JPH02208982A - Electrode for microparticle - Google Patents

Abstract

PURPOSE:To reduce the characteristics of elements in dispersion so as to improve them in reliability of reproducibility, productivity, and reliability and to reduce them in cost by a method wherein the end face of the electrode in contact with microparticles is tilted against the normal of a substrate. CONSTITUTION:Ni thin films 2 and 2' of an electrode for microparticles are formed on an insulating board 1 as thick as specified through a vacuum evaporation method to serve as a positive resist pattern of specified thickness. Then, the insulating board is subjected to ion milling by Ar<+>. At this point, the ion milling is executed while a board stage holding the board 1 is rotated as it is tilted against the direction from which Ar<+> arrives, whereby a pattern is formed in such a state that the end faces 2t and 2t' of the electrode are sloping. The milling is performed under such a condition that ths degree of vacuum, ion source pressure, and ion current density are specified. And, the end face of the electrode is tilted against the normal of the insulating board 1 by an angle of 20 degree or more, and the depth of microparticles is made half the height of the insulating board 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention enables measurement of physical properties of ultrafine particles by depositing ultrafine particles between electrodes, or by applying an electric field to ultrafine particles. Regarding the electrodes used in ultrafine particle devices that allow ultrafine particles to express their functions, the electrical contact between the electrodes and the ultrafine particles is improved by tilting the opposing electrode end surfaces with respect to the normal direction of the substrate. The present invention relates to an electrode for fine particles that enables the production of devices with high properties and always stable characteristics at a good yield.

[Prior art] Ultrafine particles have an extremely wide range of applications in industry;
Numerous properties have been discovered that are not found in bulk materials, making it a promising base material. There are physical methods and chemical methods for manufacturing, and well-known methods include an evaporation method in which the raw material is evaporated in a reduced pressure inert gas atmosphere, and a method in which the raw material gas is decomposed by plasma discharge.

In terms of applications, from a long-term perspective, there is a growing social demand for the establishment of this material technology. For example, their use is progressing in magnetic recording media in the information processing field, catalysts and various sensor materials in the chemical field, and electronic circuit elements and electrically active elements such as switching elements, memory elements, and diode light emitting elements. When using these,
Ultrafine particles are used by forming a "deposited film" directly on a substrate.

[Problems to be Solved by the Invention] However, in such conventional techniques, it is generally difficult to form geometrically fine particles on an element substrate in the form of a film or a deposited film on an element substrate. This causes many problems. That is, as shown in FIG. 2, the electrodes 2.2 formed in the same plane on the substrate i.
If a configuration is adopted in which the ultrafine particles 3 are deposited between the electrodes 2 and 2 and an electric field can be applied, the deposition situation as shown in the figure will occur, and the contact between the opposing ends of the electrodes 2.2 and the ultrafine particles 3 will be insufficient. In addition, since the contact between the ultrafine particles 3 and the opposing end surfaces of the electrodes 2 and 2 is a point contact, there is a problem that electrical reliability is not satisfied and it is often difficult to obtain the same characteristics. . For example, when ultrafine particles are deposited between electrodes, the resistance between the electrodes often shows variations of one to two orders of magnitude, and in some cases three or more orders of magnitude even if the deposited thickness is constant.

Therefore, by depositing ultrafine particles between electrodes in the same plane to create an element that can apply an electric field, and by providing multiple electrodes with the same characteristics between the elements or within the same element, sensors and electronic circuit elements can be fabricated. When used in electrical active devices, etc., it is difficult to reproduce the same characteristics, resulting in problems in terms of device manufacturing reliability, poor yield, and high defective rate.

In view of the problems of the prior art, an object of the present invention is to
An object of the present invention is to provide an electrode for ultrafine particles that has high reliability in electrical contact between the electrode and the ultrafine particles, and allows devices with stable characteristics to be manufactured at a good yield.

[Means and effects for solving the problem] In order to achieve the above object, the present invention deposits an aggregate of ultrafine particles between a pair or a plurality of opposing electrodes formed on a substrate, and In the electrode of the element having a configuration capable of applying an electric field, the surfaces of opposing electrode ends are inclined with respect to the normal direction of the substrate.

The angle of inclination of the surface at the end of the electrode is preferably 20° or more with respect to the normal direction of the substrate, and the deposited thickness of the ultrafine particles is 1 of the height of the electrode.
/2 or less is preferable.

