Deep Trench Sidewall Passivation Under Low Thermal Budget
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for passivating sidewalls of back side deep trenches in CMOS image sensors face challenges due to limited thermal budget and high dark current issues, especially in high-volume manufacturing, as high-k layers like AlOx and TaOx cannot sustain high thermal budgets.
Innovation Solution
A method involving plasma doping and low-temperature thermal treatments is used to form a doped layer along the sidewalls and base of trenches, followed by a dielectric layer formation, which enhances sidewall passivation and reduces dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-k layers (AlOx, TaOx) are used for deep trench isolation passivation, then sidewall passivation is achieved, but thermal budget is exceeded and dark current increases
Solution Approach 1:
The patent changes the doping parameters by using plasma doping at room temperature followed by low-temperature thermal treatment (400-450°C for 30-60 minutes), which achieves effective sidewall passivation without exceeding the thermal budget constraints imposed by front-side metallization processes
Solution Approach 2:
The patent replaces the conventional high-temperature thermal oxidation process with plasma doping (ion implantation) followed by low-temperature thermal treatment, substituting a mechanical/chemical doping mechanism for a purely thermal oxidation mechanism to achieve passivation at lower temperatures
2Temperature
If reduced implantation dose is used in high-k layer approach, then thermal budget is reduced, but dark current increases
Solution Approach 1:
The patent optimizes the doping dose parameter to achieve effective passivation at lower doses compared to conventional methods, while the low-temperature thermal treatment activates the dopants efficiently, achieving good passivation with reduced implantation dose and consequently lower dark current
Solution Approach 2:
The patent introduces a low-temperature thermal treatment process as an intermediary step between plasma doping and dielectric layer formation, which activates the dopants and improves passivation quality without requiring high implantation doses or high temperatures
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 improves sidewall passivation, elevates hole concentration, and significantly reduces conduction peak voltage while enhancing dark current characteristics.
Implementation Method 1
performing a plasma treatment to form a doped layer along the base and along each of the set of sidewalls
Implementation Method 2
performing a thermal treatment on the doped layer
Implementation Method 3
performing a thermal treatment on the doped layer, and forming a dielectric layer over the doped layer following the thermal treatment
Data Source
AI summary
The disclosure provides approaches for forming complementary metal-oxide-semiconductor image sensors having passivated sidewalls using plasma doping and low-temperature thermal processes. One approach may include a method may include providing a main body of a complementary metal oxide semiconductor image sensor, and forming a plurality of trenches in a back side of the main body, wherein each of the plurality of trenches includes a set of sidewalls and a base extending between the set of sidewalls. The method may further include performing a plasma treatment to form a doped layer along the base and along each of the set of sidewalls, performing a thermal treatment on the doped layer, and forming a dielectric layer over the doped layer following the thermal treatment.