N-Type Buried Layer Doping for High Breakdown Voltage
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Solution Overview
Problem
Semiconductor devices with n-type buried layers in p-type substrates experience undesirable leakage current and low breakdown voltage due to pn junction issues at high voltage biases.
Innovation Solution
A semiconductor device structure with an n-type buried layer formed by implanting heavy n-type dopants like antimony and arsenic at high dose and low energy, and lighter n-type dopant phosphorus at low dose and high energy, followed by thermal diffusion to create a narrow profile main layer and a lightly-doped layer, which reduces leakage current and prevents breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single n-type dopant is implanted at high dose to form the buried layer, then the sheet resistance is reduced, but the breakdown voltage decreases and leakage current increases
Solution Approach 1:
The patent divides the single doped layer into two distinct layers: a first n-type buried layer with heavy dopants (arsenic/antimony) at high dose for low sheet resistance, and a second n-type buried layer with lighter dopants (phosphorus) at low dose for high breakdown voltage. This segmentation allows each layer to optimize for its specific function, resolving the contradiction between low resistance and high breakdown voltage.
Solution Approach 2:
The patent applies different doping concentrations and dopant types at different depths: the first buried layer uses heavy dopants at high concentration near the surface for conductivity, while the second buried layer uses lighter dopants at lower concentration deeper in the substrate for breakdown protection. This local quality variation optimizes both electrical conductivity and voltage withstand capability in their respective regions.
2Manufacturing precision
If heavy n-type dopants are implanted at high dose and low energy, then the main buried layer profile remains narrow, but the dopants diffuse significantly during thermal processing
Solution Approach 1:
The patent performs the heavy dopant implantation at low energy to achieve precise shallow penetration and narrow profile formation before any thermal processing occurs. This preliminary action establishes the desired concentration profile that is then protected from significant diffusion by the subsequent low-temperature or short-duration thermal cycles used for activation.
3Reliability
If lighter n-type dopants are implanted at low dose and high energy, then the dopants diffuse to form a deep lightly-doped layer, but the sheet resistance remains high
Solution Approach 1:
The patent introduces a deep lightly-doped n-type layer as an intermediary between the heavily-doped buried layer and the p-type substrate. This intermediate layer acts as a buffer that prevents direct contact between high and low doping regions, reducing leakage current and improving breakdown voltage while maintaining overall electrical performance through the combined structure.
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
The structure effectively maintains a low sheet resistance and uniform bias for components above the buried layer, preventing pn junction breakdown and minimizing leakage current at high voltage biases.
Implementation Method 1
A thermal drive process diffuses and activates both the heavy dopants and the phosphorus
Implementation Method 2
The buried layer is formed by implanting heavy n-type dopants, antimony and/or arsenic, into the p-type first epitaxial layer
Data Source
AI summary
A semiconductor device has an n-type buried layer formed by implanting antimony and/or arsenic into the p-type first epitaxial layer at a high dose and low energy, and implanting phosphorus at a low dose and high energy. A thermal drive process diffuses and activates both the heavy dopants and the phosphorus. The antimony and arsenic do not diffuse significantly, maintaining a narrow profile for a main layer of the buried layer. The phosphorus diffuses to provide a lightly-doped layer several microns thick below the main layer. An epitaxial p-type layer is grown over the buried layer.