KR20140051574A - Deposition method of zirconia film doped nb - Google Patents

Abstract

The present invention relates to a deposition method of a titania thin film doped with niobium and, more specifically, to a method for depositing a titania thin film doped with niobium onto the surface of a substrate using a Nb-Ti alloy target. The deposition method of a titania thin film doped with niobium includes: a mounting step for mounting the Nb-Ti alloy target inside a vacuum chamber; and a deposition step for depositing a titania thin film doped with niobium onto a substrate installed inside the vacuum chamber by sputtering the vacuum chamber after injecting nitrogen and oxygen inside the vacuum chamber.

Description

[0001] The present invention relates to a deposition method of a niobium-doped titania thin film,

The present invention relates to a method of depositing a niobium-doped titania thin film, and more particularly, to a method of depositing a niobium-doped titania thin film on a substrate using an Nb-Ti alloy target.

Plasma is one of the most important technologies for the fabrication and processing of thin films. Especially as the interest in nanotechnology has increased, the applications of plasma processing such as nano-sized thin film deposition and etching are more important technology It is expected.

Plasma has become an important study in thin film deposition, etching, and surface modification for nano device fabrication. Precision below tens of nanometers is impossible without the help of plasma. It is no exaggeration to say that all future electronic devices will depend on the plasma process.

Titanium (TiO ₂ ) thin films doped with niobium (Nb) are widely used for transparent electrodes, solar cells, and gas sensors. A dry thin film coating process can be applied as a method for forming a titania thin film. The dry thin film coating process can be roughly classified into a PVD process and a CVD process.

The CVD method has a problem in that it is difficult to precisely control the process, and it is difficult to manufacture the precursor. On the other hand, PVD (Physical Vapor Deposition) process is an eco-friendly process with no emission of pollutants and has excellent adhesion and abrasion resistance.

 The sputtering method of the PVD method can minimize the thermal stress because the process is simple and the deposition is performed at a low substrate temperature. The formed titania thin film has a relatively high deposition rate at a low substrate temperature and can be manufactured by chemical vapor deposition (CVD) Which is known to be stable compared to the titania thin film.

However, the physical and optical properties of thin films are important for thin films to be used for optical devices and optical sensors. The titania thin film to which the other metal is added has a problem that the composition control is difficult during the deposition by the surfering method and the characteristics of the thin film are not uniform.

It is an object of the present invention to provide a method for depositing a niobium-doped titania thin film using an Nb-Ti alloy target.

Another object of the present invention is to provide a deposition method having uniform thin film characteristics by grasping deposition time and temperature conditions capable of forming a thin film having excellent characteristics.

In order to accomplish the above object, the present invention provides a method for depositing a niobium-doped titania thin film, comprising: mounting a Nb-Ti alloy target in a vacuum chamber; And depositing a niobium-doped titania thin film on a substrate provided in the vacuum chamber by introducing nitrogen and oxygen into the vacuum chamber and then performing surfering.

The deposition is performed by introducing the nitrogen and the oxygen at the same volume ratio, and then the substrate is maintained at 450 to 500 ° C. and is subjected to surfering for 1 to 4 hours at 200 W power.

As described above, according to the present invention, niobium-doped titania thin films can be deposited by precisely controlling the composition ratio of Ti and Nb using Nb-Ti alloy targets.

In addition, the present invention provides a thin film deposition method which can be effectively used as a material for a transparent electrode, a solar cell, and a sensor by improving the optical characteristics and the structural characteristics by controlling the deposition temperature and the deposition time.

FIG. 1 is a schematic view showing a downward-deposition-type sputtering apparatus applied to the present invention,
2 is a graph showing an XRD pattern of a thin film of the embodiments,
3 to 8 are SEM photographs showing the thin films of the embodiments,
9 is a graph showing the optical characteristics of the thin films of the embodiments.

