Protective Film for Semiconductor Stealth Dicing
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Solution Overview
Problem
Conventional methods for producing semiconductor chips using stealth dicing processing face challenges in concealing grinding marks on the rear surface of the chips, which are visible and affect the appearance, and existing protective films do not effectively hide these marks during visual observation.
Innovation Solution
A protective film-forming film with specific light transmittance properties at 1064 nm and 550 nm wavelengths, combined with an organic colorant and filler, is used to create a modified layer on the workpiece, allowing for the concealment of grinding marks by enhancing infrared transmittance while reducing visible light transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the light transmittance at 550 nm is increased to improve visual appearance, then grinding marks become more visible, but laser processing efficiency decreases
Solution Approach 1:
The protective film is designed with non-uniform optical properties: high transmittance (55% or more) at 1064 nm wavelength for laser processing regions, and low transmittance (20% or less) at 550 nm wavelength for visual observation regions. This local differentiation of optical characteristics allows the film to simultaneously support both laser stealth dicing and aesthetic appearance requirements.
Solution Approach 2:
The patent changes the optical parameters of the protective film by controlling light transmittance at specific wavelengths. By setting T1064 ≥ 55% and T550 ≤ 20%, the film transforms from a conventional uniform optical property state to a differentiated state that optimizes both laser processing and visual appearance.
2Object-affected harmful factors
If the light transmittance at 1064 nm is decreased to reduce laser damage, then modified layer formation is impaired, but grinding marks become less visible
Solution Approach 1:
The protective film is applied to the workpiece before laser processing. This preliminary action establishes a protective barrier that allows subsequent laser irradiation to safely form the modified layer without causing damage to the workpiece surface or surrounding areas.
Solution Approach 2:
The film's optical parameters are specifically tuned to transmit 1064 nm laser light (T1064 ≥ 55%) while blocking visible light (T550 ≤ 20%). This parameter optimization enables the film to simultaneously protect against laser damage and conceal grinding marks.
3Object-affected harmful factors
If conventional protective films with low visible light transmittance are used, then grinding marks are concealed, but laser processing efficiency is reduced
Solution Approach 1:
The protective film exhibits different transmittance characteristics for different wavelength regions: high transmittance for infrared laser wavelength (1064 nm) and low transmittance for visible light wavelength (550 nm). This local quality differentiation resolves the contradiction between concealment and processing efficiency.
Solution Approach 2:
The protective film is constructed as a composite material with specific optical properties that combine the benefits of both high and low transmittance characteristics, achieving simultaneous optimization for laser processing and appearance quality.
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 film effectively conceals grinding marks on semiconductor chips, ensuring they are not detectable by visual observation and enables the production of high-quality semiconductor chips with improved appearance.
Implementation Method 1
the light transmittance at a wavelength of 1064 nm is 55% or greater, and the light transmittance at a wavelength of 550 nm is 20% or less
Data Source
AI summary
Provided is protective film-forming sheet (2) including: a protective film-forming film (1) having a light transmittance at a wavelength of 1064 nm of 55% or greater and a light transmittance at a wavelength of 550 nm of 20% or less; and a release sheet (21) which is laminated on one or both faces of the protective film-forming film (1). According to this protective film-forming sheet (2), it is possible to form a protective film which allows a workpiece such as a semiconductor wafer to have a modified layer disposed in advance therein by a laser so that the workpiece can be split through the application of force thereon, while preventing grinding marks on the workpiece or a product formed therefrom from being visible to the naked eye.