WO2001025720A1

WO2001025720A1 - Method for preparing probes for scanning probe microscopy

Info

Publication number: WO2001025720A1
Application number: PCT/EP1999/007525
Authority: WO
Inventors: Rainer Kassing; Egbert Oesterschulze
Original assignee: Rainer Kassing; Egbert Oesterschulze
Priority date: 1999-10-07
Filing date: 1999-10-07
Publication date: 2001-04-12

Abstract

The invention relates to a method for preparing probes for scanning probe microscopy, in particular cantilever probes (10) comprising tips (12) and a flexible beam (14) whereby a two-dimensional planar cantilever geometry (16) is reproduced on a three-dimensional structured substrate (18). The free end of the cantilever probe (10) is shaped, relative to the flexible beam (14), like an angled tip (12) (figure 1).

Description

Name: Process for the production of probes for scanning probe microscopy

description

The invention relates to a method for producing cantilever beams which are clamped on one side and have a tip integrated at the end and a holder element for mechanical handling - hereinafter referred to as a cantilever probe - for use as a probe in a scanning probe microscope.

Various known manufacturing techniques have become established in the manufacture of cantilever beams with integrated tips for use in the scanning probe microscope - which are referred to below as cantilever probes. The best-known uses the different methods, such as the etching techniques used in microsystems technology, to produce a monolithic (one-piece) cantilever probe from fully crystalline semiconductor material such as silicon or gallium arsenide [1]. However, it is desirable to also have metallic cantilevers or those made of dielectric layers available. This is achieved by coating the monocrystalline cantilevers with the material of interest [2]. The finite thickness of the film rounds off the tip radius and at the same time produces a probe that is thermally sensitive due to the bimetal effect. However, this is undesirable for the pure topography mapping of a surface in an atomic force microscope.

The impression technique [3,4,5,6,7,8,9] offers a way out of this problem. For this purpose, the complete cantilever (including the tip) is etched into a substrate as a negative mold and the cantilever is then molded using this mold. The principle of such a manufacturing process is shown schematically in Fig. 3. The schematic manufacturing process of Cantilever probes with the aid of the impression technique are characterized by the following steps: According to FIG. 3a, the shape for the tip is transferred into the substrate by lithography and etching and, in the present exemplary embodiment, has the shape of an inverse pyramid which is obtained by anisotropic etching in silicon. According to FIG. 3b, the mold for the cantilever is also produced in a similar step. According to FIG. 3c, the cantilever material is deposited into the mold, for example as a thin film. FIG. 3d finally shows the cantilever membrane that has been produced in this way and is etched free. In order to obtain a sharp tip, the so-called inverse pyramid has so far been used almost exclusively as the shape that is obtained when anisotropically etching Si, for example, with KOH [3]. FIG. 4 schematically shows the production of anisotropically etched pyramid-shaped holes in, for example, Si wafers. The geometry of the opening is illustrated in a cross-sectional view in FIG. 4a. Figure 4b illustrates that with square windows in the deposited layer there are exact peaks as the common intersection of all four (111) walls, while according to Figure 4c with a deviation of a side length by the value Δ the shape of the inverse tip is the geometry of the shape Cutting length Δ results, which is limited by the four (111) walls. This well-defined shape (see Fig. 4 a) and b)) is limited by the four (111) walls of the silicon. However, an exactly square window must be etched in a mask layer for their production. Only if the window is exactly square, do all (111) planes intersect at one point, which means that (theoretically) there is a real point-like tip when molding (Fig. 4 b)). A small

Deviation Δ of a side length from the square shape automatically results in a cutting edge of length Δ as a tip shape, since it is no longer possible for all four planes to intersect in a single point (Fig. 4 c)). The cutting shape can also change

to reach. As a result, there are always different edge lengths in the x and y directions and thus, as the intersection of the four surfaces, not a point but a line segment. Typical sizes of this line segment and thus the size of the cutting edge of the molded tip are usually in the range of about 10-50 nm and are therefore unsuitable for some applications in a scanning probe microscope.

