Plasma processing apparatus and plasma monitoring method using the same

Abstract

The present disclosure relates to a plasma processing apparatus capable of monitoring plasma and a plasma monitoring method using the same. The plasma processing apparatus includes a first electrode on which an object to be processed is supported, a second electrode disposed to face the first electrode, a power supply unit configured to supply power to the first electrode, a measurement unit configured to measure a voltage Vdc of the second electrode, and a determination unit configured to determine a self-bias voltage of the object to be processed from the voltage of the second electrode. The present disclosure relates to an effect of improving measurement accuracy of a plasma state.

Description

Technical Field

[0001] This disclosure relates to a plasma processing apparatus and a plasma monitoring method using the plasma processing apparatus, and more specifically to a plasma processing apparatus capable of monitoring the state of plasma during a plasma processing process and a plasma monitoring method using the plasma processing apparatus. Background Technology

[0002] Plasma etching is a key process in semiconductor manufacturing, involving the reaction of plasma ions generated by plasma with the exposed layer of the substrate. The depth to which plasma ions can penetrate the exposed layer is determined by their energy. The energy of the plasma ions is at least partially related to the bias voltage applied to the substrate.

[0003] As semiconductor devices become smaller and more densely packed, high aspect ratios are required. To achieve high aspect ratios, high plasma ion energy levels are needed.

[0004] One method for increasing the energy of plasma ions is to increase the bias voltage. However, as the bias voltage increases, arcing occurs between the substrate and the processing chamber, and between the electrodes and the processing chamber structure. Furthermore, even a relatively small intrusion into the bias region of the substrate or the plasma electromagnetic field can cause disturbances in the corresponding electric field, thus generating localized fluctuations in plasma ion energy. Therefore, localized inhomogeneities are generated in the plasma etching process.

[0005] A common method and structure for measuring the self-bias voltage of a substrate is using contact pins. These contact pins can disturb the electric or electromagnetic field of the substrate. Furthermore, as the bias voltage level increases, an arcing discharge may occur between the substrate and the contact pins. This arcing discharge can damage the contact pins, the substrate, or electrodes, and can distort the actual level of the self-bias voltage.

[0006] Therefore, there is a need for a technology that can monitor plasma in plasma processing by accurately measuring the self-bias voltage without causing arc discharge.

[0007] [Existing technical documents]

[0008] [Patent Literature]

[0009] Korean Patent Publication No. 10-2014-0096299 Summary of the Invention

[0010] This disclosure provides a plasma processing apparatus capable of monitoring the state of plasma during a plasma processing process and a plasma monitoring method using the plasma processing apparatus.

[0011] According to an exemplary embodiment, a plasma processing apparatus includes: a first electrode on which an object to be processed is supported; a second electrode disposed facing the first electrode; a power supply unit configured to supply power to the first electrode to form plasma between the first electrode and the second electrode; a measurement unit configured to measure a voltage Vdc of the second electrode formed by the plasma; and a determination unit configured to determine a self-bias voltage of the object to be processed based on the voltage of the second electrode.

[0012] In the plasma processing device, the second electrode is a floating electrode, and the power is radio frequency (RF) power.

[0013] In the plasma processing apparatus, the determining unit is configured to determine the self-bias voltage based on the voltage of the floating electrode using a proportional relationship expression or lookup table between the voltage of the floating electrode and the self-bias voltage.

[0014] The plasma processing apparatus further includes a storage unit storing the proportional relationship expression or the lookup table, the proportional relationship expression being derived from a previously measured bias voltage and a previously measured voltage of the floating electrode of a sample of the object to be processed, and the determining unit being configured to receive the proportional relationship expression or the lookup table from the storage unit.

[0015] The plasma processing equipment further includes a monitoring unit configured to monitor the state of the plasma by determining whether the self-bias voltage is within a predetermined range or exceeds the frequency of fluctuations in the self-bias voltage relative to a normal reference value.

[0016] In the plasma processing apparatus, when the self-bias voltage exceeds the predetermined range, or when the frequency of fluctuations in the self-bias voltage exceeding the fluctuation tolerance is greater than or equal to a predetermined level, the monitoring unit is configured to determine that the plasma is in an abnormal state.

[0017] In the plasma processing apparatus, the measuring unit includes an RF filter that blocks radio frequency (RF) signals transmitted from the floating electrode.

[0018] According to another exemplary embodiment, a plasma monitoring method includes: a formation process for forming plasma in a space between a first electrode and a second electrode facing each other by supplying power to a first electrode on which an object to be processed is disposed; a measurement process for measuring a voltage Vdc of the second electrode formed by the plasma; and a determination process for determining a self-bias voltage of the object to be processed based on the voltage of the second electrode.

