JP5694207B2 - Lithography system and projection method - Google Patents

Description

  The present invention relates to a lithographic system for projecting an image pattern onto a target surface such as a wafer, wherein control data is coupled to a control unit for controlling exposure projection by means of optical signal means, so that in particular free space mutual to the system. Using a connection, such a control unit is included in the projection space, in particular close to or within the multi-beam maskless lithography system. The invention relates in principle to charged particle and light projection based lithography systems in particular.

  Such a system is known, for example, from the particular embodiment given in the applicant's international patent application WO2004038509, ie by FIG. Known systems comprise a computer system for providing pattern data of images projected by so-called beam columns for projecting charged particles, in particular electrons, onto target surfaces such as wafers and inspection tools. The beam column comprises a vacuum chamber in which one or more charged particle sources are housed, which in particular uses an electric field to attract particles from said one or more sources, in a manner known per se. Release particles.

  The beam column further comprises charged particle optical means for converging the emitted charged particle bundle into multiple charged particle beams called write beams and forming an exposure projection. A control unit for controlling the exposure projection is included in the form of charged particle optical means for shaping or guiding such a writing beam, wherein a modulator array comprising a blanker optical part or a blanking deflector and said FIG. 6 illustrates a write deflector array that uses a write beam that is not blanked by a blanking deflector to deflect the write beam for pattern writing purposes.

  For example, the blanker optical component known from the applicant's international patent application WO2004107050 is a writing beam that effectively passes through an aperture provided for each writing beam in a stop plate according to a signal provided by a computer. The write beam is deflected away from a linear trajectory parallel to the other write beams, up to an amount of tilt that prevents the portion from being present, thereby effecting the “off” state of the particular write beam.

  All the light parts in the beam column are shaped by an array of apertures, and the openings in the separate parts are aligned with each other to allow the writing beam of the column to pass in the direction of the target surface in a controlled manner. Has been. The known maskless multi-beam system is further provided with a blanking deflector having both a source and a target surface which are typically arranged in its conjugate plane, ie it is the subject of WO 2004/0819010 Can be easily combined with. In this way, the lithographic system preferably achieves optimal brightness of the source on the target surface. Also, in this way, a minimum amount of space is required for the blanker array.

  The target surface of the writing beam is held on a stage included in the beam column. The stage induced by the electronic control unit of the system is perpendicular to the emitted writing beam bundle, preferably only in the direction transverse to the direction in which such writing beam bundle is finally deflected for writing purposes. Move with. The writing of the pattern by known lithographic systems is therefore timed "on" and "on" of the relative movement of the target surface and the writing beam by the control unit, in particular by the blanker optics by means of its so-called pattern streamer. This is done by a combination of “off” switching.

  An on / off switch notification, ie, modulation of the writing beam, is present in the associated known system that is performed by using optical optics. For example, the blanker optical system includes a photosensitive portion such as a photodiode for receiving an optical signal converted into an electronic signal by applying a method as given by the international patent application WO2005010618 of the present applicant. It has. The optical signal is generated by electron-to-light conversion by the control unit of the system and is transferred to the beam column by the optical carrier, i.e. the glass fiber bundle finally projecting from "transparent part of the vacuum boundary". The optical signal is projected onto the blanker optics using a lens system, which lens system is located in a known system between the transmitter part and the photosensitive part of the deflection device included in the blanker optical part. Is disclosed. The configuration of the deflection device, the photosensitive part, and the light-to-electricity conversion part is generated using both so-called MEMS- and (Bi-) CMOS technology. In order to prevent the use of mirroring components, in the known known systems the signaling light beam is projected far from above with respect to the blanking optics, so that the incidence of the pattern information-propagating light signal on the photosensitive element is as small as possible. Realize the angle. However, publications showing related embodiments show that other positions of the projection can be realized using mirrors to correct for the greater incidence accuracy that occurs at most of these alternative positions. Teaching.

  Although the normal setup of the lithography system described above has proven satisfactory, in the illumination system with the described tilt angle, this is not optimal and has at least unsatisfactory light transmission and comparison It is recognized that there is a drawback with large aberrations. The present invention therefore seeks to improve the known maskless multi-beam lithography system, but in particular with respect to its optical system (LOS). The present invention further aims to improve the lithography system by increasing its light transmission efficiency and / or reducing the possibility of aberrations in its optic.

