DE102009035789A1 - Optical system useful in a device for laser material processing, comprises a housing, optical elements arranged inside the housing and having an optically active surface, a reception zone for receiving a flushing gas, and a flushing device - Google Patents

Abstract

The optical system comprises a housing (100), optical elements (101, 102) arranged inside the housing and having an optically active surface, on which the light vertically strikes under an incident angle of 30[deg] to the surface normal during the operation of the optical system, a reception zone for receiving a flushing gas from an immediate vicinity of the optical element, and a flushing device (130) for supporting a flushing gas flow (140) from the immediate vicinity of the optical element into the reception zone. The optical element is lens, prism, mirror or beam splitter. The optical system comprises a housing (100), optical elements (101, 102) arranged inside the housing and having an optically active surface, on which the light vertically strikes under an incident angle of 30[deg] to the surface normal during the operation of the optical system, a reception zone for receiving a flushing gas from an immediate vicinity of the optical element, and a flushing device (130) for supporting a flushing gas flow (140) from the immediate vicinity of the optical element into the reception zone. The optical element is lens, prism, mirror or beam splitter. The flushing gas flow runs at an angle of maximum 10[deg] to the optically active surface and passes vertical to a light expansion direction. The optical system includes a detachment unit (111, 112), which counteracts the flushing gas flow from the reception zone to the optical element and is formed in the form of plate, film or tubular element. The reception zone is formed by a tube-like or tubular element connected to the housing over a tapering section. The flushing device has a blower, and a suction device arranged in the reception zone. The flushing gas contains nitrogen. The optical element belongs to an elongated assembly, whose dimension along its longitudinal axis corresponds to four times the extension in a direction vertical to the longitudinal axis. The assembly is an arrangement for changing the pulse lengths of the laser pulses, and is arranged related to a contact area of the optical system, so that its longitudinal axis is inclined relative to the contact area normal. An angle between the longitudinal axis and the contact area normal is 20[deg] . The optical system has an absorbing zone and a reflecting surface that deflects the scattered light, which is produced within the optical system, in the direction of the absorbing zone. The absorbing zone is provided onto the housing, is formed at the housing, has a rib-like structure and is arranged above the optical path. An active cooling device is provided for cooling the absorbing zone. An independent claim is included for a process for operating an optical system.

Description

The The invention relates to an optical system.

The The invention is particularly advantageously applicable in optical systems with comparatively high thermal stress on the optical elements, and further particularly in connection with such optical Systems in which the beam guidance or light propagation direction to a substantial proportion in (in relation to the footprint of the optical system) in the vertical direction, such as z. B. a pulse stretcher.

in the Operation of optical systems occurs especially when using high Light power density suffers the problem that those with the high light power density accompanying increase in temperature of the optical elements (such as lenses, mirrors, prisms or beam splitters) that the respective heated surfaces surrounding gas also warms up and local fluctuations the refractive index within the optical path of the optical system causes. Such local variations in refractive index will also referred to as "streaks" and can depending on the application, a shift in focus position or otherwise Degradation of the properties of the optical system result.

Next known from astronomy active optical systems (active Mirroring) for correcting atmospheric turbulence it is to avoid the streaking u. a. known about one Blowing optical elements from the respective heated gas wegzuschublasen optical elements and thereby the formation of so-called to avoid thermal lenses.

Out US 7,277,466 B2 and EP 1 407 521 B1 It is known inter alia, in a lattice-based line narrowing device for line narrowing a laser with a grate-receiving chamber, to provide a scavenger for providing a purge gas in the chamber, which may in particular comprise a purge gas manifold having a plurality of small openings communicating a purge gas flow straighten the surface of the grid. The purging gas stream takes place here substantially along the light propagation direction extending between a barrier and the grid.

Especially problematic with regard to the problem described at the outset Streaking are optical systems in the affected area based on the footprint of vertical beam guidance, because the rising heated gas for comparatively remains in the beam path for a long time and thus the problems of Can increase streaking.

An example of systems with typically vertical beam guidance form in particular arrangements for changing the pulse length or distances of laser pulses, as z. B. off DE 10 2007 045 454 A1 are known and referred to as "pulse stretcher". Such pulse stretcher are used in order to reduce the intensity of laser pulses or to smooth out intensity peaks by laser pulses (eg having a pulse length of 120 nm) which are elongated out of comparatively short, intensive laser pulses (eg with a pulse length of 20 nanoseconds). 140 nanoseconds) with lower peak intensity.

