Laser Singulation of Brittle Materials via Two-Pass Parameter Adjustment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current laser singulation methods for semiconductor wafers face challenges such as heat affected zones (HAZ), debris re-deposition, and reduced system throughput due to the creation of a debris cloud, which can lead to device damage and decreased die break strength.
Innovation Solution
The method involves making a first cut in the wafer using initial laser parameters to minimize HAZ and debris, then adjusting parameters for subsequent cuts to increase fluence and throughput while avoiding the debris cloud by moving the laser to adjacent locations, allowing for deeper cuts without additional processing steps or equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser energy is increased to improve cutting speed and throughput, then productivity increases, but heat affected zone (HAZ) enlarges and debris re-deposition increases causing device damage
Solution Approach 1:
The cutting process is divided into multiple passes with different laser parameters. First pass uses lower energy to create initial kerf with minimal HAZ, second pass uses higher energy to complete the cut through the debris cloud. This segmentation allows each pass to be optimized for its specific function, resolving the contradiction between cutting speed and HAZ control.
Solution Approach 2:
The first laser pass performs preliminary action by creating an initial kerf and opening a pathway through the material. This preliminary action removes the barrier that would otherwise block subsequent high-energy laser pulses, enabling faster cutting in the second pass without increasing HAZ in the final cut.
2Area of stationary object
If street width is reduced to increase devices per wafer, then real estate utilization improves, but risk of device damage from HAZ and debris increases
Solution Approach 1:
The cutting process is segmented into two passes with different energy levels. The first pass creates a clean initial kerf with minimal HAZ using lower energy, while the second pass completes the cut through the debris cloud using higher energy. This allows narrower streets to be used safely because the HAZ is confined to the first pass and does not extend into the device area during the high-energy second pass.
Solution Approach 2:
The two-pass process maintains continuous useful action by ensuring the first pass prepares the material for the second pass. The initial kerf created in the first pass provides a pathway that allows the second pass to proceed efficiently, maintaining productivity while enabling narrower streets through better HAZ control.
3Productivity
If debris cloud is allowed to form during cutting, then material removal efficiency increases, but subsequent laser pulses are blocked reducing throughput
Solution Approach 1:
The cutting process is divided into two temporal phases: first pass creates kerf with debris cloud formation acceptable, second pass occurs after debris cloud has dissipated. This segmentation in time allows each phase to be optimized - first pass for initial material removal, second pass for clean high-speed cutting without debris blocking.
Solution Approach 2:
The laser cutting operates in periodic cycles: first pass creates kerf and debris cloud, then a pause allows debris to dissipate, followed by second pass with clean beam access. This periodic action pattern resolves the contradiction by allowing debris formation when acceptable and preventing it when it would block the beam.
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 enhances die break strength, reduces debris, and increases system throughput by minimizing HAZ and debris re-deposition, enabling more efficient and reliable singulation of semiconductor wafers.
Implementation Method 1
The laser typically removes material from the substrate or wafer to form the kerf by both ablation and thermal means
Implementation Method 2
Nearer the periphery of the beam or directly adjacent to the beam the material of the substrate may not receive enough energy to ablate the material but rather vaporizes or melts and boils the material
Implementation Method 3
lasers also typically create a heat affected zone (HAZ) next to the kerf due to the heat generated by the intense amount of energy required to cut the wafer or substrate
Implementation Method 4
The laser beam may be energetic enough to ablate material it impinges near the center of the beam, meaning that the material is ionized and forms a plasma cloud as it exits the kerf
Data Source
AI summary
An improved method for singulation of electronic substrates into dice uses a laser to first form cuts in the substrate and then chamfers the edges of the cuts by altering the laser parameters. The chamfers increase die break strength by reducing the residual damage and removes debris caused by the initial laser cut without requiring additional process steps, additional equipment or consumable supplies.