DE102019118676B4 - Optical system for homogenizing the intensity of light radiation and system for processing a semiconductor material layer - Google Patents

Abstract

Optical system (30, 80) for homogenizing the intensity of light radiation for processing a semiconductor material layer, in particular for producing a crystalline semiconductor layer, comprising: an optical beam transformation arrangement (32) with a first arrangement (32a) with first beam transformation elements (40), which is set up for this purpose , an incident light beam (38), the beam profile (50) of which has a short axis in an x-direction and a long axis in a y-direction, the x-direction and the y-direction each being perpendicular to a direction of propagation of the light beam , geometrically deflect and split along the long axis into partial light beams (42) so that a propagation direction of the partial light beams (42) is different from the propagation direction of the incident light beam (38), and a second arrangement (32b) with second beam transformation elements (44), which is arranged in the beam path of the partial light beams (42) u nd is set up to deflect the deflected partial light beams (42) again, with a beam profile (48) of a further deflected partial light beam (46) in the x direction, based on the direction of propagation of the again deflected partial light beam (46), a section of the beam profile (50 ) of the incident light beam (38) in the y-direction, based on the direction of propagation of the incident light beam (38), characterized in that the optical system (30, 80) further comprises one arranged in the beam path of the partial light beams (46) which are deflected again, the beam shaping device (34) arranged downstream of the optical beam transformation arrangement (32), which is set up to spatially superimpose the once again deflected partial light beams (46) with respect to the y-direction as an illumination line (14) located in an illumination plane (65), and one in the beam path of the Again deflected partial light beams (46) arranged, the optical beam transform An optical imaging device (36) arranged downstream of the ion arrangement (32), which is set up and arranged such that the first beam transformation elements (40) are optically imaged in an image plane (61) located in the illumination plane (65).

Description

The disclosure relates to an optical system for homogenizing the intensity of light radiation and an installation for processing a semiconductor material layer with such an optical system. Such optical systems for generating light radiation with a uniform intensity profile are used for processing a semiconductor material, in particular for generating a crystalline semiconductor layer.

For the crystallization of thin-film layers, for example for the production of thin-film transistors (in English: Thin Film Transistor, TFT for short), lasers are usually used. Silicon (Si for short), more precisely amorphous silicon (a-Si for short), is used as the semiconductor to be processed. The thickness of the semiconductor layer is, for example, 50 nm, which is typically located on a substrate, for example a glass substrate, or on another carrier.

The layer is illuminated with the light of the laser, for example a pulsed solid-state laser. The light with a wavelength of, for example, 343 nm is formed into a line of illumination and imaged on an image plane of the semiconductor material. The line of illumination has a short (narrow) axis and a homogeneous long beam axis. The short or narrow axis has a Gaussian or a flat intensity distribution.

The line of illumination is moved over the semiconductor layer in the direction of the short axis with a feed rate of typically approx. 5 to 50 mm / s. The power density (in the case of continuous wave lasers) or the pulse energy density (in the case of pulsed lasers) of the light beam is set in such a way that, for example, in the case of amorphous silicon, it partially melts and the melted silicon is then in a polycrystalline structure based on unmelted solid silicon solidified on the glass substrate. Melting and solidifying typically takes place on a time scale of 10 to 100 ns and the subsequent cooling of the film to room temperature typically takes several 100 microseconds.

When the layer of amorphous silicon is irradiated and converted into a layer of polycrystalline silicon, a uniform intensity of the line of illumination is particularly important, i.e. the homogeneity of the spatial intensity distribution integrated along the short and / or long axis. The more homogeneous or uniform the intensity distribution of the line of illumination, the more homogeneous or uniform the crystal structure of the thin-film layer (for example the grain size of the polycrystalline layer), and the better, for example, the electrical properties of the end product formed from the thin-film layer, for example the thin-film transistor. A homogeneous crystal structure, for example, results in high conductivity due to a high mobility of the electrons and positive charge holes. Therefore, high demands are placed on the homogeneity of the lighting line.

Inhomogeneities can occur in particular along the long beam axis and perpendicular thereto along the short beam axis when the illumination line is moved over the semiconductor layer in the direction of the short axis. These inhomogeneities are called "mura". So-called “scan mura” have their origin in inhomogeneities along the beam axis and occur as strip-shaped inhomogeneities running in the scan direction or in the feed direction. At right angles to this, so-called “shot mura” occur, which can be traced back to fluctuations in the intensity pulse to pulse during the advance.

In order to generate a regular polycrystalline grain structure during crystallization, it is known that a surface interference effect is used, which leads to a modulated intensity distribution during the exposure and, through repeated exposure during the advance, a grain structure with about the size of the wavelength of the light is reinforced. This effect is called "Laser Induced Periodical Pattern Structure" ("LIPPS" for short). At a wavelength of 343 nm, for example, grain structures of approximately 0.3 µm to 0.4 µm result.

Investigations have also shown that a flat intensity distribution in the direction of the short axis of the illumination line is also advantageous for a uniform crystallization result.

The exact course of the flat intensity distribution in the direction of the short axis is decisive here. If the flanks of the flat profile are gently sloping, there is less energy available in the central flat area than when the flanks of the flat profile are steeply sloping in comparison. With an intensity profile with relatively flat edges, it is therefore difficult to achieve a sufficient intensity in the central flat area in order to produce a uniformly crystallized semiconductor material layer of high quality. In addition, a steep flank should enable a sufficient depth of focus, so that the flank steepness changes only slightly over 100 µm to more than several 100 µm.

It is therefore desirable to have a homogeneous line of illumination along the short axis as well To have a distribution with a width of typically 30 µm to 100 µm, with the steepest possible flanks, for example a width of 10 µm between a first intensity at which the intensity corresponds to 10% of a maximum intensity and a second intensity at which the intensity 90% of the maximum intensity.

From the DE 103 31 442 A1 an arrangement for transforming an optical radiation field into a line-shaped radiation field is known which comprises transformation optics which are set up to divide and deflect the radiation field into a plurality of partial radiation fields. In one embodiment, the transformation optics comprise three Dove prisms. From the DE 11 2011 100 813 T5 an optical arrangement is known with various configurations of optical rotating devices which are suitable for rotating an input beam into a new orientation. From the DE 10 2008 033 358 A1 a device for redistributing the beam parameter product of a laser beam is known, which comprises an arrangement for beam separation, an optical component to reduce the spatial coherence of the partial beams to one another, for example in the form of a stepped mirror arrangement, a homogenizing optical component and an objective which the homogenized radiation focused into a line. From the US 2017/0176758 A1 a further optical arrangement for achieving a narrow line of illumination is known. The present invention discloses an improved optical system for homogenizing the intensity of light radiation along one direction, in particular along the short axis of the illumination line. The improved optical system is intended in particular for processing a semiconductor material, in particular for producing uniformly crystallized semiconductor layers.

The present disclosure comprises an optical system for homogenizing the intensity of light radiation for processing a semiconductor material layer, in particular for producing a crystalline semiconductor layer. The optical system has an optical beam transformation arrangement with a first arrangement with first beam transformation elements, which is set up to transmit an incident light beam whose beam profile has a short axis in an x-direction and a long axis in a y-direction, the x- The direction and the y-direction are each perpendicular to a direction of propagation of the light beam, to be geometrically divided into partial light beams along the long axis, a propagation direction of the partial light beams being different from the propagation direction of the incident light beam. The optical beam transformation arrangement also has a second arrangement with second beam transformation elements, which is arranged in the beam path of the partial light beams and is set up to deflect the deflected partial light beams again, with a beam profile of a further deflected partial light beam in the x direction, based on the propagation direction of the again deflected Partial light beam, corresponds to a beam profile section of the incident light beam in the y-direction, based on the direction of propagation of the incident light beam. The optical system also comprises a beam-shaping device arranged in the beam path of the partial light beams, downstream of the optical beam transformation arrangement, which is set up to spatially superimpose the partial light beams with respect to the y-direction as an illumination line located in an illumination plane, as well as one which is arranged in the beam path of the partial light beams Optical imaging device downstream of the optical beam transformation arrangement, which is set up and arranged such that the first beam transformation elements are optically imaged with respect to the x-axis in an image plane located in the plane of illumination.

