Transistor Field Electrode Trench Design for On-Resistance Reduction
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Solution Overview
Problem
There is a need to reduce the on-resistance of power transistors without increasing the size of the semiconductor chip, which requires minimizing the size of individual transistor cells while maintaining voltage blocking capability.
Innovation Solution
The design includes a transistor cell with a source region, body region, and drift region in a semiconductor body, featuring a gate electrode dielectrically insulated from the body region and a field electrode dielectrically insulated from the drift region, with a contact plug extending from the semiconductor body to the field electrode, allowing for a reduced lateral dimension and pitch between cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the number of transistor cells is increased to reduce on-resistance, then the on-resistance decreases, but the chip area increases
Solution Approach 1:
The patent introduces a vertical field electrode structure that extends into a trench, utilizing the third dimension (depth) to provide field control. This vertical arrangement allows the field electrode to be positioned closer to the channel region without increasing lateral dimensions, thereby reducing the lateral pitch between adjacent transistor cells and enabling higher cell density on the chip.
Solution Approach 2:
The field electrode is nested within a trench structure that is formed in the semiconductor substrate. The trench contains the field electrode and associated dielectric layers, effectively nesting multiple functional elements within a compact vertical structure. This nesting approach consolidates what would otherwise require lateral space into a vertical arrangement, reducing the lateral footprint of each transistor cell.
2Area of stationary object
If the lateral dimension of transistor cell is reduced to increase cell density, then the chip area utilization improves, but the manufacturing precision requirements increase
Solution Approach 1:
By transitioning from a lateral field electrode arrangement to a vertical trench-based field electrode structure, the patent reduces the lateral dimensions required for field control. The trench depth provides the necessary field control distance without consuming lateral space, thereby reducing the lateral pitch between cells while avoiding proportionally tighter lateral tolerances.
Solution Approach 2:
The patent changes the geometric parameters of the field electrode structure by introducing a vertical trench dimension. Instead of controlling only lateral dimensions, the design utilizes vertical depth to achieve field control, thereby relaxing lateral dimension control requirements while maintaining or improving overall device performance.
3Area of stationary object
If the pitch between transistor cells is reduced to increase cell density, then the chip area utilization improves, but the voltage blocking capability may deteriorate
Solution Approach 1:
The vertical trench structure provides an additional dimension for voltage blocking. The trench depth creates a vertical distance that contributes to voltage blocking capability, allowing reduced lateral pitch while maintaining adequate voltage blocking through the combined effect of lateral and vertical dimensions.
Solution Approach 2:
The trench structure employs composite materials including dielectric layers and conductive field electrodes in specific configurations. These composite structures provide both electrical field control and voltage blocking functions, enabling compact cell pitch while maintaining reliability through the synergistic combination of different materials and their arranged geometries.
Data Source
AI summary
A transistor device includes at least one transistor cell which includes: a source region, a body region and a drift region in a semiconductor body; a gate electrode dielectrically insulated from the body region by a gate dielectric; a field electrode dielectrically insulated from the drift region by a field electrode dielectric; and a contact plug extending from a first surface of the semiconductor body to the field electrode. A portion of the semiconductor body is arranged between the field electrode trench and the first surface of the semiconductor body. The portion of the semiconductor body that is arranged between the field electrode trench and the first surface comprises the body region. The body region directly contacts the upper surface of the field electrode dielectric.