JP2014526152A - Exposure apparatus and method for patterned exposure of photosensitive layer - Google Patents

Abstract

The present invention comprises a substrate (6) having a photosensitive layer (1) and an exposure light beam (3) having a maximum intensity greater than an intensity threshold for converting the photosensitive layer (1) from the second state to the first state. And a generating device (7) for generating a plurality of exposure rays (3) each having an exposure wavelength (λ _B ), each assigned to a partial region of the photosensitive layer (1) , A moving device (13) for moving the exposure beam (3) with respect to each assigned partial region, and an excitation wavelength (for converting the photosensitive layer (1) from the first state to the second state). The present invention relates to an exposure apparatus (5) including an excitation light source (31) for generating excitation radiation (32) having λ _A ). The invention also relates to an associated exposure method.
[Selection] Figure 9

Description

[Cross-reference to related applications]
This application claims priority to German Patent Application No. 10 2011 081 247.4 filed on August 19, 2011 under “35 U.S.C. §119 (a)”, all of which The contents are hereby incorporated by reference into the disclosure of the present application.

  The present invention relates to an exposure apparatus for exposure with a pattern of a photosensitive layer and a designated exposure method.

  An exposure apparatus for microlithography can expose a structure with high accuracy to a photosensitive layer formed on a substrate. In general, such an exposure apparatus includes a light source, an illumination system that processes the light emitted by the light source to form illumination light, a projected object, commonly referred to as a reticle or mask, and an object field. And a projection lens that forms an image on the image field. The mask or at least part of the mask is placed in the object field, and the substrate (hereinafter also referred to as wafer) or at least part of the substrate is placed in the image field of the projection lens.

  If the mask is placed entirely within the area of the object field and the wafer is exposed without relative movement of the wafer and the image field, this lithographic apparatus is commonly referred to as a wafer stepper. If only a part of the mask is placed in the region of the object field and the wafer is exposed during the relative movement of the wafer and the image field, this lithographic apparatus is generally referred to as a wafer scanner. A spatial coordinate axis determined by relative movement between the reticle and the wafer is generally called a scanning direction. An exposure apparatus for near-field lithography based on the principle of step-and-repeat exposure is a paper written by Yasuhisa Inao et al. “Near-Field Lithography as Prototype Nano-Fabrication Tool”. , Microelectronic Engineering, 84 (2007), pages 705-710.

  In addition to exposure apparatuses in which a predetermined structure fixed on the mask is imaged on the photosensitive layer, there are also exposure apparatuses based on the principle of raster scanning, in which case they are typically parallel, separated from one another. Multiple exposure rays are generated and modulated in a manner that depends on the structure generated on the photosensitive layer. In this case, the photosensitive layer can be displaced transversely to the exposure beam so that the entire exposed area can be patterned. In this case, for example, electron radiation is typically used as exposure radiation, as exemplified in the case of the system described in US Pat. No. 7,425,713 B2.

US 7425713 B2 US 2006/0044985 A1

Yasuhisa Inao et al., “Near-Field Lithography as Prototype Nano-Fabrication Tool”, Microelectronic Engineering, 84 (2007), pages 705-710. http: // en. wikipedia. org / wiki / Surface_Plasmon David O. S. Melville et al., “Super-resolution near-field lithography using planar silver lenses” (invited poster, MNE-2005 ID 00709, “http: //www.mne05”). / 3-c — 01.pdf ”) http: // www. lglog. de / 2009/06/15 / kleinstes-lcd-display-der-wel-mit-vga-auflosun / http: // www. mpibpc. mpg. de / groups / hell / STED_Dyes. html

  It is an object of the present invention to specify an exposure apparatus and associated exposure method that enables patterned exposure of a photosensitive substrate with high resolution.

  According to one aspect, the present invention provides a generating device for generating a plurality of particularly parallel exposure rays each assigned to a partial area of the photosensitive layer, and in particular over or against each assigned partial area of the exposure light. A moving device for moving in a scanning fashion and converting each exposure beam into an evanescent wave to generate a light spot on the photosensitive layer that has a smaller spread than the exposure beam spread upstream of the near-field optical unit The present invention relates to an exposure apparatus for exposure with a pattern of a photosensitive layer including a near-field optical unit disposed upstream of the photosensitive layer functioning as described above.

  In the case of such an exposure apparatus, the surface of the exposed photosensitive layer or wafer is subdivided into a plurality of partial areas in which exposure occurs simultaneously with each exposure light beam, that is, an exposure light beam is assigned to each partial area. It is done. The exposure light beam typically has a pattern generated by activation or deactivation of the individual exposure light beam transferred to the photosensitive layer, i.e., the structure generated on the photosensitive layer is defined by the pattern of exposure light beam, Depart from a two-dimensional raster and proceed in parallel.

  The process of transferring the pattern of exposure light to the photosensitive layer is repeated and the exposure light is transmitted between successive transfer steps so that each exposure light gradually reaches each location within the respective subregion. As a whole, the photosensitive layer is displaced in each case, and the entire surface to be exposed is thus given a fine structure. For this purpose, it goes without saying that the exposure rays are operated independently of one another, i.e. in particular turned on or off independently of one another.

  In this case, the extent of the partial area on the photosensitive layer is typically the same scale (ie, about 1 to 10 times) as the diffraction disk (Airy disk) generated by each exposure beam on the photosensitive layer. belongs to. In this case, the size or diameter of the diffractive disk limits the resolution performance of the exposure apparatus, so this diameter is determined by the smallest aperture diameter of the exposure apparatus (or projection lens used in the exposure apparatus). In the context of the present invention, a technique is described which makes it possible to carry out patterning of the photosensitive layer with a higher resolution compared to this so-called diffraction limit, i.e. only a part of the extent of each diffraction disk is exposed. Explain the contributing technology.

  According to the first aspect of the invention, this allows the near-field optical unit to be placed immediately upstream of the photosensitive layer, thereby reducing the spread of the exposure light beam, so that the near-field optical unit is in the near-field optical unit. This is achieved by generating on the photosensitive substrate a light spot having a spread or diameter that is significantly smaller than the spread of the diffractive disk of incident exposure light.

  In one embodiment, the side of the near-field optical unit that faces the photosensitive layer is disposed at a distance from the photosensitive layer that is shorter than the wavelength of the exposure light beam. This arrangement is advantageous because the intensity of the evanescent wave formed in the near-field optical unit decreases exponentially with the distance from the location where the evanescent wave is generated. In this case, the wavelength used for the exposure radiation can be in the near UV region, for example, 193 nm. However, exposure radiation having a wavelength in the visible wavelength range can also be used. An immersion liquid can also be used.

  If the photosensitive layer (resist) is sufficiently robust, the near-field optical unit can at least partially contact the photosensitive layer when appropriate. Since the strong distance dependence of the intensity of the exposure light coupled from above the near field into the interior can sometimes lead to non-uniform illumination of the photosensitive layer, to account for this distance dependence, the dose and / or Or focus control (see below) can be provided.

  In yet another embodiment, the exposure apparatus further includes a detector device for detecting the intensity of the exposure light beam reflected at the near-field optical unit. The intensity of the reflected light can be measured on a channel-by-channel basis, i.e., individually for each exposure beam, by a suitable spatially resolved detector device (such as a CCD camera). In this way, the energy input in the photosensitive layer of the evanescent wave generated by each exposure light or exposure light can generally be measured indirectly. The less energy is introduced into the photosensitive layer, the more energy is reflected and vice versa. By coupling the detector device to a light-emitting device (or filter device, see below), the intensity of the individual exposure rays is set independently of each other so that the photosensitive layer is (almost) uniformly exposed can do.