[0019] In the plasma monitoring method, the second electrode is a floating electrode, and the power supplied to the first electrode is RF power.

[0020] In the plasma monitoring method, in the determination process, the self-bias voltage is determined based on the voltage of the floating electrode using a proportional relationship expression or lookup table between the voltage of the floating electrode and the self-bias voltage.

[0021] The plasma monitoring method further includes a pre-preparation process for the proportional relationship expression or the lookup table by measuring the self-bias voltage of the sample of the object to be processed and the voltage of the floating electrode in advance.

[0022] The plasma monitoring method further includes a monitoring process for monitoring the state of the plasma by determining whether the self-bias voltage is within a predetermined range or exceeds the frequency of fluctuations in the self-bias voltage relative to a normal reference value.

[0023] In the plasma monitoring method, during the monitoring process, when the self-bias voltage exceeds the predetermined range or when the frequency of fluctuations in the self-bias voltage exceeding the fluctuation tolerance is greater than or equal to a predetermined level, the plasma is determined to be in an abnormal state.

[0024] In the measurement process, the voltage of the floating electrode is measured by blocking the radio frequency (RF) signal from the floating electrode. Attached Figure Description

[0025] The exemplary embodiments can be understood in more detail by reading the following description in conjunction with the accompanying drawings, in which:

[0026] Figure 1 This is a schematic diagram illustrating the configuration of a plasma processing apparatus according to an exemplary embodiment.

[0027] Figure 2 This is a graph schematically illustrating the relationship between the voltage of a floating electrode and the supply voltage measured in a plasma processing apparatus according to an exemplary embodiment.

[0028] Figure 3This is a graph schematically illustrating the relationship between the supply voltage and the self-bias voltage in a plasma processing apparatus according to an exemplary embodiment.

[0029] Figure 4 This is a graph schematically illustrating the relationship between the voltage of the floating electrode and the self-bias voltage in a plasma processing apparatus according to an exemplary embodiment.

[0030] Figure 5 This is a schematic configuration diagram of a plasma processing apparatus according to an exemplary embodiment, which also includes a storage unit and a monitoring unit.

[0031] Figure 6 This is a flowchart illustrating a plasma monitoring method according to another exemplary embodiment.

[0032] Figure 7 This is a flowchart illustrating, schematically, that a plasma monitoring method according to other exemplary embodiments also includes a monitoring process. Detailed Implementation

[0033] In the following description, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below, but will be practiced in various different forms, and these embodiments are provided only to make the disclosure complete and to fully convey the scope of the invention to those skilled in the art. In the description, the same reference numerals are designated for the same configurations, and the drawings are partially enlarged to accurately illustrate the embodiments of the present disclosure, and the same reference numerals refer to the same elements in the drawings.

[0034] Figure 1 This is a schematic diagram illustrating the configuration of a plasma processing apparatus according to an exemplary embodiment.

[0035] refer to Figure 1 According to an embodiment of the present disclosure, a plasma processing apparatus includes: a first electrode 110 on which an object 12 to be processed is supported; a second electrode 120 disposed facing the first electrode 110; a power supply unit 140b for supplying power to the first electrode 110 to form plasma 11 between the first electrode 110 and the second electrode 120; a measurement unit 130 for measuring the voltage Vdc formed by the plasma 11 on the second electrode 120; and a determination unit 150 for determining the self-bias voltage of the object 12 to be processed based on the voltage of the second electrode 120.

[0036] Preferably, the second electrode 120 is a floating electrode and the power is RF power.

[0037] Self-bias is a negative potential applied to the surface of a substrate, which accelerates positive ions in the plasma to the substrate surface and causes them to collide with the surface. This is called ion bombardment. The ion bombardment effect of plasma can be used to etch the surface of a substrate, and therefore plasma is used in etching processes.

[0038] When the self-bias voltage increases to a negative value, positive ions are accelerated more rapidly. These accelerated positive ions collide with the substrate with greater ionic energy, thus increasing the substrate etching effect. Therefore, monitoring the substrate self-bias voltage serves as the basis for various theoretical analyses of plasma-based processes, such as plasma etching quantity analysis, damage caused by plasma ion collisions with the substrate surface, and substrate temperature analysis.

[0039] If the plasma state is unstable, the self-bias voltage will increase or fluctuate abnormally and rapidly. Therefore, the state of the plasma can be confirmed by the self-bias voltage, which represents the plasma state, and damage to the substrate or the chamber due to plasma instability can be prevented or addressed in advance.

