JP2017072867A - Exposure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress contamination on a mask or an optical system due to contaminants generating in a chamber of an EUV exposure apparatus.SOLUTION: An energy ray source 41 is disposed close to a wafer stage 24 set in a chamber 25 of an EUV exposure apparatus 10A, and emission gas emitted from a resist applied on a surface of the wafer 23 is decomposed by energy rays 42 so as to protect illumination mirrors 14 to 16 constituting an illumination optical system 13, projection mirrors 31 to 36 constituting a projection optical system 37, a mask 21 and the like from contamination by contaminants.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exposure technique used for pattern transfer of an LSI or the like, and more particularly to a technique effective when applied to an exposure method and an exposure apparatus using extreme ultra-violet (hereinafter referred to as EUV) as an exposure light source. Is.

  LSI is a lithography technology that irradiates a mask (also called a reticle), which is an original plate on which a circuit pattern is drawn, with exposure light, and transfers the circuit pattern onto the surface of a semiconductor wafer (hereinafter referred to as a wafer) via a reduction optical system. Is manufactured by.

  In recent years, along with higher integration and higher speed of LSI, circuit patterns have been miniaturized rapidly. As a technique for miniaturizing a circuit pattern, generally, the wavelength of an exposure light source is shortened. Specifically, from lithography technology using ultraviolet rays such as g-line (wavelength = 436 nm) and i-line (wavelength = 365 nm) as an exposure light source, KrF excimer laser (wavelength = 248 nm) and ArF excimer laser (wavelength = 193 nm) In recent years, for further miniaturization, immersion ArF lithography using the refractive index of water and double patterning technology that performs exposure twice have been applied to mass production. It is being advanced.

  Recently, a lithography technique using EUV (wavelength = 13.5 nm) as an exposure light source has been studied as a technique using a high-energy beam having a shorter wavelength. When this EUV is used as an exposure light source, the size of a resolvable circuit pattern is 1/10 or less of the wavelength of ArF, and thus has attracted attention as a method for forming an extremely fine pattern.

  When the EUV light is used, the mask is a reflection type, and the illumination optical system and the projection optical system are all reflection types, that is, configured by mirrors. The EUV exposure apparatus includes a light source that emits an exposure light beam, an illumination optical system that illuminates an original mask with the exposure light beam, a projection optical system that projects the mask pattern onto an object to be exposed, a stage on which the mask is placed, the target The stage is configured by a stage on which an exposure body is placed, a space for housing the projection optical system, and the like. The object to be exposed is a wafer having a surface coated with a photosensitive material called a resist.

  In general, EUV light is absorbed by any substance and cannot pass through the air. For this reason, in the case of an exposure apparatus using EUV light, in order to make the exposure light reach the wafer surface with sufficient illuminance, it is necessary to reduce or eliminate the light-absorbing substance on the exposure optical path and keep the optical path space in a high vacuum state. is there. In addition, it is necessary to configure the optical path space with a substance that emits as little gas as possible.

  In the above-described exposure apparatus using EUV light as an exposure light source, the emitted gas generated from the resist by the irradiation of the EUV light and the gas generated from the substance existing in the exposure apparatus stay in the optical path space. Here, the released gas refers to a gas mainly composed of a carbon compound generated by decomposition of the resist composition during exposure. When the emitted gas is excited by EUV light, the carbon compounds are bonded to each other, and are deposited on the surface of the mask or the optical system (mirror) as so-called contamination.

  When the contamination as described above adheres to the surface of the mask or mirror, the reflectivity of the mirror decreases and the amount of EUV light reaching the surface of the wafer decreases, so that the circuit pattern of the mask is transferred to the resist. The required exposure time increases. In addition, since the optical performance of the EUV exposure apparatus is significantly deteriorated, such as uneven illuminance of the EUV light and increased wavefront aberration, the transfer accuracy of the circuit pattern also decreases.

  Therefore, as disclosed in the following Patent Documents 1 to 3 and the like, various techniques for removing the contamination generated in the EUV exposure apparatus have been proposed.

  In Patent Document 1 (Japanese Patent Laid-Open No. 2004-356410), an electrode for collecting contamination and an apparatus for ionizing the contamination are provided around an opening for transmitting EUV light formed in a blind of an optical system barrel. Thus, a technique for suppressing the adhesion of contamination to the surface of a mirror or the like is disclosed.

  In Patent Document 2 (Japanese Patent Laid-Open No. 2006-269942), an inert gas supply device is provided in the optical path space of the EUV exposure apparatus, and an exhaust space is provided between the optical path space and the wafer stage space. A technique for discharging contamination into an exhaust space together with an inert gas is disclosed.

