WO1997043693A1

WO1997043693A1 - Method of producing a structured foil and use thereof

Info

Publication number: WO1997043693A1
Application number: PCT/AT1997/000095
Authority: WO
Inventors: Ewald Cekan; Ernst Hammel; Artur Jachimowicz; Hans LÖSCHNER
Original assignee: Ims-Ionen Mikrofabrikations Systeme Gmbh
Priority date: 1996-05-13
Filing date: 1997-05-13
Publication date: 1997-11-20

Abstract

The invention concerns a method of producing a structured foil whose structures are formed by a plurality of openings, the method comprising the following steps: (a) preparation of a flat laminar substrate with one or a plurality of thin layers on the top, the material of at least one of these thin layers differing chemically from that of the substrate; (b) production, on the top of the arrangement consisting of the substrate and at least one thin layer, of a layer which constitutes the foil or forms part thereof and is structured with a plurality of openings, the material of the foil layer differing chemically from that of at least one thin layer lying therebelow; and (c) separating the structured foil from the substrate by removing the layers between the foil layer and the substrate.

Description

METHOD FOR PRODUCING A STRUCTURED FILM AND USE THEREOF

1 Field of the Invention

The present invention relates to a method for producing a structured film, the structures of which are formed by a plurality of openings, and special uses of a structured film produced in this way

2 State of the art "

Films of the type mentioned are required in many fields of technology. The production of such films is particularly difficult when these films are to be produced over a large area with a small thickness, e.g. with a diameter greater than 5 cm and a thickness in the range from 0.25 to 50 μm, and moreover, an opening structure with extremely small dimensions in the μm or sub-μm range should have foils of this type, for example for ultrafine sieves, or as Masks for a variety of processes, e.g. used in lithographic applications, for ion implantation, for ion beam etching, vapor deposition, and as grating lenses or the like.

Known manufacturing methods generally involve the thinning of thick substrates, such as silicon wafers. The opening structure of the film can be produced either before or after the substrate is thinly etched by means of a lithographic process. In the first case (film structure is created before thin etching), it is necessary to protect the opening structure from an etching attack during thin etching, for example by filling it with a certain material, which must then be removed again completely. In the second case (opening structure is produced after thinning), all the processing steps required for the structuring must be carried out on the thin film, so that it can easily be damaged or damaged. A disadvantage of these known production processes is, inter alia, that both the protection the openings and the subsequent further treatment of a film or membrane are very complex and therefore expensive It is therefore an object of the present invention to provide a novel method for producing structured, thin foils which can be carried out simply and inexpensively and changes the mechanical tension properties as little as possible during manufacture. In particular, it should be possible to use already known and easily controllable production technologies, for example technologies which have been developed for semiconductor production.

3. Summary of the Invention:

These objects are achieved with a method which has the following essential steps: a) providing a flat, flat substrate with at least one thin layer on the top, the material of this thin layer being chemically different from that of the substrate, b) producing one A film-forming layer with a plurality of openings structured on the top of the structure consisting of the substrate and at least one thin layer, the material of the film layer being chemically different from that of an underlying thin separating layer, and c) detaching the structured film from the Substrate by removing the separating layer located between the film layer and the substrate.

With this method, both the thin etching of a substrate and the complex treatment of the substrate during the etching process or the aftertreatment of the film or the membrane are dispensed with, so that the production of structured films is considerably simplified, especially when these films are large and have fine opening structures exhibit. The technological means which are required for the individual steps for executing the method are already known in part from semiconductor production, so that low development and investment costs are incurred in the implementation and implementation of the method. In the context of the present invention, the term thin layer is typically understood to mean layers in the μm and sub-μm range.

In a preferred embodiment of the method, the film is provided with a stiffening frame at least in sections in the region of its edge before it is detached from the substrate, for example by gluing or bonding to a frame or by growing or depositing a layer of material along the edge To enable safe handling of the film after it has been removed. This is of great importance in practice, particularly in the case of thin and large-area films

In a particularly advantageous embodiment of the method, step b) of producing the structured layer forming the film comprises two sub-steps, namely b) j structuring an uppermost thin layer by means of a lithographic

Method, b) 2 application of the layer forming the film to the top of the structured thin layer or the substrate, this film layer being produced in such a way that it is thin on the edges of the structures of the uppermost

Layer is interrupted and these structures subsequently form the edges of the openings of the film.This sequence of sub-steps enables a particularly stress-free film production, since the openings are formed automatically during the application of the film layer and not only afterwards. In addition, in this embodiment of the production process, etching becomes necessary completely avoided the film layer in an advantageous manner