There are also other problems. As can already be seen in Fig. 3c), the molded tip is always hidden in the substrate and must therefore be etched free. However, this has consequences for the mechanical handling of the cantilever sensor. The entire sensor, as shown in Fig. 3d), has thicknesses of typically 2-10μm with a length of quite 1-3mm. If the entire probe consisted only of this thin layer, its low mechanical stability would lead to the destruction of the layer if it was picked up with tweezers. For this reason, a solid holder element is usually applied to the holder area of the cantilever membrane. In principle, it can be made from any material and have a wide variety of geometries. The probe holder thus has sufficient stability and there are also no problems with regard to the angle of attack of the sensor to the sample surface, as illustrated in Fig. 5. FIG. 5 shows the use of a cantilever for scanning probe microscopy. In the case of the cantilever probe without a holding structure according to FIG. 5a, it can be placed on the sample surface up to an angle without impairment. However, if the probe is tilted further, the cantilever itself, but not the tip of the cantilever, touches the sample surface. As FIG. 5b shows, the usable angular range is not narrowed if a holder element is mounted on the top of the cantilever. However, if the holder element is etched from the substrate side of the cantilever wafer, it is located on the underside of the cantilever the range of the angle deteriorates drastically. This deterioration can go so far that the tip of the cantilever can no longer touch the sample surface and a cantilever designed in this way is therefore completely unsuitable for scanning probe microscopy. One could of course try to integrate the holder element into the wafer carrying the cantilever by deep etching; however, the lithography for the tip (square in the etch stop layer) would then have to be carried out in an approximately 100 μm deep trough. However, this is not possible due to the optical diffraction on the optical lithography mask and must therefore be excluded. Furthermore, the holder element then prevents the tip from making a suitable angle to the sample surface (see Fig. 5b)). The possibility of direct writing with electron beam lithography is also possible, but uneconomical.

If polycrystalline materials are deposited - an important representative is polycrystalline diamond - another problem arises. Since the visible growth surface of the diamond layer is usually very rough, an optical measurement of the cantilever deflection with the triangulation technique (beam deflection technique) is almost impossible due to the strong optical scattering on the back of the cantilever and therefore the sensor cannot be used in the scanning probe microscope.

It is also very important for the use of cantilever probes in the scanning probe microscope that the tip can be positioned on the sample surface using optical observation devices. With the usual cantilever probes, however, the tip is below the cantilever and is therefore not visually accessible. A solution is given by Toda [11]. For this purpose, it etches trough-shaped depressions in an SOI wafer substrate and applies a thick photoresist layer in the through Parallel projection the cantilever structure is transferred. However, this photoresist structure is only used as an etching mask for a plasma etching process in order to obtain Si cantilevers with an integrated Si tip from the substrate, the height of which, however, extends over the entire depth of the tub [11]. This manufacturing principle is significantly improved according to the invention in that layers which are deposited before or after are structured by the parallel projection of the mask. If Toda et al. \ Were limited to cantilevers made from the material of the SOI wafer, almost all materials can be used with the method described below. The tip no longer takes up the full height, but only has the thickness of the layer to be structured.

In contrast, the invention has for its object to avoid the disadvantages of the known methods and to provide a method for producing an improved probe for scanning probe microscopy.

This object is achieved in the method for the production of probes for scanning probe microscopy, in particular cantilever probes with a tip and a bending beam, in that a two-dimensional planar cantilever geometry is imaged on a three-dimensionally structured substrate, the free end of the cantilever probe being an angled tip with respect to the bending beam is trained.

The new method for producing probes for scanning probe microscopy is based on the transfer of a two-dimensional mask structure, which defines the geometry of the probe, to a structured substrate, so that a three-dimensional cantilever structure is obtained. The probe material can be chosen arbitrarily: such as dielectrics (silicon nitride, silicon oxide etc.), hard materials (Diamond, cubic boron nitride, titanium nitride etc.), metals, semiconductors, polymers, etc.