  Japanese Patent Application Laid-Open No. 2005-101537 discloses a technique for adsorbing contamination with a cold trap such as a cryopanel provided in the optical path space of an EUV exposure apparatus.

JP 2004-356410 A JP 2006-269942 A JP 2005-101537 A

  As a result of analyzing the emitted gas component generated from the resist in order to remove the contamination generated in the EUV exposure apparatus, the present inventor has found that the contamination of the mask and mirror due to the contamination is the emitted gas component generated from the resist. Among these, the knowledge that it originates mainly in the carbon compound whose molecular weight is about 100-300 was acquired. The inventors have found that if the partial pressure of the carbon compound in the optical path space of the EUV exposure apparatus can be reduced, contamination of the mask and mirror due to contamination can be remarkably suppressed, and the present invention has been completed.

  An object of the present invention is to provide an exposure technique capable of protecting a mirror and a mask constituting an illumination system / projection system of an EUV exposure apparatus from contamination due to contamination and improving productivity such as device manufacturing yield and reliability. It is to provide.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, one aspect of a typical one will be briefly described as follows.

  This one aspect includes an exposure light source that emits EUV, a mask stage on which a mask on which a predetermined pattern is formed, an illumination optical system that illuminates the mask with the EUV, and an object to be exposed whose resist is coated on the surface. An exposure apparatus comprising a chamber in which an exposure object stage for placing a body and a projection optical system for projecting the pattern formed on the mask onto the exposure object are housed, wherein the exposure apparatus includes: In the chamber, there are provided an energy beam generating source for generating an energy beam for decomposing the gas released from the resist, and an exhaust system for discharging the gas in the chamber.

  Among the inventions disclosed in the present application, effects obtained by one embodiment of a representative one will be briefly described as follows.

  By decomposing the emitted gas from the resist with energy rays, it is possible to suppress the occurrence of contamination caused by the emitted gas, so the mirrors and masks constituting the illumination system / projection system of the EUV exposure apparatus are contaminated. Can be protected from contamination.

It is a schematic block diagram of the EUV exposure apparatus which is Embodiment 1 of this invention. FIG. 2 is an enlarged view showing a part of FIG. 1 (near an exposure region of an object to be exposed). FIG. 2 is an enlarged plan view showing a part of FIG. 1 (near an exposure region of an object to be exposed). It is an enlarged view which shows another example of the EUV exposure apparatus which is Embodiment 1 of this invention. It is an enlarged plan view which shows another example of the EUV exposure apparatus which is Embodiment 1 of this invention. It is a timing chart which shows an example of the timing which the EUV exposure light beam emitted from an EUV light source reaches | attains a wafer, and the timing which irradiates an energy ray. It is a timing chart which shows another example of the timing which the EUV exposure light beam emitted from an EUV light source reaches | attains a wafer, and the timing which irradiates an energy ray. It is a timing chart which shows another example of the timing which the EUV exposure light beam emitted from an EUV light source reaches | attains a wafer, and the timing which irradiates an energy ray. It is a schematic block diagram of the EUV exposure apparatus which is Embodiment 2 of this invention. FIG. 10 is an enlarged view showing a part of FIG. 9 (near the exposure area of the object to be exposed). FIG. 10 is an enlarged plan view showing a part of FIG. 9 (near the exposure region of the object to be exposed). It is an enlarged view which shows another example of the EUV exposure apparatus which is Embodiment 2 of this invention. It is an enlarged plan view which shows another example of the EUV exposure apparatus which is Embodiment 2 of this invention. It is a schematic block diagram of the EUV exposure apparatus which is Embodiment 3 of this invention. FIG. 15 is an enlarged view showing a part of FIG. 14 (in the vicinity of an exposure area of an object to be exposed). It is a schematic block diagram of the EUV exposure apparatus which is Embodiment 4 of this invention. (A), (b) is an enlarged view which shows a part (near the exposure area | region of a to-be-exposed body) of FIG. It is a timing chart which shows an example of the timing which the EUV exposure light beam emitted from an EUV light source reaches a wafer, the timing which irradiates an energy ray, and the timing which opens and closes a shutter.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted. In the embodiments, the description of the same or similar parts will not be repeated in principle unless particularly necessary. Furthermore, in the drawings for describing the embodiments, hatching may be applied even in a plan view or hatching may be omitted even in a cross-sectional view for easy understanding of the configuration.

