May 23, 2024May 24, 2024 Jenny Adams Case Studies

HMDS Bake Plate

Amplifying Adhesion: HMDS Bake

Our client faced persistent issues with photoresist delamination during the photolithography process. To address this, we implemented a solution involving Hexamethyldisilazane (HMDS) priming using the Apogee® 200mm Bake Plate. This enhanced photoresist adhesion, improved yield, reduced defects, and lowered costs, ultimately streamlining project timelines. Additionally, a 75° contact angle was achieved within a 90-second process, showcasing the success of the solution.

Introduction

Facing challenges with inconsistent adhesion of photoresist in the photolithography process, the client encountered persistent issues with photoresist delamination. Initial process optimizations included surface preparation, testing different photoresists, and modifying process parameters, with no positive outcomes. As a consequence, they continued to experience reduced throughput, increased expenses, rework, and delayed project timelines. In order to establish a durable bond between the substrate and the photoresist, the wafer surface was prepped with HMDS before the coating.

Approach

A review of the client’s existing process included an analysis of the following potential causes:

Surface Contamination
Inadequate Surface Activation
Surface Roughness
Incompatible Materials
Insufficient Bake
Improper Spin Coating
Contaminated Photoresist
Substrate Temperature
Chemical Incompatibility
Aging of Photoresist

The root cause of the poor adhesion was identified as inadequate bonding of the photoresist due to absorbed water in the silicon wafer from ambient humidity. A simple dehydration bake was inadequate to resolve the issue. The use of hexamethyldisilazane (HMDS) chemical vapor deposition (CVD) was proposed for use before the application of photoresist.

Solution

HMDS priming enhances the substrate surface for photoresist adhesion through the formation of a hydrophobic monolayer, reducing surface energy to ensure uniform coating. This layer also prevents air entrapment, enhancing photoresist wetting and minimizes defects during photolithography.

The Apogee® 200mm Bake Plate served as the ideal foundation to accommodate the client’s substrate sizes. The standard bake process model was modified to include the following and then installed into the X-Pro II Workstation:

• vacuum chamber hood with an HMDS inlet
• pressure can with HMDS bubbler for vaporization
• control box with specialized valves
• recipe-controlled process parameters via Datastream™ software

Operational Flow:
1. Set the bake plate to the desired temperature.
2. Initiate vacuum inside the chamber to commence the initial dehydration bake.
3. Nitrogen pre-purge to eliminate oxygen from the chamber.
4. Introduce HMDS vapor to the chamber, promoting the formation of a monolayer on the wafer.
5. Apply vacuum to the wafer to bake off residual HMDS and displace remaining water molecules.
6. Nitrogen post-purge, ensuring complete removal of HMDS from the chamber.

Result

A contact angle measurement provides important insight into the HMDS process. For photoresist coating, a measurement between 60-90 degrees is typically desired for proper wetting and adhesion. Unfortunately, a standard silicon wafer is measured at only ~40 degrees. The application of HMDS, brings the contact angle into the acceptable range.

With this implementation, the customer was able to demonstrate a 75 degree contact angle which led to a marked improvement in:

• Photoresist Adhesion
• Throughput (90 second process)
• Minimized Defects
• Decreased Rework
• Yield

Project timelines were reduced, promoting efficiency and a reduction in costs.

Technical Details

Substrate Sizes

pieces

2″

3″

100mm

150mm

200mm

Technical Details

Vacuum Chamber: >24 inHg vacuum

HMDS canister with tube-controlled bubbler from 0-10 lpm

Rotameter-controlled pre/post inert (N2) gas purge, controlled from 0-5 lpm

Temperature range up to 180°C

Recipe controlled via Datastream™ software

Materials

hexamethyldisilazane

silicon & silicon oxide wafers

May 23, 2024May 24, 2024 Jenny Adams Case Studies

UV Cure Spin Coater

A leading nanophotonics and nano-optic security company partnered with Cee® to develop a custom UV cure spin coater. The tool integrates UV curing with spin coating, preventing oxidation and ensuring consistent, high-quality production of nanostructured materials.

Introduction

In the highly specialized field of nanophotonics and nano-optic features, precision and process control are critical. A company known for its expertise in high-volume nanoimprint lithography, needed a custom spin coater that integrated UV curing to streamline their production process and protect materials from oxidation.

Key Requirements:
Integrating a 365nm LED exposure lid with up to 18mw/cm^2 UV power
Real-time optical power measurement and control
Five automated dispense nozzles
Accommodating 150mm x 150mm square substrates
Providing an N2 purge for an inert environment to prevent oxidation

Approach

Cee® leveraged the existing Apogee® 200mm spin coater design, modifying it to incorporate a custom UV cure lid and other features to meet the client’s specifications.

