicon oxide film 16. By mixing, a silicon oxynitride film 17 was formed.

In this embodiment, the conditions for forming the silicon oxynitride film are three types shown in Table 2 below (including the conditions for forming a silicon nitride film containing no oxygen). The silicon oxynitride film 17 was formed.

Therefore, the combination of the thickness of the silicon oxide film 16 and the oxygen concentration in the silicon oxynitride film 17 is 15
Kind.

[0026]

[Table 2]

The method for forming a silicon oxynitride film according to the present invention is desirably the method described in Japanese Patent Application No. 11-335708. That is, an oxygen compound molecule (for example, oxygen gas) and a silicon compound molecule (for example, silane)
And nitrogen radicals are independently mixed on a semiconductor substrate to form a film.

Further, as shown in FIG. 1C, after a polycrystalline Si layer 14 using SiH ₄ is continuously deposited on the silicon oxynitride film 17, gate electrode processing is performed. As shown in d), the Si on both sides of the polycrystalline Si layer 14
Diffusion layer 15 as source and drain in substrate 12
Thus, 15 types of MISFETs 18 having different combinations of the thickness of the silicon oxide film 16 and the oxygen concentration in the silicon oxynitride film 17 were produced.

Next, the thickness of the silicon oxide film 16 of each MISFET 18 was measured. The thickness of the silicon oxide film 16 was derived by in-situ XPS analysis. The measurement is performed with an X-ray source of MgKα and a photoelectron escape angle of 15 °. FIG. 2 shows changes in the Si2p spectrum under each oxidation condition. The binding energy on the horizontal axis is based on the peak position of bulk Si2p, and the photoelectron intensity on the vertical axis is a value normalized by the peak intensity of bulk Si2p. FIG. 2 shows that the photoelectron intensity (SiOx signal intensity) in the range of 1 to 6 eV increases as the oxygen partial pressure, oxidation time and oxidation temperature increase. From the ratio of the SiOx signal intensity to the peak intensity ratio of bulk Si2p, Lu et al.
2.96nm photoelectron escape depth of iO ₂ (Ellipsometer, CV
Derived experimentally from the comparison of the TEM film thickness and ZH Lu
et al., Appl. Phys. Lett., 711 (19), 2794 (1997).)
When the film thickness of the silicon oxide film 16 under each oxidation condition was derived using the above, the results shown in Table 3 below were obtained.

[0030]

[Table 3]

Next, the oxygen concentration in the silicon oxynitride film 17 of each MISFET 18 was measured by in-situ XPS analysis. The measurement is performed with an X-ray source of MgKα and a photoelectron escape angle of 15 °. As a result, when the oxygen concentration in the silicon oxynitride film 17 under each oxynitride film formation condition was derived, the results shown in Table 4 below were obtained.

[0032]

[Table 4]

Next, five types of MISFETs having an oxygen concentration of 0 atm% in the silicon oxynitride film 17 and different thicknesses of the silicon oxide film 16 were extracted, and their CV characteristics were measured. The result is shown in FIG.

Further, three types of MISFETs 18 having different oxygen concentrations in the silicon oxynitride film 17 and a thickness of the silicon oxide film 16 of 0 nm were extracted, and their CV characteristics change was measured. The result is shown in FIG. FIG. 3B shows a MISFET 18 formed in the same manner as the other MISFET 18 except that only the silicon oxide film 16 (silicon oxide film thickness: 4.5 nm) was formed without forming the silicon oxynitride film 17.
The change in CV characteristics is also described.

The capacitor structure of the MISFET used here is an n + polycrystalline Si layer / insulating film / n-type silicon (10
0), the area is 100 × 100 μm, and the CV measurement conditions are 0.1 kHz in the order of f = 100 kHz, 0 V, −2 V, 2 V, and −2 V.
Voltage was applied in 1 V steps. For all measured samples, the equivalent oxide thickness EOT obtained from the saturation capacity
Is within the range of 4.2 to 4.5 nm.

The following contents can be confirmed by comparing FIGS. 3A and 3B. 1) Compared to the case where the silicon oxide film 16 is not formed ([O] bulk 0%), the silicon oxide film 16 is formed at the interface with the silicon substrate and the thickness is further increased (SiO2 0.29 nm-1.00 nm). 3.) The flat band voltage Vfb increases, approaching that in which only the silicon oxide film 16 (DryOx) is formed without forming the silicon oxynitride film 17. 2) Hysteresis ΔVfb is reduced by introducing oxygen into the silicon oxynitride film 17 ([O] bulk 0% -30%).

