How Stainless-Steel Stations Provide Safe Solvent Processing

Solvents used in semiconductor manufacturing can remove and organic contaminants from silicon wafers in preparation for further processing steps.

Acetone, isopropyl alcohol (IPA) and ethylene diproxitol (EDP) are solvents commonly used to clean wafers, remove photoresist and in pattern transfers for the creation of microscopic structures on the wafer.

But since these solvents are also inflammable, they require special safety measures to reduce the risk of fire and explosion, and they have to be disposed of safely. Stainless steel wet benches incorporating stainless steel processing tanks are designed with features that provide safe processing of solvents.

Safe operation of stainless-steel solvent stations has to include the following safety measures:

  • Fire suppression – Measures can include electrical design limiting the potential energy of sparks so they can’t ignite solvents and designing equipment to Class 1, Division 2 specifications
  • Fire fighting – It has to be able to extinguish fires. For inflammable liquids such as solvents, gas-type fire systems such as those using carbon dioxide are needed.
  • Protection against exposure – Many solvents are harmful when workers are exposed to them over extended periods, either through direct contact or through breathing the fumes. A complete enclosure of the solvent processing tanks along with effective exhausts limits the amount of solvent to which workers can be exposed.
  • Protection against leaks – A complete enclosure of the solvent processing tanks should also have a leak detection feature.
  • Safe disposal – Disposal of used solvents has to be carried out safely and according to environmental regulations. Disposal can be on site, if the facility has the corresponding capability, or the waste can be stored in a carboy for pick-up by a specialized disposal company.

Modutek’s stainless steel stations are made of 304 stainless steel and are available in fully automatic, semi-automatic, or manual versions. Dry to dry and fume hood designs are possible, and the stations feature casters and leg levelers.

Modutek’s semi-automated and fully automated wet benches have a built-in SolidWorks simulation software that calculates the process flow characteristics, and all design, assembly, and testing is carried out in-house. As a leading wet bench manufacturer, Modutek works closely with customers to design and customize equipment to meet each client’s requirements.

For more details read the complete article, “How Stainless-Steel Stations Provide Safe Solvent Processing”. If you have questions after reading the article or would like to set up a free consultation to discuss your particular needs, contact Modutek via email Sales@Modutek.com or by calling 866-803-1533,

How Teflon Tanks Improve the KOH Etching Process

Etching silicon wafers with potassium hydroxide (KOH) is a popular process for semiconductor manufacturing. It is relatively safe compared to other etching methods and features good control of the etch rate. When carried out in Teflon tanks, contamination is reduced and the etch rate can be controlled.

Determining the required etch rate is the key factor for a successful etching. An etch rate that’s too fast may mean that the KOH may etch too far into the silicon. But an etch rate that’s too slow may result in a shallow etch. Improving the KOH etching process means applying several control methods to the etch rate to ensure the resulting shapes are exactly correct.

The process factors that may affect the KOH etch rate:

  • Process temperature – The higher the temperature of the KOH solution, the faster that the KOH will etch the silicon.
  • Solution concentration – A higher concentration increases the etch rate.
  • Doping – It means adding impurities to the silicon crystal. When boron is placed into the silicon crystal lattice at a specific location, etching stops in that direction. Boron doping can influence the shapes to be etched this way.
  • Crystal lattice orientation – The silicon crystal atoms are arranged in a cubic lattice that has a greater atom density in some directions than in others. Etching is slower in directions with a higher atom density.

All four factors mentioned above need to be taken into account when designing the mask to obtain the microscopic silicon structures. The silicon wafer needs to be oriented correctly to give the different etch rates along with different lattice directions. Doping has to be in place where etching needs to stop, and the correct concentration of KOH solution has to used. These initial conditions need to be established before starting the process.

A target temperature can also be set, but the temperature will be varied to adjust the etch rate during processing. The ability to alter the etch rate by changing the temperature provides excellent control of the KOH etching process.

Modutek’s Teflon tanks provide precise control of the KOH etching process and are available in a circulating or a static design. The heat source can either be inline or immersed in the overflow weir. An all-Teflon liquid path design reduces the possibility of contamination. The use of heated tanks improves the KOH etching process with short heat up times and precise temperature control.

For more details read the complete article, “How Teflon Tanks Improve the KOH Etching Process”. Contact Modutek for free consultation to discuss your needs at 866-803-1533 or email Sales@Modutek.com.