In this embodiment, two alternative production variants have proven to be advantageous, namely a first variant in which the structures of the uppermost thin layer are formed by openings in this layer which correspond to the openings in the film to be produced, and a second variant in which the structures of the uppermost thin layer are formed by elevations which correspond to the openings of the film to be produced

In the case of the first-mentioned variant, the layer forming the film can advantageously be suspended by vapor deposition or sputtering on the structured, thin layer or the substrate, the vaporized or sputtered material particles being moved as perpendicularly as possible to the top of the thin layer or the substrate, so that the evaporated or sputtered film layer is interrupted at the edges of the openings of the structured, thin layer

In the case of the second variant mentioned, the layer forming the film can advantageously be applied by electrodeposition of a material on the top of a structured, thin, conductive layer, the material of the elevations being electrically non-conductive In order to achieve a safe and sharp-edged interruption of the vapor-coated or sputtered film layer, these interruptions are advantageously formed on an undercut of an underlying thin layer or the substrate.The undercuts can be produced on the one hand by etching openings with essentially constant cross sections into the structured one thin layer down to an underlying thin layer or up to the top of the substrate and by subsequently selectively etching this underlying thin layer or the substrate through the openings of the structured, thin layer, but also by forming openings with at least one in the direction of the substrate sectionally increasing cross-sectional area in the structured, thin layer on the top of the substrate, for example by means of electron beam lithography or by means of optical lithography using the image reversal Technology

In a further advantageous embodiment of the production method, step b) of producing the structured layer forming the film comprises the following steps b) _j applying the layer forming the film to the top of a structured thin layer, the structures of the thin layer being previously either

Elevations of this layer or an underlying layer or the substrate are formed and the applied film layer has essentially no interruptions, b) 2 removal of the section of the film layer located above the elevations in such a way that the film layer is interrupted in the region of the elevations and this Interruptions in the sequence form the edges of the openings in the film

Here, the edges or the side walls of the openings are precisely defined by the elevations. The presence of the elevations means that all known methods can also be used to produce the film layer, so that essentially the technically or economically most suitable layer manufacturing method is used for each film material and for each film thickness In a particularly simple and inexpensive variant for realizing this embodiment, the section of the film layer located above the elevations is removed by polishing this film layer

In a technologically simple embodiment which can be implemented using known means, a silicon wafer, for example a wafer, or a glass or quartz plate is used as the substrate, and a polymer, for example a polymer, for the separating layer on the top of the substrate a photoresist, and a conductive material, for example a metal, a semiconductor material or a conductive modification of the carbon is used for the structured film

In a specific embodiment, the substrate provided with the at least one thin layer on the top can also be a prefabricated mask blank, for example a standard photo mask blank. The starting point of the manufacturing process is thus created by a product that is already available in the trade, which makes a particularly cost-effective embodiment of the procedure is made possible

The invention also relates to the use of a structured film produced by the method described above as a mask or a sieve, in particular as a stencil mask for lithography by means of electromagnetic radiation, such as UV or X-ray lithography, or by means of corpuscular rays, such as Electron or ion beam lithography, and also as a Fresnel lens for X-ray projection lithography is used. Furthermore, a structured film thus produced can be used as a mask for ion implantation, for ion beam etching, as a vapor deposition mask or as a mask for the treatment of a substrate by means of directed atomic beams or Molecular rays can be used advantageously

4 Brief description of the figures

In the following, non-restrictive exemplary embodiments for carrying out the method according to the invention are described in detail using the example of the production of a stencil mask, reference being made to the attached, highly schematically illustrated figures, which show the following

FIGS. 1a, 1b, 1c, 1d, 1e are schematic cross sections which illustrate individual steps of the method in a specific embodiment in which the substrate is a Si wafer, the structured thin layer is a photoresist and the

Film layer is a vapor deposition layer,

2a, 2b, 2c and 2d are schematic cross sections, which illustrate individual sections of the method in another embodiment in which an image reversal technique is used, FIGS. 3a, 3b, 3c, 3d, 3e, 3f and 3g are schematic cross sections, which separate

To illustrate the shadow of the method in an embodiment in which a chromium photomask is used as the starting point, 4a, 4b, 4c, 4d, 4e, 4f and 4g are schematic cross sections of a further embodiment of the method using a chrome photomask,

5a, 5b, 5c, 5d, 5e and 5f are schematic cross sections of a further embodiment of the method according to the invention, in which a multi-layer process is used using the example of a three-layer process for film production,

6a, 6b, 6c, 6d, 6e, 6f and 6g are schematic cross sections of a further embodiment of the method according to the invention, in which the film layer has elevations and the openings of the film layer are produced by subsequent polishing of these elevations, and

7a, 7b, 7c, 7d, 7e, 7e ', 7f, 7g and 7h are schematic cross sections of a further exemplary embodiment in which the film layer can be produced by electrodeposition.

