KR20240020790A - Plasma process monitoring method and plasma process monitoring apparatus - Google Patents

Abstract

A plasma processing apparatus according to an embodiment includes a chamber in which plasma is generated, at least one sensor disposed inside the chamber, a voltage applicator that applies a sinusoidal voltage to the sensor, and a direct current blocking unit disposed between the voltage applicator and the chamber. A capacitor, a measurement circuit unit that measures the output current flowing through the sensor and the voltage applied to the DC blocking capacitor, and data that calculates the thickness of the dielectric inside the chamber based on the output current and the voltage applied to the DC blocking capacitor. It may include a processing unit.

Description

Plasma process monitoring method and plasma process monitoring apparatus}

The present invention relates to a plasma process monitoring method and a plasma process monitoring device, and more specifically, to a technology that can measure the thickness of a dielectric in real time by applying a single sine wave to the dielectric.

Plasma is an ionized gas, which is composed of positive ions, negative ions, electrons, excited atoms, molecules, and chemically very active radicals. It has electrically and thermally very different properties from ordinary gases, so it is a material It is also called the fourth state. This plasma contains ionized gas and is very useful in the semiconductor manufacturing process, such as accelerating it using an electric or magnetic field or causing a chemical reaction to clean, etch, or deposit a wafer or substrate.

Recently, in the semiconductor manufacturing process, plasma generators that generate high-density plasma have been used, and there are several plasma modules for generating plasma, including capacitive coupled plasma (CCP) using radio frequency. Representative examples include inductively coupled plasma (ICP).

When performing a plasma deposition and etching process using such a plasma device, it is necessary to monitor the inside of the plasma chamber and accurately check the state of the plasma (plasma density, electron temperature, etc.) and the state of the fabricated dielectric. This is because if the organic or inorganic material (dielectric layer, hereinafter referred to as dielectric) deposited on the wall of the chamber where plasma is formed comes off again and impurity particles are formed, there is a risk that product yield may decrease and the plasma may be left in an undesirable state. This is because there is a risk that reproducibility may decrease due to changes in the internal environment of the chamber.

The Langmuir probe method is widely used to diagnose plasma. The Langmuir probe method inserts a probe into a plasma chamber and applies voltage to measure various process variables such as electron temperature and plasma density from information about the current measured by the probe.

After the semiconductor process is completed, metrology is performed to analyze the internal state of the chamber and the characteristics of the device. Through measurement, the state of deposition and the degree of wear of the dielectric can be measured in various ways. Contact surface step measurement method (alpha step), which measures the thickness by measuring the change in the position of the probe while scratching the surface after creating a step in the sample coated with dielectric and then touching it with a fine probe, cutting the sample coated with dielectric The scanning electron microscope (SEM) method measures thickness through the intensity of secondary electrons emitted by scanning an electron beam, and the ellipsometer method measures thickness from changes in the polarization state of the reflected light after reflecting light onto a dielectric sample. However, these measurement methods have the disadvantage that it is difficult to directly measure the thickness of the chamber wall deposition film or edge ring during the process and that it is difficult to measure thick dielectrics. In addition, in the case of thin deposited films, although measurement is possible indirectly through sample production, real-time measurement is not possible, professional knowledge is required for sample production and analysis, and there are disadvantages in that reliability is determined by the user's skill level.

Republic of Korea Patent Publication No. 10-2009-00974627 (2009.09.08.) - Mixed plasma generating device and method, and electrothermal cooking device using mixed plasma Republic of Korea Patent No. 10-1652845 (2016.08.25.) - Plasma generation module and plasma generation device including the same

Therefore, the plasma process monitoring device and plasma process monitoring method according to one embodiment are inventions designed to solve the problems described above, and the purpose is to provide a technology that can accurately measure the thickness of a dielectric in real time more effectively than the prior art. There is.

More specifically, after applying two sinusoidal voltages or one sinusoidal voltage with different frequencies to the plasma and dielectric, the impedance value is determined based on the size and amplitude of the resulting current and the voltage of the DC blocking capacitor. The purpose is to provide a plasma process monitoring device and method that can calculate and measure the thickness of a dielectric in real time based on the calculated impedance value.

A plasma generation monitoring device according to an embodiment includes at least one sensor disposed inside a chamber in which plasma is generated, a voltage applicator that applies a sinusoidal voltage to the sensor, and a direct current blocking capacitor disposed between the voltage applicator and the chamber. , a measurement circuit unit that measures the output current flowing through the sensor and the voltage applied to the DC blocking capacitor, and a data processing unit that calculates the thickness of the dielectric inside the chamber based on the output current and the voltage applied to the DC blocking capacitor. It can be included.

