Flash Lamp Annealing Control to Prevent Wafer Cracking
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Solution Overview
Problem
Flash lamp annealing processes cause repeated stress on semiconductor wafers, leading to cracking due to rapid temperature fluctuations, which existing technologies have not adequately addressed.
Innovation Solution
A heat treatment method involving preheating with a continuous lighting lamp followed by flash irradiation from multiple flash lamps, controlled by switching elements with an on-off cycle less than 200 microseconds, to stabilize temperature fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If flash lamp annealing is used to heat the semiconductor wafer surface rapidly, then the activation temperature is reached in extremely short time, but repeated stress causes wafer cracking
Solution Approach 1:
The patent applies preliminary action by preheating the wafer to a base temperature before flash lamp irradiation. This preparatory heating step reduces the thermal shock when the flash lamp activates, preventing wafer cracking while still achieving the required activation temperature in extremely short time during the flash process.
Solution Approach 2:
The patent implements periodic action by controlling the flash lamp to operate in repeated on-off cycles with specific timing. The flash lamp irradiates the wafer surface in periodic pulses, allowing the temperature to rise and fall in a controlled manner, which prevents cumulative stress damage while maintaining effective activation treatment.
2Ease of operation
If the IGBT repeatedly turns on and off to control flash lamp current, then light emission time and intensity are adjustable, but microscopic current fluctuations cause repeated temperature changes and increased cracking susceptibility
Solution Approach 1:
The patent applies preliminary action by preheating the wafer to a base temperature before flash lamp irradiation. This preparatory heating step reduces the thermal shock when the flash lamp activates, preventing wafer cracking while still achieving the required activation temperature in extremely short time during the flash process.
Solution Approach 2:
The patent implements periodic action by controlling the flash lamp to operate in repeated on-off cycles with specific timing. The flash lamp irradiates the wafer surface in periodic pulses, allowing the temperature to rise and fall in a controlled manner, which prevents cumulative stress damage while maintaining effective activation treatment.
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
Prevents cracking in semiconductor wafers by minimizing temperature amplitude during flash irradiation, ensuring stable substrate processing.
Implementation Method 1
irradiating a substrate with light from a continuous lighting lamp to heat the substrate to a predetermined preheating temperature
Implementation Method 2
irradiating a front surface of the substrate with a flash of light from a plurality of flash lamps to increase the temperature of the front surface of the substrate to a predetermined treatment temperature
Data Source
AI summary
An IGBT controls current flowing through a flash lamp for emitting a flash of light. The IGBT repeatedly turns on and off in accordance with the waveform of a pulse signal. The repeated turning on and off of the IGBT causes the current flowing through the flash lamp to increase and decrease repeatedly, so that the front surface temperature of a semiconductor wafer increases while repeating slight increases and decreases. When an on-off cycle in the pulse signal is shortened to cause the on-off cycle of the IGBT during the repeated turning on and off to be not greater than 200 microseconds, the amplitude of the increasing and decreasing front surface temperature of the semiconductor wafer is also 10 small. Thus, the value of stress repeatedly exerted on the semiconductor wafer is not greater than the fatigue limit. This prevents cracking in the semiconductor wafer due to repeated stress.