JPH06300557A - Integrated afm sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent the contact of a lead wire fixing section with a specimen, and also a lead wire from being detached, regarding an integrated AFM sensor having a piezoelectric resistance layer on the surface of a cantilever for detecting the displacement thereof via the resistance change of the layer. CONSTITUTION:A piezoelectric resistance layer 116 is formed on the surface of a cantilever 120 in an integrated AFM sensor, or the side of the cantilever 120 faced to the surface of a specimen, and a connecting conductive layer 114 of impurity dispersion layer is provided, so as to come in contact with the end of the layer 116 and reach the reverse side of the cantilever 120, or the support side thereof. In addition, an electrode 121 for voltage supply to the layer 116 is formed on the layer 114 on the reverse side of the cantilever 120.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated AFM sensor used in an atomic force microscope and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a scanning tunneling microscope (STM: Scanni), which was invented by Binning and Rohrer, was used as an apparatus for observing a conductive sample with a resolution of atomic size order.
ng Tunneling Microscope), but in STM, the samples that can be observed are limited to conductive ones.

Therefore, an atomic force microscope is used as a microscope capable of observing an insulating sample, which has been difficult to measure with STM, with an accuracy of atomic size order while utilizing elemental technologies such as servo technology in STM. (AF
M) was proposed. This AFM is disclosed, for example, in Japanese Patent Laid-Open No. 62-
130302 (patent applicant: IBM, inventor: G. Binnig, title of invention: method and apparatus for forming an image of a sample surface).

The structure of the AFM is similar to that of the STM and is positioned as one of scanning probe microscopes.
In the AFM, a cantilever having a sharp protruding portion (probe portion) at its free end is arranged facing and close to the sample, and the interaction force acting between the atom at the tip of the probe and the sample atom causes
While measuring the function of the displacing cantilever electrically or optically, the sample is scanned in the XY directions, and the relative position of the cantilever with the probe part is changed to obtain information about the unevenness of the sample. It can be seen three-dimensionally in the order of atomic size.

FIG. 4 shows a block diagram of the AFM measuring system. In FIG. 4, 401 is a cantilever, 402 is a displacement measuring sensor, 403 is a feedback control unit, 404 is a sample, 405 is a three-dimensional scanning unit, 406 is a scanning drive signal generating unit,
407 is a monitor.

In the AFM, the displacement measuring sensor for measuring the displacement of the cantilever is generally provided separately from the cantilever. However, recently, an integrated AFM sensor in which the cantilever itself has a function of measuring displacement has been proposed by M. Tortonese et al. This integrated AFM sensor is, for example, M. Tortonese, H.Ya
mada, RC Barrett and CF Quate: Transducers
and Sensors' 91: Atomic force microscopy using a
It is disclosed in piezoresistive cantilever.

The piezoresistive effect is used as the measurement principle of this integrated AFM sensor. In other words, when the tip of the probe is brought close to the measurement sample, the interaction between the probe and the sample causes the cantilever portion to bend and cause distortion. A resistance layer is laminated on the cantilever portion, and its resistance value changes according to the strain of the cantilever portion. Therefore, if a constant voltage is applied to the resistance layer from the electrode part,
The current flowing through the resistance layer changes according to the amount of strain of the cantilever, and the amount of displacement of the cantilever can be known by detecting the change in current.

Since such an integrated AFM sensor has an extremely simple structure and is small in size, it is expected that a so-called stand-alone AFM in which the cantilever side is moved can be formed. With conventional AFM,
Since the sample is moved in the XY directions to change the relative positional relationship between the tip of the cantilever and the probe, the maximum size of the sample is limited to about several cm.
There is an advantage that the limitation of the size of the sample can be removed.

