Patent Description:
Scanning proximity microscopy or scanning probe microscopy (SPM) systems, such as an atomic force microscopy (AFM) system, a scanning tunneling microscopy (STM) system, a magnetic force microscopy (MFM) system, a spreading resistance microscopy (SSRM) system, operate by scanning the surface of a sample with a probe having a small tip. The probe configuration typically comprises a mounting or holding block to which a cantilever, also known as stylus, is mounted. Attached to this cantilever is a tip which is pointing towards the sample surface when scanning this surface. This tip preferably has a high hardness and low wear. The tip and the holding block are mounted at opposite ends along the length of the cantilever. During the scanning of the surface, the sample is moving relative to the tip either by movement of the sample only, by movement of the tip or by a combined movement of both tip and sample.

Such a probe can be used for measuring the topography of the sample's surface by sliding the probe over the surface and monitoring the position of the tip at each point along the scan line. In this application the conductive properties of the tip are less relevant and dielectric or semiconductor materials can be used to manufacture the tip. The probe can also be used for determining the electrical properties of a sample, for example the resistance and electrical carrier profile of a semiconductor sample. For these applications at least the tip of the probe must be conductive.

Another application which makes use of a probe configuration is nanoprobing. A nanoprobing system typically comprises a scanning electron microscopy (SEM) system for viewing the surface of the sample to be probed or scanned, nanomanipulators (also often referred to as nanoprober) comprising the probe configuration for contacting the surface and parameter analyzer(s) for performing electrical measurements of the sample via the nanomanipulators. So far, only manually etched tungsten probes are available as probe tips for the nanoprobing system. The tip sharpness is limited to about <NUM>-<NUM>. Such tungsten probes are easily damaged while repeatedly contacting the sample surface and they show rapid wear and have a low lifetime. They are not hard enough for probing semiconductor materials such as Si and Ge.

For SPM applications there is a strong need for highly conductive, sharp and strong tips which may overcome the disadvantages of prior art tips.

For nanoprobing applications there is a strong need for microfabricated tips instead of manually fabricated tips. Moreover alternative materials besides tungsten should be usable as tungsten tips suffer from oxidation and are not hard enough for probing on Si and Ge. The tips should also be sharper to improve the attainable resolution in the nanoprobing measurements.

<NPL> and <CIT> disclose a probe tip in silicon on which a diamond layer is deposited.

<CIT> and<NPL> disclose a method of manufacturing a probe in diamond by deposition into a mold.

<CIT> discloses a method of manufacturing a probe tip in polycrystalline carbon by deposition into a mold.

<CIT> discloses a method for manufacturing a probe configuration wherein a mold is produced by wet anisotropic etching through a rectangular or ellipse-shaped mask. The resulting probe may be a diamond probe tip.

There is thus a need for a probe configuration which allows for characterizing a sample with (ultra) high resolution with high yield, which can be manufactured cost-efficiently and where the tip has a high hardness, high conductivity and thus a high dynamic range detectability.

It is an aim of the present invention to present a probe configuration comprising a tip being highly conductive (as such being able to characterize a high dynamic range of doping concentrations), being sharp (as such being able to characterize samples with a high resolution) and being strong and wear-resistant (as such preventing breaking or wearing off during scanning and enhancing the life time of a probe).

It is an aim of the present invention to present a method for fabricating such a probe configuration.

The invention is related to a method for producing a probe configuration, as disclosed in the appended claims.

A probe configuration for characterizing a sample, the probe configuration directly obtained by the method according to the invention is disclosed, the probe configuration comprising a holder; a cantilever having a base end attached to said holder and a distal end extending away from the holder; a tip being arranged near the distal end of the cantilever, the tip having a shape with a base plane, a side surface extending from the base plane up to an apex; wherein the tip comprises a diamond body and a diamond layer covering at least an apex region, the apex region being a part of the side surface of the solid diamond body that starts from and includes the apex.

The diamond body is a molded diamond body.

The diamond body is a solid diamond body or a partially solid diamond body. A partially solid diamond body is a hollow solid diamond body.

The diamond layer is completely covering the solid diamond body.

The diamond layer is also covering part of the cantilever.

The diamond body and/or the diamond layer comprise any of microcrystalline diamond, nanocrystalline diamond, ultra-nanocrystalline diamond or diamond-like-carbon (DLC).

The tip is pyramidal shaped or knife-shaped or tapered shape or in-plane shaped.

The diamond layer and/or the diamond body is conductive.

The conductive diamond layer and/or the diamond body is boron-doped.

Diamond nanocrystals protrude from the diamond layer.

The diamond layer has a thickness between <NUM> and <NUM>. According to the claimed invention, a method for fabricating a probe configuration is disclosed, the method comprising providing a substrate, the substrate having a top side and a back side being opposite to the top side; forming a tip of the probe configuration by first forming from a first diamond layer a diamond body having an apex region and thereafter providing a second diamond layer on the nucleation side at least on the apex region of the diamond body, forming a diamond body comprising etching a mold in the substrate; depositing the first diamond layer on the substrate thereby filling the mold with the first diamond layer and forming the diamond body having an apex in the mold; patterning the first diamond layer around the mold; underetching the first diamond layer at the apex region thereby releasing the diamond body from the substrate. According to an embodiment of the method according to the invention, an array of tips is formed in the substrate.

According to embodiments of the claimed invention wherein forming the diamond body and providing the second diamond layer is done from the top side of the substrate.

According to embodiments of the claimed invention, wherein forming the diamond body is done from the top side of the substrate and wherein providing the second diamond layer is done from the back side of the substrate.

