KR20050019628A - Radio frequency power supplier for generating large-size plasma and method of power supply thereof - Google Patents

Abstract

PURPOSE: An RF power supply device for generating large-area plasma and a power supply method using the device are provided to generate stabilized and uniform large-area plasma by appropriately selecting RF power, to thereby reduce the RF power. CONSTITUTION: An RF power supply device used for manufacturing a large liquid crystal display includes a plurality of RF oscillators(200,220,240), and a plurality of impedance matchers(210,230,250). One end of each impedance matcher is connected to each RF oscillator and the other end is connected to a plasma electrode(50). The RF power supply device further includes bandpass filters placed inside the impedance matchers or between the impedance matchers and the plasma electrode. The plurality of RF oscillators include the first RF oscillator generating RF power of 13.56MHz to 100MHz and the second RF oscillator generating RF power of 400KHz to 2MHz.

Description

Radio frequency power supplier for generating large-size plasma and method of power supply

The present invention relates to an apparatus for manufacturing a large area LCD substrate, and more particularly, to a power supply apparatus capable of generating stable and uniform plasma using a plurality of high frequency oscillators.

Processes such as thin film deposition, etching, and cleaning that are required to manufacture an LCD substrate are various, but in general, chemical vapor deposition (CVD), which has good uniformity and step coverage, is commonly used. Among them, PECVD (Plasma Enhanced CVD) method using plasma is widely used because of the advantages of low temperature deposition and rapid formation of thin films.

PECVD is divided into a method using an inductively coupled plasma (ICP) and a method using a capacitively coupled plasma (CCP). The former uses an induction magnetic field generated by applying a high frequency power to an antenna coil. The latter is a method of applying a high frequency power source to the plasma electrode.

The present invention relates to a method using a capacitively coupled plasma (CCP), the large-area LCD manufacturing apparatus using the capacitively coupled plasma is not only a PECVD device for thin film deposition, but also an etcher (etcher), plasma cleaning to perform an etching process There is a dry scrubber for performing the process, but since each apparatus uses plasma and the overall process sequence is similar, the following description will focus on the PECVD apparatus.

1 is a schematic configuration diagram of a general capacitively coupled PECVD apparatus, which will be briefly described in the process order with reference to the drawings.

First, when the LCD substrate 30 is seated on the upper surface of the susceptor 20 installed in the process chamber 10 by a robot arm (not shown), the reaction gas flows into the process chamber through the gas supply pipe 60. And is sprayed. At this time, if the RF power supplied from the RF (Radio Frequency) oscillator 80 is applied to the plasma electrode 50 through the impedance matcher 70, the RF electric field is between the susceptor 20 and the plasma electrode 50. The accelerated electrons collide with the surrounding neutral gas to generate a plasma 40 containing ions or radicals.

The plasma reaction gas is used for deposition or etching on the LCD substrate 30, and the remaining reaction gas is discharged to the exhaust pipe 100 after the process is completed. In this case, a separate RF power source (not shown) may be applied to the susceptor 20 to control energy of ions incident on the LCD substrate 30.

The plasma electrode 50 and the process chamber 10 are insulated by the insulating block 90, and an O-ring between the insulating block 90 and the plasma electrode 50, the insulating block 90, and the chamber wall. ) To block the upper part of the plasma electrode 50 in the atmospheric pressure state from the lower part of the vacuum atmosphere.

On the other hand, since the RF power supplied from the RF oscillator 80 is transmitted along the surface of the plasma electrode 50 due to the skin effect, the lower portion of the plasma electrode 50 is transferred from the edge of the surface to the center, thereby A standing wave of RF power is generated on the surface.

However, because of the standing wave, the size of the RF power at the lower surface of the plasma electrode 50 varies with each position, and thus affects the plasma uniformity.

In general, in the case of 5th generation or less LCD substrates, these effects have been insignificant because the size of the LCD substrate is relatively small compared to the wavelength of standing waves, so that the difference between the RF electric field and the RF power is not large at the center and the edge of the substrate. As the size of is increasing in size as shown in Table 1 below, the influence of these standing waves is inevitably considered.

