Vertical Transfer Gate Structure for Deep-Substrate Charge Transfer
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Solution Overview
Problem
Conventional vertical gate electrode structures in semiconductor devices face challenges in generating a strong potential gradient at deep positions within a substrate, making it difficult to efficiently transfer charges from photodiode sections to FD sections, especially as the depth increases.
Innovation Solution
The semiconductor device incorporates a vertical gate electrode with an embedded electrode part that includes an embedded upper electrode and a larger embedded lower electrode on the substrate deep-portion side, forming a rectangular tube to enhance modulation and facilitate charge transfer by increasing the electrode area size in a plan view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the length of the vertical gate electrode is extended to reach deeper positions in the substrate, then the electrode can access deeper photodiode sections, but it becomes difficult to generate a potential gradient in the depth direction
Solution Approach 1:
The patent applies local quality by making the lower electrode larger than the upper electrode in the depth direction. This creates a non-uniform electrode structure where the cross-sectional area varies along the depth, enabling localized enhancement of the electric field at deeper positions. The larger lower electrode provides stronger modulation capability at the target depth region where charge transfer is needed, while the upper electrode maintains connectivity to the surface.
Solution Approach 2:
The patent transitions from a one-dimensional uniform electrode to a three-dimensional structured electrode with varying cross-sectional area. By introducing dimensional variation (larger area at lower depths, smaller area at upper depths), the electrode can generate a potential gradient along the depth direction despite its extended length. This dimensional change enables the electrode to fulfill both requirements: reaching deep positions and generating sufficient potential gradient.
2Reliability
If multiple vertical gate electrodes with different diameters are formed to create a potential gradient, then charge transfer efficiency improves, but device complexity increases
Solution Approach 1:
The patent merges multiple electrode functions into a single integrated electrode structure. Instead of forming separate electrodes with different diameters at different depths, the invention creates one continuous vertical gate electrode whose cross-sectional area naturally varies along the depth direction. This single electrode performs the work of multiple electrodes while reducing structural complexity and manufacturing steps.
Solution Approach 2:
The vertical gate electrode serves multiple functions simultaneously: it provides electrical connection from the surface to deep photodiode sections, generates the potential gradient needed for charge transfer, and acts as the gate control structure. The varying cross-sectional area enables the same electrode structure to achieve both deep penetration and effective charge modulation, embodying multi-functionality.
3Reliability
If the electrode area size is increased at the distal end to intensify modulation, then charge transfer at deep positions improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs preliminary action by forming the gate insulating film with a thickness that gradually decreases toward the transfer destination before the electrode is formed. This pre-established gradient in the insulating film thickness guides the subsequent electrode formation process, ensuring that the electrode achieves the desired larger area at the lower depth region. By preparing the insulating film structure in advance, the manufacturing process becomes more controlled and less sensitive to precision variations.
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 allows for improved charge transfer from deep positions within the substrate by intensifying the electrical field near the bottom of the embedded electrode, enabling more efficient charge accumulation and readout.
Implementation Method 1
This configuration allows for improved charge transfer from deep positions within the substrate by intensifying the electrical field near the bottom of the embedded electrode
Data Source
AI summary
A semiconductor device, a method of manufacturing the semiconductor device, and electronic equipment that make it possible to easily transfer a charge at a deep position in a substrate. A semiconductor device includes a photo-electric converting section, and a transfer transistor that transfers the charge of the photo-electric converting section to a charge accumulation section. The transfer transistor has a vertical gate electrode including an embedded electrode part embedded in a semiconductor substrate. The embedded electrode part includes an embedded upper electrode and an embedded lower electrode on a substrate deep-portion side relative to the embedded upper electrode and that has an electrode area size, in a plan view, greater than an electrode area size of the embedded upper electrode. The present disclosure can be applied to, for example, a solid-state imaging element including, in each pixel, a transfer transistor that transfers a charge accumulated in a photodiode section.