Stacked Pixel Lens Layout for Uniform Light Condensing
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Solution Overview
Problem
The challenge in solid-state imaging devices is the variation in light condensing characteristics caused by the presence of in-layer lenses, leading to deterioration of device characteristics and reduced yield due to irregularities in the planarization process, particularly near the boundary between the imaging device region and peripheral circuits.
Innovation Solution
A solid-state imaging device with a stacked structure including an in-layer lens layer, a planarization layer, and an on-chip lens layer, where the in-layer lens layer has structures at a height equal to the in-layer lenses, provided outside the imaging device region to maintain planarity and prevent irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If in-layer lenses are formed on the semiconductor substrate to improve light condensing efficiency, then sensitivity is improved and stray light is reduced, but variations in light condensing characteristics occur among on-chip lenses due to planarization irregularities
Solution Approach 1:
The patent applies local quality by providing a planarization film specifically in regions where in-layer lenses are formed, while omitting it in regions where on-chip lenses are formed. This localized approach allows the in-layer lenses to be properly planarized for improved light condensing efficiency, while preventing the planarization film from causing variations in on-chip lens characteristics. The selective placement of the planarization film addresses the uniformity issue without compromising the light condensing efficiency of in-layer lenses.
Solution Approach 2:
The patent segments the substrate into distinct regions: an imaging device region where in-layer lenses are formed with a planarization film, and a region where on-chip lenses are formed without the planarization film. This segmentation allows different planarization treatments to be applied to different lens types, thereby resolving the contradiction between improving light condensing efficiency for in-layer lenses and maintaining uniformity for on-chip lenses.
2Stability of the object's composition
If a planarization film is provided over the entire substrate to eliminate surface irregularities, then planarity is improved, but the film extends into the imaging device region causing variations in on-chip lens characteristics
Solution Approach 1:
The patent applies local quality by restricting the planarization film to specific regions (imaging device region with in-layer lenses) while excluding it from other regions (on-chip lens regions). This selective application maintains planarity where needed for in-layer lens performance, while preventing the film from causing variations in on-chip lens characteristics in regions where it is not provided.
Solution Approach 2:
The patent extracts the planarization film from regions where on-chip lenses are formed, removing the source of variation caused by the film's presence. By taking out the planarization film from specific regions while retaining it in others, the patent eliminates the harmful effect on on-chip lens uniformity while preserving the beneficial planarity in in-layer lens regions.
3Manufacturing precision
If the planarization process is intensified to completely eliminate steps at region boundaries, then surface uniformity is improved, but processing complexity and time increase
Solution Approach 1:
The patent applies preliminary action by strategically positioning the planarization film before the planarization process, such that it naturally limits the planarization effect to specific regions. This preliminary configuration of the planarization film structure prevents boundary step formation without requiring additional or intensified planarization processing, thereby achieving uniformity at region boundaries while avoiding increased processing time.
Solution Approach 2:
The planarization film acts as an intermediary that selectively enables planarization in certain regions while preventing it in others. By serving as a regional mediator, the film achieves uniformity at boundaries between imaging device regions and other regions without requiring intensified processing, as the film itself controls where planarization occurs.
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 configuration suppresses variations in light condensing characteristics among on-chip lenses, preventing deterioration of device characteristics and reducing yield issues by ensuring a uniform planar surface and consistent light focusing.
Implementation Method 1
a multi-lens structure in which in-layer lenses (also referred to as 'inner lenses') are formed on a lower layer than on-chip lenses... for efficiently introducing the light incident on each pixel to the photoelectric conversion element
Implementation Method 2
Providing the in-layer lens produces not only an effect of improving the sensitivity but also an effect of reducing stray light that causes flare as a result of condensing light that has been incident on the periphery of a light shielding section formed on the surface of one photoelectric conversion section to neighborhoods of the center of the photoelectric conversion section
Implementation Method 3
a planarization film is provided immediately on the in-layer lenses to provide a planar surface and the color filters and the on-chip lenses are then stacked on the surface
Implementation Method 4
a planarization process is performed to subject a surface of this oxide film to polishing and grinding by an approach such as chemical mechanical polishing (CMP) and to eliminate irregularities on the surface of the oxide film
Data Source
AI summary
The deterioration of light condensing characteristics of an overall solid-state imaging device resulting from providing in-layer lenses is suppressed while preventing the deterioration of device characteristics of the solid-state imaging device and reduction of yield. A solid-state imaging device including: a semiconductor substrate on which a plurality of photoelectric conversion devices are arranged in an imaging device region in a two-dimensional array; and a stacked body formed by stacking a plurality of layers on the semiconductor substrate, wherein the stacked body includes an in-layer lens layer that has in-layer lenses each provided at a position corresponding to each of the photoelectric conversion devices; a planarization layer that is stacked on the in-layer lens layer and that has a generally planarized surface; and an on-chip lens layer that is an upper layer than the planarization layer and that has on-chip lenses each provided at a position corresponding to each of the photoelectric conversion devices, and the in-layer lens layer has a plurality of structures at a height generally equal to a height of the in-layer lenses, the plurality of structures being provided on an outside of the imaging device region.