Water-Washable Plasma-Resistant Coating for Laser Singulation
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Solution Overview
Problem
Current microelectronic manufacturing processes face challenges in efficiently separating small and fragile electronic devices using laser-assisted plasma singulation, as existing coatings tend to crosslink during plasma etching, making them difficult to remove and leading to yield loss and environmental hazards.
Innovation Solution
A coating composition comprising a thermal resistant water-soluble polymer and ultraviolet light absorbing compound, which interacts with laser light to enable patterning at low energies and resists plasma chemistries, allowing for easy removal with water, thereby simplifying the process and reducing waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coatings are used for laser-assisted plasma singulation, then the coating provides initial protection and enables laser patterning, but the coating crosslinks during plasma etching and becomes difficult to remove
Solution Approach 1:
The patent applies parameter changes by carefully controlling the coating composition (specific ratios of water-soluble polymer to UV absorber), coating thickness (1-10 micrometers), and plasma process parameters to achieve sufficient protection during etching while preventing crosslinking that would hinder removal. The coating is designed to withstand plasma exposure without undergoing irreversible crosslinking reactions.
Solution Approach 2:
The patent uses composite materials by combining water-soluble polymers (such as PVA, PVP, or carboxymethyl cellulose) with ultraviolet absorbers (such as benzotriazole derivatives or benzophenone compounds) in specific ratios. This composite structure provides both the necessary plasma resistance and maintains water solubility for easy removal after the process.
2Reliability
If the coating is made highly resistant to plasma chemistries, then protection during etching is improved, but the coating becomes more difficult to remove and may require harsh chemicals
Solution Approach 1:
The patent optimizes the coating composition parameters, specifically using water-soluble polymers with appropriate molecular weights and concentrations, combined with UV absorbers at controlled ratios (typically 1-10% by weight). The coating thickness is also controlled at 1-10 micrometers to provide sufficient plasma resistance while maintaining easy water-washability, eliminating the need for harsh removal chemicals.
3Productivity
If laser energy is increased to improve patterning efficiency, then processing speed increases, but deleterious effects on underlying features occur
Solution Approach 1:
The patent uses the coating as an intermediary layer between the laser and the substrate. The coating absorbs the laser energy (particularly at UV wavelengths where the absorber is active) and converts it to heat, which is then dissipated without reaching the substrate in damaging amounts. This allows efficient laser patterning of the coating while protecting the underlying fragile substrate from thermal damage.
Solution Approach 2:
The patent employs UV absorbers in the coating that specifically absorb laser wavelengths, creating a selective interaction. The absorber compounds (such as benzotriazole or benzophenone derivatives) have high absorption coefficients at the laser wavelength, enabling efficient energy coupling and patterning at lower overall laser powers that do not damage the substrate.
4Use of energy by moving object
If the coating is made thin to allow laser penetration, then laser interaction is improved, but plasma etching protection is reduced
Solution Approach 1:
The patent uses composite materials with optimized composition to achieve the right balance. The water-soluble polymer matrix provides the structural integrity and plasma barrier properties, while the UV absorber dispersed within it provides strong laser absorption. This composite structure allows thin coating layers (1-10 micrometers) to simultaneously provide sufficient plasma protection and efficient laser interaction.
Solution Approach 2:
The patent optimizes the coating thickness parameter to 1-10 micrometers, which is thin enough to allow efficient laser energy coupling and rapid patterning, yet sufficiently thick to provide adequate plasma etching protection. The composition parameters (polymer concentration, UV absorber content) are also optimized to maximize both laser absorption and plasma resistance at this thin thickness.
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 solution provides high interaction with laser light for precise patterning, resistance to plasma etching, and easy water-based removal, enhancing manufacturing efficiency and reducing environmental impact and costs.
Implementation Method 1
ultraviolet light absorbing compound... high interaction with certain laser light to allow patterning at low energies
Implementation Method 2
thermal resistant water soluble polymer... high resistance to plasma chemistries
Implementation Method 3
water soluble polymer... easy removal with water... coating mask is washed with water
Data Source
AI summary
Compositions and methods useful for the singulation of fragile devices from substrates by the process of plasma singulation are described. Thermal resistant coatings comprising ingredients that exhibit both thermal resistance and water solubility are demonstrated. These ingredients which have high ultraviolet interaction allow laser interaction to create masks for thin and small devices, for example, substrates that are thin to 150 microns or less or have devices present that are measured 1 mm on a side or smaller. Methods are presented which apply the composition to the inorganic substrate whereby an ultraviolet sourced laser interacts with the surface and creates a mask which subsequently is processed in a plasma chamber to separate (singulate) the devices within the substrate and subsequently rinse with water to remove/dissolve the laser interactive and plasma protective layer. Once rinsed and clean, the devices proceed by pick and place tooling to final integration to electronic circuitry. The invention coating is a water rinsable creation that achieves high selectivity for both laser and plasma operations.