Bonded Wafer Surface Roughness via Low-Dose Oxygen Ion Implantation
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Solution Overview
Problem
Existing methods for producing bonded wafers face issues with surface roughness deterioration and crystal defects due to suboptimal oxygen ion implantation and heat treatment conditions, leading to irregular interfaces and increased costs from prolonged high-temperature treatments.
Innovation Solution
Optimizing ion implantation conditions by conducting oxygen ion implantation at low temperatures with controlled doses and short heat treatment times, followed by precise polishing and etching steps to form a smooth Si amorphous layer, and using a reducing atmosphere to enhance bonding strength without requiring special furnaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If oxygen ion implantation is conducted with high acceleration voltage and high dose to form a continuous SiO2 layer, then the interface regularity is improved, but the surface roughness deteriorates and the heat treatment time must be prolonged
Solution Approach 1:
The patent changes the ion implantation parameters from conventional high voltage (150-200 keV) and high dose (5.0×10^16 ions/cm²) to low voltage (100 keV) and low dose (5.0×10^15 ions/cm²). This parameter change prevents excessive oxygen concentration that would form discontinuous SiO2 particles, while the subsequent optimized heat treatment (1100-1200°C for 30-120 minutes) allows sufficient diffusion to form a continuous SiO2 layer with smooth interface and minimal surface roughness
Solution Approach 2:
The patent dynamically optimizes the heat treatment conditions based on the low-dose ion implantation. By controlling the heat treatment temperature (1100-1200°C) and time (30-120 minutes), the oxygen atoms diffuse sufficiently to form a continuous SiO2 layer without requiring prolonged treatment, thus achieving both interface regularity and surface quality
2Manufacturing precision
If heat treatment is prolonged at high temperature to form continuous SiO2 layer, then the interface regularity is improved, but the production cost increases and yield rate decreases
Solution Approach 1:
The patent performs preliminary oxygen ion implantation at low dose (5.0×10^15 ions/cm²) before heat treatment, which creates a foundation for continuous SiO2 layer formation. This preliminary action reduces the burden on the subsequent heat treatment step, allowing continuous layer formation in 30-120 minutes rather than requiring prolonged treatment, thus improving productivity and yield rate
Solution Approach 2:
By changing the ion implantation dose to a lower value (5.0×10^15 ions/cm²), the patent enables the heat treatment to be completed in 30-120 minutes at 1100-1200°C, which is sufficient to form a continuous SiO2 layer without causing excessive surface roughness or requiring extended treatment times that would reduce yield rate
3Quantity of substance
If oxygen ion implantation is conducted at conventional conditions, then the SiO2 layer formation is enhanced, but irregularity is caused at the interface between the implanted layer and surface layer
Solution Approach 1:
The patent changes the oxygen ion implantation parameters to low voltage (100 keV) and low dose (5.0×10^15 ions/cm²), which controls the oxygen concentration distribution to prevent discontinuous SiO2 particle formation. The subsequent heat treatment at 1100-1200°C for 30-120 minutes allows sufficient oxygen diffusion to form a continuous SiO2 layer with a smooth, regular interface between the implanted layer and surface layer
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
The method achieves improved surface roughness and reduced defects in bonded wafers with enhanced thickness uniformity and bonding strength, while maintaining cost-effectiveness and avoiding yield rate decreases.
Implementation Method 1
a step of implanting oxygen ions into the wafer for active layer to form an oxygen ion implanted layer in the active layer
Implementation Method 2
a step of subjecting the wafer for active layer to a heat treatment at a temperature of not lower than 1100°C in a non-oxidizing atmosphere
Implementation Method 3
the implanted oxygen ions are reacted with silicon by the heat treatment at a high temperature to form discontinuous SiO2 particles
Implementation Method 4
a step of grinding a portion of the wafer for active layer in the bonded wafer short of the oxygen ion implanted layer
Implementation Method 5
a step of further polishing or etching the wafer for active layer to expose the oxygen ion implanted layer
Implementation Method 6
a step of bonding the wafer for active layer to a wafer for support layer
Data Source
Figure 1
Figure 2(a)~3
AI summary
In a method for producing a bonded wafer by bonding a wafer for active layer and a wafer for support layer and thinning the wafer for active layer according to the invention, oxygen ions are implanted into the wafer for active layer at a state of holding a temperature of the wafer for active layer below 200°C under a dose of 5×1015 to 5×1016 atoms/cm2, whereby there can be obtained a bonded wafer being excellent in the thickness uniformity after thinning and having a dramatically improved surface roughness.