FinFET Threshold Voltage Control via Gate Recesses
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving a wide range of threshold voltages for FinFET devices, as existing manufacturing processes limit the control over the separation distance of fins from isolation features, affecting the threshold voltage of FinFETs.
Innovation Solution
The method involves controlling the separation distance of fins from etched recesses in the gate structure to adjust the threshold voltage, using a gate-last process and forming metal gates with work-function layers to tune the voltage, and using different separation distances for multiple fins on the same substrate to achieve various threshold voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the separation distance of fins from isolation features is controlled to adjust threshold voltage, then the range of threshold voltages is improved, but the device complexity increases due to additional process steps
Solution Approach 1:
The patent extracts the gate structure from the conventional fixed configuration and makes it removable and reconfigurable. By etching recesses in the gate structure and filling them with dielectric material, the gate structure is transformed into a dynamic element that can be selectively modified to control fin separation distances, thereby enabling threshold voltage adjustment without adding fundamental new process steps
Solution Approach 2:
The gate structure is prepared in advance with etched recesses that are subsequently filled with dielectric material. This preliminary configuration of the gate structure allows for controlled separation of fins from isolation features, enabling threshold voltage adjustment before final device operation. The recesses are pre-positioned to achieve desired fin separation distances
2Adaptability or versatility
If multiple work-function layers are used to achieve different threshold voltages, then the threshold voltage control is improved, but the manufacturing process complexity increases
Solution Approach 1:
Instead of changing the material composition by adding multiple work-function layers, the patent changes the geometric parameter of the gate structure by creating recesses at different positions. This modifies the effective gate-to-fin separation distance, which in turn adjusts the threshold voltage. The same gate structure material is used, but its shape is varied to achieve different electrical characteristics
Solution Approach 2:
The patent transitions from controlling threshold voltage through material composition (horizontal dimension of material selection) to controlling it through structural geometry (vertical dimension of gate structure shape). By etching recesses at different depths and positions in the gate structure, the effective separation distance between the gate and fin is adjusted, providing threshold voltage control without additional material layers
Data Source
AI summary
A method includes forming a first semiconductor fin in a substrate, forming a metal gate structure over the first semiconductor fin, removing a portion of the metal gate structure to form a first recess in the metal gate structure that is laterally separated from the first semiconductor fin by a first distance, wherein the first distance is determined according to a first desired threshold voltage associated with the first semiconductor fin, and filling the recess with a dielectric material.