TWI725336B - Lower electrode assembly and process chamber - Google Patents

Abstract

The present invention provides a lower electrode assembly and a process chamber, which includes a base and an insulating ring arranged between the base and the bottom wall of the chamber. The insulating ring can form an equivalent between the base and the bottom wall of the chamber. Capacitance, the equivalent capacitance is formed by parallel plate capacitors filled with at least two different dielectric materials in parallel. The lower electrode assembly provided by the present invention can realize the adjustment of the capacitance of the lower electrode assembly to the ground, so that the uniformity of the process devices of the same model can meet the requirements.

Description

Lower electrode assembly and process chamber

The present invention relates to the technical field of semiconductor manufacturing, in particular, to a lower electrode assembly and a process chamber.

Plasma sources can be divided into capacitively coupled plasma sources (CCP), inductively coupled plasma sources (ICP) and microwave plasma sources (Microwave Plasma, MP) according to different generation methods. Among the three types of plasma sources, upper and lower double electrode assemblies are generally used, where the upper electrode assembly is used to generate plasma, such as the coil structure in the inductively coupled plasma source. The lower electrode assembly is used to adjust the uniformity of the plasma distribution on the surface of the wafer and the size of the electric field strength to ensure that the deposition uniformity or the etching rate, the etching selection ratio, etc. meet the process requirements.

As the process accuracy requirements become higher and higher, in the mass production process, the consistency requirements of the process devices of the same model are becoming more and more stringent. Among them, the capacitance of the bottom electrode assembly to the ground is one of the key parameters that affect the process results. The inconsistent ground capacitance of the same plural process devices will directly affect the inconsistent process results.

The capacitance of the bottom electrode assembly to ground mainly refers to the equivalent capacitance formed between the base and the chamber wall of the process chamber located below it. The current bottom electrode assembly cannot adjust the equivalent capacitance, which will cause the following problems: due to the different production batches of the multiple process devices of the same model, and the errors generated during the assembly process, the bottom electrode components in the multiple process devices will be paired. The ground capacitance is inconsistent, and different ground capacitances will cause problems such as inconsistent etching rate and etching uniformity distribution, which will cause the consistency of the process devices of the same model to fail to meet the requirements, and the normal process cannot be realized.

The present invention aims to solve at least one of the technical problems existing in the prior art, and proposes a bottom electrode assembly and a process chamber, which can adjust the capacitance of the bottom electrode assembly to ground, so that the process devices of the same model can be consistent. Sex meets the requirements.

In order to achieve the objective of the present invention, a lower electrode assembly is provided, which includes a base and an insulating ring disposed between the base and the bottom wall of the chamber. The insulating ring can make the base and the bottom wall of the chamber form The equivalent capacitance is formed by parallel plate capacitances filled with at least two different dielectric materials in parallel.

Preferably, the insulating ring includes a ring body corresponding to a part of the edge area of the bottom surface of the base, and the radial width of the ring body satisfies the condition that the equivalent capacitance reaches a desired value.

Preferably, the number of the ring body is one, and the radial width of the ring body is smaller than the radial width of the edge area.

Preferably, the radial width of the ring body satisfies the following formula: L=(Rr)/4 where L is the radial width of the ring body, R is the outer diameter of the edge region, and r is the edge region the inside diameter of.

Preferably, the radial width of the ring body satisfies the following formula: L=(Rr)/2 where L is the radial width of the ring body, R is the outer diameter of the edge region, and r is the edge region the inside diameter of.

Preferably, the radial width of the ring body satisfies the following formula: L=3*(Rr)/4 where L is the radial width of the ring body, R is the outer diameter of the edge region, and r is the edge The inner diameter of the area.

Preferably, the number of the ring bodies is at least two, and they are concentric rings with each other, and in each of the two adjacent ring bodies, the inner diameter of the ring body located on the outer side and the outer diameter of the ring body located on the inner side Equal; By making the radial width of one of the ring bodies constant, and adjusting the radial width of the other ring bodies, the equivalent capacitance can reach the desired value.

