How Modutek’s Fully Automated Wafer Fabrication Equipment Improves Process Control

Particle contamination has a challenging problem when the structures and conductors on the silicon wafers are small or tightly packed. On the smallest microscopic structures, a single particle can block a conductor, distort a structure or affect diffusion. To address this issue Modutek's product line includes fully automated wafer fabrication equipment and wet bench stations. The company develops its own software for the equipment in-house and assembles all its wet stations in its San Jose facility.

Modutek makes extensive use of software control and robotics to ensure excellent process control and high-quality output. These can optimize the automation for the best possible performance and customized equipment can be used to meet specific application requirements.

The full range of benefits that Modutek's fully automated stations include the following:

• Reduced chemical usage
• Improved etch rates
• Higher yields
• Better throughput
• Excellent repeatability
• Ability to handle both acid and solvent applications
• Ability to work with standard wafer carrier sizes and custom sizes up to 30” x 60”
• Extensive tracking of process variables
• Highest output quality

The SECS (SEMI Equipment Communications Standard) and GEM (Generic Equipment Model) protocol standards both specify how automated semiconductor fabrication equipment can communicate with a host computer. These standards are developed by the Semiconductor Equipment and Materials International organization, and they define interfaces, messaging and communication capabilities.

Modutek's fully automated stations support this protocol and can supply a variety of data to the hosts while receiving remote commands to start or stop a process and to choose stored recipes or programs. Using in-house experience in wet processing semiconductor manufacturing Modutek can customize their wafer fabrication equipment to meet the specific needs of the customer’s application.

Read the complete article “How Fully Automated Wafer Fabrication Equipment Improves Process Control” which goes into greater detail. Contact Modutek at 866-803-1533 or by email Modutek@modutek.com for a free consultation to discuss your specific process requirements.

How Fully Automated Wafer Fabrication Equipment Improves Process Control

Precise process control and the elimination of particle contamination have become more important as the microscopic structures etched on silicon wafers have also become more intricate and densely packed. The accuracy of chemical dosages and the timing of the steps must be consistent and handling of wafers must be kept to a minimum. For this reason, fully automated wafer fabrication equipment is used to ensure that such conditions for the production of semiconductor components are achieved.

There is manual and semi-automatic wafer processing equipment which rely on operators to mix chemicals and transfer wafers. However, errors and inconsistencies in execution can result in defective or low-quality products and production downtime and reduced throughput. Productivity also suffers. The semiconductor manufacturing facility's general operations will become less efficient and less profitable.

Software is the key to automation. When software is used to control the wafer fabrication equipment, it eliminates the variability found in manual operation and inconsistent documentation. Using software to run fully automated stations can provide the following benefits:

• It ensures and maintains exact chemical ratios with each batch
• Precise and repeatable process steps
• Process variables can be easily optimized by programming small changes in the software
• Accurate chemical dosages result in reduced waste and lowered chemical use
• Chemical neutralization and disposal are reliable and easily documented
• Worker safety is enhanced as operators are less exposed to toxic chemicals

The benefits listed above come from programming automatic controls which manage the cleaning and etching of the silicon wafers. The software will calculate how much of each chemical is needed for a particular process step. It controls the adding of the chemicals to the process tank, times the process step, drains the chemicals and neutralizes all the waste chemicals. Once the variables in the software are optimized, the software will run the optimized process the same way every time. This allows the results to be predictable and consistent.

The complete article “How Fully Automated Wafer Fabrication Equipment Improves Process Control” provides more details. Contact Modutek at 866-803-1533 or email at Modutek@modutek.com more information or would like a free consultation to discuss your specific requirements.

Isotropic and Anisotropic Silicon Wet Etching Processes

The silicon wet etching of monocrystalline wafers produces microscopic structures that are used in mechanical devices and semiconductor parts. When the silicon wafer is immersed in a chemical bath, only the exposed parts of the silicon wafer are subject to etching. Its other parts, that are not to be etched, are protected by a mask.

Find additional details about isotropic and anisotropic silicon wet etching in these documents:

•  University of Maryland - Silicon Wet Isotropic and Anisotropic Etching

•  University of California at Irvine - Anisotropic Silicon Etch Using KOH

In isotropic etching, the isotropic etchant etches the silicon wafer equally in all directions. This means that the wafer is etched downward and sideways under the mask, resulting in a cavity which usually consists of rounded corners and edges which are bigger than the opening in the mask.

In anisotropic etching, the anisotropic etchant such as potassium hydroxide (KOH), etches at varying speeds in different directions. This means that the etch rate in the downward direction is faster than the etch rate in the sideways direction. This leaves to cavities with straight sides and less undercutting of the mask.

