Silicon tip having low mass and high aspect ratio, probe comprising such a silicon tip, microscope comprising such a probe, and method for manufacturing the silicon tip

Abstract

The invention relates to a silicon tip capable of being arranged at one end of a connecting element. The tip comprises a first portion (PT) and a second portion (ZI) arranged between the first portion (PT) and the connecting element, the first portion (PT) having a tetrahedral shape having a triangular section of continuously variable height, the second portion (ZI) having a non-triangular section (SZI), and wherein, at the interface between the first portion (PT) and the second portion (ZI) of the tip (P), the height (HPT) of the triangular section (SPT) of the first portion (PT) is less than a width of the connecting element.

Description

DESCRIPTION Title of the invention: Low mass, high aspect ratio silicon tip, probe comprising such a silicon tip, microscope comprising such a probe, and method of manufacturing said silicon tip. Technical field

[0001] The present invention relates to sensors at the base of atomic force microscopes, and more particularly to sensors comprising tips. Prior art

[0002] An atomic force microscope (AFM) is a type of local probe microscope that overcomes the resolution limitations known for light-based microscopes. It can visualize the surface topography of a sample with lateral resolution of sub-100 nanometers and vertical resolution of sub-1 nanometers. These values ​​cannot be achieved optically due to the limitations of wave diffraction.

[0003] The AFM technique exploits the interaction (attraction / repulsion) between the atoms of the nanometric apex of a tip and the atoms of the surface of a sample.

[0004] The atomic force microscope is a device that allows this principle to be put into practice by scanning the surface of a sample using a very fine tip, positioned at the free end of a flexible micro-lever, which can move in all directions in space. This is achieved by means of piezoelectric ceramics that define an X,Y scan. This is then called an 'XY scan'.

[0005] The principle of the most commonly used device is to measure in real time the deflection angle of the lever, which is considered as a measure of the interaction forces occurring between the tip and the sample. This angle is most often measured by the technique known as optical deflection of a laser beam. In this case, a laser leaves a source, is reflected on the lever, and reaches a 4-quadrant photodiode. When the angle varies under the effect of a tip-surface force, the intensities of the quadrants will vary and we will be able to generate an electrical output proportional to the deflection angle of the lever.

[0006] To obtain a 3-dimensional topography of the surface, the deflection signal serves as input to a lever height control loop.

[0007] The challenges and areas of measurements and images produced by AFM are very diverse: - In the semiconductor industry: roughness measurement, walking measurement (high resolution profilometry in x / y / z); - In biology, measurement of interaction forces, biomolecules, biomaterials, cells and bacteria in vitro / in liquid.

[0008] Various imaging modes based on AFM (electrical, optical, etc.) also make it possible to measure physical properties with a resolution of a few nanometers (optical index, permittivity, electrical charges, etc.).

[0009] It is known to manufacture probes for local probe microscopes from a silicon substrate by microfabrication processes derived from microelectronics and micromechanics.

[0010] There are thus in the prior art two families of manufacturing processes allowing the production of a local tip on a substrate.

[0011] A first method is based on a technology for manufacturing the tip out of plane of the substrate. Such a method is notably described in a first document: "Microfabrication and application of high-aspect-ratio silicon tips, July 2005, Journal of Vaccum Science & Technology B Microlectronics and Nanometer Structures 23(4), by Yaqiang Wang and Daniel W. van der Weide, doi: 10.1116 / 1.1947805".

[0012] A second method is based on a technology for manufacturing the tip in the plane of the substrate. Such a method is notably described in a second document: "RP Ried, HJ Mamin, BD Terris, Long-Sheng Fan and D. Rugar, "6-MHz 2-N / m piezoresistive atomic-force microscope cantilevers with INCISIVE tips," in Journal of Microelectromechanical Systems, vol. 6, no. 4, pp. 294-302, Dec. 1997, doi: 10.1109 / 84.650125".

[0013] This second process is illustrated in particular in Fig. 1 using extracts from a figure taken from the second document. In these extracts, a preform is etched vertically through the entire upper silicon layer of an SOI substrate (for "Silicon On Insulator" in English) until reaching an oxide layer of this substrate. The preform is then encapsulated in an oxide sheath by thermal oxidation and / or oxide deposition. An opening in a protective mask is then made above said preform. Vertical etching allows the oxide to be removed only from the surface of the preform, which leaves an oxide wall around the preform. Anisotropic chemical etching allows preferential etching of silicon planes by revealing said planes after etching.

[0014] The probe obtained by the second method is illustrated in Fig. 2. This probe consists of three parts, namely, a tip (P), a connecting element which is here a lever (C) also called “Cantilever” and a support (S).

