In a digitally connected world, there is an ever-increasing need for more powerful, smaller, faster, and smarter devices to efficiently and seamlessly perform tasks and run processes. The ability of semiconductors to impart computing capabilities and improve the performance of electronic devices makes them the foundation of most modern technological applications and devices. The increase in demand for these devices has resulted in the rapid growth of the semiconductor industry, fostering innovation in semiconductor manufacturing technology.
What Is Semiconductor Manufacturing?
Semiconductor manufacturing involves workflows where integrated circuits (ICs) comprised of components like diodes, resistors, and transistors are created on a semiconductor wafer; the wafers are then cut into individual ICs, packaged, and integrated to manufacture the final product. A semiconductor wafer is made of pure elements, typically silicon. Depending on the application, other elements, such as germanium or materials like gallium arsenide, are also used in wafer fabrication. Wafer manufacturing is a technologically advanced process in which each step requires high precision involving specialized equipment and a clean room environment.
The Semiconductor Manufacturing Process
Step 1: Design
Fabless or independent design companies and electronic manufacturers design semiconductor chips.
Step 2: Front-end manufacturing
Also known as wafer fabrication, it is a crucial step in the semiconductor industry where all the initial stages of creating various individual components of ICs takes place. It starts with slicing a pure silicon ingot into discs/wafers, continues with polishing wafers to a flawless finish, and goes on further to the creation of intricate patterns on the wafer that forms an IC in multiple extensive and advanced steps.
Step 3: Back-end manufacturing
In back-end manufacturing, the silicon wafers undergo precise cutting to form individual dies/ semiconductor chips, followed by assembly and packaging steps. The packaged chips are tested to ensure they meet specifications for final assembly on printed circuit boards (PCB). PCB manufacturing is closely linked to the packaging step in chip fabrication as the PCBs support and connect the electronic components. The PCB manufacturing process involves steps such as etching, laminating, drilling, electroplating, screen printing, and lithography.
Step 4: End-product integration
Chips are integrated to manufacture the final end-product, like a smartphone or a computer.
Wafer manufacturing processes continuously evolve with the development of new manufacturing technologies and innovations in material sciences that cater to the advancement in downstream technological applications of semiconductor chips. Following these innovations, the whole semiconductor manufacturing ecosystem (i.e., design and fabless companies, fabs/foundries, integrated device manufacturers, and material suppliers) is involved in researching and developing the new generation of semiconductor chips.
What Are Typical Challenges in the Semiconductor Manufacturing Workflow?
Creating defect-free semiconductor chips is crucial to the smooth functioning of products and processes that are essential to everyday life, including private and public services in the global economy. The semiconductor industry strives for:
In each step of wafer fabrication, such as photolithographic patterning, etching, and doping, high precision is necessary to achieve the properties and quality desired for end products.
Manufacturing steps involve comprehensive monitoring and quality control with multiple analytical techniques to meet the required quality standards for semiconductor chips. The slightest defect in the chips can lead to productivity, yield, uptime, and revenue loss.
For example, in front-end manufacturing, the composition of cleaning and etching baths and other processing chemicals is of the utmost importance to achieving the desired wafer properties for subsequent fabrication steps.
With the new era of digitalization, the demand for electronic devices and semiconductor chips is increasing. Thus, productivity pressure on the semiconductor manufacturing industry is high.
Along with productivity in fabrication workflows, it is also important to ensure safety, especially given the use of potentially hazardous chemicals, such as strong acid mixtures for etching or cleaning solutions with peroxides in chip production.
To achieve the desired quality for every chip, there are multiple steps, processes, materials and chemicals, analyses, and users involved in semiconductor manufacturing cycles. For effective quality management and workflow traceability, having a user and data management system in place is an absolute must.
Semiconductor manufacturing requires using complex and advanced equipment involving high costs, such as lithography systems and chemical processing equipment, as well as equipment for on-site QC and monitoring. Ensuring this equipment's reliability and performance and avoiding downtime is critical for demanding semiconductor manufacturing cycles.
The semiconductor industry is water and energy-intensive. Additionally, with its rapid growth, the greenhouse gas (GHG) emissions and wastewater generated during chip manufacturing is concerning, given the extensive use of hazardous chemicals in the manufacturing process. However, in response to greener supply chain pressure, large chipmakers are ramping up to reduce their environmental impact, e.g., switching to renewable energy and recycle-reuse-reclaim processes for the water used during fabrication.