  

The silicon wafer mask defines where etching can take place, however, the depth of the etched cavity and its shape can be made by selecting the right etchant and controlling the etching rate. Isotropic etching is often used to achieve larger features in the initial stages of the silicon wafer processing, while anisotropic etching is used to produce straight-edged microstructures in the final stages.

The etch rate is also a significant factor. It depends on the concentration of the etchant and the etching solution temperature. Once the etch rate is determined at a certain temperature, the masked silicon wafer is immersed into the etchant. The etching should be long enough to produce the required cavity size. The subsequent wafers will undergo the same process for reproducible results.

Silicon wet etching equipment that includes Modutek’s Teflon tanks can be used to support both isotropic and anisotropic processes. For processes that are temperature-dependant, the tank temperature controller provides rapid and accurate heating control.

The complete article “Isotropic and Anisotropic Silicon Wet Etching Processes”, explains the processes in further detail. If you have questions about selecting the right equipment for your silicon wet etching process, contact Modutek at 866-803-1533 or email Modutek@modutek.com. 

Safely Controlling the Silicon Nitride Etching Process

Silicon nitride etch removes silicon nitride from silicon wafers during the fabrication process of semiconductor components. It consists of a solution of phosphoric acid in water which etches silicon nitride. When the temperature of the solution and the concentration of phosphoric are kept constant, the etching will be carried out rapidly and consistently.

The silicon nitride wet etching process uses silicon nitride as a mask to produce the micro-structures and connections in semiconductor devices. In most etching applications the etch rate can vary by changing the temperature or chemical concentration, but the ideal conditions for a successful etch rate consist of a boiling point and a concentration of 85% phosphoric acid in a de-ionized water solution.

The high temperature will lead to water evaporation and will increase the acid concentration in the solution. Adding water is dangerous because if too much water is added at once, the solution stops boiling, and the added water will create a film above the acid. The temperature will rise again, and the acid starts boiling, the large quantity of the water from the film mixes with the acid and this may cause an explosive reaction.

That is why the accurate monitoring of the solution is extremely important for safe control of the process.

Modutek's Nb Series Wet Etching Baths ensure the safe operation of silicon nitride etching process. Here, the phosphoric acid solution is kept boiling with a heater that's constantly on which maintains the solution at the boiling point.

One of its features is the heater which constantly keeps the phosphoric acid solution at the boiling point.

Other key features are the thermocouples – the first one detects the rise of temperature (as the water evaporates and the acid concentration increases). In this case, a small amount of water is added to the solution to bring the concentration to back its manageable levels. There's also a second thermocouple which detects the presence of steam above the bath liquid and blocks the addition of water when no steam is present. The third thermocouple monitors the bath temperature to switch off the heater if the solution overheats.

The advanced features of the Modutek's Nb Series Wet Etching Baths allow semiconductor manufacturers and research labs to control the silicon nitride wet etching process safely while achieving optimum consistency characteristics.

The complete article, “Safely Controlling the Silicon Nitride Etching Process,” explains in more details. For a free quote or consultation contact Modutek at 866-803-1533 or email Modutek@modutek.com.

How Quick Dump Rinsers Improve Silicon Wet Etching Results

Manufacturing lines in semiconductor fabrication facilities and research labs use corrosive chemicals in cleaning and etching silicon wafers. A silicon wafer will undergo multiple steps in baths that contain such chemicals as hydrochloric acid or hydrogen peroxide.

Once the cleaning and etching are done, using Quick Dump Rinsers the silicon wafer then undergoes rinsing – the rinsing process should remove the contaminants from the corrosive chemicals completely without introducing new contaminants. The chemicals from the silicon wafer must be completely rinsed before the wafer can undergo further process steps.

If traces of chemicals are not completely removed, etching of the wafer may result in defective and low-quality products. That is why in many process steps, rinser performance is critical for product output quality.

When the wafers are placed into the Quick Dump Rinser tank, powerful jets spray de-ionized water over the wafers to remove all traces of chemicals. As the tank fills up, all the chemical residue and particles are flushed out and rise to the surface. A nitrogen gas bubbler system agitates the de-ionized water further, removing additional contaminants from the surface of the wafers. An overflow weir allows the surface to flush the chemical residues and other impurities out of the tank. Once the rinsing process is complete, the quick dump door at the bottom of the tank opens and drains the water in a matter of seconds.

Modutek's Quick Dump Rinsers are designed to meet the needs of advanced semiconductor fabrication. Their features include:

• Contoured vessel design
• Nitrogen bubble on all models
• Natural polypropylene or PVDF (option) tanks, nozzles and fittings
• Large machined dump door without gaskets or seals
• 360-degree overflow weir

The rinsers are available either as standalone units or integrated into a wet bench process manufacturing line.