The method is used to manufacture new types of cantilever probes for scanning probe microscopy. It avoids some of the disadvantages of the probes previously produced, for example, by taking an impression:

The smooth interface between the substrate and the deposited layer can be used for the optical triangulation measurement of the mechanical deflection of the cantilever in the scanning probe microscope. So far, one has been restricted to the possibly highly scattering surface of the growth surface of this layer, which did not allow a triangulation measurement in reflection. In particular, it offers the possibility of using polycrystalline deposited materials with rough growth surfaces (e.g. polycrystalline diamond).

The new process allows the production of cantilever probes with a free-standing tip. This allows the tip to be checked optically in the scanning probe microscope for the purpose of positioning. This is usually not possible with conventional molded tips on cantilevers or those obtained by under-etching masking layers, since the bending beam optically shadows the tip.

It avoids tips, the apex of which may not be completely filled and filled during the impression, as a multi-surface shape for the impression of the tip (previously the so-called inverse pyramid, which is created by the four (111) walls during the anisotropic etching of Si ) is replaced by a single surface. It avoids the formation of cutting edges on the apex of the tips, which usually result from the above-mentioned impression of inverse pyramids. The reason for this is the lithography for pyramid production, since an accuracy of usually 10-50nm is only achieved.

It requires the use of only a single substrate, whereas previously two substrates were usually required in the impression technique in order to work out the cantilever geometry and the holder element via etching processes, in order then to connect the cantilever to the holder element by assembly and thus to mechanically stabilize the cantilever to care. Therefore, if single-crystal wafers, such as Si wafers, are used as substrates in the new process, wafers polished on one side are sufficient, since the manufacture of the holder elements on the rough, unpolished side can be carried out without any problems and thus the overall production process can be made even cheaper.

According to a first advantageous embodiment of the invention, the cantilever geometry is imaged on the substrate by optical parallel projections of a mask.

According to another preferred development of the invention, however, there is also the possibility of imaging the cantilever geometry on the substrate by means of a focused particle beam.

It proves to be advantageous that the end tip of the cantilever geometry is defined by two intersecting straight lines.

According to an advantageous embodiment, the surface of the substrate has at least two planes which are arranged at an angle to one another. The cantilever geometry is mapped onto the two levels of the substrate.

The tip of the cantilever geometry is advantageously mapped onto the inclined plane and the rest of the cantilever geometry onto the plane parallel to the cantilever geometry.

However, there is also the possibility of realizing the surface of the substrate by means of a plane and a subsequent curved surface, for example a cylindrical surface or the like, in which case the tip of the cantilever probe is then imaged on the curved surface.

The cantilever geometry, such as the tip, bending beam and holder area, is particularly advantageously imaged on the substrate in a single projection process.

It is particularly advantageous for the holder element to be transferred into or machined out of the substrate by means of a lithography, for example a mask, and an etching process on the preferably essentially flat lower surface of the substrate. This is preferably done in the holder area of the cantilever geometry. As a result of this measure, the separate production of cantilever geometry and holder element, which is otherwise required according to the prior art, with the subsequent structural connection of the two components is avoided.

According to a preferred alternative, the holder area is integrally connected to the holder element.

The etching processes for transferring the cantilever geometry and the holder element into the substrate can advantageously be carried out essentially simultaneously or directly or indirectly one after the other. In any case, the subsequent step of mechanical connection is from Holder element and holder area of the cantilever geometry not required.

The outline of the cantilever geometry, such as the tip, bending beam and holder area, is transferred in a photoresist on a substrate in the form of a thin gap, the gap ending in the front area of the tip or having an interruption. This measure makes it possible to etch an extremely precisely and precisely defined tip of the cantilever.

The tip is formed during the etching process by two etching fronts shearing one above the other. This process has a very significant advantage over the conventional etching process for producing tips, since it is a self-adjusting process. If the two etching fronts overlap to the left and right of the tip in the area of the tip, further etching only leads to the tip being shifted towards the current intersection of the two etching fronts, but nevertheless remaining pointed.