Next, the integrated AFM sensor will be described with reference to the drawings. First, the manufacturing method will be described with reference to FIGS. Start wafer 50
As shown in FIG. 5A, as shown in FIG. 5A, a silicon wafer 502 on which a silicon layer 501 is provided via a silicon oxide separation layer 512, for example, a bonded wafer is prepared. Next, as shown in FIG. 5B, boron (B) is implanted into the extreme surface of the silicon layer 501 by ion implantation to form a piezoresistive layer 516, and the cantilever shown in FIG. 6 described later is formed. After patterning in the shape of, the surface is covered with a silicon oxide film 518. Then, a hole for bonding is made on the fixed end side of the cantilever, and aluminum is sputtered to form an electrode 520. Further, an etching mask layer 519 is formed on the lower side of the silicon wafer 502. Next, as shown in FIG. 5C, the silicon wafer 502 is etched up to the separation layer 512 with a KOH aqueous solution using the etching mask layer 519 as a mask. Finally, the separation layer 512 is removed with a hydrofluoric acid aqueous solution to form a cantilever portion 524, thereby completing the integrated AFM sensor shown in FIG.

In the integrated AFM sensor thus manufactured, a DC voltage of several volts or less is applied between the two electrodes 520 at the time of measurement to bring the tip of the cantilever portion 524 close to the sample. When an interaction acts between the tip of the cantilever portion 524 and the atom on the sample surface, the cantilever portion 524 is displaced. Since the resistance value of the piezoresistive layer 516 changes according to this, the displacement of the cantilever portion 524 causes the displacement of the two electrodes 520.
It is obtained as a current signal flowing between the two.

[0011]

By the way, in order to supply a voltage between the two electrodes 520 during measurement and to measure a current flowing between the electrodes, a lead wire from an external power source and an ammeter is connected to, for example, a conductive wire. The electrode 52 with a kind of paste
Used by adhering to 0. On the other hand, silicon wafer 502
As shown in FIG. 6, it becomes a support portion of the cantilever. According to the above-mentioned manufacturing method, since the electrode 520 is formed on the cantilever surface side, the lead wire faces the sample surface. . When a large amount of conductive paste is used to firmly fix the lead wire to the electrode 520, the distance between the sample and the cantilever support is only a few mm.
This causes contact between the conductive paste and the sample, which interferes with normal observation. Further, since the lead wire is hung and fixed on the cantilever, there is a problem that it is easily detached by its own weight during measurement.

The present invention has been made in order to solve the above-mentioned problems in the conventional integrated AFM sensor. The contact between the conductive paste for fixing the lead wire and the sample to be measured is unlikely to occur, and the lead wire is disconnected. Difficult configuration integrated type A
An object is to provide an FM sensor and a manufacturing method thereof.

[0013]

In order to solve the above problems, the present invention provides an integrated AFM sensor having a piezoresistive layer on the surface of a cantilever, and detecting the displacement of the cantilever based on the resistance change of the piezoresistive layer. A conductive impurity diffusion layer which is in contact with the end of the cantilever and reaches the back surface of the cantilever, and a voltage supply electrode for the piezoresistive layer is formed on the diffusion layer on the back surface of the cantilever.

A first method of manufacturing an integrated AFM sensor according to the present invention is a method of manufacturing an integrated AFM sensor which has a piezoresistive layer on the surface of a cantilever, and detects displacement of the cantilever based on a resistance change of the piezoresistive layer. Using a substrate in which an n-type silicon layer is epitaxially grown on a p-type silicon substrate having (100), a piezoresistive layer is formed on the n-type epitaxial silicon layer, and then p
A cantilever is formed by etching a type silicon substrate by an electrochemical etching method.

Furthermore, a second method for manufacturing an integrated AFM sensor according to the present invention is a method for manufacturing an integrated AFM sensor, which has a piezoresistive layer on the surface of a cantilever and detects displacement of the cantilever by a change in resistance thereof. Using a substrate obtained by laminating a silicon substrate having a plane orientation (111) on a silicon substrate having a plane orientation (100) and forming a piezoresistive layer on the silicon substrate having the plane orientation (111), the plane orientation ( A silicon substrate of 100) is etched by an anisotropic etching method to form a cantilever.