  The present invention solves the above-mentioned problems to at least a considerable extent by using a mirror for redirection of a light beam provided with one or more holes for exposure, for example writing projection of a part of the lithography system. To do. In particular, the free-space optical interconnection of such a system according to the invention comprises a mirror with a hole, i.e. a hole provided in the projection trajectory of the plurality of writing beams, the mirror being on-axis, i.e. Arranged with respect to the emitter and the photosensitive element to achieve at least a virtually perpendicular incidence of the light beam on the photosensitive element, allowing one or more of the writing beam to pass through the mirror. At least one hole is provided.

  Instead, in further accordance with the insight underlying the present invention, a lithographic system is provided in which an electronic image pattern is transferred to an exposure tool for projecting an image onto a target surface, said exposure tool being an exposure projection. A control unit for controlling at least partly in the projection space of the exposure tool, the control signal being provided by the optical signal, the optical signal comprising a free space optical interconnection. Using a modulated light beam coupled to the control unit and emitted to a photosensitive portion of the control unit, wherein the modulated light beam is incident on the axis of the light beam on the photosensitive portion. Is coupled to the photosensitive part using a perforated mirror, in other words a perforated mirror, wherein one or more holes of the mirror are for the passage of the exposure projection It is provided.

  Using the system according to the invention, there is at least no appreciable interference with the exposure projection of the exposure tool of the lithography system, ie minimizing the presence of aberrations by preventing it. Due to the solution claimed in the present invention, the present invention has been predicted to be new and impossible in the past, but is realized by relatively simple hindsight to perform a highly preferred method.

  The various features and characteristics described and shown in this specification can be applied individually if possible. These individual features, in particular the features and characteristics described in the dependent claims, can be the subject of divided patent applications.

1 is a schematic diagram of a prior art lithography system on which the present invention is based. 1 is a schematic diagram of an improved optical optics system of a known lithography system according to a first embodiment. FIG. 3 is a schematic diagram of a structural arrangement in the optical system of the light of FIG. 2 of the lithography system. FIG. 3 is a schematic diagram of an improved optical system of a known lithography system according to a second embodiment.

The invention is further described by way of illustration of the following embodiments of the maskless lithography system according to the invention shown in the drawings.
In the drawings, corresponding structural features, ie at least functions, are indicated by the same reference numerals.

  FIG. 1 shows an overall side view of a prior art lithography system modified according to the invention, where it is implemented by an optical fiber Fb at the end 2 of the modulating means of an optical emitter or optical transmitter Fb. The light beam 8 is projected onto the modulator array 24 using the optical system represented by the lens 54. The modulated light beam 8 from each end of the optical fiber is projected onto the photosensitive element, ie, the photosensitive part of the modulator of the modulator array 24. In particular, the end of the fiber Fb is projected onto the modulator array. Each light beam 8 holds a portion of the pattern data to control one or more modulators, and the modulation is based on the instructions of the modulator array to produce the desired image on the target surface. Has formed a notification system for forwarding.

  FIG. 1 also shows a beam generator 50, which generates a diverging charged particle beam 51, in this example an electron beam. Using the optical system 52, ie the electro-optic system, this beam 51 is shaped into a parallel beam. The collimated beam 51 impinges on the beam splitter 53 and produces a plurality of substantially parallel write beams 22 that are directed to a modulation array 24, also called a blanker array.

  Using the modulators of the modulation array 24 with electrostatic deflection elements, the write beam 27 is deflected from the optical axis of the litho system and the write beam 28 passes through the modulator without being deflected.

  Using the beam stop array 25, the deflected write beam 27 is stopped. The writing beam 28 passing through the stop array 25 is deflected by the deflector array 56 in the first writing direction, and the cross section of each beamlet is reduced using the projection lens 55. During writing, the target surface 49 moves relative to the rest of the system in the second writing direction.

  The lithography system further comprises a control unit 60 comprising a data storage device 61, a reading unit 62, a data converter 63, and includes a so-called pattern streamer. The control unit 60 is located away from the rest of the system, for example outside the interior of the clean room. Using the optical fiber Fb, the modulated light beam 8 holding the pattern data is transmitted to the projector 54, which projects the end of the fiber onto the modulation array 24.

