Method for measuring focus offsets of exposure tool
An offset and machine technology, used in microlithography exposure equipment, photolithography process exposure devices, etc., can solve the problems of low sensitivity, easy to have abnormal measurement, abnormal drift of curve vertices, etc.
Active Publication Date: 2009-06-03
SHANGHAI HUAHONG GRACE SEMICON MFG CORP
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[0004] However, the disadvantage of this method is that in a set of CD-energy-focus curves (see figure 1 ), the CD is more sensitive to the energy of the exposure; while the change of the focal length, the change of the CD is relatively slow: near the peak of the curve (often called: the best focal length), the change of the CD is very gentle, At a distance from the peak value, CD changes relatively large, but this is often at the expense of changes in the profile (pattern profile) of the pattern exposed on the silicon wafer. If the profile of a pattern in the measured pattern is relatively poor, resulting in If there is an abnormality in the measurement of the characteristic size, it will cause the abnormal drift of the vertex of the entire curve, and the measurement of the focal length will also be abnormal.
Therefore, the above-mentioned method of measuring the focal length shift of the exposure machine is not very sensitive and prone to abnormal measurement
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[0015] In the measurement method of the present invention, when utilizing the main optical axis of the exposure during exposure and the movement direction of the silicon wafer platform (the silicon wafer is placed on the platform during exposure) to be non-perpendicular, the silicon wafer is exposed under different focal lengths, and the pattern will produce horizontal deviation. The principle of shifting is used to measure the offset of the focal length of the exposure machine.
[0016] figure 2 It is a schematic diagram of the principle of the measurement method of the present invention, the inclination of the incident light is θ, exposure is performed under different focal lengths, the offset of the first exposure pattern and the second exposure pattern is S, and the focal length of the exposure machine shifts The quantity is ΔF, and when θ and S are known, ΔF can be obtained according to the following formula: tanθ=S / ΔF ΔF=S / tanθ
[0017] Utilizing the above princ...
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The invention discloses a method for measuring focus offsets of an exposure tool, comprising the following steps: (1) under the normal working state of the exposure tool, exposing silicon chips to obtain the first exposing patterns; (2) exposing the silicon chips obtained in the step (1) for the second times to obtain the second exposing patterns by using the incoming ray which is inclined with the moving platform of the silicon chips; (3) measuring the offsets of the twice exposing patterns and removing the own offsets of the tool to calculate the focus offsets of the exposure tool in combination with the degree of inclination of light. The method can accurately measure the focus offsets of the exposure tool.
Description
technical field [0001] The invention relates to a method for measuring the focal length offset of an exposure machine in semiconductor preparation. Background technique [0002] In the manufacturing process of semiconductor devices, the photolithography process is an important process. As the line width (also known as CD) becomes smaller and smaller, it is necessary to reduce the wavelength of the light source and increase the NA (referring to the value of the numerical aperture of the lens system of the exposure machine) to increase the analytical resolution, which will lead to lithography DOF ( The depth of field) is reduced, so the requirements for monitoring and controlling the focal length shift of the exposure machine are becoming more and more stringent. [0003] At present, the method of measuring the focal length offset of the exposure machine is mostly to use the method of measuring on a silicon wafer, exposing at different positions on the silicon wafer with diff...
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IPC IPC(8): G03F7/20
Inventor 陈华伦罗啸陈雄斌熊涛陈瑜
Owner SHANGHAI HUAHONG GRACE SEMICON MFG CORP