10. Micro-, Nano- and Precision Manufacturing

Introduction and Context

Micro-, nano- and precision manufacturing address a central challenge in advanced engineering: producing functional components whose dimensions, surface characteristics, geometry and performance must be controlled at scales ranging from millimetres to nanometres. These technologies are not simply smaller versions of conventional manufacturing. At reduced dimensions, surface forces become increasingly important, heat and mass transfer behave differently, measurement becomes difficult, and a single particle or defect may destroy a product.

Microfabrication is generally concerned with structures and devices having characteristic dimensions from several micrometres to a few millimetres. Nanomanufacturing extends control to approximately 1–100 nm, although many industrial processes operate across a broader nanoscale range. Precision manufacturing emphasizes exceptionally close dimensional, geometric and surface control, often at the micrometre or sub-micrometre level, even when the workpiece itself is relatively large. The three fields overlap in semiconductor devices, microelectromechanical systems (MEMS), optical components, medical devices, sensors, energy systems and high-performance tooling.

A useful distinction is that conventional manufacturing usually begins with bulk material and removes, forms or joins it. Micro- and nanofabrication often build a device through a sequence of thin-film deposition, pattern transfer, selective removal, doping, bonding and packaging. Consequently, process integration, contamination control and metrology are as important as the individual operation.

Learning Objectives

After studying this chapter, the reader should be able to:

1. Explain the principles and process sequences of lithography, etching, deposition and micromachining.

2. Distinguish subtractive, additive, replication-based and hybrid micro/nanomanufacturing routes.

3. Analyze scaling effects involving surface forces, heat transfer, fluid flow, material removal and tolerances.

4. Select suitable ultraprecision machining and nanofinishing methods for demanding applications.

5. Explain MEMS fabrication, packaging, contamination control and yield management.

6. Evaluate process capability, uncertainty, risks and trade-offs in high-value manufacturing.

7. Discuss industrial applications, emerging technologies and professional responsibilities in this field.

The Scale-Dependent Manufacturing Environment

At the macroscale, gravitational and inertial forces often dominate engineering behavior. As dimensions decrease, the surface-area-to-volume ratio increases approximately in inverse proportion to characteristic length. Adhesion, capillary forces, electrostatic attraction, friction and van der Waals interactions therefore become relatively more significant. A small component may stick to a surface, collapse under capillary forces during drying, or fail because a thin layer contains residual stress.

Scaling also changes fluid behavior. In microchannels, the Reynolds number is commonly low, producing laminar rather than turbulent flow. Mixing then depends on diffusion, channel geometry or active disturbances. Heat transfer may be rapid because of short conduction distances, but localized heat generation can still produce severe thermal gradients. In nanoscale structures, classical continuum descriptions may require correction when dimensions approach mean free paths, grain sizes or characteristic electron and phonon transport lengths.

Manufacturing tolerances must be interpreted carefully. A dimensional tolerance of 1 µm is not automatically meaningful if the measurement uncertainty is 0.8 µm, the workpiece expands by several micrometres during measurement, or the datum structure is unstable. Precision therefore includes dimensional accuracy, repeatability, form, orientation, position, surface texture, material integrity and environmental stability.

Important terms include overlay, the registration accuracy between successive patterns; critical dimension (CD), the dimension that controls device function; line-edge roughness (LER), the variation of an edge from its intended location; aspect ratio, the ratio of feature depth to width; and process window, the range of operating conditions that produces acceptable results.

Lithography: Creating the Pattern

Lithography transfers a geometric pattern to a substrate. The substrate is commonly coated with a radiation-sensitive resist, exposed through a mask or by direct writing, and developed so that selected regions remain or are removed. The resulting resist pattern acts as a temporary protective layer during etching, implantation or deposition.

A typical photolithography sequence consists of wafer cleaning, dehydration baking, adhesion promotion, resist coating, soft baking, mask alignment, exposure, post-exposure baking, development, inspection and pattern transfer. Spin coating produces a relatively uniform resist film, with thickness influenced by viscosity, rotation speed, acceleration and solvent evaporation. Exposure dose, focus, wavelength, resist chemistry and substrate reflectivity jointly determine the printed feature.