TABLE 1

division Size (mm) Short axis (mm) Major axis (mm) Rd (diagonal / 2) (mm) Area (mm ² ) 4th generation 730 x 920 730 920 587 671,600 5th generation 1100 x 1250 1100 1250 833 1,375,000 6th generation 1500 x 1850 1500 1850 1191 2,775,000 7th generation 1870 x 2200 1870 2200 1444 4,114,000 8th generation 2200 x 2550 2200 2550 1670 5,610,000

Table 2 below shows the wavelengths of standing waves formed in the plasma electrode based on the experimental results based on the theoretical calculations based on the experiments with an electron temperature of 3 eV, a chamber pressure of 0.8-2 torr, and a distance of 25.0 mm between the plasma electrode and the susceptor. As a comparison table showing the size of the LCD substrate, the lower the frequency of the RF power supply, the lower the electron density, the larger the wavelength of the standing wave. This means that the plasma uniformity on the LCD substrate also increases.

TABLE 2

division Electron Density (Number / cm-3) Standing wave wavelength (SWL, mm) Bessel Fnradial scale (mm) 27.12 MHz 1.0E + 09 6299.02 2412 5.0E + 09 4212.41 1613 1.0E + 10 3542.20 1357 5.0E + 10 2368.81 907 1.0E + 11 1991.92 763 13.56 MHz 1.0E + 09 12598.03 4825 5.0E + 09 8424.81 3226 1.0E + 10 7084.39 2713 5.0E + 10 4737.62 1814 1.0E + 11 3983.85 1526 2 MHz 1.0E + 09 85415 32711 5.0E + 09 57120 21875 1.0E + 10 48032 18394 5.0E + 10 32121 12301 1.0E + 11 27010 10344

However, since the standing wave formed on the surface of the plasma electrode is attenuated according to the distance, the radial scale obtained by the Bessel function of the first kind has a more practical meaning than the wavelength of the standing wave.

FIG. 2 is a graph comparing a radial scale and generation size of an LCD substrate by a Bessel function of a first kind, where A graph is 2 MHz, B graph is 13.56 MHz, and C graph is 27.12 MHz. Indicates.

Referring to the drawing, when the RF power is 2 MHz (A), the plasma is stably and uniformly discharged regardless of the size of the substrate. In the case of 13.56 MHz (B), the plasma is uniformly discharged regardless of the size of the substrate up to the 8th generation LCD substrate when the electron density is about 6E + 10 or less, but the plasma discharge of the 8th generation LCD substrate is limited at the electron density higher than that. .

In general, plasma non-uniformity should be less than 20% in LCD process and less than 10% in good production LCD equipment.

In the case of 27.12 MHz (C), plasma discharge of the 6th generation LCD substrate is limited even if the electron density is about 2E + 10 or more.

The higher the frequency of the RF power source, the higher the electron density, the radial scale becomes smaller than the diagonal radius (Rd) of the LCD substrate increases, which means that as the size of the LCD substrate increases It means that the discharge is limited and unstable.

In the case of the existing 13.56MHz, the lower the plasma density, the lower the productivity of the formed thin film and the deposition rate or etching rate.

Therefore, as the LCD substrate becomes larger, there is a need for a method for generating a more stable and uniform plasma by properly adjusting the RF power supply.

An object of the present invention is to provide a high frequency power supply device and a power supply method capable of generating stable and uniform plasma required for manufacturing a large area LCD substrate.

The present invention, in order to achieve the above object, a plurality of high frequency oscillator; One end of the high frequency oscillator and the other end of the high-frequency power supply for manufacturing a large-area liquid crystal display device including a plurality of impedance matching devices respectively connected to the plasma electrode.

Preferably, a band pass filter is formed inside the impedance matcher or between the impedance matcher and the plasma electrode.

The plurality of high frequency oscillators may include a first high frequency oscillator for generating high frequency power in a range of 13.56 MHz to 100 MHz, and a second high frequency oscillator for generating high frequency power in a range of 400 KHz to 2 MHz.

The plasma electrode is formed on a part of the susceptor or integrally with the susceptor.

In addition, the present invention comprises a first step of generating a plasma by connecting the first high frequency oscillator with a plasma electrode for a predetermined time; A second high frequency oscillator is connected to a plasma electrode to provide a high frequency power supply method for manufacturing a large area liquid crystal display device, the second step of maintaining the plasma uniformly.

Preferably, the first high frequency oscillator generates high frequency power in a range of 13.56 MHz to 100 MHz, and the second high frequency oscillator generates high frequency power in a range of 400 KHz to 2 MHz.

The method may further include disconnecting the first high frequency oscillator after the first step and reconnecting the first high frequency oscillator after the second step.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings, the same parts in the drawings will use the same reference numerals and names.

3 illustrates a large-area LCD manufacturing apparatus using an electrostatically coupled plasma according to an embodiment of the present invention. As described above, this is a PECVD apparatus for thin film deposition, an etcher for performing an etching process, and a plasma. Since various apparatuses using plasma, such as a dry scrubber for performing the cleaning process, may be applicable, the following description will focus on the PECVD apparatus.