The data processing unit calculates the thickness of the dielectric using an equivalent circuit model consisting of a dielectric capacitor generated by depositing the dielectric, a sheath capacitor in a sheath area generated adjacent to the plasma, a sheath resistor, and the DC blocking capacitor. can do.

When the voltage application unit applies one sinusoidal voltage, the data processing unit may measure the thickness of the dielectric based on phase information, which is information about the phase difference between the sinusoidal voltage and the output current.

When the voltage application unit applies two sinusoidal voltages having different frequencies, the data processing unit may measure the thickness of the dielectric based on the amplitude of the output current according to the sinusoidal voltage.

The data processing unit calculates the voltage applied to the DC blocking capacitor and the sheath region based on the phase information, then subtracts the voltage applied to the DC blocking capacitor measured by the measurement circuit unit to determine the sheath capacitor. Information about the voltage applied to can be calculated.

The data processing unit may measure the thickness of the dielectric based on voltage information applied to the sheath region, dielectric constant information of the dielectric, area information of the sensor, and frequency information of the sinusoidal voltage.

A plasma process monitoring method according to an embodiment includes a voltage input step of applying a sinusoidal voltage to at least one sensor disposed inside a chamber where plasma is generated, an output current flowing through the sensor, and a direct current blocking capacitor connected to the chamber. It may include a measuring step of measuring the applied voltage and a data processing step of calculating the thickness of the dielectric inside the chamber based on the output current and the voltage applied to the DC blocking capacitor.

A plasma process monitoring method and a plasma process monitoring device according to an embodiment measure the thickness of a dielectric by directly measuring the voltage of a direct current blocking capacitor without using a sensing resistor to measure the voltage. Therefore, there is an advantage in promoting space efficiency of semiconductor processing equipment by miniaturizing the measurement circuit.

In addition, in the case of the present invention, since the voltage applied to the dielectric film is measured using a method of directly measuring the voltage applied to the DC blocking capacitor, the impedance of the dielectric film can be directly measured, and repetitive calculations to measure the thickness of the dielectric are performed. This has the advantage of being able to measure in real time faster than conventional technology because it does not require

In addition, in the present invention, when voltages of two different frequencies are applied, the thickness of the dielectric is measured based on the measured impedance value rather than the phase difference of the current, so the thickness can be measured more precisely than in the prior art. There is an advantage in that the thickness of the dielectric can be accurately measured by applying not only the kHz band frequency but also the MHz band frequency.

The effects of the present invention are not limited to the technical problems mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

In order to more fully understand the drawings cited in the detailed description of the present invention, a brief description of each drawing is provided.
Figure 1 is a circuit diagram modeling the connection between plasma and the probe when voltage is applied to the probe according to the prior art.
Figure 2 is a perspective view of the plasma generating device according to an embodiment of the present invention when viewed from the side.
Figure 3 is a block diagram showing some components of a plasma process monitoring device according to an embodiment of the present invention.
Figure 4 is a flowchart showing a method for monitoring a plasma generation process according to an embodiment of the present invention.
Figure 5 is a diagram showing the inside of a chamber as an equivalent circuit, according to an embodiment of the present invention.
Figure 6 is a diagram for explaining a calculation method for measuring the voltage applied to a dielectric, according to an embodiment of the present invention.
Figure 7 is a diagram showing the results of measuring various variables in a situation where the size of the DC blocking capacitor is fixed.
Figure 8 is a diagram showing the results of measuring the capacitance of a dielectric film according to the present invention.
Figure 9 is a diagram showing the results of electron temperature and ion density measured according to the present invention and the results of measurement using the EEDF system according to changes in the dielectric film.

Hereinafter, embodiments according to the present invention will be described with reference to the attached drawings. When adding reference signs to components in each drawing, it should be noted that the same components are given the same reference numerals as much as possible even if they are shown in different drawings. Additionally, when describing embodiments of the present invention, if detailed descriptions of related known configurations or functions are judged to impede understanding of the embodiments of the present invention, the detailed descriptions will be omitted. In addition, embodiments of the present invention will be described below, but the technical idea of the present invention is not limited or limited thereto and may be modified and implemented in various ways by those skilled in the art.

Additionally, the terms used in this specification are used to describe embodiments and are not intended to limit and/or limit the disclosed invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this specification, terms such as “comprise,” “provide,” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification. It does not exclude in advance the existence or addition of other features, numbers, steps, operations, components, parts, or combinations thereof.