[0015] Throughout this document, a connecting element or lever is understood to mean a free-standing element. The lever is configured to deform preferentially in the direction of the tip. The lever also deforms in other directions. The lever has three main dimensions: - a length (Le) corresponding to the distance between a free end and an anchored end; - a width (Wc), the surface of the lever carrying the tip being constituted by the length and the width; - a thickness (te), small in comparison to the width.

[0016] The length of a tip (Lp) is defined between one end of the tip, also called the apex (AP) and the face of the lever carrying the tip.

[0017] The benchmarks are based on the following convention:

[0018] The axis of the lever is mainly along the X axis. The axis is increasing from the anchor of the lever towards the free part.

[0019] The axis of the tip is mainly along Y. The axis is increasing from the base of the tip, at the lever level towards the tip.

[0020] The Z axis is perpendicular to the X axis and the Y axis.

[0021] The user might want to use the probe in an ideal case, in which the tip is vertical above the sample. However, for experimental reasons, given the tip length dimensions available on the market, typically 10 at 15pm, the probe is mounted in the microscope with a cp angle of a few degrees: of the order of 7 to 13°.

[0022] There is therefore a need to improve the manufacturing process of a probe in the plane of a substrate in order to provide a tip with reduced mass, with an adjustable angle and this for large lever widths.

[0023] Statement of the invention

[0024] The present invention aims to at least partially address this need.

[0025] More particularly, the present invention relates to a silicon tip suitable for being arranged at one end of a lever. The tip comprises a first portion and a second portion arranged between said first portion and the lever, said first portion having a tetrahedral shape having a triangular section whose height is continuously variable. The second portion has a non-triangular section and at the interface between the first portion and the second portion of the tip. The height of the triangular section of the first portion is less than a width of the lever. The height of the triangular section of the first portion corresponds to a dimension along a direction parallel to a direction of the width of the lever.

[0026] In an alternative embodiment, the second portion comprises a first portion extending from the lever and a second portion disposed between the first portion and the first portion.

[0027] In an alternative embodiment, the first portion comprises an inclined plane, said inclined plane extending between the lever and the second portion.

[0028] Another object of the invention relates to a probe comprising a support comprising a lever extending from the support, a silicon tip according to the previous object, said silicon tip being arranged at one end of the lever, opposite the support.

[0029] In an alternative embodiment, the lever comprises a main portion connected to the support and a width-reducing portion extending the main portion.

[0030] In an alternative embodiment, the reduction portion comprises a first inclined plane extending from the main portion and a second inclined plane. extending from the first inclined plane to the probe, the inclination of the first inclined plane being different from the inclination of the second inclined plane.

[0031] In an alternative embodiment, the second inclined plane has the same inclination as the inclined plane of the first portion of the second part of the tip.

[0032] In an alternative embodiment, the first part of the tip comprises an inclined plane, said inclined plane having the same inclination as the first inclined plane of the reduction portion.

[0033] Another object of the invention relates to a local probe microscope comprising a probe according to the preceding object.

[0034] Another subject of the invention relates to a method for manufacturing a silicon tip in an SOI substrate, said substrate comprising a lower silicon layer with a thickness of between 150 pm and 700 pm, an oxide layer SiO2 resting on the lower layer, said oxide layer having a thickness of between 0.2 pm and 2 pm, an upper silicon layer with a thickness E and resting on the oxide layer, said manufacturing method comprising: - a step of etching a preform through the upper silicon layer to the oxide layer, said preform having a first part, extending in a first direction, intended to form said tip and a second part, connected to said first part, extending in a second direction intended to form a lever for connecting the tip to a support; - a step of encapsulating the preform in an oxide sheath by thermal oxidation and / or oxide deposition; - an opening step in the oxide cladding using a mask comprising a rectangular window opening onto an area of ​​the preform so as to expose an upper surface of the upper silicon layer of the SOI substrate without removing oxide from vertical parts of said preform; - a step of chemical etching of the upper silicon layer through said rectangular window, said upper layer being etched with a slope; - a step of etching the oxide around the preform.

[0035] In this manufacturing process, the first part of the preform has a first width W PF , said first width W PF being less than E / A / 2 and / or in said manufacturing process the rectangular window of the mask opens onto the whole of the first part of said preform and partially opens onto the second part of said preform.

[0036] In an alternative embodiment, the opening step includes an additional step in which all or part of the first part of the preform is partially and locally etched.

