Lower electrode assembly and plasma treatment equipment

Abstract

This invention discloses a lower electrode assembly and plasma processing equipment. The lower electrode assembly includes: a base for supporting a wafer; a focusing ring disposed on the base and surrounding the wafer; and a rounded corner at the top outer edge of the focusing ring, with a radius greater than or equal to 0.4 mm. This invention can reduce the probability of arc discharge at the top outer edge of the focusing ring and the probability of accidental breakage of the top outer edge of the focusing ring due to localized overheating.

Description

Lower electrode assembly and plasma treatment equipment Technical Field

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

[0002] Plasma processing equipment processes materials such as wafers. Examples of wafer processing include deposition, ashing, etching, cleaning, and / or other processes.

[0003] During the wafer etching process, a focus ring needs to be placed around the periphery of the electrostatic chuck in the lower electrode assembly to ensure the uniformity and consistency of etching at the wafer edges. By coupling a portion of the radio frequency energy, the focus ring can induce the formation of a uniformly distributed plasma sheath layer at the wafer edges. This sheath layer has a significant effect on improving the etching uniformity at the substrate edges.

[0004] Around the focusing ring, a cover ring is usually installed. Its main function is to protect the focusing ring and the components below it from damage caused by plasma or ions during the etching process.

[0005] As shown in Figure 1(a), in the newly installed focusing ring F and cover ring C combination, the plasma sheath layer P1 at the outermost edge of the focusing ring F changes relatively gently. This gentle distribution of the plasma sheath layer P1 means that the bombardment intensity of ions on the outer edge F1 of the focusing ring F is comparable to the bombardment intensity on the upper surface of the focusing ring F, and no significant enhancement phenomenon is observed. Therefore, in the initial stage of use, the edge portion of the focusing ring F can maintain good stability and integrity.

[0006] However, as shown in Figure 1(b), with the continuous etching process and the gradual accumulation of usage time, the upper surface of the cover ring C near the focusing ring F gradually thins due to the continuous etching action. This change results in more and more of the outer edge of the focusing ring F being exposed, which in turn affects the distribution of the plasma sheath layer P1. When the inner edge C1 of the cover ring C wears to a certain extent, the plasma sheath layer P1 at the outer edge of the focusing ring F will be significantly bent, forming an electric field distribution similar to that of a tip discharge. This change in electric field distribution not only enhances the local electric field intensity but also easily leads to the occurrence of arcing.

[0007] Furthermore, due to the increased local electric field strength, the bombardment of ions at the outer edge F1 of the focusing ring F becomes more intense. This intense bombardment can lead to excessively high local temperatures at the outer edge of the focusing ring F, resulting in thermal stress concentration and accidental fracture of the focusing ring F material. Damage to the focusing ring F not only affects the stability and uniformity of the etching process but may also lead to downtime and increased costs for the entire etching equipment.

[0008] The statements herein provide only background technology in relation to this work and do not necessarily constitute prior art. Summary of the Invention

[0009] This invention provides a lower electrode assembly and plasma processing equipment to avoid accidental arc discharge and potential problems such as focus ring edge breakage.

[0010] To achieve the above objectives, this work employs the following technical means:

[0011] A lower electrode assembly includes: a base for supporting a wafer; a focusing ring disposed on the base and surrounding the wafer; the top outer edge of the focusing ring has a rounded transition, the radius of which is greater than or equal to 0.4 mm.

[0012] Optionally, the radius of the fillet is in the range of 0.4mm to 1mm.

[0013] Optionally, the rounded corner is provided with a chamfer.

[0014] Optionally, the two ends of the chamfer are transitioned with small rounded corners.

[0015] Optionally, the radius of the small rounded corner is in the range of 1mm to 2mm.

[0016] Optionally, it also includes a cover ring, which is disposed around the focusing ring and mounted on the edge of the base.

[0017] Optionally, the upper surface of the cover ring is not lower than the upper surface of the focusing ring.

[0018] Optionally, the height difference between the upper surface of the cover ring and the upper surface of the focusing ring is 0.5mm to 1.5mm.

[0019] Optionally, a step is provided on the outer periphery of the focusing ring, and the upper surface of the focusing ring is higher than the top surface of the step; the radial cross-section of the covering ring is L-shaped, including a horizontal extension section and a vertical extension section, the inner side of the horizontal extension section covers the top surface of the step, and the vertical extension section covers part of the sidewall of the base.