In addition, throughout the specification, when a part is said to be “connected” to another part, this refers not only to the case where it is “directly connected” but also to the case where it is “indirectly connected” with another element in between. Terms including ordinal numbers, such as “first” and “second,” used in this specification may be used to describe various components, but the components are not limited by the terms.

Below, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. In order to clearly explain the present invention in the drawings, parts unrelated to the description are omitted.

Figure 1 is a circuit diagram modeling the connection between plasma and the probe when voltage is applied to the probe according to the prior art.

When voltage is applied to a probe present inside a plasma chamber, a sheath area generally occurs between the probe and the plasma.

The sheath area refers to a space where quasi-neutrality is broken. Specifically, it refers to a dark space area in which no plasma light reaction has occurred during the process of generating plasma within the chamber space, and is mainly found near the chamber walls. It happens.

In general, plasma exists in an ionized gas state in which atoms or molecules are separated into positive ions and free electrons, so free electrons move freely inside the chamber and combine with positive ions to emit light. However, in the case of the probe surface or near the chamber wall, it is negatively charged due to free electrons that arrived at the wall before the positive ions, so free electrons approaching the wall are repelled, so only positive ions and neutrons mainly remain around the probe surface or chamber wall. Therefore, a grow region, a dark space where free electrons cannot combine with positive ions, is created. And this area is called a sheath area, which also refers to a shielding layer for electrical shielding of the plasma.

Meanwhile, during the etching process, the ion energy incident on the substrate can be increased by creating a high negative bias sheath by adding a blocking capacitor to the wafer surface. This sheath voltage drop represents the difference between the plasma potential and the bias potential applied to the electrode, and ions incident on the substrate gain energy due to the sheath drop potential difference described above. However, because the bias potential of the electrode changes with time, the corresponding plasma potential also changes with time.

Meanwhile, on the wall of the chamber where plasma is formed, the deposited or etched organic or inorganic material comes off again, creating a region where impurity particles are formed, and the impurities formed in this way form a dielectric material.

Therefore, this area can be implemented as an equivalent circuit. Specifically, as shown in FIG. 1, if the applied frequency is sufficiently low (~kHz), the sheath area located on the surface of the probe can be considered as a resistance component. When an alternating voltage is applied to the floating potential probe, the corresponding voltage is applied to the plasma sheath, and the dielectric is approximated as a capacitor (Cd, capacitor), and the sheath area is approximated as a sheath resistance (Rs, sheath resistance), as shown in Figure 1 Since an equivalent model circuit can be implemented as shown, the thickness of the dielectric can be measured by analyzing it.

However, when measuring the thickness of the dielectric using the method shown in FIG. 1, if the discharge conditions such as the applied power applied to the plasma change, the error between the thickness of the dielectric calculated from the conventional circuit model and the thickness of the actually deposited dielectric increases. There is a problem that arises. Therefore, there is an urgent need to develop technology that can accurately calculate the dielectric thickness and monitor it more accurately during the deposition and etching process even if the plasma state changes due to changes in plasma discharge conditions.

Therefore, the plasma process monitoring device and plasma process monitoring method according to one embodiment are inventions designed to solve the problems described above, and provide a technology that can accurately measure the thickness of the dielectric in real time more effectively than the prior art. The purpose exists. Let us take a closer look at the configuration and operating principle of the present invention through the drawings below.

Figure 2 is a perspective view of the plasma generating device according to an embodiment of the present invention when viewed from the side.

Referring to FIG. 2, the plasma generating device 1 according to the present invention is disposed in a chamber and includes a first sensor 20A, a second sensor 20B, and a first sensor (20A), which are probes that measure various variables of plasma. 20A) and a voltage application unit 30 that applies a preset voltage to the first sensor 20A, a chamber 40 that serves as the main body of the plasma generator 1 and is a space where plasma is generated, and a plasma generator 100 ), a power module 50 that supplies power, an impedance matching unit 70 that matches the impedance of the antenna 60, a DC blocking capacitor (Cb) disposed in the chamber 40 and the voltage application unit 30, and a DC The measurement circuit unit 110 (see FIG. 3) that measures the voltage applied to both ends of the blocking capacitor (Cb) and the current flowing in the direct current blocking capacitor (Cb) and the current flowing in the first sensor (20A) and the second sensor (20B) A plasma process monitoring device 100 that measures and calculates various variables of plasma based on the measured results, and an EEPF system that measures the Electron Energy Probability Function (EEPF) inside the chamber 40 ( 200), etc. may be included.

