METHOD AND APPARATUS FOR ETCHING A LITHOGRAPHY MASK

Abstract

Method for the particle beam-induced etching of a lithography mask, more particularly a non-transmissive EUV lithography mask, having the steps of: a) providing the lithography mask in a process atmosphere, b) beaming a focused particle beam onto a target position on the lithography mask, c) supplying at least one first gaseous component to the target position in the process atmosphere, where the first gaseous component can be converted by activation into a reactive form, where the reactive form reacts with a material of the lithography mask to form a volatile compound, and d) supplying at least one second gaseous component to the target position in the process atmosphere, where the second gaseous component under predetermined process conditions with exposure to the particle beam forms a deposit comprising a compound of silicon with oxygen, nitrogen and/or carbon.

Claims

1. A method for the particle beam-induced etching of a lithography mask, more particularly a non-transmissive EUV lithography mask, having the steps of: a) providing the lithography mask in a process atmosphere, b) beaming a focused particle beam onto a target position on the lithography mask, c) supplying at least one first gaseous component to the target position in the process atmosphere, where the first gaseous component can be converted by activation into a reactive form, where the reactive form reacts with a material of the lithography mask to form a volatile compound, and d) supplying at least one second gaseous component to the target position in the process atmosphere, where the second gaseous component comprises a compound of silicon with oxygen, nitrogen and/or carbon, wherein steps c) and d) are carried out temporally before and/or synchronously to step b).

2. The method of claim 1, wherein the second gaseous component comprises a silicate, a silane, a siloxane, a silazane and/or a silicon isocyanate.

3. The method of claim 1, wherein the second gaseous component under predetermined process conditions with exposure to the particle beam forms a deposit comprising a compound of silicon with oxygen, nitrogen and/or carbon.

4. The method of claim 3, wherein a deposit formed by the second gaseous component during the etching process is removed in a step of wet-chemical cleaning of the lithography mask.

5. The method of claim 1, wherein the first gaseous component comprises one of xenon difluoride XeF.sub.2, sulfur hexafluoride SF.sub.6, sulfur tetrafluoride SF.sub.4, nitrogen trifluoride NF.sub.3, phosphorus trifluoride PF.sub.3, tungsten hexafluoride WF.sub.6, tungsten hexachloride WCl.sub.6, molybdenum hexafluoride MoF.sub.6, hydrogen fluoride HF, nitrogen oxygen fluoride NOF, triphosphorus trinitrogen hexafluoride P.sub.3N.sub.3F.sub.6.

6. The method of claim 1, wherein the supplying of the second gaseous component takes place temporally before and/or after the beaming of the particle beam onto the target position.

7. The method of claim 1, wherein the supplying of the second gaseous component takes place during the beaming of the particle beam onto the target position.

8. The method of claim 1, including: supplying a third gaseous component, which comprises an oxidizing agent and/or a reducing agent.

9. The method of claim 1, wherein the supplying of the first gaseous component, the second gaseous component and/or the third gaseous component comprises: providing a solid or liquid phase of the respective component, setting a temperature of the solid or liquid phase of the respective component such as to attain a mandated vapor pressure of the respective component over the solid or liquid phase, and supplying the respective gaseous component into the process atmosphere via a respective supply line.

10. The method of claim 9, wherein a mass flow rate and/or volume flow rate of the respective component is controlled by setting a line cross section of the respective supply line and/or by controlling a duty cycle of a closing valve.

11. The method of claim 1, wherein the particle beam consists of charged particles, more particularly of electrons.

12. The method of claim 1, wherein the lithography mask is embodied for use in EUV lithography.

13. The method of claim 1, wherein the lithography mask has an etch stop layer whose facing side carries a structured lamina composed of a material which is absorbent for the radiation used in a lithography process, where an etching rate of the activated first gaseous component in relation to the etch stop layer is lower at least by a factor of 2, preferably by a factor of 5, more preferably a factor of 10, than the etching rate in relation to the structured lamina.

14. The method of claim 12, wherein the lithography mask has a mirror layer embodied as a multilayer mirror composed of a plurality of double layers, where a respective double layer comprises a first layer composed of a first chemical composition and a second layer composed of a second chemical composition, where a respective layer thickness of the first and second layers is in a range of 3-50 nm, preferably 3-20 nm, more preferably 5-10 nm, very preferably 5-8 nm.

15. The method of claim 1, wherein the particle beam has an energy of 1 eV-100 keV, preferably of 3 eV-30 keV, more preferably of 10 eV-10 keV, very preferably of 30 eV-3 keV, more preferably still of 100 eV-1 keV.

