KR101994036B1 - Plasma monitoring apparatus - Google Patents

Abstract

Disclosed is a plasma measuring apparatus. The plasma measuring apparatus may comprise: a reactor provided with a plasma generation space therein and having a first area surrounding the plasma generation space and a second area electrically insulated with the first area; and a plasma measuring unit electrically connected to the first and second areas and measuring a state of a plasma in contact with the first and second areas by applying a voltage signal to the first and second areas and measuring a response current signal for the voltage signal.

Description

[0001] Plasma monitoring apparatus [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma measuring apparatus, and more particularly, to a plasma measuring apparatus capable of measuring a state of plasma using an inner wall surface unique to a reactor.

The Langmuir probe method inserts a cylindrical rod of ceramic material into the reactor through a hatch located on the wall of the reactor. The tip of the cylindrical rod is equipped with a metal probe that can collect DC current. When DC voltage is applied to the metal probe from the outside, current flows from the plasma. At this time, the measured current is related to the plasma parameter, and the plasma parameter can be measured by analyzing the current-voltage characteristic in a specific voltage range.

This Langmuir probe method requires a window on the reactor wall to insert the probe. This hatch must be vacuumed to hold the probe and to keep the pressure inside the reactor low. These probes and windows can be the factors that cause the plasma state to change as shown below.

First, insertion of the probe can affect the density of the plasma as it increases the area of loss of the plasma, and can hinder the electric field that generates and holds the plasma. The voltage applied to the probe can perturb the plasma potential and can affect the density of the plasma because it captures electrons and ions from the plasma. As the probe is located inside the reactor, it can affect process results such as semiconductor manufacturing / display fabrication / surface treatment. In addition, the probe needs to be periodically replaced by plasma damage and may be a source of impurities due to damage.

With such a problem, it is required to develop a device capable of measuring the plasma state without inserting a probe inside the reactor.

Korean Patent Publication No. 10-2017-0106081

The present invention provides a plasma measuring apparatus capable of measuring a plasma state using a wall surface unique to a reactor without inserting a probe inside the reactor.

A plasma measuring apparatus according to the present invention includes: a reactor having a plasma generating space provided therein, the inner wall surrounding the plasma generating space having a first region and a second region electrically insulated from the first region; And a controller coupled in electrical communication with the first and second regions for applying a voltage signal to the first and second regions and measuring a response current signal therefrom to control the contact with the first and second regions, And a plasma measuring unit for measuring the state of the plasma.

The plasma measuring unit may further include: a signal generator for generating the voltage signal; A first wiring connecting the signal generator and the first region; A second wire connecting the second region and the signal generator; A signal measuring unit for measuring the response current signal flowing through the first wiring and the second wiring; And a data operation unit for calculating the density and the electron temperature of the plasma in contact with the first region from the response current signal measured by the signal measuring unit and calculating the density and the electron temperature of the plasma in contact with the second region can do.

The first region and the second region may be made of a metal.

Each of the first region and the second region may include a window made of a dielectric material whose front surface is exposed to the plasma generating space; And a current collecting plate of a metal material coupled to a rear surface of the window and connected to the first wiring or the second wiring.

In addition, the inner wall of the reactor may be provided with an insulating ring of dielectric material which insulates the first region and the second region from other regions of the inner wall of the reactor.

The reactor may further include a top wall, a sidewall, and a bottom wall to form the plasma generating space. The first region may be located on the bottom wall, and the second region may be located on the sidewall.

The reactor may further include a top wall, a sidewall, and a bottom wall to form the plasma generating space, wherein the first region is located at the bottom wall, and the second region is located at the top wall.

According to the present invention, it is possible to directly measure the plasma state parameter by applying it to a device for a semiconductor and a display process.

In addition, according to the present invention, uniformity of process results can be obtained by minimizing the tolerance between plasma apparatuses performing the same process by measuring the state of the plasma.

