Light-Irradiation Wafer Oxidation With Atmosphere Switching
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Solution Overview
Problem
Conventional thermal oxidation methods for forming silicon oxide films on semiconductor wafers face challenges such as premature oxidation at lower temperatures, difficulty in controlling film thickness, and increased leakage current due to interface defects with high dielectric constant films.
Innovation Solution
A method and apparatus that irradiate a substrate with light to heat it, switching from an inert to an oxidizing atmosphere at a predetermined temperature to control the formation of a thin silicon oxide film, allowing precise thickness control and improved interface matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional thermal oxidation method is used to form silicon oxide film, then oxidation reaction occurs at high temperature, but oxidation starts prematurely at lower temperature during wafer transport, causing uncontrolled film formation
Solution Approach 1:
The patent applies preliminary action by pre-heating the semiconductor wafer to a high temperature (e.g., 900°C or higher) in an inert atmosphere before introducing the oxidizing gas. This ensures the wafer reaches the desired oxidation temperature in advance, preventing premature oxidation during transport and ensuring oxidation only occurs when intended.
Solution Approach 2:
The patent uses an inert atmosphere (such as nitrogen or argon) during the heating phase to prevent oxidation. The inert gas environment allows the wafer to be heated to high temperature without reacting with oxygen, and oxidation is only initiated when the inert atmosphere is replaced with an oxidizing atmosphere after the target temperature is reached.
2Manufacturing precision
If conventional thermal oxidation method is used, then silicon oxide film is formed, but film thickness cannot be controlled precisely on the order of nanometers due to long oxidation time
Solution Approach 1:
The patent changes the key parameter of oxidation time by performing oxidation at very high temperatures (900°C or higher) for extremely short durations (seconds or less). This parameter change allows precise control of film thickness on the nanometer scale, as the rapid high-temperature oxidation process can be stopped precisely when the desired thickness is achieved, unlike conventional long-duration low-temperature oxidation.
Solution Approach 2:
The patent employs periodic action by introducing the oxidizing gas for a controlled, limited time period after rapid heating. The oxidation process is applied in a brief, intense pulse rather than continuously over a long period, enabling precise thickness control while minimizing total process time.
3Ease of manufacture
If high dielectric constant film is deposited directly on silicon base layer, then gate insulator structure is formed, but interface defects increase causing higher leakage current
Solution Approach 1:
The patent uses a thin silicon oxide film as an intermediary layer between the silicon base layer and the high dielectric constant film. This intermediate oxide layer, formed by the controlled rapid thermal oxidation process, provides excellent interface quality and reduces defects, thereby lowering leakage current while still enabling the high-k gate insulator structure to be formed.
4Speed
If light irradiation is used to heat substrate, then rapid heating to high temperature is achieved, but precise control of oxidation timing requires atmosphere switching at specific temperature
Solution Approach 1:
The patent employs feedback control by monitoring the wafer temperature during light irradiation heating and using this temperature information to control the timing of oxidizing gas introduction. The system continuously adjusts the heating and gas introduction based on real-time temperature feedback, ensuring oxidation occurs at the precise moment when the target temperature is reached, thereby maintaining both rapid heating and precise timing control.
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 formation of thin silicon oxide films with good properties and reduced leakage current, achieving precise thickness control and improved interface matching with high dielectric constant films.
Implementation Method 1
irradiating the substrate with light to heat the substrate
Implementation Method 2
supplying an oxidizing gas into the chamber to change an atmosphere within the chamber from an inert gas atmosphere to an oxidizing atmosphere
Data Source
AI summary
A silicon semiconductor wafer is transported into a chamber, and preheating of the semiconductor wafer is started in a nitrogen atmosphere by irradiation with light from halogen lamps. When the temperature of the semiconductor wafer reaches a predetermined switching temperature in the course of the preheating, oxygen gas is supplied into the chamber to change the atmosphere within the chamber from the nitrogen atmosphere to an oxygen atmosphere. Thereafter, a front surface of the semiconductor wafer is heated for an extremely short time period by flash irradiation. Oxidation is suppressed when the temperature of the semiconductor wafer is relatively low below the switching temperature, and is caused after the temperature of the semiconductor wafer becomes relatively high. As a result, a dense, thin oxide film having good properties with fewer defects at an interface with a silicon base layer is formed on the front surface of the semiconductor wafer.