JP2000266659A - Cantilever for scanning probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make easily manufacturable a cantilever and to make accurately measurable the surface shape of a sample with recesses and projections having aspect ratios by sharpening the free end of a cantilever body. SOLUTION: First, a mask 120 for etching a cantilever is formed on an SOI layer 110C, the SOI layer 110C is subjected to isotropic etching, its exposed part is etched in a taper shape, and then the mask 120 is eliminated. Then, the reverse side of the SOI wafer 110 is subjected to patterning, silicon is etched from the reverse side, a burial oxide film 110B of the SOI wafer 110 is eliminated, and a lever body 3 and a base part 2 are formed, thus obtaining the cantilever 1. As a result, since no additional tip is owned, a manufacturing process can be simplified and various kinds of restrictions cannot be given to a later process. Also, an angle for mounting the cantilever to a device can be set to an angle vertical to the sample or an angle close to it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cantilever for a scanning probe microscope having no additional tip.

[0002]

2. Description of the Related Art In a scanning probe microscope conventionally used for elucidating a surface shape or a displacement of a physical quantity of a minute region in an atomic order, a probe provided with a tip at a tip portion is used as a scanning probe. We are using.
This type of probe is generally manufactured in a cantilever shape, and a probe in which a tip having a shape such as a cone or a quadrangular pyramid is fixed to a free end of a cantilever body has been conventionally used. When scanning the sample surface with the probe configured as described above, the cantilever bends due to an attractive force or a repulsive force based on an atomic force generated between the sample surface and the tip at the time of scanning. By detecting by means, the shape of the sample surface and the like can be measured.

[0003]

In the above-mentioned conventional cantilever, a tip must be manufactured separately from the cantilever body. However, the tip is usually in the shape of a cone or a quadrangular pyramid, so that a three-dimensional processing is required. Requires a great deal of trouble in its production. In addition, it is required to control the shape of the tip and to adjust the position of the tip with respect to the lever when the tip is mounted. Further, a process for protecting the tip is required, and the process is complicated.

In order to solve this problem, a technique has been disclosed in which a tip is formed integrally with a cantilever (US Pat. No. 5,444,244). However, according to this technique, a cantilever is formed using a silicon material. In order to make the tip in a few microns order above the surface, this tip imposes various restrictions on the post-process and inhibits free patterning, making it more difficult to manufacture the cantilever. Has a problem.

In the case of the conventional cantilever, it is considered that the approach angle is desirably tens of degrees. However, in the case of measuring a sample having a surface shape such as unevenness having an aspect ratio higher than the tip height, the tip angle is required. There is another problem that the lever comes into contact with the sample before the tip receives the interaction force with the sample, and it is difficult to obtain an accurate surface shape. That is, as shown in FIGS. 14A and 14B, when measuring the shape of the convex portion 201 on the surface of the sample 200 with the cantilever 210 having the tip 211, the cantilever 210 moves in the direction of the arrow. As shown in FIG. 3B, when the tip 211 gets over the convex portion 201, the front surface 211A of the tip 211 descends while tracing the corner 201A of the convex portion 201, and the measurement result is indicated by a dotted line S. In other words, the convex portion 201 is erroneously measured as a trapezoidal shape.

It is an object of the present invention to provide a cantilever for a scanning probe microscope which can solve the above-mentioned problems in the prior art.

[0007]

In order to solve the above-mentioned problems, the present invention is to sharpen the free end of the cantilever body to form a cantilever without an additional tip. The cantilever is installed at an arbitrary angle of 15 to 90 degrees with respect to the sample surface, and the bending of the cantilever body due to the interaction force between the sharply pointed portion of the free end of the cantilever and the sample is detected. Can obtain a sample surface shape.

Since the tip of the cantilever according to the present invention functions as a tip by sharpening the tip of the cantilever body, it is easier to manufacture than the prior art in which a tip is separately attached to the cantilever body. Further, since only the tip of the cantilever main body is sharpened, there is no restriction on a subsequent process for manufacturing the cantilever.

[0009] The step of sharpening the tip of the cantilever body is easily realized by performing isotropic etching of silicon using reactive ion etching (RIE) when manufacturing the cantilever body using an SOI wafer. be able to.

