Stepped Isolation Structure for Low-Resistance DRAM Contacts
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Solution Overview
Problem
In the fabrication of dynamic random access memory (DRAM) devices, the dry etching process for forming conductive electrodes in storage node contact structures often results in the production of tungsten byproducts and polymers, which can cause shorting between electrodes due to the material properties of the conductive layer.
Innovation Solution
A semiconductor structure and manufacturing method that involves forming a conductive structure with a trench extending to a stepped surface of an isolation structure, where the sidewall of the conductive structure extends beyond the second top surface of the isolation structure, increasing the cross-sectional area and reducing resistance, and using a liner layer to prevent byproducts and polymers from forming during dry etching, thereby avoiding electrode shorting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the conductive layer is dry etched to form trenches and conductive electrodes, then the conductive electrodes are formed, but byproducts and polymers are produced which may induce shorting between the conductive electrodes
Solution Approach 1:
A liner layer is introduced as an intermediary between the conductive layer and the dry etching process. This liner layer acts as a protective barrier that prevents byproducts and polymers from adhering to the conductive layer during etching, thereby eliminating the shorting issue while maintaining trench formation precision
Solution Approach 2:
The patent converts the harmful byproducts and polymers into a beneficial situation by using the liner layer to capture these byproducts on its outer surface. The byproducts that would otherwise cause shorting are instead trapped on the liner layer, which is subsequently removed, leaving the conductive electrodes clean and free from shorting defects
2Reliability
If the sidewall of the conductive structure extends beyond the second top surface of the isolation structure, then the cross-sectional area increases and resistance decreases, but the manufacturing process becomes more complex
Solution Approach 1:
The liner layer is formed on the conductive structure sidewalls before the final etching and isolation structure removal steps. This preliminary action ensures that when the isolation structure is removed, the conductive structure sidewalls are already protected and extended beyond the isolation structure surface, achieving the desired geometry without requiring complex post-processing steps
Solution Approach 2:
The patent changes the physical and chemical parameters of the conductive structure sidewalls by coating them with the liner layer. This modification allows the sidewalls to extend beyond the isolation structure surface while maintaining structural integrity and controlling the extension distance through liner layer thickness parameters
Data Source
AI summary
A semiconductor structure includes a semiconductor substrate, an isolation structure, and a conductive structure. The isolation structure is located on the semiconductor substrate. The isolation structure has a first top surface, a second top surface lower than the first top surface, and a lateral surface adjoining the first top surface and the second top surface. The conductive structure has a trench. The trench extends to the second top surface and the lateral surface of the isolation structure. The conductive structure surrounds the isolation structure. The conductive structure is in contact with the first top surface of the isolation structure. A sidewall of a lower portion of the conductive structure is in contact with the isolation structure and extends beyond the second top surface of the isolation structure.