Preferably, the number of the ring body is two, respectively a first ring body and a second ring body located outside of the first ring body, wherein the inner diameter of the first ring body is equal to the inner diameter of the edge region; The inner diameter of the second ring body is equal to the outer diameter of the first ring body; by setting the outer diameter of the second ring body, the equivalent capacitance can reach a desired value.

Preferably, the number of the ring body is two, respectively a first ring body and a second ring body located inside the ring body, wherein the outer diameter of the first ring body is equal to the outer diameter of the edge region; The outer diameter of the second ring body is equal to the inner diameter of the first ring body; by setting the inner diameter of the second ring body, the equivalent capacitance can reach a desired value.

Preferably, the number of the ring body is three, which are respectively a first ring body, a second ring body and a third ring body, wherein the center line of the first ring body coincides with the center line of the edge region; The second ring body is located on the outer side of the first ring body, and the inner diameter of the second ring body is equal to the outer diameter of the first ring body; the third ring body is located on the inner side of the first ring body, and the first ring body The outer diameter of the three-ring body is equal to the inner diameter of the first ring body; the equivalent capacitance can reach a desired value by setting the outer diameter of the second ring body and the inner diameter of the third ring body respectively.

Preferably, the insulating ring further includes an upper connecting ring and a lower connecting ring, wherein the upper connecting ring is arranged between the top surface of the ring body and the bottom surface of the base; the upper connecting ring is connected to the base and the base respectively. The ring body is fixedly connected; the lower connecting ring is arranged between the bottom surface of the ring body and the top surface of the bottom wall of the chamber; the lower connecting ring is fixedly connected to the bottom wall of the chamber and the ring body respectively.

Preferably, between the upper connecting ring and the base, between the upper connecting ring and the ring body, between the lower connecting ring and the bottom wall of the chamber, and between the lower connecting ring and the ring Sealing rings are arranged between the bodies.

As another technical solution, the present invention also provides a process chamber, which includes the above-mentioned lower electrode assembly provided by the present invention.

The present invention has the following beneficial effects: The lower electrode assembly provided by the present invention is provided with an insulating ring between the base and the bottom wall of the chamber, and the insulating ring can form an equivalent capacitance between the base and the bottom wall of the chamber, The equivalent capacitance is formed by connecting parallel plate capacitors filled with at least two different dielectrics in parallel. By setting the number of dielectrics, dielectric constant (ie, dielectric material) and radial width, the lower electrode can be The adjustment of the component-to-ground capacitance to make the bottom electrode components of the process device of the same model have the same ground capacitance, which can improve the uniformity of the etching rate and the uniformity of the etching, so that the uniformity of the process device of the same model can meet the requirements .

The process chamber provided by the present invention can improve the uniformity of etching rate and uniformity distribution of etching by adopting the above-mentioned lower electrode assembly provided by the present invention, so that the uniformity of process devices of the same model can meet the requirements.

In order to enable those skilled in the art to better understand the technical solution of the present invention, the lower electrode assembly and the process chamber provided by the present invention will be described in detail below with reference to the accompanying drawings.

Please refer to FIGS. 1A and 1B together. The first embodiment of the present invention provides a lower electrode assembly, which includes a base 1 and an insulating ring 3 disposed between the base 1 and the bottom wall 2 of the chamber. The insulating ring 3 can form an equivalent capacitance between the base 1 and the bottom wall 2 of the chamber, and the equivalent capacitance is the capacitance of the lower electrode assembly to the ground.

In addition, the equivalent capacitance is formed by connecting parallel plate capacitors filled with at least two different dielectric materials in parallel. By setting the number of dielectrics, dielectric constant (ie, dielectric material), and radial width, the bottom electrode assembly's capacitance to ground can be adjusted to make the bottom electrode assembly's capacitance to ground of the same type of process device consistent Therefore, the uniformity of etching rate and uniformity distribution of etching can be improved, and the uniformity of process devices of the same model can meet the requirements.

