Wafer Etching Process

Manufacturing integrated circuits and MEMs relies on the use of various wafer etching process methods to produce the required structures and connections. The most commonly used wet etching processes used in industry include KOH, BOE, Silicon Nitride, and Piranha etch. Etching processes can be done on silicon and gallium arsenide (GaAs) as well as with metals that include aluminum, copper, and gold. Modutek provides wet bench technology and equipment to support a wide variety of wet etching applications. Process engineers working at semiconductor manufacturing facilities and research centers use wet bench stations and other equipment from Modutek to meet the requirements of their wafer processing applications.

KOH Etching

The etching silicon wafers with potassium hydroxide (KOH) creates microscopic structures in the silicon. The etching rate is controlled by the temperature of the etching bath, the concentration of KOH and the crystalline structure along with any impurities in the silicon wafer. KOH etching provides a low cost and repeatable etching process that etches quickly. Modutek improves KOH etching applications using either the TFa or TT series of PFA Teflon tanks. For more details refer to the article “Improving the KOH Etching Process Using Teflon Tanks“.

 

Buffered Oxide Etch (BOE)

BOE is also known as buffered HF or BHF and is primarily used in etching thin films of silicon nitride or silicon dioxide. It consists of hydrofluoric acid and a buffering agent such as ammonium fluoride.  BOE provides a consistent repeatable process, does not undercut masked oxide, does not contaminate or stain diffused silicon surfaces, and is compatible with photoresist. Modutek supports the BOE process specifically with the F SERIES sub-ambient filtered etch bath.

 

Silicon Nitride Etching

Silicon nitride is used as a masking material in semiconductor manufacturing. It is deposited on the silicon wafer as a thin film and is etched with hot phosphoric acid. Hot phosphoric acid strip is performed at 180 degrees C in a nitride etch bath. Nitride etch baths provide precise temperature control by regulating the de-ionized water to phosphoric acid ratio. Modutek’s silicon nitride etch baths provide accurate process control with consistent repeatability and a high level of safety. For more details on process control and safety refer to the article “Safely Controlling the Silicon Nitride Etching Process“.

 

Copper, Gold and Aluminum Etching

Microelectronic devices developed on silicon wafers must use metallic connections to conduct electric signals. Metals that are used for this purpose include aluminum, copper or gold which are deposited on the silicon wafer. During the silicon wafer fabrication process some of the metals will need to be etched. Etching metals can be challenging and effective etching relies on selecting the appropriate chemicals and process. In these cases the use of Modutek’s Vacuum Metal Etcher provides a precise process for etching metal layers. Wafers are etched within a vacuum so that hydrogen bubbles, an etching reaction which causes “snow” and “bridging”, are immediately removed from the surface of the wafer. The hydrogen bubbles are then immediately exhausted by an evacuating pump in the Vacuum Metal Etcher. Modutek’s equipment can be use a variety of etchant solutions to etch different metals.

 

Modutek Support for Wafer Etching Process Applications

Modutek has been a premier supplier of semiconductor manufacturing equipment for over 35 years, and has a full line of wet processing equipment to support a wide variety of wafer etching process applications. Modutek’s equipment delivers reliable and repeatable results safely and accurately. For a free quote or consultation on selecting the right equipment for your wafer etching process, contact Modutek today.