Plasma processing apparatus and plasma processing method

Abstract

The present invention provides technology that enables plasma treatment which is uniform, by controlling electric field circularity to an optimal value. Provided is technology comprising: a waveguide which is connected to a vacuum container and through which an electric field for plasma generation propagates; a rectangular waveguide which is included in the waveguide and which operates in a lowest-order mode; a circular waveguide which is included in the waveguide and which operates in a lowest-order mode; a circular-rectangular converter which connects the rectangular waveguide and the circular waveguide; a treatment chamber which is disposed in the vacuum container below the circular waveguide, and in which plasma is formed by the electric field; a circularly polarized wave generator which is disposed inside the circular waveguide; a circularly polarized wave compensator which adjusts circularly polarized waves inside the circular waveguide; a control unit which adjusts the operation of the circularly polarized wave compensator; and an automatic matching unit which is connected to the end of the rectangular waveguide that is opposite from the circular-rectangular converter, which detects a reflected electric field, and which matches impedance in accordance therewith. A reflected electric field measured by the automatic matching unit, and a scattering matrix S of an electric field propagation region that connects a reflected electric field measurement plane and a plane subject to electric field distribution monitoring are used to calculate an electric field distribution. The operation of the circularly polarized wave compensator is controlled in accordance with the electric field distribution based on the calculation result.

Description

[Technical field]

[0001] The present disclosure relates to a plasma processing apparatus and a plasma processing method, and more particularly to a plasma processing apparatus that processes a sample with plasma generated by electromagnetic waves propagated through a waveguide and supplied into a processing chamber, and relates to a plasma processing technology equipped with a circular polarized wave generator that supplies a circularly polarized wave with a rotating polarization plane. [Background technology]

[0002] In conventional semiconductor device manufacturing processes, in order to achieve faster elements and lower power consumption, efforts have been made to increase speed and reduce power consumption by miniaturizing and making device structures three-dimensional. In the future, in order to achieve even higher performance in devices, it is predicted that there will be a shift to even finer and more complex structures than before. On the other hand, the difficulty of manufacturing semiconductor devices is rapidly increasing as the structures become more complex, and the increase in manufacturing costs per chip is becoming an issue.

[0003] In order to reduce the manufacturing cost per chip, it is effective to process semiconductor wafers uniformly and increase the number of chips that can be obtained from one wafer. In this context, plasma processing equipment is required to process semiconductor wafers more uniformly than before.

[0004] In response to the above demands, a technique has been reported in which circularly polarized electromagnetic waves are used to generate plasma as a method for improving the uniformity of the plasma density distribution in the processing chamber and achieving uniform wafer processing in the circumferential direction.

[0005] Patent Documents 1 and 2 disclose plasma processing apparatuses equipped with a means for monitoring the axial ratio of the circularly polarized wave in the circular waveguide and an adjustment means for adjusting the axial ratio to an optimum value again when the axial ratio of the circularly polarized wave inside the circular waveguide deteriorates due to the plasma in the processing chamber or the reflected wave from the dielectric material. Here, the axial ratio of the circularly polarized wave is a term that indicates the ratio of the maximum value to the minimum value of the electric field component of the circularly polarized wave that rotates in one period, with 1 indicating a perfect circularly polarized wave and the closer to 0, the more non-uniform the electromagnetic wave. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2011-77292 A [Patent Document 2] JP 2016-96091 A Summary of the Invention [Problem to be solved by the invention]

[0007] In order to improve the efficiency of semiconductor device processing, it is necessary to extend the operating time of the plasma processing equipment as much as possible and to produce devices for a long period of time. Therefore, it is required to minimize the number of measuring instruments installed in the plasma processing equipment and to extend the maintenance cycle as much as possible.

[0008] In Patent Documents 1 and 2, in order to control the circular polarization axial ratio inside the circular waveguide, a plurality of circular polarization monitor means are provided in the waveguide section. In this configuration, if the measurement accuracy of even one of the monitor means deteriorates, the circular polarization adjuster will not be at an optimal value, and conversely, there is a possibility that the plasma processing will be less uniform than before. Therefore, periodic maintenance of the monitor means is necessary, which may lead to a reduction in the operating time of the plasma processing apparatus.

[0009] The present disclosure provides a technique for enabling uniform plasma processing by controlling the circularity of the electric field to an optimal value. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0010] One representative plasma processing apparatus according to the present disclosure for solving the above problems is as follows: a waveguide connected to the vacuum vessel and through which an electric field for generating plasma propagates; a rectangular waveguide constituting the waveguide and operating in a lowest order mode; a circular waveguide constituting the waveguide and operating in a lowest order mode; a circular-rectangular converter connecting the rectangular waveguide and the circular waveguide; a process chamber disposed within the vacuum vessel below the circular waveguide, in which the plasma is formed by the electric field; a circular polarizer disposed inside the circular waveguide; a circular polarization compensator for adjusting the circular polarization inside the circular waveguide; A control unit that adjusts the operation of the circular polarization compensator; an automatic matching device connected to the end of the rectangular waveguide opposite to the circular-rectangle converter, for detecting a reflected electric field and matching impedance in response to the detected electric field; A technology is provided in which the electric field distribution is calculated using the reflected electric field measured by the automatic matching device and the scattering matrix S of the electric field propagation region that connects the reflected electric field measurement surface and the surface whose electric field distribution is to be monitored, and the operation of the circular polarization compensator is controlled according to the electric field distribution based on the calculated result. Effect of the Invention

