KR20080046765A - Optical system for manufacturing semiconductor device - Google Patents

Abstract

An optical system in a semiconductor light exposure apparatus is provided to suppress generation of astigmatism and prevent a projection lens from partially deformed by a diffracted light beam by installing a heater onto the projection lens for heating a portion without projection of the diffracted light beam to a predetermined temperature. An optical system in a semiconductor light exposure apparatus comprises a light source(110), an illumination system(120), a reticle(130), and a projection lens(140). The light source generates a light beam having a predetermined single wavelength. The illumination system diffracts the light beam from the light source. The reticle is configured to transfer a predetermined image by using the diffracted light beam from the illumination system. The projection lens allows the diffracted light beam to project so as to make the transferred image to be projected at a predetermined magnification, and comprises a heater(150) that heats a portion without projection of the diffracted light beam to a predetermined temperature.

Description

Optical system for manufacturing semiconductor device

1 is a diagram schematically showing an optical system of a semiconductor exposure apparatus according to the prior art.

2 is a diagram schematically illustrating an optical system of a semiconductor exposure chamber ratio according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

110: light source 120: illumination system

130: reticle 140: projection lens

150: heater

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor manufacturing equipment, and more particularly, to an optical system of semiconductor exposure equipment for photosensitive photoresist formed on a wafer.

In general, the semiconductor manufacturing process consists of a series of unit processes, such as a deposition process, a photographic process, an etching process, and an ion implantation process. The photolithography process is also referred to as a photo-lithography process and is one of the essential processes in the design of semiconductor devices requiring high integration.

In the photolithography process, a predetermined photoresist is coated on a semiconductor substrate, and light of a predetermined wavelength is passed through a photomask or reticle in which a specific circuit is formed using an exposure apparatus such as a stepper on the photoresist. Exposing and developing the pattern to form a pattern on the semiconductor substrate.

In such a photolithography process, the irradiation light having a pattern image is required to be transferred onto the photosensitive film with light energy for chemically changing to give a precise focus and the photosensitive film to a desired shape. In addition, as the degree of integration of semiconductor devices is further required, technologies for improving the light source and resolution of the exposure apparatus are being developed as the storage capacity of the semiconductor device increases and the pattern becomes smaller.

As the light source of the exposure apparatus, g-line, i-line, DUV, KrF excimer laser, ArF excimer laser, and the like, which generate light of a single wavelength, are used, respectively. In addition, research and development of an exposure process using diffracted light diffracted by the light beams generated by the light source has been actively conducted as a technique for increasing the resolution and the depth of focus of the exposure apparatus.

Hereinafter, an optical system of a semiconductor exposure apparatus according to the prior art will be described with reference to the accompanying drawings.

1 is a diagram schematically showing an optical system of a semiconductor exposure apparatus according to the prior art.

As shown in FIG. 1, an optical system of a semiconductor exposure apparatus according to the prior art includes a light source 10 for generating a light beam 12 having a predetermined single wavelength for photosensitive photoresist formed on a surface of a wafer 60; An illumination system 20 diffracting the light beam 12 generated by the light source 10, a reticle 30 formed to transfer a predetermined image using the diffracted light diffracted by the illumination system 20, and And a projection lens 40 formed to project the image at a predetermined magnification while transmitting the diffracted light from which the image is transferred in the reticle 30.

Here, the illumination system 20 is installed at the rear end of the light source 10 because the light beam 12 generated by the light source 10 is emitted to a predetermined space with respect to the light source 10, the predetermined size The light ray 12 having high straightness is selectively extracted from the light ray 12 diffracted while passing through a hole. For example, the illumination system 20 may include a conventional illumination system in which exposure is symmetrically incident about an optical axis, and an off-axis illumination system in which the exposure is asymmetrically incident about an optical axis. Are classified as). Here, the incorporation illumination system will be described. The illumination system 20 is a type of multi-pole illumination system such as an annular aperture, a dipole aperture, a quadrupole aperture, etc. according to the number of holes symmetrically formed about the optical axis. It can be divided into. In particular, since the illumination system 20 such as a dipole illumination system and a quadrupole illumination system uses zero-order light or first-order diffracted light of the light beam 12, the linearity is high, and the focus of the image projected from the projection lens 40 is increased. The depth of focus of the diffracted light can be increased by allowing the surface of the photoresist formed on the wafer 60 to form the bottom. The plurality of diffracted light generated by the illumination system 20 converges on the reticle 30 and then diverges and enters the projection lens 40.

