Coretech Application | Large Aperture 2D Motion Stage Enhances Reticle Inspection Accuracy in Mask Lithography

"Coretech's CFTCA series high-precision large-aperture 2D motion stage is widely used in microscopic imaging equipment, particularly in photomask/reticle inspection applications for lithography, thanks to its outstanding stability and minimum step capability."

01 Lithography Technology

Lithography is a critical technology commonly used in semiconductor manufacturing processes. It involves projecting designed chip patterns onto semiconductor material surfaces using a lithography system, followed by a series of processing steps, ultimately forming micron- and nanometre-scale chip structures.

The fundamental principle of lithography utilises the properties of light—through a light source, mask, photosensitive material, and development steps—to transfer patterns onto a substrate to be processed. Light passes through the transparent regions of the mask and irradiates the photosensitive material, inducing chemical or physical changes. The unexposed photosensitive material is then removed through development, ultimately forming the desired pattern. ASML is a well-known major manufacturer of lithography systems.

The basic principle of lithography includes the following steps:

1. Mask fabrication: A desired chip pattern is created on a transparent substrate and overlaid onto the semiconductor material.

2. Photoresist coating: A layer of photoresist is applied to the surface of the semiconductor material. The choice of photoresist depends on the wavelength and energy of the light source.

3. Exposure: The lithography system projects UV light carrying the chip pattern through the mask onto the photoresist. The exposure process causes chemical or physical changes in the photoresist within the illuminated areas.

4. Development: The chemical changes make the exposed photoresist soluble in a corresponding developer solution, while the unexposed areas remain unchanged, forming a lithographic pattern.

5. Pattern transfer: Using chemical or physical methods—such as shallow etching or doping—the lithographic pattern is transferred to the semiconductor material surface.

6. Process iteration: The above steps are repeated in successive iterations until the final chip structure is achieved.

02 Reticle/Photomask Inspection

A photomask (also referred to as "reticle," "mask," "photomask," or "light shield") is typically made of glass or quartz with a patterned metal layer on its surface that selectively blocks or transmits light. It is an essential tool in the microelectronic lithography process.

The mask is an indispensable component of lithography. It carries the designed circuit pattern; light passes through it, projecting the pattern onto the photoresist. The mask functions analogously to the "negative" in traditional photography. By creating patterns on the mask, the pattern is transferred to the substrate through subsequent exposure processes, forming the corresponding circuit features on the substrate.

03 Coretech Products

04 Test Results

The CFTCA series is driven by linear motors and employs precision cross-roller guides, delivering outstanding dynamic performance and positioning accuracy, with a no-load cutoff frequency exceeding 100 Hz. The CFTCA series features a refined, compact structure yet offers strong driving capability: the upper axis achieves a maximum speed of 1000 mm/s and a no-load acceleration of up to 1 g. Configured with a linear amplifier in a vibration-isolated laboratory environment, the CFTCA series large-aperture stage achieves in-position stability of 3 nm and a minimum step of less than 5 nm. Owing to its large aperture design, it is ideally suited for double-sided measurement and inspection, biological sample processing and observation, thin-film thickness measurement, and other industrial and research applications that demand nanometre-level positioning accuracy and a large central opening.