Reversed T-Shaped Conductive Plug for Low Contact Resistance
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Solution Overview
Problem
The integration of high-k/metal gate features in CMOS technology processes is hindered by material incompatibility and complex thermal budgets, leading to challenges in achieving low contact resistance and uniformity in semiconductor devices.
Innovation Solution
A reversed T-shaped conductive plug design is implemented, which laterally extends into the metal gate to increase the ohmic contact surface, combined with a wet etching process to form a recess and fill with conductive material, enhancing contact resistance and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional conductive plug design is used, then the manufacturing process is simple, but the contact resistance is high and non-uniform
Solution Approach 1:
The conductive plug transitions from a conventional vertical cylindrical structure to a reversed T-shaped structure that extends laterally into the metal gate. This dimensional change from purely vertical to including horizontal extension increases the contact surface area between the conductive plug and metal gate, thereby reducing contact resistance and improving electrical reliability.
Solution Approach 2:
The conductive plug is segmented into distinct functional regions: a vertical portion extending through the dielectric and a lateral portion extending into the metal gate. This segmentation allows optimization of each region's function - the vertical portion provides electrical connection through the dielectric while the lateral portion maximizes contact area with the metal gate, achieving low contact resistance.
2Reliability
If the contact surface area is increased, then the contact resistance decreases, but the manufacturing precision requirements increase
Solution Approach 1:
The metal gate is formed with a recessed top surface before the conductive plug is deposited. This preliminary action creates a pre-defined geometry that guides the lateral extension of the conductive plug, ensuring uniform encroachment into the metal gate across the wafer. The recess acts as a template that automatically ensures consistent contact area without requiring additional precision control during plug formation.
Solution Approach 2:
The manufacturing process utilizes wet etching to create the recessed top surface of the metal gate, changing the geometric parameters of the metal gate structure. This parameter change (creating a recess) fundamentally alters how the conductive plug contacts the metal gate, transforming the contact interface from a horizontal surface to a vertical sidewall, thereby achieving uniform lateral encroachment and consistent contact resistance across the wafer.
3Manufacturing precision
If a wet etching process is added to form a recess, then the contact uniformity improves, but the manufacturing complexity increases
Solution Approach 1:
The wet etching process serves multiple functions: it removes photoresist debris from the metal gate top surface, creates the recessed geometry for lateral encroachment, and defines the contact interface between the conductive plug and metal gate. By combining these functions into a single process step, the manufacturing complexity is minimized while achieving superior contact uniformity.
Solution Approach 2:
The wet etching process automatically performs debris removal and recess formation in one step. The etchant selectively removes photoresist material that remains on the metal gate after lithography, simultaneously creating the recessed structure. This self-service capability eliminates the need for separate debris removal steps and simplifies the overall manufacturing process.
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 reduces contact resistance and improves contact resistance uniformity within the wafer, achieving better electrical performance and physical integrity by increasing the contact surface area between the conductive plug and the metal gate.
Implementation Method 1
performing a wet etch to remove a portion of the metallic material from the top surface thereby forming a lateral recess
Implementation Method 2
increasing the ohmic contact surface with the metal gate
Data Source
AI summary
A semiconductor structure includes a substrate and a metal gate. The metal gate includes a metallic filling layer and disposed over the substrate. The semiconductor structure further includes a dielectric material over the metallic filling layer and separating the metallic filling layer from a conductive trace. The conductive trace is over the dielectric material. The semiconductor structure further includes a conductive plug extending longitudinally through the dielectric material and ending with a lateral encroachment inside the metallic filling layer along a direction. The lateral direction is substantially perpendicular to the longitudinal direction of the conductive plug.