The incident light beam is divided into partial light beams and deflected by means of the optical beam transformation device. The incident light beam has a beam profile that has a short axis and a long axis perpendicular to the direction of propagation. The direction of propagation of the incident light beam is intended to define the direction of a z-axis, the short axis being oriented in the direction of an x-axis and the long axis being oriented in the direction of a y-axis. The partial light beams have a different propagation direction to that of the incident light beam, the direction of the z-axis always being defined by the propagation direction of the respective light beam or partial light beam. The direction of the z-axis, i.e. the z-direction, thus varies in space with the propagation of the light beam or the partial light beams in the optical system. The x-direction and y-direction of a light beam or partial light beam is always defined in the direction of the propagation direction of the light beam or partial light beam concerned, namely the x-direction and the y-direction are always defined the same in relation to the z-direction.

The light beam can be the laser radiation emitted by a laser. The light radiation can be, for example, the laser radiation emitted by a UV solid-state laser with a wavelength of 343 nm.

The beam profile of the incident light beam with a long axis and a relatively short axis can be achieved by expanding a light beam, in particular a laser beam, with a round beam profile in only one direction, for example using cylindrical optics such as a cylindrical lens telescope.

By deflecting the partial light beams in space, in particular by rotating the partial light beams in space, the beam profile is also reoriented in space. The beam profile of a partial light beam along the short axis corresponds to the reorientation, i.e. after the beam transformation device, to a section of the beam profile of the incident light beam along the long axis. The section of the beam profile is determined by the division of the light beam at the first beam transformation elements. This results in a steep drop in intensity at the lateral edges of the first beam transformation elements. After the reorientation, this “sharp” intensity edge is arranged in the direction of the short axis of a partial light beam, along the upper and lower edges of a second beam transformation element. As will be described later, in one embodiment this “sharp” intensity edge can be transferred into the image plane by mapping the lateral edges of the illuminated first beam transformation elements. In particular, the illuminated first beam transformation elements can serve as objects for a cylindrical image of the lateral edges of the first beam transformation elements.

The partial light beams emerging from the optical beam transformation device then pass through the beam shaping device, by means of which the partial light beams are spatially superimposed along the long axis. The spatial overlay on an illumination field in the illumination plane can be selected in such a way that the long axis of an illumination line is formed. This results in a flat, homogeneous intensity profile along the long axis in a known manner. The beam shaping device can form anamorphic optics or be part of anamorphic optics. For example, it can have a lens array homogenizer which is based on the principle that the incident light beam or beams or partial light beams are split into many partial beams or further partial beams, which are then spatially superimposed. This results in a largely homogeneous intensity profile along the y-axis.

The superposition in the y direction also results in an overlay in the x direction, that is, in the direction of the short axis. In particular, the partial light beams are superimposed in such a way that the “sharp” intensity edges of the partial beams coincide. This also results in a flat, largely homogeneous intensity profile with steeply sloping lateral flanks in the direction of the short axis.

The optical imaging device is designed and arranged in the beam path of the optical system in such a way that the first beam transformation elements are optically imaged in an image plane located in the illumination plane. Specifically, the optical imaging device is designed and spatially arranged in the beam path of the optical system in such a way, in particular with regard to the first beam transformation elements and the desired location of the illumination plane, that the illuminated first beam transformation elements serve as objects that are optically as in the image plane formed in the illumination plane Images are mapped. The illumination plane should be a plane in which the illumination line formed by the optical system for illuminating and processing the semiconductor material layer should be located. The plane of illumination is ideally formed by the surface of the semiconductor material to be processed.

The first beam transformation elements can be arranged at a distance from one another in the z direction. They are only so slightly spaced from one another in the z-direction that the individual image positions assigned to the first beam transformation elements are only slightly spaced from one another, for example less than 5 μm from one another. In particular, the focal length of the optical imaging device, its distance from the first beam transformation device and its distance from the semiconductor material layer to be processed are selected so that the illuminated reflective elements as objects through the optical imaging device into an image plane or several image planes on the semiconductor material layer or near the surface Transfer area of the semiconductor material layer and mapped there as images.

According to one embodiment, the optical imaging device is designed such that it images the incident partial light beams only in the x direction. The optical imaging device therefore only works in the x-direction and not in the y-direction, the x-direction again being based on the direction of propagation of the partial light beams deflected again and indicating a direction of the short axis of the partial light beams or the partial light beams superimposed to form a light beam . With a reduction, only the light is bundled in the x-direction and not in the y-direction. The superimposed partial light beams can in particular be imaged on an illumination line. Since the optical imaging device acts in the x-direction, the "sharp" upper and lower intensity edges of the beam profile of the partial light beams are transferred to the image plane after a second beam transformation element and are imaged there, in particular imaged in a reduced size, which leads to a narrow line of illumination with high intensity along the x-axis.

According to the disclosure, the optical imaging device can in particular be set up and arranged such that the first arrangement lies in an object plane of the optical imaging device that is conjugate to the image plane. The first beam transformation elements are thus optically imaged as an image as objects in the image plane. In this case, if the optical imaging device has a focal length f, the equation b = f * a / (af) can apply for an image distance b, where the image distance b is the distance between the main plane of the optical imaging device and the image plane, and an object distance a is a distance between the first arrangement and the main plane of the optical imaging device on the object side. The first beam transformation elements of the first arrangement can be arranged offset to one another, so that they can lie in different object planes of the optical imaging device that are conjugate to form several image planes.

According to one variant, the optical imaging device can be set up and arranged in such a way that the first beam transformation elements are optically imaged in a reduced size. As a result, the intensity can be increased along the short axis, so that a narrow line of illumination can be imaged with high intensity, while at the same time the beam transformation elements are of sufficient size and are therefore easy to handle.

According to a further embodiment, the optical imaging device can be set up and arranged in such a way that the first beam transformation elements each have two lateral dividing edges at which the light beam is geometrically divided into the partial light beams, the two lateral dividing edges optically in the image plane or in one image plane each can be mapped. By deflecting the partial light beams in space, in particular by rotating the partial light beams in space, the beam profile is also reoriented in space. The beam profile of a partial light beam along the short axis corresponds to the reorientation, i.e. after the second beam transformation device, to a section of the beam profile of the incident light beam along the long axis. The section of the beam profile is determined by the division of the light beam at the first beam transformation elements. This results in a steep drop in intensity at the lateral edges of the first beam transformation elements. After the reorientation, this “sharp” intensity edge is arranged in the direction of the short axis of a partial light beam, along the upper and lower edges of a second beam transformation element. This “sharp” intensity edge can be transferred into the image plane by mapping the lateral edges of the illuminated first beam transformation elements. The illuminated first beam transformation elements thus serve as objects for a cylindrical image of the lateral edges of the first beam transformation elements.

The illumination plane can be formed by the surface of the semiconductor material layer to be processed and / or lie in a region of the semiconductor material layer to be processed close to the surface. The first beam transformation elements can be arranged offset from one another, so that the first beam transformation elements can be imaged in different image planes as a function of this distance. The optical imaging device is designed and arranged in such a way, for example with a relatively large distance from the first beam transformation elements, that the distance between the different image planes is small, for example less than 5 μm. In addition, different image planes can result from different distances between the light beams and the optical axis when they pass through the beam-shaping device.

The optical imaging device can have a cylindrical lens telescope arrangement arranged in the beam path of the optical system, in particular between the optical beam transformation device and the beam shaping device, which is designed to change the beam cross-section of the partial light beams in the direction of the x-axis. The imaging scale of the optical system can be changed or adjusted by means of the cylindrical lens telescope arrangement.

In one embodiment, the cylinder lens telescope arrangement can be set up in such a way that the beam cross section of the partial light beams is reduced in the x direction, i.e. the beam cross section in the x direction is larger in front of the cylinder lens telescope arrangement than the beam cross section in the x direction after the cylinder lens telescope arrangement. In this refinement, the cylindrical lens telescope arrangement is designed in such a way that it has a reducing effect.