Hereinafter, a method of depositing a niobium-doped titania thin film according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The present invention relates to a method of forming a thin film of TiO ₂ (hereinafter referred to as Nb-TiO ₂ ) doped with niobium (Nb) on a substrate, which is an object to be deposited, by using a radio-frequency sputtering method, Thin film) is formed.

First, prepare an Nb-Ti alloy target with a target to be used for sputtering.

The Nb-Ti alloy target is made of an alloy of niobium (Nb) and titanium (Ti) (hereinafter referred to as Nb-Ti alloy). For example, niobium and titanium may be vacuum-melted to prepare an Nb-Ti alloy target mixed with 97 to 99% by weight of Ti and 1 to 3% by weight of Nb. Such an alloy material has an advantage that the ratio of titanium to niobium can be easily controlled. The ratio of titanium to niobium in the thin film formed on the surface of the substrate using the Nb-Ti alloy target is determined by the ratio of titanium to niobium in the Nb-Ti alloy target.

A vacuum arc melting method can be applied for the production of Nb-Ti alloy targets. In the vacuum arc melting method, niobium and titanium to be melted are charged into a vacuum melting furnace and an arc is generated in a vacuum or inert gas atmosphere to melt the metal in the vacuum melting furnace. The molten metal is made into ingots from molds and is processed into a shape and size suitable for use as a target using a lathe or other processing machine.

When a thin film is formed using the Nb-Ti alloy target, the composition ratio of titanium and niobium can be precisely controlled. On the other hand, a thin film can be deposited on the surface of a substrate by simultaneously sputtering a Ti target and an Nb target without using an Nb-Ti alloy target, but it is very difficult to control the composition ratio precisely in this case.

When the above-mentioned Nb-Ti alloy target is prepared, a thin film is deposited on the surface of the substrate by using a downward deposition type RF stuffer apparatus.

The downward deposition type RF stuffer device applied to the present invention is shown in Fig. 1, the sputtering apparatus includes a Nb-Ti alloy target 3 installed on the upper side of the inside of the vacuum chamber 1 and a substrate holder 7 (see FIG. 1) provided at a position 70 mm downward from the Nb-Ti alloy target 1 A substrate 10 mounted on the substrate holder 7 to deposit a thin film thereon and a heater 13 provided in the substrate holder 7. [ And a gas storage bumble 17 (17) connected to the vacuum chamber 1 and a gas supply pipe for supplying inert gas and reactive gas for thin film deposition, a power supply unit 21 for applying an RF voltage, an RF plasma regulator 25, ) 19 are provided together. Inside the Nb-Ti alloy target 3, a disk-shaped permanent magnet 5 having a very large coercive force is embedded, thereby concentrating the reaction gas in one place in a plasma state so as to obtain a high plasma density in vacuum. The substrate 10 may be a wafer made of silicon having a purity of 99.99%.

The Nb-Ti alloy target 3 is mounted on the inside of the vacuum chamber 1 and then the substrate 10 is mounted on the substrate holder 7.

Before mounting the substrate 10 on the substrate holder 7, the substrate 10 was washed with ultrasonic cleaner for 15 minutes using ethanol to remove organic and inorganic substances present on the surface of the substrate 10, followed by washing with deionized water It is cleaned with nitrogen gas.

Then, the internal pressure of the vacuum chamber 1 is lowered to 2 × 10 ^-6 torr by using a vacuum pump, and the gas necessary for deposition is injected into the vacuum chamber to maintain the internal pressure of the vacuum chamber 1 at 400 mtorr. Reacted with an Nb-Ti alloy target 3 as a gas necessary for deposition to react with an inert gas and an atomic or molecular target material to make the target 3 atomic or molecular, Is a reactive gas for forming a thin film. Nitrogen is used as an inert gas and oxygen is used as a reactive gas.

In the present invention, oxygen and nitrogen gas are injected into the vacuum chamber 1, and the volume ratio of the nitrogen gas to the volume of the oxygen gas is controlled in the same manner. For example, the volumes of oxygen and nitrogen introduced into the vacuum chamber 1 per unit time through the flow regulator 15 are adjusted to 10 sccm, respectively.