Referring to FIG. 2 , the chamber 40 may refer to a container having a space where an object requiring plasma processing, such as a substrate, is provided, and a space where plasma P is generated. As shown in FIG. 2, a plurality of antennas 60 for generating plasma may be installed on the upper part of the chamber 40, and the plurality of antennas 60 may be connected to an impedance matching unit 70 (matching box). there is.

The impedance matching unit 70 may be connected to the power module 50 and the chamber 40, respectively, which supply power to the plasma generating device 100, and a source gas, which is a source of plasma generation, is placed in the lower part of the chamber 40. A pumping system 90 that performs pumping may be formed.

As shown in FIG. 2, a plasma generator that generates plasma using a plurality of antennas 60 may be referred to as an inductively coupled plasma generation field (ICP). However, the plasma generating device according to the present invention is not limited to an inductively coupled plasma generating device, and is also included in a capacitively coupled plasma generating device (CCP: Capacitively Coupled Plasma) and method for generating plasma using the capacitive coupling method. All can be applied. For convenience of explanation, the description will be made based on the inductively coupled plasma generator shown in FIG. 2.

The plasma process monitoring device 100 according to an embodiment of the present invention can measure various variables of plasma generated inside the chamber 40. The variable referred to in the present invention refers to a variable that refers to various chemical and physical characteristics related to plasma. Representative examples include the density of plasma generated inside the chamber 40, the temperature and electron energy probability distribution of electrons flowing inside the chamber, The thickness of the dielectric 10 formed on the chamber wall can be measured.

To this end, a plurality of sensors may be provided inside the chamber 40, and a representative example may include a first sensor 20A and a second sensor 20B capable of transmitting a sinusoidal wave to plasma. The first sensor 20A and the second sensor 20B may be arranged to penetrate one wall of the chamber 40 as shown in the drawing. The sensor in the present invention may be referred to by other names such as probes, probes, etc., and in the case of the present invention, the description is based on the two sensors shown, but the inside of the chamber 40 may consist of one sensor. It is also possible.

As an example, as shown in the drawing, when the first sensor 20A and the second sensor 20B pass through the chamber 40 and apply a sinusoidal signal to the plasma, the first sensor 20A and the second sensor (20B) 20B) can be said to have the form of a floating probe.

The voltage application unit 30 may generate a voltage and then apply the generated voltage to the first sensor 20A and the second sensor 20B. Specifically, the voltage application unit 30 applies a basic typical wave of several tens of KHz to induce the generation of harmonics by a sheath.

As shown in FIG. 2, the voltage application unit 30 is electrically connected to the first sensor 20A and the second sensor 20B, and the user's signal is applied to the first sensor 20A and the second sensor 20B. A preset voltage can be applied according to the settings.

The shape and size of the voltage applied by the voltage applicator 30 to the first sensor 20A and the second sensor 20B may be set differently depending on the plasma generation environment, but in the form of a sinusoidal wave generated by alternating voltage. One or more voltages may be applied. The following description will be based on the case where a sine wave having one frequency is applied, but the embodiment of the present invention is not limited to this and may be applied to two frequencies having different frequencies (w1, w2) or different frequencies (w1, Three sinusoidal voltages having w2, w3) may be applied to the sensor 20 at the same time or at different times.

When voltage is applied to the first sensor (20A) and the second sensor (20B) by the voltage application unit 30, the first sensor (20A) and the second sensor (20B) are Since current flows through the first sensor 20A and the second sensor 20B, the plasma process monitoring device 100 can measure the current flowing through the first sensor 20A and the second sensor 20B. The position where the plasma process monitoring device 100 is placed in FIG. 2 is not limited to this, and in another embodiment, the plasma process monitoring device 100 may be placed between the first sensor 20A and the voltage applicator 30. You can.

Meanwhile, in the drawing, the voltage application unit 30 and the plasma process monitoring device 100 are shown as independent and separate components, but the embodiment of the present invention is not limited thereto and the voltage application unit 30 is the plasma process monitoring device 100. ) may also be implemented as included in .

The direct current blocking capacitor Cb may serve to prevent the direct current component of the current generated by the sheath from being transmitted to the plasma analysis device 100.

A measurement circuit unit 110 may be disposed at both ends of the DC blocking capacitor Cb to measure the voltage applied to the DC blocking capacitor Cb. For example, a differential amplifier 80 is used as shown in the drawing. When measured, information about the voltage applied to the DC blocking capacitor (Cb) and information about the current flowing through the DC blocking capacitor (Cb) can be obtained.