How Process Controls Are Improved with Automated Wet Bench Equipment

When semiconductor manufacturing is automated, tight process control can improve overall facility performance.

Among the advantages of an optimized manufacturing process is the reduction of consumption of consumables and more uniform production results. Once a batch has run successfully, an automated process ensures that it will run the same way for the next batches. Well-designed automation will also help reduce silicon wafer handling and particle contamination.

Wet process equipment should also be able to customize the automated functions to meet the needs of the application. Once the process is set up, it can run with a minimum amount of operator interference and monitor.

Here are some of the advantages of an optimized automated wet bench equipment:

  • It can reduce chemical use – A fully automated wet bench equipment uses the least amount of chemicals required to carry out the etching or cleaning function and continues do so reliably.
  • Output quality is improved – With fully automated wafer fabrication equipment, semiconductor component output is consistent with fewer defects and rejections.
  • It reduces environmental impact – Automation can ensure that acid and solvent chemical waste is neutralized, and an automated system can block discharge if the output pH is not within predefined limits. Since all chemical use and discharge is tracked, compliance with environmental regulations can easily be demonstrated.

 Depending on what kind of semiconductor components are being produced, a manufacturing or research facility may require highly customized equipment to carry out the process steps required. The automation has to be flexible enough to accommodate custom process steps and the equipment provider should be experienced enough to customize both equipment and automation.

Ideally, the equipment provider should work with customers to exactly define what is required and then design and develop the wafer fabrication equipment with the required automation.

An experienced equipment provider, such as Modutek, designs and builds its own equipment in house based on extensive experience in wet process technology, leaving it in the ideal position to customize wafer processing equipment as needed to meet specific customer requirements.

Our latest article, How Process Controls Are Improved with Automated Wet Bench Equipment, goes into further detail. After you’ve read it, if you have questions or would like to set up a free consultation to discuss your specific needs, contact us at Sales@Modutek.com or by calling 866-803-1533.

How Chemical Carts Provide Safe Handling and Disposal of Chemicals

The chemicals used in the etching and cleaning semiconductor wafers are usually aggressive. That’s why it’s crucial that they should be stored, delivered to the process, and disposed of properly and safely.

Chemical handling equipment, such as chemical carts (also referred to as chemical pump carts or chemical collection carts), are a convenient way to remove waste chemicals from the process and ready them for disposal.

Modutek’s chemical carts are specifically designed for safe pumping and containment of the chemicals and for moving them to a safe location for further treatment. They allow operators to quickly remove used chemicals from a process line and let the process continue to the next step with a minimum of delay. They are easily rolled up to the process tank that contains the used chemicals and operators can safely transfer even toxic or corrosive chemicals. 

Chemical cart design features:

  • Compact profile at 36 inches long, 18 inches wide, and 42 inches high.
  • Made of white polypropylene resistant against acids (also available in stainless steel for solvent applications).
  • Mounted on lockable swivel casters.
  • Suction wand for emptying process tanks.
  • Independent discharge tube for transfer of waste chemicals to a neutralization system.
  • Pneumatic pump, three-eighths inch.
  • On-cart five-gallon chemical tank with double containment (Department of Transport-approved).
  • High-level sensor interlocked with pump for added safety.
  • All-Teflon piping.

Modutek’s chemical carts allow operators to receive, store, deliver, and discharge these toxic and dangerous chemicals safely. These well-designed carts can help reduce waste, deliver accurate dosages to the process, and track chemical use.

Containment of spills is a crucial safety and environmental issue that can be addressed by good design practices. Modutek’s extensive experience with wet process technology and acids used ensure that the company’s chemical handling equipment operate in a completely safe and reliable manner.

Units similar to chemical carts can take on other functions. For instance, chemical delivery system can handle chemical reception, storage, and delivery to the process. They can include bulk storage such as in large tote chemical containers that can supply high volumes of chemicals, or 55-gallon drums located at the process. These systems can include software for dosage control and software can also control the mixing of chemicals.

Read our newest article, How Chemical Carts Provide Safe Handling and Disposal of Chemicals, to learn more. If you would like to discuss your specific needs or get answers to your questions, contact us via email at Sales@Modutek.com or by calling 866-803-1533.

How Specialized Equipment Improves Silicon Wet Etching Process

Results from common wet etching processes, such as KOH and Piranha etch, can be improved with the use of specialized equipment.

