Flash Lamp Annealing Particle Control via Pressure and Gas Flow
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Solution Overview
Problem
The phenomenon of particles curling up and flying in the chamber during flash lamp annealing of semiconductor wafers leads to contamination issues due to the rapid heating and gas expansion, which existing technologies have not effectively addressed.
Innovation Solution
A heat treatment method and apparatus that involves irradiating the substrate with a flash of light from a xenon flash lamp, maintaining lower chamber pressure, and increasing the flow rate of an inert gas to prevent particles from attaching to the substrate by smoothly discharging them from the chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a flash of light is emitted to heat the substrate, then the substrate temperature is rapidly increased, but particles curl up and fly in the chamber causing contamination
Solution Approach 1:
The patent applies preliminary action by reducing the chamber pressure before emitting the flash of light. This preparatory step creates a low-pressure environment that prevents particles from curling up and flying when the flash is emitted, thereby eliminating contamination while still allowing rapid substrate heating
Solution Approach 2:
The patent uses an inert gas atmosphere (nitrogen or rare gas) at reduced pressure as the chamber environment. This inert low-pressure environment prevents particle generation and contamination during flash lamp annealing, while still allowing efficient heat transfer to the substrate
2Object-affected harmful factors
If pressure in the chamber is reduced to prevent particle contamination, then particle attachment is prevented, but gas flow and heat transfer may be affected
Solution Approach 1:
The patent changes the pressure parameter of the chamber environment from atmospheric pressure to reduced pressure (1/10 to 1/100 of atmospheric pressure). This parameter change prevents particle contamination while maintaining sufficient gas flow for heat transfer by optimizing the pressure level
3Duration of action of moving object
If flash lamp is used for extremely short time heating, then only surface temperature is increased without deep diffusion, but particles are generated and fly in the chamber
Solution Approach 1:
The patent applies preliminary action by reducing chamber pressure before the flash lamp emits light. This prevents particles from curling up and flying during the extremely short heating duration, eliminating contamination while preserving the benefit of rapid surface heating without deep diffusion
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 prevents particle contamination on semiconductor wafers by ensuring that particles flying in the chamber are discharged, maintaining a clean environment for subsequent wafers, thus ensuring the quality of the semiconductor wafers during the heat treatment process.
Implementation Method 1
irradiating a surface of a substrate accommodated in a chamber with a flash of light from a flash lamp... temperature of the surface of the semiconductor wafer can be increased to an activation temperature for only an extremely short time
Implementation Method 2
increasing a flow rate of an inert gas to be supplied into the chamber after the step (b), and discharging a gas in the chamber... particles flying in the chamber can be prevented from attaching to a substrate by being smoothly discharged
Data Source
AI summary
When pressure in a chamber is once reduced lower than that when a flash of light is emitted and is maintained, after a flash lamp irradiates a semiconductor wafer accommodated in the chamber with the flash of light, a portion in the chamber, where gas is liable to remain, is eliminated. Then, when a flow rate of nitrogen gas to be supplied into the chamber is increased to discharge gas in the chamber, particles flying in the chamber due to flash irradiation can be smoothly discharged. As a result, the particles flying in the chamber can be prevented from being attached to an additional semiconductor wafer.