Microlens Gap Control via Organic Seed Patterns
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Solution Overview
Problem
Existing image sensors with microlenses formed through a single patterning process followed by a reflow process often experience gaps between adjacent microlenses, leading to noise and crosstalk due to insufficient gap reduction, and excessive reflow causes microlenses to merge, forming bridges.
Innovation Solution
The image sensor incorporates a semiconductor substrate with a metal interconnection layer, an inorganic layer, and lens seed patterns made of organic material, which are used to form microlenses that maintain minimum gaps and prevent merging during the reflow process by using hydrophobic organic materials for the lens seed patterns and a hydrophilic inorganic layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single patterning process followed by a reflow process is used to form microlenses, then the manufacturing process is simple, but gaps form between adjacent microlenses causing noise and crosstalk
Solution Approach 1:
The patent applies preliminary action by forming a barrier pattern before forming the microlenses. This barrier pattern is created through photolithography exposure and development processes prior to the reflow step, establishing physical boundaries that prevent gap formation during subsequent heating. The barrier pattern serves as a pre-prepared structure that guides microlens formation and maintains proper spacing.
Solution Approach 2:
The barrier pattern acts as an intermediary element between the substrate and the microlenses. It mediates the interaction during the reflow process by providing a physical barrier that prevents excessive material flow and gap formation, while still allowing the microlenses to form properly on their respective regions.
2Manufacturing precision
If the reflow process is intensified to reduce gaps between microlenses, then gap reduction is achieved, but adjacent microlenses merge forming bridges
Solution Approach 1:
The barrier pattern is formed in advance through photolithography before the reflow process, establishing predetermined boundaries that control microlens spacing. This preliminary structure prevents excessive merging during intensified reflow while maintaining the desired gap reduction, as the barrier pattern physically constrains the material flow during heating.
Solution Approach 2:
The barrier pattern introduces local quality variations by creating regions with different material properties and structures. The patterned barrier areas provide localized resistance to material flow, allowing gaps to be reduced in specific regions while preventing bridge formation in other areas, thus achieving non-uniform control over the microlens spacing.
3Stability of the object's composition
If wide areas between microlenses are not sufficiently reduced, then bridge formation is prevented, but gaps remain causing light detection noise
Solution Approach 1:
The barrier pattern serves as an intermediary structure that actively manages the spacing between microlenses. It provides a physical barrier that prevents excessive material flow and gap formation during reflow, while still maintaining adequate separation to prevent bridge formation. This intermediary structure ensures proper light confinement to corresponding photodiodes, eliminating noise from light leakage through gaps.
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 minimizes gaps between microlenses, inhibits bridge formation, and enhances image sensor quality by maintaining the integrity of adjacent microlenses, thereby improving optical sensitivity and reducing noise and crosstalk.
Implementation Method 1
using hydrophobic organic materials for the lens seed patterns and a hydrophilic inorganic layer
Implementation Method 2
using hydrophobic organic materials for the lens seed patterns and a hydrophilic inorganic layer
Implementation Method 3
The inorganic layer 50 may be formed of a hydrophilic oxide layer
Data Source
AI summary
Provided is an image sensor and method of manufacturing the same. The image sensor can include a semiconductor substrate, a metal interconnection layer, an inorganic layer, lens seed patterns, and microlenses. The semiconductor substrate can include unit pixels. The metal interconnection layer can be disposed on the semiconductor substrate to provide signal and poser connections to the unit pixels. The inorganic layer can be disposed on the metal interconnection layer. The lens seed patterns are selectively disposed on the inorganic layer and are formed of an organic material. The microlenses are formed on the lens seed patterns.