How New Equipment Has Improved the Silicon Nitride Wet Etching Process

The silicon nitride wet etching process uses phosphoric acid to remove silicon nitride masks from silicon wafers to allow clean wafers to undergo the next fabrication steps. This process is difficult to control because the hot phosphoric acid and water mixture is unstable and that requires the periodic addition of small quantities of water in order to achieve optimum etching performance. However, adding water to phosphoric acid may result in a reactive bump. Modutek has developed a new approach that controls the nitride etching process more accurately and safely while at the same time achieving high etching rates.

Since Silicon nitride is a key component to semiconductor wafer manufacturing, Modutek has developed the new Nb series Silicon Nitride Wet Etching Bath. It provides a tighter control of the bath temperature while guaranteeing safe operations and superior etching of the silicon nitride masks.

Modutek’s silicon nitride wet etching process uses the acid mixture concentration as a reference value for adding small amounts of DI water. The boiling point of the mixture depends on the concentration, but in a normal operation, the typical mixture point is 160 degrees centigrade. When water is lost, the mixture concentration starts to rise above 160 degrees centigrade. DI water is added into the boiling acid, and the concentration of the acid is reduced bringing the temperature back to 160 degrees centigrade.

Modutek's Silicon Nitride Wet Etching Bath has the thermocouple sensor which detects the presence of steam. It closes the water valve when there's no longer steam to prevent the further addition of water to the boiling acid. This additional safety feature is designed to prevent dangerous situations as a result of mixing large amounts of water and the hot phosphoric acid.

For more details about Modutek’s silicon nitride wet etching baths and the results customers have achieved in using them read the complete article “How New Equipment Has Improved the Silicon Nitride Wet Etching Process”. If you would like to learn how Modutek’s silicon nitride wet etching bath can be used for your application, call Modutek at 866-803-1533 or email Modutek@Modutek.com.

How to Safely Use Solvents for Wafer Processing

Solvent wet bench equipment is designed for operations which include substrate cleaning, photoresist stripping, and liftoff pattern transfers. The wet bench stations provide a critical role in the semiconductor fabrication process. Since solvents are often highly inflammable, wet bench equipment needs to be designed to follow stringent safety codes.

Precautions related to fire and electrical safety is some of the most basic requirements in the design of wet bench stations. There are also requirements for safety alarms, carboy collections, heated solvent baths and process timers. Only well trained and authorized individuals should access the wet bench equipment. In many cases, added safety measures from simple approaches, such as using auto-lids made of Teflon or stainless steel used for sealing off chemical containers.

Solvent applications require the use of stainless steel. Modutek's solvent stations are constructed of 304 stainless steel, which makes them suitable for photoresist, IPA and acetone which are critical operations in the wafer processing. Plus, Modutek's solid works and professional flow simulation software provide improvements in productivity.

Modutek's safety design for solvent processing involves every required feature:

• Wiring specified to meet NFPA 70 & 70 codes;
• Emergency power off design for every safety interlock;
• Lip exhausts on all solvent tanks;
• N2 head case purge design;
• Photohelic EPO interlocks;
• Safety shields;
• Teflon N2 guns;
• Continuous flow of the water manifolds;

Modutek's stainless steel solvent stations are available in manual, dry-to-dry, semi-and-fully automated designs. Wet bench design and construction is a complicated process, but Modutek ensures their systems that are designed to meet all industry safety requirements as well as the specific requirements of individual customers.  

Our full article “How to Safely Use Solvents for Wafer Processing” explains more about this topic. Call Modutek at 866-803-1533 if you have questions or would like to get a free consultation or quote.

Improving Wafer Processing with Automated Equipment

Fully and semi-automated wafer processing equipment can help improve wafer output quality by providing consistent chemical processing dosages and timing. However process settings must first be determined manually, then in semi-automated mode where the settings can easily be adjusted or fine tuned.

This especially applies to new process development where the exact parameters are yet to be determined. Wafer fabrication facilities may try out the initial settings first in manual mode and make some appropriate adjustments. Then they may automate some of the processes using semi-automated stations for parts of the process that are finalized while making additional manual adjustments for optimize results. The final processing parameters can then be implemented in a fully automated station.

After the initial run, the problem areas can be identified, and variables such as chemical dosages and timing can be revised and adjusted. Skilled and experienced operators can do the fabrication steps and make changes easily on the manual station. In manual mode operators has complete control of the process. This control is important for determining the initial settings of a new process.

When the changes have been finally made on the major parts of the new process, there may still have some necessary minor adjustments necessary to achieve targets such as faster processing, better quality output or reduced usage of chemicals. For this reason, the semi-automated stations can be used to save time.

Once the parameters and variables for the desired yield and performance have been determined, a tailor-made software and automation package can be assembled. These packages are implemented in fully automated wafer processing equipment which can reproduce the custom settings of the manual and semi-automated process steps and use them to produce the desired results consistently.

Modutek can work closely with a customer to determine the best way to optimize a new process. For more details read the complete article, “Improving Wafer Processing with Automated Equipment.”If you have questions or would like a free consultation to discuss your specific needs call 866-803-1533 or email Modutek@modutek.com.