16. A lithography mask, more particularly a non-transmissive EUV lithography mask, produced by a method of claim 1.

17. An apparatus for the particle beam-induced etching of a lithography mask, more particularly of a non-transmissive EUV lithography mask, having a housing for the provision of a process atmosphere, a means for the focused beaming of a particle beam at a target position on the lithography mask, a means for the provision of a first gaseous component at the target position in the process atmosphere, where the first gaseous component can be converted by activation into a reactive form, where the reactive form reacts with a material of the lithography mask to form a volatile compound, a means for the provision of a second gaseous component at the target position in the process atmosphere, where the second gaseous component comprises a compound of silicon with oxygen, nitrogen and/or carbon, and a control device which for actuating the means for the focused beaming of a particle beam at the target position, for actuating the means for the provision of the first gaseous component at the target position and for actuating the means for the provision of the second gaseous component at the target position is configured in such a way that the first gaseous component and the second gaseous component are provided temporally before and/or synchronously to the focused beaming of the particle beam at the target position.

18. The apparatus of claim 17, wherein the second gaseous component comprises a silicate, a silane, a siloxane, a silazane and/or a silicon isocyanate.

19. The apparatus of claim 17, wherein the second gaseous component under predetermined process conditions with exposure to the particle beam forms a deposit comprising a compound of silicon with oxygen, nitrogen and/or carbon.

20. The apparatus of claim 17, wherein the first gaseous component comprises at least one of xenon difluoride XeF.sub.2, sulfur hexafluoride SF.sub.6, sulfur tetrafluoride SF.sub.4, nitrogen trifluoride NF.sub.3, phosphorus trifluoride PF.sub.3, tungsten hexafluoride WF.sub.6, tungsten hexachloride WCl.sub.6, molybdenum hexafluoride MoF.sub.6, hydrogen fluoride HF, nitrogen oxygen fluoride NOF, or triphosphorus trinitrogen hexafluoride P.sub.3N.sub.3F.sub.6.

Description

DESCRIPTION OF DRAWINGS

[0082] FIG. 1 shows schematically a section through a lithography mask which is undergoing a particle beam-induced processing operation;

[0083] FIG. 2 shows a schematic block diagram of an apparatus for the particle beam-induced etching of a lithography mask;

[0084] FIGS. 3A and 3B show an electron microscope image of a lithography mask before and after a particle beam-induced etching process;

[0085] FIGS. 4A-C show a known particle beam-induced etching process on a lithography mask;

[0086] FIGS. 5A-5C show a sequence of electron microscope images of a lithography mask before and after etching by a known etching process;

[0087] FIGS. 6A-6C show damage to a substrate, caused by a known etching process;

[0088] FIGS. 7A-7C show a particle beam-induced etching process of the invention on a lithography mask;

[0089] FIGS. 8A-8C show a lithography mask worked on with an etching process of the invention;

[0090] FIG. 9 shows a schematic block diagram of a method for working on a lithography mask with a particle beam-induced etching process; and

[0091] FIG. 10 shows a schematic block diagram of another apparatus for the particle beam-induced etching of a lithography mask.

DETAILED DESCRIPTION

[0092] Identical elements or elements having an identical function have been provided with the same reference signs in the figures, unless indicated to the contrary. It should also be noted that the illustrations in the figures are not necessarily true to scale.

[0093] FIG. 1 shows schematically a section through a lithography mask 100, which is undergoing a particle beam-induced processing operation. This operation is more particularly a locally induced etching process, in which material is ablated from the lithography mask 100. The etching process may also be applied (not shown) to foreign bodies, such as particles of dust, for example, which have settled on the surface of the lithography mask 100.

[0094] In the depicted example of the lithography mask 100, the mask is, for example, a mask suitable for EUV lithography, operated on a reflective basis. This means that the working light in operation impinges on the lithography mask 100 and is reflected back into the same half-space. EUV here stands for “extreme ultraviolet” and denotes a working light wavelength of between 0.1 nm and 30 nm.

