Confinement Ring Structure for Wafer Edge Etch Uniformity

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Solution Overview

Problem

Semiconductor wafer etching processes exhibit non-uniform etch rates, particularly near the wafer edge, due to back diffusion of reaction by-products and material differences between the wafer and the edge ring, leading to yield loss and performance degradation.

Innovation Solution

A confinement ring is introduced in the process chamber to confine plasma radicals, featuring a tubular extension and a foot extension that control the exhaust flow of radicals and process gases, thereby adjusting the radical velocity near the wafer edge to improve etch rate uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If radicals are allowed to flow freely in the process chamber, then the etching process can proceed, but back diffusion of radicals occurs at the wafer edge leading to non-uniform etch rates

Engineering Contradiction:

Improveetch rate uniformityVSAvoidback diffusion of radicals

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

A confinement ring is introduced as an intermediary component between the wafer edge ring and the process chamber. The confinement ring includes a tubular extension that extends downward from the showerhead and a foot extension that extends radially outward, creating a physical barrier to control radical flow. This intermediary structure prevents direct back diffusion of radicals from the exhaust port to the wafer edge while maintaining process gas flow and radical generation, thereby improving etch rate uniformity at the wafer edge.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If the separation between foot extensions and edge ring is reduced to control exhaust flow, then radical velocity increases and etch uniformity improves, but the device complexity increases

Engineering Contradiction:

Improveetch rate uniformityVSAvoidconfinement ring structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The confinement ring is segmented into two distinct functional extensions: a tubular extension that extends vertically downward from the showerhead to define the upper boundary of the confined region, and a foot extension that extends radially outward to define the lower boundary. This segmentation allows independent optimization of each extension's dimensions and positioning, enabling precise control over the gap size between the foot extension and the edge ring while maintaining structural feasibility and reducing overall device complexity.

Inventive Principle:

Principle #1Segmentation

3Manufacturing precision

If plasma radicals are confined over the wafer surface, then etch rate uniformity improves, but the device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improveetch rate uniformityVSAvoidconfinement ring fabrication

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The confinement ring is designed to be integrally formed with the showerhead assembly, merging the confinement ring structure with the existing showerhead support infrastructure. The tubular extension connects to the showerhead bottom surface, and the foot extension is continuously formed from the tubular extension, creating a single integrated component. This merging approach reduces the number of separate parts that need to be manufactured and assembled, simplifying fabrication while maintaining the precise geometric relationships needed for effective radical confinement and etch uniformity.

Inventive Principle:

Principle #5Merging (Combining)

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

The confinement ring effectively reduces back diffusion of radicals and enhances etch rate uniformity across the wafer, including the edge regions, by increasing the exit velocity of radicals and reducing concentration gradients.

Implementation Method 1

A separation between the foot extensions and the edge ring can be configured to control exhaust flow of radicals and process gas(es) out of the process region

Methodology Applied

Scientific EffectFluid flow through gap:

Implementation Method 2

The observed etch rate non-uniformity at the wafer edge may be caused by back diffusion of reaction by-products from the edge ring to the edge of the wafer

Methodology Applied

Scientific EffectBack diffusion: Diffusion

Implementation Method 3

plasma is generated in the process chamber by ionizing process gas(es) via a high-frequency electromagnetic field

Methodology Applied

Scientific EffectPlasma generation: Plasma

Implementation Method 4

plasma is generated in the process chamber by ionizing process gas(es) via a high-frequency electromagnetic field

Methodology Applied

Scientific EffectIonization: Ionisation

Data Source

PatentUS20250140529A1Etch uniformity improvement in radical etch using confinement ring

Publication Date: 2025.05.01 LAM RES CORP

AI summary

A confinement ring for use in a process chamber includes a tubular extension that is configured to surrounds a process region in the process chamber. An upper end of the tubular extension is configured to connect to a showerhead of the process chamber and a lower end that is configured to extend into the process region and proximate to an edge ring that surrounds a wafer received within the process region. A foot extension has an inner end that joins to the lower end of the tubular extension and extends outwardly from the process region to the outer end. The foot extension provides an annular surface that is configured to form a gap with a top surface of the edge ring.