Pixel Transistor GAA Structure for Noise Shielding and Scaling
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Solution Overview
Problem
The challenge in solid-state imaging apparatus manufacturing is that deepening grooves for pixel transistors can improve noise characteristics but hinder impurity atom injection, reducing impurity concentration and making further miniaturization difficult due to noise interference from wiring.
Innovation Solution
A solid-state imaging apparatus with a GAA structure is formed by having a thicker insulating film on the lower surface of the semiconductor layer, protecting it from noise, and using separate steps to form insulating films and electrodes on different surfaces, allowing for a pseudo GAA structure that enhances noise protection without plasma damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the groove is deepened to improve noise characteristics, then the noise characteristics of the pixel transistor are improved, but the impurity concentration in the channel semiconductor layer and source/drain region is reduced
Solution Approach 1:
The patent divides the insulating film into multiple layers with different thicknesses: a first insulating film layer with greater thickness and a second insulating film layer with lesser thickness. This segmentation allows the lower, thicker layer to provide impurity barrier functionality while the upper, thinner layer provides noise shielding, resolving the contradiction between noise protection and impurity concentration maintenance.
Solution Approach 2:
The patent applies different thicknesses of insulating film at different locations: the first insulating film layer has greater thickness at the lower surface of the channel semiconductor layer where impurity blocking is needed, while the second insulating film layer has lesser thickness at the upper surface where noise shielding is the primary function. This local differentiation resolves the contradiction by optimizing each region for its specific function.
2Reliability
If a GAA structure with combined insulating films from both substrates is used, then noise protection is enhanced, but plasma damage during lamination degrades the insulating film performance
Solution Approach 1:
The patent segments the insulating film formation process into two distinct stages: first forming the first insulating film layer on the first substrate before lamination, then forming the second insulating film layer on the second substrate after lamination. This segmentation prevents plasma damage to the first insulating film during the lamination process while still achieving the dual-function GAA structure for noise protection.
Solution Approach 2:
The patent performs the first insulating film formation as a preliminary action before substrate lamination, when the first substrate is still accessible for processing. This preliminary formation allows the insulating film to be created under optimal conditions without subsequent plasma damage from lamination, while the second insulating film is formed afterward to complete the GAA structure.
Data Source
AI summary
[Object]Provided are a solid-state imaging apparatus that allows a preferred transistor to be formed in a case where a photoelectric conversion section and a floating diffusion section are formed in a semiconductor substrate and a channel semiconductor layer of a transistor is formed in a semiconductor layer different from the semiconductor substrate, and a method for manufacturing the solid-state imaging apparatus.[Solving Means]A solid-state imaging apparatus according to the present disclosure includes a first semiconductor substrate including a photoelectric conversion section and a floating diffusion section, and a first transistor including a first semiconductor layer provided above the first semiconductor substrate, a first insulating film provided on a lower surface, an upper surface, and side surfaces of the first semiconductor layer, and a first electrode provided on a lower surface, an upper surface, and side surfaces of the first insulating film, and the thickness of the first insulating film on the lower surface of the first semiconductor layer is larger than the thickness of the first insulating film on the upper surface or side surfaces of the first semiconductor layer.