Secondary Flat: width 1.5-3.0 mm, length 15-30 mm

Q: What is the difference between primary flat and secondary flat on GaAs wafers?

The primary flat indicates the crystal plane orientation and is typically longer, while the secondary flat provides additional orientation information (doping type or specific crystal direction) and is shorter. Their angular relationship determines the exact crystallographic orientation.

Q: Why is secondary flat positioning critical in GaAs wafer processing?

Accurate secondary flat positioning ensures proper alignment of epitaxial layers and device structures with crystal planes, which directly affects electron mobility, optical properties, and device performance in GaAs-based semiconductors.

Component Specifications

Definition

The secondary flat is a precisely ground and polished flat surface located at a specific angular position relative to the primary flat on high-purity gallium arsenide wafer substrates. It serves as a secondary orientation reference for automated handling equipment during semiconductor device fabrication, ensuring proper crystal orientation alignment for epitaxial growth, lithography, and other critical processes. The secondary flat's position is determined by the wafer's crystal structure and doping type.

Working Principle

The secondary flat functions as a mechanical and optical reference marker that interacts with wafer handling robots, aligners, and inspection systems. Its precise angular relationship to the primary flat (typically 90° or 180° depending on crystal orientation) allows equipment to determine the wafer's exact crystallographic orientation. This ensures that semiconductor devices are fabricated along specific crystal planes for optimal electrical performance.

Materials

High-purity Gallium Arsenide (GaAs) single crystal, typically undoped or doped with specific elements (Si, Zn, Cr) depending on application requirements. Surface finish: Mirror-polished to <0.5 nm Ra roughness.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Depth	0.5-1.0 mm
Width	1.5-3.0 mm
Length	15-30 mm
Edge Chamfer	0.1-0.3 mm
Angular Tolerance	±0.5°
Position Accuracy	±0.1 mm
Surface Roughness	<0.5 nm Ra

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

SEMI M1, SEMI M20, ISO 14644, IEC 60749

Parent Products

This component is used in the following industrial products

High-Purity Gallium Arsenide Wafer Substrate

High-purity gallium arsenide (GaAs) wafer substrates are essential raw materials in the manufacture of advanced communication equipment.

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Engineering Analysis

Risks & Mitigation

Misalignment during automated handling
Contamination from improper cleaning
Mechanical damage during transport
Orientation errors in lithography

FMEA Triads

Trigger: Incorrect angular positioning during wafer fabrication
Failure: Device performance degradation due to wrong crystal orientation
Mitigation: Implement automated optical inspection with angular verification systems

Trigger: Mechanical damage from improper handling equipment
Failure: Wafer breakage or edge chipping affecting yield
Mitigation: Use compliant end-effectors with force feedback in wafer handlers

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Angular tolerance: ±0.5°, Position tolerance: ±0.1 mm, Surface roughness: <0.5 nm Ra

Test Method

Laser scanning microscopy for dimensional verification, Atomic force microscopy for surface roughness, Automated optical inspection for angular positioning

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

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Manufacturers of Secondary Flat

Manufacturer profiles associated with Secondary Flat.

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Frequently Asked Questions

What is the difference between primary flat and secondary flat on GaAs wafers?