[0011] According to the present disclosure, a technology can be provided that controls the circular polarization compensator to an optimal setting based on the electric field distribution obtained using the reflected electric field obtained by the automatic matching device and the scattering matrix S, uniformizes the microwave electric field distribution below the circular waveguide section in the waveguide, generates uniform plasma, and enables uniform plasma processing. In other words, by controlling the axial ratio of the circular polarization to an optimal value, uniform plasma is generated in the circumferential direction, thereby realizing uniform plasma processing. A detector for directly monitoring the circular polarization axial ratio inside the circular waveguide section 202 is not required, and implementation is easy. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a front cross-sectional view showing a schematic overall configuration of a plasma processing apparatus according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing details of the configuration of a waveguide of the plasma processing apparatus according to the embodiment. [Figure 3A]FIG. 3A is a cross-sectional view of a waveguide of a plasma processing apparatus according to an embodiment. [Figure 3B] FIG. 3B is a diagram illustrating a circular polarization generator and a circular polarization adjuster according to an embodiment. [Figure 4] FIG. 4 is a diagram showing the calculation results of the electric field circularity ratio inside the circular waveguide versus the amount of stub insertion when the reflection coefficient at the tuner |Γ|=0.3 and ∠Γ=60°. [Figure 5A] FIG. 5A is a diagram showing the calculation results of the electric field circularity ratio inside the circular waveguide versus the amount of stub insertion when the reflection coefficient at the tuner |Γ|=0.2 and ∠Γ=180°. [Figure 5B] FIG. 5B is a diagram showing the calculation results of the electric field circularity ratio inside the circular waveguide versus the amount of stub insertion when the reflection coefficient at the tuner |Γ|=0.4 and ∠Γ=150°. [Figure 6] FIG. 6 is a diagram showing a control chart for adjusting the amount of stub insertion in the plasma processing apparatus according to the embodiment. [Figure 7A] FIG. 7A is a diagram showing actual measurement values ​​of the distribution of the amount of etching of a wafer when no stub is inserted, using the plasma processing apparatus according to the embodiment. [Figure 7B] FIG. 7B is a diagram showing actual measurement values ​​of the distribution of the amount of etching of a wafer when the stub is adjusted to an optimal position using the plasma processing apparatus according to the embodiment. [Figure 8] FIG. 8 is a diagram showing a plasma processing method using the plasma processing apparatus according to the embodiment. [Figure 9] FIG. 9 is a diagram showing a plasma processing method using a plasma processing apparatus according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments and modified examples will be described with reference to the drawings. However, in the following description, the same components are given the same reference numerals and repeated description may be omitted. Note that the drawings may be shown more diagrammatically than the actual embodiment in order to clarify the description, but they are merely examples and do not limit the interpretation of the present disclosure. EXAMPLES

[0014] Fig. 1 is a front cross-sectional view showing a schematic overall configuration of a plasma processing apparatus according to an embodiment. Fig. 2 is a diagram showing details of a configuration of a waveguide of the plasma processing apparatus according to an embodiment. Fig. 3A is a cross-sectional view of a waveguide of the plasma processing apparatus according to an embodiment. Fig. 3B is a diagram explaining a circular polarization generator and a circular polarization adjuster according to an embodiment.

[0015] First, an outline of the configuration of a plasma processing apparatus 100 shown in Fig. 1 will be described. The plasma processing apparatus 100 includes a high-frequency power supply 101, a tuner 102, a waveguide 103, a circular polarization generator 104, a circular polarization adjuster 105, a control unit 106, and a processing chamber 108.

[0016] Waveguide 103 is connected to a vacuum vessel and an electric field for generating plasma propagates through it. As shown in Figures 2 and 3A, waveguide 103 is composed of rectangular waveguide section 201 having a rectangular (or oblong) cross section and propagating electromagnetic waves of the lowest mode (TM01 mode), circular waveguide section 202 having a circular cross section and propagating electromagnetic waves of the lowest mode (TE11 mode), and circle-to-rectangle converter section (circle-to-rectangle converter) 203 that connects rectangular waveguide section 201 and circular waveguide section 202.

[0017] The high frequency power supply 101 is a magnetron, and supplies electromagnetic waves, which are high frequency power for generating plasma, to the waveguide 103 .

[0018] The processing chamber 108 is a processing chamber in which a sample (wafer) is subjected to plasma processing, and is disposed within the vacuum vessel 120 below the circular waveguide portion 202, and electromagnetic waves are supplied to the inside of the processing chamber from the waveguide 103 to form plasma.

[0019] The circular polarizer 104 is disposed inside the circular waveguide section 202 and generates a circularly polarized wave.

[0020] The circular polarization adjuster 105 is a circular polarization corrector, and is disposed above or below the circular polarization generator 104 to adjust the distribution of the circular polarization.

