Pulsed Annealing for Semiconductor Dopant Control
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Solution Overview
Problem
Conventional thermal processing methods for semiconductor substrates, such as Rapid Thermal Processing (RTP) and impulse annealing, face challenges in achieving rapid and uniform temperature ramp rates, leading to dopant diffusion and surface damage, which are exacerbated by shrinking device sizes and increasing complexity in achieving precise dopant distribution and crystal lattice ordering.
Innovation Solution
A pulsed annealing method using a substrate support and a radiation assembly with multiple sources of electromagnetic radiation, where the substrate is subjected to a series of pulses of controlled energy to manage temperature and dopant distribution, allowing for precise control over the annealing process through detection of acoustic emissions and adjustment of energy delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional thermal processing methods (RTP, impulse annealing) are used to heat substrates to high temperatures for annealing, then dopant activation and crystal lattice ordering can be achieved, but temperature ramp rates are too slow and exposure to elevated temperatures is too long, causing dopant diffusion and loss of concentration abruptness
Solution Approach 1:
The patent applies periodic pulsed thermal processing where the substrate is subjected to multiple rapid temperature cycles (heating and cooling) rather than continuous heating. Each pulse delivers thermal energy for a brief duration followed by rapid cooling, achieving dopant activation through cumulative thermal effects while minimizing total time at elevated temperatures and preventing excessive dopant diffusion.
Solution Approach 2:
The patent implements dynamic temperature control by rapidly adjusting the thermal processing parameters during the annealing process. The system dynamically modulates heating power and timing to achieve precise temperature profiles, enabling fast ramp rates and controlled dwell times that prevent dopant diffusion while ensuring complete dopant activation and crystal lattice recovery.
2Manufacturing precision
If rapid temperature ramp rates are implemented to reduce dopant diffusion, then dopant distribution precision is improved, but thermal uniformity across the substrate becomes difficult to achieve
Solution Approach 1:
The patent segments the thermal processing into multiple discrete pulses distributed across the substrate surface. By dividing the total thermal energy delivery into many small pulses rather than one large continuous heating event, the system achieves rapid effective ramp rates while allowing heat to distribute uniformly across the substrate between pulses, preventing localized overheating and ensuring thermal uniformity.
3Productivity
If high energy density is delivered in a single impulse to achieve rapid annealing, then processing time is reduced, but surface damage occurs
Solution Approach 1:
The patent applies partial action by delivering multiple pulses at moderate energy densities rather than a single impulse at excessive energy density. Each pulse delivers sufficient thermal energy to progress the annealing process but remains below the threshold that would cause surface damage, achieving cumulative therapeutic effect without harmful overdose.
Solution Approach 2:
The patent uses periodic pulsing to deliver thermal energy in controlled intervals, allowing the substrate to partially dissipate heat between pulses. This prevents excessive energy accumulation that would cause surface damage while maintaining high overall processing efficiency through the cumulative effect of many rapid pulses.
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 precise control over dopant distribution and crystal lattice ordering, reducing dopant diffusion and surface damage, while accommodating the stringent requirements of smaller device geometries by delivering energy in a manner that is both rapid and uniform, thereby enhancing the performance of semiconductor devices.
Implementation Method 1
directing at least 100 pulses of electromagnetic energy toward the substrate
Implementation Method 2
detecting sound waves generated by the substrate when each pulse of electromagnetic energy strikes 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.