[0037] The present invention will be better understood upon reading the detailed description of embodiments taken as non-limiting examples and illustrated by the appended drawings in which:

[0038] Figure 1 illustrates a method according to the prior art based on a technology for manufacturing a tip of a probe in the plane of a substrate;

[0039] Figure 2 illustrates a probe obtained by the method of Figure 1;

[0040] Figure 3 illustrates a prior art SOI substrate suitable for use in the method of Figure 1;

[0041] Figure 4 illustrates in more detail the process of Figure 1;

[0042] Figure 5 illustrates in more detail a tip of a probe of Figure 2;

[0043] Figure 6 illustrates a probe having the tip of Figure 5;

[0044] Figure 7 illustrates the laser spot size on two probe levers of different widths;

[0045] Figure 8 illustrates a measured profile as a function of a sample and tip geometry;

[0046] Figure 9 illustrates a front and side view of the tip of Figure 5;

[0047] Figure 10 is a table giving the front and side aspect ratio of the tip of Figure 9 as a function of an angle 6;

[0048] Figure 11 is a zoom of step 1 of the method of Figure 4;

[0049] Figure 12 is a zoom of step 3 of the method of Figure 4;

[0050] Figure 13 is a zoom of step 4 of the method of Figure 4;

[0051] Figure 14 is a zoom of step 3 of the method of Figure 4 with dimensions of the preform according to a first variant embodiment of the method according to the invention;

[0052] Figure 15 is a zoom of step 4 of the method of Figure 4 with dimensions of the preform according to the first variant embodiment of the method according to the invention;

[0053] Figure 16 illustrates a probe according to a first variant embodiment obtained from the steps of the manufacturing method of Figures 14 and 15;

[0054] Figure 17 illustrates a probe according to a second variant embodiment obtained from the steps of the manufacturing method of Figures 14 and 15;

[0055] Figure 18 is a zoom of step 3 of the method of Figure 4 with a particular positioning of an opening window;

[0056] Figure 19 is a zoom of step 4 of the method of Figure 4 following step 3 of Figure 18;

[0057] Figure 20 illustrates a probe according to a third variant embodiment obtained from the steps of the manufacturing method of Figures 18 and 19;

[0058] Figure 21 illustrates the probe according to the third embodiment variant of Figure 20 according to another view;

[0059] Figure 22 illustrates a detail view of a portion of the probe of Figure 21;

[0060] Figure 23 illustrates a probe according to a fourth embodiment;

[0061] Figure 24 illustrates a portion of the probe of Figure 23;

[0062] Figure 25 illustrates a probe according to a fifth embodiment;

[0063] Figure 26 illustrates a probe according to a sixth embodiment;

[0064] Figure 27 illustrates a probe according to a seventh embodiment variant;

[0065] Figure 28 illustrates a front view of the embodiments of Figures 26 and 27;

[0066] Figure 29 illustrates a method for manufacturing probes according to the embodiments of Figures 25 to 27;

[0067] Figure 30 is a photo obtained by scanning electron microscopy illustrating the third variant embodiment of Figures 20 and 21;

[0068] Figure 31 is a photo obtained by scanning electron microscopy illustrating the third variant embodiment of Figures 20 and 21, according to another orientation.

[0069] The invention is not limited to the embodiments and variations presented and other embodiments and variations will become apparent to those skilled in the art.

[0070] Figure 3 illustrates an SOI substrate suitable for use in a process based on substrate-plane probe tip fabrication technology.

[0071] Such a substrate consists of three layers. A lower silicon layer of significant thickness (Handle Layer: HL) (150pm-700pm) which serves as mechanical support, a thin SiO2 oxide layer (0.5pm-2pm) called BOX (buried oxide), then a silicon layer called the 'active layer' or 'Device layer': DL.

[0072] Figure 4 illustrates in more detail the fabrication process of the probe tip in the plane of the SOI substrate of Figure 3.

[0073] The process thus starts on the SOI substrate. In Figure 4, the HL layer is not shown to make it easier to understand. The DL device layer is in white on the hatched BOX silicon oxide. By means of lithography, a protective mask is defined in step E1. This protects the material located inside the geometric shape. Then the silicon layer will be etched down to the BOX using plasma technology which removes the silicon outside the protective mask and produces vertical sides.

[0074] In a step E2, the surface and the sides of the structure etched in the silicon of the “device layer” are then encapsulated in silicon oxide (by thermal oxidation and / or deposition).

[0075] In step E3, an opening is made in the oxide to expose the upper surface of the silicon structure without removing the oxide on the sides.

[0076] In step E4, a specific etching using a base such as TMAH (Tetramethylammonium hydroxide) allows the silicon to be etched with a slope. This is obtained because TMAH etches the (111) planes very little (colored here in light gray).

[0077] In step E5, the oxide is finally etched all around the probe.

[0078] The tip of a probe obtained by the process steps of Figure 4 is illustrated in Figure 5 in three dimensions. This tip has a tetrahedral shape with a triangular section.

