KR20170037594A - Semiconductor device comprising metal nitride electrode - Google Patents

Abstract

The present invention relates to a semiconductor device which comprises: a semiconductor substrate; and an electrode being in contact with the semiconductor substrate. The electrode includes metal nitride in a part of the electrode. The electrode is in contact with the semiconductor substrate through the metal nitride. According to the present invention, a contact resistance can be reduced by reducing Schottky barrier by an electric dipole formed between the metal nitride and the semiconductor substrate.

Description

TECHNICAL FIELD [0001] The present invention relates to a semiconductor device including a metal nitride electrode,

The present invention relates to a semiconductor device including an electrode having a low contact resistance to a semiconductor substrate, and more particularly to a semiconductor device including a metal nitride electrode.

In order to miniaturize electronic devices and reduce power consumption, efforts have been made to improve driving current characteristics of semiconductor devices used in electronic devices. As a part of these efforts, semiconductor devices such as metal-oxide-semiconductor field effect transistors (MOSFETs) have been continuously reduced over the past several decades. This is due to the improvement in performance of semiconductor devices and electronic devices Has come.

On the other hand, in order for the miniaturization of the semiconductor element to lead to the performance improvement, it is essential to reduce the contact resistance of the electrode with respect to the semiconductor substrate. Taking the MOSFET device as an example, the resistance of the channel region is reduced due to the reduction of the channel length due to the miniaturization of the device, but this increases the specific gravity occupied by the external resistance other than the channel resistance.

This will be described using a schematic sectional view of the MOSFET device of FIG. 1, a general MOSFET device 100 includes a semiconductor substrate 110 on which a source / drain region 120 and a channel region 130 are formed, a channel region 130 of the semiconductor substrate 110, A gate metal layer 150 formed on the gate insulating layer 140 and an electrode 160 formed in contact with the semiconductor substrate 110 in the source / drain region 120. Although not shown in FIG. 1, other additional structures such as an inter-metal dielectric (IMD) for insulation between the electrode 160 and the gate metal 150 may be further included.

1, the total resistance is determined by the resistance of the electrode 160, the contact resistance between the electrode 160 and the source / drain region 120, the resistance of the source / drain region 120, And the channel resistance between the channel region 130 and the channel resistance. Since the dual channel resistance tends to decrease with the reduction of the channel region 130 length with miniaturization of the MOSFET device, the proportion of the external resistances other than the channel resistance is increasingly occupied in the total resistance.

The contact resistance between the electrode 160 and the source / drain region 120 decreases as the height of the Schottky barrier between the electrode 160 and the source / drain region 120 decreases. A metal having a low specific resistance is generally used as the electrode 160. Theoretically, if a metal having a low work function such as aluminum (Al) or tungsten (W) is used for the electrode 160, a Schottky barrier Can be reduced. However, due to the Fermi Level Pinning phenomenon in which the effective Fermi level of the metal in the metal-semiconductor junction is fixed at a specific energy in the semiconductor band gap, the Schottky barrier is actually higher than the theoretical value do.

Further, research has been conducted to lower the Schottky barrier height by moving the effective Fermi level of the metal in the direction of the conduction band of the semiconductor by inserting a very thin insulating film between the electrode 160 and the source / drain region 120 However, in this case, since the additional insulating film is required, not only the device manufacturing process and manufacturing facilities are complicated, but also the overall external resistance is increased due to the additional tunneling resistance due to the insulator inserting.

Therefore, there is a demand for a technique capable of effectively reducing the contact resistance of the electrode with respect to the semiconductor substrate by a simpler method.

J. Y. Spann, et al., IEEE Electron Device Letters, 260, 1501 (20005) Yi Zhou, et al., Applied Physics Letters 96, 10021003 (200100)

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the related art as described above, and it is an object of the present invention to reduce the contact resistance of an electrode to a semiconductor substrate without using a complicated process by using a metal nitride as an electrode in contact with a semiconductor substrate.

According to an aspect of the present invention, there is provided a semiconductor device including a semiconductor substrate and an electrode contacting the semiconductor substrate, the electrode including at least a portion of a metal nitride, And is in contact with the semiconductor substrate through a metal nitride.

At this time, the metal nitride may include at least one of tantalum nitride, titanium nitride, tungsten nitride, and hafnium nitride, and the electrode may further include a metal having a lower resistivity than the metal nitride.

Also, at least the region where the semiconductor substrate is in contact with the nitrided metal may be an n-type semiconductor.

Further, the nitrogen content of the above-mentioned nitride metal may be 30% or more.

In some embodiments of the present invention, an electrical dipole may be formed at the interface of the nitride metal and the semiconductor substrate, and the Schottky barrier between the nitride metal and the semiconductor substrate, by the electrical dipole, May be lower than the Schottky barrier when the metal is not nitrided.

