Method for monitoring focal length of photoetching machine
A technology of lithography machine and focal length, which is applied in the field of semiconductor technology, can solve problems such as inability to accurately reflect small changes in focal length
Active Publication Date: 2012-04-04
CSMC TECH FAB2 CO LTD
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Problems solved by technology
[0004] However, due to the influence of optical proximity effect in actual work, such as figure 1 As shown, the sharp corners of the diamond-shaped mark pattern after exposure and development on the wafer will become rounded, so the length of the diagonal line will not change significantly with the slight change of the focal length, so the test results cannot accurately reflect the small change of the focal length
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[0023] figure 2 It is a flowchart of a method for monitoring the focal length of a lithography machine according to an embodiment of the present invention, including the following steps:
[0024] S110, forming a test pattern on the mask. A test pattern is formed on the mask plate through a plate making process. In this embodiment, the test pattern includes two parallel long sides, and the lengths of the two parallel long sides are both greater than the distance between the long sides. Figures with this feature include ordinary parallelograms, rectangles, rhombuses and other figures.
[0025] S120, first exposing the test pattern on the wafer coated with photoresist.
[0026] After each exposure of the test pattern, a photosensitive area similar in shape to the test pattern will be formed on the photoresist of the wafer (ideally, the shape is the same, but it may not be exactly the same due to the existence of errors, and its size is determined by the projection of the photo...
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The invention relates to a method for monitoring focal length of a photoetching machine, which comprises the following steps of: A, forming a test pattern on a mask blank; B, carrying out primary exposure and secondary exposure on the test pattern on a wafer coated with photoresist, controlling exposure energy to ensure that a coincide part of photosensitive regions subjected to primary exposure and secondary exposure on the wafer reaches a reaction threshold of the photoresist; C, developing the exposed wafer, forming a mark pattern by the coincide part of the photosensitive regions after developing, wherein the mark pattern is provided with at least two wedge-shaped point ends; and D, counting parameters of the mark patterns to determine an optical focal length of the photoetching machine. The diamond mark pattern formed by the method can avoid influence of optical proximity effect, and can be used for accurately reflecting the change of the focal length of the photoetching machine so as to accurately monitor the optical focal length of the photoetching machine because acute angles of a diamond are sharp and the length of the long diagonal line remarkably changes with the change of the focal length.
Description
【Technical field】 [0001] The invention relates to a semiconductor process, in particular to a method for monitoring the focal length of a lithography machine. 【Background technique】 [0002] The optimal focal length of the lithography machine is an important control parameter in the lithography process. The small drift of the focal length of the lithography machine must be reflected in time by the change of the size of the lithography pattern for monitoring. Specifically, the test pattern is transferred to the wafer (Wafer) using different focal lengths to form a mark pattern and measure it. [0003] One method in the traditional technology is to form a diamond-shaped test pattern on the mask, and use different focal lengths to expose and develop to obtain a set of diamond-shaped mark patterns. When the exposure focal length is the best focal length, the pattern fidelity is the best and the pattern size is the largest. , the length of the long diagonal of the rhombus is the...
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IPC IPC(8): G03F7/20
Inventor黄玮
OwnerCSMC TECH FAB2 CO LTD