KR101559104B1 - MANUFACTURING METHOD OF Si THIN FILM USING COLD CATHOD PLASMA - Google Patents

Abstract

The present invention relates to a method of manufacturing a silica thin film using a cold cathode plasma, and more particularly, to a method of manufacturing a silica thin film using a cold cathode transformer as a power source for generating a plasma.
Since the manufacturing method of the silica thin film using the cold cathode plasma according to the present invention uses a leakage current transformer, a silica thin film exhibiting excellent insulating film characteristics and optical characteristics can be manufactured even at a low voltage.

Description

TECHNICAL FIELD [0001] The present invention relates to a manufacturing method of a silica thin film using a cold cathode plasma,

The present invention relates to a method of manufacturing a silica thin film using a cold cathode plasma, and more particularly, to a method of manufacturing a silica thin film by a chemical vapor deposition method using a cold cathode transformer as a power source for generating a plasma.

Plasma means ionized gas. When a gas composed of atoms or molecules is discharged using electric energy, a plasma composed of electrons, ions, decomposed gases, and photons is formed.

Depending on the type of the plasma generating electrode, a capacitively coupled plasma (inductively coupled plasma) method or an inductively coupled plasma (inductively coupled plasma) method can be used. Among these devices, a device for generating plasma using a capacitive coupling method is called a capacitively coupled plasma (CCP) generator.

The capacitor-coupled plasma generator uses the charge accumulation principle of a capacitor. The two electrodes are opposed to each other in the chamber, and high-frequency power, low-frequency power, direct-current power, or pulse power obtained by time- Can be made into structure.

The structure of the capacitively coupled electrode accelerates charge carriers such as electrons and ions by an electrostatic field between two electrodes to generate and maintain a plasma in response to interaction between the charged particles and the charged particles of the charged particles or charged particles . It is important to ensure that there is sufficient voltage difference between the two electrodes so that a plasma can occur.

Cold Cathode Transformer is a type of leakage current transformer. The leakage transformer is a transformer that can control the intensity of the secondary current by connecting leakage flux of magnetic flux using a leakage core on the magnetic circuit. Generally, a cold cathode transformer uses a leakage current principle to supply a constant current of about 400 - 4,000 V, 100 mA or less to a secondary power source.

In the conventional case, among the leakage current transformers, development of atmospheric pressure plasma using a neon transformer has been intensively studied, and there have been many reports on a device for generating plasma at atmospheric pressure and underwater (Korean Patent Publication No. 2006-0091869, 2004-311251).

However, in the case of generating a plasma at atmospheric pressure using a neon transformer that generally generates a high voltage of 5,000 V or more and a low current of about 30 mA, there are the following limitations.

1) At atmospheric pressure, the gap between the two plasma electrodes is limited. That is, in the plasma discharge, according to Paschen's law, the higher the pressure, the closer the distance between the electrodes is, the easier the plasma discharge is. Therefore, in the case of atmospheric pressure, there is a problem that the distance between the electrodes must be extremely close to several millimeters. However, if the distance between the plasma electrodes is too narrow, there is a limit to the surface treatment of materials of various sizes using plasma. For example, when the thickness of the workpiece is 10 cm or more, or when the surface of the workpiece has a curved shape, the treatment by the atmospheric pressure plasma is limited. Also, in the case of a donut-shaped material, there is a problem in the plasma treatment of the inner surface.

2) In order to discharge plasma at atmospheric pressure using a neon transformer, a relatively high voltage should be applied to both electrodes. At this time, strong arc is likely to occur between metal or conductive electrodes. This can be extremely dangerous in terms of electrical conductivity, which poses problems in terms of safety, uniformity and reproducibility of actual process development. Therefore, much research on the use of leakage current transformers in the fabrication of actual electronic materials has not been developed.

In order to solve such a problem, the inventor of the present invention has registered a plasma processing apparatus using a leakage current transformer in a vacuum (Korean Patent Registration No. 10-1147349). As shown in FIG. 1, the plasma processing apparatus using the leakage current transformer includes a chamber in which a sample to be processed is received and a plasma is formed; An exhaust unit for maintaining the inside of the chamber in a vacuum state; A plasma generating electrode fixed in the chamber and having an anode and a cathode opposite to each other; A variable power supply installed outside the chamber and supplying power to the plasma generating electrode; And a leakage current transformer installed between the variable power supply and the plasma generating electrode for adjusting a voltage and a current to be applied to the plasma electrode, wherein the variable power supply includes a primary power source And a voltmeter.

