Selecting Equipment for the KOH Wafer Etching Process

Selecting Equipment for the KOH Wafer Etching ProcessKOH etching is increasingly used for creating microscopic structures in silicon. The wafer etching process uses a 20 to 30 percent solution of potassium hydroxide to create cavities in the unmasked parts of a silicon wafer. KOH etching is comparatively safe and etching can be tightly controlled through regulation of the bath temperature and doping of the silicon. Semiconductor fabrication facilities favor this etching method because of its high precision, good repeatability and cost effectiveness.

How It Works

The silicon wafer is masked with a material impervious to KOH, usually silicon dioxide or silicon nitride. The mask is based on the layout of the structures and circuits of the final semiconductor product and determines where cavities will be etched. The silicon wafers are immersed in the KOH solution and the temperature is controlled to give the desired etch rate.

KOH etching is extremely sensitive to temperature variations at temperatures above 60 degrees centigrade, with the etch rate in microns per hour approximately doubling for every ten degree rise in temperature. A typical rate is 1 micron per minute for a bath at 80 degrees centigrade. Accurate control of the temperature is a key factor in precise etching results.

While varying the temperature can control the etch rate, the orientation of the crystal planes in the silicon and doping of the silicon with boron also influence the rate and direction of the etch. The anisotropic nature of the silicon crystal can be used to create slopes and shapes along the crystal planes and the etch can be stopped in specific locations with boron doping. This way KOH etching can create complex shapes and circuit paths for semiconductor products.

Modutek KOH Bath Equipment

Modutek supports KOH etching as one of its wafer etching process options in the company’s line of wet bench process equipment. The TFa and TT series Teflon heated tanks are ideal for the requirements of KOH etching. The tanks are available for standard carrier sizes for single or double capacity and Modutek can also build custom sizes if needed. The modular nature of the tanks means they can easily be integrated in any new or existing wet etching station.

The TFa series high temperature overflow tanks and the TT series static tanks are both PFA Teflon tanks with an all-Teflon fluid path. Heating can be inline or immersion heating in the overflow weir. The operating temperature range is from 30 to 100 degrees centigrade and the tanks can heat up at the rate of 2 to 3 degrees centigrade per minute. Temperature control accuracy is plus/minus 0.5 degrees centigrade and liquid levels and high temperatures are monitored. The high precision temperature control and the rapid heating rate ensure that heating is uniform throughout the bath.

Additional features and specifications of the Modutek KOH etching tanks include 360 degree overflow filtration through serration overflow, an optional condensing Teflon refluxor with Teflon cooling coils, a pneumatically actuated auto cover, an aspirator valve system and a Teflon gravity drain. An RS232 interface, temperature controllers and remote operation timer switches complete the remote operation capabilities.

Modutek can help customers considering KOH etching in their selection of the appropriate systems. The company has a complete range of wet bench process equipment, chemical handling systems and equipment repair capabilities. In addition to their standard lines, Modutek can customize components to meet the specific needs of their customers. Experienced company personnel can work with customers to design optimal configurations and layouts for their clean room facilities. The KOH etching tanks are the ideal solution for semiconductor fabricators that need to etch microstructures in silicon wafers.

Silicon Wafer Cleaning Solutions for Wet Processing Applications

Silicon Wafer Cleaning Solutions for Wet Processing ApplicationsModutek designs and delivers standard and customized silicon wafer cleaning equipment for semiconductor manufacturing facilities and research labs. Supported cleaning processes include RCA clean, Standard Clean 1 and 2, Piranha etch clean, and pre-diffusion clean. The company has specialized in silicon wafer cleaning equipment for over 30 years and emphasizes effective and efficient contaminant and particle removal to ensure high yields, improved throughput and high quality output.

