Achromatic position alignment optical system

Abstract

The invention discloses an achromatic position alignment optical system. The system is provided with a mask alignment optical system, a mask, an optical projection system and an exposure object, wherein the mask alignment optical system comprises a mask mark illumination system and a mask mark imaging system; an exposure object mark illumination system consists of the mask mark illumination system and the optical projection system; and an exposure object mark imaging system consists of the mask mark imaging system and the optical projection system. The achromatic position alignment optical system comprises an illumination objective lens, a beam splitting right-angle prism, an aperture diaphragm, a front imaging objective lens, the mask, the optical projection system, and the exposure object in turn along an optical axis from an emergent end of an illumination optical fiber, and a rear imaging objective lens, a field lens imaging objective lens, and a charge coupled device (CCD) camera receiving surface which are positioned on the optical axes of the aperture diaphragm and the front imaging objective lens and on the other side of the splitting right-angle prism.

Description

technical field [0001] The invention relates to an achromatic position alignment optical system, in particular to an achromatic position alignment optical system used in semiconductor lithography equipment. Background technique [0002] In semiconductor lithography equipment, the position alignment device is one of the very important devices. Structurally, position alignment devices can be divided into two categories: on-axis position alignment devices and off-axis position alignment devices. On-axis position alignment means that both the illumination and imaging of the exposure target mark pass through the optical projection system in the exposure device. [0003] The coaxial position alignment device is located above the reticle. The coaxial alignment optical system is one of the important components of the coaxial position alignment device. The quality of its design will directly affect the alignment accuracy of the coaxial position alignment device. . The design of th...

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Problems solved by technology

[0004] In U.S. Patent US 7148953B2, an exposure device is disclosed, in which a wide-band optical projection system is designed, which not only includes the ultraviolet exposure band 365nm-436nm, but also includes the visible light band for imaging of the exposed object mark 520nm~650nm; although this structure eliminates the chromatic aberration of the exposed object mark in the visible light band when it is imaged by the optical projection system, when the design field of view and numerical aperture of the optical projection system are increased, in order to meet the design index requirements, it is necessary The main reflector in the optical path of the optical projection system is designed as an aspheric surface, which not only increases the design complexity of the optical projection system, but more importantly increases the difficulty of installation and calibration and the cost of equipment processing and manufacturing

[0005] In U.S. Patent No. 4,492,459, in order to reduce the difficulty of designing and installing the optical projection system, the optical projection system only performs aberration correction for the ultraviolet exposure band, while the chromatic aberration generated by the optical projection system in the visible light band for alignment is determined by the position The alignment device is compensated, and the compensation method is mainly realized by optical elements located between the reticle and the optical projection system; although the design of this structure solves the problems existing in US Patent No. 7,148,953 B2, since the compensation optical elements are located Between the reticle and the optical projection system, on the one hand, there is a certain constraint on the distance between the reticle and the top of the mechanical housing of the optical projection system; The position alignment device is not compact enough

[0006] In US Patent US 5621813, an alignment optical system with a magnification of nearly 20 times is designed to achieve clear imaging of mask marks and exposure object marks. In order to optimize the imaging quality and ensure a long enough working distance, the alignment optical system Multiple reflectors are set in the optical path to ensure a more compact space layout between the optical elements; although this structure design can ensure higher imaging resolution, but because multiple reflectors are set in the optical path, it not only increases the The difficulty of installing and calibrating the alignment optical system also makes the spatial structure size of the alignment optical system relatively large

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