Method and apparatus for selecting cable length for plasma processing equipment

Abstract

This invention discloses a method and apparatus for selecting the cable length of a plasma process device, specifically for selecting the length of a power supply cable for such a device. The plasma process device utilizes an RF frequency of tens of MHz or higher for plasma processing. The cable length selection method includes: an impedance measurement step, measuring the impedance of the applicable power supply cable; an electrical length calculation step, calculating the electrical length of the power supply cable based on the measured impedance; and a cable length determination step, determining the length of the power supply cable based on the calculated electrical length. The cable length selection apparatus includes: an impedance measurement unit, measuring the impedance of the applicable power supply cable; an electrical length calculation unit, calculating the electrical length of the power supply cable based on the measured impedance; and a cable selection unit, determining the length of the power supply cable based on the electrical length.

Description

Technical Field

[0001] This invention relates to a method and device for selecting the cable length of a plasma process equipment, and more specifically, to a scheme for selecting the length of a power supply cable for a plasma process equipment that performs plasma processes via a power supply at an RF frequency of tens of MHz or higher. Background Technology

[0002] A plasma processing apparatus is, for example, an apparatus that supplies high-frequency power to electrodes disposed in a plasma-generating reaction chamber to generate plasma discharge, and performs surface treatment on a substrate using the generated plasma, and is used in semiconductor manufacturing, etc.

[0003] As is well known, when power is supplied to a plasma load, the discharge voltage at the load terminals decreases when the plasma begins to discharge. Therefore, if insufficient ignition power is applied, the plasma ignition can become unstable due to the reduced discharge voltage at the load terminals. To ensure stable plasma ignition, a sufficiently high voltage must be applied to the load terminals in the high-frequency power supply device supplying power to the plasma load as the ignition voltage for plasma generation.

[0004] Typically, when selecting the cable length for power supply to plasma equipment, the physical length of the cable is calculated and applied. However, based on this calculation of the cable's physical length, while there are no problems using the cable at low frequencies, when applying high frequencies above tens of MHz, there are issues with different process results due to differences in cable impedance.

[0005] (Patent Document 0001) Japanese Patent Publication No. 2004-247401

[0006] (Patent Document 0002) Japanese Patent Registration No. 5210905 Summary of the Invention

[0007] The present invention is proposed to solve the problems of the prior art as described above, and its purpose is to solve the following problem: when the cable for power supply of plasma equipment is selected by physical length, the process results vary at high frequencies due to the impedance difference of the cable.

[0008] The purpose of this invention is not limited to what has been stated above, and other purposes and advantages of the invention not mentioned here may be understood from the following description.

[0009] One embodiment of the method for selecting the cable length of a plasma process apparatus according to the present invention includes: an impedance measurement step, measuring the impedance of the power supply cable to be used; an electrical length calculation step, calculating the electrical length of the power supply cable based on the measured impedance; and a cable length determination step, determining the length of the power supply cable based on the calculated electrical length.

[0010] Preferably, the electric length calculation step utilizes the correlation between at least one of the wavelength, wave number, and measurement error of the frequency used to calculate the electric length.

[0011] As an example, the electric length calculation step calculates the electric length using the following [Equation 1],

[0012] [Formula 1]

[0013]

[0014] Where L represents the electrical length, n represents the wavelength period, λ represents the wavelength, β represents the wave number, Z represents the open-circuit impedance, and e represents the measurement error.

[0015] Preferably, the impedance measurement step may be based on the S-parameters of the power supply cable to be applied to calculate the impedance.

[0016] As an example, the impedance measurement step could be to calculate the reflection coefficient using S-parameters.

[0017] Furthermore, one embodiment of the cable length selection device for plasma process equipment according to the present invention includes: an impedance measuring unit for measuring the impedance of the power supply cable to be used; an electrical length calculation unit for calculating the electrical length of the power supply cable based on the measured impedance; and a cable selection unit for determining the power supply cable based on the electrical length.

[0018] Preferably, the electrical length calculation unit calculates the electrical length using a correlation between at least one of the wavelength, wave number, and measurement error of the frequency used.

[0019] As an example, the electrical length calculation unit calculates the electrical length using the following [Equation 1],

[0020] [Formula 1]

[0021]

[0022] Where L represents the electrical length, n represents the wavelength period, λ represents the wavelength, β represents the wave number, Z represents the open-circuit impedance, and e represents the measurement error.

[0023] Alternatively, the impedance measuring unit may calculate the impedance based on the S-parameters of the power supply cable to be applied.

