BSI Image Sensor Metal Grid Etching for Smooth Sidewalls
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Solution Overview
Problem
Conventional backside illuminated (BSI) image sensors exhibit suboptimal sidewall morphology in their metal grids, affecting performance.
Innovation Solution
A BSI image sensor substrate is developed with a metal material layer and a first nitride layer that defines a metal grid pattern, where the nitride layer serves as a mask in a dry etching process, allowing nitrogen atoms or ions to react with the metal at sidewalls, forming metal nitride and improving sidewall smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional fabrication techniques are used to create metal grids, then the manufacturing process is simple, but the sidewall morphology is suboptimal
Solution Approach 1:
A nitride layer is formed on the metal material layer before the etching process. This preliminary action prepares the surface to enable subsequent nitrogen atom release during etching, which will improve sidewall morphology. The nitride layer serves as a precursor that will decompose during the etching process to provide nitrogen for metal nitride formation at the sidewalls.
Solution Approach 2:
The etching process parameters are modified to include conditions that promote nitrogen atom release from the nitride layer. By controlling etching conditions (such as plasma parameters, temperature, or chemistry), the nitride layer decomposes to release nitrogen atoms that react with metal at the sidewalls to form metal nitride, thereby improving sidewall smoothness and morphology.
2Object-affected harmful factors
If a metal grid is added to prevent optical crosstalk, then optical performance is improved, but the device structure becomes more complex
Solution Approach 1:
The metal grid structure is combined with a nitride layer to form a composite structure. The nitride layer is integrated with the metal material layer, creating a multi-material system where the nitride provides nitrogen atoms during etching to form metal nitride at the sidewalls. This composite approach simultaneously achieves the optical crosstalk prevention function and improved sidewall morphology.
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 solution results in a metal grid layer with smooth sidewalls and enhanced morphology, improving the performance of BSI image sensors by reducing optical crosstalk and enhancing image signal capture.
Implementation Method 1
the first nitride layer is formed to serve as a mask in a first dry etching process for etching the metal material layer and thereby forming a metal grid layer with a plurality of second openings and to be bombarded during the first dry etching process so that nitrogen atoms or ions escape therefrom and react with the metal material at sidewalls of the second openings to form metal nitride
Data Source
AI summary
A backside illuminated (BSI) image sensor substrate and a method of manufacturing a BSI image sensor are disclosed. A first nitride layer (9) is formed on a metal material layer (70), and a first dry etching process is then performed on both the first nitride layer (9) and the metal material layer (70). In this way, during the etching of the metal material layer (70), the first nitride layer (9) is bombarded so that nitrogen atoms or nitrogen ions escape from the first nitride layer (9), during the formation of a metal grid layer (7), the escaping nitrogen atoms or nitrogen ions react with the metal on sidewalls of second openings (7a), forming a metal nitride layer which protects the metal grid at the sidewalls of the second openings (7a) from being damaged. As such, the resulting metal grid layer (7) has smooth sidewalls and good morphology.