  In one development, the exposure apparatus includes a distance determining device for determining the distance and preferably the tilt between the near-field optical unit and the photosensitive layer based on the particularly detected intensity. Based on the detected intensity for each channel, the energy introduced into the photosensitive layer can be estimated, and thus the distance between the near-field optical unit and the photosensitive layer can be estimated locally. By determining the distance between the near-field optical unit and the photosensitive layer at a plurality of locations, it is further possible to determine the orientation or tilt of the near-field optical unit relative to the photosensitive layer. Where appropriate, the tilt can be corrected by a manipulator (eg, in the form of a piezoelectric actuator) provided in the near-field optical unit. The manipulator can be used to set or adjust the distance between the near-field optical unit and the photosensitive layer to a desired set value (focus control or focus adjustment). Where appropriate, the distance determination device can be designed to perform a capacitive or ellipsometric determination of the distance between the near-field optical unit and the photosensitive substrate.

  In yet another embodiment, the exposure apparatus includes a filter device disposed upstream of the near-field optical unit and functioning to affect the intensity and / or polarization of the respective exposure light beam. The filter device can be embodied, for example, as a neutral (gray) filter or a polarizing filter that provides transmission that can be altered in a location dependent manner, for example by applying a voltage or affecting the polarization respectively. If the distance between the near-field optical unit and the photosensitive layer varies in a location-dependent manner, the light distribution non-uniformity obtained on the photosensitive layer is due to an appropriate effect on the intensity distribution upstream of the near-field optical unit. Can be compensated. In this case, the intensity of the individual exposure light can be appropriately modulated by, for example, a neutral filter or a polarizing filter.

  In one development, the exposure apparatus further comprises a control device for driving the filter device in a manner dependent on the intensity detected using the detector device. The control device measures the intensity and phase of the individual exposure rays (and also the exposure duration if appropriate) so that they have the desired properties when incident on the photosensitive layer or on the near-field optical unit. Or it can be used to set in a manner that depends on the detection variable. In particular, the control device can be used to minimize the intensity difference between individual exposure rays incident on the photosensitive layer, i.e. to generate as uniform an intensity distribution as possible on the photosensitive layer.

  In one embodiment, the near-field optical unit preferably has a perforated mask having a plurality of through openings having a diameter shorter than the wavelength of the exposure light. One possibility for increasing the resolution is to use a perforated mask that is transparent only to the exposure light in the through opening. In this case, the diameter of the through opening is generally shorter than the diameter of the diffraction disc of the exposure light beam, that is, the spread of the through opening in the direction transverse to the light propagation direction of the exposure light beam Shorter than the wavelength. In this case, exposure radiation as so-called evanescent waves (according to the tunneling effect of quantum mechanics) can be incident on the photosensitive layer at the position of the through opening to expose the photosensitive layer (“non-contact nanoimprint”). ), The distance between the perforated mask and the photosensitive layer is also generally smaller than the wavelength of the exposure radiation (see above).

  In one development, the perforated mask includes a substrate that is transparent to exposure light, a barrier layer that faces the photosensitive substrate, and a plurality of through openings formed in the barrier layer. In this case, a barrier layer having a through-opening is added on a transmissive substrate that functions as a carrier. As an example, when using radiation in the near UV region, eg, about 193 nm, a chrome layer can function as a barrier layer, and this chrome layer can be exposed to light of this wavelength from a thickness of about 50-80 nm. Is no longer transparent.

  In one development, the transmissive substrate is patterned on the side facing the photosensitive layer, and in particular has a tapered structure. The structure of the transmissive substrate functions as a micro-optical unit, in particular a tapered cone structure has been found to be particularly advantageous. In this case, the through-opening in the barrier layer is generally located at the position of the apex of the cone disposed at a distance shorter than the wavelength of the exposure radiation from the photosensitive layer.

  In yet another embodiment, the light propagation direction of the exposure beam extends at a certain angle with respect to the near-field optical unit (and thus with respect to the photosensitive layer), and the near-field optical unit comprises a plurality of tapered metal structures. Has a dielectric substrate embedded therein. In this case, the incident exposure radiation functions to excite surface plasmons within the tapered metal structure. The surface plasmon induces an alternating electric field in the structure, and this alternating electric field appears to concentrate at the maximum as an evanescent wave at the tip and attenuates exponentially depending on the distance from the photosensitive layer. For short distances between each tip and the photosensitive layer (typically shorter than the wavelength of the exposure light used), the intensity of the evanescent wave exposes the photosensitive layer within a very small area around the tip. Enough to do.

  In order to excite the surface plasmon in the metal tip, it is necessary to use p-polarized illumination radiation, i.e. the direction of light propagation is changed so that the incident plane (and hence p-polarized) is actually defined. Must be generated at a certain angle. In order to excite surface plasmons, the wave number of the exposure radiation used must be further adapted to the plasma frequency of the metal, this adaptation is possible through dielectrics, for a more detailed description of the generation of surface plasmons. In particular, see “http://en.wikipedia.org/wiki/Surface_Plasmon”. When using exposure light having a wavelength of about 193 nm, aluminum can serve as a plasmon source. If allowed by the mechanical resistance of the photosensitive layer, the metal tip can be in direct contact with the photosensitive layer.

  In yet another embodiment, the exposure apparatus includes a super lens element for imaging an evanescent wave emerging from the near-field optical unit on the photosensitive substrate. The term so-called superlens element refers to an arrangement that allows the evanescent wave to be carried in a (substantially) unattenuated manner and sometimes further amplified. This amplification is possible because the super lens element has a negative refractive power with respect to the wavelength of the exposure radiation.

  Surface plasmons are also excited in the case of super lens elements. In the simplest case here, the superlens element comprises a layer stack composed of a first dielectric, a metal layer and a second dielectric. In this case, the thickness of the (planar) layer is generally of the same scale as the wavelength of the exposure radiation. Such superlens elements in which silver functions as a metal layer are David O.D. S. Melville et al., “Super-resolution near-field lithography using planar silver lenses” (invited poster, MNE-2005 ID 00709, “http://www.new.mw”). .Org / 3-c — 01.pdf ”). It has been found that the use of an aluminum layer is advantageous in the near UV region, for example at wavelengths around 193 nm. At such wavelengths, quartz glass can be used as a dielectric. The super lens element can be implemented integrally with the near-field optical unit.

  Yet another aspect of the present invention is designed to generate a substrate having a photosensitive layer and an exposure beam having a maximum intensity greater than an intensity threshold for converting the photosensitive layer from the second state to the first state. A generating device for generating a plurality of particularly parallel exposure rays each having an (at least one) illumination wavelength, each assigned to a partial region of the photosensitive layer, and over each of the assigned partial regions of exposure light In contrast, a moving device for moving in particular in a scanning manner and an excitation light source for generating excitation radiation having an (at least one) excitation wavelength for converting the photosensitive layer from the first state to the second state The present invention relates to an exposure apparatus including:

  This aspect of the invention provides that the photosensitive layer is in the second state and the first state with an intensity threshold that is typically less than the maximum intensity of the exposure light beam obtained at the center of each exposure light beam, in order to increase resolution. Take advantage of changing between. In the case of reversible state transitions, what is achieved thereby is a partial area that is provided for patterning and constitutes a sub-area of the (diffraction-limited) area that is covered by the exposure light incident on the photosensitive layer Except for the inside, the photosensitive layer is converted from the second state to the first state, so that the patterning can be carried out only in this partial area provided for patterning.