In this embodiment, the insulating ring 3 includes a ring body corresponding to a part of the edge region 11 of the bottom surface of the base 1, that is, the orthographic projection of the ring body on the plane where the edge region 11 is located falls within the edge region 11. Specifically, as shown in Figure 1B, the number of ring bodies can be one, and the radial width L of the ring body is smaller than the radial width (Rr)/2 of the aforementioned edge region 11, and the edge region 11 is divided by the corresponding ring body. The space between the remaining part of the outside and the bottom wall 2 of the chamber is the process environment (usually a vacuum) in the chamber. The ring body not only functions to support the base 1, but also serves as a dielectric filling material between the base 1 and the parallel plate capacitor formed on the bottom wall 2 of the chamber to increase the capacitance value of the parallel plate capacitor. Since the ring body only corresponds to a part of the edge area 11, this makes the area where the ring body is filled with a dielectric parallel plate capacitor, and the remaining area forms a parallel plate capacitor with a vacuum filling. These two parallel plate capacitors are connected in parallel. Thus, by setting the radial width of the ring body, it is possible to adjust the capacitance of the lower electrode assembly to the ground.

In addition, the radial width of the ring body satisfies the condition for the equivalent capacitance to reach the desired value, that is, by setting different radial widths of the ring body, the ground capacitance of the lower electrode assembly can be adjusted.

其中，

為絕緣介電質31的相對介電常數，例如陶瓷為9.8，

為真空介電常數，R為邊緣區域11的外徑，r為邊緣區域11的內徑，d為平行板電容C的間距。As shown in FIG. 1C, if the radial width of the ring body is the same as the radial width of the edge region 11, a parallel plate capacitor C with an insulating dielectric 31 as the filler is formed. The parallel plate capacitance C is equal to:

among them,

Is the relative dielectric constant of the insulating dielectric material 31, for example, ceramic is 9.8,

Is the vacuum dielectric constant, R is the outer diameter of the edge region 11, r is the inner diameter of the edge region 11, and d is the spacing of the parallel plate capacitor C.

其中，C₁ 和C₃ 為兩個填充物為真空的平行板電容，C₂ 為填充物為絕緣介電質32的平行板電容。As shown in Figure 1D, if the radial width L of the ring body is smaller than the radial width (Rr)/2 of the aforementioned edge region 11, assuming that the ring body corresponds to the middle region of the edge region 11, two fillers connected in parallel are formed. The object is a parallel plate capacitor with a vacuum and a parallel plate capacitor with an insulating dielectric 32 as a filler. The total parallel plate capacitance Cr is equal to:

Among them, C ₁ and C ₃ are two parallel plate capacitors whose fillings are vacuum, and C ₂ is a parallel plate capacitor whose fillings are insulating dielectrics 32.

其中另一個填充物為真空的平行板電容C₃ 等於：

填充物為絕緣介電質32的平行板電容C₂ 等於：

由上可知，填充物只有絕緣介電質31的平行板電容C與填充物有真空和絕緣介電質32的平行板電容Cr的大小不同。因此，通過改變環體的徑向寬度，可以調節上述等效電容的大小。 _{The parallel plate capacitance C 1} with one of the fillings being vacuum is equal to:

_{The parallel plate capacitance C 3 of} which the other filling is vacuum is equal to:

_{The parallel plate capacitance C 2 where the} filler is an insulating dielectric 32 is equal to:

It can be seen from the above that only the parallel plate capacitor C with the insulating dielectric 31 and the parallel plate capacitor Cr with the vacuum and insulating dielectric 32 as the filler are different in size. Therefore, by changing the radial width of the ring body, the magnitude of the above-mentioned equivalent capacitance can be adjusted.

For example, the radial width of the ring satisfies the following formula: L=(Rr)/4 Assuming that the inner diameter r of the edge region 11 is approximately 3/4 of its outer diameter R, it can be estimated that the filler has a vacuum and an insulating medium. The parallel plate capacitance Cr of the dielectric material 32 is 28.23% of the parallel plate capacitance C of the insulating dielectric material 31 only.

