Purge Ring Geometry for Longer Edge Purge Residence in Pedestals

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional edge purging techniques in semiconductor wafer processing chambers experience a cooling effect at the wafer edge due to the pedestal assembly's lower temperature than the wafer, leading to reduced film thickness, necessitating improved methods to increase the residence time of argon (Ar) for effective purging.

Innovation Solution

A pedestal assembly incorporating a purge ring with a plurality of apertures aligned with circumferentially spaced purge outlets on the substrate support, which increases the residence time of the edge purge gas by optimizing gas flow and thermal expansion features, thereby reducing the cooling effect.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional edge purging techniques are used with a pedestal assembly at lower temperature than the wafer, then gas flow can be delivered to the wafer edge, but a cooling effect occurs at the wafer edge leading to reduced film thickness

Engineering Contradiction:

Improvepurge effectivenessVSAvoidwafer edge temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

A purge ring is introduced as an intermediary component between the gas delivery system and the wafer edge. The purge ring includes a circumferential channel that guides and conditions the purge gas flow, allowing the gas to be delivered more effectively to the wafer edge while minimizing direct thermal contact and cooling effects

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent modifies the thermal parameters of the pedestal assembly by adding heating elements to the purge ring and adjusting the temperature profile. The purge ring is heated to a temperature closer to the wafer temperature, reducing the temperature differential and minimizing the cooling effect on the wafer edge during purging

Inventive Principle:

Principle #35Parameter changes

2Temperature

If the pedestal assembly temperature is increased to reduce cooling effect, then wafer edge temperature improves, but thermal uniformity across the wafer may be compromised

Engineering Contradiction:

Improvewafer edge temperatureVSAvoidtemperature uniformity

Core Design Contradiction:

TemperatureVSStability of the object's composition

Solution Approach 1:

The patent applies local heating to the purge ring rather than uniformly heating the entire pedestal assembly. Heating elements are positioned specifically in the purge ring to provide localized thermal energy to the gas flow and immediate surrounding area, maintaining wafer edge temperature without creating excessive temperature gradients across the entire wafer surface

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The heating system is segmented into distinct zones: the main pedestal heater and separate heating elements in the purge ring. This segmentation allows independent control of thermal conditions in different regions, enabling the purge ring to be heated to reduce cooling effects while the main pedestal maintains overall thermal uniformity across the wafer

Inventive Principle:

Principle #1Segmentation

3Reliability

If argon flow rate is increased to improve purging effectiveness, then edge purge performance improves, but residence time decreases reducing temperature increase

Engineering Contradiction:

Improveedge purge effectivenessVSAvoidargon residence time

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The circumferential channel in the purge ring creates a continuous, controlled flow path for the purge gas. This continuous action allows the gas to follow a defined trajectory around the wafer edge, ensuring consistent purging effectiveness while maintaining adequate residence time through optimized channel geometry and flow distribution

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent transitions from direct radial gas delivery to a circumferential flow path in the horizontal plane. The gas flows around the wafer edge in a circular pattern within the purge ring channel, adding a dimensional aspect to the purging process that increases effective contact time with the wafer edge while maintaining purging effectiveness

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 purge ring design enhances thermal uniformity and purge efficiency, increasing the residence time of argon (Ar) and maintaining a higher edge temperature, resulting in improved film thickness and processing outcomes.

Implementation Method 1

The purge ring has a thermal expansion feature

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

wafer backside pressure control can provide improved temperature uniformity of the wafer

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS11976363B2Purge ring for pedestal assembly

Publication Date: 2024.05.07 APPLIED MATERIALS INC

AI summary

Pedestal assemblies, purge rings for pedestal assemblies, and processing methods for increasing residence time of an edge purge gas in heated pedestal assemblies are described. Purge rings have an inner diameter face and an outer diameter face defining a thickness of the purge ring, a top surface and a bottom surface defining a height of the purge ring, and a thermal expansion feature. Purge rings comprise a plurality of apertures extending through the thickness and aligned circumferentially with a plurality of circumferentially spaced purge outlets in a substrate support.