SiC Doping via Segmented Laser Pulses
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Solution Overview
Problem
Existing doping methods for silicon carbide (SiC) semiconductors face challenges in achieving deep impurity atom penetration due to high temperature material degradation and limitations in achieving high-dose implanted layers, particularly in power semiconductor devices requiring high breakdown voltage and current density, where conventional laser doping techniques result in insufficient dopant penetration depth.
Innovation Solution
A doping system and method involving a light source with controlled energy density pulses, where a first optical pulse forms a reaction-product layer, and a second optical pulse with higher energy density introduces impurity atoms deeper into the SiC substrate through the reaction-product layer, enhancing dopant penetration and concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ion implantation with high dose is used to achieve deep impurity penetration, then impurity concentration is improved, but material deterioration and degradation occur due to high temperature exposure
Solution Approach 1:
The doping process is divided into multiple sequential laser irradiation steps with decreasing energy densities, allowing impurity atoms to be gradually introduced at different depths without requiring high-temperature annealing of the entire substrate. This segmented approach achieves deep impurity penetration while avoiding material deterioration.
Solution Approach 2:
A metal film containing impurity atoms is deposited on the substrate surface before laser irradiation. This preliminary preparation enables the impurity atoms to be released and diffused into the substrate during laser processing, achieving deep doping without high-temperature exposure that would cause material degradation.
2Length of moving object
If conventional laser doping with single energy density is used, then processing simplicity is maintained, but dopant penetration depth is insufficient
Solution Approach 1:
The laser irradiation process is segmented into multiple steps with different energy densities. The first step uses high energy density to create a reaction product layer, while subsequent steps use lower energy densities to introduce impurity atoms at controlled depths. This segmentation achieves deep dopant penetration while maintaining manageable processing complexity.
Solution Approach 2:
The energy density parameter of the laser beam is changed between different irradiation steps. By varying the energy density from high to low across multiple steps, the process achieves different doping depths and concentrations, overcoming the limitation of single-energy-density laser doping.
3Length of moving object
If high energy density laser pulse is used to increase dopant penetration depth, then impurity introduction depth is improved, but surface morphology degradation occurs
Solution Approach 1:
The laser irradiation is segmented into multiple steps with decreasing energy densities. The first step creates a reaction product layer that protects the surface, while subsequent steps with lower energy densities introduce impurity atoms without causing severe surface morphology degradation. This segmented approach achieves deep doping while preserving surface quality.
Solution Approach 2:
The metal film is deposited as a preliminary layer before laser irradiation. This layer controls the laser-matter interaction, enabling deep impurity penetration while the reaction product layer formed during irradiation protects the underlying substrate surface from severe morphology degradation.
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 deeper and more efficient impurity atom doping in SiC substrates, exceeding conventional penetration depths and achieving high impurity concentrations, thus addressing the limitations of existing techniques and improving the performance of SiC semiconductor devices.
Implementation Method 1
a light source configured to emit an optical pulse; and a beam adjusting unit configured to irradiate the optical pulse to a surface of a doping-object made of silicon carbide on which an impurity-containing source-film containing impurity atoms is deposited
Implementation Method 2
irradiate a first optical pulse to the impurity-containing source-film so as to forma reaction-product layer in the doping-object
Implementation Method 3
irradiate a second optical pulse having an energy density higher than an energy density of the first optical pulse, so as to introduce the impurity atoms into the target through the reaction-product layer
Data Source
AI summary
A doping system includes a light source to emit an optical pulse; a light source controller connected to the light source, to control an energy density of the optical pulse; and a beam adjusting unit to irradiate the optical pulse to a surface of a doping-object made of silicon carbide on which an impurity-containing source-film containing impurity atoms is deposited. The light source controller irradiates a first optical pulse to the impurity-containing source-film so as to form a reaction-product layer in the doping-object, and irradiates a second optical pulse having an energy density higher than an energy density of the first optical pulse, so as to introduce the impurity atoms into the target through the reaction-product layer.