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SE case 1: a Lithography Machine

For this case we follow the steps as defined by the Pace Product Development method.

Disclaimer:
all elements in this case are inspired by the real world situation, but by no means are anywhere near the actual data. The case is intended to give a fair impression of the steps that need to be taken for completing the functional and physical system breakdowns. And also to give some idea of the size and complexity of these lithography machines. In the example, the Level Sensor system has been given more attention than the other systems, just because it is a good example of a distributed system with a clear functionality.

Step 1: identify the System Element in the System Architectures diagram

In this case we start at the beginning with the functional system breakdown. The name of the system is “System X“.

Step 2: create the outline of the system requirement specification

Normally speaking the Elicitation process step would give us all the stakeholder needs and their rationale, so we understand the stakeholders’ interests in our product and the role our System X can / should / is expected to play in their business.
For now we will skip this step and move on to the Requirements Analysis step that will bring us the outline of the System Requirements Specification. The first question of Requirements Analysis is “What is the primary function of this System Element?”

Section 2a: Primary function of System X:

Section 2b: Define the properties of the primary function:

System X’s primary function of projecting intricate patterns onto a silicon wafer to create microchips requires a series of highly sophisticated design properties. These properties are critical because they directly influence the machine’s ability to produce the high-performance, extremely miniaturized chips demanded by modern electronics. Here are the most important properties of this function, which also serve as the key determinants for the design of the machine:

Description: The ability to create extremely small and precise features on the silicon wafer.

Importance: This is perhaps the most critical property, as it determines how small the transistors and other features on a microchip can be. High resolution allows for more components to be packed onto a single chip, directly impacting processing power and efficiency.

Design Influence: The use of EUV (Extreme Ultraviolet) light with extremely short wavelengths (e.g., 13.5 nm) is crucial to achieve the needed resolution. Optical systems (lenses and mirrors) must be designed with extreme precision, often requiring flawless surfaces and vacuum environments.

Description: The precision with which each successive layer of patterns aligns with the previous ones on the wafer.

Importance: Microchips are built layer-by-layer, so accurate alignment is critical to ensure that different layers of circuits line up perfectly. Poor alignment could result in defective or inefficient chips.

Design Influence: The machine must include sophisticated sensors and control systems to ensure sub-nanometer alignment accuracy. This also necessitates highly accurate stage control to move wafers and ensure exact positioning.

Description: The number of wafers that can be processed per hour.

Importance: High throughput is crucial for the manufacturing cost-effectiveness of microchips. The faster the machine can operate without compromising quality, the lower the per-unit cost of chips produced.

Design Influence: A high throughput rate requires rapid exposure, precise wafer handling, and automated stages capable of fast movement without losing accuracy. The system must balance speed with precision and minimize downtime for wafer changes.

Description: The wavelength of light used and the consistency of its intensity during operation.

Importance: Shorter wavelengths are needed for smaller feature sizes, especially for the latest technology nodes (e.g., 5 nm and below). The light source must also be highly stable to avoid variations that could affect exposure quality.

Design Influence: XYZ inc. uses EUV light sources that require highly specialized plasma generation and mirror systems to focus and maintain light intensity. This design includes specialized reflectors to handle extremely short wavelengths that traditional lenses cannot handle.

Description: The ability to control external and internal vibrations that could affect the exposure process.

Importance: Any vibration, even on a microscopic level, can cause misalignment and compromise the precision of the pattern being printed.

Design Influence: The machine must incorporate vibration-dampening mechanisms, such as special mounting frames, vibration isolation stages, and operating in controlled environments to minimize external disturbance.

Description: The quality and precision of the optical system that projects the pattern onto the wafer.

Importance: Since the machine is essentially “printing” tiny structures, the quality of the optical system (which includes mirrors and lenses) determines the clarity and accuracy of these patterns.

Design Influence: The mirrors used in EUV lithography are made to extremely high specifications, with surface irregularities measured in angstroms. The system requires extremely precise calibration to ensure consistent light projection.

Description: The ability to move the silicon wafer with incredible precision during exposure.

Importance: The wafer needs to be moved in a way that each part of it can be exposed at just the right moment. The movements must be sub-nanometer precise to avoid defects.