Further, according to the present invention, it is possible to prevent the problems associated with the use of the probe, such as the durability and impurity release of the probe, the problem of generation of perturbation of plasma, and the problem of process failure.

1 is a view illustrating a plasma measuring apparatus according to an embodiment of the present invention.
FIG. 2 is a conceptual diagram showing the relationship between plasma, voltage, current, and electrodes in the plasma measuring apparatus of the present invention.
3 is a view illustrating a plasma measuring apparatus according to another embodiment of the present invention.
4 is a view illustrating a plasma measuring apparatus according to another embodiment of the present invention.
5 to 7 are diagrams showing the connection relationship with the plasma measuring unit according to various forms of the reactor.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the technical spirit of the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

In this specification, when an element is referred to as being on another element, it may be directly formed on another element, or a third element may be interposed therebetween. Further, in the drawings, the thicknesses of the films and regions are exaggerated for an effective explanation of the technical content.

Also, while the terms first, second, third, etc. in the various embodiments of the present disclosure are used to describe various components, these components should not be limited by these terms. These terms have only been used to distinguish one component from another. Thus, what is referred to as a first component in any one embodiment may be referred to as a second component in another embodiment. Each embodiment described and exemplified herein also includes its complementary embodiment. Also, in this specification, 'and / or' are used to include at least one of the front and rear components.

The singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. It is also to be understood that the terms such as " comprises "or" having "are intended to specify the presence of stated features, integers, Should not be understood to exclude the presence or addition of one or more other elements, elements, or combinations thereof. Also, in this specification, the term "connection " is used to include both indirectly connecting and directly connecting a plurality of components.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The plasma measuring apparatus according to the present invention can measure plasma state such as electron temperature and density of a plasma in a plasma generating apparatus in a reactor. The plasma measuring apparatus can be applied to a plasma apparatus for a semiconductor / display process, a plasma apparatus for a fusion power generation, and a plasma apparatus for surface treatment (oxidation, thin film coating, etc.) of a material. Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a view illustrating a plasma measuring apparatus according to an embodiment of the present invention. The plasma measuring apparatus 100 of the present embodiment is an inductively coupled plasma (ICP) generating apparatus, and a TOP ICP structure will be described as an example.

Referring to FIG. 1, a plasma measuring apparatus 100 includes a reactor 10, a plasma generating unit 20, and a plasma measuring unit 30.

The reactor 10 is provided with a plasma generating space 11 therein. The inner wall of the reactor (10) surrounds the plasma generating space (11). Specifically, the inner wall of the reactor 10 has an upper wall 12, a lower wall 13, a side wall 14, and a guard ring 15.

The top wall 12 is provided with a window of dielectric material. According to the embodiment, the material of the top wall 12 may be provided by aluminum oxide (Al 2 O 3).

The lower wall (13) is disposed opposite the upper wall (12). The lower wall 13 may be made of a conductive material. The lower wall 13 may be made of a metal material. According to the embodiment, the lower wall 13 may be provided with stainless steel.

The side wall 14 surrounds the space between the top wall 12 and the bottom wall 13. The side wall 14 may be provided with the same material as the lower wall 13.

A guard ring 15 is inserted between the lower wall 13 and the side wall 14 and is provided along the circumference of the lower wall 13. The guard ring 15 is provided with a non-conductive material. The guard ring 15 may be provided as a dielectric material. According to the embodiment, the guard ring 15 may be provided with aluminum oxide. The guard ring 15 electrically insulates the lower wall 13 and the side wall 14.

The plasma generating section 20 generates plasma in the plasma generating space 11. The plasma generator 20 includes an antenna coil 21, a matching network 22, and a power supply 23.

The antenna coil 21 is located at the upper portion of the upper wall 12, one end connected to the power source 23, and the other end grounded. The power supply 23 generates RF power. According to the embodiment, the power supply 23 can generate RF power of 13.56 MHz. The RF power is applied to the antenna coil 21 via the matching network 22.