Key challenges included determining the exact UV exposure dose required for the client’s proprietary process and ensuring the UV light uniformly covered the substrate without being obstructed by the dispense nozzles.

Planned modifications included a new lid design to house the UV LEDs, an integrated optical sensor for real-time power measurement, and an enhanced dispense system, all controlled by Datastream™ software.

Solution

The final product maintained the compact footprint of the Apogee® Spin Coater but featured a highly customized lid to house the UV LED system. The durable, chemically compatible design and fully programmable operation ensured the highest standard of performance.

Central features included a highly specialized lid equipped with a 365nm LED array for UV curing, automated dispense nozzles, and an N2 purge system. The N2 purge feature ensured the material was protected from oxygen exposure during the spin coating process, effectively preventing oxidation. The UV LED array enabled curing of the film directly on the coated substrate, eliminating the need for removal from the spin coater. The automated dispense system provided precise, recipe-driven, control of the dispense materials. The integrated optical sensor provided real-time feedback and control, while the modified Datastream™ software enabled precise recipe management.

Result

Since its implementation, the custom UV cure spin coater has transformed the client’s conceptual design into a practical, production-ready tool. The system streamlined the client’s process, resulting in fewer wafer defects and more consistent results. The ability to perform the entire coating and curing process within a single machine eliminated the need to transfer wafers between tools, enhancing efficiency and product quality.

Technical Details

Substrate Sizes

150mm x 150mm square substrates

Materials

Proprietary UV-curable nanomaterials requiring an inert environment to prevent oxidation

May 22, 2024May 24, 2024 Jenny Adams Case Studies

Large Format Spin Coater

In the realm of genetic engineering, diagnostic nanomaterials, and high-precision diagnostic equipment, precision and uniformity are paramount. When a leading company in this industry required a specialized spin coater to apply thin, uniform coatings of functionalized nanomaterials onto substrates, they turned to Cee®. This case study highlights the collaboration between Cee® and the client to design and deliver a custom spin coater tailored to their unique needs.

Introduction

Operating at the forefront of genetic engineering, antigen/antibody production, and in-vitro diagnostic equipment, our client specializes in developing cutting-edge solutions for diagnostics and medical research. Their requirements for precise coatings of functionalized nanomaterials and surface functionalization to enhance diagnostic assays necessitated a custom spin coater solution.

Key Requirements:
Accommodates substrates from 125-300mm round; 400mm x 400mm square.
Automated dispense of material
Programmable control of exhaust parameters with nitrogen purge
High-speed programmability up to 6,000 RPM
Precise speed control and stability during the spin cycle
Back-side rinse
Edge Bead Removal
Programmable control of exhaust parameters
Chemically compatible with SPR-3612 and Anisole.

Approach

To meet the client’s stringent requirements, Cee® leveraged the already robust design of the Apogee® 450 Spin Coater while introducing modifications tailored to the unique demands of the project. A custom spindle drive system was engineered to handle the larger, heavier substrates, ensuring precise control over spin speed and torque while a series of custom spin chucks were designed to accommodate the dimensions of various substrates.

Solution

The resulting spin coater seamlessly integrates into the client’s workflow, featuring a custom engineered, heavy-duty, high torque drive system. Additionally, an automated dispense system ensures precise recipe-driven dispensing capabilities.

Result

Since its implementation, this custom spin coater has continued to meet the client’s exacting standards for precision and uniformity in nanomaterial coatings. Client satisfaction is evident through their repeat orders for additional units as their operations continue to scale. While specific performance metrics are proprietary, the client’s continued partnership underscores the success of the custom spin coater in enhancing their diagnostic capabilities.

Technical Details

Substrate Sizes

400mm x 400mm square

125mm

150mm

200mm

300mm

Materials

Isopropanol Alcohol (IPA)

SPR-3612

Anisole

April 2, 2024April 17, 2024 Jenny Adams Spin

The Art of Manual Dispense

While automated solutions offer convenience and consistency, manual dispense for spin coating remains an invaluable technique, providing precise control and unmatched flexibility. In this article, we’ll discuss the benefits of manual dispensing for spin-coating semiconductor substrates, offering insights, tips, and best practices for this approach.

Spin Coating Basics

Spin coating is a widely used technique in semiconductor fabrication. The process involves dispensing a liquid material onto a substrate, typically a flat surface such as a silicon wafer. The substrate is then rotated, causing centrifugal force to spread the liquid evenly across its surface. As the rotation continues, the solvent evaporates, leaving behind a thin, uniform film of the desired material. The speed of rotation, viscosity of the solution, and duration of spinning all play crucial roles in determining the thickness and quality of the resulting film.