Referring to the drawings, the high frequency power supply includes a first power supply unit including a first high frequency oscillator 200 and a first impedance matcher 210, a second high frequency oscillator 220, and a second impedance matcher 230. Comprising a second power supply comprising a, each power supply is connected to the gas supply pipe 60, the gas supply pipe 60 is connected to the plasma electrode (50). In this way, the high-frequency power supply device is connected to the gas supply pipe 60 without directly connecting the plasma electrode 50 to ensure maximum symmetry of the plasma required for manufacturing a large area LCD. It is also possible to directly connect each impedance matcher 210 or 230 to the plasma electrode 50.

The impedance matchers 210 and 230 serve to match the inherent impedances of the high frequency oscillators 200 and 220 and the load impedances of the gas supply pipe 60 and the like. Also, in order to electrically insulate both of the high frequency oscillators 200 and 220 when they are simultaneously applied, the impedance matchers 210 and 230 preferably include a band path filter that passes only frequencies of a specific band therein. Do. Since the configuration of the band pass filter is conventional, a detailed description thereof will be omitted.

In addition, an independent bandpass filter may be provided between the impedance matchers 210 and 230 and the gas supply pipe 60, as described later, without installing the bandpass filter inside the impedance matchers 210 and 230. It's okay.

Since bandpass filters are used to electrically insulate each power supply, other means may be used as long as these effects can be achieved.

On the other hand, the high frequency power supplied by the high frequency oscillators 200 and 220 is preferably the first high frequency oscillator 200 supplies power in the range of 13.56 MHz to 100 MHz, and the second high frequency oscillator 220 supplies power in the range of 400 KHz to 2 MHz. Do.

For example, the first high frequency oscillator 200 may supply power of 13.56 MHz and the second high frequency oscillator 2 MHz.

The simultaneous application of multiple RF powers in different frequency bands is intended to take advantage of a phenomenon in which the density or property of the plasma generated varies depending on the frequency of the supplied power. In other words, the mobility of electrons and ions in plasma varies due to the mass difference. At frequencies above 13.56 MHz, RF power is mainly used to excite the movement of electrons. As a result, the collision frequency between electrons and neutral gas increases and radicals ( The higher the density of radicals, the better the film quality and the higher the aspect ratio.

On the other hand, the frequency below 2MHz is similar to the operating frequency of ions in the plasma, so it is mainly used to accelerate the ions by supplying RF energy to the ions. Therefore, when only high frequency power having a frequency of 2 MHz or less is applied, there is a problem that the plasma density is lowered and the film quality and aspect ratio are lowered. In addition, although high power is initially required for ignition of the plasma, a problem may occur that the ignition of the plasma may not occur when only a low frequency power source is applied.

However, high frequency power of less than 2MHz plays an important role in heating the edge of the generated plasma to make the plasma uniform.

3 shows that a plurality of power supply units are connected to the plasma electrode 50 above the process chamber 10. However, in the case of the capacitively coupled PECVD apparatus, since a configuration for applying high frequency power to the susceptor 20 is also used, 4 shows an example in which the present invention is applied in such a configuration.

In this case, the high frequency power supply device includes a first bandpass filter formed between the first high frequency oscillator 200, the first impedance matcher 210, the first impedance matcher 210 and the susceptor 20. A second band formed between the first power supply unit including the first power supply unit 310, the second high frequency oscillator 220, the second impedance matcher 230, and the second impedance matcher 230 and the susceptor 20. It consists of a second power supply including a pass filter (330).

Since the band pass filters 310 and 330 electrically insulate the power supplies, the band pass filters 310 and 330 may be included in the impedance matchers 210 and 230 as described above.

Looking at the role of the high frequency power supplied from the high frequency power supply of the configuration as described above, the high frequency power of the high frequency range supplied from the first high frequency oscillator serves to increase the density and aspect ratio of the plasma, the second high frequency oscillator The high frequency power of the low frequency range supplied from the heating the edge of the plasma serves to maintain a large area of plasma stable.

As such, the high frequency power of the low frequency range plays a role of maintaining a large area of plasma stably and uniformly, so that the overall RF power applied in terms of the overall process is lowered.

In addition, by using the above-described method, it is possible to stably and uniformly generate a large-area plasma required for the production of large-area LCD substrates of six or more generations.