Further, the cantilever can be applied to either a shining lever type or a self-sensing type using a piezoresistive type. Since the tip of the cantilever according to the present invention is brought into contact with the sample surface, the approach angle of the cantilever can be set to 90 degrees. In this regard, the cantilever is particularly suitable for a self-detecting cantilever incorporating a strain sensor. is there.

Further, the approach angle of the cantilever is set to 90.
Since it is possible to obtain a profile close to the standard, there is an advantage that the profile can be measured accurately even when the unevenness of the sample surface is steep.

[0012]

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

FIG. 1 is a view showing an embodiment of a cantilever according to the present invention. The cantilever 1 shown in FIG. 1 is for use in a shiny lever system, and is formed by integrally extending a lever body 3 from a base 2. The shape of the free end 3A of the lever body 3 is a pen point, and the surface of the lever body 3 is a surface parallel to the axis of the lever body 3, while the back surface 3Aa of the lever body 3 is tapered. I have. As a result, the tip 3Ab of the free end 3A is extremely sharp and sharp, and the tip 3Ab comes into contact with the surface of the sample (not shown).

FIG. 2 is a process chart for explaining a manufacturing process of the cantilever 1 shown in FIG. FIG.
The manufacturing process of the cantilever 1 will be described with reference to FIG. First, as shown in FIG. 2A, a silicon substrate 110A, a buried oxide film 110B, and an SOI layer 110 are formed.
An SOI wafer 110 in which C is stacked as shown is prepared, and a mask 120 for cantilever etching is formed on the SOI layer 110C.

Next, as shown in FIG. 1B, an SOI layer 1 is formed using a cantilever etching mask 120.
10C is isotropically etched using reactive ion etching (RIE), and the exposed portion 110Ca of the SOI layer 110C is etched in a tapered shape, and then the cantilever etching mask 120 is removed. As a result,
A portion corresponding to the back surface 3Aa of the lever main body 3 is formed on the SOI layer 110C (see FIG. 1).

Thereafter, as shown in FIG. 1C, the back surface of the SOI wafer 110 is patterned, silicon is etched from the back surface, and the SOI wafer 110 is etched.
The buried oxide film 110B is removed to form the lever body 3 and the base 2, and the cantilever 1 shown in FIG. 1 is obtained.

Next, the measurement of the shape of the sample surface using the cantilever 1 shown in FIG. 1 will be described with reference to FIG. FIG. 3 shows a side surface 101A perpendicular to the sample surface 100,
101B and a convex portion 101 having a horizontal upper surface 101C.
This is an example in which the shape of the convex portion 101 is measured by the cantilever 1.

The cantilever 1 is set to a substantially vertical state. The approach angle in this case is approximately 90 degrees. When the cantilever 1 is relatively moved with respect to the sample in the direction of the arrow X in a state where the tip 3Ab of the cantilever 1 is in contact with the sample surface 100, first, as shown in FIG. Contact with. Then, the cantilever 1 escapes upward by the servo operation in the Z-axis direction with respect to the cantilever 1, and thereafter, as shown in FIG. To the corner 1 of the projection 101
When the cantilever 1 reaches 01D, the cantilever 1 descends by the servo operation until the tip 3Ab comes into contact with the sample surface 100, and the state shown in FIG. Thereafter, the tip 3Ab moves in the arrow X direction while contacting the sample surface 100.

As a result, the tip 3Ab of the cantilever 1 draws a locus indicated by a dotted line R, which is obtained as a measurement result.

However, strictly speaking, after the back surface 3Aa of the cantilever 1 hits the corner 101E of the convex portion 101 (see FIG. 3A), the cantilever 1 is moved to the back surface 3Aa.
3 while maintaining contact with the corner portion 101E, the trajectory of the tip 3Ab at that time does not become as shown in FIG.
3C is inclined as shown by the two-dot chain line, and the profile of the convex portion 101 is slightly different.

FIG. 4 is a diagram for explaining a measuring method for avoiding this error.

First, as shown in FIG. 4A, the sample surface 100 is scanned in the direction of arrow X by the cantilever 1 to obtain the first trajectory data R1. Track data R
Reference numeral 1 denotes a state in which the protrusion 101 is slightly inclined on the vertical side surface 101A side.