8a, 8a ', 8b, 8c, 8d, 8e, 8e', 8f and 8g are schematic cross sections of a further exemplary embodiment, in which the film layer is also by galvanic

Deposition is generated, and Fig. 9a, 9b, 9c, 9d, 9e, 9f and 9g are schematic cross sections of a

Embodiment similar to Figures la to le, but in which the detached, structured film consists of two different thickness layers of different materials.

5 Detailed description of the invention

For the time being, reference is made to FIGS. 1 a to 1 a, in which the essential steps of the method according to the invention are shown schematically using a first embodiment variant

An Si wafer 1 is used as the substrate, on the top of which a uniformly thin layer of a resist material 2 is applied, for example by spinning (FIG. 1 a). In a lithographic process, the resist 2 is exposed to the structures of the later film, for example by means of optical lithography, electron or ion beam lithography, and the resist material removed by a developer using a positive resist in the exposed areas 3 (FIG. 1b) and a negative resist in the unexposed areas. The required lithographic process is known to those skilled in the art known and is not explained in more detail here The next step involves a typically dry etching (e.g. reactive ion etching) of the substrate through the openings 3 of the resist 2, recesses 4 being formed in the wafer 1, the lateral dimensions of which, depending on the selectivity and isotropy of the etching process, are somewhat larger than the width of the openings 3 of the resist 2, so that an undercut is formed at the interface between the wafer 1 and the resist 2 (FIG. 1 c). In the subsequent step, the top of the resist layer 2 or the wafer 1 is sputtered or sputtered with a layer of a certain material to a certain thickness, for example with a metal such as aluminum, chromium, titanium, copper, nickel, molybdenum, silver, gold or one conductive modification of the carbon The vaporized or sputtered material is directed in a straight line at right angles to the top of the substrate, so that a uniformly thick layer grows on the top of the resist layer 2 and on the bottom of the depressions 4 of the substrate, which layer on the edges of the openings 3 the resist layer 2 is interrupted.

At this point, it should be noted that the formation of an undercut is not absolutely necessary to carry out the invention, since a step with a corresponding height is already sufficient to interrupt the film layer. Furthermore, it has been shown in practice that the openings of the film layer formed during vapor deposition or sputtering have somewhat tapered side walls, so that the cross-sectional area of these openings decreases somewhat with increasing film thickness. This results in a certain shading effect on the edges of the openings in the film layer during vapor deposition which separates the material of the film layer from the material deposited on the substrate. This shading effect also makes it possible in an advantageous manner within the scope of the present method to produce films whose thickness is greater than the height of the openings in the substrate

In the subsequent step, the film layer is provided with a reinforcement on its outer edge (not shown), for example by gluing or bonding a Pyrex, silicon or metal ring, in order to ensure better handling of the film after detachment from the substrate With a small diameter and a comparatively large thickness, for example films with a diameter of less than 5 cm and a thickness of more than 5 μm, such a reinforcement is usually not required, since such films are usually sufficiently stable for handling Material can be applied to the outer edge of the film, for example by chemical or galvanic deposition, as well as by vapor deposition or sputtering In the next step of the method, the resist layer 2 is removed, for example dissolved in acetone, in order to be able to detach the film layer 5 from the substrate 1. The film is usually already ready for use after detachment from the substrate (FIG. 1e), and can optionally also be further treated, for example surface-coated or doped.

In the following, reference is made to FIGS. 2a to 2d, in which a further possible embodiment variant of the method according to the invention is described. In this embodiment variant of the method, a flat, flat substrate in the form of a silicon wafer 101 with a resist layer 102 on the top is also provided. The thickness of this layer 102 is somewhat larger than the desired thickness of the film to be produced.

However, the resist layer 102 is a special resist, namely a positive resist, which has been changed by the so-called image-reversal technique or can be changed so that it acts as a negative resist. Techniques of this type are known to the person skilled in the art and, inter alia, by S.A. MacDonald et. al. in Kodak Microelectronics Seminar, San Diego, 1982 under the title "The Production of a Negative Image in a Positive Photoresist" or by E. Alling and C. Stauffer in Proceedings SPIE, Vol. 539, Advances in Resist Technology and Processing II, Mar. 11-12, 1985 pl94 under the title "Image Reversal Process of Positive Resist".

A major advantage of the image reversal technique is that the wall inclinations of the openings in the resist layer can be influenced in a targeted manner, so that, inter alia, conical openings 103 can also be produced, the cross section of which increases in the direction of the substrate (FIG. 2b).

