Tungsten Plug Gate Contact for Trench Semiconductor Devices
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Solution Overview
Problem
Conventional semiconductor devices with gate bus-bars face issues of increased active area usage, reliability concerns due to passivation layer cracking, and high gate resistance, which are exacerbated by the need for metal connections that can lead to short circuits, and removing bus-bars significantly increases gate resistance.
Innovation Solution
The use of a tungsten plug contacting a gate trench in semiconductor devices, with a novel design featuring a narrow flat polysilicon bus-bar and a Ti/TiN barrier layer, reduces gate resistance and minimizes passivation layer cracking, allowing for a reduced risk of short circuits and enabling smaller source clips without continuous top contact layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gate bus-bar is added to reduce gate resistance, then gate resistance is reduced, but active area usage increases and die area increases
Solution Approach 1:
The invention transitions from a planar bus-bar structure to a three-dimensional structure by forming a contact hole through the passivation layer and filling it with a conductive material plug. This vertical dimensionality change allows electrical connection without occupying additional lateral die area, thus reducing gate resistance while maintaining compact device footprint.
Solution Approach 2:
The contact hole filled with conductive material plug creates a porous-like structure where the plug material (such as tungsten or copper) fills the void space formed by etching through the passivation layer. This allows efficient use of vertical space for electrical connection, avoiding the need for lateral bus-bar extensions.
2Reliability
If a metal layer is used to connect to the bus-bar, then electrical connection is improved, but area constraints and reliability concerns are exacerbated
Solution Approach 1:
The invention replaces lateral metal layer connections with vertical conductive plugs formed in contact holes. This dimensional change allows electrical connection to be achieved in the vertical direction rather than requiring extensive lateral metal routing, thereby improving electrical connection while minimizing the area occupied by connection structures.
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 significantly reduces gate resistance by utilizing tungsten plugs with lower resistivity than polysilicon, allowing for improved switching speed and uniformity while maintaining device reliability and reducing the risk of passivation layer cracking.
Implementation Method 1
The use of a tungsten plug contacting a gate trench in semiconductor devices, with a novel design featuring a narrow flat polysilicon bus-bar and a Ti/TiN barrier layer, reduces gate resistance and minimizes passivation layer cracking, allowing for a reduced risk of short circuits
Data Source
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AI summary
A method of manufacturing a semiconductor device is presented. The device has a gate bus-bar construction having a gate terminal formed from polysilicon ,e.g. within a trench (16), and covered by an insulation layer (18); and a plug (20) extending through said insulation layer to provide an electrical connection to the gate terminal. A metal layer (24) is deposited to cover at least a portion of the insulation layer. The metal layer is then etched to substantially remove the metal layer from the bus-bar area.