Trench Feed-Through Elements for Flip Chip Semiconductor Devices
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Solution Overview
Problem
Conventional flip chip semiconductor devices using isotropic diffusion sinkers result in increased cell size, higher on-resistance, and reduced throughput due to large surface area and slow manufacturing processes.
Innovation Solution
The use of trench-like feed-through elements filled with conductive materials like tungsten to connect the drain contact to the substrate, reducing surface area occupation and parasitic resistance, and facilitating faster fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isotropic diffusion sinkers are used to connect drain contact to substrate, then electrical connection is achieved, but cell density decreases due to large surface area
Solution Approach 1:
The single large sinker is segmented into multiple smaller sinkers arranged in an array. This segmentation reduces the surface area occupied by each individual sinker while maintaining the total electrical connection capability through parallel conduction paths, thereby increasing cell density without compromising electrical connection reliability.
Solution Approach 2:
The invention transitions from a planar diffusion approach to a three-dimensional trench structure. By etching vertical trenches into the semiconductor layer and filling them with conductive material, the electrical connection is achieved in the vertical dimension rather than relying solely on horizontal surface diffusion, reducing the surface footprint while maintaining connection integrity.
2Reliability
If isotropic diffusion sinkers are used to connect drain contact to substrate, then electrical connection is established, but on-resistance increases due to large surface area
Solution Approach 1:
The electrical connection is divided into multiple parallel sinker paths rather than a single large sinker. This segmentation reduces the resistance by providing multiple conduction channels in parallel, as the total resistance is inversely proportional to the number of parallel paths, thereby reducing on-resistance while maintaining reliable electrical connection.
Solution Approach 2:
The invention replaces the isotropic diffusion process with anisotropic etching followed by conductive material deposition. This substitution allows for precise control of sinker geometry and material properties, enabling optimization of electrical conductivity and reduction of parasitic resistance through selective material placement in vertical trenches.
3Reliability
If isotropic diffusion process is used to form sinkers, then electrical connection is achieved, but manufacturing throughput decreases due to slow process speed
Solution Approach 1:
The slow isotropic diffusion process is replaced with faster anisotropic etching and conductive material deposition processes. The etching process creates precise trench structures rapidly, and the subsequent deposition of conductive materials such as tungsten or copper provides immediate electrical connection, eliminating the time-consuming diffusion step while achieving reliable electrical connection.
Solution Approach 2:
The trench structures are pre-formed through anisotropic etching before the conductive material is deposited. This preliminary action creates ready-made pathways that guide the conductive material placement, enabling rapid formation of electrical connections without requiring slow diffusion processes to create the connection paths from scratch.
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 increases cell density, reduces device size, decreases on-resistance, and enhances manufacturing throughput, thereby lowering costs.
Implementation Method 1
trench-like feed-through elements that pass through the intervening layer and that are used to electrically connect the drain contact and the substrate layer
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A flip chip semiconductor device comprising: a plurality of solder balls comprising a solder ball coupled to a drain contact on a first surface of said device; a metal layer on a second surface of said device, said second surface opposite said first surface; a substrate layer adjacent said metal layer, wherein said substrate layer is separated from said drain contact by an intervening layer; and a plurality of trench elements filled with electrically conductive material and coupled to said drain contact, wherein said trench elements pass through said intervening layer and into said substrate layer, wherein in operation said device comprises a circuit from a source contact through said intervening layer, said substrate layer, and said trench elements to said drain contact.