The Advantages of Manual Dispense

Automated dispense is crucial in spin coating for its efficiency, precision, and scalability. By automating the dispense process, manufacturers can achieve consistent and uniform coatings across large batches of substrates, reducing variability and improving product quality. While automated dispense systems offer efficiency and consistency, manual dispense allows operators to exert granular control over the deposition process, making it invaluable for research and development purposes, small-scale production runs, or when dealing with delicate substrates that require special attention. Manual dispense grants operators a significant degree of flexibility and real-time control. This flexibility enables on-the-fly adjustments to parameters such as solution viscosity, and dispensing rate, facilitating precise fine-tuning to achieve optimal coating results. Additionally, manual dispense is a cost-effective solution, particularly for organizations operating under budget constraints or working with specialized substrates. This versatility makes it an ideal choice for experimental setups, custom applications, or research involving novel materials. With manual dispense, operators can tailor the process to specific requirements, ensuring consistent and high-quality results.

Best Practices for Optimal Results

Material Preparation
Before initiating the manual dispense process, it’s essential to prepare the solution meticulously. Ensure proper solvent mixing, filtration to remove impurities, and degassing to eliminate air bubbles, which can adversely affect film uniformity.

Substrate Cleaning and Preparation
Thorough cleaning and preparation of the substrate surface are paramount to achieve uniform coating. Utilize appropriate cleaning techniques such as solvent rinsing, plasma treatment, or UV ozone exposure to remove contaminants and enhance adhesion.

Dispensing Technique
When manually dispensing the solution onto the spinning substrate, maintain a consistent and controlled flow rate to achieve uniform coverage. The Cee® integrated dispense hub ensures consistent dispensing at the wafer center.

Dispense Volume
It’s important to note, that dispensing too much or too little material may lead to less than desirable results. Too little may result in uncoated areas, while dispensing too much material may result in waste and backside contamination of the substrate. In general, a good starting dispense volume is approximately one milliliter per diameter inch of the wafer. For more details on process troubleshooting, refer to our article on Spin Coat Theory.

Spin Coating Parameters
Fine-tune spin coating parameters such as rotation speed, acceleration, and duration according to the specific requirements of the material being deposited and the desired film thickness. Experimentation may be necessary to determine the optimal settings for each application.

Practice Precision
Precision is key when performing manual dispense for spin coating. Take your time to master the technique and strive for consistency in every step of the process.

Regular Maintenance
Ensure that the spin coater and dispensing equipment are well-maintained to prevent malfunctions or irregularities that could compromise coating quality. It is extremely important to ensure a smooth, clean, and unobstructed dispense tip. Regular calibration and cleaning are essential for reliable performance.

Document and Analyze
Keep detailed records of process parameters, coating results, and any observed deviations. Analysis of this data can provide valuable insights for process optimization and troubleshooting.

Conclusion

Manual dispense for spin-coating semiconductor substrates offers a blend of precision, control, and versatility that makes it a useful tool in semiconductor manufacturing. By understanding the fundamentals, adhering to best practices, and leveraging the advantages of manual dispense, operators will achieve consistent and high-quality thin film coatings, driving innovation and advancement in the field of semiconductor technology.

Did you know?

Discover the best of both worlds with Cee®! While our Apogee® line offers automated dispense options, operators retain manual dispense capabilities for ultimate control and versatility. Want to elevate your spin coating experience? Talk with our sales team today!

Jenny Adams October 3, 2023

Bonding and Debonding Indium Phosphide Wafers

Bonding_Debonding

cee March 20, 2023

Developer Configurations

Develop

cee March 21, 2023

Bake Plate Process Theory

Bake

March 18, 2024October 21, 2024 Jenny Adams Bake, Spin

NRTL! What is it good for?

NRTL certification is becoming crucial for semiconductor equipment manufacturers as it ensures compliance with safety standards set by regulatory bodies like OSHA and ANSI. It also facilitates market access, instills customer confidence, provides liability protection, and encourages continuous improvement in safety and quality practices. For custom equipment, additional evaluations may be required. In years to come, NRTL certification will become essential for ensuring safety and reliability in the semiconductor industry.

What is NRTL?

In the realm of semiconductor equipment manufacturing, precision, reliability, and safety are paramount. The semiconductor industry operates in an environment where even the slightest deviation from standards can have far-reaching consequences. One critical aspect of ensuring safety in this industry is obtaining NRTL certification. In this blog post, we’ll delve into what NRTL is, its significance, and why it’s crucial for semiconductor equipment manufacturers.

