What is in buffered oxide etch?

General description. Buffered oxide etchant (BOE) is a wet etchant used in microfabrication. Its primary use is in etching thin films of silicon dioxide (SiO2) or silicon nitride (Si3N4). It is a mixture of a buffering agent, such as ammonium fluoride (NH4F), and hydrofluoric acid (HF).

How is etch rate calculated?

Etch rate is determined by measuring the depth an etch achieves in a period of time. It is reported as distance/time with typical units being Angstroms/second, nanometers/minute, or microns/minute.

How does buffered oxide etch work?

Buffered oxide etch is used to etch thin films of oxide or polysilicate glass (some have used it to etch cavities in glass). It is a buffered HF mixture that slows down and controls the attack rate of HF on oxide. This is a level-1 process and requires basic INRF safety certification.

How the SiO2 etching is performed in the buffered HF solution?

The surface becomes highly hydrophobic [1, 2]. The BOE process is based on the complexing reaction: SiO2 + 6 HF → H2SiF6 + 2 H2O where H2SiF6 is soluble in water. This reaction is performed in a dilute solution of HF, buffered with NH4F to avoid depletion of the fluoride ions.

Does BOE etch GaN?

The oxide was patterned with photoresist and etched with buffered oxide etchant (BOE), because it does not etch the underlying GaN cap layer.

What do you mean by high aspect ratio etching?

High aspect ratio (HAR) silicon etch is also known as deep silicon etch, deep trench silicon etch, silicon deep reactive ion etch, and HAR trench silicon etch. Since the invention of the integrated circuit (IC) in 1958, silicon etching has been an important technology for the semiconductor industry.

How can I increase my etch rate?

Substrate Temperature Like in cooking, the temperature affects the results. The impact of temperature on most materials is an increase in the etch rate. While it might seem that the selectivity would stay constant with increasing temperature, not all materials increase their etch rate by the same proportionate amount.

Does HF etch SiO2?

A very “selective” chemical for SiO2 – i.e. does not etch silicon at all – is hydrofluoric acid (HF).