Modutek’s Nitrite Etch Bath's Use in Silicon Wet Etching

Modutek Corporation has been providing semiconductor manufacturing equipment solutions for more than 30 years, creating and designing Silicon Wet Etching components and similar wet processing equipment and services. Modutek presents the "Nb" series which is part of their Silicon Nitrite Etch Bath products, a remarkable improvement to the previous "Na" series.

So what does Modutek's Silicon Nitride Etch Bath line of products do and what advantage does it give? They have been created, designed and engineered to give superlative process control.

The "Nb" series of Modutek's Silicon Nitride Etch Bath's distinct feature is its two-tiered diagnostic system. The advantages of the Nb series Silicon Nitride Etch Bath system are as follows:

• Its two-tiered diagnostic system, it lets the user control the temperature
• It controls the acid-to-water ratio through supplemented D.I. (de-ionized) water through its remote DI water metering system
• It retains consistency and uniformity in Silicon Nitride Wet Etching
• It allows control in boiling chemicals to avoid what is called "bumping"

Wet etching is a technique that removes certain materials through soaking the sample into an etch bath which has the liquid solution. The etchant is a kind of acid or corrosive chemical solution used for this purpose.

In this case, etches for silicon nitrides are a combination of 85% phosphoric acid, (H3PO4) and 15% D.I. water. The water boils typically at 160°C. Since the water boils, it will evaporate and carry the solution away as steam. To abate the steaming, the Nb series silicon nitride etch bath contains a refluxor will help carry the steam back into the water, thus condensing and maintaining its composition. Be aware, though, that these refluxors aren't 100% guaranteed to be effective, so it's still advisable to add the D.I. water to the solution from time to time.

Adding water to acid isn't usually advisable, except in this case. If the acid solution rapidly boils, it is required to add a small amount of water (a safe procedure). Otherwise, when you add water to the acid solution which doesn't boil, the resulting outcome is that the water will merely float on top of the acid. The top layer of the acid will be added with more water. As the water gradually takes in the heat, this is where it starts to boil. As long as the correct reaction takes place, the water will thoroughly blend with the acid solution.

The heater in the Silicon Etching System does not have to be controlled like other systems require. You have the option to regulate it though. If you leave the heater switch on, the heater will be on. By choosing not to regulate the heater, it will leave the solution still boiling no matter what the concentration is. While the solution is boiling, the water is added to the concentration. The water will remain sitting on top of the solution.

Some features of the Silicon Wet Etching and Nitrite Etch Bath systems include an etched-foil resistance heater, Teflon-fortified refluxor with safety cover, vapor thermocouple and uniformity heat transfer. These systems are also easy to install, as well as repair, in existing process stations or in new ones.

System specifications include the ideal operating temperature range (30-180ºC), required liquid solutions (water and phosphoric acid), a vapor thermocouple (a temperature-measuring device), PVDF refluxor with Teflon© cooling coils, process temperature control: ± 0.5° C, and chemical usage: H20, H3PO4. It also comes with a one-year warranty.

The Silicon Wet Etching system can be customized depending on the clients' needs. Companies may choose additional features for their system will be able to work with Modutek to ensure that it will meet the company’s needs and specifications. These options include gravity drain system reinforced with Teflon©, process controller and timer, and remote operator timer switches, pneumatically actuated auto cover, and RS232 interface.

Modutek Corporation can provide the system you need for Silicon Wet Etching. Our products can be redesigned for your current Nitride Etch Baths or other equipment you may have. Call us at 866-803-1533 to learn more.