[0020] Optionally, there is a distance h between the upper surface of the focusing ring and the top surface of the step; the thickness h' of the horizontal extension of the covering ring satisfies the following condition: h <h’<1.3h。

[0021] On the other hand, this invention also provides a plasma treatment device, including: a reaction chamber, a lower electrode assembly as described above, disposed at the bottom of the reaction chamber; a gas spray head, located at the top of the reaction chamber and disposed opposite to the lower electrode assembly, for conveying reaction gas into the reaction chamber; and a radio frequency source, electrically connected to the base and / or the gas spray head, generating a radio frequency electric field between the base and the gas spray head to ionize the reaction gas to form plasma.

[0022] This work has at least one of the following technical effects:

[0023] This invention reduces the electric field strength near the top outer edge of the focusing ring by appropriately increasing the radius of the rounded corners. This significantly reduces the probability of arc discharge at the top outer edge of the focusing ring, and also reduces the ion bombardment intensity at that location. This helps to reduce the probability of the top outer edge of the focusing ring accidentally breaking due to excessively high local temperatures, and prevents the problem of the top outer edge of the focusing ring breaking due to strong local ion bombardment.

[0024] This design can further enhance the focusing ring by increasing the radius of the rounded corners at the top outer edge and appropriately increasing the thickness of the cover ring. Increasing the thickness of the cover ring extends its lifespan. Even when a certain thickness of the cover ring is etched away, it can still provide some protection to the top outer edge of the focusing ring, further extending its lifespan and reducing the probability of arc discharge at the top outer edge, thus preventing the focusing ring from shattering due to strong localized ion bombardment. Simple Explanation of the Diagram

[0025] Figure 1(a) shows a cross-sectional view of the focusing ring and the cover ring in the prior art when they are in a new part state; (b) shows a cross-sectional view of the focusing ring and the cover ring after a certain number of hours of use in the prior art. Figure 2 is a schematic diagram of the structure of a plasma treatment device provided in an embodiment of this invention; Figure 3 is a schematic diagram of the lower electrode assembly provided in Embodiment 1 of this invention; Figure 4 is a cross-sectional schematic diagram of the lower electrode assembly provided in Embodiment 1 after a certain number of hours of use; Figure 5 is a schematic diagram of the lower electrode assembly provided in Embodiment 2 of this invention; Figure 6 is a cross-sectional schematic diagram of the lower electrode assembly after a certain number of hours of use; Figure 7 is a schematic diagram of the lower electrode assembly provided in Embodiment 3 of this invention; Figure 8 is a schematic diagram of the lower electrode assembly provided in Embodiment 4 of this invention. Implementation

[0026] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the lower electrode assembly and plasma processing equipment proposed in this invention. The advantages and features of this invention will become clearer from the following description. 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 embodiments 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 only for illustrative purposes and to aid those skilled in the art, and are not intended to limit the implementation conditions 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 achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0027] As shown in Figure 2, this embodiment provides a plasma processing device, such as a capacitively coupled plasma (CCP) or inductively coupled plasma (ICP) device. The plasma processing device includes a vacuum-ejectable reaction chamber 10 enclosed by reaction chamber walls. A lower electrode assembly 16 is provided on the bottom wall of the reaction chamber 10. The lower electrode assembly 16 includes a base 11, disposed on the bottom wall of the reaction chamber 10, for supporting and placing the wafer W. The base 11 may be made of aluminum.

[0028] The gas spray head 12 is located at the top of the reaction chamber 10, opposite to the lower electrode assembly 16, and connected to the reaction gas source to introduce the reaction gas for the etching process and maintain a certain flow rate.

[0029] An RF source (not shown in Figure 2) is electrically connected to and applies RF power to the base 11 and / or the gas spray head 12, generating an RF electric field between the base 11 and the gas spray head 12, ionizing the reactive gas to form plasma P, and performing surface etching and other process treatments on the wafer W.

[0030] Referring to Figure 3, in this embodiment, the lower electrode assembly 16 further includes a focusing ring 13, which is disposed on the base 11 and surrounds the wafer W. The focusing ring 13 is generally made of silicon or silicon carbide. By coupling a portion of the radio frequency energy to the focusing ring 13, a uniformly distributed plasma sheath layer P1 can be formed at the edge of the wafer W, thereby improving the etching consistency at the edge of the wafer W.

