Trench Contact Structure for Semiconductor Power Device Mask Reduction
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Solution Overview
Problem
Conventional semiconductor power device manufacturing processes face challenges in reducing the number of masks used, leading to increased costs and reduced cell density due to planar contacts that induce leakage currents and lower breakdown voltage.
Innovation Solution
The implementation of trench contact structures for both gate and source-body regions with multiple trench gates connected in the termination areas, using tungsten contact plugs and Ti/TiN layers to enhance contact areas and reduce contact resistance, eliminating the need for additional masks and planar contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If planar contacts are used in termination areas, then device structure is simple, but leakage currents increase and breakdown voltage decreases
Solution Approach 1:
The patent transitions from planar (2D) contacts to trench (3D) contacts by etching vertical trenches into the semiconductor substrate. This dimensional change allows the contact to extend deeper into the substrate, providing better electrical connection to the body region while reducing surface leakage paths, thereby improving breakdown voltage without significantly increasing structural complexity.
Solution Approach 2:
The patent extracts the problematic planar contact structure and replaces it with trench contacts that physically remove the leakage-prone surface region. By etching trenches and filling them with conductive material, the design eliminates the lateral leakage paths inherent in planar contacts while maintaining electrical connection to the underlying body region.
2Manufacturing precision
If multiple masks are used in manufacturing process, then device precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent combines multiple previously separate mask steps into a single unified trench formation process. By defining both the trench gate and trench contact positions in one mask step, and using a common etch process, the design reduces the number of masks required while maintaining the precision needed for proper device alignment and function.
Solution Approach 2:
The trench structure serves multiple functions simultaneously: it acts as both the trench gate structure and the trench contact structure. This multi-functionality allows a single fabrication process to achieve what previously required separate steps, reducing manufacturing complexity and cost while maintaining device precision.
3Reliability
If trench contacts are used for gate and source-body regions, then leakage currents are prevented, but manufacturing process complexity increases
Solution Approach 1:
The patent merges the formation of trench gates and trench contacts into a single etch process using a common mask pattern. This approach prevents leakage currents by properly isolating the gate and body regions while avoiding the need for separate, complex fabrication steps, thereby maintaining manufacturing simplicity.
4Ease of manufacture
If planar contacts are used, then manufacturing process is simple, but cell density is limited due to larger occupied area
Solution Approach 1:
By transitioning from planar to trench contacts, the design utilizes the vertical dimension to provide electrical connection. This allows the contact footprint on the surface to be minimized while still achieving proper electrical connection to the body region, thereby increasing the available surface area for active cells and improving cell density.
Solution Approach 2:
The trench contact structure segments the contact function into a vertical profile rather than a lateral expansion. This segmentation allows the contact to reach deep into the substrate through a narrow trench, occupying minimal surface area while maintaining effective electrical connection, thus enabling higher cell density.
Data Source
AI summary
A semiconductor power device formed on a semiconductor substrate of a first conductivity type wherein the semiconductor power device includes trench gates surrounded by body regions of a second conductivity type encompassing source regions of the first conductivity type therein. The semiconductor power device further includes trench contact structure having a plurality of trench contacts with trenches extended into the body regions for as source-body contacts and extended into the trench gates as gate contact. The semiconductor power device further includes a termination area wherein a plurality of the trench gate contacts are electrically connected to the source-body contacts.