JP2000266657A - Self excitation type cantilever - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make excitable a silicon cantilever main body without the need of preparing a piezoelectric body such as PZT or the like additionally to the silicon cantilever main body or a holder. SOLUTION: In the self excitation type cantilever 1, a metallic layer 7 with a coefficient of thermal expansion different from silicon is set immediately above a resistance heating unit 3 on a cantilever main body 2. The resistance heating unit 3 intermittently heats when a current is intermittently sent to the resistance heating unit 3, whereby a lever part 21 is excited because of a difference in coefficient of thermal expansion between silicon as a material of the lever part 21 and aluminum as a material of the metallic layer 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-excited cantilever suitable for measuring a sample in a dynamic measurement mode using a scanning probe microscope.

[0002]

2. Description of the Related Art When the surface shape of a sample is measured using a scanning probe microscope, the cantilever is caused to resonate and vibrate to approach the sample surface. The vibration frequency of the cantilever changes. The servo system feedback-controls the position of the cantilever in the Z direction (distance between the sample and the cantilever) so that the vibration frequency or the amount of change is constant, thereby obtaining shape data of the sample surface. The measurement mode has been widely adopted in the past.

Therefore, when a sample is measured in the dynamic measurement mode, conventionally, in order to excite the cantilever, a piezoelectric body such as PZT is coupled to the cantilever body by physical contact, or a PZT or the like is attached to the cantilever itself. A configuration in which a piezoelectric thin film is formed is employed.

[0004]

However, in a configuration in which a piezoelectric body such as PZT is coupled to the cantilever main body, the transmission of vibration tends to be unstable due to the mechanical coupling state between the piezoelectric body and the cantilever, and additional vibration is required. However, there is a problem that the configuration of the device becomes complicated by providing a piezoelectric body in the apparatus.

On the other hand, in the case of a structure in which a thin film such as a piezoelectric material such as PZT is formed on the cantilever itself, it is very difficult to form a piezoelectric thin film and an electrode on the cantilever itself, and it is necessary to perform sufficient excitation. However, it is necessary to increase the thickness of the piezoelectric material, which causes cracks in the piezoelectric film and hardening of the cantilever itself, making it impossible to perform measurement depending on the sample and measurement conditions. there were.

An object of the present invention is therefore to provide a self-excited cantilever which can solve the above-mentioned problems in the prior art.

[0007]

The self-excited cantilever according to the present invention for solving the above-mentioned problems is characterized by a silicon cantilever main body, a resistance heating element formed on the silicon cantilever main body, and a resistance heating element. And a thin film made of a material having a different coefficient of thermal expansion from silicon, which is provided immediately above the silicon.

The resistance heating element can be formed by doping impurities such as boron, phosphorus and arsenic into the silicon cantilever body by ion implantation or the like. The thin film may be a metal layer such as aluminum provided directly above the resistance heating element, but if necessary, for example, an oxide film may be interposed between the resistance heating element and the thin film to ensure electrical insulation between the two. Is formed.

According to the configuration in which the resistive heating element and the thin film of a material having a different thermal expansion coefficient from silicon are provided on the silicon cantilever main body as described above, when the current flows through the resistive heating element to generate heat, the silicon cantilever main body and the thin film Are simultaneously heated, and the silicon cantilever body is bent by the bimetal effect according to the difference in the thermal expansion coefficient between the two. When the current supply is stopped, the silicon cantilever body returns to its original state. Therefore, by intermittently supplying a heating current to the resistance heating element, the silicon cantilever body can be vibrated at a cycle corresponding to the heating current.

[0010]

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 shows an embodiment of a self-excited cantilever according to the present invention. The self-excited cantilever 1 shown in FIG. 1 is configured as a cantilever used for a so-called light lever detection type scanning probe microscope that optically detects the degree of bending of the cantilever.

As will be described later, the self-excited cantilever 1 can be manufactured by photolithography using an SOI wafer or the like, and has a cantilever body 2 made of silicon. The configuration of the cantilever body 2 itself is the same as that of a conventional cantilever of this type.