[0095] In this example, the lithography mask 100 has a layered construction, in which the base is formed by a carrier or substrate 102, which may consist of fused silica, for example. Disposed on the side which is later irradiated in operation with the working light is a multilayer mirror 104, which as a Bragg mirror is embodied specifically for the respective wavelength of the working light. In this arrangement, layers of high and low refractive index, based on the wavelength of the working light, and having a layer thickness of approximately half the wavelength of the working light, multiplied by the sinus value of the incident angle of the working light on the lithography mask 100, are disposed over one another in alternation. The working light has a wavelength of 13.5 nm, for example. In that case a suitable multilayer mirror for an incident angle of 90° would be a mirror 104 comprising a plurality of double laminae of molybdenum and silicon each with a layer thickness of 6.75 nm, as a Bragg mirror. In the case of slanted incidence of light, the layer thickness selected must be smaller. The multilayer mirror 104 comprises, for example, up to 100 such double laminae. The multilayer mirror 104 may be produced by use of known deposition processes, such as chemical vapor deposition (CVD) or the like. Disposed on the multilayer mirror 104 is an etch stop layer 106. A first function of this etch stop layer 106 is to halt etching processes utilized in the structuring of the structured lamina 108, so that the multilayer mirror 104 or the substrate 102 are not attacked. Moreover, the etch stop layer 106 itself is part of the multilayer mirror 104, and therefore forms the first layer of the multilayer mirror 104. The etch stop layer 106 therefore has, in particular, a layer thickness adapted correspondingly to the working light. The etch stop layer 106 consists, for example, of ruthenium or of another noble metal.

[0096] A layer structure of this kind achieves, for example, a reflectivity of about 70% of the irradiated intensity on EUV illumination. In order to achieve the local modulation in illumination intensity that is needed for lithography, the structured layer 108 is disposed on the etch stop layer 106. The structured layer 108 comprises, for example, tantalum boron nitride TaBN, tantalum nitride TaN, tantalum boron oxide TaBO and/or tantalum oxide TaO. To produce the structured layer 108, for example, a layer of TaBN is first applied over the full area, and is then selectively etched. In regions in which the TaBN layer remains, the incident working light is greatly attenuated. Because a reflected beam bundle passes twice through the TaBN layer, less than about 10% of the incident intensity is reflected in the regions of the TaBN layer.

[0097] During the production of the lithography mask 100, defects may occur (see, for example, FIG. 3). In the case of intensity-modulating lithography masks, a distinction is made in particular between clear and opaque defects. The result of a clear defect is that, on exposure at a position at which there is to be only low intensity or none, the intensity is too high. The result of an opaque defect is the opposite: in other words, at a respective position, the intensity is absent or is too low relative to the desired intensity.

[0098] In this example, possible sources of error are, in particular, errors in the construction of the multilayer mirror 104, including the etch stop layer 106, and also errors during the structuring of the structured layer 108. The latter can be repaired in a very targeted way, since these defects lie on the surface and are therefore directly accessible. One suitable technique for this purpose are particle beam-induced processes, since they enable targeted local working. Particles contemplated in this context include ions, electrons and photons (lasers or the like). Particularly advantageous are electron beams, since on the one hand they can be focused on a very small target point and on the other hand they cause only relatively very little damage, or none, such as a structural change to the surfaces subjected to the beam, for example. The reasons for this include, in particular, the fact that electrons have a comparatively low depth of penetration. In contrast, ions in particular penetrate the material more deeply, where they sometimes lead to doping and hence to a structural alteration of the material, with possible adverse consequences. Laser beams have the disadvantage relative to electron beams that they cannot be focused onto so small an area, and hence that the spatial selectivity and therefore the resolution of the working process is lower. The radiation in this example is an electron beam 110.

[0099] In this example there is an opaque defect 112, in the form of an unremoved part of the TaBN layer in the structured layer 108. The defect 112 is removed using a locally induced etching process. Required for this purpose are firstly the activating electron beam 110 (generally: particle beam 110) and secondly a first gaseous component GK1 which can be converted by activation into a reactive form.

[0100] The focused electron beam 110 is scanned over the target position ZP, in particular. The target position ZP has an extent, for example, in the range of 5 nm-2 μm. At the point of impingement, the focused particle beam 110 preferably has an approximately gaussian beam profile (based on the intensity) with a full width at half maximum in the range of 1-50 nm. The focusing can advantageously be adjusted. The electron beam 110 is deflected in such a way that for a mandated dwell time in each case it irradiates a point with the size of the point of impingement. It is also possible here to use the term “pixel”. The target position ZP is divided, for example, into pixels, which are irradiated in succession by the electron beam 110. The dwell time is situated, for example, in the range from several hundred picoseconds to microseconds. Depending on the size of the target position ZP and of a pixel, there is a defined cycle time for a complete pass. In the case of 10.sup.6 pixels and a dwell time of 1000 ps, the cycle time amounts, for example, to 1 ms. In an etching process, for example, several million cycles are applied to a target position ZP, meaning that the electron beam 110 scans over the target position ZP several million times.

