SiC MOSFET Electric Field Relaxation Layers
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Solution Overview
Problem
Silicon carbide (SiC) semiconductor devices face challenges in suppressing electric field relaxation failures and reducing breakdown voltage due to incomplete filling of trench structures during epitaxial growth and large ion implantation areas, which can cause leakage and crystal damage.
Innovation Solution
The SiC semiconductor device incorporates a MOSFET structure with an element isolation layer and electric field relaxation layers formed in a linear stripe pattern, with specific protrusions and intervals to prevent electric field penetration and reduce the area of ion implantation, ensuring proper filling and minimizing crystal damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If electric field relaxation layers are formed to suppress electric field concentration, then breakdown voltage is improved, but manufacturing complexity increases due to multiple epitaxial growth steps
Solution Approach 1:
The electric field relaxation structure is divided into multiple discrete layers (first electric field relaxation layer and second electric field relaxation layer) formed at different stages of epitaxial growth. This segmentation allows each layer to be optimized for specific functions: the first layer suppresses electric field concentration at the element isolation layer interface, while the second layer provides additional relaxation depth control, thereby achieving improved breakdown voltage through structured segmentation of the relaxation function.
Solution Approach 2:
The first electric field relaxation layer is formed preliminarily during the early stage of drift layer epitaxial growth, before the complete drift layer structure is established. This preliminary action ensures that the electric field relaxation effect is built into the structure from the foundation, preventing electric field concentration issues before they can manifest, while the second layer is added later to fine-tune the relaxation characteristics.
2Reliability
If ion implantation area is increased to ensure complete trench filling, then manufacturing reliability is improved, but crystal damage increases
Solution Approach 1:
Ion implantation is applied locally and selectively to specific regions rather than uniformly across the entire substrate. The implantation is concentrated in the trench regions that require filling, with controlled dosage and depth parameters tailored to the local structural needs. This localized approach ensures complete trench filling in critical areas while minimizing unnecessary ion exposure and crystal damage in surrounding regions.
Solution Approach 2:
The ion implantation process parameters (dose, energy, depth) are optimized and adjusted based on the specific trench dimensions and filling requirements. By changing these parameters to match the local needs of each trench region, complete filling is achieved with minimal ion implantation area, thereby reducing crystal damage while maintaining manufacturing reliability.
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 configuration effectively suppresses electric field relaxation failures, maintains desired breakdown voltage, and reduces leakage by ensuring accurate formation of electric field relaxation layers and minimizing crystal damage during ion implantation.
Implementation Method 1
a plurality of electric field relaxation layers arranged between the main cell region and the sense cell region
Implementation Method 2
an element isolation layer arranged between the main cell region and the sense cell region, and surrounding the sense cell region
Data Source
AI summary
A silicon carbide semiconductor device includes: a main cell region; a sense cell region; a MOSFET arranged in each of the main cell region and the sense cell region and disposed in a semiconductor substrate having a high impurity concentration layer and a drift layer; an element isolation layer arranged between the main cell region and the sense cell region, and surrounding the sense cell region; and a plurality of electric field relaxation layers arranged between the main cell region and the sense cell region. The MOSFET includes: a base region; a source region; a plurality of deep layers; a trench gate structure; a source electrode; and a drain electrode. The deep layers and the electric field relaxation layers are arranged in a stripe pattern at a predetermined interval.