Further objectives, advantages, features and possible uses of the present invention result from the following description of exemplary embodiments with reference to the drawings. All of the described and / or illustrated features, alone or in any meaningful combination, form the subject matter of the present invention, regardless of how they are summarized in the claims or their relationship.

Show it:

Figure la is a schematic representation of a

Embodiment of the invention process

FIG. 1b shows a cantilever structure obtained by the method according to FIG.

Figure lc the cantilever structure of Figure lb in side view,

FIG. 1d shows a schematic illustration of the etching process of the holder element,

FIG. 1 the perspective view of the cantilever structure obtained by the etching processes of FIGS. 1 a and 1 d integrally molded with the holder area,

FIG. 1f the cantilever structure of FIG.

Figures 2a, b, c different embodiments of the

Formation of the recess in the substrate,

FIGS. 3a, b, c, d show a schematic representation of a conventional manufacturing process for cantilever probes using the impression technique,

FIGS. 4a, b, c different embodiments of etched pyramid-shaped holes in Si wafers,

Figures 5a, b, c different embodiments of cantilever probes for scanning probe microscopy and Figure 6a, b a special embodiment of the

Transfer the cantilever geometry to the substrate to create a well-defined tip.

The invention relates to an improved method for producing cantilever probes 10. In particular, this method allows the tip to be observed directly with the aid of observation optics, since the tip 12 is attached to the end of the bending beam 14 and is not shadowed by it. Another important aspect of the new process is the ability to create a well-defined tip by cutting two levels. The intersection of the planes results in a straight line which, however, is inclined with respect to the cantilever and can thus be adjusted to the sample surface in such a way that a point-like contact and thus a point results in the intersection of this straight line with the sample plane. It is assumed that the layer from which the cantilever is to be made has already been deposited on the substrate and then the cantilever is to be formed. If the tapered cantilever tip is then transferred into the layer by means of a lithography and a subsequent etching process, two etching walls limit this cantilever structure laterally. These etching walls intersect at the front at the tip and therefore form a possibly straight line that is inclined with respect to the cantilever. The direction of this straight line and of course the type of curvature, if any, is defined by the type of etching process. If this line is now cut with the sample surface, this only happens at one point, namely the tip. The same applies of course if the cantilever is not etched out of the material, but is deposited in a form. Now it's the side walls of the mold that intersect in a straight line at the top. Any sample materials, such as metals, dielectrics, semiconductors, polymers, etc. can be used for the manufacture of the probe. Only a single substrate is required for this. The overall structure of the tip shape, the bending beam arrangement and the holder structure can be varied in a targeted manner by the substrate topology (in the z direction) and the mask geometry (x and y direction). In other words, the structure of the component to be manufactured in outline (hereinafter referred to as geometry) by the parallel projection of a mask 20 and in the topology by the substrate 18, which was previously structured in depth and which itself is a homogeneous substrate or a substrate 18 can be defined with any layer system. To define the geometry of the component, a focused particle beam (photons, electrons, ions, neutral particles, etc.) can be used instead of the mask 20 to transfer the structure. An important point is that the peak height, in contrast to Toda et al. [11] is only given by the height of a structured layer and therefore does not lead to the undesired deterioration of the mechanical properties (lower resonance frequency due to an additional concentrated mass element).

