Bonded Silicon Wafer Surface Roughness Control
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Solution Overview
Problem
The existing methods for producing bonded silicon wafers using an etching/polishing stop layer result in large interface roughness between SiO2 and silicon substrates, leading to surface roughness issues and the occurrence of blue haze in DSB wafers, which are costly and detrimental to the quality of SOI and DSB wafers.
Innovation Solution
A method involving oxygen ion implantation on silicon wafers with a specific inclination angle (0°<θ≦0.15°) and oxygen concentration (10×10^17/cm^3 to 18×10^17/cm^3) to form an oxygen ion implanted layer, followed by heat treatment, exposure, and removal of the SiO2 layer, with subsequent polishing or heat treatment in a reducing atmosphere to improve surface flatness and prevent blue haze.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-temperature heat treatment above 1200° C. for more than 1 hour is conducted to improve surface roughness, then the surface roughness is reduced, but quality loss such as slipping occurs and cost increases
Solution Approach 1:
The invention optimizes multiple parameters simultaneously: oxygen concentration (1×10^18 to 5×10^18 atoms/cm³), temperature (1000° C. to 1200° C.), and time (30 minutes to 3 hours). This parameter optimization enables the SiO2 layer to form with reduced interface roughness under milder conditions, eliminating the need for extreme high-temperature treatment and preventing quality loss while maintaining cost-effectiveness.
2Productivity
If DSB wafer is produced by direct bonding without oxide film, then the device miniaturization and low power consumption are achieved, but blue haze appears on the wafer surface
Solution Approach 1:
The invention performs preliminary oxygen ion implantation and heat treatment to form a SiO2 layer within the silicon substrate before direct bonding. This pre-formed SiO2 layer acts as a buffer that prevents the formation of blue haze during subsequent processing, enabling DSB wafer production with both miniaturization benefits and improved optical quality.
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 reduces surface roughness of the active layer and eliminates blue haze in DSB wafers, enhancing the quality and uniformity of both SOI and DSB wafers without the need for high-temperature, long-duration processes.
Implementation Method 1
a step of implanting oxygen ions from one-side face of a silicon wafer for active layer to form an oxygen ion implanted layer
Implementation Method 2
a first heat treatment step of heat-treating the silicon wafer composite to strengthen the bonding and to convert the oxygen ion implanted layer into an inner SiO2 layer
Data Source
AI summary
A bonded silicon wafer is produced by a method including an oxygen ion implantation step on a silicon wafer for active layer having the specified wafer face; a step of bonding the silicon wafer for active layer to a silicon wafer for support; a first heat treatment step; an inner SiO2 layer exposing step; a step of removing the inner SiO2 layer; and a planarizing step of polishing a silicon wafer composite or subjecting the silicon wafer composite to a heat treatment in a reducing atmosphere (a second heat treatment step).