JPH0668791A - Cantilever for scanning type probe microscope and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture a cantilever simply, control height of probes and the like easily, and apply it also to an STM image. CONSTITUTION:Probes 23 are arranged on the free end tips of lever parts 22 extended from a glass body 21. Thereby, when at least one layer of the lever parts 22 is made electrically conductive, not only an AFM image but also an STM image can be obtained by seizing an electric current flowing between the probes 23 and a sample. According to the manufacturing method, a silicon nitride layer or a boron-silicon nitride layer is formed on the surface of a silicon wafer, and next, patterning is carried out on these according to a cantilever shape. Next, the glass body is joined to layers being the lever parts, and next, the etching treatment is carried out on the silicon wafer, so that the probes 23 can be formed.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an atomic force microscope (AF).
M) and the like, and a cantilever for a scanning probe microscope, and a manufacturing method thereof.

[0002]

2. Description of the Related Art An insulating sample that was difficult to measure with a scanning tunneling microscope (STM) invented by Binnig and Rohrer et al. AMF has been proposed as a new device for observing a sample of the above with an accuracy of the atomic size order (Japanese Patent Laid-Open No. 62-13030).
No. 2).

The structure of this AMF is similar to that of the STM, and is positioned as one of scanning probe microscopes. This AMF is a cantilever that has a cantilever with a sharp protrusion (probe) at its free end, faces and approaches the sample and is displaced by the interaction force acting between the atom at the tip of the probe and the sample atom. Function is observed electrically or optically, and the sample is scanned in the XY directions along with it, and the relative position of the cantilever with the probe part is relatively changed, so that the unevenness information of the sample is in the atomic size order. It is captured three-dimensionally.

As the cantilever of the AFM, a cantilever produced by using a semiconductor IC process is often used due to the relationship of mechanical resonance frequency and spring constant. Such a cantilever is preferable because the probe portion can be formed accurately and stably at a predetermined position, and the needle pressure of the probe can be made constant during AMF measurement.

S. Akamine et al. Have also proposed, as one of such cantilevers, a type of cantilever in which a tetrahedral probe portion is provided at the free end of the lever portion of the cantilever (Appl. Phys. Lett. 57 (3)). 316 19
90: S.I. Akamine R. C. Barrett and C.I. F.
Quate). Since the tip of such a tetrahedron structure intersects with three ridges at its tip, the tip is sharper in principle as compared with the conventional pyramid-type tip, and measurement with higher resolution can be performed. it can.

FIG. 6 is a perspective view of such a cantilever, and FIG. 7 is a vertical sectional side view thereof. The cantilever tip 1 includes a support portion 2 made of silicon, a lever portion 3 made of silicon nitride, and a probe portion 4 made of silicon.

Next, a method of manufacturing the cantilever tip 1 will be described with reference to FIGS. 8 and 9. First, as shown in FIG. 8A, a silicon wafer 10 having both sides polished and having a surface direction (100) is used, and silicon nitride films 11 and 12 are formed on both sides.

Next, after the silicon nitride film 12 on one surface of the silicon wafer 10, that is, the back surface, is patterned by photolithography, the remaining silicon nitride film 12 is formed.
Using the as a mask, the silicon wafer 10 is subjected to wet anisotropic etching with a potassium hydroxide aqueous solution. As a result, the silicon wafer 10 is thinly formed and the membrane 13 is formed as shown in FIG.

Next, as shown in FIG. 1C, a silicon nitride film 14 is redeposited on the back surface side of the silicon wafer 10, while a resist 15 is coated on the front surface side of the silicon wafer 10 by photolithography. Pattern.

Then, as shown in FIG.
13 as a mask and the silicon nitride film 1
4 through reactive ion etching (RIE),
Then, the resist 15 is removed. FIG. 6E is a view of the silicon wafer 10 at this time as seen from diagonally above.

Next, as shown in FIG. 1F, an oxide film 16 is formed by oxidation on the silicon surface that appears when the membrane 13 is penetrated by reactive ion etching (RIE).

Next, the silicon nitride film 11 on the surface of the silicon wafer 10 is removed by plasma etching, and then wet anisotropic etching is performed with an aqueous potassium hydroxide solution. This etching is stopped at the oxide film 16 and the silicon nitride film 14 as shown in FIG. Finally, by removing the oxide film 16 with hydrofluoric acid, as shown in FIG.
The cantilever tip 1 for a scanning probe microscope as shown in FIG.

[0013]

However, the above-mentioned S. In the manufacturing method of Akamine et al.
3 is formed, it is very difficult to handle the silicon wafer 10 so as not to break it in the subsequent manufacturing process. In addition, the manufacturing process is difficult to control as a whole and is not suitable for mass production. For example, it is difficult to control the height of the probe.

