Multi Channel Fully Automated Wet Etching System 



R.D. McFawes
Research and Development Multi Channel Fully Automated System

McFawes concept


The R.D.McFawes wet etching system has been designed with a user in mind who wantsto combine a maximum of process flexibility with a minimum of chemicalconsumption. The system can be used for process development or in lowthroughput productionlines for devices like micro-electro-mechanical systems(MEMS), nanosystems or the like, where the nature of the product or theeconomics of the manufacturing process prohibit the use of larger batchprocessing systems.  


McFawes is designed for cleaning, etching or electro-platingapplications. It is small enough to carry out economically wet process evensingle dies. McFawes accepts any chemical that is commonly used in thesemiconductor and MEMS/MST industry. The wafer/sample remains immersed in thechemicals during the whole process. One chemical is replaced by another by afull-flow process. For applications that require the wafer to stay immersed ina liquid until itis finally dried, an optionally second chamber, next to thefirst one will hold the wafer/sample. It can be filled with any chemical or DIwater. The modular design of the McFawes system allows to substitute thisoptional wet chemical chamber by a spin- or Marangoni-dryer as an alternative.

McFawes is best used for applications like removal of sacrificial layers(MEMS), production of porous silicon, electro plating or a combination of thoseprocesses.

Quick List of Benefits:

Benefit Why ?
The system is able to shorten the time. Larger wet benches are awkward for processing and for process development small samples or batches. The smaller McFawes allows for faster screening of process chemicals higher reproducibility of process The smaller volume of McFawes´ process chamber allows more accurate timing and quicker interruption of processes.
The system  runs fully automated and process parameters are controlled by the system.


Better uniformity of process results because of single wafer/sample processing. Process-chemicals are more uniformly.
Lower consumption of chemicals McFawes process chamber is small as compared to regular wet benches. The consumption of chemicals is therefore lower and allows the screening of a larger amount of chemicals and compositions higher safety standard for personnel! The user does not get exposed to neither the process nor any vapors.


Small footprint (1200mm x 950 mm x 850 mm – W47” x L37,5” x H33,5”) McFawes saves space in a laboratory environment.
Software upgrades to provide enhanced McFawes has many features that are available as functionality options. Those features can be integrated into the control system by software upgrades.


Installation of additional modules by the user can add additional modules for extended functionality later. The system can grow with the users demand.
Cost effective for small foundries due to its automation, McFawes is ideally suited to be run in smaller foundry operations that need to cover a broader variety of processes but process a smaller number of products. The MEMS/MST industry is a typical example for that kind of industry.

Technical Characteristics:

· Wafer/sample size: 200 mm or smaller (300 mm are optionally available)
· The wafer is oriented horizontally in the process chamber. The process-agent is tangentially injected into the chamber such that the liquid starts rotating to create agitation. This agitation helps remove gas bubbles from the surface of the wafer,which might have been generated by chemical reactions during the previous process.


· The process chamber closes automatically after it is loaded. The lid prevents chemical spills and the escape of harmful vapor. Chamber can be purged with nitrogen during the processes. HF as a dangerous and toxic gas will be neutralized in the same neutralization unit, which is in use to neutralize fluoric acid. The purge gastubing for removing harmful vapor is integrated in the chamber lid.


· DI water for rinsing is applied either in the full-flow process by replacing the process chemical or by an optional 120° spray-on nozzles located in the lid. Due to the small amount of process chemical in the system in general and especially in the spray process the latter reduces greatly the consumption of DI water


· A fast etch stop can be achieved by a combination of quick chemical dumb and spray rinse · Process chemicals can be recirculated with an on-board pump to minimize  the consumption of material and to replenish locally consumed process chemicals on the wafer surface.


· The spare consumption of etchants and other chemicals saves costs due to the lower consumption of fluids and for the chemicals too. The consumption of DI water is reduced too as DI-water must be applied for decontamination. So the design of the system is environment-protective.


· The system has integrated wafer holders in its lid that is operated by a lift. There are different wafer holders available depending from the actual application.· The lid is operated by a lift and will be mechanically activated and opened automatically.


 Uniformity: < 4% (depending from rotational speed of the media)
 DI water for rinsing is applied either in the full-flow process by replacing the process chemical or by 120° spray-on nozzle located in the lid-center. The latter reduces greatly the consumption of DI water.


 This 120° spray–on nozzle can also be used for spray-etching steps. After such a  spray-etching step it is necessary to purge the spray-tubing and the nozzle by DI water. Chemical delivery modules provide process chemicals.
.Any additional chemical delivery module consists the liquid container compound and a set of control valves. Waste containers ,point-of-use-filters and individual metering pumps are available as options.


When the customer wants to extend his system by an additional module he is able to install this module by himself. 


Used chemicals are being disposed off in waste containers, one for acids, and one for caustics.


Some chemicals like KOH can be recircled to extend the time of use.
Process fluids can be heated up to 80°C (optional 120 °C). For both purposes the container must be equipped with an heater. The system is easy to configure for different applications or for combined processes.
This can be realized by selecting the appropriate wafer holder.


The conductivity of the DI water during the rinse is monitored continuously.The setpoint indicating the completion of the rinse is user settable.
·It has a small footprint. Due to its single/dual chamber design it saves precious laboratory space.


Cost effective for small foundries.
The production of porous silicon and electroplating processes require special wafer-holders and power supplies which can be easily installed.
 In cases where a large number of wafers has to be kept immersed in a liquid

(e.g. iso-propylalcohol  or DI water) between production steps a container can be added to the system to serve as temporary wet storage. This container is not strictly recommended and can be ordered as an option.


The system is controlled by a PC system controller so it gives the operator total process
flexibility. Process recipes can be saved on the local hard drive. Remote process monitoring is possible via Ethernet interface.


Multi Channel Fully Automated Wet Etching system McFawes