[0040] Therefore, it is important to measure the self-bias voltage of the substrate to monitor the plasma.

[0041] There are also direct measurement methods that involve contacting a measuring tool (e.g., a probe) with the substrate to measure its self-bias voltage. However, in these direct measurement methods, the plasma is affected by the probe, resulting in plasma imbalance. Consequently, processes using plasma are affected, and arcing can occur, potentially damaging the substrate or chamber.

[0042] Therefore, indirect measurements exist, namely, calculating the self-bias voltage by mathematically collecting the power supplied by the RF power source and the power reflected from the electrodes of the substrate, or by using a peak voltage sensor to measure the peak voltage at the electrode components of the substrate and then calculating the self-bias voltage based on the measured peak voltage. However, the limitation is that this is an indirect measurement of the plasma. Furthermore, in the case of indirect measurement where the self-bias voltage is calculated based on the peak voltage, the peak voltage does not appear continuously, thus limiting the application of indirect measurements using peak voltage to monitor the state of the plasma.

[0043] However, in this disclosure, since the self-bias voltage is determined based on the voltage measured from the second electrode 120 in contact with the plasma, the accuracy of the self-bias voltage is improved. Because the measurement of the second electrode 120 is continuous, the plasma state can be monitored in real time.

[0044] When measuring the self-bias voltage using a measuring tool (e.g., a probe), the position of the measuring tool inevitably changes every time the object to be processed changes, thus reducing the reproducibility of the measurement. However, according to embodiments of this disclosure, since the self-bias voltage is determined by measuring the voltage from the second electrode 120 having a fixed position, the reproducibility of the measurement is guaranteed even when the object to be processed is replaced. That is, the voltage of the second electrode 120 is continuously measured during the ongoing plasma processing.

[0045] The first electrode 110 may be disposed on the surface of the stage 14. The first electrode 110 supports the object to be processed 12. The object to be processed 12 may be placed on a plane of the first electrode 110. An example of the object to be processed 12 may include a substrate. The first electrode 110 receives power from the power supply unit 140. The power supplied to the first electrode 110 forms plasma 11 between the first electrode 110 and the second electrode 120. Here, the power supplied to the first electrode 110 is preferably RF power.

[0046] The second electrode 120 is configured to face the first electrode 110. That is, the second electrode 120 is configured such that one surface of it faces the surface of the first electrode 110. The second electrode 120 is preferably a floating electrode. An electrode that is not grounded or an electrode connected to a blocking capacitor may also be used as the second electrode 120. The plasma 11 allows electrons to accumulate in the second electrode 120, and a potential difference is formed due to the electron accumulation. The accumulation of electrons in the second electrode 120 is limited, and the voltage formed in the second electrode 120 due to electron accumulation can be measured in the form of a series voltage Vdc.

[0047] The voltage of the second electrode 120 measured in this manner can represent the self-bias voltage of the object to be processed, which will be referred to later. Figures 2 to 4 This will be explained in more detail.

[0048] Meanwhile, when the second electrode 120 is grounded, it is difficult to measure the voltage at the second electrode 120 because electrons do not accumulate in the second electrode.

[0049] The first electrode 110 and the second electrode 120 can be disposed in a chamber that provides a space isolated from the outside.

[0050] The power supply unit 140 supplies power to the first electrode 110 to form plasma 11 between the first electrode 110 and the second electrode 120. As mentioned above, a radio frequency (RF) power supply can be used as the power supply unit 140.

[0051] The measuring unit 130 measures the voltage Vdc of the second electrode 120 formed by the plasma 11. The measuring unit 130 measures the voltage Vdc of the floating electrode that serves as the second electrode 120 (i.e., the voltage of the second electrode). Since the accumulation of electrons in the second electrode 120 is limited, the voltage of the second electrode 120 formed due to electron accumulation can be measured in the form of a series voltage Vdc.

[0052] If the power supplied to the first electrode 110 is RF power, the RF signal can be transmitted to the measurement unit 130. Therefore, the measurement unit 130 preferably includes an RF filter that blocks the radio frequency (RF) signal transmitted from the floating electrode. The RF filter filters out the RF signal transmitted from the floating electrode and measures the voltage based on the passing direct current (DC) component.

[0053] The voltage Vdc measured at the second electrode (i.e., the floating electrode) can also vary depending on the amount of power supplied by the RF power supply (i.e., the power supply unit 140). The voltage of the floating electrode (floating electrode voltage Vdc) measured by the measurement unit 130 is transmitted to the determination unit 150.