The resistance heating element 3 is formed on the surface 21A of the lever portion 21 of the cantilever body 2. The resistance heating element 3 is formed in a meandering manner in the form of a strip having a constant width by doping impurities into the lever portion 21 by ion implantation or the like, thereby securing a predetermined length and serving as a heating element. The function can be fulfilled. As the impurity, boron, phosphorus, arsenic, or the like can be used.

On the base 22 of the cantilever body 2, a pair of foil-shaped metal wirings 4, 5 are attached, and one end 4A, 5A of each of the metal wirings 4, 5 is connected to the end 3A of the resistance heating element 3. ,
3B is electrically connected. The other ends 4B and 5B of the metal wirings 4 and 5 are terminal portions, so that a current for heating can be supplied to the resistance heating element 3 from the outside through the other ends 4B and 5B. .

A metal layer 7 is applied directly above the resistance heating element 3 via an insulating film 6. The metal layer 7 is made of aluminum, which is a metal material having a different coefficient of thermal expansion from silicon. However, the material of the metal layer 7 is not limited to this.

When a current is applied to the resistance heating element 3 to cause the resistance heating element 3 to generate heat, thereby heating the lever portion 21, the silicon as the material of the lever portion 21 and the aluminum as the material of the metal layer 7 are mixed. The bimetal effect works due to the difference in the thermal expansion coefficient between them, and the lever portion 21 can be warped.

In the case of the present embodiment, the direction of the warpage of the lever portion 21 is on the near side of the drawing when heated. Reference numeral 8 denotes a tip formed integrally with the cantilever main body 2, and when the resistance heating element 3 is energized to heat the lever portion 21 and the metal layer 7, the tip 8 becomes a sample (not shown). When the power supply to the resistance heating element 3 is stopped, the tip 8 separates from the sample.

Therefore, by turning on and off the current supply to the resistance heating element 3 at appropriate time intervals, the lever portion 21 can be vibrated in synchronization with this. The current supplied to the resistance heating element 3 for heating may be either DC or AC.

If an insulating layer of an electrically insulating material having a different coefficient of thermal expansion from silicon is used instead of the metal layer 7, the formation of the insulating film 6 is unnecessary and the structure can be simplified. it can.

According to the self-excited cantilever 1, it is not necessary to prepare a piezoelectric body such as PZT in addition to the cantilever main body and the holder, so that the device configuration can be simplified, and furthermore, the mechanical coupling is unstable. The instability of the coming measurement can be eliminated.

The self-excited cantilever 1 itself has P
Since there is no need to manufacture a piezoelectric film such as ZT, the self-excited cantilever 1 can be easily manufactured.
Further, since the hardness of the self-excited cantilever 1 does not largely change, the measurement can be performed without limiting the type of the sample to be measured and the measurement mode.

Next, an embodiment of a method of manufacturing the self-excited cantilever 1 shown in FIG. 1 will be described with reference to FIG. As shown in FIG. 2A, a Si substrate 11A,
An SOI wafer 11 having a buried oxide film 11B and an SOI layer 11C laminated as shown in the figure is prepared.
The surface of 1C is oxidized to form oxide film 12.

Next, as shown in FIG. 2B, the oxide film 12 is patterned by photolithography, and a mask 12 for tip etching in the next step is formed.
Form A.

Then, the SOI layer 11 is formed by reactive ion etching (RIE) using the mask 12A.
C is isotropically etched to sharpen a part of the SOI layer 11C into a needle shape, and then the mask 12A is removed.
Is formed (FIG. 2C).

Next, the tip 8 formed as described above is oxidized by thermal oxidation or the like to further sharpen the tip 8. Reference numeral 14 denotes an oxide film (FIG. 2D).

In the state shown in FIG. 2D, the oxide film 14 is removed while leaving only the portion of the oxide film 14 corresponding to the tip 8, and thereafter, a lever forming mask (using photolithography) is used. SOI layer 11 (not shown)
Then, the SOI layer 11C is etched using reactive etching (RIE) or the like to form the lever portion 21 (FIG. 2E).

The lever portion 21 formed in the step of FIG. 2E is doped with boron as an impurity by ion implantation, thereby forming the resistance heating element 3 in the lever portion 21 (FIG. 2F). ).