The basic principle of the new manufacturing process is shown schematically in FIG. According to FIG. 1 a, a cantilever structure, in particular a bending beam with a tip tapering at the end, including the holder structure at the other end, is transferred to the structured substrate by a parallel projection process. The overlap between the cantilever structure on the mask and the side wall defines the height and width of the resulting tip at the end of the cantilever. Figure lb shows the cantilever structure in perspective. The cantilever structure is shown in side view in FIG. 1c. The planar structure of the projection mask defines the geometry of the Microcomponent obtained, that is its outline in the X, Y plane, while the topology of the structured substrate corresponds to its topology in the Z direction. It is based on the fact that a two-dimensional, planar structure, the cantilever geometry 16, which was defined, for example, on a lithography mask, is transferred to an already structured substrate 18 in shadow projection and thus assumes the topology of the substrate 18 and the geometry of the projected mask structure. The principle can therefore be generated very generally for the production of three-dimensional structures by specifying the pre-structured substrate 18 and the planar mask 20 which carries the geometry. Here, in particular, the manufacture of cantilever probes 10 with an integrated tip 12, a bending beam 14 and an integrated holder area 32 is intended, the tip 12 being able to be automatically integrated, for example, at the end (or laterally) of the bending beam 14. Tip 12 and bending beam 14 are thus transmitted through the same projection process. This is a significant advantage over conventional production, since special processes are only required for the manufacture of lace, which are correspondingly complex. Since two non-parallel straight lines 22, 24, which lie in one plane, always intersect at a point, a cantilever tip consisting of a mathematical point can be obtained in a simple manner during the projection. This is already taken into account in Fig. 1 in that the end of the cantilever consists of a tapered tip 12 which is delimited by the two straight lines 22, 24 mentioned above and therefore meet in the point-shaped tip 12. The surface of the substrate 18 has at least two planes 26, 28 which are arranged at an angle to one another, as shown in FIG. 1. The cantilever geometry 16 is mapped onto the two planes 26, 28 of the substrate 18. In particular, the tip 12 of the cantilever geometry 16 is on the inclined plane 28 and the rest of the cantilever geometry 16, like bending beam 14 and holder area 32 projected onto plane 26 parallel to cantilever geometry 16.

FIGS. 1d, e and f show how the actual holder element 34 is etched on the underside of the substrate 18. The holder element 34 is transferred into this by means of a lithography, for example with the rectangular mask 36, and an etching process on the underside of the substrate. Thus, an indication of the holder element 34 to the holder region 32 of the cantilever probe 10 is already possible during the manufacture of the cantilever. The holder element 34 is integrally formed on the holder region 32 of the cantilever probe 10, so that further steps for connecting the components which are otherwise made in one piece according to the prior art, namely the cantilever probe 10 and holder element 34, can be dispensed with. In this case, the etching processes for the cantilever probe 10 on the surface of the substrate 18 and for the holder element 34 on the lower surface of the substrate 18 can optionally be carried out simultaneously or immediately one after the other.

In addition to the preferred embodiment of providing the substrate with two angled planes 26, 28 (FIGS. 1, 2a), there is also the possibility, as shown for example in FIGS. 2b, c, of the surface of the substrate 18 through a plane 26 and to form at least one curved surface 30, for example a cylindrical surface. The quarter-circular cross section of the curved surface 30 according to FIG. 2b is very advantageous for the use of the corresponding probes in the scanning probe microscope, since the tip 12 of the probe can very easily be brought perpendicular to the surface of the sample to be examined. In certain applications, the curved surface 30 can also be formed by under-etching a side wall of the substrate 18, in which case very sharp edges of the molded structure are then obtained in shadow projection on this under-etched structure OJ

•H

TJ

JH

OJ

S ß

•H

4-J

CO

^• H YH

OJ

JH ß

OJ • H

• H QJ r _** ß— - • fr ß ß 3

QJ N

-P 4Y ß: approx

0 yh

YH QY

4H 4- ⁾

N ß

4-1 D

: <

JH

• H QJ

Q TJ

3

N • H

QJ

CG XI approx

TJ QJ

•H

- TJ ß

-H ".

JH 4-1 rd ß

TJ • H

QJ J ß rß Q)

QJ fr

4-1 co 4-1

0) ß rQ o

JH

QJ 4H

OJ N

TJ 4-1

H

Masking layer occurs) shear away from each other. In the simple case of an isotropic undercut of a masking layer, which serves to remove the functional layer located underneath, these are two approximately semicircular etching fronts that intersect and therefore form a tip.

This method can be implemented in that, when the cantilever geometry 16 is transferred, only the outline 38 of the cantilever, including the holder area 32 in the form of a thin gap 40 (according to FIG. 6a), is transferred into the photoresist, although the outline at the front does not is closed, but remains separated by an interruption 42. If the material is now removed by etching, beginning with the gap that is exposed, the photoresist or a possibly still existing masking layer is undercut on all sides, and finally the two etching fronts 44, 46 and 48, 50 shear, respectively on the right and left in front of the gap 40 the cantilever tip 12 were separated, one above the other. As a result, the inner surface enclosed by areas 44, 46 and 48, 50 in the drawing results as a cantilever / holder structure with the integrated tip. Now the front end of the cantilever has a real geometric tip.

