Trench Gate MOSFET Layout With Under-Gate Schottky Diode
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Solution Overview
Problem
Existing semiconductor devices face challenges in reducing on-resistance and power loss due to the presence of body diodes, and increasing functional density leads to complexity in processing and manufacturing, particularly in trench gate MOSFETs where vertical current flow complicates the reduction of cell pitch and resistance.
Innovation Solution
The formation of a semiconductor device with a Schottky diode integrated under the gate structure, disabling the body diode function, which reduces on-resistance and power loss, and allows for a decrease in cell pitch by positioning conductive structures within the drift region without occupying additional mesa area on the epitaxial layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conductive structures are positioned on the mesa area of the epitaxial layer, then the device structure is simplified, but the cell pitch increases and on-resistance increases
Solution Approach 1:
The conductive structures are moved from the horizontal mesa area to the vertical drift region beneath the gate structure. This dimensional relocation allows the conductive structures to be positioned in the depth direction rather than occupying lateral space, thereby reducing cell pitch while maintaining structural simplicity
Solution Approach 2:
The conductive structures are nested within the drift region under the gate structure, utilizing the vertical space beneath the existing gate structure. This nesting approach allows the conductive structures to be integrated without occupying additional lateral area, thus reducing cell pitch
2Reliability
If the body diode function is maintained, then the device has inherent protection functionality, but on-resistance and power loss increase
Solution Approach 1:
The body diode, which causes high on-resistance and power loss, is transformed into a Schottky diode by introducing a conductive structure that forms a Schottky junction with the drift region. This conversion maintains the protective functionality while significantly reducing on-resistance and power loss due to the lower forward voltage drop of the Schottky diode
3Productivity
If functional density is increased, then more components are integrated into a given area, but processing and manufacturing complexity increases
Solution Approach 1:
The conductive structures are merged with the drift region to form an integrated Schottky diode structure beneath the gate structure. This merging eliminates the need for separate body diode structures and simplifies the processing steps, allowing higher functional density without proportionally increasing manufacturing complexity
Solution Approach 2:
The conductive structures serve multiple functions: they form the Schottky diode for reduced on-resistance, provide electrical connection, and enable vertical current flow. This multi-functionality reduces the number of separate components needed, thereby increasing functional density while controlling processing complexity
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 decreases on-resistance, reduces power loss, and minimizes the cell pitch between adjacent components, thereby enhancing switching characteristics and reducing channel resistance without increasing the lateral dimension of the epitaxial layer.
Implementation Method 1
A gate electrode of the gate structure is separated from the conductive structure by the gate dielectric layer of the gate structure
Implementation Method 2
The conductive structure and the drift region form a Schottky diode, which can disable a function of a body diode, thereby decreasing an on-resistance and a power loss
Data Source
AI summary
A semiconductor device includes a substrate having a first conductivity type, an epitaxial layer formed on the substrate, a well region extending from a top surface of the epitaxial layer into the epitaxial layer, a drift region formed in the epitaxial layer and in contact with the bottom surface of the well region, a gate structure and a conductive structure. The epitaxial layer has the first conductivity type, the well region has the second conductivity type, and the drift region has the first conductivity type. The gate structure that extends from the top surface of the epitaxial layer penetrates the well region and is in contact with the drift region. The conductive structure is formed in the drift region and disposed below the gate structure. A gate electrode of the gate structure is separated from the underlying conductive structure by the gate dielectric layer of the gate structure.