Wet etching is a material removal process that uses liquid chemicals or etchants to remove materials from a various substrates.  Active etching species interact with the structure of etching material and dissolution of material takes places. Wet etching can be applied to metals, glass, silicon, compound semiconductor materials and others. RENA provides wide range of acid and alkaline etching tools for various substrates and industries.

Etching for solar cell production

There are several steps in the production of solar cells requiring one side high-performance wet etching processes in combination with additional tasks like high throughput demands or low chemical consumption.


The diffusion process in PERC cell manufacturing should build the “emitter” (positive pole) on the front side of the solar cell. On the back side, there should be no emitter layer  building a negative pole in the cell. Nevertheless, the high-temperature diffusion process will affect both sides, which would cause a short circuit in the final solar cell. A single sided etching process is implemented in order to remove the diffused back side area of the solar cell– the so-called “edge isolation”.

RENA’s patented single side etching process and a lot of advancements achieve high selectivities between etched and non-etched side in combination with a wide range of etching processes. RENA NIAK platform performs processes for “classic” acidic edge isolation and polishing with a mixture of HF/HNO3 With attention to increasing and highly variable demands of new cell concepts, RENA provides high-performance-polishing processes with hot KOH for PERC cell concept and specific high-precision processes like hot alkaline single side etching of Poly-Si deposited and diffused areas in advanced cell concepts (e.g. Topcon).

Glass etching

Glass has many useful properties such as high chemical and heat resistance, biocompatibility, large optical transition range as well as low optical absorption making it an important material for many applications. Correspondingly, there is also a large variety of glass types and compositions adapted for specific application such as life science, optics, semiconductors and displays.

Wet etching processes is commonly used for glass to create defined structures, thinning, polishing or texturing. Many applications in optics, microfluidics and semiconductor industries applications require defined structures, which can be created in a microfabrication process adapted from silicon processing.

Glass surfaces are normally protected by masking layers and etched in the exposed areas. For that purpose HF or combination of acids are commonly used. Fluoric acid is very efficient in the dissolution of oxide network structure of glass. RENA has in its portfolio of tools for glass structuring ranging from small lab scale tool to large scale manufacturing.

Some types of glasses due to special composition require other type of etching  chemicals. One of such examples alkaline etching  for display glass types. This process delivers good etching of glass, but in many cases reactions are very slow and therefore economically less attractive. Hot etching is a solution for such type of processes and allows to increase speed of etching process significantly. RENA provide tools for realization of  hot alkaline etching processes up to 170 °C.

Etching of dental implants

Today, dentals implants considered as standard procedure for replacement of missing teeth in dentistry. A dental implant is a surgical fixture that is placed into the bone and allowed to fuse with the bone within few months. It has been shown that the surface roughness of dental implants affects the osseointegration, and integration of the implant to the bone, therefore, many implant manufacturers use special treatments

designed to increase the roughness of the implant surface. One of the most common roughening methods is acid etching.

RENA offers production machines designed for wet chemical processes, such as etching, conditioning, passivating, cleaning, and anodizing of dental implants, combining the various surface finishing steps in a modular tool with minimum footprint.

SVP Technology & Innovation
Dr. Holger Kühnlein
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