Chemical vapor deposition of silica thin films using plasma is an important technology that is attracting attention for manufacturing oxide semiconductor. Conventionally, sputtering method, thermal evaporation method, plasma chemical vapor deposition method using an organometallic precursor and a high frequency plasma have been typically used for deposition of silica.

However, techniques for using cold cathode plasma in the deposition of silica thin films have not been studied.

It is an object of the present invention to provide a novel method for depositing a silica thin film economically and simply using a cold cathode plasma.

The present invention has been made to solve the above problems

Introducing a substrate into a reactor, injecting an oxygen source, and applying power to form and maintain a plasma within the reactor;

Injecting a silicon-containing precursor into the reactor in which the plasma is maintained to form a silica thin film; And

And subjecting the substrate having the silica thin film formed thereon to a heat treatment, thereby producing a silica thin film using a cold cathode plasma.

In the method for manufacturing a silica thin film using cold cathode plasma according to the present invention,

A chamber in which a sample to be processed is accommodated and a plasma is formed;

An exhaust unit for maintaining the inside of the chamber in a vacuum state;

A plasma generating electrode fixed in the chamber and having an anode and a cathode opposite to each other;

A variable power supply installed outside the chamber and supplying power to the plasma generating electrode;

And a leakage current transformer provided between the variable power supply and the plasma generating electrode for adjusting a voltage and a current to be applied to the plasma electrode.

In the method of manufacturing a silica thin film using a cold cathode plasma according to the present invention, an inert gas is further injected in the step of forming and holding a plasma in the reactor. Examples of the inert gas include Ar, N ₂ Etc. can be used.

In the method for producing a silica thin film using a cold cathode plasma according to the present invention, the silicon-containing precursor is a gas containing a silicon element or a liquid.

In the method of manufacturing a silica thin film using a cold cathode plasma according to the present invention, the silicon-containing precursor is selected from the group consisting of tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), and SiH ₄ do.

In the method of manufacturing a silica thin film using a cold cathode plasma according to the present invention, acetic anhydride is further added to a liquid precursor containing the silicon element.

In the method for producing a silica thin film using cold cathode plasma according to the present invention, the acetic anhydride is mixed at a ratio of 0.15 to 0.5 mol per 1 mol of the liquid precursor. .

In the method of manufacturing a silica thin film using a cold cathode plasma according to the present invention, the substrate may be a silicon substrate, a sapphire substrate, a glass, an organic polymer substrate, a polyethylene naphthalate (PEN), a polyethylene terephthalate (PET) PES), a polyimide, a polycarbonate, a cyclic olefin copolymer, or a mixture thereof.

In the method of manufacturing a silica thin film using cold cathode plasma according to the present invention, a power source applied to the leakage current type transformer during the plasma formation is 60 to 90 V.

In the method of manufacturing a silica thin film using cold cathode plasma according to the present invention, the pressure inside the reactor is 400 to 1000 mTorr.

The manufacturing method of the silica thin film using the cold cathode plasma according to the present invention can produce an excellent insulating film and a silica thin film exhibiting optical characteristics even at a low voltage because a leakage current transformer is used.

Further, the silicon oxide thin film produced by the method of the present invention can be used as an insulating film of an electronic device including a semiconductor, a sensor, a transmission preventing film of a gas which deteriorates the performance of an organic or inorganic transparent electronic device, or an optical material for anti- have.