Thereafter, a silicon oxide film is formed as an electrical insulating film on the resistance heating element 3 on the lever portion 21 by chemical vapor deposition (CVD) to provide an insulating film 6. An aluminum layer is formed thereon and patterned to form a metal layer 7 (FIG. 2G).

When the resistance heating element 3, the insulating film 6, and the metal layer 7 are thus formed on the lever portion 21,
The silicon is etched from the back surface of the SOI wafer 11, the buried oxide film 11B of the SOI wafer 11 is removed, and the cantilever body 2 is separated. Finally, by removing the oxide film 14 on the tip 8, the self-excited cantilever 1 shown in FIG. 1 is obtained (FIG. 2 (H)).

The embodiment of the method for manufacturing the self-excited cantilever 1 has been described above. However, the self-excited cantilever 1 according to the present invention is not obtained only by this manufacturing method, but uses another known manufacturing process. The present invention is not intended to limit the method of manufacturing the self-excited cantilever 1 according to the present invention to only the above-described process.

FIG. 3 shows an example of an apparatus configuration of a scanning probe microscope using the self-excited cantilever 1 shown in FIG. In FIG. 3, 101 is the main body frame, 1
Reference numeral 02 denotes a sample, and 103, an XYZ scanner for moving the sample 102 in the XYZ directions. The self-excited cantilever 1 is fixed to the arm portion 101A of the main body frame 101 by an appropriate means, and a heating current is supplied to a resistance heating element 3 of the self-excited cantilever 1 from a heating power supply (not shown) for a predetermined time. It is supplied intermittently at intervals t.
Therefore, as described above, the lever portion 21 of the self-excited cantilever 1 vibrates at a period T (= 2t), and the tip 8 taps the surface of the sample 102.

The amount of deflection of the lever portion 21 depends on the laser light source 1.
04 is applied to the tip of the lever portion 21 and the reflected laser beam LR is applied to the photodetector 10.
5 allows the instantaneous position of the lever portion 21 to be detected. The detection of the position of the cantilever by the light lever itself can have a known configuration.

As described above, as an embodiment of the present invention, a self-excited light lever cantilever has been described. However, the present invention is not limited to the above embodiment. Can be applied.

FIG. 4 shows an embodiment in which the present invention is applied to a self-excited cantilever of the piezoresistive type to apply a self-excited type. The self-excited self-detecting cantilever 31 has basically the same configuration as the self-exciting cantilever 1 shown in FIG. The same reference numerals as those of the self-excited cantilever 1 denote parts corresponding to the respective parts, and a description thereof will be omitted.

In the self-excited self-detecting cantilever 31, a piezoresistor 32 for detecting the amount of deflection of the lever portion 21 is formed near the base 22 of the cantilever body 2, and the piezoresistor 32 is electrically connected to the outside. The only difference from the self-excited cantilever 1 is that electrodes 33 and 34 for connecting to the cantilever 1 are formed on the base 22.

The piezoresistor 32 can be formed by doping the lever portion 21 with a boron-based impurity by ion implantation or the like.
3 and 34 can be formed on the base 22 as aluminum wirings in the same process as the metal wirings 4 and 5.

In the self-excited self-sensing cantilever 31, the piezoresistor 32 is thus connected to the lever portion 21.
When the sample is measured using the self-excited self-detection type cantilever 31, the piezoresistor 32 is electrically connected to the detection circuit via the electrodes 33 and 34 because the element is provided in advance as an element for detecting the amount of deflection of the piezoresistor. Connection, lever part 2
The amount of bending of the lever portion 21 can be electrically detected from the change in the electrical resistance of the piezoresistive body 32 due to the bending of (1).

FIG. 5 is a process chart showing an example of a manufacturing process of the self-excited self-sensing cantilever 31 shown in FIG. Among the steps (A) to (I) shown in FIG. 5, the steps (A) to (F) are the same as the steps (A) to (F) shown in FIG.

Therefore, here, description will be made from the step of FIG. After the formation of the heating resistor 3, the lever portion 21 is further doped with boron as an impurity by ion implantation or the like to form a piezoresistor 32 on the lever portion 21.