Design Influence: Linear motors and feedback control systems are designed for extremely high speed and precision, allowing the wafer to be positioned with nanometer accuracy. The design also needs to accommodate large wafers (typically 300 mm).

Description: Creating a controlled vacuum environment where the light source and optical systems can operate.

Importance: EUV light is easily absorbed by air, so a vacuum is essential to prevent light scattering and ensure that the desired wavelength reaches the wafer without degradation.

Design Influence: The machine must include robust vacuum chambers and seals that maintain near-perfect vacuum conditions while allowing the light source to function reliably and consistently.

Description: The quality of the photomask (reticle) that contains the pattern and how it is handled during the lithography process.

Importance: The photomask holds the intricate designs that are projected onto the wafer. Any contamination or imperfection can result in defective chips.

Design Influence: The system includes automated, ultra-clean handling of the mask and sophisticated defect detection mechanisms to ensure that only high-quality masks are used.

Section 2c: Define the constraints for the primary function:

These restrictions and constraints help ensure that System X functions properly, safely, and complies with industry standards.

Since System X uses extreme ultraviolet (EUV) or deep ultraviolet (DUV) light, it must comply with laser safety standards (such as IEC 60825), including enclosures that prevent hazardous exposure to users.

System X uses a variety of chemicals for the lithography process, such as photoresist and solvents. It must comply with hazardous materials handling regulations (like REACH in Europe and EPA standards in the U.S.) to ensure that chemical waste is disposed of properly.

System X must be designed to be energy-efficient and comply with emission standards (including greenhouse gas emissions for energy usage). Regulatory guidelines like ISO 14001 for environmental management systems may be relevant.

If System X uses proprietary technologies (such as advanced optics or specialized light sources), it must respect existing patents and licensing agreements. XYZ Inc. must ensure that no infringement occurs and that all necessary technology licenses are obtained.

As System X is a high-tech piece of equipment with potential dual-use (commercial and military applications), it could fall under export control regulations (e.g., EAR in the United States). Special export licenses might be needed to sell the machine to certain countries.

Section 3 & 4: define the secondary functions, their properties and constraints. There can be multiple secondary functions. Just for the sake of keeping this case simple, we skip these sections. One of the important aspects of the method is, that when a secondary function fails during operation, the primary function may not be affected. [MP001]

Section 5: there are properties of the system that are not associated to functions (either primary or secondary). These properties reflect the overall physical, environmental, and performance characteristics of System X as a complete entity.

Section 5: there are properties of the system that are not associated to functions (either primary or secondary). These properties reflect the overall physical, environmental, and performance characteristics of System X as a complete entity.

  • Description: The overall dimensions (height, width, depth) and weight of System X.
  • Importance: These properties are crucial for ensuring that System X fits within the cleanroom environment. Additionally, the weight impacts the design of the floor structure in the semiconductor fab. Overly large or heavy equipment could create logistical and structural challenges.

  • Vibration Sensitivity:
    • System X must operate with minimal impact from environmental vibrations. Its sensitivity to vibration defines the extent to which it needs to be isolated from external influences. This affects cleanroom positioning and floor requirements.
  • Temperature Range and Stability:
    • The operating environment must maintain tight control over temperature to ensure precision in lithography. The property defines the temperature range within which System X can function effectively, without leading to thermal expansion and misalignment.

  • Cleanroom Class Compliance:
    • System X needs to be designed for a specific cleanroom class (e.g., ISO Class 3 or 4), ensuring it does not generate excessive particulates during operation. This is critical for semiconductor manufacturing, where even a tiny particle can cause defects.
  • Airflow Requirements:
    • System X must not disrupt the laminar airflow within the cleanroom. The design should ensure minimal interference with air patterns, preventing contamination risks.

  • Mean Time Between Failures (MTBF):
    • This property measures how reliable System X is over time. It is a key property for minimizing downtime, as frequent failures would severely impact production schedules.
  • Maintainability:
    • The ease with which System X can be maintained, including Mean Time To Repair (MTTR). A low MTTR ensures that, when issues arise, they can be resolved quickly, minimizing disruption.