According to a further variant, the optical imaging device can comprise a cylindrical lens objective arrangement which is arranged in the beam path behind the beam shaping device and is set up to image in the x direction. In particular, the cylindrical lens lens arrangement is provided to image the first beam transformation arrangement as an object in the image plane, in particular to image it in a reduced size. The reduction in size by the cylindrical lens arrangement can, in the case of the embodiment of FIG Cylindrical lens telescope arrangement as a reducing cylinder lens telescope arrangement, through which the reducing cylinder lens telescope can be enlarged by a factor corresponding to the reduction in size of the cylinder lens telescope.

genügen, wobei die Bildweite b der Abstand zwischen der bildseitigen Hauptebene der Zylinderlinsenobjektivanordnung mit der Zylinderlinsenteleskopanordnung und der Bildebene ist, und eine Objektweite a ein Abstand zwischen der ersten Anordnung und der objektseitigen Hauptebene der Zylinderlinsenobjektivanordnung mit der Zylinderlinsenteleskopanordnung ist. Obige Beziehung ist aus der Abbildungsgleichung hergeleitet. Die Brennweite f ist also die Gesamtbrennweite der optischen Abbildungseinrichtung bestehend aus der Zylinderlinsenobjektivanordnung mit der Zylinderlinsenteleskopanordnung, und die Hauptebenen sind die Hauptebenen des gesamten optischen Abbildungssystems, der optischen Abbildungseinrichtung bestehend aus der Zylinderlinsenobjektivanordnung mit der Zylinderlinsenteleskopanordnung.The cylinder lens arrangement with the cylinder lens telescope arrangement can in particular have a focal length f, and an image distance b of the imaging through the cylinder lens arrangement with the cylinder lens telescope arrangement can correspond to the equation $$\text{b}=\text{f}*\text{a}/\left(\text{a}-\text{f}\right)$$

suffice, where the image distance b is the distance between the image-side main plane of the cylinder lens lens arrangement with the cylinder lens telescope arrangement and the image plane, and an object distance a is a distance between the first arrangement and the object-side main plane of the cylinder lens lens arrangement with the cylinder lens telescope arrangement. The above relationship is derived from the mapping equation. The focal length f is the total focal length of the optical imaging device consisting of the cylindrical lens arrangement with the cylindrical lens telescope arrangement, and the main planes are the main planes of the entire optical imaging system, the optical imaging device consisting of the cylindrical lens arrangement with the cylindrical lens telescope arrangement.

If the cylinder lens telescope arrangement is used as a collimated cylinder lens telescope arrangement, i.e. if the cylinder lens telescope arrangement is set to infinite-infinite and the beam path of the incident partial light rays is parallel and the exiting partial light rays are slightly divergent, the focal length of the above equation corresponds to the focal length of the cylinder lens lens arrangement, the image distance b is the distance between the image-side main plane of the cylinder lens lens arrangement and the image plane, and the object distance a is a distance between the first arrangement and the object-side main plane of the cylinder lens lens arrangement.

According to yet another variant, the second beam transformation elements can each be adjustable with respect to a spatial position and an angle of inclination relative to the direction of propagation of the incident partial light beam. These possibilities of fine adjustment can achieve that the intensity profile of the partial beams is superimposed in the x-direction in such a way that the sharp edges of the intensity profile of the beam profile of the partial beams coincide and a flat combined intensity profile results.

In one possible arrangement, the first beam transformation elements can be designed and arranged so that the direction of propagation of the partial light beams is deflected by 90 ° with respect to the direction of propagation of the incident light beam, and / or that the second beam transformation elements are designed and arranged so that a propagation direction of the once again deflected Partial light beams is deflected by 90 ° with respect to the direction of propagation of the partial light beams. In such an arrangement, for example, the direction of propagation of the partial beams deflected again can correspond to the y-direction of the incident light beam, that is to say the direction of the long axis of the incident light beam.

In one configuration, the first and / or second arrangement each comprise two or more reflective elements. In this embodiment, the beam transformation elements form or include the reflective elements. The change in the direction of propagation is then caused by the reflection of the light on the reflective elements. In an alternative embodiment, the beam transformation elements can form or comprise refractive elements, the direction of propagation changing due to the refraction of the light at the interfaces of the refractive elements.

The first arrangement can comprise a first staircase mirror arrangement with first reflective elements, which are arranged offset from one another, and the second arrangement can comprise a second staircase mirror arrangement with second reflective elements, which are respectively arranged offset from one another.

In some optical arrangements, such as arrangements for annealing thin semiconductor layers, for example thin a-Si layers, several light beams, in particular laser beams, are required in order to provide sufficient pulse energy in a long line. The optical system can in particular have at least one light source for providing a plurality of light beams, a plurality of optical beam transformation arrangements each with a first arrangement with a plurality of first beam transformation elements, the first optical arrangements each being set up to receive an incident light beam from the plurality of incident light beams whose beam profile each has a short axis in an x-direction and a long axis in a y-direction, the x-direction and the y-direction each being perpendicular to a direction of propagation of the respective light beam, along the long axis geometrically in partial light beams to be divided, with a direction of propagation of the partial light beams different from the direction of propagation of the respective incident Light beam is. The plurality of optical beam transformation arrangements each also have a second arrangement with second beam transformation elements, the second arrangements each being arranged in the beam path of one of the partial light beams split off from an incident light beam and each being set up to deflect the deflected partial light beams again, with a beam profile one more The deflected partial light beam in the x direction, based on the direction of propagation of the partial light beam deflected again, corresponds to a beam profile section of the respective incident light beam in the y direction, related to the propagation direction of the respective incident light beam. The optical system can furthermore have a beam-shaping device arranged in the beam path of the partial light beams divided from the plurality of incident light beams and arranged downstream of the plurality of optical beam transformation arrangements, which is configured to spatially separate the partial light beams from the plurality of incident light beams as one to superimpose an illumination line located in an illumination plane, and an optical imaging device arranged downstream of the plurality of optical beam transformation arrangements and arranged in the beam path of the partial light beams separated from the plurality of incident light beams, which is set up and arranged such that the first beam transformation elements of the plurality of first arrangements in a are optically imaged in the image plane located in the illumination plane. In this arrangement, an optical beam transformation arrangement is provided for each light beam. The same can apply to each of these optical beam transformation arrangements, as was explained above with regard to the arrangement with only one optical beam transformation arrangement. In this system, as in the system discussed above, only one beam-shaping device and only one optical imaging device are provided, as in the system discussed above, for which the same can then also apply.

• - 1 eine schematische Ansicht einer Halbleitermaterialschicht, die mit einer bezüglich der Halbleitermaterialschicht in Vorschubrichtung bewegten Beleuchtungslinie belichtet wird zur Bearbeitung der Halbleitermaterialschicht;
• - 2a bis 2c die Liniengeometrie der abgebildeten Beleuchtungslinie;
• - 3a und 3b eine schematische Ansicht eines optischen Systems für eine Homogenisierung der Intensität von Lichtstrahlung, mittels dem eine Beleuchtungslinie mit homogener Intensität sowohl in der kurzen Achse als auch in der langen Achse geformt und auf einem Halbleitermaterial abgebildet werden kann;
• - 4 in schematischer Ansicht eine Ausführungsform der optischen Strahltransformationseinrichtung als Anordnung zweier Treppenspiegelanordnungen;
• - 5a in schematischer Ansicht das Gaußsche Intensitätsprofil des einfallenden Lichtstrahls in Richtung der langen Achse des einfallenden Lichtstrahls, das an den ersten Strahltransformationselementen in einzelne Intensitätsabschnitte aufgeteilt wird;
• - 5b-1 bis 5b-4 die den einzelnen, den ersten Strahltransformationselementen zugeordneten Intensitätsabschnitte nach Durchlaufen der optischen Abbildungseinrichtung, aber ohne Überlagerung durch die Strahlformungseinrichtung;
• - 5c den kombinierten Intensitätsverlauf, der sich durch Überlagerung der Intensitätsprofilabschnitte ergibt; und
• - 6 in schematischer Ansicht eine Ausführungsform eines optischen Systems, bei dem ein Bildlagenausgleich durch Verstellen der Zylinderlinsenteleskopanordnung und/oder durch Vorsehen einer oder mehrerer Strahlumwege erreicht werden kann.

The disclosure is explained further below with reference to the accompanying drawings. In these show:

• - 1 a schematic view of a semiconductor material layer which is exposed to an illumination line moved in the feed direction with respect to the semiconductor material layer for processing the semiconductor material layer;
• - 2a until 2c the line geometry of the imaged lighting line;
• - 3a and 3b a schematic view of an optical system for a homogenization of the intensity of light radiation, by means of which an illumination line with homogeneous intensity can be formed both in the short axis and in the long axis and can be imaged on a semiconductor material;
• - 4th a schematic view of an embodiment of the optical beam transformation device as an arrangement of two staircase mirror arrangements;
• - 5a in a schematic view the Gaussian intensity profile of the incident light beam in the direction of the long axis of the incident light beam, which is divided into individual intensity sections at the first beam transformation elements;
• - 5b-1 until 5b-4 the intensity sections assigned to the individual, the first beam transformation elements after passing through the optical imaging device, but without superimposition by the beam shaping device;
• - 5c the combined intensity profile that results from the superposition of the intensity profile sections; and
• - 6th a schematic view of an embodiment of an optical system in which an image position compensation can be achieved by adjusting the cylindrical lens telescope arrangement and / or by providing one or more beam detours.