At this point it should be noted that an effect comparable to the image reversal effect can be achieved by an electron beam recorder if the resist layer has a certain thickness, since the electrons are scattered more laterally with increasing thickness when penetrating into the resist layer. Resist layers for electron beam lithography are therefore usually made particularly thin in order to avoid such lateral scattering, the so-called proximity effect. The envelope of the electron path ends relevant for exposure of a correspondingly thicker resist forms an essentially drop-shaped surface, so that the lateral spread of this exposure initially increases with increasing depth. Similar to the image reversal technique, after developing the resist thus openings with at least partially inclined side walls are formed

This arrangement 101, 102, 103 of FIG. 2b is now vaporized or sputtered in the manner described above with reference to FIG. 1d, so that a uniformly thick layer 105 is deposited on the top of the layers 101, 102, which is on the edges of the openings 103 is interrupted The part of this vapor-deposited or sputtered layer deposited over the resist layer 102 again forms the structured film layer 105, which is optionally provided with a reinforcing ring or frame in the subsequent steps and is detached from the substrate by dissolving or etching away the resist 102 ( Fig 2d)

If the portion of the vapor-deposited or sputtered layer 105 remaining on the upper side of the substrate 101 can be selectively etched away, there is possibly the possibility that the substrate can be reused for further film production by the method according to the invention

In a variant of this method, as in the exemplary embodiment shown in FIGS. 1 a-1, etching of recesses in the substrate can additionally be provided, in particular in order to be able to produce foils whose thickness should be substantially greater than that of the resist layer.

With reference to the exemplary embodiments according to FIGS. 3a-3g and 4a-4g, two embodiment variants of the method according to the invention are explained, in which essentially a conventional photomask is used as the starting point of the production method, which consists of a flat quartz plate 201, 301, on which one thin chrome layer 207, 307 is applied, which is already structured by means of a lithographic process in such a way that the structures of the film to be produced are transparent to visible or UV light (FIGS. 3a, 4a)

By masking the chrome layer 207, depressions 204 are etched into the quartz plate 201 in the first variant, for example by means of reactive ion etching (FIG. 3b), after which a separating layer 202 is applied to the top of this structure, which is applied to the openings of the chrome Layer 207 or the recesses 204 of the quartz plate 201 is interrupted. Such a separating layer 202 can be, for example, an Nb vapor deposition layer, which is vapor-deposited or galvanically deposited at a right angle to the upper side of the structure (FIG. 3c) The film layer 205, for example an Mo layer, is then applied to the Nb separating layer 202, this Mo layer 205 being produced in such a way that the film layer 205 on the edges of the depressions 204 or the openings of the chrome layer 207 and the like Nb separating layer 202 is interrupted, as a result of which the structures of the chrome layer 207 of the photomask are transferred as openings 206 to the Mo layer 205 during the production of the film layer 205 (FIG. 3d)

In the subsequent work step (FIG. 3e), the created structure is attached with the film layer 205 to a suitable mask frame 210, for example by bonding, after which the Nb separating layer can be removed by a selective etching process in order to remove the film 205 from the photo mask 201, 207 to separate (FIG. 3f) FIG. 3g shows the mask produced by the method according to the invention in its ready-to-use state

In the second variant, shown in FIGS. 4a to 4g, a layer of a photoresist 302 is applied to the top of the photomask 301, 307, for example by spinning on a 2-3 μm thick layer (FIG. 4b). The photoresist 302 is removed from the bottom of the quartz substrate 301 is exposed through the structures of the Cr layer 307, for example by means of short-wave UV light, and developed (FIG. 4c), so that the structures of the photomask 301, 307 are transferred as openings 303 to the resist layer 302

The film layer is then applied to the resist layer 302, which will later be used as a separating layer, in such a way that interruptions of the film layer 305 in the form of openings 306 are formed at the edges of the openings 303 of the resist layer 302, for example by vertical vapor deposition or sputtering on of a metallic material or of carbon (Fig. 4d)

In this state, the structure 301, 307, 302, 305 is again attached to a mask frame 310, for example by bonding (FIG. 4e)

The structured film (or the mask) is then detached from the photomask 301, 307 by dissolving the resist layer 302 in a suitable solvent, such as acetone (FIG. 4e). FIG. 4g shows the mask in its ready-to-use state again

As can already be seen from FIGS. 3a-3g and 4a-4g, it may be advisable or necessary in the context of the present invention to arrange a plurality of layers, for example an additional layer, between the film layer and the substrate contrast-enhancing resist layer (CEL Contrast Enhancement Layer) in order to obtain particularly sharp-edged edges of the openings.