A simplified representation of a pulse stretcher is in 7 shown in which a beam splitter 703 serves to partial beams of an incident in the x-direction laser beam 705 decouple so that these partial beams due to possibly multiple reflection on mirrors 701 . 702 be routed through different delay lines before coming to terms with the beam splitter 703 superimpose transmitted sub-beams, so that out of the beam splitter 703 an elongated laser pulse with lower peak intensity emerges. As a result, depending on the application z. B. damage to materials to be examined or, as in microlithography, aging effects of the optical system are counteracted.

such optical systems, which - as in the case of Pulsstretchers - also Modules within a larger overall system can conventionally be so far vertically arranged as the longitudinal axis (i.e. Direction of greater spatial extent pointing axis) vertically or perpendicular to the footprint of the optical system is oriented to the required footprint during operation of the optical system (eg during the Manufacture of components by means of a microlithographic projection exposure apparatus) keep as low as possible. This is just for a pulse stretcher in so far as of particular importance, as a result of the underlying Principle of exploiting the speed of light by multiple Fold the beam path as long as possible are to be provided for the path difference achieved, so that the distances between the mirrors are relatively large, why again to minimize the footprint in the Wafer factory in principle, a vertical placement desirable is.

In front In the above background, it is an object of the present invention to to provide an optical system which is an effective prevention local refractive index fluctuations at the same time low footprint of the system.

These The object is achieved by the features of the independent claims solved.

According to one Aspect of the invention, an optical system comprises a housing, at least one disposed within the housing optical Element which has at least one optically effective surface wherein, during operation of the optical system, light is applied thereto Area under an impact angle of maximum 60 ° to Surface normal impinges, a recording area for recording of purge gas from an immediate vicinity of the optical element and at least one flushing device for assistance a purge gas flow from the immediate environment of the optical element in the receiving area.

Of the Invention is based in particular on the concept, in an optical System heated gas in the range of strong light output exposed optical elements as soon as possible from the optically used area to remove local variations of the Refractive index or Schlieren formation within the beam path to avoid.

One Another advantage of the invention is that due to the effective Avoiding streaking on a principle also eligible, but relatively expensive and costly flushing of the optical system with helium (in which the refractive index change due to temperature influences comparatively small to negligible) is omitted can be and instead a simpler and cheaper to be handled, preferably inert purge gas such as nitrogen can be used.

According to one Embodiment meets light in the operation of the optical system on the optically effective surface under an impact angle of a maximum of 50 ° to the surface normal, in particular an impact angle of maximum 45 ° to the surface normal, continue in particular an impact angle of maximum 30 ° to the surface normal, and further in particular perpendicular.

According to one Embodiment runs the purge gas flow at an angle of at most 30 °, in particular an angle of a maximum of 20 °, further in particular an angle of maximum 10 ° to the optically effective surface (this Criterion in the case of a curved surface the angle to the respective surface tangent be related can).

According to one Embodiment runs the purge gas flow substantially perpendicular to the light propagation direction. Thereby, that the purge gas flow generated according to the invention transverse to the light propagation direction as well as to a receiving area runs, can lead to streaking, temporally extended whereabouts of this heated gas in the Beam path can be effectively avoided.

According to one Embodiment, at least one partition is provided, which a purge gas flow from the receiving area counteracts back to the optical element. The separation can in particular in the form of a plate or foil or as a tubular Element be formed.

According to one Embodiment, the receiving area by a to the Housing connected tubular or tubular Element formed, whereby even in comparatively narrow spaces a particularly effective dissipation of the heated Gases is enabled. The tubular or tubular Element can in particular over to the housing be connected to a tapered section.

The Flushing device can be a blower and / or a preferably have arranged in the receiving area suction device.

According to one Embodiment belongs to the optical element of a elongated assembly, whose dimension along its longitudinal axis at least four times the extent in one to the longitudinal axis vertical direction corresponds. The assembly can in particular an arrangement for changing the pulse length of Be laser pulses (Pulse Stretcher). In conjunction with such an assembly the invention is particularly as already explained advantageous because of elongated assemblies for reasons the parking space minimization basically a vertical The aim is to set up, where the problem of streaking particularly serious and thus the use of the invention especially is effective.