  By using the excitation light source, the photosensitive layer can be converted from the first state to the second state. In contrast, the exposure light has the opposite effect, i.e. functions to convert the photosensitive layer from the second state to the first state. Excitation can be achieved before or during exposure. It goes without saying that both the excitation radiation and the exposure radiation need not have only a single wavelength, and where appropriate, each wavelength range can be an effective range. However, since both the excitation light source and the light emitting device typically include a laser light source, the radiation generated by them has only a single wavelength with a good approximation.

  In one embodiment, the transition from the first state to the second state is reversible, and the photosensitive layer can be converted to a chemical state that is permanently changed only in the second state. Since the transition between the two states is reversible, excitation of the photosensitive layer can be achieved before exposure and excitation radiation can be applied to the photosensitive layer particularly uniformly. In this case, as an example, the exposure method described in US 2006/0044985 A1 can be carried out, all of which is incorporated by reference in the subject matter of the present application. In the method described in this document, the photosensitive layer is converted from the second state to the first state by using exposure radiation after excitation, and in this case, a narrowly delimited region is omitted. That is, the exposure radiation is not incident on this area, or the intensity of the exposure radiation is very low in this area, so that the intensity of the exposure light remains below the intensity threshold in this area so that the photosensitive layer is Stay in the state.

  In yet another embodiment, the partial areas to which the respective exposure rays are assigned overlap at least partially. In order to obtain an intensity that clearly exceeds the intensity threshold outside the narrowly bounded area having the above-mentioned very low intensity, the adjacent partial areas to which the respective exposure rays are assigned partially overlap. It is advantageous if the intensity distribution of the adjacent exposure rays also overlaps in the outer region of these exposure rays and is superimposed there to form a total intensity that is greater than the intensity threshold.

  In one development, the exposure apparatus includes a fixing light source for converting the photosensitive layer from a second state to a permanently changed chemical state. In this case, the photosensitive layer can be converted into a chemical state that has been permanently changed by the fixing light source within the region in which it is in the second state, and can thus be patterned. The areas of the photosensitive layer, after being converted to a permanently altered chemical state, will no longer react to excitation radiation or exposure light for subsequent exposure.

  In yet another embodiment, the excitation light source has an intensity profile that varies in a location-dependent manner on the photosensitive layer, and preferably has a maximum intensity between two exposure rays incident adjacently on the photosensitive substrate. Designed to generate excitation radiation. By generating a location-dependent excitation radiation intensity profile, a maximum intensity value is formed in a narrowly bounded area, similar to a STED (“Stimulated Emission Suppression”) microscope, and the photosensitive layer is brought into the first state. The exposure light and excitation radiation can be superimposed so as to convert.

  In yet another embodiment, the transition from the second state to the first state is irreversible, i.e., the second state constitutes a state that already has a permanently altered chemical property. The photosensitive layer having such characteristics can be used particularly in the case of simultaneous use of the above-described excitation radiation and exposure radiation. In this case, if the combined intensity of excitation radiation and exposure radiation is greater than the intensity threshold, the photosensitive layer obtains a first permanently altered chemical state within the relevant region.

  Alternatively, the use of excitation radiation can be dispensed with entirely where appropriate, i.e. the intensity threshold is very high (e.g. 80% or 90% of the maximum intensity of the exposure beam) and thus, e.g. Use a photosensitive layer (resist) in which the photosensitive layer is irreversibly converted from the second state to the first state only within a sub-region of a small intensity distribution equal to or less than 30% of the area covered by the exposure light. be able to. In this case, within the region where the intensity threshold has not been exceeded, the resist must “forget” the exposure as quickly as possible, ie use a so-called Alzheimer resist. This type of resist is used, for example, in rewritable DVDs and can be embodied, for example, as a chalcogenide in which the transition between the two states occurs in particular thermally between the amorphous and crystalline phases.

  In other words, the surface area intended to be patterned is located in the center when the intensity threshold is exceeded at the center of each exposure ray, or (almost) no exposure radiation is incident on the photosensitive layer. It can be either the center of the non-performing region, that is, it is located within the region of the minimum value of the intensity distribution on the photosensitive layer. In order to make each surface area as small as possible and thus as high as possible, it may sometimes require a significant maximum intensity of exposure radiation.

  In yet another embodiment, the photosensitive layer comprises a switchable organic dye or a switchable chalcogenide. A switchable organic dye comprises a dye molecule that can be switched from a second state to a first state (and vice versa) using light. As described above, in the case of chalcogenides, the transition between the two states is typically caused by thermal excitation, strictly speaking, between the amorphous and crystalline phases.

  In one development, the second state of the switchable organic dye can be converted to the first state of the switchable organic dye by stimulated emission. In this case, as in the STED microscope, the dye can be converted from the first energetically low state to the second energetically high state using excitation radiation, from which the second state The first state can be returned by stimulated emission using exposure light in the appropriate wavelength range. In this case, the wavelength required to excite the dye to the second state and the wavelength required to excite the stimulated emission to the ground state are typically different.

  The first and second states are different structural isomeric states of the switchable organic dye, for example the cis-trans transition of each dye molecule, as described in US 2006/0044985 A1 cited above, for example. Two isomeric states can be represented. Dye molecules in a first state (eg, a trans state) can be converted to a permanently changed chemical state by irradiation with fixing light, whereas a second state (eg, a cis state) This conversion is not possible.

  In addition to the use of fluorescent dyes that can generate a transition from an energy-excited state to a ground state using stimulated emission, of course, photosensitive layers having other types of (reversible) state transitions, eg, amorphous phases and The chalcogenides described above can be used for an exposure apparatus in which the transition between crystalline phases is thermally induced (eg excited by an exposure pulse).

  In yet another embodiment relating to both aspects, the generating device comprises a plurality of switchable raster elements designed to turn on or off each exposure beam in a manner that depends on the structure produced on the photosensitive layer. Having a raster arrangement. Using a raster arrangement, a pattern of light spots corresponding to the actuated, ie turned on, raster element can be generated on the photosensitive layer.

  In one development, the raster arrangement of raster elements is embodied as a switchable stop for each exposure beam. In this case, the raster arrangement transmits the exposure radiation only in the area where the raster element is activated, i.e. in the area where the raster element does not function as a stop. In contrast, illumination radiation is shielded in areas where the raster element is turned off.

  In one development, the raster arrangement is implemented as an LCD array, a laser diode array, or an OLED array. In the first case, an illumination device that illuminates the LCD array on the back side of the photosensitive substrate is required. When a laser diode array or OLED array is used, each raster element has a dedicated light source that can be individually activated to generate a respective exposure beam. Both LCD arrays and laser diode arrays or OLED arrays are commercially available, in which the raster elements are small enough to obtain very high resolution. In particular, the switching time of commercially available OLED arrays is short enough to ensure high throughput during exposure.

  In another embodiment, the raster element is embodied as a switchable reflector for each exposure beam. In this case, the raster element can deflect the exposure radiation onto the photosensitive layer at the first effective switching position, whereas it does not deflect the exposure radiation onto the photosensitive layer at the second invalid switching position. , Deflect in different spatial regions.

  In one development, the raster arrangement is implemented as a micromirror array (MMA). The MMA raster element is very small and has a switchable reflector switching time that is short enough to allow high throughput during exposure.

