Wafer Thinning via Compensatory Mold Layer for Thickness Uniformity
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Solution Overview
Problem
Current wafer thinning processes face challenges in achieving uniform thickness and flatness due to thickness variations in protective materials, which affect the reliability and performance of semiconductor devices.
Innovation Solution
The method involves forming a protective adhesive layer on the wafer surface, followed by molding a compensatory mold layer to offset thickness deviations, and then grinding the backside while protecting the front side with the mold layer, and finally removing the layers to ensure uniformity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective material is placed over the front side of the wafer to protect the electronic circuitry during grinding, then the reliability of the wafer handling is improved, but the thickness uniformity and flatness of the wafer after grinding deteriorate due to thickness variation in the protective material
Solution Approach 1:
The patent applies preliminary action by performing a first grind to reduce the wafer thickness to an intermediate value before applying the protective material, and then performing a second grind after protective material application to achieve the final target thickness. This preliminary thickness reduction allows the protective material thickness variation to have minimal impact on the final thickness uniformity, as the majority of material removal occurs before protective material application.
Solution Approach 2:
The patent changes the parameter of wafer thickness through a two-stage grinding process. The first grind reduces thickness from the initial value (600-750 microns) to an intermediate value, and the second grind achieves the final target thickness (<75 microns). This parameter change strategy allows the process to accommodate protective material thickness variations while maintaining final thickness uniformity.
2Reliability
If the wafer is thinned to meet size and performance requirements, then the device performance is improved, but the thickness variation affects the reliability of the final individual semiconductor devices
Solution Approach 1:
The patent performs preliminary grinding to reduce wafer thickness to an intermediate value before protective material application. This preliminary action ensures that the majority of thickness reduction occurs when protective material is not present, thereby minimizing the impact of protective material thickness variation on final device thickness uniformity and reliability.
Solution Approach 2:
The patent maintains continuity of useful action by performing sequential grinding operations - first grind to intermediate thickness, then protective material application, then second grind to final thickness. This continuous process ensures consistent thickness control throughout the thinning operation, improving final device reliability.
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 improves the yield and reliability of semiconductor devices by reducing thickness variations and enhancing the uniformity of the wafer, thereby minimizing device failures.
Implementation Method 1
a rotating work chuck, which typically includes a rotating diamond cup wheel, sweeps across the wafer to remove material from the backside thereof
Data Source
AI summary
In one embodiment, a method for forming an electronic device includes providing a substrate having a plurality of electronic devices formed therein, forming a protective layer over a major surface of the substrate containing the plurality of electronic devices, forming a mold layer over the protective layer, thinning a major surface of the substrate opposite to the major surface containing the plurality of electronic devices, and removing the adhesive layer and the mold layer. In another embodiment, a zone coating layer can be included between the protective layer and the mold layer.