Semiconductor Doped Layer Activation Using Pulsed Laser Irradiation
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Solution Overview
Problem
Current methods for manufacturing semiconductor elements, such as IGBTs, face challenges in activating doped layers effectively, leading to device failures due to inadequate diffusion of dopants and heat-induced issues during laser irradiation, particularly with thin wafers, where previous techniques result in shallow activation and increased leakage current.
Innovation Solution
A method involving ion-implantation of dopants with high diffusion coefficients, like lithium, sulfur, or selenium, followed by pulsed laser irradiation using multiple devices or a combination of solid-state and semiconductor lasers, allowing for deeper diffusion and activation without long-term heat treatment, and fixing the wafer to an electrostatic chuck stage to control temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional laser irradiation is used for activating doped layers, then activation can be achieved, but dopant diffusion is insufficient leading to shallow activation and increased leakage current
Solution Approach 1:
The patent changes the physical parameters of laser irradiation by using multiple laser devices with different wavelengths (e.g., 1064nm and 532nm) and controlling irradiation conditions to achieve deeper and more uniform dopant activation. This resolves the contradiction by enabling sufficient activation depth while maintaining low leakage current through optimized parameter selection.
Solution Approach 2:
The patent divides the laser irradiation process into multiple stages using different laser devices. A first laser performs initial activation, followed by a second laser for deeper penetration and uniform distribution. This segmented approach achieves both deep activation and low leakage current by addressing different depth requirements in sequence.
2Length of stationary object
If ion implantation with high diffusion coefficient dopants is performed, then deeper diffusion is achieved, but heat-induced breakage occurs during laser irradiation
Solution Approach 1:
The patent uses periodic pulsed laser irradiation with controlled duty cycles and intervals. The first laser irradiates in pulses, followed by cooling periods, then the second laser irradiates. This periodic action allows deep dopant diffusion while preventing heat accumulation that would cause wafer breakage.
Solution Approach 2:
The patent introduces a second laser device as an intermediary step between initial doping and final activation. The first laser creates initial dopant distribution, then the second laser completes the activation process with gentler heating. This intermediary approach enables deep diffusion without direct high-heat exposure that causes breakage.
3Productivity
If thin wafers are used to reduce total thickness, then cost is reduced and switching speed is improved, but heat control during laser irradiation becomes difficult causing device failures
Solution Approach 1:
The patent applies different laser wavelengths and power levels to different regions and depths of the thin wafer. The first laser (1064nm) provides deeper penetration with lower absorption, while the second laser (532nm) provides surface-level activation. This local quality approach enables effective activation of thin wafers without excessive heat generation that would cause failures.
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 enables the formation of thicker, properly formed n-buffer layers, reducing device failures and heat-induced breakage, while achieving satisfactory device characteristics by controlling dopant diffusion and activation.
Implementation Method 1
fixing the wafer to an electrostatic chuck stage to control temperature
Implementation Method 2
pulsed laser irradiation using multiple devices or a combination of solid-state and semiconductor lasers
Implementation Method 3
allowing for deeper diffusion and activation without long-term heat treatment
Data Source
AI summary
A method of manufacturing a semiconductor element includes implanting ions of a dopant having a large diffusion coefficient into a semiconductor to provide a doped layer; and irradiating the doped layer with a plurality of pulsed laser beams supplied by a plurality of laser irradiation devices to activate the doped layer and provide an activated doped layer. The activated doped layer may be one of a single doped layer or a plurality of successive doped layers which each have respective conduction types that are one of identical or different. Device breakage and failure of the manufactured semiconductor element due to heat induced during laser irradiation are substantially prevented by this method.