Semiconductor manufacturing requires many process steps that must be followed and controlled in a very precise manner. Process requirements can include cleaning, etching, developing and stripping. Handling the aggressive chemicals means special attention has to be given to safety and disposal. The physical characteristics required in the production line have to be considered as well. Special features such as recirculation, heating, additional process control and degree of automation can be ordered.
Not all semiconductor equipment manufacturers can offer a complete line of wet bench stations incorporating the latest technology and using their own software. The many options and differing process requirements mean that almost every installation is customized to some extent. An experienced supplier who can provide advice and deliver the best systems is needed for achieving optimal results.
Physical Requirements Affect the Ordering Process
The three types of physical factors influencing the wet bench equipment specifications are the available space, wafer size and wafer throughput. Limited space for new installations or a requirement to integrate with an existing system may mean that compact stations are required. The baths must be able to accommodate the wafer size proposed for the application. Throughput is governed by the number of cassettes that can be processed per bath, the number of stations, the estimated process duration and the estimated downtime for replacing chemicals, maintenance and other process-related factors.
Space limitations are often critical. Factors that can reduce space requirements are what functions a station can execute and whether some functions, such as rinsing and drying, can be combined or need separate spaces. Chemical delivery systems can take space or might be placed remotely or behind the productions line. Such questions can be explored with a qualified supplier.
Throughput is often a critical variable affecting profitability. Automatic transfer of wafers between stations and automatic process control may save time. How the process is controlled, for example in a piranha “feed and bleed” type of operation, may affect how long a chemical bath can be used without changing the chemicals and may also affect downtime for maintenance. Often advanced technology from a leading supplier can increase throughput.
Wet Bench Equipment, Controls and Accessories Have to Support the Process Chemistry
Wet bench equipment that supports processes such as RCA clean, KOH and Piranha use highly aggressive chemicals. The equipment has to resist the corrosive substances and feature safeguards to keep operators secure. Some processes, such as silicon nitride etching, have to have special controls. Processes using especially dangerous chemicals such as hydrofluoric acid require additional safety measures.
Equipment for specific wet bench processes can include the following:
- Quartz baths for cleaning etching and stripping applications. High temperature recirculating or constant temperature baths.
- Teflon tanks for etching applications. Heated, recirculating and ambient temperature.
- Silicon nitride wet etching bath. Special control features for silicon nitride removal with phosphoric acid.
Semiconductor fabrication facilities, research labs and universities that require wet process equipment first have to make sure that prospective suppliers can provide equipment with the special features needed. Heating control accuracy and precise calculation of dosages is essential for high quality output and a low product failure rate. Suppliers who manufacture, assemble and program their own equipment can be relied upon for complete after sales support and service.
Modutek Can Help
Modutek has worked closely with semiconductor fabricators and has extensive experience in providing semiconductor manufacturing equipment. The company assembles its own systems in their San Jose California facility and company specialists program their own software and controls. Modutek has state of the art wet bench stations and has pioneered improvements for processes such as silicon nitride removal and Piranha etching. With its in house expertise, the company can analyze customer requirements and propose the best solutions.
Reviewed and Approved by Douglas Wagner
President & CEO, Modutek Corporation