[0101] The first gaseous component GK1, for example XeF.sub.2, is preferably supplied in a targeted way to the target position ZP. In this case, individual XeF.sub.2 molecules may be adsorbed on the surface of the lithography mask 100. In the adsorbed state, interaction between the adsorbed molecules and the surface atoms is comparatively strong. As a result of the activating electron beam 110 and/or as a result of secondary processes triggered by the electron beam 110 in the target point ZP, and especially by secondary electrons from near-surface atoms, the molecules of the first gaseous component GK1 are activated. In the example of XeF.sub.2, this molecule is, for example, dissociated, with the resultant fluorine atoms or fluorine radicals reacting with surface atoms of the TaBN layer and forming volatile gaseous compounds which volatilize via the process atmosphere ATM. In this way there is a localized ablation of material.

[0102] Since XeF.sub.2 is a comparatively reactive substance, there is to some extent, even without activation by a particle beam 110, a spontaneous reaction with surface atoms, which can lead to uncontrolled etching. This depends greatly on the combination utilized between first gaseous component GK1 (etching gas) and the chemistry of the free surface. To gain more effective control over the etching process it is possible to supply various additive gases, which fulfil a buffer function or a passivating function. Known in this context is the use of water in an etching process, which has a passivating effect. A problem with water, however, is that it may attack the etch stop layer 106, which consists, for example, of ruthenium or another noble metal. An alternative to water supplied in this example as second gaseous component GK2 is tetraethyl orthosilicate (Si(OC.sub.2H.sub.5).sub.4, also referred to as tetraethoxysilane, hereinafter TEOS for short). TEOS is a known deposition gas in particle beam-induced processes, and is used, for example, for the local generation of a layer of silicon oxide. Firstly, TEOS has a passivating effect, so that spontaneous etching processes do not occur substantially, or not at all, and secondly the etch stop layer 106 is not attacked. Under exposure to the electron beam 110, TEOS may lead to a deposit comprising silicon oxide, silicon nitride and silicon carbide, and also mixed phases of these compounds. This may contribute to the selectivity or control of the etching process. It may be noted, moreover, that silicon oxide, silicon nitride and silicon carbide carry out only relatively little attenuation of EUV radiation, and so a thin layer possibly formed in this case, with silicon oxide, silicon nitride and silicon carbide, is negligible.

[0103] In the etching process of the invention, the first and second gaseous components GK1, GK2 are preferably supplied to the target position ZP temporally before and/or during the beaming of the electron beam 110 onto the target position ZP. Accordingly, the composition of the process atmosphere ATM may be controlled while the electron beam 110 is being beamed onto the target position ZP, so that the advantageous effects described above and below are achieved through the use of the second gaseous component GK2 in the etching process.

[0104] FIG. 2 shows a schematic block diagram of an apparatus 200 for the particle beam-induced etching of a lithography mask 100, for example the EUV lithography mask 100 from FIG. 1. The apparatus 200 has a housing 210 which is evacuated by a vacuum pump 250 to a pressure in the range of 10.sup.−2-10.sup.−8 mBar in order to create a process atmosphere ATM in the housing 210. The apparatus 200 has a means 220, disposed in the vacuum housing 210, for the provision of a focused particle beam 110. The means 220 has a beam preparation unit 222 and also one or more beam-guiding and/or beam-shaping means 224, 225, which direct the particle beam 110 in the desired way to the target point ZP. The device in question here is, for example, an electron column 220, which is configured for providing a focused electron beam 110. The beam-guiding and beam-shaping elements 224, 225 are embodied in this case, in particular, as multipoles. Further provided, advantageously, is a detector 226, which detects backscattered electrons and/or secondary electrons and is therefore configured for capturing an electron microscope image of the lithography mask 100. In this way it is possible to follow an operation of working on the lithography mask 100 in situ.

[0105] The apparatus 200 has a sample platform 202 for holding and positioning the lithography mask 100 to be worked on, and this platform can be actuated preferably in two, more preferably three, directions in space. Furthermore, the sample platform 202 may be mounted so as to be tiltable and rotatable, in order to align (not shown) the lithography mask 100 with the greatest possible precision in relation to the means 220, more particularly in relation to the particle beam 110. The sample platform 202 is advantageously mounted with vibration damping and is mechanically decoupled (not shown) from the rest of the construction.