This process has a very significant advantage over the conventional etching process for producing tips, since it is a self-adjusting process. If the two etching fronts overlap, a further etching only leads to the tip being moved to the current intersection of the two etching fronts, but still remaining pointed. This was indicated in Figure 6b by the fact that two etching fronts are shown. The etching fronts 44, 46 represent the point in time at which the two etching fronts 44, 46 are overlapping, the etching fronts 48, 50 occur at a later point in time. The tip as the intersection of the The two etching fronts 48, 50 are still preserved, but have slipped a little downwards relative to the tip of the etching fronts 44, 46, so that at most there is a less high tip on the cantilever. The layer that lies outside the gap is of no further interest, since it does not hinder the definition of the cantilever.

In contrast to Toda et al. which forms the cantilever including the tip from the substrate material, the substrate is not necessarily used here as a bending beam and tip material. However, this opens up a completely new possibility to functionalize the cantilever probe.

Of course, the lithography in the tub will be accompanied by diffraction phenomena, but these can be controlled or reduced well by suitable projection methods (for example X-ray or ion beam lithography). On the other hand, these effects do not necessarily disturb, since this only slightly (but reproducibly identical) changes the shape of each cantilever.

The special features and advantages of the new process can be summarized as follows:

The process for the production of probes for scanning probe microscopy, which consist of a mechanical bending beam with an integrated tip and an integrated holder element - called a cantilever for short - is based on the following principle: The possibility is used by an optical parallel projection of a mask onto an already structured one Produce a three-dimensional structure that takes the outline of the mask and the topology of the substrate. In the case of the cantilever, the end of a plane-parallel cantilever structure is projected onto the side wall of a depression. This creates a cantilever structure whose topology matches the structured substrate and its outline projected mask corresponds (see Fig. 1) and is transferred in the form of a layer.

Instead of the projection mask, focused particle beams can be used to transfer the geometry.

The topology of the component to be manufactured can be influenced by the type of etching process (see also Fig. 2). In the case of pure anisotropic etching, for example in the case of (100) Si surfaces, the typical (111) oriented side walls and thus the corresponding inclination of the tip result, as is shown schematically in Fig. 2a). Isotropic etching results in a quarter-circular cross-section of the side wall (Fig. 2b)). This is very advantageous for use in a scanning probe microscope, since the tip can very easily be brought perpendicular to the surface of the sample to be examined. It is also possible to use an underetched structure of the side wall according to FIG. 2c), in which case very sharp edges of the molded structure can then be obtained in shadow projection on this underetched structure. The structure of the probe is at best limited by what is technologically feasible.

The structure is transferred into a layer or a layer system on a substrate. Each of these layers can also be structured in any way and also does not need to be homogeneous in its thickness, that is to say, for example, that the bending beam and the tip can be made of different materials by transferring a depression of varying thickness into a layer system. Layers of any material, such as metals, dielectrics, semiconductors, polymers, etc., can be used as the material to be deposited. This makes it possible to integrate any layered components of electronic, magnetic and optical structure into the structure to be produced, such as metal / metal thermocouples, semiconductor / metal components (Schottky diodes), light-sensitive photodiodes, optical waveguides, microwave lines etc.

The geometry of the cantilever (the geometry is understood here as that in the (x, y) plane (see also Fig. 1)) can be changed as desired by the projected geometry, such as a single cantilever, a V-shaped cantilever two legs, etc. Several cantilevers can also be produced on the same side wall of a depression. Furthermore, cantilever structures can also be produced simultaneously on the side walls opposite and also on the side. In order to increase the moment of inertia of the cantilever, further depressions can also be transferred into the shape by etching processes before the material is deposited; This means that the cross-section can be changed from a plane-parallel plate to a more complex structure (for example, V-shaped depressions can be obtained by anisotropic etching, which have a significantly increased area moment of inertia.)

