SRAM Cell T-Shaped Contacts for Alignment Precision
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Solution Overview
Problem
In integrated circuits, SRAM cells with T-shaped contacts face challenges in optimizing the photolithographic exposure steps for forming electrical connections between transistors, which can affect the separation and alignment of gate and drain connecting segments, impacting the performance and reliability of the SRAM cells.
Innovation Solution
The use of T-shaped contacts with laterally offset and tilted gate connecting segments, which are formed through separate photolithographic exposure steps, ensures increased separation and perpendicular alignment, enhancing the electrical connections between driver and load transistors in cross-coupled inverters within SRAM cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate photolithographic exposure steps are used for gate and drain connecting segments, then alignment precision and separation are improved, but manufacturing complexity and process time increase
Solution Approach 1:
The contact structure is divided into two distinct segments: a drain connecting segment and a gate connecting segment. These segments are formed through separate photolithographic exposure steps, allowing independent optimization of each segment's alignment and separation. The drain connecting segment connects to the drain node while the gate connecting segment connects to the gate electrode, with a lateral offset between them to prevent shorting and improve reliability.
2Reliability
If T-shaped contacts are used to connect drain nodes and gate electrodes, then electrical connection reliability is improved, but photolithographic exposure difficulty increases
Solution Approach 1:
The contact structure transitions from a traditional planar configuration to a T-shaped three-dimensional configuration. The drain connecting segment extends laterally offset from the gate connecting segment, creating a T-shape when viewed in cross-section. This dimensional change allows both segments to be formed through separate photolithographic steps with improved alignment control, while maintaining reliable electrical connections to both the drain node and gate electrode.
Data Source
AI summary
An integrated circuit containing an array of SRAM cells with T-shaped contacts in the inverters, in which drain connecting segments may extend beyond gate connecting segments by a distance greater than 10 percent of a separation distance between ends of opposite drain connecting segments. The drain connecting segments may also extend beyond gate connecting segments by a distance greater than one-third of the width of the gate connecting segments. A process of forming an integrated circuit containing an array of SRAM cells with T-shaped contacts in which drain connecting segments may extend beyond gate connecting segments by a distance greater than 10 percent of a separation distance between ends of opposite drain connecting segments. A process may also form the drain connecting segments to extend beyond gate connecting segments by greater than one-third of the width of the gate connecting segments.