METHOD AND DEVICE FOR EXPOSURE OF PHOTOSENSITIVE LAYER

Abstract

A method and device for exposing a light-sensitive layer, said method comprising: generating at least one light ray by use of at least one light source, illuminating pixels of an exposure pattern by use of at least one micromirror device having a plurality of micromirrors with respective mirror intensity profiles, and overlaying the mirror intensity profiles of adjacent micromirrors to provide a pattern intensity profile of the exposure pattern by summing the mirror intensity profiles of each illuminated pixel of the exposure pattern.

Claims

1. A method for exposing a light-sensitive layer, said method comprising: generating at least one light ray by use of at least one light source, illuminating pixels of an exposure pattern by use of at least one micromirror device having a plurality of micromirrors with respective mirror intensity profiles, and overlaying the mirror intensity profiles of adjacent micromirrors to provide a pattern intensity profile of the exposure pattern by summing the mirror intensity profiles of each illuminated pixel of the exposure pattern.

2. The method according to claim 1, wherein the pattern intensity profile due to the overlaying is more homogeneous than each mirror intensity profile.

3. The method according to claim 1, wherein the method includes: generating the pixels from the mirror intensity profiles on the basis of a geometric shape of the plurality of micromirrors, wherein the pixels are larger than individual patterns of the exposure pattern.

4. The method according to claim 1, wherein at least two exposure patterns are illuminated, and the pattern intensity profiles of the at least two exposure patterns are overlaid as a sum to form an exposure intensity profile of the light-sensitive layer.

5. The method according to claim 1, wherein the overlaying takes place by means of unsharp imaging of the micromirrors in the exposure pattern.

6. The method according to claim 4, wherein the at least two exposure patterns are illuminated sequentially one behind the other and are displaced with a relative displacement between the micromirror device and the light-sensitive layer of less than one pixel width.

7. The method according to claim 1, wherein exposure pattern grid lines of the exposure pattern which are horizontal and/or are vertical, are arranged running obliquely and/or are distorted.

8. A device for exposing a light-sensitive layer, said device comprising: an optical system including: at least one light source for generating at least one light ray, at least one micromirror device having a plurality of micromirrors, wherein each micromirror is used for illuminating a pixel of an exposure pattern with a mirror intensity profile, wherein an overlay of mirror intensity profiles of adjacent micromirrors forms a pattern intensity profile of the exposure pattern as a sum of the mirror intensity profiles of each illuminated pixel of the exposure pattern.

9. The method according to claim 4, wherein the at least two exposure patterns are illuminated sequentially.

10. The method according to claim 7, wherein the exposure pattern grid lines of the exposure pattern are horizontal, running parallel to one another.

11. The method according to claim 7, wherein the exposure pattern grid lines of the exposure pattern are vertical, running parallel to one another.

12. The method according to claim 7, wherein the exposure pattern grid lines are distorted affinely.

Description

[0176] Further advantages, features and details of the invention result from the following description of preferred exemplary embodiments, as well as on the basis of the drawings. In the figures:

[0177] FIG. 1 shows a first embodiment of the device according to the invention,

[0178] FIG. 2 shows a second embodiment of the device according to the invention,

[0179] FIG. 3 shows a third embodiment of the device according to the invention,

[0180] FIG. 4a shows a schematic illustration, which is not true-to-scale, of a DMD (micromirror device j with an enlarged part section with micromirrors in a first position,

[0181] FIG. 4b shows a schematic illustration, which is not true-to-scale, of a DMD (micromirror device) with an enlarged part section with micromirrors in a second position,

[0182] FIG. 5a shows a schematic illustration, which is not true-to-scale, of a plan view onto a first exposed section of a layer to be exposed,

[0183] FIG. 5b shows a schematic illustration, which is not true-to-scale, of a plan view onto a second exposed section of the layer to be exposed, which is slightly offset with respect to the first,

[0184] FIG. 6a shows a schematic illustration, which is not true-to-scale, of a plan view onto a substrate with a first exposed section,

[0185] FIG. 6b shows a schematic illustration, which is not true-to-scale, of a plan view onto a substrate with a second exposed section,

[0186] FIG. 6c shows a schematic illustration, which is not true-to-scale, of a plan view onto a substrate with the overlaid first and second exposed sections,

[0187] FIG. 7a shows a schematic illustration, which is not true-to-scale, of a further embodiment of the device according to the invention,

