Gate-Source-Drain Interconnect Structure for Low-Resistance Contacts
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Solution Overview
Problem
As semiconductor devices approach nanometer scales, the resistivity of contacts increases due to surface scattering, and metal silicide is prone to damage during manufacturing, leading to high interface resistance between via contacts and metal contacts.
Innovation Solution
A new metal contact structure and manufacturing method are introduced, involving the formation of lower and upper metal contacts with different metal materials, and a via contact made of the same material as the upper metal contact, to reduce resistance and protect metal silicide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the contact critical dimension is reduced to nanometer scale, then the device density is improved, but the contact resistivity increases rapidly due to surface scattering
Solution Approach 1:
The contact structure is divided into multiple segments: a via contact portion extending through the gate dielectric, a metal contact portion in the trench, and an optional cap portion. This segmentation allows each portion to be optimized independently - the via contact provides vertical connection, the metal contact provides low-resistance horizontal connection, and the cap protects the underlying structures, thereby reducing overall contact resistivity while maintaining small footprint
Solution Approach 2:
The contact structure employs nested configurations where the cap contact is disposed over the metal contact, and the via contact integrates with both. This nested arrangement maximizes the effective contact area and creates multiple parallel conduction paths within a minimal horizontal footprint, reducing resistivity without increasing device area
2Area of moving object
If the interface between via contact and metal contact is made narrow, then the device density is improved, but the interface resistance cannot be reduced effectively
Solution Approach 1:
The contact structure exhibits local quality variations: the cap contact has a larger top surface area for low-resistance via-to-cap interface, while the metal contact provides extensive lateral coverage for low-resistance cap-to-metal interface. The via contact maintains a narrow profile through the gate dielectric for high density. This localized optimization of cross-sectional areas at different positions reduces interface resistance without compromising overall device density
3Ease of manufacture
If the metal silicide is directly exposed during manufacturing, then the manufacturing process is simplified, but the metal silicide is easily damaged leading to increased resistance
Solution Approach 1:
The cap contact material is deposited preliminarily to cover and protect the metal silicide surface before subsequent manufacturing steps. This preliminary protective action prevents damage to the metal silicide during etching, cleaning, and other processing steps, maintaining its low-resistance properties without significantly complicating the manufacturing flow
Solution Approach 2:
The cap contact serves as an intermediary protective layer between the manufacturing environment and the metal silicide. It acts as a sacrificial or permanent protective barrier that shields the sensitive metal silicide from mechanical damage, chemical contamination, and oxidation during subsequent processing steps, thereby preserving the metal silicide's electrical properties
Data Source
AI summary
A method for manufacturing a semiconductor device includes: forming a lower metal contact in a trench of a first dielectric structure, the lower metal contact having a height less than a depth of the trench and being made of a first metal material; forming an upper metal contact to fill the trench and to be in contact with the lower metal contact, the upper metal contact being formed of a second metal material different from the first metal material and having a bottom surface with a dimension the same as a dimension of a top surface of the lower metal contact; forming a second dielectric structure on the first dielectric structure; and forming a via contact penetrating through the second dielectric structure to be electrically connected to the upper metal contact, the via contact being formed of a metal material the same as the second metal material.