[0054] The determining unit 150 determines the self-bias voltage of the object to be processed 12 based on the voltage Vdc of the floating electrode (i.e., the second electrode 120) measured by the measuring unit 130. For reference, in the description of this specification, the self-bias voltage will be simply referred to as self-bias voltage.

[0055] The determination unit 150 uses the proportional relationship expression between the voltage of the floating electrode and the self-bias voltage (the proportional relationship expression between the voltage of the floating electrode and the self-bias voltage) or a lookup table to determine the self-bias voltage based on the voltage of the floating electrode.

[0056] Figure 2 This is a graph schematically illustrating the relationship between the voltage of the floating electrode and the measured supply voltage in a plasma processing apparatus according to an exemplary embodiment. Figure 3 This is a graph schematically illustrating the relationship between the supply voltage and the self-bias voltage in a plasma processing apparatus according to an exemplary embodiment, and Figure 4 This is a graph schematically illustrating the relationship between the voltage of the floating electrode and the self-bias voltage in a plasma processing apparatus according to an exemplary embodiment.

[0057] Further reference Figures 2 to 4 First, such as Figure 2 As explained, it appears that there is a linear proportional relationship between the voltage supplied to the first electrode by the power supply unit 140 and the voltage of the floating electrode (floating electrode voltage Vdc) measured based on the voltage supplied to the first electrode.

[0058] like Figure 3 As explained, it appears that there is a linear relationship between the voltage applied to the first electrode by the power supply unit 140 and the self-bias voltage of the object to be processed, as measured based on the voltage supplied to the first electrode.

[0059] Therefore, as Figure 2 and Figure 3 As explained in the text, the relationship between the voltage of the floating electrode measured based on the voltage supplied to the first electrode and the self-bias voltage of the object to be processed measured based on the voltage supplied to the first electrode can be derived from... Figure 4 The relationship between the floating electrode voltage (floating electrode voltage Vdc) and the self-bias voltage, as described in the diagram, is used to represent this. The floating electrode voltage and the self-bias voltage are linearly proportional. Based on this, a lookup table can be formed, and the lookup table can be represented by the following linear proportional relationship.

[0060] y = ax + b

[0061] Here, x is the voltage of the floating electrode, y is the self-bias voltage, a is a proportionality constant, and b is a constant.

[0062] Figure 4 The voltage and self-bias voltage of the floating electrode described herein are expressed by the following relationship expression.

[0063] Y = 1.16018x – 123.2

[0064] Here, x is the voltage of the floating electrode, and y is the self-bias voltage. The coefficient of determination is approximately 0.9918. As the correlation between the dependent and independent variables increases, the coefficient of determination gets closer to approximately 1. Therefore, it can be said that the correlation between the voltage of the floating electrode and the self-bias voltage is very high, and it can be seen that the voltage of the floating electrode can represent the self-bias voltage.

[0065] Therefore, the voltage of the floating electrode can be measured, and the determining unit 50 can determine the self-bias voltage based on the measured voltage of the floating electrode.

[0066] The linear proportional relationship expression or lookup table between the voltage of the floating electrode and the self-bias voltage is obtained in advance from measurement data obtained by matching the voltage of the floating electrode, measured according to the voltage applied to the first electrode 110, with the self-bias voltage of the sample of the object to be processed. As described above, the self-bias voltage of the substrate (i.e., the object to be processed 12) can be determined using the pre-obtained linear proportional relationship expression or lookup table between the voltage of the floating electrode and the self-bias voltage.

[0067] The plasma processing apparatus according to this disclosure may also include Figure 5 The storage unit 160 described herein. Figure 5This is a schematic configuration diagram of a plasma processing apparatus according to an exemplary embodiment, which also includes a storage unit and a monitoring unit. Preferably, the proportional relationship expression or lookup table between the voltage of the floating electrode and the self-bias voltage is stored in advance in the storage unit 160.

[0068] The proportional relationship expression or lookup table can be obtained by measuring the self-bias voltage and the voltage of the floating electrode of the sample of the object to be processed in advance, and stored in the storage unit 160. The proportional relationship expression or lookup table stored in the storage unit 160 is transmitted to the determination unit 150, and the determination unit 150 uses it to determine the self-bias voltage of the object to be processed based on the voltage of the floating electrode.

[0069] The determination unit 150 uses the proportional relationship expression between the voltage of the floating electrode and the self-bias voltage received from the storage unit 160 or a lookup table to determine the self-bias voltage based on the voltage of the floating electrode measured in the measurement process.

[0070] The plasma processing apparatus according to embodiments of this disclosure may further include a monitoring unit 170.

