Light-Receiving Device Self-Alignment for Balanced Charge Transfer
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Solution Overview
Problem
In miniaturized pixel structures of distance measuring sensors, the alignment accuracy of the hole storage layer reduces, leading to an imbalance in transfer capability between transfer transistors, which compromises distance measurement accuracy.
Innovation Solution
A light receiving device with an embedded photodiode having a charge storage layer of a second conductivity type surrounded by the gates and sidewalls of transfer and discharge transistors, ensuring balanced transfer capabilities through self-alignment during manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the pixel is miniaturized to improve integration and reduce device size, then productivity and device compactness are improved, but alignment accuracy of the hole storage layer deteriorates, causing imbalance in transfer capability between transfer transistors and reducing distance measurement accuracy
Solution Approach 1:
The gates and sidewalls of the transfer transistors are formed in advance before forming the hole storage layer. These pre-formed structures serve as alignment references that ensure the hole storage layer is positioned accurately relative to the transfer transistors, even in miniaturized pixels where alignment accuracy is critical for maintaining balanced transfer capability.
2Volume of moving object
If the pixel is miniaturized to improve integration, then device compactness is improved, but distance measurement accuracy deteriorates due to broken balance of transfer capability
Solution Approach 1:
By forming the gates and sidewalls of transfer transistors before the hole storage layer, the patent establishes precise alignment references that ensure uniform charge distribution to all transfer transistors. This preliminary structuring maintains balanced transfer capability in miniaturized pixels, preserving distance measurement accuracy despite reduced pixel size.
3Measurement precision
If self-alignment manufacturing method is used to maintain balance of transfer capability, then distance measurement accuracy is improved, but device complexity increases due to additional manufacturing steps
Solution Approach 1:
The patent combines multiple functions into the gates and sidewalls of the transfer transistors, which serve both as transistor control elements and as alignment reference structures for the hole storage layer. This merging eliminates the need for separate alignment reference structures, reducing overall device complexity while maintaining the benefits of self-alignment manufacturing.
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
Maintains the balance of transfer capability between transistors, thereby improving distance measurement accuracy in miniaturized pixel structures.
Implementation Method 1
a charge generated by photoelectrically converting received reflected light
Data Source
AI summary
The present technology relates to a light receiving device, a method for manufacturing the same, and a distance measuring device capable of improving distance measurement accuracy by maintaining the balance of transfer capability between transfer transistors.A light receiving device includes a pixel including: an embedded photodiode having a charge storage layer of a second conductivity type different from a first conductivity type of a photoelectric conversion region in a region in the vicinity of a second surface on the opposite side to a first surface that is a light incident surface of a substrate; at least two transfer transistors that transfer a charge stored in the photodiode; and at least one discharge transistor that discharges a charge stored in the photodiode; in the light receiving device, the charge storage layer of the second conductivity type is placed to be, in a planar view, surrounded by gates and sidewalls of the transfer transistors, or gates and sidewalls of the transfer transistors and the discharge transistors. The present technology can be applied to, for example, a distance measuring module that measures the distance to a subject, or the like.