[0106] Disposed outside the housing 210 are a means 230 for the provision of a first gaseous component GK1, and a means 240 for the provision of a second gaseous component GK2. The embodiment of the respective means 230, 240 is preferably such that they control a temperature of a solid or liquid phase of the respective component, in order to set a vapor pressure of the respective gaseous component GK1, GK2. In this way it is possible advantageously to achieve a gas flow of the respective gaseous component GK1, GK2 that is optimized for the respective process, without valves or the like. However, this is not to rule out the additional provision of valves or the like, since valves advantageously enable a very rapid changing of the gas flows. Each of the means 230, 240 has a supply line 232, 242 into the housing 210, which opens into a respective nozzle. The nozzle is directed advantageously at the target point ZP, so that the gas GK1, GK2 supplied comes into contact in a targeted way, at the target point ZP, with the surface of the lithography mask 100. This increases process control and also efficiency of the etching process. Further to the means 230, 240, there may be further means (not shown) provided, embodied in a similar way, for supplying further gaseous components, such as buffer gases, oxidizing or reducing gases, into the process atmosphere ATM.

[0107] Also shown is a suction withdrawal unit 260, which is configured to draw off excess gas and also, in particular, volatile reaction products under suction from the region of the target point ZP; this is done, for example, using a further vacuum pump 250. This allows the composition of the process atmosphere ATM to be controlled more effectively, and in particular it prevents reaction products from settling elsewhere on the lithography mask 100 or other, unforeseen processes taking place with excess gas.

[0108] FIGS. 3A and 3B show an electron microscope image of a lithography mask 100 before and after a particle beam-induced etching process. The example depicted here has parallel structures; this, however, is merely illustrative and should not be interpreted as imposing any limitation. Other lithography masks may have various other geometric forms. The lithography mask 100 depicted is, in particular, an EUV lithography mask, having the layer structure shown in FIG. 1, for example.

[0109] FIG. 3A shows the lithography mask 100 with a defect in the form of an absorbing region, which is not intended at this point. The box with white dashes serves to emphasize the defective region. The EUV lithography mask 100 is subjected with the apparatus 200 of FIG. 2, for example, to the proposed particle beam-induced etching process, with the target position ZP (see FIG. 1) specified being the region of the lithography mask 100 whose material is to be removed.

[0110] FIG. 3B shows the EUV lithography mask 100 after the etching process has been carried out. It is apparent that the defect has been successfully removed and the lines on the lithography mask 100 are now all separate from one another. The white box serves to emphasize the repair site. The lithography mask 100 now has the intended structure and can be used, for example, in an EUV lithography process.

[0111] FIGS. 4A-4C show schematically a known particle beam-induced etching process on a lithography mask 100. With the known process there are unwanted side effects, as elucidated below. FIG. 4A shows the initial situation, with the lithography mask 100 disposed in the process atmosphere ATM1. A structured layer 108 consisting substantially of a first material 108a, such as of tantalum nitride TaN, for example, is being etched. The surface of the layer 108 consists of a different material 108b, comprising tantalum oxide TaO and/or tantalum oxynitride TaON, for example. A near-surface layer 108b of this kind may be formed spontaneously by itself, with the layer 108b in that case having a thickness of a few nanometers, or may be deposited in a targeted way, in which case the layer thickness can be set arbitrarily, for example. The lithography mask 100 may have further layers, as shown in FIG. 1, which have not been shown here, for reasons of clarity. The etching process is carried out, for example, by use of the apparatus 200 of FIG. 2.

[0112] The process in FIGS. 4A-4C is carried out with a process atmosphere ATM1 which comprises, for example, XeF.sub.2 as etching gas and Hao as passivating gas. The intention, for example, is to remove a defect 112, as shown in FIG. 3A. The defect 112 is bounded here by the dashed lines. The target position ZP is placed correspondingly in the region of the defect 112.

[0113] As shown in FIG. 4B, the etching process is carried out in a targeted way by the particle beam 110, with the layer 108 in the target position ZP being removed down to the substrate 101. The target position ZP is divided, for example, into pixels, with one pixel corresponding to the area of impingement of the focused particle beam 110 on the layer 108, and the particle beam 110 scans over the target position pixel by pixel. In each cycle, a number of layers of atoms of the layer 108 are ablated. In this case, the outer layer 108b first of all and then the inner layer 108a are exposed in sections.

[0114] During the etching process there may be unwanted instances of damage DMG1, DMG2. Thus, for example, the substrate 101 of the lithography mask 100 may be damaged, as represented by the rough surface DMG1. Because the etching procedure does not always take place with exactly the same rapidity at every pixel of the target position ZP, a situation occurs in which the substrate 101 has already been exposed at certain pixels, while at others there remains material to be ablated. The etching process is therefore continued, and this, in the regions in which the substrate 101 is already lying open, may result in instances of damage DMG1 by the particle beam 110 and also by the aggressive etching gas, especially in activated form, and/or by the water which is present as passivating gas in the process atmosphere ATM1.