Positive resists become more soluble in developer in exposed regions, whereas negative resists cross-link and become less soluble. The choice depends on required resolution, film thickness, etch resistance, sensitivity and process compatibility. Resolution is limited by wavelength, numerical aperture, focus, resist chemistry, diffraction and process-induced distortion. In optical projection systems, a simplified relationship is often written as R approximately equal to k1 lambda divided by NA, where R is resolution, lambda is exposure wavelength, NA is numerical aperture and k1 represents process factors. This expression is a guide rather than a complete design law.

Electron-beam lithography writes patterns directly using a focused electron beam. It offers excellent flexibility and resolution but is comparatively slow and can suffer from proximity effects caused by electron scattering. Nanoimprint lithography mechanically replicates a nanoscale pattern from a mould into a resist. It can provide high resolution and throughput, but mould fabrication, defect control, residual-layer management and demoulding are critical.

Other approaches include focused-ion-beam patterning, interference lithography, extreme-ultraviolet lithography and scanning-probe-based methods. No single method is universally superior. A production process must balance resolution, throughput, overlay, defect density, cost, material compatibility and equipment availability.

Etching and Pattern Transfer

Etching removes material selectively to transfer the resist image into the substrate or an underlying film. Wet etching uses liquid chemicals and may be isotropic or crystallographically anisotropic. For example, alkaline etchants can produce orientation-dependent shapes in silicon. Wet processes are attractive because of their high selectivity and throughput, but liquid handling, undercutting and waste treatment require control.

Dry etching uses plasma or reactive species. In reactive-ion etching (RIE), chemical reactions provide material removal while ion bombardment enhances directionality. Deep reactive-ion etching (DRIE) produces high-aspect-ratio silicon structures through alternating etch and passivation steps. The Bosch process is a well-known example, although it may generate scalloping on sidewalls. Inductively coupled plasma systems permit relatively independent control of plasma density and ion energy.

Etch performance is assessed through etch rate, selectivity, anisotropy, uniformity, sidewall roughness, profile control and damage. Excessive ion energy can cause crystal damage, charging or redeposition. Insufficient selectivity may consume the resist before the pattern is fully transferred. Microloading occurs when local pattern density changes the availability of reactive species, producing different etch rates in different regions.

A robust process uses test structures, endpoint detection, statistical monitoring and post-etch inspection. Pattern transfer should be designed together with the lithography step because the final CD may differ substantially from the resist CD due to isotropic undercut, sidewall taper, polymer deposition or mask erosion.

Deposition and Materials Engineering

Deposition creates films that serve as conductors, insulators, structural layers, barriers, optical coatings or sacrificial materials. Physical vapour deposition (PVD), including evaporation and sputtering, transfers material through a vapour phase. Chemical vapour deposition (CVD) forms a solid film through chemical reactions at or near the substrate. Atomic layer deposition (ALD) uses sequential, self-limiting surface reactions to produce highly conformal films with atomic-scale thickness control.

PVD can provide relatively pure films but may have limited conformality in deep features. CVD generally offers better coverage, while plasma-enhanced CVD lowers reaction temperature at the cost of possible plasma damage and film stress. ALD is particularly valuable for nanoscale barriers, high-k dielectrics and three-dimensional structures, although its cycle-by-cycle growth makes throughput a consideration.

Film properties include thickness, composition, density, grain structure, roughness, adhesion, residual stress, electrical resistivity, dielectric constant and optical response. Residual stress may arise from intrinsic growth mechanisms or thermal-expansion mismatch. In a suspended MEMS beam, excessive tensile stress can prevent deflection, whereas compressive stress can cause buckling. Deposition conditions must therefore be selected with the final mechanical function in mind.

Micromachining and MEMS Fabrication

Micromachining converts thin films and substrates into mechanical, electrical, optical or fluidic structures. Bulk micromachining removes material from the substrate to form cavities, membranes and channels. Surface micromachining builds structures from deposited films over sacrificial layers. The sacrificial layer is later removed, releasing beams, membranes, gears or resonators.

A simplified surface-MEMS sequence may include substrate preparation, deposition of an insulating layer, deposition and patterning of a sacrificial film, deposition and patterning of a structural film, opening of release windows, sacrificial etching, rinsing, drying and packaging. Release drying is a critical stage because capillary forces can pull a flexible structure into contact with the substrate, a failure known as stiction. Supercritical drying, vapour-phase release and hydrophobic surface treatments can reduce this risk.

MEMS devices often combine mechanical and electrical functions. Sensors may detect acceleration, pressure, temperature, chemical concentration or biological interaction. Actuators may use electrostatic, piezoelectric, thermal, magnetic or shape-memory effects. The fabrication process must preserve compatibility between materials, temperatures, electrical isolation, mechanical stress and packaging requirements.

