Etch Stop Layer for CMOS Image Sensor Photodiode Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The manufacturing of CMOS image sensors faces challenges in efficiently removing opaque capping layers over photodiodes without damaging the photodiode or reducing light transmittance, especially in multi-layered structures where etching processes are difficult and can lead to residual opaque materials blocking light.
Innovation Solution
A method involving the formation of an etch stop layer pattern over the photodiode and a multi-layered structure with opaque and transparent layers, where the etch stop layer prevents the transparent lower portion from being etched, allowing for controlled etching to expose the photodiode while minimizing residual opaque material, thus enhancing light transmittance and protecting the photodiode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an opaque capping layer is formed to prevent copper diffusion, then copper diffusion is prevented, but light transmittance to the photodiode is blocked
Solution Approach 1:
The capping layer is segmented into two distinct layers: a lower opaque capping layer (first capping layer) for copper diffusion prevention and an upper transparent capping layer (second capping layer) for light transmittance. This segmentation allows each layer to fulfill its specific function without compromising the other, resolving the contradiction between copper protection and light transmission.
2Illumination intensity
If etching is performed to remove opaque material over photodiode, then light transmittance is improved, but photodiode damage occurs
Solution Approach 1:
The etch stop layer is formed preliminarily over the photodiode before the opaque capping layer is deposited. This preliminary action creates a protective barrier that prevents etching damage to the photodiode during subsequent manufacturing processes, while still allowing the opaque capping layer to be formed and later removed selectively to improve light transmittance.
Solution Approach 2:
The etch stop layer acts as an intermediary protective layer between the photodiode and the etching process. It prevents direct contact between the etchant and the photodiode, thereby protecting the photodiode from damage while enabling the necessary etching operations to remove opaque materials and improve light transmittance.
3Reliability
If multi-layered structure is used to protect photodiode, then photodiode protection is improved, but manufacturing complexity increases
Solution Approach 1:
The etch stop layer serves multiple functions: it protects the photodiode during manufacturing, acts as a barrier layer, and enables selective etching of the opaque capping layer. By combining multiple functions into a single layer, the design achieves photodiode protection without proportionally increasing manufacturing complexity.
Solution Approach 2:
The invention changes the material parameters of the capping layers, using an opaque material for the first capping layer and a transparent material for the second capping layer. This parameter change allows the layers to be differentiated and processed selectively, simplifying the manufacturing process while maintaining photodiode protection.
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 effectively reduces damage to the photodiode and improves light transmittance, enhancing the electrical characteristics and reliability of the image device by ensuring precise removal of opaque layers without exposing the photodiode or blocking light.
Implementation Method 1
an etch stop layer pattern is formed on the first structure. The etch stop layer pattern is positioned over the photodiode
Implementation Method 2
The opaque capping layer may prevent copper included in the copper wire from being easily diffused
Implementation Method 3
The CMOS image sensor may convert an optical image into an electrical signal by using a photodiode
Data Source
AI summary
In methods of manufacturing an image device, a first structure including a transparent lower portion and an opaque upper portion is formed on a substrate having a photodiode. An etch stop layer pattern positioned over the photodiode is formed on the first structure. A second structure having at least one opaque capping layer is formed on the first structure to cover the etch stop layer pattern. An opening partially exposing the lower portion of the first structure is formed over the photodiode by etching the second structure, the etch stop layer pattern and the opaque upper portion of the first structure.