Variable Thickness Ceramic Layer for Arcing Prevention

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Solution Overview

Problem

Substrate processing systems face issues with electrical discharge (arcing) and heat transfer gas ignition due to high RF voltages applied during plasma etch processes, which cause damage to components and non-uniform etch processes, particularly because of the uniformity challenges posed by the thickness of the ceramic layer in substrate supports.

Innovation Solution

Implementing a ceramic layer with varying thickness across its radius, where the center region is thicker (greater than 2 mm) and the outer region is thinner (less than 2 mm), and strategically placing heat transfer gas supply holes under the thinner regions to reduce RF voltage drop and prevent arcing, while maintaining temperature and RF flux uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a uniform thickness ceramic layer is used, then manufacturing is simpler, but electrical arcing and heat transfer gas ignition occur due to high RF voltage drop

Engineering Contradiction:

Improveceramic layer fabricationVSAvoidprevention of electrical arcing

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The ceramic layer is designed with non-uniform thickness, featuring a center region with greater thickness and an outer region with lesser thickness. This local variation in geometry allows different regions to serve different functions: the thicker center provides electrical insulation and protection, while the thinner outer region reduces RF voltage drop and prevents arcing at the edges where heat transfer gas supply holes are located.

Inventive Principle:

Principle #3Local quality

2Strength

If the ceramic layer thickness is increased, then protection to the bond layer is improved, but RF flux uniformity deteriorates

Engineering Contradiction:

Improveprotection to bond layerVSAvoidRF flux uniformity

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

Different thicknesses are applied to different regions of the ceramic layer. The thicker center region provides enhanced protection to the bond layer and substrate support, while the thinner outer region maintains RF flux uniformity across the substrate processing area, preventing hot spots and ensuring consistent plasma distribution.

Inventive Principle:

Principle #3Local quality

3Temperature

If heat transfer gas supply holes are placed under the ceramic layer, then cooling efficiency is improved, but electrical discharge occurs at the holes

Engineering Contradiction:

Improvecooling efficiencyVSAvoidelectrical discharge at gas holes

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The ceramic layer thickness is specifically reduced in the outer region where heat transfer gas supply holes are located. This thinner configuration lowers the RF voltage drop across the ceramic at the hole locations, preventing electrical discharge and ignition of the heat transfer gas, while the thicker center region maintains overall structural integrity and insulation.

Inventive Principle:

Principle #3Local quality

4Manufacturing precision

If the ceramic layer is made thinner, then RF flux uniformity is improved, but protection to the bond layer is reduced

Engineering Contradiction:

ImproveRF flux uniformityVSAvoidprotection to bond layer

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The ceramic layer employs a non-uniform thickness profile where the center region maintains greater thickness to protect the bond layer and substrate support, while the outer region is thinner to ensure RF flux uniformity. This regional differentiation allows both requirements to be satisfied simultaneously without compromise.

Inventive Principle:

Principle #3Local quality

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 configuration reduces the likelihood of arcing and heat transfer gas ignition, enhances temperature and RF flux uniformity, and provides adequate protection to the bond layer, thereby improving the reliability and efficiency of substrate processing systems.

Implementation Method 1

reduce RF voltage drop and prevent arcing

Methodology Applied

Scientific EffectRF voltage drop: Electrical Resistance

Implementation Method 2

heat transfer gas supply holes arranged to supply heat transfer gas to an underside of the ceramic layer

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentUS11069553B2Electrostatic chuck with features for preventing electrical arcing and light-up and improving process uniformity

Publication Date: 2021.07.20 LAM RES CORP

AI summary

A substrate support for a substrate processing system includes a baseplate, a bond layer provided on the baseplate, and a ceramic layer arranged on the bond layer. The ceramic layer includes a first region and a second region located radially outward of the first region, the first region has a first thickness, the second region has a second thickness, and the first thickness is greater than the second thickness.