  In yet another embodiment, the moving device has at least one displacement unit for displacing the raster arrangement relative to the photosensitive layer, preferably in synchronism with the near-field optical unit. In order to displace the exposure light beam in the respective partial areas, it is advantageous to displace the raster arrangement in a plane parallel to the photosensitive layer. For this purpose, the moving device can include two linear displacement units that displace the raster arrangement in this plane in two preferably perpendicular directions. In this way, these partial areas can be scanned in order to pattern the partial areas of the photosensitive layer over the entire area. Alternatively, it will be appreciated that the raster arrangement can remain stationary when appropriate and the photosensitive layer or substrate can be displaced. Of course, the substrate and raster arrangement can be moved in the opposite direction simultaneously and where appropriate.

  In yet another embodiment, the generating device includes an illumination device for illuminating the raster arrangement particularly uniformly. In this case, the illuminating radiation is incident over the entire area on the raster arrangement, and the individual exposure rays are generated in the raster elements switched to the active state of the raster arrangement, whereas by other (invalid) raster elements It is not transmitted to the photosensitive layer.

  In yet another embodiment, the exposure apparatus includes a lens for reduced imaging of a raster arrangement on the photosensitive layer or near-field optical unit. For example, a 10x reduction imaging increases the resolution during exposure of the photosensitive layer. If the exposure apparatus includes a near-field optical unit, the imaging is generally performed on this near-field optical unit or on the side facing away from the photosensitive layer of the near-field optical unit, ie, near-field. The optical unit forms the image plane of the lens.

  The invention also includes generating a plurality of particularly parallel exposure rays, each assigned to a partial area of the photosensitive layer, moving the exposure light over or relative to each assigned partial area, and each exposure. Placing the near-field optical unit upstream of the photosensitive layer to convert the light into an evanescent wave for generating on the photosensitive layer a light spot having a spread smaller than that of the exposure light beam upstream of the near-field optical unit A method associated with a first aspect for patterned exposure of a photosensitive layer comprising:

  As described above, the exposure of the photosensitive layer is performed by causing a plurality of exposure light rays to be simultaneously emitted onto the layer to be exposed and enter each of the partial areas of the same size as the diffraction disk on the photosensitive layer. Process in parallel as much as possible. The near-field optical unit functions to increase the resolution beyond the diffraction limit, i.e., the exposure light beam is reduced to a light spot having a spread that can be, for example, smaller than the diffraction limit, thereby making the light sensitive. In order to pattern the entire layer, the exposure light beam is guided in particular in a scanning manner over the photosensitive layer or corresponding partial areas.

  The method specified in the second aspect for the patterned exposure of the photosensitive layer comprises the steps of generating a plurality of particularly parallel exposure rays, each assigned to a partial area of the photosensitive layer, and the photosensitive layer in the second state. Moving the exposure light beam generated to have a maximum intensity greater than an intensity threshold to convert from the first state to the first state, respectively over or relative to the assigned subregion, and the photosensitive layer in the first state Exciting the photosensitive layer with excitation radiation to convert from a second state to a second state and returning the photosensitive layer from the second state to the first state in a region not provided for patterning .

  As described above, the second embodiment uses a photosensitive layer having a defined intensity switching threshold so that the resolution can be increased beyond the diffraction limit by appropriate selection of the intensity of the exposure light beam. In this case, the photosensitive layer can be reversibly converted from the first state to the second state by the excitation radiation, and the exposure light is used to make the first layer within the region that is not prepared for patterning. It can be returned to the state. The exposure radiation is the minimum (or maximum, see above) that the photosensitive layer is not converted to the first state, and therefore can be converted to a permanent chemical change state using, for example, fixing radiation. Only within the region to be patterned.

  Further features and advantages of the present invention will be apparent from the following description of exemplary embodiments of the invention and from the claims, with reference to the drawings, in which essential details for the invention are shown. . The individual features can be realized in each case by these features themselves or as a plurality in any desired combination in a variant of the invention.

  Exemplary embodiments are illustrated in the schematic drawings and described in the following description.

FIG. 3 is a detailed view of a photosensitive layer having a plurality of partial regions each assigned an exposure light beam. It is the schematic of the exposure apparatus for producing | generating a some exposure light beam simultaneously including a near-field optical unit. FIG. 6 is a schematic diagram of different exemplary embodiments of a near-field optical unit. FIG. 6 is a schematic diagram of different exemplary embodiments of a near-field optical unit. FIG. 6 is a schematic diagram of different exemplary embodiments of a near-field optical unit. FIG. 6 is a schematic diagram of different exemplary embodiments of a near-field optical unit. FIG. 3 is a schematic view of an exposure apparatus including a raster arrangement in the form of an LCD array. 1 is a schematic view of an exposure apparatus including a raster arrangement in the form of a light emitting diode array. It is the schematic of the intensity distribution depending on the location of exposure radiation, and the intensity threshold value of a photosensitive layer. It is a figure similar to FIG. 6 whose intensity | strength minimum value is smaller than an intensity | strength threshold value. It is the schematic of intensity distribution generated by superposition of exposure radiation and excitation radiation. It is the schematic of the exposure apparatus containing an excitation light source, a fixing light source, and an LED array. FIG. 10 is a schematic diagram similar to FIG. 9 with an OLED array and illumination system.

  FIG. 1 schematically shows details of a photosensitive layer 1 having a plurality of square partial areas 2a to 2h, each of which is assigned an exposure beam 3. As can be seen in FIG. 1, the spread of the respective partial areas 2 a to 2 h is of the same scale as the spread 4 represented by the broken-line circle of the exposure light beam 3, that is, in this case, the spread 4 of the exposure light beam 3. About 10 times the size. The photosensitive layer 1 is simultaneously exposed with a plurality of exposure rays 3 that are individually turned on or off depending on the structure produced on the photosensitive substrate 1, as will be described below with reference to FIG.

  FIG. 2 shows an exposure apparatus 5 for exposing the photosensitive layer 1 applied on the substrate 6 (wafer). The exposure apparatus 5 includes a light emitting device 7. The light emitting device 7 includes a light source 7a, for example in the form of a laser for generating exposure radiation having a wavelength of 193 nm or 157 nm. The light source 7a functions to illuminate the entire area of the raster arrangement 8 embodied as a micromirror array (MMA). The micromirror array includes a plurality of individual drivable raster elements 9 in the form of mirror elements. In this case, the micromirror array 8 can have, for example, a matrix arrangement of about 4000 × 2000 raster elements 9, and one raster element 9 (hereinafter individual mirror) can be, for example, about 16 μm × 16 μm. You can have an area of The commercially available MMA is only for a single individual mirror 9 for the sake of simplicity in FIG. 2 from the (effective) basic position in which the individual mirrors 9 are arranged in a plane 10 parallel to the plane of the photosensitive layer 1. It has a switching frequency in the range of about 5 kHz to move to a tilt position not shown. The throughput of the exposed wafer 6 is about 100 wafers per hour given a switching frequency of about 5 kHz.

  Since the individual mirrors 9 of the MMA 8 are separated from each other in each case by a non-reflective region, a plurality of exposure rays 3 are generated in the MMA 8, and these exposure rays are photosensitized based on the position of each individual mirror 9. It is deflected in a spatial region side by side with layer 1 or photosensitive layer 1. The respective switching positions of the individual mirrors 9 and thus the pattern generated by the MMA 8 depends on the structure generated on the photosensitive layer 1. The control device 11 functions to drive the MMA 8 in a manner that depends on the predetermined structure generated on the photosensitive layer 1.