RCA Clean

The RCA clean process is based on a cleaning method developed at RCA Corporation to remove organic residue from silicon wafers. The cleaning solution is made up of 5 parts water, 1 part 27% ammonium hydroxide and 1 part 30% hydrogen peroxide. It removes organic contaminants and leaves a thin layer of oxidized silicon on the surface of the wafer.

Standard Clean 1 and 2

The RCA cleaning process is often carried out in two steps called SC1 and SC2. The SC1 step uses the APM (ammonia/peroxide mixture) solution of the RCA cleaning method to remove organic matter and particles. The SC2 cleaning method uses a solution of hydrochloric acid and hydrogen peroxide or HPM (hydrochloric/peroxide mixture) to remove metallic ions. The two steps prepare the silicon wafer for further processing.

Piranha Etch Clean

The Piranha etch clean removes large amounts of organic material. It is used when there are visible organic contaminants such as photoresist or other hard to remove organic materials. It uses the Piranha solution, made up of a mixture of hydrogen peroxide and sulphuric acid, to clean silicon wafers and hydroxylate surfaces making them hydrophilic. Typical mixture ratios are 3 parts of sulphuric acid and 1 part of 30 percent hydrogen peroxide or higher sulphuric acid ratios of up to 7 to 1. The mixture is highly corrosive and has to be handled with special care.

Pre-Diffusion Clean

The pre-diffusion clean is the final step before the silicon wafer goes into the diffusion furnace. The wafer surfaces must be free from particles and from metallic and organic contaminants. Native oxides or chemical oxide films may have to be removed.

Depending on the nature of the contaminant, a variety of aggressive chemicals, including those from the above cleaning methods, may be used to achieve clean surfaces. Pre-diffusion cleaning is critical because particles or contaminants on the wafer surface may affect the diffusion process and result in defective or low-quality semiconductor output.

Modutek’s Silicon Wafer Cleaning Equipment

Modutek’s dual tank rotary wafer etching system provides a convenient silicon wafer cleaning solution in a compact design. Once the operator loads the wafers and closes the fume door, the wafers are moved to a chemical process tank. After a pre-programmed agitation cycle, the wafers are transferred to the quenching tank where they undergo a set series of rinse cycles. When the set number of cycles is reached, an alarm sounds and the operator can remove the wafers.

Cleaning stations can be manually operated, semi-automatic or fully automated. Modutek’s SolidWorks Simulation Professional and Flow Simulation software allows customers to optimize their operation, reliably reproduce cleaning procedures and precisely control cleaning.

Modutek can evaluate the cleaning requirements of semiconductor manufacturing facilities and research labs and provide custom solutions for their specific requirements. The company’s equipment combines the latest technology with the highest quality and reliability. Modutek can provide their expertise and experience and work directly with clients to improve the silicon wafer cleaning processes for their specific application. For a free quote or consultation on call 866-803-1533 or email [email protected].

Tips on Selecting the Right Options for Your Wet Bench Equipment

Tips on Selecting the Right Options for Your Wet Bench EquipmentModutek wet benches are of white polypropylene construction with 304 stainless steel construction available for solvent applications. The company will build any size and length to meet customer requirements. Safety features include safety interlocks, PVC safety shields, emergency power off mushroom buttons and wiring to NFPA 70 and 79. All models have a Teflon N2 gun, a deionized water hand spray and a continuous flow deionized water manifold.

Fully Automated Stations

Modutek’s fully automated wet bench stations use SolidWorks Simulation Professional and SolidWorks Flow Simulation software to optimize the semiconductor fabrication processes and improve performance. The cost of the units covers the basic station and robotics to handle automated operation. These wet process stations are suitable for customers who need high yields, improved etch rates, better throughput and who want the highest output quality.

In addition to increased performance, fully automated stations eliminate human operator error in calculating the chemical dosage and operating the station. The automated system tracks chemical usage to reduce waste and maintain a consistent process environment. Once programmed, the automated station runs the same software and the process is fully repeatable.