  • Corrosion Resistance:
    • The materials used in System X must resist corrosion, particularly for components exposed to harsh chemicals (like photoresists and solvents used during lithography). This property impacts the longevity and durability of the system.
  • Thermal Expansion Coefficients:
    • Materials must be selected with low or consistent thermal expansion properties to maintain the system's structural stability during operation.

Acoustic Emissions:

  • The noise generated by System X during operation, typically measured in decibels (dB). Excessive noise can be problematic for personnel working in close proximity to the system, impacting workplace safety and comfort.

Electromagnetic Emissions and Immunity:

  • System X should have minimal electromagnetic emissions, and it must also be resistant to electromagnetic interference from other equipment in the facility. This property ensures that System X doesn’t interfere with other sensitive equipment in the fab, and vice versa.

System Lifespan:

  • The intended lifespan of System X before major overhaul or replacement is required. A longer operational life is a key property in minimizing total cost of ownership and ensuring sustained use in a production environment without frequent major upgrades.

  • Installation Footprint:
    • The floor space required for installation, including any additional clearance needed for maintenance access.
  • Access Panels and Maintenance Space:
    • Accessibility properties define how much space is needed around the system for technicians to perform routine maintenance. It ensures ergonomic considerations for ease of access during repairs and component replacement.

Thermal Output:

  • The amount of heat generated by System X during operation. Heat dissipation impacts the cleanroom HVAC system design, as excessive heat could affect temperature control and need additional cooling infrastructure.

Vibration Damping and Stiffness:

  • System X must be designed to withstand internal forces generated during operation without flexing. The property of structural rigidity ensures that vibrations and movements are minimized internally, contributing to system precision.

  • Shipping Configuration:
    • Properties related to the ability of System X to be broken down into components for shipment. Since semiconductor fabs often have tight installation pathways, System X’s design must allow modular disassembly and reassembly.
  • Weight Distribution:
    • The even distribution of weight to avoid point loads during transportation or installation. It ensures that the system can be transported without risking damage to critical components.

  • Fail-Safe Mechanisms:
    • Properties related to ensuring safety, such as automatic shutdown features in the event of system errors. System X must have integrated fail-safe mechanisms to protect operators from UV exposure or mechanical failures.
  • Chemical Containment:
    • In case of leakage of any hazardous chemicals, System X should have containment properties that prevent chemical spills from affecting the surrounding area.

  • Total Power Consumption:
    • The overall power requirement for System X. This property is essential for planning the infrastructure of the semiconductor fab, as power usage must be within facility capacity and optimized for efficiency.
  • Power Quality Sensitivity:
    • The tolerance of System X to power fluctuations or interruptions. Any sensitivity would require additional UPS (Uninterruptible Power Supply) or conditioning systems to ensure continuous and stable operation.

Step 3: specify & quantify the functions, properties and constraints as identified in step 2

In this step the functions, properties and constraints are made specific, and in case of properties also quantified.

Step 4: baseline the requirements for review, review & correct, baseline for use and release the baseline

Requirements are baselines (frozen), reviewed and corrected if appropriate, baselined again and released for use in the development projects.

Step 5: create designs that satisfy the baselined requirements; this includes the system-level functional system breakdown and the physical system breakdown

Step 6: evaluate the design alternatives/options/solutions and decide on the best match (taking cost and side-effects and emerging properties into account)

Step 7: baseline the outcome of the decision-making process (decision-preparation and outcome, all design decisions)

Step 8: based on the system architectures from step 5, the functional subsystems are identified, together with their primary function and properties; and the physical modules are identified together with their property budgets (like mass) if available

Step 8a: part of the System Architecture & Design is the Functional System Breakdown.

Primary Function:

  • To securely transport reticles (masks) to and from the projection system while preventing damage or contamination.

Key Properties:

  1. Contamination Prevention: Must maintain a high level of cleanliness to protect the reticle from dust or particles.
  2. Precise Positioning: Must deliver reticles to their exact positions to align the pattern accurately.
  3. Secure Retention: The system must securely hold reticles to prevent movement or vibration during handling.

Primary Function:

  • To accurately position wafers in preparation for exposure.