NRTL, which stands for Nationally Recognized Testing Laboratory, is a designation granted by the Occupational Safety and Health Administration (OSHA) in the United States to organizations meeting specific qualifications for testing and certifying products. These independent organizations have demonstrated proficiency in evaluating products for compliance with established safety standards. Once a product and its manufacturer pass all required tests, the manufacturer receives Authorization to Mark (ATM). This allows them to affix the designated NRTL label to the product. Subsequently, the product is subject to strict control, prohibiting the substitution of unauthorized components or any variance in construction.

Importance of NRTL Certification in Semiconductor Equipment Manufacturing:

Compliance with Safety Standards

NRTL certification ensures that semiconductor equipment meets rigorous safety standards set by regulatory bodies such OSHA, the American National Standards Institute (ANSI), and UL. This includes standards for electrical safety, fire resistance, mechanical integrity, and other critical safety parameters. Compliance with these standards not only ensures the safety of workers but also minimizes the risk of equipment malfunction or accidents in semiconductor manufacturing facilities.

Market Access

Many countries around the world recognize NRTL certification as a benchmark for product safety. This opens doors to global markets, enabling manufacturers to expand their reach and compete more effectively on a global scale.

Customer Confidence

NRTL certification serves as a hallmark of safety for semiconductor equipment. Customers, including semiconductor manufacturers and facilities utilizing semiconductor processes, prioritize products certified by reputable testing laboratories for their safety assurance. It cultivates trust between manufacturers and customers, ensuring the equipment’s safety in operation.

Liability Protection

Obtaining NRTL certification can also offer liability protection for semiconductor equipment manufacturers. In the event of an accident or malfunction, having certified equipment demonstrates that the manufacturer took necessary precautions to ensure safety and compliance with standards. This may help mitigate legal risks and potential liabilities associated with product-related incidents.

Continuous Improvement

NRTL certification is not a one-time achievement; it requires ongoing adherence to standards and periodic audits by the certifying body. This encourages semiconductor equipment manufacturers to maintain a culture of continuous improvement in safety and quality practices. By staying up to date with evolving standards and best practices, manufacturers can enhance the safety, performance, and reliability of their products over time.

Custom Equipment Considerations:

While standardized equipment may undergo a streamlined certification process, custom equipment introduces variability that may necessitate additional evaluations. Manufacturers developing custom solutions should be aware that deviations from standard designs could impact safety and regulatory compliance. In such cases, obtaining Limited Production Certification or undergoing supplementary evaluations becomes imperative to validate the safety of custom equipment. As a best practice, manufacturers should be familiar with, and integrate these standards into their equipment design practices.

Conclusion:

In the dynamic and high-stakes environment of semiconductor equipment manufacturing, NRTL certification will become crucial for prioritizing safety and adherence to industry standards. Through collaboration with accredited testing laboratories and obtaining NRTL certification, semiconductor equipment manufacturers showcase their dedication to safety standards. In an industry where safety is paramount, NRTL certification serves as a key assurance for manufacturers, customers, and stakeholders alike.

Did You Know?

Beginning in November 2024, standard Cee® X-Pro II Workstations will feature the TÜV SÜD NRTL mark, showcasing our compliance with applicable US and Canadian safety standards. This latest development follows our recent authorizations to apply the TÜV SÜD NRTL mark to all standard Cee® Apogee Bake Plates and the Intertek cETLus mark to all standard Cee® Apogee® Spin Coater and Developer models. These certifications underscore our proactive stance and unwavering commitment to safety across our entire product range. As Cee® continues to pursue NRTL listing for all standard products, we remain dedicated to consistently exceeding expectations in providing top-tier semiconductor processing equipment to our esteemed customers.

January 3, 2024May 24, 2024 Jenny Adams Case Studies

Mini-Spin Coater

A photovoltaic research institute required a compact spin coater to integrate with a robotic work cell. Cee® created a custom coater with a 120mm Teflon™ bowl, a mechanized lid, and auto-dispense functionality. This solution met the institute’s high-speed control needs, chemical compatibility, and space constraints. In production, the coater exceeded expectations, delivering safety and seamless communication with robotic handlers.

Introduction

The client, a photovoltaic research institute, required a compact spin coater optimized for 40mm x 40mm square substrates for solar applications. This system was required to integrate into their robotic work cell for automated wafer handling.

Key Requirements:
Compact size to fit into existing robotic work cells
Automated control interface for robotic synchronization
Vacuum chuck capable of operating with their end effector
Mechanized cover for robotic access
Automated dispense of materials
Programmable control of exhaust parameters with nitrogen purge
High-speed programmability up to 12,000 RPM
Precise speed control and stability during the spin cycle

Approach

The customer had a pre-defined process flow requiring a specialized cluster of tools. Additionally, the chemistry used in these processes raised operator safety and material compatibility concerns.

Readily available, turn-key, automated systems were inadequate to meet the customer’s functionality, integration, and budgetary needs.