[0031] Please continue to refer to Figure 3. The top outer edge of the focusing ring 13 is provided with a rounded corner 130 transition, and the radius of the rounded corner 130 is greater than or equal to 0.4mm.

[0032] This embodiment reduces the electric field strength near the top outer edge of the focusing ring by appropriately increasing the radius of the rounded corner. This significantly reduces the probability of arc discharge at the top outer edge of the focusing ring, and also reduces the ion bombardment intensity at that location. This helps to reduce the probability of the top outer edge of the focusing ring accidentally breaking due to excessively high local temperature, and prevents the problem of the top outer edge of the focusing ring breaking due to strong local ion bombardment.

[0033] In this embodiment, the radius of the fillet 130 ranges from 0.4mm to 1mm. Within this radius range, the fillet 130 is large enough to reduce the probability of arc discharge at the top outer edge of the focusing ring and accidental breakage of the top outer edge of the focusing ring due to excessive local temperature, while also preventing the fillet 130 from being too round, which could reduce the plasma blocking effect.

[0034] Referring to Figure 3, this embodiment also includes a cover ring 14, which surrounds the focusing ring 13 and is mounted on the edge of the base 11. The cover ring 14 is typically made of quartz. Figure 4 shows a cross-sectional view of the focusing ring 13 and the cover ring 14 in the lower electrode assembly shown in Figure 3 after a certain number of hours of use. The top edge 140 of the inner ring of the cover ring 14 is thinned by etching, causing more of the top outer edge of the focusing ring 13 to be exposed to ion bombardment.

[0035] For the tip discharge model, the electric field intensity E at the tip is: in, For surface charge density, Let be the vacuum permittivity. The surface charge density of a conductor is related to its surface radius of curvature R as follows: Therefore, the electric field intensity E near the surface of the conductor is inversely proportional to the surface radius of curvature R, that is: .

[0036] Based on the above relationship, this embodiment increases the radius of the fillet 130 of the top outer edge of the focusing ring 13 (for example, to 1.0 mm), thereby reducing the electric field strength near the position, thus reducing the probability of arc discharge at this position. At the same time, the ion bombardment intensity at this position is also reduced accordingly, which helps to reduce the probability of the top outer edge of the focusing ring 13 accidentally breaking due to excessive local temperature.

[0037] As shown in Figure 5, in this embodiment or some other embodiments, the upper surface B1 of the cover ring 14 is not lower than the upper surface B2 of the focusing ring 13. Therefore, this embodiment can further increase the thickness of the cover ring by increasing the radius of the rounded corner of the top outer edge of the focusing ring. Increasing the thickness of the cover ring can extend its service life. As shown in Figure 6, when a certain thickness of the cover ring 14 is etched away, the cover ring 14 can still provide some protection for the top outer edge of the focusing ring 13, thereby further extending the service life of the focusing ring 13, further reducing the probability of arc discharge at the top outer edge of the focusing ring 13, and preventing the top outer edge of the focusing ring 13 from cracking due to strong local ion bombardment.

[0038] Please continue referring to Figure 5. In this embodiment or some other embodiments, the height difference h'' between the upper surface B1 of the covering ring 14 and the upper surface B2 of the focusing ring 13 is 0.5mm~1.5mm. If the upper surface B1 of the covering ring 14 is too high, it will increase the flow resistance of the reactive gas and disrupt the uniformity of the reactive gas flow.

[0039] Please continue to refer to Figures 2 and 5. In this embodiment, a step 131 is provided on the outer periphery of the focusing ring 13, and the upper surface B2 of the focusing ring 13 is higher than the top surface B3 of the step 131. The radial cross-section of the covering ring 14 is L-shaped, including a horizontal extension 141 and a vertical extension 142. The inner side of the horizontal extension 141 covers the top surface B3 of the step 131, and the vertical extension 142 covers part of the sidewall of the base 11.

[0040] In this embodiment, there is a gap h between the upper surface B2 of the focusing ring 13 and the top surface B3 of the step 131; the thickness h' of the horizontal extension 141 of the covering ring 14 satisfies the following condition: h < h' < 1.3h. Thus, both the service life of the focusing ring can be extended and the uniformity of the reaction gas flow can be not affected.

