Imaging Device Ion Implantation for Charge Isolation
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Solution Overview
Problem
Existing imaging devices struggle to suppress the mixing of electric charges generated at deep positions of semiconductor substrates into photoelectric conversion portions of adjacent pixels when exposed to long wavelength light, such as infrared, due to difficulties in forming P-type semiconductor regions at the required depths, leading to inefficient charge isolation.
Innovation Solution
A manufacturing method for imaging devices that involves ion-implanting impurity ions of a second conductivity type into specific regions using masks with varying thicknesses and apertures to create continuous P-type semiconductor regions at different depths, forming effective potential barriers that prevent charge mixing across pixel boundaries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick mask is used to prevent impurity permeation in the second ion implantation step, then electrical isolation is improved, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The patent divides the mask formation process into two separate steps with different mask thicknesses. The first mask is formed with a thickness that allows impurity permeation for creating the P-type semiconductor region at a first depth, while the second mask is formed with a greater thickness to prevent impurity permeation for creating the P-type semiconductor region at a second depth. This segmentation of the masking process enables precise control over impurity distribution at different depths.
Solution Approach 2:
The first mask is formed preliminarily before the second mask in the manufacturing sequence. This preliminary action allows the P-type semiconductor region at the first depth to be established before proceeding to form the P-type semiconductor region at the second depth with the second mask, ensuring proper layering and electrical isolation.
2Object-affected harmful factors
If ion implantation is performed to create P-type semiconductor regions at deep positions, then charge mixing suppression is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by creating P-type semiconductor regions at different local depths within the semiconductor substrate. The first P-type semiconductor region is formed at a first depth under the photoelectric conversion portion, while the second P-type semiconductor region is formed at a second depth under the element isolation region. Each region has locally optimized properties to address specific isolation requirements at different depths.
Solution Approach 2:
The patent changes the parameter of mask thickness between two separate ion implantation steps. The first mask has a thickness that permits impurity permeation at controlled levels, while the second mask has a greater thickness to prevent impurity permeation. This parameter change enables precise control over the depth and concentration profiles of the P-type semiconductor regions.
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 method effectively suppresses the mixing of electric charges from deep positions into adjacent pixel photoelectric conversion portions, enhancing sensitivity to long wavelength light while maintaining electrical isolation and stability of peripheral circuits.
Implementation Method 1
ion-implanting impurity ions of a second conductivity type different from the first conductivity type into a first region and a second region using a first mask
Data Source
AI summary
A manufacturing method of an imaging device includes ion-implanting impurity ions of a second conductivity type into a first region and a second region using a first mask, the first region being disposed under a region to be an electric charge accumulation region and the second region being under an element isolation portion, continuous with the first region, and positioned shallower than the first region, and ion-implanting impurity ions of the second conductivity type into a third region and a fourth region using a second mask, the third region being disposed under the region and positioned shallower than the first region, and the fourth region being under the element isolation portion, continuous with the third region and the second region, and positioned shallower than the third region and the second region, wherein the first and the second mask cover a part of the element isolation portion and have an aperture.