Semiconductor Isolation Structure for Thick Epitaxial Layers
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Solution Overview
Problem
In BCD processes, increasing the thickness of the epitaxial layer leads to circuit disconnection between the deep well and the buried layer, preventing effective isolation of high-voltage devices from low-voltage devices, and complicates the manufacturing process, increasing costs and cycle time.
Innovation Solution
A method involving first and second ion implantations to form a buried layer and pre-dopant with higher thermal diffusion capability, followed by epitaxial growth and third ion implantation to form a deep well, ensuring thermal annealing connects the buried layer, pre-dopant, and deep well, allowing for effective device isolation without significant process changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the epitaxial layer is increased to improve device isolation, then the isolation effect is enhanced, but the manufacturing process becomes more complicated
Solution Approach 1:
The patent applies preliminary ion implantation to form the pre-dopant region before epitaxial growth. This preliminary action prepares the thermal diffusion pathway in advance, simplifying subsequent processing steps and avoiding the need for complex post-epitaxial modifications to achieve buried layer extraction through thick epitaxial layers
2Reliability
If the thickness of the epitaxial layer is increased to improve device isolation, then the isolation effect is enhanced, but processing costs increase
Solution Approach 1:
The patent utilizes standard ion implantation and thermal annealing parameters that are compatible with existing manufacturing equipment. By optimizing the doping concentration and thermal diffusion conditions of the pre-dopant, the patent achieves effective buried layer extraction through thick epitaxial layers using conventional processing techniques, avoiding the need for expensive specialized equipment or processes
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
Enables smooth extraction of the buried layer, effectively isolating high-voltage devices from low-voltage devices, reducing processing costs and shortening manufacturing cycles while maintaining compatibility with existing processes.
Implementation Method 1
performing first ion implantation into a first area of a substrate to form a buried layer
Implementation Method 2
performing second ion implantation into a second area of the substrate to form a pre-dopant
Implementation Method 3
forming an epitaxial layer on a side, of the substrate, on which the buried layer and the pre-dopant are disposed
Implementation Method 4
performing, in correspondence to the second area, third ion implantation into the epitaxial layer to form a deep well
Implementation Method 5
performing thermal annealing, to thermally diffuse ions at the buried layer, in the pre-dopant, and in the deep well, so that the buried layer, the pre-dopant, and the deep well are sequentially connected
Data Source
AI summary
An example manufacturing method includes performing first ion implantation into a first area of a substrate to form a buried layer. Second ion implantation into a second area of the substrate is performed to form a pre-dopant, where the second area is disposed around a periphery of the first area, and a thermal diffusion capability of ions in the pre-dopant is higher than a thermal diffusion capability of ions at the buried layer. An epitaxial layer is formed on a side, of the substrate, on which the buried layer and the pre-dopant are disposed. Third ion implantation into the epitaxial layer is performed, in correspondence to the second area, to form a deep well. Thermal annealing is performed to thermally diffuse ions at the buried layer, in the pre-dopant, and in the deep well.