Silicon Wafer Oxygen Precipitation Control via Nitrogen
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Solution Overview
Problem
The rapid temperature-rising-and-falling thermal treatment processes, such as FLA and Spike-RTA, generate high thermal stress in silicon wafers, leading to wafer deformation, slip dislocation, and reduced yield due to oxygen precipitate formation, which is challenging to suppress without compromising dopant activation and diffusion control.
Innovation Solution
A method for manufacturing silicon epitaxial wafers involves setting specific oxygen and boron concentrations, and performing precipitation, dissolution, and thermal treatment processes under controlled conditions to prevent oxygen precipitate formation, thereby reducing thermal stress and slip extension, even under severe thermal treatment conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen precipitates are formed in the substrate wafer, then metal dopants can be captured (gettering), but wafer deformation and slip dislocation occur during rapid thermal treatment
Solution Approach 1:
The patent extracts the harmful effect of oxygen precipitates by introducing nitrogen impurities that suppress oxygen precipitation, while retaining the beneficial gettering function through controlled oxygen concentration. This resolves the contradiction by removing the cause of deformation (oxygen precipitates) while preserving the dopant capture capability.
Solution Approach 2:
The patent changes the chemical composition parameters by introducing nitrogen impurities at specific concentrations (1×10^13 to 5×10^14 atoms/cm³) and controlling oxygen concentration (1.5×10^18 to 5×10^18 atoms/cm³). This parameter modification suppresses oxygen precipitation during rapid thermal treatment while maintaining dopant gettering capability.
2Productivity
If rapid temperature-rising-and-falling thermal treatment is performed, then dopant activation and diffusion are improved, but thermal stress increases causing wafer deformation
Solution Approach 1:
The patent performs preliminary action by introducing nitrogen impurities before the rapid thermal treatment process. This preliminary modification of the wafer's chemical composition prevents oxygen precipitation during the subsequent high-stress thermal treatment, enabling dopant activation without wafer deformation.
Solution Approach 2:
Nitrogen impurities act as an intermediary that mediates between the rapid thermal treatment process and the wafer structure. The nitrogen atoms suppress oxygen precipitation that would otherwise cause slip dislocation, allowing the thermal treatment to proceed without deformation while still achieving dopant activation.
3Strength
If oxygen concentration is increased to suppress slip, then slip extension is reduced, but oxygen precipitate formation is promoted
Solution Approach 1:
The patent uses nitrogen impurities as a substitute that copies the beneficial effect of high oxygen concentration (slip suppression) without the harmful effect (oxygen precipitate formation). The nitrogen atoms provide similar structural stabilization that prevents slip extension while avoiding the precipitation issue.
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 wafer deformation and slip dislocation, maintaining excellent slip resistance and yield in silicon wafers during rapid thermal processes, even at high temperatures and rapid temperature changes, thus enhancing device manufacturing reliability.
Implementation Method 1
a precipitation, dissolution, and thermal treatment process of treating a wafer in the treatment temperature range of 1150° C. to 1300° C., the retention time range of 5 sec to 1 min, and the temperature-falling rate range of 10° C./sec to 0.1° C./sec
Implementation Method 2
treating a wafer in the treatment temperature range of 1150° C. to 1300° C.
Implementation Method 3
a temperature difference of 100° C. is caused between the front surface and the back surface of a wafer, a stress much greater than that in the RTA process which has been previously performed may be loaded. Specifically, a thermal stress greater than 20 MPa may be partially generated.
Implementation Method 4
the rapid temperature-rising-and-falling thermal treatment process such as the FLA process
Data Source
AI summary
A method of manufacturing a silicon wafer provides a silicon wafer which can reduce the precipitation of oxygen to prevent a wafer deformation from being generated and can prevent a slip extension due to boat scratches and transfer scratches serving as a reason for a decrease in wafer strength, even when the wafer is provided to a rapid temperature-rising-and-falling thermal treatment process.