Flash Lamp Heat Treatment for Deep Junction Activation
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Solution Overview
Problem
Conventional heat treatment apparatuses using xenon flash lamps struggle to activate deep junctions in semiconductor wafers without causing substrate warpage or cracking due to excessive thermal stress.
Innovation Solution
A heat treatment apparatus employing a combination of flash lamps with different pulse widths, where a first lamp group emits light for a short duration and a second lamp group emits light for a longer duration, with staggered start timings to superimpose their light on the substrate, allowing for deep junction activation without overheating the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the duration of light emission from flash lamps is increased to raise the temperature of deep portions of the semiconductor wafer, then the activation of deep junctions becomes possible, but the surface temperature rises more than necessary, causing wafer warpage or cracking due to thermal stress
Solution Approach 1:
The flash lamp system is divided into multiple groups (first lamp group and second lamp group) with different pulse widths. The first lamp group emits light for a shorter duration (e.g., 1-10 ms) while the second lamp group emits light for a longer duration (e.g., 10-100 ms). This segmentation allows different regions of the wafer to receive different heating profiles, enabling deep junction activation without excessive surface heating that would cause warpage or cracking.
Solution Approach 2:
The invention changes the temporal parameter (pulse width) of the flash lamp emission by using multiple lamp groups with different pulse durations. By controlling the start timing and duration of each lamp group, the system achieves different temperature penetration depths. The longer pulse width lamps heat deeper portions while the shorter pulse width lamps control surface temperature, thus activating deep junctions without causing thermal stress damage.
2Temperature
If conventional halogen lamps are used to heat the semiconductor wafer, then the activation of ions is achieved, but the ions are deeply diffused by heat, causing the junction depth to exceed the required level
Solution Approach 1:
The invention uses periodic flash lamp emission with controlled pulse widths instead of continuous heating. The flash lamps emit light in short, intense pulses that rapidly heat the wafer to the required temperature for ion activation. This periodic action allows the wafer to be heated quickly to the activation temperature and then cooled just as quickly, minimizing the time available for thermal diffusion of ions, thus maintaining precise junction depth control.
Solution Approach 2:
The invention changes the heating rate parameter by using flash lamps with extremely short pulse widths (milliseconds or less) compared to conventional continuous or long-pulse heating methods. This rapid heating and cooling cycle achieves ion activation while limiting thermal diffusion, thereby maintaining the required junction depth precision.
3Manufacturing precision
If xenon flash lamps are used to raise the temperature of only the surface of the semiconductor wafer in an extremely short time, then ion activation is achieved without deep ion diffusion, but the activation of deeper junctions becomes difficult
Solution Approach 1:
The flash lamp system is segmented into multiple groups with different pulse widths to provide different heating depths. The first lamp group with shorter pulse width maintains surface temperature control for shallow junctions, while the second lamp group with longer pulse width extends heating to deeper portions. This segmentation enables the system to handle both shallow and deep junction activation requirements within a single apparatus.
Solution Approach 2:
The multi-group flash lamp system achieves multi-functionality by being capable of activating both shallow and deep junctions using the same apparatus. By controlling which lamp groups are activated and their respective pulse widths, the system can adapt to different junction depths, making it a universal solution for various semiconductor processing requirements.
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 the activation of deep junctions in semiconductor wafers without causing warpage or cracking, by precisely controlling the temperature distribution across the substrate, ensuring efficient heat treatment without thermal stress.
Implementation Method 1
The flash lamps have a spectral distribution of radiation ranging from ultraviolet to near-infrared regions. The wavelength of light emitted from the flash lamps is shorter than that emitted from conventional halogen lamps, and it approximately coincides with a basic absorption band of a silicon semiconductor wafer. It is therefore possible to, when a semiconductor wafer is irradiated with a flash of light emitted from the flash lamps, rapidly raise the temperature of the semiconductor wafer
Implementation Method 2
raise the temperature of not only the surface (a shallow portion) but also a deep portion of a semiconductor wafer by heat conduction
Data Source
AI summary
Flash lamps connected to short-pulse circuits and flash lamps connected to long-pulse circuits are alternately arranged in a line. The duration of light emission from the flash lamps connected to the long-pulse circuits is longer than the duration of light emission from the flash lamps connected to the short-pulse circuits. A superimposing of a flash of light with a high peak intensity from the flash lamps that emit light for a short time and a flash of light with a gentle peak from the flash lamps that emit light for a long time can increase the temperature of even a deep portion of a substrate to an activation temperature or more without heating a shallow portion near the substrate surface more than necessary. This achieves the activation of deep junctions without causing substrate warpage or cracking.