Susceptor Support Pin Layout for Flash Annealing Wafer Integrity
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Solution Overview
Problem
Flash-lamp annealing for semiconductor wafers causes abrupt thermal expansion at the front surface, leading to stress concentration and potential breakage due to uneven temperature distribution, as the back surface does not increase in temperature significantly.
Innovation Solution
A heat treatment susceptor with upright support pins positioned to contact the substrate at areas experiencing no stress, preventing stress concentration and substrate breakage during flash light exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flash light is irradiated to the front surface of the semiconductor wafer, then the temperature of the front surface rapidly increases and impurities are activated, but the back surface temperature does not increase significantly causing stress concentration and wafer breakage
Solution Approach 1:
The patent applies local quality by positioning support pins at specific locations on the wafer back surface where stress is minimized during flash annealing. The support pins are strategically placed at positions corresponding to stress-free zones (e.g., at a distance of approximately 0.707 times the wafer radius from the center), providing localized support precisely where needed to prevent breakage while maintaining the rapid heating effect on the front surface.
Solution Approach 2:
The patent implements preliminary action by pre-positioning the support pins on the susceptor before wafer placement. The support pins are arranged in advance at calculated stress-free positions based on the wafer dimensions and flash lamp configuration, so that when the wafer is placed and subjected to flash annealing, the support structure is already optimized to prevent stress concentration and breakage.
2Strength
If support pins are placed on the back surface of the substrate, then the substrate is supported during heating, but stress concentration occurs at the contact points causing breakage
Solution Approach 1:
The patent applies local quality by positioning support pins at specific locations on the wafer back surface where stress is minimized during flash annealing. The support pins are strategically placed at positions corresponding to stress-free zones (e.g., at a distance of approximately 0.707 times the wafer radius from the center), providing localized support precisely where needed to prevent breakage while maintaining the rapid heating effect on the front surface.
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 susceptor design ensures that the substrate is supported at stress-free areas, preventing breakage during flash light application and maintaining substrate integrity.
Implementation Method 1
The xenon flash lamps have a spectral distribution of radiation ranging from ultraviolet regions to near-infrared regions. The wavelength of light emitted from the xenon flash lamps is shorter than that of light emitted from conventional halogen lamps and substantially coincides with the fundamental absorption band of a silicon semiconductor wafer. Thus, the temperature of the semiconductor wafer can be rapidly increased with a small amount of transmitted light when the semiconductor wafer is irradiated with flash light from the xenon flash lamps.
Implementation Method 2
Since the flash lamps instantaneously emit the flash light having extremely high energy to the front surface of the semiconductor wafer, the temperature of the front surface of the semiconductor wafer instantaneously rapidly increases while the temperature of the back surface does not increase so much. Thus, abrupt thermal expansion occurring only in the front surface of the semiconductor wafer causes deformation in the semiconductor wafer such that the front surface warps and becomes raised.
Data Source
AI summary
A plurality of substrate support pins are provided upright on a holding plate so as to contact a position on which no stress is exerted in a lower surface of a semiconductor wafer when an upper surface of the semiconductor wafer is irradiated with flash light emitted from a flash lamp and thus reaches a maximum temperature. When the application of the flash light causes the upper surface of the semiconductor wafer to warp such that the upper surface becomes raised, stress concentration does not occur in the contact position of the lower surface of the semiconductor wafer that contacts the plurality of substrate support pins. The semiconductor wafer can be prevented from breaking during the application of the flash light.