A semiconductor device according to another aspect of the present invention includes: a semiconductor substrate including a source / drain region and a channel region; A gate insulating film formed on the channel region; A gate metal formed on the gate insulating film; Drain electrode, wherein at least a portion of the source / drain electrode is made of a metal nitride, and the source / drain electrode is in contact with the source / drain region through the nitride metal, .

According to the present invention, by using a metal nitride as an electrode to be in contact with the semiconductor substrate, the contact resistance of the electrode with respect to the semiconductor substrate can be reduced without a complicated process.

Further, according to the present invention, by using a thin metal nitride layer and a low resistivity metal layer as electrodes, it is possible to reduce contact resistance without increasing electrode resistance.

According to the present invention, since it is easy to control the degree of nitriding of the nitride metal in accordance with the kind of the semiconductor substrate and the characteristics of the contact region, it is possible to provide an electrode optimized for each device .

1 is a schematic cross-sectional view of a general MOSFET device;
2 is a schematic cross-sectional view of a semiconductor device according to one embodiment of the present invention.
3 is a cross-sectional view of various embodiments of electrodes according to the present invention.
4 is a band diagram when tantalum nitride (TaN) is contacted on an n-type germanium substrate.
5 is a graph of current-voltage diode characteristics of tantalum nitride-germanium junction samples.
6 is a graph of current-voltage diode characteristics of tantalum nitride-silicon junction samples.
7 is a graph of current-voltage diode characteristics of electrodes and germanium junction samples in which tantalum nitride and metal are stacked.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited to or limited by the embodiments. In describing the various embodiments of the present invention, corresponding elements are denoted by the same names and the same reference numerals. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The present invention is characterized in that a contact resistance between an electrode and a semiconductor substrate is lowered by using a metal nitride as an electrode to be formed on a semiconductor substrate.

When the metal is nitrided, the work function may be increased rather than pure metal, which increases the height of the Schottky barrier against the electron flow. Therefore, theoretically, when the metal nitride is used as the electrode, the contact resistance with the semiconductor substrate increases Can be expected. According to the study of the present inventors, when a metal nitride is in contact with a semiconductor substrate, an electric dipole is formed between the nitrogen and the substrate element at the interface, so that the height of the Schottky barrier to electrons is rather reduced , And the present invention has been made in view of such findings.

The present invention can be applied to various semiconductor devices including bonding of a semiconductor and a metal electrode. For example, the present invention can be applied to reduce the contact resistance between a source / drain region of a semiconductor substrate and an electrode in a MOSFET device.

2 is a schematic cross-sectional view of a semiconductor device according to an embodiment of the present invention. 2, a semiconductor device 200 according to an embodiment of the present invention includes a semiconductor substrate 110 having a source / drain region 120 and a channel region 130 formed thereon, A gate insulating film 140 formed on the channel region 130 of the semiconductor substrate 110 and a gate metal 150 thereon and an electrode 260 formed to contact the semiconductor substrate 110 in the source / drain region 120. Although not shown in FIG. 2, other additional structures such as an inter-metal dielectric (IMD) for insulation between the electrode 260 and the gate metal 150 may be further included.

The semiconductor substrate 110 may be carbon (C), silicon (Si), germanium (Ge), or a combination thereof, which are Group 4 element semiconductors. In addition, the semiconductor substrate 110 may be a bulk wafer or a silicon-on-insulator (SOI) substrate having a semiconductor material of a thickness of several hundred nanometers formed on an insulating substrate. The semiconductor substrate 110 may be a substrate doped with at least a donor or an acceptor and may be, for example, a p-type substrate.

The source / drain region 120 may be an area doped with a donor or acceptor depending on the type of the semiconductor device 200 and may be a region doped with a donor if the semiconductor device 200 is an N-MOSFET device, for example. .

The electrode 260 contacts the semiconductor substrate 110 in the source / drain region 120 and is formed of a metal nitride. The nitrided metal is a metal containing nitrogen in a predetermined composition ratio, and may be tantalum nitride (Ta-N), titanium nitride (Ti-N), hafnium nitride (Hf-N), tungsten nitride (WN) But it is not limited thereto and may be a nitride metal containing two or more elements other than nitrogen such as Ta-Si-N. In the present invention, the metal nitride may be in the form of a mixture or compound of metal and nitrogen, depending on the nitrogen content, process conditions, and the like, and may be crystalline or amorphous.

The electrode 260 may be entirely formed of a nitride metal, or a portion thereof may be formed of a metal nitride. The portion of the electrode 260 that contacts the source / drain region 120 may be a metal nitride. When the portion of the electrode 260 which is in contact with the source / drain region 120 is formed of a metal nitride, the remaining portion of the electrode 260 may be formed of a metal having a low resistivity.