For another example, the radial width of the ring body satisfies the following formula: L=(Rr)/2 Assuming that the inner diameter r of the edge region 11 is approximately 3/4 of its outer diameter R, it can be estimated that the filler has vacuum and insulation The parallel plate capacitance Cr of the dielectric material 32 is 50.73% of the parallel plate capacitance C of the insulating dielectric material 31 only.

For another example, the radial width of the ring satisfies the following formula: L=3*(Rr)/4 Assuming that the inner diameter r of the edge area 11 is approximately 3/4 of its outer diameter R, it can be estimated that the filling has a vacuum The parallel plate capacitance Cr of the insulating dielectric material 32 is 77.06% of the parallel plate capacitance C of the insulating dielectric material 31 only.

It can be seen that the larger the radial width L of the ring body, the larger the parallel plate capacitance Cr; conversely, the smaller the radial width L of the ring body, the smaller the parallel plate capacitance Cr.

It should be noted that in this embodiment, the ring body corresponds to the middle area of the edge area 11, but the present invention is not limited to this. In practical applications, the ring body can also be made close to the outer edge or the inner edge of the edge area 11. The edge area, or the outer diameter of the ring body is equal to the outer diameter of the edge area 11, or the inner diameter of the ring body is equal to the inner diameter of the edge area 11.

Compared with the above-mentioned first embodiment, the lower electrode assembly provided by the second embodiment of the present invention differs only in the number and arrangement of the ring bodies.

Specifically, the number of ring bodies can also be at least two, and they are concentric rings, and in each of the two adjacent ring bodies, the inner diameter of the ring body located on the outer side is equal to the outer diameter of the ring body located on the inner side. ; By making the radial width of one of the ring bodies constant and adjusting the radial width of the remaining ring bodies, the equivalent capacitance can reach the desired value, thereby reducing the difficulty of adjustment.

In this embodiment, as shown in Figure 2A, the number of ring bodies is two, namely the first ring body 33 and the second ring body 34 located outside of it, wherein the inner diameter of the first ring body 33 is equal to The inner diameter r of the edge region 11 is equal. The inner diameter of the second ring body 34 is equal to the outer diameter of the first ring body 33. In this case, the size of the equivalent capacitance can be adjusted in the following manner, that is, by setting the outer diameter of the second ring body 34, the equivalent capacitance can reach the desired value. Furthermore, the radial width of the first ring body 33 is constant. On this basis, if the outer diameter of the second ring body 34 is set to be different, the radial width L1 of the second ring body 34 will change, that is, the larger the outer diameter of the second ring body 34, the larger the outer diameter of the second ring body 34 will be. The larger the radial width L1, the larger the sum of the radial widths of the first ring body 33 and the second ring body 34; conversely, the smaller the outer diameter of the second ring body 34, the smaller the diameter of the second ring body 34 The smaller the radial width L1 is, the smaller the sum of the radial widths of the first ring body 33 and the second ring body 34 is. Therefore, only by setting the outer diameter of the second ring body 34, the equivalent capacitance can be adjusted, so that the adjustment difficulty can be reduced.

Similar to the above-mentioned way of adjusting the size of the equivalent capacitance, as shown in Figure 2B, the number of ring bodies is two, namely the first ring body 33 and the second ring body 34 located inside it. The outer diameter of a ring 33 is equal to the outer diameter R of the edge region 11. The outer diameter of the second ring body 34 is equal to the inner diameter of the first ring body 33. In this case, the size of the equivalent capacitance can be adjusted in the following manner, that is, by setting the inner diameter of the second ring body 34, the equivalent capacitance can reach the desired value. Furthermore, the radial width of the first ring body 33 is constant. On this basis, if the inner diameter of the second ring body 34 is set to be different, the radial width L1 of the second ring body 34 will change, that is, the smaller the inner diameter of the second ring body 34, the second ring body 34 The larger the radial width L1, the larger the sum of the radial widths of the first ring body 33 and the second ring body 34; conversely, the larger the inner diameter of the second ring body 34, the larger the diameter of the second ring body 34 The smaller the radial width L1 is, the smaller the sum of the radial widths of the first ring body 33 and the second ring body 34 is. Therefore, only by setting the inner diameter of the second ring body 34, the equivalent capacitance can be adjusted, so that the adjustment difficulty can be reduced.

