Trench Capacitor Structure for Low ESL and Voltage Handling
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Solution Overview
Problem
Conventional semiconductor capacitors face challenges in high power applications due to inductive and capacitive parasitic losses, high cost, and limitations in low equivalent series inductance and voltage handling, particularly in multi-chip module packaging, which leads to electromagnetic interference and increased manufacturing complexity.
Innovation Solution
The formation of capacitors with trenches in a doped semiconductor substrate, a conformal dielectric layer, and a polysilicon top plate, along with optional guard rings and series resistors, to reduce electric field crowding and inductance, while minimizing masking steps and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional surface mount capacitors are used to achieve low ESL and low profile, then about four patterning levels are required which increases manufacturing cost and complexity
Solution Approach 1:
The capacitor structure is segmented into distinct functional regions: a trench region for the capacitor element, a guard ring region for field management, and a resistor region for series resistance. This segmentation allows each region to be optimized independently while reducing the overall patterning complexity to fewer masking steps compared to conventional four-level patterning processes.
2Ease of manufacture
If high-k dielectric capacitors are fabricated using emerging silicon technologies, then voltage handling is limited to less than about 10 volts
Solution Approach 1:
The patent modifies the physical and chemical parameters of the dielectric layer by forming it conformally over the trench structure and controlling its thickness and material composition. This allows the dielectric to withstand higher voltages while maintaining compatibility with emerging silicon technologies, overcoming the sub-10V limitation of conventional high-k dielectric capacitors.
3Reliability
If trenches are formed in the substrate to define capacitor bottom plate, then electric field crowding occurs at end trench corners
Solution Approach 1:
A guard ring region of opposite conductivity type is introduced as an intermediary structure between the trench corners and the surrounding substrate. This guard ring acts as a mediator that redistributes the electric field lines, preventing field crowding at the trench corners while maintaining the capacitor's performance characteristics.
4Reliability
If series resistor is provided in the polysilicon layer, then additional masking steps are required which increases manufacturing complexity
Solution Approach 1:
The series resistor is merged with the polysilicon top plate structure, allowing both the capacitor element and the series resistance to be formed in the same material layer. This integration eliminates the need for separate masking steps for the resistor, reducing manufacturing complexity while maintaining the required series resistance functionality.
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 results in low equivalent series inductance capacitors suitable for high power applications with reduced electric field crowding, lower costs, and improved voltage handling, effectively addressing the challenges of parasitic losses and manufacturing complexity in multi-chip module packaging.
Implementation Method 1
Capacitors and methods of forming
Implementation Method 2
a dielectric layer is formed conformally over the substrate within the trenches
Data Source
AI summary
Capacitors and methods of forming semiconductor device capacitors are disclosed. Trenches are formed to define a capacitor bottom plate in a doped upper region of a semiconductor substrate, a dielectric layer is formed conformally over the substrate within the trenches, and a polysilicon layer is formed over the dielectric layer to define a capacitor top plate. A guard ring region of opposite conductivity and peripheral recessed areas may be added to avoid electric field crowding. A central substrate of lower doping concentration may be provided to provide a resistor in series below the capacitor bottom plate. A series resistor may also be provided in a resistivity region of the polysilicon layer laterally extending from the trenched area region. Contact for the capacitor bottom plate may be made through a contact layer formed on a bottom of the substrate. A top contact may be formed laterally spaced from the trenched area by patterning laterally extended portions of one or more of the dielectric, polysilicon and top metal contact layers.