Semi-Automated Stations

The semi-automated stations give customers the advanced features and precision of fully automated stations without having to pay the fully automated price. Stations have a graphic user interface on a PCL touch screen to control servomotors with three degrees of freedom and with encoder feedback. Customers can get process uniformity and accurate handling while saving money.

Modutek semi-automated stations are an excellent option for customers who want the precision of robotic controls without paying for full automation. The semi-automated stations still use the SolidWorks Professional and Flow software packages to ensure customers achieve excellent results while spending less.

Manual Stations

Manual wet benches are a cost effective way for customers to get the safety features and operating characteristics of the Modutek wet process equipment family with competitive pricing and an overall low cost of ownership. The manual stations are an effective way for customers to start using wet process equipment and they can later expand the units to add automation options. The manual equipment is of the same quality as the automated stations and delivers excellent performance without the cost of robotics.

Solvent Stations

For solvent stations Modutek uses a 304 stainless steel construction with fire suppression. Solvent stations are available with the same fully automated, semi-automated or manual options as the other wet processing stations and they share the same advanced features. Solvent stations are for customers who have applications with acetone or IPA or who want to carry out photo resist stripping or EDP etching.

Dry to Dry Wet Process Equipment

Modutek’s Dry to Dry equipment saves time by eliminating transfers and increases throughput and yield. It uses an IPA dryer to avoid having to dry in a separate tool. The same automation options as for other wet processing equipment are available for the Dry to Dry models. The unit is a convenient option for customers who want to simplify their process and increase output.

Custom Options

Because Modutek designs and produces all wet benches and related equipment in house without subcontracting, the company can use in house expertise to develop custom solutions for particular applications that may not fall within the standard option set. Customers can be assured that, no matter what the wet process application, Modutek engineers can propose a custom solution if the broad range of standard options is not suitable. For more information or for a free quote contact Modutek at 866-803-1533 or email [email protected].

Advantages Modutek Offers Over Other Semiconductor Equipment Manufacturers

Advantages Modutek Offers Over Other Semiconductor Equipment ManufacturersFounded in 1980, the Modutek Corporation has established itself as an industry leader among semiconductor equipment manufacturers. Modutek provides a full product line of wet process equipment and related products, including wet bench stations, nitride etch baths, high temperature quartz-heated baths, sub ambient filtration, rinsing systems as well as chemical delivery systems. The company has maintained its position through a focus on innovation and on delivering high quality semiconductor equipment. In addition to offering a broadly based standard product line, the company can design custom solutions for a wide variety of applications according to the specific requirements of customers.

 

Key Company Characteristics

 

Modutek has been in the semiconductor equipment manufacturing business for over 35 years and has developed a reputation for high quality and reliability during that time. The company retains a skilled group of design engineers who keep up with new technology and innovate in areas such as process automation. Modutek leverages its expertise developed over the years to deliver solutions that respond exactly to the particular needs of each customer.

 

Located in San Jose, California, Modutek designs and builds its equipment in house and does not subcontract out the manufacture or assembly of its products. This policy allows the company to ensure that all equipment is of the highest quality and Modutek stands behind its products with its warranties and guarantees.

 

A key part of the company’s success is its outstanding customer support. Extensive customer support manpower is not only available but has unparalleled expertise because all equipment and software is designed and produced in San Jose. This insures that local personnel have the experience and product information required to deliver support to customers.

 

Specific Advantages of Ordering From Modutek

 

Decision-makers and production managers at manufacturing plants, research facilities or university labs that have a need for semiconductor manufacturing equipment look for companies with specific characteristics. They want reliable suppliers who can deliver high quality equipment that meets their needs. They need expert help in working through the design process, purchasing the right configuration and with post sales support.

 

Because of Modutek’s long history as a supplier in this industry, the company has a proven reputation that customers can verify. The record of existing installations and the experiences of current customers allow potential buyers to evaluate Modutek’s record and confirm company claims for high quality equipment and reliability of supply before making a purchase.

