Knowledge Base - Wet benches - Process Baths - Acid Baths
What is a Wet Bench?
“Wet Bench” “WetDecks” “Wet Process” “Process Baths” or “Sinks” are terms used in semiconductor manufacturing to describe the machine or machines used to sequentially process a batch of wafers (or single wafers) through a variety of chemical steps.
Typical processes can be cleaning, etching, or even electroplating - each carried out in a dedicated process bath containing chemicals dependent on the substrate material being processed.
Common chemicals used are HF, Hydrofluoric Acid, H2SO4 Sulphuric Acid, H2O2 Hydrogen Peroxide or Piranha (H2SO4 + H2O2 mix). Most rinsing is carried out with DI, (De-ionised Water). Proprietary solvents are also used.
Manual Spinners & Hotplates
Ideal for laboratory use or for putting into wet benches
Defining a Wet Bench
Benches and baths need to be made from suitable materials depending on the chemistry to be used in the processes and often involve polypropylene, PVDF, Stainless Steel. Fire retardant materials may be required depending on certain processes or insurance requirements. These materials are normally available but at additional cost.
Wafers or batches of wafers are then sequenced through the wet processes with each stage being monitored and timed depending on the required result.
Handling of wafers or batches of wafers can be fully automatic, semi-automatic or manual. Most wet benches are designed and configured to a specific customer need and while there are “standard systems” most need to be custom made.
Defining a wet bench can be quite difficult so we provide on-site meetings for design and work with you every step of the way.
Cleaning and Drying
As the wafers are normally immersed in chemicals it is essential they are rinsed at the end of the process. There are two main reasons A: to stop the etching process and remove any active chemical and B: to clean and remove any loose debris or particles.
Cleaning and Rinsing - (Usually with DI Water) There are a variety of options the most common is a simple rinse tank with an overflow weir to make sure particle that float on the top surface are removed from the tank. This is important to prevent any loose particles removed during the rinse do not re-adhere when the wafers are removed through the top surface of the rinse tank
Quick Dump Rinse Tanks are when the rinse step is finished large valves at the bottom of the tank open to allow the water to flow very fats out of the rinse tank - further reducing the possibility of adding particles in the removal step of the process: - The clean but wet wafers are now ready for the "drying" process.
The most common form of drying wafers is in a spin rinse dryer (SRD) that gives the wafers a final rinse and dry process. More details can be found on the link