Adjustable capacitor and impedance matching device

Abstract

The present invention provides an adjustable capacitor, comprising a ferroelectric dielectric layer and a first electrode and a second electrode located on opposite sides of the ferroelectric dielectric layer; the adjustable capacitor also comprises a first control electrode and a second control electrode insulated from the first electrode and the second electrode; the first control electrode and the second control electrode are used to provide an electric field to the ferroelectric dielectric layer, so as to adjust the dielectric constant of the ferroelectric dielectric layer by controlling the electric field strength of the electric field, thereby adjusting the capacitance between the first electrode and the second electrode. The present invention also provides an impedance matching device and a semiconductor processing equipment. The adjustable capacitor, the impedance matching device and the semiconductor processing equipment can achieve the adjustment of the capacitance of the dielectric adjustable capacitor in milliseconds or even faster, thereby accelerating the matching speed, and can achieve a matching speed in milliseconds or even faster.

Description

Technical Field

[0001] The invention belongs to the technical field of microelectronic processing, and in particular relates to an adjustable capacitor and impedance matching device. Background Art

[0002] Plasma technology is widely used in the field of semiconductor device manufacturing technology. In plasma deposition and etching systems, a radio frequency power supply is used to load energy into the reaction chamber to excite the process gas in the chamber to form plasma; plasma contains a large number of active particles such as electrons, ions, excited atoms, molecules and free radicals. These active particles undergo various physical and chemical reactions with the surface of the substrate placed in the cavity and exposed to the plasma environment, causing changes on the substrate surface, thereby completing the etching, deposition and other processes.

[0003] In applications, the output impedance of the RF power supply is generally 50Ω. In order to enable the reaction chamber to obtain the maximum power from the RF power supply and reduce the reflected power of the reaction chamber, an impedance matching device is generally provided between the RF power supply and the reaction chamber to match the output impedance of the RF power supply with the load impedance. The load impedance is equal to the sum of the impedance of the impedance matching device and the impedance of the reaction chamber.

[0004] Figure 1 This is a block diagram of the principle of semiconductor processing equipment using existing impedance matching devices. Figure 1 The impedance matching device is connected in series between the RF power supply 10 and the reaction chamber 20, and includes a collection unit 1, a control unit 2, an execution unit 3 and a matching network 4, wherein the collection unit 1 is connected in series between the RF power supply 10 and the matching network 4, and the collection unit 1 is used to collect the electrical signal (voltage V and current I) on the transmission line where it is located and send it to the control unit 2; the matching network 4 includes adjustable capacitors C1, C2 and a fixed inductor L; the execution unit 3 includes motors M1 and M2; the control unit 2 performs an impedance matching algorithm according to the electrical signal sent by the collection unit 1 to obtain the change of the adjustable capacitors C1 and C2, and controls the motors M1 and M2 to adjust the capacitance values ​​of the adjustable capacitors C1 and C2 respectively according to the change. Based on the above, it can be known that the impedance matching device performs impedance matching on the output impedance and load impedance of the RF power supply by adjusting its own impedance.

[0005] However, using Figure 1 The impedance matching device shown has the following problems in practical application: Figure 1 The impedance matching device shown changes the capacitance of the capacitor by rotating the motor, and the impedance matching speed is limited by the rotation speed of the motor, which usually makes the matching speed only in the second level, and it is difficult to achieve a matching speed in the millisecond level. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art, and proposes an adjustable capacitor and an impedance matching device, which can adjust the capacitance of the adjustable capacitor in milliseconds or shorter.

[0007] To solve one of the above problems, the present invention provides an adjustable capacitor, comprising a ferroelectric dielectric layer and a first electrode and a second electrode located on opposite sides of the ferroelectric dielectric layer;

[0008] The adjustable capacitor further includes a first control electrode and a second control electrode which are insulated from the first electrode and the second electrode;

[0009] The first control electrode and the second control electrode are used to provide an electric field to the ferroelectric dielectric layer, so as to adjust the dielectric constant of the ferroelectric dielectric layer by controlling the electric field strength of the electric field, thereby adjusting the capacitance between the first electrode and the second electrode.

