CaF2

CaF2

Calcium fluoride crystal thin film of PAM-XIAMEN is provided with high band gap, high dielectric constant and high dielectric strength, which is an ideal dielectric material for preventing leakage current effectively. CaF2 is calcium fluoride chemical formula. The evaporation temperature of CaF2 in a vacuum of 10-2Pa is 1100℃. It can be evaporated by heating with tantalum, molybdenum, tungsten boat or coil, or by heating with quartz crucible. The transparent area of the CaF2 film is 150nm ~ 12μm, and calcium fluoride refractive index is 1.36~1.42, and the refractive index of the CaF2 substrate changes with time. In addition, its refractive index value is related to the temperature of the substrate when the film is deposited.

Calcium fluoride wafer substrate

1. Calcium Fluoride Crystal Wafer Specifications

PAM210713-2-CAF2

Material Orientation Diameter Thickness Surface Finish
Calcium Fluoride Wafer (100) 2” 500 +/- 25um Single side polished
Calcium Fluoride Substrate (111) 2” 500 +/- 25 um Single side polished
Calcium fluoride thin film (100) 2” 2.0 mm Single side polished
CaF2 crystal wafer (111) 1” 1.0 mm Double sides polished
CaF2 wafer (100) 10×10 mm 1.0 mm Single side polished
CaF2 sheet (100) 10×10 mm 1.0 mm Double sides polished
CaF2 crystal substrate (111) 10×10 mm 1.0 mm Single side polished
Calcium fluoride crystal wafer (111) 10×10 mm 1.0 mm Double side polished
CaF2 Thin Film (100) 10×10 mm 0.5 mm Double sides polished
CaF2 substrate (100) 10×10 mm 0.5 mm Single side polished
CaF2 film (111) 10×10 mm 0.5 mm Double sides polished

Calcium fluoride structure

Calcium Fluoride Structure

2. Physical Properties of CaF2 Wafer Substrate

Here are calcium fluorid physical properties shown in the following diagram:

CaF2 Properties

3. Preparation and the Challenges in Integration Process of CaF2 Thin Film

Generally, CaF2 thin films are grown by synthetic methods (chemical vapor deposition, atomic layer deposition and thermal evaporation) in the industry. The lower cost of these methods enable the semiconductor wafer foundry to further synthesize and optimize calcium fluoride dielectric substrates. In addition, different electronic devices require different defect concentrations, and the wafers synthesized using these methods can be used in other types of micro-nano electronic devices.

Some challenges of CaF2 wafers in the integration process of two-dimensional micro-nano electronic devices, and potential solutions are proposed:

a) The interface between the film of CaF2 and the two-dimensional material: theoretically, a van der Waals-like structure can be formed between the CaF2 wafer (111) crystal plane and the two-dimensional material. However, the existing research has not yet involved the characterization of the quality of the interface between the CaF2 crystal wafer and the adjacent two-dimensional material. The interface between the calcium fluoride substrate and the two-dimensional material will be characterized by Raman spectroscopy and cross-sectional transmission electron microscopy.

b) The combination of CaF2 thin film and two-dimensional material: Most of the reported methods are to transfer two-dimensional materials to calcium fluoride wafers. How to directly grow two-dimensional materials on ultra-thin calcium fluoride wafer will be very prospective research direction.

c) Dielectric breakdown in CaF2 substrate: The dielectric breakdown process of micro-nanoelectronic devices with CaF2 sheet as the dielectric layer has not been fully understood, including tunneling current, different types of defects, charge trapping and release, random telegraph noise, etc.

d) New micro-nano electronic devices based on calcium fluoride substrates, such as memristors, still have a lot of room for development.

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