How To Utilize the Rotational Stage for Automated Wafer Mapping?
Contact angle measurements on silicon and other wafers in the semiconductor industry are used to evaluate the cleanliness, surface treatment homogeneity, and photoresist adhesion. Wafers range typically from 4” up to 12” in diameter. Ideally, the contact angle measurement on a wafer can be done by automatic mapping of the whole wafer without user interference. For small wafers, this can be achieved by automated XYZ-stage and dispensers but when wafers are 12” in diameter, an additional rotational axis is required to achieve fully automated mapping. In this blog post, the use of the rotational stage is explained in detail.
Attension Theta Wafer
Attension Theta Wafer is a special instrument designed for contact angle measurements on wafers. It consists of a Theta Flow optical tensiometer frame, automated drop placement with four automated disposable tip dispensers, and an automated XYZ-stage with automatic rotational movement. The four dispensers in the instrument allow for the use of several different measurement liquids for surface free energy measurements or longer continuous runtime if water is used in all four dispensers. The automated XYZ-stage together with the rotational stage allows automated movement of the wafer for mapping of the full surface.
Positioning of the Wafer
The wafer stage includes a motorized rotational stage together with the separate wafer stage top. The wafer stage top includes movable pins that can be positioned depending on the size of the wafer used. The pins will guide the wafer, ensuring repeatable positioning of the wafer. In addition, the rotational stage is readily equipped with the connection port for the vacuum, making it possible to add extra hold if needed.
Automated Wafer Mapping – Setting Up the Measurement
To measure contact angles automatically on different locations on the wafer requires some initial setup. Still, once the parameters are set, the measurement can be conducted the same way to as many wafers as needed. In addition, the recipe can be saved, which allows the use of the same measurement parameters between different wafer batches, ensuring the measurement repeatability.