  The exposure light beams 3 deflected to the photosensitive layer 1 in the MMA 8 are directed parallel to each other, and their propagation directions extend perpendicular to the photosensitive layer 1. The lens 12 functions to reduce the image of the exposure light beam 3 or the plane 10 onto the photosensitive layer 1 by the MMA 8 (for example, 10 times).

  As can be seen in FIG. 1, each exposure light beam 3 covers only a part of the surface of the partial areas 2 a to 2 h assigned to each exposure light beam 3. Therefore, in order to pattern the entire area of the photosensitive layer 1 in the region to be patterned, the exposure apparatus 5 includes a linear moving unit 14 for displacing the MMA 8 along the X direction of the XYZ coordinate system shown in FIG. Including mobile device 13. A corresponding linear movement unit (not shown) functions to displace the MMA in the Y direction. In order to pattern the entire photosensitive layer 1 within the desired area, the moving device 13 is used to displace the MMA 8 in the X and Y directions over a distance approximately corresponding to the edge length of each of the partial areas 2a-2h. be able to. In this case, the control device 11 is coupled to the linear movement unit 14 in order to control the displacement of the linear movement unit in the X direction (and the displacement of the linear movement unit in the Y direction). It goes without saying that a plurality of adjacent regions are formed on the wafer 6 that can be patterned in the manner described above using a moving device 13 that appropriately controls the movement of the MMA 8 (if appropriate, the wafer 6). The exposure apparatus 5 further includes a near-field optical unit 15 disposed in the immediate vicinity of the photosensitive layer 1. In order to displace the near-field optical unit 15 in the X direction in synchronization with the MMA 8, another linear movement unit 14 a is coupled to the control device 11. Similarly, there is a corresponding coupling to yet another linear displacement unit (not shown) for displacing the near-field optical unit 15 in the Y direction.

  The near-field optical unit 15 functions to convert each exposure light beam 3 into an evanescent wave. In this way, the spread of the exposure beam 3 is the size of a light spot 16 (see FIG. 1) significantly smaller than the spread 4 (due to the diffraction limit) of the exposure beam 3 upstream of the near-field optical unit 15. Can be reduced. As a result, the resolution of the exposure apparatus 5 can be increased beyond the diffraction limit using the near-field optical unit 15.

Several exemplary embodiments of the near-field optical unit 15 are described in more detail below with reference to FIGS. 3a-3d. What is common to the exemplary embodiments shown in these figures is that the distance a between the near-field optical unit 15 and the side where the evanescent wave appears is of the same size as the wavelength λ _{B of the} exposure radiation. 3a to 3c, the distance a is smaller than the wavelength λ _B.

As described above, the intensity of the evanescent wave 17 respectively emitted from the near-field optical unit 15 decreases exponentially with the distance “a” from the emission part, that is, I ₀ represents the intensity at the emission, and k is It is advantageous that I (a) = I ₀ × Exp (−k ^* a) holds when expressing the proportionality constant. Accordingly, when the near-field optical unit 15 is too far from the photosensitive layer 1, the intensity of the evanescent wave is too low to expose the photosensitive layer 1.

In the example shown in FIG. 3 a, the near-field optical unit 15 is embodied as a perforated mask and faces the photosensitive substrate 1 with a substrate 18 as a carrier that is transmissive to the exposure light beam 3. And a planar barrier layer 19 made of chromium having a plurality of through-openings having a diameter D shorter than the use wavelength λ _B. The barrier layer 19 has a thickness of about 80 nm and is not transmissive to the exposure light beam 3 having a working wavelength λ _B of 193 nm. The spread (Airy disk) 4 due to the diffraction limit of the exposure light beam 3 caused by the lens 12 when entering the near-field optical unit 15 is spread using the barrier layer 19 or the through opening 20 to spread the light spot 16 shown in FIG. Reduced to

FIG. 3b shows an exemplary embodiment of the near-field optical unit 15 in which the transmissive substrate 19 has a surface structure in the form of a conical tip 21 that functions as a micro-optical unit. In this case, the through-opening 20 in the barrier layer 19 is placed at the outermost end of the cone tip 21 disposed at a distance from the photosensitive layer 1 shorter than the wavelength λ _{B of the} exposure radiation.

  In the two examples shown in FIGS. 3 c and 3 d, the light propagation direction of the exposure light beam 3 extends at a certain angle with respect to the near-field optical unit 15 or the photosensitive substrate 1. In the exposure apparatus 5 shown in FIG. 2, this light propagation direction can be brought about by deflecting from the parallel direction of the MMA 8 with respect to the photosensitive layer 1. In this case, the exposure light beam 3 is polarized parallel to the incident plane corresponding to the drawing. The exposure light beam 3 can be polarized by a suitable polarizing filter (not shown). In general, the laser light source 7 (see FIG. 2) generates linearly polarized exposure radiation anyway, so that it is appropriate when an appropriate orientation of the laser light source 7 is given to the photosensitive layer 1. If necessary, the polarizing filter can be omitted.

  In the example shown in FIG. 3c, the near-field optical unit includes a dielectric substrate 22 having a plurality of metal tips 23 embedded in the dielectric substrate 22 and electrically isolated from each other. In this case, the incident exposure light beam 3 functions to excite surface plasmons within each metal tip 23, and induces an alternating electric field concentrated at the tapered end of the metal tip 23 to the maximum, The evanescent wave 17 is emitted from the tapered end portion. If a short distance a is provided between each tip 23 and the photosensitive layer 1, the intensity of the evanescent wave 17 is sufficient to expose the photosensitive layer 1 within a very small area around the metal tip 23. is there. If allowed by the mechanical resistance of the photosensitive layer, the metal tip 23 can be in direct contact with this layer.

In order to excite the surface plasmons, the wave number of the exposure beam 3 used must be adapted to the plasma frequency of the metal used, and this adaptation can be performed through the dielectric substrate 22. In this example, the exposure light beam 3 has a wavelength λ _{B of} about 193 nm, for example, aluminum is suitable as the material for the metal tip 23.

In the exemplary embodiment shown in FIG. 3 d, the near-field optical unit 15 described in FIG. 3 c is extended by a so-called super lens element 24. The super lens element 24 is mounted on the side facing the photosensitive layer 1 of the near-field optical unit 15, and is composed of a first dielectric layer 24a and a second dielectric layer 24c with a metal layer 24b disposed therebetween. Is done. Also in the case of the super lens element 24, the surface plasmon is excited. This surface plasmon makes it possible to image the evanescent wave 17 emitted from the near-field optical unit 15 on the photosensitive substrate 1, and in this case, the evanescent wave 17 is transmitted in a substantially non-attenuating manner. Since the super lens element 24 has a negative refractive index with respect to the wavelength λ _B of the exposure light beam 3, this transmission is possible. In this case, the thickness of the (planar) layers 24 a to 24 c is generally the same as the wavelength λ _B of the exposure light beam 3. In this example with a wavelength λ _B of about 193 nm, it has been found advantageous to use a metal layer 24b composed of aluminum. In this case, for example, a quartz glass layer can be used as the dielectric layers 24a and 24c. Similarly, as can be seen from 3d, the distance a between the emitting portion of the evanescent wave 17 and the photosensitive substrate 1 can be selected to be longer than that in the example described in FIGS. 3a to 3c. It goes without saying that the super lens element 24 can be used for the near-field optical unit shown in FIGS. 3a to 3c.