[0041] In some other embodiments, as shown in FIG. 7, a chamfer 133 is provided on the rounded corner 130 on the outer edge of the top of the focusing ring 13. In this embodiment, both ends of the chamfer 133 are transitioned by small rounded corners 132.

[0042] That is, in this embodiment, the chamfer 133 can be specifically made on the basis of the rounded corner 130, or the fold angle at the outer edge of the top of the focusing ring 13 can be directly changed to a bevel surface to form the chamfer 133, and both ends of the bevel surface are transitioned by rounded corners (i.e., small rounded corners 132), which can also reduce the probability of arc discharge and the probability of fragmentation of the outer edge of the focusing ring 13.

[0043] In this embodiment, the radius range of the small rounded corner 132 is 1 mm to 2 mm.

[0044] In some other embodiments, as shown in FIG. 8, based on the embodiment shown in FIG. 7, on this basis, appropriately increasing the thickness of the covering ring 14 can further extend the service life of the focusing ring 13.

[0045] Specifically, please continue to refer to FIG. 8. The upper surface B1 of the covering ring 14 is not lower than the upper surface B2 of the focusing ring 13. It can be seen from this that in this embodiment, the thickness of the covering ring can be appropriately increased on the basis of increasing the radius of the rounded corner of the outer edge of the top of the focusing ring. Increasing the thickness of the covering ring can extend the service life of the covering ring. In this way, when a certain thickness of the covering ring 14 is etched away, the covering ring 14 can still play a certain protective role for the outer edge of the top of the focusing ring 13, thereby further extending the service life of the focusing ring 13 and further reducing the probability of arc discharge at the outer edge of the top of the focusing ring 13, and preventing the problem that the outer edge of the top of the focusing ring ️13 is fragmented due to relatively strong local ion bombardment.

[0046] Please continue to refer to FIG. 8. In this embodiment or some other embodiments, the height difference h'' between the upper surface B1 of the covering ring 14 and the upper surface B2 of the focusing ring 13 is 0.5 mm to 1.5 mm. If the upper surface B1 of the covering ring 14 is too high, the flow resistance of the reaction gas will be increased, and the uniformity of the reaction gas flow will be damaged.

[0047] Please continue to refer to FIGS. 2 and 8. In this embodiment, a step 131 is provided on the outer peripheral side of the focusing ring 13, and the upper surface B2 of the focusing ring 13 is higher than the top surface B3 of the step 131; the radial cross-section of the covering ring 14 is L-shaped, including a horizontally extending section 141 and a vertically extending section 142. The inner side of the horizontally extending section 141 covers the top surface B3 of the step 131, and the vertically extending section 142 covers part of the side wall of the base 11.

[0048] In this embodiment, there is a gap h between the upper surface B2 of the focusing ring 13 and the top surface B3 of the step 131; the thickness h' of the horizontally extending section 141 of the covering ring 14 satisfies the following condition: h < h' < 1.3h. Thus, it can not only extend the service life of the focusing ring but also not affect the uniformity of the reaction gas flow.

[0049] Please continue to refer to FIG. 2. The lower electrode assembly 16 may further include: a plasma confinement ring 17 disposed around the covering ring 14. The plasma confinement ring 17 is provided with an exhaust channel. By reasonably setting the depth-width ratio of the exhaust channel, while discharging the reaction gas, the plasma is confined in the reaction area between the upper and lower electrodes, avoiding the leakage of the plasma to the non-reaction area and causing damage to the components in the non-reaction area. A ground ring assembly 15 is also provided below the covering ring 14, that is, the covering ring 14 can be disposed on the ground ring assembly 15, and its vertically extending section 142 can partially cover the side wall of the ground ring assembly 15. Generally, the ground ring assembly 15 includes a ground ring (not shown in the figure) and a shielding ring (not shown in the figure) that are sequentially disposed around the base 11. The shielding ring is used to shield the RF signal applied to the base 11 within the base 11.

[0050] An electrostatic chuck (not shown in the figure) is also provided above the base 11. The electrostatic chuck is used to generate an electrostatic suction force to support and fix the wafer W during the manufacturing process. The focusing ring 13 can be disposed around the electrostatic chuck and the wafer W.

