1. Destructive Inspection — Calibration Benchmark for Non-Destructive Detection of Quartz Wafers

Destructive inspection physically removes and chemically etches the surface layer of quartz substrate wafers to fully expose the subsurface damage layer (SSD). This method enables intuitive observation of internal microcrack morphology, accurate quantification of damage depth, and statistical analysis of full-field defect density. It delivers highly credible and repeatable quantitative data, serving as the universal calibration benchmark for all emerging non-destructive detection technologies for quartz wafers.
Nevertheless, destructive inspection has inherent limitations. The tested wafers suffer permanent damage after detection. It only supports single-point and local sampling, and cannot be applied to full inspection of finished wafers or on-line monitoring in semiconductor production lines. It is merely suitable for laboratory research on wafer machining mechanisms, parameter verification of new grinding and polishing processes, and calibration of optical detection algorithms. This chapter categorizes and elaborates four mainstream inspection methods for quartz substrate wafers, including polishing stripping, chemical etching, cross-section observation, and special dynamic detection, with corresponding schematic illustrations.

2. Polishing Stripping Inspection (Wafer-Level and Single-Chip Detection for Quartz Wafers)

 
Fig.1 Subsurface crack morphology of quartz substrates after grinding with different abrasives
 

2.1 Taper Polishing

Working Principle for Quartz Wafers: An inclined taper surface is fabricated on the machined surface of quartz wafers, converting the micron-scale subsurface damage depth into millimeter-scale inclined length for measurement. The geometric calculation formula is as follows:
H=L⋅sin⁡α 
Where  = subsurface damage depth of the wafer,  = length of the damaged area on the tapered surface, and = included angle between the tapered surface and the original wafer surface.
Advantages: Simple equipment, extremely low testing cost and low operational threshold; applicable to large-area measurement of 4/6/8-inch quartz wafers.
Disadvantages: Friction generated during taper grinding induces new microcracks on the wafer surface, interfering with the true measurement of original SSD depth caused by machining.
Engineering Conclusion: Wafer grinding experiments verify that larger grinding wheel or abrasive particle sizes significantly increase the maximum crack depth, crack cluster thickness and surface defect density of quartz substrates.

2.2 Dimpling Polishing

 
Fig.2 Optical morphology of dimpling polishing on quartz substrate wafers
 
Working Principle for Quartz Wafers: A standard stainless steel ball is used to fabricate an arc-shaped pit vertically on the wafer surface. The local SSD depth of the wafer is calculated geometrically based on the steel ball radius, the maximum outer diameter of the damaged pit area , and the central damage-free zone diameter .
Advantages: Enables fixed-point detection of key local positions such as wafer edges, lithography areas and coating areas with intuitive crack morphology and flexible operation.
Limitations: Fused silica features high hardness, resulting in low polishing removal efficiency. Polishing stress propagates original wafer cracks and introduces measurement errors. Dilute HF acid pre-etching is commonly adopted to improve the optical contrast of internal wafer defects.

2.3 Magnetorheological Finishing (MRF) — Preferred for High-Precision Quartz Wafers

 
Fig.3 Subsurface crack morphology at different depths of quartz substrate processed by 1–4 groups of technological parameters
 
Working Principle for Quartz Wafers: Integrating electromagnetism and fluid mechanics, MRF utilizes a magnetic field to modulate magnetorheological fluid into a rigid-free flexible polishing pad. It removes wafer surface materials via pure shear force, generating almost no new subsurface damage. It is divided into MRF taper polishing for large-area detection of full quartz wafers and MRF spot polishing for precise detection of local wedge-shaped regions. HF acid etching is performed after polishing to fully expose internal microcracks.
Advantages: Stable material removal rate and extremely low secondary damage. The polishing process simultaneously repairs surface scratches, improving the laser-induced damage threshold and optical transmittance of quartz substrates. The Lawrence Livermore National Laboratory has combined MRF taper polishing with scanning optical microscopy to realize quantitative damage characterization of multiple quartz wafer grinding processes.
Disadvantages: Ultra-fine iron powder residues remain on the wafer surface after polishing, requiring multiple high-purity acid-base cleaning and ultrasonic precision cleaning procedures to avoid impurity contamination of coating and lithography working surfaces.