  As shown in FIG. 3 c, the exposure apparatus 5 further includes a detector device 25 for spatially resolved detection of the intensity of the exposure light beam 3 reflected on the dielectric substrate 22 of the near-field optical unit 15. The intensity of the reflected light can be measured on a channel-by-channel basis, i.e. for each exposure light beam 3, by means of a spatially resolved detector device 25, for example in the form of a CCD camera. As less energy is introduced into the photosensitive layer 1, more energy is reflected and vice versa, so that the energy input of each exposure beam 3 or the evanescent wave 17 generated thereby is thus obtained. Can be measured indirectly.

  In contrast to the near-field optical unit 15 in the form of a perforated mask shown in FIGS. 3a and 3b, when surface plasmons are excited, the plasmons absorb light energy “over a large area” and this Since light energy can be emitted again substantially through the metal tip 23, energy transfer is more efficient. In the exemplary embodiment described in FIGS. 3a, 3b, the geometric ratio between the diameter D of the through opening 20 and the total area of the perforated mask is very important.

  Since the intensity coupled from above to the inside of the photosensitive layer 1 within the near field greatly depends on the distance, the distance between the near field optical unit 15 and the photosensitive substrate 1 within the exposure apparatus 5 as shown in FIG. A distance determination device 26 can be arranged to determine. The distance determination device 26 can determine the local distance a, in particular the possible inclination of the near-field optical unit 15 relative to the photosensitive substrate 1, based on the intensity picked up by the detector device 25. By determining the distance a at a plurality of locations, the tilt of the near-field optical unit 15 can be estimated and, if appropriate, this tilt is compensated using a manipulator (not shown), for example in the form of a piezoelectric actuator. can do. The distance a determined using the distance determination device 26 can be set or adjusted to a desired distance to enable focus control or focus position adjustment.

  When the distance a between the cone tip 21 and the photosensitive layer 1 varies locally and varies, the light distribution on the resulting photosensitive layer 1 is obtained due to an appropriate influence on the intensity distribution upstream of the near-field optical unit 15. The exponential dependence of tunneling efficiency on the distance a can be used to compensate for the non-uniformity of

  For this purpose, the detector device 25 and, if appropriate, the distance determining device 26 are connected to the control device 11 (see FIG. 2), which evaluates the detection or measurement data. Then, a neutral filter 27 is driven for each channel of the intensity of each individual exposure light beam 3, that is, upstream of the lens 12 enabling individual modulation, in a manner depending on this evaluation. In this case, the control device 11 modulates the intensity of the exposure light beam 3 so that the intensity of the exposure light beam 3 is as uniform as possible on the photosensitive layer 1. In addition to or as an alternative to setting the intensity, a further means for modulating the exposure beam 3 is provided, for example the polarization of the exposure beam 3 by means of a polarizer device that generates the modulation for each channel, ie individually. Needless to say, it can affect

  4 and 5 show two further examples of the exposure apparatus 5 in which the light emitting device 7 is different from that shown in FIG. The light emitting device 7 shown in FIG. 4 has an illumination system 7b that magnifies the laser radiation emitted from the laser radiation source 7a and uniformly illuminates the matrix arrangement in the form of the LCD array 8a. Depending on the structure produced on the photosensitive layer 1, the individual raster elements 9a (pixels) of the LCD array 8a can be turned on or off so that the desired pattern of the exposure light beam 3 is obtained. In this case, for example, an LCD having the VGA resolution described in “http://www.lgblog.de/2009/06/15/kleins-lcd-display-der-wel-mit-vga-auflosun/” As in the array, the raster elements 9a can have a spread of 2.9 μm × 2.9 μm, for example given a size of 100 mm × 100 mm.

  In the case of FIG. 2, the light distribution of the exposure light beam 3 generated by the LCD array 8a is such that a pattern image of the effective raster element 9a of the LCD array 8a is generated on the photosensitive layer 1 with a size of, for example, 10 mm × 10 mm. Similarly, the light is transmitted by the lens 12 having the numerical aperture NA = 1 on the image plane having the photosensitive layer 1 in a manner of being reduced by at least 10 times. In this case, the spread of each exposure light beam 3 on the photosensitive layer 1 corresponds to the resolution (by Abbe) of the lens 12 used.

Assuming a lens 12 with a numerical aperture NA = 1, 0.5 k coefficient (eg, generated by an annular stop in the pupil plane of the lens 12) and a wavelength λ _B of 193 nm of the exposure ray 3, The equation for the possible distance that can still be resolved between the light spots (d = k × λ _B / NA) yields d = 0.5 × 193 nm / 1, ie about 100 nm. If the resolution actually obtained by appropriate means (see above and below) is fixed at 10 nm, the area of 100 nm × 100 nm formed on the photosensitive layer 1 by the incident exposure beam 3 is at least 20 Scan must be done in x20 = 400 sub-stages.

  For this purpose, the LCD array 8a can be stepped and repeated in steps of 5 nm in the z direction using the moving device 13 or the linear moving unit 14 or can be moved continuously (at a constant speed). This movement can be synchronized with the exposure, ie the switchable raster element 9a is turned on or off depending on the structure produced in each case. It goes without saying that the second linear displacement unit (not shown) functions to displace the LCD array 8a in the Y direction. Furthermore, it goes without saying that the wafer 6 can be displaced additionally or alternatively in the plane in which the photosensitive layer 1 is arranged using a suitable displacement device.

  Assuming that the LCD array 8a operates at a switching frequency of 500 Hz, a 10 mm × 10 mm field on the wafer 6 can be exposed in about 0.8 seconds. A commercially available wafer 6 has about 700 such 10 mm × 10 mm cells and can therefore be exposed after about 560 seconds, resulting in a throughput of about 8 wafers per hour. In this case, mainly the switching frequency (switching time is about 2 ns) of the raster element 9a (pixel) of the LCD array 8a has a limiting effect on the exposure speed. In the case of LCD arrays to be developed in the future, the switching frequency will probably be increased, or the switching time can be improved by adapting the LCD array to this application (on / off only). Therefore, it goes without saying that it is possible to increase the achievable throughput using the exposure apparatus 5 shown in FIG.

The light emitting unit 7 has a raster arrangement in the form of a laser diode array 8b having a plurality of switchable laser diodes 9b as light sources, the number of these light sources being substantially equal to the number of LCD arrays 8a shown in FIG. In the case of the corresponding exposure apparatus 5 shown in FIG. 5, the switching time can be significantly shortened. In the case of the laser diode array 8b, the switching time can be shortened by about 2000 times, so that a theoretical throughput of about 16000 wafers is possible, ie if there is sufficient exposure radiation, The switching time has no limiting effect. Instead of the laser diode 9b, an OLED can be used, but the OLED generates only about 10 mW / cm ² of power on the photosensitive substrate 1, whereas the power that can be generated by a conventional 193 nm laser. is about 100W / cm ^2, i.e., about 10,000 times greater. Using an OLED array, due to this low available light intensity, potentially only about 5 wafers per hour can be exposed as well. Furthermore, the OLED operates with visible light, so that the spread of the exposure light beam 3 incident on the photosensitive layer 1 is relatively large.

  In order to provide the desired improvement in resolution, the exposure apparatus 5 shown in FIGS. 4 and 5 can be combined with the near-field optical unit 15 shown in FIGS. 2 and 3a-3d. Instead of using the near-field optical unit 15 to increase the resolution described above, the characteristics of the photosensitive layer 1 can be used in providing improved resolution.