In addition, the projection lens 40 is configured to cause the plurality of diffracted light incident through the reticle 30 to be incident on the surface of the wafer 60 and to enlarge and project the surface of the wafer 60. For example, the projection lens 40 may include a plurality of high-order color reduction objective lenses formed to reduce and project the pattern image transferred from the reticle 30. In this case, the projection lens 40 may reduce and project the pattern image formed on the reticle 30 to about 1/4 times. Here, reference numeral 70 is a wafer stage.

Accordingly, the optical system of the semiconductor exposure apparatus according to the prior art diffracts the light beams 12 generated by the light source 10 so that the reticle 30 and the projection lens 40 are transferred through the projection lens 40 to the wafer 60. The photoresist formed on the surface of the wafer 60 by being incident on the photoresist is formed.

However, the optical system of the semiconductor exposure apparatus according to the prior art has the following problems.

The optical system of the semiconductor exposure apparatus according to the prior art deforms a sphere at a corresponding position by locally heating a projection lens 40 to which diffracted light is incident when the exposure process is continuously performed in a semiconductor production line, and the projection As the spherical deformation of the lens 40 causes astigmatism in which the focal point of the diffracted light incident on the projection lens 40 does not coincide exactly on the surface of the wafer 60, a defective production process is caused. There was a downside.

SUMMARY OF THE INVENTION An object of the present invention is to solve a problem according to the prior art, and prevents spherical deformation caused by local heating of the projection lens 40 even if the exposure process is continuously performed in a semiconductor production line, and the focus of diffracted light is on the wafer. (60) An object of the present invention is to provide an optical system of a semiconductor exposure apparatus that can increase or maximize productivity by preventing defects in the exposure process caused by astigmatism that does not exactly coincide with a surface.

An optical system of a semiconductor exposure apparatus according to an aspect of the present invention for achieving the above object comprises a light source for generating light rays having a predetermined single wavelength; An illumination system diffracting the light beams generated by the light source; A reticle formed to transfer a predetermined image using diffracted light diffracted by the illumination system; And a projection lens having a heater configured to transmit the diffracted light to project the image transferred from the reticle at a predetermined magnification and to heat a portion where the diffracted light is not transmitted to a predetermined temperature. .

Hereinafter, an optical system of a semiconductor exposure apparatus in an embodiment of the present invention will be described with reference to the accompanying drawings. Although the present invention has been described in detail only with respect to specific embodiments, it will be apparent to those skilled in the art that modifications and variations can be made within the scope of the technical idea of the present invention, and such modifications or changes belong to the claims of the present invention. something to do.

2 is a diagram schematically illustrating an optical system of a semiconductor exposure chamber ratio according to an embodiment of the present invention.

As shown in FIG. 2, the optical system of the semiconductor exposure apparatus according to the present invention includes a light source 110 for generating a light beam 112 having a predetermined single wavelength, and the light beam 112 generated by the light source 110. ), A reticle 130 formed to transfer a predetermined image using the diffracted light diffracted by the illumination system 120, and the image transferred from the reticle 130 And a projection lens 140 formed with a heater 150 for transmitting the diffracted light to project at a magnification and heating the portion where the diffracted light is not transmitted to a predetermined temperature.

Here, the light source 110 generates the light beam 112 having a single wavelength of a predetermined intensity for photosensitive photoresist formed on the wafer 160 supported on the stage. Although not shown, the light source 110 may include a lamp that generates light having a predetermined intensity by a power supply voltage applied from an external or power supply, and the reticle 130 or the wafer 160. And a condensing cover for condensing the light to make it incident. In this case, the lamp is input by a light source 110 control unit or an exposure control unit for receiving a detection signal detected by an optical sensor (not shown) formed at the edge of the light collecting cover to generate a control signal for controlling the output of the power voltage supply unit. Light intensity can be adjusted. In addition, the exposure controller outputs the control signal to a power supply for adjusting a power voltage applied to adjust the intensity of light emitted from the lamp. For example, the lamp may include an i-line (365 nm), a KrF excimer laser (248 nm), an ArF excimer laser (193 nm), and a flow that emit light of a constant wavelength while the outermost electrons of a specific material transition from a metastable state to a stable state. Ride dimmers (F _2, 157 nm), and extreme ultraviolet rays (EUV, 13 nm) that emit light from the collision of accelerated particles may be used. In addition, the light ray 112 generated by the light source 110 must be selectively incident on the reticle 130 by shielding means such as a shutter to terminate the exposure process when the exposure process of the wafer 160 is completed. You can.