According to embodiments of the claimed invention, the method further comprises attaching a cantilever structure to the tip after providing the second diamond layer. The tip is attached at one side of the cantilever structure.

According to embodiments of the claimed invention, attaching the cantilever structure comprises manufacturing the cantilever structure separately and attaching the cantilever structure to the tip by gluing or soldering.

According to embodiments of the claimed invention, the method further comprises attaching the cantilever with the tip attached thereto to a holder. The cantilever with the tip attached thereto at one side of the cantilever structure is attached to the holder with the other opposite side of the cantilever structure. The tip is attached to the cantilever structure at its distal end whereas the holder is attached to the cantilever at its base end.

Outside the scope of the claims, a method for fabricating a probe configuration comprising a cantilever and connected to the cantilever, a tip with a diamond body is disclosed, the method comprising providing a substrate having a top side and a back side being opposite to the top side; etching a mold in the substrate from the top side of the substrate; depositing a first diamond layer on and from the top side of the substrate thereby filling the mold with the first diamond layer thereby forming a diamond body having an apex region; patterning the first diamond layer from the top side of the substrate; underetching the first diamond layer at the apex region from the back side of the substrate thereby releasing the diamond body; providing from the back side of the substrate a second diamond layer at least on the apex region of the solid diamond body.

This method further comprises attaching a cantilever structure to the tip after providing the second diamond layer. The tip is attached at one side of the cantilever structure.

Attaching the cantilever structure comprises manufacturing the cantilever structure separately and attaching the cantilever structure to the tip by gluing or soldering.

The method further comprises attaching the cantilever with the tip attached thereto to a holder. The cantilever with the tip attached thereto at one side of the cantilever structure is attached to the holder with the other opposite side of the cantilever structure. The tip is attached to the cantilever structure at its distal end whereas the holder is attached to the cantilever at its base end.

An array of multiple tips is provided each of the tips comprising a diamond body and a diamond layer at least partially covering the diamond body at the apex region.

It is an advantage of embodiments of the present invention that the probe configuration manufactured by the claimed invention has both a high hardness and a high conductivity. Thereby the probe configuration of the present invention has the advantage that a high dynamic range of dopant concentrations in the sample can be detected when using the probe configuration for electrical characterization. A range in between 5e14 and 1e21/cm<NUM> may be detected.

It is an advantage of embodiments of the present invention that the probe configuration manufactured by the claimed invention has a high mechanical stability such that the tip cannot break/wear off. Thereby the life-time of the probe for measuring at very high resolution (in the nanometer range) is enhanced and thus performance is maximized and costs are reduced.

It is an advantage of embodiments of the present invention that the probe configuration manufactured by the claimed invention allows for nanoprobing of hard semiconductor materials (which is not possible with prior art tungsten nanoprobe needles). It is not manually fabricated like tungsten wire tips but is made by microfabrication techniques which allow for cost-efficient mass production.

It is an advantage of embodiments of the present invention that the probe configuration manufactured by the claimed invention allows for improved resolution measurements since the probe configuration provides a sharp tip with extending diamond crystals making the contact with the sample to be characterized. A resolution in the sub-nanometer (≤ <NUM>) may be achieved.

The terms so used are interchangeable under appropriate circumstances and the embodiments of the invention described herein can operate in other orientations than described or illustrated herein.

The term "comprising", used in the claims, should not be interpreted as being restricted to the elements or steps listed thereafter; it does not exclude other elements or steps. It needs to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising A and B" should not be limited to devices consisting only of components A and B, rather with respect to the present invention, the only enumerated components of the device are A and B, and further the claim should be interpreted as including equivalents of those components.

When referring to a probe configuration (or shortly said 'a probe'), a tip and a cantilever, the following is meant. A 'probe configuration' (or shortly 'probe') typically comprises a 'mounting block' or 'holding block' to which a 'cantilever', also known as stylus, is mounted. Attached to this cantilever is a 'tip', which is pointing towards the sample surface when scanning this surface. The tip and the holding block are typically mounted at opposite ends along the length of the cantilever. During the scanning of the surface, the sample is moving relative to the tip either by movement of the sample only, by movement of the tip or by a combined movement of both tip and sample.

<FIG> shows an example of an AFM probe (configuration) <NUM> as known in the art, comprising a cantilever <NUM> with a tip <NUM> arranged at the distal end <NUM> of the cantilever <NUM>, the cantilever <NUM> being attached at its base end <NUM> to a holder <NUM>. The tip <NUM> shown in <FIG> has a pyramidal shape.

Sharp, strong and highly conductive diamond tips are crucial components for carrying out carrier profiling of semiconducting devices on the nanometer and sub-nanometer scale. The leading technique is scanning spreading resistance microscopy (SSRM). SSRM is based on atomic force microscopy (AFM) whereby the tip is scanning across the sample surface, and whereby the local spreading resistance underneath the tip is being measured. An ultra-high pressure in the GPa range is needed for SSRM measurements on Si and Ge structures to obtain a good electrical contact by establishing a so-called beta-tin phase underneath the tip. Only diamond can withstand these high pressures and therefore SSRM measurements rely on the availability of conductive diamond tips.

Nowadays two types of probes comprising diamond tips are widely used: coated diamond probes (CDP) with diamond coated silicon tip (CDT) and full diamond probes (FDP) with full diamond tip (FDT).

A coated diamond probe configuration (CDP) comprises a Si cantilever and a diamond coated silicon tip, which is a Si tip attached to the Si cantilever, the Si tip having a thin diamond layer coated over it. For electrical measurements a conductive diamond coating is used. Diamond coated silicon tips are for example disclosed in an article from <NPL>).

