Bonded SOI Wafer Base Oxidation Suppressing Precipitates
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Solution Overview
Problem
The formation of oxide precipitates in the base wafer during the BOX oxidation heat treatment for manufacturing bonded SOI wafers leads to increased density and size, which can impede etching and cause slip dislocation, especially when using wafers with low oxygen concentration and long heat treatment times.
Innovation Solution
A method involving a silicon single crystal base wafer with an initial interstitial oxygen concentration of 15 ppma or more, subjected to a heat treatment at 800° C. or higher in an oxidizing atmosphere, followed by RTA heat treatment, to suppress oxide precipitate nuclei and prevent slip dislocation, while forming a thick silicon oxide film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a thick BOX layer is formed by base oxidation method, then the BOX layer thickness is increased, but the oxide precipitates in the base wafer grow and increase in density and size
Solution Approach 1:
The patent changes the parameter of initial interstitial oxygen concentration in the base wafer from low (≤15 ppma) to high (≥15 ppma). This parameter change allows the base wafer to withstand long-duration BOX oxidation heat treatment without excessive oxide precipitate formation, enabling thick BOX layer formation while maintaining manufacturing precision.
2Manufacturing precision
If a silicon single crystal wafer with low oxygen concentration is used as base wafer, then the oxide precipitates are suppressed, but slip dislocation occurs during heat treatment
Solution Approach 1:
The patent inverts the parameter of initial interstitial oxygen concentration from low to high (≥15 ppma). This high oxygen concentration provides sufficient oxygen reservoir to suppress oxide precipitate formation during heat treatment while preventing slip dislocation, resolving the contradiction between precipitate suppression and structural reliability.
3Length of stationary object
If BOX oxidation heat treatment is performed for long time to form thick BOX layer, then the BOX layer thickness is increased, but the heat treatment time is extremely long
Solution Approach 1:
By changing the initial interstitial oxygen concentration parameter to ≥15 ppma, the base wafer can undergo prolonged BOX oxidation heat treatment without degradation from oxide precipitates. This enables formation of thick BOX layers (several micrometers) that would otherwise be impossible, accepting longer heat treatment time as necessary for achieving the required thickness.
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 reduces the density and size of oxide precipitates and prevents slip dislocation, enabling efficient manufacturing of bonded SOI wafers with desired BOX layer thickness.
Implementation Method 1
forming a silicon oxide film on a surface of the base wafer by performing a heat treatment on the base wafer in an oxidizing atmosphere
Implementation Method 2
oxide precipitates in the base wafer can impede the etching and obstruct the formation of the configurations
Implementation Method 3
when a thick BOX layer is formed on the bond wafer side where the SOI layer is formed, it is necessary to deeply implant the ions forming the delamination layer
Data Source
AI summary
The present invention is a method for manufacturing a bonded SOI wafer, including: preparing, as a base wafer, a silicon single crystal wafer whose initial interstitial oxygen concentration is 15 ppma or more ('79ASTM); forming a silicon oxide film on a surface of the base wafer by heating the base wafer in an oxidizing atmosphere such that a feeding temperature at which the base wafer is fed into a heat treatment furnace for the heat treatment is 800° C. or more, and the base wafer is heated at the feeding temperature or higher; bonding the base wafer to the bond wafer with the silicon oxide film interposed therebetween; and thinning the bonded bond wafer to form an SOI layer. This provides a method for manufacturing a bonded SOI wafer by a base oxidation method which suppresses the formation of oxide precipitates in a base wafer while suppressing slip dislocation.