[0079] More specifically, the DCA, BCD and ACB planes intersect at point C and are respectively formed by the lower surface of the SOI device layer, by the (111) crystal plane exposed using chemical etching and by a vertical plane defined using vertical etching. The (111) plane is etched at least 10 times slower than the other planes. The etching can then be stopped when only the (111) planes remain visible.

[0080] The tip thus formed at point C is in the plane of the substrate. The line (DC) follows the crystalline direction

[0110] while an angle 9 is imposed between (DC) and (AC). This angle is defined during the design while the values ​​of a (BCD) and (3(BCÀ) depend only on 9 and the crystalline planes of the silicon and are imposed by:

[0081] a = tan -1 ( 3 tan 0) (1 )

[0082] / ? = tan _1 (V2 sin 0) (2)

[0083] The angle between the (111) plane and the (001) plane is fixed by the silicon crystal lattice, i.e. 54.7° (tan -1 (2))-

[0084] The length of the tip, i.e. the DC distance, depends only on the angle 9 and the thickness of the silicon layer E:

[0086] Figure 6 illustrates in more detail a variant of a probe obtained by the method of Figure 4. This probe consists mainly of four zones.

[0087] The PT zone is made up of a tetrahedron: the sections of this zone, in the XZ plane, are right triangles that become larger and larger as one travels through the PT zone along the y axis from the apex of the AP point towards the ZI zone.

[0088] The ZI zone is an intermediate zone extending the tip but not being part of the tetrahedron. Its sections in the XZ plane can be of arbitrary size, for example, a rectangular shape.

[0089] The PT zone and the ZI zone constitute the tip of the probe.

[0090] The EM zone belongs to a lever C of the probe. This lever is connected to a support of the probe (not shown in figure 6).

[0091] Figure 7 shows a top view of a probe when the AFM laser is focused to obtain a reflection giving the measurement signal.

[0092] In the case of an in-plane AFM lever, the lever is formed by vertically etching the device layer of the SOI substrate along the Z axis. Thus, the width Wc of the lever is equal to the thickness E of the SOI device layer. More precisely, and throughout this document, the width Wc of the lever corresponds to the dimension of the lever along the Z axis at the level of the lever anchoring (i.e. at the level of the anchored end). The thickness t of the lever is given by photolithography.

[0093] The choice of the SOI substrate to be used in manufacturing is therefore critical for the subsequent operations.

[0094] In Figure 7, there is a point under each lever, referenced C1 and C2. The points are not visible here.

[0095] S D is the diameter of the LS laser spot sent to the lever.

[0096] If Wc > to S D or slightly lower than S D(Wc=W1 ), a large part of the laser light will be reflected on the photodiode.

[0097] If Wc is small compared to SD (WC=W2), only part of the laser is reflected on the photodiode to allow control.

[0098] As a first approximation, the proportion of reflected light is equivalent to the ratio between the illuminated lever surface and the laser spot surface.

[0099] In the case where the laser spot does not protrude from the lever along the X axis, then the approximation is made that the illuminated surface is a rectangle of length SD and width Wc, i.e. S D * Wc. We also assume a circular laser spot with a total spot area of ​​^S D 2 The proportion of reflected light is equal to first approximation to 7T S[). For a spot of S D =40pm and a width lever Wc=30pm, the laser is reflected at 95%. For a spot of SD =40pm and a lever of width Wc=20pm, the laser is reflected at 63%. For a spot of S D =40pm and a lever of width Wc=10pm, the laser is reflected at 31%.

[0100] A first problem to solve is to have a sufficient signal level to ensure the control and consequently maintain Wc=S D -

[0101] Furthermore, in the prior art, the length of the tip L P of out-of-plane probes is typically 10 to 15 pm. There are several tip geometries: pyramidal or tetrahedral.

[0102] On the other hand, the presence of the cp angle, illustrated in Figure 2, will lead to difficulties because the tip profile is not symmetrical with respect to the normal to the imaged surface. Tip manufacturers seek to mitigate the effects of the cp angle by attempting to compensate for it in order to have a symmetrical tip during imaging.

[0103] To have a tip with an edge normal to the surface once the probe is mounted in the AFM, you must choose =(p.

[0104] To have a symmetrical tip in the XY plane once mounted in the AFM, it is necessary to choose =(p-0 / 2.

[0105] Regardless of the geometry chosen, the profile obtained during a scan line is always the convolution of the profile of the tip and the local flank of the sample.

[0106] Figure 8 illustrates a typical profile obtained as a function of the sample.

[0107] The main observable artifacts are: - The radius of curvature at the apex AP; - The angle of the half-cone; - The aspect ratio of the tip.

[0108] For a given sample, the measured profile SP presents several types of defects: - D1: slope due to the half-cone angle HCA; - D2: convolution due to the radius of curvature AR; - D3: effective width of a pattern with a high aspect ratio large compared to the actual width of the pattern (D1 + D2); - D4: the tip does not fit into a narrow, deep trench: the aspect ratio of the tip is low compared to that of the trench.

