Monthly Archives: June 2017

Tips on Improving Your Silicon Wafer Etching Process

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Tips on Improving Your Silicon Wafer Etching ProcessSemiconductor manufacturing facilities and research labs need silicon wafer etching equipment that delivers accurate and repeatable results in a safe and reliable environment. The structures on semiconductor wafers and for micro-electromechanical systems (MEMS) have to be produced to meet tight tolerances and with no contamination by impurities or stray particles. An improved silicon wafer etching process depends on selecting the right etching process and using high-quality equipment, which are key factors for consistent output with a low rate of defects.

Silicon Wafer Etching Processes

Wafer etching is a multi-stage fabrication process and different chemical baths are used to achieve specific purposes. Process steps include cleaning, masking and etching of the wafers themselves or deposited metal. These steps result in the production of microscopic structures in the silicon wafer and in electrical connections where required. Key factors for improved etching performance are control of etching speed and the cleanliness of the fabrication environment.

Silicon nitride is used as a masking material and is etched with hot phosphoric acid. Key factors for improved results are the accurate control of the acid concentration and temperature through the addition of de-ionized water.

Piranha etching is carried out with a mixture of sulfuric acid and hydrogen peroxide. The etching solution cleans organic residue from silicon wafers and is often used to remove photoresist. Cleaning with piranha etching can be appropriate at various stages of the semiconductor fabrication process, and its effective application depends on the correct mixture and accurate control of the process.

The KOH etching process creates microscopic structures in the silicon using a solution of potassium hydroxide. Variables controlling the etch rate include bath temperature, KOH concentration, silicon crystal orientation and impurities in the silicon. Improved etching performance means tightly controlling the etch rate to get the precise structures needed.

Buffered oxide etch (BOE) uses hydrofluoric acid and a buffering agent to etch thin masking films of silicon nitride or silicon dioxide. If properly controlled, it results in a highly consistent and repeatable process that is compatible with photoresist.

The key to improving silicon etch performance is to use wet process equipment from a supplier that has the required experience and who can deliver high-quality equipment designed for excellent etching performance. Modutek has over 35 years experience in the field, and can advise customers on which equipment best supports their particular wet processing requirements and can offer standard or customized equipment as needed.

Etching Equipment Design Features

Choosing the right wafer etching process for each stage of semiconductor fabrication is important, but it is the design characteristics of the equipment that ensure improve etching results. Critical design features of Modutek’s etching equipment include the following:

  • Filtration and flow control. Filtered etch baths feature continuous filtration in the 10- to 0.2-micron range and reduced acid consumption.
  • Temperature control. Temperature controlled circulators can heat or cool an etching bath and keep the temperature at the required levels. Operating range is 10 to 60 degrees centigrade with an accuracy of plus/minus 1 degree.
  • Tank design. Teflon tanks for KOH etching are available in many configurations and in standard carrier sizes for single or double capacity. Quartz baths for a variety of etching applications including piranha clean are available in a range of sizes.

Modutek helps customers improve their silicon etching performance by advising them on the right equipment for their specific etching applications and by ensuring the equipment delivers accurate performance in a consistent way. When silicon etching processes are carried out reliably with repeatable results, facility productivity increases and output quality improves.

Designing Semiconductor Manufacturing Equipment for Ergonomics and Safety

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Designing Semiconductor Manufacturing Equipment for Ergonomics and SafetySemiconductor manufacturing processes routinely use chemicals and procedures that could result in accidents if the manufacturer did not have a serious commitment to safety. Safety guidelines such as SEMI S2, published by the global industry association for microelectronics manufacturers, help manufacturers implement safe operating protocols. Ergonomic designs for semiconductor manufacturing equipment as described in SEMI S8 help ensure a safe operating environment by reducing operator strain and fatigue.

In semiconductor facilities, fire is one of the most damaging threats and burning plastic releases toxic fumes while contaminating clean areas. The Cleanroom Materials Flammability Test Protocol (Class 4910) or the FM 4910 specification allows manufacturers to specify the use of non-flammable materials for their equipment. A comprehensive approach to safety, including ergonomic design and the reduction of fire hazards is the most effective strategy for reducing accidents in a semiconductor manufacturing environment.

Prioritizing Safety When Purchasing Semiconductor Manufacturing Equipment

Installations that have been in operation for a number of years may no longer satisfy current safety standards or may not meet the safety goals of the owner. The purchase of new equipment is an ideal opportunity to upgrade existing safety features and to ensure that the new equipment is as safe as possible.

Modutek follows the SEMI safety and ergonomics guidelines to design equipment that is easy to use and doesn’t require excessive reach or strength to operate. Typical examples include the Modutek wafer holding tray and a swing-arm operator interface mount. The wafer holding tray on the Modutek wet benches includes a robot arm that moves the tray to the front of the station for optimal loading with a minimum of effort.

The Modutek operator interface is normally out of the way along the side of the station, but that position is hard to see when an operator is monitoring the process. The ergonomic design allows the operator to swing the interface out and angle it for optimal viewing. The swing arm can rotate along three axes so the operator can place it in whatever position is the most convenient. Once in position, the operator can lock it into place securely, so it doesn’t move inadvertently.

Both of these examples demonstrate how Modutek implements ergonomic designs to help operators and technicians carry out their work safely and with a minimum of effort. The result is often higher productivity, more satisfied employees and fewer accidents.

Reducing Fire Hazards on New Equipment

Traditionally clean rooms are fitted with sprinkler systems or other specialized fire protection. An array of sensors detects flames, smoke, chemical vapors or heat and triggers the fire extinguishing system. By this time contamination of the facility is severe and re-establishing clean room manufacturing capability is time-consuming and expensive.

Semiconductor manufacturers and research centers with clean room facilities can reduce the threat of a fire that could disable their production by minimizing the use of flammable materials. Many wet bench processes use corrosive chemicals in tanks and piping made of plastic or other normally flammable synthetic material. Modutek can support efforts to minimize the use of flammable materials by supplying equipment that meets the FM 4910 flammability specifications and reduces the threat of fire.

Increased Safety with New Equipment from Modutek

Modutek has over 35 years experience in designing and manufacturing wet bench stations. The company has a broad range of standard equipment and can customize all aspects of semiconductor manufacturing to meet specific specialized needs.

While Modutek wet benches have a high degree of safety and ergonomic design built in, special customer requests can always be accommodated. Specific safety features or special ergonomic requirements can be added if not already present, and additional precautions against fire and other hazards can be incorporated as needed. Modutek equipment already includes many safety features, but the company has the experience and expertise to meet any additional customer requirements.