To illustrate this procedure, FIG. 6 shows the intensity I of three adjacent exposure rays 3 each having a central intensity maximum value I _MAX and incident on the photosensitive layer 1 as a function of position P (in the X direction). Is shown. The photosensitive layer 1 has an intensity threshold I _S which in this case is about 10% of the maximum intensity I _MAX . In this case, the intensity threshold value _IS defines the intensity with which the photosensitive layer 1 undergoes a transition from the second state B to the first state A. Here it is seen a second state B when the intensity I is smaller than the threshold I _S, the first state A is observed when the intensity I is greater than the threshold value I _S. In this case, the maximum intensity I _MAX of the exposure light beam 3 is selected to be larger than the intensity threshold I _S.

There are various possibilities regarding the two states A and B of the photosensitive layer 1, and as an example, the transition from the second state B to the first state A can be made irreversible. In this case, after the intensity threshold value _IS is exceeded, the photosensitive layer 1 cannot subsequently return to the second state B and remains in the permanent chemical change state A or permanently during subsequent fixing. It is further converted into a chemical change state (so-called Alzheimer resist). In the case of such resists, it may be necessary to perform a thermal treatment between two successive exposures that results in some “de-exposure” of previously lightly exposed areas. In this case, in particular, a resist that reacts very nonlinearly to exposure can be used as the photosensitive layer.

When using a photosensitive layer (resist) having such an irreversible transition, the intensity of the exposure light beam 3 is generally shown in FIG. 6 so that the intensity threshold value I _S is relatively close to the maximum intensity value I _MAX . For example, IS = 0.9 × I _MAX can be selected. In this way, the photosensitive layer can only be within a relatively small area 16 (see FIG. 1) of, for example, less than 20% or less than 10% of the surface area 4 of the incident exposure light beam 3, respectively. It is not converted from the second state B to the first state A, so that the desired resolution improvement can be provided.

  As an alternative to the use of the photosensitive layer 1 which can be irreversibly switched from the second state B to the first state A using the exposure light beam 3, the second state B to the first state A (and vice versa) A photosensitive layer 1 can be used in which the transition to ()) occurs in a reversible manner. In this case, the photosensitive layer 1 can be implemented so that it can only be converted into a chemical state that has changed permanently only in the second state B, not in the first state A.

  The photosensitive layer 1 having such properties can be realized by specific switchable molecules, especially in the form of switchable organic dyes. In this case, the switching of molecules between the two states A, B can be effected by light, and the wavelength of the light that functions to switch from the second state B to the first state A is the first It is different from the wavelength of light used for switching from the state A to the second state B. In the case of fluorescent organic dyes, the transition from the second excited state B to the first state A can occur, for example, by stimulated emission. First, if the entire photosensitive layer is converted from the first state A to the second state B, and then the photosensitive layer 1 is illuminated unevenly in the manner shown in FIG. It remains in the second state B only in a very narrow intensity range and can be converted from this state into a permanent chemical change state C. In this way, the resolution can be increased during exposure as well.

  An exposure apparatus 5 designed for this purpose is illustrated in FIG. The exposure apparatus 5 corresponds to the one shown in FIG. 4 and converts the excitation light source 31 for generating the excitation radiation 32 and the photosensitive layer 1 from the second state B to the chemical state C that is permanently changed. Supplemented with an additional light-emitting unit 30 including a fixing light source 34 for generating fixing radiation 33 for.

During exposure using the exposure apparatus 5, first, the photosensitive layer 1 is irradiated uniformly over a large area by the excitation radiation 32, and for this purpose a partial transmission that deflects the excitation radiation 32 onto the photosensitive layer 1. A mirror 36 is used. In this case, the excitation radiation 32 has an excitation wavelength λ _A that can be in the range between 400 nm and 650 nm in this example in which the photosensitive layer 1 is formed from an organic dye (eg RH414), for example , Λ _A = at a wavelength of about 500 nm. The photosensitive layer 1 is converted from the first state A to the second state B by the excitation radiation 32. In the subsequent stage, the exposure light beam 3 is emitted onto the photosensitive layer 1 using the light emitting unit 7, and in this case the wavelength of this radiation is λ _B = 745 nm.

The exposure light beam 3 generates an intensity profile in the photosensitive layer 1 that can be implemented, for example, as shown in FIG. In this case, the individual exposure rays 3 overlap and are superimposed so as to form a substantially uniform intensity I _HOM which is interrupted only in a small area 37 where the intensity drops to approximately zero. In this case, the exposure light beam 3 or the associated raster element 9a for the omitted area 37 is turned off. The intensity I _HOM outside the omitted region 37 is not greater than the intensity threshold I _S and is therefore sufficient to convert the photosensitive layer 1 from the second state B to the first state A.

It is only in the omitted area 37 along the distance d _min that the intensity I remains lower than the intensity switching threshold I _S , so that the photosensitive layer 1 remains in the second state B along this section. . In the subsequent stage, when the fixing radiation 33 is applied to the photosensitive layer 1 over a large area using the fixing light source 34, this layer can only be converted into a permanently changed chemical state C within the omitted region 37. As can also be seen in FIG. 7, the distance d _min is shorter than the distance d corresponding to the spread of the exposure light beam 3, and therefore the resolution of the exposure apparatus 5 is also set to the diffraction limit or maximum using the means described above. It can be increased beyond the resolvable distance d.

When using a wavelength λ _{B of} about 500 nm, a k coefficient of 0.5, and a numerical aperture NA = 1, the maximum resolvable distance is d = 0.5 × 500 nm / 1 = 250 nm. In contrast, if the resolution d _min is fixed as 10 nm, the corresponding partial area of about 250 nm × 250 nm must be scanned in at least 25 × 25 = 625 steps, In some cases, instead of a plurality of individual steps, a constant speed continuous movement can be carried out. In this case, three successive steps of excitation, exposure and fixing must be adjusted with the respective displacements by the control device 11.

  In the exemplary embodiment of the exposure apparatus 5 shown in FIG. 9, as in FIG. 4, the throughput is limited by the switching speed of the LCD array 8a of about 500 Hz, resulting in a throughput of about 4 wafers per hour. Is possible. Alternatively, an exposure apparatus 5 similar to FIG. 5 can be used as shown in FIG. The exposure apparatus 5 shown in FIG. 10 is different from that shown in FIG. 5 in that an OLED array 8c having a plurality of OLEDs 9c is used instead of a laser diode array. In this case, the excitation light source 31 and the fixing light source 34 are embodied as in FIG. 9, and the excitation, exposure, and fixing that must be performed in each scanning stage are similarly adjusted or synchronized using the control device 11. It becomes.

If the OLED array 8c is used, the switching speed can be increased by about 2000 times as described above with respect to FIG. Accordingly, a throughput of about 8000 wafers per hour is possible. In this case, the excitation light source 31 and the fixing light source 34 must operate in the MHz range, but this operation does not cause any problems when using laser light sources having wavelengths λ _A and λ _F in the visible range. Yes, without it. In this case, the OLED array 8c can be displaced using the moving device 13 at a constant synchronization speed of, for example, about 0.1 m / sec.

  The above-described procedure, which uses each exposure beam as a “write signal” to a minimum, in this case allows for a particularly high resolution since no imaging-related secondary radiation is generated as a result of the fluorescence photons. To do.

As an alternative to the procedure described above, the excitation radiation 32 is applied onto the photosensitive layer 1 by means of an excitation light source 31 provided, for example, with a suitable illumination system, if appropriate with a further raster arrangement (not shown) or (neutral) filter. The exposure that is not uniformly incident can be performed using the exposure apparatus 5 shown in FIGS. When the intensity I _A location dependent on the photosensitive layer 1 is also location dependent intensity I _B at the same time as the incident, as is generally known from the STED microscope, when superposition of two intensity distributions, Figure 7 In contrast to the intensity distribution shown, an intensity distribution I _AB = with a maximum value (peak with a spread in the nm range) limited to a very small spatial region instead of a minimum value limited to a very small spatial region = I _A × Exp (−I _B ) (see FIG. 8) is provided.