(Embodiment 1)
FIG. 1 is a schematic block diagram showing a scanning EUV exposure apparatus of the present embodiment. The EUV exposure apparatus 10A includes an EUV light source 11 that generates an EUV exposure light beam 12, an illumination optical system 13 that includes illumination mirrors 14, 15, and 16, and a projection optical system 37 that includes projection mirrors 31, 32, 33, 34, 35, and 36. , A folding mirror 17, a mask stage 22 on which a reflective mask 21 is mounted, a wafer stage 24 on which a wafer 23 as an object to be exposed is mounted, a chamber 25 in which these are housed, and a plurality of pumps for exhausting the chamber 25 26A, 26B, 26C, 26D, etc.

  A multilayer film (not shown) for specularly reflecting the EUV exposure light beam 12 is formed on each surface of the folding mirror 17, the mask 21, and the projection mirrors 31 to 36. Although not shown, an EUV resist is applied to the surface of the wafer 23. The mask stage 22 and the wafer stage 24 have a mechanism for scanning in synchronization with a speed ratio proportional to the reduction magnification. Hereinafter, the scanning direction in the plane of the mask 21 or the wafer 23 is defined as the Y-axis direction, the direction perpendicular thereto is defined as the X-axis direction, and the direction perpendicular to the plane of the mask 21 or wafer 23 is defined as the Z-axis direction.

  In general, in a scanning exposure apparatus, a mask and a wafer are scanned synchronously to perform one shot exposure (referred to as scan exposure). That is, the exposure light beam emitted from the light source scans the mask and the object to be exposed (wafer) simultaneously and exposes the wafer. After one shot of exposure is performed, the exposure light beam stops or reaches the wafer surface with a shutter or the like. When it stops, one shot (also called one scan) is completed. Next, the wafer moves to the initial position of the next exposure shot called a step. Thereafter, exposure (second scan) is performed again by scanning the mask and the wafer. As described above, in the scanning exposure apparatus, almost the entire surface of the wafer is exposed while alternately repeating scanning and steps.

  As shown in FIG. 1, the EUV exposure apparatus 10A of the present embodiment includes an energy beam generation source 41 that emits an energy beam 42 for decomposing emitted gas. Here, examples of the energy ray 42 include light rays such as visible infrared rays, ultraviolet rays, deep ultraviolet rays, extremely short ultraviolet rays, vacuum ultraviolet rays, and soft X-rays, charged particles such as electrons and ions, and neutral molecular beams. Examples of the energy beam generation source 41 include a mercury lamp, a xenon lamp, an excimer lamp, an excimer laser, a semiconductor laser, a laser excitation plasma light source, a discharge excitation plasma light source, an electron beam source, an ion beam source, and a proton beam.

  In order to improve the directivity of the energy beam 42, the energy beam source 41 that emits light rays such as visible infrared rays, ultraviolet rays, deep ultraviolet rays, extremely short ultraviolet rays, vacuum ultraviolet rays, and soft X-rays is collected in the energy ray 42 as necessary. It is preferable to provide an optical optical system. Moreover, it is preferable to provide an electromagnetic optical system in the energy beam generation source 41 that emits charged particles such as electrons and ions.

  The energy rays 42 emitted from the energy ray generating source 41 are generated from the resist applied on the surface of the wafer 23 and decompose the emitted gas existing in the chamber 25. At that time, since a molecule having a higher molecular weight is more easily decomposed, a partial pressure of a carbon compound having a molecular weight of about 100 to 300, which is a main cause of contamination, among the emitted gas components is significantly reduced.

  The energy beam generation source 41 can be installed at an arbitrary location in the chamber 25, but it is desirable to arrange the energy beam generation source 41 in the vicinity of the wafer stage 24 on which the wafer 23, which is a generation source of the released gas, is mounted. The emitted gas generated from the resist can be rapidly decomposed.

  Further, the energy ray generation source 41 can be installed not only at one place in the chamber 25 but also at a plurality of places. At that time, not only the same type of energy beam generation sources 41 may be installed at a plurality of locations, but also different types of energy beam generation sources 41 may be installed in combination.

  FIG. 2 is an enlarged view showing the vicinity of the exposure area of the object to be exposed (wafer 23) in the EUV exposure apparatus 10A, and FIG. 3 is an enlarged plan view showing the vicinity of the exposure area of the object to be exposed in the EUV exposure apparatus 10A. It is.