According to one embodiment, this assembly is arranged with respect to a footprint of the optical system such that its longitudinal axis is inclined relative to the footprint normal. In this case, the angle between the longitudinal axis and the contact surface normal is preferably less than 45 ° and is more preferably at least 10 °, in particular at least 20 °. As a result, heated purge gas, which flows from the flushing device adjacent to the respective optical element region, for. B. rise laterally on the housing wall and thus reaches -and other than in a vertical with respect to the contact surface arrangement- no longer in the beam path. Thus, according to this embodiment, a certain increase in the uprising required during operation of the optical system (eg during the microlithography process) becomes conscious surface compared to a precisely vertical arrangement accepted, so as to reduce the targeted in the context of the invention problem of streaking.

Although the above-described concept of tilted installation a elongated assembly advantageous in conjunction with the invention Flushing device, this concept is not on the presence a flushing device limited.

According to one In another aspect, the invention thus also relates to an optical System with an elongated assembly whose dimension is along its longitudinal axis at least four times the extent in a direction perpendicular to the longitudinal axis, in particular an arrangement for changing the pulse length of laser pulses (Pulse Stretcher), the assembly based on a footprint of the optical system is arranged is that its longitudinal axis relative to the contact patch normal is inclined.

According to one Embodiment further extends the optical system at least an absorbent region and at least one reflective surface on which stray light generated within the optical system deflects in the direction of the absorbent area. The absorbent Area can be formed in particular on the housing. Of Further, the absorbent portion can increase the heat dissipation at least partially have a rib-shaped structure. Of the absorbing area is preferably above the beam path, so that rising warm air no longer enters the beam path.

Although the concept of targeted combination of a reflective surface with an absorbent region advantageous in conjunction with the Flushing device according to the invention, Also, this concept is not based on the presence of a flushing device limited. According to another aspect Thus, the invention also relates to an optical system with a Housing, at least one provided on the housing absorbent area and at least one reflective surface, which scattered light generated within the optical system in the direction of the absorbent area deflects.

According to one In another aspect, the invention relates to a method of operation an optical system, in particular an optical system according to one of the preceding claims, wherein the optical system a housing and at least one within the housing arranged optical element having at least one has optically effective surface on which light in the operation of the optical system impinges at an angle of at least 60 °, with the step of: supporting a purge gas flow from an immediate vicinity of the optical element into one Pickup area.

To preferred embodiments and advantages of the method is on the above statements in connection with the invention directed optical system.

The Invention is generally advantageous in devices and methods used for laser material processing, for example for laser crystallization (eg in the ELA method well-known in the literature, SLS method, TDX method and ZMR method), as well as in devices and method of laser doping (i.e., activation of dopants in semiconductors), for laser hardening, for laser cutting, for Laser welding etc.

The The invention thus further relates to a device for laser material processing, in particular for laser crystallization, wherein the device a having optical system with the features described above.

Further Embodiments of the invention are the description and the dependent claims refer to.

The Invention is described below with reference to the attached Figures illustrated embodiments closer explained.

It demonstrate:

1 - 5 schematic representations of various embodiments of the present invention;

6 a schematic representation of a device for laser crystallization as an exemplary application of the invention; and

7 a simplified schematic representation of a conventional pulse stretcher.

According to 1 For example, an optical system in a first embodiment of the invention includes a housing 100 in which optical elements 101 . 102 are arranged, which by a border rays S ₁ , S ₂ limited light beam S one (in 1 not shown) light source are irradiated, wherein the light propagation direction in the coordinate system also shown in the z-direction. At the optical elements 101 . 102 of which only two are indicated by way of example, it may be any optical Ele elements, in particular mirrors, beam splitters, lenses, prisms or gratings. Also indicated is the course of an optical axis OA of the optical system, which by definition runs along the centers of curvature of the rotationally symmetrical optical components.