Although not shown, the optical system of the semiconductor exposure apparatus of the present invention transmits the light beam 112 generated by the light source 110 to the illumination system 120, and transmits the diffracted light diffracted by the illumination system 120. It further comprises a light guide unit for transmitting to the reticle (130). The light guide unit is configured to minimize the loss of the light ray 112 and minimize the interference from the outside while changing the path of the light ray 112 generated by the light source 110. For example, the light guide unit may be configured to equalize the plurality of reflectors generated by the light source 110 to reflect the light rays 112 incident in a predetermined direction at a predetermined angle, and the light rays 112 reflected through the reflectors. It comprises a light guide tube formed to proceed by mixing. Here, the reflector is a mirror used to reflect the light ray 112, and the surface of glass or metal is polished well, or silver, aluminum, gold, zinc sulfide, rhodium or the like is deposited on the surface thereof. A planar mirror using a plane according to the shape of the surface, a spherical mirror including a concave mirror or a convex mirror having a lens-like action using a spherical surface, and a parabolic mirror in a parabolic shape It consists of an aspherical mirror or the like. In addition, the light guide tube is a waveguide formed for the purpose of uniformly mixing the light ray 112 and to increase the transmission efficiency, and has an optical fiber having a cross section that is significantly larger than that commonly used in terms of the size of the cross section. It is made, including. Although not shown, the light guide tube is made of glass or synthetic resin having a high transmittance of the core to which the light ray 112 is transmitted. In addition, the core portion of the center of the core (core) has a double cylindrical shape enclosed by a portion called a cladding (cladding) of a material such as aluminum having excellent reflectivity around. The outside is coated with a synthetic resin coating to protect it from impact, and the overall size of the light guide tube is about 15 cm. Accordingly, the light guide tube is formed such that the cladding of the material having excellent reflectivity surrounds the periphery of the core of the material having excellent transparency so that the light ray 112 having a cross section of a predetermined size transmitted through the core has a uniform intensity. You can have it.

As described above, the illumination system 120 is an incidence illumination system, because the light beam 112 generated by the light source 110 is emitted to a predetermined space with respect to the light source 110. Installed at the rear end of the (110) and diffracts the light beam 112 generated by the light source 110 using the imaging principle of the 0th order and ± 1st order diffracted light, and has a high linearity among the diffracted light. 112 is formed to be selectively extracted. In addition, the illumination system 120 may increase the depth of focus (DOF) by using a modified illumination method that diffracts the light rays 112 generated by the light source 110. For example, the incident illumination system 120 includes an annular aperture having one hole and a dipole dipole having two holes according to the number of holes symmetrically formed about the optical axis of the light ray 112. aperture, a quadrupole aperture with four holes. For example, in the dipole illumination system, the light ray 112 is passed through two holes to inject zeroth order and ± first order diffracted light into the reticle 130. In this case, the ± first-order diffracted light may be transmitted with focus in the reticle 130 and then collected by the projection lens 140 to be incident on the surface of the wafer 160.

The reticle 130 is formed with the pattern image to be projected onto the wafer 160. For example, the reticle 130 has a pattern image of a metal material having excellent reflectivity such as chromium or molybdenum which absorbs the diffracted light on a glass plate that transmits the diffracted light. In this case, the semiconductor exposure apparatus is configured such that one die corresponding to the pattern image repeated in a predetermined shape according to the diffracted light incident on the reticle 130 is projected onto the entire reticle 130 at once. And a stepper and an exposure apparatus (hereinafter referred to as a scanning apparatus) for scanning the pattern image by an alternative means of the stepper. Here, in the scanning facility, the light passing through the rectangular slit having a horizontal length close to the diameter of the projection lens 140 is gradually moved while the reticle 130 and the wafer 160 are moved in parallel to each other. The exposure process takes place by exposure to light. Although not shown, the reticle 130 is horizontally moved while being supported by the reticle stage, and the wafer 160 is supported by the wafer stage 170 to be moved in a direction parallel to each other with the reticle 130. For example, the pattern image projected on the reticle 130 is reduced to about 1/4 by the projection lens 140 and is projected onto the wafer 160. Therefore, the reticle 130 should be scanned at a speed four times faster than the speed at which the wafer 160 is moved. In this case, the plurality of diffracted light for transferring the pattern image of the reticle 130 is converged on the upper portion of the reticle 130 and then emitted from the lower portion of the reticle 130.

The projection lens 140 is positioned near the wafer 160 and is formed to reduce and project the pattern image transferred from the reticle 130. Also, the projection lens 140 may be referred to as an objective made of glass having excellent transparency. In addition, the projection lens 140 not only reduces the projection of the pattern image on the surface of the wafer 160, but also creates an enlarged image of the surface of the wafer 160, thereby sufficiently correcting various aberrations. It consists of a plurality of lenses for this purpose. The low magnification projection lens 140 does not require exact correction of the chromatic aberration, so the color magnification objective lens is used. Is used. For example, the projection lens 140 includes a plurality of high-order color reduction objective lenses.