As a further example of a multi-layer process, a three-layer process is described in detail with reference to FIGS. 5a to 5f. In an embodiment of this type, a substrate 401 is provided with an uppermost cover layer 408, which is made of a resist material, an intermediate view 409, e.g. a titanium layer, and a base layer 402, which for example also consists of a resist material. In a first step, the opening structure of the film to be produced is lithographically imaged on the cover layer 408 and this structure is developed (FIG. 5b).

Subsequently, the intermediate layer 409 is etched through a suitable, as possible anisotropic etching process through the openings 403 of the cover layer 402, e.g. by a reactive ion etching process (Fig. 5c). After this step, the cover layer 408 is removed and the base layer 402 is etched through the openings of the intermediate layer 409 up to the top of the substrate 401, this etching process not being completely anisotropic if possible. Due to the peculiarity of this etching process, the walls of the openings 403 in the base layer 402 are somewhat inclined with respect to the normal, so that an undercut is formed at the interface between the base layer 402 and the intermediate layer 409 (FIG. 5d).

At this point it should be mentioned that it is often desirable to form barrel-shaped side walls instead of the inclined side walls, which also form a suitable undercut. Such openings are produced using a so-called barrel technique, which is known to the person skilled in the art and is therefore not explained in more detail here. One advantage of the barreling technique is that the intermediate layer has no overhanging sections at the edges of the openings and is therefore mechanically more stable.

The arrangement 401, 403, 402, 409 thus created is then vaporized or sputtered again with a suitable material, so that a film layer 405 forms on the upper side of the intermediate layer 409, the openings 406 of which are essentially identical to the openings of the intermediate view 409. If necessary, a reinforcement is again applied to the outer edge of the film layer in the manner described above.

The film is detached from the substrate by etching or dissolving the base layer 408 and / or the intermediate layer 409. However, if desired, only the base layer 408 is etched away and the intermediate layer 409 as a part of the film is detached from it together with the substrate 401, so that the intermediate layer is an integral part of the film after vapor deposition or sputtering

In the aforementioned case, it would also be possible to select the same material for the intermediate layer as for the film to be produced, so that the intermediate layer can no longer be distinguished from the film layer. If the thickness of the intermediate layer also already corresponds to the desired thickness of the film to be produced, it can be said later Evaporation or sputtering of this intermediate layer can be dispensed with at all. With this production variant, other isotropic layer production techniques could also be used, e.g. LPCVD or chemical or electrochemical processes. The production of openings in the base layer is also not necessary with this particular variant, since that subsequent vapor deposition or sputtering is completely eliminated

The methods described so far with reference to the figures are comparable in some steps to a technique known in semiconductor production, which is referred to as lift-off patterning or lift-off metallization. It is therefore understandable that in the context of the present invention, all of them This known lift-off method used steps and materials can be used. Among other things, a method of this type is described in detail, for example, in US 4,204,009 (Feng et al) or in US 4,218,532 (Dunkelberger). A detailed description of the lift-off method can also be found in LJ Fried et al in IBM J Res Devel 26, May 82 P 362 entitled "A VLSI Bipolar Metallization Design with 3-Level Wiring and Array Solder Connections

FIGS. 6a to 6g show a further embodiment for the method according to the invention, in which a silicon wafer substrate 501 is used. Elevations 511 are formed on the surface of the substrate 501 at those points at which the film to be produced should have openings (FIG. 6a), the cross-section of which decreases with increasing distance from the top of the substrate, for example conical or pyramid-shaped elevations. A uniformly thick, uninterrupted layer 502 is applied over the top of the substrate 501 with the tapered elevations 51 1 Separating layer is used Due to the elevations 511, the separating layer 502 has similar elevations 512, which are automatically aligned with the elevations 51 1, but whose lateral dimensions are larger by a certain amount than that of the elevations 51 1 (FIG. 6) In the subsequent process step, the film layer 505 is applied over the separating layer, which in this exemplary embodiment is preferably a metal layer (FIG. 6c). The film layer 505 now also forms elevations 513, which are aligned with the elevations 51 1, but have a correspondingly larger lateral dimension Making the desired openings in the film layer 505, the surface of the film layer is polished to remove the bumps 513 until the film layer has breaks instead of the bumps 513 which form the openings 506 of the film to be produced. Usually, the top of the film layer is polished until a single flat surface is formed, the film layer located between the elevations being only slightly removed (FIG. 6d)

The method just described with reference to FIGS. 6a to 6d has similarities to a method for producing so-called FED screens (field emitting displays), in which a silicon wafer is used as the substrate, the elevations made of a semiconducting or conductive material are produced, the separating layer is made of a dielectric material, for example SiO 2 or SiN, and the film layer is a metal layer

