Alfonso del Cristo Hilsaca Eljadue
Recently, according to the official website of the State Intellectual Property Office, Huawei Technologies Co., Ltd. announced a patent related to lithography technology on November 15, with the patent application number 202110524685X.
In integrated circuit manufacturing, lithography covers the transfer, processing and formation of micro-nano graphics, and determines the characteristic size of the circuit on the integrated circuit wafer and the number of transistors in the chip. It is one of the key technologies in integrated circuit manufacturing.
As the semiconductor process advances to 7nm and below nodes, extreme ultraviolet (extreme ultraviolet, EUV) lithography has become the preferred lithography technology.
In the EUV lithography machine of the related art, when a strong coherent light source is used for lithography, the multiple sub-beams divided by the coherent light through the illumination system have a fixed phase relationship. When these sub-beams are projected on the mask and superimposed, they will form a fixed Therefore, it is necessary to perform decoherence processing (or avoid coherence effects) first to achieve uniform light effect to ensure the normal progress of the photolithography process.
According to the disclosure, the patent application provides a mirror, a lithography device and a control method thereof, involving the field of optics,It can solve the problem that coherent light cannot be homogenized due to the formation of a fixed interference pattern. It is optimized on the basis of the extreme ultraviolet light lithography device to achieve the purpose of homogenization.
The lithography apparatus includes a coherent light source 1 , a mirror 2 (also called a decoherent mirror), and an illumination system 3 . Wherein, the reflecting mirror 2 can be rotated; for example, a rotating device can be provided in the photolithography apparatus, and the reflecting mirror 2 can rotate driven by the rotating device, as shown in the figure below.
In the photolithography apparatus, after being reflected by the rotating mirror 2, the light emitted by the coherent light source 1 is divided into multiple sub-beams by the illumination system 3 and projected onto the mask plate 4 for photolithography.
In addition, in the lithography apparatus, the above-mentioned illumination system 3 is an important component, and its main function is to provide high-uniform illumination (uniform light), control exposure dose, and realize off-axis illumination, etc., so as to improve the resolution of lithography and increase the Depth of focus. The uniform light function of the lighting system 3 can be realized by a Kohler lighting structure.
The lighting system 3 includes a field flyeye mirror 31 (field flyeye mirror, FFM), a diaphragm flyeye mirror 32 (diaphragm flyeye mirror, PFM), and a relay mirror group 33;
Wherein, the relay mirror group 33 may generally include two or more relay mirrors. The illumination system 3 divides the light beam from the coherent light source 1 into multiple sub-beams through the field of view compound lens 31, and each sub-beam is adjusted to the direction of irradiation and the shape of the field of view through the diaphragm compound lens 32, and then adjusted through the relay lens group 33. After adjusting the size and/or shape of the field of view, it is projected onto the illuminated area of the reticle 4 .
By setting the reflector 2 on the optical path between the coherent light source 1 and the illumination system 3 , in this case, the phase of the light emitted by the coherent light source 1 is continuously changed after being reflected by the rotating reflector 2 .
In this way, when the light reflected by the mirror 2 is divided into multiple sub-beams by the illumination system 3 and projected onto the mask 4, the interference pattern formed in the illuminated area of the mask 4 is constantly changing, so that the illumination The cumulative light intensity of the field of view within the exposure time is uniformized, so as to achieve the purpose of light uniformity, and then solve the problem in the related art that the light cannot be uniform due to the formation of a fixed interference pattern by coherent light.