In a region outside the optical beam path is a flushing device 130 , The flushing device 130 For example, it can be configured as a nozzle, as a tube with a plurality of openings, as a gap or in another suitable manner. From the rinsing device 130 Purging gas exits. Generally this is an inert gas such as. For example, nitrogen is preferred to avoid unwanted reactions that may occur at short wavelengths in the UV range, such as when using air with the oxygen contained, but it is about when operating under visible wavelengths in principle also operate with air or with a other purge gas possible. Suitable flow rates of purge gas flow may be, for example only and without limitation, in the range of 0.1 l / min to 20 l / min.

As a result of absorption at the optically active layers of the optical elements 101 . 102 These are heated during operation of the optical system. Also, the gas in the heats up to the optical element 101 . 102 adjacent areas. The purge gas stream 140 is in the range of the optical element 101 now directed so that it runs transversely to the optical path and this either on the optical element 101 impinges or passes directly above it.

According to 1 the purge gas flow occurs 140 from the optically used or through the light beam S traversed area 110 by a side wall forming a partition between two 111 . 112 opening in one of the flushing device 130 opposite side of the housing 100 located receiving area 120 passing through the side walls 111 . 112 from the optically used or by the light beam S traversed area 110 is separated. Thus, the purge gas flow occurs 140 in the further course no longer in the beam path. The optical element 102 as well as possibly further optical elements can be acted upon in a corresponding manner with a purge gas stream.

2 shows a further embodiment of the invention, wherein the embodiment of 1 corresponding or substantially functionally identical elements with " 100 "Increased reference numerals are marked.

The embodiment in 2 is different from the one 1 in that the purge gas stream 240 over a tapered section 250 in one to the housing 200 connected, a recording area 220 forming tubular or tubular section is initiated. It can assist in the movement or removal of the purge gas stream 240 the purge gas is sucked off by means of a suction device (not shown) connected to the tubular or tubular section.

3 shows a further embodiment of the invention, wherein the embodiment of 2 appropriate or substantially functionally identical elements turn around with " 100 "Increased reference numerals are marked.

The embodiment in 3 is different from the one 2 in that the light beam S bounded by marginal rays S ₁ , S ₂ or the optical beam path of components 305 - 307 surrounded so that in the field of optical elements 301 . 302 heated purge gas stream 340 after flowing past the optical elements 301 . 302 no longer enters the optical path and instead from one or more openings 370 exits the assembly. It is in accordance with 3 through the components 305 - 307 again a first, optically used area 310 and a second area or receiving area located outside the optical beam path 320 Are defined. With the components 305 - 307 It can be massive components, but also thin sheets or foils. The components 305 - 307 at the same time shield the beam path against other heat sources such. As screens, motors, heated socket parts, etc. from.

4a -C show schematic diagrams for explaining further embodiments of the invention, in which an optical assembly in addition to one or more optical elements (of which only two examples 401 . 402 are shown) provided with a reflective surface aperture 480 (in the form of a scattered light aperture or an additionally optically active element). The aperture 480 couples stray light 485 in such a way that the reflected scattered light 486 on an absorbent area 490 incident. This absorbing area 490 is located so far away from the optical path that the consequent heating of the absorbing area 490 has no significant impact on the optical properties of the system. Preferably, this absorbing region is located above the beam path.

Furthermore, according to 4a -C the absorbing area 490 (respectively. 491 and 493 in 4b , c) arranged relative to the beam path such that heated gas (eg air) coming from the area 490 ascending (as with the reference numbers 492 respectively. 495 in 4b and 4c indicated) no longer enters the optical path. In particular, according to 4b or 4c the absorbing area 491 respectively. 493 Part of the housing wall or be connected to the housing wall. As schematically in 4c shown, the housing wall to increase the heat transfer to the outside in the absorbent area 493 a rib-shaped structure 494 exhibit. Furthermore, active cooling (eg in the form of a blowing device (blower) for blowing with a gas or in the form of a water cooling or a cooling circuit with a liquid or gaseous cooling medium) may be provided in this region.

Furthermore, the optical elements 401 . 402 or their surroundings analogous to the embodiments 1 . 2 and 3 be subjected to a purge gas flow. The basis of 4 described concept, within the optical system deflected scattered light with at least one reflective surface to an absorbing area out, but is also independent of the generation of such purge gas flow feasible and advantageous, so that corresponding embodiments without the purge gas flow generated in the embodiments described above to be encompassed by the present application.