To produce a mask, as can be seen in FIG. 6e, the top of the structure 501, 502, 505 is attached to a frame 510 with the film layer 505, which facilitates the later handling of the mask film. The film is again removed by removing the separating layer 502 from detached from the substrate 501 (FIG. 6f) If necessary, the elevations 511 can also be removed at the same time. FIG. 6g shows the mask in its ready-to-use state

The exemplary embodiment described in FIGS. 7a-7h uses a so-called three-layer technique as the starting point of the method, in which three layers are applied to the top of the substrate 601, namely a base layer 602 (for example 1.5 μm AZ1350J, FIG. 7a), one above thin, electrically conductive layer 609, for example made of titanium (FIG. 7b) and over it a resist layer 608 (FIG. 7c). The resist layer 608 is structured in such a way that the layer is retained in the form of elevations 611 at those locations at which the openings of the film to be produced are provided. This can be done, for example, by exposing a negative resist to the structure of the film or by exposing a positive resist to the negative structure of the film and subsequently developing the resist, or by exposing a positive resist to the structure and subsequent image reversal development ( Fig 7d) On top of this arrangement 601, 602, 609, 611, a film layer 605 is now electrodeposited on the conductive layer 709, which, due to the non-conductive resist material, only separates between the elevations 61 1 and is therefore interrupted by the elevations 611 (FIG. 7e) For certain applications, it may be desirable to reinforce the film layer in the less structured areas, in which case the steps shown in FIGS. 7c to 7f are carried out again (FIG. 7e) after completion of the film layer 605, which may be in the areas 610 is reinforced, a mask frame 612 is attached, for example bonded (FIG. 7f), then the elevations 61 1 are removed by a suitable means, for example ashes in oxygen plasma, in order to expose the openings 606 of the film layer (FIG. 7g). An advantage of this Design variant is, inter alia, that the inclination and nature of the side walls of the openings dur ch selection and appropriate treatment of a suitable resist can be precisely specified. Furthermore, no elevated temperatures advantageously occur during the electrodeposition, so that the film layer does not have to be exposed to thermal stresses at any time during its production

If the intermediate layer 609 is selectively detachable from the electrodeposited layer, the film layer 605 can be detached from the substrate by removing this intermediate layer, which in this case is the separating layer. If this is not the case, the intermediate layer 609 becomes through the openings 606 the film layer 605 is etched (for example with Ar plasma) in order to also produce corresponding openings in this layer (FIG. 7e), after which the film can be detached from the substrate by dissolving the base layer 602, which in this case forms the separating layer (FIG 7h)

If necessary, it is also possible, in an alternative partial variant, first to detach the film layer 605 together with the unstructured intermediate layer 609 from the substrate and then to etch the intermediate layer 609 through the openings 606 in the film layer 605. A slower detachment process will be expected since the detachment the film layer can only take place over the lateral edges of the structure and not through the openings. In contrast, the film layer is mechanically more stable during the detaching process, so that damage to the structures is reliably avoided in this process

FIGS. 8a to 8g show a further exemplary embodiment in which the film layer is electrodeposited. First (FIG. 8a), a substrate 701 with a first, unstructured base resist layer 702 is provided. The resist can be, for example, a bare exposed, negative resist which is used in approx. 125 ° C, or e.g. an AZ1350J, which was also conditioned at approx. 125 ° C. In the first case, an intermediate layer 7021, for example “spin-on-glass”, which was cured at 120 ° C., is applied to the base resist 702 (FIG. 8a ¹ ) further resist layer 708 applied, for example NOVA-2071 by spinning (FIG. 8b). According to FIG. 8c, the layer 708 is structured in such a way that the remaining elevations 711 correspond to the holes in the film to be produced. According to FIG. 8d, a thin, electrically conductive layer 709, 7091 (eg Ti), and then by contacting the layer 709 in the areas between the elevations, a metal (eg Ni) layer 705 is grown (FIG. 8e) Structured areas 710 can be reinforced by repeating the steps shown in FIGS. 8b, 8c, 8d (FIG. 8e '). After attaching a reinforcement frame 712 (FIG. 8f), the base resi st layer 702 and optionally the intermediate layer 7021 removed, so that a film with openings 706 is formed (FIG. 8g)

