Method and device for detecting focal plane change of exposure machine table

Abstract

The invention discloses a method for detecting focal plane change of an exposure machine table, which comprises the following steps: carrying out exposure and development on a control wafer by using a photomask to form a first-layer overlay precise measurement mark (OVL mark); carrying out exposure and development for a second time by using the photomask with a wedge to form a second-layer OVL mark on the first-layer OVL mark, wherein the photomask with a wedge resolves the focal length Z-axis component into an X-axis component and a Y-axis component; measuring the overlay degree of the first-layer OVL mark and the second-layer OVL mark by using an overlay precise measuring instrument to obtain the overlay value of the first-layer OVL mark and the second-layer OVL mark in the X-axis direction and the Y-axis direction according to the change of the focal length variable delta Z in the second exposure; and determining whether the focal plane is changed according to the intersection point of the overlay value curve, which is formed by delta Z and X-axis direction, and the overlay value curve formed by delta Z and Y-axis direction. The invention also discloses an exposure machine table for detecting the focal plane change of the exposure machine table. The method and the device can be used for precisely determining whether the focal plane of the exposure machine table is changed with high efficiency.

Description

technical field [0001] The invention relates to the technical field of lithography for semiconductor manufacturing, in particular to a method and device for detecting changes in the focal plane of an exposure machine. Background technique [0002] At present, in semiconductor process technology, photolithography technology is becoming more and more important with the improvement of critical dimension technology. [0003] The stability of the exposure machine is affected by many aspects, such as the offset of the wafer platform or lens on the exposure machine, the flattening degree of the wafer surface, the change of the laser wavelength, and the environment, etc., will cause the exposure machine to The focal plane (focal length) of the exposure machine changes, that is, the real focal length value of the exposure machine is different from the initial set value, which will cause the size and profile of the exposed wafer to be different from the preset value. [0004] In orde...

AI Technical Summary

Problems solved by technology

In order to monitor the change of the focal plane of the exposure machine, it is necessary to obtain an optimal focal length value according to the above method at regular intervals. If the focal plane changes, the optimal focal length value obtained each time is different from the previous one. And because the Bossung Curve needs to be formed every time, the Curve is sensitive to changes in the environment. If some unnecessary and negligible factors change, it is likely to cause the formed Bossung Curve to change accordingly. Once the Bossung Curve changes, It is considered that the focal plane of the exposure machine changes, and the exposure machine needs to be adjusted in time. BossungCurve reflects the insubstantial change of the exposure machine, which is not expected to happen in the specific process, so this method is relatively inaccurate and time consuming

Images