If a differential amplifier 80 with an appropriate bandwidth suitable for the experimental environmental conditions is used, the magnitude of the current can be accurately measured, and the measured current can be converted to a voltage Vout and output. And the components of Vout output in this way can be analyzed by the measurement circuit unit 110, and for example, an FFT unit (Fast Fourier Transform) can be applied. If multiple sinusoidal voltages are applied, the FFT unit can accurately separate the vibration frequencies w and 2w and the harmonic components by frequency. When configured as an FFT, the FFT has the advantage of being resistant to noise because it processes signals digitally.

Figure 3 is a block diagram showing some components of a plasma process monitoring device according to an embodiment of the present invention.

Referring to FIG. 3, the plasma process monitoring device 1 includes a sensor 20 installed on one side of the plasma chamber 40, a measurement circuit unit 110 that measures the output current of the sensor 20, and an alternating voltage. After application, a data processing unit 120 calculates the thickness of the dielectric 10 deposited inside the chamber 40 based on the measured data, and an interface unit 130 transmits the output current to the data processing unit 120. and a display unit 140 that displays monitoring information calculated from the data processing unit 120.

The data processing unit 120 (microcontroller unit) can measure and process the output current from the sensor 20. For this purpose, the data processing unit 120 includes a control unit 121 that receives the output current obtained from the measurement circuit unit 110 and calculates the thickness of the dielectric 10, and calculates the thickness of the dielectric 10 from the actual output current. It may include an arithmetic unit 122 that transmits and receives the calculated monitoring information to an external device and an external communication unit 123 that transmits and receives the calculated monitoring information.

The control unit 121 is a plasma process monitoring device that oscillates an alternating voltage with a single frequency, commands the measurement circuit unit 110 to measure the output current, and outputs or receives the thickness of the dielectric 10 to the outside. (1) can control the overall operation performed. A digital-to-analog converter 124 may be placed adjacent to the control unit 121.

The calculation unit 122 receives the output current of the measurement circuit unit 110 and calculates the thickness information of the dielectric 10 of the sensor 20 from the magnitude and phase difference of the output current. In this embodiment, the sheath resistance (Rsh) described above, the sheath capacitor (Cs), and the thickness of the dielectric 10 calculated therefrom can be calculated. Additionally, the external communication unit 123 transmits and receives the calculated monitoring information to and from external devices, mainly the computer 150. The external communication unit 123 may be a wireless or wired communication means.

While the existing plasma process monitoring device must necessarily be equipped with a computer connected to the process monitoring device, in this embodiment, the process monitoring device 100 includes a data processing unit 120 that performs calculations and analyzes, thereby performing calculations. There is an advantage that the computer that performs the analysis can be omitted.

Meanwhile, the data processing unit 120 may be manufactured in the form of a single chip, or may be manufactured as the plasma process monitoring device 100 in the form of a single board including the measurement circuit unit 110 and the interface unit 130, which will be described later. Accordingly, the data processing unit 120 may be a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable array (FPA), a programmable logic unit (PLU), a microprocessor, or an instruction. It can be implemented as a device that can execute (instruction) and respond.

The measurement circuit unit 110 is disposed between the data processing unit 120 and the sensor 20 and amplifies the alternating current voltage oscillated in the data processing unit 120 through an op-amp (111) to produce the sensor 20. , and the output current flowing through the sensor 20 can be detected. The output current is output to the analog-to-digital converter (141, ADC) through a current measurement unit (112) equipped with a measurement resistor (113) and a differential amplifier (114). Meanwhile, in this embodiment, it has been described in detail that information on the thickness of the dielectric 10 is calculated by measuring only the output current from the measurement circuit unit 110, but the output voltage obtained by energizing the probe may also be used.

The analog-to-digital converter 141 is provided adjacent to the measurement circuit unit 110 and can convert analog signals into digital signals and output them to the data processing unit 120 through the interface unit 130.

The display unit 140 displays the monitoring information calculated from the data processing unit 120 to the operator. The operator uses the thickness of the dielectric 10 calculated by the data processing unit 120 through the display unit 140, specifically, in this embodiment, the output current measured from the measurement circuit unit 110 and the thickness calculated through the data processing unit 120. The thickness of the dielectric 10 can be easily monitored.

The plasma process monitoring device, including the data processing unit 120, the measurement circuit unit 110, the analog-to-digital converter 141, the measurement circuit unit 110, and the interface unit 130, is detachably installed on one side of the chamber 40. It can be.

The plasma process monitoring device 100 with this configuration can be made more compact than before. That is, a conventional plasma process monitoring device must be separately equipped with an external device such as a computer to calculate and analyze output data, and a data acquisition board (DAQ) to connect to the computer. In particular, the size of the DAQ was large, causing problems in miniaturizing the process monitoring device.

