Stacked Trench Contacts for Wider Gate Registration Margin
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Solution Overview
Problem
Contact to gate shorts become increasingly difficult in integrated circuits with scaled dimensions, and existing metal gate processes do not adequately reduce these shorts to a manufacturable level.
Innovation Solution
A method involving the formation of a stacked trench contact structure with a dual metal gate process, where a first contact metal is polished to planarize the surface, and a second contact metal is conductively coupled to increase the contact to gate registration margin and reduce shorts, using a combination of dry etching, salicide formation, and chemical mechanical polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If contact dimensions are reduced to scale with integrated circuit dimensions, then device density is improved, but contact to gate shorts increase
Solution Approach 1:
The patent introduces a vertical stacked contact structure with multiple contact levels (first contact, second contact, third contact) at different heights. This dimensional transition from planar to vertical stacking allows the contact structure to maintain electrical connectivity while increasing the vertical separation from the gate, thereby reducing contact-to-gate shorts even as lateral dimensions are scaled down.
Solution Approach 2:
The contact structure is divided into multiple segmented contact levels (first contact metal, second contact metal, third contact metal) separated by intermediate dielectric layers. Each contact level serves as an independent conductive element, and the segmentation allows for better control of electrical paths and reduced interference with the gate structure.
2Reliability
If stacked trench contact structure is formed to increase registration margin, then contact to gate shorts are reduced, but device complexity increases
Solution Approach 1:
The patent combines multiple contact functions into a single integrated stacked contact structure. The first, second, and third contacts are merged vertically to form one unified contact system that provides both electrical connectivity and increased registration margin, eliminating the need for separate contact structures for different functions.
Solution Approach 2:
The stacked contact structure serves multiple functions simultaneously: it provides electrical connectivity to the semiconductor device, increases the registration margin to prevent shorts, and maintains scalability for different device configurations. The same basic stacked structure can be adapted for various contact requirements.
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 significantly increases the contact to gate registration margin, reduces contact to gate shorts, and allows for larger contacts with improved registration while maintaining a small process window, making it scalable to small technology nodes without affecting overlap capacitance.
Implementation Method 1
polishing the first contact metal to planarize a top surface of the first contact metal with a top surface of a gate disposed on the substrate
Implementation Method 2
forming a second contact opening in the second ILD, and forming a second contact metal in the second contact opening
Implementation Method 3
forming a silicide on the source/drain contact area
Data Source
AI summary
Methods and associated structures of forming a microelectronic device are described. Those methods may include forming a structure comprising a first contact metal disposed on a source/drain contact of a substrate, and a second contact metal disposed on a top surface of the first contact metal, wherein the second contact metal is disposed within an ILD disposed on a top surface of a metal gate disposed on the substrate.