[0024] Furthermore, the method for selecting the cable length of the plasma process equipment according to the present invention may include: an impedance measurement step, which calculates and measures the impedance based on the S-parameters of the power supply cable to be applied; an electrical length calculation step, which calculates the electrical length based on the measured impedance using the correlation between at least one of the wavelength, wavenumber, and measurement error of the frequency used in the power supply cable; and a cable length determination step, which determines the length of the power supply cable based on the electrical length calculated in a manner corresponding to the electrical length required according to the power supply matters in the corresponding plasma process equipment.

[0025] According to the present invention as described above, a solution is proposed to eliminate process errors caused by impedance differences in power supply cables when performing plasma processes generated at high-frequency RF frequencies above tens of MHz.

[0026] The problem that can be solved is that when the power supply cable is selected with the existing physical length, there is no problem at low frequencies, but the impedance changes at high frequencies due to differences of tens of millimeters.

[0027] In particular, the problem that can be solved is that the state of the cable core and insulation also affects the impedance at high frequencies. When the cable is simply selected based on its physical length, the impedance changes depending on the state of the cable and insulation, thereby reducing the yield of the process.

[0028] Furthermore, for proper impedance matching, the physical length of the power supply cable is selected by reflecting the electrical length, thereby improving impedance deviation when power supply cables for power supply are configured in plasma process equipment.

[0029] The effects of the present invention are not limited to those mentioned above. Other effects not mentioned can be clearly understood by those skilled in the art from the following description. Attached Figure Description

[0030] Figure 1 A structural diagram of an embodiment of the cable length selection device according to the present invention is shown.

[0031] Figure 2 A flowchart illustrating an embodiment of a method for selecting the cable length of a plasma process apparatus according to the present invention is shown.

[0032] Figure 3 This shows an example of impedance when the cable is selected by its physical length.

[0033] Figure 4 This shows an example of the process execution results when the cable is selected by physical length.

[0034] Figure 5 A conceptual diagram of the S-parameters used for impedance measurement in this invention is shown.

[0035] Figure 6 An example of reflection coefficient measurement used for impedance measurement in this invention is shown.

[0036] Figure 7 An example of selecting a cable based on electrical length using the present invention is shown.

[0037] (Explanation of reference numerals in the attached diagram)

[0038] 100: Cable length selection device

[0039] 110: Impedance Measurement Section

[0040] 130: Electrical Length Calculation Department

[0041] 150: Cable Selection Section Detailed Implementation

[0042] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited or restricted by the embodiments.

[0043] To illustrate the advantages of the present invention and the objectives achieved through its implementation, preferred embodiments of the present invention will be described below with reference to these embodiments.

[0044] First, the terminology used in this application is only for describing specific embodiments and is not intended to limit the scope of the invention. Singular expressions may include plural expressions as long as there is no obvious difference in meaning within the context. Furthermore, it should be understood in this application that terms such as "comprising" or "having" are used to specify the presence of features, numbers, steps, operations, constituent elements, components, or combinations thereof described in the specification, without precluding the possibility of the presence or addition of one or more other features or numbers, steps, operations, constituent elements, components, or combinations thereof.

[0045] When describing this invention, detailed descriptions of related announcement structures or functions are omitted if they are deemed to obscure the key points of the invention.

[0046] This invention relates to a scheme for selecting the length of a power supply cable for a plasma process apparatus that performs plasma processes via a power supply at an RF frequency of tens of MHz or higher.

[0047] Figure 1A structural diagram of an embodiment of the cable length selection device according to the present invention is shown.

[0048] The cable length selection device 100 according to the present invention may generally include an impedance measuring unit 110, an electrical length calculation unit 130, a cable selection unit 150, etc.

[0049] The impedance measuring unit 110 may include an impedance measuring instrument that measures the impedance of the power supply cable to which it is to be applied.

[0050] Impedance measurement can be performed in various ways. For example, the impedance can be calculated based on the S-parameters of the power supply cable to which it is applicable. That is, the impedance can be measured using parameters derived from comparing the input and output voltages across the frequency distribution of the RF characteristics.

[0051] Preferably, when calculating the open-circuit impedance S11, S11 is used as the reflection coefficient, which means that the amount of reflection caused by the impedance difference is calculated as the ratio of the input voltage to the reflected voltage. The smaller the value of S11, the less the reflection, thus indicating that the impedance matching is appropriate.

[0052] The electrical length calculation unit 130 can calculate the electrical length of the power supply cable based on the measured impedance.

[0053] The electrical length calculation unit 130 can calculate the electrical length using the correlation between at least one of the wavelength, wavenumber, and measurement error of the frequency used.

[0054] As an example, the electrical length calculation unit 130 can calculate the electrical length using the following [Equation 1].