Solutions for Front-End Manufacturing
It is the first step of wafer fabrication, where a silicon ingot is cut to obtain silicon wafers. The wafers undergo several chemical and mechanical processes in foundries and fabs to achieve the needed planarity and quality. They are processed through a series of steps in wafer fabrication, such as photolithography, etching, cleaning, and doping, to create the various components of an IC. A sequence of wet processing steps, such as etching, cleaning, and polishing, involve a variety of specialty chemicals.
Quality Control of Process Chemicals, Etching, Plating, and Cleaning Baths
In wafer fabrication, electroplating, and PCB processing, it is important to frequently monitor the different plating, etching, and cleaning baths. If the concentration of the active dissolved substances (acid, base, ions) becomes lower than desired, timely replenishment is necessary.
METTLER TOLEDO offers an automated titration process, result calculations performed by automatic titrators, sample preparation steps, and an operator-independent sample series analysis. Titration Excellence solutions connected with the InMotion™ autosampler increase throughput with minimal operator intervention. Operational safety can be achieved through automatic reagent dispensing and waste disposal, therefore limiting exposure to dangerous chemicals. The automated lid handling system, CoverUp™ sample covers, simply and effectively protects operators from hazardous solvents and fumes.
The etching process aims to selectively remove the top layer on the substrate surface. A commonly used etching solution is composed of an acid mixture of hydrofluoric acid and nitric acid or a mixture of nitric, phosphoric, and acetic acid. Since the etch rate mainly relies on the concentration of free acid in the solution, regularly monitoring the acid content becomes essential. Bases like sodium hydroxide and potassium hydroxide are commonly used in alkaline cleaning or etching baths; titration is employed as a method of choice for monitoring their content in alkaline baths.
For a thorough cleaning between etching or polishing steps, mixtures of hydrogen peroxide and non-ionic surfactants are often used. To check for the effectiveness of cleaning solutions, the concentration of active ingredients like peroxide or surfactant must be determined. An optimal choice can be made for the surfactant of interest from several available methods for surfactant titration.
At-line monitoring of various parameters like base and acid contents in an electroplating bath can be automated. The DispenSix liquid handler or TV 6 sampling valve automates aspirating and dispensing samples directly from the bath; when combined with an Aliquot beaker or InMotion™ Aliquot kit, the sampling, draining, and cleaning processes can also be automated.
Quality, data security, and efficiency can be boosted by avoiding transcription errors. SmartSample™ integrates the workflow into a single interface of the Excellence Analytical Balance. The Excellence Titrator can automatically read all sample information from the beaker RFID tag when the InMotion™ Autosampler is equipped with the SmartSample kit. SmartChemicals ensure instant data transfer from titration chemicals to a titrator with a quick scan.
Preventive quality control for incoming chemicals is often necessary to avoid risks due to the manual handling of containers or impacts on quality due to external system or equipment failures. The undesirable composition of processing chemicals may lead to inferior-quality silicon wafers, equipment failures, and chemical wastage. A quick and easy check for the concentration of incoming chemicals can be done by measuring the density and refractive index.
METTLER TOLEDO offers a range of solutions for density and refractive index measurement with various automation and data management possibilities, depending on the application.
We offer portable handheld solutions and automated multiparameter solutions for refractive index and density measurements.
Fast and accurate quantitative determination of various analytes can be achieved by measuring the absorbance at a specific wavelength. UV/Vis spectrophotometers offered by METTLER TOLEDO have a robust design and a long-lasting xenon lamp, offering a full-spectrum scan in a second with no warmup time required. They fit seamlessly into an analytical workflow with a small footprint on the lab bench, modularity according to the application requirement, easy cleaning, and a OneClick user interface that allows for standalone and automated measurements. LabX™ for UV/Vis offers various data management possibilities for a secure laboratory workflow. METTLER TOLEDO offers an integrated workflow solution for XPR Analytical Balances and UV/Vis spectrophotometers through LabX, ensuring accurate and repeatable measurements and an automated workflow with guidance through each step.
Some of the applications of interest in front-end manufacturing workflows include easy determination of nitric acid concentration by measuring absorbance at 300 nm for nitrate or quantitative determination of metal ion concentration like manganese, copper, gold, etc., in electroplating solutions.
Impurities and residues resulting from improper cleaning can impact downstream processing steps in wafer fabrication and the quality of the final product. Precise in-situ monitoring of the quality of cleaning and washing bath composition can help to avoid corrective actions and costs.
