JPH06187905A - Manufacture of cantilever - Google Patents

Abstract

PURPOSE:To simultaneously achieve both a characteristic required for a cantilever and a characteristic required for a probe by forming the probe and the cantilever out of the mat suitable materials in the most suitable shape. CONSTITUTION:A silicon nitride film 44 is formed on a first silicon wafer 40 with a hole 42 formed, by a CVD method, and patterning is applied to the part of the hole 42 so that the silicon nitride film 44 having the shape of a probe 38 is left therein. Also, dry-etching is applied to a silicon nitride film 48 formed on a second silicon wafer 46 through a double-surface photo-lithographic method to form a lever pattern 50 having the same shape as that of a cantilever 36. Next, an anode is connected under the condition that the corresponding part of the lever pattern 50 to the free end of the cantilever 36 abut on the silicon nitride film 44 remaining in a probe-like form in the part of the hole 42.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a cantilever applied to measure the shape of a sample surface.

[0002]

2. Description of the Related Art A scanning tunneling microscope (STM; Scan) is used as an apparatus for observing a conductive sample with atomic resolution.
The Ning Tunneling Microscope was invented by Binnig and Rohrer et al. In this STM, the samples that can be observed are limited to those that are conductive. Therefore, atomic force microscope (AFM) is used as a device that can observe an insulating sample with atomic-order resolution using STM elemental technology such as servo technology.
pe) was proposed. This AFM is disclosed, for example, in Japanese Patent Laid-Open No. 62-
130302.

The AFM structure is similar to the STM and is positioned as one of scanning probe microscopes. Such an AFM has a cantilever having a sharply pointed protrusion (probe) at its free end. When the probe is brought close to the sample, the free end of the cantilever is displaced by the interaction force (atomic force) acting between the atom at the tip of the probe and the atom at the sample surface. By scanning the probe in the XY directions along the sample surface while electrically or optically measuring the displacement of the free end, it is possible to three-dimensionally capture the unevenness information of the sample.

The cantilever for a scanning probe microscope is
Since TR Albrecht et al. Proposed a SiO ₂ cantilever chip manufactured by applying the semiconductor IC manufacturing process (Th
omasR. Albrecht Calvin F. Quate: Atomic resolution Im
aging of a nonconductor

By atomic force Mic
rocopy J. Appl. Pys, 62 (198
7) 2599), it can be manufactured with micron accuracy and extremely reproducibility, and the cost is excellent by manufacturing by a batch process. Therefore, the cantilever chip manufactured by applying the semiconductor IC manufacturing process has become the mainstream.

For example, J.Vac.Sci.Technol.A8 (4) 3386 19
90: T. Albrecht, S. Akamine, TECaver and CFQuate, a cantilever chip using a silicon nitride film as a cantilever constituent material instead of a SiO ₂ film is already on the market. The cantilever has a size and shape of about 50 to 200 μm in length, about 0.5 to 1 μm in thickness, and a hollow triangular or rectangular shape. Hereinafter, a method for manufacturing such a silicon nitride cantilever will be described with reference to FIG.

First, a silicon wafer 2 having a plane orientation (100) is prepared as a start wafer, and a silicon nitride film 4 is formed on the silicon wafer 2 by a CVD method (FIG. 5).
(See (a)).

Next, by the photolithography method,
An opening 6 for a probe is formed at a location on the silicon nitride film 4 where the probe 16 (see FIG. 6H) should be formed (see FIG. 3B).

Thereafter, the silicon wafer 2 exposed in the probe opening 6 is subjected to wet anisotropic etching,
An inverted quadrangular pyramid-shaped hole 8 to be the mold of the probe 16 is formed (see FIG. 7C).

After the silicon nitride film 10 (film thickness 0.4 to 1 μm) is formed by the CVD method on the surface of the silicon wafer 2 on the side where the hole 8 is formed (FIG. 2 (d)).
Then, the silicon nitride film 10 is patterned into a cantilever shape (see (e) in the figure).

On the other hand, a Pyrex glass 12 serving as a holding substrate is prepared, and the Pyrex glass 12 is processed in accordance with the cantilever-shaped pattern of the silicon nitride film 10 (see FIG. 6 (f)). After that, the silicon nitride film 10 on the silicon wafer 2 and the Pyrex glass 12 are anodically bonded (see FIG. 6G).

Then, the silicon wafer 2 has a concentration of 40%.
After being etched with the potassium hydroxide solution described above, a silicon nitride film 10 having a Pyrex glass 12 and a probe 16 formed at the tip is coated with gold (not shown).
(The silicon nitride film 10 functions as a cantilever portion.) Is completed (see (h) of the same figure).