2.4 Ion Beam Etching (IBF) — Nanoscale Characterization of Ultra-Thin Quartz Wafers

 
Fig.4 Defect scattering morphology of quartz substrates at different etching depths
 
 
Fig.5 Statistical curve of defect quantity and area versus etching depth for quartz substrates
 
Working Principle for Quartz Wafers: High-energy ion beams are generated by ionizing high-purity argon gas in a vacuum chamber, achieving atomic-level layer-by-layer sputtering removal of the wafer surface. The entire process introduces no mechanical stress, edge chipping or metal impurities. Confocal fluorescence microscopy is adopted for layer-by-layer scanning after etching to statistically analyze the quantity and area distribution of defects at different depths.
Measured Etching Law for Quartz Wafers: The surface defect area ratio of original wafers is only 0.0903%. After 500 nm etching, subsurface defects covered by the surface deposition layer are fully exposed, with the defect ratio rising to 0.5371%. When the etching depth exceeds 1000 nm, the quantity and area of internal defects tend to stabilize, enabling accurate determination of the ultimate damage depth of full quartz substrates.
Advantages: Enables precise nanoscale layer-by-layer characterization without secondary damage, suitable for ultra-thin and optical-grade quartz wafer detection.
Disadvantages: Extremely low material removal efficiency and high-cost vacuum ion beam equipment limit its application to high-precision laboratory mechanism research, making it unsuitable for mass production testing.

3.Chemical Etching Inspection — Rapid Batch Screening for Quartz Wafers

 
Fig.6 Etching rate comparison curve between intact substrate and damaged layer of quartz substrates
 
 
 
Fig.7 Schematic diagram of layer-by-layer polishing and etching detection process for quartz substrate wafers
Rapid characterization of wafer subsurface defects is realized based on the difference in hydrofluoric acid corrosion rate between the damaged layer and the dense intact substrate of quartz wafers. Three process methods adapted for quartz wafers are classified as follows:
1. Selective Etching: HF acid preferentially corrodes loose damaged regions inside wafers to rapidly reveal microcracks. It features simple sample preparation and fast detection speed, yet it is only applicable to pure fused silica substrates with poor universality for doped and modified quartz wafers due to inconsistent corrosion performance.
2. Etching Rate Differential Detection: The porous SSD regions exhibit faster corrosion rates, and the inflection point of the corrosion rate curve corresponds to the ultimate subsurface damage depth. Differential calculation based on corrosion data of defect-free substrates eliminates measurement errors caused by temperature and HF concentration fluctuations. However, it cannot acquire the 3D morphology of wafer defects.
3. Stepwise Etching: HF etching duration is controlled in segments to form stepped corrosion surfaces on the wafer for layered observation of crack distribution at different depths. The main limitation is unstable etching uniformity, leading to large measurement errors for ultra-thin quartz substrates with shallow damage.

4. Cross-Section Observation Inspection — Longitudinal Damage Mechanism Research for Quartz Wafers

Two sample preparation methods are adopted for longitudinal cross-section observation of quartz substrate wafers:
1. Bonded Cross-Section Method: Two wafers are bonded face-to-face and integrally ground. The adhesive is dissolved to expose the longitudinal cross-section, enabling intuitive comparison of crack depth differences under various grinding grain sizes and polishing processes.
2. Polished Cross-Section Method: The cut wafer edge is polished synchronously with a defect-free auxiliary wafer to reduce observation distortion. FIB (Focused Ion Beam) technology can be applied to prepare ultra-thin cross-sections with nanometer precision for observing nanoscale microcracks induced by lithography and grinding.
Common Limitations: Complicated and time-consuming sample preparation; only local single-section observation is available, unable to reflect the full-field damage distribution of entire wafers.