As described above, the oxygen gas and the nitrogen gas are adjusted to the same volume ratio and injected into the vacuum chamber 1, and then the RF power is applied from the power supply unit 21 to generate plasma. Preferably, after plasma formation, the plasma is pre-sputtered for 20 minutes to remove impurities on the Nb-Ti alloy target surface when the plasma is in a stable state. In this case, in order to prevent impurities from being deposited on the surface of the substrate 10, the shutter 11 of the substrate holder 7, on which the substrate 10 is mounted, is pre-surferred while being closed.

After free surfering, the shutter 11 is removed and then a thin film is deposited on the substrate 10 by surfering. In the deposition, the substrate 10 is maintained at 450 to 500 DEG C by using the heater 13, and is subjected to surfering for 1 to 4 hours at 200 W power. In the deposition of the thin film, the nitrogen gas makes the target material into an atomic or molecular state in a state where the plasma is concentrated by the permanent magnet, and the atomic state or the molecular state titanium is oxidized by the oxygen gas to deposit a thin film on the substrate, do. Since niobium contained in the alloy target is very small compared to titanium, most oxygen reacts with titanium to form TiO ₂ , and niobium is contained in the thin film in the form of TiO ₂ .

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, it should be understood that the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

(Example)

 As shown in FIG. 1, a thin film was deposited on the surface of a substrate by using a downward deposition type RF-sputtering apparatus.

A Nb-Ti alloy target (length: 102 mm, diameter 6.35 mm) mixed with a weight ratio of Ti: Nb of 98: 2 was used as a target for thin film deposition. The substrate was a p-type silicon wafer.

In order to remove organic and inorganic substances present on the surface of the substrate, the substrate was washed with an ultrasonic washing machine for 15 minutes using ethanol, washed with deionized water, and then cleaned with N ₂ gas. The temperature of the substrate was maintained at 450 ° C and 500 ° C through a heater for heating the substrate, respectively. After the vacuum inside the vacuum chamber was lowered to 3 × 10 ^-6 torr by using a vacuum pump, the nitrogen gas and the oxygen gas were adjusted to 10 sccm through a flow controller (G mate 2000 A MFC controller, lokas co. And the pressure after the gas injection was maintained at 400 mTorr.

The plasma, which is an important condition for plasma formation, was formed through an RF plasma regulator (XSP-06MF RF-plasma generator, youngsin. Eng). When the plasma was in a stable state, the shutter attached to the substrate holder was closed, and pre-sputtering was performed for about 20 minutes to remove impurities on the target surface. After removing the shutter, the thin film was deposited on the substrate. The experimental conditions of each example are specifically shown in Table 1 below.

division Deposition time (hr) Substrate temperature (캜) N ₂ : O ₂ (sccm) Power (W) Example 1 (S401) One 500 10:10 200 Example 2 (S402) 2 500 10:10 200 Example 3 (S403) 3 500 10:10 200 Example 4 (S502) 2 450 10:10 200 Example 5 (S503) 3 450 10:10 200 Example 6 (S504) 4 450 10:10 200

<1. XRD Pattern Analysis>

2 is a graph showing the XRD patterns of the thin films prepared in the examples.

Referring to FIG. 2, in Examples 1 to 3 in which the temperature of the substrate is fixed at 500 ° C, the intensity of the peak (2Theta = 22.5 °) decreases as the deposition time increases, and the crystallinity of the thin film decreases , The intensity of the peak (2Theta = 22.5 °) was constant regardless of the deposition time in Examples 4 to 6 in which the temperature of the substrate was fixed at 450 ° C. When the deposition temperature of the thin film was low, .