[0071] The monitoring unit 170 monitors the state of plasma 11 by determining whether the self-bias voltage is within a predetermined range or exceeds the frequency of self-bias voltage fluctuations that exceed the fluctuation tolerance relative to the normal judgment reference value.

[0072] The monitoring unit 170 is connected to the determination unit 150 to transmit and receive electrical signals. Therefore, the monitoring unit 170 can receive information about the self-bias voltage determined by the determination unit 150.

[0073] Here, the normal judgment reference value refers to the self-bias voltage value that appears when the plasma 11 formed in response to the application of voltage to the first electrode 110 is in a stable state, and may be referred to as the reference value, which indicates that the plasma 11 is in a stable state.

[0074] The self-bias voltage of plasma 11 in a steady state varies depending on the amount of voltage applied to the first electrode 110, and the self-bias voltage is proportional to the amount of power supplied to the first electrode 110.

[0075] Therefore, when plasma 11 is in a stable state, the self-bias voltage value corresponding to the amount of power supplied to the first electrode 110 is a normal judgment reference value. The state of plasma 11 can be determined by comparing the measured self-bias voltage with the normal judgment reference value.

[0076] If the self-bias voltage determined by the determining unit 150 is within a predetermined range relative to the normal judgment reference value, then the state of plasma 11 is determined to be in a normal state. Here, the predetermined range refers to the allowable voltage difference that allows plasma 11 to be determined to be in a normal state even if there is a voltage difference with the normal judgment reference value.

[0077] For example, if the permissible voltage difference is set to 10V, the normal reference value for the self-bias voltage supplied to the first electrode 110 is 150V, and the self-bias voltage determined based on the measured voltage of the floating electrode is 155V, then since the voltage difference is 5V, which is within the 10V permissible voltage difference, the state of plasma 11 can be determined to be normal. However, if the self-bias voltage determined based on the measured voltage of the floating electrode is 172V, then the voltage difference is 22V, exceeding the 10V permissible voltage difference, and therefore the state of plasma 11 can be determined to be abnormal.

[0078] Although the power supplied to the first electrode 110 is constant, the self-bias voltage, determined based on the voltage measured at the floating electrode, may vary each time the self-bias voltage is measured. This difference can be referred to as self-bias voltage fluctuation. Furthermore, the acceptable error in self-bias voltage fluctuation can be referred to as fluctuation tolerance. If the self-bias voltage fluctuation is within the fluctuation tolerance, it is determined that the self-bias voltage remains constant. That is, it is determined that the self-bias voltage fluctuation is at a negligible level and the self-bias voltage remains constant.

[0079] However, if the self-bias voltage fluctuation exceeds the fluctuation tolerance, it is determined that self-bias voltage fluctuation is occurring, rather than the self-bias voltage remaining constant. When the frequency of self-bias voltage fluctuation is equal to or greater than a predetermined level, plasma 11 can be determined to be in an abnormal state.

[0080] For example, if the allowable voltage difference is set to 10V, the normal reference value for the self-bias voltage supplied to the first electrode 110 is 150V, and the fluctuation tolerance is set to 2V, then the self-bias voltage determined based on the measured voltage of the floating electrode is within the allowable voltage difference of 10V. However, if the self-bias voltage determined when measuring the voltage of the floating electrode twice consecutively is 147V and 156V, it exceeds the fluctuation tolerance of 2V, and therefore it can be seen that this self-bias voltage fluctuation is not negligible. If the frequency of such fluctuations is more frequent than the predetermined level, then the state of plasma 11 is determined to be abnormal.

[0081] As mentioned above, when the self-bias voltage exceeds the predetermined range or when the frequency of self-bias voltage fluctuations exceeding the fluctuation tolerance is greater than or equal to the predetermined level, the monitoring unit 170 determines that the plasma 11 is in an abnormal state.

[0082] When plasma 11 is determined to be in an abnormal state, the abnormal state can be displayed via an information display unit (not described) such as a display, so that the user can recognize the abnormal state of plasma 11.

[0083] Figure 6 This is a flowchart illustrating a plasma monitoring method according to another exemplary embodiment.

[0084] Further reference Figure 6 According to another embodiment of the present invention, a plasma monitoring method includes: a formation process S110 of forming plasma 11 in the space between a first electrode 110 and a second electrode 120 facing each other by supplying power to a first electrode 110 on which an object to be processed 12 is disposed; a measurement process S120 of measuring the voltage of the second electrode 120 formed by the plasma 11; and a determination process S130 of determining the self-bias voltage of the object to be processed 12 based on the voltage of the second electrode 120.