The RF power applied to the antenna coil 21 forms an electric field in the plasma generating space 11. The electric field excites the source gas staying in the plasma generating space 11 into a plasma state.

The plasma measuring unit 30 includes a first wiring 31, a second wiring 32, a signal generator 33, an RF choke filter 34, and a signal measuring unit 35.

The first wiring 31 connects the signal generator 33 to the first region of the reactor 10 and the second wiring 32 connects the power source 33 to the second region of the reactor 10. [ And the second wiring 32 may be grounded. Here, the first region and the second region of the reactor 10 are insulated different regions. According to an embodiment, the first region is the lower wall 13 of the reactor 10 and the second region is the reactor 10, As shown in FIG.

The signal generator 33 generates a voltage signal and applies it to the first region 13. The signal generator 33 can generate a sinusoidal voltage signal. According to the embodiment, the signal generator 33 is capable of generating a sinusoidal voltage signal having a frequency of 10 kHz and an amplitude of 0.5V.

The RF choke filter 34 is connected in series with the signal generator 33. The RF choke filter 34 is designed to resonate at a specific frequency signal. According to the embodiment, the RF choke filter 34 can be designed to resonate at 13.56 MHz and 27.12 MHz.

The signal measuring section 35 measures a response current signal flowing along the first wiring 31 and the second wiring 32. The signal measuring unit 35 may include a sense resistor 36, an analog-to-digital converter 37, and a data operation unit 38.

The sensing resistor 36 is connected in series with the RF choke filter 34 and the signal generator 33 and generates a potential difference by a response current signal flowing along the first wiring 31 and the second wiring 32.

The analog-to-digital converter 37 measures the potential difference generated in the sense resistor 35 at regular intervals and converts it into a current waveform. According to the embodiment, the analog-to-digital converter 37 measures the potential difference at a sampling rate of 1.25 MSs < ^{-1 &} gt ;.

The data calculating unit 38 calculates the density and the electron temperature of the plasma in contact with the first region 13 from the measured response current signal and calculates the density and the electron temperature of the plasma in contact with the second region 14. [

Hereinafter, a specific method of calculating the plasma density and the electron temperature in the first region 13 and the second region 14 will be described.

FIG. 2 is a conceptual diagram showing the relationship between plasma, voltage, current, and electrodes in the plasma measuring apparatus of the present invention.

Referring to Figures 1 and 2, the first region 13 and the second region 14 of the reactor serve as electrodes. For convenience of explanation, the first region 13 of the reactor is referred to as a first electrode, and the second region 14 is referred to as a second electrode.

When the voltage signal V _B is applied from the signal generator 33, a plasma current flows through the first electrode 13 and the second electrode 14. The current flowing through the first electrode 13 and the current flowing through the second electrode 14 may be defined as I ₁ and I ₂ , respectively. In order to maintain the quasi-neutrality of the plasma, the net current between the plasma and the plasma measurement unit 30 is zero, and the sum of I ₁ and I ₂ is the sum of the loop current current, I). The relationship of these currents is defined by the following equation (1).

식(1)

Equation (1)

Each I ₁ and I ₂ consists of an ion and an electron current. Plasma parameters such as the electron temperature T _e , the plasma density n ₁ , n ₂ , and the plasma potential V _p , if the first electrode 13 and the second electrode 14 are sufficiently small and not very close, . Assuming that the values of T _e and V _p are constant and n ₁ and n ₂ change only spatially, n ₁ and n ₂ can be understood as the local densities of the first electrode 13 and the second electrode 14 have. This assumption can be tolerated under low pressure discharge conditions and the spatial gradient of the gas pressure which causes a spatial variation of T _e is minimized by the low gas flow rate. The potential difference between V ₁ and V ₂ is determined by V _B (see equation (2)).

식(2)

Equation (2)

A first electrode 13, an ion current (I _i1) and electron currents (I _e1) and the ionic current (I _i2) and an electron current (I _e2) of the second electrode 14 on the formula (3) as shown below .

