1. Field of the Invention
The present invention relates to an apparatus and a method for patterning a semiconductor device. In particular, the present invention relates to an apparatus and a method for patterning a semiconductor device using an anti-reflective coating layer.
2. Description of the Related Art
As semiconductor device sizes shrink, the formation of accurately-sized contact regions using lithographic images becomes more important. Conventional lithographic techniques involve depositing an underlayer, such as a metal film layer 20, onto a semiconductor substrate 10. A metal film layer 20 is shown in FIG. 1. Then, a photo-resist (or resist) layer 30 is spin-coated onto the underlayer 20. The photo-resist layer 30 is then patterned using a conventional patterning. For example, as shown in FIG. 1, light is shined down onto the semiconductor substrate 10 from above, using a photo-lithographic mask (or reticle) 40, in order to pattern the photo-resist layer 30 to a desired pattern. The photo-lithographic mask 40 is constructed, for example, with a glass plate and with a chromium metal layer disposed onto portions of the glass plate where a photo-resist layer, which is situated between the mask 40 and a substrate, is not to be exposed to light from the light source.
As shown in FIG. 1, the reticle 40 has a width of W1, which is the desired size of a gap to be placed in the photo-resist layer 30, so as to provide a contact region or the like to the underlayer 20. However, due to reflections of light from the top surface of the underlayer 20, some of the light reflects upwards and in a skewed direction, thereby exposing more of the photo-resist layer 30 to the light than is desired. This problem has been found by the inventors, and results in an "exposed" photo-resist width of W2, which is greater than the desired width of W1. FIG. 2 shows the result of the problems caused by the reflected light during the photo-lithographic step, in which a gap of W2 is formed in the photo-resist layer 30 after developing of the photoresist due to the light being exposed onto it, with the actually-obtained gap having a width of W2 that is larger than the desired gap of W1.
Thus, in the conventional photo-lithographic process, contact points made for an underlayer can sometimes be larger than desired, due to unwanted reflections of light during the patterning of the photo-resist. This is undesirable, and can result in defective operation of semiconductor devices.