Similar to the above-mentioned way of adjusting the size of the equivalent capacitance, as shown in Figure 2C, the number of ring bodies can also be three, namely the first ring body 33, the second ring body 34, and the third ring body 35. , Wherein the center line of the first ring body 33 coincides with the center line of the edge region 11; the second ring body 34 is located outside the first ring body 33, and the inner diameter of the second ring body 34 is the same as that of the first ring body 33. The outer diameters are equal; the third ring body 35 is located inside the first ring body 33, and the outer diameter of the third ring body 33 is equal to the inner diameter of the first ring body 33. In this case, the size of the equivalent capacitance can be adjusted in the following manner, that is, by setting the outer diameter of the second ring body 34 and the inner diameter of the third ring body 35 respectively, so that the equivalent capacitance reaches the desired value. Furthermore, the radial width of the first ring body 33 is constant. On this basis, the larger the outer diameter of the second ring body 34, and the smaller the inner diameter of the third ring body 35, the greater the radial width L1 of the second ring body 34, and the greater the radial width of the third ring body 35. The larger L2 is, the larger the sum of the radial widths of the first ring body 33, the second ring body 34, and the third ring body 35; on the contrary, the smaller the outer diameter of the second ring body 34, the larger the diameter of the third ring body 35 The larger the inner diameter, the smaller the radial width L1 of the second ring body 34, and the smaller the radial width L2 of the third ring body 35, so that the first ring body 33, the second ring body 34, and the third ring body 35 The smaller the sum of the radial widths. Therefore, only by setting the outer diameter of the second ring body 34 and the inner diameter of the third ring body 35 respectively, the equivalent capacitance can be adjusted, thereby reducing the difficulty of adjustment.

Of course, in practical applications, any other method may be used to change the radial width of the ring body to achieve the adjustment of the equivalent capacitance.

Please refer to FIGS. 3A to 3D together. The bottom electrode assembly provided by the third embodiment of the present invention is based on the above-mentioned first and second embodiments. The insulating ring 3 also includes an upper connecting ring 4 and a lower connecting ring 4 Ring 5 to facilitate the installation of the ring body.

Specifically, the upper connecting ring 4 is arranged between the top surface of the ring body and the bottom surface of the base 1, and the upper connecting ring 4 is fixedly connected to the base 1 and the ring body, respectively. Wherein, a plurality of connecting holes 41 are provided at a position close to the outer edge of the upper connecting ring 4 for fixing the upper connecting ring 4 to the base 1 by screws. A plurality of connecting holes 42 are provided on the upper connecting ring 4 opposite to the ring body, and a plurality of threaded holes 301 are provided on the surface of the ring body opposite to the upper connecting ring 4 for connecting the upper connecting ring with screws. 4Fixed connection with the ring body.

The lower connecting ring 5 is arranged between the bottom surface of the ring body and the top surface of the chamber bottom wall 2, and the lower connecting ring 5 is fixedly connected to the chamber bottom wall 2 and the ring body, respectively. Wherein, a plurality of connecting holes 51 are provided at a position close to the outer edge of the lower connecting ring 5 for fixing the lower connecting ring 5 to the bottom wall 2 of the chamber by screws. A plurality of connecting holes 52 are provided at the appropriate positions of the lower connecting ring 5 opposite to the ring body, and a plurality of threaded holes 301 are provided on the surface of the ring body opposite to the lower connecting ring 5 for connecting the lower connecting ring 5 with screws. Fixed connection with the ring body.

