Pulsed Laser Oscillation Modes for Wafer Debris Suppression
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Solution Overview
Problem
Existing laser processing apparatuses face challenges in efficiently removing molten debris and growing debris generated during the laser processing of wafers, particularly those with copper interconnects on silicon substrates, which affects the quality of device chips.
Innovation Solution
A laser processing apparatus that utilizes a pulsed laser beam with a laser oscillation mechanism capable of operating in multiple modes. These modes include settings for breaking growing debris, suppressing molten debris generation, and simultaneously forming grooves and removing debris, thereby eliminating the need for additional laser irradiation to remove debris.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a laser beam is used to form grooves in a workpiece, then groove formation is achieved, but molten debris and growing debris are generated that adhere to devices and deteriorate device chip quality
Solution Approach 1:
The patent applies preliminary action by irradiating the workpiece with a laser beam to form grooves before the debris removal step. This sequential approach allows the groove formation to be completed first, establishing the structural division, and then subsequently removing the generated debris in a second irradiation step, thereby preventing debris adhesion to devices while maintaining groove formation capability
Solution Approach 2:
The patent extracts the harmful debris from the system by using a second laser irradiation step specifically dedicated to removing molten and growing debris. This separate extraction process isolates the debris removal function from the groove formation process, allowing each to be optimized independently - grooves are formed in the first step and debris is removed in the second step, preventing quality deterioration
2Object-affected harmful factors
If a second laser irradiation is performed to remove debris, then device chip quality is improved, but productivity is reduced due to additional processing time
Solution Approach 1:
The patent merges two previously separate processes - groove formation and debris removal - into a single integrated laser processing system. By using the same laser beam for both functions in sequence, the system eliminates the need for separate processing equipment and reduces overall processing time, thereby improving productivity while maintaining the quality benefits of debris removal
Solution Approach 2:
The patent implements continuity of useful action by performing groove formation and debris removal in consecutive laser irradiation steps without interrupting the processing flow. The laser beam continuously acts on the workpiece, first forming grooves and then removing debris, thereby maximizing processing efficiency and eliminating idle time between operations
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 apparatus improves productivity by allowing simultaneous groove formation and debris removal, ensuring high-quality device chips without the need for additional debris removal processes.
Implementation Method 1
irradiation with the pulsed laser beam is carried out in a time required until plasma generated from the workpiece due to the irradiation of the workpiece with the pulsed laser beam disappears to continue the plasma without interruption and break growing debris
Implementation Method 2
a time required until heat generated due to irradiation with the pulsed laser beams of the first group cools down as a time interval between the first group and the adjacent first group
Implementation Method 3
molten debris generated due to irradiation with the laser beam
Implementation Method 4
a time when molten debris solidifies
Implementation Method 5
a beam condenser that condenses the pulsed laser beam emitted by the laser oscillation mechanism and irradiates the workpiece held by the chuck table with the pulsed laser beam
Data Source
AI summary
A laser oscillation mechanism of a laser beam irradiation unit has a first mode to break growing debris, a second mode to suppress generation of molten debris, and a third mode to break the growing debris and suppress generation of the molten debris. The laser oscillation mechanism includes a selecting part that selects any of the first mode, the second mode, and the third mode. The laser oscillation mechanism sets a repetition frequency with a first group being one unit in the first mode, and sets a repetition frequency with a second group being one unit in the second mode, and sets a repetition frequency with a third group being one unit in the third mode.