Etching baths with varying concentrations of potassium hydroxide (KOH) and controlled temperatures are used in creating microscopic structures on silicon wafers. Modutek can supply equipment such as PFA Teflon tanks, circulation and filtering systems and cassette handling equipment that supports KOH etching. The company designs and builds individualized systems for customers who want to use KOH etching and the resulting systems deliver accurate control, high repeatability, consistent performance and superior output quality.
The KOH Etching Process
The KOH etching process is well understood and is a preferred method for creating silicon wafer nano structures for semiconductor manufacturing and in research facilities. The process delivers controlled and uniform results with high precision and it is relatively safe.
The silicon surface is masked to allow etching and cavity creation in specific areas according to the layout of the final semiconductor product. The etch rate can be controlled by varying the concentration of KOH and the bath temperature. KOH etching is also impacted by the following:
- The lattice planes of the crystalline silicon
- Boron doping of the silicon
- The presence of atomic defects in the silicon crystal
- Natural impurities
Orienting the lattice planes in a particular direction can influence and control the direction of the etching and the shape of the cavities created in the silicon. Similarly, boron doping can be used to stop etching in a particular direction. Together with the mask, these factors permit the creation of cavities of the required shapes and orientations. Defects in the silicon crystal or natural impurities may reduce the quality of the final product and can result in defective items.
Advantages of KOH Etching
KOH etching provides excellent results and is used extensively because of the following advantages:
- Safe and easy to handle
- Rapid etching
- Excellent reproducibility
- Low cost
- High precision when process variables are tightly controlled
Modutek can supply equipment that builds on the listed advantages to deliver corresponding benefits to the customer.
Modutek’s KOH Etching Process Equipment
Modutek’s wet bench technology supports KOH processing, and Modutek examines each request in detail before building the equipment for a particular application. This includes the KOH processing tank, the recirculating system and the silicon wafer handling. Sizes, capacities and control characteristics are adjusted for the customer’s requirements.
The systems supplied by Modutek use the latest technology to provide high accuracy and excellent output quality. Etch rates can be controlled precisely and etch uniformity is guaranteed. Even long etch times, such as up to 3 days, can be handled reliably and safely.
Modutek’s KOH processing tanks are PFA Teflon with all-Teflon fluid paths. The tanks are manufactured onsite using advanced PFA sheet welding techniques designed to minimize impurities and unwanted by-products. The tanks are available as static or as recirculating baths.
The static baths can be ambient temperature baths or temperature controlled from 30 to 100 degrees centigrade. The recirculating temperature controlled baths feature heat-up rates of 2 to 3 degrees centigrade per minute and a temperature control accuracy of plus/minus 0.5 degrees centigrade. The available semi automatic cassette handling reduces costs and increases reliability.
In each case Modutek makes sure that the equipment supplied fits into the existing or a new installation and is compatible with any other wet processing systems. Modutek’s specialists work to ensure the supplied equipment satisfies the customer’s requirements and meets or exceeds performance expectations.