FIG. 4 shows the tendencies 1) and 2). FIG.
(A) shows the thickness of the silicon oxide film 16 and Vfb or ΔV
FIG. 4B is a graph showing the relationship between the oxygen concentration in the silicon oxynitride film 17 and Vfb or ΔVfb. 4A, Vfb is the silicon oxide film 1 at the interface.
6 increases linearly with increasing thickness. In general, when the allowable value of Vfb is -0.5 V or more, the film thickness needs to be about 0.6 nm or more, which is equivalent to about 1 nm (DryOx) in which only the silicon oxide film 16 is formed. Considering the influence of a decrease in the dielectric constant, it is preferable that the thickness be 1.2 nm or less at the maximum. This phenomenon that Vfb increases with an increase in the thickness of the silicon oxide film 16 is thought to correspond to the termination of oxygen atoms to defects that become positive fixed charges near the interface between the silicon oxynitride film 17 and the silicon substrate 12. Can be On the other hand, since ΔVfb does not depend on the thickness of the silicon oxide film 16, this ΔVfb
Vfb is considered to be caused by a defect in the silicon oxynitride film 17.

FIG. 4B shows the silicon oxynitride film 1.
Vfb increases with an increase in the oxygen concentration in 7 because the oxygen concentration near the interface with the silicon substrate also increases. On the other hand, ΔVfb sharply decreases, and when the allowable value of ΔVfb is set to 0.02 V or less, the silicon oxynitride film 17
20atm% or more is required at an oxygen concentration of about 30at.
It is about the same as (DryOx) in which only the silicon oxide film 16 is formed at m%. In addition, considering the effect of a decrease in the dielectric constant, a maximum of 4
0 atm% or less is desirable. This decrease in ΔVfb is considered to correspond to the fact that oxygen atoms terminate defects in the silicon oxynitride film 17.

From the above results, an ideal structure in which the gate insulating film has few defects and a decrease in the dielectric constant is minimized is an oxygen concentration in the silicon oxynitride film 17 formed on the silicon substrate 12. 20 atm% or more and 40 atm% or less, and the thickness of the silicon oxide film 16 is 0.6 nm or more and 1.2
nm or less.

The above results show that the oxygen concentration of the silicon oxynitride film 17 is 0%, the five types of MISFETs having different thicknesses of the silicon oxide film 16 and the three types of MISFETs having the thickness of the silicon oxide film 16 of 0 nm. , The silicon oxynitride film 1 actually formed
7 has an oxygen concentration of 20 atm% or more and 40 atm% or less,
The thickness of the silicon oxide film 16 is 0.6 nm or more and 1.2 nm
Similarly, Vfb and ΔVf also apply to the following MISFETs.
b was measured, and it was confirmed that Vfb was in the range of −0.5 V or more and ΔVfb was in the range of 0.02 V or less.

In the present invention, the main bonds constituting the silicon oxynitride film are N≡Si ₃ bond and O = Si ₂ bond.

The following is a detailed description based on the data obtained from the silicon oxynitride film 17 in the MISFET 18.

The N and O atoms in the silicon oxynitride film 17 of the gate insulating film having the silicon oxide film 16 having a thickness of 1.0 nm obtained by the method of the present embodiment and the silicon oxynitride films 17 having various oxygen concentrations. The coupling state is changed to In-situ XP
A description will be given based on the result of the S analysis. In-situ XPS
In the analysis, the measurement was performed with an X-ray source of monochrom-AlKα and a photoelectron escape angle of 15 °. Here, the spectrum shape of the binding energy of N1s and O1s in the silicon oxynitride film 17 was measured.

FIG. 5 shows a silicon oxynitride film 1 having various oxygen concentrations.
7 shows the N1s and O1s spectra of FIG. The binding energy on the horizontal axis is based on the peak positions of N1s and O1s, and the photoelectron intensity on the vertical axis is N1s and O1s.
It is normalized based on the peak intensity of s.

The contents obtained from FIG. 5 are as follows: 1) Both N1s and O1s are single peaks; 2) The half width of N1s slightly increases with the increase in oxygen concentration, while O1s decreases.

First, let us consider N1s based on this result.

In general, N≡Si ₃ , Si ₂ ＮNO and S
When i-N = O bonds coexist in the film, the N≡Si ₃ N
Based on 1s, each chemical shift is about 2e
V, 5 eV (SW Novac, JR Sha
lleberger, DA Cole and J. W. Marino, Mat. Res. S
oc. Symp. Proc. Vol. 567, 579 (1999).). This time SiN
Even if oxygen is added to the film at 10 to 30 atm%, such a chemical shift is not observed.
It can be said that it has no NO bond.

When oxygen enters the second proximity of the N atom (for example, Si ₂ = N—Si—O—Si), the chemical shift of N1s is reported to be about 0.4 eV (G.
M. Ringnanese, A. Pasquaello, JC Charlier, X. G
onze and R. Car, Phys. Rev. Lett., 79, 25, 5174 (19
97).) In this case, the reason why the half value width of N1s slightly increases with the addition of oxygen can be said to be that the ratio of the oxygen atoms in the second proximity increases.