Next, as shown in FIG. 4B, the direction of the cantilever 1 is inverted by 180 °, and
The second track data R2 is obtained by scanning the cantilever 1 in the arrow Y direction different from the 80-direction. Track data R
In No. 2, the trajectory is inclined on the vertical side surface 101B side of the convex portion 101.

By performing a comparison process using the trajectory data R1 and the trajectory data R2 thus obtained,
Since the vertical side surfaces 101A and 101B of the convex portion 101 are found to be vertical, respectively, a correct trajectory R12 matching the shape of the convex portion 101 is obtained as shown in FIG.
Is obtained.

As described above, as an example of the embodiment of the present invention,
The case of the cantilever used in the shiny lever method has been described. However, the cantilever according to the present invention is not limited to the cantilever of the scanning probe microscope of the shining lever type, but can be widely applied to the case of a self-detecting cantilever.

FIG. 5 shows a self-sensing cantilever according to the present invention. FIG. 5 shows a self-sensing cantilever 11 of the piezoresistive type, and its basic configuration is the same as that of the cantilever 1 shown in FIG. Therefore, in FIG. 5, portions corresponding to the respective portions in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 5, reference numeral 12 denotes a piezoresistor for enabling the amount of deflection of the lever body 3 to be electrically detected, and ends 12A and 12B of the piezoresistor 12 include Metal wirings 13 and 14 are electrically connected. The metal wirings 13 and 14 are formed on an interlayer insulating layer 15 formed on the base 2, and the piezoresistor 12 can be connected to an external circuit via the metal wirings 13 and 14. It has become.

FIG. 6 shows another embodiment of a self-sensing cantilever using a piezoresistive method. The self-detecting cantilever 21 shown in FIG. 6 is provided with a window 22 near the base of the lever main body 3, and the self-detecting cantilever 21 shown in FIG. This is different from the cantilever 11. Therefore, among the parts of the self-detecting cantilever 21, the parts corresponding to the parts of the self-detecting cantilever 11 are denoted by the same reference numerals, and the description thereof is omitted.

Next, an example of a method for manufacturing the self-sensing cantilever 11 shown in FIG. 5 will be described with reference to FIG. First, as shown in FIGS. 7A and 7B, the lever body 3 having the back surface 3Aa is formed in the same process as in FIGS. 2A and 2B.

In the step of FIG. 7C, the lever body 3 is doped with boron as an impurity by ion implantation, thereby forming the piezoresistor 12 on the lever body 3. Then, in a step shown in FIG. 4D, an insulating film 15 is formed on the base 2, and a window is formed in the insulating film 15 so that the ends 12 A, 12 B
Next, metal wirings 13 and 14 are performed. Thereby, the metal wiring 1
3 and 14 are electrically connected to ends 12A and 12B of the piezoresistor 12, respectively (see FIG. 5).

7E, the back surface of the SOI wafer 110 is patterned, silicon is etched from the back surface, and the buried oxide film 1 of the SOI wafer 110 is etched.
10B is removed to form the lever body 3 and the base 2.

FIG. 8 shows another self-sensing cantilever according to the present invention. FIG. 8 shows a self-sensing cantilever 3 using a piezoelectric material.
The basic configuration is the same as that of the self-sensing cantilever 11 shown in FIG. Therefore, in FIG. 8, the portions corresponding to the respective portions in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 8, reference numeral 32 denotes a piezo-electric body for enabling the amount of deflection of the lever main body 3 to be electrically detected, and ends 32A and 32B of the piezo-piezo body 32 include: Metal wiring 3
3, 34 are electrically connected. The metal wiring 3
3 and 34 are interlayer insulating layers 35 formed on the base 2.
And the piezoelectric piezoelectric body 32 can be connected to an external circuit via the metal wirings 33 and 34. According to this embodiment, the piezoelectric body 32 is distorted in accordance with the amount of bending of the lever body 3, and a voltage output corresponding to this is obtained between the metal wires 33 and 34.