However, in the case of the plasma process monitoring device 100 according to the present invention, the data processing unit 120 receives output signals such as output current and calculates and analyzes them on its own, so the computer 150 is not necessarily required. DAQ can be omitted, so it can be miniaturized. Instead of DAQ being omitted, connection with an external device can be performed through wired or wireless communication through the external communication unit 123. Since plasma can be monitored only with the miniaturized process monitoring device 100, it is easy to move and has advantages in terms of installation and maintenance.

Meanwhile, as previously described in FIG. 1, in the method of measuring the thickness of the dielectric 10 using phase difference according to the prior art, as the deposited film becomes thicker, a large error occurs in the phase difference measurement, lowering reliability. exists.

Therefore, the plasma process monitoring method according to one embodiment is an invention designed to solve the above problem, and is provided by applying one alternating current voltage (V(t)=cos*w*t) with a single frequency to the sensor 20. ) Or, after applying two alternating current voltages with different frequencies, create an equivalent circuit model using the information about the current output for the applied voltage and the voltage information applied to the DC blocking capacitor, and based on this, the dielectric The purpose is to provide a technology that can measure the thickness of the dielectric 10 more accurately and in real time by calculating the thickness of (10). Hereinafter, a plasma process monitoring method according to an embodiment of the present invention will be described with reference to the drawings. The plasma process monitoring method in the present invention refers to a method of monitoring the plasma state inside the chamber 40 using the above-described plasma process monitoring device 100.

FIG. 4 is a flowchart showing a method for monitoring a plasma generation process according to an embodiment of the present invention, FIG. 5 is a diagram showing the inside of a chamber as an equivalent circuit according to an embodiment of the present invention, and FIG. 6 is a flow chart of the plasma generation process monitoring method according to an embodiment of the present invention. This is a diagram to explain a calculation method for measuring the voltage applied to a dielectric, according to one embodiment.

Referring to the flow chart shown in FIG. 4, the plasma process monitoring method according to the present invention includes applying one alternating voltage with a single frequency to the sensor 20 (S110), and A step of measuring the output current and the voltage applied to the DC blocking capacitor (S120), a step of calculating the impedance of the equivalent circuit model based on the equivalent circuit model, the size of the current, and the measured information (S130), and the calculated impedance It may include calculating the thickness of the dielectric based on the value (S140) and transmitting information about the calculated dielectric thickness to the outside (S150).

The step of applying a plurality of alternating current voltages to the sensor 20 (S110) is a step of applying alternating current voltages from the data processing unit 120 or the voltage applying unit 30 of the plasma process monitoring device 100. For convenience of explanation below, it is assumed that voltage is applied from the data processing unit 120.

The data processing unit 120 may apply a plurality of alternating current voltages having different frequencies to the sensor 20 simultaneously or sequentially. The applied alternating voltage is supplied to the sensor 20 through the op-amp 111 and the current measurement unit 112 of the measurement circuit unit 110.

In the step S120 of measuring the output current generated in the sensor 20, the output current flowing in the sensor 20 and the voltage applied to the DC blocking capacitor are measured through the measurement circuit unit 110.

The measurement circuit unit 110 includes a measurement resistor 113 and a differential amplifier 114 to amplify a small output current and remove noise. Afterwards, it can be output to the analog-to-digital converter 141, and the output signal converted into a digital signal can be transmitted to the data processing unit 120 through the interface unit 130.

In the step of calculating impedance based on the equivalent circuit model and the measured information (S130), an equivalent circuit model is constructed as shown in FIG. 5 for the metal structure installed inside the chamber, and the entire equivalent circuit model is based on this. This is the step of calculating impedance.

Specifically, when applying a single sinusoidal voltage to the sensor installed on the inner wall of the chamber 40, the entire equivalent circuit consists of the voltage application part 30, the DC blocking capacitor region 210, and the dielectric region ( 220) and a sheath region 230, the direct current blocking capacitor region 210 can be expressed as a direct current blocking capacitor (Cb), the dielectric region 220 can be expressed as a dielectric capacitor (Cdep), and the sheath region ( 230) can be expressed as sheath resistance (Rsh).

Based on the equivalent circuit model as shown in FIG. 5, after applying the applied voltage Vo, measuring the phase difference between the applied voltage and the corresponding current, as shown in FIG. 6 using the measured phase and applied voltage, each The relationship between voltages can be obtained. And since the applied voltage Vo, the phase difference Θ, and the voltage Vd applied to both ends of the DC blocking capacitor can all be measured, the value of Vd can be calculated, and Vd is Vd=Ip*Xd according to the relationship between current and impedance. It can be expressed as, and if organized based on impedance, it can be expressed as equation (1) below.