<FIG> are secondary electron microscopy (SEM) images of a prior art coated diamond probe configuration <NUM>.

<FIG> illustrate a prior art coated diamond probe configuration <NUM> comprising a Si tip <NUM> which is coated by a thin (~<NUM>-<NUM>) diamond layer <NUM> which is for electrical applications (such as for example SSRM doped with boron). The diamond coated Si tip is mounted at an end of a cantilever <NUM>.

<FIG> illustrates a major problem with such a CDT. When used in SSRM, due to the high lateral scanning forces resulting from high vertical tip pressures, which are in the order of GPa, onto the substrate surface, they are breaking off/shearing off close to the apex region. Basically all SSRM measurements carried out with a CDT are done with a broken tip apex resulting in a blunt tip: using a diamond crystal sticking out from the sidewall of the broken tip. This tip configuration is highly undesirable as the blunt tip is reducing the attainable resolution in SSRM and causes measurement artefacts, such as for example multiple tip images.

A full diamond probe configuration (FDP) comprises a metal, Si or diamond cantilever with a solid diamond pyramidal tip (FDT) attached thereto. Full diamond probes and their manufacturing method are for example disclosed in an article of <NPL>).

<FIG> illustrates a SEM image of a prior art full diamond probe configuration <NUM>. The full diamond probe <NUM> comprises a full diamond tip <NUM> which is a solid diamond pyramid obtained by a molding process whereby an inverted pyramid is first anisotropically etched into Si. This mold is then filled up with diamond and finally the Si mold is etched away. The pyramidal diamond tip <NUM> is doped with boron for electrical applications such as for example SSRM. The tip <NUM> is fixed to an end of a cantilever <NUM>. The cantilever is preferably a metal cantilever, such as for example a Ni cantilever but can also be Si or diamond.

Most advanced FDTs have a spatial resolution of <NUM> which is higher than the spatial resolution of CDTs being limited due to their coating, and are fabricated on wafer scale using standard <NUM>-mm Si wafer technology. Despite the ultra-high resolution of FDT, CDT however show a higher electrical conductivity. This is because CDT use the last grown (outer and higher quality) diamond layer whereas FDT use the first grown diamond layer. Recent research from <NPL>) has shown that this first grown diamond layer suffers from poorer quality such as a lower level of electrically active boron and SiC/SiOxCx-related interfacial layers in the initial growth phase.

<FIG> shows typical (SSRM) calibration curves taken on Si doping staircase structures using FDT (top curve) and CDT (bottom curve). <FIG> shows typical (SSRM) calibration curves taken on Ge doping staircase structures using FDT (top curve) and CDT (bottom curve). The resistance is plotted as a function of the measured sample resistivity which is linked to the doping concentration of the sample calibration curve. The FDT curves are positioned above the CDT curves which indicates their higher sharpness and thus higher resolution. The more shallow slope of the FDT compared to CDT in the highly conductive region (left side of the curves) indicates its lower electrical conductivity. In <FIG> the curves are also shown as obtained from simulations (open dots) and are in good agreement with the experimental results (full dots). This is also presented by <NPL>).

Therefore, a tip configuration is highly desired for scanning probe microscopy (SPM) which results in both sharp, strong and highly conductive tips.

Besides the need for SPM applications, there is also a need for sharp and hard tips in nanoprobing. Nanoprobing commonly refers to a technique whereby a micromanipulator, often also referred to as nanomanipulator, is used to manipluate, measure and pick-and-place small structures on micrometer and nanometer scale. Nanoprobing uses commonly electro-chemically etched tungsten wire needle tips which are prone to oxidation and are not hard enough for measuring on semiconductors like Si and Ge.

The present invention discloses a method for manufacturing a probe configuration.

<FIG> illustrate schematically a tip <NUM> of a probe configuration manufactured according to embodiments of the present invention. The tip <NUM> of the probe configuration comprises a diamond body <NUM> and a diamond film or thin diamond layer <NUM> covering at least the apex region <NUM> of the tip <NUM> as shown schematically in <FIG>. According to embodiments the diamond film <NUM> may also completely cover the diamond body <NUM> as is schematically shown in <FIG>.

Whereas <FIG> only show the tip <NUM> part of the probe configuration manufactured according to embodiments of the invention, the probe configuration <NUM> as a whole manufactured according to embodiments is more schematically shown in <FIG>. The figure distinguishes a holder <NUM> with a cantilever <NUM> having a base end (not shown) attached to the holder <NUM> and having a distal end <NUM> extending away from the holder <NUM> and a tip <NUM> being arranged near the distal end <NUM> of the cantilever <NUM>, the tip <NUM> having a pyramidal shape with four side surfaces <NUM> and a base plane <NUM>, the side surfaces extending from the base plane <NUM> and adjoining at the apex <NUM>. The tip <NUM> comprises a diamond body <NUM> covered (in <FIG> completely) with a thin diamond layer <NUM>. In <FIG>, the diamond body is not really visible as it is completely covered by the diamond layer <NUM>. The diamond body <NUM>, made by a molding technique, is coated with a thin diamond layer or film <NUM>. This results in a tip with superior mechanical stability (overcoming tip breaking), high electrical conductivity (due to the excellent conductivity properties of the diamond layer <NUM>) and high spatial resolution (due to sharp diamond nanocrystals protruding from the apex <NUM>). The probe manufactured according to this invention is also referred to as overcoated diamond probe (ODP) comprising an overcoated diamond tip (ODT).

