Handling Wafer Oxide Protection via Thermal Inversion

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Solution Overview

Problem

The existing semiconductor fabrication methods fail to adequately protect the back side of handling wafers during thermal oxidation, leading to defects and malfunctions in the circuit elements due to direct contact with supporting pins, which results in incomplete oxide coverage and subsequent damage.

Innovation Solution

The method involves flipping the handling wafer during thermal oxidation to ensure the back side is protected, followed by a wet cleaning process to remove the oxide layer partially and form additional oxide layers for better coverage, and using a nitride layer for enhanced protection, thereby preventing pin-induced defects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the substrate is placed with the back side down on supporting pins during thermal oxidation, then the oxidation process can be performed, but the back side of the substrate is not well protected and the supporting pin region is damaged

Engineering Contradiction:

Improvecircuit functionVSAvoidpin-induced damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The substrate is inverted during the thermal oxidation process, placing the front side down on the supporting pins instead of the back side. This inversion ensures that the back side is properly protected by the oxide layer formed during oxidation, preventing pin-induced damage while maintaining circuit functionality.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If the substrate is flipped during thermal oxidation to protect the back side, then pin-induced defects are prevented, but additional process steps are required

Engineering Contradiction:

Improveback side protectionVSAvoidfabrication process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The substrate is pre-inverted before the thermal oxidation process begins, so that the correct side (front side) is positioned on the supporting pins from the start. This preliminary positioning action ensures proper oxide layer formation on the back side without requiring complex mid-process interventions or additional protective measures.

Inventive Principle:

Principle #10Preliminary action

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 approach effectively prevents pin-induced defects by ensuring comprehensive oxide coverage on the back side of the handling wafer, maintaining circuit functionality and integrity during subsequent fabrication processes.

Implementation Method 1

A first oxide layer is formed surrounding the substrate

Methodology Applied

Scientific EffectThermal oxidation: Oxidation

Implementation Method 2

A portion of the first oxide layer is removed to expose the front side of the substrate

Methodology Applied

Scientific EffectWet cleaning:

Data Source

PatentUS10109474B1Method for fabricating handling wafer

Publication Date: 2018.10.23 UNITED MICROELECTRONICS CORP

AI summary

A method for fabricating handling wafer includes providing a substrate, having a front side and a back side. The front side of the substrate is disposed on a supporting pin. A first oxide layer is formed surrounding the substrate. A portion of the first oxide layer is removed to expose the front side of the substrate. An alignment mark is formed on the front side of the substrate.