A Fully Integrated Solid-State Charge Detector with through Fused Silica Glass via Process
Citation
Wu, X.; Wen, L.; Cao, L.; Cao, G.; Li, G.; Fu, Y.; Yu, Z.; Fang, Z.; Wang, Q. A Fully Integrated Solid-State Charge Detector with through Fused Silica Glass via Process. Electronics 2023, 12, 1045. https://doi.org/10.3390/electronics12041045
Keywords
- charge detection
- low radioactive background
- through glass via (TGV)
- fully filled
- photosensitive material
- electrical property
Brief
This article presents a novel method to manufacture a fully integrated, solid-state charge detector on a fused silica glass substrate using a through glass via (TGV) structure.
Summary
The article presents a novel design and fabrication process for a solid-state charge detector, intended for use in particle physics experiments, particularly those involving neutrinos and dark matter detection. The detector is designed for high charge collection efficiency and low noise, crucial for accurate particle identification.
Here are the key points of the article:
- Substrate Selection: Fused silica glass was chosen as the substrate due to its low radioactive background, crucial for minimizing interference in particle detection experiments. Fused silica glass also offers compatibility with semiconductor processes, enabling modular integration of components like detection parts and computing chips.
- Detector Design and Optimization: The detector design prioritizes spatial resolution, high collection efficiency, and low crosstalk between channels. A square flat pad structure with a charge deflector was implemented to maximize the collection of charge particles. Simulations demonstrated a collection efficiency of 98.07% with the deflector, significantly higher than the 89.8% efficiency without it.
- Through Glass Via (TGV) Structure: To address the limitations of conventional wire-based charge collection, a novel TGV structure was introduced. This structure enables vertical electrical interconnection between the collection pads on the front side and the readout module/chip on the backside of the fused silica substrate, reducing noise and assembly complexity.
- TGV Fabrication and Material Selection: Fabricating the TGVs on fused silica glass posed challenges due to the material's drilling and polishing difficulties. A novel TGV fabrication process was developed, employing laser drilling, wet etching, and a unique filling method using a photosensitive material called TAIYO INK SR3. SR3 was selected for its intermediate coefficient of thermal expansion (CTE) to mitigate reliability issues arising from CTE mismatches between fused silica glass and copper used in the detector. The process ensures full filling of high-aspect-ratio vias, maintains a flat substrate surface, and leaves no organic residue, making it suitable for low-background applications.
- Material Characterization and Electrical Testing: The curing properties of SR3 were characterized using differential scanning calorimetry (DSC), revealing that it could be fully cured through exposure, UV irradiation, and heat baking. Electrical tests conducted on fabricated detectors confirmed the effectiveness of the TGV interconnections, demonstrating low resistance and capacitance values, critical for efficient signal transmission.
The authors conclude that the developed solid-state charge detector, with its innovative TGV structure and fabrication process, presents a promising advancement in particle detection technology.Further testing of the prototype in an experimental TPC is planned.