[0188] FIG. 7b shows a schematic illustration, which is not true-to-scale, of a further embodiment of the device according to the invention,

[0189] FIG. 7c shows a schematic illustration, which is not true-to-scale, of a further embodiment of the device according to the invention,

[0190] FIG. 8a shows a schematic illustration, which is not true-to-scale, of a plan view onto a further exposed section of a layer to be exposed according to a first embodiment of the method according to the invention,

[0191] FIG. 8b shows a schematic illustration, which is not true-to-scale, of a plan view onto a further exposed section of a layer to be exposed according to a second embodiment of the method according to the invention,

[0192] FIG. 9a shows a schematic enlarged view, which is not true-to-scale, of a first embodiment of an exposure pattern according to the invention,

[0193] FIG. 9h shows a schematic enlarged view, which is not true-to-scale, of a first embodiment of an exposure pattern according to the invention,

[0194] FIG. 10 shows a schematic view of an intensity distribution of two adjacent pixels with three different intensity strengths,

[0195] FIG. 11 shows a schematic view of an exposure pattern with a plurality of exposed pixels, and

[0196] FIG. 12 shows a schematic view of an exposure pattern distorted by optical elements.

[0197] In the figures, the same components or components with the same function are labelled with the same reference numbers.

[0198] FIG. 1 shows a first embodiment, consisting of an optical system 8, having at least one light source 7 and at least one DMD 1 (micromirror device), a substrate holder 11. The substrate holder 11 can be moved in relation to a coordinate system K3.

[0199] A substrate 10 is fixed on the substrate holder 11 using fixing means 13, on which substrate a light-sensitive layer 9 made from a material which can be exposed is located, which layer is exposed by means of the device.

[0200] The coordinate origin of a sample-fixed coordinate system K2 (that is to say fixed to the substrate 10 or the layer 9 to be exposed) is preferably placed in the centre of the surface 90 of the layer 9.

[0201] A light ray 6 (primary light ray), which is emitted by the light source 7, and can pass a plurality of optical elements (not marked) on the way to the DMD 1, is converted by the DMD 1 into a structured light ray 6 (secondary light ray). This can pass a plurality of optical elements (not marked) on the way to the layer 9.

[0202] A detector 19, particularly a camera, more preferably a CCD or CMOS camera, can capture and/or measure the surface 90 of the layer 9 to be exposed by means of a semi-transparent mirror 14. The measured results are preferably used for the direct control of the method and/or calibration of the device. For the sake of clarity, the illustration of such measuring means is dispensed with in the further description of the figures and figures. The measuring means according to the invention can however be used in each mentioned embodiment according to the invention.

[0203] FIG. 2 shows a second embodiment, wherein the optical system 8 is here equipped with two light sources 7, 7. Light rays 6 are emitted by the two light sources 7, 7. One of the light rays 6 is diverted by a mirror 14 onto a ray splitter 14 and combined with the light ray 6 of the second light source 7 by means of the same.

[0204] The combined light ray 6 is conducted onto the DMD 1 and converted by the same into a structured light ray 6, which in turn can pass a plurality of optical elements (not marked) on the way to the layer 9.

[0205] One, in particular independent, aspect according to the invention here consists primarily in it being possible for the two light sources 7 to differ in terms of radiation intensity, wavelength, coherence length and, if appropriate, further properties or parameters, so that a laser ray 6 can be generated using a multiplicity of different optical parameters.

[0206] According to the invention, in particular more than 2, particularly more than 5, more preferably more than 10, most preferably more than 20 light sources 7, 7 can be used. Each light source can preferably also be an LED field or LD (laser diode) field.

[0207] FIG. 3 shows a third embodiment, consisting of an optical system 8 having at least one light source 7 and two DMDs 1.

[0208] A light ray 6 is emitted by the light source 7 and split by means of a ray splitter 14. A first split light ray 6.1 is modified by a first DMD 1 to form a first modified ray 6.1. The layer 9 is exposed using the first modified ray 6.1. The second split light ray 6.2 is diverted by means of a mirror 14 onto a second DMD 1 and forwarded as a second modified ray 6.2 onto the layer 9. Preferably, a different position of the layer 9 to be exposed is exposed with the second modified ray 6.2 than with the first modified light ray 6.1. All of the light rays mentioned can pass a plurality of optical elements (not marked).

