I. WAT Testing Overview

Wafer Acceptance Test (WAT) is a critical electrical parameter testing process conducted prior to the shipment of semiconductor wafers. This process utilizes specialized test structures located on the wafer scribe lines to monitor manufacturing process stability and deviation. The results provide essential data support for yield management and process optimization.

Figure 1. Test structures on the wafer scribe line

System Architecture

The Semight Instruments WAT Parameter Test System utilizes a modular architecture consisting of three main components:

• Test Cabinet: Integrates high-precision instrumentation and the main system controller.

• Test Head: Houses the switch matrix, Source Measure Units (SMUs), and the probe card interface subsystem.

• Prober: Manages automatic wafer loading and precise positioning; the system is compatible with a wide range of commercial wafer probers.

II. Technical Challenges & Core Requirements

As semiconductor processes advance to nanometer-level nodes, manufacturing sequences become increasingly complex. The exponential growth in the number of test structures and parameters places stringent demands on WAT systems:

• Extreme Precision: Current measurement resolution must reach the femtoampere (fA) level, with accuracy requirements better than sub-picoampere (sub-pA).

• High-Efficiency Throughput: Support for parallel testing architectures is essential to maximize production throughput.

• Comprehensive Parameter Coverage: The system must integrate a diverse range of measurement modules, including:

• SMU (Source Measure Unit)

• FMU (Frequency Measure Unit)

• SPGU (Semiconductor Pulse Generator Unit)

• CMU (Capacitance Measure Unit)

• DMM (High-Precision Digital Multimeter)

• SWM (Semiconductor Switch Matrix)

III. Semight Instruments Core Technology Platform

Semight Instruments is dedicated to the field of electrical test and measurement, committed to the proprietary development of critical instrumentation. We have successfully launched a portfolio of core instruments specifically designed for WAT applications:

• High-Precision Digital Source Measure Units: The S2012C and S2016C series, achieving pA-level measurement accuracy.

• Low-Leakage Semiconductor Matrix Switches: The RM1010-LLC, engineered to ensure superior signal integrity.

• High-Voltage Pulse & Source Units: The S3023P Pulse Source and S3030F High Voltage SMU (supporting up to 3500V).

• Modular System Architecture: Based on the PXIe platform, facilitating flexible configuration and functional expansion.

IV. Product Portfolio

1. WAT6200S Serial Parametric Test System

• Material Compatibility: Comprehensive support for Si, GaN, SiC, and other wafer materials.

• Electrical Performance: Maximum voltage of 200V, maximum current of 1A.

• Precision Specs: pA-level current accuracy, fully meeting mass production testing requirements.

• System Features: Utilizes proprietary Semight SMUs and low-leakage switch cards; supports the integration of third-party instruments and user-defined test algorithms.

2. WAT6600 Parallel Parametric Test System

• High-Efficiency Architecture: Features a Per-Pin SMU configuration, supporting parallel testing with up to 48 SMUs.

• High-Precision Measurement: Sub-pA level current resolution, suitable for both process R&D and high-volume manufacturing.

• Electrical Range: Maximum voltage up to 200V, maximum current up to 1A.

• Open Compatibility: Supports integration with a full range of commercial probers and third-party instrumentation.

3. WAT6300 High Voltage Serial Parametric Test System

• High-Power Output: Equipped with Per-Pin SMUs supporting 200V/1A high-voltage/high-current testing. Integrated with Per-Pin PGUs (±40V) to meet diverse signal excitation requirements.

• High-Configurability: Supports up to 48 channels with full Kelvin (4-wire) connections.

• Superior Accuracy: System accuracy reaches the 1pA level, with typical leakage current below 500fA.

• Advanced Integration: Designed for seamless integration with mainstream probers and automated production lines; ideal for rigorous testing scenarios involving power devices and high-voltage ICs.