Flash Lamp Silicide Formation Oxygen Control
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Solution Overview
Problem
Flash lamp annealing for silicide formation in semiconductor wafers leads to degraded interface characteristics and oxidation issues due to residual oxygen in the chamber, causing increased resistance and oxidation of silicides, especially in finer geometries where silicides are susceptible.
Innovation Solution
A method and apparatus that reduce oxygen concentration in the chamber by controlling pressure and gas flow rates during flash lamp irradiation, involving steps like reducing chamber pressure, increasing exhaust flow rates, and supplying inert gases to prevent oxygen entry and particle swirling, thereby maintaining a controlled atmosphere for silicide formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flash lamp annealing is performed in a chamber with residual oxygen, then silicide formation is achieved, but interface characteristics are degraded and resistance increases due to oxidation
Solution Approach 1:
The patent applies inert atmosphere by introducing nitrogen gas into the chamber before and during flash lamp annealing. The nitrogen gas replaces residual oxygen in the chamber, creating an inert environment that prevents oxidation of the silicide layer while maintaining the heat treatment process. This is achieved through gas supply systems that introduce nitrogen at controlled flow rates before, during, and after the flash lamp irradiation.
2Object-affected harmful factors
If chamber pressure is reduced to remove oxygen, then oxidation is suppressed, but particle swirling may occur affecting manufacturing precision
Solution Approach 1:
The patent applies preliminary action by introducing nitrogen gas into the chamber before reducing the pressure and before performing the flash lamp annealing. This pre-filling with inert gas ensures that when pressure reduction occurs, there is no oxygen present to cause oxidation, and particles are less likely to swirl because the inert gas cushion stabilizes the environment during pressure changes.
Solution Approach 2:
The patent uses pneumatic control of gas flow rates and pressure changes to manage the chamber environment. By controlling the nitrogen gas supply flow rate and exhaust flow rate, the system manages pressure reduction while preventing particle swirling through controlled gas flow dynamics that maintain stability during the annealing process.
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 suppresses the increase in resistance and oxidation of silicides by minimizing oxygen exposure during the flash heating process, improving the interface characteristics and preventing excessive silicide thickness, thus enhancing the performance and reliability of semiconductor devices.
Implementation Method 1
irradiate a surface of a semiconductor wafer with a flash of light, thereby raising the temperature of only the surface of the semiconductor wafer in an extremely short time
Implementation Method 2
flash lamp annealing (FLA) which heats a semiconductor wafer in an extremely short time
Implementation Method 3
reducing the pressure in the chamber to a first pressure lower than atmospheric pressure
Implementation Method 4
supplying inert gases to prevent oxygen entry and particle swirling
Data Source
AI summary
A metal film is deposited on a front surface of a semiconductor wafer of silicon. After the semiconductor wafer is received in a chamber, the pressure in the chamber is reduced to a pressure lower than atmospheric pressure. Thereafter, nitrogen gas is supplied into the chamber to return the pressure in the chamber to ordinary pressure, and the front surface of the semiconductor wafer is irradiated with a flash of light, so that a silicide that is a compound of the metal film and silicon is formed. The oxygen concentration in the chamber is significantly lowered during the formation of the silicide because the pressure in the chamber is reduced once to the pressure lower than atmospheric pressure and then returned to the ordinary pressure. This suppresses the increase in resistance of the silicide resulting from the entry of oxygen in the atmosphere in the chamber into defects near the interface between the metal film and a base material.