The geometrical shape of the tip (the geometry is understood here as that in the (x, y) plane (see also Fig. 1)) can be modified as desired. For example, it can have a pointed, circular, triangular or other type of geometry. It is also possible to integrate two or more tips instead of a single one.

Polycrystalline material (for example polycrystalline diamond, which can be doped and is therefore electrically conductive) can also be used for the impression. After the structure has been etched free, the smooth growth side, that is to say the side which is in contact with the substrate, is on the side facing away from the tip. This means that a laser beam (s) can also be reflected on this smooth surface without strong optical scattering and thus an optical measuring technique (such as the beam deflection method or the Interferometry) can be used to measure the bending beam deflection. In addition, there is the advantage that a possible intermediate layer between the substrate and the deposited film, which does not have the quality of the solid material, is on the side facing away from the tip, that is to say the material of the tip is of better quality.

The shape of the cantilever probe is transferred into a layer that is used as a template for the local diffusion of dopants into the substrate. For example, in the case of a silicon substrate, the cantilever zone could be doped on board, which makes it possible to implement an etching stop. It is known that, for example, doped silicon structures with a high boron doping only have a very low etching rate compared to KOH and are therefore used to produce etching stop layers. This could be used to produce cantilevers of homogeneous thickness (via the dopant profile of the dopant) and in particular of such very small thickness. The doping can be done with any method (thermal diffusion, ion implantation, etc.). However, by diffusion and reaction with oxygen in accordance with the LOCOS process (and its modifications), the structure can be oxidized in a targeted manner, for example in order to produce thin cantilevers from oxidized materials.

A local dopant is introduced into the structure or a local change in the substrate material at the location of the structure, for example as an etching stop layer, is used to etch the substrate from the cantilever side. Instead of the structure, the area outside the structure could also be changed in order to specifically vary the properties of the material there with the aim of making the structure easier. Electrically conductive, molded layers are used as the starting layer for the galvanic deposition of other layers or layer systems such as metals, polymers, etc. Local doping can also be introduced into the starting layer.

LIST OF REFERENCE NUMBERS

10 - Cantilee probe

12 - tip

14 - bending beam

16 - Cantilever geometry

18 - substrate

20 - mask

22 - Straight

24 - straight

26 - level

28 - level

30 - curved surface 32 - holder area

34 - holder element

36 - Mask for holder element definition 8 - Outline 0 - Gap 2 - Interruption 4 - Etching front at a first time 6 - Etching front at a first time 8 - Etching front at a second, later time 0 - Etching front at a second, later time

bibliography

[I] US 5, 789, 666 A.

[2] T. Trenkler, T. Hantschel, R. Stephenson, P. De Wolf, W. Vandervorst, L. Hellemans, A. Malave, D. Büchel, E. Oesterschulze, W. Kulisch, P. Niedermann, T. Sulzbach, and O. Ohlson. Evaluating probes for 'electrical' atomic force microscopy. Paper submitted to J. Vac. Be. Technol. , 1998.

[3] US 4,307,507 A.

[4] US 4,312,117 A ..

[5] US 4,916,002 A.

[6] US 5,066,358 A.

[7] US 5,221,415 A.

[8] US 5,399232 A.

[9] EP 0 786 642 AI.

[10] US 5,116,462 A.

[II] US 5,386,720 A.

[12] US 5,883,387 A.

[13] E. Oesterschulze, W. Scholz, C. Mihalcea, D. Albert, B. Sobisch, and W. Kulisch. Fabrication of Small Diamond Tips for Scanning Probe Microscopy Application, Appl. Phys. Lett., 70: 435-437, 1996.

[14] W. Kulisch, A. Malave, G. Lippold, C. Mihalcea, and E. Oesterschulze. Fabrication of Integrated Diamond Cantilevers with Tips for SPM Applications, Diamond. Relat. Mater., 6: 906-911, 1997.