Although not shown, the plurality of high-order color reduction objectives pass through the plurality of diffracted light so that the plurality of diffracted light may be spaced apart beyond their respective focal lengths to converge and emit the plurality of diffracted light. In this case, when the plurality of diffractive light lenses are continuously incident at the position, the aberration aberration may occur because the position is locally heated and deformation occurs. Theoretically, the high-order chromatic objective lens has a transmittance of 100%, but no material existing in nature has a material having a transmittance of 100%. In addition, the diffracted light that does not contribute to the transmittance and is absorbed by the high-order color objective lens is generated to locally deform the spherical surface of the high-order color objective lens, thereby preventing the plurality of diffracted light from focusing at one point on the surface of the wafer 160. Can cause astigmatism. Therefore, the optical system of the semiconductor exposure apparatus according to the embodiment of the present invention, the projection lens 140 is provided with a projection lens 140 is formed with a heater 150 for heating a portion where the diffracted light is not incident to a predetermined temperature ) Can be prevented from being locally deformed by the diffracted light and to prevent astigmatism from occurring, thereby increasing or maximizing the production yield.

For example, the heater 150 is a heating wire that is generated by a power voltage applied from the outside, and includes a zinc oxide (ZnS) thin film of a transparent material formed to have a predetermined thickness on the surface of the higher order blocking object lens. The zinc oxide thin film is a material mainly used as a transparent electrode of a liquid crystal display and may be used as a hot wire having a high specific resistance. The zinc oxide thin film has a resistance proportional to the length of the zinc oxide thin film and inversely proportional to the line width. Although not shown, a housing surrounding the plurality of hyperchromic objective lenses is formed, and a temperature measuring instrument for measuring heat generated by the plurality of hyperchromic objective lenses within the housing and outputting a temperature sensing signal. The temperature measuring device is configured to measure the surface temperatures of the plurality of high color difference objective lenses. The control unit may determine a heat generation degree of the plurality of higher order obstruction objective lenses heated by the diffracted light by using the temperature sensing signal output from the temperature measuring instrument, and the heater may be heated to a temperature corresponding to the heat generated by the diffracted light. A control signal is output to apply a power supply voltage for heating 150. Accordingly, the heater 150 may prevent the occurrence of astigmatism by heating the entire surface of the plurality of higher order obstruction objective lenses, which is equivalent to a temperature at which the plurality of high order objective objects are locally heated by the diffracted light. have.

As a result, an optical system of a semiconductor exposure apparatus according to an embodiment of the present invention includes a projection lens 140 having a heater 150 for heating a portion where diffracted light is not incident, thereby continuously exposing the semiconductor production line. Even if this is done, spherical deformation due to local heating of the projection lens 140 is prevented, and defects in the exposure process due to astigmatism that do not coincide exactly with the surface of the wafer 160 due to diffraction light are prevented, thereby improving productivity. Can be increased or maximized.

In addition, the description of the above embodiment is merely given by way of example with reference to the drawings in order to provide a more thorough understanding of the present invention, it should not be construed as limiting the invention. In addition, for those skilled in the art, various changes and modifications may be made without departing from the basic principles of the present invention.

As described above, according to the present invention, a projection lens having a heater for heating a portion where diffracted light is not incident is provided, and even though the exposure process is continuously performed in a semiconductor production line, There is an effect of preventing spherical deformation and preventing the defect of the exposure process due to the generation of astigmatism, in which the focal point of the diffracted light does not exactly match the wafer surface, thereby increasing or maximizing productivity.

Claims (3)

A light source for generating light rays having a predetermined single wavelength; An illumination system diffracting the light beams generated by the light source; A reticle formed to transfer a predetermined image using diffracted light diffracted by the illumination system; And And a projection lens having a heater configured to transmit the diffracted light to project the image transferred from the reticle at a predetermined magnification, and to heat a portion where the diffracted light is not transmitted to a predetermined temperature. Optical system of exposure equipment. The method of claim 1, And said heater comprises a zinc oxide thin film. The method of claim 1, A temperature measuring signal output by measuring a heat generation of the projection lens in the housing, a temperature surrounding the projection lens, and a temperature sensing signal output from the temperature measuring instrument, and being heated by the diffraction light. And a controller configured to determine a degree of heat generation of the plurality of higher order obstruction objective lenses and to output a control signal to apply a power voltage for heating the heater to a temperature corresponding to the heat generated by the diffracted light. Optical system of exposure equipment.

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