[0016]

In the integrated AFM sensor according to the present invention, since the conductive impurity diffusion layer is provided so as to contact the end of the piezoresistive layer and reach the back surface of the cantilever, the piezoresistive layer formed on the cantilever surface is , And is electrically connected to the voltage supply electrode formed on the diffusion layer on the back surface of the cantilever. Therefore, the lead wire for voltage supply is fixed to the support part side of the back surface of the cantilever, so even if a large amount of conductive paste used for fixing is used, the paste does not contact the measurement sample and good measurement It can be performed. Also, since the lead wire is fixed to the cantilever so as to be installed from above, there is no fear that it will come off due to its own weight.

Further, according to the first manufacturing method of the integrated AFM sensor of the present invention, it is possible to easily etch only the p-type silicon substrate of the substrate by performing the etching by using the electrochemical etching method. Cantilevers can be formed in the.

Furthermore, according to the second manufacturing method of the integrated AFM sensor of the present invention, since the etching rate of the plane orientation (111) is significantly lower than that of the plane orientation (100),
A silicon substrate having a plane orientation (111) attached to a silicon substrate having a plane orientation (100) is hardly etched. Therefore, the thickness of the cantilever is adjusted to the plane orientation (111).
It can be controlled by the thickness of the silicon substrate.

[0019]

EXAMPLES Next, examples will be described. Figure 1 (A)
7A to 7F are cross-sectional views showing the procedure of the manufacturing process of the embodiment of the integrated AFM sensor according to the present invention. First, as shown in FIG. 1A, an oxide film 11 is formed on a double-sided mirror n-type silicon substrate (start wafer) 100 having a plane orientation (100).
2 is formed, and then PEP (Phot (Phot) is formed according to a conventional method only on the conductive layer forming portion for connecting the piezoresistive layer and the back electrode.
o Engraving Process) to form the window 113. Then, as shown in FIG. 1B, a p-type impurity, for example, boron is diffused so as to have a surface concentration of 5 × 10 ¹⁸ atoms cm ³ and a depth of about 10 μm to form a connection conductive layer 114.

Next, as shown in FIG. 1C, the piezoresistive layer forming region 115 is similarly subjected to PEP to open a window, and p type impurities such as boron are diffused to diffuse the piezoresistive layer.
Form 116. At this time, the sheet resistance value of the piezoresistive layer 116 is, eg, 150 Ωsq. As shown,
The end of the piezoresistive layer 116 is in contact with the conductive layer 114 for connecting to the back electrode described above. Next, as shown in FIG. 1D, the substrate surface is covered again with an oxide film, and a cantilever pattern 117 is formed on the oxide film by PEP. The silicon substrate 100 is RIEed using this oxide film as a mask.
Dip about 10 μm by (Reactive Ion Etching) method.

After that, as shown in FIG. 1E, the oxide film on the substrate is once peeled off, and the substrate is again thermally oxidized by about 40 nm, and then the silicon nitride film 118 is LP-CVD (Low).
It is deposited by the pressure chemical deposition method. Further, a cantilever support pattern 119 is formed on the back surface of the substrate with PEP, and the substrate 100 is etched with an anisotropic silicon etching solution such as KOH to form a cantilever 120. Finally, as shown in Fig. 1 (F),
A metal film of Al or the like is formed, an electrode pattern is formed by the PEP method, and then heat treatment is performed to form ohmic contact, so that the voltage supply electrode 121 to the piezoresistive layer 116 is provided on the cantilever support portion side. Obtain an integrated AFM sensor.