Exceptionally corrosive materials were not compatible with standard spin bowl construction materials such as HDPE or stainless steel. Work cell size constraints were incompatible with the standard 8″ Apogee® spin bowl and a mechanized spin lid was required to facilitate robotic interaction. In close collaboration, with the client and their chosen robotic integrator, a custom spin coater was designed.

Solution

To accommodate the client’s process needs, Cee® delivered a compact mini-spin coater with a 120mm teflon spin bowl, featuring an automated lid with auto dispense and nitrogen blow-off capabilities. The coater included nitrogen purge for operator safety and full recipe control of lid movement, dispense, exhaust, spin speed, auto-chuck homing, and communication protocols.

The custom spin chuck was designed to accommodate end-effector access allowing ample room for the robot to place and remove substrates.

Sample Process:
1. Command: Open lid
2. Wafer loaded by robot
3. Command to Datastream™ GUI: Start recipe
4. Spin coater recipe is executed
5. Recipe Complete
6. Command: Open Lid
7. Wafer removed by robot

Result

In production, the spin coater performed exceptionally well and met or exceeded expectations by delivering on the following key requirements:

• robotic handler integration
• seamless communication
• chemical compatibility
• operator safety requirements
• honors space constraints
• automates essential process parameters

Technical Details

Substrate Sizes

40mm x 40mm x 2mm

Materials

Chlorobenzene
DMF
DMSO
IPA
Acetonitrile
Ethyl acetate
Toluene
CBZ
Chloroform

November 13, 2023November 14, 2023 Jenny Adams Bonding_Debonding

Beyond the Bond: Semiconductor Debonding Practices

Debonding is a vital step in advanced semiconductor manufacturing and 3D Packaging that involves separation of the device wafer from its carrier. This article includes an overview of a variety of debonding methods, including Laser, Thermal, Chemical, and Mechanical Debonding along with crucial factors for success.

The Vital Role of Debonding in Semiconductor Manufacturing

Before advanced manufacturing processes can take place, semiconductor wafers are temporarily bonded to carrier substrates. This temporary bond provides mechanical stability during processes like thinning, layer deposition, and device integration. Temporary bonding safeguards the delicate semiconductor components from damage, ensuring their integrity throughout the manufacturing process.

Debonding involves carefully detaching the device wafer from its temporary carrier substrate once the desired processes have been completed. This delicate procedure requires precision and finesse, and significantly impacts the quality, performance, and viability of the final device. Through precise debonding practices, manufacturers can fine-tune wafer properties, such as thickness, stress distribution, and material composition thereby optimizing electronic functionality.

Crucial Factors for Successful Debonding

For successful debonding, several factors must be considered:

Adhesive Material Selection: Choosing the appropriate adhesive material is essential. The adhesive’s properties, such as its strength, compatibility with the debonding method, and thermal and material tolerance impact the success of the debonding process.

Process Control and Parameters: Maintaining precise control over process parameters like temperature, pressure, and force is critical. Deviations from optimal conditions can lead to inconsistent or undesirable debonding outcomes.

Surface Preparation: Properly preparing the substrate surface is vital for achieving optimal adhesion and subsequent successful debonding. Adequate cleaning, surface treatment, and roughness can impact the bonding strength and efficiency of the debonding process.

Carrier Design: The design of the temporary carrier substrate affects the ease of debonding. An optimized carrier design can minimize stress concentrations and ensure uniform force distribution during the debonding process. Matching the carrier’s coefficient of thermal expansion to that of the device wafer helps prevent issues like wafer warpage and breakage post-debonding.

Compatibility with Substrate Material: Consider the compatibility of the debonding method with the properties of the substrate material, such as its thermal sensitivity, brittleness, and anisotropic behavior. Certain debonding methods may be better suited for specific materials.

Quality Control and Inspection: Regular monitoring and inspections throughout the debonding process help identify potential issues early on. This practice minimizes waste and ensures consistent, high-quality results.

Post-Debonding Processes: Account for any subsequent processes the substrate will undergo after debonding, such as cleaning, further material deposition, or device integration. Compatibility with these steps is crucial for the overall success of the manufacturing process.

Techniques for Debonding Semiconductor Substrates

Laser Debonding

Laser debonding employs high-energy lasers to selectively heat the adhesive interface, facilitating the separation of the wafer and carrier. This method offers precise control, minimizing wafer stress and ensuring a smooth detachment process. While laser debonding is adaptable, it doesn’t suit every scenario. Consider substantial equipment costs, challenges with materials that share similar thermal coefficients, and the potential for contamination from vaporized materials.

