How Stainless-Steel Wet Benches Ensure Safety When Using Solvents

How Stainless Steel Wet Benches Ensure Safety When Using SolventsWhen solvents are used in stainless steel wet benches during semiconductor manufacturing, special measures are required to reduce the risk of fire or explosions. Solvents such as acetone are highly flammable. They are used for silicon wafer cleaning and stripping to remove contaminants from the silicon wafer and to remove photoresist. Essential safety measures include reducing the risk of igniting solvent vapors, eliminating containers and piping that might burn, and installing fire extinguishing equipment. Safety regulations govern the use of solvents in industrial operations, and equipment manufacturers can exceed basic requirements to ensure operator safety. When adequate safety measures are designed for the wet bench equipment and employees are properly trained, solvent-based stainless steel wet benches can be operated safely.

Applicable Safety Regulations Need to Be Followed

The following organizations or agencies have regulations that apply to the use of flammable solvents in industrial facilities. These are:

  • The National Fire Protection Association Regulations (NFPA)
  • The Occupational Safety and Health Administration Standards (OSHA)
  • The National Electrical Code (NEC)

In addition, a manufacturer may have internal safety guidelines and policies that apply.

NFPA is concerned with preventing fires, and the organization develops codes and standards for materials and equipment used in industrial processes. For using solvents in semiconductor manufacturing, NFPA 30, the Flammable and Combustible Liquids Code, applies. It governs the storage, handling, and use of combustible and flammable liquids. In addition, NFPA 70 and 79 deal with the safety of electrical equipment.

OSHA makes sure employees have safe working conditions. It publishes standards for worker safety, and the 1910.106 standard applies to operations that use flammable liquids. This standard deals with workplace-related issues such as ventilation, fire resistance, and fire extinguishing.

The NEC governs the safe installation of electrical equipment. It includes classifying flammable liquids and resulting measures required for safe operation. Class I, Division 1 areas are locations where a flammable liquid vapor is usually present. Class I, Division 2 refers to locations where the vapor of flammable liquids may be present under unusual conditions, such as equipment failure. The NEC measures include limiting the energy of electrical signals and avoiding high temperatures for components.

Internal manufacturer safety guidelines can include other safety measures such as using interlocks, safe disposal of waste, and lids that close automatically. An experienced wet bench manufacturer will develop an integrated safety concept that ensures the safe operation of equipment.

Modutek Designs and Builds Safe Stainless Steel Wet Bench Systems

Modutek’s stainless steel wet bench systems are designed to be used with solvents and incorporate various safety features to ensure safe operation. In addition to meeting all compliance and relevant safety regulations, Modutek’s systems include additional safety measures based on the company’s experience. Safety features include the following:

  • Electrical equipment controls are intrinsically safe, i.e., the electrical signals are too weak to cause sparks or heat wires.
  • Equipment is designed to and certified for NEC Class I, Division 1 or 2
  • Wiring complies with NFPA 70 and 79
  • Safety interlocks to avoid unsafe operation.
  • Monitors with alarms for dangerous conditions
  • Liquid spills are detected
  • Operators have a mushroom button for emergency off
  • Auto lids seal chemical containers
  • Carboys collect solvent waste for disposal
  • Only qualified persons can access the controls to operate the equipment
  • A gaseous automatic fire suppression system extinguishes fires

The Fire Suppression System Is a Key Safety Component

The Modutek fire suppression system removes oxygen from a solvent fire, extinguishing the flames. When a fire is detected via an IR Flame Detection Nozzle, the fire suppression system floods the area with carbon dioxide. The system comes with an Engineered Carbon Dioxide Fire System Package of documents. These include the following:

  • Hazard Report
  • Agent source report
  • Battery backup calculation report
  • System acceptance report
  • Suppression summary
  • Local application nozzle summary
  • Pipe network report

Drawings that come with the system include a bill of materials, electrical schematics, and plumbing and instrumentation diagrams.

Modutek’s Expertise and Experience

Modutek works closely with customers to design and build safe wet bench equipment that meets their specific requirements. In addition, Modutek’s uses its in-house expertise from over 40 years of industry experience to provide innovative solutions to meet customer needs. Modutek’s wet bench systems and equipment are reliable and efficient in delivering excellent semiconductor manufacturing performance.

Silicon Wafer Etching Processes for Wet Processing Applications

Silicon Wafer Etching Processes for Wet Processing ApplicationsEditor’s Note: This article was originally published in September 2016 and has been updated with additional information and reposted in June 2023.