식(3)

Equation (3)

Here, n ₁ is the plasma density in the first electrode 13, n ₂ is the plasma density, and, A ₁ is the area of the first electrode 13 of the second electrode (14), A ₂ is the second Is the area of the electrode 14, u _B is the Bohm velocity, and V _e is the average electron velocity.

This is rearranged from Equation (1), which is expressed by Equation (4) below,

식(4)

Equation (4)

From equation (2), equation (3), and equation (4), equation (5) can be obtained as follows.

식(5)

Equation (5)

Here, when a sinusoidal voltage having an amplitude V ₀ and an angular frequency ω is applied to the first electrode 13 and the second electrode 14, a time-varying probe current, i _p ) is given by the following equation (6).

식(6)

Equation (6)

The above equation (6) is developed as shown in equation (7).

식(7)

Equation (7)

Where v if ₀ is less than T _e, v high-order term of the ₀ / T _e is negligible, then the amplitude of the harmonic component of the i _p (i _ω, i _{2 ω,} and i _{3 ω)} is approximated as follows: .

식 (8)

Equation (8)

i _p and derives the amplitude of the harmonic currents through a fast Fourier transform.

The coefficient b is determined according to the following equation (9) by a combination of | i _ω |, | i _{2 ω} |, and | i _{3 ω} |.

식 (9)

Equation (9)

In a similar way, T _e is calculated from equation (10).

식(10)

Equation (10)

Given b and T _e from Eqs. (9) and (10), n ₁ and n ₂ are determined by the amplitude of the harmonic current. Specifically, the ion density at the edge of the sheath region on the second electrode 14 is calculated from equation (11).

식 (11)

Equation (11)

And the ion density at the edge of the sheath region on the first electrode 13 is calculated from equation (12) using b.

식(12)

Equation (12)

By the above-described process, the plasma density and the electron temperature in contact with the first region 13 and the second region 14 can be calculated.

3 is a view illustrating a plasma measuring apparatus according to another embodiment of the present invention.

Referring to FIG. 3, the plasma measuring apparatus 200 may have a solenoidal type ICP (Solenoidal type ICP) structure.

The side wall 214 of the reactor 210 is provided with a dielectric material, and the upper wall 212 and the lower wall 213 may be made of a metal material, respectively. The upper wall 212 and the lower wall 213 are electrically insulated.

The antenna coil 221 is wound around the sidewall 214 of the reactor 210 and RF power is applied from the power source 223. A matching network 222 is connected between the antenna coil 221 and the power source 223. The RF power applied to the antenna coil 221 forms an electric field in the plasma generating space 211. The electric field excites the source gas staying in the plasma generating space 211 into a plasma state.

The first wiring 231 of the plasma measurement unit 230 is connected to the lower wall 213 of the reactor 210 and the second wiring 232 is connected to the upper wall 212 of the reactor 210.

The voltage signal generated in the signal generator 233 is applied to the lower wall 213 of the reactor 210 and the response current signal transmitted from the plasma to the lower wall 213 and the upper wall 212, respectively, 235). The data operating section 238 calculates the density and the electron temperature of the plasma in contact with the lower wall 213 and the density and the electron temperature of the plasma in contact with the upper wall 212 from the measured response current signal.

4 is a view illustrating a plasma measuring apparatus according to another embodiment of the present invention.

Referring to FIG. 4, the plasma measuring apparatus 300 may have a capacitively coupled plasma structure.

The plasma measuring apparatus 300 is provided with a pair of electrodes in which the upper wall 311 and the lower wall 312 of the reactor 310 face each other and the side wall 313 is provided with an insulating material. The lower wall 312 is grounded.

The first wiring 331 of the plasma measurement unit 330 is connected to the lower wall 312 of the reactor 310 and the second wiring 332 is connected to the upper wall 311 of the reactor 310.