(Equation 2)

Xd=1/(w*Cdep)

And, the dielectric capacitor can be expressed again as Equation 2 below.

(Equation 2)

Cdep=A/(ε*d)

In Equations 1 and 2, ε means the dielectric constant of the deposited film, A means the area of the sensor, and w means the applied frequency.

And if the thickness of the dielectric is organized based on Equation 2, the final thickness d of the dielectric can be expressed as Equation 3 below.

(Equation 3)

d=A/(Cdep*ε)

Once the thickness of the dielectric has been calculated in this way, the calculated results can be output externally (S240).

Specifically, step S240 is a step of displaying the thickness of the dielectric to the user through the display unit 140. In this case, communication with an external computer 150, etc. is possible using the external communication unit 123 within the data processing unit 120. .

Meanwhile, in FIG. 4, the description is based on applying one sinusoidal voltage, but in the case of the present invention, the principles of the present invention described above can be applied even when two sinusoidal voltages with different frequencies are applied. When two sinusoidal voltages are applied, the thickness of the dielectric can be measured based on the amplitude information of the output current, unlike when only one sinusoidal voltage is applied.

As such, according to the plasma process monitoring device 100 and the plasma process monitoring method according to the present embodiment, the discharge conditions (e.g., applied power, gas type and flow rate, internal pressure, etc.) applied to the chamber 40 are Even if it is changed, the thickness of the dielectric can be calculated relatively accurately to the thickness of the actual deposited dielectric. Additionally, there is an advantage of being able to monitor the thickness of the dielectric in real time even when the dielectric is being created while the actual deposition process is performed inside the chamber.

In addition, when data outside the error range set by the user is obtained while monitoring the thickness of the dielectric during the deposition process or after the process is completed, it is necessary to check what the state of the plasma is, whether the discharge conditions are performed within the chamber 40, and whether the deposition process is performed smoothly. Qualitative analysis, such as whether it is being carried out, becomes possible. When data is extracted outside the actual error range, there is an advantage in being able to quickly stop the deposition process, change plasma discharge conditions, or repair plasma deposition equipment.

Figures 7 to 9 are diagrams showing experimental results according to the present invention. Figure 7 is a diagram showing the results of measuring various variables in a situation where the size of the direct current blocking capacitor is fixed, and Figure 8 is a diagram showing the results of measuring various variables according to the present invention. This is a diagram showing the results of measuring the capacitance of the film, and Figure 9 is a diagram showing the results of measuring the electron temperature and ion density according to the present invention according to changes in the dielectric film and the results of measuring using the EEDF system. .

Specifically, Figure 7 shows the sheath measured while applying an alternating voltage of 200 W, fixing the direct current blocking capacitor (Cb) at 10 nF, and changing the capacitance of the dielectric film to 5 nF, 10 nf, 15 nF, and 20 nF at a pressure of 20 mTorr. , a graph showing the voltages applied to the dielectric film and the direct current blocking capacitor, and Figure 8 is a diagram showing the measurement results of the capacitance of the dielectric film measured at a pressure of 20 mTorr by applying an alternating voltage of 200 W. This is a graph comparing the results of electron temperature and ion density measured according to changes in the dielectric film by applying an alternating voltage and changing the dielectric film at a gas pressure of 20 mTorr, compared with the results measured from EEDF.

Referring to the experimental results shown in the drawing, it can be seen that the results of measuring the thickness of the dielectric and various variables by applying the principles of the present invention are very similar to the actual results.

So far, we have looked at the plasma process monitoring device and plasma process monitoring method according to an embodiment through the drawings.

Since the device and plasma generator measure the thickness of the dielectric by directly measuring the voltage of the direct current blocking capacitor without using a sensing resistor to measure the voltage, the measurement circuit is miniaturized to improve the semiconductor process. There is an advantage in promoting equipment space efficiency.

In addition, in the case of the present invention, since the voltage applied to the sheath is measured using a method of directly measuring the voltage applied to the DC blocking capacitor, the sheath voltage can be measured directly, requiring repeated calculations to measure the thickness of the dielectric. There is an advantage of being able to measure in real time faster than conventional technology.

In addition, since the present invention measures the thickness of the dielectric based on the measured impedance value rather than the phase difference of the current, it is possible to measure the thickness more precisely than the prior art, and furthermore, it can apply not only the frequency in the kHz band but also the frequency in the MHz band. Even so, there is an advantage of being able to accurately measure the thickness of the dielectric.