 

Keeping design and production of products and software in house allows Modutek to fully control and maintain high quality of its products. Customers wanting information about materials used or design practices can get answers first hand from the people responsible. This is especially valuable when discussing guarantees and warranties.

 

With their own engineers working on all aspects of semiconductor equipment supply, Modutek can easily make changes to designs and customize products to meet specific needs. Customers can start by evaluating the wide range of standard products but, if they have specific applications that require unusual features or requirements, Modutek can accommodate them.

 

Modutek’s in house design and production practices give customers access to technical specialists who have hands-on experience with the equipment. A Modutek design engineer can give customers information about a product or even suggest design changes for custom equipment. This capability, together with a commitment to a high level of customer service, lets Modutek offer service before and after a sale that is both customer-oriented and effective in solving problems.

 

For customers that need highly reliable wet process or related equipment, Modutek stands out among semiconductor equipment manufacturers as a supplier that fulfills requirements and provides outstanding customer support. For a free quote or consultation call Modutek at 866–803-1533 or email [email protected]

Modutek’s Wet Bench Design Process

Modutek's Wet Bench Design ProcessIn an effort to meet the highest customer expectations, Modutek has developed a wet bench design process that emphasizes collaboration with customers and dedicates the full resources of the company to identifying and satisfying customer requirements. Key features of the process are an emphasis on quality, an orientation toward partnering with the customer, a project-based account management structure and the use of the latest design tools. With this approach to wet bench equipment design, Modutek intends to ensure that the company meets the highest levels of customer satisfaction.

Design Goals

While meeting and exceeding customer expectations is the overall goal, Modutek emphasizes wet bench process results as well. A high-quality wet bench must be designed for high throughput with a long service life and a low level of downtime. High product quality requires a high level of extremely precise control. Based on these essential features, Modutek starts a conversation with the customer to identify his particular needs.

Partnership Design Program

To begin with the process, Modutek technical personnel gather all the details of their customer’s application. Specifications, data, descriptions and parameters are collected to allow Modutek to understand the customer’s business. The company can then develop the criteria for a successful design together with the customer. The business needs for wet benches, wet process tools, chemical delivery systems or custom semiconductor equipment are explored in detail. At the end of this process the requirements for a successful design are clear.

Design Tools

Once the design requirements have been identified together with the customer, Modutek uses advanced tools to help with design and modeling. Three dimensional design tools ensure precision and the accuracy of the models. Such 3-D designs are created for all wet process and chemical delivery systems, to show the positions of all components and to form the basis for a detailed design review. Once approved, the same material is used to create complete documentation, including post installation maintenance manuals. Using a single set of designs to generate all the documentation ensures that performance is always consistent, even when many units are produced.

Project Management

To execute the production as specified in the designs, Modutek focuses on managing accounts as projects. For each order, the company assigns a dedicated project manager to lead the work. He coordinates with the customer to make sure the design, engineering, manufacturing and integration remain on track. Delivery and installation at the end of the project are handled the same way. The project manager is responsible for ensuring basic technical requirements are met and the customer’s input is respected, leading to a high quality design that meets the customer’s needs.

Factors for a Successful Design Process

Four factors allow Modutek to offer a collaborative design process that gives superior results. First, the company has the experience and broad line of wet bench equipment to respond to a wide variety of customer requirements. Secondly, the company designs and builds all process, etching or cleaning components of its wafer fabrication equipment in house. Thirdly, all automation design is carried out in house, with Modutek engineers designing and writing the software. Lastly, Modutek’s SolidWorks Simulation Professional and SolidWorks Flow Simulation tools help design the system to get the end results specified. All of these factors must be in place for the successful implementation of the type of design process offered by Modutek, and the company works hard to ensure these prerequisites are retained in order to deliver the superior customer-centric service they make possible.