[0109] To reduce the difference between the actual profile and the measured profile - at a constant radius of curvature - the half-cone angle must be reduced. In addition, to image the bottom of a narrow trench, a high aspect ratio is required.

[0110] Figure 9 illustrates a front and side view of the tip of Figure 5.

[0111] According to the observed plane, we have HCA= [3 / 2 or 9 / 2. According to the equations (4) and (5) below, the front or side aspect ratio of the PT area depends only on 6:

[0114] Figure 10 details the measurement of the front and side aspect ratio as a function of angle 6.

[0115] The constraint given by the first problem imposes Wc>30 pm. Furthermore, to have a large aspect ratio, i.e. greater than 4, we impose 6 less than 10°. Consequently, for the parameters Wc=40pm, 9 =9°, the PT zone is 179pm long.

[0116] The resonant frequency of the probe is given by the following equation:

[0118] With k the stiffness of the lever, m EM , m Z | and m PT respectively the masses of the PT, ZI and EM zones. When the mass increases, the resonance frequency decreases. However, the performance of AFM probes is directly linked to the frequency couple of resonance and stiffness. The mass m E M is given by the lever chosen during design.

[0119] In the case of a standard probe:

[0120] L=125pm, Wc=30pm, tc=4pm; i.e. a stiffness of 42N / m. A PT zone of 179pm therefore has a mass of 2.5 times that of the lever. This mass will lower the resonance frequency by 40%.

[0121] A second problem to be solved is to achieve a tip with a high aspect ratio and low mass, without reducing Wc.

[0122] Finally, in the prior art, for tips manufactured out of plane, the reduction of the half-cone angle or the increase of the aspect ratio are achieved at the tip end over the last few hundred nanometers up to 1 pm.

[0123] Technical solutions to achieve the largest aspect ratios are generally: - Use localized growth by electron beam (EBD). The principle is to use a molecule as a carbon precursor, this molecule will be dissociated under the beam and a small deposit will form. This deposit can be optimized to make a tip; - localized etching by focused ion beam (FIB).

[0124] In both cases, these operations are costly in terms of machine time. In addition, the probes are made tip by tip. This results in a final price higher than the identical model of a high-aspect-ratio tipless lever.

[0125] A third problem is therefore to use a collective manufacturing technique (called "batch process" in English) on a substrate allowing a large aspect ratio to be obtained on all the probes during the manufacturing process.

[0126] Figures 11, 12 and 13 illustrate in more detail certain steps of the prior art manufacturing method shown in Figure 4.

[0127] Thus, Figure 11 is a zoom of step 1 of the process of Figure 4.

[0128] The preform here is a silicon part whose sides are vertical. It is made up of two portions. The portion PF extends mainly along the Y axis, forming here a non-zero angle 0 with this axis. The Y axis corresponds to the crystalline direction

[0110] . The portion C extends mainly along the X axis, forming here a non-zero angle T with this axis. The X axis thus corresponds to the normal to the crystal direction

[0110] . These two angles are defined by the designer of the probe. As explained previously, 0 directly impacts the aspect ratio of the tetrahedron of the PT zone, while by fixing T, the designer can choose the angle formed between the tip and the lever. This angle can, for example, be used to compensate for the angle cp to present a tip vertical to the sample. Depending on the intended applications, this angle can vary between -90 and + 180°.

[0129] A second reference point is defined with OR as its origin, the inflection point between the two preform portions. The axes X1 and X2 are noted such that X1 = -X and Y1 = - Y. The process starts on an SOI substrate with an active layer DL of thickness E etched until reaching the oxide BOX. The top view shows the future lever C associated with the portion PF of width W PF and length L PFBeing produced by engraving along Z, the width Wc of the lever is given by the thickness E of the DL layer while its thickness te is adjustable during design.

[0130] It should be noted that the thickness E of the active layer DL is between 0.1 pm and 100 pm.

[0131] Preferably, the thickness E of the active layer DL is between 2 pm and 40 pm.

[0132] Figure 12 is a zoom of step 3 of the process of Figure 4.

[0133] After oxidation of the substrate, a silicon oxide sheath encapsulates all the silicon in the DL layer. Using photolithography, a resin mask is defined that will protect the entire surface except the FO window. By etching, this mask allows the upper layer resting on top of the DL to be removed while retaining the MO oxide walls.

[0134] In Figure 12 the oxide layer is not shown in the area outside the FO but it is present. It is possible to see this layer on the section AA'. We denote it SO. We denote OR as the origin of the reference frame used to measure the position of FO. OR corresponds to the point of intersection of the lever C and the preform PF. MO dx and MO dy measures the window offset at the origin OR along the X1 / Y1 reference frame. In figure 12 MO dx and MO dy are negative.