[0115] Moreover, at an edge of the target position ZP, where a side wall of the layer 108 is exposed as the etching procedure progresses, there may be further instances of damage DMG2. Examples of this are etching processes which attack the exposed side wall of the layer 108, possibly leading to degradation of the side wall.

[0116] After the end of this etching process at the target position ZP shown, an etching process is carried out (not shown), for example, at another position of the lithography mask 100. During this procedure the gases in the process atmosphere ATM1 continue to be in direct contact with the exposed layer 108a. In this scenario there may be spontaneous reactions in which the exposed material 108a is attacked. As a result, an unwanted etching process may occur, and may lead to further damage DMG3 in the form of an under-etching of the surface layer 108b, as shown in FIG. 4C. This process, proceeding without control, may therefore stand in the way of a targeted etching process. The damage DMG3 occurs, for example, when the near-surface layer 108b is not attacked, or is only insubstantially attacked, by the first gaseous component GK1, whereas the material 108a is attacked significantly.

[0117] FIGS. 5A-5C show a sequence of electron microscope images of a lithography mask 100 before (FIG. 5A) and after (FIGS. 5B and 5C) a particle beam-induced etching with the etching process described with reference to FIGS. 4A-4C. The lithography mask 100 has, for example, a structure as shown in FIG. 1.

[0118] The substrate 106 and the structured layer 108 are clearly visible in the electron microscope images. FIG. 5A shows the target position ZP in the form of a dashed box. In this case the target position ZP is located on the substrate 106. The focused particle beam 110 scans over the target position ZP (see FIG. 1 or 2) as described with reference to FIG. 1.

[0119] FIG. 5B shows the worked-on region after the etching process, the image having been captured with an electron beam energy of 600 V. With this energy it is possible to capture topological structures in particular. In the region subjected to the particle beam 110, a slight discoloration is perceptible, which indicates that in this region the substrate surface is damaged. The damaged region is emphasized by the dashed line DMG1. Furthermore, a comparison of the edges of the layer 108 with FIG. 5A shows that these edges likewise exhibit damage DMG2 and are no longer so sharply defined.

[0120] FIG. 5C shows a further image of the worked-on region, the image having been captured with a higher electron beam energy, causing contrasts of material, in particular, to become visible. The dark points DMG1 indicate that at these sites the etch stop layer 106 has been etched away entirely. At these sites it is also not possible to rule out even deeper damage, to the multilayer mirror 104, for example (see FIG. 1).

[0121] The instances of damage DMG1, DMG2 shown lead, for example, to reduced reflection of EUV radiation in a lithography process, with the possible consequence of errors in the production of microstructured components. At the frayed edges, more radiation is scattered, and this may likewise impair an exposure process.

[0122] FIGS. 6A-6C show further damage, caused by a known etching process, to an etch stop layer 106 on an EUV lithography mask 100, having the same construction, for example, as the lithography mask shown in FIG. 1. In this case, for example, the etching process used involved the supplying of XeF.sub.2 as etching gas, H.sub.2O as passivating gas, and NO.sub.2 as buffer gas. The etching process was used to remove a column of tantalum boron nitride TaBN material located in the region of the target position ZP.

[0123] FIG. 6A shows an electron microscope image of the worked-on region of the lithography mask 100. A distinct lightening is visible in the region of the target position ZP, and suggests damage DMG1. Also in evidence are four positional markers DC. For reasons of clarity, only one has been labelled with a reference sign. The purpose of the positional markers DC is to visualize and compensate a relative shift between the lithography mask 100 and the means 220 (see FIG. 2) for providing the focused particle beam 110 (see FIG. 1 or 2) during the beaming process. In this case the positional markers DC are regularly scanned during the etching process, and for this reason a lightened, damaged region is visible around them as well.

[0124] FIG. 6B shows an image of the lithography mask 100, captured with actinic radiation. FIG. 6B shows, for example, a two-dimensional intensity distribution of the reflected radiation, such as would occur on the sample in a lithography process with the lithography mask 100. Differences in lightness correspond to differences in intensity. The reflected intensity is about 70% in the region of the etch stop layer 106 and less than 10% in the region of the structured layer 108. The damaged region DMG1 can likewise be recognized as lightening. A region of interest ROI is shown, which passes through the damaged region DMG1. The intensity values of the region of interest ROI are plotted in FIG. 6C as a function of position, with the markers (“z” and “0”) coinciding with FIG. 6B.