Thermal Debonding

Thermal debonding relies on controlled heating to weaken the adhesive bond between the wafer and the carrier. This technique is well-regarded for its broad compatibility with various materials and efficiency in high-volume production scenarios. The controlled application of heat helps mitigate the risk of thermal damage to the wafer, preserving its structural integrity. Precise platen leveling is vital to prevent wafer stress, while accurate temperature control is crucial to avoid thermal damage. It’s noteworthy that the adhesives employed in thermal debonding are constrained to lower process temperatures when compared to alternative methods.

Mechanical or ‘Peel’ Debonding

Mechanical debonding relies on mechanical forces to separate the wafer from the carrier. This straightforward technique minimizes the risk of wafer damage when executed precisely. Also known as ‘peel’ debonding, the method employs mechanical forces to separate device wafers from carriers. It offers advantages such as simplicity, low risk of wafer damage, room temperature operation, and suitability for specific applications. However, anisotropic properties of the wafer (if applicable) should be considered, and careful application of force is extremely important.

Chemical Debonding

Chemical debonding employs specialized solvents to dissolve the adhesive layer, simplifying the substrate detachment process. Its ability to adapt to different materials makes it a versatile choice for various applications. Drawbacks include the necessity for chemical handling precautions, potential environmental repercussions, operator safety concerns, the need for specialized solvents, and the required use of perforated wafers. This debonding method is notably the most time-consuming.

Conclusion

Debonding device wafers holds immense significance in the multifaceted world of semiconductor manufacturing. Through laser, thermal, chemical, and mechanical debonding techniques, manufacturers achieve exceptional wafer quality and superior electronic performance. Furthermore, recognizing the critical factors for successful debonding ensures consistent and efficient outcomes. As the semiconductor landscape continues to evolve, debonding techniques will continue to drive progress, ushering in a new era of groundbreaking electronic advancements.

October 11, 2023October 11, 2023 Jenny Adams Uncategorized

Bond_Debond

Bond / Debond

Blog Navigation

Bonding_Debonding

Beyond the Bond: Semiconductor Debonding Practices

November 13, 2023

Bonding_Debonding

Bonding and Debonding Indium Phosphide Wafers

October 3, 2023

Bonding_Debonding

Wafer Bonding Theory

August 8, 2023

October 3, 2023October 3, 2023 Jenny Adams Bonding_Debonding

Bonding and Debonding Indium Phosphide Wafers

Indium phosphide (InP) wafers present challenges in bonding/debonding due to thermal mismatch, surface damage risks, and material compatibility issues. Cee® provides precision wafer handling tools with customized process controls designed to tackle the challenges presented by InP wafers. Experience reliable wafer handling and fully utilize the exceptional properties of InP for advanced electronics/photonics.

Introduction

Indium Phosphide (InP) wafers are prized for their exceptional electronic and optical properties, making them a cornerstone of cutting-edge semiconductor and photonic technologies.

Working with InP wafers presents unique challenges during bonding and debonding processes stemming from the material’s delicate nature and susceptibility to thermal stress. In this post, we’ll discuss the complexities of bonding and debonding InP wafers and how our state-of-the-art equipment mitigates these obstacles.

Obstacles in InP Wafer Bonding and Debonding

The bonding and debonding of InP wafers presents several key difficulties:

Thermal Mismatch – InP has a high coefficient of thermal expansion that differs significantly from common substrate materials like silicon or sapphire. Directly bonding InP to these materials with mismatched coefficients can lead to tremendous thermal stress. This stress can cause the wafer to warp, delaminate, or cleave during processing. It can also propagate through to fabricated devices, causing early failure. Careful and uniform thermal management is essential.
Material Compatibility – Not all adhesives are suitable for direct bonding to InP. Some may chemically interact with InP, etching the surface or leaving residues that contaminate devices. Strict selection of inert, non-reactive bonding materials is essential to avoid damage.
Surface Damage – The brittle nature of InP leads to significant debonding process risks that can damage the wafer. Examples of defects include microcracks, particulates, or other defects. Even minor damage can significantly hamper the performance and yield of devices fabricated on the wafer.
Bond Strength and Uniformity – Localized weak points can result from poor bond uniformity and strength which causes unwanted stress across the wafer. This often results in microcracks during wafer thinning leading to distortion, delamination, and premature device failure. Carefully optimized bonding processes are needed to ensure uniformly robust bonds.
Debonding Stressors – Careful control of debond process parameters such as temperature uniformity, force application, and handling is critical due to the fragile nature of thinned InP.
Adhesive Removal – Following debond both the carrier and device wafer must be cleaned, removing any residual adhesives from the delicate substrate. This is challenging, as any remaining adhesive or chemical damage during removal will degrade performance.

Meeting the Challenge Head On

At Cee®, we understand the complexities and challenges of using InP in bonding and debonding. Our advanced equipment has been meticulously designed and engineered to process fragile thinned wafers with precision and care. How do we accomplish this?