In the 1 is shown schematically how a semiconductor material is irradiated with a laser beam to produce homogeneously crystallized layers. A carrier 10 , for example a glass substrate, is with one layer 12th coated from the semiconductor material to be processed. In the present example, the semiconductor material to be processed is amorphous silicon. The thickness of the semiconductor material layer 12th is typically around 50 nm.

A laser beam 14th in line form is imaged on the semiconductor material and moved relative to this in a feed direction X, so that the laser line 14th at least a portion of the semiconductor material layer 12th brushed over and illuminated. In the example shown here, the carrier 10 with the semiconductor material layer 12th in space and thus relative to the laser beam 14th , which is stationary, moved. The laser line 14th can be relative to the semiconductor material layer 12th be moved so that the entire semiconductor material layer 12th from the laser line 14th is irradiated. Typically the laser line 14th so relative to the semiconductor material layer 12th that moves a certain area several times by a laser line 14th is irradiated.

Typical feed speeds are in the range between 5 mm / s and 50 mm / s.

The direction of propagation of the laser beam 14th is perpendicular to the surface of the semiconductor material layer in the exemplary embodiment shown here 12th , ie the laser beam 14th meets here perpendicularly on the surface of the semiconductor material layer 12th on, with an angle of incidence of 0 °.

Possible line geometries of the laser beam 14th are in the 2a until 2c shown. In the 2a until 2c the intensity is shown as a function of a certain direction.

The 2a the intensity of the laser line in the direction of the long axis, namely an intensity distribution integrated along the short axis (along the x-axis) 16 , where the so integrated intensity distribution 16 along the long axis (along the y-axis). By convention, the short axis should run parallel to the x-axis and the long axis parallel to the y-axis in the figures. As can be seen in this figure, the distribution is 16 approximately rectangular, that is, ideally homogeneously formed along the long axis. The length of the illumination line in the y direction can typically be between 100 mm and 1000 mm, for example 100 mm, 250 mm, 750 mm or 1000 mm, or more than 1000 mm.

In the 2 B and 2c the intensity of the laser line in the direction of the short axis is shown in each case, namely an intensity distribution integrated along the long axis (i.e. along the y-axis) 18th , 20th , wherein the intensity distribution integrated in this way is shown along the short axis (that is, along the x-axis). The intensity in the 2 B has a Gaussian course 18th on. Alternatively, as in 2c shown, a flat course 20th ("Flat-top"), that is, have an approximately rectangular shape.

Typical widths for the intensity in the x direction are between 30 µm and 100 µm. With the Gaussian course 18th the 2 B the width is specified as a full width at half maximum, FWHM, in the case of the flattened course 20th the 2c than the width that the curve has at an intensity that corresponds to 90% of the maximum intensity (FW 90%, English: Full Width at 90%).

The flat course 20th causes a uniform crystallization of the semiconductor material layer to be processed 12th . In addition to the homogeneous intensity curve in the flat, middle curve, it is important that the lateral flanks run as steeply as possible. 2c shows a relatively steep course of the flanks. The edges shown each have a width of approximately 10 μm between a first intensity I ₁ , at which the intensity corresponds to 10% of a maximum intensity, and a second intensity I ₂ , at which the intensity corresponds to 90% of the maximum intensity.

Will be the lighting line 14th over the semiconductor material layer to be processed 12th run like a-Si, this causes the semiconductor material layer 12th briefly melts and solidifies as a crystalline layer with improved electrical properties.

In the 3a and 3b is schematically an optical system 30th for a system for processing semiconductor material layers, by means of which a lighting line 14th with a flat profile both in the x-direction and in the y-direction, i.e. along the short axis and the long axis of the illumination line 14th , molded and on a semiconductor material 12th can be mapped.

The optical system 30th comprises an optical beam transformation device 32 which is set up to split the incident light beam into partial light beams and deflect it in such a way that the beam profile of the partial light beams has a different orientation in relation to the direction of propagation of the partial light beams than the orientation of the beam profile of the incident light beam in relation to the direction of propagation of the incident light beam, one in the beam path of the light beam the beam shaping device arranged downstream of the beam transformation device 34 which is set up to shape the light beam in such a way that a beam profile of the light beam has a long axis and a short axis, with a flat, homogeneous intensity profile in both the long axis and in the short axis, as well as one in the beam path of the light beam the beam transformation device 32 downstream imaging device 36 that is set up to use the light as a line of illumination 14th map.

The light radiation can be, for example, the laser radiation emitted by a UV solid-state laser with a wavelength of 343 nm. In principle, however, it is also possible to use other light sources, in particular other laser light sources such as other solid-state laser sources, for example solid-state lasers which emit in the green spectral range.

It is in the 3a and 3b , as in the 1 and 2 , the short axis is shown parallel to the x-axis and the long axis is shown parallel to the y-axis. The z-direction or the z-axis is intended to indicate the direction of propagation of the light beam or of partial light beams, as will be explained later. The x-axis and the y-axis are each arranged perpendicular to the z-axis. Because the light beam is deflected and the direction of propagation in space changes as a result, as it did later is explained in more detail, the orientation of the x-direction, the y-direction and the z-direction changes in space with the propagation of the light beam in the optical system.

the 3a shows the imaging characteristics of the optical system 30th in the x-direction, i.e. along the short axis of the reshaped laser beam and the line of illumination, and the 3b shows the imaging characteristics of the optical system 30th in the y-direction, i.e. along the long axis of the reshaped light beam and the line of illumination.

The optical beam transformation device 32 is a staircase mirror arrangement in the example shown here. In particular, the optical beam transformation device comprises 32 a first arrangement 32a and a second arrangement 32b , in the example shown here a first staircase mirror arrangement 32a and a second staircase mirror assembly 32b .

The first and second stair mirror assemblies 32a , 32b should now be more detailed based on 4th explained. A ray of light 38 , here a laser beam, with an oval beam profile falls on a first staircase mirror arrangement 32a . In the example shown here, the light beam is a beam emitted by a laser with a round beam profile, which by means of a beam in the beam path in front of the optical beam transformation device 32 arranged cylindrical optics is expanded in the direction of the y-axis, while the beam profile is unchanged in the x-direction, so that the now expanded light beam 38 has an oval beam profile with a short axis in the direction of the x-axis and a long axis in the direction of the y-axis. The cylindrical optics can be, for example, a cylindrical lens telescope.

The first staircase mirror arrangement 32a has four stair mirror elements 40 as the first beam transformation elements. The four stair mirror elements 40 form first reflective elements. The four stair mirror elements 40 are arranged along the x-direction so that the reflective surfaces have an extension in the x-direction, and they are in the direction of propagation of the light beam 38 arranged offset to one another, so arranged at a distance from one another. A typical distance in the z-direction between two adjacent stair mirror elements 40 is 50 mm or less. Furthermore, each of the stair mirror elements is 40 aligned obliquely to the direction of propagation, that is to say to the z-direction, in particular each of the staircase mirror elements is arranged with a tilt angle of 45 ° with respect to the direction of propagation. This becomes the part of the incident light beam 38 referring to the 4th left staircase mirror 40 hits, deflected by 90 ° and thus separated from the rest of the light beam. The remaining light beam propagates further in the z-direction until it reaches the next stair mirror element 40 meets, in 4th the second stair mirror element 40 from the left. The part of the remaining light beam that hits this staircase mirror element 40 hits, is deflected again by 90 ° and thus separated from the rest of the light beam. This is how the incident light beam becomes 38 in four partial light beams 42 divided, whose direction of propagation differs by 90 ° from the direction of propagation of the incident light beam 38 . In the 4th the incident light beam spreads in the horizontal and is deflected by the first staircase mirror arrangement by 90 °, with respect to 4th deflected upwards. In the example shown here, the width of the first staircase mirror arrangement is 32a in the y-direction essentially the width of the beam profile of the incident light beam 38 in the y-direction, i.e. in the direction of the long axis. In general, the width of the first staircase mirror arrangement in the y-direction is at least the width of the beam profile of the incident light beam in the y-direction, that is, in the direction of the long axis. The first staircase mirror arrangement 32a thus functions, among other things, as a beam splitter.