Packaging is not an afterthought. It provides mechanical protection, electrical connection, environmental sealing and, in some devices, controlled access to pressure, fluid or chemical conditions. Package stress can shift sensor calibration or resonance frequency. Thermal expansion mismatch can produce drift. Wafer-level packaging, anodic bonding, fusion bonding and adhesive bonding are used according to material and application requirements.

Ultraprecision Machining

Ultraprecision machining is used when optical quality, sub-micrometre form accuracy or extremely low surface roughness is required. Diamond turning, ultra-high-speed milling, precision grinding and single-point diamond machining are important examples. Typical workpieces include infrared optics, moulds for replication, optical mirrors, precision bearings, aerospace components and medical parts.

The machine tool must possess high structural stiffness, thermal stability, low vibration, accurate motion, controlled spindle behavior and suitable environmental isolation. Hydrostatic or air bearings, linear motors, error mapping and active thermal control are frequently employed. Tool geometry, edge radius, crystallographic orientation and wear influence the machined surface. In brittle materials, ductile-regime cutting may be achieved under suitable conditions so that material is removed through plastic flow rather than fracture.

Errors arise from machine geometric error, tool runout, tool wear, servo following error, thermal drift, workholding distortion, vibration and material inhomogeneity. A useful error budget assigns a magnitude and uncertainty to each source. Compensation can be performed through calibration maps, real-time sensors or adaptive control, but compensation cannot reliably correct unstable fixturing or poorly characterized thermal behavior.

Ultraprecision cutting differs from ordinary machining not only in nominal tolerance but also in process philosophy. The cutting edge, machine, workpiece, measurement system and environment form one integrated system. Temperature gradients of even a fraction of a degree may be significant when nanometre-level form is required.

Nanofinishing and Surface Integrity

Nanofinishing aims to reduce roughness, waviness, defects and functional surface variation. Techniques include chemical-mechanical polishing (CMP), magnetic abrasive finishing, abrasive flow machining, ion-beam figuring, electropolishing, laser polishing, elastic emission machining and magnetorheological finishing.

CMP combines controlled chemical reaction with nanoscale abrasive removal. It is widely used for planarization of semiconductor wafers and multilayer devices. The process must control removal rate, selectivity, dishing, erosion, slurry contamination, pad condition and post-polish cleaning. Magnetorheological finishing uses a magnetically stiffened abrasive fluid to provide localized, controllable polishing, particularly for optical surfaces. Ion-beam figuring can correct low-amplitude form errors without mechanical contact, but it requires vacuum equipment and careful control of redeposition and subsurface damage.

Surface integrity includes roughness, residual stress, microcracks, transformed layers, dislocations, contamination and changes in functional properties. A surface with low arithmetic roughness may still be unacceptable if it contains buried damage or chemically active residues. Consequently, atomic force microscopy, white-light interferometry, scanning electron microscopy, X-ray methods, Raman spectroscopy, ellipsometry and contact or non-contact profilometry may be combined for characterization.

Contamination Control and Yield

In micro- and nanomanufacturing, contamination is a process variable rather than merely a housekeeping issue. Particles can cause open circuits, shorts, pinholes, local stress concentrations and optical defects. Organic residues can alter adhesion and wetting. Metallic impurities can change semiconductor behavior, while moisture and ionic contamination can promote corrosion or electrical leakage.

Cleanroom control addresses airborne particles, temperature, humidity, pressure differentials, personnel behavior, material flow and equipment cleanliness. However, a cleanroom alone does not guarantee a clean process. Contamination can be generated by resist outgassing, chamber memory, worn seals, slurry particles, inadequate rinsing, handling tools and poorly designed transfer systems. Chemical segregation, validated cleaning, filtered fluids, controlled storage and scheduled chamber conditioning are essential.

Yield is strongly affected by defect density and process variation. Statistical process control, fault detection, run-to-run control and design-for-manufacturing rules are used to stabilize production. Critical dimensions, overlay, film thickness, etch depth and particle counts should be monitored using control charts and appropriate sampling plans. A high nominal performance is not sufficient if the process window is narrow or if yield varies between lots.