3 is a cross-sectional view of various embodiments in which a portion of the electrode 260 is a metal nitride. 3 shows only the semiconductor substrate 110 and the electrode 260, but other structures such as an insulating film may be formed around the electrode 260. [ 3, the electrode 260 may be composed of a lamination of a metal nitride layer 261 and a metal layer 262, and at least a portion of the semiconductor substrate 110 which contacts the source / 261). 3 (a), the metal nitride layer 261 may be formed only on a portion of the metal 262 that is in contact with the source / drain region 120, Or may be formed to surround the entire circumference of the metal 262 as shown in FIG. 3 (c).

The metal 262 may be a single metal or an alloy having a low resistivity to reduce the resistance of the electrode 260 itself and may be made of a metal such as aluminum (Al), titanium (Ti), chromium (Cr) ), Cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), ruthenium (Ag), lanthanum (La), hafnium (Hf), tantalum (Ta), tungsten (W), platinum (Pt), gold (Au), erbium (Er), yttrium Or a combination thereof.

The metal 262 may be the same material as the metal element contained in the metal nitride 261. [ For example, the electrode 260 may be composed of tantalum nitride (Ta-N) as the metal nitride 261 and tantalum (Ta) as the metal 262. In this case, the nitriding metal 261 and the metal 262 can be deposited in-situ in one process chamber, so that the electrode deposition process is simple and can be performed between the metal nitride 261 and the metal 262 It is possible to prevent interfacial contamination. For example, the semiconductor substrate 110 is placed in a sputtering chamber equipped with a tantalum (Ta) target. During the first predetermined period of time, nitrogen (N ₂ ) gas is introduced into the chamber and sputtering is performed to form a tantalum nitride And then sputtering is performed in a state where nitrogen (N ₂ ) gas is shut off for a predetermined time thereafter to continuously form a tantalum film on the tantalum nitride.

The electrode structure of FIG. 3 (a) can be formed by a method of sequentially depositing a metal nitride layer 261 and a metal layer 262 and patterning the same, and the electrode structure of FIG. 3 (b) A contact hole for forming an electrode may be formed and then the nitride metal 261 and the metal 262 may be sequentially deposited in the contact hole. In addition, the structure of FIG. 3 (c) can be formed by depositing a metal nitride on the upper surface of the structure of FIG. 3 (b) and removing the metal nitride on the insulating film not shown.

Fig. 4 shows a band diagram when n-type germanium (Ge) semiconductor is in contact with tantalum nitride (TaN). In the figure, Evac is the vacuum level, Ec and Ev are the lowest level of the conduction band and the highest valence band of the conduction band of the germanium semiconductor, respectively, and Ef is the Fermi level. To facilitate understanding, the interface between tantalum nitride and germanium is plotted as a space (shaded area).

Referring to FIG. 4, the vacuum work function of tantalum nitride is Φ _{TaN, vac,} which is the difference between the Fermi level and the vacuum level _, and the work function of Φ _{TaN, pinned} by the Fermi level pinning phenomenon under contact with the germanium I have. By the way, an electric dipole is formed between the nitrogen in the tantalum nitride and the germanium of the substrate (- + dipole shown in the drawing), so that the work function of the tantalum nitride seen from the germanium side is reduced, Φ _{TaN, which} is smaller than _pinned . That is, the effective work function of the tantalum nitride at the interface by electrical dipole formation is Φ _{TaN, eff} , which is a small value Φ _{b, e} as compared to Φ _{TaN, pinned} . That is, the effect of nitriding tantalum is reduced and the effective work function is reduced, which may lower the height of the Schottky barrier to the electron flow and decrease the contact resistance.

The effects of the present invention will be described below with reference to experimental examples.

<Experimental Example 1>

A tantalum nitride film was deposited on an N-type semiconductor substrate to form a Schottky diode, and then diode characteristics were measured. Ge and Si substrates were used as semiconductor substrates and reactive sputtering was performed under nitrogen atmosphere. At this time, a plurality of samples were prepared by varying the nitrogen flow rate from 0 to 12 sccm, and the characteristics of the samples were measured according to the nitrogen content. The tantalum nitride film was deposited to a thickness of 150 nm. After the deposition, the substrate was heat-treated at 300 ° C. for 10 minutes under a nitrogen atmosphere at normal pressure.

FIG. 5 is a graph of current-voltage diode characteristics of tantalum-germanium nitride junction samples, and FIG. 6 is a graph of current-voltage diode characteristics of tantalum nitride-silicon junction samples. As can be seen from FIGS. 5 and 6, the reverse current was increased when nitrogen-containing tantalum nitride was used compared to pure tantalum with a nitrogen flow rate of 0 sccm. The nitrogen flow rate was 8 sccm, A larger reverse current was measured at 12 sccm. From this, it can be seen that the Schottky barrier height decreases with electron flow as the degree of nitridation increases with the use of a tantalum nitride electrode compared to a pure tantalum metal electrode.

