Ramped Ledge Susceptor for Epitaxial Wafer Flatness

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Solution Overview

Problem

Existing susceptor designs for epitaxial deposition lead to back surface defects and uneven deposition rates due to leaking silicon source gas at the wafer notch, causing flatness issues in semiconductor wafers.

Innovation Solution

A susceptor with a ramped ledge design that includes a first surface oriented at a shallow angle and a second surface oriented at a steeper angle, aligned with the wafer notch, to direct the silicon source gas away from the notch, preventing gas leakage and excess epitaxial layer buildup.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a concave or sloped ledge is used in the susceptor design, then damage to the polished back surface is reduced, but source gas leaks at the wafer notch causing excessive growth on the back surface and degrading wafer flatness

Engineering Contradiction:

Improvedamage to polished back surfaceVSAvoidwafer flatness

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The ledge is segmented into multiple surfaces with different orientations: a first surface at a first angle, a second surface at a second angle (greater than the first angle), and a third surface at a third angle. This segmentation allows each surface to perform a specific function in controlling gas flow while maintaining structural support, thereby preventing both back surface damage and gas leakage-induced flatness degradation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the ledge are given different local properties through varying surface angles. The first surface provides gentle support, the second surface (with greater angle) acts as a barrier to gas leakage at the notch, and the third surface completes the transition. This local differentiation of surface angles optimizes both protective and flow-control functions in different regions of the ledge.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If the susceptor rotates during deposition, then even epitaxial layer growth is achieved, but source gas still leaks at the notch causing back surface defects

Engineering Contradiction:

Improveuniformity of epitaxial layer growthVSAvoidback surface defects from gas leakage

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The multi-surface ledge structure acts as an intermediary barrier between the silicon source gas and the wafer notch. The sequence of surfaces with increasing angles creates a progressive barrier that intercepts and redirects gas flow away from the notch, preventing gas from reaching the back surface even during rotation, while still allowing uniform front surface deposition.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 ramped ledge design effectively reduces back surface defects and ensures even deposition rates, improving the flatness of semiconductor wafers by preventing source gas leakage and controlling epitaxial layer thickness near the notch.

Implementation Method 1

The ramped ledge design includes a first surface oriented at a first angle with respect to the upper surface, a second surface oriented at a second angle with respect to the upper surface, and a third surface oriented at a third angle with respect to the upper surface. The second angle is greater than the first angle. This geometric configuration directs the silicon source gas away from the notch, preventing gas leakage.

Methodology Applied

Scientific EffectGas flow direction control through geometric orientation:

Implementation Method 2

A vaporous silicon source gas is introduced to the front surface of the wafer to deposit and grow an epitaxial layer of silicon on the front surface. The ramped ledge design ensures even deposition rates by preventing source gas leakage, controlling epitaxial layer thickness near the notch, and improving the flatness of semiconductor wafers.

Methodology Applied

Scientific EffectEpitaxial deposition: Epitaxy

Data Source

PatentUS10184193B2Epitaxy reactor and susceptor system for improved epitaxial wafer flatness

Publication Date: 2019.01.22 GLOBALWAFERS CO LTD

AI summary

A susceptor supports a semiconductor wafer and includes a substantially cylindrical body comprising an outer rim having an upper surface. The body also includes a recess extending into the body from the upper surface to a recess floor such that the recess is sized and shaped for receiving the wafer therein. The body further includes a ledge extending between the rim and the recess floor. The ledge includes a ramp comprising a first surface, a second surface, and a third surface. The first surface is oriented at a first angle with respect to the upper surface; the second surface is oriented at a second angle oriented with respect to the upper surface; and the third surface is oriented at a third angle with respect to the upper surface. Further, the second angle is greater than the first angle.