UV-ozone cleaning is a cleaning process of sample surfaces used in material and device research. It is one of the popular techniques as well as oxygen plasma cleaning. In this process, photochemical reaction happens on sample surfaces in an unique approach.
This page describes fundamentals, advantages and applications of UV-ozone cleaning. Furthermore, as a supplier of UV-ozone cleaners, we show how Samco supports research and industry customers using our UV-ozone cleaners.
The Mechanisms of UV-Ozone Cleaning (How the UV-Ozone cleaning works?)
Several factors are involved in UV-ozone cleaning for surface chemical reaction.
Ultraviolet light (UV) lamp irradiates two types of wavelength (185 and 254 nm). Each wavelength has different roles for chemical reaction. 185-nm UV light dissociates molecular oxygen O2 into triplet atomic oxygen O(3P). Triplet atomic oxygen O(3P) combines with molecular oxygen O2 and generates ozone O3.
On the other hand, 254-nm UV light dissociates ozone O3 and forms molecular oxygen O2 and singlet atomic oxygen O(1D). Singlet atomic oxygen O(1D) has strong oxidation power, and it reacts with substrate surfaces. In this reaction, the surfaces were oxidized on inorganic substrates such as silicon wafers. In the case of organic materials, chain scission of molecules happens and organic residue contaminants are gently removed from the substrates as volatile byproduct molecules such as CO2, H2O and O2.
Sample stage temperature
Stage temperature is also one of the important factors in UV-ozone treatment. Even though 254-nm UV light dissociates ozone and forms singlet atomic oxygen, the reactive species has short lifetime (around 10 ms). Therefore, the density of singlet atomic oxygen is a bottleneck in UV-ozone cleaning process. The key to improve density of the reactive species is to raise stage temperature. Thermal dissociation of ozone is accelerated in higher temperature over 100°C, and higher density of singlet atomic oxygen is provided to sample surfaces.
Adjustment of sample stage temperature works well for some applications. Photoresist ashing rate significantly increases with higher stage temperatures due to higher atomic oxygen density caused by thermal ozone dissociation.
What is the advantage of UV-Ozone Cleaning over Other Techniques?
While there are several options for surface cleaning and sample preparation methods, UV-ozone cleaning shows several advantages over other methods.
Low charging damage on substrates
In case of plasma treatment, charging damage caused by ion bombardment can be a serious challenge. It leads to degradation of electrical characteristics of devices. UV-ozone treatment offers surface treatment using oxygen radicals without plasma discharge.
No hazardous effluent
Wet cleaning requires effluent disposal of chemicals. In contrast to the wet cleaning method, UV-ozone treatment is a completely dry process. Our UV-ozone cleaners are equipped with ozone killer, and exhaust ozone is decomposed inside the system. There is no need to worry about ozone hazard inside a cleanroom.
What is UV-Ozone Cleaning used for?
There are several applications of UV-ozone surface cleaning in material research and device fabrication.
These are some examples.
- surface cleaning of silicon wafers and plastic packages
- surface cleaning of III-V compound semiconductor wafers such as GaAs and InP prior to MOCVD and ALD process
- lead frame and bond pad cleaning for device packaging
- surface modification of polymer substrates
- surface activation
- wettability improvement of microfluidics channels
- adhesion improvement for direct substrate bonding such as glass, PDMS, PMMA, COC and COP
- surface oxidation (thin oxidized layer deposition)
- organic contamination removal
- photoresist ashing and stripping
- UV curing, outgassing and hardbaking of photoresist
- photoresist descum
- cleaning of AFM tips
- surface cleaning of Quartz Crystal Micro-balance (QCM) sensors
- cleaning of Surface Plasmon Resonance (SPR) chips
- UV crosslinking of polymers and photoresist
We provide UV-ozone process technologies to research communities and industrial customers using our UV-ozone cleaners.
If you are interested in research papers which used our UV-ozone cleaners, please check the customer publication page below.
Samco Customer Publication using UV-Ozone Treatment
System Lineup for UV-Ozone Cleaning
Samco UV-ozone cleaners are equipped with ozone generator and stage heating for effective surface treatment of samples.
The systems are used in research labs and industry customers.