Dopant Injection Sublimation Rate Control for Silicon Monocrystal Growth
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Solution Overview
Problem
Existing methods for doping silicon monocrystals with N-type dopants face challenges such as low absorption rates and difficulties in achieving desired resistance values due to excessive sublimation and blowing pressure, leading to inefficient doping and hindered monocrystal formation.
Innovation Solution
A doping method and device that control the sublimation rate of dopants between 10 g/min to 50 g/min, using a cylindrical portion with a controlled gas flow and inert gas flow to prevent excessive pressure and ensure efficient dopant absorption, while maintaining the dopant gas within a specific temperature and pressure range to enhance doping efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If solid dopant is vaporized by silicon melt heat to blow dopant gas to the melt, then dopant gas is generated, but the pressure within storage greatly increases causing vigorous blowing that deteriorates absorption rate
Solution Approach 1:
An inert gas (argon or nitrogen) is introduced as an intermediary carrier gas to transport the vaporized dopant to the silicon melt. The inert gas flow rate is controlled at 50-400 L/min to regulate dopant delivery, preventing excessive pressure buildup while ensuring sufficient dopant absorption by the melt.
Solution Approach 2:
The sublimation rate of the dopant is precisely controlled within the range of 10-50 g/min by adjusting temperature and inert gas flow parameters. This parameter control prevents excessive pressure increase in the storage chamber while maintaining adequate dopant supply to the melt.
2Quantity of substance
If dopant gas is blown vigorously to the silicon melt, then dopant is delivered to the melt, but silicon melt is blown off hindering monocrystal formation
Solution Approach 1:
The inert gas serves as a gentle intermediary that carries dopant vapor to the melt surface without causing violent disruption. By controlling the inert gas flow rate, the system achieves dopant delivery while avoiding the violent blow-off of silicon melt that would hinder monocrystal formation.
Solution Approach 2:
The sublimation rate is controlled within 10-50 g/min and inert gas flow within 50-400 L/min to achieve moderate, controlled dopant delivery. This parameter optimization ensures sufficient dopant absorption without excessive kinetic energy that would blow off the melt and disrupt monocrystal growth.
3Stress or pressure
If dopant gas outbursts too fast to be dissolved in the melt, then pressure is relieved, but only a tiny fraction of dopant is absorbed
Solution Approach 1:
The inert gas acts as a rate-controlling intermediary that delivers dopant to the melt at a controlled pace. The inert gas flow rate (50-400 L/min) is optimized to balance pressure relief with sufficient contact time for dopant dissolution, ensuring high absorption efficiency.
Solution Approach 2:
The sublimation rate is precisely controlled at 10-50 g/min to match the inert gas delivery capacity and melt absorption rate. This parameter synchronization prevents both pressure buildup and excessive outburst, maintaining optimal dopant absorption efficiency.
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 allows for stable and efficient doping of silicon monocrystals, ensuring sufficient dopant absorption and preventing monocrystal formation issues, thereby enabling the production of semiconductor wafers with desired resistance values.
Implementation Method 1
the solid microelement is vaporized in a high-temperature atmosphere in a chamber of a pull-up device, thus blowing the microelement gas to the surface of the silicon melt
Implementation Method 2
a cylindrical portion into which a gas ejected from the accommodating portion is introduced, the cylindrical portion having an opening on a lower end surface to guide the gas to the melt
Implementation Method 3
it is difficult for the gas to be dissolved into the silicon melt, or the gas is discharged out of the furnace without touching the silicon melt
Data Source
AI summary
In a dopant-injecting method for injecting a volatile dopant into a semiconductor melt, a doping device having an accommodating portion for accommodating a solid dopant and a cylindrical portion into which a gas ejected from the accommodating portion is introduced, a lower end surface of the cylindrical portion being opened to guide the gas to the melt, is used. The sublimation rate of the dopant in the accommodating portion is set in a range from 10 g/min to 50 g/min. Since a flow volume of the volatilized dopant gas is controlled by setting the sublimation rate of the dopant gas in the accommodating portion in the range from 10 g/min to 50 g/min, the melt is not blown off when the gas is blown onto the melt.