Etching Techniques in Photolithography

What is the primary purpose of etching in microfabrication?

What type of etching process is classified as isotropic?

Which of the following chemicals is commonly used in wet etching?

What is a characteristic of dry etching?

Reactive Ion Etching (RIE) is known for which of the following?

What follows the etching process as an essential step?

Which statement accurately describes wet etching?

What is an important characteristic of dry etching compared to wet etching?

Which application is particularly associated with Reactive Ion Etching (RIE)?

Which property differentiates anisotropic etching from isotropic etching?

Etching Techniques

Etching removes unprotected material layers after photolithography.
Utilizes reactions between chemicals (wet etching) or ionized gas (dry etching).
Requires high selectivity to ensure etchant acts more rapidly on material than photoresist.

Wet Etching

Employs chemicals, commonly diluted HF acid (Buffered Oxide Etch - BOE), to etch silicon dioxide.
Considered hazardous but is simple and cost-effective.
Isotropic process results in uniform etching in all directions, potentially causing undercut.

Dry Etching

Uses RF excitation to ionize gases like CF4 in a vacuum to etch silicon dioxide.
Less hazardous compared to wet etching but is more complex and expensive.
Anisotropic process minimizes undercutting, providing directional etching.

Reactive Ion Etching (RIE)

Combines plasma etching with sputtering action of ionized gas.
Effective for creating deep trenches, particularly useful in MEMS (Microelectromechanical Systems) applications.
Known for its highly anisotropic etching capabilities.

Isotropic vs. Anisotropic Etching in MEMS

Isotropic etching results in uniform rates in all directions, potentially affecting design precision.
Anisotropic etching provides controlled and directional material removal, crucial for detailed fabrication.

Photoresist Removal

Typically performed after etching, although it is not classified as etching.
Involves using resist strippers or acetone to remove photoresist, revealing the un-etched patterns as per the mask from photolithography.

This quiz explores the fundamentals of etching in photolithography, focusing on the two main techniques: wet etching and dry etching. Understand how each method utilizes chemical reactions or ionized gases to selectively remove material layers. Test your knowledge on the importance of selectivity in the etching process.