Safely Controlling the Silicon Nitride Etching Process

Silicon nitride etch removes silicon nitride from silicon wafers during the fabrication process of semiconductor components. It consists of a solution of phosphoric acid in water which etches silicon nitride. When the temperature of the solution and the concentration of phosphoric are kept constant, the etching will be carried out rapidly and consistently.

The silicon nitride wet etching process uses silicon nitride as a mask to produce the micro-structures and connections in semiconductor devices. In most etching applications the etch rate can vary by changing the temperature or chemical concentration, but the ideal conditions for a successful etch rate consist of a boiling point and a concentration of 85% phosphoric acid in a de-ionized water solution.

The high temperature will lead to water evaporation and will increase the acid concentration in the solution. Adding water is dangerous because if too much water is added at once, the solution stops boiling, and the added water will create a film above the acid. The temperature will rise again, and the acid starts boiling, the large quantity of the water from the film mixes with the acid and this may cause an explosive reaction.

That is why the accurate monitoring of the solution is extremely important for safe control of the process.

Modutek's Nb Series Wet Etching Baths ensure the safe operation of silicon nitride etching process. Here, the phosphoric acid solution is kept boiling with a heater that's constantly on which maintains the solution at the boiling point.

One of its features is the heater which constantly keeps the phosphoric acid solution at the boiling point.

Other key features are the thermocouples – the first one detects the rise of temperature (as the water evaporates and the acid concentration increases). In this case, a small amount of water is added to the solution to bring the concentration to back its manageable levels. There's also a second thermocouple which detects the presence of steam above the bath liquid and blocks the addition of water when no steam is present. The third thermocouple monitors the bath temperature to switch off the heater if the solution overheats.

The advanced features of the Modutek's Nb Series Wet Etching Baths allow semiconductor manufacturers and research labs to control the silicon nitride wet etching process safely while achieving optimum consistency characteristics.

The complete article, “Safely Controlling the Silicon Nitride Etching Process,” explains in more details. For a free quote or consultation contact Modutek at 866-803-1533 or email Modutek@modutek.com.

How Quick Dump Rinsers Improve Silicon Wet Etching Results

Manufacturing lines in semiconductor fabrication facilities and research labs use corrosive chemicals in cleaning and etching silicon wafers. A silicon wafer will undergo multiple steps in baths that contain such chemicals as hydrochloric acid or hydrogen peroxide.

Once the cleaning and etching are done, using Quick Dump Rinsers the silicon wafer then undergoes rinsing – the rinsing process should remove the contaminants from the corrosive chemicals completely without introducing new contaminants. The chemicals from the silicon wafer must be completely rinsed before the wafer can undergo further process steps.

If traces of chemicals are not completely removed, etching of the wafer may result in defective and low-quality products. That is why in many process steps, rinser performance is critical for product output quality.

When the wafers are placed into the Quick Dump Rinser tank, powerful jets spray de-ionized water over the wafers to remove all traces of chemicals. As the tank fills up, all the chemical residue and particles are flushed out and rise to the surface. A nitrogen gas bubbler system agitates the de-ionized water further, removing additional contaminants from the surface of the wafers. An overflow weir allows the surface to flush the chemical residues and other impurities out of the tank. Once the rinsing process is complete, the quick dump door at the bottom of the tank opens and drains the water in a matter of seconds.

Modutek's Quick Dump Rinsers are designed to meet the needs of advanced semiconductor fabrication. Their features include:

• Contoured vessel design
• Nitrogen bubble on all models
• Natural polypropylene or PVDF (option) tanks, nozzles and fittings
• Large machined dump door without gaskets or seals
• 360-degree overflow weir

The rinsers are available either as standalone units or integrated into a wet bench process manufacturing line.

The rapid operation of Modutek's Quick Dump Rinsers help reduce the use of de-ionized water as well as save process time. It removes contaminants completely without introducing new chemicals. Modutek has an extensive line of silicon wet etching equipment from which to choose.

For more information read the blog article titled “How Quick Dump Rinsers Improve Silicon Wet Etching Results” . For a free consultation or quote contact Modutek at Modutek@modutek.com or call 866-803-1533 to discuss your specific requirements.