Wafer Laser Dicing via Annular Modified Layer Isolation
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Solution Overview
Problem
In semiconductor wafer processing, the application of a laser beam through a dicing tape from the back side to form a modified layer along division lines can cause stress on devices with projecting bump electrodes, potentially damaging them due to the depression force of the dicing tape.
Innovation Solution
A method where an annular modified layer is first formed between the device area and the peripheral marginal area using a laser beam applied through the dicing tape, isolating the device area from the peripheral marginal area, followed by forming modified layers along division lines, thereby preventing stress transmission and device damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laser beam is applied through the dicing tape from the back side to form a modified layer along division lines, then the modified layer can be formed inside the wafer along division lines, but the devices with projecting bump electrodes may be damaged due to stress generated by the depression force of the dicing tape
Solution Approach 1:
The patent divides the wafer into two distinct areas: a device area where devices are formed and a peripheral marginal area surrounding the device area. By applying the laser beam only within the device area and excluding the peripheral marginal area, the method segments the processing zone to avoid stress transmission to devices with bump electrodes while still forming the necessary modified layers for division line formation.
Solution Approach 2:
The patent applies different processing conditions to different regions of the wafer. The laser beam is applied with specific parameters (wavelength, pulse duration, frequency, power) tailored for forming modified layers in the device area, while the peripheral marginal area is excluded from laser processing. This local differentiation ensures precise modified layer formation where needed while protecting sensitive devices from stress damage.
2Ease of operation
If the dicing tape is attached to the back side of the wafer and supported to an annular frame, then the wafer can be held for processing, but the peripheral portion of the wafer is depressed by the dicing tape causing stress on devices
Solution Approach 1:
The patent segments the wafer into a device area and a peripheral marginal area, and specifically excludes the peripheral marginal area from laser beam application. This segmentation ensures that even though the dicing tape causes depression force in the peripheral area, the stress does not transmit to the devices in the device area where the modified layers are formed, thus protecting device integrity while maintaining ease of wafer handling.
Solution Approach 2:
The patent introduces the peripheral marginal area as an intermediary zone between the dicing tape's depression force and the devices. By excluding this peripheral area from laser processing, it acts as a buffer that absorbs the stress from the dicing tape attachment, preventing stress transmission to the sensitive devices with bump electrodes.
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 effectively prevents device damage by isolating the device area from stress generated by the dicing tape, ensuring accurate and undamaged formation of modified layers along division lines in semiconductor wafers with bump electrodes.
Implementation Method 1
applying a pulsed laser beam having a transmission wavelength to the wafer from one side thereof in the condition where the focal point of the pulsed laser beam is set inside the wafer along each division line, thereby continuously forming a modified layer as a break start point inside the wafer along each division line
Data Source
AI summary
A method of processing a wafer having a device area where a plurality of devices are formed and a peripheral marginal area surrounding the device area on the front side of the wafer is disclosed. The devices are formed in regions defined by division lines. Each device has a plurality of bump electrodes on the front side. A first laser beam is applied through dicing tape from the back side along the boundary between the device area and the peripheral marginal area, with the focal point of the first laser beam set inside the wafer, thereby forming an annular modified layer inside the wafer. A second laser beam is applied through the dicing tape from the back side along each division line with the focal point of the second laser beam set inside the wafer, thereby forming a modified layer inside the wafer along each division line.