[0021] Tuner 102 is an automatic matching device that is connected between high frequency power supply 101 and waveguide 103, and prevents high frequency power from flowing from waveguide 103 to high frequency power supply 101 by matching the impedance. Tuner 102 is connected to rectangular waveguide section 201, calculates the impedance on the load side based on the reflected electromagnetic wave, and achieves a matching state with the impedance on the oscillator side. That is, tuner 102 is connected to the end of rectangular waveguide section 201 opposite to circle-to-rectangle conversion section 203, detects the reflected electric field, and matches the impedance accordingly.

[0022] The control unit 106 includes an arithmetic processing unit 106a and an operation control unit 106b. The arithmetic processing unit 106a of the control unit 106 is connected to the tuner 102, and calculates the distribution of the circularly polarized wave supplied to the processing chamber 108 from the reflected electromagnetic wave measured by the tuner 102 and the scattering matrix S of the waveguide 103, the circular polarization generator 104, and the circular polarization adjuster 105. The operation control unit 106b of the control unit 106 controls the operation of the circular polarization adjuster 105 based on the calculation result calculated by the arithmetic processing unit 106a, and adjusts the insertion amount of the circular polarization adjuster 105. For example, when the adjustment of the insertion amount of the circular polarization adjuster 105 is performed by a motor, the operation control unit 106b of the control unit 106 is connected to the motor and controls the rotation of the motor. When the circular polarization adjuster 105 is configured with two rod-shaped members serving as stubs (for example, an x-stub 105x as the first stub and a y-stub 105y as the second stub (see FIG. 3B)), the motor is configured to include a first motor M1 that adjusts the insertion amount DX of the x-stub 105x and a second motor M2 that adjusts the insertion amount DY of the y-stub 105y. The operation control unit 106b of the control unit 106 is configured to be able to control the first motor M1 and the second motor M2 individually.

[0023] In other words, control unit 106 calculates the electric field distribution using the reflected electric field measured by automatic matching unit (tuner) 102 and the scattering matrix S of the electric field propagation region connecting reflected electric field measurement surface FA1 (see Figure 1) of automatic matching unit (tuner) 102 and surface FA2 (see Figure 1) whose electric field distribution is to be monitored, and controls the operation of circular polarization corrector (circular polarization adjuster) 105 in accordance with the electric field distribution based on the calculation result.

[0024] As a result, the circular polarization compensator 105 is controlled to an optimal setting based on the reflected electric field obtained by the automatic matching box 102 and the electric field distribution obtained using the scattering matrix S, and the microwave electric field distribution in the vacuum vessel 120 below the circular waveguide 202 of the waveguide 103 is made uniform in the circumferential direction, so that a plasma that is uniform in the circumferential direction can be generated in the processing chamber 108. As a result, uniform plasma processing can be performed on the sample 109 in the processing chamber 108 of the plasma processing apparatus 100.

[0025] Further, the configuration of the plasma processing apparatus according to the first embodiment of the present disclosure will be described with reference to FIG. 1. As shown in FIG. 1, in the plasma processing apparatus 100 of this embodiment, an electromagnetic wave is supplied from a magnetron 101, which is a high-frequency power source, through a waveguide 103 and a dielectric window 107 to a processing chamber 108. A solenoid coil 111 is a magnetic field generating mechanism for generating a magnetic field. The electromagnetic wave and electrons moving in cyclotron motion due to a static magnetic field generated by the solenoid coil 111 cause electron cyclotron resonance (ECR) to generate plasma. For example, when a microwave with a frequency of 2.45 GHz is used as a plasma source, a static magnetic field of 0.0875 Tesla is generated in the processing chamber 108 by the solenoid coil 111, causing an electron cyclotron resonance phenomenon, and plasma is efficiently generated.

[0026] A base electrode 110, which is a sample stage for placing a sample 109 thereon, is provided in the processing chamber 108. A high-frequency power source 115 for supplying bias power to the sample 109 to be processed is connected to the base electrode 110 via a matching unit 114.

[0027] The processing chamber is connected to a gas supply unit 117 via a valve , so that gas can be supplied into the processing chamber . The amount of gas supplied is controlled by the opening of the valve .

[0028] The inside of the processing chamber 108 is connected to a pump 113 via a valve 112, and gas inside the processing chamber 108 supplied from a gas supply unit 117 is exhausted. By controlling the gas exhaust speed by the opening of the valve 112, the pressure inside the processing chamber 108 can be adjusted to a constant value.

[0029] Furthermore, in this plasma processing apparatus 100, a tuner 102 is provided between the magnetron 101 and the waveguide 103. The tuner 102 calculates the impedance of the load side from the measurement result of the reflected wave from the load side, and matches the impedance of the high frequency power supply 101 side with the impedance of the load side from the waveguide 103 to the processing chamber 108, thereby efficiently supplying electromagnetic waves to the load side.

[0030] The control unit 106 can further control the high frequency power supply of the magnetron 101, the magnetic field of the solenoid coil 111, the opening degree of the valves 112 and 116, the high frequency power supply 115, and the like.