[0085] Preferably, the second electrode is a floating electrode, and the power supplied to the first electrode is RF power.

[0086] The plasma monitoring method according to embodiments of the present disclosure can be implemented in the plasma processing apparatus described above according to embodiments of the present disclosure. In the formation process S110, power is supplied to a first electrode 110 on which an object 12 is disposed to form plasma 11 in the space between the first electrode 110 and the second electrode 120 facing each other. Plasma 11 is formed between the first electrode 110 and the second electrode 120 by the power supplied to the first electrode 110. Here, preferably, the second electrode 120 is a floating electrode, and the power supplied to the first electrode 110 is RF power. A representative example of the object 12 to be processed may include a substrate.

[0087] If a plasma is formed between the first electrode 110 and the second electrode, the voltage Vdc of the floating electrode (i.e., the second electrode 120) formed by the plasma 11 is measured in measurement process S120. The plasma 11 allows electrons to accumulate in the second electrode 120, and a potential difference is formed due to the accumulation of electrons. The accumulation of electrons in the second electrode 120 is limited, and the voltage of the second electrode 120 formed due to the accumulation of electrons can be measured in the form of a series voltage Vdc.

[0088] Meanwhile, when the second electrode 120 is grounded, it is difficult to measure the voltage at the second electrode 120 because electrons do not accumulate in the second electrode.

[0089] Here, the voltage of the floating electrode is preferably measured by blocking the radio frequency (RF) signal transmitted from the floating electrode. The RF filter of the measurement unit 130 can filter out the RF signal transmitted from the floating electrode and can measure the voltage based on the passed DC component. The measured voltage of the floating electrode is transmitted to the determination unit 150.

[0090] In process S130, the self-bias voltage of the object to be processed 12 is determined based on the voltage of the second electrode 120. Since the self-bias voltage is determined based on the voltage measured from the second electrode 120 which is in contact with the plasma, the accuracy of the self-bias voltage is improved. Because the self-bias voltage is determined by measuring the voltage from the second electrode 120, which has a fixed position, the reproducibility of the measurement is ensured even when the object to be processed is replaced. That is, the voltage of the second electrode 120 is continuously measured during the ongoing plasma process.

[0091] More specifically, in determining process S130, the self-bias voltage is determined based on the voltage of the floating electrode using a proportional relationship expression or lookup table between the voltage of the floating electrode and the self-bias voltage.

[0092] Here, as mentioned above, preferably, the proportional relationship expression or lookup table between the voltage of the floating electrode and the self-bias voltage is stored in the storage unit 160 in advance. For this purpose, a pre-preparation process may also be included. In the pre-preparation process, the proportional relationship expression or lookup table is prepared in advance by first measuring the self-bias voltage and the voltage of the floating electrode of the sample of the object to be processed. That is, the proportional relationship expression or lookup table derived from the self-bias voltage and the voltage of the floating electrode of the sample of the object to be processed is stored in the storage unit 160 in advance. Then, the proportional relationship expression or lookup table stored in the storage unit 160 is transmitted to the determination unit 150. Therefore, the determination unit 150 can use the proportional relationship expression or lookup table stored in the storage unit 160 to determine the self-bias voltage based on the voltage of the floating electrode measured in the measurement process S120.

[0093] Based on the measurement data obtained by matching the voltage of the floating electrode, which is measured according to the voltage applied to the first electrode 110, with the self-bias voltage, a linear proportional relationship expression or lookup table between the voltage of the floating electrode and the self-bias voltage can be obtained in advance.

[0094] Therefore, in determining process S130, the self-bias voltage of the substrate (i.e., the object to be processed 12) can be determined using a linear proportional relationship expression between the voltage of the floating electrode and the self-bias voltage or a lookup table.

[0095] Here, as Figure 7 The document mentions that it may also include monitoring process S140. Figure 7 This is a flowchart illustrating, illustratively, that a plasma monitoring method according to another exemplary embodiment also includes a monitoring process.

[0096] In monitoring process S140, the state of plasma 11 is monitored by determining whether the self-bias voltage determined in determination process S130 is within a predetermined range or exceeds the frequency of self-bias voltage changes that exceed the fluctuation tolerance, relative to the normal determination reference value.

[0097] Here, the normal judgment reference value refers to the self-bias voltage value that appears when the plasma 11 formed in response to the application of voltage to the first electrode 110 is in a stable state, and may be referred to as the reference value, which indicates that the plasma 11 is in a stable state.

