How Are Isotropic and Anisotropic Processes Used to Improve Silicon Wet Etching?

The microscopic structures produced by silicon wet etching can be created with a high degree of precision using both isotropic and anisotropic processes.

Hydrofluoric acid is one of the etchants used in isotropic etching. It etches at the same speed in all directions, independently of silicon atom density. For etchants used for anisotropic etching, such as potassium hydrochloride (KOH), the etching speed depends on the number of silicon atoms in a crystal lattice plane. It, therefore, depends on the direction of the different planes.

While isotropic etching is faster, it may etch under masks to create rounded shapes and is also harder to control. On the other hand, anisotropic KOH etching can be controlled more precisely and produce straight sides with precise dimensions.

In silicon wet etching, the etch speed also depends on the temperature. For precise control of etching processes Modutek's Teflon tanks provide rapid heating and tight temperature control. The tanks are either static or recirculating, and they can be built into any new wet bench configuration. The tanks have 360-degree overflow filtration and even heating throughout the bath. The heat-up rate is two to three degrees centigrade per minute. The temperature control accuracy is plus/minus 0.5 degrees centigrade, making these tanks ideal for both isotropic and anisotropic etching.

As for controlling etchant concentration, Modutek can provide for the injection of de-ionized water into the tanks. Because the etch speed depends on the etchant concentration, accurate concentration is essential for the final product quality and repeatability.

For more details read the recent article, “How are Isotropic and Anisotropic Processes Used to Improve Silicon Wet Etching?” . If you would like to set up a consultation, or would like to receive a free estimate, contact Modutek at 866-803-1533 or email Modutek@modutek.com.

 

 

 

How Megasonic Cleaning Reduces Cost and Improves Silicon Wafer Yields

Semiconductor manufacturing relies on wafer cleaning to remove material from previous process steps and microscopic contaminating particles. As the size of structures and circuits on wafers decreases, the tiniest particles can interfere with etching and the creation of circuits and micro-structures. Such interference can cause defects in the final semiconductor product, lower product performance, or cause reduced product lifespan.

Therefore, megasonic cleaning is the ideal cleaning process because it removes particles thoroughly but gently, leaving the wafer and its circuits and structure undamaged.

Megasonic cleaning systems generate microscopic cavitation bubbles in the cleaning solution. When the bubble bursts, it produces a tiny but powerful jet that dislodges particles from the parts' surfaces to be cleaned. Lower frequencies generate comparative larger bubbles and more powerful jets, while high frequencies produce smaller bubbles and less powerful jets.

Megasonic cleaning produces a quick and thorough cleaning of silicon wafers and does not require cleaning chemicals. As a result, it reduces the need to purchase, store, handle, and dispose of hazardous chemicals, therefore reducing costs. As megasonic cleaning reduces the need for cleaning chemicals, it results in a safer working environment for the operators who do not need to wear protective clothing when handling chemicals, which can otherwise reduce their productivity.

The effective use of megasonic cleaning that Modutek provides is through the partnership the company has with Kaijo Corporation. Kaijo is world leader in megasonic and ultrasonic cleaning technology, which provides megasonic cleaning to semiconductor manufacturing. Modutek has integrated Megasonic Cleaners into the company's wet bench equipment to produce exceptional low particle counts.

For further details read the blog article titled “How Megasonic Cleaning Reduces Cost and Improves Silicon Wafer Yields”. If you questions, or would like to set up a consultation, please call 866-803-1533 or email Modutek@modutek.com.