If you need wet bench equipment designed and built for your specific process requirements, contact Modutek at 866-803-1533 or email [email protected].

Wet Bench Ergonomics and Safety

Wet Bench Ergonomics and SafetyImplementing ergonomic engineering principles to reduce operator strain and effort can increase safety and help prevent accidents. Established safety guidelines such as those of the Semiconductor Equipment and Materials International (SEMI), the “SEMI S8-0712 – Safety Guidelines for Ergonomics Engineering of Semiconductor Manufacturing Equipment,” can help manufacturers design their installations accordingly. Such designs make it easy for operators and technicians to reach controls and work with semiconductor wafers. Modutek follows these guidelines and has included specific features in their wet benches and other equipment to allow for ergonomic and safe operation. In addition, when dealing with specific customer requirements or retrofitting existing installations, Modutek can develop customized ergonomic solutions.

Swing Arm Interface Mount

When technicians have to monitor a process or operate tools when troubleshooting they must be able to see the operator interface and input commands safely and ergonomically without stretching or assuming unnatural positions. The normal resting location of the interface is to the side and out of the way. The swing arm allows operators to pull the interface out and over so it is visible and within reach when they are monitoring the process or handling tools.

The swing arm can rotate on three axes and tilt to let operators place it in any desired position. Once the operator pulls the interface into place and orients it in an optimal way, a single push button actuates pneumatic locking by pressing two large bearings together, preventing further movement. With this rigid and low bounce design, the interface can be positioned with one hand, and the design eliminates further movement such as might result from the operation of the touch screen.

Its epoxy powder coating and anodized aluminum finish together with its internal cabling make the swing arm easy to clean with low particulate generation for clean room applications. The fact that one technician can place the arm into a convenient position and lock it with one hand means that a second person to assist with the operations is often not required.

Easy to Load Wafer Holding Devices

The impact of safe and ergonomic design increases greatly when applied to operations that have to be carried out regularly and frequently. When wafer trays and holding devices are designed to make it easy for operators and technicians to use them, even small improvements in ergonomic design can make a big difference in both productivity and safety.

In Modutek wet benches, robot arms move the wafer holding trays to the front of the station to a position optimally located for easy and effortless loading and unloading. Modutek applies such ergonomic design principles to wet bench access for increased safety of operators and technicians working in semiconductor fabrication facilities and research labs.

Ergonomically Designed Upgrades and Customization

When a facility is upgraded or additional equipment is retrofitted, standard ergonomic designs may not meet the needs of the completed installation. Equipment that fully satisfies ergonomic design principles on its own may be difficult to operate when placed in specific configurations. Modutek can apply the company’s experience with ergonomic design to customize installations, ensuring that a customer’s specific ergonomic requirements are met and that the installation as a whole is easy and safe for operators and technicians.

Modutek processing stations are available in a wide variety of configurations and the company works with the customer’s engineering team to custom design the best processing equipment for the particular application. The ergonomic engineering required to ensure easy and safe operation is integrated in these designs and guides the company when customizing their equipment for specialized needs.

If you need help selecting or upgrading wet bench equipment for your application and have specific ergonomic requirements, contact Modutek at 866-803-1533 or email [email protected].

How Technology Manufacturers Use Chemical Delivery Systems

How-Chemical-Delivery-Systems-are-Used-by-Technology-Manufacturers

Technology manufacturing requires the safe handling of chemicals as well as their delivery in accurate amounts. Corrosive chemicals are used for etching, cleaning and plating materials such as silicon chips, metal parts, solar system components and printed circuit boards. The chemicals have to be stored securely, delivered to the process in precise amounts, and neutralized before disposal. Automated chemical delivery systems reduce waste and operator error while allowing the supply of defined amounts of each chemical with a high degree of precision.