[0098] The self-bias voltage value of plasma 11 when it is in a steady state varies depending on the amount of voltage applied to the first electrode 110, and the self-bias voltage value is proportional to the amount of power supplied to the first electrode 110.

[0099] Therefore, when plasma 11 is in a stable state, the self-bias voltage value corresponding to the power supplied to the first electrode 110 is a normal judgment reference value. The state of plasma 11 can be determined by comparing the measured self-bias voltage with the normal judgment reference value.

[0100] If the self-bias voltage determined in process S130 is within a predetermined range relative to the normal judgment reference value, then the state of plasma 11 is determined to be in a normal state. Here, the predetermined range refers to the allowable voltage difference that allows plasma 11 to be determined to be in a normal state even if there is a voltage difference with the normal judgment reference value.

[0101] Although the power supplied to the first electrode 110 is constant, the self-bias voltage determined based on the voltage measured at the floating electrode may vary each time a measurement is performed. This difference can be referred to as self-bias voltage fluctuation. The acceptable error in self-bias voltage fluctuation can be referred to as fluctuation tolerance. If the self-bias voltage fluctuation is within the fluctuation tolerance, it is determined that the self-bias voltage remains constant. That is, it is determined that the self-bias voltage fluctuation is at a negligible level and the self-bias voltage remains constant.

[0102] However, when the self-bias voltage fluctuation exceeds the fluctuation tolerance, it is determined that a self-bias voltage fluctuation is occurring, rather than the self-bias voltage remaining constant. When the frequency of self-bias voltage fluctuations exceeding the fluctuation tolerance is equal to or greater than a predetermined level, it can be determined that plasma 11 is in an abnormal state.

[0103] As described above, in monitoring process S140, when the self-bias voltage exceeds a predetermined range, or when the frequency of self-bias voltage fluctuations exceeding the fluctuation tolerance is equal to or greater than a predetermined level, it is determined that plasma 11 is in an abnormal state. Here, the monitoring unit can determine that the plasma is in an abnormal state.

[0104] In the plasma monitoring method according to the embodiments of the present disclosure described above, the progress sequence of each process is not limited to a specific order, and the progress sequence of each process can be changed when necessary, and each process can be repeated as needed.

[0105] As described above, plasma can be monitored according to the plasma monitoring method according to the embodiments of this disclosure.

[0106] When the intention is to directly monitor the state of plasma according to relevant technologies, the monitoring component (e.g., a probe in contact with the plasma) should be inserted into the plasma. However, the insertion of the measuring component can affect the state of the plasma. Even when a thin probe is specifically inserted to minimize the impact on the plasma, the plasma may still concentrate on the probe or easily trigger an arc discharge. The resulting plasma arc discharge can damage the plasma processing equipment. Therefore, the self-bias voltage is measured indirectly through a correlated variable that can represent the actual measured value.

[0107] However, as described above, in the plasma processing apparatus and plasma monitoring method using the plasma processing apparatus according to embodiments of the present disclosure, the floating electrode (i.e., the second electrode in contact with the plasma) is used as a probe, and more specifically, since the floating electrode with a large area is used as a probe, the possibility of arc discharge can be reduced while ensuring the stability of the plasma.

[0108] Because the state of the plasma is monitored in real time, damage to the object being processed or the chamber due to abnormal plasma conditions can be prevented by confirming whether the plasma is abnormal.

[0109] Since the self-bias voltage is related to the amount of etching in the etching process, it can be used as a parameter for analyzing etching process results. Specifically, because the accuracy of the self-bias voltage obtained through this disclosure is higher than that of self-bias voltage indirectly measured in related art, it has the advantage of helping to improve the accuracy of analysis.

[0110] Preferred embodiments of this disclosure have been described and illustrated above. However, this disclosure is not limited to the embodiments described above, and those skilled in the art will understand that various modifications and equivalent embodiments can be derived from the preferred embodiments without departing from the essential points of this disclosure claimed in the claims. Therefore, the scope of protection of this disclosure should be defined by the following claims.

[0111] According to the plasma processing apparatus and plasma monitoring method using the plasma processing apparatus according to embodiments of this disclosure, since a floating electrode (i.e., a second electrode in contact with the plasma) is used to measure the self-bias voltage of the object to be processed, a separate probe is not required. Therefore, it has the following advantages: it eliminates the possibility of arcing due to the probe in related technologies and allows for accurate monitoring of the plasma state.

[0112] In addition, since the state of the plasma is monitored in real time, it is possible to determine whether the state of the plasma is normal, and thus it has the effect of preventing the object to be processed or the chamber from being damaged due to abnormal state of the plasma.

