Lateral Transistor Body Implant Alignment for Precise Channel Length
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Solution Overview
Problem
Lateral transistors require short channel lengths with minimal variability for stable performance, but high-temperature annealing is often not sufficient for achieving sufficient diffusion length due to limited thermal budget in the doping process.
Innovation Solution
A method involving dopant implantation with precise control of the overlap between the gate layer and body region, using a photoresist layer with controlled opening sizes to define the lateral boundary of the body region, allowing for the formation of a lateral transistor with a controlled channel length without the need for high-temperature annealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If lateral diffusion of body doping is used to achieve short channel length, then channel length precision is improved, but thermal budget requirement increases
Solution Approach 1:
The patent changes the fundamental parameter of dopant introduction from thermal diffusion to ion implantation. This substitution allows precise control of channel length through implantation depth and lateral offset control, eliminating the need for high-temperature annealing while achieving the required channel length precision for advanced lateral transistors
Solution Approach 2:
The patent replaces the thermal field mechanism (diffusion process requiring high temperature) with a mechanical/physical field mechanism (ion implantation followed by low-temperature activation). This substitution enables precise channel length control without consuming excessive thermal budget, resolving the contradiction between precision and temperature requirement
2Length of moving object
If high-temperature annealing is used for dopant diffusion, then diffusion length is improved, but thermal budget is exceeded
Solution Approach 1:
The patent performs preliminary dopant placement through ion implantation at precisely controlled depths and lateral positions before final activation. This preliminary action eliminates the need for extensive high-temperature diffusion, as the dopant locations are pre-determined by implantation parameters rather than requiring thermal migration to achieve desired distribution
Solution Approach 2:
The patent fundamentally changes the dopant introduction mechanism from thermal diffusion (temperature-dependent) to ion implantation (energy-dependent). This parameter change enables achieving sufficient dopant distribution and channel length without exceeding the available thermal budget, as implantation depth and lateral offset are controlled by ion energy and angle rather than temperature
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 approach enables the manufacturing of lateral transistors with consistent channel lengths and reduced variability, suitable for various devices, while avoiding the constraints of limited thermal budgets and achieving precise control over the channel length.
Implementation Method 1
The photoresist layer is opened by lithography to form a first opening of a first opening size in the photoresist layer
Implementation Method 2
A body region is formed in the semiconductor substrate by dopant implantation
Data Source
AI summary
A method of manufacturing a lateral transistor is described. The method includes providing a semiconductor substrate. A dielectric layer is formed over the semiconductor substrate. A gate layer is formed over the dielectric layer. A photoresist layer is applied over the gate layer. The photoresist layer is opened by lithography to form a first opening of a first opening size in the photoresist layer. The first opening is transferred into a second opening of a second opening size, the second opening being either formed in the photoresist layer or in an auxiliary layer. A body region is formed in the semiconductor substrate by dopant implantation. Further the gate layer is structured to form a gate edge. An overlap between the structured gate layer and the body region is controlled by an offset between the first opening size and the second opening size.