  FIG. 2 schematically illustrates an optical system of an improved lithography system according to the first embodiment. This uses a perforated mirror 104, which is provided to achieve in-axis incidence of the light beam 8 on the photosensitive element of the modulator array 24. The perforated mirror is either a relatively large hole through which all blanked deflected write beam 27 and all undeflected write beam 28 can pass, or each deflected or deflected. It has a plurality of relatively small holes 105, one for each non-writing beam. According to preference, the mirror 104 has a substantially flat reflective surface included in the system at an angle of 45 degrees, thereby maintaining the normal incidence of the incident beam 8 at the modulator 24 while maintaining light The amount of space required in this optical system is axially minimal. This minimized axial space requirement allows design freedom to place the LOS above or below the modulator array 24, which increases the manufacturing freedom of the array 24, which is It is a very complex part that is manufactured using CMOS and MEMS technology. Through the use of a perforated mirror 104, the focusing lens 106, preferably implemented by a lens system performing the focusing function, can be located as close to the latter as possible, at least closer to the fiber end 2. By positioning the focusing lens 106 close to the perforated mirror 104, the perforated mirror can be provided without excessive loss of optical signal intensity, and can be preferably realized due to the presence of the hole 105. .

  The array of fiber ends 2 is completed according to the invention by a virtual fiber array 103, in fact a microlens array 101 that forms an array spot in the focal plane of the microlens 101. In accordance with certain, independent features of the present invention, the microlens of the microlens array 101 according to the presently preferred embodiment performs an expansion function on the optical signal transmitted by a particular fiber of the fiber array Fb. The lens system according to the invention thus establishes a dual image system in which each signal is magnified by a microlens and subsequently focused by said lens 106 common to all emitted light signals. In this way, independence of the setting for increasing the effective spot size of each fiber and the setting for decreasing the fiber pitch is preferably realized.

  With respect to the first effect mentioned above, according to the present invention, it eliminates the need for a strong focus of the optical signal 8, thereby reducing the possibility of aberrations and further increasing the light transmission to reduce its loss. A favorable effect of covering the area of the photosensitive element as much as possible is obtained. The desired and generated light spot is not as large as the photosensitive area so as to minimize light loss by projecting the light onto the surrounding inactive portions. However, this arrangement makes the projection of light relatively sensitive to the position error of the light beam 8 because its small displacement makes it expected to reduce the amount of light over that received by the associated photosensitive element, eg a photodiode. Suggests that. Therefore, by increasing the size of the incident spot 24i but not larger than the photosensitive area, the present invention can reduce the sensitivity of the incident light beam portion due to misalignment, while reducing the sensitivity of the expensive and complicated optical element to free of LOS. It is prevented from being required for space interconnection. In this regard, misalignment may be due to the actual state of the litho system, structural inaccuracies, or a combination thereof. For the second effect described hereinabove, in particular, the pitch of the end of the fiber Fb, which is larger than the pitch of the photosensitive elements on the modulator array 24, is not suitable unless excessive and consequently uneconomical manufacturing efforts are made. It is. With the dual lens and dual imaging system of the present invention, both parameters are set independently and implemented in a preferred manner.

  FIG. 3 represents a preferred built-in configuration of the optical optical system described along FIG. 2 in a lithography system according to the invention. The figure shows a holder 24S of the aforementioned blanker or modulator array 24, by which the modulator array 24 is placed in a charged particle column. Such a load current element column is arranged in a housing Hv together with a holder for holding a wafer or other target surface, whereby the load current element column and the target stage are placed in a vacuum state. The array of fibers Fb is provided here through the openings in the removable part of the housing Hv by using a sealing material that accommodates a large amount of vacuum in order to achieve a hermetic seal of the fibers in the openings. The inner housing end Fbv of the fiber is thereby fixed to a considerable extent from outside the mechanical impulse that can act there. The end Fbv of the array of fibers is mechanically fixed to the housing HI at its end 2 with respect to the lens and mirror part of the optical system of light. Further, the housing HI is fixed to the modulator array holder 24S. In this way, the preferred mechanical method ensures that the position of the fiber end 2 and the modulator array, in particular its photosensitive area, are fixed relative to each other. Next, the array holder 24S is connected to a frame (not shown) such as a collimator 52 and a splitter 53, and further constitutes a charged particle column as described with reference to FIG.

  As shown in one dimension in FIG. 3, the perforated mirror 104 covers the entire area of the modulator array, and similarly the lens 106 covers the entire area of the tilted mirror 104. The lens 106 is thereby axially incorporated close to the holder 24S.

  From the foregoing description it will be clear that the principle of the dual lens system, the mechanical fixing of the lens housing HI to the blanker 24, and the particular application of the perforated mirror 104 can all be applied independently of one another. Further to the latter, the principle of dual imaging can be applied when using off-axis projection instead of the preferred vertical projection of the present invention.