[0031] 2 shows an enlarged view of waveguide 103. Waveguide 103 is composed of rectangular waveguide section 201 with a rectangular cross section, circular waveguide section 202 with a circular cross section, and circular-to-rectangle conversion section 203 that connects rectangular waveguide section 201 and circular waveguide section 202. Rectangular waveguide section 201 has a dimension that allows only electromagnetic waves in the TM01 mode, which is the lowest mode, to propagate, and circular waveguide section 202 has a dimension that allows only electromagnetic waves in the TE11 mode, which is the lowest mode, to propagate.

[0032] 2, one end of the rectangular waveguide section 201 is connected to an automatic matching box (tuner) 102. In this example, a reflected electric field measurement plane FA1 of the automatic matching box (tuner) 102 is set between the automatic matching box (tuner) 102 and one end of the rectangular waveguide section 201. The other end of the rectangular waveguide section 201 is connected to one end of a circular-to-rectangle conversion section 203. The other end of the circular-to-rectangle conversion section 203 is connected to one end of a circular waveguide section 202, and the other end of the circular waveguide section 202 is connected to a vacuum vessel 120. In this example, a plane FA2 where the electric field distribution is to be monitored is set between the other end of the circular waveguide section 202 and the vacuum vessel 120.

[0033] A circular polarizer 104 that generates a circularly polarized wave is installed in the circular waveguide section 202 .

[0034] Here, we will briefly explain circular polarization. When the electric field vector of an electromagnetic wave is defined on the central axis of a circular waveguide, the plane consisting of the electromagnetic wave's traveling direction and electric field vector is called the polarization plane. An electromagnetic wave in which this polarization plane rotates over time and the locus of the electric field vector forms a perfect circle is defined as a circularly polarized wave. On the other hand, an electromagnetic wave in which the polarization plane does not rotate over time is called a linearly polarized wave. A circularly polarized wave can be generated by superimposing two linearly polarized waves whose polarization planes are perpendicular to each other and have a phase difference of 90 degrees.

[0035] Various types of circularly polarized wave generating means using the above-mentioned circularly polarized wave generating mechanism have been conventionally known, and in the present disclosure, any type can be used as long as the surface of the waveguide 103 that contacts the dielectric window 107 as a quartz window is circular. In particular, in the plasma processing apparatus 100 of FIG. 1, a plate-like member 104 made of dielectric material is introduced into the waveguide 103 as a circularly polarized wave generator so that its surface is parallel to the waveguide 103. In this configuration, the wavelength of the linearly polarized wave introduced from the upper part of the waveguide 103 is reduced for the component parallel to the longitudinal direction LO (see FIG. 3B) of the circularly polarized wave generator 104 due to the difference in dielectric constant with vacuum. On the other hand, the wavelength of the component parallel to the transverse direction SO (see FIG. 3B) of the circularly polarized wave generator 104 is not reduced. Therefore, by optimally adjusting the length of the circular polarizer 104 parallel to the waveguide 103, a phase difference of exactly 90° can be generated between the component of the linearly polarized wave parallel to the longitudinal direction LO of the circular polarizer 104 and the component parallel to the short direction SO of the circular polarizer 104, and these components are combined below the circular polarizer 104 to generate a circularly polarized wave.

[0036] Various circular polarization compensators for controlling the axial ratio of the circularly polarized wave have been known in the past, and any of them can be used in the present disclosure. As shown in Fig. 2 and Fig. 3B, in this embodiment, two rod-shaped members 105 called stubs are attached to the circular waveguide section 202 so as to be perpendicular to each other, and the electric field circularity of the circularly polarized wave is adjusted by controlling the insertion amounts (DX, DY) of the rod-shaped members 105. The circular polarization compensator 105 can be installed at a first position Pa above the circular polarizer 104 or at a second position Pb below the circular polarizer 104.

[0037] As shown in FIG. 3B, in this example, one of the two stubs 105 that are circular polarization compensators is installed parallel to the longitudinal direction LO of the circular polarizer 104. This stub 105 is hereinafter referred to as the x stub (105x, first stub). Moreover, the other of the two stubs 105 that are circular polarization compensators is installed parallel to the transverse direction SO of the circular polarizer 104. This stub 105 is hereinafter referred to as the y stub (105y, second stub). Note that the installation directions of the x stub (105x) and y stub (105y) can be set regardless of the longitudinal direction LO and transverse direction SO of the circular polarizer 104. That is, the x stub (105x) has its longitudinal direction aligned along the first direction X, and is set to be insertable into the circular waveguide section 202 along the first direction X so that its insertion amount DX is controlled by the first motor M1. On the other hand, the y stub (105y) has its longitudinal direction aligned along a second direction Y intersecting or perpendicular to the first direction X, and is set to be insertable into the circular waveguide section 202 along the second direction Y so that its insertion amount DX is controlled by the second motor M2. That is, the insertion amounts (DX, DY) of the stubs 105 (105x, 105y) are adjustable.

[0038] A description will now be given of a means for controlling the stub 105. In this disclosure, the electric field circularity inside the circular waveguide portion 202 is calculated, and the insertion amount (DX, DY) of the stub 105 (105x, 105y) is controlled so as to improve the calculated electric field circularity.