Technology manufacturers use these systems to supply chemicals to wet processing equipment. Acids are used to etch away layers of material on wafers of silicon, printed circuit boards or other substrates. Sections of the layers to be etched are covered in protective material and are not removed by the etching. In this way microscopic structures and conducting paths can be created. The requirements for chemical delivery systems depend on the application of the wet processing equipment and on the chemicals to be used.

The key to supplying effective chemical delivery systems is a flexible approach combined with the ability to develop systems customized to meet the needs of the manufacturer. Companies that manufacture silicon wafers have different requirements from those that manufacture micro-electro-mechanical systems, hard disk drives or solar cells. The cleaning and etching processes of different technology manufacturers use various chemicals and widely varying amounts and process control strategies. Their chemical delivery systems must be resistant to corrosion, be safe to operate, allow the storage of large amounts of chemicals and include flexible software to control distribution. An equipment supplier has to have a good understanding of the processes involved so that they can standardize the parts of the system that can remain the same while developing custom solutions to match the needs of each technology manufacturer.

Modutek specializes in designing and manufacturing systems that provide outstanding performance and reliability with the ability to be highly customizable. The systems incorporate user-friendly features that promote safe and cost-effective operation. In a typical custom application, water use, and the number of defective parts produced is reduced while consistency of results increases.

Modutek’s chemical delivery systems feature all Teflon fluid paths, double containment cabinet construction, leak detection and chemical level sensing. Double wall plumbing and system data logging are available. Chemical storage can be in large tote chemical containers or 55-gallon drums close to the wet process station. Manufacturers that use different chemicals can improve throughput because the Modutek’s systems are designed for quick chemical change.

The software that automates a chemical delivery system is a key factor in the system’s flexibility and Modutek can customize the software to meet the needs of the technology manufacturer. Typically a touch screen shows error messages on start-up and then displays a flow diagram showing the status of key components such as metering pumps, valves and level switches. Since these may be different for particular customized applications, the software must be easily adaptable. All the software for Modutek’s chemical delivery systems is written in house. This means that Modutek has the in house expertise and capability to make changes in the software as needed and can provide excellent technical support without having to rely on exterior sources.

The Modutek chemical delivery systems are suitable for any technology manufacturer application. They are specifically designed for easy customization and provide reliable, cost-effective operation. For additional information about Modutek’s Chemical Delivery Systems or related products call 866-803-1533 or email [email protected]

Wet Processing Equipment Applications

Wet Processing Equipment ApplicationsModutek provides a complete line of silicon processing solutions with state-of-the-art wet processing equipment designed to deliver high quality output at a low total cost of ownership. Applications include wafer etching, cleaning, drying, stripping and metal etching. Specific solutions include KOH etch and nitride etch. State-of-the-art design and engineering ensures that equipment is reliable, safe and low-maintenance.

The rotary wafer etching system can etch, clean, reclaim, develop and strip semiconductor wafers and substrates. It features a dual tank design with a transfer between tanks for etching and cleaning or rinsing. A carrier assembly holds the wafer boats and takes up to 50 six-inch or 25 eight-inch wafers at a time. When the operator closes the fume door and presses the start button, the carrier assembly carries out a continuous rotational agitation in the chemical tank for a pre-set time. The assembly then automatically transfers the wafers to the rinse tank in less than three seconds. After the Quench-Quick Dump-Overflow rinse cycles, the wafers can be moved to the drying unit.

The system can be programmed with up to five process recipes and a touch screen controller displays a summary of the recipe and the process. Axial rotation of the wafers at up to 80 rpm ensures adequate agitation for consistent results. The system is flexible enough to handle different semiconductor processing applications and can carry out automatic batch processing.

Modutek’s vacuum metal etcher is designed for precision etching of aluminum layers on semiconductor wafers. The fully automated unit etches aluminum in a vacuum to eliminate hydrogen bubbles that interfere with the etching and produce “snow” and bridging on the etched wafers. At the beginning of a cycle, the unit evacuates the plenum, drawing acid into the etch tank. Etching continues until the preset time is elapsed or the end-point detector senses that lines have been etched through the aluminum layer. When etching is complete, the acid drains back into the acid reservoir and nozzles spray deionized water over the wafers. The metal etcher is characterized by a fast throughput and a high yield.

