SiC Backside Ohmic Contact Formation After Wafer Thinning
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Solution Overview
Problem
The existing manufacturing processes for SiC electronic devices face challenges in reducing the thickness of the SiC substrate, which leads to increased fragility and damage during handling and processing, particularly due to the need for multiple flipping and processing steps.
Innovation Solution
A method for manufacturing SiC electronic devices that involves thinning the substrate to a desired thickness after completing the processing of the front side, using a laser annealing process to form a stable ohmic contact on the back side, thereby reducing the risk of damage and improving the quality of the ohmic contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of the SiC substrate is reduced to decrease the resistive contribution, then the on-state resistance is improved, but the wafer becomes excessively thin and subject to cracking, warping or damage
Solution Approach 1:
The patent performs the thinning operation after completing all front-side processing steps, including metallization and passivation. This preliminary completion of critical steps ensures that the thin wafer (最终厚度100-180μm) will not be further processed on its front side, eliminating the need for subsequent handling and flipping that would risk damage to the already-thinned substrate.
Solution Approach 2:
The patent inverts the conventional processing sequence by completing all front-side operations first, then thinning the substrate, and finally forming the back ohmic contact. This reversal eliminates the need to flip the wafer multiple times during processing, thereby preventing damage to the thin substrate while achieving the desired low on-state resistance through reduced substrate thickness.
2Ease of manufacture
If multiple flipping and processing steps are used to form ohmic contact on the back, then the manufacturing process is complete, but the handling complexity and risk of damage increase
Solution Approach 1:
The patent completes all front-side processing steps (metallization, passivation, etc.) before thinning the substrate and forming the back contact. This preliminary completion means that once the wafer is thinned, no further front-side operations are needed, eliminating the need for repeated flipping and handling that would increase complexity and damage risk.
Solution Approach 2:
The patent merges the thinning operation with the back-side processing sequence. By thinning the substrate to 100-180μm and immediately proceeding with back ohmic contact formation in the same processing cycle, the patent eliminates intermediate handling steps and wafer flipping, thereby reducing overall process complexity while achieving complete manufacturing.
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 simplifies the process flow, enhances the quality of the ohmic contact, reduces the risk of wafer cracking, and significantly decreases the resistive contribution of the substrate to the total on-state resistance of the device.
Implementation Method 1
heating said intermediate layer by means of a laser beam so as to form an ohmic contact region
Implementation Method 2
heating (in particular at or above a melting temperature of the material of layer 72)
Data Source
AI summary
A method for manufacturing an electronic device based on SiC includes forming a structural layer of SiC on a front side of a substrate. The substrate has a back side that is opposite to the front side along a direction. Active regions of the electronic device are formed in the structure layer, and the active regions are configured to generate or conduct electric current during the use of the electronic device. A first electric terminal is formed on the structure layer, and an intermediate layer is formed at the back side of the substrate. The intermediate layer is heated by a LASER beam in order to generate local heating such as to favor the formation of an ohmic contact of Titanium compounds. A second electric terminal of the electronic device is formed on the intermediate layer.