S. Akamine et al. Made the entire cantilever tip 1 including the support portion 2 from silicon,
With respect to the thickness of the start wafer, for example, in the case of a 4-inch size wafer, it is difficult to control the thickness beyond a variation of about 525 μm thickness ± 20 μm. S. When the cantilever tip is manufactured by the manufacturing method of Akamine et al., The variation of the thickness of the membrane 13 is ± 20 μm, and the length of the probe is determined by the thickness of the membrane 13. Well ±
A variation of 20 μm remains, and the cantilever tip 1 for a scanning probe microscope cannot be stably manufactured.

On the other hand, as described in Japanese Patent Application No. 3-115069, a bonded wafer having an etching stopper layer inside the wafer as a start wafer or an S wafer.
If an IMOX wafer or the like is used, this variation can be suppressed considerably, but the cost of the wafer is high and an increase in cost cannot be avoided.

In addition, S. In the cantilever manufactured by Akamine et al., The probe part is made of silicon, but since this cantilever is made of silicon nitride, it is insulative as a whole, and the current flowing between the probe part and the sample is It cannot be applied to a measurement in which an STM image and an AFM image are simultaneously obtained by measurement.

Therefore, the present invention provides a cantilever for a scanning tunneling scanning probe microscope which can be easily manufactured and can easily control the height of a probe or the like, and can also be applied to an STM image, and a manufacturing method thereof. To aim.

[0018]

According to the present invention, there is provided a support portion formed of glass and a lever portion extending from the support portion and having a free end and formed of at least one layer of silicon or a silicon compound. And a probe formed of silicon provided at the tip of the free end of the lever portion, which is a cantilever for a scanning probe microscope to achieve the above object.

The present invention also provides a first step of forming at least one layer of silicon or a silicon compound on the surface of a silicon wafer, a second step of patterning the silicon wafer and the layer according to the shape of a cantilever, and a silicon wafer. With the third step of bonding the supporting glass body to the layer formed above and the fourth step of etching the silicon wafer to form a probe at the tip of the patterned layer This is a method for manufacturing a cantilever for a scanning probe microscope, which aims to achieve

[0020]

By providing such means, a probe is provided at the tip of the free end of the lever portion extended from the support portion made of glass, and at least one lever portion is formed.
If the layer is made conductive, the current flowing between the probe and the sample can be captured to obtain not only an AFM image but also an STM image.

Further, in the manufacturing method, at least one layer of silicon or a silicon compound is formed on the surface of the silicon wafer in the first step, and in the next second step, the silicon wafer and the layer are patterned according to the shape of the cantilever. . Next, a glass body is bonded to the patterned layer in the third step, and a silicon wafer is etched in the next fourth step to form a probe at the tip of the lever portion.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an external view of a cantilever for a scanning probe microscope. The cantilever tip 20 includes a support portion 21 formed of glass, a triangular lever portion 22 and a tetrahedral probe 23.
Next, a method of manufacturing the cantilever tip 10 will be described with reference to FIG.

First, as shown in FIG.
The silicon nitride layer 3 is formed on the surface of the silicon wafer 30 of 0).
1 is deposited by LP-CDV to a thickness of 5000 Å.

Next, using the etching pattern shown in FIG. 3, reactive ion etching (RIE) is used to form the same drawing (b).
The portion 32 shown in is etched. This etching pattern is a triangle 33 having a shape of the lever portion 22 when viewed from above the surface of the silicon wafer 30, and the etching depth thereof is 5 μm. Next, it is oxidized in a thermal diffusion furnace, and a silicon oxide film 34 is formed on the silicon surface of the portion 32 exposed by RIE as shown in FIG.

On the other hand, a glass body 35 (actually, trade name Pyrex glass is used) partially processed by a dicing saw is prepared, and this glass body 35 is anodically bonded as shown in FIG. It is bonded to the silicon nitride layer 31 on the surface of the silicon wafer 30.

Next, as shown in FIG. 7E, the glass body 35 is ground again to form a predetermined shape. After that, the silicon wafer 30 is subjected to wet anisotropic etching in a potassium hydroxide solution. At this time, since the silicon oxide film 34 is formed, the silicon oxide film 34 and the silicon nitride layer 3 are formed.
In the part that becomes a shadow with 1, the (111) plane appears and the figure
As shown in (f), the tetrahedral silicon 36 remains. This silicon 36 serves as a probe. Finally, the silicon oxide film 34 is removed by hydrofluoric acid to obtain the cantilever for scanning probe microscope shown in FIG.

As described above, in the first embodiment, the silicon nitride layer 31 is formed on the surface of the silicon wafer 30 and patterned according to the shape of the cantilever, and then the glass body 35 is formed on the silicon nitride layer 31. Since the probe 23 is formed by joining the silicon wafer 30 and then etching the silicon wafer 30, the manufacturing process does not make the silicon wafer 30 thin until the end, and the silicon wafer 30 is handled particularly so as not to be broken. Easy to manufacture without any care.

Further, the height of the probe 23 is equal to that of the silicon wafer 3.
0 is processed by RIE, that is, it is determined by the depth of dry etching.
It is extremely easy to control the height of the probe 23 to about 10 μm, and the height of the probe 23 can be designed to be about 5 μm, for example. Next, a second embodiment of the present invention will be described.