The second staircase mirror arrangement 32b also has four stair mirror elements 44 as second beam transformation elements. The four second stair mirror elements 44 form second reflective elements, each of the four second staircase mirror elements 44 one of the stair mirror elements 40 the first staircase mirror arrangement 32a assigned. The four second stair mirror elements 44 are along the z-direction (based on the coordinates of the incident light beam 38 ) so that the reflective surfaces have an extension in the z-direction, and they are in the y-direction (based on the coordinates of the incident light beam 38 ) arranged offset to one another, that is, arranged at a distance from one another. The second stair mirror elements 44 are rotated by 90 ° with respect to the first stair mirror elements 40 arranged. The four second stair mirror elements 44 are related to the first four stair mirror elements 40 shifted by the same distance in the x-direction, i.e. with respect to 4th shifted upwards, arranged. Each of the four re 4th upward propagating partial light rays 42 meets one of the four second stair mirror elements 44 , which are diagonally opposite to the direction of propagation of the deflected partial light beams hitting them 42 are arranged. In doing so, they are reflected and redirected. In particular, each of the second stair mirror elements is 44 with a tilt angle of 45 ° with respect to the direction of propagation of the partial light beams 42 arranged. This means that every incident partial light beam becomes 42 deflected again by 90 °, so that the now deflected partial beams are now in the y-direction, based on the coordinates of the incident light beam 38 , propagate.

In the example shown here there are four stair mirror elements 40 , 44 shown. According to the disclosure, there are two or more stair mirror elements (beam transformation elements) per stair mirror device 32a , 32b provided, so for example also 3, 5, 6 or 7. The first and the second arrangement 32a , 32b of the optical beam transformation arrangement ( 32 ) usually the same number of beam transformation elements. Furthermore, the beam transforming elements of the first and second arrangements 32a , 32b usually the same dimensions.

Again 4th It can also be seen that the path difference between the partial light beams is 42 after the reflection on the first stair mirror elements 40 due to the offset of the individual elements 40 in the z-direction, essentially due to the offset of the second staircase mirror elements 44 in y-direction (based on the coordinates of the incident light beam 38 ) and compensated for the resulting difference in travel distance.

4th also shows schematically the beam profiles 48 the partial light rays 46 after the second reflection on the second staircase mirror elements 44 compared to the beam profile 50 of the incident light beam 38 . In particular is the beam profile 50 of the incident light beam 38 Shown divided into sections according to the division of the incoming light beam 38 on the first stair mirror elements 40 .

Again 4th can be seen by the division of the light beam 38 Partial light beams deflected in 90 ° 42 and the subsequent repeated deflection of the partial light beams 42 the beam profile by 90 ° 48 of a partial light beam 46 relative to the direction of propagation of the partial light beam 46 reoriented. This is the originally long axis of the beam profile 50 of the incident light beam 38 now in the direction of the short axis of the partial light rays 46 formed light beam arranged, and the originally short axis of the beam profile 50 of the incident light beam 38 is in the direction of the long axis of the partial light rays 46 formed light beam arranged. Based on the 4th are now the side sharp edges 52 the individual staircase mirror elements 40 assigned beam profile sections 50 each in the vertical direction of the rotated beam profile sections 48 arranged, that is, along the x-axis, ie the short axis of the partial light rays 46 . The later superposition of the partial light rays 46 so that the sharp edges 52 coincide, and the illustration of the sharp edges 52 by the imaging device 36 on the image plane 61 has a line of illumination 14th with a flat and homogeneous intensity profile with steep edges along the short axis, as will be described in more detail below.

The optical beam transforming device described above 32 thus creates one out of several partial light beams 46 formed light beam with compared to the input light beam 38 modified beam profile 48 .

These partial light rays 46 now propagate in the optical system of 3a and 3b . In the following, reference is made to a propagating light beam. This means those from the optical beam transformation arrangement 32 exiting partial light rays 46 that form a beam of light. The partial light rays 46 can be spaced in the direction of the long axis from the optical beam transformation device 32 exit, but they can also exit the optical beam transformation device flush in the direction of the long axis or with only a very small distance from one another 32 step out. The distance depends on the size of the distance between the first stair mirror elements 40 in the z-direction.

The light beam consisting of the partial light beams 46 resulting from the optical beam transformation device 32 emerges, hits in the beam path of the optical system 30th on a cylindrical lens telescope assembly 54 . The cylindrical lens telescope assembly 54 is part of the imaging facility 36 . The cylindrical lens telescope arrangement has in the direction of the long axis of the beam profile 54 no effect on the light beam, like 3b can be found. The cylindrical lens telescope arrangement acts in the direction of the short axis 54 so that the diameter of the incoming light beam is changed, like 3a can be found. In the example shown here is the cylindrical lens telescope arrangement 54 a scaling down cylindrical lens telescope assembly 54 . Since the reduction (V) is determined by the ratio of the beam diameter in the direction of the short axis at the entrance of the cylindrical lens telescope arrangement 54 (D _in ) to the beam diameter in the direction of the short axis at the exit of the cylindrical lens telescope arrangement 54 (D _out ) determined, ie V = D _{in /} D _out , the cylinder lens telescope arrangement acts 54 in the direction of the short axis so that the beam diameter of the incoming light beam is reduced.

In the beam path after the cylinder lens telescope arrangement 54 is an anamorphic homogenization optic 56 provided that is part of the beam shaping device 34 of the optical system 30th the 3a and 3b is. The anamorphic homogenization optics 56 is set up to increase the intensity of the incident light rays in the direction of the y-axis of the illumination line homogenize. The anamorphic homogenization optics 56 comprises, for example, two cylindrical lens arrays arranged parallel to one another. The cylindrical lens arrays divide the incident radiation into individual partial bundles and superimpose them over the whole area or at least over part of the area, so that the light radiation is largely homogenized. If there are several incident light beams, each light beam is divided into individual partial bundles and superimposed in a homogenized manner. If there are several incident light beams, each partial light beam is divided into individual partial bundles and superimposed in a homogenized manner. Such homogenization optics are used, for example, in the prior art included here in the disclosure DE 42 20 705 A1 , DE 38 29 728 A1 or DE 102 25 674 A1 described in more detail.

The beam shaping device 34 of the optical system 30th also points in the beam path behind the anamorphic homogenization optics 56 a condenser cylinder lens 58 which is set up for this purpose, based on the anamorphic homogenization optics 56 to direct redistributed light beams or partial light beams telecentrically onto the lighting line and superimpose them there with respect to the long axis, i.e. in the y-direction. The combination of the anamorphic homogenization optics 56 and the condenser cylinder lens 58 thus allows the formation of a single line of illumination, or several individual lines of illumination in the case of several incident light rays, to form a (overall) line of illumination.

The combination of the anamorphic homogenization optics 56 and the condenser cylinder lens 58 can be anamorphic optics or be part of such optics. In particular, they can be part of an anamorphic optics, as they are in the 4th until 6th of the document incorporated in the present disclosure DE 10 2012 007 601 A1 regarding anamorphic optics 42 is described.

• - eine erste Kollimationszylinderlinse, in der DE 10 2012 007 601 A1 mit Bezugszeichen 54 versehen, zur Kollimation von bezüglich der x-Achse emittierten Laserstrahlen,
• - eine zweite Kollimationszylinderlinse, in der DE 10 2012 007 601 A1 mit Bezugszeichen 56 versehen, zur Kollimation von bezüglich der y-Achse emittierten Laserstrahlen,
• - eine im Strahlengang hinter der ersten Kollimationszylinderlinse angeordnete Zylinderlinse, in der DE 10 2012 007 601 A1 mit Bezugszeichen 58 versehen, zur Fokussierung der Lichtstrahlen bezüglich der x-Achse auf ein Zwischenbild, in der DE 10 2012 007 601 A1 mit Bezugszeichen 60 versehen,
• - eine im Strahlengang hinter der ersten Kollimationszylinderlinse angeordnete Zwischenkollimationszylinderlinse zur Kollimation der Lichtstrahlen des ersten Zwischenbildes, und/oder
• - eine im Strahlengang hinter dem ersten Zwischenbild, insbesondere hinter der Zwischenkollimationszylinderlinse angeordnete weitere Zylinderlinse, in der DE 10 2012 007 601 A1 mit Bezugszeichen 62 versehen, zur Fokussierung der Lichtstrahlen bezüglich der x-Achse auf ein zweites Zwischenbild, in der DE 10 2012 007 601 A1 mit Bezugszeichen 64 versehen.