[0135] Figure 13 is a zoom of step 4 of the process of Figure 4.

[0136] The silicon oxide then serves as a mask for a chemical etching step (TMAH) which has the particularity of anisotropically etching the different crystalline planes of the silicon. The intersection of the (1 1 1 ) plane, the right vertical face of the preform and the lower face (in contact with the SiO2 layer (BOX), makes it possible to form a tetrahedron.

[0137] Figure 14 is a zoom of step 3 of the method of Figure 4 with dimensions of the preform according to a first variant embodiment of the method according to the invention.

[0138] In this first variant, the first part PF of the preform has a first width W PF and the second part C of the preform has a second width t. In this first variant, we have the following relationship between the widths: W PF <E / A / 2.

[0139] Figure 15 is a zoom of step 4 of the method of Figure 4 with dimensions of the preform according to the first variant embodiment of the method according to the invention.

[0140] This process consists of using the MO oxide wall so as to block the etching on the (1 1 1 ) crystal plane as shown in section AA' of figure 15. A small tetrahedral portion is then obtained only at the end of the tip. The tetrahedron is truncated and the mass of the tip is reduced.

[0141] Note that for the preform in Figures 14 and 15, the value of MO dy is greater than t. As a reminder, t corresponds to the thickness of the lever as illustrated in Figure 2.

[0142] Alternatively, the equation W PF <E / A / 2 est également valable pour des valeurs de MO d y less than or equal to t.

[0143] Figure 16 illustrates a probe according to a first variant embodiment obtained from the steps of the manufacturing method of Figures 14 and 15.

[0144] As already described, the probe comprises a lever C and a tip. This tip comprises the first part PT and the second part ZI. This second part ZI is arranged between the first part PT and the lever C.

[0145] The first part PT of the tip has a tetrahedral shape. It has a triangular section whose height is continuously variable.

[0146] The second part ZI of the tip has a non-triangular section.

[0147] At the interface between the first part PT and the second part ZI, the height of the triangular section is less than the width Wc of the lever C.

[0148] The probe in Figure 16 is made using the following manufacturing parameters: - MO dy >t ; - W PF <E / A / 2 ; - MOdx<0.

[0149] Figure 17 illustrates a probe according to a second embodiment variant obtained from the steps of the manufacturing method of Figures 14 and 15.

[0150] As already described, the probe comprises a lever C and a tip. This tip comprises the first part PT and the second part ZI. This second part ZI is arranged between the first part PT and the lever C.

[0151] The first part PT of the tip has a tetrahedral shape. It has a triangular section whose height is continuously variable.

[0152] The second part ZI of the tip has a non-triangular section.

[0153] At the interface between the first part PT and the second part ZI, the height of the triangular section is less than the width Wc of the lever C.

[0154] The probe in Figure 17 is made using the following manufacturing parameters: - MO dy >t ; - WPF <E / A / 2 ; - MO dx =0.

[0155] Figure 18 is a zoom of step 3 of the process of Figure 4 with preform dimensions identical to those of Figure 14 and with a particular manufacturing rule. This rule consists of shifting the FO window along the X axis so as to obtain MOdx > 0.

[0156] Thus, the FO window here opens onto the entire first part PF of the preform.

[0157] In the specific embodiment of Figure 18, the window FO also partially opens onto the second part of the preform. In other words, the window FO is offset by a length MO dx towards the second part of the preform. This window FO then contains the point OR. This point OR corresponds to an inflection point between the first part PF of the preform and the second part of said preform.

[0158] Thus the etching of the crystalline planes starts on an area of ​​this second part. The length necessary to reveal the tip of the probe is thus reduced.

[0159] Additionally, depending on the MOdx offset, the tip length can be modulated.

[0160] Note that, alternatively, the rule consisting of shifting the FO window along the X axis so as to obtain MO dx > 0, is associated with a width W PF of the first part of the preform greater than or equal to E / A / 2.

[0161] In the embodiment of Figure 18, the MO value dy is greater than t.

[0162] Alternatively, this MO value dy is less than or equal to t.

[0163] Finally, it should be noted that etching on the area of ​​the second part of the preform opened by the FO window could create an asymmetrical profile on the lever and consequently degrade the frequency of this lever. In such a case, it will be sufficient to slightly modify the length of the lever to reach a target frequency value.

[0164] Figure 19 is a zoom of step 4 of the process of Figure 4 with preform dimensions identical to those of Figure 18. The area etched by the TMAH (gray area) extends partially over the second part of the preform. The total mass of the tip is reduced and the polyhedra forming said tip have thicknesses less than E.

