Vertical Transistor Grain Control With Laser-Annealed Channel Doping
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Solution Overview
Problem
Current methods for forming integrated circuitry, particularly in memory cells, face challenges in achieving precise control over the crystallinity and dopant distribution in transistors, which affects the conductivity and reliability of the circuitry.
Innovation Solution
The method involves forming transistors with crystalline source/drain and channel regions, using laser annealing to activate conductivity-increasing dopants, and structuring the channel region with varying dopant concentrations to optimize conductivity, while a gate insulator and gate are laterally-adjacent to the channel, ensuring precise control over the transistor's construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to form transistors in memory cells, then the manufacturing process is simpler, but the control over crystallinity and dopant distribution is insufficient
Solution Approach 1:
The channel region is segmented into multiple portions (first channel portion, second channel portion, third channel portion) with different dopant concentrations. This segmentation allows precise control over dopant distribution and crystallinity in each region, enabling optimized conductivity profiles while maintaining manufacturing feasibility through standardized formation processes.
Solution Approach 2:
Different regions of the transistor are given different local properties: the first channel portion has a first dopant concentration, the second channel portion has a second dopant concentration, and the third channel portion has a third dopant concentration. This local quality variation enables precise control over electrical characteristics in different areas of the channel, improving overall transistor performance.
2Reliability
If laser annealing is used to activate dopants and control crystallinity, then the conductivity and reliability are improved, but the manufacturing process becomes more complex
Solution Approach 1:
Dopants are implanted into the channel region before the laser annealing process. This preliminary doping action allows the subsequent laser annealing to focus solely on activating the dopants and controlling crystallinity, rather than having to perform both doping and annealing in a single complex step. The preliminary doping simplifies the overall process by separating the doping and activation functions.
Solution Approach 2:
Laser annealing utilizes phase transitions in the semiconductor material to control crystallinity. The rapid heating and cooling cycles induced by laser annealing cause controlled phase transitions between amorphous and crystalline states, enabling precise control over the crystal grain structure and dopant activation without requiring excessively complex manufacturing equipment.
3Manufacturing precision
If the channel region has uniform dopant concentration, then the manufacturing process is simpler, but the conductivity control is less precise
Solution Approach 1:
The channel region is divided into multiple segments (first, second, and third channel portions) each with distinct dopant concentrations. This segmentation enables precise control over the conductivity profile along the channel length, allowing optimization of carrier injection at source/drain interfaces while maintaining appropriate barrier heights in the middle region.
Solution Approach 2:
The dopant concentration parameter is varied across different channel portions to optimize transistor performance. By changing the dopant concentration from the first channel portion to the second and third portions, the invention achieves precise control over conductivity without requiring complex multi-step doping processes, as the concentration gradients can be established through controlled implantation and annealing.
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 results in transistors with consistent and controlled crystal grain sizes, enhanced conductivity, and improved reliability, enabling more efficient integrated circuitry formation.
Implementation Method 1
The source/drain and channel regions are laser annealed to form crystalline regions
Implementation Method 2
melt and then crystallize the at least one of the source/drain and channel regions to be crystalline
Implementation Method 3
laser annealing to activate conductivity-increasing dopants
Implementation Method 4
The source/drain and channel regions are laser annealed to form crystalline regions
Implementation Method 5
a thin gate insulator... separated therefrom by a thin gate insulator
Implementation Method 6
activate conductivity-increasing dopants... dopant concentrations to optimize conductivity
Data Source
AI summary
A transistor comprises a top source/drain region, a bottom source/drain region, a channel region vertically between the top and bottom source/drain regions, and a gate operatively laterally-adjacent the channel region. At least one of the top source/drain region, the bottom source/drain region, and the channel region are crystalline. All crystal grains within the at least one of the top source/drain region, the bottom source/drain region, and the channel region have average crystal sizes within 0.064 μm3 of one another. Other embodiments, including methods, are disclosed.