Solid-state imaging device antireflection structure reflectivity reduction
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Solution Overview
Problem
Conventional solid-state image sensors experience increased processing damage and residue issues due to deep concave moth-eye structures, leading to deteriorated dark characteristics and flare/ghost occurrences, necessitating a method to further decrease reflectivity without these drawbacks.
Innovation Solution
A solid-state imaging device with an antireflection structure featuring multiple types of projections of different heights on the light incident surface, formed through staged processing with varying conditions to minimize reflectivity and prevent processing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the moth-eye structure with deep concave portion is formed by dry etching with long processing time, then the reflectivity is decreased, but the processing damage increases and dark characteristic is deteriorated
Solution Approach 1:
The patent divides the single deep etching process into multiple sequential etching steps with different conditions. The first etching step creates initial concave portions, and the second etching step forms projections of different heights. This segmentation allows control of processing damage while achieving the desired antireflection structure.
Solution Approach 2:
The first etching step performs preliminary action by creating initial concave portions before the second etching step forms the final multi-height projection structure. This preliminary action prepares the surface for subsequent processing while limiting initial damage accumulation.
2Object-affected harmful factors
If the moth-eye structure with deep concave portion is formed, then the reflectivity is decreased, but the residue occurs in post process due to increased unevenness
Solution Approach 1:
The patent segments the etching process into two distinct steps with different parameters. The first step creates a controlled initial structure, and the second step refines it into the final multi-height projection structure. This segmentation reduces cumulative processing damage and residue compared to a single long etching process.
Solution Approach 2:
The patent changes etching parameters (such as etching time, power, gas flow rate) between the first and second etching steps. These parameter changes allow optimization of each step to achieve the desired structure while minimizing processing damage and residue formation.
3Object-affected harmful factors
If the fine uneven structure is periodically arranged to prevent light reflection, then the flare and ghost are decreased, but the processing complexity increases
Solution Approach 1:
The patent simplifies processing complexity by dividing the formation of the fine uneven structure into two etching steps rather than requiring a single complex step. This segmentation makes the process more controllable and easier to manufacture while achieving the same antireflection effect.
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 effectively reduces reflectivity to 1% or less across specific wavelengths, improving image sensitivity and preventing flare/ghost issues while maintaining excellent device characteristics.
Implementation Method 1
a structure in which a fine uneven structure is periodically arranged, a so-called moth-eye structure is known. In the moth-eye structure, a refractive index gradually changes, so that reflectivity may be decreased.
Data Source
AI summary
The present disclosure relates to a solid-state imaging device capable of further decreasing reflectivity, a method of manufacturing the same, and an electronic device. The solid-state imaging device includes a semiconductor substrate on which a photoelectric converting unit is formed for each of a plurality of pixels, and an antireflection structure provided on a light incident surface side from which light is incident on the semiconductor substrate in which a plurality of types of projections of different heights is formed. The antireflection structure is formed by performing processing of digging a light incident surface of the semiconductor substrate in a plurality of stages with different processing conditions. The antireflection structure is the structure in which a second projection lower than a first projection is formed between the first projections of predetermined height. The present technology may be applied to a CMOS image sensor, for example.