[0010] Preferably, at least a portion of the ferroelectric layer is located in both the electric field between the first control electrode and the second control electrode and the electric field between the first electrode and the second electrode.

[0011] Preferably, the first electrode and the first control electrode are both arranged on the upper side of the ferroelectric dielectric layer, and the first electrode is located on the left side, and the first control electrode is located on the right side;

[0012] The second electrode and the second control electrode are both arranged at the lower side of the ferroelectric dielectric layer, the second electrode is located at the right side, and the second control electrode is located at the left side;

[0013] Orthographic projections of the first control electrode and the second control electrode on the ferroelectric layer do not overlap.

[0014] Preferably, the number of the second control electrodes is two, and the second electrode is located between the two second control electrodes;

[0015] The number of the first electrodes is two, and the first control electrode is located between the two first electrodes.

[0016] Preferably, the second control electrodes are arranged opposite to the first electrodes in a one-to-one correspondence;

[0017] The first control electrodes are arranged opposite to the second electrodes in a one-to-one correspondence.

[0018] Preferably, the orthographic projections of the second control electrode and the first electrode arranged opposite to each other on the ferroelectric dielectric layer completely overlap;

[0019] The orthographic projections of the first control electrode and the second electrode which are arranged opposite to each other on the ferroelectric dielectric layer completely overlap.

[0020] Preferably, the first electrode and the second electrode are respectively arranged on the upper side and the lower side of the ferroelectric dielectric layer;

[0021] The first control electrode and the second control electrode are disposed on the left and right sides of the ferroelectric dielectric layer, respectively.

[0022] Preferably, the material of the ferroelectric dielectric layer includes at least one of BaTiO3, BaO-TiO2, KNbO3, K2O-Nb2O5, LiNbO3, Li2O-Nb2O5, potassium dihydrogen phosphate, triglycine sulfate and Roche salt.

[0023] Correspondingly, the present invention further provides an impedance matcher, comprising a collection unit, a matching network and a control unit, wherein the matching network is connected in series between the radio frequency power supply and the reaction chamber, the matching network comprises the above-mentioned adjustable capacitor provided by the present invention, and the first electrode and the second electrode are connected to the circuit of the matching network, the first control electrode is electrically connected to the control unit, and the second control electrode is grounded;

[0024] The acquisition unit is used to collect the electrical signal on the transmission line between the RF power supply and the matching network and send it to the control unit;

[0025] The control unit is used to perform impedance matching operation according to the electrical signal collected by the collection unit and control the voltage loaded between the first control electrode and the second control electrode according to the operation result to adjust the capacitance between the first electrode and the second electrode.

[0026] Preferably, a low-pass filter is further included, and the low-pass filter is arranged between the control unit and the first control electrode.

[0027] Preferably, there are multiple adjustable capacitors, and the low-pass filters are arranged in one-to-one correspondence with the adjustable capacitors and are equal in number.

[0028] The present invention has the following beneficial effects:

[0029] The adjustable capacitor in the present invention can control the electric field strength of the electric field where the ferroelectric dielectric layer is located by controlling the voltage between the first control electrode and the second control electrode. The rapid change of the electric field strength can cause a rapid change in the dielectric constant of the ferroelectric dielectric layer. Therefore, compared with the mechanical adjustment method of the prior art, the present invention can adjust the capacitance of the adjustable capacitor in milliseconds or less.

[0030] The impedance matching device of the present invention can achieve a matching speed of milliseconds because the adjustable capacitor provided by the present invention is adopted. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A block diagram of the principle of semiconductor processing equipment using an existing impedance matching device;

[0032] Figure 2 Schematic diagram of the relationship between the polarization intensity P of the ferroelectric dielectric layer and the electric field E;

[0033] Figure 3 A schematic diagram of the structure of an adjustable capacitor in Embodiment 1 of the present invention;

[0034] Figure 4 Another structural schematic diagram of the adjustable capacitor in Embodiment 1 of the present invention;

[0035] Figure 5 It is another structural schematic diagram of the adjustable capacitor in Embodiment 1 of the present invention;

[0036] Figure 6 A schematic diagram of the structure of an impedance matching device provided in Embodiment 2 of the present invention;

[0037] Figure 7 This is a schematic structural diagram of the semiconductor processing equipment provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the technical solution of the present invention, the adjustable capacitor and impedance matching device provided by the present invention are described in detail below with reference to the accompanying drawings.

