JPH04238203A - Probe for scanning type capacity microscope and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide high resolution by exposing only the tip of a metal needle, and covering the other portions with a metal film via an insulating film. CONSTITUTION:A probe 10 is covered with a metal oxide film 13 except the tip of a metal needle 12, and a metal film 14 is covered on it. The probe 10 is fixed to a piezoelectric element 15, the metal needle 12 is connected to a capacity sensor 16, and the metal film 14 is connected to the earth. AC voltage is applied to the element 15 to vertically vibrate the probe 10 at the time of measurement, a feedback is applied to the element 15, and the distance from a sample 11 is kept constant. The voltage applied to the sample 11 is vibrated, and the capacity change in the sample 11 is measured by the sensor 16. Only the tip of the metal needle 12 generates the electric field, the sensor 16 catches only the AC change, the capacity of the portion other than the tip has no effect, and high resolution can be obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a probe for a scanning capacitance microscope and a method for manufacturing the same. Binning and Ro
The scanning tunneling microscope (ST
M) uses a piezoelectric element and a probe attached to it to capture the tunneling current flowing between the sample and the probe and observe the surface structure with atomic-scale resolution. An improved version of this is the scanning capacitance microscope (SCM). This scanning capacitance microscope measures the capacitance between the sample and the probe to observe the surface of the sample.

0002

2. Description of the Related Art FIG. 4 is a diagram for explaining a conventional scanning tunneling microscope and a scanning capacitance microscope. In the figure, 1 is a piezoelectric element, 2 is a probe that is driven up and down by the piezoelectric element, and 3 is a sample to be measured. and sample 3
A voltage is applied between the probe 2 and the probe 2, and the probe 2 scans the surface of the sample. At this time, in the scanning tunneling microscope, the probe 2
A current is passed through the piezoelectric element 1 so that the current flowing between the piezoelectric element 1 and the sample is constant (about 1 nA), and the irregularities on the sample surface can be measured by changes in the current. On the other hand, in a scanning capacitance microscope, the piezoelectric element 1 is driven so that the capacitance between the probe 2 and the sample is constant, and the unevenness of the sample surface is measured from the current.

0003

[Problems to be Solved by the Invention] In the above scanning tunneling microscope, the tunneling current rapidly decreases in proportion to the index of the distance between the sample 3 and the probe 2, as shown by curve A in FIG. Therefore, a resolution of several Å or less can be obtained. On the other hand, the scanning capacitance microscope captures the electric field 4 between the sample 3 and the probe 2, as shown in FIG. 6, and this decreases in proportion to the square of the distance, as shown by curve B in FIG. Therefore, a scanning capacitance microscope cannot achieve the high resolution of a scanning tunneling microscope, and its limit is about 250 Å.

The present invention attempts to realize a probe capable of improving the resolution of a scanning capacitance microscope.

[0005]

[Means for Solving the Problems] A probe for a scanning capacitance microscope according to the present invention includes a metal needle, a metal oxide film coated on a portion other than the tip of the metal needle, and a metal oxide film coated on the metal oxide film. It is characterized by being composed of a coated metal film. Further, the method for manufacturing a probe for a scanning capacitance microscope of the present invention includes a step of sharpening the tip of the metal needle by electric field evaporation, and a step of heating the metal needle to form a metal oxide film on the entire surface. , a step of depositing a metal on the metal oxide film to form a metal film, and a step of removing the metal film and the metal oxide film at the tip by electric field evaporation to expose the tip of the metal needle. It is characterized by consisting of.

[0006]

[Operation] If the metal film 14 is connected to the ground as shown in FIG.
Since the electric field 18 is generated only at the tip of the tip of the needle, and the influence of capacitance other than the tip is eliminated, higher resolution can be obtained than in the past.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing an embodiment of the probe of a scanning capacitance microscope according to the present invention together with a sample. In the same figure, 1
0 is a probe, and 11 is a sample to be measured. The probe 10 includes a metal needle 12 whose portion other than the tip is coated with a metal oxide film 13, and further coated with a metal film 14 thereon. Note that metal such as tungsten is used for the metal needle 12 and the metal film 14, and tungsten oxide is used for the metal oxide film 13 when the metal needle is tungsten. Furthermore, if silicon doped with impurities at a high concentration by ion implantation or the like is used as the material of the metal needle, SiO2, which is a highly reliable insulating film, can be obtained as a metal oxide film.

