Outer edge ring for etching and electrostatic chuck assembly

Abstract

The technical scheme of the utility model provides an outer edge ring for etching. The outer edge ring is a revolving body taking a central shaft as a shaft, wherein an inner ring surface is provided with a base ring surface extending axially from a first end surface; a first step part which is higher towards the inside of the ring is formed on the other side, opposite to the first end face, of the base ring face, and the first step part comprises an annular first step face and a first side face which is connected with the first step face and the base ring face; and a second step part which is recessed towards the outside of the ring is formed on the other side of the first step part relative to the first end surface, the second step part comprises an annular second step surface and a second bottom surface which is connected with the second step surface and the first step surface, and the second step surface is connected with the second end and is not lower than the top surface of the etched wafer. According to the outer edge ring for etching, good positioning and connection between the limiting ring and the electrostatic chuck are achieved, effective protection on the side face of the edge of the electrostatic chuck is guaranteed, excessive corrosion to the edge of the wafer in the etching process is avoided, and the non-uniform etching degree of the surface of the wafer is reduced.

Description

Technical Field

[0001] This utility model relates to the field of plasma etching technology, specifically to an outer edge ring for etching. Background Technology

[0002] Plasma etching is one of the key steps in semiconductor manufacturing. One of the key issues in wafer etching is ensuring the overall uniformity of the etching depth on the wafer surface and avoiding excessive differences in etching depth. Otherwise, it will be difficult to stably control the stability of the surface process and increase the defect rate.

[0003] The wafer edge is a major area of ​​uneven etching depth. In the etching process, a limiting ring is often designed during the plasma chamber design to constrain and shape the electric field, thereby optimizing the problem of uneven etching depth that occurs during the etching process. Taking the utility model patent entitled "Limiting Ring for Plasma Etching" with authorization announcement number CN220474566U as an example, although the etching uniformity can be optimized by the constraint effect of the limiting ring on the plasma, there is still space between the limiting ring and the wafer edge. Although the etching uniformity at the edge is optimized, it still exists. Utility Model Content

[0004] To optimize the edge etching effect during the plasma etching process of wafers, this application provides an outer edge ring for etching.

[0005] The present invention provides an outer ring for etching, which is a rotating body about a central axis and is ring-shaped. It has a first end face, a second end face, and an inner ring face. The inner ring face has a base ring face extending axially from the first end face. A first step portion is formed on the other side of the base ring face relative to the first end face, which is radially higher than the ring. The first step portion includes an annular first step surface and a first side surface that joins the first step surface and the base ring face. A second step portion is formed on the other side of the first step portion relative to the first end face, which is radially recessed outward. The second step portion includes an annular second step surface and a second bottom surface that joins the second step surface and the first step surface. The second step surface joins the second end face. The height of the second end face is not lower than the top surface of the wafer being etched.

[0006] Preferably, the first step surface of the first step portion is located radially inside the edge of the wafer, and the wafer blocks the junction between the first step surface and the electrostatic chuck mounted thereon.

[0007] Preferably, the height of the second bottom surface of the second step is lower than the top surface of the electrostatic chuck.

[0008] Preferably, the second step surface includes a cylindrical surface below the wafer top surface and a frustum surface above the wafer top surface, the frustum surface engaging the cylindrical surface and the second end face. The diameter of the frustum surface expands from one end of the cylindrical surface to the end engaging with the second end face.

[0009] Preferably, the height of the second step surface is 3.6-4.0 mm.

[0010] Preferably, the height of the second step surface is 3.73-3.82 mm.

[0011] Preferably, the single-sided gap between the cylindrical surface and the edge of the wafer is 0.43-0.56 mm.

[0012] Preferably, it includes the etching outer ring and electrostatic chuck as described in any of the above claims, with the defining ring surrounding the electrostatic chuck.

[0013] The etching outer edge ring of this application achieves good positioning and connection between the limiting ring and the electrostatic chuck through the setting of multi-level steps. At the same time, the structural design ensures effective protection of the edge side of the electrostatic chuck, avoiding excessive corrosion of the wafer edge during the etching process. Furthermore, since the end face of the second end face is higher than the wafer, the degree of etching unevenness on the wafer surface is also reduced. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of the etching outer ring of this utility model;

[0015] Figure 2 This is a partially enlarged schematic diagram of the outer edge ring for etching according to this utility model;

[0016] Figure 3 This is a schematic diagram of the overall structure of the electrostatic chuck assembly of this utility model;

[0017] Figure 4 This is a partially enlarged schematic diagram of the electrostatic chuck assembly of this utility model.