[0165] Figure 20, Figure 21, Figure 30 and Figure 31 illustrate a probe according to a third variant embodiment obtained from the steps of the manufacturing method of Figures 18 and 19.

[0166] As already described, the probe comprises a lever C and a tip.

[0167] Lever C has a main portion C y intended to be connected to a support (not shown here) and a portion C x reduction in width extending said main portion C y .

[0168] The main portion C y has a width Wc. The reduction portion C x has a width decreasing continuously between the width Wc and the width of an interface zone between the reduction portion C x and the tip.

[0169] The tip comprises the first part PT and the second part ZI. This second part ZI is arranged between the first part PT and the lever C.

[0170] The first part PT of the tip has a tetrahedral shape. It has a triangular section whose height is continuously variable.

[0171] The second part ZI of the tip has a non-triangular section.

[0172] As is more particularly visible in figure 22, at the interface between the first part PT and the second part ZI, said first part PT has a certain height H PT in the triangular section SPT. This height H PT is, here, less than the width Wc of the main part C y of lever C.

[0173] The probe in Figure 20 is made using the following manufacturing parameters: - MO dy >t ; - W PF <E / A / 2 ; - MO dx >0.

[0174] Figures 23 and 24 illustrate a probe according to a fourth embodiment obtained from the steps of the manufacturing method of Figures 18 and 10.

[0175] As already described, the probe comprises a lever C and a tip.

[0176] Lever C has a main portion C y intended to be connected to a support (not shown here) and a portion C x reduction in width extending said main portion C y .

[0177] The main portion C y has a width Wc. The reduction portion C x has a width decreasing continuously between the width Wc and the width of an interface zone between the reduction portion C x and the tip. In addition, the reduction portion C x has a first inclined plane P1 cx extending from the main portion C y and a second inclined plane P2cx extending from the first inclined plane P1 ex to the probe. The inclination of the first inclined plane P1 cx is here different from the inclination of the second inclined plane P2 CX .

[0178] The tip comprises the first part PT and the second part ZI. This second part ZI is arranged between the first part PT and the lever C.

[0179] The first part PT of the tip has a tetrahedral shape. It has a triangular section whose height is continuously variable. In a particular embodiment, the first part PT comprises an inclined plane P PT . This inclined plane PPT has the same inclination as the first inclined plane P1 ex of the reduction portion Cx-

[0180] The second part ZI of the tip has a non-triangular section. This second part here comprises a first portion Zh extending from the lever C and a second portion Zl2 arranged between the first portion Zh and the first part PT of the tip. The first portion Zh comprises an inclined plane Pzn, this plane extending between the lever C and the second portion Zl2. It will also be noted that the inclined plane P Zn of the first portion Zh of the second part ZI of the point has the same inclination as the second inclined plane P2cx of the reduction portion C x .

[0181] As is more particularly visible in figure 24, at the interface between the first part PT and the second part ZI, said first part PT has a certain height H PT in the triangular section S PT . This height H PT is, here, less than the width Wc of the main part C y of lever C.

[0182] The probe in Figures 23 and 24 is made using the following manufacturing parameters: - MO dy >t ; - W PF <W / A / 2 ; - MO d x>0.

[0183] Figures 25, 26 and 27 respectively illustrate a fifth embodiment, a sixth embodiment and a seventh embodiment of the invention.

[0184] As already described, the probe comprises a lever C and a tip.

[0185] Lever C has a main portion C y intended to be connected to a support (not shown here) and a portion C x reduction in width extending said main portion C y .

[0186] The main portion C y has a width Wc. The reduction portion C x has a width decreasing continuously between the width Wc and the width of an interface zone between the reduction portion C x and the tip.

[0187] The tip comprises the first part PT and the second part ZI. This second part ZI is arranged between the first part PT and the lever C.

[0188] The first part PT of the tip has a tetrahedral shape. It has a triangular section whose height is continuously variable.

[0189] The second part ZI of the tip has a non-triangular section.

[0190] At the interface between the first part PT and the second part ZI, said first part PT has a certain height in the triangular section. This height is, here, less than the width Wc of the main part C y of lever C.

[0191] In these embodiments, the zone referenced ZI consists of a portion of arbitrary shape, here a rectangular parallelogram.

[0192] Figures 26, 27 and 28 show more specifically a tetrahedral part with a plane followed by a trapezoidal zone ZI. The aspect ratio seen from the front is constant and equal to HP / B. Then this ratio decreases, if we measure it more and more towards the lever. It is thus equal to HT / B if we consider the entire zone under the lever C, that is to say the part referenced ZI associated with the part referenced PT.

[0193] Figure 29 illustrates a manufacturing method for producing the embodiments of Figures 25, 26, 27 and 28. This method includes an additional step 3b in which the PF portion is partially and locally etched.

