KR20240046967A - Method for manufacturing capacitor with low leakage current and high capacitance using high work function oxide semiconductor interlayer and capacitor manufactured thereby - Google Patents

Abstract

The present invention discloses a method of manufacturing a capacitor with low leakage current and high electric capacity using a high work function oxide semiconductor intermediate layer, and a capacitor manufactured thereby. According to the present invention, forming a lower electrode made of TiN on a substrate; Forming an oxide semiconductor intermediate layer composed of one of V ₂ O ₅ and In ₂ O ₃ on the lower electrode; Forming a dielectric layer made of TiO ₂ on the oxide semiconductor intermediate layer; and forming an upper electrode on the dielectric layer.

Description

Method for manufacturing capacitor with low leakage current and high capacitance using high work function oxide semiconductor interlayer and capacitor manufactured thereby}

The present invention relates to a method of manufacturing a capacitor with low leakage current and high electric capacity using a high work function oxide semiconductor intermediate layer.

In order to improve the integration of DRAM and achieve high speed, the size of individual cells decreases, resulting in a decrease in electrical capacitance and an increase in leakage current.

Small capacitance and high leakage current require frequent refresh and can cause reliability problems.

Although high-k materials with high dielectric constant are widely used to increase electrical capacitance, leakage current due to narrow band gap is still a major problem.

Methods of blocking leakage paths by laminating or doping aluminum oxide on high-k materials or removing grain boundaries by inducing an amorphous phase of the dielectric are being used.

However, this may cause defective atomic layer deposition of ternary oxide and may cause problems of lowering the crystallinity of the dielectric.

Titanium dioxide (TiO ₂ ) has a high dielectric constant (anatase ~40, rutile ~100) among high-k materials, but there is a limitation in that a large leakage current occurs due to a particularly narrow band gap (3.2 eV).

To solve this problem, an electrode with a high work function is required, and a capacitor using Ru or RuO ₂ with a high work function as an electrode replaces the TiN electrode, which is most commonly used in recent metal-insulator-metal (MIM) capacitors. is being developed.

This can significantly reduce leakage current by increasing the Schottky barrier, but Ru, a noble metal material, has the disadvantage of being very expensive compared to existing TiN electrodes.

The following table summarizes methods and limitations for reducing the leakage current of capacitors.

Capacitor element structure result maximum TiN - ZrO ₂ /Al ₂ O ₃ /ZrO ₂ - TiN By layering Al ₂ O ₃ on ZrO ₂ , leakage path is blocked, grain boundaries are removed, and leakage current is reduced by 32 times. Decrease in crystallinity of dielectric, causing imperfect ternary oxide deposition TiN - Al ₂ O ₃ - ZrO ₂ - Al ₂ O ₃ - TiN Leakage current is reduced by more than 100 times by inserting an Al ₂ O ₃ layer with a wide band gap at the interface. Equivalent oxide thickness (EOT) is increased by inserting Al ₂ O ₃ , an insulator with a relatively low dielectric constant. RuO ₂ - TiO ₂ - RuO ₂ Leakage current reduced by more than 100 times by using RuO _-2 electrode with high work function Cost problems arise due to the use of precious metal electrodes

KR Registered Patent Publication 10-0455287

In order to solve the problems of the prior art described above, the present invention proposes a method of manufacturing a capacitor with low leakage current and high electric capacity using a high work function oxide semiconductor intermediate layer that can increase the energy barrier between the electrode and the dielectric.

In order to achieve the above object, according to an embodiment of the present invention, a capacitor manufacturing method includes forming a lower electrode made of TiN on a substrate; Forming an oxide semiconductor intermediate layer composed of one of V ₂ O ₅ and In ₂ O ₃ on the lower electrode; Forming a dielectric layer made of TiO ₂ on the oxide semiconductor intermediate layer; and forming an upper electrode on the dielectric layer.

The oxide semiconductor intermediate layer may have a thickness ranging from 0.5 to 1.5 nm.

The step of forming the oxide semiconductor intermediate layer includes forming the oxide semiconductor intermediate layer through atomic layer deposition using a VTIP (Vanadium(V) oxytriisopropoxide) or DADI ([3-(dimethylamino)propyl]dimethyl indium) precursor. It can be included.

According to another aspect of the present invention, a substrate consisting of a Si wafer; a lower electrode formed on the substrate and into which an oxide semiconductor intermediate layer is inserted; A dielectric layer made of TiO ₂ formed on the lower electrode; and a capacitor including an upper electrode formed on the dielectric layer.

According to the present invention, there is an advantage in providing a capacitor with low leakage current and high electric capacity by forming a high work function oxide semiconductor intermediate layer on the lower electrode.