In order to achieve sealing, between the upper connecting ring 4 and the base 1, between the upper connecting ring 4 and the ring body, between the lower connecting ring 5 and the bottom wall 2 of the chamber, and between the lower connecting ring 5 and the ring body. A sealing ring is provided. Specifically, an annular groove 302 for installing a sealing ring may be provided on the surface of the ring body opposite to the upper connecting ring 4 and the lower connecting ring 5; on the surface of the upper connecting ring 4 opposite to the base 1 and the ring body, respectively An annular groove 43 for installing the sealing ring is provided on the upper part; and an annular groove 53 for installing the sealing ring is provided on the surface of the lower connecting ring 5 opposite to the bottom wall 2 of the chamber and the ring body, respectively.

As another technical solution, as shown in FIG. 4, an embodiment of the present invention also provides a process chamber 100, which includes the lower electrode assembly provided in the foregoing various embodiments of the present invention.

In this embodiment, the lower electrode assembly includes a base 101, and a focusing ring 102, a base ring 103, an isolation ring 104, and an insulating ring 105 are sequentially arranged around the base 101 from top to bottom. Moreover, the bottom wall of the chamber located below the bottom surface of the base 101 forms an equivalent capacitance between the bottom surface of the base 101 and the bottom chamber wall.

The process chamber provided by the embodiment of the present invention can improve the uniformity of the etching rate and uniformity distribution of the etching by adopting the above-mentioned lower electrode assembly provided in the above-mentioned various embodiments of the present invention, so that the uniformity of the process devices of the same model can be achieved fulfil requirements.

It can be understood that the above implementations are merely exemplary implementations used to illustrate the principle of the present invention, but the present invention is not limited thereto. For those of ordinary skill 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 deemed to be within the protection scope of the present invention.

1,101‧‧‧Base 2,‧‧‧Chamber bottom wall 3,105‧‧‧Insulation ring 4‧‧‧Upper connecting ring 5‧‧‧Lower connecting ring 11‧‧‧Edge area 31,32‧‧‧ Insulating dielectric 33‧‧‧First ring 34‧‧‧Second ring 35‧‧‧Third ring 41,42,51,52‧‧‧Connecting hole 43,53,302‧‧‧Annular recess Road 100‧‧‧Process chamber 102‧‧‧Focus ring 103‧‧‧Base ring 104‧‧‧Isolation ring 301‧‧‧Threaded holes C, C ₁ , C ₂ , C ₃ ‧‧‧Parallel plate capacitor I‧ ‧‧Area L, L1, L2‧‧‧Radial width r‧‧‧Inner diameter R‧‧‧Outer diameter

Fig. 1A is a structural diagram of the lower electrode assembly provided by the first embodiment of the present invention; Fig. 1B is a bottom view of the ring body in the first embodiment of the present invention; Fig. 1C is a capacitance equivalent diagram of a ring body; Fig. 2A is a bottom view of a ring in the second embodiment of the present invention; Figure 2B is a bottom view of another ring in the second embodiment of the present invention; Figure 2C is a bottom view of yet another ring body in the second embodiment of the present invention; Figure 3A is a structural view of the lower electrode assembly provided by the third embodiment of the present invention; Figure 3B is an enlarged view of area I in Figure 3A Figure 3C is a top view of the ring body in the third embodiment of the present invention; Figure 3D is a top view of the upper connecting ring in the third embodiment of the present invention; Figure 4 is a cross-sectional view of the process chamber provided by the present invention.

