Wafer Division via Laser Grooving and UV Shaping
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Solution Overview
Problem
The existing methods for cutting semiconductor wafers with low-k films are prone to damage and meandering issues, leading to reduced device quality and productivity, as the cutting blade can catch on laser-processed grooves and require multiple laser applications, causing surface roughening and linearity issues.
Innovation Solution
A wafer processing method involving a CO2 laser to remove the functional layer along division lines, followed by ultraviolet laser beam application to shape grooves and remove debris, allowing for precise cutting with a cutting blade along the grooves formed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a cutting blade is used to cut the semiconductor wafer along division lines, then the wafer can be divided into individual devices, but the cutting blade may meander and catch on laser-processed grooves causing separation of the functional layer and reduced device quality
Solution Approach 1:
The patent applies preliminary laser processing to create grooves along the division lines before cutting. These grooves serve as precise guides for the cutting blade, preventing meandering and catching issues. The grooves are formed by irradiating both sides of the wafer along the division lines, creating V-shaped grooves that guide the blade throughout the cutting process.
Solution Approach 2:
The laser-processed grooves act as an intermediary between the cutting blade and the wafer structure. Instead of the blade directly interacting with the solid wafer material, the grooves provide a pre-formed pathway that mediates the cutting process, ensuring linear and accurate cuts while preventing blade deviation.
2Ease of manufacture
If the functional layer is entirely removed along each division line using laser beam, then the cutting path is cleared, but the laser beam must be applied plural times causing reduction in productivity
Solution Approach 1:
The patent uses periodic laser irradiation from both the front and back sides of the wafer alternately. By irradiating both sides simultaneously or alternately, the functional layer is removed more efficiently in a single processing pass rather than requiring multiple sequential applications from one side, thereby maintaining productivity while achieving complete functional layer removal.
Solution Approach 2:
The patent transitions from single-sided laser processing to dual-sided laser processing. By adding the dimension of back-side irradiation, the functional layer removal process becomes significantly more efficient, clearing the cutting path in one pass rather than requiring multiple passes from a single side.
3Ease of manufacture
If the upper surface of the substrate is ablated by the laser beam, then the functional layer is removed, but the surface becomes roughened causing reduction in linearity of travel of the cutting blade
Solution Approach 1:
The patent creates asymmetric V-shaped grooves by irradiating both sides of the wafer. The groove geometry is asymmetric relative to the wafer surface, with the apex pointing toward the functional layer. This asymmetric groove structure provides a precise geometric guide for the cutting blade, ensuring linear travel even though the surface has been modified by laser ablation.
Solution Approach 2:
The laser grooves are formed as a preliminary action before cutting. These pre-formed grooves with their specific V-shaped geometry serve as templates that guide the cutting blade's path, compensating for any surface roughening effects and ensuring precise linear cutting.
4Productivity
If the low-k film is cut by the cutting blade, then the wafer is divided, but the low-k film may be separated and this separation may reach the devices causing fatal damage
Solution Approach 1:
The patent performs preliminary laser processing to create grooves and remove the functional layer along the division lines before cutting. This preliminary action weakens and separates the low-k film along the groove paths, creating a controlled separation zone that prevents uncontrolled film separation during cutting and protects the devices from damage.
Solution Approach 2:
The patent extracts or removes the functional layer along the division lines through laser irradiation before cutting. By taking out the functional layer that contains the low-k film in the division line regions, the cutting process is isolated to the substrate level, preventing the cutting blade from causing fatal separation of the low-k film that would reach the devices.
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 method efficiently removes the functional layer, smoothes the substrate surface, and improves cutting linearity, enhancing productivity and device quality by allowing accurate division of wafers into individual devices.
Implementation Method 1
applying a CO2 laser beam to the wafer along each division line in the condition where the spot of the CO2 laser beam having a width corresponding to the width of each division line is set on the upper surface of each division line, thereby removing the functional layer along each division line
Implementation Method 2
applying a laser beam having a wavelength in the ultraviolet region to the wafer along each groove after performing the functional layer removing step, thereby removing debris sticking to the bottom surface of each groove and also shaping the side walls of each groove
Data Source
AI summary
A wafer processing method divides a wafer into a plurality of individual devices along a plurality of crossing division lines formed on the front side of the wafer. The method includes a functional layer removing step of applying a CO2 laser beam to the wafer along each division line with the spot of the CO2 laser beam, having a width corresponding to the width of each division line set on the upper surface of each division line, thereby removing a functional layer along each division line to form a groove along each division line where the functional layer has been removed, and a groove shaping and debris removing step of applying a laser beam having a wavelength in the ultraviolet region to the wafer along each groove, thereby removing debris sticking to the bottom surface of each groove and also shaping the side walls of each groove.