Silicon Wafer Drying via Ozone Gas and HF Acid
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Solution Overview
Problem
The challenge in semiconductor wafer processing is to achieve a stable, dry surface state for shipping, as high-speed spin drying can affect the wafer's properties, especially with larger diameters, and existing methods like spin drying are inefficient and may cause deformation due to high centrifugal forces.
Innovation Solution
A processing method using a wafer processing apparatus that jets aqueous hydrofluoric acid, ozone water, and ozone gas at controlled speeds to convert the surface between water-repellent and hydrophilic states, allowing for gentle liquid removal without high-speed rotation, using nozzles to distribute fluids uniformly and a liquid removing gas to facilitate drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-speed spin drying is used to dry the wafer surface, then drying efficiency is improved, but wafer deformation and property changes occur due to high centrifugal forces
Solution Approach 1:
The patent replaces the mechanical spin drying system with a chemical field-based drying method. Ozone gas is introduced to react with and remove the oxide film, and a liquid removing gas is used to evaporate and remove liquid from the surface, eliminating the need for high-speed mechanical rotation and associated centrifugal forces that cause wafer deformation
Solution Approach 2:
The patent uses ozone gas, a strong oxidant, to rapidly remove the oxide film from the wafer surface. This chemical oxidation process replaces the mechanical action of spin drying, achieving effective surface treatment without subjecting the wafer to high centrifugal forces that would cause deformation
2Manufacturing precision
If aqueous hydrofluoric acid is used to remove oxide film, then oxide film removal is improved, but water remains on the surface requiring additional drying steps
Solution Approach 1:
The patent combines multiple functions in a continuous process: aqueous hydrofluoric acid removes the oxide film, followed immediately by ozone gas treatment and liquid removing gas application. This continuous sequence ensures that liquid removal is integrated into the same processing step rather than requiring separate drying operations
Solution Approach 2:
The patent introduces ozone gas and liquid removing gas as intermediary substances that facilitate the transition from wet to dry state. These gases act as mediators that remove both the oxide film and surface liquid, bridging the gap between chemical etching and drying operations
3Manufacturing precision
If the wafer surface is made hydrophilic to prevent contaminant adhesion, then surface cleanliness is improved, but water and liquid films remain on the surface
Solution Approach 1:
The patent dynamically changes the surface property parameter from hydrophilic to hydrophobic by sequential application of different gases. Ozone gas creates a hydrophilic surface for cleanliness, then liquid removing gas transitions the surface to hydrophobic state for liquid removal, demonstrating controlled parameter transformation to achieve multiple objectives
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 method effectively maintains the wafer's properties by reducing processing time, minimizing particle deposition, and avoiding deformation, while allowing for high-quality oxide film formation and surface cleanliness, even for larger diameter wafers, without the need for high-speed spin drying.
Implementation Method 1
the semiconductor wafer is processed with aqueous hydrofluoric acid or hydrogen fluoride gas to remove an oxide film on the surface
Implementation Method 2
the surface is then oxidized by ozone water and the surface is made hydrophilic
Implementation Method 3
the semiconductor wafer is processed with aqueous hydrofluoric acid or hydrogen fluoride gas to remove an oxide film on the surface
Implementation Method 4
using ozone water again, a hydrophilic film is formed on the surface of the semiconductor wafer so as to make the surface hydrophilic
Implementation Method 5
the liquid on the surface of the semiconductor wafer is scattered by spin drying to dry the semiconductor wafer surface
Data Source
Figure 1A
Figure 1B~2
Figure 3
AI summary
A processing method of a semiconductor wafer is provided. The method comprising the steps of: removing at least part of oxide film from a surface of the semiconductor wafer; removing liquid from the surface; and providing at least partial oxide film on the surface by applying an oxidizing gas wherein a gas flow of the oxidizing gas and/or an ambient gas involved by the oxidizing gas is characterized by an unsaturated vapor pressure of the liquid such that the liquid on the surface vaporizes. The above-described steps are conducted in this order.