Tailored Process Control – Recipe-driven processes offer exceptional control during bonding, debonding, and cleaning.

Material Compatibility – Our equipment is compatible with a wide range of bonding materials that are carefully selected for their compatibility with InP, ensuring reliable bonds without compromising device performance.

Uniform Bonding – We specialize in achieving uniform and strong bonds across entire wafers. Our equipment’s precision engineering guarantees consistent quality, preventing stress-related issues.

Gentle Debonding – When it’s time to debond, our equipment ensures a controlled and gentle process, minimizing the risk of surface damage.

Handling – Specially engineered vacuum and handling solutions safeguard sensitive substrates through all steps of the bond, debond, and clean processes.

Cleaning – Baths are risky for fragile substrates such as InP. Gentle spray cleaning is efficient and safe, reducing time and the risk of breakage during the removal of residual adhesive material.

Application Support – With 35+ years of experience, our team has a high-degree of familiarity with process optimizations and support for a broad range of substrate materials and temporary adhesives.

Customized Solutions – We understand that every application is unique. Our equipment can be tailored to meet your specific bonding and debonding requirements, ensuring optimal results for your InP wafers.

InP Wafer Bond/Debond Process Data

Following spin coat and bake processing on the Apogee® suite of tools, device substrate pairs 1-5 were bonded in the order shown using the bonding process below. All substrate pairs were successfully bonded with less than 5% bonded pair Total Thickness Variation (TTV) using the recipe shown below.

Apogee Bonder Recipe
Temperature: 130° C Force: 2000 N Time: 180 sec
Evacuate Chamber To: 0.5 kPA Pre-bond Delay: 15 sec

Device (100mm Indium Phosphide)	Carrier (150mm Sapphire)
Sample 1	112
Sample 2	213
Sample 3	391
Sample 4	366
Sample 5	402

The wafers were sent out to be thinned to 100µm. All 5 wafers were subsequently debonded without incident. Below are the 1300CSX recipe parameters.

Wafer Size: 100mm on 150mm Upper and Lower Platen Temp: 190°C

Lift Pin Descent: 60sec Lower Platen Stabilization: 15sec Force: 4lbs

Maximum Velocity: 2mm/s Press Up Stabilization: 30sec

Average Process Time per Wafer: 6min 8sec

Following debond, the device wafers were released onto custom handling devices. Both the device and carrier wafers were then cleaned on the Apogee® Spin Developer without issue.

*Process optimization is expected to reduce process time by as much as 20%.

Unlocking the Potential of InP

As InP continues to drive innovation in electronics and photonics, addressing the challenges of bonding and debonding is paramount. With our specialized equipment, you can overcome these challenges with ease, confident that your delicate InP wafers will be handled with the precision and care they deserve.

At Cee®, we’re dedicated to empowering your research and manufacturing processes. Our equipment not only streamlines the intricate world of InP bonding and debonding but also unlocks the full potential of this remarkable material for your applications.

Want to learn more? Contact our sales team today!

August 8, 2023August 22, 2023 cee Bonding_Debonding

Wafer Bonding Theory

Wafer bonding is crucial for compact and powerful devices. It involves coating a full thickness wafer with adhesive, bonding it to a support carrier wafer, and thinning it for downstream processes. Key factors impacting bonding quality include flatness (TTV), alignment, voids, temperature control, CTE match, and bonding force. Addressing these factors ensures uniform bonding, precise processing, and high device yield, leading to reliable and high-quality semiconductor devices.

Wafer Bonding Overview

Over the past years, temporary substrate bonding gained popularity alongside the demand for smaller, more powerful devices. Thin substrates (<100µm) pose challenges in handling, but a temporary wafer bonder solves this, reducing breakage risks.

In the bonding process, a full thickness wafer with devices is coated with a temporary adhesive to withstand downstream stresses. It’s bonded to a support carrier wafer. After thinning and backside processing (e.g., TSV, metal-plating), the stack undergoes debonding, cleaning, dicing, and packaging.

Bonding Process Description

*This process description pertains to the Cee® Apogee® Bonder. While the processes of other manufacturers may vary slightly, the basic principles remain consistent throughout the industry.

After referring to the adhesive material manufacturer’s specifications, the bonder platens are heated to the temperature required for the bonding adhesive. This temperature is chosen based on the point that the material liquifies in order to maximize adhesion.

The device wafer is loaded onto the lower platen and centered using the built-in alignment fixtures. The carrier wafer is then placed and aligned on top of the device wafer. The mechanical alignment fixtures keep the carrier and device wafers separated at loading.