5 shows a schematic representation for explaining a further embodiment of the invention. In this embodiment, an optical element 501 . 502 and 503 comprising assembly 505 an elongated shape. As a criterion for the elongated shape z. B. specified that the dimension of the assembly 505 along its longitudinal axis is at least four times the extent in the direction perpendicular to the longitudinal axis direction. The assembly may be, for example, a pulse stretcher, wherein the optical element 503 is a beam splitter and the optical elements 501 . 502 Form mirror elements of the pulse stretcher. However, the assembly may also be another elongate assembly.

According to 5 is the assembly 505 relative to a footprint of the optical system (which is perpendicular to the z-axis in the coordinate system also shown) arranged so that its longitudinal axis is inclined relative to the contact surface normal (extending in the z-direction). In this case, the angle between the longitudinal axis and the contact surface normal is preferably less than 45 ° and is more preferably at least 10 °, in particular at least 20 °.

In other words, the entire assembly 505 around a (in 5 Tilted in the y-direction) horizontal axis tilted. As a result, heated purge gas increases 541 respectively. 542 which is from the rinsing devices 531 . 532 to the optical elements 501 respectively. 503 flows through the adjacent area, laterally on the wall of the housing 500 up and then no longer enters the beam path.

6 shows in a merely schematic representation as a generic system, a device for laser material processing, in particular for laser crystallization or laser hardening.

The The invention is in addition to the use for laser crystallization (eg. in the known ELA method, SLS method, TDX method and ZMR method) or for laser hardening z. B. also in devices and method of laser doping (i.e., activation of dopants in semiconductors), for laser cutting or for laser welding and other devices and methods for laser material processing applicable.

The device according to 6 includes a lighting device 620 and a projection optics module (POM) 630 and an optical system according to the invention in the illumination device and / or projection optical module or else in a pulse stretcher (analogous to, for example, arranged in front of the illumination device) 5 respectively. 7 ) exhibit.

According to 6 becomes one of a laser light source 610 generated laser beam 605 initially via a deflection mirror 615 deflected and passes through the lighting device 620 in which the laser beam 605 is homogeneously mixed without significant change in its cross-section.

The projection optics module 630 has a plurality of mirrors (of which in 6 merely an example of two mirrors 631 and 632 are indicated), which the of the lighting device 620 with still nearly square cross cut incoming laser beam 605 transform into a substantially line-shaped cross-section. The reshaped laser beam then meets in the application example of laser crystallization z. B. on a silicon (Si) layer 640 on a substrate 650 in which it is z. B. may be a serving for the production of semiconductor displays and in electronic devices of different types (such as flat screen televisions or mobile phone displays) used panel can act. The substrate 650 is for laser crystallization via a mobile support 660 transverse to the direction of the laser beam 605 (in the direction of the double arrow 661 ) movable.

If the invention also uses special Has been described embodiments, will be apparent to those skilled numerous variations and alternative embodiments, for. B. by combination and / or exchange of features of individual embodiments. Accordingly, it will be understood by those skilled in the art that such variations and alternative embodiments are intended to be embraced by the present invention, and the scope of the invention is limited only in terms of the appended claims and their equivalents.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 7277466 B2 [0005]
• EP 1407521 B1 [0005]
• DE 102007045454 A1 [0007]

Claims (25)