FIG. 2 is a sectional view showing a procedure of another method of manufacturing the integrated AFM sensor according to the present invention. In this manufacturing method, a substrate (start wafer) 200 in which an n-type silicon layer 201 having a thickness of about 5 μm is epitaxially grown on a double-sided mirror p-type silicon substrate 202 having a plane orientation (100)
To use. First, as shown in FIG. 2A, as in the embodiment shown in FIG. 1, oxide films 212 are formed on both surfaces of the substrate, and n
A window portion 213 is formed by applying PEP to the conductive layer forming portion for connecting the piezoresistive layer on the type epitaxial silicon layer 201 and the back surface electrode. Next, FIG. 2B
As shown in FIG. 3, the connection conductive layer 21 is formed by diffusing p-type impurities.
Forming 4 Next, as shown in FIG. 2C, a piezoresistive layer formation region 215 is opened by PEP, and p-type impurities such as boron are diffused to form a piezoresistive layer 216.
After that, as shown in FIG. 2D, a cantilever pattern 217 is formed on the n-type epitaxial silicon layer 201 by the same method as in the embodiment of FIG.

Next, as shown in FIG. 2E, the oxide film on the substrate is once peeled off, the substrate is again thermally oxidized, and then a silicon nitride film 218 is deposited by the LP-CVD method.
Next, a cantilever support pattern 219 is formed on the p-type silicon substrate 202 side by PEP, and then a positive voltage is applied to the n-type epitaxial silicon layer 201 to form a p-type silicon substrate.
With a negative voltage applied to 202, the cantilever 22 is etched by etching (electrochemical etching) the p-type silicon substrate 202 with an anisotropic silicon etching solution such as KOH.
Form 0. By using this etching method,
Only the p-type silicon substrate 202 can be etched. Finally, as shown in FIG. 2 (F), a metal film such as Al is formed on the back surface of the cantilever, that is, on the p-type silicon substrate 202 side, and the electrode pattern is formed by the PEP method. Moreover, an integrated AFM sensor having a voltage supply electrode 221 to the piezoresistive layer 216 can be obtained.

FIG. 3 is a sectional view showing a procedure of still another method of manufacturing the integrated AFM sensor according to the present invention. In this manufacturing method, a double-sided mirror p-type silicon substrate 302 having a plane orientation (100) and a double-sided mirror n-type silicon substrate 301 having a plane orientation (111) having a thickness of about 10 μm are bonded (start wafer). Use 300. Then, the cantilever is formed by the same procedure as the manufacturing method shown in FIG. 2 except for the anisotropic etching step of the p-type silicon substrate 302 described below. That is, as shown in FIG. 3A, first, an oxide film 312 is formed on both surfaces of the substrate, and a PEP is formed on the conductive layer forming portion for connecting the piezoresistive layer on the n-type silicon substrate 301 and the back electrode. By applying the window portion 313
To form. Then, as shown in FIG. 3B, a p-type impurity is diffused to form a connection conductive layer 314. Next, as shown in FIG. 3C, a window is opened in the piezoresistive layer forming region 315 by PEP, and a p-type impurity such as boron is diffused to form a piezoresistive layer 316. After that, as shown in FIG. 3D, by the same method as in the embodiment of FIG.
A cantilever pattern 317 is formed on the die silicon substrate 301.

Then, as shown in FIG. 3E, the oxide film on the substrate is once peeled off, and the substrate is thermally oxidized again, and then a silicon nitride film 318 is deposited by the LP-CVD method.
Next, a cantilever support pattern 319 is formed by PEP on the p-type silicon substrate 302 side. In the embodiment shown in FIG. 2, the anisotropic etching process of the p-type silicon substrate was performed by electrochemical etching, but in this embodiment, as in the embodiment shown in FIG. 1, KOH was applied without applying a voltage to the substrate. P-type silicon substrate 30 with anisotropic silicon etching liquid such as
The cantilever 320 is formed by etching 2. In the anisotropic silicon etchant, the etching rate in the <111> direction is significantly lower than that in the <100> direction, so the n-type silicon substrate 301 having the plane orientation (111) attached to the p-type silicon substrate 302 is used. Are hardly etched. Therefore, in this embodiment, the thickness of the cantilever can be controlled by the thickness of the n-type silicon substrate 301. Finally, as shown in FIG. 3 (F), a metal film such as Al is formed on the back surface of the cantilever, that is, on the p-type silicon substrate 302 side, and the electrode pattern is formed by the PEP method. An integrated AFM sensor having an electrode 321 for supplying a voltage to the resistance layer 316 is obtained.

