Backside Irradiation CMOS Sensor Infrared Sensitivity
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Solution Overview
Problem
Back side irradiation CMOS image sensors have reduced sensitivity to infrared light due to a thinner semiconductor substrate, leading to uneven sensitivity among pixels.
Innovation Solution
Incorporating a reflective film between the semiconductor substrate and the wiring layer, with a thicker interlayer film and a reflective film that overlaps with the photoelectric converting unit, optimized in thickness and refractive index to enhance infrared light reflection, and adjusting the shape, size, and position of the reflective film for each pixel to improve sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the semiconductor substrate is made thinner for back side irradiation, then manufacturing is easier, but sensitivity to infrared light decreases
Solution Approach 1:
The patent introduces an intermediary optical structure (the differentially thickened interlayer film) between the thin substrate and the external environment. This intermediary layer with specific thickness variation creates optical interference that compensates for the reduced light absorption in the thinner substrate, particularly for infrared wavelengths, thereby maintaining sensitivity despite substrate thinning for backside irradiation.
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 significantly improves the sensitivity to infrared light and reduces variation among pixels, enhancing the overall performance of the CMOS image sensor.
Implementation Method 1
a reflective film arranged between the insulating film and the wire and overlapping with at least a part of the photoelectric converting unit of each pixel
Implementation Method 2
a first interlayer film between the insulating film and the reflective film, the first interlayer film being thicker than the insulating film
Data Source
AI summary
The present technology relates to an imaging element and an electronic device capable of improving sensitivity to infrared light in a back side irradiation imaging element.An imaging element is provided with a semiconductor substrate on which a photoelectric converting unit is formed, a wiring layer arranged on a side opposite to a light receiving surface of the semiconductor substrate, and provided with a wire and a reflective film, and an insulating film stacked between the semiconductor substrate and the wiring layer, in which the reflective film is arranged between the insulating film and the wire and overlaps with at least a part of the photoelectric converting unit of each pixel in a first direction in which the semiconductor substrate and the wiring layer are stacked, and a first interlayer film between the insulating film and the reflective film is thicker than the insulating film. The present technology is applicable to a back side irradiation CMOS image sensor, for example.