FIG. 9 shows another embodiment of a self-detecting cantilever of the piezoelectric type. FIG.
The self-detecting cantilever 41 shown in FIG.
8 differs from the self-detecting cantilever 31 shown in FIG. 8 only in that a window 42 is opened in the vicinity of the base and the lever body 3 is configured to be more easily bent. Therefore, of the respective portions of the self-detecting cantilever 41, portions corresponding to the respective portions of the self-detecting cantilever 31 are denoted by the same reference numerals, and description thereof is omitted.

Next, an example of a method for manufacturing the self-sensing cantilever 31 shown in FIG. 8 will be described with reference to FIG. First, as shown in FIGS. 10A and 10B, the lever body 3 having the back surface 3Aa is formed. This is the same step as FIGS. 2A and 2B.

In the step shown in FIG. 10C, a chemical vapor deposition (CV) process is performed on the lever body 3 formed as described above.
By forming the piezoelectric film by D), the piezoelectric piezoelectric body 32 is formed.

In the next step shown in FIG. 10D, a silicon oxide film 35 as an interlayer insulating layer is formed on the lever body 3.
Is formed by a chemical vapor deposition method, followed by patterning to form metal wirings 33 and 34.

Finally, in the step of FIG.
The back surface of the I wafer 110 is patterned, silicon is etched from the back surface, the buried oxide film 110B of the SOI wafer 110 is removed, and the lever body 3 and the base 2 are formed.

FIG. 11 shows yet another self-sensing cantilever according to the present invention. FIG. 11 shows a self-detecting cantilever 51 of the PN junction type, and its basic configuration is the same as that of the self-detecting cantilever 11 shown in FIG. Therefore, FIG.
In FIG. 5, portions corresponding to the respective portions in FIG. In FIG. 11, reference numeral 52 denotes a PN junction for enabling the amount of deflection of the lever body 3 to be electrically detected, and ends 52A and 52B of the PN junction 52 include Metal wirings 53 and 54 are electrically connected. The metal wirings 53 and 54 are formed on an interlayer insulating layer 55 formed on the base 2 so that the PN junction 52 can be connected to an external circuit via the metal wirings 53 and 54. ing.

FIG. 12 shows another embodiment of a self-sensing cantilever of the PN junction type. FIG.
The self-detecting cantilever 61 shown in FIG.
11 is different from the self-detecting cantilever 51 shown in FIG. 11 only in that a window 62 is opened in the vicinity of the base and the lever body 3 is configured to be more easily bent. Therefore, of the respective portions of the self-detecting cantilever 61, portions corresponding to the respective portions of the self-detecting cantilever 51 are denoted by the same reference numerals, and description thereof is omitted.

Next, an example of a method for manufacturing the self-sensing cantilever 11 shown in FIG. 5 will be described with reference to FIG. First, as shown in FIGS. 13A and 13B, the lever main body 3 having the back surface 3Aa is formed. This is the same step as FIGS. 2A and 2B.

In the step of FIG. 13C, a P-type impurity (for example, phosphorus) is deposited on the lever body 3 formed as described above.
And an N-type impurity (for example, boron) are doped by ion implantation to form a PN junction 52.

In the next step shown in FIG. 13D, a silicon oxide film 55 as an interlayer insulating layer is formed on the lever body 3.
Is formed by chemical vapor deposition, and then patterned to form metal wirings 53 and 54.

Finally, in the step of FIG.
The back surface of the I wafer 110 is patterned, silicon is etched from the back surface, the buried oxide film 110B of the SOI wafer 110 is removed, and the lever body 3 and the base 2 are formed.

The cantilever 1 thus obtained,
11, 21, 31, 41, 51, and 61 correspond to FIGS.
As described above, the probe may be used substantially vertically, but it is needless to say that each approach can be appropriately set within a range of, for example, 15 to 90 degrees and used in the same manner as a conventional probe with a tip.

[0044]

According to the present invention, it is possible to obtain a cantilever having a sharp pointed free end and no additional tip. Since no tip is provided on the cantilever, a process for protecting the tip can be omitted, and the manufacturing process can be simplified. Also, since there is no need to provide a tip, various patterns can be freely formed without imposing various restrictions on a process in a later step, and cantilever production can be made into various shapes without restrictions, and Various additional elements can easily be added.

