Semiconductor Wafer Thinning Using Handling Wafer Support
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Solution Overview
Problem
Conventional semiconductor manufacturing processes face limitations in achieving minimum thickness for vertical MOS transistor elements due to insufficient mechanical stability of thin wafers, restricting the reduction of on-resistance and power consumption.
Innovation Solution
A process involving a semiconductor wafer with a patterned polyimide-based adhesive layer for mechanical coupling to a handling wafer, followed by thinning and selective etching, allowing for the formation of semiconductor elements with substrate thicknesses below 50 μm, and subsequent connection to a lead frame using solder materials that form intermetallic phases by isothermal solidification, enabling mechanical and electrical bonding while releasing the handling wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the silicon wafer is thinned to reduce substrate thickness, then the on-resistance is reduced, but the mechanical stability deteriorates
Solution Approach 1:
A handling wafer is introduced as an intermediary support structure to hold the thinned semiconductor wafer during processing. The handling wafer provides mechanical stability while allowing the semiconductor wafer to be processed at reduced thickness, enabling thinning below the conventional 50 μm limit without compromising structural integrity during manufacturing steps.
Solution Approach 2:
The system is segmented into two separate wafers: the semiconductor wafer containing the active device structures and the handling wafer providing mechanical support. This segmentation allows each component to fulfill its specific function - the semiconductor wafer can be extremely thin for low resistance while the handling wafer maintains structural stability during processing.
2Use of energy by moving object
If the substrate thickness is reduced to decrease on-resistance, then power consumption is reduced, but the ease of manufacture deteriorates
Solution Approach 1:
The handling wafer serves as a mediator that enables manufacturing processes on thinned semiconductor wafers. By providing a stable base, it allows conventional manufacturing steps (implantation, metallization, etc.) to be performed on ultra-thin substrates that would otherwise be too fragile to handle, thus maintaining ease of manufacture while achieving reduced power consumption through thinner substrates.
Solution Approach 2:
The semiconductor wafer is bonded to the handling wafer before the thinning process begins. This preliminary action ensures that the wafer has adequate mechanical support throughout subsequent processing steps, enabling the substrate to be thinned to very low thicknesses while maintaining ease of manufacture through the supported structure.
3Manufacturing precision
If conventional thinning processes are used to achieve low thickness, then substrate thickness is reduced, but the reliability deteriorates due to wafer damage
Solution Approach 1:
The handling wafer provides beforehand cushioning and mechanical support to the semiconductor wafer during the thinning and subsequent processing steps. This support structure prevents wafer damage that would otherwise occur during handling of ultra-thin substrates, thereby maintaining high reliability while achieving the desired low substrate thickness.
Solution Approach 2:
The handling wafer acts as a protective intermediary between the fragile thinned semiconductor wafer and the external handling equipment. This intermediary structure absorbs mechanical stresses and prevents direct handling of the ultra-thin substrate, ensuring reliability is maintained throughout the manufacturing process.
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 enables the production of semiconductor elements with low on-resistance and power consumption, achieving high-yield and cost-efficient manufacturing by allowing for very thin substrate thicknesses and secure bonding to a lead frame.
Implementation Method 1
the solder layer connecting the backside metallization to the lead frame comprises a solder material of a type which forms intermetallic phases by isothermal solidification
Data Source
AI summary
Shown are embodiments where a process of manufacturing a semiconductor element on a semiconductor wafer is shown. The semiconductor element is obtained by dividing the function-providing semiconductor wafer into functional elements. The function-providing semiconductor wafer is, at its first main surface, mechanically coupled to a handling wafer. The thinning is carried out in the coupled state of the function-providing semiconductor wafer, and the function-providing semiconductor wafer is divided in its state coupled to the handling wafer. During or after connecting the semiconductor element to a lead frame the mechanical coupling between the semiconductor element and the corresponding part of the handling wafer is destroyed. Other embodiments are also shown.