[0125] The diagram of FIG. 6C shows the reflected intensity R of the EUV radiation in the region of interest ROI as a function of the position. The positions “z” and “0” coincide with FIG. 6B. The vertical axis shows the intensity I, which is normalized, for example, to the highest value. The measurement shows that there is a minimum in the reflected intensity at the position “z”. This shows that the damage to the etch stop layer 106 leads to poorer reflectivity of EUV radiation, and hence to a poorer lithography process.

[0126] FIGS. 7A-7C show, in analogy to FIGS. 4A-4C, an etching process, which here, however, is carried out in accordance with the invention. Consequently the unwanted or uncontrolled side effects elucidated with reference to FIGS. 4A-4C are substantially suppressed.

[0127] In the example of FIGS. 7A-7C, the process atmosphere ATM comprises, for example, XeF.sub.2 as etching gas and TEOS as additive gas. The etching process proceeds in a targeted way, as in the case of the example of FIG. 4B as well, as shown in FIG. 7B. In contrast to FIG. 4B, however, the presence of TEOS in the process atmosphere ATM leads to the formation of a passivating layer 109, consisting substantially of silicon oxide or silicon dioxide, for example. This passivating layer 109 may be generated, for example, by the deposition of the second gaseous component GK2 from the process atmosphere ATM, and/or by chemical reactions of molecules of the second gaseous component GK2 with the exposed material 108a. The passivating layer 109 has the advantageous effect that the exposed surface of the substrate 101 and also of the layer 108a is sealed or passivated, and so damage of the kind explained with reference to FIG. 3B does not occur, or occurs only insubstantially. It may be noted that the layer 109 as well can be ablated by the activated etching process. Advantageously, therefore, a high layer thickness of the layer 109 is not formed. The process is controlled in particular by the control of the gas supply, which determines the composition of the process atmosphere ATM in the region of the target position ZP.

[0128] The passivating layer 109 therefore has the advantage that damage to the substrate 101 is reduced or entirely suppressed. Furthermore, spontaneous etching reactions which may likewise limit the quality of the lithography mask 100 are prevented. A very targeted and clean etching process is therefore possible.

[0129] In particular it may be the case that a unified layer 109 is not formed, and that instead only a number of atoms of the second gaseous component GK2 are deposited from the process atmosphere ATM on the surface ablated by the etching process, and/or react with atoms from the surface layer. Layer formation is therefore avoided.

[0130] FIGS. 8A-8C show a lithography mask 100 worked on with an etching process of the invention. The lithography mask 100 has, for example, the layer construction elucidated with reference to FIG. 1. Visible on the top side is, partially, the structured layer 108 and, partially, the etch stop layer 106. The lithography mask 100 was subjected to an etching process in which the first gaseous component GK1 supplied (see FIG. 1 or 2) was XeF.sub.2 and the second gaseous component supplied (see FIG. 1 or 2) was TEOS. No further additive gases were used. The gas flow was controlled via the temperature of the respective liquid or solid phase of the component, with XeF.sub.2 being held in this example at a temperature of −20° C., and TEOS at a temperature of −33° C. To activate the first gaseous component GK1, a focused electron beam 110 (see FIG. 1 or 2) was used. The etching process was carried out on two adjacent, rectangular target positions ZP on the exposed etch stop layer 106.

[0131] FIG. 8A here shows an electron microscope image of the worked-on region of the lithography mask 100, which was captured with an electron energy of 600 V, meaning that surface structures are readily apparent. In the region of the two target positions ZP, a very slight lightening is perceptible, suggesting a slight alteration to the surface structure, for example the surface roughness.

[0132] FIG. 8B shows an electron microscope image of the worked-on region of the lithography mask 100, captured with a higher electron energy, producing sharp contrasts of material. In this image it would be apparent if a deposit has formed on the etch stop layer 106 or if the etch stop layer 106 has been etched away, as can be seen in FIG. 5C. FIG. 8B shows that essentially no deposit has formed and also that the etch stop layer 106 has not been substantially attacked during the etching process.

[0133] FIG. 8C shows an image of the lithography mask 100 taken with actinic radiation, showing the reflected intensities. The reflected intensity is about 70% in the region of the etch stop layer 106 and less than 10% in the region of the structured layer 108. In the region of the target positions ZP, only very insubstantial deviations can be seen in comparison to the remaining, unirradiated surface of the etch stop layer 106.