1 is a diagram illustrating a capacitor structure according to an embodiment of the present invention.
Figure 2 shows the chemical structure of the precursor used for atomic layer deposition of the oxide semiconductor intermediate layer and dielectric according to this embodiment.
Figure 3 shows the types and energy bands of each component used in the capacitor according to this embodiment.
Figures 4 and 5 show micrographs of the intermediate layer according to this embodiment.
Figure 6 is a diagram showing an X-ray Photoelectron Spectroscopy (XPS) graph of Ti 2p and O 1s of a TiO ₂ thin film.
Figure 7 is an Ultraviolet Photoelectron Spectroscopy (UPS) graph showing the change in work function of the electrode into which the intermediate layer is inserted according to this embodiment.
Figure 8 is a diagram showing an X-Ray Diffraction (XRD) graph of a TiO ₂ thin film grown on an intermediate layer according to this embodiment.
Figure 9 is a diagram showing the capacitance density of the capacitor at 100 kHz.
Figure 10 is a graph showing the leakage current of the capacitor.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

The terms used herein are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “comprise” or “have” are intended to indicate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

In addition, the components of the embodiments described with reference to each drawing are not limited to the corresponding embodiments, and may be implemented to be included in other embodiments within the scope of maintaining the technical spirit of the present invention, and may also be included in separate embodiments. Even if the description is omitted, it is natural that a plurality of embodiments may be re-implemented as a single integrated embodiment.

In addition, when describing with reference to the accompanying drawings, identical or related reference numbers will be assigned to identical or related elements regardless of the drawing symbols, and overlapping descriptions thereof will be omitted. In describing the present invention, if it is determined that a detailed description of related known technologies may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

1 is a diagram illustrating a capacitor structure according to an embodiment of the present invention.

As shown in Figure 1, the capacitor according to this embodiment is composed of a substrate (Si wafer, 100), a lower electrode 102, an oxide semiconductor middle layer 104, a dielectric layer 106, and an upper electrode 108. You can.

The lower electrode 102 may be made of TiN.

The oxide semiconductor intermediate layer 104 according to this embodiment has a high work function and may be composed of V ₂ O ₅ and In ₂ O ₃ .

Additionally, the dielectric layer 106 may be composed of TiO ₂ and the upper electrode 108 may be Ag.

Figure 2 shows the chemical structure of the precursor used for atomic layer deposition of the oxide semiconductor intermediate layer and dielectric according to this embodiment.

Referring to Figure 2, the precursors of V ₂ O ₅ , In ₂ O ₃ , and TiO ₂ are VTIP (Vanadium(V) oxytriisopropoxide), DADI ([3-(dimethylamino)propyl]dimethyl indium), and TDMAT (titanium dioxide based), respectively. on tetrakis-dimethyl-amido titanium).

Figure 3 shows the types and energy bands of each component used in the capacitor according to this embodiment.

The existing lower electrode made of TiN generates a large leakage current due to hot electron emission in a capacitor using TiO ₂ due to its low work function (4.5 eV).

However, the high work function of the oxide semiconductor middle layer 104 (hereinafter referred to as the middle layer) according to this embodiment can reduce leakage current by increasing the barrier height between the lower electrode 102 and the dielectric layer 106.

Figures 4 and 5 show micrographs of the intermediate layer according to this embodiment.

Figure 4 shows a Transmission Electron Microscope (TEM) photograph for confirming the insertion of the intermediate layer, and Figure 5 shows an Atomic Force Microscope (AFM) photograph for confirming the electrode surface roughness.

Figure 4a shows a device without an intermediate layer inserted, and Figure 4b shows a device with an intermediate layer inserted.

Referring to FIG. 4, in the case of the device in which the intermediate layer 104 is inserted according to the present embodiment, the intermediate layer 104 of a thinner thickness is between the TiN electrode 102 and the TiO ₂ dielectric layer 106 compared to the device in which the intermediate layer 104 is not inserted. You can confirm that it has been deposited.

Here, the thickness of the intermediate layer 104 may be 0.5 nm to 1.5 nm, and preferably 1 nm.

In addition, referring to Figure 5, in the case of the electrode on which the intermediate layer 104 composed of In ₂ O ₃ is deposited, the RMS (Root Mean Square) roughness is 0.23 nm, which is 3 times that of the electrode using only TiN (RMS: 0.71 nm). It is lower than above, and this can be seen as being flattened by inserting an amorphous intermediate layer through atomic layer deposition on the relatively rough surface of the crystallized TiN thin film.

In addition, even in the case of the electrode on which the intermediate layer 104 composed of V ₂ O ₅ was deposited, it can be confirmed that planarization was achieved compared to the electrode using only TiN.

Figure 6 is a diagram showing an X-ray Photoelectron Spectroscopy (XPS) graph of Ti 2p and O 1s of a TiO ₂ thin film.

Figure 6 shows the binding energy of Ti 2p and O 1s in TiO ₂ thin film through X-ray photoelectron spectroscopy, and the two normal distribution curves in Ti 2p can be deconvoluted into Ti ⁴⁺ and Ti ³⁺ , respectively. and Ti ³⁺ means deoxidized.

In all conditions, Ti 2p and O 1s showed the same graph, which suggests that the ratio of oxygen vacancies inside the TiO ₂ thin film is almost the same, and the oxygen vacancies act as traps inside the dielectric and cause leakage current.

Figure 7 is an Ultraviolet Photoelectron Spectroscopy (UPS) graph showing the change in work function of the electrode into which the intermediate layer is inserted according to this embodiment.

