Gallium Arsenide (GaAs) Semiconductor Processing Technology
Introduction
Application Requirements
System Specifications
Processing Flow
Customer Case
Gallium Arsenide (GaAs) is widely used in high-frequency communications, photoelectric conversion, solar cells, and microwave devices due to its high electron mobility, direct bandgap, and excellent RF performance. GaAs-based devices play an irreplaceable role in 5G communication, radar systems, and integrated optoelectronic circuits. To meet the demands of high-performance device manufacturing, GaAs wafers require precision grinding to remove cutting damage, followed by Chemical Mechanical Polishing (CMP) to achieve an ultra-smooth surface, ensuring the accuracy and reliability of subsequent device fabrication.
Application Requirements
GaAs wafer processing must achieve the following objectives:
Surface Roughness: Post-polishing Ra ≤ 1 nm
Total Thickness Variation (TTV): Final wafer TTV ≤ 2 µm
Thickness Control: Target thickness 150 µm (subject to customer requirements)
Edge Flatness: Prevent chipping and ensure integrity of the device area.
System Specifications
The HSM Precision Lapping and Polishing System provides a full-process solution.
Processing Flow
Lapping Preparation
Use a flatness test gauge to calibrate the convexity of the glass Lapping platen (used to compensate for polishing edge effects).
Load the GaAs wafer onto the dedicated fixture (ASJ). Perform two-stage Lapping using alumina slurry:
Stage 1: Remove previous damage, reducing roughness to 250-350 nm.
Stage 2: Improve flatness, achieving roughness of 200-350 nm and TTV ≤ 3 µm.
Note: The abrasive particle size should be determined based on the initial and final thickness of the sample; there is no fixed abrasive size.
Polishing Preparation
Replace the grinding platen with a polishing pad and switch the abrasive to HSM specialized polishing slurry.
Control key parameters via the graphical interface:
Polishing platen speed: ≤ 100 rpm
Slurry flow rate: Monitored by a real-time drip feed control system (reduces waste)
Pressure load: Dynamically adjusted based on thickness requirements.
Target: Remove sub-surface damage and achieve an atomically smooth surface (Ra ≤ 1 nm).
Results
The 4-inch GaAs wafers processed by the HSM-LP system achieved the following performance:
Customer Case
A customer used the HSM-LP system to process a 3-inch GaAs wafer. The process and results are as follows:
Two-Stage Grinding:
Grinding platen convexity calibrated to the target curvature, effectively controlling edge warping.
Material removed stepwise with alumina slurry, TTV stabilized at 3 µm.
Polishing:
Polishing slurry flow rate set to 50 ml/min, platen speed at 80 rpm.
Surface roughness reduced from 250 nm to 0.8 nm (verified by White Light Interferometer).
Final Metrics:
Thickness: 150 ± 0.5 µm
Flatness: TTV ≤ 1 µm
Edge Integrity: No chipping, good edge flatness.
Technical Validation
Schematic: Surface morphology of the GaAs wafer after processing by the HSM-LP system.
Notes:
Measurement Equipment: Bruker ContourGT White Light Interferometer
Full-Process Yield: ≥ 96% (batch size of 30 wafers)