The rapid operation of Modutek's Quick Dump Rinsers help reduce the use of de-ionized water as well as save process time. It removes contaminants completely without introducing new chemicals. Modutek has an extensive line of silicon wet etching equipment from which to choose.

For more information read the blog article titled “How Quick Dump Rinsers Improve Silicon Wet Etching Results” . For a free consultation or quote contact Modutek at Modutek@modutek.com or call 866-803-1533 to discuss your specific requirements.

How Quartz Tube Stations Work and the Benefits They Provide

High-temperature operations that include diffusion of materials into the silicon wafers are some of the processing steps involved in the manufacture of semiconductor components. Quartz tubes are the ideal vessel for such processing steps because they can withstand even the highest temperatures and are inert enough to reduce contamination.

Usually, the silicon wafers are placed in a horizontal quartz tube that is big enough to contain wafers and their supports. In horizontal quartz tube cleaning stations, the tube is inserted into the cleaning enclosure and cleaned with an acid spray. The acid dissolves and removes the contaminants from the high temperature furnace. A couple of cycles are then followed: the rinse cycle which removes the traces of the acid, and the drying cycle which speeds up the drying process without introducing particles into the cleaning enclosure. Mechanical handling of the tubes helps in minimizing possible damage due to human error and decreases the chances of contamination from foreign particles.

Modutek’s quartz tube cleaning stations offer a lot of advantages, especially when they're customized to accommodate the requirements of a specific application. Aside from providing customized equipment, Modutek can supply the degree of automation requested by the client. Cleaning process steps can be performed manually or fully automated. Full automation minimizes human error and keeps operators safe by allowing them to remotely monitor the cleaning process.

Modutek's horizontal quartz tube cleaning stations provide an excellent solution for semiconductor manufacturers and research facilities. Rugged and reliable, the basic unit offers many options for additional features according to specific customer requirements such as: holding tanks, automation features, a T/C sheath cleaner or a bottle washer. As a leading semiconductor equipment manufacturer Modutek provides continuous product innovations and improvements and offers the highest degree of customer service and support.

For more details read the complete article “How Quartz Tube Stations Work and the Benefits They Provide”. To discuss your specific needs, contact Modutek at 866-803-1533 or email Modutek@modutek.com to schedule a free consultation.

Why High Temperature Quartz Baths Are Required for Silicon Wafer Cleaning

Silicon wafers undergo many process steps during the manufacture of semiconductor components. Cleaning the wafers properly is a key factor for successful fabrication. These process steps include etching and diffusion, both of which involve the use of a masking material which helps guide the etching chemicals or diffusion targets. When the cleaning is done, the masking material is removed. If traces of contaminants are left or introduced, it will result in an inferior and defective semiconductor product.

Aggressive chemicals are used in silicon wafer cleaning to remove organic masking material and other possible impurities. In this cleaning application, there needs to be a container that can resist the action of these aggressive chemicals, while remaining inert so as not to become the source of contamination itself.

 Quartz baths provide an ideal solution to the challenges of silicon wafer cleaning and for maintaining the high levels of wafer cleanliness. They provide a clean and safe container for silicon wafer cleaning because they can withstand the chemical reactions. Quartz baths typically hold the wafers and the cleaning chemicals, but some processes require heating, circulating the solution or adding chemicals, depending on the various materials used.

Quartz baths are impervious to strong chemicals such as hydrochloric acid, sulfuric acid, and hydrogen peroxide. The baths remain unaffected by these chemicals while the chemicals clean the silicon wafers. With SPM clean, sulfuric acid and hydrogen peroxide are mixed at a constant temperature of 100 degrees centigrade. Periodic spiking of hydrogen peroxide is necessary because it decomposes in the solution. This mixture of these strong chemicals, combined with high temperature, effectively cleans the silicon wafer without affecting the quartz bath container.

The electrical and physical structures that make up the semiconductor components are ultra-sensitive to contaminants. Even a single contaminant can interfere with the entire etching or diffusion process. Such interference from these contaminants can reduce the yield of the semiconductor components and affect the productivity of the semiconductor manufacturing facility. That is why it is extremely important to use bath containers for these process steps — they should be inert and should not become another source of contamination themselves.

If you would like more information about Modutek’s quartz baths, read the complete article “Why High Temperature Quartz Baths Are Required for Silicon Wafer Cleaning”. Contact Modutek at 866–803–1533 for a free consultation to discuss your needs.