US-12620562-B2 - Focus ring for a plasma-based semiconductor processing tool

US12620562B2US 12620562 B2US12620562 B2US 12620562B2US-12620562-B2

Abstract

A focus ring for a plasma-based semiconductor processing tool is designed to provide and/or ensure etch rate uniformity across a wafer during a plasma etch process. The focus ring may include an angled inner wall that is angled away from a center of the focus ring to direct a plasma toward the wafer. The angle of the angled inner wall may be greater than approximately 130 degrees relative to the top surface of the wafer and/or may be less than approximately 50 degrees relative to an adjacent lower surface of the focus ring to reduce and/or eliminate areas of overlapping plasma on the wafer (which would otherwise cause non-uniform etch rates). Moreover, an inner diameter may be configured to be in a range of approximately 209 millimeters to 214 millimeters to further reduce and/or eliminate areas of overlapping plasma on the wafer. In this way, the focus ring provides and/or increases etch rate uniformity across the wafer, which may reduce structural variations across semiconductor devices being formed on the wafer and/or may increase processing yield.

Inventors

Sheng-Chieh Huang
Chang Kuang TSO
Chou Feng LEE
Chung-Hsiu Cheng
Jr-Sheng Chen
Chun Yan Chen
Chih-Hsien Hsu
Chin-Tai HUNG

Assignees

TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY, LTD.

Dates

Publication Date: 20260505
Application Date: 20230810

Claims (20)

1 . A method, comprising: forming a bottom surface of a plasma focus ring, wherein the bottom surface resides entirely on a same plane; forming a lower surface of the plasma focus ring above the bottom surface such that an inner diameter of the plasma focus ring is in a range of approximately 209 millimeters to approximately 214 millimeters, wherein a straight inner wall of the plasma focus ring intersects with the bottom surface and the lower surface; forming an angled inner wall of the plasma focus ring above the bottom surface and intersecting with the lower surface such that the angled inner wall is angled away from a center of the plasma focus ring at an angle less than 50 degrees relative to the lower surface; forming an angled outer wall of the plasma focus ring residing entirely at or above the lower surface and intersecting with a straight outer wall, wherein at least one of: a width of the bottom surface is in a range of approximately 19 millimeters to approximately 21 millimeters, a width of the lower surface is in a range of approximately 16 millimeters to approximately 18 millimeters, or a height of the angled inner wall is in a range of approximately 19 millimeters to approximately 24 millimeters; and forming a curved top surface of the plasma focus ring intersecting with the angled inner wall and the angled outer wall.
2 . The method of claim 1 , wherein forming the curved top surface comprises: forming the curved top surface to have a width of less than approximately 10 millimeters.
3 . The method of claim 1 , wherein the bottom surface is orthogonal with the straight outer wall.
4 . The method of claim 1 , wherein the height of the angled inner wall is approximately equal to a height of the angled outer wall.
5 . The method of claim 1 , further comprising: placing the plasma focus ring on and around a chuck.
6 . The method of claim 5 , wherein a bottom surface of the chuck resides on the same plane as the bottom surface.
7 . The method of claim 6 , wherein the lower surface of the plasma focus ring resides on a portion of a top surface of the chuck, and wherein a sidewall of the chuck interfaces directly with the straight inner wall.
8 . The method of claim 1 , wherein a height of the straight inner wall is approximately equal to a height of the straight outer wall.
9 . A method, comprising: forming a bottom surface of a focus ring, wherein the bottom surface resides entirely on a same plane; forming a lower surface of the focus ring above the bottom surface and adjacent to an open center of the focus ring, wherein a straight inner wall of the focus ring intersects with the bottom surface and the lower surface; forming an angled inner wall of the focus ring above the bottom surface and adjacent to the lower surface such that the angled inner wall is structured to direct or redirect plasma to the open center of the focus ring; forming an angled outer wall of the focus ring residing entirely at or above the lower surface and intersecting with a straight outer wall; and forming a curved top surface of the focus ring intersecting with the angled inner wall and the angled outer wall, wherein a width of the curved top surface is less than approximately 10 millimeters, wherein at least one of: a width of the bottom surface is in a range of approximately 19 millimeters to approximately 21 millimeters, a width of the lower surface is in a range of approximately 16 millimeters to approximately 18 millimeters, or a height of the angled inner wall is in a range of approximately 19 millimeters to approximately 24 millimeters.
10 . The method of claim 9 , wherein the angled inner wall is angled away from the open center of the focus ring at a uniform angle along a circumference of the focus ring.
11 . The method of claim 9 , wherein the angled inner wall defines the open center of the focus ring.
12 . The method of claim 9 , wherein the angled inner wall is above the lower surface.
13 . The method of claim 9 , wherein the angled inner wall intersects with the lower surface.
14 . A method, comprising: forming a bottom surface of a plasma focus ring, wherein the bottom surface resides entirely on a same plane; forming a lower surface of the plasma focus ring above the bottom surface, wherein a straight inner wall of the plasma focus ring intersects with the bottom surface and the lower surface; forming an angled inner wall of the plasma focus ring above the bottom surface and intersecting with the lower surface; forming an outer wall of the plasma focus ring above the bottom surface and intersecting with the angled inner wall; forming an angled outer wall of the plasma focus ring residing entirely at or above the lower surface and intersecting with a straight outer wall, wherein at least one of: a width of the bottom surface is in a range of approximately 19 millimeters to approximately 21 millimeters, a width of the lower surface is in a range of approximately 16 millimeters to approximately 18 millimeters, or a height of the angled inner wall is in a range of approximately 19 millimeters to approximately 24 millimeters; and forming a curved top surface of the plasma focus ring intersecting with the angled inner wall and the angled outer wall.
15 . The method of claim 14 , wherein the angled inner wall intersects with the lower surface.
16 . The method of claim 14 , wherein the outer wall comprises at least one of an angled portion or a straight portion.
17 . The method of claim 14 , further comprising: placing the plasma focus ring on and around a chuck.
18 . The method of claim 17 , wherein a bottom surface of the chuck resides on the same plane as the bottom surface.
19 . The method of claim 18 , wherein the lower surface of the plasma focus ring resides on a portion of a top surface of the chuck, and wherein a sidewall of the chuck interfaces directly with the straight inner wall.
20 . The method of claim 14 , wherein a height of the straight inner wall is approximately equal to a height of the straight outer wall, and wherein the height of the straight inner wall is less than each of a height of the angled inner wall and the height of the angled outer wall.

