Angled Edge Support Ring for Wafer Spin Etch
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Solution Overview
Problem
The existing processes for forming ultra thin wafers with edge support rings often interfere with the spin etch process, leading to incomplete chemical etching and drying issues, which complicate the fabrication and may affect the quality of the ohmic contact.
Innovation Solution
The process involves forming an ultra thin wafer with an edge support ring that has an angled inner wall, allowing chemicals and de-ionized water to be effectively spun off during the spin etch process, thereby facilitating the preparation for back metallization without additional complexity or delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a support ring is formed at a wafer edge to facilitate handling and processing of the ultra thin wafer, then the handling and processing of the ultra thin wafer is facilitated, but the spin etch process is interfered with, leading to incomplete chemical etching and drying issues
Solution Approach 1:
The support ring is segmented into a multi-layer structure with a porous lower layer and a non-porous upper layer. This segmentation allows the porous layer to facilitate chemical etching and drying during spin etching, while the non-porous layer provides mechanical support and protection, thus resolving the conflict between ease of handling and spin etch process quality.
Solution Approach 2:
Different regions of the support ring are given different properties: the lower portion near the wafer surface is made porous to allow chemical penetration and etching, while the upper portion is made non-porous to provide structural strength. This local differentiation of properties enables the support ring to simultaneously facilitate spin etching and provide mechanical support.
2Strength
If the edge support ring is made wider to increase strength, then the mechanical strength is improved, but the space available to form dies is reduced
Solution Approach 1:
The support ring utilizes local quality by creating a porous structure in the lower portion that provides mechanical strength without requiring increased width. The porous architecture delivers high strength-to-weight ratio, allowing the ring to maintain adequate strength while preserving maximum wafer area for die formation.
Solution Approach 2:
The support ring is constructed as a composite structure with porous and non-porous layers, combining the advantages of both materials. The porous layer provides strength and chemical permeability, while the non-porous layer adds protective functionality, achieving adequate strength without increasing the ring width and thus preserving die formation space.
3Productivity
If conventional spin etch processes are used with edge support rings, then additional complexity or delays in the fabrication process may be introduced, but the quality of the back metal contact may be adversely affected
Solution Approach 1:
The porous support ring structure performs self-service during the spin etch process by automatically allowing chemical etchants to penetrate through to the wafer surface and enabling complete drying. This self-facilitating property eliminates the need for additional process steps or modifications, maintaining fabrication efficiency while ensuring high-quality back metal contact.
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 solution enables the use of conventional spin etch processes with edge support rings, enhancing the mechanical strength of the wafer and ensuring a good ohmic contact by ensuring complete etching and drying, thus simplifying the fabrication process and improving the quality of the back metal contact.
Implementation Method 1
grinding the wafer backside while gradually reducing a distance between a grinding wheel axis of rotation and a wafer chuck axis of rotation
Implementation Method 2
rotation of the wafer causes the chemical etch and de-ionized water to flow outwardly
Data Source
AI summary
A process of forming ultra thin wafers having an edge support ring is disclosed. The process provides an edge support ring having an angled inner wall compatible with spin etch processes.