Referring to Figure 7, it can be seen that inserting an intermediate layer into a TiN electrode with a low work function (4.45 eV) increases the work function (In ₂ O ₃ : 5.04 eV, V ₂ O ₅ , 5.17 eV) by up to about 16%. there is.

When the work function increases in this way, leakage current can be reduced by increasing the energy barrier between the lower electrode and the dielectric layer.

Figure 8 is a diagram showing an X-Ray Diffraction (XRD) graph of a TiO ₂ thin film grown on an intermediate layer according to this embodiment.

_Figure 8 shows the crystallinity _of the TiO _{2 thin} film through The peak decreased, and for TiO ₂ grown on In ₂ O ₃ , the peak at the same position increased.

In this way, crystallinity is one of the most important factors that determine the capacitance of a capacitor, and therefore, in the case of an In ₂ O ₃ intermediate layer with increased crystallinity, a larger capacitance can be obtained compared to when a V ₂ O ₅ intermediate layer is inserted.

Figure 9 is a diagram showing the capacitance density of the capacitor at 100 kHz.

Referring to Figure 9, the capacitance densities of the TiN only, TiN/In ₂ O ₃ , and TiN/V ₂ O ₅ electrodes are 8.8 fF/μm ² and 9.9 fF/μm ² , respectively. In the case of the capacitor with In ₂ O ₃ inserted at 6.3 fF/μm ² , it increased by 12.5% compared to the TiN only device, and conversely, in the case of V ₂ O _{5 ,} it was confirmed that it decreased by 28.4%.

Capacitance density is proportional to the dielectric constant of the dielectric and inversely proportional to the thickness of the dielectric.

In the case of V ₂ O _{5 ,} the thickness of the dielectric increases because it is an insulator (10 ^-3 -10 ^-4 S/cm), and the dielectric constant of V ₂ O ₅ is very low compared to TiO ₂ , so the capacitance density is higher than that of TiN only devices. decreases.

On the other hand, In ₂ O ₃ is a conductive material (~1289 S/cm), so it does not affect the thickness of the insulator, and can have a higher capacitance density because crystallinity is increased as seen in X-ray diffraction.

Figure 10 is a graph showing the leakage current of the capacitor.

As shown in FIG. 10, as a result of atomic force microscopy measurement, the difference in surface roughness of the electrodes is approximately similar at less than 1 nm, and it can be predicted by X-ray photoelectron spectroscopy that the oxygen vacancies inside the dielectric will be similar.

This implies that the size of the leakage current due to the trap will be similar in all conditions, and in fact, the capacitor with V ₂ O ₅ and In ₂ O ₃ inserted shows a similar size of leakage current.

In general, in the case of TiO ₂ dielectric, leakage current is known to be more affected at the interface than inside, and as the work function increases, the interface-related leakage current (Schottky emission, Fowlter-Nordheim tunneling) decreases exponentially. tends to do so.

Through ultraviolet photoelectron spectroscopy, it was confirmed that the work function increased after insertion of the intermediate layer according to this embodiment, and the difference in leakage current can be considered to be based on the difference in work function.

The above-described embodiments of the present invention have been disclosed for illustrative purposes, and those skilled in the art will be able to make various modifications, changes, and additions within the spirit and scope of the present invention, and such modifications, changes, and additions will be possible. should be regarded as falling within the scope of the patent claims below.

Claims (7)

As a capacitor manufacturing method,
Forming a lower electrode made of TiN on a substrate;
Forming an oxide semiconductor intermediate layer composed of one of V ₂ O ₅ and In ₂ O ₃ on the lower electrode;
Forming a dielectric layer made of TiO ₂ on the oxide semiconductor intermediate layer; and
A capacitor manufacturing method including forming an upper electrode on the dielectric layer. According to paragraph 1,
A method of manufacturing a capacitor wherein the oxide semiconductor intermediate layer has a thickness in the range of 0.5 to 1.5 nm. According to paragraph 1,
The step of forming the oxide semiconductor intermediate layer is,
A capacitor manufacturing method comprising forming the oxide semiconductor intermediate layer through atomic layer deposition using a VTIP (Vanadium(V) oxytriisopropoxide) or DADI ([3-(dimethylamino)propyl]dimethyl indium) precursor. A substrate consisting of a Si wafer;
a lower electrode formed on the substrate and into which an oxide semiconductor intermediate layer is inserted;
A dielectric layer made of TiO ₂ formed on the lower electrode; and
A capacitor including an upper electrode formed on the dielectric layer. According to paragraph 4,
The lower electrode is,
a TiN layer formed on the substrate; and
A capacitor including an oxide semiconductor intermediate layer made of one of V ₂ O ₅ and In ₂ O ₃ formed on the TiN layer to a preset thickness. According to clause 5,
A capacitor in which the lower electrode into which the oxide semiconductor intermediate layer is inserted has an RMS roughness that is more than 1.5 times lower than that of the lower electrode composed only of TiN. According to clause 5,
A capacitor in which the lower electrode into which the oxide semiconductor intermediate layer is inserted increases the work function by more than 10% compared to the lower electrode composed only of TiN.