[0055] [Formula 1]

[0056]

[0057] Where L represents the electrical length, n represents the wavelength period, λ represents the wavelength, β represents the wavenumber, Z represents the open-circuit impedance, and e represents the measurement error. The measurement error e can be a value calculated from repeated experimental results.

[0058] The cable selection unit 150 can select the length of the applicable power supply cable based on the power supply requirements of the corresponding plasma process equipment and taking into account the electrical length.

[0059] For example, the power supply cable could be selected based on the electrical length, which takes into account impedance differences in various states such as cables and insulators, in addition to the physical length used to supply power to the antenna of the plasma reaction chamber via the RF high-frequency generator.

[0060] Furthermore, this invention proposes a method for selecting the cable length of plasma process equipment using the cable length selection device. Figure 2 A flowchart illustrating an embodiment of a method for selecting the cable length of a plasma process apparatus according to the present invention is shown.

[0061] The method for selecting the cable length of a plasma process apparatus according to the present invention may include: a cable impedance determination step (S100) for determining the impedance of a power supply cable to be applied; an electrical length calculation step (S200) for calculating the electrical length of the power supply cable based on the measured impedance; and a cable length determination step (S300) for determining the length of the power supply cable based on the calculated electrical length.

[0062] In this invention, when selecting a high-frequency power supply cable for plasma processes, not only the simple physical length but also the electrical length is calculated to determine the power supply cable, thereby achieving appropriate impedance matching.

[0063] Typically, when the measured physical length of the power supply cable is suitable for plasma process equipment, there is no problem with low-frequency power supplies. However, when high-frequency power supplies are supplied at frequencies above tens of MHz, the state impedance of the cable and insulator changes, making proper impedance matching impossible.

[0064] As an example, Figure 3 This illustrates an example of impedance when the cable is selected based on its physical length. Figure 4 This shows an example of the process execution results when the cable is selected by physical length.

[0065] As described Figure 3 As shown, the measured physical length of the power supply cable is approximately 3m, which is within a certain error range. However, even with this physical length, the impedance may vary significantly depending on the condition of the power supply cable.

[0066] When power supply cables of the same physical length are used, as described Figure 4 As shown in (a), there are significant differences in impedance, and due to the impedance variation, as described... Figure 4 As shown in (b), the stability and reliability of the process results cannot be guaranteed, resulting in a significant reduction in process yield.

[0067] Therefore, in this invention, the impedance of the power supply cable is measured, and the electrical length of the power supply cable is calculated based on this. A power supply cable with an appropriate electrical length is selected, thereby achieving impedance matching efficiency.

[0068] First, the cable length selection device 100 measures the impedance (S100) of the power supply cable to be used. The impedance measurement can be calculated based on the S-parameters of the power supply cable to be used.

[0069] At high frequencies, due to the short period, it is difficult to determine a specific measurement point to measure impedance. Therefore, the characteristics of the RF circuit can be analyzed by using the ratio of voltage (V) to current (I) on the frequency distribution and the relative values ​​between the input and output signals. In this case, S-parameters can be applied.

[0070] Furthermore, the cable length selection device 100 calculates the electrical length of the power supply cable based on the measured impedance (S200). At this time, the electrical length can be calculated using the correlation between at least one of the wavelength, wave number, and measurement error of the frequency used.

[0071] As an example, the electrical length L can be calculated using the following [Equation 1].

[0072] [Formula 1]

[0073]

[0074] Where L represents the electrical length, n represents the wavelength period, λ represents the wavelength, β represents the wave number, Z represents the open-circuit impedance, and e represents the measurement error, which can be a value calculated from repeated experimental results.

[0075] The open-circuit impedance Z is applicable in [Equation 1]. Figure 5 A conceptual diagram of the S-parameters used for impedance measurement in this invention is shown.

[0076] In the Figure 5 In a two-port circuit, the input and output values ​​can be represented by the S-parameters as shown in Equation 2 below.

[0077] [Equation 2]

[0078]

[0079] Where S11 represents the input port voltage reflection coefficient, S12 is the reverse voltage gain, S21 is the forward voltage gain, and S22 represents the output port voltage reflection coefficient.

[0080] Impedance matching is crucial in RF circuits; inadequate impedance matching can lead to reflected waves. Therefore, proper impedance matching is essential to minimize reflected waves.

[0081] The figure illustrates an example of reflection coefficient measurement used for impedance measurement in this invention.

[0082] The reflection coefficient can be used as an indicator to calculate the amount of reflection caused by the impedance difference by comparing the input voltage and the reflected voltage.

[0083] For example, in the Figure 6 In this context, the reflection coefficient Г can be calculated using the following [Equation 3].

