Semiconductor Device Dopant Retarding Region Boron Diffusion
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Solution Overview
Problem
In semiconductor devices, particularly power transistors like LDMOS, it is challenging to prevent unintentional co-doping of n-type junctions with boron atoms during diffusion processes, which can lead to undesirable diffusion of boron into neighboring regions, affecting device performance and reliability.
Innovation Solution
A dopant retarding region doped with materials like carbon, nitrogen, or fluorine is introduced between the n-doped drift region and the p-doped channel region to block boron diffusion, using selective diffusion retarding agents that alter the diffusion rate and prevent boron from intermixing with arsenic or phosphorous.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a diffusion process is used to dope the semiconductor body, then dopants can be introduced into the desired regions, but unintentional co-doping of adjacent regions occurs due to boron diffusion
Solution Approach 1:
A dopant retarding region is introduced between the drift region and channel region to act as an intermediary barrier. This region is doped with materials such as carbon, nitrogen, or fluorine that have low diffusion coefficients, thereby preventing boron atoms from diffusing into the drift region while still allowing the desired doping of the channel region
Solution Approach 2:
The dopant retarding region is created with locally different doping characteristics - it has high concentration of dopants with low diffusion coefficients (carbon, nitrogen, or fluorine) specifically at the interface between drift and channel regions, while other regions maintain their original doping profiles. This localized modification prevents boron diffusion only where needed
2Reliability
If the dopant retarding region is doped with carbon, nitrogen or fluorine, then boron diffusion is blocked, but the device structure becomes more complex
Solution Approach 1:
The dopant retarding region is formed in advance before the final doping steps. By pre-establishing this barrier region with low-diffusion dopants, the patent prevents boron diffusion issues that would otherwise require complex post-processing or redesign, thereby improving reliability without proportionally increasing overall device complexity
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 effectively prevents boron diffusion into sensitive regions, maintaining desired doping levels and improving the reliability and performance of power transistors by avoiding unintentional co-doping, thereby enhancing the stability and efficiency of the devices.
Implementation Method 1
dopants of the second conductivity type are driven into the semiconductor body at a first diffusion rate. The dopant retarding region prevents the dopants from diffusing into the drift region at the first diffusion rate
Implementation Method 2
The semiconductor body is annealed to form a body region so that dopants of the second conductivity type are driven into the semiconductor body at a first diffusion rate
Data Source
AI summary
A semiconductor device includes a drift region in a first region of a semiconductor body. The drift region includes dopants of a first conductivity type. A dopant retarding region is formed at least adjacent an edge of the drift region. Dopants of a second conductivity type are implanted into the semiconductor body. The semiconductor body is annealed to form a body region so that dopants of the second conductivity type are driven into the semiconductor body at a first diffusion rate. The dopant retarding region prevents the dopants from diffusing into the drift region at the first diffusion rate.