Deep Buried Channel JFET for Low Noise Analog Circuits
Solution Overview
Problem
High-performance precision analog applications require transistors with extremely low noise and high disturbance immunity, which existing junction field effect transistors (JFETs) do not fully meet due to surface non-uniformities and interference from overlying conductive materials.
Innovation Solution
A deep buried channel junction field effect transistor (DBCJFET) is fabricated with the channel located below the surface of the semiconductor workpiece, reducing noise and interference by creating a more regular current path and isolating it from surface irregularities and conductive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the channel is located at the surface of the workpiece, then the fabrication process is simpler, but the transistor is affected by surface non-uniformities and overlying conductive materials causing higher noise and lower disturbance immunity
Solution Approach 1:
The channel is moved from the surface plane to a deeper vertical position within the workpiece, transitioning from a two-dimensional surface location to a three-dimensional subsurface location. This dimensional change places the channel below surface non-uniformities and overlying conductive materials, thereby reducing noise and interference while maintaining fabrication feasibility through standard diffusion processes.
2Ease of manufacture
If the channel is located at the surface of the workpiece, then the fabrication process is simpler, but the current path is interrupted by surface non-uniformities causing higher noise
Solution Approach 1:
The channel is positioned at a greater vertical depth within the workpiece, moving the current path from the surface plane to a subsurface location. This dimensional relocation allows the current to flow through more uniform bulk material, avoiding interruptions from surface non-uniformities while maintaining consistent electrical characteristics.
3Object-affected harmful factors
If the channel is deeply buried within the workpiece, then noise and interference are reduced, but the fabrication process becomes more complex
Solution Approach 1:
The channel depth is controlled by adjusting diffusion parameters such as temperature, time, and dopant concentration during the fabrication process. By optimizing these parameters, the channel can be positioned at the appropriate depth to reduce noise and interference while using standard semiconductor fabrication techniques, avoiding the need for complex additional processing steps.
Data Source
AI summary
A junction field effect transistor (JFET) is fashioned where a channel of transistor is buried deeply within the workpiece within which the JFET is formed. Burying the channel below the surface of the workpiece and/or away from overlying conductive materials distances a current that flows in the channel from outside influences, such as the effects of the overlying conductive materials. The deep channel also provides a more regular path for the current flowing therein by moving the channel away from non-uniformities on or near the surface of the workpiece, where said non-uniformities or irregularities would interrupt or otherwise disturb current flowing in a channel that is not as deep. These aspects of the deep channel serve to reduce noise and allow the transistor to operate in a more repeatable and predictable manner, among other things.