[0209] One, in particular independent, aspect according to the invention here consists in at least two DMDs 1 being used, by means of which the layer 9 can be exposed at two different positions simultaneously, wherein preferably a single, particularly combined, light ray is used for loading the DMDs. This leads in particular to a propagation of the exposure section, particularly an exposure strip, and therefore to an increase of the throughput.

[0210] FIG. 4a shows the DMD 1 with a mirror surface 2. The enlarged illustration of a part of the mirror surface 2 shows a plurality of (16) mirrors 3 of a multiplicity of mirrors 3. The mirrors are arranged in a non-tilted alignment, which is designated as the initial position. A coordinate system K1 is assigned to the DMD 1. The Z axis of K1 (that is to say K1z) is normal to the mirror surface 2, the x and the y coordinates lie parallel to the mirror surface edges 2kx and 2ky of the mirror surface 2 and define a mirror plane.

[0211] FIG. 4b shows the same DMD 1, wherein one of the mirrors 3 is arranged in a position tilted or rotated about the x axis. The part of the light ray 6, which impinges onto the tilted mirror 3, is therefore reflected in a direction, which is not identical to the reflection direction of the parts of the light ray 6 reflected by the non-tilted mirrors 3.

[0212] FIG. 5a shows a schematic view of the mirror surface 2 with a central, particularly strip-shaped, write area 4 and two, preferably parallel, buffer regions 5 adjacent to the write area 4 at the edge in each case.

[0213] Instead of the mirrors 3, the pixels 23 of an exposure pattern 24 reflected by the mirror surface 2 are illustrated, which correspond to forming structures 12 at the position K2y=12 on the layer 9 to be exposed (possibly modified by optical elements between the DMD 1 and the layer 9 to be exposed).

[0214] According to an advantageous embodiment according to the invention, only the mirrors 3 arranged in the write area 4 are used for exposure, so that a write buffer is formed by the buffer regions 5, which is explained in the following. The centre line D runs through the fixed centre point 0 of the K2x axis of the sample coordinate system.

[0215] The FIG. 5b shows the same DMD 1, but after a relative movement in the K2y direction by 0.5 a.u. The DMD 1 is therefore located at the position K2y=12.5 a.u. At the same time, one can see that a relative movement by approx. 2 a.u. in the K2x direction has taken place. This relative movement is undesired and originates for example from a fault in the mounting. It can clearly be seen how the structure 12 has been displaced to the left in relation to the DMD coordinate system K1, in order to expose the same correctly in relation to the coordinate system K2y. The write buffer is therefore used.

[0216] The targeted programming of the DMD therefore allows the correction of mechanical faults. The substrate holder 9 therefore does not move the substrate 10 and thus the layer 9 in the direction K2y in a completely straight line, rather there is a slight displacement towards K2x during the movement in the direction K2y.

[0217] According to the invention (independent aspect of the invention), the mechanism of the substrate holder 9 is preferably not used for fault correction, rather the write area 4 and the buffer regions 5 are programmed/controlled electronically in such a manner that the structures 12 to be exposed are correspondingly displaced (here in the negative K1x direction). Thus, the electronics and/or the mechanism of the DMD 1 compensates write errors, here the mechanical fault of the substrate holder 11.

[0218] FIG. 6a shows a plan view of a layer 9 exposed along a first strip 15. The strip 15 corresponds to the area of the layer 9 exposed by means of the write area 4 of the DMD 1 after a movement of the DMD 1 relative to the exposed layer 9 in the K2y direction.

[0219] In a region between intensity variation regions 16l, 16r of the strip 15, the illuminated pixels 23 are illuminated with an intensity which is as homogeneous as possible.

[0220] By contrast, the illuminated pixels 23 in the intensity variation regions 16l, 16r are controlled in such a manner that the intensity of the reflected light ray 6 from the write area 4 in the direction of the edge of the DMD 1 falls, particularly continuously, preferably proportionally to the distance from the write area 4. A corresponding pattern intensity profile, on which one can read the intensity curve as a function of the position is marked (intensity/position). The intensity, with which the layer 9 is exposed, therefore has a maximum in the region of the strip 15 and normally falls laterally thereto, preferably steadily and/or linearly, down to zero.

[0221] FIG. 6b shows an analogous illustration to FIG. 7a relating to a second strip 15 directly adjacent to the exposure of the first strip 15 in particular. This is displaced so far to the right compared to the first strip 15 that the right intensity variation region 16r from FIG. 6a overlaps with, preferably is congruent to, the left intensity variation region 16l from FIG. 7b. The pixels 23 are connected in the precisely distributed manner in the right intensity variation region 16r as in the left intensity variation region 16l, wherein the intensity of the corresponding pixels 23 are in each case summed to give a pixel intensity which corresponds to the intensity in the strip 15.