  The EUV exposure light beam 12 has, for example, a planar pattern on an arc, and is irradiated from the Z-axis direction to the XY plane direction. On the other hand, the energy beam 42 is irradiated in the Y-axis direction. As shown in FIGS. 4 and 5, the EUV exposure light beam 12 may be irradiated from the Z-axis direction to the XY plane direction, and the energy beam 42 may be irradiated in the X-axis direction.

  The energy beam generation source 41 is desirably provided with means for expanding the irradiation area in the XY plane direction as necessary. As such means, for example, when the energy ray 42 is a light ray such as visible infrared ray, ultraviolet ray, deep ultraviolet ray, extremely short ultraviolet ray, vacuum ultraviolet ray, soft X-ray, etc., an optical that makes the incident angle with respect to the energy ray 42 movable. The system can be mentioned. Further, when the energy beam 42 is a charged particle such as an electron or ion, an electromagnetic optical system capable of electrostatic deflection or electromagnetic deflection can be used.

  In the EUV exposure apparatus 10A, the timing of irradiating the energy beam 42 when exposing one wafer 23 may be various in consideration of the amount and components of the emitted gas.

  FIG. 6 is a timing chart showing an example of the timing at which the EUV exposure light beam 12 emitted from the EUV light source 11 reaches the wafer 23 and the timing at which the energy rays 42 are irradiated. In this example, the EUV exposure light beam 12 reaches the wafer 23 and the scanning exposure is started, and at the same time, the energy beam 42 is irradiated. Thereafter, the irradiation of the energy beam 42 is continuously performed while the scanning exposure and the movement (step) of the wafer stage 24 are alternately repeated.

  In the timing example shown in FIG. 7, the energy beam 42 is irradiated at the same time as the scanning exposure is started, and the irradiation of the energy beam 42 is stopped when one shot of exposure is completed. Next, after the movement (step) of the wafer stage 24, when the next scan exposure is started, the energy beam 42 is irradiated again. Thereafter, the energy beam 42 is irradiated only during the scanning exposure in the same manner.

  In the example shown in FIG. 8, the scanning exposure timing and the energy beam 42 irradiation timing are opposite to the example shown in FIG. That is, during the scanning exposure, the irradiation of the energy beam 42 is stopped, and the energy beam 42 is irradiated only while the movement (step) of the wafer stage 24 is performed.

  In this way, by decomposing the gas released from the resist with the energy beam 42, it is possible to suppress the occurrence of contamination caused by the gas released. Thereby, the illumination mirrors 14 to 16 constituting the illumination optical system 13 of the EUV exposure apparatus 10A, the projection mirrors 31 to 36 constituting the projection system optical system 37, the mask 21 and the like can be protected from contamination due to contamination. Thus, productivity such as device manufacturing yield and reliability can be improved.

(Embodiment 2)
FIG. 9 is a schematic block diagram showing a scanning EUV exposure apparatus 10B of the present embodiment. The EUV exposure apparatus 10B according to the present embodiment is characterized in that an aperture 43 having an opening 44 that allows the EUV exposure light beam 12 to pass therethrough is disposed between the space for housing the projection optical system 37 and the wafer stage 24, and EUV. A system 45 is provided between the light source 11 and the energy ray generation source 41 to link the operations of the two.

  In addition, a shutter (not shown) interlocked with the operation of the energy ray generation source 41 is disposed in the optical path space between the EUV light source 11 and the mask 21 so that the EUV exposure light beam 12 is irradiated or not irradiated on the mask 21. You may control by opening and closing of this shutter. The other configuration of the EUV exposure apparatus 10B is the same as that of the EUV exposure apparatus 10A of the first embodiment.

  By providing the system 45 as described above in the EUV exposure apparatus 10B, it is possible to control the timing of scan exposure and the timing of irradiation of the energy beam 42 with high accuracy. In addition, by providing the aperture 43 as described above in the EUV exposure apparatus 10B, it becomes difficult for the gas emitted from the resist to diffuse into the illumination optical system 13, the projection optical system 37, the mask 21, and the like. Contamination of the optical system 13, the projection optical system 37, the mask 21, etc. can be effectively suppressed.

  As shown in FIGS. 10 to 13, the aperture 43 can be arranged either above or below the energy ray generation source 41. Moreover, the irradiation direction of the energy beam 42 can be either the Y-axis direction or the X-axis direction.

(Embodiment 3)
FIG. 14 is a schematic block diagram showing a scanning EUV exposure apparatus 10C of the present embodiment, and FIG. 15 is an enlarged view showing the vicinity of an exposure area of an object to be exposed (wafer 23) in the EUV exposure apparatus 10C.