When specialized equipment is used in a silicon wet etching process, wafer output can increase, defects can be reduced, and output quality can improve. Equipment such as temperature controls, recirculating baths, and special control strategies can optimize specific processes and positively impact facility importance.

1) KOH (potassium hydroxide) etching is a popular process for applications requiring tight control of the etch rate. The KOH speed depends on the concentration of the bath and the temperature. A base etch rate can be attained by using an appropriate concentration and the rate can then be varied by controlling the temperature.

For KOH etching, Modutek Teflon tanks are suitable as they reduce contamination and feature tight temperature control. The TI static tanks and the TFa recirculating tanks are temperature-controlled models while the TT series tanks operate at ambient temperature.

2) Piranha etching, on the other hand, uses a mixture of sulfuric acid and hydrogen peroxide to quickly remove organic residue, such as photoresist from silicon wafer surface. The mixture has to be handled carefully as it is highly exothermic when first prepared.

Modutek quartz baths are specially suitable tanks for Piranha etching, as they can withstand high temperature and can be heated. The QFa series can withstand the initial temperature spike from mixture preparation and the subsequent heating to operating temperature.

3) Buffered oxide etch uses buffered hydrofluoric acid to etch thin films of silicon dioxide or silicon nitride. The Modutek F-series sub-ambient circulating baths are specially designed for buffered oxide etch as they reduce consumption of acid and filter out contaminating particles. It delivers a safe and reliable process with low-cost operation.

4) Silicon nitride etching composes of phosphoric acid and de-ionized water and requires special control measures. The mixture usually operates at its boiling point of about 160 degrees centigrade. As the etching proceeds, de-ionized water evaporates, leaving a more concentrated acid behind. The high the concentration of the acid leads to the increase of the boiling point and the etch rate.

The concentration of the acid has to remain to the lower level to keep the process working consistently, which means adding water to it. However, doing so risks an explosive reaction when the water mixes with acid. Modutek has a control system that frequently adds small quantities of water to the silicon nitride wet etching baths whenever the temperature rises, keeping the concentration stable. The control system ensures a safe and stable operation. You can learn more by reading our recent article, How Specialized Equipment Improves Silicon Wet Etching Processes. If you have questions or would like to set up a free consultation to discuss your needs, contact Modutek Corporation via email at sales@modutek.com or by calling 866-803-1533.

How Robotics Have Revolutionized Semiconductor Manufacturing

The use of robotic automation in wet bench stations over the last 25 years has dramatically improved production efficiencies and output quality.  The manual handling and mixing of chemicals, silicon wafers and following process steps can be tedious and error prone and mistakes could result in defective products. Semiconductor equipment manufacturers have developed automated process controls that have significantly improved wafer yields and reduced the use of chemicals.

Modutek has been at the forefront in developing robotics and process control software to provide fully automatic or semi-automatic processing of silicon wafers. Their focus in developing automation and control systems that meet all customer requirements has resulted in improved yields, less waste, and less operator mistakes.

Through the use of robotics and process control software the entire semiconductor equipment manufacturing process is controlled accurately and reliably. Advances in robotics have enabled Modutek and other semiconductor equipment manufacturers to offer fully automated and semi-automated stations. These wet benches and chemical stations can control the entire semiconductor manufacturing process with limited or no operator intervention.

Both semi-automated and fully automated wafer fabrication equipment provides excellent process uniformity. The main difference is the lower cost of semi-automated stations may be ideal if full automation is not required. A key advantage Modutek offers over other semiconductor equipment manufacturers is that all robotics and control software is designed, assembled and tested in-house. This ensures that their equipment will meet the specific requirements of each customer and provide the following advantages which include:

  • Reduced costs and improved output quality
  • Elimination of human error
  • Accurate and precise chemical use
  • Less waste
  • Increased reliability
  • Improved safety
  • Reduced contamination

Although some semiconductor manufacturing applications can be automated with standard solutions, in many cases the specific needs of a customer often require a degree of customization with both the process control software and the robotics. With Modutek’s experience and in house expertise in developing robotics and custom software controls, developing custom applications for customers is never a problem. The development team at Modutek knows how each part of the automated system works and can make any necessary changes based on a customer’s requirements.

For more details read the complete article, “How Robotics Have Revolutionized Semiconductor Manufacturing”, on how Robotics has make the wafer fabrication process more efficient, predictable and safer. Contact Modutek for a free consultation or quote at 866-803-1533 or email Modutek@modutek.com.