[0113] Furthermore, the self-bias voltage in the plasma processing is related to the etching amount in the etching process, and therefore the self-bias voltage can be used as an analytical parameter for the results of the etching process. Specifically, unlike conventional methods that indirectly measure the self-bias voltage, the self-bias voltage obtained through this disclosure is measured using the voltage of a floating electrode (i.e., a second electrode in contact with the plasma), and therefore the measurement accuracy is relatively high. Thus, it can greatly contribute to improving the accuracy of plasma state analysis.

[0114] As described above, according to the plasma processing apparatus and plasma monitoring method using the plasma processing apparatus disclosed herein, the occurrence of arc discharge in the plasma processing process is significantly reduced, thus preventing damage to the substrate (i.e., the object to be processed) and the plasma processing apparatus. Furthermore, it allows for rapid response to the plasma state through accurate monitoring and improves the accuracy of plasma state measurement.

[0115] Although the plasma processing apparatus and the plasma monitoring method using the plasma processing apparatus have been described with reference to specific embodiments, they are not limited thereto. Therefore, those skilled in the art will readily understand that various modifications and changes can be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A plasma processing apparatus, comprising: The first electrode, on which the object to be processed is supported; The second electrode is configured to face the first electrode; A power supply unit is configured to supply power to the first electrode to form plasma between the first electrode and the second electrode; The measuring unit is configured to measure the DC voltage of the second electrode formed by the accumulation of plasma electrons; as well as The determining unit is configured to determine the self-bias voltage of the object to be processed based on the DC voltage of the second electrode.

2. The plasma processing apparatus according to claim 1, wherein the second electrode is a floating electrode and the power is radio frequency power.

3. The plasma processing apparatus according to claim 2, wherein the determining unit is configured to determine the self-bias voltage based on the voltage of the floating electrode using a proportional relationship expression or lookup table between the voltage of the floating electrode and the self-bias voltage.

4. The plasma processing apparatus according to claim 3, further comprising: A storage unit storing the proportional relationship expression or the lookup table, the proportional relationship expression being derived from a previously measured self-bias voltage and a previously measured voltage of the floating electrode of a sample of the object to be processed. The determining unit is configured to receive the proportional relationship expression or the lookup table from the storage unit.

5. The plasma processing apparatus according to claim 1, further comprising: The monitoring unit is configured to monitor the state of the plasma by determining whether the self-bias voltage is within a predetermined range or exceeds the frequency of fluctuations in the self-bias voltage relative to a normal reference value.

6. The plasma processing apparatus of claim 5, wherein the monitoring unit is configured to determine that the plasma is in an abnormal state when the self-bias voltage exceeds the predetermined range or when the frequency of fluctuations in the self-bias voltage exceeding the fluctuation tolerance is greater than or equal to a predetermined level.

7. The plasma processing apparatus of claim 2, wherein the measuring unit includes a radio frequency filter that blocks radio frequency signals transmitted from the floating electrode.

8. A plasma monitoring method, comprising: A plasma formation process that forms in the space between a first electrode and a second electrode facing each other by supplying power to a first electrode on which an object to be processed is disposed; A measurement process for measuring the DC voltage of the second electrode formed by the accumulation of plasma electrons; as well as The process for determining the self-bias voltage of the object to be processed based on the DC voltage of the second electrode.

9. The plasma monitoring method according to claim 8, wherein the second electrode is a floating electrode and the power supplied to the first electrode is radio frequency power.

10. The plasma monitoring method according to claim 9, wherein in the determining process, The self-bias voltage is determined based on the voltage of the floating electrode using a proportional relationship expression or lookup table between the voltage of the floating electrode and the self-bias voltage.

11. The plasma monitoring method according to claim 10, further comprising: The pre-preparation process for the proportional relationship expression or the lookup table is achieved by measuring the self-bias voltage of the sample of the object to be processed and the voltage of the floating electrode in advance.

12. The plasma monitoring method according to claim 9, further comprising: A monitoring process for monitoring the state of plasma by determining whether the self-bias voltage is within a predetermined range or exceeds the fluctuation tolerance relative to a normal reference value.

13. The plasma monitoring method according to claim 12, wherein in the monitoring process, When the self-bias voltage exceeds the predetermined range, or when the frequency of fluctuations in the self-bias voltage exceeding the fluctuation tolerance is greater than or equal to a predetermined level, the plasma is determined to be in an abnormal state.

14. The plasma monitoring method according to claim 9, wherein in the measurement process, The voltage of the floating electrode is measured by blocking the radio frequency signal from the floating electrode.

Images