[0194] It will also be noted that in the embodiments of figures 16, 17, 20, 21, 22, 23, 24, 25, 26, 27, each tip comprises the first part PT and the second part ZI. As already specified, this second part ZI is arranged between the first part PT and the lever C.

[0195] In these embodiments, the first part PT has a tetrahedral shape having a triangular section whose height is continuously variable. second part ZI has a non-triangular section. At the interface between the first part PT and the second part ZI, the height of the triangular section of the first part PT is less than the width Wc of the lever C.

[0196] The invention has been presented here in the context of the use of a silicon tip for a probe of an atomic force microscope.

[0197] The silicon tip can be used in any device intended to evaluate the topography of a surface.

[0198] Alternatively, the silicon tip can be integrated into any device having microelectrodes.

[0199] Alternatively, the silicon tip may serve as a microanode or microcathode in a field emission device.

Claims

CLAIMS 1. Silicon tip suitable for being arranged at one end of a lever (C) characterized in that said tip comprises a first part (PT) and a second part (ZI) arranged between said first part (PT) and the lever (C), said first part (PT) having a tetrahedral shape with a triangular section whose height is continuously variable, said second part (ZI) having a section (S Z (i) non-triangular and in that, at the interface between the first part (PT) and the second part (ZI) of the tip (P), the height (H PT ) of section (S PT ) triangular of the first part (PT) in a direction parallel to a direction of a width (Wc) of the lever (C) is less than the width (Wc) of the lever (C).

2. Silicon tip according to claim 1, wherein the second part (ZI) comprises a first portion (Zh) extending from the lever (C) and a second portion (Zl2) disposed between the first portion (Zh) and the first part (PT).

3. Silicon tip according to claim 2, wherein the first portion (Zl-i) comprises an inclined plane (Pzn), said inclined plane extending between the lever (C) and the second portion (Zl2).

4. Probe comprising: - a support; - a lever (C) extending from the support; - a silicon tip according to any one of claims 1 to 3, said silicon tip being arranged at one end of the lever (C), opposite the support.

5. Probe according to claim 4, in which the lever (C) comprises a main portion (C y ) connected to the support and a portion (C x ) of reduction in width extending the main portion (Cy ).

6. Probe according to claim 4, in which the reduction portion (C x ) comprises a first inclined plane (P1 cx) extending from the main portion (C y ) and a second inclined plane (P2c x ) extending from the first inclined plane (P1 cx) to the probe (ZI, PT), the inclination of the first inclined plane (P1 cx) being different from the inclination of the second inclined plane (P2 Cx ).

7. Probe according to claim 4, in which the second inclined plane (P2c x ) has the same inclination as the inclined plane (Pzn) of the first portion (Zh) of the second part (ZI) of the point.

8. Probe according to one of claims 6 or 7, in which the first part (PT) of the tip comprises an inclined plane (PPT), said inclined plane (P PT ) having the same inclination as the first inclined plane (P1 Cx ) of the reduction portion (C x ).

9. Local probe microscope comprising a probe according to any one of claims 4 to 8.

10. Method for manufacturing a silicon tip in an SOI substrate, said substrate comprising a lower layer (HL) of silicon with a thickness of between 150 pm and 700 pm, an oxide layer (BOX) SiO2 resting on the lower layer (HL), said oxide layer (BOX) having a thickness of between 0.2 pm and 2 pm, an upper layer (DL) of silicon with a thickness E and resting on the oxide layer (BOX), said manufacturing method comprising: - a step (E1) of etching a preform through the upper silicon layer (DL) to the oxide layer (BOX), said preform having a first part (PF), extending in a first direction, intended to form said tip and a second part, connected to said first part, extending in a second direction intended to form a lever (C) for connecting the tip with a support; - a step (E2) of encapsulating the preform in an oxide sheath by thermal oxidation and / or oxide deposition; - a step (E3) of opening in the oxide cladding using a mask comprising a rectangular window (FO) opening onto an area of ​​the preform so as to expose an upper surface of the upper silicon layer (DL) of the SOI substrate without removing oxide from vertical parts of said preform; - a step (E4) of chemical etching of the upper layer (DL) of silicon through said rectangular window (FO), said upper layer (DL) being etched with a slope; - a step (E5) of etching the oxide around the preform, said manufacturing method being characterized in that the first part (PF) of the preform has a first width W PF , said first width W PF being less than E / A / 2 and / or said manufacturing method being characterized in that the rectangular window (FO) of the mask opens onto the entire first part (PF) of said preform and partially opens onto the second part of said preform.

11. Manufacturing method according to claim 10, in which the opening step (E3) comprises an additional step (E3b) in which all or part of the first part (PF) of the preform is partially and locally etched.

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