[15] W. Scholz, D. Albert, A. Malave, S. Werner, Ch. Mihalcea, W. Kulisch, and E. Oesterschulze. Fabrication of Monolithic Diamond Probes for Scanning Probe Microscopy Applications, In SPIE proeeedings volume 3009-09, pages 61-71, 1997.

[16] C. Mihalcea, W. Scholz, A. Malave, D. Albert, W. Kulisch, and E. Oesterschulze. Fabrication of monolithic diamond probes for scanning probe microscopy applications, Appl. Phys. A}, 66: 87-90, 1998. [17] W. Kulisch, D. Albert, A. Malave, W. Scholz, C. Mihalcea, S. Werner, and E. Oesterschulze. Fabrication of diamond sensors for SPM applications. Paper presented at the 8th European Conference on Diamond, Diamond-Like and Related Material (DIAMOND '97), Edinburgh, 1997.

[18] T. Hantschel, T. Trenkler, W. Vandervorst, A. Malave, D. B chel, W. Kulisch, and E. Oesterschulze. Tip-on-tip: a novel AFM tip configuration for the electrical characterization of semiconductor devices. Paper presented at the International Conference Mircro- and Nanoengineering 09 (MNE98), Leuven, Belgium; submitted to Microelectronic Engineering, 1998.

Claims

claims

1. A method for producing probes for scanning probe microscopy, in particular cantilever probe (10) with tip (12) and bending beam (14), characterized in that a two-dimensional planar cantilever geometry (16) is mapped on a three-dimensionally structured substrate (18), wherein the free end of the cantilever probe (10) is designed as a tip (12) angled with respect to the bending beam (14).

2. The method according to claim 1, characterized in that the cantilever geometry (16) by optical parallel projection of a mask (20) on the substrate (18), preferably on a surface, is mapped.

3. The method according to claim 1, characterized in that the cantilever geometry (16) is imaged by means of a focused particle beam on the substrate (20).

4. The method according to any one of the preceding claims, characterized in that the end tip (12) of the cantilever geometry (16) by two intersecting curves, in particular straight lines (22, 24) is defined.

5. The method according to any one of the preceding claims, characterized in that the surface of the substrate (18) has at least two planes (26, 28) which are arranged at an angle to one another.

6. The method according to any one of the preceding claims, characterized in that the cantilever geometry (16) on the two planes (26, 28) of the substrate (18) is imaged.

7. The method according to any one of the preceding claims, characterized in that the tip (12) of the cantilever geometry (16) on the inclined plane (28) and the rest of the cantilever geometry (16) is mapped onto the plane (26) parallel to the cantilever geometry (16).

Method according to one of the preceding claims 1 to 4, characterized in that the surface of the substrate (18) is formed by a plane (26) and at least one subsequent curved surface (30), for example a cylindrical surface or the like.

Method according to one of the preceding claims, characterized in that the cantilever geometry (16), such as tip (12), bending beam (14) and holder area (32), is imaged on the substrate (18) in a single projection process.

10. The method according to any one of the preceding claims, characterized in that the holder element (34) by means of a lithography, for example a mask (36), and an etching process on the preferably substantially planar lower surface of the substrate (18) into the substrate (18) transferred or worked out from this.

11. The method according to claim 10, characterized in that the holder region (32) and holder element (34) are integrally connected.

12. The method according to claim 10 or claim 11, characterized in that the etching processes for the transmission of the cantilever geometry (16) and the holder element (34) in the substrate (18) substantially simultaneously or immediately be carried out one after the other.

13. The method according to any one of the preceding claims, characterized in that the outline (38) of the

Cantilever geometry (16), such as tip (12), bending beam (14) and holder area (32), are transferred into a photoresist on a substrate (18) in the form of a thin gap (40), the gap (40) ending in the front tip area ,

14. The method according to claim 13, characterized in that the gap (40) in the front region of the tip (12) has an interruption (42).

15. The method according to claim 13 or claim 14, characterized in that the tip (12) is formed during the etching process by two overlapping etching fronts (44, 46 and 48, 50).