Key Properties:

  1. Sub-Nanometer Precision: Essential for ensuring that each wafer layer is correctly aligned with the previous layer during exposure.
  2. Vibration Damping: Must minimize vibrations during positioning to avoid alignment errors.
  3. Speed of Adjustment: The positioning system needs to make rapid yet precise adjustments to align wafers correctly.

Primary Function:

  • To accurately align the reticle with respect to the wafer to ensure proper pattern transfer.

Key Properties:

  1. Alignment Accuracy: Ensures that the reticle’s pattern aligns precisely with the wafer below.
  2. Temperature Stability: Must maintain thermal stability to prevent expansion/contraction, which could misalign the reticle.
  3. Locking Mechanism: A precise locking system to keep the reticle in place during the exposure process.

Primary Function:

  • To measure and verify the alignment between the wafer and reticle for optimal exposure accuracy.

Key Properties:

  1. High Sensitivity: Must detect small deviations to ensure precise alignment.
  2. Real-Time Data Processing: Needs to provide alignment data instantly to adjust the positioning system as needed.

Primary Function:

  • To capture and analyze the light reflected from the wafer for monitoring exposure quality.

Key Properties:

  1. Resolution: High resolution to capture minute details on the wafer for effective quality assessment.
  2. Speed of Image Capture: Fast image capture to support high throughput without delaying production.
  3. Light Sensitivity: High sensitivity to accurately measure reflected light under varying illumination conditions.

Primary Function:

  • To measure the topography of the wafer to ensure it is at the correct focal plane during exposure.

Key Properties:

  1. Measurement Accuracy: Must measure the wafer height with extremely high accuracy to keep it in the focal plane.
  2. Fast Response Time: Needs to quickly detect and report height variations for real-time corrections.
  3. Environmental Tolerance: Must function accurately despite slight temperature fluctuations or airflow in the cleanroom.

Primary Function:

  • To detect any discrepancies or defects in the exposure process through real-time monitoring.

Key Properties:

  1. Defect Detection Sensitivity: Must detect even the smallest defects or discrepancies during exposure.
  2. Wide Field of View: Needs to cover the entire wafer surface for complete analysis.
  3. Data Processing Capability: High-speed data processing to analyze and relay defect information instantly.

Primary Function:

  • To control the amount of light (dose) that reaches the wafer during exposure.

Key Properties:

  1. Dose Accuracy: Must precisely control the amount of energy delivered to avoid overexposure or underexposure.
  2. Uniform Light Distribution: Needs to ensure that the entire wafer receives a uniform dose.
  3. Feedback Control: Real-time monitoring and adjustment to compensate for fluctuations in light intensity.

Primary Function:

  • To generate and deliver uniform illumination to the reticle for pattern projection.

Key Properties:

  1. Light Intensity Uniformity: Ensures even illumination across the reticle to prevent inconsistencies in the projected pattern.
  2. Wavelength Control: Must maintain a specific wavelength (e.g., EUV) to achieve the desired resolution.
  3. Stability: Must deliver consistent light output without fluctuations during the exposure.

Primary Function:

  • To block unwanted parts of the reticle to ensure that only the desired portion of the pattern is projected onto the wafer.

Key Properties:

  1. Precision Masking: Must be able to accurately control which parts of the reticle are masked.
  2. Rapid Adjustment: Should allow for quick changes to masking settings to adapt to different reticle patterns.
  3. Contamination Resistance: Needs to prevent contamination from affecting the masked areas.

Primary Function:

  • To project the reticle pattern onto the wafer with extreme precision to create the microchip features.

Key Properties:

  1. Optical Quality: The lenses and mirrors must have near-perfect surfaces to prevent distortion in the projected pattern.
  2. Focus Control: Must maintain perfect focus across the entire wafer to ensure each feature is accurately printed.
  3. Thermal Stability: The system must be designed to minimize any thermal distortion that could affect projection accuracy.

Step 9: for each functional subsystem follow steps 2 to 8 and iterate until you reach the level of building blocks

Step 10: for each building block specify the physical requirements in cooperation with the physical module owners from step 8 that hold the budgets (mass, volume, …) and with the discipline architects as appropriate for each building block

For each building block (BB) the requirements must be completed by looking from the different perspectives.