[0222] FIG. 6c shows a plan view, wherein the intensity variation region 16r of the first strip 15 is brought into congruence with the intensity variation region 16l of the second strip 15, so that a constant intensity profile results. The exposure therefore takes place homogeneously, as the intensities of the first strip 15 are summed with the intensities of the second strip 15.

[0223] FIG. 7a shows an enlarged section of an embodiment according to the invention having a DMD 1, optical paths of the primary light ray 6 and the secondary light ray 6 and the layer 9 to be exposed. The primary light ray 6 and the secondary light ray are here only symbolized by the optical paths 6, 6 and are preferably so large that the entire DMD 1 is illuminated. The secondary light ray 6 is normal to the layer 9 to be exposed. The focal plane 17 in particular lies parallel to the, preferably on the, surface 9o. A depth of field range 18 indicates the depth, within which a sharp imaging of the pixels 23 can take place.

[0224] FIG. 7b shows an enlarged section of a preferred embodiment according to the invention, which is changed compared to the embodiment according to FIG. 7a. The secondary light ray 6 is reflected onto the layer 9 to he exposed at an angle . The focal plane 17 therefore intersects the layer 9 to be exposed at the angle . On the left side, it lies outside the layer 9 to be exposed, on the right side in the layer 9 to be exposed. The depth of field range 18 therefore penetrates deeper into the layer 9 on the right side and can therefore be used, in order to create sharp structures in three-dimensional structures in depressions, without moving the focal plane 17 in the K2z direction by moving the DMD 1.

[0225] The displacement of the DMD 1 in the K2z direction in order to be able to image deeper lying structures more sharply can in particular he avoided by tilting the DMD 1. Dynamic displacements of the exposure regions on the DMD 1 therefore allow a targeted, sharp exposure at corresponding depths. An important advantage compared to multiple exposure is the possibility of creating structures highly precisely without mechanical faults in all spatial directions.

[0226] FIG. 7c shows an enlarged section of a more preferred embodiment according to the invention, which is changed compared to the embodiments according to FIG. 7a and/or FIG. 7b. The secondary light ray 6 is deflected in such a manner by means of optical elements (not shown), which are located between the DMD 1 and the layer 9 to be exposed, that the focal plane 17 is inclined by an angle with respect to the substrate surface 9o.

[0227] FIG. 8a shows a plan view onto a part section of the layer 9 to be exposed. A pixel 23 (smallest unit of an exposure pattern 24) was illuminated along a length l by means of the DMD 1, in that a relative movement has taken place between the DMD 1 (not shown) and the layer 9 to be exposed and an exposure of the layer 9 in the region of the width b during the entire travel along the length l has taken place by illuminating the pixel 23. The exposed regions correspond to the pixels 23, wherein the intensity of the exposure is controlled by the illumination intensity. In the case of overlaps, the intensities are summed in the overlapping regions.

[0228] The exposure took place from the K2y position 0 up to K2y position 3. Washing out in the relative movement direction is created in that a plurality of exposures take place within the range from approx. 2 to 5 during the relative movement. The intensity profiles of the pixels :23 are overlaid and generate a strong intensity increase along the path 1.

[0229] FIG. 8b shows an alternative embodiment to FIG. 8a, wherein the difference from FIG. 8a is that the smaller length l was created in that the corresponding mirror 3 of the DMD 1 (both not shown) first started with the exposure from the K2y position 1 and the exposure ended already from the K2y position 2. An increase in the resolution in the K2y direction is therefore possible by means of the targeted control of the mirrors 3, particularly the later switching on or earlier switching off. In the actual case, the exposure of the pixel 23 is therefore started delayed by 33.33% and ended 33.33% earlier. As it is not possible to expose the pixel 23 quadratically, as each ray has an intensity profile which deviates from a stepped-shape. The exposure patterns 24, 24, 24, 24 are illustrated as auxiliary lines, which one can imagine lying over the layer 9 to be exposed. The patterns preferably correspond to the dimensions of the pixels 23.

[0230] FIG. 9a shows a first exposure pattern 24 which is less preferred according to the invention and has equidistant spacings of the exposure pattern grid lines 27 in the two mutually orthogonal directions K2x, K2y. The exposure pattern 24 is therefore isotropic and homogeneous in both directions K2x and K2y.

