Segmented Gate Structure for Halo Implant Positioning
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Solution Overview
Problem
The challenge in semiconductor device manufacturing is to reduce the short channel effect in MOS transistors, which is limited by the gate pitch, gate height, and mask layer height, preventing effective positioning of angled halo implants under the gate, leading to inferior device performance.
Innovation Solution
A transistor structure is developed with a pair of lower gates positioned under the upper gate within an isolation structure, allowing for angled halo implants at angles between 17° and 32°, enhancing the positioning of halo regions and improving device performance by forming a frame-like structure with trenches and gates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an angled halo implant is used to reduce short channel effect, then the channel length is reduced and punch-through current is controlled, but the implant is blocked by gate pitch, gate height, and mask layer height, preventing effective positioning under the gate
Solution Approach 1:
The gate structure is segmented into an upper gate and a lower gate at different depths. The lower gate is positioned beneath the upper gate, allowing the halo implant to reach the channel region under the gate through the space between these segmented gate structures. This segmentation enables the halo implant to be effectively positioned where it is needed without being blocked by a single continuous gate structure.
Solution Approach 2:
The invention introduces a vertical dimensionality change by placing the lower gate at a different depth level than the upper gate. This creates a three-dimensional gate structure where the lower gate operates at a deeper level, allowing the halo implant to access the channel region from above without being blocked by the upper gate, thus solving the positioning problem in the vertical dimension.
2Reliability
If the gate height is increased to improve device performance, then the control over the channel is enhanced, but the angled halo implant is blocked from reaching the channel region under the gate
Solution Approach 1:
The gate is segmented vertically into upper and lower components. The lower gate is positioned at a depth that allows the halo implant to pass through and reach the channel region, while the upper gate provides the necessary height for device performance. This segmentation resolves the conflict between needing tall gates for performance and needing implant access for manufacturing.
Solution Approach 2:
The lower gate acts as an intermediary structure that facilitates the halo implant process. By positioning the lower gate at a specific depth, it serves as a mediator that allows the implant to reach the channel while still providing gate control functionality, thus enabling both high device performance and ease of manufacture.
3Productivity
If the gate pitch is reduced to increase device density, then more devices can be packed, but the angled halo implant is blocked from effectively positioning under the gate
Solution Approach 1:
By introducing a vertical dimension with the lower gate positioned at a different depth, the invention allows the halo implant to access the channel region without being constrained by the horizontal gate pitch. This dimensional change enables effective halo implant positioning even when gates are closely spaced horizontally, thus maintaining device density while improving implant precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration improves drain-to-source current and reduces current leakage, while maintaining or exceeding performance even when the angled halo implant is blocked, compared to devices without lower gates or those with H-shaped gates.
Implementation Method 1
a pair of first lower gates disposed under the first upper gate and isolated from the active region by the isolation structure
Implementation Method 2
allowing for angled halo implants at angles between 17° and 32°
Data Source
AI summary
The present disclosure provides a transistor device and a method for preparing the same. The transistor device includes an isolation structure disposed in a substrate, an active region disposed in the substrate and surrounded by the isolation structure, a first upper gate disposed over the active region and a portion of the isolation structure, a source/drain disposed at two sides of the gate, and a pair of first lower gates disposed under the first upper gate and isolated from the active region by the isolation structure. In some embodiments, the pair of first lower gates extend in a first direction, the first upper gate extends in a second direction, and the first direction and the second direction are different.