The diamond body <NUM> may be a solid diamond body (<FIG>) or the diamond body may be a partially solid diamond body or hollow diamond body (<FIG>) wherein the diamond shape comprises a hollow inner region <NUM> and a solid outer region.

For use as a scanning probe, the ODT is preferably integrated into a cantilever structure, comprising a cantilever <NUM> with the ODT attached near the distal end of the cantilever <NUM>. The cantilever <NUM> can be made of metal such as for example nickel, but also other materials may be used such as for example silicon, silicon nitride, diamond and other materials.

The diamond body <NUM> of the tip <NUM> is made by a molding process with the nucleation side or interfacial side of the diamond material, for the second diamond layer <NUM>, at the apex side. The nucleation side or interfacial side of the diamond is the side which is in contact with the mold surface. It is the side where the diamond growth nucleates from the nanometer-size diamond seed crystals. The nucleation side of the diamond body <NUM> is smooth (due to the molding process) and grain boundaries of the diamond crystals are present.

The nucleation side of the diamond body <NUM> is then covered at least partially at the apex region <NUM> or completely with a diamond layer or film <NUM>. The overcoated diamond tip (ODT) manufactured according to embodiments of the present invention uses the last grown diamond layer which is of higher quality compared to the nucleation side. The diamond coated film <NUM> has sharp diamond crystals extending which is beneficial for tip resolution.

The thickness of the diamond layer <NUM> may be in the range of about <NUM> to about <NUM>, more preferably the diamond layer is in the range between about <NUM> and about <NUM>.

For electrical SPM applications such as SSRM, both the diamond body <NUM> and the diamond layer <NUM> are preferably doped, e.g. by boron because of its high electrical conductivity, by phosphorus or by other diamond dopants. The diamond body <NUM> may also be undoped whereas the diamond layer <NUM> may be doped.

<FIG> shows different shapes possible for a tip of a probe configuration manufactured according to embodiments of the present invention. The tip is preferably pyramidal shaped (<FIG>) obtainable by anisotropic etching to form a mold in a (<NUM>)-Si substrate, and thereafter filling the mold with diamond material to form the diamond body <NUM>, releasing/underetching said diamond body and depositing the diamond layer <NUM> on at least a part of said diamond body (described in more detail further in this description). Alternatively, knife-edge shaped tips (<FIG>) are possible as well by etching a mold in a (<NUM>)-Si substrate and similarly forming a diamond body and diamond layer formed thereon. Another possibility are three-sided pyramids (<FIG>) as obtained from anisotropic etching of a mold in (<NUM>)-oriented Si substrates. The mold might also be defined into other materials than Si and use dry etching approaches such as reactive ion etching (RIE) for obtaining differently shaped molds. This results in differently shaped tips like high-aspect ratio tips with a tapered shape (f<FIG>). In-plane tips as typically used for nanoprobing might be used as well (<FIG>). The in-plane tips equally have a base plane <NUM> and side surfaces <NUM> extending from the base plane up to the apex <NUM>.

<FIG> shows a schematic overview for a fabrication method for a probe configuration according to embodiments of the present invention.

First a substrate <NUM> is provided. The substrate <NUM> may be a (<NUM>)-Si wafer. A top side <NUM> and a back side <NUM> of the substrate <NUM> is defined. For patterning the substrate, a hardmask <NUM> is provided on the top side <NUM> of the substrate <NUM>. The hardmask <NUM> may for example comprise SiO<NUM> or Si<NUM>N<NUM> (<FIG>). The substrate <NUM> is patterned using the hardmask <NUM> thereby creating a mold <NUM> in the substrate <NUM>. The mold is thus created by etching from the top side <NUM> of the substrate <NUM>, in other words, the mold <NUM> is created in the top side <NUM> of the substrate <NUM>. The mold <NUM> has a shape which will define the final shape of the tip. In <FIG> for example an inverted pyramid-shaped mold is etched into the (<NUM>)-Si wafer. For example a wet etching may be used for providing the mold <NUM>, such as KOH etching. The mold may be further shaped for a sharper apex by a low temperature oxidation.

After providing the mold <NUM>, a first diamond layer <NUM> is provided on the structure (at the top side <NUM>). Before providing the first diamond layer <NUM> the hardmask <NUM> may be removed. The diamond material of the first diamond layer <NUM> is thus also provided in the mold <NUM>. Providing the first diamond layer <NUM> is done using deposition techniques such as for example chemical vapour deposition (CVD) (<FIG>).

Next, another patterned hardmask layer <NUM> (not shown in <FIG> but shown later in <FIG>) is provided on the first diamond layer <NUM> and the first diamond layer <NUM> is etched by a dry etching technique such as for example reactive ion etching (RIE) (<FIG>) thereby forming a diamond body of the tip and creating a cavity <NUM> around the first diamond layer of the mold <NUM>. This is done from the top side <NUM> of the substrate. The Si-substrate is not etched in this step.

The diamond body may be a solid diamond body (<FIG>) completely consisting of the first diamond layer material or the diamond body may be a partially solid diamond body or hollow diamond body (<FIG>) wherein the diamond shape comprises a hollow inner region <NUM> and a solid outer region, the solid outer region consisting of the first diamond layer material.

In a following step a releasing etching step is performed to release the diamond body <NUM> (made of the first diamond layer <NUM>) of the tip from the substrate <NUM> at the apex region <NUM> (<FIG>), by underetching from the top side <NUM> of the substrate <NUM>. This underetching and releasing etching step is preferably an anisotropic etching step for example wet etching such as KOH etching. The diamond body <NUM> with pyramidal shape is thereby completely released at the apex region <NUM> (<FIG>) leaving a recessed part <NUM> in the substrate <NUM>. In the embodiment shown in <FIG>, this is done from the top side <NUM>, however as will be explained further, the releasing step may also be done from the back side <NUM> of the substrate.

