Metal Gate Structures with Selective Channel Material Formation
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Solution Overview
Problem
Conventional replacement metal gate (RMG) processes damage channel stress materials like Ge, SiGe, or SiC due to thermal and implant processes, impairing device performance by affecting the quality and properties of these materials.
Innovation Solution
Forming the Ge or SiGe channel material during a later processing stage, minimizing damage and allowing for better control over its properties, and forming metal gate structures with insulating, high-k dielectric, and metal materials to create reliable and accurate transistor threshold voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If channel stress materials are formed early in the process and subjected to thermal and implant processes, then device performance can be enhanced through stress induction, but the channel stress material quality and properties deteriorate due to processing damage
Solution Approach 1:
The patent applies preliminary action by forming the channel stress material early in the process before other structures are added, then using selective removal and protection strategies. The stress material is formed first, followed by formation of mandrels and sacrificial layers, with selective etching and deposition steps that protect the stress material from damage while maintaining its stress-inducing properties throughout subsequent processing.
2Ease of manufacture
If sacrificial layers are removed through etching processes to form trenches, then metal gate structures can be formed, but the channel stress material is attacked and its quality deteriorates
Solution Approach 1:
The patent uses intermediary protective layers and selective etching approaches. Sacrificial layers are introduced as intermediaries that can be selectively removed without directly exposing the channel stress material to damaging etchants. The process includes forming sacrificial layers over the stress material, then using selective removal techniques that target the sacrificial material while leaving the stress material intact, thereby protecting it from etching damage.
3Reliability
If channel stress materials are formed prior to high-k material deposition, then stress effects can be established, but the materials become damaged during subsequent processing
Solution Approach 1:
The channel stress material is formed in advance before high-k material deposition and other processing steps. This preliminary formation allows the stress material to establish its crystalline structure and stress properties early, then subsequent processing steps are designed to protect rather than damage this pre-formed structure through selective etching, deposition, and patterning operations.
Solution Approach 2:
Protective measures are implemented beforehand to cushion the channel stress material from subsequent processing damage. This includes forming protective sacrificial layers over the stress material, using selective etching processes that spare the stress material, and designing process sequences that minimize exposure to damaging conditions while still enabling necessary manufacturing steps.
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 enhances the reliability and mobility of charge carriers, allowing for more precise control over transistor performance and reducing damage from earlier processing stages.
Implementation Method 1
removing the insulator layer forming a bottom portion of the second trench while protecting the insulator layer in the first trench
Implementation Method 2
filling remaining portions of the first trench and the second trench with gate material
Data Source
AI summary
A metal gate structure with a channel material and methods of manufacture such structure is provided. The method includes forming dummy gate structures on a substrate. The method further includes forming sidewall structures on sidewalls of the dummy gate structures. The method further includes removing the dummy gate structures to form a first trench and a second trench, defined by the sidewall structures. The method further includes forming a channel material on the substrate in the first trench and in the second trench. The method further includes removing the channel material from the second trench while the first trench is masked. The method further includes filling remaining portions of the first trench and the second trench with gate material.