[0134] In this case, in comparison to the conventional process, which leads to damage (see FIGS. 5A-5C and also 6A-6C), the etch stop layer 106 is not damaged.

[0135] FIG. 9 shows a schematic block diagram of a method for working on a lithography mask 100 (see FIGS. 1-8) with a particle beam-induced etching process. In a first step S1, the lithography mask 100 is provided in a process atmosphere ATM (see FIGS. 1, 2 and 7). For example, the lithography mask 100 is arranged on the sample platform 202 of the apparatus 200 and the housing 210 is evacuated to a pressure of about 10.sup.−6-10.sup.−8 mBar. In a second step S2, a focused particle beam 110 (see FIG. 1 or 2) is beamed onto a target position ZP (see FIGS. 1-8) on the lithography mask 100. In a third step S3, a first gaseous component GK1 (see FIG. 1 or 2) is supplied to the target position ZP in the process atmosphere ATM. The first gaseous component GK1 can be converted by activation into a reactive form, with the reactive form reacting with a material of the lithography mask 100 to form a volatile compound. The first gaseous component GK1 is activated in particular by the particle beam 110 and/or by secondary effects triggered by the particle beam 110. In a fourth step S4, at least one second gaseous component GK2 (see FIGS. 1 and 2) is supplied to the target position ZP in the process atmosphere ATM. Under predetermined process conditions, on exposure to the particle beam 110, the second gaseous component GK2 forms a deposit comprising a compound of silicon with oxygen, nitrogen and/or carbon. The process conditions in the etching process are preferably selected such that no deposit or only a very slight deposit is formed.

[0136] In the method, the third step S3 and the fourth step S4 are carried out, in particular, temporally before and/or synchronously to the second step S2.

[0137] FIG. 10 shows a schematic block diagram of another embodiment of an apparatus 200 for the particle beam-induced etching of a lithography mask 100. The apparatus 200 of FIG. 10 has all of the features of the apparatus 200 elucidated with reference to FIG. 2, and for that reason these features are not elucidated again here. The apparatus 200 is operated, in particular, by use of the method elucidated with reference to FIG. 9.

[0138] In addition, the apparatus 200 in FIG. 10 has a control device 270. The control device 270 is embodied, for example, as a part of a control computer for controlling the apparatus 200. The control device 270 is configured for actuating the means 220 for the focused beaming of the particle beam 110 at the target position ZP, for actuating the means 230 for the provision of the first gaseous component GK1 at the target position ZP, and for actuating the means 240 for the provision of the second gaseous component GK2 at the target position ZP. In this arrangement, the control device 270 actuates the means 230 and the means 240 in such a way that the first gaseous component GK1 and the second gaseous component GK2 are provided temporally before and/or synchronously to the focused beaming of the particle beam 110 at the target position ZP.

[0139] The concept of the control device 270 actuating the respective means is understood, for example, to mean that the control device 270 sends a control command to the respective means, more particularly to a controller of the respective means, this control command comprising the settings for the respective means that are intended at a respective point in time in the method. The control command may be transmitted by wire or else wirelessly, via an optical transmission section, for example.

[0140] Although the present invention has been described on the basis of exemplary embodiments, it is modifiable in diverse ways.

LIST OF REFERENCE SIGNS

[0141] 100 Lithography mask [0142] 101 Substrate [0143] 102 Substrate [0144] 104 Multilayer mirror [0145] 106 Etch stop layer [0146] 108 Structured layer [0147] 108a Layer [0148] 108b Layer [0149] 109 Layer [0150] 110 Particle beam [0151] 112 Defect [0152] 200 Apparatus [0153] 202 Sample platform [0154] 210 Housing [0155] 220 Means [0156] 222 Beam preparation unit [0157] 224 Beam-guiding means [0158] 225 Beam-shaping means [0159] 226 Detector [0160] 230 Means [0161] 240 Means [0162] 250 Vacuum pump [0163] 260 Suction withdrawal unit [0164] 270 Control device [0165] ATM Process atmosphere [0166] ATM1 Process atmosphere [0167] DC Positional marker [0168] DMG1 Damage [0169] DMG2 Damage [0170] DMG3 Damage [0171] GK1 Gaseous component [0172] GK2 Gaseous component [0173] I Intensity [0174] POS Position [0175] R Reflected intensity [0176] ROI Region of interest [0177] S1 Method step [0178] S2 Method step [0179] S3 Method step [0180] S4 Method step [0181] z Position [0182] ZP Target point