FZ Silicon Recombination Lifetime Control via Nitrogen Diffusion
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Solution Overview
Problem
There is a challenge in precisely controlling the recombination lifetime of carriers in silicon single crystal substrates, particularly in nitrogen-added FZ silicon substrates, which leads to variations in device characteristics, and existing methods are ineffective in reducing these variations, especially when oxygen concentrations are high.
Innovation Solution
A method involving a preparation step for nitrogen-added silicon single crystal substrates grown by the floating zone melting method, followed by heat treatment to adjust nitrogen concentration based on oxygen concentration, and subsequent particle beam irradiation and recovery heat treatment to control recombination lifetime with high precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitrogen is added during crystal growth to prevent electric discharge and improve wafer strength, then device reliability is improved, but recombination lifetime control precision deteriorates due to nitrogen concentration variations
Solution Approach 1:
The patent applies preliminary action by performing a first heat treatment before particle beam irradiation to adjust the nitrogen concentration in the silicon substrate. This preliminary adjustment of nitrogen concentration (to 1×10^14 to 1×10^15 atoms/cm³) ensures that subsequent recombination lifetime control is not affected by nitrogen variations, thereby resolving the contradiction between maintaining nitrogen for reliability and controlling recombination lifetime precision.
2Speed
If charged particle beams are used to control recombination lifetime, then switching speed is improved, but device characteristics vary due to substrate-dependent recombination lifetime variations
Solution Approach 1:
The patent applies parameter changes by systematically adjusting the nitrogen concentration parameter through a first heat treatment step before particle beam irradiation. By controlling nitrogen concentration to a specific range (1×10^14 to 1×10^15 atoms/cm³), the substrate's influence on recombination lifetime is minimized, ensuring uniform device characteristics across different substrates while maintaining the desired switching speed.
3Manufacturing precision
If heat treatment is performed to adjust nitrogen concentration before particle beam irradiation, then recombination lifetime control precision is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent applies universality by designing a standardized two-step process (first heat treatment to adjust nitrogen, then particle beam irradiation for recombination lifetime control) that can be universally applied to nitrogen-added FZ silicon substrates. This multi-functional approach simultaneously achieves nitrogen concentration adjustment and recombination lifetime control through a systematic sequence that, while adding a step, provides a universal solution for precision control across different substrate batches.
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 method allows for precise control of recombination lifetime, reducing variations and maintaining high productivity and quality by adjusting nitrogen concentration before particle beam irradiation, thereby addressing the limitations of existing technologies.
Implementation Method 1
a nitrogen concentration Cn of the silicon single crystal substrate is adjusted in the heat treatment by outwardly diffusing nitrogen in the silicon single crystal substrate
Implementation Method 2
a particle beam irradiation step of irradiating the silicon single crystal substrate after the heat treatment step A with a particle beam
Data Source
Figure 1~2(g)
Figure 3(a)~4(d)
AI summary
The present invention is a method for controlling recombination lifetime for controlling recombination lifetime of carriers in a silicon single crystal substrate by performing: a preparation step of preparing a silicon single crystal substrate from a nitrogen-added silicon single crystal grown by an FZ method; a heat treatment step A of heat-treating; a particle beam irradiation step of irradiating the silicon single crystal substrate with a particle beam; and a heat treatment step B of heat-treating the silicon single crystal substrate, where in the heat treatment step A, a nitrogen concentration Cn of the silicon single crystal substrate is adjusted by outwardly diffusing nitrogen in the silicon single crystal substrate in accordance with an oxygen concentration Co of the silicon single crystal substrate prepared in the preparation step, then the particle beam irradiation step is performed. Consequently, a method for controlling recombination lifetime which can reduce a variation in recombination lifetime caused by a nitrogen-added FZ silicon single crystal substrate with certainty and highly precisely control the recombination lifetime is provided.