[0039] A method for calculating the electric field circularity ratio will be described with reference to Fig. 3A. Since only electromagnetic waves in TM01 mode propagate inside rectangular waveguide section 201, the electric field component at the surface connected to tuner 102 (corresponding to reflected electric field measurement surface FA1) is limited to one-directional components along the A axis. Furthermore, since only electromagnetic waves in TE11 mode propagate inside circular waveguide section 202, the electric field vector can be described by two-directional components when two mutually perpendicular axes, the B axis and the C axis, are considered.

[0040] The connection surface (FA1) of the rectangular waveguide section 201 with the tuner 102 is taken as port 1, and the B-axis component at the lower end of the circular waveguide section 202 (corresponding to the surface FA2 where the electric field distribution is to be monitored) is taken as port 2, and the C-axis component is taken as port 3. In this case, the incident waves at ports 1, 2, and 3 are respectively a i , the reflected wave is b i (where i is the port number: 1, 2, 3), these relationships can be expressed using the scattering matrix S as shown in (Equation 1).

[0041]

number

[0042] Here, the scattering matrix S is generally a matrix describing the relationship between the initial state and the final state, and in this disclosure in particular, is a matrix describing the relationship between the incident wave and the reflected wave at the port. In other words, the scattering matrix S is the scattering matrix of the electric field propagation region connecting the reflected electric field measurement surface FA1 of the tuner 102 and the surface FA2 whose electric field distribution is to be monitored.

[0043] The reflection coefficient Γ of the electromagnetic wave measured by tuner 102 corresponds to the ratio of the incident wave to the reflected wave at port 1. Therefore, the relationship between the incident wave a1 and the reflected wave b1 can be expressed as (Equation 2) using the reflection coefficient Γ.

[0044] b1=Γa1 (formula 2) Using the reflection coefficient R at the bottom end of the circular waveguide section 202, the relationship between the incident wave a2 and the reflected wave b2, and the relationship between the incident wave a3 and the reflected wave b3 can be expressed by (Equation 3) and (Equation 4), respectively.

[0045] a2=Rb2 (formula 3) a3 = Rb3 (Equation 4) Here, the reflection coefficient R of the magnetized plasma is a tensor. However, when the reflection coefficient R is expressed as a tensor, the number of unknowns becomes large compared to the number of equations, and simultaneous equations cannot be solved. Therefore, in this disclosure, the reflection coefficient R in the magnetized plasma is approximated by a scalar value.

[0046] By setting the incident wave at port 1 as 1 and using (Eqs. 1) to (Eq. 4), we obtain (Eq. 5).

[0047]

number

[0048] Equation 5 is a system of three simultaneous equations for three unknowns, a2, a3, and R. Therefore, by solving equation 5, the electric field circularity inside circular waveguide portion 202 can be found from the reflection coefficient Γ of the electromagnetic wave at tuner 102.

[0049] Thereafter, the control unit 106 calculates the insertion amount (DX, DY) of the stubs 105 (105x, 105y) that improves the electric field circularity inside the circular waveguide portion 202, and adjusts the insertion amount (DX, DY) of the stubs 105 (105x, 105y) based on the result.

[0050] However, a change in the insertion amount (DX, DY) of the stub 105 (105x, 105y) changes the scattering coefficient S and the reflection coefficient Γ of the waveguide 103. Therefore, in the present disclosure, it is preferable to gradually change the insertion amount (DX, DY) of the stub 105 (105x, 105y) and perform the calculations of (Equation 1) to (Equation 4) and (Equation 5) again using the changed scattering coefficient S each time to calculate the electric field circularity.

[0051] The above-mentioned operation of the stubs 105 (105x, 105y) is repeated until the calculated value of the electric field circularity ratio becomes equal to or greater than a desired value, thereby making it possible to achieve the target value of the electric field circularity ratio.

[0052] The scattering matrix S can be obtained by simulation or prior measurement. The scattering matrix S varies depending on the configuration of the waveguide 103, but is determined once the configuration of the waveguide 103 is determined. The scattering matrix S is preferably stored in a database stored in a storage area of ​​the control unit 106.

[0053] FIG. 4 is a diagram showing the calculation results of the electric field circularity inside the circular waveguide section 202 with respect to the stub insertion amount (DX, DY) when the reflection coefficient at the tuner |Γ|=0.3 and ∠Γ=60°. The scattering matrix S was obtained using a simulation of the finite element method, and the electric field circularity with respect to the insertion amount (DX, DY) of each of the two stubs 105 (105x, 105y) was calculated, and is shown in FIG. 4. In FIG. 4, the horizontal axis x indicates the insertion amount DX of the x-stub (105x), the vertical axis y indicates the insertion amount DY of the y-stub (105y), and the contours indicate the electric field circularity. The stub insertion amount is shown in m, and the maximum insertion amount for both x and y is 80 mm. FIG. 4 also shows the result of the electric field circularity when the magnitude of the reflection coefficient |Γ| of the electromagnetic wave at the tuner 102 is 0.3 and the phase ∠Γ is 60°.

[0054] It can be seen from FIG. 4 that the electric field circularity is highest when the x stub (105x) is inserted at 35 mm and the y stub (105y) is inserted at 20 mm.

