The role of silicon wafers in BOE etching process

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Process Technology

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Release time:

2025-05-12

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Buffered Oxide Etch (BOE) is a commonly used wet etching technique in semiconductor manufacturing, primarily used to remove the oxide layer from the surface of silicon wafers. Silicon wafers, as the core material in the etching process, directly impact the etching results through their properties and behavior. This article will analyze the mechanism of silicon wafers in the BOE corrosion process from multiple perspectives to provide a reference for optimizing the etching process.

I. Silicon Wafers as the Main Body of the Chemical Reaction

1. Chemical Reaction Mechanism

The main component of silicon wafers, silicon, undergoes the following chemical reaction with hydrofluoric acid (HF) in the BOE solution:

Si + 4HF → SiF₄↑ + 2H₂↑

This reaction causes the silicon on the surface of the silicon wafer to gradually corrode and dissolve, removing the oxide layer.

2. Factors Affecting Corrosion Rate

Silicon Purity: High-purity monocrystalline silicon exhibits a stable corrosion rate under specific BOE conditions

Crystal Structure: The atomic arrangement density of different crystal orientations affects the reaction activity

Defects and Impurities: May alter the surface chemical state, leading to abnormal corrosion rates

II. Protective Film Formation and Its Role

1. Formation of Fluorosilicate Protective Film

During the corrosion process, a side reaction produces fluorosilicates (such as Na₂SiF₆), forming a protective film on the surface of the silicon wafer: SiF₄ + 2NaF → Na₂SiF₆

2. Functions of the Protective Film

Slows down the corrosion rate: Limits the contact of reactants through physical blocking

Controls the corrosion depth: Precise control of film thickness and stability can be achieved by adjusting process parameters

Improves process controllability: Provides dimensional accuracy assurance for semiconductor device manufacturing

III. Factors Affecting Corrosion Uniformity

1. Crystal Orientation Effect

Differences in corrosion rates for different crystal orientations:

Crystal Orientation	Corrosion Rate	Reason
(100)	Faster	Lower atomic density
(110)	Medium	Medium atomic density
(111)	Slower	Highest atomic density

2. Surface State Influence

Surface roughness: Uneven surfaces lead to differences in local corrosion rates

Pretreatment requirements: Polishing can improve surface flatness and ensure uniform corrosion

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