UV Laser Ablation of Polyimide Adhesive in Semiconductor Packaging
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Solution Overview
Problem
Current polyimide removal methods in semiconductor manufacturing, such as wet etching and plasma ashing, are slow and can damage semiconductor chips due to isotropic etching and high temperatures, limiting throughput and selectivity.
Innovation Solution
Laser ashing using an ultraviolet (UV) laser to ablate polyimide glue on semiconductor chips, which is a fast, anisotropic, and low-temperature process, accompanied by short plasma cleaning steps to remove carbon debris and residues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wet etching with NMP is used to remove polyimide, then the polyimide can be removed, but the etch rate is relatively slow, limiting throughput
Solution Approach 1:
The patent replaces wet chemical etching with laser ablation technology. The laser beam directly ablates the polyimide glue through photothermal decomposition, eliminating the need for chemical solvents and significantly increasing the removal speed. This substitution of mechanical/optical energy for chemical reaction enables faster processing and improved throughput.
Solution Approach 2:
The patent changes the processing parameters by using laser energy with specific wavelength, power, and scanning speed to achieve rapid polyimide removal. By adjusting laser parameters such as power density and scanning velocity, the process achieves high etch rates while maintaining selectivity, directly addressing the throughput limitation of conventional wet etching.
2Productivity
If plasma ashing with O2 is used to remove polyimide, then the polyimide can be removed, but the etch rate is slow and the temperature is high (up to 250°C), which may damage the semiconductor chip
Solution Approach 1:
The patent replaces thermal plasma ashing with laser ablation technology. Instead of using high-temperature plasma to decompose polyimide, the laser directly ablates the material through localized photothermal effects at lower temperatures, preventing damage to underlying semiconductor structures while maintaining efficient removal capability.
Solution Approach 2:
The laser ablation process creates localized heating only at the polyimide surface being processed, rather than heating the entire semiconductor chip structure. This localized energy delivery allows rapid polyimide removal while keeping the bulk temperature low, protecting temperature-sensitive semiconductor components from thermal damage.
3Speed
If hydrofluoric plasma ashing is used to increase etch rate, then the etch rate may be higher, but other materials in the semiconductor chip, such as silicon oxide, silicon nitride, or metal may also be etched along with the polyimide, damaging the semiconductor chip
Solution Approach 1:
The patent replaces chemical plasma etching with laser ablation technology. The laser selectively ablates polyimide based on its specific absorption characteristics at the laser wavelength, achieving high removal speeds without the non-selective chemical reactions that cause damage to other semiconductor materials like silicon oxide, silicon nitride, and metals.
Solution Approach 2:
The laser ablation process exploits the differential optical absorption properties of different materials. Polyimide has high absorption at the laser wavelength used, enabling selective and rapid ablation, while other semiconductor materials have lower absorption and remain unaffected. This optical selectivity achieves both high speed and high precision without cross-contamination of etching.
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
Laser ashing significantly increases throughput while minimizing damage to semiconductor chips by being highly selective to polyimide and maintaining low temperatures, reducing polyimide undercutting and processing time.
Implementation Method 1
ashing the polyimide glue on the semiconductor chip using an ablating laser
Implementation Method 2
accompanied by short plasma cleaning steps to remove carbon debris and residues
Data Source
AI summary
A system for laser ashing of polyimide for a semiconductor manufacturing process is provided. The system includes: a semiconductor chip, a top chip attached to the semiconductor chip by a connection layer, a supporting material, a polyimide glue layer disposed between the supporting material and semiconductor chip, a plasma asher, and an ashing laser configured to ash the polyimide glue on the semiconductor chip.