[0055] However, as described above, when the insertion amount (DX, DY) of stub 105 is changed, the scattering matrix S and the reflection coefficient Γ of waveguide 103 change. Therefore, if stub 105 is suddenly changed to the optimum stub insertion amount derived from the reflection coefficient Γ when stub 105 is not inserted, there is a possibility that the optimum stub insertion amount will not be achieved.

[0056] An explanation will be given using actual measurement results. Fig. 5A is a diagram showing the calculation results of the electric field circularity ratio inside circular waveguide section 202 versus the amount of stub insertion when the reflection coefficient at the tuner |Γ|=0.2 and ∠Γ=180°. Fig. 5B is a diagram showing the calculation results of the electric field circularity ratio inside circular waveguide section 202 versus the amount of stub insertion when the reflection coefficient at the tuner |Γ|=0.4 and ∠Γ=150°. In Figs. 5A and 5B, the amount of stub insertion is shown in m.

[0057] FIG. 5A shows the relationship between the stub insertion amount (DX, DY) and the field circularity when the stub 105 is not inserted (|Γ|=0.2, ∠Γ=180 degrees). From FIG. 5A, it can be seen that the optimum field circularity is achieved by inserting the x stub (105x) by 70 mm and the y stub (105y) by 20 mm. However, when the x stub (105x) is actually inserted by 70 mm and the y stub (105y) is inserted by 20 mm, the reflection coefficient Γ in the tuner 102 changes to |Γ|=0.4, ∠Γ=150° due to the influence of the electric field reflection at the stub 105. The relationship between the stub insertion amount and the field circularity in this case is shown in FIG. 5B. In this case, the optimum stub insertion amount is the x stub 40 mm and the y stub 15 mm, and it can be seen that the optimum stub insertion amount is not achieved.

[0058] As described above, the reflection coefficient Γ of the electromagnetic wave in tuner 102 and the stub insertion amount (DX, DY) are not independent variables, but affect each other. Therefore, even if the stub insertion amount is changed to the optimal value obtained from the reflection coefficient Γ when stubs 105 (105x, 105y) are not inserted, the optimal field circularity cannot be achieved, and a control mechanism is required.

[0059] 6 is a diagram showing a control chart for adjusting the amount of stub insertion in the plasma processing apparatus according to the embodiment. The control chart for the amount of stub insertion based on the measured value of the reflection coefficient Γ at the tuner 102 will be described with reference to FIG.

[0060] (Step S1) First, the control unit 106 acquires the measured value of the reflection coefficient Γ of the reflected electromagnetic wave measured by the tuner 102 .

[0061] (Step S2) The control unit 106 acquires the scattering matrix S of the waveguide 103 from the database of the control unit 106 .

[0062] (Step S3) The control unit 106 obtains the electric field circularity from the acquired reflection coefficient Γ and scattering matrix S. Then, the control unit 106 calculates the insertion amount (DX, DY) of the stub 105 that improves the electric field circularity, and controls the motors M1 and M2 based on the calculation result to adjust the insertion amount (DX, DY) of the stub 105. In other words, the control unit 106 calculates the stub insertion amount (DX, DY) that improves the electric field circularity, and predicts the stub insertion amount.

[0063] (Step S4) The control unit 106 judges whether the stub insertion amount (DX, DY) is optimal. If the stub insertion amount (DX, DY) is optimal (Yes), the control chart ends. On the other hand, if the stub insertion amount (DX, DY) is not optimal (No), the process proceeds to step S5.

[0064] (Step S5) Next, the control unit 106 finely adjusts the stub insertion amount by controlling the insertion amount (DX, DY) of the stub 105 (i.e., the first motor M1 and the second motor M2 are controlled by the control unit 106). Then, steps S1-S3 are repeated again. At this time, the control unit 106 gradually changes the control amount, which is the stub insertion amount (DX, DY), and updates the optimal stub insertion amount by referring to the reflection coefficient Γ each time.

[0065] The above operations (S1 to S5) are repeated, and the control chart ends when the current stub insertion amount (DX, DY) of the stub 105 coincides with the optimal stub insertion amount.

[0066] The results of wafer processing when the stub insertion amount is adjusted using the calculation results of the electric field circularity rate will be described with reference to Figures 7A and 7B. Figure 7A is a diagram showing the actual measurement values ​​of the wafer etching amount distribution when no stub is inserted, using the plasma processing apparatus according to the embodiment. Figure 7B is a diagram showing the actual measurement values ​​of the wafer etching amount distribution when the stub is adjusted to the optimal position, using the plasma processing apparatus according to the embodiment.

[0067] Figures 7A and 7B show the experimental results of a microwave plasma etching apparatus that supplies 2.45 GHz microwaves to a vacuum processing chamber and uses plasma generated by electron cyclotron resonance to etch a 30 mm wafer, which is a material for semiconductor devices. The contours show the amount of etching on the wafer surface over a certain time span. The lines with equal etching amounts are also shown as contour lines.

[0068] Figure 7A shows the etching results when no stub is inserted. When no stub is inserted, the electric field circularity calculated from the tuner's reflection coefficient Γ is 0.38. Also, looking at the etching results, it can be seen that the peak of the etching amount is shifted from the center of the wafer, and the distribution is non-uniform in the circumferential direction of the wafer.

