Semiconductor Wafer Back Surface Electrode Manufacturing
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Solution Overview
Problem
Conventional semiconductor device manufacturing methods result in significant bending of semiconductor wafers during thermal processing, leading to transportation errors and defective bonding during die attachment.
Innovation Solution
A method that involves forming a first metal layer on the back surface of the semiconductor wafer, followed by thermal processing to create an ohmic contact, and then forming a second metal layer of Ni without subsequent thermal processing, which reduces bending by maintaining low temperatures for the subsequent metal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple metal layers are formed on the back surface of the semiconductor wafer and thermal processing is performed, then an excellent ohmic contact is created, but the semiconductor wafer bends significantly
Solution Approach 1:
The patent applies preliminary action by forming the first metal layer (Al or Al-Si alloy) and performing thermal processing to create the ohmic contact before forming the subsequent metal layers (barrier metal layer and second metal layer). This sequence ensures that the critical ohmic contact is established while the wafer is still relatively flat, preventing bending issues in later processing steps.
Solution Approach 2:
The patent utilizes parameter changes by controlling the thickness of each metal layer and the thermal processing conditions. Specifically, the first metal layer is kept thin (200 nm) to minimize bending, while still achieving adequate ohmic contact. The thermal processing temperature and duration are optimized to create the necessary contact quality without excessive wafer deformation.
2Reliability
If the semiconductor wafer is thinned to reduce resistance, then the resistance of the semiconductor element is reduced, but the wafer becomes more susceptible to bending
Solution Approach 1:
The patent performs the thinning operation (polishing the back surface to thickness t2) before forming the metal layers and performing thermal processing. This preliminary thinning reduces the resistance of the semiconductor element while the wafer is still structurally sound. Subsequent metal layer formation and thermal processing are then performed on the thinned wafer with controlled parameters to minimize additional bending.
Solution Approach 2:
The patent changes the thickness parameter of the semiconductor wafer through controlled polishing to achieve the desired resistance reduction. The final thickness t2 is optimized to balance resistance reduction with mechanical stability during subsequent processing steps.
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 effectively minimizes wafer bending, preventing transportation errors and ensuring reliable die bonding by maintaining low temperatures for the second and third metal layers, thereby creating an excellent ohmic contact and reducing wafer deformation.
Implementation Method 1
The semiconductor wafer 1 and the first metal layer 3 to diffuse into each other, which creates an excellent ohmic contact
Data Source
AI summary
A method of manufacturing a semiconductor device having a back surface electrode, including: a step of preparing a semiconductor wafer having a front surface and a back surface; a thermal processing step of forming a first metal layer on the back surface of the semiconductor wafer and executing thermal processing, thereby creating an ohmic contact between the semiconductor wafer and the first metal layer; and a step of forming a second metal layer of Ni on the back surface of the semiconductor substrate after the thermal processing step.