SiC Surface Electrode Reflectance Control for Wire Bonding
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Solution Overview
Problem
Existing methods for manufacturing semiconductor devices with silicon carbide (SiC) struggle to form surface electrodes that closely cover uneven Schottky contacts and achieve suitable reflectance for image recognition during automatic wire bonding, often resulting in element defects and poor recognition rates.
Innovation Solution
A method involving the formation of a Schottky layer with metals like titanium, tungsten, or molydenum on a SiC substrate, followed by a surface electrode made of aluminum or aluminum silicon, using sputtering with specific pressure and temperature conditions to ensure close coverage and optimal reflectance, while forming a nickel silicide layer with titanium carbide for the rear surface electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal layer is formed on the Schottky contact to create the surface electrode, then the electrode structure is completed, but voids are generated when the Schottky contact is not completely covered, causing element defects
Solution Approach 1:
The patent applies parameter changes by controlling the substrate temperature during the sputtering process. By maintaining the substrate temperature at 100°C to 500°C, the surface mobility of aluminum atoms is enhanced, enabling them to flow into and cover uneven portions of the Schottky contact effectively, thus preventing void formation while maintaining manufacturing precision
Solution Approach 2:
The patent implements preliminary action by pre-heating the substrate to a specific temperature range (100°C to 500°C) before depositing the aluminum layer. This preliminary heating prepares the substrate surface to facilitate better metal atom distribution and coverage, ensuring complete coverage of the Schottky contact before the electrode formation is finalized
2Manufacturing precision
If the surface electrode is formed to closely cover the uneven pattern of the Schottky contact, then coverage is improved, but the reflectance may not be suitable for image recognition during automatic wire bonding
Solution Approach 1:
The patent simultaneously optimizes two parameters: substrate temperature (100°C to 500°C) for coverage and aluminum layer thickness (1 μm to 10 μm) for reflectance. By carefully controlling both parameters within specific ranges, the patent achieves complete coverage of uneven Schottky contacts while maintaining reflectance levels suitable for automatic wire bonding image recognition
3Illumination intensity
If the surface electrode is formed with high reflectance, then image recognition during automatic wire bonding is improved, but voids are more likely to be generated on uneven Schottky contacts
Solution Approach 1:
The patent resolves this contradiction by establishing an optimal parameter window: substrate temperature of 100°C to 500°C and aluminum layer thickness of 1 μm to 10 μm. Within this parameter range, the aluminum atoms have sufficient surface mobility to cover uneven Schottky contacts completely (preventing voids) while maintaining adequate reflectance for wire bonding recognition
Solution Approach 2:
The patent uses preliminary substrate heating to 100°C to 500°C before aluminum deposition to enhance surface mobility. This preliminary action ensures that aluminum atoms can effectively cover uneven surfaces, preventing void formation while the controlled deposition process maintains appropriate reflectance levels
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 the close coverage of uneven Schottky contacts and achieves the most suitable reflectance for image recognition in automatic wire bonding, enhancing the reliability and yield of SiC semiconductor devices.
Implementation Method 1
the Schottky layer is heated to form a Schottky electrode which has a Schottky contact with the silicon carbide semiconductor substrate
Implementation Method 2
the surface electrode is heated in a temperature range suitable for conditions that the surface electrode closely covers an uneven portion of the Schottky electrode and has a predetermined reflectance or less
Implementation Method 3
a surface electrode which is made of aluminum or aluminum including silicon is formed on a surface of the Schottky electrode
Data Source
AI summary
A method for manufacturing a semiconductor device includes (a) providing a silicon carbide semiconductor substrate; and (b) forming an electrode structure on the silicon carbide semiconductor substrate by (i) forming a Schottky layer including a metal selected from the group consisting of titanium, tungsten, molybdenum, and chrome on a front surface of the silicon carbide semiconductor substrate; (ii) heating the Schottky layer to form a Schottky electrode which has a Schottky contact with the silicon carbide semiconductor substrate; and (iii) forming a surface electrode comprised of aluminum or aluminum including silicon on a surface of the Schottky electrode, while heating at a temperature range effective for the surface electrode to closely cover any uneven portion of the Schottky electrode and provide a surface electrode having a predetermined reflectance that is equal to or less than 80% so that an improved recognition rate by an automatic wire bonding apparatus is obtained.