The device described above may be implemented with hardware components, software components, and/or a combination of hardware components and software components. For example, devices and components described in embodiments may include, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable array (FPA), It may be implemented using one or more general-purpose or special-purpose computers, such as a programmable logic unit (PLU), microprocessor, or any other device capable of executing and responding to instructions. A processing device may perform an operating system (OS) and one or more software applications that run on the operating system. Additionally, a processing device may access, store, manipulate, process, and generate data in response to the execution of software. For ease of understanding, a single processing device may be described as being used; however, those skilled in the art will understand that a processing device includes multiple processing elements and/or multiple types of processing elements. It can be seen that it may include. For example, a processing device may include multiple processors or one processor and one controller. Additionally, other processing configurations, such as parallel processors, are possible.

Software may include a computer program, code, instructions, or a combination of one or more of these, which may configure a processing unit to operate as desired, or may be processed independently or collectively. You can command the device. Software and/or data may be used on any type of machine, component, physical device, virtual equipment, computer storage medium or device to be interpreted by or to provide instructions or data to a processing device. It can be embodied in . Software may be distributed over networked computer systems and stored or executed in a distributed manner. Software and data may be stored on one or more computer-readable recording media.

Methods according to embodiments may be implemented in the form of program instructions that can be executed through various computer means and recorded on computer-readable media. Examples of computer-readable recording media include hard disks, floppy disks, and magnetic tapes. Magnetic media, optical media such as CD-ROM and DVD, magneto-optical media such as floptical disk, and ROM and RAM ( It includes specially configured hardware devices to store and execute program instructions, such as RAM, flash memory, etc. Examples of program instructions include machine language code, such as that produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc.

As described above, although the embodiments have been described with limited examples and drawings, various modifications and variations can be made by those skilled in the art from the above description. For example, the described techniques are performed in a different order than the described method, and/or components of the described system, structure, device, circuit, etc. are combined or combined in a different form than the described method, or other components are used. Alternatively, appropriate results may be achieved even if substituted or substituted by an equivalent. Therefore, other implementations, other embodiments, and equivalents of the claims also fall within the scope of the claims described below.

10: Plasma generator
20: sensor
30: Voltage application unit
40: chamber
70: DC blocking capacitor
100: Plasma generator
110: measurement circuit part
120: data processing unit
121: Control unit
130: Interface unit
220: dielectric
230: Sheesh

Claims (7)

At least one sensor disposed inside the chamber where plasma is generated;
a voltage application unit that applies a sinusoidal voltage to the sensor;
a direct current blocking capacitor disposed between the voltage application unit and the chamber;
a measurement circuit unit that measures the output current flowing through the sensor and the voltage applied to the DC blocking capacitor; and
A data processor that calculates the thickness of the dielectric inside the chamber based on the output current and the voltage applied to the DC blocking capacitor.
Plasma process monitoring device. According to claim 1,
The data processing unit,
Calculating the thickness of the dielectric using an equivalent circuit model consisting of a dielectric capacitor generated by depositing the dielectric, a sheath capacitor in a sheath area generated adjacent to the plasma, a sheath resistor, and the direct current blocking capacitor,
Plasma process monitoring device. According to claim 1,
The data processing unit,
When the voltage application unit applies one sinusoidal voltage, the thickness of the dielectric is measured based on phase information, which is information about the phase difference between the sinusoidal voltage and the output current.
Plasma process monitoring device. According to claim 1,
The data processing unit,
When the voltage application unit applies two sinusoidal voltages with different frequencies, the thickness of the dielectric is measured based on the amplitude of the output current according to the sinusoidal voltage.
Plasma process monitoring device. According to clause 3,
The data processing unit,
After calculating the voltage applied to the DC blocking capacitor and the sheath region based on the phase information, the voltage applied to the DC blocking capacitor measured by the measurement circuit is subtracted from the voltage applied to the sheath capacitor. Calculating information about
Plasma process monitoring device. According to clause 3,
The data processing unit,
Measuring the thickness of the dielectric based on voltage information applied to the sheath region, dielectric constant information of the dielectric, area information of the sensor, and frequency information of the sinusoidal voltage,
Plasma process monitoring device. A voltage human step of applying a sinusoidal voltage to at least one sensor disposed inside a chamber where plasma is generated;
A measurement step of measuring the output current flowing through the sensor and the voltage applied to a direct current blocking capacitor connected to the chamber; and
A data processing step of calculating the thickness of the dielectric inside the chamber based on the output current and the voltage applied to the DC blocking capacitor.
Plasma process monitoring method.