This configuration brings out the characteristics of the ultrafine particles, reduces variation in characteristics, facilitates stable device fabrication, and improves reliability in device manufacturing.

In the present invention, in order to bring the ultrafine particles deposited at the electrode end into a good contact state, we adopted a structure that is inclined with respect to the normal direction of the surface of the electrode end and the substrate. This increases the reliability of measuring the physical properties of ultrafine particles. Figure 1 is a cross-sectional view between the electrodes of an element that shows the features of the present invention.Compared to the conventional example shown in Figure 2, the characteristics of the conventional example were easily influenced by the electrode ends; In the present invention, the characteristics of the ultrafine particle portion set to a predetermined deposition thickness in the center between the electrodes can be observed more easily. In the configuration as shown in FIG. 1, the effect is particularly exhibited when the ultrafine particle deposition thickness is less than or equal to the electrode height.

The ultrafine particles used in the present invention are primary particles with a particle size of 1000°C or less, and include inorganic materials such as known metals, semimetals, semiconductors, and insulators, as long as they are materials that exhibit properties and functions by applying an electric field. Organic ultrafine particles can be used.

As the electrode material, numerically conductive materials such as Au, A
In addition to metals such as fl, Pt, and Ag, conductive materials such as oxides such as SnO2 and ITO, and compounds such as molybdenum silicide can be used.

Although there is no particular restriction on the thickness, for the above-mentioned ultrafine particles, the thickness is preferably 500 Å or more, and particularly preferably 1000 to several μm.

[Example] Hereinafter, the present invention will be explained in detail using the drawings.

Figure 3 is a plan view showing the concept of an embodiment of an electrode for ultrafine particles according to an embodiment of the present invention.In this embodiment, the electrode for ultrafine particles was constructed as follows. Manufactured.

That is, first, 300
A thin Ni film with a thickness of 2.2° was formed using a vacuum evaporation method, and an approximately 30°
A turn equivalent to 0 people was formed. However, the gap G between the electrodes in the figure
The dimension is 30 μm, and the width W of the electrode portion is 400 μm.

Next, ion milling was performed on the insulating substrate 1 using Ar+.

At this time, move the substrate stage holding the insulating substrate 1 to
By rotating and milling while tilting with respect to the flying direction of r'', it is possible to form a pattern in which the electrode end surfaces (4 surfaces) 2t and 2t' are inclined.The milling conditions at this time are as specified by Technics Co. Ion milling device TLA-20
was used, and the ultimate vacuum level was 5xlO-' Torr or more, the ion source current was 17.5 V, the acceleration voltage aoov, the ion current was 150 mA, and the ion current density was 0.5 mA/cm2.

In this way, the angle at which the substrate stage is tilted with respect to the Ar'' flying direction can be varied. As shown in FIG. 4, the inclination angle α at the end of the end faces 2t and 2t' is defined as 20".
Samples with ultrafine particle electrode patterns having angles of 30° and 45° were prepared. The inclination angle α was measured by cross-sectional observation using an electron microscope, and the accuracy was ±2@.

Next, the sample was set in a vacuum device in order to deposit ultrafine particles on the electrode gear G that was formed by removing the remaining resist of the pattern thus formed. As shown in FIG. 5, this device is composed of an ultrafine particle generation chamber 4, an ultrafine particle deposition chamber 5, and a contraction/expansion nozzle 6 that connects these two chambers.The set position of the substrate holder H in the ultrafine particle deposition chamber 5 Sample 7 is attached to. Then, the vacuum level inside the device is evacuated to 1xlO-'Torr or higher using the exhaust system 8, and A
SosccM of r gas 9 was introduced into the ultrafine particle generation chamber 4.

At this time, the pressure in the ultrafine particle generation chamber 4 is 5xlO-'To
rr, the pressure in the ultrafine particle deposition chamber 5 is 1xlO-'Torr
, the distance between the reduction and expansion nozzle 6 and the substrate (sample 7) was 150 mm.

Next, Pd was evaporated from the evaporation source 10 of the carbon crucible, and the generated Pd ultrafine particles were blown out from the nozzle 6 and deposited on the sample 7. At this time, the Pd ultrafine particles had a particle size of 5
FE-3 is 0 to 120 people and the median particle size is 80 people.
Confirmed by EM.

The deposition thickness was set to be equivalent to approximately 300 people. At that time, Pd
The ultrafine particles are placed over the entire surface of the sample 7, but unnecessary parts are masked in advance, and the Pd ultrafine particles deposited around the area other than the electrode gear G do not pose any problem because no electric field is substantially applied to them. .