[0039] Example 1

[0040] An embodiment of the present invention provides an adjustable capacitor, which includes a ferroelectric dielectric layer 1 and a first electrode 21 and a second electrode 22 located on opposite sides of the ferroelectric dielectric layer 1; the adjustable capacitor also includes a first control electrode 31 and a second control electrode 32 insulated from the first electrode 21 and the second electrode 22; the first control electrode 31 and the second control electrode 32 are used to provide an electric field to the ferroelectric dielectric layer 1, so as to adjust the dielectric constant of the ferroelectric dielectric layer 1 by controlling the electric field strength of the electric field, thereby adjusting the capacitance value of the capacitor between the first electrode 21 and the second electrode 22.

[0041] The adjustable capacitor provided in this embodiment can control the electric field strength of the electric field where the ferroelectric dielectric layer 1 is located by controlling the voltage between the first control electrode 31 and the second control electrode 32. The rapid change of the electric field strength can cause a rapid change in the dielectric constant of the ferroelectric dielectric layer 1. Therefore, compared with the mechanical adjustment method of the prior art, the present invention can adjust the capacitance of the adjustable capacitor in milliseconds or less.

[0042] For ease of understanding, the capacitance value adjustment principle of the adjustable capacitor provided in this embodiment will be explained below. Figure 2 The figure is a schematic diagram showing the relationship between the polarization intensity P of the ferroelectric material and the applied electric field E. Under the action of the electric field, the ferroelectric material of the ferroelectric dielectric layer 1 will have macroscopic dipoles inside the dielectric (ferroelectric material) along the direction of the electric field, and polarized charges will appear on the surface of the dielectric. The polarization intensity P of the polarized charges (the vector sum of the electric dipole moment of the dielectric per unit volume) is related to both the magnitude and direction of the electric field. The electric susceptibility of the dielectric χ = P / E, from Figure 2 It can be obtained that the larger the electric field, the smaller the electric susceptibility χ of the dielectric. For the dielectric, the relationship between the electric induction intensity D, the electric field intensity E and the polarization intensity P is as follows:

[0043] D=ε0E+P

[0044] D=(ε0+χ)E=ε0ε r E

[0045] ε r =1+χ / ε0

[0046] Where: ε0 represents the dielectric constant of vacuum, ε r Represents the relative dielectric constant.

[0047] For a dielectric parallel plate capacitor, its capacitance value C = ε0ε r S / d, S is the equivalent facing area of ​​the electrode plates of a parallel plate capacitor, and d is the distance between the electrode plates.

[0048] From the above analysis, we can see that for a capacitor with ferroelectric material as the dielectric, when the electric field in which the capacitor is located changes rapidly, its relative dielectric constant ε r It will change rapidly, thus enabling rapid adjustment of the capacitance of the adjustable capacitor.

[0049] In summary, by adjusting the electric field strength of the electric field where the dielectric adjustable capacitor is located in milliseconds or less, the purpose of changing the capacitance of the adjustable capacitor in milliseconds or less can be achieved.

[0050] In this embodiment, at least part of the ferroelectric dielectric layer 1 is simultaneously located in the electric field between the first control electrode 31 and the second control electrode 32 and in the electric field between the first electrode 21 and the second electrode 22. In this way, the dielectric constant of the part of the ferroelectric dielectric layer 1 will change due to the electric field between the first control electrode 31 and the second control electrode 32. The part of the ferroelectric dielectric layer 1 with the changed dielectric constant serves as the dielectric layer between the first electrode 21 and the second electrode 22. According to the capacitance formula, it can be known that the capacitance between the first electrode 21 and the second electrode 22 changes accordingly, thereby ensuring that the capacitance between the first electrode 21 and the second electrode 22 can be effectively adjusted by changing the electric field strength provided to the first control electrode 31 and the second control electrode 32, that is, the capacitance of the adjustable capacitor can be adjusted.