[0069] Here, as a value for quantitatively evaluating the distribution of the amount of etching, the uniformity U of the amount of etching at a wafer radius of 100 mm is defined by (Equation 6).

[0070] U = ((Maximum value - Minimum value) / (Maximum value + Minimum value)) x 100% (Equation 6) A larger value of the uniformity U indicates that the distribution of the amount of etching is more non-uniform in the circumferential direction, and a value closer to 0 indicates that the amount of etching is more uniform.

[0071] Using the above (Equation 6), the uniformity U of the etching amount in FIG. 7A is expressed as U=2.4%.

[0072] Next, FIG. 7B shows the results when the stub insertion amount was adjusted using the method proposed in this disclosure and the distribution of the amount of etching was obtained. At this time, the amount of stub insertion was x stub 70 mm and y stub 15 mm, and the field circularity calculated from the reflection coefficient Γ measured by the tuner 102 was 0.59. This value of the field circularity is an improvement compared to the field circularity value of 0.38 before control. The uniformity U of the amount of etching defined by (Equation 6) is calculated as U=0.7%. Therefore, it can be seen that the distribution of the amount of etching improved from 2.4% to 0.7% as a result of controlling the stub 105 using the method proposed in this disclosure.

[0073] As described above, by controlling stub 105 to an optimal setting based on the electric field distribution obtained using the reflected electric field obtained by tuner 102 and the scattering matrix S, the microwave electric field distribution inside circular waveguide portion 202 of waveguide 103 can be made uniform, and therefore the microwave electric field distribution inside processing chamber 108 below waveguide 103 can be made uniform. As a result, uniform plasma can be generated inside processing chamber 108, and uniform plasma processing of the wafer can be achieved in plasma processing apparatus 100. In particular, since plasma that is uniform in the circumferential direction with respect to the center of the wafer can be generated inside processing chamber 108, uniform plasma processing of the wafer can be achieved in plasma processing apparatus 100.

[0074] Next, a plasma processing method for a wafer (semiconductor wafer) using the plasma processing apparatus 100 will be described with reference to Fig. 8. Fig. 8 is a diagram showing a plasma processing method using the plasma processing apparatus 100 according to an embodiment.

[0075] (Step S10) First, in the plasma processing apparatus 100, the control chart of the stub insertion amount described in Fig. 6 is executed. As a result, the stub 105 is controlled to an optimal setting so that a uniform plasma can be generated in the processing chamber 108. Step S10 is also called a first process.

[0076] (Step S11) A sample 109, which is a semiconductor wafer, is carried into the processing chamber 108, and the sample 109 is placed on a base electrode 110, which is a sample stage. Step S11 is also called a second process.

[0077] (Step S12) Next, plasma is generated inside the processing chamber 108, and the sample 109 is processed by the plasma. This plasma processing is, for example, an etching process, a film formation process, or the like. In the case of an etching process, an etching gas is supplied from the gas supply unit 117 to the inside of the processing chamber 108. In the case of a film formation process, a film formation gas is supplied from the gas supply unit 117 to the inside of the processing chamber 108. Since known gases can be used as the etching gas and the film formation gas, detailed explanations will be omitted. Step S12 is also referred to as a third process.

[0078] (Step S13) Next, the sample 109, which is a semiconductor wafer, is carried out from the inside of the processing chamber 108. Step S13 is also called a fourth step.

[0079] This completes the plasma processing method for the plasma processing of semiconductor wafer 109. Therefore, since the semiconductor wafer 109 is processed by plasma in the processing chamber 108 of the plasma processing apparatus 100 in which the microwave electric field distribution is made uniform, uniform plasma processing can be achieved. In particular, uniform plasma processing can be performed in the circumferential direction about the center of semiconductor wafer 109.

[0080] 8, after performing step S10, steps S11 to S13 can be repeated to perform plasma processing on a plurality of semiconductor wafers 109. That is, since the scattering matrix S is determined once the configuration of waveguide 103 of plasma processing apparatus 100 is determined, uniform plasma processing can be performed on semiconductor wafers 109 by performing step S10 once.

[0081] (Modification) Fig. 9 is a diagram showing a plasma processing method using a plasma processing apparatus according to a modified example. The plasma processing method of the modified example shown in Fig. 9 differs from the plasma processing method of the embodiment shown in Fig. 8 in that step S20 (also called a fifth step) in which the control chart of the stub insertion amount shown in Fig. 6 is executed is added between step S11 (second step) and step S12 (third step). Step S20 is a stub insertion amount control chart step, similar to step S10.

[0082] Therefore, as shown in step SB, when steps S11, S20, S12, and S13 are repeated to plasma process a plurality of semiconductor wafers 109, step S20 is performed for each repetition. In this manner, step S20 is performed for each repetition, so that the microwave electric field distribution inside the circular waveguide portion 202 of the waveguide 103 can be made more uniform, and therefore the microwave electric field distribution inside the processing chamber 108 below the waveguide 103 can be made more uniform. As a result, a more uniform plasma can be generated in the processing chamber 108, and more uniform plasma processing can be performed on the semiconductor wafers 109 in the plasma processing apparatus 100.