In the manufacturing method shown in FIG. 3, as the substrate (start wafer) 300, the plane orientation (100
Although an example in which the n-type silicon substrate 301 having the plane orientation (111) is bonded to the p-type silicon substrate 302 in (1) is used, the base substrate is not limited to the p-type silicon substrate, and the plane orientation is ( If it is 100), an n-type silicon substrate can also be used, and the substrate to be bonded is not limited to an n-type silicon substrate, and if the plane orientation is (111), a p-type silicon substrate can also be used.

[0027]

As described above with reference to the embodiments, according to the present invention, since the voltage supply electrode for the piezoresistive layer can be installed on the support portion side of the back surface of the cantilever, the voltage applied to the piezoresistive layer can be reduced. When fixing the supply lead wire to the voltage supply electrode, even if a large amount of conductive paste or the like is used, good measurement can be performed without the paste or the like coming into contact with the measurement sample. Further, since the lead wire can be fixed to the cantilever so as to be installed from above, there is an effect that there is no fear that the lead wire will come off due to its own weight.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram for explaining a manufacturing method of an integrated AFM sensor according to the present invention.

FIG. 2 is a manufacturing process diagram for explaining another manufacturing method of the integrated AFM sensor according to the present invention.

FIG. 3 is a manufacturing process diagram for explaining still another manufacturing method of the integrated AFM sensor according to the present invention.

FIG. 4 is a block diagram showing an AFM measurement system.

FIG. 5 is a manufacturing process diagram for describing a manufacturing method of a conventional integrated AFM sensor.

6 is a top view of the integrated AFM sensor obtained by the manufacturing method shown in FIG.

[Explanation of symbols]

 100, 200, 300 Start wafer 112, 212, 312 Oxide film 113, 213, 313 Conductive layer forming window 114, 214, 314 Conductive layer 115, 215, 315 Piezoresistive layer forming region 116, 216, 316 Piezoresistive layer 117, 217, 317 Cantilever pattern 118, 218, 318 Silicon nitride film 119, 219, 319 Cantilever support pattern 120, 220, 320 Cantilever 121, 221, 321 Voltage supply electrode

Front page continuation (72) Inventor Katsuhiro Matsuyama 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd.

Claims (3)

[Claims] 1. An integrated AFM sensor having a piezoresistive layer on the surface of a cantilever, and detecting a displacement of the cantilever by a change in resistance thereof, wherein a conductive impurity diffusion layer is in contact with an end of the piezoresistive layer and reaches a back surface of the cantilever. And an electrode for supplying voltage to the piezoresistive layer is formed on the diffusion layer on the back surface of the cantilever, the integrated AFM sensor. 2. A method of manufacturing an integrated AFM sensor, which has a piezoresistive layer on the surface of a cantilever, and detects displacement of the cantilever based on a resistance change of the piezoresistive layer.
0) is used to form a piezoresistive layer on the n-type epitaxial silicon layer, and then the p-type silicon substrate is etched by an electrochemical etching method. A method of manufacturing an integrated AFM sensor, which comprises forming a cantilever by means of a cantilever. 3. A method for manufacturing an integrated AFM sensor, which has a piezoresistive layer on the surface of a cantilever and detects displacement of the cantilever based on a resistance change of the piezoresistive layer.
A silicon substrate having a plane orientation (111) is bonded to a silicon substrate having a plane orientation (111).
2.) A method for manufacturing an integrated AFM sensor, comprising forming a piezoresistive layer on a silicon substrate of 1) and then etching the silicon substrate having the plane orientation (100) by an anisotropic etching method to form a cantilever.