[0051] In this embodiment, optionally, Figure 3 As shown, it is a structural schematic diagram of the adjustable capacitor in this embodiment. In this embodiment, the first electrode 21 and the first control electrode 31 are both arranged on the upper side of the ferroelectric dielectric layer 1, and the first electrode 21 is located on the left side, and the first control electrode 31 is located on the right side; the second electrode 22 and the second control electrode 32 are both arranged on the lower side of the ferroelectric dielectric layer 1, and the second electrode 22 is located on the right side, and the second control electrode 32 is located on the left side; the orthographic projections of the first control electrode 31 and the second control electrode 32 on the ferroelectric dielectric layer 1 do not overlap. In this embodiment, when the adjustable capacitor is connected to the impedance matching device, the first electrode 21 and the second electrode 22 are connected to the circuit of the matching network, and the first control electrode 31 and the second control electrode 32 are controlled by the control unit in the impedance matching device to adjust the voltage between the two. Please refer to Figure 6 .

[0052] Further optionally, the second control electrode 32 and the first electrode 21 are arranged opposite to each other in a one-to-one correspondence; the first control electrode 31 and the second electrode 22 are arranged opposite to each other in a one-to-one correspondence, which makes the adjustable capacitor smaller in size and simple in structure.

[0053] More preferably, the orthographic projections of the relatively arranged second control electrode 32 and the first electrode 21 on the ferroelectric dielectric layer 1 completely overlap; the orthographic projections of the relatively arranged first control electrode 31 and the second electrode 22 on the ferroelectric dielectric layer completely overlap, which can make the components of the adjustable capacitor more concentrated, thereby making the adjustable capacitor smaller in size and simpler in structure.

[0054] In practical applications, the adjustable capacitor can also be used as follows Figure 4 The structure shown in Figure 3The difference is that: the number of the second control electrodes 32 is two, and the second electrode 22 is located between the two second control electrodes 32 ; the number of the first electrodes 21 is two, and the first control electrode 31 is located between the two first electrodes 21 . Figure 4 The adjustable capacitor shown is Figure 3 Compared with the example shown in FIG. 1 , more of the ferroelectric dielectric layer 1 is simultaneously in the electric field between the first control electrode 31 and the second control electrode 32 and the electric field between the first electrode 21 and the second electrode 22, so that Figure 3 In terms of the above, under the condition of the same electric field change, the change of the capacitance value of the adjustable capacitor can be increased, thereby further improving the adjustment rate of the capacitance value of the adjustable capacitor.

[0055] In this embodiment, optionally, Figure 5 As shown, the first electrode 21 and the second electrode 22 of the adjustable dielectric capacitor in this embodiment are respectively arranged on the upper side and the lower side of the ferroelectric dielectric layer 1; the first control electrode 31 and the second control electrode 32 are respectively arranged on the left side and the right side of the ferroelectric dielectric layer 1. Of course, the first electrode 21 and the second electrode 22 of the adjustable dielectric capacitor can also be respectively arranged on the left side and the right side of the ferroelectric dielectric layer 1; the first control electrode 31 and the second control electrode 32 are respectively arranged on the upper side and the lower side of the ferroelectric dielectric layer 1. Figure 5 In the adjustable capacitor shown, the entire ferroelectric dielectric layer 1 can be simultaneously in the electric field between the first control electrode 31 and the second control electrode 32 and the electric field between the first electrode 21 and the second electrode 22, so that under the same electric field change, the change in the capacitance of the adjustable capacitor is further increased, thereby further improving the adjustment rate of the capacitance value of the adjustable capacitor.

[0056] Among them, the ferroelectric material of the ferroelectric dielectric layer 1 includes but is not limited to at least one of BaTiO3, BaO-TiO2, KNbO3, K2O-Nb2O5, LiNbO3, Li2O-Nb2O5, potassium dihydrogen phosphate, triglycine sulfate and Roche salt.

[0057] Example 2

[0058] This embodiment provides an impedance matching device, such as Figure 6 As shown, the impedance matching device includes a matching network 50, a collection unit 51 and a control unit 52, the matching network 50 includes the adjustable capacitor provided in the above-mentioned embodiment 1, and the first electrode 21 and the second electrode 22 are connected to the circuit of the matching network 50, the first control electrode 31 is electrically connected to the control unit 52, and the second control electrode 32 is grounded; wherein:

[0059] The matching network 50 is connected in series between the RF power supply 10 and the reaction chamber 20; the collection unit 51 is used to collect the electrical signal on the transmission line between the RF power supply 10 and the matching network 50 and send it to the control unit 52; the control unit 52 is used to perform impedance matching operation according to the electrical signal collected by the collection unit 51 and control the voltage loaded between the first control electrode 31 and the second control electrode 32 according to the operation result, so as to adjust the capacitance between the first electrode 21 and the second electrode 22.

[0060] The acquisition unit includes but is not limited to a sensor. The type of the matching network 50 is but is not limited to an L-type. The form of each unit in the impedance matching device in this embodiment is not unique, such as the control unit 52 can be a DSP, or a single-chip microcomputer, etc. Regarding the specific algorithm when the control unit 52 performs impedance matching calculation, this embodiment does not specifically limit it, and it is sufficient to ensure that after adjusting the voltage according to the calculation result, the output impedance of the RF power supply 10 can be equal to the load impedance.

[0061] The impedance matching device in this embodiment does not need to be controlled by the execution unit to adjust the capacitance of the capacitor in the matching network, but uses the adjustable capacitor in Example 1. Therefore, it only needs to control the control voltages V1 and V2 output by the control unit 52 to achieve rapid changes in the capacitance of the adjustable capacitor, thereby achieving rapid matching and achieving a matching speed of milliseconds or faster.

[0062] For ease of understanding, the following Figure 6 The impedance matching device in this embodiment is explained in detail.

[0063] like Figure 6As shown, in this embodiment, the acquisition unit 51 in the impedance matching device is located at the front end of the matching network 50, and is used to detect electrical signals such as voltage V and current I on the transmission line of the RF power supply 10. The control unit 52 uses a certain amplitude and phase detection algorithm to obtain the modulus |Z| and phase θ of the load impedance viewed from the input end to the output end of the matching network 50, and provides the control quantity required for the matching control algorithm calculation. The components used in the matching network 50 are composed of adjustable capacitors C1, C2 and inductors L, wherein the capacitors C1 and C2 are the adjustable capacitors described in Example 1; the adjustable capacitors C1 and C2 are respectively in the electric field E1 and E2 environment provided by their control electrodes, wherein the electric field strength of E1 and E2 can be achieved by the control unit 52 controlling the control voltages V1 and V2 loaded on the control electrodes; the control unit 52 adjusts the control voltages V1 and V2 loaded on the control electrodes according to the electrical signal provided by the acquisition unit 51 through the matching control algorithm, thereby achieving rapid adjustment of the capacitance of the adjustable capacitors C1 and C2, thereby making the load impedance of the matching network 50 equal to the output impedance of the RF power supply 10 (usually 50Ω), so that the two achieve rapid conjugate matching. At this time, the reflected power on the transmission line of the RF power supply 10 is zero or very small, and all the power generated by the RF power supply 10 is delivered to the reaction chamber 20.

[0064] Alternatively, if Figure 6 As shown, the impedance matching device also includes a low-pass filter 53; the low-pass filter 53 is arranged between the control unit 52 and the first control electrode 31. Regarding the specific composition structure of the low-pass filter, this embodiment does not make specific restrictions. For example, the low-pass filter 53 includes an inductor and a capacitor. Among them, one end of the inductor is connected to the output end of the control unit 52, and the other end is connected to one end of the capacitor, and the other end of the capacitor is grounded and the control electrode. After the control unit 52 adjusts the voltages V1 and V2 of the two control electrodes, the sizes of E1 and E2 are controlled by low-pass filters F1 and F2 respectively, and some signal interference can be filtered out with the help of the low-pass filter.

[0065] Optionally, there are multiple adjustable capacitors, and the low-pass filters are arranged in one-to-one correspondence with the adjustable capacitors and the number is equal. Figure 6 As shown, there are two adjustable capacitors, namely C1 and C2, and two low-pass filters, namely F1 and F2. The adjustable capacitor C1 is connected to the control unit 52 through the low-pass filter F1, and the adjustable capacitor C2 is connected to the control unit 52 through the low-pass filter F2.

[0066] It should be noted that the impedance matching device in this embodiment is not limited to application in plasma systems, but can also be applied to other systems such as communications, nuclear magnetic resonance, and power transmission lines.

[0067] Example 3

[0068] This embodiment provides a semiconductor processing device, such as Figure 7 As shown, the semiconductor processing equipment includes a radio frequency power supply 10, an impedance matching device 60 and a reaction chamber 20. The impedance matching device 60 is connected in series between the radio frequency power supply 10 and the reaction chamber 20 to match the output impedance of the radio frequency power supply 10 and the load impedance. The impedance matching device 60 adopts the impedance matching device provided in the above-mentioned embodiment 2.

[0069] The semiconductor processing equipment in this embodiment adopts the impedance matching device provided in Embodiment 2 to improve the process effect.

[0070] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. An adjustable capacitor, characterized in that: comprising a ferroelectric dielectric layer and a first electrode and a second electrode located at opposite sides of the ferroelectric dielectric layer; The adjustable capacitor further includes a first control electrode and a second control electrode which are insulated from the first electrode and the second electrode; The first control electrode and the second control electrode are used to provide an electric field to the ferroelectric dielectric layer, so as to adjust the dielectric constant of the ferroelectric dielectric layer by controlling the electric field strength of the electric field, thereby adjusting the capacitance between the first electrode and the second electrode; The first electrode and the first control electrode are both arranged on the upper side of the ferroelectric dielectric layer, the second electrode and the second control electrode are both arranged on the lower side of the ferroelectric dielectric layer, and the orthographic projections of the first control electrode and the second control electrode on the ferroelectric dielectric layer do not overlap.

2. The adjustable capacitor according to claim 1, characterized in that: At least a portion of the ferroelectric layer is located in the electric field between the first control electrode and the second control electrode and in the electric field between the first electrode and the second electrode simultaneously.

3. The adjustable capacitor according to claim 1, characterized in that: The number of the second control electrodes is two, and the second electrode is located between the two second control electrodes; The number of the first electrodes is two, and the first control electrode is located between the two first electrodes.

4. The adjustable capacitor according to claim 1 or 3, characterized in that: The second control electrodes are arranged opposite to the first electrodes in a one-to-one correspondence; The first control electrodes are arranged opposite to the second electrodes in a one-to-one correspondence.

5. The adjustable capacitor according to claim 4, characterized in that: The orthographic projections of the second control electrode and the first electrode, which are arranged opposite to each other, on the ferroelectric dielectric layer completely overlap; The orthographic projections of the first control electrode and the second electrode which are arranged opposite to each other on the ferroelectric dielectric layer completely overlap.

6. The adjustable capacitor according to claim 1, characterized in that: The material of the ferroelectric dielectric layer includes at least one of BaTiO3, BaO-TiO2, KNbO3, K2O-Nb2O5, LiNbO3, Li2O-Nb2O5, potassium dihydrogen phosphate, triglycine sulfate and Roche salt.

7. An impedance matcher, comprising a collection unit, a matching network and a control unit, characterized in that: The matching network is connected in series between the radio frequency power supply and the reaction chamber, the matching network comprises the adjustable capacitor according to any one of claims 1 to 6, and the first electrode and the second electrode are connected to the circuit of the matching network, the first control electrode is electrically connected to the control unit, and the second control electrode is grounded; The acquisition unit is used to collect the electrical signal on the transmission line between the RF power supply and the matching network and send it to the control unit; The control unit is used to perform impedance matching operation according to the electrical signal collected by the collection unit and control the voltage loaded between the first control electrode and the second control electrode according to the operation result to adjust the capacitance between the first electrode and the second electrode.

8. The impedance matching box according to claim 7, characterized in that: A low-pass filter is also included, and the low-pass filter is arranged between the control unit and the first control electrode.

9. The impedance matching box according to claim 8, characterized in that: The number of the adjustable capacitors is multiple, and the low-pass filters are arranged in one-to-one correspondence with the adjustable capacitors and the number is equal.

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