Semiconductor Substrate Leakage Current Control
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Solution Overview
Problem
Semiconductor devices experience significant leakage current issues due to low dopant concentration in parasitic PNP transistor bases, which is exacerbated by the shrinking size of semiconductor components, leading to inefficiencies and increased processing costs.
Innovation Solution
The implementation of heavily doped buried layers and buried well regions with opposite conductivity types in the semiconductor substrate, creating multiple PN junctions both vertically and horizontally, prevents leakage current by arranging well regions in a staggered manner within the epitaxial layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the size of semiconductor devices is reduced to follow Moore's law, then the operation speed and processing technique are improved, but the leakage current becomes more significant
Solution Approach 1:
The semiconductor substrate is segmented into multiple regions with different conductivity types (P-type and N-type buried well regions, P-type and N-type buried layers). This segmentation creates multiple PN junctions that divide and control the current flow paths, preventing leakage current while maintaining device miniaturization and speed performance.
Solution Approach 2:
Different regions of the semiconductor substrate are assigned different doping concentrations and conductivity types locally. The buried well regions and buried layers have heavily doped regions with high dopant concentration specifically positioned to block leakage current paths, while other regions maintain appropriate doping for device operation. This local quality variation allows simultaneous achievement of high speed and low leakage current.
2Object-generated harmful factors
If heavily doped buried layers and buried well regions are disposed in the semiconductor substrate to prevent leakage current, then leakage current is reduced, but the device structure becomes more complex
Solution Approach 1:
The P-type and N-type buried well regions are merged into a single substrate along with the P-type and N-type buried layers to form an integrated multi-layer structure. This merging approach consolidates multiple doping regions into a unified architecture that prevents leakage current while avoiding the need for separate processing steps for each region, thereby reducing overall structural complexity.
Solution Approach 2:
The solution extends from two-dimensional surface doping to three-dimensional subsurface doping by creating buried well regions and buried layers at different depths within the substrate. This dimensional transition allows leakage current prevention throughout the substrate volume without increasing surface area or device footprint, effectively managing complexity through spatial optimization.
3Object-generated harmful factors
If multiple PN junctions are created between the epitaxial layer and semiconductor substrate to prevent vertical leakage current, then leakage current is reduced, but the manufacturing process becomes more difficult
Solution Approach 1:
The P-type and N-type buried well regions are formed in the semiconductor substrate before the epitaxial layer is grown. This preliminary action establishes the doping profile and conductivity type distribution in advance, so that when the epitaxial layer is formed, the PN junctions are automatically created during the growth process rather than requiring additional post-growth processing steps, thereby simplifying manufacturing.
Solution Approach 2:
The epitaxial layer serves as an intermediary that bridges the semiconductor substrate and the upper device structures. By forming the buried well regions and buried layers in the substrate first, the epitaxial layer growth process naturally creates the required PN junctions at the substrate-epitaxial interface, using the epitaxial layer itself as the medium through which the junctions are formed without additional complex processing.
Data Source
AI summary
A semiconductor substrate structure includes a semiconductor substrate (P-type), a first buried well region (N-type) disposed in the semiconductor substrate, a first buried layer (N-type) and a second buried layer (P-type) disposed in the semiconductor substrate and on the first buried well region. The first buried layer has a first portion and a second portion. The second buried layer is located between the first portion and the second portion. A top surface of the first portion, a top surface of the second buried layer, and a top surface of the second portion are level with a top surface of the semiconductor substrate, a sidewall of the first portion is aligned with a sidewall of the first buried well region, and a sidewall of the second portion is aligned with another sidewall of the first buried well region. A semiconductor device includes the semiconductor substrate structure and an epitaxial layer.