In this way, 12 samples each having the above-mentioned inclination angle α of 20°, 30°, and 45° were prepared, and variations in resistance values were examined.

The results are shown in Table 1 as Examples 1 to 3.

Twelve samples were prepared under the same conditions as in Example 1, except that the angle of inclination α was 0°, and the variation in resistance was examined. The results are shown in Table 1 as Comparative Example 1.

Comparing Examples 1 to 3 and Comparative Example 1, it can be seen that the variation in resistance value is reduced by tilting the surface of the electrode end with respect to the normal direction of the substrate.

Flow side 4 to 6 and H Example 2 Same as Examples 1 to 3 and Comparative example 1 except that Au was used as the ultrafine particle material and the conditions were set so that the interelectrode resistance during deposition was 10Ω±2Ω. Ten samples were prepared in the same manner, and the thickness of the film formed in the electrode gap G by the ultrafine particles was measured. The variation in film thickness at this time was measured in Example 4~
The Au ultrafine particles shown in Table 2 as Comparative Example 2 and Comparative Example 2 had a particle size of 40 to 90 particles, and a median particle size of 60 particles.

A 900mm thick NaIl thin film was formed on a 1 inch x 2 inch square quartz insulating substrate by vacuum evaporation, and a photolithography technique was used to form the film on the single substrate as shown in Figure 3. Ten electrode resist patterns of 2°2° were prepared. however,
The dimensions of the electrode gap G and W are the same as in Example 1,
The dimensions including a pair of electrodes were 6 mm x 15 mm (not shown).

Next, the above AJ1111 pattern was bevel etched using a known acidic An etching solution.
ng) Shita. At this time, since isotropic etching is performed by the etching solution, the surface of the electrode end becomes tapered. The inclination angle α at this time is 20° ~
It was 25°.

Next, ultrafine particles were deposited in the same manner as in Example 4.

Then, the film thickness was measured for the 10 samples thus obtained. The results are shown in Table 2.

As shown in the table, it can be seen that the variation in the film thickness within the substrate is smaller when the tilt angle α is 20° to 25° than when the tilt angle α is 0°.

Note that although the ion milling method and wet etching method are shown here as taper etching methods,
RI E (Reactive Ion Etchin)
g) Law and RI B (Reactive Ion Be)
am etching) method can also be used, and the present invention is not limited to these examples.

[Effects of the Invention] As explained above, according to the present invention, in an electrode for ultrafine particles of an element having a configuration in which an electric field can be applied by depositing ultrafine particles between electrodes in the same plane, Since the surface of the electrode end that comes into contact with the particles is tilted with respect to the normal direction of the substrate, variations in characteristics between elements are reduced, improving reliability in reproducing the same function, and improving productivity and yield. It is possible to improve the quality, reduce the defective rate, and easily manufacture stable devices.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of the state of ultrafine particle deposition between the ultrafine particle electrodes of the present invention; FIG. 2 is a cross-sectional view showing an example of the state of ultrafine particle deposition between the electrodes in a conventional type; FIG. 3 is a schematic plan view showing the concept of an embodiment of the ultrafine particle electrode of the present invention, FIG. 4 is an explanatory diagram showing the inclination angle of the surface of the electrode end with respect to the normal line of the substrate, and FIG. FIG. 1 is a configuration diagram of a vacuum device for illustrating the principle of producing ultrafine particles. 1: Substrate, 2, 2°; Electrode (pattern), 3 Ultrafine particles, 4: Ultrafine particle generation chamber, 5: Ultrafine particle deposition chamber, 6: Nozzle, 7: Sample, 8: Exhaust system, 9: Introduced gas ( Ar), t
o: evaporation source, 11-shutter.

Claims (3)

[Claims] (1) The electrodes of an element having a configuration in which an aggregate of ultrafine particles is deposited between a pair or a plurality of opposing electrodes formed on a substrate and an electric field can be applied to the ultrafine particles, the electrodes having opposing electric fields. An electrode for ultrafine particles characterized by an extreme surface inclined with respect to the normal direction of the substrate. (2) The electrode for ultrafine particles according to claim 1, wherein the inclination angle of the surface of the electrode end is 20 degrees or more with respect to the normal direction of the substrate. (3) The electrode for ultrafine particles according to claim 1, wherein the deposited thickness of the ultrafine particles is 1/2 or less of the height of the electrode.