METTLER TOLEDO’s ReactIR™ and ReactRaman™ probes come with a robust and portable design. One Click Analytics™ offers ease of conversion of the obtained process data. Further integration with an overarching iC software suite delivers in-depth process understanding, which can be used in R&D to further optimize the composition of washing and cleaning solutions.
Chemical-Mechanical-Polishing (CMP) Slurry Preparation and Quality Control
A CMP slurry mix contains chemicals as dispersed particles in a liquid phase. Accurate weighing of the individual components of the polishing slurry is critical to avoid damaging wafers and wafer processing equipment. PBK9/PFK9-APW platforms allow weighing up to 3000 kg, offer ease of integration in automated weighing processes, and can be set to compensate for environmental influences that could impact the weighing results. For up to 5000 kg in tank weighing applications, PowerMount™ weigh modules are ideal, as they offer high accuracy, reliability and condition monitoring to give you peace of mind that the system is performing to your expectations. To find the best-suited weighing solution for slurry processes, METTLER TOLEDO suggests the GWP® Recommendation.
During the polishing process, it is essential to monitor the percent of dispersed solids in the slurry blend at various stages to ensure the optimum degree of polishing. This can easily be achieved at high speed by using a moisture analyzer. The Halogen Moisture Analyzer HX204 comes with advanced features that offer ease of use, data and user management, and instant decision-making with customizable control limits. With the integrated method development wizard, it is very easy to develop a robust method to match the result of the reference drying oven procedure in a fraction of the time, resulting in increase in productivity.
Monitoring the pH and conductivity of the CMP slurry is extremely important to maintain a stable colloidal slurry; this can be easily achieved by selecting the right single or multiparameter benchtop pH meter or automated system with data management options and suitable accessories, sensors, and consumables.
Hydrogen Peroxide (H2O2) is a commonly used chemical oxidizer in CMP slurry blends. The efficiency of polishing depends on the oxidation process on the silicon wafer. Many techniques, such as titration, can be used to determine the concentration of H2O2 in a solution that is used to produce the slurry. Alternatively, density or refractive index measurement offers a fast, simple and safe analysis that can be easily performed with a benchtop density meter and refractometer or portable solution by METTLER TOLEDO. For cost-effective and high-quality wafer yields, the quality of a CMP slurry blend can be controlled before its use in downstream polishing applications by ensuring its density in a predefined range.
Accurate On-Line Measurement Solutions for Water Cycle Management
In a typical semiconductor fab, thousands of cubic meters of ultrapure water (UPW) are used daily in the cleaning, etching, and rinsing of wafers and substrates. Precise and reliable process analytical measurements are essential for ensuring that UPW is fit for use in chip manufacturing steps and for optimizing water usage to maximize recovery and reuse. Recognized by standards setting groups throughout the world, METTLER TOLEDO Thornton’s UPW monitoring solutions ensure the highest quality of water is being utilized for chip fabrication. Our UniCond™ sensors and 6000TOCi, 2850Si, and 2300Na analyzers can be installed in deionizing water systems to detect any changes in resistivity, TOC, silica, and sodium, with minimal operator intervention.
Wafer/Chip Weighing
Wafer weighing in fabs and QC can be challenging as the weighing stations are often close to a wet bench and in a clean room environment. Given the harsh conditions and productivity demands, the weighing solutions must be robust and provide stable measurements at a high weighing speed. METTLER TOLEDO’s XPR Analytical Balances combine a high-performance load cell with active temperature control technology and a SmartGrid weighing pan for fast and accurate weighing. The SmartPan in XPR Precision Balances provides the necessary stability to obtain weighing results up to twice as fast as a standard weighing pan.
Professional accessories, such as ErgoClips for convenient wafer weighing and easy operation, further support efficient workflows in semiconductor manufacturing operations. Connectivity and data management, such as LabX software, help ensure regulatory compliance and data traceability.
Photoresist Testing in the Lithographic Process
Photoresists are light-sensitive materials coated on the chips, which are then partially exposed to light through a patterned mask in a photolithography process to create an IC circuit. Differential Scanning Calorimetry (DSC) is a powerful tool for understanding the physicochemical behavior of the chemically amplified resists (CAR) (a photoresist material) and for optimizing the lithographic process. One single measurement with temperature-modulated DSC (TMDSC) can reveal information about thermal effects associated with the lithographic process, such as vaporization, cross-linking and the glass transition temperature of the photoresist material.