Thereafter a second diamond layer <NUM> is provided on the structure. The second diamond layer <NUM> may be provided using deposition techniques such as CVD. The second diamond layer <NUM> is rather thin with a thickness in the range of <NUM>-<NUM>, more preferably in a range of <NUM>-<NUM>. The second diamond layer <NUM> is thus also formed on top of the diamond body <NUM> on the nucleation side (<FIG>). During this step at least the apex region <NUM> of the diamond body is covered by the thin second diamond layer <NUM>. <FIG> is a schematic example of an embodiment wherein the diamond body <NUM> is completely covered with the second diamond layer <NUM>. The resulting structure is a tip <NUM> consisting of a diamond body <NUM> and covered or coated at least partially at the apex region by a thin diamond layer <NUM>.

As a limit at least one single diamond grain may be placed at the tip apex in the second diamond layer deposition step, as this single diamond grain is sufficient to make a physical and electrical contact with the sample.

Alternatively only a bottom region of the mold <NUM> (which will be the apex region of the tip) is filled with the first diamond layer <NUM>. This may be done by a selective seeding process and growth step. Thereafter the remaining part of the mold is filled with another material such as for example Si<NUM>N<NUM>. The partial diamond body is then etched and released from the substrate. After tip release, the second diamond layer <NUM> is selectively deposited/grown on the apex region of the tip which is the part of the tip consisting of the first diamond layer material.

<FIG> shows microscopy images of a tip configuration <NUM> in top view fabricated according to embodiments as described in <FIG>. <FIG> shows the patterned hardmask <NUM> on top of the first diamond layer <NUM> deposited into a pyramidal mold <NUM>. <FIG> shows the patterned first diamond layer after the hardmask <NUM> has been removed (in accordance with the step as shown in <FIG>). The exposed Si-substrate <NUM> is visible. In this figure the tip is not released yet. <FIG> shows the tip after coating the diamond pyramid onto the nucleation side with the second diamond layer <NUM> (in accordance with the step as shown in <FIG>). The second diamond layer <NUM> preferably has a thickness which is smaller than the thickness of the first diamond layer <NUM>. The first diamond layer <NUM> preferably has a thickness in the range of <NUM> to <NUM>. The second diamond layer <NUM> preferably has a thickness in the range of <NUM> to <NUM>.

The first and/or second diamond layer may comprise microcrystalline diamond (MCD), which has as an advantage to have a superior electrical conductivity. Other types of diamond material such as nanocrystalline diamond (NCD), ultra-nanocrystalline (UNCD) and diamond-like-carbon (DLC) might be used as well.

To complete the method of manufacturing the probe configuration, the tip <NUM> needs to be attached to a cantilever <NUM> and this may be done as schematically shown in <FIG>.

After providing the second diamond layer <NUM> on the tip <NUM> (<FIG>), the recessed part <NUM> of the resulting tip structure (<FIG>) may be filled with a sacrificial layer <NUM> (e.g. by deposition or spinning) and is planarized (for example by chemical mechanical polishing (CMP)) (<FIG>). The sacrificial material <NUM> may be an oxide or a polymer. For example silicon oxide, spin-on-glass or BCB may be used.

A hardmask <NUM> is then used to define a tip area and the first <NUM> and second diamond layer <NUM> are patterned, using an etching step such as RIE (<FIG>). The hardmask <NUM> corresponds at least to the outer circumference of the planarized sacrificial material <NUM>. As a result, part of the first <NUM> and second diamond layer <NUM> surrounding the tip area are removed. After removal of the hardmask <NUM>, the cantilever <NUM> is defined on top of the overcoated tip using another hardmask (not shown) and a deposition step such as for example Ni electroplating for a Ni cantilever (<FIG>). The tip <NUM> is hereby attached to the cantilever <NUM> at one end, whereas the cantilever is patterned at the other end with a so-called cantilever membrane <NUM>, which has a larger width than the cantilever <NUM> beam in order to be able to attach the cantilever to a probe holder. Thereafter the cantilever <NUM> and the overcoated tip (not visible) are underetched (<FIG>) and the cantilever membrane <NUM> structure is peeled off using a needle <NUM> (<FIG>). A probe holder <NUM> is fixed to the cantilever <NUM> via the cantilever membrane <NUM> (<FIG>), and finally the probe configuration is removed from the wafer (<FIG>).

According to embodiments, illustrated in <FIG>, an array <NUM> of overcoated tip structures <NUM> manufactured according to embodiments of the present invention may be fabricated on a substrate (wafer) <NUM> with a high packing density, e.g. about <NUM> to <NUM> structures on a <NUM> wafer. The cantilever <NUM> of the probe fabrication can be fabricated by a separate procedure avoiding more complex and challenging integration procedures. As such, the separate cantilever fabrication <NUM> and the array of overcoated tip structures <NUM> has the advantage of a cost-efficient probe fabrication.

As an example of such a separate procedure, a tip <NUM> as fabricated according to embodiments of the present invention may be attached to a cantilever <NUM> by a bonding process using a gluing step. For example a metal cantilever may be glued with conductive silver epoxy onto a tip <NUM> (<FIG>). This might be done manually or by an automated assembly procedure (e.g. using robotics). The result of this assembly step is a probe configuration <NUM> according to embodiments of the present invention comprising a cantilever <NUM> and a tip <NUM> attached at the end of the cantilever <NUM> (<FIG>). The cantilever <NUM> may be attached to a holder <NUM>.

