Semiconductor Die Singulation With High-Modulus Backside Support
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Solution Overview
Problem
The existing methods for singulating semiconductor dies with a thick backside metal layer often result in metal burrs during sawing, leading to electrical shorts and defects in subsequent packaging steps, which reduce yield and increase costs.
Innovation Solution
A high modulus layer with a modulus greater than 4000 MPa and up to 8000 MPa is formed over the backside metal layer before singulation, using a conductive die attach film, to support the metal during sawing and prevent burr formation, and a non-conductive die attach is used for electrical isolation while maintaining thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a thick backside metal layer is used in semiconductor dies, then thermal conductivity is improved, but metal burrs form during sawing causing electrical shorts and defects
Solution Approach 1:
A high modulus layer is introduced as an intermediary between the thick backside metal layer and the sawing process. This intermediate layer has a modulus greater than 4000 MPa and serves as a protective barrier that prevents the saw blade from directly contacting and deforming the metal layer, thereby preventing burr formation while maintaining the thermal conductivity benefits of the thick metal layer.
Solution Approach 2:
The high modulus layer is applied to the backside metal layer before the singulation/sawing process. This preliminary action prepares the metal layer by providing protective support in advance, ensuring that when the sawing occurs, the metal layer is already protected and will not form burrs that could cause electrical shorts.
2Manufacturing precision
If a high modulus layer with modulus greater than 4000 MPa is formed over the metal layer, then metal burr formation is prevented, but process complexity increases
Solution Approach 1:
The invention changes the physical parameter of the protective layer by specifying a minimum modulus greater than 4000 MPa. This parameter change ensures the layer is sufficiently rigid to prevent burr formation during sawing. The high modulus property is achieved through material selection and curing conditions, transforming a soft protective coating into a rigid support structure that effectively prevents metal deformation.
3Productivity
If dicing tape stretching is used to separate semiconductor dies, then singulation efficiency is improved, but cut expansion between dies increases
Solution Approach 1:
The high modulus layer serves as a cushioning layer applied beforehand to the backside metal layer. During the dicing tape stretching process, this rigid layer absorbs and distributes the mechanical stresses, preventing excessive expansion of the cuts between dies. The cushioning effect maintains cut accuracy while still allowing the dicing tape stretching mechanism to achieve efficient singulation.
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 prevents metal burrs, reduces defects, and increases the yield of packaged semiconductor devices by ensuring electrical isolation and thermal conductivity, thereby lowering costs.
Implementation Method 1
forming a layer with a modulus greater than about 4000 MPa and up to about 8000 MPa over the metal layer
Implementation Method 2
mounting the backside of the semiconductor wafer including the metal layer and the layer with a modulus greater than about 4000 MPa and up to about 8000 MPa on a first side of a dicing tape having an adhesive
Data Source
AI summary
In a described example, a method includes: forming a metal layer on a backside surface of a semiconductor wafer, the semiconductor wafer having semiconductor dies spaced apart by scribe lanes on an active surface of the semiconductor wafer opposite the backside surface; forming a layer with a modulus greater than about 4000 MPa up to about 8000 MPa over the metal layer; mounting the backside of the semiconductor wafer on a first side of a dicing tape having an adhesive; cutting through the semiconductor wafer, the metal layer, and the layer with a modulus greater than about 4000 MPa up to about 8000 MPa along scribe lanes; separating the semiconductor dies from the semiconductor wafer and from one another by stretching the dicing tape, expanding the cuts in the semiconductor wafer along the scribe lanes between the semiconductor dies; and removing the separated semiconductor dies from the dicing tape.