One Article Summary | Multiple Applications of Precision Motion Stages in Wafer Defect Inspection

Semiconductor manufacturing involves complex processes; to ensure quality, nearly every process step requires rigorous inspection. If defective dies proceed to subsequent stages, they not only severely compromise the overall product quality but also lead to significant increases in production costs. In this context, whether in automated optical inspection (AOI) systems or scanning electron microscope (SEM) systems, the precision motion stage that carries the wafer is the core component determining inspection accuracy and efficiency.

Addressing the requirements for wafer surface defect and dimension inspection, the various series of motion stages from Geocentric Technology can provide diversified performance solutions for automated inspection equipment integrators. They support multiple modes, including serpentine reciprocating on‑the‑fly linear scanning, area‑scan camera point‑to‑point region inspection, and high‑speed spiral trajectory inspection, enabling accurate and efficient wafer screening.

Comparison of characteristics between raster‑type and spiral‑type wafer inspection

Raster scanning, also known as grid scanning, is one of the most widely adopted path‑planning methods in wafer inspection. The motion stage performs continuous reciprocating scans along the X‑axis; after completing each row, the Y‑axis steps by a fixed distance, and the process repeats, forming a path resembling the character "工" (or a raster pattern).

This inspection method features a simple and clear path plan, straightforward motion control logic, and relatively modest demands on the controller. The algorithms for image stitching and data correlation are also mature and stable. Meanwhile, the acquired image data is arranged in a row‑column matrix format, facilitating storage, localization, and traceability of defect positions.

Geocentric Technology has extensive experience in the custom development of raster‑scan motion stages and can perform targeted optimisations based on specific customer application requirements, ensuring seamless adaptation to production line processes.

OneXY Linear Stage + ART165V‑5 Z‑Lift Stage

Function: Fast step‑and‑settle

Product: OneXY‑350‑350

Specifications:

• Y‑axis step: 1.47 mm (IMA10T exposure field width), motion time 50 ms, settling window 50 nm

• X‑axis step: 1.47 mm (IMA10T exposure field width), settling time 205 ms, settling window 50 nm

To address the auto‑focus challenges caused by wafer surface non‑flatness or warpage, Geocentric Technology offers a classic solution: an open‑frame platform with an integrated XY design (ONEXY‑350‑350), paired with a high‑precision Surface Z lift stage. The X‑axis performs step motions, the Y‑axis executes the raster scanning, and the Z‑lift stage compensates for wafer height fluctuations in real time, ensuring that the surface under inspection remains within the optimal depth of focus of the camera.

As a vertical motion platform designed specifically for precision positioning, the Surface Z employs a linear motor drive and cross‑roller guide structure, achieving nanometre‑level positioning accuracy and excellent dynamic performance. With a no‑load closed‑loop cutoff frequency exceeding 200 Hz, it offers rapid response, stability, and reliability.

Function: Auto‑focus

Product: Surface Z‑5 (suitable for 8‑inch to 12‑inch wafers)

Performance: 3 μm amplitude, 40 Hz @ ±150 nm dynamic following error

Features: Direct‑drive motor / Optional built‑in zero‑friction air cylinder for load balancing