[0084] [Formula 3]

[0085] Γ=V - / V + =(Z L -Z O ) / (Z L +Z O )

[0086] That is, the value of S11 can be calculated using [Equation 3].

[0087] As described above, the open-circuit impedance Z can be calculated based on the calculated S11, and then reflected in the [Equation 1] to calculate the electrical length.

[0088] Furthermore, the cable length selection device 100 can select the required physical length of the power supply cable by reflecting the electrical length of the power supply cable used for impedance matching (S300).

[0089] Figure 7 An example of selecting a cable based on electrical length using the present invention is shown.

[0090] As described Figure 7 As shown, although there are significant differences in the physical length of the cables, the impedance can also exhibit a certain level of similarity, and this impedance can be used to select the electrical length of the cable required for impedance matching.

[0091] That is, in order to achieve proper impedance matching, the physical length of the power supply cable is selected based on the electrical length, so that impedance deviation can be improved when power supply cables for power supply are configured in plasma process equipment.

[0092] According to the present invention as described above, when performing plasma processes generated at high-frequency RF frequencies of tens of MHz or higher, process errors caused by impedance differences in the power supply cable can be eliminated.

[0093] The above description is merely illustrative of the technical concept of the present invention. Anyone skilled in the art can make various modifications and variations without departing from the essential characteristics of the invention. Therefore, the embodiments described in this invention are not intended to limit the technical concept of the invention but rather to illustrate it; the technical concept of the invention is not limited to these embodiments. The scope of protection of this invention should be interpreted by the appended claims, and all technical concepts within the same scope should be interpreted as included within the scope of the claims of this invention.

Claims

1. A method for selecting the cable length of a plasma process equipment, characterized in that, include: Impedance measurement procedure: Measure the impedance of the power supply cable to be used. The steps for calculating the electrical length are as follows: calculate the electrical length of the power supply cable based on the measured impedance; as well as The steps for determining cable length include determining the length of the power supply cable based on the calculated electrical length. The electric length calculation step calculates the electric length using the following [Equation 1], [Formula 1] Where L represents the electrical length, n represents the wavelength period, λ represents the wavelength, β represents the wave number, Z represents the open-circuit impedance, and e represents the measurement error.

2. The method for selecting the cable length of plasma process equipment according to claim 1, characterized in that, The impedance measurement step calculates the impedance based on the S-parameters of the power supply cable to be applied.

3. The method for selecting the cable length of plasma process equipment according to claim 1, characterized in that, The impedance measurement step calculates impedance based on parameters obtained by analyzing RF characteristics through a comparison of input and output voltages across the frequency distribution.

4. The method for selecting the cable length of plasma process equipment according to claim 3, characterized in that, The impedance measurement step calculates the reflection coefficient using S-parameters.

5. The method for selecting the cable length of plasma process equipment according to claim 1, characterized in that, The cable length determination step is based on determining the length of the power supply cable by means of an electrical length calculated in a manner corresponding to the electrical length required for the power supply in the respective plasma process equipment.

6. A cable length selection device for plasma process equipment, characterized in that, include: Impedance measurement unit measures the impedance of the power supply cable to be used. The electrical length calculation unit calculates the electrical length of the power supply cable based on the measured impedance; as well as The cable selection department determines the power supply cable based on its electrical length. The electrical length calculation unit calculates the electrical length using the following [Equation 1], [Formula 1] Where L represents the electrical length, n represents the wavelength period, λ represents the wavelength, β represents the wave number, Z represents the open-circuit impedance, and e represents the measurement error.

7. The cable length selection device for plasma process equipment according to claim 6, characterized in that, The impedance measurement unit calculates the impedance based on parameters that analyze RF characteristics by comparing the input and output voltages across the frequency distribution.

8. The cable length selection device for plasma process equipment according to claim 7, characterized in that, The impedance measurement unit calculates the impedance based on the S-parameters of the power supply cable to be applied.

9. The cable length selection device for plasma process equipment according to claim 6, characterized in that, The cable selection unit determines the length of the power supply cable based on an electrical length calculated in a manner corresponding to the electrical length required for the power supply in the corresponding plasma process equipment.

10. A method for selecting the cable length of a plasma process equipment, characterized in that, include: The impedance measurement procedure involves calculating and measuring the impedance based on the S-parameters of the power supply cable to be applied. The electric length is calculated based on the measured impedance and by the following [Equation 1]; as well as The cable length determination step involves determining the length of the power supply cable based on an electrical length calculated in a manner corresponding to the electrical length required for the power supply in the respective plasma process equipment. [Formula 1] Where L represents the electrical length, n represents the wavelength period, λ represents the wavelength, β represents the wave number, Z represents the open-circuit impedance, and e represents the measurement error.

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