Next, consider O1s.

In the case of a SiO ₂ film, Si-OS of 144 ° is used.
It is known that the i-bond angle is dominant and the half-width of O1s is small (JT Titch, CH Bjorkman, G. Luco
vsky, FH Pollak and X. Yin, J. Vac. Sci. Techno
l. B7., 755 (1989).). In contrast to the case where the oxygen concentration in the silicon oxynitride film is reduced in this case, the half width of O1s is increased because the variation in the Si—O—Si bond angle is increased. It is known that when the Si—O—Si bond angle changes from 125 to 185 °, the O1s bond energy changes by 1-2 eV (FJ Grunt
haner, PJ Grunthaner, RP Vasques, BF Lewi
s and Maserjian, J. Vac.Sci. Technol., 16 (5), 144
3 (1979).), Which corresponds to the spread of the half width of O1s.

From the above results, the main bonding states of N atoms, O atoms, and Si atoms in the silicon oxynitride film of this embodiment are N≡Si ₃ bond and O = Si ₂ bond, respectively, and further, Si—O— It was confirmed that the variation in the Si bond angle was larger than that in the SiO ₂ film.

In the present invention, the main bond is N≡
It is desirable that the number of bonds including both Si ₃ bonds and O = Si ₂ bonds exceeds 90% of the total number of bonds in the film.

Next, these N≡Si ₃ bonds and O = S
An attempt was made to derive the ratio of i ₂ bonds present in the bulk to minimize the defects based on the Alloy model. FIG. 6 shows a ternary phase diagram of the deposited silicon oxynitride film at 500 ° C. and room temperature at various oxygen partial pressures. The change in the composition of this film is based on the Alloy model (xSi ₃ N ₄ +
(1-x) it can be seen that according to SiO _2). This All
Assuming that the oy model is occupied by two bond states of N≡Si ₃ bond and O = Si ₂ bond, xSi ₃ N ₄ + (1-x)
SiO ₂ = 4x (N≡Si ₃ ) +2 (1-x) (O = Si ₂ ).

Accordingly, the ratio of the desired number of bonds is expressed by the following relational expression.

(N≡Si ₃ bond): (O = Si ₂ bond) =
2x: 1-x (0 ≦ x ≦ 1), especially the silicon oxynitride film 17
In order to minimize defects therein, it is desirable that 0.2 ≦ x ≦ 0.6.

[0056]

As described above, the semiconductor device of the present invention suppresses a decrease in the dielectric constant in the gate insulating film of the MISFET and has few defects, so that the leak current can be suppressed low, and the operation speed and the power consumption can be reduced. A semiconductor device which can achieve high performance such as power consumption can be provided.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a MIS semiconductor device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a change in Si2p spectrum under each oxidation condition.

FIG. 3 is a characteristic diagram illustrating CV characteristics of a transistor and an oxygen concentration of an interface and a bulk of a gate insulating film.

FIG. 4 is a graph showing the relationship between the interface and bulk oxygen concentrations of a gate insulating film and Vfb or ΔVfb of a transistor.

FIG. 5 shows N1 of silicon oxynitride film 17 having various oxygen concentrations.
s and O1s spectra.

FIG. 6 is a ternary phase diagram of a deposited silicon oxynitride film at 500 ° C. and room temperature at various oxygen partial pressures.

FIG. 7 is a model diagram showing a bonding state of atoms in a gate insulating film according to the present invention.

FIG. 8 is a schematic diagram of a MIS transistor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... MIS transistor 12 ... Silicon substrate 13 ... Oxygen-added SiN film 14 ... Polycrystalline Si film 15 ... Source / drain region 16 ... Silicon oxide film 17 ... Silicon oxynitride film 18 ... MIS transistor

Claims (3)

[Claims] 1. A semiconductor device comprising a MISFET in which a gate electrode is stacked on a silicon substrate with a gate insulating film interposed therebetween, wherein the gate insulating film includes a silicon oxynitride film, the silicon oxynitride film, and the substrate. A semiconductor device provided with a silicon oxide film provided therebetween, and a main bond constituting the silicon oxynitride film is an N≡Si ₃ bond and an O = Si ₂ bond. . 2. The method according to claim 1, wherein said N≡ in said silicon oxynitride film is
The abundance ratio of Si ₃ bonds and O = Si ₂ bonds (N≡Si ₃ bonds: O = Si ₂ bonds) 2x: 1−x (0.2 ≦ x ≦ 0.
6. The semiconductor device according to claim 1, wherein 6). 3. The silicon oxide film has a thickness of 0.6 n.
2. The structure according to claim 1, wherein the thickness is not less than m and not more than 1.2 nm.
13. The semiconductor device according to claim 1.