Wafer Grinding With Side Contact To Protect Low-k Film
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Solution Overview
Problem
The existing method of grinding wafers with low dielectric constant insulating films (low-k films) from the back side using a grinding stone can break the low-k film, leading to reduced device quality due to vertical pressure.
Innovation Solution
A method involving dividing the wafer into individual devices, bonding electrodes to a wiring board, filling the gap with resin for sealing, and grinding the devices from the side surface using a grinding apparatus with a predetermined height to avoid vertical load on the low-k film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a grinding stone is pressed against the back side of the wafer to grind it, then the wafer can be machined to the desired thickness, but the low-k film may be broken by the vertical pressure, leading to lowered device quality
Solution Approach 1:
The grinding operation is transitioned from vertical direction (pressing grinding stone against back side) to horizontal direction (moving wiring board so grinding stone contacts from side surface). This dimensional change eliminates vertical pressure on the low-k film while achieving the same thickness control through lateral material removal.
Solution Approach 2:
The wafer is divided into individual devices, bonded to wiring board, and sealed with resin before the grinding operation. These preliminary actions protect the low-k film structure and enable subsequent horizontal grinding without vertical loading that would break the film.
2Manufacturing precision
If the wafer is ground from the back side using vertical pressure, then thickness control is achieved, but device quality is reduced due to low-k film breakage
Solution Approach 1:
The grinding force is applied horizontally by moving the wiring board past a stationary grinding stone, rather than applying vertical pressure. This eliminates the harmful vertical pressure effect while maintaining thickness control capability through the horizontal grinding process.
Solution Approach 2:
The wiring board and resin sealing act as intermediaries that support the device during grinding. The resin fills gaps and provides protective encapsulation, allowing the device to be ground from the side without direct vertical pressure on the fragile low-k film.
3Productivity
If conventional wafer grinding is used, then production efficiency is maintained, but the low-k film breaks under pressure
Solution Approach 1:
The wafer is pre-divided and bonded to wiring board with resin sealing before grinding. This preliminary preparation enables the subsequent horizontal grinding process to proceed efficiently without the risk of film breakage, maintaining productivity while improving reliability.
Solution Approach 2:
By changing the grinding direction to horizontal, the process maintains continuous operation and high productivity while eliminating the vertical pressure that causes film breakage. The wiring board movement enables efficient material removal without compromising film integrity.
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
Prevents the low-k film from being broken during grinding, ensuring higher device quality by eliminating vertical pressure and allowing for precise thickness adjustment without damaging the film.
Implementation Method 1
a grinding stone fixed at a predetermined height is brought into contact with each of the devices from a side surface of the device to grind the back side of the device
Implementation Method 2
filling a gap between the wiring board and each of the bonded devices with a resin for sealing
Data Source
AI summary
A method of machining a wafer, wherein a wafer provided with devices each having a low dielectric constant insulating film (low-k film) stacked on the face side thereof is divided into the individual devices, the devices thus divided are mounted on a wiring board, and then a grindstone is brought into contact with each of the mounted devices from the side of a side surface of the devices, to grind the back side of the device by a desired amount. Since no vertical load is exerted on the low-k film, the low-k film can be prevented from being broken, and device quality is not lowered.