While the two wafers are held, the bonding chamber closes and vacuum is applied, evacuating air from the bonding chamber. Programmable piston force “squeezes” the wafers together for a specified period of time, planarizing the bonding adhesive and ensuring full wafer coverage.

Once complete, the chamber opens and the bonded wafer pair is removed and placed on a cooling plate. This allows the wafer stack to cool, setting the adhesive for maximum bond strength. The bonded wafer pair is then ready for the next downstream process step.

Bonding Factors

In the realm of wafer bonding, various critical factors profoundly impact quality. During the early days of Moore’s law, these parameters held less significance. However, with shrinking feature sizes and sub-100 micron thicknesses, and the growing number of devices per wafer, addressing these challenges has become crucial. Any alteration in these five parameters can significantly influence repeatability and throughput.

Flatness (TTV)

A high total thickness variation (TTV) can result in poor bonding uniformity, causing voids or incomplete bonding between the wafers. These voids can create weak spots in the bond interface, affecting the overall structural integrity and performance of the bonded device. Later, when the device is ground thin, non-uniformity, or in severe cases, grinding through the wafer can impact depth and conductivity leading to device yield loss and affecting the depth of focus for photolithography.

Alignment of Device Wafer to Carrier

The alignment of the device wafer to the carrier is of utmost importance in semiconductor manufacturing. It ensures uniform bonding, precise processing, and high device yield for downstream processes such as patterning, handling fixtures, and feature placement. Accurate alignment enhances overlay accuracy, eliminates edge issues, and optimizes throughput efficiency.

Voids

Voids in wafer bonding present significant challenges. They cause total thickness variation issues (see Flatness (TTV) above), impacting the uniformity of the bonded layers and potentially leading to breakage or de-lamination. Additionally, voids can trap and expand air during high-temperature processes or debonding, increasing the risk of structural damage or device failure. To ensure the integrity and reliability of the bonded wafers, avoiding voids is crucial, and precise control of the bonding process is essential to mitigate these problems effectively.

Temperature

Precise temperature control is crucial for successful wafer bonding. It ensures uniform adhesive reflow, preventing TTV and material distortions. With accurate control, adhesion issues are minimized, guaranteeing reliability and repeatability. By using dual platens for heating and carefully monitoring material bonding temperature, optimal results are achieved without compromising material integrity.

Coefficient of Thermal Expansion (CTE) Match

A good CTE match reduces stress and strain during temperature variations, preventing delamination and cracking in the bonded layers. This alignment guarantees the stability and reliability of the bonded structure, vital for the performance and longevity of the semiconductor devices. Without a proper CTE match, the wafer bonding may result in defects and compromised device functionality, making it a critical consideration to achieve high-quality and durable wafer bonds.

Bonding Force

Bonding force determines the strength and integrity of the bond between two wafers or substrates. Optimal bonding force ensures that the wafers are firmly and uniformly pressed together, leading to a robust and reliable bond interface. Low bonding force can result in weak bonding and delamination, while excessive force can damage the wafers or lead to undesirable stress in the bonded layers. Achieving the right bonding force is essential for high-quality semiconductor devices, as it directly impacts their performance, yield, and overall reliability.

The Cee® Apogee® Bonder

Tailored for semiconductor production, the Apogee® Bonder is ideal for permanent and temporary adhesive bonding and accommodates a wide range of debonding materials such as peel, thermal slide, laser lift-off, and chemical release. It prioritizes high yield and throughput without the expense and complexity of full automation. With precise bonding for wafer sizes from 50mm to 300mm and a weekly volume of 400-1,000 wafers, it ensures critical process control for downstream thinned wafer processing, achieving an impressive ≥98% yield.

The bonder’s onboard control panel offers a user-friendly browser interface for real-time status updates. It enables schedule creation, remote process parameter updates, tool usage monitoring, and access to complete process history, logs, and analytics—tracking piston pressure, force, temperature, vacuum, and cycle time. With offline backup, data analysis, and push notifications to web-enabled devices, you’ll always stay informed

about the tool’s functionality and status, ensuring ultimate awareness of your process’ status anytime, anywhere.

The mechanical alignment fixtures are highly compatible with wafer notches and support the use of nonstandard wafers and carriers (alignment accuracy ≤ 0.5mm). Prior to bonding, the carrier and device wafer are separated, allowing for pre-bond evacuation and eliminating voids in the bond line. The dual ultra-flat (0.0005″ flatness specification), self-leveling heated platens with independent temperature controls ensure temperature uniformity of < 1% and bonding TTV as low as 5%. With a maximum bonding temperature of 300ºC and adjustable piston force (3.5 N – 12k N), accurate and precise bonds are guaranteed every time, with 10-N force resolution starting at 500 N.

Want to learn more? Contact our sales team today for more information!