Biomedical Engineering Reference
In-Depth Information
Figure 4.25
Process flow of micromachining process used for top and bottom parts
4.2.3.1 Primary Cleaning
As the first step in the fabrication process, silicon parts were cleaned in order to ensure for-
mation of a homogenous oxide layer. To remove any contamination from the silicon parts,
a primary cleansing was performed, mainly for the purpose of removing grease and dust.
4.2.3.2 Pre-cleaning
The samples were placed in a sample holder and immersed in Acetone ((CH
3
)
2
CO) for
10 minutes and then cleaned with isopropanol (CH
3
CHOH - CH
3
) for 10 minutes. To
accelerate the cleaning process, ultrasonic cleaning was applied at 20 kHz. The samples
were then rinsed with DI water and afterwards dried using compressed nitrogen gas.
4.2.3.3 Cleaning
To remove any contamination that could still have remained on the surface of the samples,
a commonly used Piranah solution (also known as Caro's acid or sulfuric peroxide) [18]
was used. Piranah is a solution of two parts by volume of sulfuric acid (H
2
SO
4
) and one