1 is a block diagram showing an embodiment of a plasma processing apparatus using a cold cathode transformer of the present invention.
FIG. 2 is a graph showing a voltage applied from the cold cathode transformer to the plasma electrode when the voltage applied to the cold cathode transformer in the slidax is 60 V to 90 V. FIG.
FIG. 3 is a graph illustrating a peak-to-peak voltage of a voltage applied from a cold cathode transformer to a plasma electrode according to a voltage input to a cold cathode transformer in a variable voltage generator.
FIG. 4 is a graph illustrating the results of measurement of the deposition rate of a silica thin film produced by changing the voltage applied to an electrode in a cold cathode transformer according to an embodiment of the present invention.
5 shows a result of measuring the refractive index of a silica thin film manufactured in an embodiment of the present invention.
FIG. 6 shows the results of measuring the refractive index of a silica thin film prepared according to the mixing molar ratio of acetic anhydride to TEOS, which is a silicon precursor, in the preparation of a mixed liquid precursor.
FIG. 7 shows the results of measurement of the change in the deposition rate of the silica thin film according to the precursor concentration according to an embodiment of the present invention.
FIG. 8 shows the results of FTIR measurement of changes in the composition of SiO ₂ deposited according to the change in the molar ratio of the acetic anhydride to the TEOS.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited by the following examples.

< plasma  Processing equipment>

1 is a block diagram showing an embodiment of a plasma processing apparatus using a cold cathode transformer of the present invention.

The plasma processing apparatus using the cold cathode transformer of the present invention includes two grounded reactors, a plasma generating electrode, a cold cathode transformer, a variable voltage regulator, a vacuum gauge, a vacuum pump mechanical pump, and precursor vaporizer.

The cold cathode transformer is a type of leakage current transformer. The primary power source usually uses about 1 - 500 V, preferably about 12 - 220 V. The output voltage is typically around 300 - 5,000V. The magnitude of the output voltage generated at this time can be adjusted by using the variable power supply. The variable power supply may be manufactured using a transistor or the like, or a commercially available slider or a dimmer may be used. In this embodiment, the slider duck is used as a variable voltage regulator. Between the slidax and the cold cathode transformer, the amperemeter and the voltmeter were connected and the values of the primary voltage and current applied to the cold cathode transformer were accurately displayed.

2 shows a voltage applied from the cold cathode transformer to the plasma electrode when the voltage applied to the cold cathode transformer changes from 60 V to 90 V in the slidax. It can be seen that the cold cathode transformer used in this experiment has various peaks.

FIG. 3 is a graph illustrating a peak-to-peak voltage of a voltage applied from a cold cathode transformer to a plasma electrode according to a voltage input to a cold cathode transformer in a variable voltage generator. As the voltage applied to the cold cathode transformer increased from 60 V to 90 V, the voltage from the cold cathode transformer to the plasma electrode increased from 624 V to 800 V.

< Example  1> Fabrication of silica thin films according to substrate type

A silica precursor, TEOS, was mixed with acetic anhydride. A mixed solution of 5.71 ml of TEOS and 5 ml of acetic anhydride was prepared so that the mixing molar ratio of acetic anhydride to TEOS was 1: 0.43. The mixed solution was stirred at 120 DEG C for 8 hours to make a clear and stable solution. A transparent liquid precursor solution was placed in a vacuum precursor vessel made of stainless steel and used in cold cathode plasma thin film deposition. In the plasma deposition experiment, the vacuum pressure of the reactor was tested in the range of 400 to 1000 mTorr.

In order to investigate the efficiency of thin film fabrication according to the type of substrate, a silicon (Si: 3 × 3 cm ² ), a glass (2 × 3 cm ² ) and a polycarbonate (2 × 3 cm ² ) Thin films were prepared. Each of the substrates was ultrasonically cleaned for 5 minutes each in the order of methanol, acetone and distilled water (DI water).

< Experimental Example  1-1> Measurement of deposition rate

FIG. 4 shows the results of measurement of the deposition rate of the silica thin film produced while varying the voltage applied to the electrodes in the cold cathode transformer, with respect to the substrate used.

As shown in FIG. 4, in the case of the glass substrate and the polycarbonate substrate, the deposition rate of SiO ₂ was as low as 30-60 A / min. In contrast, the deposition rate of the silicon substrate was about 350 to 650 A / min, which is about 10 times higher.

It is considered that the deposition rate of the glass substrate and the polycarbonate substrate is low because the sticking coefficient of the materials is low at room temperature.

According to the embodiment of the present invention, when a cold cathode plasma source is used, it can be confirmed that SiO ₂ is deposited on glass and polycarbonate at a temperature of 300K at a rate of 30 - 60 A / min.