5. Nanoindentation & Time-Resolved Dynamic Imaging — Mechanical and Laser Damage Mechanism Research for Quartz Wafers

5.1 Nanoindentation Detection

 
Fig.8 2D/3D surface morphology of quartz substrate wafers via nanoindentation testing
 
Working Principle for Quartz Wafers: The hardness of loose SSD regions in quartz substrates is significantly lower than that of dense defect-free substrates. The hardness mutation and recovery point on the load-displacement curve corresponds to the subsurface damage depth. This method is suitable for various hard quartz substrates with simple sample preparation.
Limitations: Not applicable to ultra-thin wafers with extremely shallow damage. Indentation load propagates original microcracks and destroys the initial defect morphology.

5.2 Time-Resolved Ultrafast Imaging

 
Fig.9 Dynamic time-sequence diagram of laser-induced damage in quartz substrate wafers
 
Working Principle for Quartz Wafers: Nanosecond/femtosecond pulsed lasers combined with high-speed synchronous cameras capture the whole process of internal crack initiation and radial/circumferential crack propagation with ultra-high time resolution. It is specially applied to dynamic research on laser-induced damage and high-energy irradiation failure mechanisms of quartz wafers.
Limitations: The complete optical imaging system is complex and costly, only applicable to fundamental laboratory research.
 

6. Summary of Advantages and Disadvantages of Various Destructive Detection Methods for Quartz Substrate Wafers

Detection Method	Core Advantages for Quartz Wafers	Main Limitations for Quartz Wafers	Wafer Application Scenarios
Taper/Dimpling Polishing	Low equipment cost, simple operation, suitable for rough detection of single small-size wafers	Grinding easily induces new surface cracks and causes measurement deviation	Batch sampling of grinding processes and preliminary production line process screening
MRF Magnetorheological Polishing	Extremely low secondary damage; synchronously repairs surface defects and improves optical performance	Iron powder residues after polishing require multiple high-precision cleaning procedures	Process verification for high-precision optical quartz wafers and laser substrates
IBF Ion Beam Etching	Atomic-level layer-by-layer quantitative characterization; no edge effect or impurity contamination	Ultra-low material removal rate and extremely high equipment investment	Nanoscale precise characterization of ultra-thin quartz substrates and research-grade samples
HF Chemical Etching	Fast sample preparation, supports batch processing of multiple wafers at one time	Only observes 2D cracks without 3D defect distribution information	Rapid damage screening for mass quartz substrates
Wafer Cross-Section Observation	Intuitively displays full longitudinal crack depth distribution	Complicated sample preparation; only local observation, not representative of full wafer status	Fundamental research on grinding and polishing damage mechanisms of quartz wafers

7. Quartz Substrate Wafer Supply Specification

To meet the application demands of quartz substrate wafers in optics, semiconductors and laser industries, JXT provides full-spec high-precision fused silica substrate wafers with various sizes and thicknesses. All products undergo ultra-precision polishing and strict cleaning treatment with controllable subsurface defects, adapting to high-precision detection and industrial mass production scenarios.
Our product size coverage includes mainstream industrial specifications such as 2-inch, 4-inch and 6-inch standard quartz wafers, with customized square and special-shaped substrates available. The thickness range covers full series from ultra-thin to conventional specifications, including 100 μm, 150 μm, 200 μm, 400 μm, 500 μm, 625 μm, 725 μm, 775 μm and 1000 μm, with customized thickness tolerances according to customer process requirements.
The supplied quartz substrates feature high flatness, low impurity content and minimal subsurface microcracks. They are perfectly applicable to high-end scenarios such as optical coating, lithography processing, laser devices and precision sensing, effectively reducing performance loss caused by subsurface defects and adapting to both scientific research experiments and industrial batch applications.

 

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