T-Shaped Capping Structure for Gate Erosion Control
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Solution Overview
Problem
As semiconductor processes scale down, fabricating back end of line (BEOL) and middle of line (MOL) metallization features becomes challenging due to critical dimension scaling and material erosion issues, leading to metal shorts and macro-loading problems during chemical mechanical polishing (CMP) processes, especially in non-self-aligned contact (SAC) and extreme ultra violet (EUV) schemes.
Innovation Solution
A T-shaped capping structure, typically made of SiN/SiCN, is formed over gate structures in different density locations to protect the metal gate structures from erosion and macro-loading issues, using techniques such as deposition, photolithographic patterning, and etching to ensure uniform final gate height and prevent work function material exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If etching process is used to remove dielectric material adjacent to gate structures, then openings for drain and source contacts are formed, but spacer material of the gate structure is eroded away exposing metal material resulting in shorts
Solution Approach 1:
A capping structure is formed over the gate structure before the etching process that removes dielectric material. This preliminary protective action prevents the etching process from eroding the spacer material and exposing the metal gate material, thereby avoiding shorts between the gate and contact metals while still allowing contact openings to be formed.
2Manufacturing precision
If CMP process is used for tungsten gate polishing, then gate height is controlled, but macro-loading issues cause work function materials to become exposed in long gate locations
Solution Approach 1:
A capping structure is deposited over the gate structure before the CMP process. During CMP, this cap structure protects the underlying work function material and gate metal from being removed, ensuring that the gate height is controlled without exposing the work function material in long gate locations, thereby preventing shorts.
Solution Approach 2:
The capping structure provides localized protection specifically where needed - over the gate structure in long gate locations - allowing the CMP process to proceed uniformly across the wafer while preventing material removal from critical areas where work function material exposure would cause shorts.
3Adaptability or versatility
If gate structures with different densities are fabricated, then device functionality is achieved, but non-uniform gate height results due to macro-loading in CMP
Solution Approach 1:
The capping structure serves multiple functions simultaneously: it protects gate structures in high-density macros, protects gate structures in low-density macros, and ensures uniform gate height across all macro types during CMP processing, thereby achieving both adaptability to different densities and manufacturing precision.
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
The T-shaped capping structure effectively mitigates metal gate CMP macro-loading issues, ensuring uniform gate height across different macros and preventing source/drain to gate shorting during contact processes, thereby enhancing device performance and reliability.
Implementation Method 1
a T-shaped capping structure protecting the plurality of gate structures in the first location and in the second location
Implementation Method 2
mitigates metal gate CMP macro-loading issues, ensuring uniform gate height across different macros
Implementation Method 3
preventing source/drain to gate shorting during contact processes
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to capping structures and methods of manufacture. The structure includes: a plurality of gate structures in a first location with a first density; a plurality of gate structures in a second location with a second density different than the first density; and a T-shaped capping structure protecting the plurality of gate structures in the first location and in the second location.