Diode Formation via Masked Implantation on Insulating Layer
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Solution Overview
Problem
The formation of diodes in semiconductor substrates often results in undesirable bipolar effects due to parasitic PN junctions and poorly controlled dopant diffusion, especially when doped regions are directly implanted in the substrate, leading to unpredictability and alignment issues in diode characteristics.
Innovation Solution
A method involving the implantation of dopants of a second type of conductivity in a semiconductor layer on an insulating layer, using projecting regions as a hard mask to form PN junctions that extend to the edge of these regions, thereby avoiding parasitic effects and allowing for precise control of dopant distribution without strict alignment requirements, and alternating P-type and N-type implantations to create diodes suitable for Graetz bridges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If doped regions are directly implanted in the substrate to form diodes, then the diode structure is simple, but parasitic PN junctions are created causing undesirable bipolar effects
Solution Approach 1:
The invention segments the semiconductor structure by introducing an insulating layer that divides the substrate into isolated regions. This segmentation prevents the formation of parasitic PN junctions between adjacent doped regions by electrically isolating them, thereby eliminating undesirable bipolar effects while maintaining structural simplicity.
Solution Approach 2:
The insulating layer acts as an intermediary element between the substrate and the doped regions. This intermediary prevents direct electrical interaction between adjacent doped regions, blocking the formation of parasitic junctions and eliminating harmful bipolar effects without complicating the overall device structure.
2Manufacturing precision
If conventional implantation masks are used for diode manufacturing, then alignment precision is required, but strict alignment is difficult to establish leading to unpredictability
Solution Approach 1:
The insulating layer structure serves as a self-aligning reference that eliminates the need for precise mask alignment. The physical boundaries of the insulating regions automatically define the implantation areas, allowing the process to self-correct and eliminating unpredictability associated with alignment errors.
Solution Approach 2:
The insulating layer is formed beforehand to establish precise physical boundaries before the doping process. This preliminary action creates predetermined implantation zones that eliminate the need for subsequent alignment operations, thereby removing the source of unpredictability and manufacturing difficulty.
3Quantity of substance
If dopant diffusion processes are used in diode manufacturing, then doping can be achieved, but diffusion is poorly controlled leading to unpredictable diode characteristics
Solution Approach 1:
The insulating layer creates locally distinct regions with controlled doping characteristics. Each isolated region can be doped independently with precise control over dopant concentration and distribution, eliminating the poor control and unpredictability associated with conventional diffusion processes.
Solution Approach 2:
The invention enables precise control of dopant distribution by changing the physical parameters of the insulation structure. The thickness, material composition, and geometric configuration of the insulating layer can be adjusted to precisely control dopant diffusion boundaries, achieving predictable and repeatable diode characteristics.
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 approach effectively suppresses bipolar parasitic effects, ensures precise control over dopant diffusion, and allows for the formation of diodes that are fully insulated from the substrate, reducing surface area and maintaining compatibility with non-volatile memory technology without additional critical masking steps.
Implementation Method 1
a first implantation of dopants having a second type of conductivity, of the P-type for example, in a first semiconductor layer having a first type of conductivity
Implementation Method 2
some dopant diffusion processes in the usual diode manufacturing methods are poorly controlled
Data Source
AI summary
A method can be used to make a semiconductor device. A number of projecting regions are formed over a first semiconductor layer that has a first conductivity type. The first semiconductor layer is located on an insulating layer that overlies a semiconductor substrate. The projecting regions are spaced apart from each other. Using the projecting regions as an implantation mask, dopants having a second conductivity type are implanted into the first semiconductor layer, so as to form a sequence of PN junctions forming diodes in the first semiconductor layer. The diodes vertically extend from an upper surface of the first semiconductor layer to the insulating layer.