Tolerances, Metrology and Decision-Making

Tolerance allocation in advanced manufacturing must consider function, process capability and measurement uncertainty. If a device requires a gap to remain within a specified range, the tolerance must include lithographic bias, etch variation, film thickness variation, stress-induced deformation and inspection uncertainty. Statistical tolerance allocation may be appropriate for independent random errors, whereas worst-case allocation is more conservative when failure consequences are severe or errors are correlated.

Metrology should be selected according to the measurand. Scanning electron microscopy provides high-resolution imaging but may cause charging, requires vacuum and may not directly provide traceable three-dimensional dimensions. Atomic force microscopy measures surface topography at high resolution but has limited scan area and tip-convolution effects. Optical interferometry is rapid and non-contact but depends on reflectivity and surface slope. Stylus methods are robust but contact the surface and may damage delicate structures.

Measurement system analysis should estimate repeatability, reproducibility, bias, stability and resolution. Traceability to standards is especially important where components affect safety, medical performance or optical system alignment. The manufacturing engineer must avoid confusing a visually sharp image with a valid dimensional measurement.

Applications and Industrial Significance

Micro- and nanomanufacturing support a wide range of high-value products. Semiconductor fabrication uses lithography, deposition, etching, implantation, planarization and packaging to create integrated circuits. MEMS accelerometers and gyroscopes support navigation, automotive safety and consumer electronics. Microfluidic devices enable compact chemical analysis, drug delivery and diagnostic testing. Nanoscale coatings improve wear resistance, corrosion protection, optical transmission and catalytic activity.

Precision machining is central to freeform optics, satellite mechanisms, moulds for polymer replication, fuel-injection components, hard-disk systems and medical implants. The economic value of these products arises not from material volume but from functional performance, reliability and intellectual content. Production decisions must therefore include equipment utilization, yield, inspection time, contamination risk, intellectual-property protection and supply-chain resilience.

Illustrative Case Study: MEMS Pressure Sensor Production

Background

Consider an illustrative industrial case involving a silicon piezoresistive pressure sensor for an automotive control system. The sensor contains a thin silicon diaphragm, implanted resistors near its surface and a bonded package that exposes one side of the diaphragm to pressure.

Situation and Problem

During pilot production, electrical sensitivity is acceptable, but batch-to-batch zero offset is excessive. Cross-sectional inspection reveals variation in diaphragm thickness and residual stress. Several devices also fail after packaging because bonding-induced stress deforms the diaphragm.

Analysis

The process flow includes anisotropic bulk etching, oxide deposition, resistor formation, contact metallization, wafer thinning, dicing and package bonding. Variation in etch rate changes diaphragm thickness. Oxide stress and thermal mismatch contribute to deflection. In addition, the bonding temperature varies across the wafer, and the electrical test does not distinguish fabrication offset from package-induced offset.

An engineering analysis separates the error sources. Thickness is measured at multiple wafer locations by profilometry and cross-sectional microscopy. Film stress is characterized using wafer curvature. Bonding temperature and pressure are recorded. A designed experiment is used to determine the influence of etch time, agitation, oxide deposition conditions and bonding parameters.

Approach and Solution

The manufacturer introduces a timed-plus-endpoint etch strategy, improves bath temperature uniformity and adds monitor structures. Oxide deposition is adjusted to reduce residual stress, while a lower-stress bonding process is qualified. Wafer-level calibration is correlated with post-package calibration to identify package contribution. Control limits are established for diaphragm thickness, oxide stress, etch uniformity and bond temperature.

Outcome

The process becomes more stable, and the principal variation shifts from uncontrolled fabrication effects to measurable package variation. The company can screen abnormal lots earlier, reduce destructive analysis and improve calibration efficiency. The result is not attributed to one machine setting; it comes from integrating process control, metrology, packaging analysis and functional testing.

Learning Points

The case demonstrates that MEMS performance depends on the complete process chain. Dimensional control alone is inadequate when stress and packaging alter device behavior. It also illustrates the importance of separating sources of variation, using monitor structures and linking process measurements to functional requirements.

Challenges, Risks and Professional Considerations

The principal technical risks include particle defects, process drift, thermal instability, tool wear, charging, residual stress, stiction, pattern collapse, line-edge roughness, subsurface damage and inadequate measurement capability. Economic risks include low yield, long qualification cycles, expensive equipment and dependence on specialized suppliers.

Safety and environmental responsibilities are substantial. Lithography and etching may use flammable solvents, corrosive acids, oxidizers, toxic gases and high-voltage plasma equipment. Engineers must apply chemical compatibility rules, ventilation, gas detection, interlocks, waste segregation and emergency procedures. Nanomaterials may present inhalation or ecological risks that are not captured by bulk-material safety assumptions. Regulatory compliance, worker training and documented process ownership are therefore essential.