Modutek’s IPA Vapor Dryer provides a way to clean dry wafers without water spots. The unit can introduce ozone into the drying chamber to eliminate organic impurities. Most drying cycles take only 10 to 15 minutes. As low-cost drying solution, Modutek can custom design their IPA vapor dryers to meet your specific requirements and application.

In addition to equipment that can be used for a variety of semiconductor processing, Modutek offers specific solutions such as KOH etching and nitride etching. For KOH etching, Modutek uses an individualized approach that produces solutions for specific customer applications with the company’s Teflon tanks. The tanks are all-PFA material and sheets are welded using advanced techniques designed to reduce impurities. Modutek KOH etching solutions are designed to work with a customer’s existing wet bench equipment.

For nitride etching, Modutek provides a new Nb series Silicon Nitride Etch Bath. The system features a dual system that monitors the chemical boiling while ensuring tight control of the nitride etching process. As a result, the system provides unparalleled control of the nitride etch process and uniformity while achieving elevated levels of safety and reliability.

Modutek’s wet processing equipment is designed to meet the application needs of any semiconductor fabrication or research facility, either with standard products or with custom-designed solutions. Call Modutek at 866-803-1533 for any questions you have about wet processing equipment or if you need help in choosing the right equipment for your specific requirements.

MEMS Manufacturing with Wet Processing Equipment

MEMS Manufacturing with Wet Processing EquipmentMEMS (Micro Electro Mechanical Systems) are made up of miniature components that can acquire, analyze and process data and generate a desired mechanical output. Wet processing equipment can be used to manufacture these mechanical components and create electrical links. The structures in MEMS that are fabricated using wet processing equipment can range in size from several micrometers to millimeters. Devices using MEMS are characterized by high performance, excellent reproducibility and low cost. When wet processing equipment is used in their manufacture, these characteristics may be enhanced and costs may even decrease.

The components making up MEMS include sensors, electronics, transducers and micro-structures. Micro-sensors can acquire practically any physical quantity, such as temperature, pressure, magnetic fields or radiation. Micro-electronics can range from simple circuits to powerful microprocessors. Micro-transducers change electrical quantities to physical outputs and the outputs can act on microstructures included in the MEMS. For example, a temperature sensor might detect a high temperature. The micro-electronics evaluate the process and determine that cooling liquid is required. A transducer receives a corresponding command and opens a valve, allowing cooling liquid to flow. Other possible micro-structures include micro-motors which can drive miniature pumps, micro-flaps to control gas flow and miniature mirrors to control light beams.

Wet processing equipment provides the micro-fabrication capabilities to meet some of the requirements of MEMS manufacturing. The production of electrical links, the removal of sacrificial layers and the creation of micro-structures to support components are all possible in chemical baths. For example, a sensor, microprocessor and actuator all need to be supplied with electrical power and their signals must be electrically interconnected. A metal etcher can create the necessary conductor links. A miniature mechanical actuator or a micro-motor may have to be supported and they can be placed on layers built up and etched for that purpose. Then these components, which have moving parts, must be given space for that motion. A sacrificial layer underneath the parts which move can be etched away.

While wet processing can help with MEMS fabrication, it can support this new technology in other ways as well. A key characteristic of MEMS is excellent reproducibility of performance outputs when their fabrication is accurate. Automated wet processing equipment ensures that process parameters are consistent and product variability is low. The dimensions of the resulting micro-structures are accurate enough that the resulting MEMS can maintain a high and consistent performance.

Another advantage of using wet process is production cost. The attractiveness of MEMS is high performance at low cost, and wet process equipment batch manufacturing can decrease the cost of producing MEMS compared to other fabrication options. Overall, using wet processing equipment to support MEMS manufacturing is an attractive option worth considering.