When it comes to sample preparation for DSC measurements of a few milligrams, XPR microbalances are a key asset. With XPR balances, weighing results can be transferred to the STARe software with a single click. METTLER TOLEDO offers a complete workflow solution that includes DSC instruments, balances, software, and accessories, as well as extensive application expertise in both micro-weighing and thermal analysis.
Wastewater Quality
Etching solutions and the CMP process during chip fabrication use hydrofluoric acid, leading to high fluoride concentrations in effluents from the semiconductor industry. Precipitation, flocculation, and filtration are often used to remove potential contaminants. Successful precipitation can occur only at an optimum pH range; therefore, the pH of effluent indirectly indicates if the concentration of contaminants is below a certain limit. Alternatively, a direct measurement of ion concentration using Ion Selective Electrodes (ISE), e.g., perfectION™ comb F electrode fluoride ions, can also be used to monitor the wastewater.
Solutions for Back-End Manufacturing
This is the assembly and packaging stage, where individual semiconductor chips are cut from the wafer and packaged in a case. In the next step, bonding wires connect the chip to the external circuit. The process also includes testing and final inspection of the ICs according to the standards and regulations.
Packaging and Assembly of Semiconductor Chips
In the IC packaging process, epoxies are used to set the silicon die securely into the lead frame. To gain knowledge on setting times for desirable packaging, optimize processes, and to encounter fewer failures in chip packaging, the curing kinetics of the epoxy polymers can be studied. STARe software offers an option called Model Free Kinetics (MFK) to predict the curing and vitrification behavior of an epoxy.
Wire bonding is the process of creating electrical interconnections between microchips or other integrated circuits and chip substrates using fine bonding wires and is carried out in cleanroom conditions. A standard method such as ASTM-F205 suggests measuring the diameter of the fine wire used in wire bonding by weighing. XPR microbalances are ideal for use in clean room environments, thanks to their small footprint and ergonomic two-terminal concept with flexible positioning. The high accuracy of the XPR microbalances, together with suitable accessories such as a weighing pan for tubular samples, makes it easy to weigh fine metal wires.
Precise and accurate weighing solutions can be used for a variety of other applications, such as calibrating glue dispensing machines at the packaging step or preparing samples for quantitative analytical techniques such as titration and DSC.
Software Solutions for Seamless, Traceable, and Secure Laboratory Workflows
METTLER TOLEDO’s laboratory software solutions accelerate the processing speed through electronic data collection and powerful data evaluation, aiding the automation of workflows and reducing manual administration by centralizing asset management. Enabling the connectivity of instruments allows for simple and centralized control of the interconnected equipment. Easy retrieval of the data laboratory software supports data integrity needs for internal regulations and external compliance.
LabX™ laboratory software manages your instruments, SOPs, and users. It enables productivity gain through digitalization, electronic data management, and workflow guidance to meet required regulatory standards and data integrity needs through a single software solution. LabX fully networks METTLER TOLEDO balances, titrators, pH meters, UV/Vis spectrophotometers, density- and refractometers, melting point systems, and automation solutions.
STARe Excellence Thermal Analysis Software is a powerful platform that connects METTLER TOLEDO’s thermal analysis systems and enables modularity, flexibility, and automation.
iC Software Suite for automated reactors and in-situ analyses integrates the entire experimental workflow in automated synthesis reactor and in-situ analysis, making it simple to visualize process data and interpret and report results in order to gain a real-time, interconnected picture from each experiment and help in decision making in R&D for further optimization of processes and products.
Service Offerings for Reliable Performance
METTLER TOLEDO’s professional services cover the entire lifetime of the product, starting from secure device selection, correct installation, and user training for a perfect start with initial and recurring calibration. They also include verification to ensure the performance and reliability of your equipment, support as you strive to comply with local and global norms and regulations, and preventive maintenance to help minimize risk and extend the lifetime of your equipment.
Explore and choose the right care package for your needs from a wide variety of different service offerings at the time of purchase with ExtendedCare or at a later point with BasicCare, StandardCare, and ComprehensiveCare.
With our Good Measuring Practices offering, we help you find the right instruments for your needs, providing advice and training on how to operate, calibrate, and maintain your instruments effectively.
Analytical Excellence for Semiconductor Manufacturing Brochure
For efficient, safe, and cost-effective manufacturing processes and laboratory analysis in the semiconductor industry, METTLER TOLEDO has created a brochure that gives a complete overview of our analytical competence combined with our software and service offerings.
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FAQ
How is water used in semiconductor manufacturing and what is the typical amount needed?