An alternative method for fabricating the probe configuration is schematically shown in <FIG>. For this manufacturing method the probe configuration is mainly formed from the back side <NUM> of the substrate (wafer), wherein in <FIG> the probe configuration is mainly formed from the top side <NUM> of the substrate (wafer).

First a substrate <NUM> is provided. The substrate <NUM> may be a (<NUM>)-Si wafer. A top side <NUM> and a back side <NUM> of the substrate <NUM> is defined. For patterning the substrate, a hardmask <NUM> is provided on the top side <NUM> of the substrate <NUM>. The hardmask <NUM> may for example comprise SiO<NUM> or Si<NUM>N<NUM> (<FIG>). The substrate <NUM> is patterned using the hardmask <NUM> thereby creating a mold <NUM> in the substrate <NUM> (at the top side <NUM>). The mold has a shape which will define the final shape of the tip. In <FIG> for example an inverted pyramid-shaped mold is etched into the (<NUM>)-Si wafer. For example a wet etching may be done, such as KOH etching. The mold may be further shaped for a sharper apex by a low temperature oxidation.

After providing the mold <NUM>, a first diamond layer <NUM> is provided on the structure from the top side <NUM>. Before providing the first diamond layer <NUM>, the hardmask <NUM> may be removed. The diamond material of the first diamond layer <NUM> is thus also provided in the mold <NUM>. Providing the first diamond layer <NUM> is done using deposition techniques such as for example chemical vapour deposition (CVD) (<FIG>).

Next, another hardmask layer (not shown) is provided on the first diamond layer and the first diamond layer <NUM> is patterned using this hardmask (<FIG>). The first diamond layer <NUM> is thus etched in this patterning step thereby forming the diamond body of the tip. The etching may be done using a dry etching technique such as for example reactive ion etching (RIE). Thereby a diamond body of the tip <NUM> is formed. The diamond body is thus formed from the top side <NUM> of the substrate <NUM>.

The diamond body may be a solid diamond body (<FIG>) completely consisting of the first diamond layer material or the diamond body may be a partially solid diamond body or hollow diamond body (<FIG>) wherein the diamond shape comprises a hollow inner region and a solid outer region, the solid outer region consisting of the first diamond layer material.

In a following step, from the back side <NUM> of the substrate <NUM> a releasing etching step is performed to release the tip <NUM> from the substrate <NUM> at the apex region <NUM> (<FIG>). This releasing etching step is preferably an anisotropic etching step for example wet etching such as KOH etching. The diamond body <NUM> with pyramidal shape is thereby at least partially released at the apex region <NUM> (<FIG>). In this step, the apex region <NUM> of the diamond body is underetched from the back side of the substrate, leaving only said apex region extending from the remaining substrate material (see the small point indicated by the numeral <NUM> and shown enlarged in each of the <FIG>).

Thereafter a second diamond layer <NUM> is provided on the released (i.e. underetched) structure (i.e. on the apex region <NUM>) from the back side <NUM> of the wafer. The second diamond layer <NUM> may be provided using deposition techniques such as CVD. The second diamond layer <NUM> is rather thin with a thickness in the range of <NUM>-<NUM>, more preferably in a range of <NUM>-<NUM>. The second diamond layer <NUM> is thus also formed on top of the diamond body <NUM> on the nucleation side (<FIG>). During this step at least the apex region <NUM> of the diamond body <NUM> is covered by the thin second diamond layer <NUM>.

The resulting structure is then integrated onto a cantilever structure <NUM> (with a cantilever membrane <NUM>) by patterning and deposition (for example sputtering and electroplating) (<FIG>) and the cantilever <NUM> and overcoated tip structure <NUM> are then released (for example by wet etching) (<FIG>). The cantilever membrane <NUM> is then peeled off (<FIG>) using a needle <NUM> and a probe holder <NUM> is fixed to the cantilever membrane <NUM>(<FIG>), and finally the probe configuration <NUM> is removed from the substrate <NUM> (<FIG>). The resulting structure at the end of the cantilever <NUM> is a tip <NUM> consisting of a diamond body <NUM> and covered at least partially at the apex region by a thin diamond layer <NUM>.

Alternatively only a bottom region (which will be the apex region of the tip) is filled with the first diamond layer <NUM>. This may be done by a selective seeding process and growth step. Thereafter the remaining part of the mold is filled with another material such as for example Si<NUM>N<NUM>. The partial diamond body is then etched and released from the substrate. After tip release the second diamond layer <NUM> is selectively deposited/grown on the apex region of the tip from the backside of the wafer (which is part of the tip consisting of the first diamond layer material).

The cantilever <NUM> of the probe configuration <NUM> preferably comprises a metal such as for example Ni. However also other materials may be used such as for example silicon, diamond, silicon oxide, silicon nitride.

The method for fabricating a probe configuration according to embodiments as described in <FIG> has the advantage over the method for fabricating a probe configuration according to embodiments as described in <FIG> that a smaller base width may be used (about a minimum base width of <NUM>×<NUM><NUM> compared to <NUM>×<NUM>-<NUM>×<NUM><NUM>).

<FIG> shows a SEM image of an overcoated tip <NUM> manufactured according to embodiments of the present invention (<FIG>). The base plane of the tip is <NUM>×<NUM><NUM>. The inset (<FIG>) shows a more zoomed SEM image of the apex region <NUM> of the overcoated tip <NUM>. Sharp protruding diamond crystals of the diamond coating <NUM> are clearly visible at the surface of the apex region.

