Deep-UV Laser Wafer Cutting to Prevent Low-k Film Delamination
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Solution Overview
Problem
The use of a laser beam to cut wafers with a low-k film stacked on a silicon substrate often results in delamination at the interface between the low-k film and the silicon substrate, degrading the quality of the devices.
Innovation Solution
A laser processing machine that employs a pulsed laser beam with a wavelength of 266 nm or shorter, a pulse width of 200 fs or less, and a pulse interval shorter than the thermal diffusion time in the SiO2 film to suppress leakage light and prevent delamination during the cutting process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a laser beam is applied to cut the wafer with low-k film, then the wafer can be divided into individual device chips, but leak light of the laser beam causes delamination at the interface between the low-k film and silicon substrate
Solution Approach 1:
The patent changes the laser beam parameters by using deep ultraviolet light with wavelength of 266 nm or shorter and pulse width of 200 fs or shorter. This parameter change allows the laser to process the low-k film effectively while suppressing leak light that causes delamination, thus resolving the contradiction between cutting efficiency and device quality
Solution Approach 2:
The patent employs pulsed laser irradiation with pulse intervals shorter than the thermal diffusion time in the SiO2 film. This periodic action with controlled timing prevents heat accumulation and thermal diffusion that would otherwise cause delamination, enabling both efficient cutting and protection of the low-k film interface
2Temperature
If the pulse interval is extended to allow thermal diffusion, then heat accumulation is reduced, but delamination occurs at the low-k film interface due to leak light
Solution Approach 1:
The patent uses deep ultraviolet light with wavelength of 266 nm or shorter and extremely short pulse width of 200 fs or shorter. These parameter changes enable the laser to interact with the material on a timescale faster than thermal diffusion, reducing heat accumulation while minimizing leak light effects that cause delamination
Solution Approach 2:
The patent employs pulsed irradiation with pulse intervals shorter than the thermal diffusion time in the SiO2 film. This timing strategy allows each pulse to complete its interaction before significant thermal diffusion occurs, preventing both heat accumulation and delamination simultaneously
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
Effectively prevents delamination at the interface between the low-k film and the silicon substrate, ensuring the quality of the devices is maintained during the wafer cutting process.
Implementation Method 1
a laser oscillation unit that oscillates a pulsed laser of deep ultraviolet light at a pulse interval shorter than a thermal diffusion time in an SiO2 film stacked on an upper surface of the silicon substrate, and to emit the initial pulsed laser beam
Implementation Method 2
The laser beam irradiation unit includes a laser oscillation unit that oscillates a pulsed laser of deep ultraviolet light
Implementation Method 3
a condenser that condenses the initial pulsed laser beam emitted by the laser oscillation unit and focuses a pulsed irradiation laser beam on the wafer held on the chuck table
Data Source
AI summary
A laser beam irradiation unit of a laser processing machine includes a laser oscillation unit that emits an initial pulsed laser beam, and a condenser that condenses the initial pulsed laser beam emitted by the laser oscillation unit and focuses a pulsed irradiation laser beam on a wafer having a silicon substrate and held on a chuck table. The laser oscillation unit is configured to oscillate a pulsed laser of deep ultraviolet light at a pulse interval shorter than a thermal diffusion time in an SiO2 film stacked on an upper surface of the silicon substrate, and to emit the initial pulsed laser beam.