At present, a projection expose method using a stepper is mainly used for fabricating a semiconductor device. In the projection expose method, a tip pattern formed on a photo reticle is projected on a wafer set on a X-Y stage of the stepper. A photo reticle is fabricated by photolithographic technology using an original layout pattern which has a predetermined tip pattern and alignment marks in a scribe region thereof.
Recently, a reticle which is provided with a plurality of same tip patterns therein has been proposed in order to increase a fabrication efficiency of a semiconductor device. In fabrication of the reticle, a reticle film is exposed to a light passing through an original layout pattern in times corresponding to the number of the tip patterns so that the plural tip patterns are formed on parallel planes defined on the reticle side by side. At the same time, alignment marks are also formed with the tip patterns on the scribe region of the photo reticle.
Next, in projection of a wafer, a wafer base is exposed to a light passing through the reticle at predetermined times, so that the plural reticle patterns are formed on horizontally and vertically defined regions on the wafer side by side. At this time, a rotation of the reticle is monitored on the wafer by using alignment marks positioned along sides of the reticle, and a deviation of a presently used reticle relatively to the position of a former reticle used at a precedent step is monitored by using alignment marks positioned at an inner portion between the tip patterns of the reticle.
According to the conventional photo reticle, however, it is difficult to discriminate the alignment marks between at the inner portion of the reticle and at the sides of the reticle, because the alignment marks are common in configuration between the detection of rotation from a standard angle and deviation from a previous step. The necessity of the alignment mark discrimination is due to the fact that the alignment marks at the inner portion of the reticle are preferably used for the detection of the deviation from the previous step, because these alignment marks are not affected by the rotation from the standard angle, and that the rotation must be detected by use of the alignment marks at the sides of the reticle.
This necessity can be avoided by different alignment marks formed at the sides and the inner portion of the reticle, that is, a specific mark is provided at the inner portion thereof to detect the deviation from the previous step. If this is applied to practical use, however, data for parallel planes on the both sides of the inner portion of the reticle must be prepared, so that the amount of data is increased to manufacture a reticle having a plurality of tip patterns.
USPTO Backgrounds
USPTO Backgrounds