Table 1 below summarizes the composition and work function values of each sample deposited on a germanium semiconductor substrate. The composition of the tantalum nitride film was measured by X-ray photoelectron spectroscopy (XPS).

N ₂ flow (sccm) Ta (%) N (%) Vacuum work function (eV) The effective work function in Ge (eV) 0 100 0 4.36 4.552 4 66.51 33.49 4.56 4.467 8 48.03 51.97 4.57 4.277 12 45.82 54.18 4.686 4.220

As shown in Table 1, the effective work function of pure tantalum nitride in contact with the germanium substrate is increased by the Fermi level pinning phenomenon compared to the vacuum work function, whereas the tantalum nitride The effective work function in contact with the germanium substrate was rather low. In addition, as the nitrogen content increased, the vacuum work function increased, while the effective work function tended to decrease in the contact state with the germanium substrate. Since the reduction of the effective work function means the reduction of the Schottky barrier and the reduction of the contact resistance, the tendency of this work function value is consistent with the results of FIGS. 5 and 6 in which the reverse current increases as the nitrogen content increases.

On the other hand, according to the results of FIGS. 5 and 6, the reverse current value does not differ greatly at a nitrogen flow rate of 8 sccm or more, that is, a nitrogen content of about 50% or more. Therefore, about 30% or more, preferably about 50% Of nitrogen can be used.

<Experimental Example 2>

As shown in FIGS. 5 and 6, the reverse current increases while the forward current decreases with increasing nitrogen content. This is because the resistance of the electrode increases as the nitrogen content increases. Therefore, in Experimental Example 2, the characteristics were compared with the metal nitride electrode by using a thin layer of a metal nitride and a low resistivity metal as electrodes.

An n-type germanium semiconductor substrate was used as a semiconductor substrate, and a Schottky diode was formed by sequentially depositing tantalum nitride and a metal film on a semiconductor substrate, and then diode characteristics were measured. Tantalum nitride was deposited to a thickness of 3 nm and was deposited by reactive sputtering under a nitrogen flow rate of 12 sccm. In addition, nickel (Ni), ytterbium (Yb), and tantalum (Ta) films of 100 nm were deposited as a metal film by sputtering. For comparison, a sample using only a 150 nm tantalum nitride film was also measured.

Referring to FIG. 7, the reverse current value was high even when using 3 nm thin tantalum nitride, and the reverse current characteristic was better than that of the sample using only 150 nm tantalum nitride. In addition, the positive current value also increased significantly compared with the case of using only tantalum nitride, which is a result of reducing the thickness of the tantalum nitride having a relatively high specific resistance and forming the electrode with a metal having a low resistivity.

From the above results, it can be seen that by using a laminated structure of metal nitride and metal as the electrode, it is possible to keep the resistance of the electrode low while reducing the contact resistance with the semiconductor substrate. That is, it is possible to greatly improve only the reverse current characteristic without sacrificing the forward current. In addition, it was confirmed that the contact resistance was excellent even when only a thin thickness of about 3 nm was used for the metal nitride.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. For example, while the embodiments have been described using MOSFET devices, the present invention is also applicable to other semiconductor devices having metal-semiconductor junctions. That is, the semiconductor device of the present invention should be understood as a concept including all elements in which a metal-semiconductor junction exists, and it is known that the application of a nitride metal to a contact portion with a semiconductor in a semiconductor device reduces contact resistance, . Accordingly, the scope of protection of the present invention should be determined by the description of the claims and their equivalents.

100, 200: semiconductor element
110: semiconductor substrate
120: source / drain region
130: channel region
140: gate insulating film
150: gate metal
160, 260: electrode
261: metal nitride
262: Metal

Claims (6)

Germanium substrate;
A first electrode comprising a metal nitride on the germanium substrate; And
And a second electrode on the first electrode, the second electrode further comprising a metal having a lower resistivity than the nitrided metal, wherein the Schottky barrier between the nitrided metal and the germanium substrate further comprises a Schottky barrier where the nitrided metal is not nitrided And the semiconductor element The method according to claim 1,
Wherein the nitride metal comprises at least one of tantalum nitride, titanium nitride, tungsten nitride, and hafnium nitride. The method according to claim 1,
Wherein the metal nitride has a nitrogen content of 50% or more and 55% or less. The method according to claim 1,
Wherein the metal having a lower resistivity than the metal nitride includes at least one of aluminum, gold, copper, chromium, nickel, tungsten, ruthenium, cobalt, titanium and platinum. The method according to claim 1,
Wherein the germanium substrate is an n-type semiconductor at least in a region in contact with the nitride metal. The method according to claim 1,
And an electric dipole is formed at an interface between the nitride metal and the germanium substrate.

Images