Semiconductor Substrate Laser Annealing for Abrupt Junctions
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Solution Overview
Problem
Current manufacturing processes for power semiconductor devices, such as high-voltage diodes and IGBTs, face challenges in reducing the drift region width while maintaining high reverse blocking voltage, requiring optimized doping profiles that balance blocking capability, on-state losses, and robustness.
Innovation Solution
The method involves introducing specific doping regions with peak concentrations at different depths and using laser annealing to partially melt the semiconductor substrate, creating plateau-like doping profiles with steep sidewalls, which enhances the formation of abrupt pn-junctions and improves device characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the width of the drift region is reduced to improve on-state characteristics, then on-state losses are reduced, but the reverse blocking voltage capability deteriorates
Solution Approach 1:
The patent applies local quality by creating a structured p-doped region with specific spatial distribution (alternating doped and undoped zones) rather than uniform doping. This localized structural variation enables the drift region to simultaneously achieve low on-state resistance in doped zones and high reverse blocking capability in undoped zones, resolving the contradiction between reducing on-state losses and maintaining reverse blocking voltage.
Solution Approach 2:
The drift region is segmented into alternating doped and undoped zones along the direction of current flow. This segmentation allows different portions to perform different functions: doped zones provide low resistance paths for forward current, while undoped zones provide high electric field regions for reverse blocking, thus resolving the contradiction between on-state losses and reverse blocking capability.
2Ease of manufacture
If conventional doping processes are used to create doping profiles, then manufacturing simplicity is maintained, but the precision and abruptness of doping profiles deteriorate
Solution Approach 1:
The patent replaces conventional thermal diffusion or ion implantation processes with laser annealing. The laser beam precisely controls the doping profile by selectively melting and redistributing dopants only in targeted regions, achieving abrupt junctions and precise depth control without the need for complex masking or multiple implantation steps, thus improving manufacturing precision while maintaining simplicity.
Solution Approach 2:
The patent uses laser annealing to change the physical state of the semiconductor material during doping, creating a molten layer that allows precise dopant redistribution. By controlling laser parameters (energy density, pulse duration, wavelength), the process achieves precise doping profiles with abrupt transitions that cannot be obtained by conventional thermal processes, resolving the contradiction between ease of manufacture and doping precision.
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 results in higher activation ratios of dopants, improved device softness and robustness, and the formation of sharp pn-junctions, effectively addressing the challenges of reducing drift region width while maintaining high reverse blocking voltage.
Implementation Method 1
directing at least one laser beam pulse onto the second surface to melt the semiconductor substrate, at least in sections, at the second surface
Implementation Method 2
to melt the semiconductor substrate, at least in sections, at the second surface
Implementation Method 3
The generation of the hole current can be caused by avalanche and provides additional charge carrier to prevent that the load current undergoes chopping during commutation of the device
Data Source
AI summary
A method for manufacturing a semiconductor device by laser annealing. One embodiment provides a semiconductor substrate having a first surface and a second surface. The second surface is arranged opposite to the first surface. A first dopant is introduced into the semiconductor substrate at the second surface such that its peak doping concentration in the semiconductor substrate is located at a first depth with respect to the second surface. A second dopant is introduced into the semiconductor surface at the second surface such that its peak doping concentration in the semiconductor substrate is located at a second depth with respect to the second surface, wherein the first depth is larger than the second depth. At least a first laser anneal is performed by directing at least one laser beam pulse onto the second surface to melt the semiconductor substrate, at least in sections, at the second surface.