FIG. 4 is an external view of a cantilever for a scanning probe microscope. The cantilever tip 40 includes a support portion 41 made of glass, a triangular lever portion 42, and a tetrahedral probe 43.
Of these, the lever portion 42 is formed of two layers 42a and 42b, and the layer 42b and the probe 43 are made conductive. Next, a method of manufacturing the cantilever tip 40 will be described with reference to FIG.

As shown in FIG. 3A, the P-type plane orientation (10
Boron 51 is diffused on the surface of the silicon wafer 50 of 0). At this time, the distribution of the boron concentration in the depth direction is SR
When measured by the method, it is 4x at the highest density position.
10 [20 pieces / cm ³ ] Concentration was shown. The position is 2000 angstroms from the surface.
Next, a silicon nitride layer 52 is formed by LP-CVD in the same figure (b).
Deposit 3000 Angstroms thick as shown.

The subsequent steps are the same as those in the first embodiment. That is, the etching pattern shown in FIG. 3 is used, and the same figure is obtained by reactive ion etching (RIE).
The portion 52 shown in (c) is etched. Then, it is oxidized in a thermal diffusion furnace to form a silicon oxide film 54 on the silicon surface of the portion 53 as shown in FIG.

On the other hand, a glass body 55, a portion of which has been previously processed with a dicing saw, is bonded to the silicon nitride layer 52 on the surface of the silicon wafer 50 by anodic bonding as shown in FIG.

Next, as shown in FIG. 3F, the glass body 35 is ground again to form a predetermined shape, and then the silicon wafer 50 is subjected to wet anisotropic etching in a potassium hydroxide solution. In this case, since the boron 51 is highly doped, the etching stops at the doping layer. At this time, similarly to the above, the tetrahedral silicon 56 remains as shown in FIG. 6 (f) in the portion shaded by the silicon oxide film 54 and the silicon nitride layer 54. Finally, the silicon oxide film 54 is removed by hydrofluoric acid to obtain the cantilever for a scanning probe microscope shown in FIG.

As described above, in the second embodiment, the boron 51 and the silicon nitride layer 52 are formed on the surface of the silicon wafer 50, patterned according to the shape of the cantilever, then the glass body 55 is bonded, and then the glass body 55 is bonded. Since the probe 43 is formed by etching the silicon wafer 50, as in the first embodiment, the manufacturing process does not thin the silicon wafer 50 to the end, and the silicon wafer 50 is not broken. No special care is required for handling, and the manufacturing is simple. Further, since it is extremely easy to control the depth of dry etching, the probe 43
The height can be configured according to your design.

Further, since the lever portion 42 is formed of two layers of the boron 51 and the silicon nitride layer 52, the boron concentration distribution is 4 × 10 [20 pieces / cm ^{3 as} described above. ], The concentration is sufficient to have conductivity. Thereby, the conductive lever portion 42 and the conductive probe 4
3 will be joined. When this cantilever was incorporated into a scanning probe microscope apparatus and measured,
Not only the AFM image was obtained, but the STM image was also obtained.

The present invention is not limited to the above-mentioned embodiment, and may be modified within the scope of the invention. For example, the probe 23 in each lever portion 22, 42,
The surface opposite to the surface provided with 43 may be coated with gold or the like depending on the application.

[0038]

As described above in detail, according to the present invention, a cantilever for a scanning tunnel scanning probe microscope can be manufactured easily, the height of a probe or the like can be easily controlled, and can be applied to an STM image. And the manufacturing method thereof can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a cantilever for a scanning tunnel scanning probe microscope according to the present invention.

FIG. 2 is a manufacturing process drawing of the cantilever.

FIG. 3 is a view showing patterning used in the manufacturing process.

FIG. 4 is a configuration diagram showing a second embodiment of the present invention.

FIG. 5 is a manufacturing process drawing of the cantilever.

FIG. 6 is an external view of a conventional cantilever.

FIG. 7 is a side view of the cantilever.

FIG. 8 is a manufacturing process drawing of the cantilever.

FIG. 9 is a manufacturing process drawing of the cantilever.

[Explanation of symbols]

20 ... Cantilever chip, 21 ... Glass body, 22 ... Lever part, 23 ... Probe, 30 ... Silicon wafer, 31 ... Silicon nitride layer, 34 ... Silicon oxide film, 35 ... Glass body, 51 ... Boron.

Claims (2)

[Claims] 1. A support part formed of glass, a lever part extending from the support part and having a free end, the lever part being formed of at least one layer of silicon or a silicon compound, and a free end of the lever part. And a probe formed of silicon provided at the tip of the cantilever for a scanning probe microscope. 2. A first step of forming at least one layer of silicon or a silicon compound on the surface of a silicon wafer, a second step of patterning the silicon wafer and the layer according to the shape of a cantilever, and a step of forming on the silicon wafer. For joining glass bodies to the laminated layer
A method of manufacturing a cantilever for a scanning probe microscope, comprising: a step; and a fourth step of etching the silicon wafer to form a probe at the tip of the patterned layer.