Flat Bottom Shadow Ring for Uniform Etching

Solution Overview

Problem

Existing Bottom Shadow Rings (BSRs) in semiconductor manufacturing often cause non-uniform radial gradients and depth uniformity issues during deep silicon etch operations, particularly in narrow edge exclusion zones, due to obstructing profiles that can lead to etching and processing defects like black silicon formation and breakage.

Innovation Solution

A flat Bottom Shadow Ring (fBSR) with a radially extending overhang and a flat zone parallel to the substrate's upper surface, which covers the substrate's edge without obstructing profiles, providing a longer radial length and uniform thickness to enhance etching uniformity and prevent defects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional Bottom Shadow Ring with a ramp profile is used to cover the substrate edge, then the edge is protected from etching, but the ramp creates obstructions that cause non-uniform radial gradients, shadows, and no etch zones

Engineering Contradiction:

Improveedge protectionVSAvoidetching uniformity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The invention inverts the traditional ramp profile of the Bottom Shadow Ring by using a flat top surface instead of an inclined ramp. This inversion eliminates the obstructing profile that causes shadows and non-uniform etching, while maintaining the edge coverage function. The flat top surface allows plasma and RF fields to pass uniformly without creating the harmful obstructions associated with traditional ramp designs.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention changes the geometric parameters of the Bottom Shadow Ring by extending the radial length of the flat top surface and optimizing the overhang dimensions. These parameter changes allow the structure to provide adequate edge coverage while maintaining uniform plasma distribution and avoiding the creation of shadow zones that occur with shorter, ramped profiles.

Inventive Principle:

Principle #35Parameter changes

2Area of stationary object

If the radial length of the BSR lip is increased to improve edge coverage, then better protection is achieved, but the ramp profile still causes shadows and misalignment issues

Engineering Contradiction:

Improveedge coverage areaVSAvoidshadows and misalignment

Core Design Contradiction:

Area of stationary objectVSObject-generated harmful factors

Solution Approach 1:

The invention inverts the traditional ramp profile of the Bottom Shadow Ring by using a flat top surface instead of an inclined ramp. This inversion eliminates the obstructing profile that causes shadows and non-uniform etching, while maintaining the edge coverage function. The flat top surface allows plasma and RF fields to pass uniformly without creating the harmful obstructions associated with traditional ramp designs.

Inventive Principle:

Principle #13The other way round (Inversion)

3Device complexity

If a short lip BSR is used, then the structure is simpler, but it cannot deliver uniform radial gradients in narrow edge exclusion zones

Engineering Contradiction:

ImproveBSR structureVSAvoidradial gradient uniformity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The invention changes the geometric parameters of the Bottom Shadow Ring by extending the radial length of the flat top surface and optimizing the overhang dimensions. These parameter changes allow the structure to provide adequate edge coverage while maintaining uniform plasma distribution and avoiding the creation of shadow zones that occur with shorter, ramped profiles.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20230223292A1Flat bottom shadow ring

Publication Date: 2023.07.13 LAM RES CORP

AI summary

In some examples, a flat Bottom Shadow Ring (fBSR) is provided for processing a substrate in a processing chamber. An example fBSR comprises an overhang for covering an edge of the substrate in the processing chamber. The overhang includes a fiat zone that extends radially outward over the outer edge of the substrate.