Optical system comprising: 100 . 200 . 300 . 500 ); At least one optical element arranged inside the housing ( 101 . 102 . 201 . 202 . 301 . 302 . 401 . 402 . 501 . 503 ), which has at least one optically active surface, wherein in the operation of the optical system light impinges on this surface at an angle of incidence of a maximum of 60 ° to the surface normal; • a recording area ( 120 . 220 . 320 ) for receiving purge gas from an immediate vicinity of the optical element; and at least one flushing device ( 130 . 230 . 331 . 332 . 531 . 532 ) for assisting a purge gas flow from the immediate vicinity of the optical element ( 101 . 102 . 201 . 202 . 301 . 302 . 401 . 402 . 501 . 503 ) in the reception area ( 120 . 220 . 320 ). Optical system according to claim 1, characterized that light in the operation of the optical system on the optically effective Area under an impact angle of maximum 50 ° to Surface normal, in particular an impact angle of maximum 45 ° to the surface normal, more particularly one Impact angle of maximum 30 ° to the surface normal, and further in particular impinges vertically. Optical system according to claim 1 or 2, characterized characterized in that the purge gas flow in a Angle of maximum 30 °, in particular an angle of maximum 20 °, in particular an angle of at most 10 ° the optically active surface extends. Optical system according to one of claims 1 to 3, characterized in that the purge gas flow is substantially perpendicular to the light propagation direction. Optical system according to one of the preceding claims, characterized in that at least one separation ( 111 . 112 ) is provided, which counteracts a purge gas flow from the receiving area back to the optical element. Optical system according to claim 5, characterized in that the at least one partition ( 111 . 112 ) is formed in the form of a plate or foil or as a tubular element. Optical system according to one of the preceding claims, characterized in that the receiving area ( 220 ) by a to the housing ( 200 ) connected tubular or tubular element is formed. Optical system according to claim 7, characterized in that the tubular or tubular element to the housing ( 200 ) over a tapered section ( 250 ) connected. Optical system according to one of the preceding claims, characterized in that the flushing device ( 130 . 230 . 331 . 332 . 531 . 532 ) has a fan. Optical system according to one of the preceding claims, characterized in that the flushing device is a preferably Having arranged in the receiving area suction device. Optical system according to one of the preceding claims, characterized in that the purge gas comprises an inert gas, in particular nitrogen (N ₂ ). Optical system according to one of the preceding claims, characterized in that the optical element is a lens, a Prism, a mirror or a beam splitter is. Optical system according to one of the preceding claims, characterized in that the optical element ( 501 . 503 ) of an elongate assembly ( 505 ) whose dimension along its longitudinal axis corresponds to at least four times the extent in a direction perpendicular to the longitudinal axis direction. Optical system according to claim 13, characterized in that the assembly ( 505 ) is an arrangement for changing the pulse length of laser pulses (Pulse Stretcher). Optical system according to claim 13 or 14, characterized in that this assembly ( 505 ) is arranged with respect to a footprint of the optical system such that its longitudinal axis is inclined relative to the footprint normal. Optical system with an elongate assembly ( 505 ) whose dimension along its longitudinal axis corresponds to at least four times the extent in a direction perpendicular to the longitudinal axis, in particular an arrangement for changing the pulse length of laser pulses (pulse stretcher), wherein the assembly ( 505 ) is arranged with respect to a footprint of the optical system such that its longitudinal axis is inclined relative to the footprint normal. An optical system according to claim 15 or 16, characterized in that an angle between the longitudinal axis and the contact patch normal is less than 45 ° and preferably less at least 10 °, in particular at least 20 °. Optical system according to one of the preceding claims, characterized in that it further comprises: - at least one absorbing region ( 490 ), and - at least one reflective surface ( 480 ), which scattered light generated within the optical system in the direction of the absorbing region ( 490 ) distracts. Optical system comprising: a housing; At least one absorbent region provided on the housing ( 490 . 491 . 493 ), and • at least one reflective surface ( 480 ), which scattered light generated within the optical system in the direction of the absorbing region ( 490 . 491 . 493 ), where the absorbing area ( 490 . 491 . 493 ) is arranged above the beam path. Optical system according to claim 18 or 19, characterized in that the absorbing region ( 490 . 491 . 493 ) is formed on the housing. Optical system according to one of claims 18 to 20, characterized in that the absorbing region ( 493 ) a rib-shaped structure ( 494 ) having. Optical system according to one of claims 18 to 21, characterized in that the absorbing region ( 493 ) is arranged above the beam path. Optical system according to one of claims 18 to 22, characterized in that an active cooling device for cooling the absorbent region ( 490 . 491 . 493 ) is provided. Method for operating an optical system, in particular an optical system according to one of the preceding claims, wherein the optical system comprises a housing and at least one optical element ( 101 . 102 . 201 . 202 . 301 . 302 . 401 . 402 . 501 . 503 ), which has at least one optically effective surface, wherein in operation of the optical system light impinges on this surface at an impact angle of maximum 60 ° to the surface normal, comprising the step of: supporting a purge gas flow from an immediate vicinity of the optical element into a receiving region (US Pat. 120 . 220 . 320 ). Apparatus for laser material processing, wherein the device is an optical system according to one of the claims 1 to 23.