[0018] In the picture:

[0019] 1: Limiting ring; 11: Inner ring surface; 111: Base ring surface; 112: First step portion; 1121: First side surface; 1122: First step surface; 113: Second step portion; 1131: Second bottom surface; 1132: Second step surface; 114: First end face; 115: Second end face; 2: Electrostatic chuck; 3: Wafer; 321: Cylindrical surface; 322: Frustum surface; O: Central axis. Detailed Implementation

[0020] The present patent type will be described in detail below with reference to the accompanying drawings and specific embodiments. In this specification, the dimensions in the drawings do not represent actual scale; the drawings are only used to illustrate the relative positional and connection relationships between the components. Components with the same name or reference numerals represent similar or identical structures, and are limited to illustrative purposes. In this application, terms such as "high" and "low," which have directional indications, are used to define the normal operating state of the outer edge ring used for etching.

[0021] Figure 1 This is a schematic diagram of the outer edge ring for etching in this application. Figure 2 This is a cross-sectional schematic diagram of the limiting ring 1. The limiting ring 1 is a rotating body about the central axis O, and is annular in shape. Its inner annular surface 11 has an axially extending base annular surface 111 starting from the first end face 114. The inner annular surface forms a first step portion 112 that is radially inwardly higher than the base annular surface 111 on the other side of the base annular surface relative to the first end face 114. The first step portion 112 includes an annular first step surface 1122, which can be as follows: Figure 1 The cylindrical surface shown has a first step portion with a first side surface 1121, which connects the base ring surface 111 and the first step surface 1122. The inner ring surface 11 has a second step portion 113 recessed outwards from the defining ring 1 on the other side of the first step portion 112 relative to the base ring surface 111. The second step portion 113 has an annular second step surface 1132, which can be a cylindrical surface. The second step portion 113 also includes a second bottom surface 1131, which engages with the first step surface 1122 and the second step surface 1132. The second step surface 1132 extends to a second end face 115. The second step surface 1132 and the first step surface 1122 can be cylindrical surfaces coaxial with the central axis O, and the first side surface 1121 and the second bottom surface 1131 can be planes perpendicular to the central axis O.

[0022] Figure 3 This is a schematic diagram of the electrostatic chuck assembly. Figure 4 for Figure 3A partially enlarged schematic diagram. A limiting ring 1 surrounds the electrostatic chuck 2, engaging with the electrostatic chuck 2 via a first stepped portion 112. The first side surface 1121 of the first stepped portion 112 adheres to the surface of the electrostatic chuck 2 for axial positioning, achieving a tighter fit compared to the stepless state. The first stepped surface 1122 is used for radial positioning of the limiting ring 1, ensuring the coaxiality of the limiting ring 1 and the electrostatic chuck 2, and thereby ensuring the coaxial accuracy of the second stepped surface 1132, preventing interference during wafer placement. The first stepped surface 1122 is not used for precise positioning, but only for controlling coaxial accuracy; therefore, its machining accuracy control can be reduced, facilitating milling of the first stepped surface 1122 during the machining of the limiting ring 1. The second stepped portion 113 surrounds the wafer, focusing the plasma and thus preventing the plasma from penetrating deep into the side regions of the wafer 3 and etching the sidewalls of the wafer 3. Wafer 3 is typically made of materials such as silicon or silicon carbide. The height difference between its surface and wafer 3 is not large, which helps to ensure the uniform distribution of plasma at the edge of wafer 3 surface and thereby further optimizes the etching uniformity at the edge of the wafer surface.