In such a manufacturing method, since the probe 16 and the silicon nitride film (that is, the cantilever portion) 10 are integrally manufactured, they are made of the same material. Also,
Silicon nitride film 1 on the side opposite to the surface on which the probe 16 is formed
Since the concave portion 10a is formed on the surface of 0, when the displacement of the cantilever 14 is optically detected, the probe 16
The displacement is detected by shining light on the flat surface of the cantilever portion in the vicinity.

In contrast to the above-described cantilever, recently, an integrated type A in which a sensor function capable of measuring the displacement is added to the cantilever itself by M. Tortonese et al.
FM sensors have been proposed.

This integrated AFM sensor is, for example, M.
Tortonese, H.Yamada, RCBarrettand CFQuate, Transd
ucers and Sensors '91: Atomic force microscopy using
It is disclosed in apiezoresistive cantilever. Hereinafter, a method of manufacturing such an integrated AFM sensor will be described with reference to FIG.

First, a start wafer is prepared by providing a silicon layer 22 on a silicon wafer 18 with a silicon oxide separating layer 20 interposed therebetween, for example, a bonded silicon wafer (see FIG. 6A).

Boron (B) is implanted into the extreme surface of the silicon layer 22 by ion implantation to form a piezoresistive layer 24, which is patterned into the shape shown in FIG. Cover with.
Then, a hole for bonding is made on the fixed end side of the cantilever, and aluminum is sputtered to form the electrode 28. Further, a resist layer 30 is formed on the lower side of the silicon wafer 18, and the resist layer 30 is patterned into a predetermined shape (see FIG. 3B).

Subsequently, after heat treatment for making ohmic contact, wet anisotropic etching is performed using the resist layer 30 as a mask to scrape off the silicon wafer 18 to the separation layer 20. Finally, the separation layer 20 below the silicon layer 22 is etched with hydrofluoric acid (see FIG. 7C). As a result, the cantilever portion 32 as shown in FIG. 3D is formed, and the integrated AFM sensor is completed.

In the integrated AFM sensor manufactured as described above, a DC voltage of several volts or less is applied between the two electrodes 28 during measurement so that the tip of the cantilever portion 32 approaches the sample. When an atomic force acts between the tip of the cantilever portion 32 and the atoms on the sample surface, the cantilever portion 32 is displaced. Since the resistance value of the piezoresistive layer 24 changes accordingly, the displacement of the cantilever portion 32 is caused by the two electrodes 2
It is obtained as a change in the current signal flowing during 8.

[0020]

However, the cantilever 1 manufactured by the batch process as shown in FIG.
In No. 4, since the probe 16 and the silicon nitride film (that is, the cantilever portion) 10 are integrally formed, the surface of the cantilever portion can be formed in a shape capable of detecting the displacement of the tip of the probe with high accuracy. There is a problem that it is difficult.

In addition, in the integrated AFM sensor as shown in FIG. 6, it is difficult to provide a sharp probe at the free end of the cantilever portion 32 because of adding a sensor function. For this reason, in the conventional integrated AFM sensor, the free end of the cantilever portion 32 is formed into a flat plate shape with only a narrowed angle without providing a probe, and the free end is brought close to the measurement sample to cause the AFM to move. Measurements are being taken. But,
In such an AFM measurement, there is a problem that high resolution in the direction of the sample surface cannot be expected.

The present invention has been made to solve the above problems, and an object thereof is to make both the probe and the cantilever part into optimum materials and shapes, and to obtain the characteristics required for the cantilever part. An object of the present invention is to provide a cantilever capable of satisfying the characteristics required of a probe.

[0023]

In order to achieve such an object, the present invention provides a cantilever portion whose base end is attached to a holding substrate, and a probe provided at the free end of the cantilever portion. It is applied to a method of manufacturing a cantilever including, a step of manufacturing the cantilever portion,
The method has a step of manufacturing the probe and a step of integrally joining the probe to the free end of the cantilever portion.

[0024]

In the next step, the cantilever part and the probe manufactured through separate steps are integrally joined to the free end of the cantilever part.

[0025]

EXAMPLES A method of manufacturing a cantilever according to a first example of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the cantilever applied to the present embodiment has a hollow triangular triangular cantilever portion 3 having a base end attached to a holding substrate 34.
6 and a silicon nitride probe 38 provided at the free end of the cantilever portion 36.

The holding substrate 34 is composed of a silicon wafer, and silicon nitride films (50, 52) are coated on both surfaces thereof. The silicon nitride film 50 on the lower side in FIG. 1B is the holding substrate. Cantilever portion 36 extending from 34
Are configured. Gold 56 is coated from the holding substrate 34 to the cantilever portion 36. The probe 38 is joined to the free end of the cantilever portion 36 via the joining portion 38a.

The method of manufacturing the cantilever of this embodiment will be described below with reference to FIG. First, a first silicon wafer 40 having a plane orientation (100) is prepared as a start wafer (see FIG. 2A), and the probe 38 is etched on the first silicon wafer 40 by photolithography.
(See FIG. 1) Form a hole 42 (see FIG. 1B).
reference).

Next, C is deposited on the first silicon wafer 40.
The silicon nitride film 44 (film thickness 0.4 to 1 μm by the VD method)
m) is formed (see FIG. 3C), patterning is performed so that the silicon nitride film 44 remains in the hole 42. As a result, the silicon nitride film 44 having the same shape as the probe 38 (see FIG. 1B) remains in the hole 42 portion (see FIG. 1D).

On the other hand, a second silicon wafer 46 having a plane orientation (100) to be the holding substrate 34 (see FIG. 1) is prepared (see FIG. 1E), and a silicon nitride film is formed thereon by the CVD method. 48 (film thickness 0.4 to 1 μm) is formed (see FIG. 6F).

After that, the silicon nitride film 48 is dry-etched through the double-sided photolithography method to form a lever pattern 50 having the same shape as the cantilever portion 36 (see FIG. 1A) and the holding substrate 34. And a mask 52 used for forming (see (g) of the same figure).

Next, after placing the first silicon wafer 40 on the heater portion 54, the second silicon wafer 46 is positioned on the first silicon wafer 40 and anodic bonding is performed.

Specifically, the second portion of the lever pattern 50 is brought into contact with the silicon nitride film 44 remaining in the shape of a probe in the hole 42 so that the portion corresponding to the free end of the cantilever portion 36 contacts. The silicon wafer 46 is positioned on the first silicon wafer 40 and anodic bonding is performed (see FIG. 6H).

Thereafter, the first and second silicon wafers 40 and 46 are etched with a potassium hydroxide solution having a concentration of 40%, so that only the portion of the second silicon wafer 46 to be the holding substrate 34 remains. . As a result, from the remaining portion as the holding substrate 34, the cantilever portion 3
The lever pattern 50 functioning as 6 extends, and the probe 38 anodically bonded is attached to the free end of the lever pattern 50 via the bonding portion 38a (see (i) of the same figure). Finally, by coating the surface of the holding substrate 34 side with gold 56 (see FIG. 1J), the cantilever as shown in FIG. 1 is completed.

As described above, in the cantilever manufacturing method of this embodiment, the cantilever portion 36 is formed through a process different from that of the probe 38. For this reason, the cantilever portion 36 applied to the present embodiment is configured to have a flat shape over the front and back surfaces without the concave portion 10a (see FIG. 5 (h)) that exists in the conventional free end of the cantilever portion. Can be made. Therefore, with the cantilever manufactured by the method of the present embodiment, the displacement of the tip of the probe can be detected and highly precise measurement on the sample surface becomes possible.

Although the cantilever portion 36 and the probe 38 are both formed of a silicon nitride film in the above-described embodiment, the invention is not limited to this, and for example, a magnetic force microscope (MFM).
In this case, the cantilever portion 36 and the probe 38 may be formed of different materials according to the measurement environment, for example, only the probe is made of a magnetic material. Hereinafter, a method of manufacturing a cantilever according to a second embodiment of the present invention will be described with reference to FIGS.
Will be described with reference to. In this embodiment, as the cantilever, an integrated AFM sensor in which a sensor function capable of measuring the displacement of the cantilever itself is added is applied. As shown in FIG. 3, the integrated AFM sensor includes a cantilever portion 60 having a probe 58 provided at its free end.

The cantilever portion 60 is provided with two beams 60a and 60b extending from the holding substrate 62, and these two beams 60a and 60b are integrated at the tips to form a triangular free end. A sharpened probe 58 is provided at the free end.

In such a cantilever portion 60, the piezoresistive layer 7 is provided between the silicon layer 72 and the silicon oxide film 78.
An electrode 80 electrically connected to the piezoresistive layer 76 through a bonding hole formed in the silicon oxide film 78 is provided at the base end thereof. Hereinafter, a method of manufacturing such an integrated AFM sensor will be described with reference to FIG.

First, a first silicon wafer 64 having a plane orientation (100) is prepared as a starting wafer (see FIG. 4A), and the probe 58 is etched on the first silicon wafer 64 by photolithography. A hole 66 that serves as a mold (see FIG. 3) is formed (see FIG. 3B).

Next, C is formed on the first silicon wafer 64.
The silicon nitride film 68 (film thickness 0.4 to 1 μm is formed by the VD method.
m) is formed (see FIG. 3C), patterning is performed so that the silicon nitride film 68 remains in the hole 66. As a result, the silicon nitride film 68 having the same shape as the probe 58 (see FIG. 3B) remains in the hole 66 (see FIG. 3D).

On the other hand, as another start wafer, a second silicon wafer 74 having a silicon layer 72 laminated thereon with a silicon oxide separation layer 70 interposed therebetween, for example, a bonded silicon wafer is prepared (see FIG. 2E). ).

Next, boron (B) is implanted into the very surface of the silicon layer 72 by ion implantation to form a piezoresistive layer 76, and then the cantilever portion 60.
The silicon layer 72 and the piezoresistive layer 76 are patterned so as to have the same shape (see FIG. 3A). After the patterned surface is covered with the silicon oxide film 78, a bonding hole communicating with the piezoresistive layer 76 is opened in a portion of the silicon oxide film 78 that should be the base end of the cantilever portion 60. Then, aluminum is sputtered from above to form an electrode 80 as shown in FIG. Further, after forming a resist layer 82 on the back surface of the second silicon wafer 74 (the surface opposite to the surface on which the electrode 80 is provided), the resist layer 82 is patterned to form an opening 82a having a predetermined shape. Then, heat treatment for making ohmic contact is performed (see FIG. 6F).

Next, after setting the first silicon wafer 64 in which the probe-shaped silicon nitride film 68 remains in the hole 66 portion on the heater portion 84, the silicon oxide film is formed on the first silicon wafer 64. The second silicon wafer 74 is set so that the portion of the film 78 that should be the free end of the cantilever portion 60 is brought into contact with the remaining silicon nitride film 68. Then, a voltage is applied to the first and second silicon wafers 64 and 74, and the silicon nitride film 6
8 and the silicon oxide film 78 are anodically bonded (see FIG. 6H).

Finally, wet anisotropic etching is performed on the second silicon wafer 74 from the resist layer 82 side to the silicon oxide separation layer 70. As a result, the cantilever portion 60 to which the probe 58 is anodically bonded is exposed at its free end (see FIG. 11 (j)). Thus, the integrated AFM sensor is completed.

In the integrated AFM sensor manufactured by the method of this embodiment, the probe 58 is anodically bonded to the free end of the cantilever portion 60, so that the resolution is high with respect to the sample surface not only in the vertical direction but also in the horizontal direction. Can be obtained. Furthermore, in the present embodiment, the probe 58 is manufactured through a process different from the cantilever portion 60, so that it is possible to protect the probe 58 until the final process, and as a result, it seems that the probe 58 existed in the past. It is possible to prevent the risk of damage to the probe when the cantilever portion 60 is manufactured.

In the above-mentioned embodiment, in order to strengthen the bonding between the probe 58 and the cantilever portion 60 in the anodic bonding, the probe manufacturing wafer before the anodic bonding (that is,
It is also preferable to add a step of sputtering a low melting point glass to the probe portion of the first silicon wafer 64). Further, in order to prevent the portion other than the probe from being joined to the portion that should become the cantilever portion, a step of interposing chromium or the like to the portion other than the probe of the probe-fabricated wafer before anodic bonding is added. Is also preferable.

[0047]

According to the present invention, both the probe and the cantilever portion can be made of optimal materials and shapes, and the characteristics required for the cantilever portion and the characteristics required for the probe can be compatible with each other. Therefore, it is possible to provide a method for manufacturing a cantilever capable of detecting the displacement of the tip of the probe with high accuracy and ensuring high resolution with respect to the sample surface.

[Brief description of drawings]

FIG. 1 (a) is an enlarged perspective view showing a portion of a cantilever applied to a first embodiment of the present invention, and FIG. 1 (b) is
The sectional view.

2A to 2D are views sequentially showing a manufacturing process of the cantilever shown in FIG.

FIG. 3A is an enlarged perspective view showing a portion of an integrated AFM sensor applied as a cantilever according to a second embodiment of the present invention, and FIG. 3B is a sectional view thereof.

4A to 4D are views sequentially showing a manufacturing process of the integrated AFM sensor shown in FIG.

FIG. 5 is a diagram sequentially showing a manufacturing process of a conventional silicon nitride cantilever.

FIG. 6 is a diagram sequentially showing a manufacturing process of a conventional integrated AFM sensor.

[Explanation of symbols]

36 ... Cantilever part, 38 ... Probe, 40 ... First silicon wafer, 42 ... Hole, 44 ... Silicon nitride film, 48
... Silicon nitride film, 46 ... Second silicon wafer, 5
0 ... Lever pattern.

Claims (1)

[Claims] 1. A cantilever part having a base end attached to a holding substrate and a probe provided at a free end of the cantilever part is applied to a method of manufacturing the cantilever part, and the cantilever part is manufactured. A method of manufacturing a cantilever, comprising: a step, a step of manufacturing the probe, and a step of integrally bonding the probe to a free end of the cantilever portion.