Description

RELATED APPLICATION This application is a divisional of U.S. patent application Ser. No. 17/446,399, filed Aug. 30, 2021, which is incorporated herein by reference in its entirety. BACKGROUND A plasma-based semiconductor processing tool may be used to etch various types of semiconductor materials from a substrate. Examples of plasma-based semiconductor processing tools include a decoupled plasma source (DPS) tool, an inductively coupled plasma (ICP) tool, and a transformer coupled plasma (TCP) tool. BRIEF DESCRIPTION OF THE DRAWINGS Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. FIG. 1 is a diagram of an example plasma-based semiconductor processing tool described herein. FIGS. 2A and 2B are diagrams of an example focus ring for use in the plasma-based semiconductor processing tool of FIG. 1. FIG. 3 is a diagram of an example implementation described herein. FIG. 4 is a diagram of example components of one or more devices of FIG. 1. FIG. 5 is a flowchart of an example process relating to forming a focus ring for a plasma-based semiconductor processing tool. FIG. 6 is a flowchart of an example process relating to etching a wafer using a focus ring in a plasma-based semiconductor processing tool. DETAILED DESCRIPTION The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. A plasma-based semiconductor processing tool may include various components such as a processing chamber, a plasma source including processing gas supplying components and plasma generating components, a chuck to hold a wafer in the processing chamber, and an electrode below the chuck to attract plasma ions in the processing chamber toward the wafer. In some cases, the plasma directed toward the wafer may be uneven and/or non-uniform. For example, a greater density of plasma ions may be directed toward the center of the wafer relative to the outer areas of the wafer toward the edge of the wafer. This can result in non-uniform etch rates across the wafer, which can cause some areas of the wafer to be etched faster than other areas of the wafer. Non-uniform etch rates across the wafer can result in non-uniform layer thicknesses and/or non-uniform semiconductor device feature sizes across the wafer, which can result in structural variations across semiconductor devices being formed on the wafer. Moreover, in some cases, non-uniform etch rates across the wafer can lead to over-etching in some areas of a wafer, which can destroy some of the semiconductor devices being formed thereon, thereby reducing processing yield. Some implementations described herein provide a focus ring for a plasma-based semiconductor processing tool. The focus ring may be placed around a chuck that is configured to hold a wafer in a processing chamber of the plasma-based semiconductor processing tool. The wafer may be placed on the chuck such that the focus ring surrounds the wafer. The focus ring is designed to provide and/or ensure etch rate uniformity across the wafer during a plasma etch process. For example, the focus ring may include an angled inner wall that is angled away from a center of the focus ring to direct a plasma toward the wafer. Th