Observation of the peak at 2Theta = 29.5 deg. Showed that the deposition time was almost unchanged at 1 and 2 hr in Examples 1 to 3 in which the temperature of the substrate was fixed at 500 deg. C, but the peak intensity was drastically decreased at 3 hr. In the case of Examples 4 to 6 in which the temperature of the substrate is fixed at 450 占 폚, the intensity is increased and then decreased as the deposition time is increased, so that it does not seem to have a certain tendency. The crystal growth direction of the thin film has a close influence on the internal energy in the thin film or the mutual atomic force relationship of the atoms existing in the thin film. Therefore, at 2 Theta 39.5 °, the growth direction of the thin film does not grow in a certain direction due to any one influence.

Observation of the peak at 2Theta = 44.25 ° shows that the cases of Examples 1 to 3 in which the temperature of the substrate is fixed at 500 ° C and the cases of Examples 4 to 6 in which the temperature of the substrate is fixed at 450 ° C are increased The intensity of the peak was found to be decreased constantly. It can be understood that the crystallinity of the thin film is affected by the deposition time regardless of the deposition temperature of the thin film.

Observation of peaks at 2Theta = 46 ° shows that the cases of Examples 1 to 3 in which the temperature of the substrate is fixed at 500 ° C and the cases of Examples 4 to 6 in which the temperature of the substrate is fixed at 450 ° C are 1, 2 hrs, there was almost no change, but at 3 hrs, the peak intensity showed a steep tendency when the intensity decreased sharply.

<2. Particle size analysis of thin films>

Fig. 3 shows the thin film produced in Example 1, Fig. 4 shows the thin film produced in Example 2, Fig. 5 shows the thin film produced in Example 3, Fig. 6 shows the thin film produced in Example 4, FIG. 8 is a SEM photograph of the thin film prepared in Example 6. FIG.

Referring to FIG. 8, in Examples 1 to 3 in which the temperature of the substrate was fixed at 500 ° C., the particle size of the thin film was increased with the increase of the deposition time, and the shape of the amorphous particles was observed on the thin film surface. On the other hand, in Examples 4 to 6 in which the temperature of the substrate was fixed at 450 캜, the particle size was increased as the deposition time was increased, but the shape of the amorphous particles was hardly observed on the surface of the thin film. This indicates that the deposition temperature of the thin film affects the appearance of the amorphous particles in the thin film. The increase of the deposition temperature leads to the increase of the strain energy inside the thin film, and thus the atypical particles appear in the thin film.

<3. Optical properties>

FIG. 9 is a PL graph showing the optical characteristics of the thin films of Examples using photoluminescence (PL) analysis.

(6K) using a closed-cycle liquid helium cryogenator (APD, Japan) with a wavelength of 325nm and a power of 50mW as an excitation source for PL measurement. SH-4, USA), spectrometer (f = 0.5m, Acton Research Co., Spectrograph 500i, USA), intensified photo diode array detector (Princeton Instrument Co., IRY1024, USA).

Referring to FIG. 9, in the case of a thin film having a deposition time of 2 hr, the intensity of the binding energy at 460 nm and 470 nm was decreased as the deposition temperature was increased. On the contrary, when the deposition time was 3 hr, the intensity of the binding energy at 460 and 470 nm was increased as the deposition temperature was increased. This indicates that the deposition time of the thin film is related to the binding energy inside the thin film.

Through the above experiments, it was confirmed that the characteristics of the thin film can be changed by the deposition temperature and the deposition time of the thin film. Therefore, the deposition temperature and time of the thin film are important for the properties of the thin film.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation.

1: Chamber 3: Target
7: substrate holder 10: substrate
11: Shutter 15: Flow regulator
21: Power supply

Claims (2)

A mounting step of mounting an Nb-Ti alloy target inside the vacuum chamber;
And depositing a niobium-doped titania thin film on a substrate provided in the vacuum chamber by surfering the nitrogen and oxygen introduced into the vacuum chamber to deposit the niobium-doped titania thin film on the substrate. Deposition method. The method of claim 1, wherein the deposition is performed by introducing the nitrogen and the oxygen at the same volume ratio, and then the substrate is maintained at 450 to 500 DEG C and is subjected to surfering at 200 W for 1 to 4 hours. And depositing the doped titania thin film.

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