Back-Illuminated CMOS Pixel Isolation via Insulating Trenches
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Solution Overview
Problem
In solid-state imaging devices, particularly CMOS and CCD types, color mixing due to electron leakage from the back surface of the device substrate to adjacent pixels leads to signal characteristic deterioration, and existing methods like deep trench formation with metal embedding cause interference, resulting in noise and image quality degradation.
Innovation Solution
A solid-state imaging device with a semiconductor substrate featuring recessed portions between photoelectric conversion units, filled with an insulating film and a convex-shaped light shielding portion on the back surface to prevent electron leakage, improving light shielding without degrading image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a deep trench is formed and metal is embedded to suppress color mixing, then color mixing is suppressed, but interference characteristics deteriorate causing noise and white spots
Solution Approach 1:
The patent removes the metal material from the trench structure, keeping only the insulating film filling. This extraction of the harmful metal component eliminates the interference effects (noise and white spots) while maintaining the light-shielding function through the insulating film alone, thus resolving the contradiction between color mixing suppression and image quality
Solution Approach 2:
The patent uses a simple insulating film material instead of expensive metal embedding, achieving the light-shielding function with a less complex, easier-to-manufacture material that avoids the interference problems associated with metal while maintaining effective color mixing suppression
2Ease of manufacture
If ion implantation is performed from the front surface to form impurities for element isolation, then element isolation is achieved, but ions diffuse in transverse direction making it difficult to suppress color mixing in deep positions
Solution Approach 1:
Instead of performing ion implantation from the front surface (conventional approach), the patent performs ion implantation from the back surface of the semiconductor substrate. This inverted approach allows ions to reach deep positions directly without transverse diffusion, enabling effective color mixing suppression at the back surface where photoelectric conversion occurs most frequently
Solution Approach 2:
The patent changes the direction dimension of ion implantation from front-surface (top-down) to back-surface (bottom-up) approach. This dimensional change in the implantation process allows precise control of impurity distribution at deep positions without transverse spreading, effectively addressing color mixing at the photoelectric conversion region
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 effectively suppresses color mixing, enhances light shielding, and maintains image quality by preventing electron leakage and reducing noise and dark current issues.
Implementation Method 1
a plurality of photoelectric conversion units, each of which receives light to generate charges
Implementation Method 2
a light shielding portion that is laminated on the insulating film and is formed into a convex shape protruding to the semiconductor substrate
Data Source
AI summary
The present disclosure relates to a solid-state imaging device and a manufacturing method of the same, and an electronic apparatus, capable of more reliably suppressing occurrence of color mixing. A trench is formed between PDs so as to be opened to a light receiving surface side of a semiconductor substrate on which a plurality of the PDs, each of which receives light to generate charges, are formed, an insulating film is embedded in the trench and the insulating film is laminated on a back surface side of the semiconductor substrate. Then, a light shielding portion is formed so as to be laminated on the insulating film and to have a convex shape protruding to the semiconductor substrate at a location corresponding to the trench. The present technology can be applied to a back surface irradiation type CMOS solid-state imaging device.