The voltage signal generated in the signal generator 333 is applied to the lower wall 312 and the upper wall 311 of the reactor 310 and the response currents transmitted from the plasma to the lower wall 312 and the upper wall 311, A signal is measured in the signal measuring unit 335. The data operation unit 338 calculates the density and the electron temperature of the plasma in contact with the lower wall 312 and the density and the electron temperature of the plasma in contact with the upper wall 311 from the measured response current signal.

According to the above-described embodiments of the present invention, the plasma measuring apparatus applies a voltage signal to the wall surface of the reactor and collects a response current signal therefrom through the wall surface of the reactor. Since the wall surface of the reactor is provided in a wider area than the probe, the collection of the response current signal is sufficiently possible even with the application of a small voltage signal. In addition, the density and the electron temperature of the plasma in contact with each of the wall regions of the reactor connected to the first wiring and the second wiring of the plasma measuring unit can be locally measured.

5 to 7 are diagrams showing the connection relationship with the plasma measuring unit according to various forms of the reactor.

Referring to FIG. 5, when the first area 13 and the second area 14 of the reactor 10 are provided with a metal material, the first wiring 31 and the second wiring 31 of the plasma measuring part 30 32 are directly connected to the first region 13 and the second region 14 of the reactor 10. In this case, the signal generator 33 can apply an AC voltage or a DC voltage.

6, when the first region 13 and the second region 14 of the reactor 10 are provided as windows of a dielectric material, the first wiring 31 and the second wiring 32 are formed on the rear surface of the window Through the current collecting plate 16 made of a metal material. In this case, the signal generator 33 can apply an AC voltage.

7, when the inner wall 10 of the reactor is provided with a metal material, the first region 13 and the second region 14 are insulated from the remaining region by a dielectric insulating ring 17 made of a dielectric material. The plasma measuring unit 30 can measure the state of the plasma locally through the first region 13 and the second region 14. In this case, the signal generator 33 can apply an AC voltage or a DC voltage.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments. It will also be appreciated that many modifications and variations will be apparent to those skilled in the art without departing from the scope of the present invention.

100: Plasma measuring device
10: Reactor
20: Plasma generator
21: Antenna coil
22: matching network
23: Power supply
30: Plasma measuring unit
31: first wiring
32: second wiring
33: Signal generator
34: RF choke filter
35: Signal measurement section

Claims (7)

A reactor having a plasma generating space provided therein, the inner wall surrounding the plasma generating space having a first region and a second region electrically insulated from the first region; And
And a second region electrically connected to the first region and the second region and configured to apply a voltage signal to the first region and the second region and measure a response current signal therefrom to contact the first region and the second region And a plasma measuring unit for measuring a state of the plasma.
The method according to claim 1,
The plasma measuring unit includes:
A signal generator for generating the voltage signal;
A first wiring connecting the signal generator and the first region;
A second wire connecting the second region and the signal generator;
A signal measuring unit for measuring the response current signal flowing through the first wiring and the second wiring; And
Calculating a density and an electron temperature of the plasma in contact with the first region from the response current signal measured in the signal measuring unit and calculating a density and an electron temperature of the plasma in contact with the second region; Plasma measuring device.
3. The method according to claim 1 or 2,
Wherein the first region and the second region are made of metal.
3. The method of claim 2,
Wherein each of the first region and the second region includes:
A window of a dielectric material whose front surface is exposed to the plasma generating space;
And a current collecting plate of a metal material coupled to a rear surface of the window and connected to the first wiring or the second wiring.
3. The method according to claim 1 or 2,
Wherein an insulating ring of a dielectric material is provided on an inner wall of the reactor to insulate the first region and the second region from other regions of the inner wall of the reactor.
3. The method according to claim 1 or 2,
The reactor has a top wall, a side wall, and a bottom wall combined to form the plasma generating space,
Wherein the first region is located on the lower wall and the second region is located on the sidewall.
3. The method according to claim 1 or 2,
The reactor has a top wall, a side wall, and a bottom wall combined to form the plasma generating space,
Wherein the first region is located at the lower wall and the second region is located at the upper wall.

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