Further, by using a self-sensing cantilever capable of detecting the bending of the cantilever itself, the angle at which the cantilever is attached to the apparatus can be set to an angle perpendicular to or close to the sample. . This makes it possible to measure the surface shape of a sample having irregularities with an aspect ratio, which has been difficult to measure with a conventional cantilever.

Further, after scanning the sample surface with the cantilever attached at the above-mentioned angle, the cantilever or the sample is rotated 180 degrees around the Z axis, and scanning is performed again to obtain a more accurate surface shape. It is.

In addition, since no tip is required, the step of manufacturing the tip becomes unnecessary and the cost can be reduced. In addition, there is no problem in controlling the shape of the tip or in the accuracy of alignment with the lever, so that the manufacturing process can be extremely simplified, and a significant cost reduction can be expected.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of a cantilever according to the present invention, wherein (A) is a front view and (B) is a right side view.

FIG. 2 is a process chart for explaining an example of a manufacturing process of the cantilever shown in FIG.

FIG. 3 is an explanatory diagram for describing shape measurement of a sample surface using the cantilever shown in FIG. 1;

FIG. 4 is an explanatory diagram for explaining a method for more accurately measuring the shape of the sample surface using the cantilever shown in FIG. 1;

FIG. 5 is a view showing an embodiment of a piezoresistive self-sensing cantilever according to the present invention, wherein (A) is a front view,
(B) is a left side view.

6A and 6B are views showing a modified example of the cantilever shown in FIG. 5, wherein FIG. 6A is a front view and FIG. 6B is a left side view.

FIG. 7 is a manufacturing process diagram for explaining an example of a method of manufacturing the self-sensing cantilever shown in FIG.

8A and 8B are views showing a piezo piezoelectric type self-detecting cantilever according to an embodiment of the present invention, wherein FIG. 8A is a front view and FIG. 8B is a left side view.

9A and 9B are views showing a modified example of the cantilever shown in FIG. 8, in which FIG. 9A is a front view, and FIG. 9B is a left side view.

FIG. 10 is a process chart for explaining an example of a method of manufacturing the self-sensing cantilever shown in FIG. 8;

FIG. 11 is a view showing an embodiment of a PN junction type self-sensing cantilever according to the present invention, wherein (A) is a front view,
(B) is a left side view.

12A and 12B are views showing a modified example of the cantilever shown in FIG. 11, wherein FIG. 12A is a front view and FIG. 12B is a left side view.

FIG. 13 is a process chart for explaining an example of a method for manufacturing the self-sensing cantilever shown in FIG.

FIG. 14 is a view for explaining sample measurement using a conventional cantilever with a tip.

[Explanation of symbols]

 Reference Signs List 1 cantilever 2 base 3 lever body 3A free end 3Aa back surface 3Ab tip 110 SOI wafer 110A silicon substrate 110B buried oxide film 110C SOI layer 120 cantilever etching mask

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Takahashi 1-8-1, Nakase, Mihama-ku, Chiba-shi, Chiba Inside Seiko Instruments Inc. (72) Yoshiharu Shirakawabe 1-8-1, Nakase, Mihama-ku, Chiba-shi, Chiba Within Seiko Instruments Inc. (72) Inventor Tadashi Arai 1-8-8 Nakase, Mihama-ku, Chiba-shi, Chiba F-term within Seiko Instruments Inc. MM04 MM11 MM23 MM32 PP02 QQ05

Claims (7)

[Claims] 1. A cantilever for a scanning probe microscope, wherein a free end of a cantilever body is sharpened sharply to form a contact portion with a sample. 2. The cantilever for a scanning probe microscope according to claim 1, wherein a detecting element for detecting distortion of the cantilever main body is provided on the cantilever main body. 3. The cantilever for a scanning probe microscope according to claim 2, wherein said detection element is a piezoresistor. 4. The cantilever for a scanning probe microscope according to claim 2, wherein said detecting element is a piezoelectric material. 5. The cantilever for a scanning probe microscope according to claim 2, wherein the detection element is a PN junction. 6. The cantilever for a scanning probe microscope according to claim 1, wherein the free end is pointed like a pen point. 7. The free end according to claim 6, wherein one surface of the free end is a surface parallel to the axis of the cantilever body, and the other end is tapered so that the free end is sharply pointed. Cantilever for scanning probe microscope.