<FIG> shows a SEM image of an array <NUM> of overcoated tips as manufactured according to embodiments of the present invention. Three different base widths of the tip are manufactured: bottom three rows have a base width of <NUM>, middle three rows have a base width of <NUM> and the upper three rows have a base width of <NUM>. <FIG> show an zoomed SEM image of one of the overcoated tips at the apex region <NUM>, analogue to the SEM image of <FIG>. Again the sharp diamond crystals of the diamond layer <NUM> are clearly visible.

The overcoated tips as shown in <FIG> were manufactured using a first diamond layer with a thickness of about <NUM>. The second diamond layer has a thickness of about <NUM>. In different experiments, the diamond thickness of the second diamond film was varied between <NUM> and <NUM>.

<FIG> shows SEM images of fabricated probe configurations according to embodiments of the present invention with a base width of <NUM> (<FIG>), <NUM> (<FIG>), and <NUM> (<FIG>). Top images show a zoomed image of the apex region <NUM> of the tips <NUM> shown in the bottom images. The method according to embodiments as described in <FIG> was used. The diamond crystals of the diamond layer coated on the diamond body are clearly visible.

<FIG> shows SEM images of fabricated probe configurations according to embodiments of the present invention which have a knife-shape (<FIG>) and an in-plane shape (<FIG>). From left to right more zoomed SEM images are shown from the apex region.

<FIG> shows SEM images of fabricated probe configurations according to embodiments of the present invention assembled according to the method as described in <FIG> (i.e. by gluing). A tip-less Ni cantilever <NUM> is used and is bonded onto a pyramidal overcoated tip <NUM> module using silver epoxy <NUM>. <FIG> shows a cantilever <NUM> (with cantilever membrane <NUM> at one end) fabricated separately. In <FIG> the probe configuration is shown wherein the overcoated tip <NUM> is glued to the cantilever using silver epoxy.

<FIG> shows SEM images at three different zoom levels (A, B, C and higher zoom factor from left to right) of fabricated probe configurations (cantilever <NUM> with tip <NUM> glued to it) according to embodiments of the present invention which is scanned in SSRM mode for several hours on a Si substrate sample at GPa pressures. Although Si debris (<NUM>) from scanning can be seen (<FIG>), all diamond nanocrystals <NUM> of the diamond layer <NUM> are still in place (<FIG>).

The Si substrate, which is scanned, comprises Si calibration structures having a staircase doping profile. From SSRM experiments performed with overcoated tips according to embodiments of the present invention, it could be shown clearly that the tips do not suffer from tip breaking. The zoom-in image (<FIG>) illustrates further that there is no visible wear of the nanocrystals in contact during the measurements which emphasizes the high bonding strength of the overcoated crystals onto the first diamond layer.

<FIG> shows a two-dimensional (2D) SSRM image (<FIG>) and its averaged line profile (figure 23B) taken on a special p-type Si staircase calibration structure. The structure involves differently doped Si regions ranging from about <NUM>*<NUM><NUM> to <NUM>*<NUM><NUM> at/cm<NUM>, a <NUM> wide silicon oxide layer and a <NUM> wide Ni silicide layer. The SSRM image clearly shows all doped regions (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>). The oxide peak <NUM> and the silicide region <NUM> are also observed.

<FIG> shows the calibration curves made from a prior art full diamond probe FDT, a prior art diamond coated probe CDT and six different overcoated tips ODT manufactured according to embodiments of the present invention. The calibration curves illustrate the higher dynamic range of the ODT tips compared to CDT and FDT. This can be seen by evaluating the slope of the curves. The FDT tip shows a shallow slope at the highly doped region illustrating its lower conductivity (albeit highest sharpness). The CDT shows a slightly steeper slope than the FDT. The ODT clearly shows the highest dynamic range and a steeper slope in the highly doped regions, which is a clear advantage compared to prior art probes.

<FIG> illustrates that besides the application of overcoated tips in SPM, overcoated tips manufactured according to the invention can also be used for nanoprobing. <FIG> shows an overcoated tip <NUM> manufactured according to embodiments of the present invention glued at the end of a tapered needle structure <NUM>. The tapered needle structure <NUM> which may be seen as the cantilever of the probe configuration is usually a tungsten wire. Thereto at the end of the tungsten wire a tip <NUM> manufactured according to embodiments of the present invention may be attached. <FIG> shows a probe configuration <NUM> with a mounting holder <NUM>, a cantilever structure104, <NUM> and an integrated overcoated in-plane tip <NUM> which is glued to a wire needle <NUM> for mounting to a micromanipulator.

Nanoprobing commonly uses micro manipulators, often also called nanomanipulators, with sharp needle-like tips. These tips are commonly electro-chemically etched tungsten-wire tips. The current invention can also be used for such nanoprobing applications. <FIG> illustrates that for example in-plane ODT attached to the end of a cantilever structure can be used for this or for example a pyramidal ODT can be attached directly to the end of a metal needle, e.g. etched tungsten wire tip (<FIG>). Such ODT structures in nanoprobing allow for measurements which are not possible with common tungsten wire tips, e.g. electrical probing of hard semiconductors like Si and Ge, and the local material removal of hard materials on the nano- and micro-meter scale.

