SOI Wafer Bonding Speed Control via Pre-Bond Storage
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Solution Overview
Problem
The existing methods for manufacturing SOI wafers often result in the generation of outer-peripheral micro voids due to increased bonding speed, which are difficult to suppress effectively without complex facility modifications or adjustments.
Innovation Solution
A method involving cleaning and drying of wafers with a hydrophilic cleaning liquid, followed by storage for a period of 50 minutes or more in a controlled atmosphere before bonding at a speed of 20 mm/second or less, effectively reducing the generation of outer-peripheral micro voids without requiring new facility investments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bonding speed is increased to improve productivity, then the manufacturing efficiency is improved, but outer-peripheral micro voids are generated reducing bonding quality
Solution Approach 1:
The patent applies preliminary action by storing the cleaned wafers for 50 minutes or more before bonding to allow the water layer thickness to naturally increase. This pre-conditioning of the wafer surface ensures that when bonding occurs at higher speeds, the adequate water layer prevents micro void formation, thus resolving the contradiction between high bonding speed and bonding quality.
2Strength
If plasma treatment is applied to increase bonding strength, then the bonding strength is improved, but bonding speed increases causing outer-peripheral micro voids
Solution Approach 1:
The patent applies preliminary action by implementing a storage step before bonding where cleaned wafers are stored for 50 minutes or more. This allows the water layer on the wafer surface to reach an optimal thickness that enables both strong bonding and controlled bonding speed, counteracting the excessive bonding speed caused by plasma treatment.
Solution Approach 2:
The patent applies parameter changes by controlling the storage time (50 minutes or more), temperature (25±5°C), and humidity (40±20%) to optimize the water layer thickness on the wafer surface. These parameter adjustments ensure that even with plasma treatment increasing bonding strength and speed, the bonding speed remains at 20 mm/second or less, preventing micro void formation.
3Manufacturing precision
If the water layer thickness is increased to suppress micro voids, then bonding quality is improved, but the time required for water layer formation increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the storage temperature (25±5°C) and humidity (40±20%) to optimize the rate of water layer formation. These controlled conditions allow the water layer to reach the necessary thickness for preventing micro voids within 50 minutes or less, balancing bonding quality with time efficiency.
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 allows for the simple suppression of outer-peripheral micro voids during SOI wafer manufacturing, maintaining bonding strength while avoiding facility remodels, thus being economical and productive.
Implementation Method 1
a cleaning step of cleaning the bond wafer and the base wafer with a hydrophilic cleaning liquid
Implementation Method 2
a drying step of drying the cleaned bond wafer and base wafer by at least any one drying method of suction drying and spin drying
Implementation Method 3
a drying step of drying the cleaned bond wafer and base wafer by at least any one drying method of suction drying and spin drying
Implementation Method 4
during the storage, the bond wafer and the base wafer are stored to be in contact with an atmosphere having a temperature of 25±5°C and a humidity of 40±20%
Implementation Method 5
bonding a bond wafer composed of a silicon wafer and a base wafer composed of a silicon wafer at room temperature with a silicon oxide film interposed therebetween
Data Source
Figure 1(a)~1(g)
Figure 2~3
AI summary
The present invention is a method for manufacturing an SOI wafer, including steps of: bonding a bond wafer and a base wafer each composed of a silicon wafer at room temperature with a silicon oxide film interposed therebetween; a thinning the bond wafer; and before the bonding step, cleaning the wafers with a hydrophilic cleaning liquid and drying the cleaned wafers by suction drying or spin drying. After the drying step is ended and before the bonding step is started, the wafers are stored until a state where a bonding speed at which the bonding step is to be performed is 20 mm/second or less. The bonding is performed with the bonding speed of 20 mm/second or less. This provides a method for manufacturing an SOI wafer by which an SOI wafer can be manufactured while generation of outer-peripheral micro voids is suppressed in a simple manner.