  The EUV exposure apparatus 10C according to the present embodiment is characterized in that the apertures 43 described in the second embodiment are arranged one above and below the energy beam generation source 41, respectively, and the pair of apertures 43 and 43 is used. The pump 26E for exhausting the gas in the enclosed space is provided. Other configurations are the same as those of the EUV exposure apparatus 10B of the second embodiment.

  By providing the pair of apertures 43 and 43 and the pump 26E as described above in the EUV exposure apparatus 10C, the gas emitted from the resist and the low molecular weight decomposition gas generated by the irradiation of the energy beam 42 are removed from the EUV exposure apparatus 10C. It is possible to discharge efficiently. Therefore, contamination of the illumination optical system 13, the projection optical system 37, the mask 21, etc. can be more effectively suppressed.

(Embodiment 4)
FIG. 16 is a schematic block diagram showing a scanning EUV exposure apparatus 10D of the present embodiment, and FIGS. 17A and 17B show the vicinity of an exposure area of an object to be exposed (wafer 23) in the EUV exposure apparatus 10D. It is an enlarged view.

  The EUV exposure apparatus 10D according to the present embodiment is characterized in that a shutter 46 is disposed in the optical path space near the wafer stage 24, and this shutter 46 is connected to the system 45, and the EUV light source 11, the energy beam generation source 41, and the shutter. This is because the operation of 46 is linked. Other configurations are the same as those of the EUV exposure apparatus 10B of the second embodiment.

  FIG. 18 is a timing chart showing an example of the timing at which the EUV exposure light beam 12 emitted from the EUV light source 11 reaches the wafer 23, the timing at which the energy beam 42 is irradiated, and the timing at which the shutter 46 opens and closes.

  During the scanning exposure, the shutter 46 is opened to retract from the vicinity of the exposure area of the wafer 23 and the irradiation of the energy beam 42 is stopped (see FIG. 17A). Further, during the movement (step) of the wafer stage 24, the energy ray 42 is irradiated with the shutter 46 closed (see FIG. 17B). In this way, since the energy beam 42 does not reach the surface of the wafer 23, excessive exposure of the resist by the energy beam 42 is prevented particularly when the energy beam 42 is a light beam having a short wavelength.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  The present invention can be applied to an exposure technique using EUV as an exposure light source.

10A, 10B, 10C, 10D EUV exposure apparatus 11 EUV light source 12 EUV exposure light beam 13 Illumination optical system 14, 15, 16 Illumination mirror 17 Folding mirror 21 Mask 22 Mask stage 23 Wafer 24 Wafer stage 25 Chambers 26A, 26B, 26C, 26D 26E Pump 31, 32, 33, 34, 35, 36 Projection mirror 37 Projection optical system 41 Energy beam source 42 Energy beam 43 Aperture 44 Aperture 45 System 46 Shutter

Claims (4)

An exposure light source that emits EUV; a mask on which a predetermined pattern is formed; a projection optical system that includes a plurality of projection mirrors; an object to be exposed with a resist applied to the surface; the projection optical system and the object to be exposed; Using a scanning exposure apparatus having an energy ray generating source for irradiating energy rays between and a shutter disposed between the projection optical system and the object to be exposed,
(A) a first exposure step in which an exposure light beam emitted from the exposure light source exposes a first region of the object to be exposed while scanning the mask and the object to be exposed;
(B) moving the object to be exposed;
(C) a second exposure step in which an exposure light beam emitted from the exposure light source exposes a second region different from the first region of the object to be exposed while scanning the mask and the object to be exposed;
Have
In the step (b), the energy beam is placed between the projection optical system and the object to be exposed in a state where the shutter is closed so as to prevent the energy beam from being irradiated to the object to be exposed. By irradiating with energy rays, the emitted gas from the resist is decomposed,
The said (a) and (c) process is an exposure method implemented in the state which opened the said shutter and stopped the irradiation of the said energy beam. The exposure method according to claim 1,
The energy beam includes at least one of infrared rays, visible light, ultraviolet rays, deep ultraviolet rays, extremely short ultraviolet rays, vacuum ultraviolet rays, soft X-rays, charged particles made of electrons or ions, and beams made of neutral molecules. . The exposure method according to claim 1,
The energy beam is an exposure method in which a carbon compound having a molecular weight of 100 to 300 is mainly decomposed among components of the emitted gas. The exposure method according to claim 1,
The scanning exposure apparatus includes an aperture having an aperture through which the exposure light beam passes between the projection optical system and the object to be exposed.

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