Lamp Array Radial Uniformity via Asymmetric Axis Offset

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Solution Overview

Problem

Rapid thermal processing (RTP) systems face challenges in achieving uniform radiation patterns due to radial ripples and excessive heating at the center of substrates, primarily caused by the hexagonal array configuration and the central lamp's position aligned with the rotation axis, leading to inefficiencies in thermal processing.

Innovation Solution

Modifying the RTP system by replacing the center lamp with a non-standard lamp producing a more diffuse pattern, adjusting filament lengths, using diffusing materials, and altering the wafer rotation axis position to reduce radial non-uniformity and ripple effects, while maintaining compatibility with existing reactors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a hexagonal array of lamps is used with the center lamp aligned with the rotation axis, then the substrate can be heated quickly and uniformly, but radial ripples and excessive heating at the center occur

Engineering Contradiction:

Improvethermal processing uniformityVSAvoidradial uniformity

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The patent applies asymmetry by displacing the wafer rotation axis from the geometric center of the hexagonal lamp array. Specifically, the rotation axis is positioned at a distance of 0.05 to 0.15 times the distance between adjacent lamps from the center, creating an asymmetric configuration that eliminates radial ripples and center overheating while maintaining uniform thermal processing across the substrate surface.

Inventive Principle:

Principle #4Asymmetry

2Device complexity

If the center lamp is positioned on the rotation axis, then the lamp array structure is simple and symmetric, but it causes excessive heating at the center and radial non-uniformity

Engineering Contradiction:

Improvelamp array configurationVSAvoidradiation pattern uniformity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent introduces asymmetry into the lamp array configuration by offsetting the wafer rotation axis from the center of the hexagonal arrangement. This asymmetric positioning, while maintaining the overall hexagonal symmetry of the lamp positions, resolves the radiation uniformity issue without requiring complex modifications to the lamp array structure itself.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent applies local quality by creating different thermal conditions in different regions of the substrate. The asymmetric positioning ensures that the center region receives appropriate radiation intensity while edge regions maintain uniform heating, with each area receiving optimized thermal treatment based on its specific requirements.

Inventive Principle:

Principle #3Local quality

3Ease of operation

If standard incandescent lamps are used in a hexagonal array, then the system is simple to operate, but it produces radial ripples in the radiation pattern

Engineering Contradiction:

Improvesystem operation simplicityVSAvoidradiation pattern uniformity

Core Design Contradiction:

Ease of operationVSIllumination intensity

Solution Approach 1:

The patent resolves the radiation pattern uniformity issue through asymmetric positioning of the wafer rotation axis relative to the hexagonal lamp array, rather than modifying the lamps themselves or complicating the control system. This maintains ease of operation while achieving uniform illumination.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent changes the geometric parameter of the system by adjusting the position of the wafer rotation axis. This parameter change, specifically the offset distance of 0.05 to 0.15 times the lamp spacing, transforms the radiation pattern from non-uniform with radial ripples to uniform across the substrate surface.

Inventive Principle:

Principle #35Parameter changes

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

Significant reductions in radiation pattern ripple and non-uniformity are achieved, improving thermal processing consistency and reducing thermal edge effects, with modifications that can be retrofitted onto existing systems.

Implementation Method 1

an array of high-intensity incandescent lamps fit into a lamphead and directed at the substrate or wafer

Methodology Applied

Scientific EffectThermal radiation: Thermal Radiation

Implementation Method 2

using diffusing materials, and altering the wafer rotation axis position to reduce radial non-uniformity and ripple effects

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS7509035B2Lamp array for thermal processing exhibiting improved radial uniformity

Publication Date: 2009.03.24 APPLIED MATERIALS INC

AI summary

A thermal processing chamber includes a substrate support rotating about a center axis and a lamphead of plural lamps in an array having a predetermined difference in radiance pattern between them. The radiance pattern includes a variation in diffuseness or collimation. In one embodiment, the center lines of all of the lamps are disposed away from the center axis. The array can be an hexagonal array, in which the center axis is located at a predetermined position between neighboring lamps.