Semiconductor Transistor Dopant Profile Optimization
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Solution Overview
Problem
Transistor devices face performance degradation due to fluctuations in processing operations that affect the precise placement and concentration of dopant impurities in the channel and source/drain regions, leading to variations in dopant profiles.
Innovation Solution
A semiconductor transistor with a tailored dopant profile is formed using an epitaxially-formed semiconductor material layer and a sequence of processing operations, including a well/Vt implant, annealing, and angled ion implantation, to create high concentration dopant regions at the edges of the channel and a reduced concentration at the interface with the gate dielectric, enhancing resistance to processing variations and short channel effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple separate processing operations are used to introduce and place dopant impurities, then the dopant profile can be controlled, but processing variations cause performance degradation
Solution Approach 1:
The dopant introduction process is divided into multiple sequential implantation steps (first dopant implantation, second dopant implantation, third dopant implantation), each targeting specific regions with different dopant types and concentrations. This segmentation allows precise control over the dopant profile while isolating each step's impact, reducing the cumulative effect of processing variations.
Solution Approach 2:
Different dopant impurities are introduced into different regions of the channel at different concentrations. The first dopant is placed in a first region, the second dopant in a second region, and the third dopant in a third region, creating locally optimized dopant profiles that enhance performance consistency by addressing specific regional requirements rather than applying uniform doping.
2Speed
If dopant concentration is increased to improve transistor performance, then switching speed increases, but short channel effects worsen
Solution Approach 1:
The patent introduces different dopant impurities at different concentrations into different regions along the channel. High concentration dopant regions are created in specific areas to enhance carrier injection and improve switching speed, while other regions maintain lower concentrations to minimize short channel effects. This spatial variation in dopant quality allows simultaneous optimization of speed and suppression of harmful effects.
Solution Approach 2:
A lightly-doped drain region is introduced as an intermediary between the high-doped source and the channel region. This intermediate region with moderate dopant concentration acts as a buffer that facilitates carrier injection (improving speed) while preventing excessive doping in the channel that would cause short channel effects. The intermediary region mediates between the conflicting requirements of high speed and low short channel effects.
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
The method results in transistors that are resistant to processing variations and short channel effects, maintaining optimal performance even as integration levels and operational speed increase, with a controlled dopant profile that suppresses random fluctuations.
Implementation Method 1
performing an angled ion implant to introduce further dopant impurities of the first impurity type, into the semiconductor substrate at edges of the channel region
Implementation Method 2
annealing
Implementation Method 3
at least one epitaxially-formed semiconductor material layer disposed over the substrate channel region
Data Source
AI summary
Provided is a transistor and a method for forming a transistor in a semiconductor device. The method includes performing at least one implantation operation in the transistor channel area, then forming a silicon carbide/silicon composite film over the implanted area prior to introducing further dopant impurities. A halo implantation operation with a very low tilt angle is used to form areas of high dopant concentration at edges of the transistor channel to alleviate short channel effects. The transistor structure so-formed includes a reduced dopant impurity concentration at the substrate interface with the gate dielectric and a peak concentration about 10-50 nm below the surface. The dopant profile also includes the transistor channel having high dopant impurity concentration areas at opposed ends of the transistor channel.