For the fabrication of a pyramidal diamond tip for nanoprobing according to <FIG>, first a substrate is provided. The substrate may be a (<NUM>)-Si wafer. For patterning the top side of the substrate, a hardmask is provided on the top side of the substrate. The hardmask may for example comprise SiO<NUM> or Si<NUM>N<NUM>. The substrate is patterned using the hardmask thereby creating a mold in the substrate. The mold is thus created by etching from the top side of the substrate, in other words, the mold is created in the top side of the substrate. The mold has a shape which will define the final shape of the tip; for example an inverted pyramid-shaped mold is etched into the (<NUM>)-Si wafer. For example a wet etching may be used for providing the mold, such as KOH etching. The mold may be further shaped for a sharper apex by a low temperature oxidation.

After providing the mold, a first diamond layer is provided on the structure (at the top side). Before providing the first diamond layer the hardmask may be removed. The diamond material of the first diamond layer is thus also provided in the mold. Providing the first diamond layer is done using deposition techniques such as for example chemical vapour deposition (CVD).

Next, another patterned hardmask layer is provided on the first diamond layer and the first diamond layer is etched by a dry etching technique such as for example reactive ion etching (RIE) thereby forming a diamond body of the tip and creating a cavity around the first diamond layer of the mold. This is done from the top side of the substrate. The Si-substrate is not etched in this step.

The diamond body may be a solid diamond body completely consisting of the first diamond layer material or the diamond body may be a partially solid diamond body or hollow diamond body wherein the diamond shape comprises a hollow inner region and a solid outer region, the solid outer region consisting of the first diamond layer material.

In a following step a releasing etching step is performed to release the diamond body (made of the first diamond layer) of the tip from the substrate at the apex region by underetching from the top side of the substrate. This underetching and releasing etching step is preferably an anisotropic etching step for example wet etching such as KOH etching. The diamond body with pyramidal shape is thereby completely released at the apex region leaving a recessed part in the substrate.

Thereafter a second diamond layer is provided on the structure. The second diamond layer may be provided using deposition techniques such as CVD. The second diamond layer is rather thin with a thickness in the range of <NUM>-<NUM>, more preferably in a range of <NUM>-<NUM>. The second diamond layer is thus also formed on top of the diamond body on the nucleation side. During this step at least the apex region of the diamond body is covered by the thin second diamond layer. The resulting structure is a tip consisting of a diamond body and covered or coated at least partially at the apex region by a thin diamond layer.

The resulting ODT may be arranged into an array as shown in <FIG>. The ODT is then attached to a tapered metal needle by a gluing step. The resulting ODP shown in <FIG> can then be used in nanoprobing.

For the fabrication of an in-plane diamond tip for nanoprobing according to <FIG>, first a substrate is provided. The substrate may be a (<NUM>)-Si wafer. A first diamond layer is provided on the top side of the substrate. Providing the first diamond layer is done using deposition techniques such as for example chemical vapour deposition (CVD). Next, a patterned hardmask layer defining the shape of an in-plane tip as shown in <FIG> is provided on the first diamond layer and the first diamond layer is etched by a dry etching technique such as for example reactive ion etching (RIE) thereby forming a diamond body of the tip and creating a cavity around the first diamond layer of the in-plane tip. This is done from the top side of the substrate. The Si-substrate is not etched in this step.

In a following step a releasing etching step is performed to release the diamond body (made of the first diamond layer) of the in-plane tip from the substrate, by underetching from the top side of the substrate. This underetching and releasing etching step is preferably an anisotropic etching step for example wet etching such as KOH etching. The diamond body with in-plane tip shape is thereby completely released at the apex region leaving a recessed part in the substrate.

Thereafter a second diamond layer is provided on the structure. The second diamond layer may be provided using deposition techniques such as CVD. The second diamond layer is rather thin with a thickness in the range of <NUM>-<NUM>, more preferably in a range of <NUM>-<NUM>. The second diamond layer is thus also formed on top of the diamond body on the nucleation side. During this step at least the apex region of the diamond body is covered by the thin second diamond layer. The resulting structure is an in-plane tip consisting of a diamond body and covered or coated at least partially at the apex region by a thin diamond layer.

To complete the method of manufacturing the in-plane probe configuration, the in-plane tip needs to be attached to a cantilever. After providing the second diamond layer on the in-plane tip, the recessed part of the resulting in-plane tip structure may be filled with a sacrificial layer (e.g. by deposition or spinning) and is planarized (for example by chemical mechanical polishing (CMP)). The sacrificial material may be an oxide or a polymer. For example silicon oxide, spin-on-glass or BCB may be used.

Claim 1:
Method for fabricating a probe configuration for characterizing a sample comprising the steps of :
• forming a tip (<NUM>) of the probe configuration by first forming from a first diamond layer (<NUM>) a diamond body (<NUM>) having a nucleation side at the apex region (<NUM>) and thereafter providing a second diamond layer (<NUM>) on the nucleation side at least on the apex region of the diamond body, the second diamond layer being conductive;
• attaching a cantilever (<NUM>) to the tip,
• attaching the cantilever (<NUM>) with the tip attached to it, to a holder (<NUM>),
the step of forming a diamond body (<NUM>) from the first diamond layer (<NUM>) comprising :
• providing a substrate (<NUM>), the substrate having a top side (<NUM>) and a back side (<NUM>) being opposite to the top side;
• etching a mold (<NUM>) in the substrate in the top side of the substrate,
• depositing the first diamond layer (<NUM>) on the top side of the substrate thereby filling the mold with the first diamond layer and forming in the mold the diamond body having an apex;
• patterning the first diamond layer (<NUM>) to form the diamond body (<NUM>) around the mold;
• underetching the first diamond layer (<NUM>) at least at the apex region (<NUM>) thereby at least partially releasing the diamond body (<NUM>) from the substrate.