Semiconductor manufacturing involves multiple processing steps which includes cleaning silicon wafers using wet bench technology. The SPM (sulfuric peroxide mix) clean process uses a solution of approximately 3 parts sulfuric acid to 1 part of hydrogen peroxide at about 130 degrees centigrade to strip organic material and photoresist from silicon wafers quickly and effectively.
Process engineers and facility managers using the SPM process in semiconductor fabrication have to make sure that the chemical ratio and temperature are maintained within safe limits and that the solution and wafers are contained safely in impervious baths. While the concentration may vary from 3 to 1 to a maximum of 7 to 1 and the temperature used may be as high as 140 degrees centigrade, once the solution operating values are chosen, the baths should be maintained at those concentration and temperature values to keep the strip rate uniform.
Modutek’s wet benches support the SPM process with manual, semi-automatic and fully automatic versions. Wet Bench stations are available in a wide variety of configurations as well as in custom designs. The fully automated stations use Modutek’s in house software for automatic process execution with high accuracy, reliability and repeatability. The semi-automated stations can achieve similar results with robotic controls at a lower cost. The manual stations have the same safety and process features without the cost of automation.
Quartz Recirculating Baths
To work well, the SPM solution has to be heated rapidly in a bath that can withstand high temperatures and that will not react with the aggressive chemicals. Heating has to be even and controlled within a narrow range. At high temperatures, hydrogen peroxide decomposes and the solution has to be spiked with more peroxide to maintain its concentration.
Quartz recirculating baths fulfill these requirements. The quartz can be manufactured in a pure enough form to withstand the temperatures and corrosion while the recirculation allows tight control of concentration with the adding of chemicals as required.
This spiking allows operators to use the solution for a longer period of time rather than discarding the solution when the concentration falls below acceptable levels. Re-using the sulfuric acid for as long as possible reduces costs and is desirable from an environmental point of view as well.
Modutek Series QFa Series Quartz Baths
Modutek’s Quartz Baths support the SPM clean process and satisfy key conditions for high safety and reliability as well as low cost of ownership. The tanks are made of semiconductor grade flame-polished quartz and are insulated with high density alumina silica fiber rated to 1260 degrees centigrade. The four-sided heating element promotes fast, even heating and the seamless sloped flange and the dual safety snap switch help ensure safe and convenient operation.
The quartz baths have an operating temperature range of 30 to 180 degrees centigrade and they feature a standard heat up rate of 2 degrees centigrade per minute. Operating temperature can be controlled to within plus/minus 1 degree centigrade and a liquid level sensor is available as an option.
Standard tanks are available in dimensions ranging from 7.75 to 21.5 inches inner side length and in square and rectangular formats. Depths range from 6.75 to 14.5 inches and available heaters are rated 2 to 6 KW. Modutek can design systems with custom vessel sizes to satisfy particular requirements.
Modutek’s wet bench stations and quartz baths are designed with low cost of ownership in mind while emphasizing features that reduce errors and improve reliability. Semiconductor manufacturers can achieve higher throughput and better output quality using the SPM process on the Modutek units. If you want a free consultation or quote on using quartz baths to support your wafer cleaning processes, call Modutek or email [email protected].