In particular, the beam shaping device 34 furthermore comprise one or more of the following optical elements:

• - a first collimation cylinder lens in which DE 10 2012 007 601 A1 with reference numerals 54 provided, for the collimation of laser beams emitted with respect to the x-axis,
• - a second collimation cylinder lens in which DE 10 2012 007 601 A1 with reference numerals 56 provided, for the collimation of laser beams emitted with respect to the y-axis,
• - A cylinder lens arranged in the beam path behind the first collimation cylinder lens, in which DE 10 2012 007 601 A1 with reference numerals 58 provided, for focusing the light rays with respect to the x-axis on an intermediate image in which DE 10 2012 007 601 A1 with reference numerals 60 Mistake,
• an intermediate collimation cylinder lens arranged in the beam path behind the first collimation cylinder lens for collimation of the light rays of the first intermediate image, and / or
• - A further cylindrical lens arranged in the beam path behind the first intermediate image, in particular behind the intermediate collimation cylinder lens, in which DE 10 2012 007 601 A1 with reference numerals 62 provided, for focusing the light beams with respect to the x-axis on a second intermediate image in which DE 10 2012 007 601 A1 with reference numerals 64 Mistake.

The anamorphic homogenization optics described above 56 for example, the 4th until 6th the DE 10 2012 007 601 A1 shown component 68 represent or include.

The condenser cylinder lens described above 58 for example, the 4th until 6th the DE 10 2012 007 601 A1 shown condenser cylinder lens 74 represent or include.

The condenser cylinder lens 58 is in the beam path of the optical system 30th a cylindrical lens assembly 60 subordinate. The cylindrical lens assembly 60 is part of the imaging facility 36 .

The cylindrical lens assembly 60 is designed in such a way that it only acts in the direction of the x-axis (short axis) in such a way that incident light hits the illumination line with respect to the short axis 14th is imaged or focused. In other words: the cylindrical lens arrangement 60 forms the rays of light as the line of illumination 14th from, whereby only the short axis of the beam profile, but not the homogenized long axis of the beam profile is focused. The short axis is also homogenized, as will be explained later. The cylindrical lens assembly 60 can for example be a focusing cylinder lens optics.

The optical system 30th is by means of a between the cylindrical lens assembly 60 and the protective window arranged on the semiconductor material layer to be processed 63 protected from contamination.

In accordance with the present disclosure, the optical imaging device is now 36 so designed and with respect to the first staircase mirror assembly 32a and the illumination plane on the semiconductor material layer to be processed, which forms an image plane or in which the image plane is located, so arranged that the illuminated stair mirror elements 40 the first staircase mirror arrangement 32a as objects from the optical imaging device 36 are transferred into the image plane or into the image planes and mapped there. More precisely, the illuminated side dividing edges 52 of the first stair mirror elements 40 are mapped in the image plane or in the image planes. The illuminated side dividing edges 52 of the first stair mirror elements 40 are in the beam profile rotated by 90 ° 48 according to the second staircase mirror elements 4th arranged above and below, that is to say arranged in the x-direction, and can by the optical imaging device acting in the direction of the x-axis (short axis) 36 be mapped in the image plane.

In the 3a and 3b the object distance a is shown, ie the distance between the first stair mirror elements 40 and the main plane of the cylindrical lens arrangement on the object side 60 with the cylindrical lens telescope arrangement 54 , and the image distance b, ie the distance between that of the image-side main plane of the cylindrical lens arrangement 60 with the cylindrical lens telescope arrangement 54 and the image plane 61 . The first stair mirror elements 40 lie in one object plane 67 . Has the imaging system with the cylindrical lens arrangement 60 and the cylindrical lens telescope assembly 54 a focal length f must be used for imaging the first stair mirror elements 40 through the imaging system 36 on the image plane 61 the image width b satisfy the equation b = (f * a) / (af). This relationship is from the mapping equation 1 / f = 1 / b + 1 / a derived.

The image plane 61 is in a lighting plane 63 located, i.e. a flat surface into which the lighting line 14th should be mapped to this with the lighting line 14th to illuminate. The lighting level 63 and with it the image plane 61 can be located on a substrate to be treated, such as the semiconductor material layer to be processed, which is to be illuminated by means of the illumination line and to be processed thereby. It can also be located in a region near the surface of the substrate to be treated or of the semiconductor material layer to be processed.

The cylindrical lens assembly 60 is also a reducing cylindrical lens assembly. The first stair mirror elements 40 are thus shown reduced in the direction of the x-axis on the image plane, ie the image scale is smaller than 1. The size of the reduction can be determined via the ratio of the object width to the focal length f of the lens arrangement 60 (in the event that the cylindrical lens telescope arrangement is set to infinity-infinity). Typical reductions due to the cylindrical lens arrangement 60 are, for example, in the range from a 20-fold reduction to a 100-fold reduction.

To the reduced image through the cylindrical lens arrangement 60 there is also the above-described reduction in size due to the cylindrical lens telescope arrangement 54 . Is the magnification of the cylindrical lens arrangement 60 for example 1/40, which corresponds to a 40-fold reduction, and the cylindrical lens telescope assembly 54 reduced by the factor 3 , which corresponds to a reduction of 1/3, is the magnification of the entire optical system 30th in the direction of the short axis (x-axis) 1/120. The image scale M2 for the entire optical system 30th So M2 = V * M1, where M1 is the image scale of the cylindrical lens arrangement 60 and V is the reduction in size of the cylindrical lens telescope assembly 54 is.

In this way, it is possible to form small images of the staircase mirror elements in the direction of the x-axis on the image plane, that is to say on the illumination plane of the semiconductor material layer. The images of the staircase mirror elements result in the short axis of the lighting line. This results in a narrow line with a relatively high intensity in the x direction.

The intensity is also homogeneous along the x-axis, with relatively steep lateral flanks, as will be explained in more detail below.

As above with regard to the anamorphic homogenization optics 56 has been described, is that of the partial light rays 46 existing light beam using the anamorphic homogenization optics 56 spatially superimposed along the long axis (y-axis) in order to obtain a homogeneous intensity along the y-axis. This also creates a superimposition of the light beam along the short axis. In particular, the first stair mirror elements are superimposed 40 imaging partial light rays 46 in the image plane.

The partial light rays 46 the short axis result in partial images of the first stair mirror elements 40 with the intensity distributions in the incident light beam 38 with an oval beam profile are available. This will be explained in more detail below with the aid of 5a , 5b-1 until 5b-4 and 5c explained.

5a shows schematically the division of the Gaussian intensity profile 62 of the incident light beam 38 along the long axis (y-axis) on the first beam transformation elements 40 . By reflecting on the first Beam transformation elements 40 becomes the incident light beam 38 in partial light beams 42 divided, their beam profile along the long axis each a section of the beam profile 50 of the incident light beam 38 is equivalent to. The intensity along the long axis thus corresponds to a partial light beam 42 a section of the in 5a intensity curve shown 62 . The sections of the intensity curve 62 , which are each assigned to a partial light beam, are in the 5a with the reference number 64 marked. It is in the 5a it can be seen that the intensity of the beam profile sections drops off steeply to the side due to the division of the light beam 38 on the side sharp edges 52 of the first beam transformation elements 40 . In the example shown here, the incident light beam has 38 a Gaussian profile with a width of 20 mm and is formed by the four first beam transformation elements 40 into beam profile sections with a width (y-direction of the incident light beam 38 ) divided by 5 mm each.

the 5b-1 until 5b-4 now show the intensity of the individual beam profile sections.