Modutek Corporation provides advanced semiconductor manufacturing and wet processing equipment and provides extensive experience in customizing equipment to meet all their customer’s requirements. If you have any questions about using Modutek’s wet processing equipment or other products or need help in choosing the right equipment for your application, email us at [email protected] or call us at 866-803-1533.

How the Silicon Nitride Etch Process Is Supported By Modutek

The silicon nitride etch process is used in the manufacture of integrated circuits to selectively remove silicon nitride with respect to silicon oxide. Engineers and process specialists in the industry who work with semiconductor equipment manufacturers owe a great deal of their expertise to the quality of the etching equipment at their disposal today.

Background

Integrated circuit fabrication processes include selectively removing silicon nitride using wet or dry etching. Selectivity between materials removed and not removed should be high. However, selectivity is not the only consideration, in a manufacturing environment a process engineer needs consistent and repeatable results from high quality and reliable equipment.

Field Oxides Provide Mask Layer

Field oxides deposit a dielectric mask layer over silicon using a patterning mask layer exposing the silicon or oxide, and growing the thick oxide called field oxide. The preferred choice of dielectric for the mask layer is silicon nitride. This process is LOCOS, Localized Oxidation of Silicon. A poly silicon layer is frequently present beneath the nitride. This is a Poly Buffered LOCOS stack. Thus, both silicon nitride and poly silicon must be removed without affecting the silicon oxide.

Aging Effects and High Particle Count

Wet etching techniques are used for stripping nitride and silicon when oxides are present. Silicon nitride is etched in phosphoric acid that is boiling. Amounts of nitric acid may be in the bath. These baths are susceptible to aging and having higher particle counts because the silicate concentration in the bath increases. Others use separate baths for nitride and poly silicon. This increases the number of baths required and can lead to pitting of the pad oxide, which engineers overcome by using a bath with phosphoric, hydrofluoric, and nitric acids. Bath life is extended by hydrofluoric and nitric acids. Nitric acid is required to oxidize silicon. The initial etching selectivity of nitride to oxide may be undesirably low, selectivities of 9:1 observed, and depends on fluorine concentration. Higher initial etch selectivities are preferred.
Before etching silicon nitride or poly silicon to silicon oxide, you should add silicon to the etch process bath. The silicon enhances initial etch selectivity. Fluorosilicates also can be used. These compounds dissolve readily in phosphoric acid without particles. The compounds increase the etch selectivities to 40:1 and 33:1 for silicon nitride and poly silicon. The additional silicon stabilizes may be in the bath from initial use until its use is terminated. Variations of this procedure are tested and reviewed by engineers and researchers.

Equipment Innovations

IC equipment suppliers provide manufacturers and researchers with leading edge products required for producing smaller geometry semiconductors, thin-film heads, and MEMS, and also need to offer service, support, and retrofitted systems. These products are usually designed to meet specific requirements of manufacturers.

Silicon Nitride Etch Baths that Provide Safety, Control and Flexibility

The Nb Series Operation Process used with Modutek’s silicon nitride etch bath guarantees process control, safety and flexibility with a two-level diagnostic system monitoring temperature while maintaining acid to water ratio through D.I. water supplementation. By using a new remote metering system, the Nb Series is easy to install and service in new or existing stations. Process engineers know that this kind of equipment needs to be manufactured and supported by a company that:

  • Has extensive experience and expertise;
  • Uses the latest technology;
  • Meets specific customer requirements;
  • Provides high quality and reliable equipment;
  • Offers excellent technical support and onsite repairs

Modutek has over 30years of experience providing high quality and reliable equipment to support the silicon nitride etch process and is a leader among semiconductor equipment manufacturers. If you need to discuss your process requirements or would like a free quote, call Modutek at 866-803-1533 or visit www.modutek.com.