Trench Capacitor Layout Along Maximum Elastic Modulus
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Solution Overview
Problem
Existing trench capacitors face issues with high intrinsic mechanical stress, which can lead to mechanical breakdown, reduced breakdown voltage, and increased leakage currents due to high temperature and electromagnetic disturbances, particularly in power management applications.
Innovation Solution
The design of trench capacitors with trenches following the direction of maximum elastic modulus in the substrate, using a dielectric layer to separate electrodes, and arranging trenches concentrically to minimize stress and maximize capacitance, with optional integration into an RC-snubber circuit for transient suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trenches are etched in conventional directions, then capacitor integration is achieved, but intrinsic mechanical stress increases leading to wafer bow and reliability issues
Solution Approach 1:
The patent applies asymmetry by orienting trenches along specific crystallographic directions ([110] for cubic substrates, <100> for hexagonal substrates) where the substrate exhibits maximum elastic modulus. This asymmetric orientation relative to conventional trench patterns reduces intrinsic mechanical stress by aligning with the substrate's natural elastic properties, thereby reducing wafer bow and improving reliability without requiring additional stress compensation structures.
Solution Approach 2:
The patent changes the critical parameter of trench orientation angle relative to the substrate crystal structure. By specifically selecting orientations where the elastic modulus is maximized (e.g., 45 degrees for cubic substrates), the design optimizes mechanical stress distribution. This parameter change transforms the stress state from harmful to beneficial, reducing wafer bow while maintaining capacitor functionality.
2Reliability
If capacitor size is increased to achieve higher capacitance, then unit capacitance improves, but device area increases and integration density decreases
Solution Approach 1:
The patent transitions from planar capacitor design to three-dimensional trench structures etched into the substrate. By utilizing the vertical dimension and substrate depth, the effective capacitance area is dramatically increased without proportionally increasing the surface footprint. Multiple trenches can be packed in parallel within a compact area, achieving high unit capacitance while maintaining high integration density.
3Object-affected harmful factors
If high voltage transients are suppressed using snubber structures, then electromagnetic disturbances are reduced, but parasitic inductances increase connection complexity
Solution Approach 1:
The patent merges the snubber capacitor directly with the substrate by etching trenches into the substrate itself and filling them with dielectric and electrode materials. This integration eliminates separate discrete capacitor components and their associated lead connections, thereby minimizing parasitic inductances. The snubber function is achieved through the integrated trench capacitor structure with direct electrical connection to the power rails.
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
Reduces intrinsic mechanical stress, minimizes wafer bow, and enhances reliability by aligning trenches with substrate elasticity, allowing for higher capacitance and reduced leakage currents, while providing a compact and efficient capacitor structure.
Implementation Method 1
a dielectric layer (120), a first electrode (112) and a second electrode (130), wherein walls of the one or more trenches are covered by the dielectric layer (120) which separates the first electrode (112) from the second electrode (130)
Implementation Method 2
each trench follows a closed curve, and the closed curve of each trench has one or more elongated parts in directions in which the substrate has a maximum elastic modulus
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A unit trench capacitor (100) in a substrate (110). The unit trench capacitor (100) comprising one or more trenches (131) in the substrate (110), a dielectric layer (120), a first electrode (112) and a second electrode (130). Walls of the one or more trenches (131) are covered by the dielectric layer (120) which separates the first electrode (112) from the second electrode (130). Each trench follows a closed curve. The closed curve of each trench has one or more elongated parts (150) in directions in which the substrate (110) has a maximum elastic modulus, or the closed curve of each trench has a circular shape if the substrate (110) has an isotropic elastic modulus.