The line shows 68 the 5b-1 the intensity curve that the partial light beam 42 of the outermost first stair mirror element 40 the first staircase mirror arrangement 32a is to be assigned, so the staircase mirror element 49 that regarding 4th is arranged on the far left. The line 70 the 5b-2 shows the intensity profile of the partial light beam 42 of the second first stair mirror element 40 is to be assigned to the line 72 the 5b-3 shows the intensity profile of the partial light beam 42 of the third first stair mirror element 40 is to be assigned, and the line 74 the 5b-4 shows the intensity profile of the partial light beam 42 of the fourth first stair mirror element 40 is to be assigned (on the far right with respect to 4th ). It is in the 5b-1 until 5b-4 the intensity profile of the partial light beams before they are superimposed and after passing through the optical imaging device 36 to see. By turning the second beam transformation element by 90 ° 44 is the long axis of the beam profile of the incident light beam 38 and thus the partial beam sections 50 after the second beam transformation elements 44 in the direction of the short axis of the partial light beams deflected again 46 aligned. Accordingly, the direction of the x-axis corresponds to 5b-1 until 5b-4 in each case the direction of the short axis of the partial light beams deflected again 46 , so that the steep lateral decrease in intensity is now the (with respect to 4th ) top and bottom edges 52 the beam profile sections 48 are to be assigned. In the example shown here, the optical imaging device is reduced in size 36 along the short axis by a factor 100x . Consequently, the extension of the beam profile sections is 5 mm in the y-direction 50 after the 90 ° rotation on the second beam transformation elements 44 the extent in the x-direction (along the short axis) of the beam profile sections 48 after imaging by the optical imaging device 36 reduced to 50 µm. This expansion in the x-direction is in the 5b-1 until 5b-2 shown by the expansion of the intensity profile along the x-axis. In addition, the steep side flanks of the 5a "Softened", that is, the steep lateral flanks fall flatter than in 5a shown and are therefore a bit wider. This softening is due to the diffraction limitation of the optical imaging device 36 , which is explained in more detail below. In particular, there is a smearing, ie an edge sharpness that is less than 10 μm (a width of less than 10 μm between a first intensity, at which the intensity corresponds to 10% of a maximum intensity, and a second intensity, at which the intensity 90 % of the maximum intensity).

Due to the second deflection at the second beam transformation elements 44 the partial light beams are arranged next to one another in such a way that they can be superimposed in such a way that the steep flanks of the intensity gradients coincide. This should now be done using 5c will be explained in more detail.

5c shows the superimposed intensity profile, ie the intensity profile that results when the partial light beams are superimposed. In the overlaid intensity curve 66 the result is an almost constant intensity over the entire width, ie a flat intensity curve (“flat-top”). As in 5c can be seen, the partial light rays 42 superimposed so that the "sharp" edges of the intensity profiles of the partial light rays 42 coincide. These "sharp" edges are in the 5c Shown laterally on the left and right. The intensity drops off steeply at these “sharp” edges. In the overlaid intensity curve 66 This also results in a steeply sloping course 71 on the sides. The superimposed intensity curve 66 runs almost constantly over the entire width with steeply sloping flanks 71 .

As explained above, because the partial light rays 42 on the second beam transformation elements 44 the second arrangement 32b be deflected again by 90 ° and thereby also the beam profiles of the individual partial light beams 42 rotated 90 ° before they are superimposed, the in 5c side edges 70 after turning up and down, i.e. on the sharp edges 52 the 4th , arranged along the x-direction (short axis), and the flat superimposed intensity profile resulting from the superposition 66 the 5c is the intensity profile along the short axis (x-axis) after the rotation and superposition. Due to the division on the first beam transformation elements 40 , the 90 ° rotation on the second beam transformation elements 44 and the superposition of the partial light beams 46 in the y-direction, which also necessitates an overlay in the x-direction, the result is the homogenized intensity profile running flat in the x-direction 66 with the steeply sloping edges 71 .

Around the flat homogenized intensity curve 66 The stair mirror elements are able to adjust sensitively 44 the second staircase mirror arrangement 32b finely adjustable in angle and position. In particular, the angle of inclination with respect to the direction of propagation of the incident light rays 42 can be changed sensitively (for example by 1/10 °) as well as the position in all three spatial directions, especially in the x-direction.

By imaging in the x direction by the imaging device 36 there is a smearing in the x-direction, due to the limited resolution due to diffraction (diffraction limitation). As a result, the steeply sloping flanks of the 5a shown with a smear. The numerical aperture of the cylindrical image is now selected so that the smearing, ie the desired edge sharpness, is less than 10 µm (a width of less than 10 µm between a first intensity, at which the intensity corresponds to 10% of a maximum intensity, and a second intensity, at which the intensity corresponds to 90% of the maximum intensity), but still results in a depth of focus of several 100 µm. The numerical aperture is therefore relatively small.

• An der ersten Treppenspiegelanordnung 32a wird ein zylindrisch aufgeweiteter Lichtstrahl 38 von 20 mm x 4 mm in 4 Teillichtstrahlen 42 geteilt. Die ersten Treppenspiegelelemente 40 haben jeweils eine Breite (Ausdehnung in y-Richtung des Lichtstrahls 38) von 5 mm, so dass die Teillichtstrahlen 42 auch eine entsprechende Abmessung in dieser Richtung haben. Die ersten Treppenspiegelelemente 40 haben typischerweise einen Abstand im Bereich von 3 m bis 5 m zur Abbildungslinse 60, er kann sogar noch mehr betragen. Eine Abbildungslinse 60 mit der Brennweite f=150 mm führt zu einem Verkleinerungsmaßstab von ca. 30x. Stellt man die Verkleinerung mit dem kollimierten Zylinderlinsenteleskop 54 auf z. B. 100x ein, so erhält man 5mm/100= 50 µm als Breite für die Treppenspiegelelementbilder. Da die Treppenspiegelelementbilder gedreht wurden, ist diese Breite die Abmessung in x-Richtung (kurze Achse).

The following example is intended to explain the relationships discussed above:

• At the first staircase mirror arrangement 32a becomes a cylindrically expanded light beam 38 of 20 mm x 4 mm in 4 partial light beams 42 divided. The first stair mirror elements 40 each have a width (expansion in the y-direction of the light beam 38 ) of 5 mm, so that the partial light rays 42 also have a corresponding dimension in this direction. The first stair mirror elements 40 typically have a distance in the range of 3 m to 5 m from the imaging lens 60 , it can be even more. An imaging lens 60 with the focal length f = 150 mm leads to a reduction scale of approx. 30x. If you set the reduction with the collimated cylindrical lens telescope 54 on z. B. 100x, you get 5mm / 100 = 50 µm as the width for the stair mirror element images. Since the stair mirror element images were rotated, this width is the dimension in the x-direction (short axis).

The diffraction-limited resolution of the cylindrical image provides for typical numerical apertures between 0.1 and 0.15 of the cylindrical lens lens arrangement 60 a resolution that falls below the desired 10 µm edge sharpness. The depth of field results for a smear of 10 µm to +/- 10 µm / 0.05 = +/- 200 µm.

Again 4th can be seen, are the first stair mirror elements 40 positioned differently in the z-direction, so that their distance to the cylindrical lens arrangement 60 and so the object width is different. The image widths and thus image levels of the individual staircase mirror elements 40 are, however, only slightly different because the stair mirror elements 40 typically not more than 50 mm apart in the z-direction. The image plane for an object distance of 5000 mm is in comparison to an image plane for an object distance of 5050 mm, for a 30-fold reduction with a cylindrical lens arrangement 60 with a focal length of f = 150 mm, only spaced by less than 50 µm in the z-direction. Taking into account a collimated cylindrical lens telescope 58 with 3-fold reduction in the beam path on the object side, the difference becomes less than 5 µm.

Arrangements for annealing thin semiconductor layers, for example thin a-Si layers, require several laser beams in order to provide sufficient pulse energy in a long line. When multiple laser beams are used, the optical system becomes 30th the 3a and 3b changed so that for each laser beam a parallel beam path with a first and second transformation device 32a , 32b and a reducing cylinder lens telescope assembly 54 is being built. The beam shaping device 34 with the anamorphic homogenization arrangement 56 and the condenser lens 58 as well as the cylindrical lens assembly 60 are then used jointly for all laser beams. In this way, further lines are superimposed in the image plane.

For reasons of geometric arrangement, greater path differences from the staircase mirror arrangements can be used 32a , 32b for cylindrical lens arrangement 60 occur when multiple laser beams are combined. Beam path differences of up to 500 mm can occur. In addition, it must be taken into account that the image of the staircase mirror elements 40 receives a shorter z-position, and thus has a smaller image range, the further the laser beam is in the 90 ° rotated axis away from the optical axis through the anamorphic homogenization arrangement 56 to be led. This is because the off-axis light rays have a longer path through the material of the cylindrical imaging arrangement 60 have as near-axis rays.

