SiC Device Multistage Heating to Reduce Interface State Density
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Solution Overview
Problem
High-temperature heating processing for silicon carbide semiconductor devices leads to increased interface state density between silicon carbide and silicon dioxide, resulting in high contact resistance and switching losses, while conventional methods fail to maintain low interface state densities and reduce on-voltage effectively.
Innovation Solution
A multistage heating process is employed, where the first heating is performed at a superhigh temperature (1800° C. or more and 2000° C. or less) followed by a second heating at a lower temperature (1600° C. or more and 1700° C. or less, with a cooling process in between, to enhance ion activation and reduce lattice damage, thereby decreasing interface state density and contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heating processing is performed at superhigh temperature (1900°C to 2000°C) to activate implanted ion species, then the activation rate is increased and contact resistance is reduced, but the interface state density between silicon carbide and silicon dioxide substantially rises
Solution Approach 1:
The heating process is divided into two distinct stages: first heating at superhigh temperature (1900-2000°C) to activate ion species and reduce contact resistance, then second heating at lower temperature (1600-1700°C) to reduce interface state density. This segmentation allows each parameter to be optimized independently at different process stages.
Solution Approach 2:
The first heating processing at superhigh temperature is performed as a preliminary action to activate the implanted ion species and establish low contact resistance before forming the silicon dioxide film. This preliminary activation ensures that the contact resistance is already reduced before the oxide formation process begins.
2Loss of energy
If heating processing is performed at superhigh temperature to activate implanted ion species, then switching loss is reduced, but sublimation from silicon carbide surface and resolution and withdrawal of silicon become increasingly remarkable
Solution Approach 1:
The heating process is segmented into two stages with different temperature levels and durations. The first stage at superhigh temperature (1900-2000°C) is kept brief to activate ions without excessive material loss, while the second stage at lower temperature (1600-1700°C) is extended to achieve the desired activation level with minimal sublimation and silicon withdrawal.
Solution Approach 2:
The temperature parameter is changed between two distinct heating stages. The first heating uses superhigh temperature (1900-2000°C) for brief activation, then the temperature is reduced to (1600-1700°C) for the second heating. This parameter change allows achieving ion activation while controlling material loss from sublimation and silicon withdrawal.
3Manufacturing precision
If various atmosphere processings are executed after formation of oxide film to reduce interface state density, then interface state density decreases, but the interface with low interface state density can no longer be realized
Solution Approach 1:
The ion species activation is performed as a preliminary action before oxide film formation. By activating the ions first through superhigh temperature heating, the contact resistance is reduced before the oxide film is formed, ensuring that subsequent atmosphere processings to reduce interface state density do not compromise the already-improved contact characteristics.
4Reliability
If b bipolar PiN diode structure is used to reduce contact resistance, then contact resistance is reduced, but on-voltage rises
Solution Approach 1:
Instead of changing the device structure to bipolar PiN diode, the invention changes the thermal processing parameters - using two-stage heating with superhigh temperature followed by lower temperature heating. This parameter change in the manufacturing process achieves low contact resistance through improved ion activation without the structural modifications that would increase on-voltage.
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 significantly reduces interface state density, backward leakage current, and on-voltage in silicon carbide semiconductor devices, improving channel mobility and contact characteristics while minimizing thermal stress and economic processing time.
Implementation Method 1
When heating processing is performed at a superhigh temperature such as 1900° C. to 2000° C. to activate implanted ion species, the activation rate is increased by a mechanism which can restore lattice damage upon ion implantation
Implementation Method 2
implanting ions in a silicon carbide substrate
Data Source
AI summary
A method of manufacturing a silicon carbide semiconductor device of an embodiment includes: implanting ions in a silicon carbide substrate; performing first heating processing of the silicon carbide substrate in which the ions are implanted; and performing second heating processing of the silicon carbide substrate for which the first heating processing is performed, at a temperature lower than the first heating processing.