RPO Layer Nitrogen Control for Image Sensor White Pixel Failures
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Solution Overview
Problem
Existing semiconductor image sensors face issues with white pixel failures and charge leakage due to the formation of silicide layers over photo diodes, which are protected by resist protection oxide (RPO) layers, but these layers often have high nitrogen content and deposition rates that can affect film quality and functionality.
Innovation Solution
A semiconductor structure and method for forming an image sensor with a resist protection oxide (RPO) layer having a nitrogen level of 0.35 atomic % or less, using nitrogen-free precursors and controlled deposition rates to prevent silicidation of photo diodes and enhance film quality, thereby reducing white pixel failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a CVD process using silane and N2O as precursors is used to form the RPO layer, then the oxide deposition rate is high (about 40 Å/sec or more), but the nitrogen content in the RPO layer becomes high (adversely affecting photo diode performance)
Solution Approach 1:
The patent changes the chemical parameters of the CVD process by replacing N2O precursor with alternative precursors (such as O3, O2, or H2O), and adjusts deposition conditions to achieve low nitrogen content (≤0.35 atomic %) while maintaining high deposition rates (≥40 Å/sec). This resolves the contradiction by decoupling nitrogen content from deposition rate through parameter optimization.
Solution Approach 2:
The patent converts the potential harm of high nitrogen content into a benefit by establishing precise control over nitrogen levels. By using modified CVD processes with controlled nitrogen introduction, the RPO layer achieves the optimal nitrogen content range that prevents white pixel failures while maintaining protective functionality and high deposition efficiency.
2Ease of manufacture
If the RPO layer has high nitrogen content, then the deposition process is simpler, but white pixel failures occur due to charge leakage in photo diodes
Solution Approach 1:
The patent modifies deposition parameters including precursor selection, temperature control, and pressure conditions to achieve precise nitrogen content control (≤0.35 atomic %). This maintains manufacturing simplicity while dramatically improving film quality and eliminating white pixel failures through optimized process parameters.
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 approach effectively reduces white pixel failures and improves film quality by maintaining a low nitrogen level in the RPO layer, ensuring efficient photoelectric effect operation without adverse effects on deposition rates.
Implementation Method 1
a resist protection oxide (RPO) layer is formed over the photo diode to protect the photo diode from silicide formation
Implementation Method 2
The photo diode is subjected to a light exposure which generates electron and hole charges
Data Source
AI summary
A semiconductor structure includes a transistor formed over a substrate. The transistor includes a transistor gate and at least one source/drain region. The semiconductor structure includes a pre-determined region coupled to the transistor. The semiconductor structure further includes a resist protection oxide (RPO) layer formed over the pre-determined region, wherein the RPO layer has a level of nitrogen of about 0.35 atomic % or less.