Segmented Contact Plug Structure for DRAM Bit Line Coupling Reduction
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Solution Overview
Problem
Conventional contact plug structures in dynamic random access memory (DRAM) cause significant bit line coupling due to their large volume and overlapping area with word lines, which is a critical issue in advanced memory development.
Innovation Solution
A dual-damascene technique is employed to create a contact plug structure with two leg portions and a dielectric block, reducing the overlap between the bit line and word line by electrically isolating the leg portions from each other, thereby minimizing the contact plug's volume and overlap area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single contact plug structure is used to electrically connect two doped regions positioned at different sides of the bit line, then electrical connection is achieved, but the overlapped area with the word line becomes very large causing serious bit line coupling
Solution Approach 1:
The contact plug structure is divided into two separate leg portions (first leg portion and second leg portion) that are electrically isolated from each other by a shallow trench isolation structure. Each leg portion connects to one doped region independently, eliminating the need for a single large-volume contact plug that overlaps with the word line, thereby reducing bit line coupling while maintaining electrical connectivity.
2Reliability
If the contact plug structure extends over two doped regions and one shallow trench isolation structure to achieve electrical connection, then connectivity is established, but the volume of the contact plug becomes very large
Solution Approach 1:
The contact plug is segmented into two separate leg portions that are isolated by the shallow trench isolation structure. This segmentation allows each leg portion to have a smaller individual volume compared to a single contact plug spanning both doped regions, thereby reducing the overall volume while maintaining the electrical connection function.
Solution Approach 2:
The shallow trench isolation structure is extracted and positioned between the two leg portions to provide electrical isolation. This extraction of the isolation structure into a separate functional element enables the leg portions to be smaller and more compact, reducing the total contact plug volume while ensuring proper electrical connectivity to each doped region.
Data Source
AI summary
A contact plug structure for a checkerboard dynamic random access memory comprises a body portion, two leg portions connected to the body portion and a dielectric block positioned between the two leg portions. Each leg portion is electrically connected to a deep trench capacitor arranged in an S-shape manner with respect to the contact plug structure via a doped region isolated by a shallow trench isolation structure. Preferably, the body portion and the two leg portions can be made of the same conductive material selected from the group consisting of polysilicon, doped polysilicon, tungsten, copper and aluminum, while the dielectric block can be made of material selected from the group consisting of borophosphosilicate glass. Particularly, the contact plug can be prepared by dual-damascene technique. Since the overlapped area between the contact plug structure and a word line can be dramatically decreased, the bit line coupling (BLC) can be effectively reduced.