Wafer Laser Dicing with Wet Etching to Remove Altered Regions
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Solution Overview
Problem
The existing methods for cutting wafers with metallic films and brittle materials like GaAs result in burr formation, chipping, and reduced flexural strength, along with cutting blade clogging and prolonged processing times, while laser ablation creates altered regions that decrease chip quality and increase processing time.
Innovation Solution
A method involving a frame unit with an extensible tape, a protective film formed by liquid resin on both surfaces, cutting with a laser beam along planned dividing lines, expanding intervals between chips, and removing altered regions through wet etching to enhance flexural strength and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a cutting blade is used to cut the wafer, then the wafer can be divided, but burrs are formed on the cut surface and chipping occurs at chip ends
Solution Approach 1:
The patent replaces the mechanical cutting blade system with a laser beam system to perform the cutting operation. The laser beam irradiates the wafer along planned dividing lines to form dividing grooves through ablation, eliminating mechanical contact that causes burrs and chipping. This substitution of mechanical cutting with laser processing resolves the contradiction between cutting efficiency and cut surface quality.
Solution Approach 2:
The patent changes the processing parameters by using specific laser wavelengths that are absorbable by the wafer material (such as 532nm for GaAs). By controlling laser power, pulse duration, and scanning speed, the cutting process achieves high precision without mechanical contact, thereby improving cut surface quality while maintaining productivity.
2Productivity
If a cutting blade cuts a wafer with metallic film, then the wafer is divided, but the metallic film creates burrs and chipping
Solution Approach 1:
The patent replaces mechanical cutting with laser ablation to process wafers with metallic films. The laser beam selectively removes material through ablation without mechanical contact, preventing the metallic film from being dragged and forming burrs. This resolves the contradiction by eliminating the mechanical interaction that causes quality degradation.
3Productivity
If laser ablation is used to divide the wafer, then cutting time is reduced, but altered regions are formed on cut surfaces
Solution Approach 1:
The patent extracts or removes the harmful altered regions formed by laser ablation through a subsequent wet etching process. By applying etchant to the cut surfaces, the altered regions are chemically removed, leaving clean surfaces without compromising the benefits of fast laser cutting. This resolves the contradiction between cutting speed and surface integrity.
4Manufacturing precision
If cutting blade is used on brittle wafer, then wafer can be divided, but processing time increases due to mild conditions requirement
Solution Approach 1:
The patent replaces mechanical cutting with laser ablation for brittle wafers. The laser process can be precisely controlled to avoid mechanical stress that would require mild processing conditions. By using laser parameters such as pulse duration and power density, the wafer can be divided quickly without compromising integrity, resolving the contradiction between precision and processing time.
5Productivity
If cutting blade cuts metallic film, then wafer is divided, but cutting blade clogs and life decreases
Solution Approach 1:
The patent replaces the mechanical cutting blade with a laser beam system. This eliminates the physical contact between the blade and the metallic film, preventing swarf generation and blade clogging. The laser processing maintains wafer division capability while indefinitely extending the 'life' of the cutting tool by having no consumable mechanical parts.
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 forms chips with high flexural strength by removing altered regions and preventing chip damage, while reducing processing time and blade clogging, and improving chip quality.
Implementation Method 1
the wafer can be divided when the wafer is irradiated with a laser beam of a wavelength absorbable by the wafer (wavelength that can be absorbed by the wafer), and dividing grooves are thus formed in the wafer along planned dividing lines by ablation processing
Implementation Method 2
laser beam of a wavelength absorbable by the wafer
Implementation Method 3
an etching step of removing altered regions formed in cut surfaces of the respective chips by application of the laser beam in the cutting step by wet etching
Data Source
AI summary
A method of processing a workpiece includes: a frame unit preparing step of preparing a frame unit including a tape affixed to an undersurface of the workpiece; a protective film forming step of forming a protective film on a top surface of the workpiece; a cutting step of cutting the workpiece by applying a laser beam; an interval expanding step of widening intervals between chips formed in the cutting step by expanding the tape outward in a radial direction; and an etching step of removing altered regions formed in the respective chips.