Two-Stage Flash Heating for Shallow Junction Wafer Annealing
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Solution Overview
Problem
Conventional heat treatment methods for semiconductor wafers using halogen lamps or xenon flash lamps face challenges in achieving shallow ion junctions without deep diffusion of ions, and existing solutions either result in excessive surface heating or introduce new crystal defects.
Innovation Solution
A heat treatment method involving a two-stage light irradiation process, where a peak emission output is followed by a supplemental irradiation with reduced output, maintaining the surface temperature and gradually raising temperatures at defect depths within a total irradiation time of one second or less to activate ions and restore defects without damaging the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If extremely high-energy light is emitted from flash lamps to raise temperature at defect depth within one millisecond, then defect restoration is enabled, but surface temperature rises considerably causing substrate damage
Solution Approach 1:
The light emission is divided into multiple discrete pulses instead of a single continuous emission. The controller causes the flash lamps to emit light in a first pulse, then a second pulse, then a third pulse, with intervals between pulses. This segmentation allows the substrate to dissipate heat between pulses, preventing excessive surface temperature rise while still achieving the required temperature at defect depth over the extended treatment time.
Solution Approach 2:
The light emission follows a periodic pattern with controlled intervals between pulses. The controller is configured to emit light at specific periodic intervals, creating a rhythm of heating and cooling cycles. This periodic action enables cumulative heating effect at depth while allowing surface temperature to reset between pulses, resolving the contradiction between achieving deep temperature rise and preventing surface damage.
2Temperature
If light irradiation time is extended to raise temperature at defect depth, then defect restoration is improved, but surface temperature rises excessively causing substrate damage
Solution Approach 1:
The total light irradiation time is segmented into multiple discrete pulses rather than a single continuous emission. The controller divides the treatment into a first pulse, second pulse, and third pulse with intervals between them. This segmentation extends the effective treatment time for deep defect restoration while allowing heat dissipation at the surface during intervals, preventing excessive surface temperature rise.
Solution Approach 2:
The first light pulse serves as a preliminary action that begins the heating process and starts restoring defects at depth. Subsequent pulses build upon this preliminary heating effect, progressively achieving the required temperature at defect depth without requiring a single excessively long continuous emission that would cause surface damage.
3Device complexity
If conventional halogen lamps are used for heating, then equipment complexity is low, but ion diffusion occurs leading to deeper junctions than desired
Solution Approach 1:
The invention changes the temporal parameters of light emission from continuous (halogen lamps) to pulsed intervals (flash lamps with controlled timing). By adjusting the duration, intensity, and spacing of light pulses, the heating profile is optimized to achieve shallow junction formation with minimal ion diffusion, thereby improving manufacturing precision while maintaining relatively simple equipment architecture.
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 activates implanted ions and restores defects at depth without excessive surface heating, ensuring reliable prevention of substrate damage and achieving both ion activation and defect restoration efficiently.
Implementation Method 1
The wavelength of the light emitted from xenon flash lamps is shorter than that of the light emitted from conventional halogen lamps, and it almost coincides with a fundamental absorption band of a silicon semiconductor wafer. Thus, when a semiconductor wafer is irradiated with the flash light emitted from xenon flash lamps, the temperature of the semiconductor wafer can be raised rapidly
Implementation Method 2
the speed of a temperature rise at the surface of the semiconductor wafer is higher than the speed of heat transmission to the inside of the semiconductor wafer by thermal conductivity of silicon
Data Source
AI summary
In light-irradiation heating with a total irradiation time of one second or less, two-stage irradiation is performed, including a first stage of light irradiation of a semiconductor wafer, which irradiation produces an output waveform that reaches a peak at a given emission output; and a second stage of supplemental light irradiation of the semiconductor wafer, which irradiation is started after the peak, producing an emission output smaller than the above given emission output. The emission output in the second stage is two thirds or less than the above given emission output at the peak. The first-stage light-irradiation time is between 0.1 and 10 milliseconds, and the second-stage light-irradiation time is 5 milliseconds or more.