< Experimental Example  1-2> Measurement of refractive index

The refractive index of the silica thin film deposited on the silicon substrate prepared in the above example was measured and the result is shown in FIG.

In FIG. 5, when the mixing molar ratio of acetic anhydride to TEOS is 1: 0.43, the refractive index gradually increases as the voltage applied to the electrode increases

In this embodiment, when the content of Si contained in SiO ₂ is large in the plasma deposition, the refractive index becomes larger than 1.46.

< Example  2> Preparation of Silica Thin Films According to Precursor Concentration Change

As a liquid precursor, a silica thin film was prepared at an applied voltage of 696 V at about 1.5 Torr and room temperature for 20 minutes while varying the mixing molar ratio of acetic anhydride to TEOS in the preparation of the mixed precursor.

< Experimental Example  2-1> Measurement of refractive index

FIG. 6 is a graph showing a change in refractive index according to a mixed molar ratio of acetic anhydride to TEOS in the preparation of a mixed liquid precursor. As the mixing molar ratio increased, the refractive index increased.

In addition, when the molar ratios were 0.23 and 0.33, the refractive indices were 1.44 and 1.48, respectively, and plasma deposition was possible in the refractive index range of pure SiO ₂ of 1.46.

< Experimental Example  2-2> Measurement of deposition rate

The variation of deposition rate according to the mixing molar ratio of acetic anhydride to TEOS was measured and the result is shown in FIG. In Figure 7 SiO ₂ The deposition rate was hardly affected by the change in mole ratio and was in the range of about 400 A / min.

< Experimental Example  2-3> FTIR  Measure

FIG. 8 is a graph showing FTIR measurement of the change in the composition of SiO ₂ deposited according to the change of molar ratio of acetic anhydride to TEOS. The CH peak and the Si-OC peak were detected at 2359 cm ^-1 and 1056 cm ^-1 , respectively. Therefore, silicon (Si) and oxygen (O) components were detected in the SiO ₂ thin film deposited by the cold cathode plasma, and it was confirmed that silica was deposited.

FTIR measurements indicate that the carbon in the TEOS component used as a precursor is partially contained in the silica film without being completely vaporized during the plasma deposition. Some of the carbon components included in the silica deposition in the room temperature deposition may be used in the development of a silica protective film and an insulating film process that do not greatly affect the properties of the thin film, Mechu may be used for the purpose of improving the fluidity in the development of the special insulating film process.

Claims (11)

Introducing a substrate into a reactor, injecting an oxygen source, and applying power to form and maintain a plasma within the reactor;
Injecting a silicon-containing precursor into the reactor in which the plasma is maintained to form a silica thin film; And
And heat treating the substrate having the silica thin film formed thereon
The silicon-containing precursor is a liquid precursor containing a silicon element,
Wherein the liquid precursor further comprises Acetic anhydride,
The plasma is generated in a low vacuum using a cold cathode transformer power source inside the reactor,
The pressure inside the reactor is 400 to 1000 mTorr,
And the power applied to the cold cathode transformer is 60 to 90 V.
The method according to claim 1,
The reactor
A chamber in which a sample to be processed is accommodated and a plasma is formed;
An exhaust unit for maintaining the inside of the chamber in a vacuum state;
A plasma generating electrode fixed in the chamber and having an anode and a cathode opposite to each other;
A variable power supply installed outside the chamber and supplying power to the plasma generating electrode; And
And a cold cathode transformer provided between the variable power supply and the plasma generating electrode for adjusting a voltage and a current to be applied to the plasma electrode.
The method according to claim 1,
Wherein an inert gas is further injected in the step of forming and holding a plasma in the reactor.
delete delete The method according to claim 1,
Wherein the silicon-containing precursor is selected from the group consisting of tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), and SiH ₄ .
delete The method according to claim 1,
Wherein the acetic anhydride is mixed at a ratio of 0.15 to 0.5 mole per mole of the liquid precursor.
The method according to claim 1,
The substrate may be a silicon substrate, a sapphire substrate, a glass, an organic polymer substrate, or a polymer substrate such as polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyethersulfone (PES), polyimide, polycarbonate, cyclic olefin copolymer And a mixture thereof. The method of claim 1, wherein the plastic substrate is a plastic substrate.
delete delete

Images