Exclusion Ring Assembly for Wafer Edge Deposition Control
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Solution Overview
Problem
Achieving uniform semiconductor processing across the entire wafer, particularly at the edge regions, is challenging due to discontinuities that allow process gases to access the underside, leading to unwanted processing.
Innovation Solution
The use of an exclusion ring assembly comprising upper and lower annular rings with controlled gas flow passages and a pedestal with backside gas injection to manage gas flow and prevent deposition at the edge, combined with selective exposure to deposition inhibitors and etchants to ensure uniform film deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If process gases are allowed to flow freely across the wafer, then complete area coverage is achieved, but unwanted deposition occurs at the edge regions on the underside and bevel
Solution Approach 1:
The exclusion ring assembly extracts and removes process gases from the edge region before they can reach the underside and bevel of the wafer. The annular gap in the exclusion ring creates a dedicated flow path that channels gases away from the edge area, effectively separating the main processing zone from the edge region to prevent harmful deposition.
Solution Approach 2:
The exclusion ring assembly creates a localized modified flow environment at the wafer edge while maintaining normal processing conditions across the rest of the wafer surface. By positioning the exclusion ring at a specific radial distance from the wafer center, the system achieves different gas flow characteristics in different regions - controlled exclusion at the edge and uniform processing in the center.
2Object-generated harmful factors
If exclusion rings are positioned close to the wafer edge, then edge deposition is prevented, but uniformity across the wafer surface is compromised
Solution Approach 1:
The exclusion ring assembly operates in a radial dimension rather than vertically, creating an annular flow passage that extends outward from the wafer edge. By controlling the radial position and dimensions of the exclusion ring, the system manages gas flow in the horizontal plane to achieve both edge protection and central uniformity.
Solution Approach 2:
The system controls the annular gap dimensions and exclusion ring positioning parameters to optimize the balance between edge exclusion effectiveness and central uniformity. By adjusting the radial distance of the exclusion ring from the wafer center and the gap size, the gas flow distribution is tuned to achieve less than 1% non-uniformity in the processed area.
3Object-generated harmful factors
If backside gas injection is used to prevent edge deposition, then gas flow control is improved, but device complexity increases
Solution Approach 1:
The exclusion ring assembly serves multiple functions simultaneously: it acts as a physical barrier to prevent direct gas access to the wafer edge, creates a controlled annular flow path for gas management, and works in conjunction with backside injection to establish pressure differentials. This multi-functionality reduces the need for separate complex control mechanisms.
Solution Approach 2:
The system utilizes pneumatic principles by injecting gas through the backside of the wafer and using pressure differentials to control gas flow direction. The backside gas injection creates a pressure gradient that directs gases away from the edge region, working synergistically with the exclusion ring's physical structure to achieve edge protection without complex mechanical controls.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves uniform film deposition up to the edge of the wafer, inhibiting or etching the edge region to maintain uniformity within 1-3 mm of the edge, reducing non-uniformity to less than 1%, while preventing unwanted deposition on the bevel edge.
Implementation Method 1
the upper annular ring is disposed over the lower annular ring to define an annular gas flow passage between the upper annular ring and the lower annular ring
Implementation Method 2
a pedestal with backside gas injection to manage gas flow and prevent deposition at the edge
Implementation Method 3
selective exposure to deposition inhibitors and etchants to ensure uniform film deposition
Data Source
AI summary
Provided herein are methods and apparatuses for controlling uniformity of processing at an edge region of a semiconductor wafer. In some embodiments, the methods include exposing an edge region to treatment gases such as etch gases and/or inhibition gases. Also provided herein are exclusion ring assemblies including multiple rings that may be implemented to provide control of the processing environment at the edge of the wafer.