VCSEL-Assisted Wafer Flash Heating for Uniform Preheating
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Solution Overview
Problem
Current heat treatment methods for semiconductor wafers, such as those using halogen lamps, face inefficiencies in preheating due to long wavelength infrared light absorption, leading to incomplete impurity activation and diffusion, while LED lamps provide insufficient heating intensity despite high absorption efficiency at lower temperatures.
Innovation Solution
A heat treatment apparatus employing a combination of vertical cavity surface emitting lasers (VCSELs) and LED lamps, where VCSELs are used to preheat the substrate efficiently with high-intensity, directionally focused light, and LED lamps supplement heating in the center to achieve uniform temperature distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If halogen lamps are used for preheating, then the heating process can be performed, but the heating efficiency is low due to poor absorption of infrared light at low temperatures
Solution Approach 1:
The patent changes the wavelength parameter of the light source from infrared (halogen lamp) to visible light (LED lamp). LED lamps emit visible light with wavelengths of 400-700nm, which has a much higher absorption coefficient in silicon at low temperatures compared to infrared light. This parameter change resolves the contradiction by enabling efficient heating without requiring excessive energy input or prolonged exposure time.
2Use of energy by moving object
If LED lamps are used for preheating, then the absorption efficiency is high at lower temperatures, but the heating intensity is insufficient
Solution Approach 1:
The patent combines multiple LED lamps to form an array configuration. By merging the output of numerous individual LED lamps (typically 10-100 lamps arranged in arrays), the system achieves both high absorption efficiency (inherent LED property) and sufficient heating intensity (collective output of multiple lamps). This merging principle resolves the contradiction between individual lamp limitations and system-level performance requirements.
3Temperature
If halogen lamps are used for preheating, then heating can be performed, but the preheating time is prolonged causing impurity diffusion
Solution Approach 1:
The patent changes the spectral characteristics parameter of the light source from infrared to visible light range. Since silicon has a much higher absorption coefficient for visible light (400-700nm) at low temperatures compared to infrared wavelengths, this parameter change enables rapid energy absorption and temperature rise. The result is that preheating time is reduced from minutes to seconds, preventing impurity diffusion while achieving the required temperature.
4Power
If multiple LED lamps are disposed to achieve high irradiation intensity, then the heating intensity can be increased, but the device complexity increases
Solution Approach 1:
The patent segments the lighting system into multiple discrete LED lamp units that can be independently controlled and arranged in modular arrays. Each LED lamp is a simple, standardized component, and by segmenting the system this way, the patent achieves high irradiation intensity through quantity while maintaining ease of manufacture and system simplicity. The modular nature allows flexible configuration without proportionally increasing overall system complexity.
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 apparatus achieves efficient and uniform heating of semiconductor wafers by increasing light intensity and directionality with VCSELs, reducing impurity diffusion and ensuring thorough activation, while maintaining cost-effectiveness through strategic placement of LED lamps.
Implementation Method 1
The LED lamp mainly emits visible light. Thus even in a case of a semiconductor wafer having a relatively low temperature of 500° C. or less, an absorption index of light emitted from the LED lamp is high
Implementation Method 2
the auxiliary light source including a plurality of vertical cavity surface emitting lasers
Implementation Method 3
a wavelength of the xenon flash lamp is shorter than that of a conventional halogen lamp, and almost coincides with a basic absorption band of a silicon semiconductor wafer. Thus, when the semiconductor wafer is irradiated with a flash of light emitted from the xenon flash lamp, the temperature of the semiconductor wafer can be rapidly increased
Implementation Method 4
The flash lamp anneal is a heat treatment technique of irradiating a surface of a semiconductor wafer with a flash of light using a xenon flash lamp
Data Source
AI summary
Provided is a flash heating part including a plurality of flash lamps on an upper side of a chamber housing a semiconductor wafer, and also provided is an auxiliary heating part including a plurality of VCSELs (vertical cavity surface emitting lasers) on a lower side thereof. After the semiconductor wafer is preheated by light irradiation from the VCSELs, a front surface of the semiconductor wafer is irradiated with a flash of light from the flash lamps to instantaneously increase a temperature of the surface thereof. The VCSELs can emit light having relatively higher intensity than the LEDs. Thus, when light irradiation from the plurality of VCSELs is performed, intensity of light emitted to the substrate can also be increased, and the semiconductor wafer can be efficiently heated.