Protective Wafer Coating for Epitaxial Flatness Control

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Solution Overview

Problem

Existing semiconductor wafer processing methods result in inhomogeneities in radial and circumferential directions, particularly due to fourfold symmetry issues and edge roll-off, affecting the flatness and thickness distribution of the wafers.

Innovation Solution

A method involving protective coating of one side of the wafer and anti-fourfold symmetry etching using a mixture of hydrogen chloride and hydrogen gas to selectively remove or deposit material, ensuring controlled processing of both sides independently, with the use of a protective layer to prevent unwanted material deposition and enhance flatness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional epitaxial coating is performed without protective layer, then material deposition occurs on wafer surfaces, but inhomogeneities and fourfold symmetry defects appear in radial and circumferential directions

Engineering Contradiction:

Improvewafer flatness and thickness uniformityVSAvoidprocess complexity

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

A protective layer is applied to one side of the semiconductor wafer before the epitaxial coating process. This preliminary action prevents material deposition on the protected side, allowing selective processing. The protective layer is removed after processing, revealing the desired thickness profile and eliminating fourfold symmetry defects while maintaining improved manufacturing precision.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The wafer processing is segmented into distinct phases: coating the protective layer on one side, performing the epitaxial deposition, and then removing the protective layer. This segmentation allows independent control of material deposition on different wafer sides, enabling precise thickness control and eliminating the fourfold symmetry problem without requiring complex real-time adjustments.

Inventive Principle:

Principle #1Segmentation

2Productivity

If material is deposited epitaxially on semiconductor wafers, then coating operation is achieved, but material is also deposited within the epitaxial reactor on surfaces requiring subsequent cleaning

Engineering Contradiction:

Improvecoating efficiencyVSAvoidmaintenance requirements

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The harmful effect of uncontrolled material deposition on reactor surfaces is extracted and isolated by applying the protective layer only to the wafer, not to the reactor surfaces. This allows the deposition process to proceed efficiently without requiring extensive cleaning of reactor surfaces, as the protective layer confines material deposition control to the wafer itself.

Inventive Principle:

Principle #2Taking out (Extraction)

3Manufacturing precision

If double-sided polishing is performed to achieve flatness, then both sides are processed simultaneously, but inhomogeneities remain in radial and circumferential directions

Engineering Contradiction:

Improveglobal and local flatnessVSAvoidprocessing operation complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The invention changes the fundamental parameter of material deposition by using epitaxial growth instead of mechanical removal through polishing. By controlling the deposition process with a protective layer, the method achieves superior flatness and thickness uniformity without the inhomogeneities that persist even after double-sided polishing, simplifying the overall processing sequence.

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

The method achieves semiconductor wafers with improved flatness and homogeneous thickness profiles, reducing ESFQRmax to less than 5 nm with minimal edge exclusion, addressing the challenges of fourfold symmetry and edge roll-off.

Implementation Method 1

In the course of the etching step, an etching gas is passed through the coating apparatus. The etching gas preferably consists of a mixture of hydrogen chloride and hydrogen

Methodology Applied

Scientific EffectEtching:

Implementation Method 2

protectively coating one side of a wafer to be treated

Methodology Applied

Scientific EffectProtective coating: Coatings

Implementation Method 3

In epitaxial coating of semiconductor wafers, for example, in an epitaxial reactor, a deposition gas is passed through the epitaxial reactor, as a result of which material can be epitaxially deposited on a surface of the semiconductor wafers

Methodology Applied

Scientific EffectEpitaxial deposition: Epitaxy

Data Source

PatentUS12381074B2Method, control system, and system for machining a semiconductor wafer, and semiconductor wafer

Publication Date: 2025.08.05 SILTRONIC AG

AI summary

The invention relates to an epitaxially coated semiconductor wafer, processed by a method in which the semiconductor wafer is disposed on a susceptor in a coating apparatus and processed, wherein an etching gas is passed through the coating apparatus in an etching step. A first side of the semiconductor wafer which has been subjected to a polishing operation by CMP, or a second side of the semiconductor wafer opposite the first side, is coated with a protective layer before processing. The resulting wafer has exceptional geometry, as reflected by low ESFQR values.