[0051] In summary, by appropriately increasing the radius of the rounded corner of the outer edge of the focusing ring, the electric field strength near this position can be reduced, and thus the probability of arc discharge at the top outer edge of the focusing ring can be significantly reduced. At the same time, the ion bombardment intensity at this position is also correspondingly reduced, which helps to reduce the probability of accidental fragmentation of the outer edge of the focusing ring due to excessive local temperature and prevent the problem of fragmentation of the top outer edge of the focusing ring due to relatively strong local ion bombardment.

[0052] This design can further enhance the focusing ring by increasing the radius of the rounded corners at the top outer edge and appropriately increasing the thickness of the cover ring. Increasing the thickness of the cover ring extends its lifespan. Even when a certain thickness of the cover ring is etched away, it can still provide some protection to the top outer edge of the focusing ring, further extending its lifespan and reducing the probability of arc discharge at the top outer edge, thus preventing the focusing ring from shattering due to strong localized ion bombardment.

[0053] In the description of this work, it should be understood that the terms "center," "height," "thickness," "upper," "lower," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the diagrams and are used only for the convenience of describing this work and for simplification, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this work. In the description of this work, unless otherwise stated, "multiple" means two or more.

[0054] In the description of this work, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixation" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this work according to the specific circumstances.

[0055] 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.

[0056] 10: Reaction Chamber 11: Base 12: Gas spray head 13: Focusing Ring 130: Rounded corners 131: Steps 132: Small rounded corners 133: Chamfer 14: Covering ring 140: Top edge 141: Horizontal extension segment 142: Vertical extension section 15: Grounding ring assembly 16: Lower electrode assembly 17: Plasma confinement ring B1: Upper surface B2: Upper surface B3: Top surface C: Covering ring C1: Inner edge F: Focusing ring F1: Outer edge P: Plasma P1: Plasma sheath W: Wafer

Claims

1. A lower electrode assembly, characterized in that it comprises: A base for supporting a wafer; A focusing ring is disposed on the base and surrounds the wafer; The top outer edge of the focusing ring has a rounded transition, and the radius of the rounded corner is greater than or equal to 0.4 mm.

2. The lower electrode assembly as claimed in claim 1, wherein the radius of the fillet ranges from 0.4 mm to 1 mm.

3. A lower electrode assembly, characterized in that it comprises: A base for supporting a wafer; A focusing ring is disposed on the base and surrounds the wafer; The focusing ring has a sloping surface at the top outer edge.

4. The lower electrode assembly as claimed in claim 3, wherein the two ends of the inclined surface are transitioned with small rounded corners.

5. The lower electrode assembly as claimed in claim 4, wherein the radius of the small fillet ranges from 1 mm to 2 mm.

6. The lower electrode assembly as described in any one of claims 1 to 5, further comprising: A cover ring is disposed around the outside of the focusing ring.

7. The lower electrode assembly as claimed in claim 6, wherein the upper surface of the cover ring is not lower than the upper surface of the focusing ring.

8. The lower electrode assembly as claimed in claim 7, wherein the height difference between the upper surface of the cover ring and the upper surface of the focusing ring is 0.5 mm to 1.5 mm.

9. The lower electrode assembly as claimed in claim 6, wherein a step is provided on the outer periphery of the focusing ring, and the upper surface of the focusing ring is higher than the top surface of the step; the radial cross-section of the covering ring is L-shaped, including a horizontal extension and a vertical extension, the inner side of the horizontal extension covers the top surface of the step, and the vertical extension covers part of the sidewall of the base.

10. The lower electrode assembly as claimed in claim 9, wherein the upper surface of the focusing ring and the top surface of the step have a distance h; the thickness h' of the horizontal extension of the covering ring satisfies the condition: h < h' < 1.3h.

11. A plasma treatment apparatus, characterized in that it comprises: The reaction chamber, as described in any one of claims 1 to 10, is disposed at the bottom of the reaction chamber; A gas spray head, located at the top of the reaction chamber and opposite to the lower electrode assembly, is used to deliver reaction gas into the reaction chamber; a radio frequency source, electrically connected to the base and / or the gas spray head, generates a radio frequency electric field between the base and the gas spray head to ionize the reaction gas into plasma.

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