Asymmetric Preheat Ring Gap for Epitaxial Thickness Uniformity

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Solution Overview

Problem

Conventional epitaxial growth apparatuses experience deviations in epitaxial layer thickness profiles due to misalignment of the susceptor and semiconductor wafer, leading to inhomogeneous reactant gas flow and compromised thickness uniformity, primarily caused by fluctuations in the gap between the preheat ring and susceptor.

Innovation Solution

The epitaxial growth apparatus features a preheat ring with a gap width between the susceptor and preheat ring that is longer in certain areas, particularly opposite the reactant gas inlet, to reduce blowup of atmospheric gas and enhance thermal uniformity, thereby improving the thickness uniformity of the epitaxial layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a preheat ring with center-symmetric structure is used, then thermal uniformity of the susceptor and semiconductor wafer is improved, but misalignment between the susceptor and wafer causes gap fluctuations that lead to inhomogeneous reactant gas flow and thickness deviations

Engineering Contradiction:

Improvethermal uniformityVSAvoidthickness uniformity

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The preheat ring is designed with an asymmetric structure where the gap width varies around the circumference. Specifically, the gap width is smaller in the region opposite to the reactant gas inlet and larger in other regions. This asymmetric gap configuration compensates for the misalignment between susceptor and wafer, ensuring that the reactant gas flows more uniformly across the wafer surface despite the offset, thereby improving thickness uniformity while maintaining thermal uniformity through the preheating function.

Inventive Principle:

Principle #4Asymmetry

2Use of energy by moving object

If the gap between preheat ring and susceptor is reduced for better thermal contact, then preheating efficiency is improved, but misalignment causes inhomogeneous gas flow and thickness deviations

Engineering Contradiction:

Improvepreheating efficiencyVSAvoidthickness uniformity

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The preheat ring incorporates local variation in gap width around its circumference. The gap is made smaller in specific regions (particularly opposite the reactant gas inlet) and larger in other regions. This local quality variation allows the system to maintain good thermal contact in regions where it benefits preheating efficiency while creating a compensatory effect in other regions that corrects for misalignment-induced gas flow non-uniformity, thus achieving both efficient preheating and uniform thickness.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If misalignment between susceptor and wafer occurs, then manufacturing simplicity is maintained, but gap fluctuations cause inhomogeneous reactant gas flow and thickness profile deviations

Engineering Contradiction:

Improvealignment toleranceVSAvoidthickness profile uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The preheat ring is designed with an asymmetric gap width configuration that intentionally creates different gap sizes at different angular positions. The gap width is smaller in the region opposite to the reactant gas inlet and larger in other regions. This asymmetric design compensates for misalignment between susceptor and wafer by creating a flow pattern that uniformizes reactant gas distribution across the wafer surface, thereby maintaining thickness uniformity even when alignment is not perfect.

Inventive Principle:

Principle #4Asymmetry

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 results in improved thickness uniformity of the epitaxial film, reducing deviations by up to 58% compared to conventional methods, as demonstrated in experimental examples.

Implementation Method 1

The preheat ring 60 preheats the reactant gas GP before the reactant gas GP is introduced to the epitaxial film formation chamber and contacts the semiconductor wafer W

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

The preheat ring 60 also preheats the susceptor 20. In this manner, the preheat ring 60 improves the thermal uniformities of the susceptor 20 and the semiconductor wafer before and during a film formation

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

An epitaxial wafer is a semiconductor wafer having an epitaxial film grown in a vapor phase on its surface

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Implementation Method 4

a monocrystalline silicon thin film is grown on a silicon wafer in a vapor phase (epitaxially)

Methodology Applied

Scientific EffectChemical vapor deposition: Chemical Vapour Deposition

Data Source

PatentUS10975495B2Epitaxial growth apparatus, preheat ring, and method of manufacturing epitaxial wafer using these

Publication Date: 2021.04.13 SUMCO CORP

AI summary

An epitaxial growth apparatus that can provide an improved thickness uniformity of an epitaxial film is provided. An epitaxial growth apparatus in accordance with the present disclosure includes a susceptor and a preheat ring surrounding a side of the susceptor having a gap interposed therebetween. A width of the gap at least in part between the susceptor and the preheat ring is set to be longer than a width w1 of the gap between the susceptor and the preheat ring in the vicinity of the reactant gas inlet.