3‧‧‧Insulation ring

11‧‧‧Edge area

L‧‧‧radial width

r‧‧‧Inner diameter

R‧‧‧Outer diameter

Claims (12)

A lower electrode assembly includes a base and an insulating ring arranged between the base and a bottom wall of a chamber, and the insulating ring can form an equivalent capacitance between the base and the bottom wall of the chamber, It is characterized in that the equivalent capacitor is formed by parallel plate capacitors filled with at least two different dielectrics in parallel, wherein the insulating ring includes a ring body, and the ring body is on the plane where an edge area of the bottom surface of the base is located. The orthographic projection of the ring body falls within the edge area, and the area where the ring body is located forms a parallel plate capacitor filled with a dielectric substance, and the remaining area forms a parallel plate capacitor filled with a vacuum, and the radial width of the ring body satisfies To make the equivalent capacitance reach the desired value. The lower electrode assembly according to the first item of the scope of patent application, wherein the number of the ring body is one, and the radial width of the ring body is smaller than the radial width of the edge area. As for the lower electrode assembly described in item 2 of the scope of patent application, wherein the radial width of the ring body satisfies the following formula: L=(Rr)/4 where L is the radial width of the ring body, and R is the The outer diameter of the edge area, r is the inner diameter of the edge area. As for the lower electrode assembly described in item 2 of the scope of patent application, wherein the radial width of the ring body satisfies the following formula: L=(Rr)/2 where L is the radial width of the ring body, and R is the The outer diameter of the edge area, r is the inner diameter of the edge area. The lower electrode assembly as described in item 2 of the scope of patent application, wherein the radial width of the ring body satisfies the following formula: L=3*(R-r)/4 where L is the radial width of the ring body, R is the outer diameter of the edge region, and r is the inner diameter of the edge region. The lower electrode assembly according to the first item of the scope of patent application, wherein the number of the ring bodies is at least two, and they are concentric rings with each other, and in each of the two adjacent ring bodies, the outer ring body The inner diameter of is equal to the outer diameter of the inner ring body; the equivalent capacitance can reach the desired value by making the radial width of one of the ring bodies constant and adjusting the radial width of the rest of the ring bodies. The lower electrode assembly described in item 6 of the scope of patent application, wherein the number of the ring body is two, respectively a first ring body and a second ring body located on the outer side thereof, wherein the first ring body The inner diameter of is equal to the inner diameter of the edge area; the inner diameter of the second ring body is equal to the outer diameter of the first ring body; the equivalent capacitance reaches the desired value by setting the outer diameter of the second ring body . The lower electrode assembly according to item 6 of the scope of patent application, wherein the number of the ring body is two, respectively a first ring body and a second ring body located inside the lower electrode assembly, wherein the first ring body The outer diameter of is equal to the outer diameter of the edge area; the outer diameter of the second ring body is equal to the inner diameter of the first ring body; by setting the inner diameter of the second ring body, the equivalent capacitance reaches the desired value . The lower electrode assembly described in item 6 of the scope of patent application, wherein the number of the ring body is three, which are respectively a first ring body, a second ring body and a third ring body, wherein the first ring body The center line of the ring body coincides with the center line of the edge area; The second ring body is located on the outer side of the first ring body, and the inner diameter of the second ring body is equal to the outer diameter of the first ring body; the third ring body is located on the inner side of the first ring body, and the The outer diameter of the third ring body is equal to the inner diameter of the first ring body; by setting the outer diameter of the second ring body and the inner diameter of the third ring body respectively, the equivalent capacitance can reach a desired value. The lower electrode assembly according to any one of items 1 to 9 of the scope of the patent application, wherein the insulating ring further includes an upper connecting ring and a lower connecting ring, wherein the upper connecting ring is arranged on the ring body Between the top surface and the bottom surface of the base; the upper connecting ring is respectively fixedly connected with the base and the ring body; the lower connecting ring is arranged between the bottom surface of the ring body and the top surface of the bottom wall of the chamber; The lower connecting ring is respectively fixedly connected with the bottom wall of the chamber and the ring body. The lower electrode assembly according to claim 10, wherein between the upper connecting ring and the base, between the upper connecting ring and the ring body, between the lower connecting ring and the chamber bottom A sealing ring is arranged between the walls and between the lower connecting ring and the ring body. A process chamber is characterized by comprising the lower electrode assembly according to any one of items 1 to 11 of the scope of patent application.

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