FIGS. 9a to 9g schematically show how the inventive method can be used to produce an opening provided with an opening which is provided on one side with a thin layer of a different material. According to FIG. 9a, one with a resist 802 (e.g. positive Resist NOVA-2041, Hoechst) provided substrate 801 and the resist 802 is structured by means of a lithographic process, so that the openings 811 correspond to the later openings of the film. Through these openings, the underlying substrate (for example a Si wafer) is etched with an undercut ( e.g. by means of reactive ion etching), and the depressions 8111 (FIG. 9b) are formed. Two chemically different layers 804, 805 are then deposited in succession (FIGS. 9c, 9d), which layers, for example, have a relatively thin Ti layer (804) and can be a thicker graphite layer (805) or a relatively thin SiÜ2 layer (804) and a thicker Si layer (805) Before removing the resist layer 802 (FIG. 9f), the entire arrangement can be connected to a reinforcing frame 812 (FIG. 9e). The film shown in FIG. 9f now consists of the two layers 804 and 805. FIG. 9g shows that it is at This embodiment variant does not mind if the openings 806 of the thicker layer 805, due to the growth of the thicker layer 805, for example in a conventional vapor deposition system, have a cross-section 807 which is to be tapered upwards by vertical etching (e.g. reactive ion beam etching) underneath Using the layer 804 as a masking layer, the areas protruding beyond the edges of this masking layer are etched away, so that in the end the walls of the edges of the openings become vertical 6. Description of an example:

In the example described below, a film production of the type according to the invention is explained in detail using the example of a mask for lithographic applications, the production of which basically makes use of the embodiment according to FIGS.

A DX-561 resist (Hoechst) with a thickness of approximately 1.5 μm is applied to an Si wafer with a diameter of 100 mm by spinning. This resist is structured using an electron beam recorder and subsequent development. Alternatively, a NOVA-2071 resist is applied with a thickness of 1.5 μm, and the structures are structured by means of optical lithography (laser writer or optical wafer stepper exposure).

In the next step, the top side of the Si wafer exposed through the openings of the resist is etched with .CF4 / θ2 plasma for a time of about 25 minutes, so that depressions are formed which are shown schematically in FIG. 1c. The depth of the recesses is approx. 2 μm and the lateral undercut is approx. 0.1 μm.

The structure thus created is coated in a vapor deposition chamber with Ag to a thickness of approximately 2 μm, this layer being interrupted at the edges of the openings in the resist, as is shown schematically in FIG. 1d.

The size of the openings in this film is approximately 0.5 to 10 μm, the opening density within the structured area of the mask being up to 45%.

A metal ring is glued to the edges of the mask layer for easier handling, e.g. using an epoxy resin.

After the adhesive has hardened, the wafer with the mask layer and the reinforcement ring is immersed in acetone for a few minutes in order to dissolve the resist layer and thus be able to lift the finished mask off the substrate.

Finally, it should be noted that the above description of some possible design variants is in no way restrictive. In particular, it is permissible within the scope of the present disclosure to combine method steps or method sequences of various exemplary embodiments with one another as desired in order to arrive at further exemplary embodiments of the present invention. The reference to Techniques of semiconductor manufacturing technology are not to be regarded as a limitation, but should only be used to indicate that some process steps can be implemented with little effort using known techniques. In the context of the present invention, however, all conceivable material combinations and process sequences are permissible, which enable film production according to claim 1. In particular, all materials that can be produced in layers, including metal, semiconductor or insulator layers or combinations of such layers, and all known layer production techniques can be used for film production of the type according to the invention.

The use of the mask produced by means of the method according to the invention is not restricted to the uses mentioned. All conceivable uses of such a mask are encompassed within the scope of the present invention. Furthermore, the present invention is fundamentally not tied to specific film dimensions, such as length, width, diameter or thickness, or to specific opening structures. However, the method according to the invention can be implemented particularly advantageously in the areas mentioned at the beginning.

Claims

EXPECTATIONS

1. A method for producing a structured film, the structures of which are formed by a plurality of openings, the method comprising the following steps:

a) providing a flat, flat substrate with one or more thin layers on the upper side, the material of at least one of these thin layers being chemically different from that of the substrate, b) producing a film forming or belonging to it with a plurality of openings structured layer on the top of the arrangement consisting of the substrate and at least one thin layer, the material of the film layer chemically differing from that of at least one underlying thin layer, c) detaching the structured film from the substrate by removing the between the film layer and layers located on the substrate.

2. The method according to claim 1, characterized in that the film is at least partially provided with a stiffening frame in the region of its edge before detaching from the substrate, e.g. by gluing or bonding to a frame or by growing or depositing a layer of material along the edge to enable safe handling of the film after it has been removed.

3. The method according to any one of claims 1 or 2, characterized in that step b) of producing the structured layer forming the film comprises the following steps: b) j structuring the top, thin layer by means of a lithographic process, b) 2 application of the layer forming the film on top of the structured thin layer or of the substrate, this film layer being produced in such a way that it is interrupted at the edges of the structures of the uppermost thin layer and these interruptions subsequently result in the edges of the openings in the Form a film.

