Wafer Processing Method for Projection Electrodes
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Solution Overview
Problem
The bonding process of wafers with projection-shaped electrodes is hindered by the formation of an oxide film and contamination on the metallic surfaces over time, especially after the head portions of the electrodes are cut, which can occur during storage before the bonding step.
Innovation Solution
A wafer processing method that includes a cutting step to uniform the height of the electrodes, a thermocompression bonding step using a polyolefin-based or polyester-based sheet to shield the electrodes from air, and a peeling step to prevent oxidation and contamination, along with an optional plating step to enhance bonding, ensuring the electrodes remain suitable for bonding even after a delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wafer is not divided into individual device chips and subjected to bonding immediately after cutting, then productivity is improved by allowing storage time, but the metallic surfaces of the electrodes form oxide films and contaminants adhere, hampering subsequent bonding
Solution Approach 1:
A protective film is introduced as an intermediary layer between the metallic electrode surfaces and the external environment. This protective film prevents oxidation and contamination during storage, allowing delayed bonding without compromising bonding quality. The film acts as a mediator that shields the sensitive metallic surfaces while permitting the wafer to be stored and handled.
Solution Approach 2:
The patent creates an inert protective environment over the metallic electrode surfaces by forming a protective film that excludes oxygen and moisture. This inert environment prevents oxidative reactions and contaminant adhesion, enabling the wafer to be stored for extended periods before bonding without degradation of the electrode surfaces.
2Reliability
If a protective measure is applied to prevent oxidation during storage, then bonding reliability is maintained, but the process complexity increases
Solution Approach 1:
The protective film formation step is merged with the existing wafer processing sequence, integrating the protection function into the standard manufacturing flow. By combining the protective measure with routine processing steps rather than adding entirely separate complex systems, the patent maintains bonding reliability while minimizing increases in overall process complexity.
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
The method effectively prevents oxidation and contamination of the metallic surfaces, ensuring reliable bonding by shielding the electrodes with a thermocompression bonding sheet, which maintains their integrity until division and bonding to a circuit board.
Implementation Method 1
a thermocompression bonding step of heating and pressing the thermocompression bonding sheet to perform thermocompression bonding
Data Source
AI summary
A wafer processing method for processing a wafer formed on a front surface thereof with a plurality of devices having projection-shaped electrodes, the devices being partitioned by streets, includes a cutting step of holding a back surface of the wafer by a holding surface of a chuck table and cutting head portions of the projection-shaped electrodes by a cutting tool slewed in parallel to the holding surface, to make uniform the electrodes in height and expose metallic surfaces; a thermocompression bonding sheet laying step of laying a thermocompression bonding sheet on the front surface of the wafer; a thermocompression bonding step of heating and pressing the thermocompression bonding sheet to perform thermocompression bonding; and a peeling step of peeling off the thermocompression bonding sheet from the wafer, before dividing the wafer into individual device chips and bonding the electrodes to a circuit board.