III-Nitride Cap Contact Bus Layout for Lower Parasitic Capacitance

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Solution Overview

Problem

In larger multifinger III-Nitride transistors, the placement of cap layer contacts along the sides of the device leads to additional capacitance between the cap layer contact area and the source/drain metallization, impacting performance.

Innovation Solution

A contact structure is disposed at the end of the transistor device, connecting to the cap layer of individual fingers via a cap contact bus, effectively moving the cap layer contact away from the individual fingers and reducing capacitance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If cap layer contacts are placed along each finger outside the active region, then the cap layer can be accessed for gate formation, but additional capacitance is introduced between the cap layer contact area and source/drain metallization

Engineering Contradiction:

Improvecap layer accessibilityVSAvoidparasitic capacitance

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The cap layer contact function is extracted from the finger region and relocated to a separate contact region. The cap layer contact area is taken out from under the source/drain metallization and positioned in a dedicated contact region, separating the gate formation function from the high-capacitance finger area.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

A cap layer contact region acts as an intermediary structure between the cap layer and the external circuit. This intermediate region provides a dedicated pathway for electrical contact to the cap layer without requiring direct contact under the source/drain metallization, thereby reducing parasitic capacitance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If larger multifinger transistor devices are created, then device capacity and current handling increase, but the complexity of accommodating cap layer contacts becomes challenging

Engineering Contradiction:

Improvedevice capacityVSAvoidcontact structure complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

Multiple cap layer contacts from different fingers are merged into a single shared cap layer contact region. Instead of providing separate contact structures for each finger's cap layer, the invention combines all cap layer contacts into one common region, significantly reducing the overall contact structure complexity in larger multifinger devices.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The shared cap layer contact region serves as a universal contact structure for all fingers in the multifinger device. This single contact region performs the gate formation function for multiple fingers simultaneously, reducing the number of required contact structures and simplifying the overall device architecture.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS20250022928A1Contact structure for iii-nitride transistors with cap layers

Publication Date: 2025.01.16 FINWAVE SEMICONDUCTOR INC

AI summary

A technique for making contact to the cap layers in multifinger III-Nitride transistors with cap layers is described. A contact structure is disposed at an end of the transistor device and connects to the cap layer of individual fingers of the transistor device using a cap contact bus. A transistor is also described that includes a contact structure that is used to move the cap layer contact away from the individual fingers. Transistors may be created using unit cells, wherein each unit cell includes a contact structure and cap contact bus.