Isolated Metal Gate Structure for Semiconductor Reliability
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Solution Overview
Problem
Conventional poly-silicon gates in semiconductor devices face issues such as boron penetration and depletion, leading to inferior performance and reduced gate capacitance, necessitating the use of work function metals as control electrodes, which requires adjustments in semiconductor processes to improve performance.
Innovation Solution
A semiconductor process that forms a metal gate strip, cuts off the cap layer and metal gate strip to create an isolation slot, avoiding residues and voids, reducing etching height, and enhancing miniaturization of semiconductor components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional poly-silicon gates are used, then the gate structure is simple to manufacture, but boron penetration and depletion occur leading to inferior performance and reduced gate capacitance
Solution Approach 1:
The patent changes the material parameter of the gate electrode from conventional poly-silicon to work function metals (such as titanium nitride, tantalum nitride, or tungsten). This material substitution eliminates boron penetration and depletion issues while maintaining gate control functionality, directly resolving the performance degradation problem.
Solution Approach 2:
The patent employs composite material structures including work function metal layers combined with high-k dielectric materials. This composite approach provides both the electrical functionality of metal gates and the enhanced capacitance of high-k dielectrics, improving gate performance without excessive complexity.
2Manufacturing precision
If isolation slots are formed in sacrificial gate strips before forming metal gates, then the isolation structure is established early, but residues of sacrificial gate materials remain in the trench and voids generate due to gap filling difficulty
Solution Approach 1:
The patent inverts the conventional sequence by forming metal gates first and then creating isolation slots. This reversal eliminates the problem of sacrificial material residues and voids, as the metal gates are already in place and the isolation slots are formed by removing only the sacrificial gate material that was temporarily used to define the isolation regions.
Solution Approach 2:
The patent performs preliminary actions by forming the metal gate structure and cap layer completely before creating the isolation slots. This ensures that all critical gate structures are established and protected before the isolation process begins, preventing damage to the gate materials during slot formation.
3Reliability
If the cap layer and metal gate strip are cut off to form isolation slots, then residues and voids are avoided, but the etching height of the trench increases
Solution Approach 1:
The patent applies local quality by forming isolation slots with specific depth characteristics at different locations. The etching depth is controlled to reach only the required level for effective isolation without unnecessarily increasing the overall trench depth, optimizing the balance between isolation quality and manufacturing complexity.
4Ease of manufacture
If metal gates are formed without isolation slots, then the manufacturing process is simpler, but critical dimension enlargement occurs and polishing loading effect increases
Solution Approach 1:
The patent segments the gate structure by introducing isolation slots that divide the continuous metal gate into isolated sections. This segmentation prevents critical dimension enlargement during subsequent processing steps and reduces the loading effect on polishing equipment by creating smaller, more manageable gate structures.
Data Source
AI summary
A semiconductor process includes the following step. A metal gate strip and a cap layer are sequentially formed in a trench of a dielectric layer. The cap layer and the metal gate strip are cut off to form a plurality of caps on a plurality of metal gates, and a gap isolates adjacent caps and adjacent metal gates. An isolation material fills in the gap. The present invention also provides semiconductor structures formed by said semiconductor process. For example, the semiconductor structure includes a plurality of stacked structures in a trench of a dielectric layer, where each of the stacked structures includes a metal gate and a cap on the metal gate, where an isolation slot isolates and contacts adjacent stacked structures at end to end, and the isolation slot has same level as the stacked structures.