[0023] refer to Figure 4 In the embodiment, for the limiting ring 1, in order to reduce the etching degree at the edge of wafer 3, the height of the second end face 115 should not be lower than the surface height of wafer 3, so that the second end face 115 is relatively higher than the surface of wafer 3, thereby reducing the etching degree on the side of wafer 3. To ensure this requirement, specifically in the limiting ring 1 of this application, the height of the second step surface 1132 is 3.6-4.0 mm. The minimum height of 3.6 mm is mainly to ensure the service life of the limiting ring 1. During the etching process, the height of the second end face 115 will gradually decrease due to the etching effect of plasma. Setting a reasonable minimum height can ensure the service life of the limiting ring 1, avoid frequent downtime for replacement, and reduce the usage cost of the limiting ring 1. The limit of 4.0 mm is mainly to ensure the etching uniformity of the top edge of wafer 3. When the height of the second step surface 1132 of the limiting ring 1 is too high, the height difference between the second end face 115 and the limiting ring 1 will increase, which will affect the plasma distribution at the edge of wafer 3, thus hindering the improvement of uniformity. Guided by the aforementioned design direction, further verification showed that the height of the second step surface 1132 can be further controlled between 3.73-3.82 mm to achieve a balance between lifetime and etching effect. Furthermore, the single-sided gap between the second step surface 1132 and the edge of wafer 3 is preferably controlled at 0.43-0.56 mm. This is to avoid excessively small gaps that could cause rubbing during wafer 3 loading and unloading, and to avoid excessively large gaps that could lead to edge side etching. (Continue to refer to...) Figure 4In this embodiment, for the electrostatic chuck assembly, the height of the second bottom surface 1131 should be lower than the top surface of the electrostatic chuck 2. This is to prevent interference between the second bottom surface 1131 of the second step portion 113 and the bottom surface of the wafer 3 when the electrostatic chuck 2 adsorbs the wafer 3. The first step surface 1122 is located radially inside the wafer edge, so that during the etching process, the junction between the first step portion 112 and the electrostatic chuck 2 is blocked by the wafer 3. This prevents the plasma from etching the first step portion 112 and the electrostatic chuck 2, reducing the generation of etching impurities.

[0024] refer to Figure 4 In one embodiment, the second step surface 1132 can be further segmented to optimize the etching effect. It includes a cylindrical surface 321 below the top surface of wafer 3 and a frustum surface 322 above the top surface of wafer 3. The frustum surface 322 joins the cylindrical surface 321 and the second end face 115, with its diameter expanding from one end of the cylindrical surface 321 to the end joined by the second end face 115. The frustum surface 322 ensures a smooth transition in height between the second end face 115 and the top surface of wafer 3, guaranteeing the uniformity of the surface etching depth of wafer 3 during long-term etching.

[0025] The above description is merely a preferred embodiment of this patent type and is not intended to limit the scope of this patent type. Without departing from the design spirit of this patent type, all modifications and improvements made by those skilled in the art to the technical solutions of this patent type should fall within the protection scope defined by the claims of this patent type.

Claims

1. An outer ring for etching, which is a rotating body about a central axis (O), is ring-shaped, and has a first end face (114), a second end face (115), and an inner ring face (11), characterized in that, The inner annular surface (11) has an axially extending base annular surface (111) starting from the first end face (114); a first step portion (112) is formed on the other side of the base annular surface (111) relative to the first end face (114) along the axial direction, which is radially higher than the annular surface (112). The first step portion (112) includes an annular first step surface (1122) and a first side surface (1121) that joins the first step surface (1122) and the base annular surface (111); at the first step portion (112) A second step portion (113) is formed on the other side of the first end face (114) that is radially recessed outward. The second step portion (113) includes an annular second step surface (1132) and a second bottom surface (1131) that joins the second step surface (1132) and the first step surface (1122). The second step surface (1132) joins the second end face (115). The height of the second end face (115) is not lower than the top surface of the etched wafer (3).

2. The etching outer ring as described in claim 1, characterized in that, The first step surface (1122) of the first step portion (112) is located on the radial inner side of the edge of the wafer (3), and the wafer (3) blocks the junction of the first step surface (1122) and the electrostatic chuck (2) on which it is mounted.

3. The etching outer edge ring as described in claim 2, characterized in that, The height of the second bottom surface (1131) of the second step (113) is lower than the top surface of the electrostatic chuck (2).

4. The etching outer edge ring as described in any one of claims 1-3, characterized in that, The second step surface (1132) includes a cylindrical surface (321) below the top surface of the wafer (3) and a frustum surface (322) above the top surface of the wafer (3). The frustum surface (322) joins the cylindrical surface (321) and the second end face (115). The diameter of the frustum surface (322) expands from one end of the cylindrical surface (321) to the end joined by the second end face (115).

5. The etching outer ring as described in claim 4, characterized in that, The height of the second step surface (1132) is 3.6-4.0 mm.

6. The etching outer ring as described in claim 4, characterized in that, The height of the second step surface (1132) is 3.73-3.82 mm.

7. The etching outer ring as described in claim 4, characterized in that, The single-sided gap between the cylindrical surface (321) and the edge of the wafer (3) is 0.43-0.56 mm.

8. An electrostatic chuck assembly, characterized in that, Includes an etching outer edge ring as described in any one of claims 1-7 and an electrostatic chuck (2), wherein a defining ring (1) is disposed around the electrostatic chuck (2).

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