In order to obtain the intensity profile I _{AB according} to FIG. 8 having a significant peak, the intensity of the excitation radiation 32 is at a maximum value I at a position where the total intensity I _AB is also maximum between two adjacent exposure rays 3. Selected to have _MAX . As in the case of the exposure process described with respect to FIGS. 6 and 7, the excitation radiation 32 causes a transition from the first state A to the second state B, whereas the exposure light 3 has the opposite effect, That is, the transition from the second state B to the first state A is caused by stimulated emission. It is only in the peak region that the photosensitive layer 1 remains in the second state B and can be converted to the permanently changed chemical state C using the fixing light source 34. Needless to say, when the transition between the first state A and the second state B is irreversible, the use of the fixing light can be omitted.

  The procedure described with respect to FIG. 8 represents in this case the application of the principle of the STED microscope to lithography. In the case of the use of organic dyes as photosensitive layer 1, these dyes remain excited only in the peak region, and thus, for example, forster resonance energy transfer (dipole-dipole interaction) or Dexter energy transfer (electron exchange) can be used to chemically convert and fix adjacent molecules in the photosensitive layer 1. The “secondary emission” as a result of fluorescent photons that are thought to cause expansion also does not occur in this case.

  In the STED microscope, the photosensitive layer 1 composed of a switchable organic dye is generally used, and the second fluorescence state B can be returned to the first state A of the switchable organic dye by stimulated emission. Numerous dyes that can be used for this purpose are available, see for example “http://www.mpibpc.mpg.de/groups/hell/STED_Dyes.html”. If necessary, it will also be possible to produce new organic dyes, each optimized for the required chemical properties.

  It goes without saying that the exposure described above is not limited to the use of fluorescent dyes whose return from the second state B to the first state A occurs based on stimulated emission. Instead of these states, the two states are, for example, different structural isomeric states of a switchable organic dye (the first state is a state having a fluorescence function, whereas the second state is not) For example, cis-trans isomer). This principle is used, for example, for so-called RESOLFT (Reversible Saturable Optical Fluorescence Transitions), in which switchable proteins can be used with organic dyes. The use of such materials in the photosensitive layer has the advantage that the required intensity for anything greater than the intensity threshold is lower than is typical for transitions as a result of stimulated emission.

  Where appropriate, other types of photosensitive layers can be used in the exposure process described herein. In this case, all that is essential is that the photosensitive layer has molecules with at least two states in which switching can take place in a reversible manner.

  In summary, in the manner described above, it is possible to carry out parallel exposure of the wafer in a plurality of partial areas each having a spread that is of the same magnitude as the diffraction limit. Using the means described above, the resolution can be increased beyond the diffraction limit, thereby allowing patterning within each subregion using scanning exposure. That is, it is possible to provide effective and cost-effective exposure of the photosensitive layer with high resolution.

DESCRIPTION OF SYMBOLS 1 Photosensitive layer 3 Exposure light 13 Moving device 32 Excitation radiation (lambda) _B exposure wavelength

Claims (18)

A substrate (6) having a photosensitive layer (1);
An exposure light beam (3) having a maximum intensity (I _MAX ) greater than an intensity threshold (I _S ) to convert the photosensitive layer (1) from the second state (B) to the first state (A) Generation for generating a plurality of exposure rays (3) designed to generate and having an exposure wavelength (λ _B ), each ray being assigned to a partial area (2a-2h) of the photosensitive layer (1) Device (7);
A moving device (13) for moving the exposure beam (3) relative to the respective assigned partial areas (2a-2f);
An excitation light source for generating excitation radiation (32) having an excitation wavelength (λ _A ) to convert the photosensitive layer (1) from the first state (A) to the second state (B); 31) and
An exposure apparatus (5) comprising:   The transition from the first state (A) to the second state (B) is reversible, and the photosensitive layer (1) has changed permanently only in the second state (B). The exposure apparatus according to claim 1, wherein the exposure apparatus can convert the chemical state (C).   The fixing light source (34) for converting the photosensitive layer (1) from the second state (B) to the permanently changed chemical state (C). Exposure equipment.   The exposure apparatus according to any one of claims 1 to 3, wherein the partial areas (2a to 2h) to which the respective exposure rays (3) are assigned overlap at least partially. The excitation light source (30) is designed to generate excitation radiation (32) having an intensity profile (I _A ) that varies in a location-dependent manner on the photosensitive layer (1);
The excitation radiation (32) preferably has a maximum intensity (I _MAX ) between two exposure rays (3) incident in an adjacent manner on the photosensitive substrate,
The exposure apparatus according to any one of claims 1 to 4, wherein the exposure apparatus is characterized in that:   The exposure apparatus according to claim 1, wherein the transition from the second state (B) to the first state (A) is irreversible.   The exposure apparatus according to any one of claims 1 to 6, wherein the photosensitive layer (1) contains a switchable organic dye or a switchable chalcogenide.   8. The exposure according to claim 7, wherein the second state (B) of the switchable organic dye can be converted to the first state (A) of the switchable organic dye by stimulated emission. apparatus.   9. The exposure apparatus according to claim 7, wherein the first and second states (A, B) are different structural isomeric states of the switchable organic dye.   The generating device (7) comprises a plurality of switchable raster elements (which are designed to turn on or off each exposure light beam (3) in a manner dependent on the structure produced on the photosensitive layer (1). The exposure apparatus according to any one of claims 1 to 9, wherein the exposure apparatus has a raster arrangement (8, 8a to 8c) having 9, 9a to 9c).   11. The exposure apparatus according to claim 10, wherein the raster elements (8a-8c) of the raster arrangement (9a-9c) are embodied as a switchable stop for the respective exposure beam (3). .   12. The raster arrangement according to any one of claims 10 and 11, characterized in that the raster arrangement is embodied as an LCD array (9a), as a laser diode array (9b) or as an OLED array (9c). Exposure equipment.   13. The exposure apparatus according to claim 12, wherein the raster elements are embodied as switchable reflectors (9) for respective exposure rays (3).   The exposure apparatus according to claim 13, wherein the raster arrangement is embodied as a micromirror array (8).   11. The moving device (13) has at least one displacement unit (14) for displacing the raster arrangement (8, 8a-8c) relative to the photosensitive layer (1). The exposure apparatus according to claim 14.   16. The exposure apparatus according to any one of claims 10 to 15, wherein the generating device (7) comprises an illumination device (7b) for illuminating the raster arrangement (8a).   17. A lens (12) according to any one of claims 10 to 16, further comprising a lens (12) for reduced imaging of the raster arrangement (8, 8a-8c) on the photosensitive layer (1). The exposure apparatus described in 1. A method of exposure with a pattern of the photosensitive layer (1), comprising:
Generating a plurality of exposure rays (3), each of which is assigned to a partial area (2a-2h) of the photosensitive layer (1);
Said generated to have a maximum intensity (I _MAX ) greater than an intensity threshold (I _S ) to convert said photosensitive layer (1) from a second state (B) to a first state (A) Moving the exposure beam (3) relative to the respective assigned partial areas (2a-2h);
Exciting the photosensitive layer with excitation radiation (32) to convert the photosensitive layer (1) from the first state (A) to the second state (B);
Returning the photosensitive layer (1) from the second state (B) to the first state (A) in an area not provided for patterning;
A method comprising the steps of:

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