Ethically, manufacturers must not report dimensional capability without including measurement uncertainty, conceal defect trends, or transfer an inadequately validated process to a safety-critical product. Data integrity is particularly important when automated inspection and machine-learning systems make accept/reject decisions.

Digital Manufacturing and Emerging Directions

Digital tools increasingly connect design, process simulation, equipment sensors, metrology and production databases. Digital twins can represent thermal behavior, tool condition or process drift, although their usefulness depends on validated physical models and reliable data. Machine learning can classify wafer defects, predict tool maintenance needs and identify relationships among process variables. It should support, rather than replace, engineering judgment, traceability and physical verification.

Emerging directions include heterogeneous integration, three-dimensional semiconductor structures, wafer-level packaging, flexible and stretchable electronics, roll-to-roll nanomanufacturing, additive microfabrication, hybrid laser–mechanical processing and nanoscale surface engineering. Advanced lithography is being combined with directed self-assembly and multipatterning to extend feature density. Atomic-scale deposition and selective-area growth are enabling new electronic, photonic and catalytic structures.

The best future processes will be hybrid. A component may be additively built, lithographically patterned, selectively etched, ultraprecision finished and assembled through wafer-level bonding. The engineering challenge is to manage interfaces between these operations while preserving traceability, yield and functional performance.

Best Practices for Process Selection and Implementation

A sound implementation begins with the functional requirement rather than the available machine. Define the critical dimensions, allowable defects, surface condition, material compatibility, throughput and life-cycle constraints. Select the simplest process capable of meeting those requirements, then evaluate its process window and scale-up behavior.

Design rules should account for minimum feature size, spacing, aspect ratio, alignment, release access, stress relief and inspection access. Use monitor structures and statistically designed experiments during development. Control contamination at its source, qualify cleaning and handling procedures, and separate development from production recipes where appropriate.

Finally, integrate manufacturing, metrology, packaging and reliability testing from the beginning. A process is successful only when it produces a stable, inspectable and reliable product—not merely an attractive laboratory specimen.

Chapter Summary

Micro-, nano- and precision manufacturing require integrated control of geometry, material properties, surfaces, environment and measurement. Lithography defines patterns; etching transfers them; deposition builds functional films; micromachining creates mechanical and fluidic structures; and packaging converts fragile structures into usable products. Ultraprecision machining and nanofinishing extend control to optical and sub-micrometre surfaces.

Scaling increases the influence of adhesion, capillarity, electrostatics, residual stress, roughness and contamination. Therefore, process selection must consider resolution, throughput, aspect ratio, selectivity, defect density, tolerance, uncertainty and yield. MEMS fabrication illustrates the importance of linking materials, mechanical design, electronics, release, packaging and calibration. Advanced digital tools and emerging hybrid processes offer new capability, but they require validated models, secure data and responsible engineering practice.

Key Terms

Lithography: Pattern-transfer process using radiation, a mask or direct writing to define selected regions on a substrate.

Photoresist: Radiation-sensitive polymer film used as a temporary masking layer.

Critical dimension: Feature dimension that strongly influences device or process performance.

Overlay: Registration accuracy between patterns formed in successive process layers.

Etch selectivity: Ratio of removal rates of the target material and the masking or underlying material.

Anisotropic etching: Etching that proceeds preferentially in one direction, producing relatively vertical or crystal-dependent profiles.

Reactive-ion etching: Plasma etching combining chemical reactions with directional ion bombardment.

Deposition: Formation of a solid film on a substrate by physical or chemical means.

Atomic layer deposition: Sequential, self-limiting surface-reaction process for controlled conformal film growth.

Micromachining: Fabrication of micrometre-scale structures by removing, depositing or patterning material.

MEMS: Devices integrating microscale mechanical and electrical functions.

Sacrificial layer: Temporary layer removed to release a suspended or movable structure.

Stiction: Unwanted adhesion of a released microstructure to a nearby surface.

Ultraprecision machining: Machining performed with exceptionally small dimensional, form and surface errors.

Nanofinishing: Surface-processing methods that produce nanoscale roughness or form control.

Line-edge roughness: Statistical variation of a patterned edge from its intended position.

Aspect ratio: Ratio of feature depth or height to its lateral width.