The probe of this embodiment constructed as described above is used by being connected to a measuring circuit as shown in FIG. The figure shows sample 1
Using Si on which a SiO2 film was formed as 1, the S
This is an example of determining the capacity of an iO2 film. The probe 10 is fixed to a piezoelectric element 15, and the metal needle 12 is connected to a capacitive sensor 16.
The metal film 14 is connected to ground. Also, between the metal needle 12 and the sample 11, Vb = V + ΔV (
A voltage oscillating at ω2) is applied, and the capacitance sensor 16 captures the capacitance change during this period.

[0009] During measurement, the piezoelectric element 15 is moved in the x direction, but at this time it is necessary to keep the distance between the probe 10 and the sample 11 constant. For this purpose, piezoelectric element 1
An alternating current voltage is applied to 5 to cause the probe 10 to vibrate up and down at ω1. The capacitance Cair between the probe 10 and the sample 11 is Cai
r = ε0S/d(x), and the change in capacitance due to voltage oscillation ΔCair is ΔCair = -ε0S/d2(
x). Then, if feedback is applied to the piezoelectric element 15 so that ΔCair becomes constant, d becomes constant. On the other hand, the voltage applied to the sample 11 is ω2(≠ω
1), and by passing it through the capacitance sensor 16 and catching it with the lock-in amplifier 17, it is possible to measure the capacitance change (dc/dVb) in the sample. Furthermore, by integrating this with respect to voltage, the capacitance Cs of the SiO2 film can be calculated.

Although there is a capacitance Ct between the metal needle 12 on the inside of the probe 10 and the metal film 14 on the outside, this Ct is excluded because the capacitance sensor 16 catches only the alternating current change. According to the present embodiment described above, the metal needle 1 as shown in FIG.
No electric field is generated from any part other than the tip of 2, and the electric field 1 is generated only at the tip.
8 is generated, higher resolution can be obtained than in the past. Next, a method for manufacturing a probe for a scanning capacitance microscope according to the present invention will be explained with reference to FIG.

First, as shown in FIG. 3(a), a tungsten metal needle 12 is made sharp at its tip 12a by electric evaporation. Field evaporation may be performed at several KV for 2 to 3 minutes. Next, as shown in FIG. 3(b), it is heated in air to form a metal oxide film 13 on the surface with a thickness of 1.
Tungsten oxide with a thickness of about 0.00 Å is formed. Next, as shown in FIG. 3C, tungsten is deposited on the metal oxide film (tungsten oxide) 13 to a thickness of about 1 μm to form a metal film 14. Finally, as shown in FIG. 3(d), the metal film 14 and metal oxide film 13 at the tip are removed by electric field evaporation, and the tip 12a of the metal needle 12 is exposed to a thickness of about 100 Å and made sharp.

According to the present embodiment described above, a probe capable of obtaining high resolution can be easily produced.

[0013]

According to the present invention, only the tip of the metal needle is exposed and the other part is covered with a metal film via an insulating film, so that when used in a scanning capacitance microscope, an electric field is generated only from the tip. is generated and not generated from other parts, so higher resolution can be obtained than in the past.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a probe of a scanning capacitance microscope according to the present invention together with a sample to be measured.

FIG. 2 is a diagram showing how the probe of the scanning capacitance microscope of the present invention is used.

FIG. 3 is a diagram for explaining a method of manufacturing a probe for a scanning capacitance microscope according to the present invention.

FIG. 4 is a diagram for explaining a conventional scanning tunneling microscope and a scanning capacitance microscope.

FIG. 5 is a diagram showing characteristic curves of a conventional scanning tunneling microscope and a scanning capacitance microscope.

FIG. 6 is a diagram showing an electric field between a probe and a sample of a conventional scanning capacitance microscope.

[Explanation of symbols]

10... Probe 11...Sample 12...Metal needle 13...Metal oxide film 14...Metal film 15...Piezoelectric element 16...capacitance sensor 17...Lock-in amplifier 18...Electric field

Claims (3)

[Claims] [Claim 1] A metal needle (12) and the metal needle (12)
A metal oxide film (13) coated on a portion other than the tip of the metal oxide film (13), and a metal film (14) coated on the metal oxide film (13).
A probe for a scanning capacitance microscope characterized by comprising: 2. The probe for a scanning capacitance microscope according to claim 1, wherein silicon doped with impurities at a high concentration is used for the metal needle (12). 3. A step of sharpening the tip (12a) of the metal needle (12) by electric field evaporation, and a step of heating the metal needle (12) to form a metal oxide film (13) on the entire surface. ,
A metal is deposited on the metal oxide film (13) to form a metal film (1).
4) and a step of removing the metal film (14) and metal oxide film (13) at the tip by electric field evaporation to expose the tip (12a) of the metal needle (12). A method of manufacturing a probe for a scanning capacitance microscope, comprising: