Lower electrode assembly and plasma treatment equipment

Abstract

This invention provides a lower electrode assembly and a plasma processing device. The lower electrode assembly includes: a base for supporting a wafer; a focusing ring assembly disposed at the edge region of the base, the focusing ring assembly including a focusing ring and an edge electrode located below the focusing ring; the base and the edge electrode are electrically connected to an radio frequency power supply; the edge electrode is disposed radially inward near the focusing ring, and the ratio of the axial projected area of ​​the edge electrode to the axial projected area of ​​the focusing ring is 10% to 70%. This invention aims to extend the service life of the focusing ring.

Description

Lower electrode assembly and plasma treatment equipment Technical Field

[0001] This invention relates to the field of semiconductor equipment technology, and in particular to a lower electrode assembly and plasma processing equipment. Prior Technology

[0002] Plasma technology plays a crucial role in semiconductor manufacturing. It can be applied to many semiconductor processes, such as deposition processes (e.g., chemical vapor deposition) and etching processes (e.g., dry etching).

[0003] In existing plasma processing equipment, the wafer is placed on a substrate. To improve the etching uniformity of the wafer edges, a focus ring is typically placed around the wafer, and an edge electrode is positioned below the focus ring. The edge electrode is connected to a low-frequency (LF) bias power supply to adjust the plasma sheath thickness in the wafer edge region, thereby improving edge etching uniformity.

[0004] However, as the radio frequency hours increase, the focusing ring will be gradually consumed, resulting in a decrease in its thickness and a shortened lifespan. Summary of the Invention

[0005] The purpose of this invention is to provide a lower electrode assembly and plasma treatment equipment for extending the service life of the focusing ring.

[0006] To achieve the above objectives, this work employs the following technical solution: A lower electrode assembly, comprising: The base is used to support the wafer; A focusing ring assembly is disposed in the edge region of the base, the focusing ring assembly including a focusing ring and an edge electrode located below the focusing ring; The base and the edge electrode are electrically connected to a radio frequency power supply; The edge electrode is disposed close to the radial inner side of the focusing ring, and the ratio of the axial projected area of ​​the edge electrode to the axial projected area of ​​the focusing ring is 10% to 70%.

[0007] Optionally, the focusing ring assembly further includes an insulating ring located below the focusing ring.

[0008] Optionally, the edge electrode is located inside the insulating ring.

[0009] Optionally, the minimum distance between the edge electrode and the inner wall of the insulating ring is not less than the arc breakdown distance of the insulating ring.

[0010] Optionally, the edge electrode is located at the lower part of the focusing ring.

[0011] Optionally, the minimum distance between the edge electrode and the inner wall of the focusing ring is not less than the arc breakdown distance of the focusing ring.

[0012] Optionally, the edge region of the base is formed with an annular recess, and the focusing ring assembly is disposed within the annular recess.

[0013] Optionally, a heat-conducting layer is provided between the insulating ring and the focusing ring, and a heat-conducting layer is provided between the insulating ring and the annular recess.

[0014] Optionally, a variable capacitor is connected between the edge electrode and the radio frequency power supply, and the variable capacitor has an adjustment range of 100pF-1000pF.

[0015] Optionally, the radio frequency power supply includes a low-frequency bias power supply.

[0016] A plasma treatment device, comprising: reaction chamber; The lower electrode assembly, as described above, is located at the bottom of the reaction chamber; An upper electrode assembly is disposed opposite to the lower electrode assembly, and a high-frequency radio frequency power supply applies a high-frequency radio frequency voltage to the upper electrode assembly and / or the lower electrode assembly to generate plasma between the upper electrode assembly and the lower electrode assembly.

[0017] Compared with conventional techniques, this creation has the following advantages: The lower electrode assembly and plasma processing equipment provided in this invention place the edge electrode on the radially inner side near the focusing ring, making the edge electrode closer to the wafer and reducing the axial projected area of ​​the edge electrode. As a result, the radio frequency power of the focusing ring branch can be concentrated and coupled to the inner area of ​​the focusing ring near the wafer, thereby ensuring the maintenance of the plasma sheath thickness on the inner surface of the focusing ring. Compared with the existing focusing ring scheme that couples the radio frequency power to the entire focusing ring, this scheme concentrates the radio frequency power coupling to the inner side of the focusing ring, increasing the radio frequency power that the focusing ring can couple and expanding the adjustment range of the radio frequency power coupled by the focusing ring. This can effectively compensate for the impact of physical consumption of the focusing ring on the plasma sheath thickness, thereby extending the service life of the focusing ring. Simple Explanation of the Diagram

[0018] To more clearly illustrate the technical solution of this invention, the drawings used in the description will be briefly introduced below. Obviously, the drawings described below are one embodiment of this invention. For those skilled in the art, other drawings can be obtained from these drawings without any further effort. Figure 1 is a partial schematic diagram of an existing lower electrode assembly; Figure 2 is a schematic diagram of a plasma treatment device provided in an embodiment of this invention; Figure 3 is a partial schematic diagram of a lower electrode assembly provided in one embodiment of this invention; Figure 4 is the equivalent circuit diagram of the lower electrode assembly shown in Figure 1; Figure 5 is the equivalent circuit diagram of the lower electrode assembly shown in Figure 3; Figure 6 is a partial schematic diagram of another lower electrode assembly provided in one embodiment of this invention. Implementation

[0019] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the proposed solution. The advantages and features of this invention will become clearer from the following explanation. It should be noted that the drawings are in a very simplified form and use non-precise proportions, intended only to facilitate and clearly illustrate the implementation of this invention. Please refer to the drawings for a clearer understanding of the purpose, features, and advantages of this invention. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are solely for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of this invention, should still fall within the scope of the technical content disclosed in this invention.

[0020] Figure 1 shows a conventional lower electrode assembly installed in a plasma processing device, including a base 111. A ceramic layer is disposed on the base 111, and a wafer W is placed on the ceramic layer. The base 111 is connected to an RF power supply via an RF matching unit 115 to generate plasma and a bias voltage (only the low-frequency bias power supply LF is shown in Figure 1). An insulating ring 114 is placed above the edge region of the base 111, and a focusing ring 112 is placed above the insulating ring. An electrode 113 is disposed inside the insulating ring, and the electrode 113 is connected to the low-frequency bias power supply LF via a variable capacitor C2 to couple RF power to the focusing ring 112, adjust the plasma sheath thickness in the edge region of the wafer W, and improve the edge etching uniformity. As the RF hours increase, the focusing ring 112 is gradually consumed, resulting in a decrease in its thickness and a reduction in the RF power coupled to the focusing ring 112, thereby changing the plasma sheath characteristics in the edge region. To ensure uniform etching at the wafer edges, the impedance of the focusing ring branch can be adjusted by regulating the variable capacitor C2, thereby coupling more RF power to the focusing ring 112 to compensate for the impact of its physical consumption on the sheath thickness. However, the capacitance range of the variable capacitor C2 is limited. When the focusing ring 112 is consumed to a certain extent, even if the variable capacitor C2 is adjusted to its maximum value, the power cannot be further increased, leading to compensation failure and ultimately shortening the lifespan of the focusing ring 112.

[0021] To address the aforementioned issues, this invention proposes a lower electrode assembly and a plasma processing device. The lower electrode assembly includes a base and a focusing ring assembly. The focusing ring assembly is disposed in the edge region of the base and includes a focusing ring and an edge electrode located below the focusing ring. The base and the edge electrode are electrically connected to an RF power supply. The edge electrode is positioned radially inward of the focusing ring, and the ratio of the axial projected area of ​​the edge electrode to the axial projected area of ​​the focusing ring is 10% to 70%. It is understood that, due to the impedance of the focusing ring, the inner and outer regions opposite the edge electrode are not RF equipotential. Maintaining the plasma sheath thickness on the inner surface of the focusing ring is crucial for wafer etching; therefore, more RF power needs to be coupled to the inner region of the focusing ring. This invention places the edge electrode on the radially inner side near the focusing ring, bringing it closer to the wafer and reducing its axial projected area. This allows the RF power of the focusing ring branch to be concentrated and coupled to the inner region of the focusing ring near the wafer, thus maintaining the plasma sheath thickness on the inner surface of the focusing ring. Compared to existing focusing ring designs that couple RF power across the entire focusing ring, this design concentrates the RF power coupling to the inner side of the focusing ring, increasing the amount of RF power that the focusing ring can couple and expanding the adjustment range of the coupled RF power. This effectively compensates for the impact of physical wear on the sheath thickness, thereby extending the lifespan of the focusing ring.

[0022] The lower electrode assembly and plasma treatment equipment of this embodiment will be described in detail below.

[0023] Figure 2 illustrates a plasma processing apparatus provided in this embodiment. In this embodiment, the plasma processing apparatus is a capacitively coupled plasma processing apparatus; in other embodiments, the plasma processing apparatus may also be an inductively coupled plasma processing apparatus. Specifically, the plasma processing apparatus includes a reaction chamber 200, which contains a lower electrode assembly 210. The lower electrode assembly 210 includes a base 211, which has a bearing surface. The wafer W to be processed, which is introduced into the reaction chamber 200, is placed on the bearing surface. The reaction chamber 200 also includes an upper electrode assembly 220 disposed opposite to the lower electrode assembly 210. The upper electrode assembly 220 serves as both a radio frequency electrode and a gas distributor. A high-frequency radio frequency (HF) power supply applies a high-frequency radio frequency voltage to the upper electrode assembly 220 and / or the lower electrode assembly 210 to generate a plasma between the upper electrode assembly 220 and the lower electrode assembly 210. The plasma contains a large number of active particles such as electrons, ions, excited-state atoms, molecules, and free radicals. These active particles can undergo various physical and / or chemical reactions with the surface of the wafer W to be processed, thereby changing the morphology of the wafer W to be processed and completing the processing of the wafer W to be processed.

[0024] Referring to Figure 3, the lower electrode assembly 210 further includes a focusing ring assembly 212, disposed in the edge region of the base 211. The focusing ring assembly 212 includes a focusing ring 2121 and an edge electrode 2122 located below the focusing ring 2121. The base 211 and the edge electrode 2122 are electrically connected to an RF power supply. The edge electrode 2122 is disposed close to the radially inner side of the focusing ring 2121, and the ratio of the axial projected area of ​​the edge electrode 2122 to the axial projected area of ​​the focusing ring 2121 is 10%~70%. The RF power supply includes the aforementioned high-frequency RF power supply HF and low-frequency bias power supply LF. The low-frequency bias power supply LF applies a low-frequency RF voltage to the base 211 and the edge electrode 2122 through an RF matching unit 213, generating a bias voltage in the middle and edge of the wafer W, adjusting the plasma state in the middle and edge of the wafer W, and achieving precise control of the plasma distribution in different regions of the middle and edge of the wafer W, thereby improving the uniformity of edge processing.

[0025] Optionally, the focusing ring 2121 is made of silicon, silicon carbide, or any one or more of these materials. The edge electrode 2122 is made of copper, aluminum, tungsten, or other metals or conductive alloys. It is understood that the materials used to prepare the focusing ring 2121 and the edge electrode 2122 are not limited to those described above. In other embodiments, they can be made of other materials, as long as they can achieve their corresponding functional effects.

[0026] Furthermore, to isolate the focusing ring 2121 from the base 211 and prevent crosstalk between their electric fields, the focusing ring assembly 212 further includes an insulating ring 2123 located below the focusing ring 2121. Optionally, the insulating ring 2123 can be made of one or more of doped ceramic, undoped ceramic, or quartz; it can also be made of other materials with good electrical insulation properties. The edge electrode 2122 can be disposed inside the insulating ring 2123, close to its radially inner side. The minimum distance between the edge electrode 2122 and the inner wall of the insulating ring 2123 is not less than the arc breakdown distance of the insulating ring 2123, to prevent the edge electrode 2122 from breaking down the insulating ring 2123 under the action of radio frequency voltage and to reduce the possibility of arcing inside the insulating ring 2123.

[0027] As shown in Figure 3, most of the RF power emitted by the low-frequency bias power supply LF is applied to the base 211, and a small portion of the power is applied to the edge electrode 2122 and then coupled to the focusing ring 2121. An annular recess is formed in the edge region of the base 211, and the focusing ring assembly 212 is disposed within the annular recess. This allows a portion of the RF power applied to the base 211 to be coupled to the focusing ring 2121 through the annular recess at the edge of the base 211, thereby increasing the RF power coupled to the focusing ring 2121. Furthermore, the temperature of the focusing ring 2121 directly affects the deposition of polymer on the focusing ring surface and the etching accuracy of the wafer edge W. In this embodiment, a heat-conducting layer 2124 is provided between the insulating ring 2123 and the focusing ring 2121, and a heat-conducting layer 2124 is provided between the insulating ring 2123 and the annular recess. By providing the heat-conducting layer 2124, the heat conduction between the focusing ring 2121, the insulating ring 2123, and the base 211 can be improved, which helps to control the temperature of the focusing ring 2121.

[0028] As shown in Figure 3, a variable capacitor C2 is connected between the edge electrode 2122 and the RF power supply. The adjustable range of the variable capacitor C2 is 100pF-1000pF. The low-frequency RF power delivered to the focusing ring 2121 is adjusted by adjusting the capacitance value of the variable capacitor C2. When the reaction chamber 200 is in the initial state, the variable capacitor C2 is at its initial value. After a long period of plasma processing, it is detected that the processing effect of the edge region of wafer W is different from that of the center. The value of the variable capacitor C2 can be adjusted according to the set parameters, so that more low-frequency RF power is delivered to the focusing ring 2121 located at the edge of wafer W, thereby raising the plasma sheath layer at the focusing ring 2121, so that there is a plasma sheath layer of the same height from the edge of wafer W to the top of the focusing ring 2121, thus improving the etching uniformity.

[0029] The technical effect of the lower electrode assembly in this embodiment being able to couple more radio frequency power to the inside of the focusing ring will be explained below with reference to the equivalent circuit diagrams of the lower electrode assembly shown in Figures 1 and 3.

[0030] Figure 4 is the equivalent circuit diagram of the lower electrode assembly shown in Figure 1. Z is the impedance of the focusing ring branch to the right of the variable capacitor C2 during the manufacturing process. Assuming Z is R / 2-jX / 2 (Ω), the adjustment range of the variable capacitor C2 is 100pF-1000pF. C1 is the capacitance brought by the insulating ring 114 between the base 111 and the focusing ring 112, which is approximately 800pF. By adjusting the size of the variable capacitor C2, the impedance of the focusing ring branch can be adjusted, thereby changing the RF power through the focusing ring branch. When the variable capacitor C2 is set to 1000pF, the RF power through the focusing ring branch is the maximum. Now, the RF power through the focusing ring branch under this condition is calculated. Assuming the output voltage of the low-frequency bias power supply LF is V and the frequency is 400kHz, in order to ensure the uniformity and stability of wafer etching, this voltage V should not change with the size of the variable capacitor C2 and the focusing ring structure. Therefore, the total power coupled to the focusing ring 112 can be obtained as follows: Thus, the power coupled to the inner side of the focusing ring 112 is obtained as .

[0031] Figure 5 is an equivalent circuit diagram of the lower electrode assembly 210 shown in Figure 3. It is assumed that the edge electrode 2122 is located radially inside the focusing ring 2121, and the ratio of the axial projected area of ​​the edge electrode 2122 to the axial projected area of ​​the focusing ring 2121 is 50%. Z1 is the impedance of the inner focusing ring connected to the right side of the variable capacitor C2 during the manufacturing process, Z1 = R - jX (Ω). The adjustment range of the variable capacitor C2 is 100pF-1000pF. C11 is the capacitance between the base 211 and the inner side of the focusing ring 2121 caused by the insulating ring 2123, approximately 400pF. C12 is the capacitance between the base 211 and the outer side of the focusing ring 2121 caused by the insulating ring 2123, approximately 400pF. By adjusting the size of the variable capacitor C2, the impedance inside the focusing ring 2121 can be adjusted, thereby changing the RF power through the inner branch of the focusing ring. When the variable capacitor C2 is set to 1000pF, the RF power obtained by the inner branch of the focusing ring is maximized. The RF power through the inner branch of the focusing ring under this condition is calculated. Assuming the output voltage of the low-frequency bias power supply LF is V, and the frequency is 400kHz, to ensure the uniformity and stability of wafer etching, this voltage V should not change with the size of the variable capacitor C2 or the focusing ring structure. Therefore, the power coupled to the inner side of the focusing ring 2121 can be obtained as follows: Comparison of power and As can be seen, the structure of this embodiment enables higher power coupled to the inner side of the focusing ring 2121, which can increase the power by about 10%-50%. Therefore, this embodiment can extend the service life of the focusing ring 2121.

[0032] In another embodiment, as shown in FIG6, the edge electrode 2122 may also be disposed at the lower part of the focusing ring 2121, directly in electrical contact with the focusing ring 2121. Furthermore, the minimum distance between the edge electrode 2122 and the inner wall of the focusing ring 2121 is not less than the arc breakdown distance of the focusing ring 2121, to prevent the edge electrode 2122 from breaking down the focusing ring 2121 under the action of radio frequency voltage, thereby reducing the possibility of arcing occurring inside the focusing ring 2121.

[0033] In summary, the lower electrode assembly and plasma processing equipment provided in this invention place the edge electrode on the radially inner side near the focusing ring, making the edge electrode closer to the wafer and reducing its axial projected area. This allows the RF power of the focusing ring branch to be concentrated and coupled to the inner region of the focusing ring near the wafer, thus maintaining the plasma sheath thickness on the inner surface of the focusing ring. Furthermore, compared to existing focusing ring schemes that couple RF power across the entire focusing ring, this scheme concentrates the RF power coupling to the inner side of the focusing ring, increasing the amount of RF power that the focusing ring can couple and expanding the adjustment range of the coupled RF power. This effectively compensates for the impact of physical wear on the plasma sheath thickness, thereby extending the lifespan of the focusing ring.

[0034] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0035] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above content. Therefore, the scope of protection of the present invention should be defined by the appended claims.

[0036] 111: Base 112: Focusing Ring 113: Electrode 114: Insulating ring 115: RF Matching Unit 200: Reaction Chamber 210: Lower electrode assembly 211: Base 212: Focusing Ring Component 2121: Focusing Ring 2122: Edge Electrode 2123: Insulating ring 2124: Thermal conductive layer 213: Radio Frequency Matching Unit 220: Upper electrode assembly C2: Variable capacitor HF: High-frequency radio frequency power supply LF: Low-frequency bias power supply W: Wafer

Claims

1. A lower electrode assembly, characterized in that it comprises: The base is used to support the wafer; A focusing ring assembly is disposed in the edge region of the base. The focusing ring assembly includes a focusing ring and an edge electrode located below the focusing ring. The base and the edge electrode are electrically connected to an radio frequency power supply. The edge electrode is disposed close to the radially inner side of the focusing ring, and the ratio of the axial projected area of ​​the edge electrode to the axial projected area of ​​the focusing ring is 10% to 70%.

2. The lower electrode assembly as described in claim 1, wherein, The focusing ring assembly also includes an insulating ring located below the focusing ring.

3. The lower electrode assembly as described in claim 2, wherein, The edge electrode is located inside the insulating ring.

4. The lower electrode assembly as described in claim 3, wherein, The minimum distance between the edge electrode and the inner wall of the insulating ring is not less than the arc breakdown distance of the insulating ring.

5. The lower electrode assembly as described in claim 1, wherein, The edge electrode is located at the lower part of the focusing ring.

6. The lower electrode assembly as described in claim 5, wherein, The minimum distance between the edge electrode and the inner wall of the focusing ring is not less than the arc breakdown distance of the focusing ring.

7. The lower electrode assembly as described in claim 2, wherein, The edge region of the base has an annular recess, and the focusing ring assembly is disposed within the annular recess.

8. The lower electrode assembly as described in claim 7, wherein, A heat-conducting layer is provided between the insulating ring and the focusing ring, and a heat-conducting layer is provided between the insulating ring and the annular recess.

9. The lower electrode assembly as claimed in claim 1, wherein, A variable capacitor is connected between the edge electrode and the radio frequency power supply. The variable capacitor has an adjustment range of 100pF-1000pF.

10. The lower electrode assembly as claimed in claim 1, wherein, The radio frequency power supply includes a low-frequency bias power supply.

11. A plasma treatment apparatus, characterized in that it comprises: reaction chamber; The lower electrode assembly as described in any one of claims 1 to 10 is disposed at the bottom of the reaction chamber; An upper electrode assembly is disposed opposite to the lower electrode assembly, and a high-frequency radio frequency power supply applies a high-frequency radio frequency voltage to the upper electrode assembly and / or the lower electrode assembly to generate plasma between the upper electrode assembly and the lower electrode assembly.

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