On the other hand, as a method of applying high frequency power in a power supply device including a plurality of high frequency oscillators, first, a high frequency range, for example, high frequency power of 13.56 MHz is transmitted through the first high frequency oscillator 200 to the plasma electrode 50. ) To ignite the plasma, and then apply a high frequency power of a low frequency range, for example, 2 MHz, to the plasma electrode 50 through the second high frequency oscillator 220 to heat the edge of the generated plasma, thereby making the overall uniform. Generate a plasma.

As another method of applying the high frequency power, first, a high frequency range, for example, 13.56 MHz high frequency power is applied to the plasma electrode 50 through the first high frequency oscillator 200 to ignite the plasma, For example, after a few seconds, the first high frequency oscillator 200 is cut off or off. Next, a high frequency power of a low frequency range, for example, 2 MHz, is applied to the plasma electrode 50 through the second high frequency oscillator 220, thereby heating the edge of the already generated plasma, thereby generating a plasma with a large uniform area as a whole. After the connection, the first high frequency oscillator 200 is connected again to increase the plasma density and stably maintain the plasma of the large area.

In the above description, only the high frequency power supply is composed of two power supply units, but it is natural that more power supply units may be included as necessary in the process. 3 and 4, the third power supply unit is shown by a dotted line, and the fourth and fifth power supply units may also be connected in a similar manner.

The third power supply unit includes a third high frequency oscillator 240, a third impedance matcher 250, and a third band pass filter 350, and the third band pass filter 350 is similar to the case of FIG. 3. Likewise, the third impedance matcher 250 may be included, or may be formed independently between the third impedance matcher 250 and the susceptor 20, as shown in FIG. 4.

In order to further increase the density of the plasma and to improve the film quality, the third high frequency oscillator 240 may be expected to apply high frequency power of 27.12 MHz.

In the above description of the preferred embodiment of the present invention, various modifications or changes by those skilled in the art are possible, such modifications or changes are naturally included in the scope of the present invention based on the technical spirit of the present invention. will be.

According to the present invention, by appropriately selecting the RF power source, it is possible to overcome the limitations due to standing waves, and to generate a stable and uniform large-area plasma compared to the conventional method, and to lower the high frequency power than when using one high frequency oscillator. There are advantages to it.

1 is a schematic configuration diagram of a conventional capacitively coupled PECVD apparatus

Figure 2 is a graph comparing the size of the LCD substrate by generation and the radial scale calculated by the Bessel function

3 is a schematic structural diagram of a PECVD apparatus according to an embodiment of the present invention;

4 is a schematic structural diagram of a PECVD apparatus according to another embodiment of the present invention;

Explanation of symbols on the main parts of the drawings

10: process chamber 20: susceptor

30: LCD substrate 40: plasma

50: plasma electrode 60: gas supply pipe

70: impedance matcher 80: RF oscillator

90: insulation block 100: exhaust pipe

200, 220, 240: 1st, 2nd, 3rd high frequency oscillator

210, 230, 250: first, second, third impedance matcher

310, 330, 350: 1st, 2nd, 3rd band pass filter

Claims (9)

A plurality of high frequency oscillators; A plurality of impedance matching devices, each connected to the high frequency oscillator and the other end to the plasma electrode High frequency power supply for manufacturing a large area liquid crystal display comprising a The method of claim 1, A high frequency power supply for manufacturing a large area liquid crystal display device having a band pass filter formed inside the impedance matcher or between the impedance matcher and the plasma electrode. The method of claim 1, The plurality of high frequency oscillators include a first high frequency oscillator for generating high frequency power in the range of 13.56 MHz and 100 MHz, and a second high frequency oscillator for generating high frequency power in the range of 400 KHz to 2 MHz. The method according to any one of claims 1 to 3, The plasma electrode is a high frequency power supply for manufacturing a large area liquid crystal display device formed on a part of the susceptor or integrally with the susceptor. A first step of generating a plasma by connecting the first high frequency oscillator to the plasma electrode for a predetermined time; A second step of maintaining the plasma uniformly by connecting a second high frequency oscillator with a plasma electrode; High frequency power supply method for manufacturing a large area liquid crystal display comprising a The method of claim 5, The first high frequency oscillator generates high frequency power in the range of 13.56 MHz to 100 MHz, and the second high frequency oscillator generates high frequency power in the range of 400 KHz to 2 MHz. The method according to claim 5 or 6, A method for supplying a high frequency power supply for manufacturing a large area liquid crystal display device further comprising the step of disconnecting the connection between the first high frequency oscillator and the plasma electrode after the first step. The method according to claim 5 or 6, And reconnecting the first high frequency oscillator and the plasma electrode after the second step. The method of claim 7, wherein And reconnecting the first high frequency oscillator and the plasma electrode after the second step.