  FIG. 4 schematically illustrates an optical system of an improved lithography system according to a second embodiment. This is applied to use the perforated mirror 107 to achieve in-axis incidence of the incident beam 8 on the photosensitive element of the modulator array 24. The perforated mirror is one relatively large hole 108 through which all blanking deflected write beam 27 and all undeflected write beam 28 can pass, or deflected or undeflected respectively. A plurality of relatively small holes for the writing beam are provided. Depending on preference, the mirror 104 comprises a reflecting surface that converges, the reflecting surface being arranged at an angle that reflects the incident light beam 8 in the direction of the modulator 24, said reflecting surface being in particular incident light. It is concave to allow the beam 8 to focus simultaneously on the modulator 24.

  Through the use of a perforated mirror having a reflective surface 107 for focusing, the focusing lens 106 can be omitted. A favorable effect is obtained that the loss of optical signal intensity can be further reduced, especially due to reflection at the surface of the focusing lens 106.

  Furthermore, the focusing element of this second embodiment, in particular the concave reflective surface of the perforated mirror 107, can be much closer to the modulator array array 24 than the lens 106 of the first embodiment. With this close distance, the optical system of this second embodiment can be designed with a large number of holes, and thus with the increased resolution of the optical system of light.

  Also, in the second embodiment of FIG. 4, the array of fiber ends 2 is completed with a microlens array 101, forming a virtual fiber array 103, effectively an array of spots, on the focal plane of the microlens 101. The microlens of the microlens array 101 performs an expansion function on an optical signal transmitted by a specific fiber of the fiber array Fb. The concave reflective surface of the perforated mirror 107 according to the second embodiment thus magnifies each signal by a microlens, followed by the concave reflective surface of the perforated mirror 107 common to all emitted optical signals. A dual image system is formed that focuses the signal.

  In addition, a perforated mirror having a focusing reflective surface 107 as shown in FIG. 4 can also be combined with a focusing lens 106 as shown in FIG. In this case, the focusing elements 106, 107 constitute two optical components, both optical components can contribute to the focusing effect and / or can be used to further reduce optical aberrations.

  Apart from the concepts indicated in the above description and all the relevant details, the present invention is also directly or obvious to the person skilled in the art from all the features as defined in the set of claims and from the preceding drawings. For all details relating to the invention as obtained. In the claims, rather than being fixed to the meaning of the aforementioned terms, any reference signs corresponding to the structures shown in the drawings are merely exemplary meanings of the aforementioned terms when reading the claims. Included as

Claims (4)

In a charged particle multi-beam maskless lithography system for projecting an image pattern onto a target surface,
An electronic image pattern is transmitted to an exposure tool that projects an image onto the target surface;
The lithography system comprises:
A multi-beam projection source for generating a plurality of writing beams (22) for writing an image pattern onto the target surface;
An optical system;
A vacuum housing (Hv);
Comprising
The writing beam (22) is directed to a blanker array (24) comprising a plurality of modulators,
The plurality of modulation devices comprise a plurality of electrostatic deflection devices that respectively deflect the writing beam according to the received image pattern information,
The plurality of modulation devices comprise a plurality of photosensitive elements for receiving a plurality of modulated light beams (8),
The plurality of photosensitive elements are provided near the plurality of electrostatic deflection devices,
The optical system comprises:
A plurality of optical transmission parts for transmitting a plurality of image pattern information signals;
An array of fibers (Fb) for emitting a plurality of modulated light beams to the plurality of photosensitive elements;
Comprising
In order to provide a vacuum space for the charged particle beam column of the exposure tool, the exposure tool is incorporated in the vacuum housing (Hv),
The lithography system comprises a holder (24S),
By the holder (24S), the blanker array (24) including the plurality of modulation devices is disposed in the charged particle beam column,
The array of fibers (Fb) comprises an inner housing end portion (Fbv) having an end (2), the end (2) being mechanically fixed to the holder (24S), so that The positions of the end portion (2) of the fiber of the inner housing end portion (Fbv) and the plurality of photosensitive elements are mutually determined,
The array of fibers (Fb) is fed through an opening in a removable part of the vacuum housing (Hv);
To achieve the hermetic sealing of the fibers in the openings, using a compatible sealing materials in a vacuum, the lithography system. The holder (24S)
A frame arranged to hold a plurality of elements constituting the charged particle beam column;
The lithography system of claim 1, wherein the lithography system is connected to the lithographic system.   The lithographic system of claim 1, wherein the fiber end (2) and the plurality of photosensitive elements of the plurality of modulators are spaced apart from each other.   4. A lithographic system according to any one of the preceding claims, wherein an emitter is incorporated to emit the plurality of modulated light beams at least substantially perpendicular to the direction of exposure projection.

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