[0231] FIG. 9b shows a second, more preferred exposure pattern 24 according to the invention, which has a separate spacing for each direction, which is equidistant with respect to the direction in particular, between the exposure pattern grid lines 27. The exposure pattern 24 is therefore anisotropic, but homogeneous in each of the directions K2x and K2y.

[0232] It is also conceivable that the exposure takes place at exposure pattern grid line intersection points 25 and/or partial exposure pattern areas 26 and does not take place inside the individual pattern areas.

[0233] The different exposure patterns 24, 24, 24, 24 can in particular be created/modified by means of optical elements (not shown) mounted upstream and/or downstream of the DMD 1 (not shown). The DMD (not shown) would preferably be isotropic and homogeneous, wherein the, particularly the downstream, optical elements (not shown) are constructed to effect an anisotropic and/or homogeneous imaging of the DMD.

[0234] FIG. 10 shows a schematic cross-sectional illustration of two mirrors 3 and also the mirror intensity profiles 22, 22, 22 (Gaussian profiles in particular) which come to pass by means of three different parameter sets and/or constructional changes to the mirrors 3, and also the pixels 23, 23, 23 created by these mirror intensity profiles 22, 22, 22. It is possible to see that the intensity distribution with increasing parameters, which characterize the distribution functions, particularly the full widths at half maximum (FWHM) FWHM, FWHM, FWHM, overlap ever more strongly, so that two mutually adjacent pixels 23, 23, 23 are washed out more strongly. The result is a very homogeneous exposure pattern in the case of the most strongly overlaid pixels 23.

[0235] FIG. 11 shows a schematic plan view, which is not true-to-scale, of a plurality of pixels 23 on a 55 exposure pattern 24. A pattern 28 can be seen, which is illuminated by the targeted connection of the corresponding mirrors 3. The mirror intensity profiles of the mirrors 3 are so sharp that the intensity maxima can be seen clearly and the drop in the intensity is so stark that the intensity distribution per mirror 3 (not shown) is very strongly limited to the assigned partial exposure pattern area 26. In particularly preferred embodiments according to the invention, the mirror intensity profiles are partially overlaid beyond the partial exposure pattern area 26, as would be the case in the realization of the pixels 23 according to FIG. 1.0.

[0236] FIG. 12 shows a schematic plan view, which is not true-to-scale, of an exposure pattern 24 distorted by optical elements of the optical system 8 in particular. The partial rays reflected by the mirrors 3 of the DMD 1 are reflected orthogonally onto the layer 9 to be exposed by means of the optical elements, but a distortion takes place, preferably exclusively, within the K2x-K2y plane. An exposure pattern 24 can be created by means of this method according to the invention, which leads to an increase according to the invention of the overlay. In this embodiment, the DMD 1 is preferably not inclined, rather the original image of the DMD 1 is distorted affinely, in order to effect the inclination of the exposure pattern 24.

REFERENCE LIST

[0237] 1 DMD [0238] 2 Mirror surface [0239] 2kx, 2ky Mirror surface edges [0240] 3, 3 Mirrors [0241] 4 Write area [0242] 5 Buffer region [0243] 6 Light ray [0244] 6 Modified/structured light ray [0245] 6.1 First modified ray [0246] 6.2 Second modified ray [0247] 7, 7 Light sources [0248] 8 Optical system [0249] 9 Layer [0250] 10 Substrate [0251] 11 Substrate holder [0252] 12, 12, 12 Structures [0253] 13 Fixing means [0254] 14 Mirror [0255] 14 Ray splitter [0256] 14 Semi-transparent mirror [0257] 15, 15, 15 Strips [0258] 16l, 16r, 16l, 16r, 16r Intensity variation region [0259] 17 Focal plane [0260] 18 Depth of field [0261] 19 Detector [0262] 20 Dot pattern [0263] 22, 22, 22 Mirror intensity profiles [0264] 23, 23 Pixels [0265] 24, 24, 24, 24 Exposure patterns [0266] 25 Exposure pattern grid line intersection point [0267] 26 Partial exposure pattern area [0268] 27 Exposure pattern grid line [0269] 28 Pattern [0270] l, l Length [0271] b Width [0272] D Direction of travel [0273] V Vertical dot pattern spacing [0274] h Horizontal dot pattern spacing [0275] r Exposure point radius [0276] p Mirror centre distance