In order to compensate for these differences in the image positions, the optical system is either designed in such a way that by means of additional reflective elements in the beam path, beam detours are built in for some light beams. Such additional reflective elements 82 are schematically in 6th for an optical system 80 shown. The relative position of the reflective elements 82 change to each other, around the beam detour 84 to be able to adjust variably. Alternatively, the distance 86 between the optical elements of the cylindrical lens telescope arrangement 54 to be changed. Since there are separate cylindrical lens telescope arrangements with several laser beams 54 are available for each laser beam, can be done by detuning the individual cylindrical lens telescope arrangements 54 an image position compensation for the different laser beams can be achieved so that no depth of field is lost.

The disclosed optical system is designed so that the first elements of the beam transformation arrangement illuminated by the incident light beam serve as objects that are optically reduced as images in the illumination plane on or in the semiconductor material layer by the optical imaging device. By means of the beam shaping device, the images are spatially superimposed in the y-direction (long axis) and are thus mapped spatially superimposed. In particular, the optical imaging device shows the edges of the illuminated beam transformation arrangement so reduced that there is a narrow line of illumination in the x direction with high, approximately constant intensity in the x direction, the intensity falling steeply at the edges of the line of illumination. Both the cylindrical lens telescope arrangement and the optical imaging device have the effect of reducing the size. A line of illumination with this characteristic along the short axis can produce regular polycrystalline grain structures.

Claims (16)

Optical system (30, 80) for homogenizing the intensity of light radiation for processing a semiconductor material layer, in particular for producing a crystalline semiconductor layer, comprising: an optical beam transformation arrangement (32) with a first arrangement (32a) with first beam transformation elements (40) which are set up for this purpose is, an incident light beam (38) whose beam profile (50) has a short axis in an x-direction and a long axis in a y-direction, the x-direction and the y-direction each perpendicular to a direction of propagation of the light beam are to be geometrically deflected and divided along the long axis into partial light beams (42) so that a direction of propagation of the partial light beams (42) is different from the direction of propagation of the incident light beam (38), and a second arrangement (32b) with second beam transformation elements (44) , which is arranged in the beam path of the partial light beams (42) t and is set up to deflect the deflected partial light beams (42) again, with a beam profile (48) of a further deflected partial light beam (46) in the x direction, based on the direction of propagation of the again deflected partial light beam (46), a section of the beam profile ( 50) of the incident light beam (38) in the y-direction, based on the direction of propagation of the incident light beam (38), characterized in that the optical system (30, 80) further comprises a beam path of the further deflected partial light beams (46) arranged beam shaping device (34) arranged downstream of the optical beam transformation arrangement (32), which is set up to spatially superimpose the once again deflected partial light beams (46) with respect to the y-direction as an illumination line (14) located in an illumination plane (65), and a in the beam path of the again deflected partial light beams (46), the optical beam transp Optical imaging device (36) arranged downstream of the formation arrangement (32), which is set up and arranged such that the first beam transformation elements (40) are optically imaged in an image plane (61) located in the illumination plane (65). Optical system (30, 80) according to Claim 1 , wherein the optical imaging device (36) is designed such that it images the partial light beams (46) only in the x-direction. Optical system (30, 80) according to Claim 1 or 2 wherein the optical imaging device (36) is set up and arranged such that the first arrangement (32a) lies in an object plane (67) of the optical imaging device (36) conjugate to the image plane (61). Optical system (30, 80) according to one of the preceding claims, wherein the optical imaging device (36) is set up and arranged such that the first beam transformation elements (40) are optically imaged in a reduced size. Optical system (30, 80) according to one of the preceding claims, wherein the optical imaging device (36) is set up and arranged such that the first beam transformation elements (40) each have two lateral dividing edges (52) on which the incident light beam (38) is geometrically divided into the partial light beams (42), and the two lateral dividing edges (52) are optically imaged in the image plane. Optical system (30, 80) according to one of the preceding claims, wherein the illumination plane (65) is formed by the surface of the semiconductor material layer to be processed and / or lies in a region near the surface of the semiconductor material layer to be processed. Optical system (30, 80) according to one of the Claims 2 until 6th , wherein the optical imaging device (36) has a cylindrical lens telescope arrangement (54) which is arranged in the beam path of the optical system (30, 80), in particular between the optical beam transformation device (32) and the beam shaping device (34), which is designed to capture the beam cross section of the To change partial light beams (46) in the x-direction. Optical system (30, 80) according to Claim 7 , wherein the cylindrical lens telescope arrangement (54) is set up to reduce the beam cross section of the partial light beams (46) in the x-direction. Optical system (30, 80) according to one of the Claims 2 until 8th wherein the optical imaging device (36) comprises a cylindrical lens objective arrangement (60) which is arranged in the beam path behind the beam shaping device (34) and is set up to image in the x-direction. Optical system (30, 80) according to Claim 9 and Claim 7 or after Claim 9 and Claim 8 wherein the cylinder lens lens arrangement (60) with the cylinder lens telescope arrangement (54) has a focal length f, and wherein an image distance b of the equation $$\text{b}=\text{f}*\text{a}/\left(\text{a}-\text{f}\right)$$

is sufficient, where the image distance b is the distance between the image-side main plane of the cylinder lens lens arrangement (60) with the cylinder lens telescope arrangement (54) and the image plane (61), and an object distance a is a distance between the first arrangement (32a) and the object-side main plane of the cylinder lens lens arrangement (60) with the cylindrical lens telescope assembly (54). Optical system (30, 80) according to one of the preceding claims, wherein the second beam transformation elements (44) are each adjustable with respect to a spatial position and an angle of inclination relative to the direction of propagation of the incident partial light beam (42). Optical system (30, 80) according to one of the preceding claims, wherein the first beam transformation elements (40) are designed and arranged such that the direction of propagation of the partial light beams (42) is deflected by 90 ° with respect to the direction of propagation of the incident light beam (38), and / or wherein the second beam transformation elements (44) are designed and arranged in such a way that a direction of propagation of the partial light beams (46) deflected again is deflected by 90 ° with respect to the propagation direction of the partial light beams (42). Optical system (30, 80) according to one of the preceding claims, wherein the first and / or second arrangement (32a, 32b) each comprise two or more reflective elements. Optical system (30, 80) according to one of the preceding claims, wherein the first arrangement comprises a first staircase mirror arrangement (32a) with first reflective elements (40) which are arranged offset from one another, and wherein the second arrangement comprises a second staircase mirror arrangement (32b) second reflective elements (44), which are each arranged offset to one another. Optical system (30, 80) according to one of the preceding claims, comprising at least one light source for providing a plurality of light beams, a plurality of optical beam transformation arrangements (32) each having a first arrangement (32a) with first beam transformation elements (40), the first Arrangements (32a) are each set up to capture an incident light beam (38) from the plurality of incident light beams, the beam profile of which each has a short axis in an x-direction and a long axis in a y-direction, the x-direction and the y-direction are each perpendicular to a direction of propagation of the respective light beam (38), to be geometrically deflected and divided along the long axis into partial light beams (42) so that a propagation direction of the partial light beams (42) differs from the propagation direction of the respective incident light beam (38 ) is, and each with a second arrangement (32b) with zw eide beam transformation elements (44), the second arrangements (32b) each being arranged in the beam path of the partial light beams (42) of a first arrangement (32a) and each being set up to deflect the deflected partial light beams (42) again, with a beam profile (48) a once more deflected partial light beam (46) in the x direction, based on the direction of propagation of the once again deflected partial light beam (46), a beam profile section (50) of the respective incident light beam (38) in the y direction, related to the propagation direction of the respective incident light beam ( 38), corresponds to one of the plurality of optical beam transformation arrangements (32) arranged in the beam path of the once more deflected partial light beams of the large number of incident light beams downstream beam-shaping device (34), which is set up to spatially superimpose the further deflected partial light beams of the plurality of incident light beams with respect to the y-direction as an illumination line (14) located in an illumination plane (65), and one in the beam path of the further deflected partial light beams (46) the plurality of incident light beams arranged downstream of the plurality of optical beam transformation arrangements (32) optical imaging device (36) which is set up and arranged such that the first beam transformation elements (40) of the plurality of first arrangements (32a) in an in the image plane (61) located in the illumination plane (65) can be optically imaged. System for processing a semiconductor material layer, in particular for producing a crystalline semiconductor layer, with an optical system according to one of the Claims 1 until 15th comprising: - a carrier (10) to which a semiconductor material layer (12) is applied, the system being designed and arranged to apply the illumination line (14) of the optical system to the semiconductor material layer (12).

Images