In the course of processing substrates, for example semiconductor wafers or other kinds of substrates, photolithography is often performed to provide a mask for processing steps like etching or other operations which are to be applied only to part of the substrates. Typically, for photolithography a photoresist is applied to the substrate, the photoresist is exposed through a mask such that only defined regions of the photoresist are exposed to light, and the photoresist is subsequently developed. In case of positive photoresists, the regions exposed to light may be removed during the development, while for negative photoresists the regions not exposed to light are removed during the development of the photoresist.
In typical processing environments, substrates are transferred between the various processing steps like applying photoresist, exposing the substrate to light and developing the photoresist, by means of a mechanical gripper arm or other similar device which grips the substrate at a periphery thereof. However, this may lead to problems in some cases when the gripping device grips the periphery of the substrate where photoresist is applied, as the photoresist may for example adhere to the gripping device.
In some conventional solutions, the photoresist may be removed at the peripheral portion of the substrate prior to transferring the substrate using the gripping device. However, at least for some kinds of processing it may be desirable that the peripheral portion of the substrate remains coated with photoresist.