Step 11: use Configueres to check if the functional and physical system breakdowns are complete. This is done by selecting the starting point of the functional system breakdown (OBJ-0752) as viewpoint, select the ‘consists of’ relations, go to the ‘Configure’ tab. In the ‘Configuration table’ you see all the selected Building Blocks that are part of the functional system breakdown.
By selecting the starting point of the Physical System Breakdown for ‘Assembly item’ and the ‘is assembled from’ as relation, the bar chart will show if any building blocks are left behind on the Configuration table and are not part of the configuration on the assembly table.

Step 12: ensure that at the end of the engineering cycles the default configuration is functionally and physically complete, in order to be ready for specifying variants at the different levels. The ‘default’ configuration is defined as the collection of Building Blocks that are part of the configuration that has no Conditions.
Presence and completeness of individual subsystems (e.g. Level Sensor System – OBJ-0295) can be shown by taking the perspective of the Level Sensor System, assigning a color to it and selecting one or more relations.

In the example above it is shown that some Building Blocks of the Level Sensor system are located in the physical module WSMF, some of them in MBBM WC and two of them in ELEC. In this case the Level Sensor system uses a building block from another subsystem. That building block is also located in the physical module ELEC.
In case the initial scope of the functional system breakdown would be narrowed down to the Level Sensor system itself (viewpoint = OBJ-0295, relations = ‘consists of’, ‘uses’ ) , the assembly table shows just the relevant Building Blocks with their physical modules.
After step 10 the functional and physical structures are visualized as above. In the top-left the functional elements or functional subsystems are positioned (in blue), on the lower-left the physical elements or production modules are shown. All the green boxes are Building Blocks.

Step 13: map the Building Blocks onto the manufacturing / logistics domain. In this case the BB numbers are mapped onto order numbers that have a 12 digit numerical code. The 12NC’s are not shown here, instead the object ID’s are shown. This makes it a bit more difficult to understand, but on the other hand we should not reveal too much. Not all BB’s are mapped to 12NC’s.
The Dose Control system serves as an example of what we can do with the information we have gathered so far.

(9) – Dose Control system is selected as viewpoint, with consists of relations. (9) consists of 6 Building Blocks.
The selected viewpoint object has a red background color and the selected endpoints when the consists of relation is followed, are colored orange.

When the is implemented by relation is added to the list of relations to be followed, the Building Blocks become in between steps (with a green background color) and the endpoints of the path created by the consists of and is implemented by relations are colored orange.

When the inverse relation of is assembled of is added, it completes the steps from selecting a functional system (Dose Control) following the consists of relation shows the Building Blocks that are part of the Dose Control system, the is implemented by relation leads the BB’s to their implemented counterparts (as orderable 12NC type parts). The last step is created by the (inverse) of the is assembled of relation, that shows how the 12NC part are assembled into larger assemblies, and finally in the implemented system assembly (iSystem Assembly).

1. What is the starting point for the Functional System Breakdown (give object ID from Configueres)?

 
 
 
 

2. What is the starting point for the physical system breakdown?

 
 
 
 

3. Which relations should be used to visualize the functional system breakdown? Enter OBJ-0752 or Functional System Structure in the Select viewpoint  dropdown.

 
 
 
 

4. Given the result of the previous question, where all selected elements of the functional system structure are on the virtual Configuration table, which Assembly item and which Assembly relations should be chosen to see where the selected elements are positioned in the physical system structure?

Hint: select the Configure tab to see the Configuration and Assembly table.

 
 
 
 

5. As a Function Cluster owner I need to know which of the Building Blocks that belong to my cluster (FC009 – Dose Control system) have a direct connection to their implemented counterparts (12NC’s).

Which viewpoint and which relations are needed to generate the following visualization:

Hint: use the isolate switch () to isolate the elements in the trace from all other elements.

 
 
 
 

6. As a diagnostics expert I need to know when a component (12NC) fails in the field, which function or functions are possibly affected by this component?

Let’s assume component X with object ID OBJ-1355 (normally speaking we would know what the type number of the component is, this is similar to the 12NC). Which viewpoint and which relations do I need to select in order to answer the question of the diagnostics expert?

Hint: in this case it may help to show the name of the relation in the diagram. Go to the Filter tab, and check the Relation type box.

 
 
 
 

Question 1 of 6

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