Process window: Range of process conditions that produces acceptable output.

Metrology: Science and practice of measurement, including uncertainty and traceability.

Chemical-mechanical polishing: Planarization process combining chemical surface reaction with abrasive mechanical removal.

Review Questions

Short Answer Questions

1. Why do surface forces become increasingly important as feature size decreases?

2. Distinguish positive and negative photoresists.

3. What is the purpose of a sacrificial layer in surface micromachining?

4. Define overlay and explain its significance.

5. Why is packaging considered part of MEMS fabrication?

Long Answer Questions

1. Explain the complete photolithography and pattern-transfer sequence, including major sources of dimensional error.

2. Compare wet etching, reactive-ion etching and deep reactive-ion etching in terms of mechanism, profile and application.

3. Discuss the material, stress and release problems encountered in surface micromachined MEMS.

4. Explain the machine, tool, thermal and metrology requirements of ultraprecision machining.

5. Describe contamination-control and yield-management practices for a microfabrication facility.

Analytical / Application Questions

1. A MEMS beam collapses onto its substrate after liquid drying. Analyze the likely mechanism and recommend two process modifications.

2. A nanoscale coating must cover the sidewalls of a deep, narrow trench uniformly. Select a deposition method and justify the choice using process principles.

3. A precision optical component shows excellent roughness but unacceptable form error after machining. Develop an investigation plan using error budgeting and suitable metrology.

22. Multiple Choice Questions with Answers

Question 1

Which factor becomes relatively more influential as the characteristic dimension of a component decreases?

A. Gravity compared with surface forces

B. Surface adhesion and capillary forces

C. Bulk inertia compared with viscosity

D. Macroscopic cutting temperature only

Correct Answer: B. Surface adhesion and capillary forces

Question 2

In a positive photoresist, the exposed region generally becomes:

A. Less soluble in developer

B. More soluble in developer

C. Metallic after exposure

D. Permanently bonded to the substrate

Correct Answer: B. More soluble in developer

Question 3

Which process is most directly associated with highly conformal, self-limiting thin-film growth?

A. Mechanical milling

B. Wet isotropic etching

C. Atomic layer deposition

D. Wire electrical discharge machining

Correct Answer: C. Atomic layer deposition

Question 4

The principal function of a sacrificial layer in surface micromachining is to:

A. Increase substrate thickness

B. Protect the cleanroom from particles

C. Be removed to release a structural layer

D. Provide permanent electrical conduction

Correct Answer: C. Be removed to release a structural layer

Question 5

A major cause of stiction in released MEMS structures is:

A. Capillary force during liquid drying

B. Excessive bulk density of silicon

C. High Reynolds number flow

D. Insufficient optical resolution alone

Correct Answer: A. Capillary force during liquid drying

Question 6

Which combination best describes reactive-ion etching?

A. Chemical dissolution without directional effects

B. Mechanical abrasion using a bonded wheel

C. Chemical plasma reactions enhanced by directional ion bombardment

D. Deposition by sequential surface saturation

Correct Answer: C. Chemical plasma reactions enhanced by directional ion bombardment

Question 7

For a deep narrow trench requiring uniform sidewall coating, which process is generally the most suitable?

A. Atomic layer deposition

B. Conventional surface grinding

C. Single-point diamond turning

D. Simple line-of-sight evaporation only

Correct Answer: A. Atomic layer deposition

Question 8

Why can a low surface roughness value fail to guarantee acceptable surface integrity?

A. Roughness has no relation to any surface property

B. Subsurface damage or residual stress may still be present

C. All smooth surfaces are dimensionally inaccurate

D. Surface roughness can only be measured visually

Correct Answer: B. Subsurface damage or residual stress may still be present

Question 9

In the illustrative pressure-sensor case, which approach best addresses batch-to-batch offset variation?

A. Ignore packaging because only etching affects sensitivity

B. Measure and control etch thickness, film stress and bonding conditions

C. Increase particle concentration to stabilize the process

D. Replace functional testing with visual inspection

Correct Answer: B. Measure and control etch thickness, film stress and bonding conditions

Question 10

A precision measurement with uncertainty nearly equal to the specified tolerance is problematic because:

A. The measurement may not reliably distinguish conforming from nonconforming parts

B. The component automatically becomes more accurate

C. The process window necessarily becomes wider

D. Uncertainty improves overlay accuracy

Correct Answer: A. The measurement may not reliably distinguish conforming from nonconforming parts