Coterminous Gate Structure for SRAM Bitcell Area Reduction
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Solution Overview
Problem
Existing semiconductor device layouts require significant layout area due to the need for gate layer endcaps to accommodate overlay misalignment and process variations, leading to increased costs in integrated circuits.
Innovation Solution
Forming semiconductor devices before isolation trenches, eliminating endcaps and allowing the gate to be coterminous with the active area, thereby reducing the distance between active areas and minimizing layout area requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate layer endcaps are added to accommodate overlay misalignment and process variations, then manufacturing reliability is improved, but layout area increases
Solution Approach 1:
The patent applies preliminary action by forming the semiconductor devices (transistors, gates, active areas) before forming the isolation trenches. This sequence allows the gate to be made coterminous with the active area without requiring endcaps, as the isolation structures are established after the critical device features are already in place. The preliminary formation of devices enables tighter spacing while maintaining manufacturing reliability.
2Manufacturing precision
If endcaps are used to allow for overlay misalignment, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent forms the gate and active area to be coterminous before trench formation, establishing precise device boundaries in advance. This preliminary action eliminates the need for endcaps while maintaining the necessary alignment tolerance, as the isolation trenches are formed subsequently to accommodate the already-defined device edges.
3Reliability
If the gate extends beyond the active area with endcaps, then overlay misalignment is compensated, but the distance between active areas increases
Solution Approach 1:
The patent establishes the gate and active area boundaries to be coterminous before forming isolation trenches. This preliminary definition of device boundaries allows the active areas to be placed closer together, as the isolation structures are formed afterward to provide necessary separation without requiring gate extension beyond active areas.
Data Source
AI summary
A semiconductor device is formed on a semiconductor layer. A gate dielectric layer is formed over the semiconductor layer. A layer of gate material is formed over the gate dielectric layer. The layer of gate material is patterned to form a gate structure. Using the gate structure as a mask, an implant into the semiconductor layer is performed. To form a first patterned gate structure and a trench in the semiconductor layer surrounding a first portion and a second portion of the semiconductor layer and the gate, an etch through the gate structure and the semiconductor layer is performed. The trench is filled with insulating material.