The production of semiconductor components relies on the etching of silicon wafers using various processes like KOH etching to create the necessary structures and connections. To meet etching requirements, Modutek offers cutting-edge wet bench technology and equipment suitable for many applications. Whether you are a manager overseeing semiconductor manufacturing facilities, a university researcher, or a process engineer within these organizations, Modutek’s equipment will fulfill your silicon wafer etching requirements.

KOH Etching:

KOH etching utilizes potassium hydroxide (KOH) to etch microscopic structures on silicon wafers. This process is highly dependent upon factors that include temperature of the etching bath, the concentration of KOH, and the crystalline structure and impurities within the silicon. KOH etching is known for being a cost-effective and repeatable technique and is well-known in the industry for its rapid etching capabilities.

Modutek provides PFA Teflon tanks from the TFa or TT series specifically tailored for KOH etching applications. These tanks offer excellent chemical resistance and ensure the safe and efficient implementation of this process. By using Modutek’s state-of-the-art wet bench technology and process components, semiconductor manufacturing facilities, research centers, and universities can rely on Modutek to meet their silicon wafer etching requirements.

Silicon Nitride Etch:

Silicon nitride is a commonly used masking material during the fabrication of integrated circuits. A thin silicon nitride film is applied on silicon wafers before being selectively etched away using hot phosphoric acid. The temperature bath is about 180 degrees Celsius, which is the boiling point of phosphoric acid.

Modutek provides Nb series silicon nitride etch baths that are part of a comprehensive suite of wet bench process components to achieve precise temperature control during silicon nitride etching processes. The silicon nitride etch bath achieves accurate process control and excellent repeatability by carefully controlling the ratio of deionized water to phosphoric acid. In addition, the high level of safety provided by Modutek’s equipment ensures a secure working environment.

Piranha Etch:

In semiconductor manufacturing, the Piranha Etch process is used for cleaning silicon wafers. The process consists of a mixture of sulfuric acid and hydrogen peroxide – typically in proportions of 3:1 for concentrated sulfuric acid to one part 30% hydrogen peroxide. This solution effectively removes organic compounds from wafer surfaces and oxidizes most metals.

Modutek focuses on understanding each customer’s specific silicon wafer cleaning requirements and offers tailored solutions from their extensive wet processing equipment selection. The in-house expertise Modutek provides heated quartz tanks to ensure that the Piranha etch process is carried out with precision and efficiency to ensure silicon wafers are clean and ready for additional processing.

Hydrofluoric Acid (HF) Clean:

Hydrofluoric Acid (HF) is used to specifically remove silicon dioxide (SiO2) layers from wafer surfaces. This is an essential process in semiconductor manufacturing applications, such as creating thin films and depositing new materials. Hydrofluoric Acid has high selectivity for SiO2, which makes it an effective choice for etching oxide layers.

Modutek provides specialized equipment to support the HF clean process. This includes wet benches and chemical delivery systems that offer precise control over HF solution, optimizing the etching process while maintaining a safe and controlled environment. By employing Modutek’s expertise and state-of-the-art equipment, semiconductor manufacturers can efficiently remove SiO2 layers to produce superior silicon wafers.

RCA (SC1&2) Clean:

The RCA Clean process consists of two sequential steps known as SC1 and SC2, and is an established method for eliminating organic and inorganic contaminants from silicon wafers. In the SC1 step, wafers are submerged in a solution consisting of deionized water, hydrogen peroxide (H2O2), and ammonium hydroxide (NH4OH). This solution effectively eliminates organic residues, particles, and metal ions from silicon wafers.

After the SC1 step, wafers undergo the SC2 step, which uses a solution of deionized water, hydrogen peroxide, and hydrochloric acid (HCl). SC2 removes metallic contaminants, native oxides, and any remaining impurities to achieve an ultra-clean surface.

Modutek offers advanced wet bench systems with precise chemical delivery and control systems to support the RCA (SC1&2) clean process. These systems ensure accurate mixing and consistent delivery of chemicals for reliable and consistent cleaning results.

In addition, Modutek’s wet bench technology also provides comprehensive rinsing capabilities for efficient removal of cleaning solutions that reduce contamination risks. Rinsing plays an integral part in eliminating residual cleaning solutions while mitigating the risk of contamination. By including advanced rinsing mechanisms, Modutek’s equipment ensures that wafers are thoroughly cleansed before moving on to further manufacturing steps.

Modutek’s Wet Bench and Process Component Solutions

As a premier provider of semiconductor manufacturing equipment for over 40 years, Modutek provides wet process equipment for a wide variety of semiconductor etching and cleaning applications. Modutek’s wet bench technology delivers reliable, repeatable results safely and accurately. In addition, Modutek helps customers find solutions that meet their semiconductor manufacturing requirements. Contact Modutek for a free consultation on selecting the right equipment to support your specific processing needs.