18 SPARE BLADES (RULE 26)

4. The method according to any one of claims 1 or 2, characterized in that the

Step b) of the manufacturer of the structured layer forming the film comprises the following steps: b) j application of the layer forming the film on top of a thin, unstructured layer, b) 2 application of a further thin layer and structuring of this layer by means of a lithographic Method, b) 3 etching openings in the layer forming the film through the openings of the structured, top layer.

5. The method according to claim 3, characterized in that the structures of the uppermost thin layer are formed by openings of this layer which correspond to the openings of the film to be produced.

6. The method according to claim 3, characterized in that the structures of the uppermost thin layer are formed by elevations which correspond to the openings of the film to be produced.

7. The method according to claim 6, characterized in that the application of the layer forming the film is carried out by electrodeposition of a material on the top of a thin, conductive layer which is arranged directly below or between the elevations, the material of the elevations being electrical is not conductive.

8. The method according to claim 7, characterized in that the thin, conductive layer is first applied to a substrate provided with at least one unstructured layer, then another electrically non-conductive layer is applied and structured, and the layer forming the film by electrodeposition is produced on the top of the thin, conductive layer.

9. The method according to claim 7, characterized in that first the uppermost, elec¬ trically non-conductive, thin layer is structured, then a thin, conductive layer is applied to the top of the arrangement thus formed, and the layer forming the film by galvanic Deposition is produced on the top of the thin, conductive layer located between the elevations of the structured layer.

19

REPLACEMENT BUTT (RULE 26)

10. The method according to claim 5, characterized in that the application of the layer forming the film is carried out by vapor deposition or sputtering of the structured, thin layer or the substrate.

11. The method according to any one of claims 10 or 11, characterized in that the evaporated or sputtered material particles are moved perpendicular to the top of the thin layer or the substrate, so that the vapor-deposited or sputtered film layer on the edges of the openings of the structured , thin layer is interrupted.

12. The method according to claim 10, characterized in that the structures of the vapor-deposited or sputtered film layer are formed by interruptions at an undercut of an underlying thin layer or the substrate.

13. The method according to claim 12, characterized in that the undercut by etching openings with substantially constant cross sections in the structured thin layer to an underlying thin layer or to the top of the substrate and by subsequent selective etching of the underlying thin layer or of the substrate is formed through the openings of the structured thin layer.

14. The method according to claim 12, characterized in that the undercut by forming openings with a cross-sectional area increasing at least in sections in the direction of the substrate in the structured thin layer on the top of the substrate, e.g. is formed by means of electron beam lithography or by means of optical lithography using the image reversal technique.

15. The method according to 1 or 2, characterized in that step b) of producing the structured layer forming the film comprises the following steps: b) j applying the layer forming the film to the top of a structured thin layer, the structures of the thin layer beforehand either

Elevations of this layer or an underlying layer or the

Substrate are formed and the applied film layer has essentially no interruptions, b) 2 Removing the section of the film layer located above the elevations in such a way that the film layer is interrupted in the region of the elevations and these breaks subsequently form the edges of the openings in the film.

16. The method according to claim 15, characterized in that the portion of the foam layer located above the elevations is removed by means of this foam layer.

17. The method according to any one of claims 1 to 16, characterized in that a silicon wafer, e.g. a wafer, or a glass or quartz plate is used.

18. The method according to any one of claims 1 to 16, characterized in that the at least one thin layer on the top of the substrate is a polymer, e.g. is a photoresist.

19. The method according to any one of claims 1 to 16, characterized in that the structured film made of a conductive material, e.g. a metal, a semiconductor material or a conductive modification of the carbon is produced by vapor deposition, sputtering or, if appropriate, by galvanic or chemical deposition.

20. The method according to claims 17 and 18, characterized in that the substrate provided with the at least one thin layer on the top of a prefabricated mask blank, e.g. is a photo mask blank.

21. Use of a structured film produced by the method according to one of claims 2 to 20 as a mask or a sieve.

22. Use according to claim 21, characterized in that the structured film as a stencil mask for lithography by means of electromagnetic radiation, such as e.g. UV or X-ray ultrathography, or for lithography using corpuscular rays, such as Electron or ion beam ultrasound, as well as being used as a Fresnel lens for projection urography.

23. Use according to claim 21, characterized in that the structured film is used as a mask for ion implantation, for ion beam etching, as a vapor deposition mask or as a mask for the treatment of a substrate by means of directed atomic rays or molecular beams.