September 2019 – Paul Wu's Blog

Laser ablation mechanisms

There are two mechanisms to explain laser ablation process: Classical beam-matter interaction mechanism for micro- and nano-second pulse laser ablation and two temperature mechanism for pico-and femto-second pulse laser ablation.

Laser ablation

In the publication of Brian Q, et al., Optics and Laser Technology (2012), the authors reported a laser ablation method to pattern ITO film on a glass substate for the solar cell fabrication.

Al Vs Cu

Traditionally, IC interconnects formed from Al; however due to scaling and performances needs, Copper is gradually replacing Aluminum.

Deep reactive ion etching (DRIE)

Deep receive ion etching (DRIE) include two process: Bosch process and Cryogenic process (Reference 1).

Dry etching

It is difficult for wet etching to achieve good anisotropy in fabrication; therefore dry etching is adopted to solve this problem.

Wet etching

Etching is an important step in the fabrication of semiconductor devices and other similar process. It includes wet etching, a solution based method, and drying etching, based on vacuum process typically.

Photo elastic modulator

photo elastic modulator

Photo elastic modulator (PEM) is one the critical components in a phase modulated ellipsometer, which modulates phase and amplitude changes in detected signal, based on that Psi and Delta will be measured and n, k, d, and others accordingly in principle.

Ellipsometry

Ellipsometry is a powerful tool in thin film field to characterize film properties, e.g. refractive index (n), extinction coefficiency (k), surface roughness, crystallinity, etc.

Transmittance/Haze/Clarity measurement-ASTM D 1003

As a simplified view, light is incident upon a sample, three processes occur: transmission, absorption, and reflection, as schematically shown in the follow figure, including retroflection, diffuse reflection, specular reflection, diffuse transmission, and specular transmission.

Hardness measurement-ASTM D2240

Material hardness represents the capability of resisting the penetration of a harder body. The harder material wears or scratches the softer material.