Water plays an important role in semiconductor manufacturing by serving as a solvent, coolant, and cleaning agent and for waste management. Ultra-pure water (UPW), which is typically produced on-site in Fabs, is used for wafer surface cleaning. Semiconductor manufacturing consumes thousands of cubic meters of UPW daily. A recent survey estimates the worldwide daily water use in the semiconductor industry to be 1.7 million cubic meters.
To achieve sustainable development in the semiconductor industry, water usage is one of the key factors to optimize given the significant freshwater consumption and wastewater generation by the industry. Strategies including water recycling, reclamation, and reuse could be crucial for future developments in the semiconductor industry.
How tightly should ultrapure water be controlled?
Wafer yield is becoming more important in the economic viability of producing ICs, and as UPW quality is a significant influencing factor on yield, tight UPW control is critical. Current linewidths are between 5 and 7 nanometers, with some manufacturers moving to 3 nanometers. This requires UPW to meet new purity recommendations.
SEMI F63 has published updated water specifications:
- Resistivity: 25 °C > 18.18 MΩ - cm
- TOC: < 1.0 ppb
- Particles / ml: < 0.3 at 0.05 μm
- Bacteria by culture: ≤ 1 / 100ml
To detect trace ppb levels of contaminants, real-time monitoring is vital to reduce product loss and prevent production interruptions.
Is it important to minimize the dissolved oxygen level of ultrapure water?
Yes. High levels of dissolved oxygen in UPW are a source of oxidation on wafers, leading to reduced wafer yield. Therefore, the various deionized water rinse steps require accurate and fast measurements to maintain ultra-low DO levels.
Reducing dissolved oxygen also helps maintain the high resistivity of the water, which is critical for subsequent treatment steps and the control of the deionization and continuous electrode deionization purification process.
What is the impact of silica in ultrapure water?
Silica that dries on the surface of integrated circuits will lead to a number of quality issues, including reduced film adhesion and contact resistance. Therefore, the discovery of out-of-spec silica levels results in product delays and lost earnings while the source of the contamination is found and remediated.
To minimize these issues, the silica level in UPW has to be continuously monitored at the proper locations and controlled at sub-ppb levels.
Can I use titration to monitor acid or base content in the electroplating process directly from the bath?
Yes, you can monitor them with METTLER TOLEDO Excellence Titrators connected to a TV6 sampling valve or a DispenSix liquid handler. The process of monitoring the acid or base concentration can be fully automated. The TV6 sampling valve or a DispenSix liquid handler automatically takes an exact sample amount from the electroplating bath and transfers it into the titration aliquoting beaker. The measuring process does not require any user attention. Furthermore, the "scheduling" functionality of LabX software allows for starting the analysis according to a schedule with planned recurrences. See an example of the application note here.
Which analytical method is recommended for determining water content in solvents used in semiconductor manufacturing?
Karl Fischer titration is a commonly used analytical method to determine the water content in a sample. The determination of water content can be done by METTLER TOLEDO Karl Fischer (KF) titrator. We have developed many application notes for water determination in solvents.
How can METTLER TOLEDO’s XPR Analytical Balances support your titration workflows?
To complete the solution, METTLER TOLEDO’s XPR Analytical Balances offer a titration method that allows wireless titration weighing technology. Thanks to RFID technology, the SmartSample™ solution provides a seamless interaction between a Titration Excellence titrator and an Excellence analytical balance. Automated data transfer prevents errors and saves valuable time.
How can the stability and purity of processing chemicals and materials in semiconductor manufacturing be determined using UV/Vis spectrophotometry?
UV/Vis spectrophotometry can be used in semiconductor manufacturing processes in several ways:
Stability/ degradation/ shelf-life determination: By measuring the absorbance of a solution at specific wavelengths, it is possible to determine the stability of the solution. If the absorbance changes significantly over time, this may indicate that the solution is unstable and will eventually degrade. This information can then be used to determine the best storage conditions for the solution and ensure that it remains stable for the longest possible period.
Impurity identification: UV/Vis spectrophotometry can be used to identify specific impurities by comparing the absorbance spectra of a sample to that of a reference material. It is possible to identify specific impurities based on the differences in absorbance between the two substances. Alternatively, by measuring the absorbance of a series of reference materials with known impurity concentrations, a calibration curve can be generated. This curve can then be used to determine the concentration of impurities in the semiconductor material based on its absorbance. Overall, UV/Vis spectrophotometry provides valuable information about the concentration of impurities in processing chemicals/materials, which can be used to control and optimize the quality of the final products.