5H, a silicon oxide film is formed as an electrical insulating film on the resistance heating element 3 on the lever portion 21 by chemical vapor deposition (CVD). An insulating film 6 is provided, and an aluminum layer is formed on the insulating film 6 and patterned to form a metal layer 7. Further, the silicon oxide film is used as an interlayer insulator, and wirings 33 and 34 for the piezoresistor 32 are formed as an aluminum layer like the metal layer 7.

When the resistance heating element 3, the insulating film 6, the metal layer 7, and the like are formed on the lever portion 21 in this manner, silicon is etched from the back surface of the SOI wafer 11 and the buried oxidation of the SOI wafer 11 is performed. Membrane 11
B is removed, and the cantilever body 2 is separated. Finally, by removing the oxide film 14 on the tip 8,
The self-excited self-sensing cantilever 31 shown in FIG. 4 is obtained ((I) in FIG. 5).

The self-excited self-detecting cantilever 31 shown in FIG. 4 can also be used in the same manner as that shown in FIG. 3 as a cantilever of a scanning probe microscope. Since it is a self-detection type, the laser light source 104 and the photodetector 105 are not required, and the amount of bending of the lever portion 21 can be detected by using the piezoresistor 32 formed on the lever portion 21.

[0043]

According to the present invention, a bimetal effect is produced between the silicon cantilever body and the thin film by the resistive heating element provided on the silicon cantilever body and the thin film having a different thermal expansion coefficient from silicon. This makes it possible to excite the silicon cantilever body without having to prepare a piezoelectric body such as PZT in addition to the cantilever body or holder, thereby simplifying the device configuration and further causing instability of the mechanical coupling. Measurement instability can be eliminated.

The silicon cantilever body itself has a P
Since it is not necessary to manufacture a piezoelectric film such as ZT, the cantilever can be easily manufactured, and since the hardness of the cantilever does not greatly change, measurement can be performed without limiting the type of sample to be measured or the measurement mode. It can be carried out.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an embodiment of a self-excited cantilever according to the present invention.

FIG. 2 is a process chart for explaining one embodiment of a method for manufacturing the self-excited cantilever shown in FIG.

3 is a schematic configuration diagram showing an example of a device configuration of a scanning probe microscope using the self-excited cantilever shown in FIG.

FIG. 4 is a diagram showing an embodiment in which the present invention is applied to a self-excitation type cantilever of a piezoresistive type to be a self-excitation type.

FIG. 5 is a process chart showing an example of a manufacturing process of the self-excited self-sensing cantilever shown in FIG. 4;

[Explanation of symbols]

 Reference Signs List 1 self-excited cantilever 2 cantilever main body 3 resistance heating element 4, 5 metal wiring 6 insulating film 7 metal layer 8 tip 11 SOI wafer 11A Si substrate 11B buried oxide film 11C SOI layer 14 oxide film 21 lever portion 22 base 31 self-excited self Detection type cantilever 32 Piezoresistor 33, 34 Electrode 101 Body frame 102 Sample 103 XYZ scanner 104 Laser light source 105 Photodetector

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadashi Arai 1-8-8 Nakase, Mihama-ku, Chiba-shi Inside Seiko Instruments Inc. (72) Inventor Yoshiharu Shirakawabe 1-8-1, Nakase, Mihama-ku, Chiba-shi, Chiba Inside Seiko Instruments Co., Ltd. (72) Inventor Chiaki Amuro 1-8 Nakase, Mihama-ku, Chiba-shi, Chiba F-term inside Seiko Instruments Co., Ltd. JJ25 LL03 MM04 MM11 MM23 MM32 PP02 QQ05

Claims (4)

[Claims] 1. A semiconductor device comprising: a silicon cantilever main body; a resistance heating element formed on the silicon cantilever main body; and a thin film made of a material having a thermal expansion coefficient different from that of silicon and provided immediately above the resistance heating element. A self-excited cantilever characterized by the following: 2. The self-excited cantilever according to claim 1, wherein said resistance heating element is formed by doping impurities into said silicon cantilever body by ion implantation. 3. The self-excited cantilever according to claim 1, wherein said thin film is formed immediately above said resistance heating element via an electrical insulating film. 4. The self-excited cantilever according to claim 3, wherein said thin film is a metal layer made of aluminum or the like.