[0083] While the present disclosure has been specifically described above based on the embodiments, it goes without saying that the present disclosure is not limited to the above embodiments and can be modified in various ways. [Explanation of symbols]

[0084] 100: plasma processing apparatus, 102: tuner (automatic matching device), 103: waveguide, 104: circular polarization generator, 105: circular polarization adjuster (circular polarization corrector), 106: control unit, 108: processing chamber, 109: sample (semiconductor wafer), 110: base electrode (sample stage)

Claims

1. a waveguide connected to the vacuum vessel and through which an electric field for generating plasma propagates; a rectangular waveguide constituting the waveguide and operating in a lowest order mode; a circular waveguide constituting the waveguide and operating in a lowest order mode; a circular-rectangular converter connecting the rectangular waveguide and the circular waveguide; a processing chamber disposed within the vacuum vessel below the circular waveguide, in which a plasma is formed by the electric field; a circular polarizer disposed inside the circular waveguide; a circular polarization compensator for adjusting the circular polarization inside the circular waveguide; A control unit that adjusts the operation of the circular polarization compensator; an automatic matching device connected to the end of the rectangular waveguide opposite to the circular-rectangle converter, for detecting a reflected electric field and matching impedance in response to the detected electric field; Calculating an electric field distribution using the reflected electric field measured by the automatic matching device and a scattering matrix S of an electric field propagation region connecting a reflected electric field measurement surface and a surface for which an electric field distribution is to be monitored, and controlling the operation of the circular polarization compensator in accordance with the electric field distribution. Plasma processing equipment.

2. 2. The plasma processing apparatus according to claim 1, further comprising: A high frequency power source that supplies high frequency power for generating plasma; A magnetic field generating mechanism for generating a magnetic field; The processing chamber includes a sample stage for placing a sample thereon.

3. 2. The plasma processing apparatus according to claim 1, The control unit controls the operation of the circular polarization compensator, and then repeatedly calculates the electric field distribution using the reflected electric field measured by the automatic matching device and a scattering matrix S of an electric field propagation region connecting the reflected electric field measurement surface and a surface whose electric field distribution is to be monitored, and controls the operation of the circular polarization compensator in accordance with the electric field distribution.

4. 4. The plasma processing apparatus according to claim 3, the circular polarization compensator includes a first stub whose insertion amount into the circular waveguide is adjustable along a first direction, and a second stub whose insertion amount into the circular waveguide is adjustable along a second direction intersecting the first direction, The control unit individually controls an insertion amount of the first stub into the circular waveguide and an insertion amount of the second stub into the circular waveguide in accordance with the electric field distribution.

5. a high frequency power supply for supplying high frequency power for plasma generation, a magnetic field generating mechanism for generating a magnetic field, a waveguide connected to a vacuum vessel and through which an electric field for plasma generation propagates, a rectangular waveguide constituting the waveguide and operating in a lowest order mode, a circular waveguide constituting the waveguide and operating in a lowest order mode, a circular-rectangle converter connecting the rectangular waveguide and the circular waveguide, a processing chamber disposed within the vacuum vessel below the circular waveguide and including a sample stage for placing a sample thereon, in which plasma is formed by the electric field, and a processing chamber disposed within the circular waveguide. a control unit for controlling the operation of the circular polarization compensator; and an automatic matching device connected to the opposite end of the rectangular waveguide from the circular-to-rectangle converter, for detecting a reflected electric field and matching impedance accordingly. The automatic matching device calculates an electric field distribution using a reflected electric field measured by the automatic matching device and a scattering matrix S of an electric field propagation region connecting a reflected electric field measurement surface and a surface whose electric field distribution is to be monitored, and controls the operation of the circular polarization compensator according to the electric field distribution; a second step of carrying a sample into the processing chamber and placing the sample on the sample stage; and a third step of generating plasma inside the processing chamber and plasma processing the sample.

6. 6. The plasma processing method according to claim 5, In the first step, the control unit controls the operation of the circular polarization compensator, and then repeatedly calculates the electric field distribution using the reflected electric field measured by the automatic matching device and a scattering matrix S of an electric field propagation region connecting the reflected electric field measurement surface and a surface whose electric field distribution is to be monitored, and controls the operation of the circular polarization compensator according to the electric field distribution.

7. 7. The plasma processing method according to claim 6, the circular polarization compensator includes a first stub whose insertion amount into the circular waveguide is adjustable along a first direction, and a second stub whose insertion amount into the circular waveguide is adjustable along a second direction intersecting the first direction, A plasma processing method, in which in the first step, the control unit individually controls an insertion amount of the first stub into the circular waveguide and an insertion amount of the second stub into the circular waveguide in accordance with the electric field distribution.

8. The plasma processing method according to claim 7, further comprising: a fourth step of unloading the sample from the processing chamber; A fifth step is included between the second step and the third step, In the fifth step, the control unit calculates an electric field distribution using the reflected electric field measured by the automatic matching device and a scattering matrix S of an electric field propagation region connecting the reflected electric field measurement surface and a surface whose electric field distribution is to be monitored, and controls the operation of the circular polarization compensator in accordance with the electric field distribution.

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