Pulse Train Annealing for Precise Dopant Activation
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Solution Overview
Problem
Current semiconductor manufacturing processes, such as Rapid Thermal Processing (RTP) and impulse annealing, face challenges in achieving rapid and uniform temperature ramp rates necessary for precise control of dopant placement and crystal lattice ordering in small device geometries, leading to issues like dopant diffusion and surface damage.
Innovation Solution
A method and apparatus for pulsed annealing using a series of electromagnetic energy pulses with controlled energy density and duration, monitored by acoustic emission detection, to achieve precise temperature control and minimize dopant diffusion, allowing for the formation of smaller, high-performance semiconductor devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional thermal processes (RTP, impulse annealing) are used to heat substrates to high temperatures for annealing, then dopant activation and crystal lattice ordering can be achieved, but the temperature ramp rates are too slow and exposure to elevated temperatures is too long, causing dopant diffusion and loss of manufacturing precision
Solution Approach 1:
The patent applies periodic action by using multiple short-duration electromagnetic energy pulses instead of continuous heating. The substrate is subjected to a series of discrete pulses (e.g., 10-1000 pulses of 1-100 microseconds each), allowing rapid temperature cycling that achieves dopant activation while minimizing total exposure time at elevated temperatures, thus preventing dopant diffusion and improving placement precision.
Solution Approach 2:
The patent segments the thermal processing into multiple discrete electromagnetic energy pulses rather than applying continuous heat. Each pulse delivers energy for a brief duration (1-100 microseconds), and the cumulative effect of many such pulses achieves the required annealing while maintaining extremely high instantaneous ramp rates and limiting total time at high temperature, thereby resolving the contradiction between achieving activation and preventing diffusion.
2Manufacturing precision
If higher temperature ramp rates are used to reduce dopant diffusion, then manufacturing precision improves, but surface damage and harmful factors increase
Solution Approach 1:
The patent applies partial action by using multiple sub-critical pulses instead of a single high-intensity pulse. Each individual pulse delivers insufficient energy to cause surface damage or melting, but the cumulative effect of many such pulses (10-1000 pulses) achieves the required thermal budget for dopant activation and lattice ordering, thus controlling dopant concentration precisely without causing surface damage.
Solution Approach 2:
The patent provides beforehand cushioning by distributing the total energy delivery across many low-intensity pulses with cooling intervals between them. This prevents any single pulse from delivering excessive energy that would cause surface damage, while the cumulative thermal effect still achieves the necessary annealing, thus protecting the substrate surface while maintaining manufacturing precision.
3Stability of the object's composition
If longer processing times are used to achieve uniform temperature distribution, then temperature uniformity improves, but productivity decreases due to extended exposure at elevated temperatures
Solution Approach 1:
The patent uses periodic action with multiple short pulses (1-100 microseconds each) delivered in rapid succession or with minimal spacing. This creates a cumulative thermal effect that achieves uniform temperature distribution across the substrate while keeping the total processing time extremely short (microseconds to milliseconds), thus maintaining both temperature uniformity and high productivity by minimizing total exposure time at elevated temperatures.
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 controlled diffusion and activation of dopants, reduces surface damage, and improves uniformity, effectively addressing the limitations of existing methods by allowing for precise atomic-level control in semiconductor processing.
Implementation Method 1
delivering a plurality of electromagnetic energy pulses to a surface of the substrate, each pulse having a duration of 1 nanosecond to 10 milliseconds
Implementation Method 2
detecting an acoustic response from the substrate
Data Source
AI summary
The present invention generally describes apparatuses and methods used to perform an annealing process on desired regions of a substrate. In one embodiment, pulses of electromagnetic energy are delivered to a substrate using a flash lamp or laser apparatus. The pulses may be from about 1 nsec to about 10 msec long, and each pulse has less energy than that required to melt the substrate material. The interval between pulses is generally long enough to allow the energy imparted by each pulse to dissipate completely. Thus, each pulse completes a micro-anneal cycle. The pulses may be delivered to the entire substrate at once, or to portions of the substrate at a time. Further embodiments provide an apparatus for powering a radiation assembly, and apparatuses for detecting the effect of pulses on a substrate.